Please look at the links I have provided, I think they will assist you or at least provide an good overview to start.

http://large.stanford.edu/courses/2019/ph241/clark1/

Article Consequences of thermal pollution from a nuclear plant on la...

Chapter Responses to Stress, Toxic Chemicals, and Other Pollutants i...

Dear Osama,

Firstly, nuclear power plants are not the only sources of thermal pollution. Various industries also discharge cooling water into the rivers. This is also the case for conventional thermal power plants. From the ecological point of view, the discharge into a river of a large quantity of water, whose temperature is appreciably higher than that of the water of the river, is likely to generate considerable disturbances in it. It can, among other things, prevent winter cooling, even freezing of rivers. This is of great importance. Indeed, the density of water reaches a maximum around 4 ° C. In winter, the bottom is close to this temperature, while the surface is colder. We have the opposite situation in summer: the bottom is always around 4 ° C, but the surface is warmer. During the intermediate seasons, spring and autumn, there is a temperature inversion, one of the consequences of which is a mixing of the layers of water. In these natural conditions, a whole flora and fauna, adapted for centuries to this regime, flourish normally. There are plants that need fresh water at temperature to about constant; they grow at the bottom. Others, on the contrary, adapt to more changing conditions. As for fish, their adaptation is based on both the flora and the temperature of the water. If large amounts of warmer water are dumped into a river, this natural balance is profoundly disrupted. Some distance downstream of the plants, the water warms, and this prevents the mixing of different layers of water. Result: oxygenation of water is no longer. We then see the plants wither away and the fish disappear. From this ecological point of view, it is absolutely essential to cool the wastewater before returning it to the river. This cooling can be achieved by the installation of cooling towers. Such tours should be made mandatory regardless of their cost.

With my best regards

Bachir ACHOUR

According to Wikipedia, thermal pollution is the degradation of water quality by any process that changes ambient water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature, the sudden change in temperature decreases oxygen supply and affects ecosystem composition. Fish and other organisms adapted to particular temperature range can be killed by an abrupt change in water temperature (either a rapid increase or decrease) known as "Thermal shock."

The main thermal pollution caused by a nuclear power plant is the degradation of the water quality used as coolant of the nuclear power reactor.

Thermal water increase temperature in water which reach optimum level of temperature in some species so they can die

Phytoplankton cannot live high water temperature

So entire energy transfer disturbed