Pollution affects dolphins by contaminating food sources and causing dead zones that are void of fish and other important staples in the diet of dolphins, as explained by the Seattle Post-Intelligencer. Contamination can damage a dolphin's immune system, and dead zones can force dolphins to move to new habitats.
When a dolphin eats an organism contaminated by certain pollutants, it stores the chemicals in its fat reserves and other parts of its body. The pollutant can go on to damage the reproductive systems of adult dolphins and even cause calves to be born with birth defects. These toxins can also damage the dolphin's immune system, leaving it open to infections, such as pneumonia, which may result in death. The bodies of dolphins already host parasites, which are capable of growing out of control when a dolphin's immune system is compromised.
Dead zones can occur without human activity, the National Ocean Service states that nutrient pollution creates new dead zones in once-healthy areas. Algae blooms can occur when water is exposed to excess nutrient runoff from farms. When large numbers of algae die and begin decomposing, the process depletes the oxygen in the water, which results in a dead zone that's void of marine life. Dolphins that once thrived in these areas are then forced to find new habitats with stable food sources.