Final answer:
La Niña causes ocean temperatures off the west coast of South America to decrease, impacting marine life and potentially causing flooding.
Step-by-step explanation:
An effect of La Niña is that ocean temperatures off the west coast of South America decrease. During La Niña, there is a cooling of the water in the equatorial Pacific, which leads to colder ocean temperatures off the west coast of South America. This cooling can have significant impacts on marine life, causing die-offs of fish and marine mammals, and sometimes resulting in catastrophic flooding on the coast.