Cold-blooded animals cannot survive in temperatures below 0 degrees Celsius, and warm water animals cannot tolerate anything warmer than 36 degrees Celsius. In warmer waters, the DO levels may go down, and the BOD levels may go up because of the increased decomposition of plant matter. Some organisms may have metabolic rates that increase to a point at which it is impossible for them to survive. Water temperature increases causing the rate of photosynthesis by algae to increase. Increased water temperature will speed up bacterial decomposition and result in higher BOD levels.
Temperature influences the survival of aquatic organisms.
Warm water increases the metabolic rates of aquatic organisms. Warm water temperatures may keep some species from being able to reproduce. The removal of vegetation in the water causes more sunlight, which may increase its temperature drastically. Bacteria and other diseases grow faster in warm water, and susceptibility of aquatic organisms to disease in warm water increases as well. Thermal pollution, which is the discharge of large amounts of warm water from industrial plants, may cause increases in temperature.