Climate change exerts profound and multifaceted impacts on ocean ecosystems, disrupting the delicate balance that sustains marine life and the services it provides to humanity. One of the most significant consequences is ocean warming, driven by the accumulation of greenhouse gases in the atmosphere. As oceans absorb the majority of excess heat from the planet, surface and subsurface temperatures rise, altering physical and biological processes. Warmer waters reduce the solubility of oxygen, contributing to deoxygenation and creating hypoxic zones where marine organisms struggle to survive. Thermal stress affects the physiology, reproduction, and distribution of species, prompting poleward migrations and shifts in community composition, thereby undermining the stability of marine food webs. Coral reefs, among the most biodiverse marine habitats, are particularly vulnerable to elevated sea temperatures. Prolonged exposure to heat triggers coral bleaching, a stress response in which corals expel their symbiotic algae, losing color and essential energy sources. If temperatures remain high, mortality rates increase, leading to the collapse of reef structures that shelter thousands of species. These losses have cascading effects, diminishing fish populations and compromising coastal protection, tourism, and fisheries on which millions of people depend. Bleached or degraded reefs also lose their capacity to store carbon and maintain water quality, exacerbating broader ecological decline. Another major impact is ocean acidification, a result of the absorption of atmospheric carbon dioxide by seawater. This chemical process lowers the pH and reduces carbonate ion availability, impairing the ability of calcifying organisms such as corals, mollusks, and certain plankton to build and maintain shells and skeletons. Weakening of these foundational organisms reverberates through trophic levels, threatening the survival of species that depend on them for food and habitat. Acidification also alters sensory perception and behavior in fish and invertebrates, reducing their capacity to detect predators or locate spawning grounds, which can destabilize predator-prey relationships and recruitment success. Melting of polar ice due to rising global temperatures contributes to changes in ocean salinity and circulation