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How El Niño affects marine ecosystems
El Niño is a widespread climate phenomenon that has large-scale and profound impacts on marine ecosystems. The changing climate changes the distribution and life cycle of many marine organisms and can sometimes cause major changes in their distribution and chances of survival. This article explains how El Niño works and how it affects marine ecosystems. The Meteorology of El Niño What is El Niño? El Niño is a climate phenomenon characterized by an irregular change in the temperature distribution in the Pacific Ocean. Normally, warm water from the tropics is pushed westward toward Asia by the trade winds, which...
How El Niño affects marine ecosystems
El Niño is a widespread climate phenomenon that has large-scale and profound impacts on marine ecosystems. The changing climate changes the distribution and life cycle of many marine organisms and can sometimes cause major changes in their distribution and chances of survival. This article explains how El Niño works and how it affects marine ecosystems.
The meteorology of El Niño
What is El Niño?
El Niño is a climate phenomenon characterized by an irregular change in the temperature distribution in the Pacific Ocean. Normally, warm water from the tropics is pushed westward toward Asia by the trade winds, allowing cold, nutrient-rich water to move upward into the ocean. This process is called buoyancy.
However, during an El Niño period, the trade winds weaken or even change direction, causing warm ocean waters to push back toward the Americas. This process suppresses the upward movement of cold, nutrient-rich water and leads to warming of the ocean surface in the eastern parts of the Pacific.
Periodicity of El Niño
Although El Niño is an irregular event, it typically occurs every two to seven years and can last from several months to a year or longer, depending on intensity and duration.
Impact on marine ecosystems
The impact of El Niño on marine ecosystems is far-reaching, affecting all levels of the food web, from the smallest planktonic organisms to the largest marine mammals.
Impact on primary production
The upward movement of cold, nutrient-rich water is critical to primary production in the oceans, providing necessary nutrients to plankton and other microorganisms. The absence of this upward stratification during an El Niño event reduces the supply of nutrients to the sea surface, resulting in a large reduction in primary production. This has dramatic effects on the entire food web below this level.
Impact on fish populations
Fish are one of the groups most affected by El Niño, particularly species that depend on the cold, nutrient-rich waters. The fishing industry often experiences significant losses during El Niño years, particularly in the anchovy and sardine fishery. But other fish species, including many important commercial species, can also be affected.
Impacts on marine mammals
Marine mammals such as sea lions, elephant seals and whales also suffer greatly from the effects of El Niño. By reducing primary production and fish populations, the food supply of these animals is severely limited. This can lead to reduced reproductive rates, increased mortality and even mass extinctions.
Long-term impacts and climate change
In recent decades, El Niño has become more intense and frequent. Some scientists suggest that this could be a result of global climate change. If this trend continues, the impacts on marine ecosystems could be even more serious and lasting.
Changes in species compositions
As a result of El Niño, species compositions in many marine systems may change significantly. There are reports of invasive species moving into new areas during El Niño events and displacing native species.
Shift in distribution areas
El Niño can also cause the ranges of certain species to shift, particularly in terms of water temperature and nutrient levels. This may have long-term impacts on marine ecosystems and human use of these resources.
El Niño is a powerful and far-reaching force in the global ecological network. While its immediate effects are mostly temporary, its long-term impacts could be exacerbated by climate change. It is therefore essential to further research the phenomenon and understand its effects in order to better protect the future health of the oceans and their inhabitants.
Sources:
Wang, C., Deser, C., Yu, J. Y., DiNezio, P., & Clement, A. (2017). El Niño and Southern Oscillation (ENSO): A Review. In Coral Reefs of the Eastern Tropical Pacific (pp. 85-106). Springer, Dordrecht.
Barber, R. T., & Chavez, F. P. (1983). Biological consequences of El Niño. Science, 222(4629), 1203-1210.
Brander, K. (2010). Impacts of climate change on fisheries. Journal of Marine Systems, 79(3-4), 389-402.