Climate change has emerged as one of the most profound threats to aquatic ecosystems, impacting freshwater, coastal, and marine environments through a complex interplay of physical, chemical, biological, and socio-economic processes. This review synthesizes recent evidence from the Intergovernmental Panel on Climate Change (IPCC, 2023) [25], United Nations Environment Programme (UNEP, 2022) [55], National Oceanic and Atmospheric Administration (NOAA, 2023) [40], and peer-reviewed studies (2023–2025). It highlights the cascading effects of a 1.1 °C rise in global temperatures above pre-industrial levels, including ocean acidification, hydrological disruptions, sea-level rise, and oxygen depletion.

Recent satellite observations indicate increasing chlorophyll concentrations (“greening”) in polar oceans and declining productivity (“blue shifting”) in equatorial regions—signifying large-scale phytoplankton community shifts (Polovina et al., 2020) [46]. Coral reef systems are facing mass mortality, with up to 84% of global reefs experiencing bleaching events by 2025 (Hughes et al., 2017) [21]. Hypoxic “dead zones” and cyanobacterial blooms are spreading globally, resulting in major wildlife die-offs and food web disruptions (Diaz & Rosenberg, 2008) [15].

Freshwater species now face a 24% extinction risk due to compounded climate and anthropogenic pressures (IPBES, 2022) [24]. Marine biomass is projected to decline by 15%, while fish catch could drop by 21–24% by 2100 (Lotze et al., 2019) [31]. These findings emphasize the urgency for integrated mitigation and ecosystem-based adaptation strategies.