How does this abiotic factor affect life?
Life on Earth could not be sustained without ocean currents. Ocean currents are driven by a variety of factors and affect a variety of ecosystems. The ocean exercises an incredibly large influence on ecosystems because it circulates nutrients, organisms, and so much more around the world (1). These currents are mainly generated by differences in water density, related to salinity and temperature. Salt concentration positively correlates with water density, and higher temperatures negatively correlates with density (1). Denser water sinks to the bottom of the ocean, and the less dense water is circulated at the surface by the global wind patterns. Warmer water near the equator is blown towards the poles, where it cools and sinks towards the bottom of the ocean, eventually cycling back to the equator. Ocean currents are also created by the spinning of Earth and the resulting Coriolis Effect, which causes a curve in all global wind and ocean currents (2).
The movement of the ocean currents brings a lot of nutrients with it. Most dead organisms fall to the bottom of the ocean to decay, and the decay disperses at the bottom of the ocean, making the water nutrient-rich (4). When water on the surface is blown away by wind, upwelling occurs, bringing the nutrient-rich water up to the surface and providing nutrients for primary production (3). Primary production generally occurs through photosynthesis, and it harnesses energy from the sun by creating chemical compounds to store energy (7). Upwelling mainly happens in equatorial regions, since the global winds blow surface water in both the northern and southern directions, hence upwelling is increased. Thus, the equator is known to be especially productive for harnessing energy (3). Nutrient-rich water makes various organisms more productive, which allows an entire ecosystem to thrive. These nutrients contribute to not only the ocean environment but also the land ecosystems because many land organisms eat ocean-dwelling organisms.
Upwelling also allows dissolved carbon dioxide to be brought to the surface. This allows the photosynthetic organisms at the ocean’s surface to perform more photosynthesis, releasing more oxygen into the atmosphere and surrounding water (5). Downwelling, the opposite of upwelling, circulates the dissolved oxygen in the surface water down to the bottom of the ocean, helping organisms survive at the depths of the ocean (5).
Ocean currents also influence ecosystems by helping reproduction. Many species depend on ocean currents for the survival of their offspring; ocean currents carry offspring to certain regions of the ocean that allows them to thrive. According to a study done on the relationship between pelagic eggs (eggs laid in the open sea) and upwelling regions, “deep-water spawning and vertical migration of larvae are likely mechanisms for reducing the advective loss of eggs and larvae” (6). Thus, vertical migration allows for the survival of eggs and larvae by preventing them from being swept away in ocean currents. The study also states that “regular diurnal [vertical] migrations begin after the larvae have started feeding,” which is optimal timing for larvae, allowing them to survive on the nutrients provided by the upwelling (6).
Ocean currents sustain life by cycling nutrients around the world and bringing offspring to where they need to be to survive. These currents are generated by the various densities of ocean water, moving dissolved gasses, other nutrients, and organisms to where they’re needed most. They allow the equator to be the most productive place on the planet and essentially allow life to exist on Earth.
Diagram of the global ocean currents
Fish laying pelagic eggs
- Ocean Circulation. University of California Regents. Retrieved from https://ugc.berkeley.edu/background-content/ocean-circulation/.
- (2011, August 1). Ocean currents. NOAA. Retrieved from https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-currents.
- 9.5 Currents, Upwelling and Downwelling. Roger Williams University. Retrieved from https://rwu.pressbooks.pub/webboceanography/chapter/9-5-currents-upwelling-and-downwelling/.
- Dissolved Nutrients. Penn State’s College of Earth and Mineral Sciences. Retrieved from https://rwu.pressbooks.pub/webboceanography/chapter/9-5-currents-upwelling-and-downwelling/.
- 5.5 Dissolved Gases: Carbon Dioxide, pH, and Ocean Acidification. Roger Williams University. Retrieved from https://rwu.pressbooks.pub/webboceanography/chapter/5-5-dissolved-gases-carbon-dioxide-ph-and-ocean-acidification/.
- Parrish, Richard H., Nelson, Craig S., Bakun, Andrew. (1981). Transport Mechanisms and Reproductive Success of Fishes in the California Current. Biological Oceanography. Retrieved from https://doi.org/10.1080/01965581.1981.10749438.
- Britannica, T. Editors of Encyclopaedia (2022, January 24). Primary productivity. Encyclopedia Britannica. Retrieved from https://www.britannica.com/science/primary-productivity.