Climate change is a global issue whose impacts are starting to be felt in various aspects of life, one of which is the marine ecosystem. Rising sea surface temperatures, increased ocean acidification, and changes in rainfall patterns pose serious threats to marine organisms and biodiversity. One of the biggest impacts of climate change is global warming which causes sea temperatures to increase. According to NASA data, average sea surface temperatures have increased by about 1 degree Celsius since the beginning of the 20th century. These high temperatures have a direct impact on coral reef life, which is very sensitive to temperature changes. Warming water causes coral bleaching conditions, where corals lose the symbiotic algae that give them color and nutrition. Research shows that more than 50% of corals worldwide have experienced bleaching due to these high temperatures, worsening the ecosystems that depend on them. Apart from rising temperatures, ocean acidification is also a serious problem. The presence of carbon dioxide (CO2) gas in the atmosphere, which is increasing due to human activities, means that the sea absorbs most of the CO2. This process increases acid levels in the ocean, making conditions difficult for marine organisms that have shells, such as molluscs and coral. Research shows that ocean acidification can disrupt the shell formation process, thereby threatening the survival of important species in the food chain. Climate change also affects fish migration and reproductive patterns. As temperatures rise, many fish species seek cooler waters, which sometimes makes fisheries ecosystems in certain areas no longer able to support their fish populations. For example, cod normally found in the North Atlantic has now moved to more northerly locations, affecting local fishermen who depend on this species. Apart from that, the impact of climate change on marine ecosystems can also be seen from the increasing frequency and intensity of storms. Storms and high waves can destroy coral reefs, forget fish habitats, and change seabed channels. This has the potential to harm the economy of coastal communities who depend on marine resources. Loss of biodiversity is also a real threat. As more and more species become endangered, we lose the important functions they offer, such as water filtration, carbon storage and support for human life. A study shows that healthy marine ecosystems can mitigate climate change by absorbing carbon more effectively. We must also pay attention to the impact on human communities living around marine ecosystems. The problems of overfishing and pollution, coupled with climate change, could lead to food insecurity for millions of people, especially in developing countries that rely heavily on seafood. Efforts to reduce the impact of climate change on marine ecosystems must include reduced greenhouse gas emissions, stricter protection of marine protected areas, and sustainable farming and fishing practices. Through a better understanding of the impacts of climate change and more proactive action, we can contribute to maintaining the sustainability of marine ecosystems and increasing the resilience of coastal communities.