The primary effect of pollution on marine ecosystems is the degradation of habitat and biodiversity. Pollutants such as plastics, heavy metals, and chemicals can harm aquatic life, disrupt food chains, and lead to phenomena like eutrophication, which depletes oxygen levels. The presence of toxins can affect fish reproduction, health, and survival, leading to population declines. Overall, pollution poses a significant threat to the stability and functionality of marine ecosystems, necessitating conservation efforts and policy changes.