Marine heatwaves driven by El Niño are expected to cause widespread ecological disruptions. Key risks include starvation and disease among marine species, such as seabirds, sea lions, and whales. Reduced prey availability and harmful algal blooms, which produce toxins like domoic acid, threaten marine mammals and seabirds. Historical data from past El Niño events reveal catastrophic impacts, including mass die-offs and reproductive failures. For example, the 2014-2016 heatwave led to record strandings and starvation among species like Cassin's auklets and humpback whales. Additionally, warming waters may compress marine species closer to shore, increasing risks of ship strikes and fishing gear entanglements. These disruptions could have cascading effects on marine ecosystems and human activities.