Water salinity
Water salinity is a core factor regulating the structure and function of aquatic ecosystems. Its changes directly affect the survival and reproduction of organisms, community structure, nutrient cycling, and can even trigger regional ecological imbalances. The specific impacts are as follows: I. Direct Impacts on Aquatic Organisms Impact on Cell Osmolarity and Survival Aquatic organisms have specific tolerance ranges for salinity; exceeding these thresholds disrupts cellular osmolarity balance: Freshwater organisms: such as carp and grass carp, have a higher internal osmolarity than the surrounding freshwater and rely on ion regulation systems in their gills and skin to maintain balance. A sudden increase in salinity can lead to cell dehydration and shrinkage, resulting in respiratory distress and death. Marine organisms: such as corals and tuna, have a lower internal osmolarity than seawater and need to excrete excess salt through their salt-excreting organs. A sudden drop in salinit...