Global warming has a significant impact on marine ecosystems around the world. The rise in global average temperature has caused profound changes in marine environmental conditions. Higher temperatures contribute to the bleaching of coral reefs, which is especially harmful to marine biodiversity. Coral reefs are often considered “marine rainforests,” supporting thousands of species. When water temperatures rise more than 1.5 degrees Celsius, zooxanthellae, the symbiotic algae that feed coral, begin to die. As a result, corals lose their color and source of nutrition, causing mass death. Apart from that, global warming also contributes to increasing sea water levels. Melting ice at the North and South Poles is contributing to this rise, threatening coastal ecosystems such as mangroves, seagrass beds and estuaries. This habitat loss disrupts species that depend on these environments, from commercial fish to migratory birds, all of which play an important role in the marine food web. Changes in sea water temperature also affect fish migration patterns. Species such as tuna and cod are starting to move to cooler waters, seeking more comfortable temperatures. This displacement can have a negative impact on the fishing industry, forcing fishermen to look for alternatives and adapt to new conditions. In addition, fish that move to new areas often enter less controlled waters, threatening the existence of local species and disrupting the balance of the ecosystem. Ocean acidification, caused by increasing CO2 levels, is also a serious problem. When CO2 is absorbed by seawater, carbonic acid is formed and lowers the water’s pH. This process is detrimental to marine organisms that have shells or skeletons, such as molluscs and coral. With a lower pH, their ability to form shells is reduced, impacting the fisheries sector and global food security. Apart from direct impacts, global warming also affects the health and productivity of marine ecosystems. Changes in temperature can trigger increased proliferation of harmful algae, which can produce toxins and cause harm to other species, as well as harm humans. This detrimental phenomenon, known as algal “blooms,” often creates “dead zones” where no marine life can survive. Furthermore, the tourism industry which depends on the natural beauty of the sea is also experiencing negative impacts due to global warming. Damage to coral reefs and reduction of marine species attracts visitors, which has a negative impact on the local economy. As more and more areas experience damage, the challenge of maintaining healthy ecosystems increases. All these factors indicate the need for urgent action to reduce greenhouse gas emissions and protect marine ecosystems from the impacts of global warming. Conservation and sustainable management efforts are very important to restore and maintain marine biodiversity.