Explain the relationship between ocean circulation patterns and the marine food chain, and how

this is affected by an El Nino event,

Ocean circulation patterns is directly linked with the marine ecosystem. El Nino event hinders the climate interaction of ocean.

Explanation:

The disturbance in the ocean climate interaction transfers the essential nutrients into the deep down ocean leaving very tiny amount at the surface. It lacks the support to plankton growth. Ocean circulation patterns can sometime make the ocean food ecosystem less productive. El Nino event reverses the ocean current. Surface waters in the central and eastern Pacific Ocean become significantly warmer than usual during this event. So the drifting starts towards east direction (normally driven west).