Forces of Change
Normal Conditions

Under normal conditions, fish feed on phytoplankton near the surface, in easy reach of birds and mammals (left). In an El Niņo, warmer water at the surface kills the phytoplankton, and fish swim out of reach of birds and mammals (right).

Fish-eating birds and sea mammals get clobbered during an El Niņo. Why? Ocean surface waters warm and keep deep, cooler water with nutrients from reaching the surface.

A chain reaction occurs:

  • Microscopic plants (phytoplankton) die without nutrients.
  • Fish swim deeper in search of phytoplankton.
  • The fish go too deep for pelicans, sea lions, and other diving animals to reach them.