Global warming has a significant impact on marine ecosystems, which are an important part of the Earth’s biosphere. As the global average temperature increases, there is a marked change in the balance of marine ecosystems, which disrupts the lives of various species. One of the biggest impacts of global warming is warming ocean temperatures. Higher temperatures cause stress on marine biota, including highly sensitive coral reefs. Rising temperatures cause the phenomenon of coral bleaching, where the symbiotic algae that provide food and color to corals is lost. As a result, coral reefs become more susceptible to disease and reduced reproduction. The survival of various species of fish and marine animals that depend on coral reefs as habitat is also threatened, and this can lead to a decline in biodiversity. In addition, dissolved oxygen in seawater decreases as temperatures increase, which can result in dead zones. Dead zones are areas with low oxygen levels that do not support life. This occurs because global warming causes increased water stratification, where warm water sits at the surface and inhibits mixing with deeper, more oxygen-rich water. Fish species and other organisms struggle to survive in these conditions, which can shake up the ocean’s food chain. Changes in ocean current patterns due to global warming also affect the distribution of subsequent species. Some fish species can move to cooler areas, while others may not be able to adapt to these changes. This could lead to conflict in global fisheries, as fishermen have to adapt to new locations where target species may shift. The rise in sea levels caused by melting polar ice is another impact of global warming. This has the potential to affect coastal ecosystems, including mangroves and coral reefs, and threaten habitats for various species. Mangroves serve as protection from storms and as mating grounds for many species of fish. As water levels rise, these coastal areas are at risk of being lost, posing a risk to the lives and livelihoods of communities that depend on marine resources. The accumulation of carbon dioxide (CO2) in the atmosphere due to human activities also causes ocean acidification. When CO2 is absorbed by the ocean, it produces carbonic acid, which lowers the pH of seawater. This process impacts organisms such as shellfish, lime deposits, and coral reefs, which require calcium carbonate to reproduce. A decrease in the availability of calcium carbonate has a negative impact on the survival of various marine species and can change the ecosystem as a whole. The impact of global warming on marine ecosystems is very complex and interacts with each other. Mitigation and adaptation efforts are critical to protecting biodiversity and healthy marine ecosystems. Public knowledge and awareness must also be increased to ensure long-term protection of our oceans.