Global warming has a significant impact on marine ecosystems, including temperature changes, rising sea levels and ocean acidification. These changes not only affect marine life, but also the communities that depend on marine resources. One of the most obvious impacts of global warming is an increase in sea water temperatures. Higher temperatures disrupt important habitats such as coral reefs, which are sensitive to temperature changes. Coralne experiences bleaching when temperatures exceed its tolerance threshold, which results in the death of coral colonies and loss of habitat for various fish species. According to research, more than 30% of the world’s coral reefs have experienced significant damage in recent decades. Apart from warming, rising sea levels also pose a threat. The ice at the poles is melting, causing the volume of sea water to increase and resulting in coastline erosion. This can alter coastal ecosystems, such as mangroves and seagrass beds, which serve as refuge for many species and put pressure on water quality. Ocean acidification, which results from the absorption of carbon dioxide, is another serious problem due to global warming. The carbonic acid formed impacts the ability of organisms such as molluscs and crustaceans to build shells and other hard structures. A decrease in pH levels could worsen the crisis for the fishing industry. Coral-dependent species and organisms affected by acidification may experience drastic population declines. In addition, changes in ocean current patterns due to global warming can change the distribution of species. Fish and marine mammals such as whales and dolphins may move to cooler areas, leaving areas that were previously their habitat. This can cause a domino effect on the food chain, harming predators and other species in the ecosystem. Affected marine ecosystems also pose a risk to the food security of marine-dependent communities. As marine resources become increasingly scarce, coastal communities will face challenges in maintaining their livelihoods. An increase in the frequency and intensity of extreme weather phenomena, such as storms and floods, can also damage infrastructure that supports the fisheries sector. The impact of global warming on marine ecosystems is very complex and interrelated. By paying attention to these various aspects, the global community needs to take immediate action to reduce greenhouse gas emissions and protect marine ecosystems. Implementing strong ocean protection policies, pollution reduction, and conservation initiatives can help mitigate the effects of climate change and maintain the sustainability of marine resources for future generations.