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Some parts of the ocean hold far more life than others

The oceans are far from homogenous; concentrations of life vary greatly from place to place due to differences in physical, chemical, and biological factors 1. Some parts of the ocean are the equivalent of deserts in that they contain almost no life 2, while other regions are densely packed with huge populations of countless species of animals and plants 3. Here's a breakdown of some of the key factors that create these variations:

Nutrient availability​

  1. Upwelling zones: Areas where deep, nutrient-rich waters rise to the surface, such as the coasts of Peru and California, have high concentrations of life. The influx of nutrients supports large populations of phytoplankton, which in turn support abundant marine life 4 5 6.

  2. Oligotrophic regions: Open ocean areas, such as the central gyres, are nutrient-poor and support much less life. These regions are characterized by low productivity and clear, blue waters 7 8.

Light penetration​

  1. Photic zone: The upper layer of the ocean where sunlight penetrates, allowing photosynthesis to occur. Most marine life is concentrated here because phytoplankton, the base of the food web, can only thrive where there is light 9 10.

  2. Aphotic zone: Below the photic zone, light does not penetrate, and life is sparse. Organisms in this zone rely on the organic matter falling from above or on chemosynthesis near hydrothermal vents 11 12.

Temperature​

  1. Polar regions: These areas have cold waters that can hold more dissolved oxygen, supporting rich marine ecosystems, including large populations of krill and other zooplankton 13 14 15.

  2. Tropical regions: Warm waters near the equator have higher biodiversity but often lower productivity compared to temperate regions, due to less mixing and nutrient availability 16 17.

Ocean currents​

  1. Currents and gyres: Ocean currents distribute nutrients and heat around the globe, creating regions of high productivity. For example, the Gulf Stream transports warm water from the Gulf of Mexico to the North Atlantic, affecting marine life along its path 18 19 20.

Coastal vs. open ocean​

  1. Coastal waters: Generally more productive than the open ocean due to nutrient runoff from land and shallower depths allowing for more light penetration 21 22 23 24 25.

  2. Deep ocean: Much less productive due to the lack of light and nutrients. Life here is often sparse and adapted to extreme conditions 2 11 12 26 27.

Sources​

Footnotes​

  1. Larsen, D. (2023, February). Distribution of life in the ocean. LibreTexts. https://geo.libretexts.org/Bookshelves/Oceanography/Book%3A_Oceanography_(Hill)/10%3A_An_Ocean_Full_of_Life/Distribution_of_Life_in_the_Ocean ↩

  2. Ramirez-Llodra, E., Brandt, A., Danovaro, R., De Mol, B., Escobar-Briones, E., German, C. R., Levin, L. A., Martínez Arbizu, P., Menot, L., Buhl-Mortensen, P., Narayanaswamy, B. E., Smith, C. R., Tittensor, D. P., Tyler, P. A., Vanreusel, A., & Vecchione, M. (2010). Deep, diverse and definitely different: Unique attributes of the world's largest ecosystem. Biogeosciences, 7(9), 2851-2899. https://doi.org/10.5194/bg-7-2851-2010 ↩ ↩2

  3. Glass, J., Dierssen, H. M., Glein, C. R., Schmidt, B. E., & Winebrenner, D. P. (2022). Defining and characterizing habitable environments in ocean world systems. Oceanography, 35(1), 27-39. https://doi.org/10.5670/oceanog.2021.414 ↩

  4. Álvarez-Borrego, S. (2012). Phytoplankton biomass and production in the Gulf of California: A review. Botanica Marina, 55(2), 117-134. https://doi.org/10.1515/bot.2011.105 ↩

  5. Chávez, F. P., & Messié, M. (2009). A comparison of Eastern Boundary Upwelling Ecosystems. Progress in Oceanography, 83(1-4), 80-96. https://doi.org/10.1016/j.pocean.2009.07.032 ↩

  6. Umasangaji, H., & Ramili, Y. (2021). Mini review: Characteristics of upwelling in several coastal areas in the world. IOP Conference Series: Earth and Environmental Science, 890(1), 012004. https://doi.org/10.1088/1755-1315/890/1/012004 ↩

  7. Duarte, C. M., Regaudie-de-Gioux, A., Arrieta, J. M., Delgado-Huertas, A., & Agustí, S. (2013). The oligotrophic ocean is heterotrophic. Annual Review of Marine Science, 5(1), 551-569. https://doi.org/10.1146/annurev-marine-121211-172337 ↩

  8. Karl, D. M. (2002). Nutrient dynamics in the deep blue sea. Trends in Microbiology, 10(9), 410-418. https://doi.org/10.1016/s0966-842x(02)02430-7 ↩

  9. NOAA Ocean Explorer. (2023, February). How far does light travel in the ocean? NOAA. https://oceanexplorer.noaa.gov/facts/light-distributed.html ↩

  10. New Hampshire Public Television. (2023, February). Ocean zones. NHPTV. http://www.nhptv.org/natureworks/nwep6c.htm ↩

  11. Orcutt, B. N., Sylvan, J. B., Knab, N. J., & Edwards, K. J. (2023, February). Microbial ecology of the dark ocean above, at, and below the seafloor. Microbiology and Molecular Biology Reviews. https://journals.asm.org/doi/10.1128/mmbr.00039-10 ↩ ↩2

  12. Guidi, L., Chaffron, S., Bittner, L., Eveillard, D., Larhlimi, A., Roux, S., Darzi, Y., Audic, S., Berline, L., Brum, J. R., Ignacio-Espinoza, J. C., Malviya, S., Sunagawa, S., Dimier, C., Kandels-Lewis, S., Picheral, M., Poulain, J., Searson, S., Stemmann, L., … Bowler, C. (2016). Plankton networks driving carbon export in the oligotrophic ocean. Nature, 532(7600), 465-470. https://doi.org/10.1038/nature16942 ↩ ↩2

  13. Chown, S. L. (2012). Antarctic marine biodiversity and deep-sea hydrothermal vents. PLoS Biology, 10(1), e1001232. https://doi.org/10.1371/journal.pbio.1001232 ↩

  14. Day, J. C., Mordida, B. J., & Bacon, F. (1994). Polar marine communities. Integrative and Comparative Biology, 34(1), 90-99. https://doi.org/10.1093/icb/34.1.90 ↩

  15. Kędra, M., & Grebmeier, J. M. (2023, November). Ecology of Arctic shelf and deep ocean benthos. Wiley Online Library. https://onlinelibrary.wiley.com/doi/10.1002/9781118846582.ch12 ↩

  16. Richardson, K., & Bendtsen, J. (2017). Photosynthetic oxygen production in a warmer ocean: The Sargasso Sea as a case study. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 375(2102), 20160329. https://doi.org/10.1098/rsta.2016.0329 ↩

  17. Schott, F., Xie, S.-P., & McCreary, J. P. (2009). Indian Ocean circulation and climate variability. Reviews of Geophysics, 47(1). https://doi.org/10.1029/2007rg000245 ↩

  18. Pelegrí, J. L., Marrero-Díaz, Á., & Ratsimandresy, A. W. (2006). Nutrient irrigation of the North Atlantic. Progress in Oceanography, 70(2-4), 366-406. https://doi.org/10.1016/j.pocean.2006.03.018 ↩

  19. Schmitz, W. J., & McCartney, M. S. (1993). On the North Atlantic circulation. Reviews of Geophysics, 31(1), 29-49. https://doi.org/10.1029/92rg02583 ↩

  20. NOAA. (2023, February). Ocean currents. NOAA. https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-currents ↩

  21. EPA. (2023, February). Coastal waters. EPA. https://www.epa.gov/report-environment/coastal-waters ↩

  22. USGS. (2023, April). Coastal ecosystems. USGS. https://www.usgs.gov/science/science-explorer/coasts/coastal-ecosystems ↩

  23. Suchanek, T. H. (1994). Temperate coastal marine communities: Biodiversity and threats. American Zoologist, 34(1), 100-114. https://doi.org/10.1093/icb/34.1.100 ↩

  24. Carr, M. H., Neigel, J. E., Estes, J. A., Andelman, S. J., Warner, R. R., & Largier, J. L. (2003). Comparing marine and terrestrial ecosystems: Implications for the design of coastal marine reserves. Ecological Applications, 13(sp1), 90-107. https://doi.org/10.1890/1051-0761(2003)013[0090:cmatei]2.0.co;2 ↩

  25. Snelgrove, P. V. R., & Grassle, J. F. (2023, November). Deep-sea fauna. ScienceDirect. https://www.sciencedirect.com/science/article/pii/B012227430X002142 ↩

  26. Thurber, A. R., Sweetman, A. K., Narayanaswamy, B. E., Jones, D. O. B., Ingels, J., & Hansman, R. L. (2014). Ecosystem function and services provided by the deep sea. Biogeosciences, 11(14), 3941-3963. https://doi.org/10.5194/bg-11-3941-2014 ↩

  27. National Park Service. (2023, February). Ocean habitats. NPS. https://www.nps.gov/subjects/oceans/ocean-habitats.htm ↩