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es el estudio de la vida  (bio) en el océano. Las oceanógrafas estudian las plantas y los animales marinos.

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es el estudio del ambiente físico del océano. Este estudio se enfoca en las temperaturas,  olas,  mareas y  corrientes del océano. El interés aquí es en el movimiento del océano.

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es el estudio de la tierra al fondo del océano.

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es el estudio de la química en el océano. Este estudio se enfoca en como la contaminación humana afecta a los animales marinos.

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Seahorses are some of the strangest looking creatures in the sea. This diagram from the NOVA: Kingdom of the Seahorse website reveals some of their more remarkable physical traits that assist in movement, vision, and reproduction.

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Explore aspects of the biology and ecology of the seahorse with this video from ThinkPort. Unlike most other type of fish in form and behavior, the seahorse is not well understood. One scientist is trying to change that by collecting data on the hippocampus erectus species, which is native to the Chesapeake Bay.

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Pygmy Seahorses: Masters of Camouflage | Deep Look | PBS LearningMedia

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Tiny and delicate, pygmy seahorses survive by attaching to vibrant corals where they become nearly invisible to both predators and researchers. Now, biologists at the California Academy of Sciences have successfully bred them in captivity for the first time. Finally, they're able to study the seahorses' amazing act of camouflage up close.

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Bioluminescence is light produced by a chemical reaction within a living organism. Bioluminescence is a type of chemiluminescence, which is simply the term for a chemical reaction where light is produced. (Bioluminescence is chemiluminescence that takes place inside a living organism.)

Bioluminescence is a "cold light." Cold light means less than 20% of the light generates thermal radiation, or heat.

Most bioluminescent organisms are found in the ocean. These bioluminescent marine species include fish, bacteria, and jellies. Some bioluminescent organisms, including fireflies and fungi, are found on land. There are almost no bioluminescent organisms native to freshwater habitats.

Chemistry

The chemical reaction that results in bioluminescence requires two unique chemicals: luciferin and either luciferase or photoprotein. Luciferin is the compound that actually produces light. In a chemical reaction, luciferin is called the substrate. The bioluminescent color (yellow in fireflies, greenish in lanternfish) is a result of the arrangement of luciferin molecules.

Some bioluminescent organisms produce (synthesize) luciferin on their own. Dinoflagellates, for instance, bioluminesce in a bluish-green color. Bioluminescent dinoflagellates are a type of plankton-tiny marine organisms that can sometimes cause the surface of the ocean to sparkle at night.

Some bioluminescent organisms do not synthesize luciferin. Instead, they absorb it through other organisms, either as food or in a symbiotic relationship. Some species of midshipman fish, for instance, obtain luciferin through the "seed shrimp" they consume. Many marine animals, such as squid, house bioluminescent bacteria in their light organs. The bacteria and squid have a symbiotic relationship.

Luciferase is an enzyme. An enzyme is a chemical (called a catalyst) that interacts with a substrate to affect the rate of a chemical reaction. The interaction of the luciferase with oxidized (oxygen-added) luciferin creates a byproduct, called oxyluciferin. More importantly, the chemical reaction creates light. Bioluminescent dinoflagellates produce light using a luciferin-luciferase reaction. The luciferase found in dinoflagellates is related to the green chemical chlorophyll found in plants.

Bioluminescent dinoflagellate ecosystems are rare, mostly forming in warm-water lagoons with narrow openings to the open sea. Bioluminescent dinoflagellates gather in these lagoons or bays, and the narrow opening prevents them from escaping. The whole lagoon can be illuminated at night. Biologists identified a new bioluminescent dinoflagellate ecosystem in the Humacao Natural Reserve, Puerto Rico, in 2010.

Most bioluminescent reactions involve luciferin and luciferase. Some reactions, however, do not involve an enzyme (luciferase). These reactions involve a chemical called a photoprotein. Photoproteins combine with luciferins and oxygen, but need another agent, often an ion of the element calcium, to produce light.

Photoproteins were only recently identified, and biologists and chemists are still studying their unusual chemical properties. Photoproteins were first studied in bioluminescent crystal jellies found off the west coast of North America. The photoprotein in crystal jellies is called "green fluorescent protein" or GFP.

Bioluminescence is not the same thing as fluorescence, however. Florescence does not involve a chemical reaction. In fluorescence, a stimulating light is absorbed and re-emitted. The fluorescing light is only visible in the presence of the stimulating light. The ink used in highlighter pens is fluorescent. Phosphorescence is similar to florescence, except the phosphorescent light is able to re-emit light for much longer periods of time. Glow-in-the-dark stickers are phosphorescent.

Bioluminescent Light

The appearance of bioluminescent light varies greatly, depending on the habitat and organism in which it is found.

Most marine bioluminescence, for instance, is expressed in the blue-green part of the visible light spectrum. These colors are more easily visible in the deep ocean. Also, most marine organisms are sensitive only to blue-green colors. They are physically unable to process yellow, red, or violet colors.

Most land organisms also exhibit blue-green bioluminescence. However, many glow in the yellow spectrum, including fireflies and the only known land snail to bioluminesce, Quantula striata, native to the tropics of Southeast Asia.

Few organisms can glow in more than one color. The so-called railroad worm (actually the larva of a beetle) may be the most familiar. The head of the railroad worm glows red, while its body glows green. Different luciferases cause the bioluminescence to be expressed differently.

Some organisms emit light continuously. Some species of fungi present in decaying wood, for instance, emit a fairly consistent glow, called foxfire.

Most organisms, however, use their light organs to flash for periods of less than a second to about 10 seconds. These flashes can occur in specific spots, such as the dots on a squid. Other flashes can illuminate the organism's entire body.

Bioluminescence is used by living things to hunt prey, defend against predators, find mates, and execute other vital activities.
Defensive Adaptations
Some species luminesce to confuse attackers. Many species of squid, for instance, flash to startle predators, such as fish. With the startled fish caught off guard, the squid tries to quickly escape.

The vampire squid exhibits a variation of this defensive behavior. Like many deep-sea squid, the vampire squid lacks ink sacs. (Squid that live near the ocean surface eject dark ink to leave their predators in the dark.) Instead, the vampire squid ejects sticky bioluminescent mucus, which can startle, confuse, and delay predators, allowing the squid to escape.

Many marine species use a technique called counterillumination to protect themselves. Many predators, such as sharks, hunt from below. They look above, where sunlight creates shadows beneath prey. Counterillumination is a type of camouflage against this predatory behavior.

Hatchetfish use counterillumination. Hatchetfish have light-producing organs that point downward. They adjust the amount of light coming from their undersides to match the light coming from above. By adjusting their bioluminescence, they disguise their shadows and become virtually invisible to predators looking up.

Some bioluminescent animals, such as brittle stars, can detach body parts to distract predators. The predator follows the glowing arm of the brittle star, while the rest of the animal crawls away in the dark. (Brittle stars, like all sea stars, can re-grow their arms.)

When some animals detach body parts, they detach them on other animals. When threatened, some species of sea cucumber can break off the luminescent parts of their bodies onto nearby fish. The predator will follow the glow on the fish, while the sea cucumber crawls away.

Biologists think that some species of sharks and whales may take advantage of defensive bioluminescence, even though they are not bioluminescent themselves. A sperm whale, for instance, may seek out a habitat with large communities of bioluminescent plankton, which are not part of the whale's diet. As the plankton's predators (fish) approach the plankton, however, their glowing alerts the whale. The whale eats the fish. The plankton then turn out their lights.

Some insect larvae (nicknamed "glow worms") light up to warn predators that they are toxic. Toads, birds, and other predators know that consuming these larvae will result in illness and possible death.
Offensive Adaptations
Bioluminescence may be used to lure prey or search for prey.

The most famous predator to use bioluminescence may be the anglerfish, which uses bioluminescence to lure prey. The anglerfish has a huge head, sharp teeth, and a long, thin, fleshy growth (called a filament) on the top of its head. On the end of the filament is a ball (called the esca) that the anglerfish can light up. Smaller fish, curious about the spot of light, swim in for a closer look. By the time the prey sees the enormous, dark jaws of the anglerfish behind the bright esca, it may be too late.

Other fish, such as a type of dragonfish called loosejaws, use bioluminescence to search for prey. Loosejaws have adapted to emit red light; most fish can only see blue light, so loosejaws have an enormous advantage when they light up a surrounding area. They can see their prey, but their prey can't see them.
Attraction
Adult fireflies, also called lightning bugs, are bioluminescent. They light up to attract mates. Although both male and female fireflies can luminesce, in North America most flashing fireflies are male. The pattern of their flashes tells nearby females what species of firefly they are and that they're interested in mating.
Other Bioluminescence
Organisms can luminesce when they are disturbed. Changes in the environment, such as a drop in salinity, can force bioluminescent algae to glow, for instance. These living lanterns can be seen as spots of pink or green in the dark ocean.

"Milky seas" are another example of bioluminescence. Unlike bioluminescent algae, which flash when their environment is disturbed, milky seas are continuous glows, sometimes bright and large enough to be visible from satellites in orbit above the Earth.

Scientists think milky seas are produced by bioluminescent bacteria on the surface of the ocean. Millions of bacteria must be present for milky seas to form, and conditions must be right for the bacteria to have enough chemicals to light up. Satellite imagery of milky seas have been captured in tropical waters such as the Indian Ocean.

Bioluminescence and People

Biologists and engineers are studying the chemicals and circumstances involved in bioluminescence to understand how people can use the process to make life easier and safer.

Green fluorescent protein (GFP), for instance, is a valuable "reporter gene." Reporter genes are chemicals (genes) that biologists attach to other genes they are studying. GFP reporter genes are easily identified and measured, usually by their fluorescence. This allows scientists to trace and monitor the activity of the studied gene-its expression in a cell, or its interaction with other chemicals.

Other uses are more experimental. Bioluminescent trees, for instance, could help light city streets and highways. This would reduce the need for electricity. Bioluminescent crops and other plants could luminesce when they needed water or other nutrients, or when they were ready to be harvested. This would reduce costs for farmers and agribusiness.

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Bioluminescence is light produced by a chemical reaction within a living organism. Bioluminescence is a type of chemiluminescence, which is simply the term for a chemical reaction where light is produced. (Bioluminescence is chemiluminescence that takes place inside a living organism.) Bioluminescence is a "cold light."

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Las adaptaciones son cambios en los genes que ayudan a los organismos a sobrevivir y cambiar con el tiempo. Algunas adaptaciones crean nuevos tipos de plantas y animales.

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Deep Sea Creatures Exhibit Bioluminescence | Blue Planet | BBC Earth

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Newsela | Bioluminescence: a chemical reaction that lights up fireflies and jellyfish

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Living organisms emit light through a chemical reaction in their body.

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Newsela | Meet these cephalopod creatures, from cute to weird

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Cephalopods include octopuses, squids and other sea creatures with large heads and tentacles.

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Everyone knows that an octopus has eight legs with tons of tentacles. But what are all those arms and tentacles used for? Learn this and more alongside beautiful, full-bleed color photographs. Complete with glossary, index, and table of contents.

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Everyone knows that an octopus has eight legs with tons of tentacles. But what are all those arms and tentacles used for? Learn this and more alongside beautiful, full-bleed color photographs. Complete with glossary, index, and table of contents.

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Cómo afectan desechos plásticos a los animales del mar

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Cómo afectan desechos plásticos a los animales del mar

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Cómo afectan los Desechos plásticos a los Animales en el océano

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CONTAMINACIÓN MARINA - Causas y soluciones

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Newsela- Plástico en los estomagos de las criaturas del mar

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Newsela- Plástico en los estomagos de las criaturas del mar

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Newsela | Encuentran plástico en el estómago de criaturas que habitan en las aguas más profundas del mar

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Ni siquiera las zonas más profundas del océano se salvan de la contaminación por plástico

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Newsela- ¿Qué causa las mareas en el océano?

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Newsela- ¿Qué causa las mareas en el océano?

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Newsela | ¿Qué causa las mareas en el océano?

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No solamente la luna afecta a las mareas

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La contaminación del océano reduce el oxígeno en el agua y perjudica la vida del océano.

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Easily create beautiful interactive video lessons for your students you can integrate right into your LMS. Track students' progress with hassle-free analytics as you flip your classroom!

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Newsela | Scientist At Work: I dive into the deep sea to study volcanoes

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"It's been more than 45 years I've been researching the geologic features of the seafloor and I'm still excited about taking dives in Alvin."

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Underwater Volcanoes Attract a Variety of Sea Creatures

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Newsela | Unexplored seamounts could be home to many new species of marine life

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How Volcanoes Formed The Hawaiian Islands

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Newsela | How volcanoes formed the Hawaiian Islands

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The Hawaiian Islands were formed by a volcanic hot spot, an upwelling plume of magma, that creates new islands as the Pacific Plate moves over it.

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Use this code: grape63929

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Inspire your students with thousands of free teaching resources including videos, lesson plans, and games aligned to state and national standards.

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Eruptions and lava flow from submarine volcanoes allow volcanic islands to grow and develop thriving ecosystems.

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From Hawaii to Indonesia to Iceland, hundreds of islands across the globe have been formed by submarine volcanoes. Submarine volcanoes are exactly what they sound like-volcanoes located beneath the ocean's surface.

Because they erupt into water instead of air, submarine volcanoes behave quite differently than terrestrial volcanoes. For instance, it's uncommon for submarine volcanoes to have explosive eruptions. The sheer weight of the water above them creates very high pressure, usually resulting in what are known as passive lava flows along the seafloor. Most submarine eruptions do not disturb the ocean surface.

Charles Mandeville is the program coordinator for the Volcano Hazards Program of the United States Geological Survey ( USGS). He and his colleagues are responsible for monitoring all 169 active volcanoes-all terrestrial-in the United States. Prior to joining the USGS, Mandeville focused his research on submarine volcanology, becoming an expert on the famous 1883 eruption of the island of Krakatoa in Indonesia.

According to Mandeville, there are two main factors that contribute to submarine volcanoes eventually forming islands: the supply of magma and tectonic activity.

"The first thing you need is a supply of magma," he says. "Typically, in the origin of most oceanic island volcanoes or submarine volcanoes, you need to melt the Earth's mantle."

Most volcanic islands originate from passive lava flows on the seafloor. These passive flows harden into rock and build up the height of the underwater mountain over millions of years. Eventually, some volcanoes reach heights above the seafloor where lower pressure allows for explosive eruptions. Submarine volcanoes that do not reach sea level are called seamounts.

In addition to magma supply, plate tectonics play a large part in determining which submarine volcanoes will eventually form islands. Tectonic activity can sometimes "take the island volcano away from the source of magma that originates in the mantle, because the tectonic plate that the volcano is growing upon is moving," says Mandeville.
Volcanic Island Ecosystems
Formed from nothing but rock, volcanic islands have surprisingly vibrant ecosystems. These ecosystems evolve over millions of years, along with the island itself. Life on volcanic islands starts with the most basic building blocks-autotrophic bacteria.

"There are bacteria that can make their food from just the chemical elements and parts of the elements that are being emitted from volcanoes," Mandeville says. " . . . Once you have a microscopic ecosystem established, you have enough of a food supply to support larger life."

Species from nearby landforms also contribute to the developing ecosystem. Passing birds may stop to nest on the new island, bringing seeds and spores from the mainland or other islands. Plant life can float through the ocean to end up on the island's shores.

Because they evolve in such an isolated environment, many organisms are considered endemic species-unlike any others in the world. The finches endemic to the Galapagos Islands, described by naturalist Charles Darwin in the 19th century, are one famous example of this. These birds are found only in the isolated Galapagos Islands. The Hawaiian Islands, even more isolated, have over 1,000 endemic plant species alone.
World's Youngest Island
One of the world's most recently formed volcanic islands is part of the island nation of Tonga, in the South Pacific Ocean. Tonga is an archipelago of 170 volcanic islands. The new landmass formed in March 2009 as an explosive eruption sent steam, volcanic gases, and volcanic ash roughly 800 meters (2,625 feet) into the sky, covering the uninhabited island of Hunga Ha'apai-63 kilometers (39 miles) away-in black, volcanic ash.

Days later, a second, smaller eruption from a vent between Hunga Ha'apai and the new landmass combined with rock and debris from the initial eruption to fill the space between the two. The result was a single landmass nearly double the original size of Hunga Ha'apai.

Though Hunga Ha'apai previously had rich plant and animal life, the ash from the eruption devastated its ecosystem. It's unclear whether the new island will evolve to be able support larger life forms.

"The wind and the waves are constantly trying to erode that island back below sea level. The only thing that's going to outpace the effects of the wave and storm erosion is if the magma supply produces enough lava flows and explosive deposits to keep pace with that erosion," Mandeville says.

Increasing the height of the island above sea level-through lava flows and eruptions-is critical to allowing birds from nearby islands to "seed the new island with life," he says.

In the years since the 2009 eruption, the young island has maintained itself above sea level and experienced significant growth after a series of eruptions in late 2014 and early 2015 added to its landmass. It is still attached to Hunga Ha'apai and is in the very early stages of developing an ecosystem. Other submarine volcanoes near Tonga remain active.

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From Hawaii to Indonesia to Iceland, hundreds of islands across the globe have been formed by submarine volcanoes. Submarine volcanoes are exactly what they sound like-volcanoes located beneath the ocean's surface. Because they erupt into water instead of air, submarine volcanoes behave quite differently than terrestrial volcanoes.

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Pez globo de agua dulce · Variedades y comportamiento 🐡

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While most octopuses hunt at night, this species spends its days stalking crabs, clams and fishes.

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Whales

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Corals are sessile, which means that they permanently attach themselves to the ocean floor, essentially "taking root" like most plants do. We certainly cannot recognize them by their faces or other distinct body parts, as we can most other animals.

So what exactly are corals?

Corals actually comprise an ancient and unique partnership, called symbiosis, that benefits both animal and plant life in the ocean. Corals are animals, though, because they do not make their own food, as plants do. Corals have tiny, tentacle-like arms that they use to capture their food from the water and sweep into their inscrutable mouths.

Most structures that we call "coral" are, in fact, made up of hundreds to thousands of tiny coral creatures called polyps. Each soft-bodied polyp-most no thicker than a nickel-secretes a hard outer skeleton of limestone (calcium carbonate) that attaches either to rock or the dead skeletons of other polyps.

In the case of stony or hard corals, these polyp conglomerates grow, die, and endlessly repeat the cycle over time, slowly laying the limestone foundation for coral reefs and giving shape to the familiar corals that reside there. Because of this cycle of growth, death, and regeneration among individual polyps, many coral colonies can live for a very long time.

Most corals contain algae called zooxanthellae (pronounced zo-UH-zan-thuh-lay), which are plant-like organisms. Residing within the coral's tissues, the microscopic algae are well protected and make use of the coral's metabolic waste products for photosynthesis, the process by which plants make their own food.

The corals benefit, in turn, as the algae produce oxygen, remove wastes, and supply the organic products of photosynthesis that corals need to grow, thrive, and build up the reef.

More than merely a clever collaboration that has endured between some of the tiniest ocean animals and plants for some 25 million years, this mutual exchange is the reason why coral reefs are the largest structures of biological origin on Earth, and rival old-growth forests in the longevity of their ecological communities.

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national oceanic and atmospheric administration

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Corals are sessile, which means that they permanently attach themselves to the ocean floor, essentially "taking root" like most plants do. We certainly cannot recognize them by their faces or other distinct body parts, as we can most other animals. So what exactly are corals?

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Why Is Ocean Water Salty? | Earth's Ocean | Dr Binocs Show | Peekaboo Kidz

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Why is the Ocean Salty?

You may know that the cover about 70 percent of the of Earth's surface, and that about 97 percent of all water on and in the Earth is saline-there's a lot of salty water on our planet. By some estimates, if the salt in the ocean could be removed and spread evenly over the Earth's land surface it would form a layer more than 500 feet (166 meters) thick, about the height of a 40-story office building (Source: NOAA). But, where did all this salt come from? If you get into folk stories and mythology you will see that almost every culture has a story explaining how the oceans became salty. The answer is really very simple. Salt in the ocean comes from rocks on land. Here's how it works...

From precipitation to the land to the rivers to the sea

Thethat falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly due to carbonic acid. The rain physically erodes the rock and the acids chemically break down the rocks and carries salts and minerals along in a dissolved state as ions. The ions in the are carried to the streams and rivers and then to the ocean. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Others are not used up and are left for long periods of time where their concentrations increase over time.

The two ions that are present most often in seawater are chloride and sodium. These two make up over 90% of all dissolved ions in seawater. By the way, the concentration of salt in seawater (salinity) is about 35 parts per thousand. In other words, about 35 of 1,000 (3.5%) of the weight of seawater comes from the dissolved salts; in a cubic mile of seawater the weight of the salt, as sodium chloride, would be about 120 million tons. And, just so you don't think seawater is worthless, a cubic mile of it also can contain up to 25 pounds of gold (at a concentration of 0.000005 parts per million). Before you go out and try alchemy on seawater, though, just think about how big a cubic mile is (1 cubic mile contains 1,101,117,147,000 gallons!).

Salt comes up from below, too

Rivers and surface runoff are not the only source of dissolved salts. Hydrothermal vents are recently-discovered features on the crest of oceanic ridges that contribute dissolved minerals to the oceans. These vents are the exit point on the ocean floor from which sea water that has seeped into the rocks of the oceanic crust has become hotter, has dissolved some of the minerals from the crust, and then flows back into the ocean. With the hot water comes large amounts of dissolved minerals. Estimates of the amount of hydrothermal fluids now flowing from these vents indicate that the entire volume of the oceans could seep through the oceanic crust in about 10 million years. Thus, this process has a very important effect on salinity. The reactions between seawater and oceanic basalt, the rock of ocean crust, are not one-way, however; some of the dissolved salts react with the rock and are removed from seawater.

A final process that provides salts to the oceans is submarine volcanism, the eruption of volcanoes under water. This is similar to the previous process in that seawater is reacting with hot rock and dissolving some of the mineral constituents.
Source: Argonne National Laboratory and The University of Texas at Dallas.

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You may know that the cover about 70 percent of the of Earth's surface, and that about 97 percent of all water on and in the Earth is saline-there's a lot of salty water on our planet.

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Ocean acidification is an emerging global problem. Over the last decade, there has been much focus in the ocean science community on studying the potential impacts of ocean acidification.

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¿Que es la acidificación de los oceanos?

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Acidificación - el efecto en los arrecifes

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Acidificación - el efecto en los arrecifes

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La acidificación del océano y de los arrecifes

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La acidificación del océano es el experimento de química más grande del mundo. Se desarrolla en el 70 por ciento de la superficie mundial y tiene el potencial de alterar profundamente los ecosistemas marinos globales.

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How well do you know your ocean?

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Transcript

NARRATOR:

Even though the ocean covers seventy percent of the Earth's surface, people tend to know more information about land than the sea. As a result, our understanding of the ocean is often incomplete or full of misconceptions. How well do you know the ocean?

You may think Earth has five separate oceans. They're clearly labeled on our maps. But, in actuality, these are all connected, and part of one global ocean system.

Ever wonder why the ocean is blue? You may have heard its because the water reflects the color of the sky. Not quite. Sunlight contains all the colors of the rainbow. When it hits the ocean, it gets scattered by the water molecules. Blue light is scattered the most, which is why the ocean appears blue. Even more interesting is that floating plants and sediments in the water can cause light to bounce in such a way for the ocean to appear green, yellow, and even red!

Another idea some people have is that the sea floor is flat. Actually, just like land, the sea floor has canyons, plains, and mountain ranges. And many of these features are even bigger than those found on land.

You may also think that our ocean's saltwater is just a mix of water and table salt. Not so. Seawater's "salt" is actually made of dissolved minerals from surface runoff. That is, excess water from rain and melting snow flowing over land and into the sea. This is why the ocean doesn't have the same level of salinity everywhere. Salinity varies by location and season.

Finally, you may have heard that melting sea ice will cause sea levels to rise. In reality, sea ice is just frozen seawater, and because it routinely freezes and melts, its volume is already accounted for in the ocean. Sea levels can rise, however, from ice that melts off land and into the ocean.

Understanding basic facts about the ocean is important since it affects everything from our atmosphere to our ecosystems. By knowing your ocean, you are better prepared to help protect it.

Transcripción

NARRADOR:

A pesar de que el océano cubre el setenta por ciento de la superficie de la Tierra, la gente tiende a saber más acerca de la tierra que del mar. Como resultado, nuestra comprensión del océano está a menudo incompleta o con conceptos erróneos. ¿Qué tan bien conoces tú el mar?

Puedes pensar que la Tierra tiene cinco océanos separados. Están claramente identificados en nuestros mapas. Pero en realidad, todos ellos están conectados y son parte de un sistema mundial de océanos.

es azul? Seguramente habrás oído que es porque el agua refleja el color del cielo. No del todo. La luz del sol contiene todos los colores del arco iris. Cuando golpea al océano, se dispersa por las moléculas de agua. La luz azul es la que se dispersa más, por lo tanto el mar se ve azul. Aún más interesante es el que las plantas flotantes y sedimentos en el agua pueden provocar que la luz rebote de tal manera que el océano se vea verde, amarillo e incluso rojo.

Otra idea que algunas personas tienen, es que el fondo del mar es plano. En realidad, al igual que la tierra, el suelo marino tiene cañones, llanuras y cordilleras. Y muchas de estas características son incluso más grandes que las que se encuentran en tierra.

También puedes pensar que el agua salada de nuestro océano es sólo una mezcla de agua y sal de mesa. No es así. La "sal" del agua de mar está en realidad hecha de minerales disueltos de la escorrentía superficial. Es decir, del exceso de agua de lluvia y nieve derretida que fluye sobre la tierra al mar. Es por esto que el océano no tiene el mismo nivel de salinidad en todos lados. La salinidad varía según la ubicación y la temporada.

Finalmente, habrás oído que el derretimiento del hielo del mar hará que los niveles del mar aumenten. En realidad, el hielo marino es agua de mar congelada, y porque se congela y se derrite de forma rutinaria, su volumen ya se contabiliza en el océano. El nivel del mar puede elevarse pero es a partir del hielo que se derrite en la tierra que va al océano.

Comprender los hechos básicos sobre el océano es importante, ya que afecta a todo, desde la atmósfera hasta nuestros ecosistemas. Al conocer tu océano, estarás mejor preparado para ayudar a protegerlo.

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NARRATOR: Even though the ocean covers seventy percent of the Earth's surface, people tend to know more information about land than the sea. As a result, our understanding of the ocean is often incomplete or full of misconceptions. How well do you know the ocean? You may think Earth has five separate oceans.

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Most people know that oceans cover about 70 percent of Earth's surface. Fewer people realize that the crust beneath oceans and continents is fundamentally different. Why this is so remains a mystery that scientists are still trying to solve.

Oceanic crust is generally composed of dark-colored rocks called basalt and gabbro. It is thinner and denser than continental crust, which is made of light-colored rocks called andesite and granite. The low density of continental crust causes it to "float" high atop the viscous mantle, forming dry land. Conversely, dense oceanic crust does not "float" as high-forming lower-lying ocean basins. As oceanic crust cools, it becomes denser and ultimately sinks back into the mantle under its own weight after about 200 million years.

Earth's continental crust, on the other hand, is up to 4 billion years old, and it is thought to be the product of geologic recycling processes far more complicated than those that create ocean crust. If we can decode and read the relatively simple story of how oceanic crust is formed, we may someday be able to decipher the more complex record of how the continents developed.

Sounding out seafloor structure

Because most oceanic crust is hidden from view beneath many kilometers of water, our research must be conducted "remotely," often using acoustic techniques. Sound-emanating from an earthquake, an explosion, or a relatively benign source known as an airgun-travels through different rocks at different speeds. Geophysicists infer the basic geologic structure of underlying rocks by measuring the time it takes for sound to travel from one source to many different receivers, or from many sources to a single receiver.

In the oceans, this technique has yielded a simple picture of a basaltic, layered crust about 7 kilometers (4.3 miles) thick, underlain by the mantle. Rock samples obtained via dredging, submersible operations, and drilling confirm that the top of the oceanic crust, where it is not obscured by sediments, is composed of basaltic lava that originates in the mantle.

At the dawn of the modern theory of plate tectonics in the 1960s, geologists and geophysicists realized that the entire oceanic crust was created from basaltic lava along linear chains of seafloor volcanoes known as mid-ocean ridges, or spreading ridges. Seafloor spreading carries older oceanic crust away from the ridges over tens of millions of years, until it cools, becomes denser, and "falls" back into the mantle in areas known as subduction zones.

Seafloor clues in the desert

In a few places on Earth, blocks of oceanic crust, called "ophiolites," have been thrust, relatively intact, onto the continents during collisions between tectonic plates. Tilting and subsequent erosion allow scientists to walk through a section that once extended 25 kilometers (15 miles) into Earth's interior. The largest and best exposed of these, the Oman ophiolite near the Persian Gulf, comprises about ten blocks that together cover roughly the same area as Massachusetts.

The great extent of these ophiolites, once deep beneath the seafloor but now exposed, provides a comprehensive view of the internal geometry of oceanic plates that is unmatched by any sampling or imaging technique at sea. Like pot shards covered with hieroglyphics, ophiolites open a window onto an ancient, largely vanished world, and provide a rare avenue for systematic investigation.

In the late 1960s and early 1970s, geologists and geophysicists observed similarities between the layered structure of oceanic crust, as interpreted from sound velocities, and the layering in ophiolites. A thin, upper layer in oceanic crust (with low sound velocities) corresponds to a layer of sediments and lava flows in ophiolites. A deeper layer (with faster sound velocities) corresponds to an ophiolite layer of "gabbro," which formed when molten basalt solidified beneath Earth's surface. In both oceanic crust and ophiolites, the gabbro layer is underlain by the mantle, which extends thousands of kilometers down to Earth's core.

A striking feature of well-exposed ophiolites is a continuous layer of "sheeted dikes," which lies between the lava and the gabbro. These are tabular rock formations, about a meter wide, created by periodic bursts of molten rock. The dikes stand side-by-side, like soldiers in formation, each dike adjacent to neighboring dikes, or sometimes leaning or intruding into them.

This recurring structural pattern occurs because all oceanic crust is newly created at spreading mid-ocean ridges on a kind of continuous conveyor belt: Each dike, in a simple view, forms directly at the center of a ridge. It then spreads out from the ridge center, as another dike forms behind it, in an ongoing process that creates the continuous layer observed in ophiolites. Nothing like that happens in continental crust, where new dikes more randomly intrude older rock.

Going with the flow

During the 1970s and 1980s, geophysicists and geologists strove to understand how basaltic lava forms beneath spreading ridges. They theorized that because the oceanic plates pull apart at the surface, new material must rise to fill the gap. As the material rises, the pressure that helps keep it solid decreases. This allows hot mantle rocks to partially melt and produce basaltic liquid. This so-called "melt" is less dense than surrounding solids, and so it buoyantly rises to the surface to form the crust.

However, this theory raises as many questions as it answers. From lava compositions, we know that from an enormous volume of mantle rock, only small amounts of rock partially melt to create oceanic crust. Melt forms in micron-size pores along the boundaries of innumerable crystal grains across a mantle region that is 100 to 200 kilometers wide and 100 kilometers deep. From this vast region, however, the melt somehow is focused into only a 5-kilometer-wide zone at the spreading ridge. How is lava channeled from tiny pores in a broad region of melting into a narrow region where it forms new oceanic crust topped by massive lava flows?

My colleagues in exploring this mystery, working in various combinations, have included Greg Hirth, Nobu Shimizu, and Jack Whitehead at Woods Hole Oceanographic Institution (WHOI), Marc Spiegelman of the Lamont-Doherty Earth Observatory, French geologists Adolphe Nicolas and Françoise Boudier, Massachusetts Institute of Technology graduate student Vincent Salters, and MIT/WHOI Joint Program students Einat Aharonov, Mike Braun, Ken Koga, and Jun Kornaga. Our research has been funded by the U.S. National Science Foundation, the WHOI Interdisciplinary and Independent Study Award program, and the Adams Chair at WHOI.

We have shown that melt travels through the mantle in porous channels, similar to channels filled with gravel that provide permeable pathways through clay-rich soil. Melt rising through the hot mantle can partially dissolve minerals around them and gradually enlarge the pores along the boundaries between individual crystal grains. This, in turn, creates a favorable pathway through which more melt can flow-in a positive feedback loop that spontaneously creates channels that focus the flow.

Small channels formed in this fashion coalesce to form larger channels, in a network analogous to a river drainage system. The number and size of melt flow channels we observe in the mantle section of ophiolites supports these theories.

Melt lenses and periodic bursts

New questions arose. If melt flows through the mantle in micron-scale pores along the boundaries of crystal grains, where does it accumulate to form massive lava flows at spreading ridges? And, if porous flow is a continuous, gradual process, what causes the periodic bursts of molten rock that create new dikes?

Once again, the Oman ophiolite provided clues. Embedded in the shallowest mantle rocks, Nicolas and Boudier found small formations of gabbro, called sills. Chemical analyses of these sills indicated that they crystallized from the same melt that formed gabbro, sheeted dikes, and lava flows in the crust. In addition, the gabbro, dikes, and lava flows all had an identical, distinctive pattern of alternating bands of dark and light minerals.

It seemed to us that the entire gabbro layer in the Oman ophiolite crust, from uppermost mantle to the surface, could have formed when melt material periodically collected in relatively small pools that subsequently crystallized into solid "melt lenses." Over time, a myriad of these melt lenses accumulates-embedded within each other and stacked atop each other or side by side-to produce gabbro's rocky, banded fabric.

Clogged pores build up pressure

Why would melt lenses first appear in the uppermost mantle, immediately beneath the base of the crust? We propose that such lenses form where melt, approaching the seafloor, begins to cool. Melt rising through the hot mantle can dissolve minerals surrounding it to create pore spaces, but cooling melt will begin to crystallize and clog pores.

Two scenarios are possible: When the supply of melt from below is low, conduits become narrower. The melt is forced outward around impermeable barriers, migrating via diffuse porous flow along crystal grain boundaries throughout surrounding rock.

But when melt supply is large, as it is immediately beneath a spreading ridge, buoyant melt accumulates beneath impermeable barriers and creates excess pressure. Eventually, the melt bursts through the barriers and creates a melt-filled fracture that intrudes the overlying crust. If the fracture propagated high enough in the crust, it would form a sheeted dike, and if it reached even higher, it would spill out onto the seafloor and feed a lava flow.

In this cycle of buildup and release, minerals alternately crystallize and melt under conditions of higher and lower pressure. At relatively high pressure, much less of the light-colored mineral (plagioclase) is formed, compared to darker-colored minerals. At lower pressure, the proportion of plagioclase is larger. Thus, periodic pressure changes result in the light-and-dark banding observed in ophiolite gabbros.

Paths of most resistance

Working from geological evidence in ophiolites, together with physical and chemical theory, we hypothesize that there are two distinct ways to transport melt that forms oceanic crust. Within the melting region in the mantle, melt can dissolve minerals and create additional pore space. As a result, continuous, high-porosity conduits form a coalescing drainage network that focuses melt transport to the spreading ridge.

At shallow levels beneath the ridge, cooling melt begins to crystallize, clogging pore space along crystal grain boundaries. As a result, flow becomes diffuse, melt accumulates beneath impermeable barriers. Pressure builds up until the melt periodically bursts through overlying barriers, and melt-filled fractures are injected into overlying rocks to feed dikes and lava flows. Together, these processes form a highly organized system that consistently produces new oceanic crust with a regular structure along spreading ridges.

In our ongoing research, we are more rigorously testing theories about how porous conduits form in the mantle. We seek to understand in more detail how melt lenses form beneath spreading ridges. And we want to figure out the factors that determine why and when diking and eruption events occur.

Exploring a universal pattern of fluid flow

There are intriguing parallels between the mechanisms that lead to the creation of seafloor and to erosion on Earth's surface.

Consider water flowing over a sandy surface. Where the slope is steep enough (but not too steep), water begins to move sand grains downward and form channels. As the channels grow, water flows faster, leading to more vigorous erosion of sand at the leading edge of the flow. An analogous process occurs beneath the seafloor, as rising, hot melt dissolves minerals in rocks to form porous channels.

When the slope decreases downstream in an erosional system, water begins to deposit sand grains that were carried in suspension. The deposited grains begin to construct barriers that block flow and force it to diverge away from the main channel. Water accumulates behind these barriers to form temporary lakes. These lakes periodically overflow the old channel and create transient, new pathways, which in turn are clogged and abandoned. A delta or alluvial fan forms.

Analogous processes occur beneath the seafloor as rising melt cools, precipitates crystals that block pore spaces, causes flow to diverge and accumulate, and periodically bursts through impermeable barriers to form dikes and fractures.

Optimizing fluid flow

What lies behind these apparent fundamental similarities between fluid transport during erosion on Earth's surface and melt transport in the mantle?

Basically, where energy is available for fluid to create new pathways-via physical erosion or chemical dissolution-drainage networks evolve from relatively inefficient, slow moving, diffuse flow to faster, focused, steady flow in well-defined channels. Where energy is lost-via a decrease in slope angle in erosion or a decrease in temperature of melt-the drainage network becomes inefficient and disorganized, with quick shifts in flow rate and location.

Scientists working on the evolution of river drainage systems propose that erosion tends to produce an "optimal" drainage network that maximizes flow velocity and minimizes loss of energy via friction. This is an intriguing idea, offering the vision of a systematic, "thermodynamic" theory of drainage morphology. (It is also controversial theory, since river drainages inherit much of their complicated structure from the prior geologic history of a watershed.)

It is difficult to use ophiolites to explore a themodynamic theory of drainage morphology for mantle melt transport mechanisms-because ophiolites constitute a "frozen" system. So I began to look elsewhere for an active fluid transport system that developed channels within an initially diffuse flow pattern.

Finally, I realized that erosional channels form twice a day as the tide falls on beaches all over Cape Cod. Cautiously, Dan Rothman, a geophysicist at MIT, and I are learning about beach erosion and making observations on channel formation. We hope to determine whether the evolving channel network gradually approaches an "optimal" geometry that allows water to flow over the beach surface with minimal frictional energy loss.

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Most people know that oceans cover about 70 percent of Earth's surface. Fewer people realize that the crust beneath oceans and continents is fundamentally different. Why this is so remains a mystery that scientists are still trying to solve. Oceanic crust is generally composed of dark-colored rocks called basalt and gabbro.

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Topics: currents, ocean formation, fishing, ocean floor, climate, life zones, pollution

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The ocean covers 70 percent of Earth's surface.

Subjects

Biology, Earth Science, Oceanography, Geography, Physical Geography

This article is also available in Spanish.
The ocean covers 70 percent of Earth's surface. It contains about 1.35 billion cubic kilometers (324 million cubic miles) of water, which is about 97 percent of all the water on Earth. The ocean makes all life on Earth possible, and makes the planet appear blue when viewed from space. Earth is the only planet in our solar system that is definitely known to contain liquid water.

Although the ocean is one continuous body of water, oceanographers have divided it into five principal areas: the Pacific, Atlantic, Indian, Arctic, and Southern Oceans. The Atlantic, Indian, and Pacific Oceans merge into icy waters around Antarctica.

The ocean plays a vital role in climate and weather. The sun's heat causes water to evaporate, adding moisture to the air. The oceans provide most of this evaporated water. The water Climate vapor condenses to form clouds, which release their moisture as rain or other kinds of precipitation. All life on Earth depends on this process, called the water cycle.

The atmosphere receives much of its heat from the ocean. As the sun warms the water, the ocean transfers heat to the atmosphere. In turn, the atmosphere distributes the heat around the globe.

Because water absorbs and loses heat more slowly than land masses, the ocean helps balance global temperatures by absorbing heat in the summer and releasing it in the winter. Without the ocean to help regulate global temperatures, Earth's climate would be bitterly cold.

Ocean Formation
After Earth began to form about 4.6 billion years ago, it gradually separated into layers of lighter and heavier rock. The lighter rock rose and formed Earth's crust. The heavier rock sank and formed Earth's core and mantle.

The ocean's water came from rocks inside the newly forming Earth. As the molten rocks cooled, they released water vapor and other gases. Eventually, the water vapor condensed and covered the crust with a primitive ocean. Today, hot gases from the Earth's interior continue to produce new water at the bottom of the ocean.

Ocean Floor
Scientists began mapping the ocean floor in the 1920s. They used instruments called echo sounders, which measure water depths using sound waves. Echo sounders use sonar technology. Sonar is an acronym for SOund Navigation And Ranging. The sonar showed that the ocean floor has dramatic physical features, including huge mountains, deep canyons, steep cliffs, and wide plains.

The ocean's crust is a thin layer of volcanic rock called basalt. The ocean floor is divided into several different areas. The first is the continental shelf, the nearly flat, underwater extension of a continent. Continental shelves vary in width. They are usually wide along low-lying land, and narrow along mountainous coasts.

A shelf is covered in sediment from the nearby continent. Some of the sediment is deposited by rivers and trapped by features such as natural dams. Most sediment comes from the last glacial period, or Ice Age, when the oceans receded and exposed the continental shelf. This sediment is called relict sediment.

At the outer edge of the continental shelf, the land drops off sharply in what is called the continental slope. The slope descends almost to the bottom of the ocean. Then it tapers off into a gentler slope known as the continental rise. The continental rise descends to the deep ocean floor, which is called the abyssal plain.

Abyssal plains are broad, flat areas that lie at depths of about 4,000 to 6,000 meters (13,123 to 19,680 feet). Abyssal plains cover 30 percent of the ocean floor and are the flattest feature on Earth. They are covered by fine-grained sediment like clay and silt. Pelagic sediments, the remains of small ocean organisms, also drift down from upper layers of the ocean. Scattered across abyssal plains are abyssal hills and underwater volcanic peaks called seamounts.

Rising from the abyssal plains in each major ocean is a huge chain of mostly undersea mountains. Called the mid-ocean ridge, the chain circles Earth, stretching more than 64,000 kilometers (40,000 miles). Much of the mid-ocean ridge is split by a deep central rift, or crack. Mid-ocean ridges mark the boundaries between tectonic plates. Molten rock from Earth's interior wells up from the rift, building new seafloor in a process called seafloor spreading. A major portion of the ridge runs down the middle of the Atlantic Ocean and is known as the Mid-Atlantic Ridge. It was not directly seen or explored until 1973.

Some areas of the ocean floor have deep, narrow depressions called ocean trenches. They are the deepest parts of the ocean. The deepest spot of all is the Challenger Deep, which lies in the Mariana Trench in the Pacific Ocean near the island of Guam. Its true depth is not known, but the most accurate measurements put the Challenger Deep at 11,000 meters (36,198 feet) below the ocean's surface-that's more than 2,000 meters (6,000 feet) taller than Mount Everest, Earth's highest point. The pressure in the Challenger Deep is about eight tons per square inch.

Ocean Life Zones
From the shoreline to the deepest seafloor, the ocean teems with life. The hundreds of thousands of marine species range from microscopic algae to the largest creature to have ever lived on Earth, the blue whale.

The ocean has five major life zones, each with organisms uniquely adapted to their specific marine ecosystem.

The epipelagic zone (1) is the sunlit upper layer of the ocean. It reaches from the surface to about 200 meters (660 feet) deep. The epipelagic zone is also known as the photic or euphotic zone, and can exist in lakes as well as the ocean.

The sunlight in the epipelagic zone allows photosynthesis to occur. Photosynthesis is the process by which some organisms convert sunlight and carbon dioxide into energy and oxygen. In the ocean, photosynthesis takes place in plants and algae. Plants such as seagrass are similar to land plants-they have roots, stems, and leaves. Algae is a type of aquatic organism that can photosynthesize sunlight. Large algae such as kelp are called seaweed.

Phytoplankton also live in the epipelagic zone. Phytoplankton are microscopic organisms that include plants, algae, and bacteria. They are only visible when billions of them form algal blooms, and appear as green or blue splotches in the ocean.

Phytoplankton are a basis of the ocean food web. Through photosynthesis, phytoplankton are responsible for almost half the oxygen released into Earth's atmosphere. Animals such as krill (a type of shrimp), fish, and microscopic organisms called zooplankton all eat phytoplankton. In turn, these animals are eaten by whales, bigger fish, ocean birds, and human beings.

The next zone down, stretching to about 1,000 meters (3,300 feet) deep, is the mesopelagic zone (2). This zone is also known as the twilight zone because the light there is very dim. The lack of sunlight means there are no plants in the mesopelagic zone, but large fish and whales dive there to hunt prey. Fish in this zone are small and luminous. One of the most common is the lanternfish, which has organs along its side that produce light.

Sometimes, animals from the mesopelagic zone (such as sperm whales ( Physeter macrocephalus) and squid) dive into the bathypelagic zone (3), which reaches to about 4,000 meters (13,100 feet) deep. The bathypelagic zone is also known as the midnight zone because no light reaches it.

Animals that live in the bathypelagic zone are small, but they often have huge mouths, sharp teeth, and expandable stomachs that let them eat any food that comes along. Most of this food comes from the remains of plants and animals drifting down from upper pelagic zones. Many bathypelagic animals do not have eyes because they are unneeded in the dark. Because the pressure is so great and it is so difficult to find nutrients, fish in the bathypelagic zone move slowly and have strong gills to extract oxygen from the water.

The water at the bottom of the ocean, the abyssopelagic zone (4), is very salty and cold (2 degrees Celsius, or 35 degrees Fahrenheit). At depths up to 6,000 meters (19,700 feet), the pressure is very strong-11,000 pounds per square inch. This makes it impossible for most animals to live. Animals in this zone have bizarre adaptations to cope with their ecosystem. Many fish have jaws that look unhinged. The jaws allow them to drag their open mouth along the seafloor to find food, such as mussels, shrimp, and microscopic organisms.

Many of the animals in this zone, including squid and fish, are bioluminescent. Bioluminescent organisms produce light through chemical reactions in their bodies. A type of angler fish, for example, has a glowing growth extending in front of its huge, toothy mouth. When smaller fish are attracted to the light, the angler fish simply snaps its jaws to eat its prey.

The deepest ocean zone, found in trenches and canyons, is called the hadalpelagic zone (5). Few organisms live here. They include tiny isopods, a type of crustacean related to crabs and shrimp.

Invertebrates such as sponges and sea cucumbers thrive in the abyssopelagic and hadalpelagic zones. Like many sea stars and jellyfish, these animals are almost entirely dependent on falling parts of dead or decaying plants and animals, called marine detritus.

Not all bottom dwellers, however, depend on marine detritus. In 1977, oceanographers discovered a community of creatures on the ocean floor that feed on bacteria around openings called hydrothermal vents. These vents discharge superheated water enriched with minerals from Earth's interior. The minerals nourish unique bacteria, which in turn nourish creatures such as crabs, clams, and tube worms.

Ocean Currents
Currents are streams of water running through a larger body of water. Oceans, rivers, and streams have currents. The ocean's salinity and temperature and the coast's geographic features determine an ocean current's behavior. Earth's rotation and wind also influence ocean currents. Currents flowing near the surface transport heat from the tropics to the poles and move cooler water back toward the Equator. This keeps the ocean from becoming extremely hot or cold.

Deep, cold currents transport oxygen to organisms throughout the ocean. They also carry rich supplies of nutrients that all living things need. The nutrients come from plankton and the remains of other organisms that drift down and decay on the ocean floor.

Along some coasts, winds and currents produce a phenomenon called upwelling. As winds push surface water away from shore, deep currents of cold water rise to take its place. This upwelling of deep water brings up nutrients that nourish new growth of plankton, providing food for fish. Ocean food chains constantly recycle food and energy this way.

Some ocean currents are enormous and extremely powerful. One of the most powerful is the Gulf Stream, a warm surface current that originates in the tropical Caribbean Sea and flows northeast along the eastern coast of the United States. The Gulf Stream measures up to 80 kilometers (50 miles) wide and is more than a kilometer (3,281 feet) deep.

Like other ocean currents, the Gulf Stream plays a major role in climate. As the current travels north, it transfers moisture from its warm tropical waters to the air above. Westerly, or prevailing, winds carry the warm, moist air to the British Isles and to Scandinavia, causing them to have milder winters than they otherwise would experience at their northern latitudes. Northern parts of Norway are near the Arctic Circle but remain ice-free for most of the year because of the Gulf Stream.

The weather pattern known as El Niño includes a change to the Humboldt Current (also called the Peru Current) off the western coast of South America. In El Niño conditions, a current of warm surface water travels east along the Equator and prevents the normal upwelling of the cold, nutrient-rich Humboldt Current. El Niño, which can devastate the fisheries of Peru and Ecuador, occurs every two to seven years, usually in December.

The paths of ocean currents are partially determined by Earth's rotation. This is known as the Coriolis effect. It causes large systems, such as winds and ocean currents that would normally move in a straight line, to veer to the right in the northern hemisphere and to the left in the southern hemisphere.

People and the Ocean
For thousands of years, people have depended on the ocean as a source of food and as a route for trade and exploration. Today, people continue to travel on the ocean and rely on the resources it contains.

Nations continue to negotiate how to determine the extent of their territory beyond the coast. The United Nations' Law of the Sea treaty established exclusive economic zones (EEZs), extending 200 nautical miles (230 miles) beyond a nation's coastline. Even though some countries have not signed or ratified the treaty (including the U.S.), it is regarded as standard.

Russia has proposed extending its EEZ beyond 200 nautical miles because two mid-ocean ridges, the Lomonosov and Medeleev Ridges, are extensions of the continental shelf belonging to Russia. This territory includes the North Pole. Russian explorers in a submersible vehicle planted a metal Russian flag on the disputed territory in 2007.

Through the centuries, people have sailed the ocean on trade routes. Today, ships still carry most of the world's freight, particularly bulky goods such as machinery, grain, and oil.

Ocean ports are areas of commerce and culture. Water and land transportation meet there, and so do people of different professions: businesspeople who import and export goods and services; dockworkers who load and unload cargo; and ships' crews. Ports also have a high concentration of migrants and immigrants with a wide variety of ethnicities, nationalities, languages, and religions.

Important ports in the U.S. are New York/ New Jersey and New Orleans. The busiest ports around the world include the Port of Shanghai in China and the Port of Rotterdam in the Netherlands. Ocean ports are also important for a nation's armed forces. Some ports are used exclusively for military purposes, although most share space with commercial businesses. "The sun never sets on the British Empire" is a phrase used to explain the scope of the empire of Great Britain, mostly in the 19th century. Although based on the small European island nation of Great Britain, British military sea power extended its empire from Africa to the Americas, Asia, and Australia.

Scientists and other experts hope the ocean will be used more widely as a source of renewable energy. Some countries have already harnessed the energy of ocean waves, temperature, currents, or tides to power turbines and generate electricity.

One source of renewable energy are generators that are powered by tidal streams or ocean currents. They convert the movement of currents into energy. Ocean current generators have not been developed on a large scale, but are working in some places in Ireland and Norway. Some conservationists criticize the impact the large constructions have on the marine environment.

Another source of renewable energy is ocean thermal energy conversion (OTEC). It uses the difference in temperature between the warm, surface water and cold, deep water to run an engine. OTEC facilities exist in places with significant differences in ocean depth: Japan, India and the U.S. state of Hawai'i, for instance.

An emerging source of renewable energy is salinity gradient power, also known as osmotic power. It is an energy source that uses the power of freshwater entering into saltwater. This technology is still being developed, but it has potential in delta areas where fresh river water is constantly interacting with the ocean.

Fishing
Fishers catch more than 90 million tons of seafood each year, including more than 100 species of fish and shellfish. Millions of people, from professional fishers to business owners like restaurant owners and boat builders, depend on fisheries for their livelihood. Fishing can be classified in two ways. In subsistence fishing, fishers use their catch to help meet the nutritional needs of their families or communities. In commercial fishing, fishers sell their catch for money, goods or services. Popular subsistence and commercial fish are tuna, cod, and shrimp.

Ocean fishing is also a popular recreational sport. Sport fishing can be competitive or noncompetitive. In sport fishing tournaments, individuals or teams compete for prizes based on the size of a particular species caught in a specific time period. Both competitive and noncompetitive sport fishers need licenses to fish, and may or may not keep the caught fish. Increasingly, sport fishers practice catch-and-release fishing, where a fish is caught, measured, weighed, and often recorded on film before being released back to the ocean. Popular game fish (fish caught for sport) are tuna and marlin.

Whaling is a type of fishing that involves the harvesting of whales and dolphins. It has declined in popularity since the 19th century but is still a way of life for many cultures, such as those in Scandinavia, Japan, Canada, and the Caribbean.

The ocean offers a wealth of fishing and whaling resources, but these resources are threatened. People have harvested so much fish and marine life for food and other products that some species have disappeared.

During the 1800s and early 1900s, whalers killed thousands of whales for whale oil (wax made from boiled blubber) and ivory (whales' teeth). Some species, including the blue whale ( Balaenoptera musculus) and the right whale, were hunted nearly to extinction. Many species are still endangered today.

In the 1960s and 1970s, catches of important food fish, such as herring in the North Sea and anchovies in the Pacific, began to drop off dramatically. Governments took notice of overfishing-harvesting more fish than the ecosystem can replenish. Fishers were forced to go farther out to sea to find fish, putting them at risk. (Deep-sea fishing is one of the most dangerous jobs in the world.) Now, they use advanced equipment, such as electronic fish finders and large gill nets or trawling nets, to catch more fish. This means there are far fewer fish to reproduce and replenish the supply.

In 1992, the collapse, or disappearance, of cod in Canada's Newfoundland Grand Banks put 40,000 fishers out of work. A ban was placed on cod fishing, and to this day, neither the cod nor the fisheries have recovered.

To catch the dwindling numbers of fish, most fishers use trawl nets. They drag the nets along the seabed and across acres of ocean. These nets accidentally catch many small, young fish and mammals. Animals caught in fishing nets meant for other species are called bycatch. The fishing industry and fisheries management agencies argue about how to address the problem of bycatch and overfishing. Those involved in the fishing industry do not want to lose their jobs, while conservationists want to maintain healthy levels of fish in the ocean.

A number of consumers are choosing to purchase sustainable seafood. Sustainable seafood is harvested from sources (either wild or farmed) that do not deplete the natural ecosystem.

Mining and Drilling
Many minerals come from the ocean. Sea salt is a mineral that has been used as a flavoring and preservative since ancient times. Sea salt has many additional minerals, such as calcium, that ordinary table salt lacks.

Hydrothermal vents often form seafloor massive sulfide (SMS) deposits, which contain precious metals. These SMS deposits sit on the ocean floor, sometimes in the deep ocean and sometimes closer to the surface. New techniques are being developed to mine the seafloor for valuable minerals such as copper, lead, nickel, gold, and silver. Mining companies employ thousands of people and provide goods and services for millions more.

Critics of undersea mining maintain that it disrupts the local ecology. Organisms-corals, shrimp, mussels-that live on the seabed have their habitat disturbed, upsetting the food chain. In addition, destruction of habitat threatens the viability of species that have a narrow niche. Maui's dolphin ( Cephalorhynchus hectori maui), for instance, is a critically endangered species native to the waters of New Zealand's North Island. The numbers of Maui's dolphin are already reduced because of bycatch. Seabed mining threatens its habitat, putting it at further risk of extinction.

Oil is one of the most valuable resources taken from the ocean today. Offshore oil rigs pump petroleum from wells drilled into the continental shelf. About one-quarter of all oil and natural gas supplies now comes from offshore oil deposits around the world.

Offshore drilling requires complex engineering. An oil platform can be constructed directly onto the ocean floor, or it can "float" above an anchor. Depending on how far out on the continental shelf an oil platform is located, workers may have to be flown in. Underwater, or subsea, facilities are complicated groups of drilling equipment connected to each other and a single oil rig. Subsea production often requires remotely operated underwater vehicles (ROVs).

Some countries invest in offshore drilling for profit and to prevent reliance on oil from other regions. The Gulf of Mexico near the U.S. states of Texas and Louisiana is heavily drilled. Several European countries, including the United Kingdom, Denmark, and the Netherlands, drill in the North Sea. Offshore drilling is a complicated and expensive program, however. There are a limited number of companies that have the knowledge and resources to work with local governments to set up offshore oil rigs. Most of these companies are based in Europe and North America, although they do business all over the world.

Some governments have banned offshore oil drilling. They cite safety and environmental concerns. There have been several accidents where the platform itself has exploded, at the cost of many lives. Offshore drilling also poses threats to the ocean ecosystem. Spills and leaks from oil rigs and oil tankers that transport the material seriously harm marine mammals and birds. Oil coats feathers, impairing birds' ability to maintain their body temperature and remain buoyant in the water. The fur of otters and seals are also coated, and oil entering the digestive tract of animals may damage their organs.

Offshore oil rigs also release metal cuttings, minute amounts of oil, and drilling fluid into the ocean every day. Drilling fluid is the liquid used with machinery to drill holes deep in the planet. This liquid can contain pollutants such as toxic chemicals and heavy metals.

Most oil pollution does not come from oil spills, however. It comes from the runoff of pollutants into streams and rivers that flow into the ocean. Most runoff comes from individual consumers. Cars, buses, motorcycles, and even lawn mowers spill oil and grease on roads, streets, and highways. (Runoff is what makes busy roads shiny and sometimes slippery.) Storm drains or creeks wash the runoff into local waterways, which eventually flow into the ocean.

The largest U.S. oil spill in the ocean took place in Alaska in 1989, by the tanker Exxon Valdez spilled at least 10 million gallons of oil into Prince William Sound. In comparison, American and Canadian consumers spill about 16 million gallons of oil runoff into the Atlantic and Pacific Oceans every year.

For centuries, people have used the ocean as a dumping ground for sewage and other wastes.

In the 21st century, the wastes include not only oil, but also chemical runoff from factories and agriculture. These chemicals include nitrates and phosphates, which are often used as fertilizers. These chemicals encourage algae blooms. An algae bloom is an increase in algae and bacteria that threatens plants and other marine life. Algae blooms limit the amount of oxygen in a marine environment, leading to what are known as dead zones, where little life exists beneath the ocean's surface. Algae blooms can spread across hundreds or even thousands of miles.

Another source of pollution is plastics. Most ocean debris, or garbage, is plastic thrown out by consumers. Plastics such as water bottles, bags, six-pack rings, and packing material put marine life at risk. Sea animals are harmed by the plastic either by getting tangled in it or by eating it.

An example of marine pollution consisting mainly of plastics is the Great Pacific Garbage Patch. The Great Pacific Garbage Patch is a floating dump in the North Pacific. It's about twice the size of Texas and probably contains about 100 million tons of debris. Most of this debris comes from the western coast of North America (the U.S. and Canada) and the eastern coast of Asia (Japan, China, Russia, North Korea, and South Korea). Because of ocean currents and weather patterns, the patch is a relatively stable formation and contains new and disintegrating debris. The smaller pieces of plastic debris are eaten by jellyfish or other organisms, and are then consumed by larger predators in the food web. These plastic chemicals may then enter a human's diet through fish or shellfish.

Another source of pollution is carbon dioxide. The ocean absorbs most carbon dioxide from the atmosphere. Carbon dioxide, which is necessary for life, is known as a greenhouse gas and traps radiation in Earth's atmosphere. Carbon dioxide forms many acids, called carbonic acids, in the ocean. Ocean ecosystems have adapted to the presence of certain levels of carbonic acids, but the increase in carbon dioxide has led to an increase in ocean acids. This ocean acidification erodes the shells of animals such as clams, crabs, and corals.

Global warming contributes to rising ocean temperatures and sea levels.

Warmer oceans radically alter the ecosystem. Global warming causes cold-water habitats to shrink, meaning there is less room for animals such as penguins, seals, or whales. Plankton, the base of the ocean food chain, thrives in cold water. Warming water means there will be less plankton available for marine life to eat.

Melting glaciers and ice sheets contribute to sea level rise. Rising sea levels threaten coastal ecosystems and property. River deltas and estuaries are put at risk for flooding. Coasts are more likely to suffer erosion. Seawater more often contaminates sources of fresh water. All these consequences-flooding, erosion, water contamination-put low-lying island nations, such as the Maldives in the Indian Ocean, at high risk for disaster.

To find ways to protect the ocean from pollution and the effects of climate change, scientists from all over the world are cooperating in studies of ocean waters and marine life. They are also working together to control pollution and limit global warming. Many countries are working to reach agreements on how to manage and harvest ocean resources.

Although the ocean is vast, it is more easily polluted and damaged than people once thought. It requires care and protection as well as expert management. Only then can it continue to provide the many resources that living things-including people-need. Pollution Exxon Valdez. The Global Warming

Fast Fact

The Most Coast
. . . Canada has 202,080 kilometers (125,567 miles) of coastline.

Short But Sweet
. . . Monaco has four kilometers (2.5 miles) of coastline.

Fast Fact

No, the Toilet Doesn't Flush Backward in Australia
The Coriolis effect, which can be seen in large-scale phenomena like trade winds and ocean currents, cannot be duplicated in small basins like sinks.

Fast Fact

Extraterrestrial Oceans
Mars probably had oceans billions of years ago, but ice and dry seabeds are all that remain today.

Europa, one of Jupiter's moons, is probably covered by an ocean of water more than 96 kilometers (60 miles) deep, but it is trapped beneath a layer of ice, which the warmer water below frequently cracks.

One of Saturn's moons, Enceladus, has cryovolcanism, or ice volcanoes. Instead of erupting with lava, ice volcanoes erupt with water, ammonia, or methane. Ice volcanoes may indicate oceanic activity.

Fast Fact

International Oil Spill
The largest oil spill in history, the Gulf War oil spill, released at least 40 million gallons of oil into the Persian Gulf. Valves at the Sea Island oil terminal in Kuwait were opened on purpose after Iraq invaded Kuwait in 1991. The oil was intended to stop a landing by U.S. Marines, but the oil drifted south to the shores of Saudi Arabia.

A study of the Gulf War oil spill (conducted by the United Nations, several countries in the Middle East and the United States) found that most of the spilled oil evaporated and caused little damage to the environment.

Fast Fact

Ocean Seas
The floors of the Caspian Sea and the Black Sea are more like the ocean than other seas they do not rest on a continent, but directly on the ocean's basalt crust.

Fast Fact

Early Ocean Explorers
Polynesian people navigated a region of the Pacific Ocean now known as the Polynesian Triangle by 700 C.E. The corners of the Polynesian Triangle are islands: the American state of Hawai'i, the country of New Zealand, and the Chilean territory of Easter Island (also known as Rapa Nui). The distance between Easter Island and New Zealand, the longest length of the Polynesian Triangle, is one-quarter of Earth's circumference, more than 10,000 kilometers (6,200 miles). Polynesians successfully traveled these distances in canoes.

It would be hundreds of years before another culture explored the ocean to this extent.

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Mary Crooks, National Geographic Society

Editors

Jeannie Evers, Emdash Editing, Emdash Editing

Expert Reviewer

Sarah Wilson, National Geographic Society

Producer

National Geographic Society

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The ocean covers 70 percent of Earth's surface.

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Also known as thermohaline circulation. Thermo means heat. Haline means salt.

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Friday, January 21, 2011

The ocean is in constant motion. You can see this for yourself when you watch waves crash onto shore. If you go swimming, you may even feel an ocean current pulling you along. Surface currents, such as the Gulf Stream, move water across the globe like mighty rivers. Surface currents are powered by Earth's various wind patterns.

The ocean also has deep underwater currents. These are more massive but move more slowly than surface currents. Underwater currents mix the ocean's waters on a global scale. A process known as thermohaline circulation, or the ocean conveyor belt, drives these deep, underwater currents.

Thermohaline Circulation

Thermohaline circulation moves a massive current of water around the globe, from northern oceans to southern oceans, and back again. Currents slowly turn over water in the entire ocean, from top to bottom. It is somewhat like a giant conveyor belt, moving warm surface waters downward and forcing cold, nutrient-rich waters upward.

The term thermohaline combines the words thermo (heat) and haline (salt), both factors that influence the density of seawater. The ocean is constantly shifting and moving in reaction to changes in water density. To best understand ocean-water dynamics, or how water moves, there are a few simple principles to keep in mind:

Water always flows down toward the lowest point.

Water's density is determined by the water's temperature and salinity (amount of salt).

Cold water is denser than warm water.

Water with high salinity is denser than water with low salinity.

Ocean water always moves toward an equilibrium, or balance. For example, if surface water cools and becomes denser, it will sink. The warmer water below will rise to balance out the missing surface water.

Ocean Layers

The ocean can be divided into several layers. The top layer of the ocean collects the warmth and energy of sunlight, while the bottom layers collect the rich, nutrient-filled sediment of decayed plant and animal matter.

The top ocean layer is about 100 meters (330 feet) deep. Enough sunlight reaches that depth for organisms, such as phytoplankton, to carry out photosynthesis. Phytoplankton makes up the first part of the marine food chain and is essential to all ocean life.

The middle, or barrier, layer is called the thermocline. The ocean's temperature and density change very quickly at this layer. The barrier layer is about 200 to 1,000 meters (656 to 3,300 feet) deep.

Below the barrier layer is the bottom layer, referred to as the deep ocean. It averages about three kilometers (two miles) in depth.

The Conveyor Belt

Scientists have long understood how nutrients move from the ocean's surface to its depths. As phytoplankton die, they sink and collect on the ocean floor. But if nutrients are continually sinking to the depths of the ocean, how are surface waters replenished with nutrients? Scientists discovered that in certain regions of the ocean, the nutrient-rich deep water was upwelling, or rising to the surface.

Scientists realized that the ocean was slowly turning over from top to bottom in a continuous global loop. Like a conveyor belt, thermohaline circulation moves nutrients from one part of the ocean to another.

Let's start in the northern Atlantic Ocean and follow the conveyor belt as it moves water around the planet.

In the seas near Greenland and Norway, the water is cold. Some of it freezes, leaving salt behind. The cold, salty water becomes dense and sinks to the ocean floor. This water is known as the North Atlantic Deep Water, and it is one of the primary driving forces of the conveyor belt.

The force of the sinking, cold water pushes the existing North Atlantic Deep Water south, toward Antarctica, in a slow-moving underwater current. When it reaches Antarctica, the water flows east with the Antarctic Circumpolar Current, a massive and powerful current that circles the continent.

Parts of the Antarctic Circumpolar Current flow northward and move into the Indian and Pacific Oceans. As the deep, cold water travels through the oceans, it mixes with warmer water. The water eventually becomes warm enough to rise, creating a slow upwelling that brings nutrients to the surface.

In the Pacific, the surface water flows through the Indonesian islands into the Indian Ocean, around southern Africa, and back into the Atlantic. The warm waters eventually travel back to the North Atlantic Deep Water, completing the global loop.

It takes about 500 years for the conveyor belt to turn over the ocean's waters and make one complete trip around Earth.

The North Atlantic Deep Water

The deep water in the Greenland Sea flows along toward the lowest point on the floor of the North Atlantic. The water collects in a basin, the same way river water flows into a lake or pond. The basin is the North Atlantic Deep Water.

Other seas feed their cool ocean waters into the North Atlantic Deep Water. In the Labrador Sea, off the coast of northeastern Canada, the cold water sinks to depths of 3,000 meters (9,900 feet) at a rate of 10 centimeters (about four inches) per second.

Another source of the North Atlantic Deep Water is the Mediterranean Sea. As the warm surface water of the Mediterranean evaporates, the water grows saltier and denser. This water exits the Mediterranean through the Strait of Gibraltar, the narrow channel between Spain and Morocco that connects the sea to the Atlantic Ocean. The Mediterranean's deep water pours into the Atlantic at a rate of two meters (about 6.5 feet) per second and helps raise the overall salinity of the Atlantic Ocean.

The Antarctic Circumpolar Current

When the conveyor belt reaches the southern part of the globe, it is driven back to the northern oceans by the Antarctic Circumpolar Current.

Western winds are very strong in the Antarctic. They help create the intensely powerful Antarctic Circumpolar Current. The current moves a lot of water very quickly around the continent of Antarctica-about 140 million cubic meters (4.9 billion cubic feet) of water per second.

Overturning occurs in the waters around Antarctica. Overturning happens when the extremely frigid Antarctic surface water sinks. This forces the nutrient-rich deep water to rise. Overturning moves massive amounts of water. An estimated 35 million to 45 million cubic meters (between 1.2 billion and 1.6 billion cubic feet) of water per second are continually moved from the ocean bottom to the surface.

The Antarctic Circumpolar Current and overturning make the waters around Antarctica an ideal habitat for many marine mammals. Many types of whales, for instance, migrate to the waters around Antarctica every year to feed on phytoplankton and other tiny sea creatures churned up by overturning waters.

Climate Change

Ocean temperature plays a key role in the conveyor belt, so a change in Earth's climate might have drastic effects on the system. If one part of the conveyor belt were to break down-if cold water is not lifted to the surface in upwelling, for instance-nutrients will not be distributed to start the food chain. Organisms, such as phytoplankton, need those nutrients to thrive. Severe climate change slows phytoplankton from forming the first link in the marine food chain. If the first link is threatened, all life in the oceans is threatened.

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Friday, January 21, 2011 The ocean is in constant motion. You can see this for yourself when you watch waves crash onto shore. If you go swimming, you may even feel an ocean current pulling you along. Surface currents, such as the Gulf Stream, move water across the globe like mighty rivers.

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Image

Photograph by Georg Gerster

Plate tectonics is a scientific theory that explains how major landforms are created as a result of Earth's subterranean movements. The theory, which solidified in the 1960s, transformed the earth sciences by explaining many phenomena, including mountain building events, volcanoes, and earthquakes.

In plate tectonics, Earth's outermost layer, or lithosphere-made up of the crust and upper mantle-is broken into large rocky plates. These plates lie on top of a partially molten layer of rock called the asthenosphere. Due to the convection of the asthenosphere and lithosphere, the plates move relative to each other at different rates, from two to 15 centimeters (one to six inches) per year. This interaction of tectonic plates is responsible for many different geological formations such as the Himalaya mountain range in Asia, the East African Rift, and the San Andreas Fault in California, United States.

The idea that continents moved over time had been proposed before the 20th century. However, a German scientist named Alfred Wegener changed the scientific debate. Wegener published two articles about a concept called continental drift in 1912. He suggested that 200 million years ago, a supercontinent he called Pangaea began to break into pieces, its parts moving away from one another. The continents we see today are fragments of that supercontinent. To support his theory, Wegener pointed to matching rock formations and similar fossils in Brazil and West Africa. In addition, South America and Africa looked like they could fit together like puzzle pieces.

Despite being dismissed at first, the theory gained steam in the 1950s and 1960s as new data began to support the idea of continental drift. Maps of the ocean floor showed a massive undersea mountain range that almost circled the entire Earth. An American geologist named Harry Hess proposed that these ridges were the result of molten rock rising from the asthenosphere. As it came to the surface, the rock cooled, making new crust and spreading the seafloor away from the ridge in a conveyer-belt motion. Millions of years later, the crust would disappear into ocean trenches at places called subduction zones and cycle back into Earth. Magnetic data from the ocean floor and the relatively young age of oceanic crust supported Hess's hypothesis of seafloor spreading.

There was one nagging question with the plate tectonics theory: Most volcanoes are found above subduction zones, but some form far away from these plate boundaries. How could this be explained? This question was finally answered in 1963 by a Canadian geologist, John Tuzo Wilson. He proposed that volcanic island chains, like the Hawaiian Islands, are created by fixed "hot spots" in the mantle. At those places, magma forces its way upward through the moving plate of the sea floor. As the plate moves over the hot spot, one volcanic island after another is formed. Wilson's explanation gave further support to plate tectonics. Today, the theory is almost universally accepted.

Director

Tyson Brown, National Geographic Society

Author

National Geographic Society

Production Managers

Gina Borgia, National Geographic Society

Jeanna Sullivan, National Geographic Society

Program Specialists

Sarah Appleton, National Geographic Society, National Geographic Society

Margot Willis, National Geographic Society

Last Updated

August 17, 2022

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The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, volcanoes, and earthquakes.

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¿Cómo se forman las corrientes oceánicas?

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¿Cómo se forman las corrientes oceánicas?

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Transcript of "How do ocean currents work?"

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TED Talk Subtitles and Transcript: In 1992, a cargo ship carrying bath toys got caught in a storm. Shipping containers washed overboard, and the waves swept 28,000 rubber ducks and other toys into the North Pacific. But they didn't stick together -- the ducks have since washed up all over the world.

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Global Conveyor belt-Ocean Currents caused by temperature and Salinity

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Global Conveyor belt-Ocean Currents caused by temperature and Salinity

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Global Conveyor belt-Ocean Currents caused by temperature and Salinity

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Have you wondered why we call our ocean project MARE? Here's the inspiration.

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DIVERSITY, EQUITY, INCLUSION & BELONGING AT MARE
The environmental movement is part of the social justice movement and is inextricably entwined with the values of diversity, equity, inclusion, and belonging. MARE is committed to fostering a culture, based on these values, which recognizes and appreciates differences in order to foster strength and resilience within and beyond the organization.

MARE is committed to integrating these principles into every aspect of our business and ensuring that all we do is accessible and inclusive. We believe practicing these values, and prioritizing them throughout the organization and our partnerships, is key to our shared efforts to explore, discover, and protect our oceans.

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DIVERSITY, EQUITY, INCLUSION & BELONGING AT MARE The environmental movement is part of the social justice movement and is inextricably entwined with the values of diversity, equity, inclusion, and belonging. MARE is committed to fostering a culture, based on these values, which recognizes and appreciates differences in order to foster strength and resilience within and beyond the organization.

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Utiliza este código: https://edpuzzle.com/join/bejladl

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Easily create beautiful interactive video lessons for your students you can integrate right into your LMS. Track students' progress with hassle-free analytics as you flip your classroom!

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Newsela is an Instructional Content Platform that supercharges reading engagement and learning in every subject.

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"To understand tides, we start with gravity".

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Tides | Crash Course Astronomy | PBS LearningMedia

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Explore the world of tides, and learn how they have shaped most objects in the universe. What is the relationship between tides and gravity? How do planets and their moons become tidally locked? What would happen if you were 300km tall? Find out in this episode.

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Are you curious to know how tides are measured in Chrissy Field? Watch this video.

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The rise and fall of ocean tides are influenced by the gravitational forces of the sun and moon. In this video from QUEST produced by KQED, explore how tides work and see the oldest continually operating tidal gauge in the Western Hemisphere.

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Spanish - Coral Reefs Cities in the Sea - Coral Reef Living - Annie Crawley

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Colección de libros sobre varias creaturas marinas.

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Families, start reading! Educators, get it free

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online access fun thousands children great kids ebooks books

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Instantly access over 40,000 of the best books & videos for kids on Epic

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Families, start reading! Educators, get it free MORE FEATURES AT YOUR FINGERTIPS Personalize their daily reading. Daily age- and level-appropriate recommendations customized to their interests. Track progress. See what books your kid likes, time spent reading and more. Get content that grows with them. Quality books they'll love at every step of their reading journey.

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Spanish - Sea Anemones and Clownfish - Annie Crawley

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Spanish - Cephalopods - Cuttlefish - Octopus - Squid - Nautilus - Annie Crawley

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Fireworks!

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Like fireworks exploding in water, rare jellyfish lit up in the darkest depths of the ocean, in a dazzling display, surprising a few lucky scientists who happened upon it.

The Halitrephes maasi jellyfish lives at a depth of 4,000 feet underwater within the Revillagigedo Archipelago off Baja California, Mexico. Check out the Halitrephes Jelly shooting its fireworks in this video!|

Few humans have ever traveled so deep beneath the ocean surface. But the Exploration Vehicle Nautilus, operated by Ocean Exploration Trust, has enabled researchers to reach this previously unexplored region.

The 211 foot-long E/V Nautilus is equipped with some of the latest technological systems, helping to advance the frontiers of ocean exploration. Primary capabilities include "science class" remotely operated vehicles (ROVs), high-resolution seafloor mapping, and real-time satellite transmission of data.

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Rare Jellyfish Makes Underwater Fireworks | E/V Nautilus | BeautifulNow

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Like fireworks exploding in water, rare jellyfish lit up in the darkest depths of the ocean, in a dazzling display, surprising a few lucky scientists who happened upon it. The Halitrephes maasi jellyfish lives at a depth of 4,000 feet underwater within the Revillagigedo Archipelago off Baja California, Mexico.

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Welcome to Britannica School, a safe, up-to-date, and age-appropriate information resource for Elementary, Middle, and High School.

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Dentro de el orden de los y concretamente del de lo s cetaceos misticetos se encuentran las ballenas, las cuales conforman la familia de los balaénidos o de las ballenas barbadas. Estas están clasificados en tan solo cuatro especies divididas en dos géneros, Balaena y Eubalaena. Estos animales pueden llegar a medir entre 25 y 32 metros y los ejemplares más grandes pueden llegar a pesar hasta 180 toneladas. De hecho, una de estas especies de balaenidos, la ballena azul, es el animal más grande del mundo en la actualidad.

Estos mamíferos, a diferencia de los peces, tienen la cola dispuesta en horizontal, lo que les facilita la ascensión a la superficie, donde deben subir para respirar. Pueden permanecer bajo el agua aproximadamente una hora. Con grandes requerimientos energéticos, las ballenas se alimentan generalmente de pequeños crustáceos y de krill, que obtienen por la filtración del agua del mar a través de sus barbas. Habitan en todos los océanos en los que se desplazan en largos viajes migraciones desde los mares fríos, donde se alimentan, a los más cálidos, donde se aparean y reproducen. Después de una gestación de casi doce meses, dan a luz a una sola cría, cuya esperanza de vida está en torno a los 30 años. Aquí tienes una galería fotográfica con decenas de imágenes de ballenas de distintas especies:

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Ballenas - Curiosidades de las ballenas y cuáles son las más grandes del mundo

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Las ballenas son los cetáceos que viven más tiempo. Algunas, como la ballena azul y la ballena jorobada, son los animales más grandes que existen. Descubre dónde y por cuánto tiempo viven, qué comen, cómo se comunican y otras curiosidades.

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Scientific Name:

Tetraodontidae

Size relative to a teacup:

Biologists think pufferfish, also known as blowfish, developed their famous "inflatability" because their slow, somewhat clumsy swimming style makes them vulnerable to predators. In lieu of escape, pufferfish use their highly elastic stomachs and the ability to quickly ingest huge amounts of water (and even air when necessary) to turn themselves into a virtually inedible ball several times their normal size. Some species also have spines on their skin to make them even less palatable.

Toxicity

A predator that manages to snag a puffer before it inflates won't feel lucky for long. Almost all pufferfish contain tetrodotoxin, a substance that makes them foul tasting and often lethal to fish. To humans, tetrodotoxin is deadly, up to 1,200 times more poisonous than cyanide. There is enough toxin in one pufferfish to kill 30 adult humans, and there is no known antidote.

As Food

Amazingly, the meat of some pufferfish is considered a delicacy. Called fugu in Japan, it is extremely expensive and only prepared by trained, licensed chefs who know that one bad cut means almost certain death for a customer. In fact, many such deaths occur annually.

Population

There are more than 120 species of pufferfish worldwide. Most are found in tropical and subtropical ocean waters, but some species live in brackish and even fresh water. They have long, tapered bodies with bulbous heads. Some wear wild markings and colors to advertise their toxicity, while others have more muted or cryptic coloring to blend in with their environment.

They range in size from the 1-inch-long dwarf or pygmy puffer to the freshwater giant puffer, which can grow to more than 2 feet in length. They are scaleless fish and usually have rough to spiky skin. All have four teeth that are fused together into a beak-like form.

Diet

The diet of the pufferfish includes mostly invertebrates and algae. Large specimens will even crack open and eat clams, mussels, and shellfish with their hard beaks. Poisonous puffers are believed to synthesize their deadly toxin from the bacteria in the animals they eat.

Theats to Survival

Some species of pufferfish are considered vulnerable due to pollution, habitat loss, and overfishing, but most populations are considered stable.

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Scientific Name: Tetraodontidae Size relative to a teacup: Biologists think pufferfish, also known as blowfish, developed their famous "inflatability" because their slow, somewhat clumsy swimming style makes them vulnerable to predators. In lieu of escape, pufferfish use their highly elastic stomachs and the ability to quickly ingest huge amounts of water (and even air when necessary) to turn themselves into a virtually inedible ball several times their normal size.

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Pufferfish can inflate into a ball shape to evade predators. Also known as blowfish, these clumsy swimmers fill their elastic stomachs with huge amounts of water (and sometimes air) and blow themselves up to several times their normal size.

Scientific Name:

Tetraodontidae

Some pufferfish species also have spines on their skin to ward off predators. Even if a predator gobbles up a puffer before it inflates, it won't enjoy the snack. Most pufferfish contain a toxic substance that makes them foul tasting and potentially deadly to other fish. The toxin is deadly to humans. There is enough poison in one pufferfish to kill 30 adult humans, and there is no known antidote.

In Japan, they are called fugu and are a very expensive, delicious treat. They are prepared only by trained, licensed fugu chefs. Most puffers are found in tropical and subtropical ocean waters, but some species live in brackish and even fresh water. Some species of pufferfish are considered vulnerable due to pollution, habitat loss, and overfishing, but most populations are considered stable.

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Pufferfish can inflate into a ball shape to evade predators. Also known as blowfish, these clumsy swimmers fill their elastic stomachs with huge amounts of water (and sometimes air) and blow themselves up to several times their normal size. Some species also have spines on their skin to ward off predators.

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Although electric eels have the power to be the bullies of the Amazon, they are actually not very aggressive animals. The eel uses its shock to stun prey and keep predators at bay.

Electric eels are nocturnal, live in muddy, dark waters, and have poor eyesight. So instead of using eyes, electric eels emit a weak electric signal, which they use like radar to navigate, to find a mate, and to find prey. Once prey is found, electric eels will use a much stronger shock to stun prey, usually smaller fish.

Electric eels can grow up to 8 feet (2.5 meters) in length. Despite their appearance, electric eels aren't actually eels at all! They are more closely related to carp and catfish.

The shock of an electric eel has been known to knock a horse off its feet. Now that's shocking!

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The electric eel gets its name from its shocking abilities! Special organs in the eel's body release powerful electric charges of up to 650 volts-that's more than five times the power of a standard United States wall socket! Although eels have the power to be the bullies of the Amazon, they are actually not very aggressive animals.