In 1969, the United States constructed a nuclear power plant on the shores of Bistan Bay. Before the plant was built, the tide flowed southwest and receded northeast. However, once the nuclear power plant became operational, over 2000m3 of cooling water was discharged into the sea every minute, reversing the tidal flow at Bistan Bay.
Furthermore, the hot water released by the plant raised the temperature of a vast area of sea, covering 60 hectares, from an initial surface temperature of 30 – 31 degrees Celsius to as high as 33 – 35 degrees Celsius, with 10 – 12 hectares reaching temperatures of 35 – 36 degrees Celsius. Around the hot water discharge pipe, temperatures soared to 40 degrees Celsius.
In total, approximately 900 hectares of sea surface were heated due to the wastewater from the nuclear power plant. In the area of 10 – 12 hectares with the highest temperatures, virtually no marine life could be found. Common algae types such as green algae, red algae, and purple algae were completely wiped out, leaving only blue-green algae.
In other warm water regions, marine species also significantly decreased. Particularly in the summer, small dead shrimp and crabs were often seen floating on the water’s surface.
In warm water areas, marine species also significantly decreased.
Why is this happening?
This is because the elevated water temperature reduces the amount of dissolved oxygen in the water, affecting the cellular processes of marine life. Organisms that thrive in normally temperate seawater will either die or flee to cooler waters as the sea temperature rises. Some fish species, due to the increased sea temperature, fail to find suitable spawning grounds or become confused about the timing and location for spawning, preventing them from reproducing.
The higher sea temperatures cause warm-water species to proliferate rapidly, while economically valuable species such as shrimp, fish, clams, and oysters decline rapidly, leading to the destruction of the marine ecosystem in that area. Such phenomena usually occur when sea temperatures rise more than 4 degrees Celsius above normal levels, a situation referred to as thermal pollution. In reality, even temperatures that are not excessively high can still lead to thermal pollution.
Thermal pollution is primarily caused by cooling water discharged from equipment and machinery, mainly from the power generation industry. Other industries such as metallurgy, chemicals, petroleum, and machinery also contribute significantly to thermal pollution, but the impact of the power generation sector is the most notable. Currently, global electricity production increases by 7.2% each year, and it is expected to double in about 10 years.
Thermal pollution in the sea can sometimes bring certain benefits. For instance, during winter, increased sea temperatures help some fish species avoid freezing. However, ultimately, the disadvantages outweigh the advantages. Therefore, it is generally advisable to seek ways to prevent this phenomenon.
There have been proposals to use long pipes to discharge cooling water far offshore or to draw cold water from the ocean floor for cooling. Whether these solutions are effective remains to be seen in practice.
