Fish, thermal pollution effects

By contrast, thermal pollution can have some significant effects on the natural ecosystem. As the temperature of water rises, its ability to hold dissolved oxygen declines. The graph shows how the solubility of oxygen varies with temperature. Since fish are cold-blooded animals, they are unable to regulate their own temperatures, and... 

Fish are ectothermic vertebrates, and as such are susceptible to fluctuations in temperature of their immediate environment. This has relevance to sewage and industrial effluents, which can be significant sources of thermal pollution in aquatic environments. Recent evidence demonstrating that heat shock can induce apoptosis in a variety of fish tissues21,111,136 suggests that some deleterious effects of thermal pollution may be mechanistically linked to increased apoptosis of susceptible cell types. 

The decreased solubility of O2 in water as temperature increases is one of the effects of thermal pollution of lakes and streams. The effect is particularly serious in deep lakes because warm water is less dense than cold water. Warm water therefore tends to remain on top of cold water, at the surface. This situation impedes the dissolving of oxygen in the deeper layers, thus stifling the respiration of all aquatic life needing oxygen. Fish may suffocate and die under these conditions. 

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