Marine Ecosystem : Pelagic Ecosystems by

References

ecrisalli24 — 2025-05-21 19:10:37 UTC

Ducklow, H., Cimino, M., Dunton, K. H., Fraser, W. R., Hopcroft, R. R., Ji, R., Miller, A. J., Ohman, M. D., & Sosik, H. M. (2022, August 16). Marine Pelagic Ecosystem Responses to Climate Variability and Change. Academic.oup.com. https://academic.oup.com/bioscience/article/72/9/827/6653562

Kaiser, M. J., Attrill, M. J., Simon, Thomas, D. N., Barnes, D. K. A., Brierly, A. S., Graham, N. A. J., Hiddink, J. G., Howell, K., & Kaartokallio, H. (2020). Marine Ecology: Processes, Systems, and Impacts (3rd ed., pp. 208-235). Oxford University.

Sciencedirect (n.d.). Pelagic Zone - an overview. sciencedirect.com. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/pelagic-zone

The Ecosystem

ecrisalli24 — 2025-05-21 21:40:26 UTC

The Pelagic ecosystem extends across the whole of the water column and ends just before the benthic (seafloor) zone. It can be subdivided into two zones as a result of depth, that being the Neritic and Oceanic zones. The Oceanic zone can be further divided depending on depth.

In the photic zone is the Epipelagic zone, which is the upper 200m of the water column. Following the photic zone is the aphotic zone, which is comprised of the Mesopelagic (200m-1000m), the Bathypelagic (1000m-4000m), and the Abyssopelagic (4000m-6000m) zones (Kaiser et al., 2020).

The pelagic ecosystem has functions like nutrient cycling, primary production, and habitat provision within the vertically layered zones (Sciencedirect, n.d.)

A key primary producer in the pelagic zone is phytoplankton. They reside within the epipelagic zone, which has the highest photic availability. These phytoplankton use sunlight to photosynthesize, producing oxygen and forming the base of the food web within the pelagic ecosystem. Phytoplankton also support higher trophic levels, like zooplankton and nekton (fish and marine mammals) and play a vital role in carbon fixation within the ecosystem (Kaiser et al., 2020).

The Ecological Relationship

ecrisalli24 — 2025-05-21 21:55:40 UTC

The most prominent ecological relationship within the Pelagic ecosystem is predation.

The smallest planktic organisms, viruses, bacteria, and protozoa, are consumed by zooplankton of increasing size and those zooplankton are in turn consumed by chains of predators including fish, birds, and mammals (Kaiser et al., 2020).

Disruption in this energy transfer relationship--such as changes in the abundance of planktic organisms as a result of climate change or pollution--can affect all organisms higher in the trophic levels, thus affecting biodiversity, carbon cycling, and oxygen production (Sciencedirect, n.d.).

An Influencing Factor

ecrisalli24 — 2025-05-21 22:47:39 UTC

A major influencing factor on the pelagic ecosystem is climate change, which is widely human-induced. The warming of the ocean causes the layers of the pelagic zones to stratify, highly stratified layers cause a decrease in vertical mixing--leading to less nutrients being brought up to the upper layers from the deeper pelagic zones (Ducklow et al., 2022). As a result, phytoplankton in the epipelagic zones don't receive adequate nutrients, thus leading to a decline in population growth.

Climate change affects the overall stability of the ecosystem as it lowers the productivity of phytoplankton, which affects the entirety of primary production and additionally the food web within the pelagic ecosystem (Kaiser et al, 2020; Sciencedirect, n.d.; Ducklow et al., 2022). The decline in primary production can additionally weaken the ocean's ability to absorb atmospheric CO₂ (Ducklow et al., 2022).