El Nino's Effect On Nature
Animals and the Ocean
El Nino can affect the lives of many animals, but mainly those in or near the sea.
In the coastal waters off of Peru and Ecuador there are many fish, (especially anchovies,) and seabirds and marine mammls. Normally, cold water from the bottom that is full of nutrients such as nitrates, rises, and the phytoplankton are fed. In turn, the phytoplankton feed things like the fish and some birds. Then the fish get eaten by other types of birds and marine mammls.
However, during an El Nino, warm water with little nutrients covers the nutrient-filled water, preventing it from rising. So a chain reaction starts, starting with the phytoplankton not being able to get food. Lots of the animals leave those waters in search of food. But, after a hard El Nino, many birds and mammls starve to death.
In the central Pacific, along the Equator, there is an island called Christmas Island. The 1982 El Nino flooded the island. The flooding, along with disruptions to the marine food supply, drove away all of the island's 14 million sea bird inhabitants. Lots of those birds died from heavy storms and lack of food. Only about 1 million came back.
The 1982-83 El Nino increased the water temperature in the Pacific so dramatically that some of the coral started turning white, a process called bleaching. Bleaching takes place when coral evict the algae in their tissues that gives them their color. This gives them their bleached appearance, and makes them weak. Death is a possibilty.
On the bright side, some animals don't die from El Nino.
During the 1982-83 El Nino, the Galapagos islands got 10 times more rain than usual, and there was a population increase among certain birds. After the rain, there were more seeds and caterpillars for food for 2 types of Darwin's finches that were being observed. The finches responded to this by reproducing more offspring. At the end of 1983, the 2 Darwin's finches numbers were 1,900, compared to only 450 in 1981. It is thought that the population grows after each El Nino. Maybe the population is even mainly determined by El Nino's effects.
The waters of Peru are normally very cold. During an El Nino, the coastal waters and a cold current called the Peru Current grow warm. This prevents the cold, nutrient-rich waters from coming up. The warm waters spread westward along the equator, covering more than 1/4 of the way around the Earth. The warming and cooling of the surface in the eastern and central Pacific alternates regularly.
In the Indian Ocean, there is usually a low average pressure. In the central Pacific, there is usually a higher average pressure. During an El Nino, the Indian Ocean's usually low average pressure increases. In the central Pacific, its usually higher average pressure decreases.