In temperate estuaries, temperature-related fish mortalities are common. Estuarine fish that normally migrate to the ocean in the fall when water temperatures drop may become marooned in a thermal discharge plume over the winter. Higher temperatures often exacerbate low dissolved oxygen level problems in lakes and reservoirs. High temperatures encourage the microbial breakdown of organic matter, a process that requires dissolved oxygen. Unfortunately, warm water naturally holds less dissolved oxygen.
Temperature often serves as a behavioral cue.
Higher temperatures can shift the timing of reproduction such that predators are most abundant during the early stages of life. Such mis-timing can cause changes in the community structure. Temperature will increase because a wider channel has more surface area exposed to the sun's rays. The deposition of large quantities of sediment on a lake or river bottom will decrease the channel capacity and force the water to spread out over the banks. A wider channel has more surface area exposed to the sun's rays and temperature will increase.