Global warming is an increasingly urgent environmental issue and has a significant impact on various aspects of life, including marine ecosystems. Rising sea surface temperatures due to climate change have serious impacts that can change the structure and function of marine ecosystems. One of the most striking impacts of global warming is an increase in ocean temperatures. Higher temperatures are detrimental to coral reefs, which are important habitats for many species of fish and other marine organisms. Coralls exposed to high temperatures experience bleaching, where symbiotic algae, which provide color and nutrition, are excreted from the coralll’s tissue. If this condition persists for a long time, coral reefs can die, which means a loss of biodiversity and the ability of marine ecosystems to provide ecosystem services such as coastal protection and tourism. In addition, global warming causes ocean acidification caused by increased levels of carbon dioxide (CO2) in the atmosphere. About 30% of CO2 produced by human activities is absorbed by the ocean, changing the pH of seawater. This process has a negative impact on organisms that have calcium-based shells or skeletons, such as molluscs and crustaceans. Ocean acidification disrupts the shell formation process, which can reduce their populations and affect food chains in marine ecosystems. Changes in ocean temperatures also alter the distribution and behavior of species. Many migratory fish species, such as tuna and salmon, seek cooler waters. This forces these fish to move far from their native habitat and can have an impact on the global fishing industry. Fishing may decrease in traditional areas while increasing in new locations, causing conflict between bordering countries and threatening local food security. Furthermore, global warming is triggering an increase in the frequency and intensity of extreme weather, such as tropical storms and floods. These events can damage coastal habitats, such as mangrove and seagrass ecosystems, which serve as natural buffers and breeding locations for many marine species. This damage not only reduces biodiversity but also increases the vulnerability of coastal communities to the impacts of climate change. Water quality is also threatened by global warming. Rising temperatures reduce oxygen levels in water, which is crucial for marine life. Under conditions of hypoxia, many species will experience stress, triggering migration, or even death. Additionally, pollutants from land, such as pesticides and waste, tend to be more concentrated in high temperature conditions, damaging the health of marine ecosystems. These impacts show that global warming not only affects temperature and water quality, but also damages existing ecosystem connections. Mitigating these impacts requires global collaborative action to minimize greenhouse gas emissions, protect important habitats, and develop sustainable adaptation strategies to protect marine ecosystems and their biodiversity.