The impact of global climate change on marine ecosystems is very complex and diverse. One of the most significant impacts is rising sea water temperatures. Higher temperatures cause bleaching of coral reefs, which are important habitats for many species of fish and other marine organisms. When coral reefs bleach, they not only lose their color, but also their ability to provide shelter and food sources. Furthermore, changes in rainfall patterns and increased frequency of storms result in greater freshwater runoff into the sea. This changes salinity, which can affect marine organisms such as fish, invertebrates and marine plants. In addition, chemicals and pollutants carried by fresh water can pollute marine ecosystems, disrupt the balance of the ecosystem and damage vulnerable species. Ocean acidification is also a serious impact of climate change. Increasing concentrations of carbon dioxide (CO2) in the atmosphere cause more CO2 to dissolve in seawater, producing carbonic acid. This process is detrimental to organisms with hard shells such as clams, molluscs, and even some types of coral. A decline in the population of these organisms can disrupt the food chain and reduce biodiversity. Climate change also has an impact on shifting the distribution of marine species. Many fish species strive to find more suitable water temperatures, often moving towards the poles or to greater depths. This phenomenon can impact local fishing industries, which depend on certain species for income and sustainability. Climate change triggers acidification and the “dead zone” phenomenon. Dead zones are areas with low oxygen levels, which can be deadly for many marine species. Rising temperatures and nutrient pollution exacerbate this phenomenon, making many ocean areas unfit for habitation. Attacks by pests such as jellyfish are also increasing, creating new challenges for marine ecosystems. Excessive jellyfish populations can compete with other fish species for food and disrupt existing food webs. The socio-economic impact of climate change on marine ecosystems is enormous. Coastal communities that depend on marine ecosystems for their livelihoods, such as fishing and tourism, face great risks. Reductions in biodiversity and declining ocean health can result in job and income losses, adding to economic instability in many regions. On the other hand, changes in marine ecosystems can affect human health. Deteriorating water quality and increasing marine pathogens have the potential to exacerbate food-borne diseases, and impact global food security. Mitigation efforts to overcome the impacts of climate change on marine ecosystems are very important. Implementing conservation measures such as sustainable fisheries management, coral reef protection, and reducing carbon emissions is key to protecting marine ecosystems. Global awareness and cooperation in maintaining ocean health is very necessary to maintain the balance of this fragile marine ecosystem.