Effects of Rising Ocean Temperature
Effects of Rising
Ocean Temperature
<Biological Influence>
1) Changing Marine biodiversity
It is the fact that when the atmospheric temperature and sea temperature change, the physiological, ecological features and regional distribution of living organisms in the ocean change. In particular, since the ocean has a higher specific heat than the land, the speed of change is not large compared to the land. Therefore, marine life is very vulnerable to rapid environmental changes.
Changes in marine species can take place over a long period of time or proceed at a rapid pace. The scale also varies from small-scale regional changes to large-scale over a wide area of sea. It also leads to a reorganization of all the ecosystems, from the tiny plankton to the top predator fish. In the case of fish, even a change of 2℃ is greatly affected on distribution, growth, and reproduction.
Salmon is one of the fish species greatly affected by changes in water temperature. This is because the higher the water temperature, the more food a salmon needs to eat. If water temperatures continue to rise, salmon in the North Pacific will move in order to seek cold sea water in the Bering Sea, or to bottom water with relatively little change in water temperature. Otherwise, salmon will become extinct due to intensifying food competition.
Unlike highly active fish, it is a more serious situation for creatures with less mobility or living in trapped places. Freshwater fish, sea algae, and shellfish will survive to a biologically tolerable temperature range, but if the temperature exceeds a certain range when organisms cannot escape, they will die.
2) Changing in fishery resources and catches
As the water temperature rises, each fish species gradually moves its habitat to higher latitude, searching suitable water temperatures to survive. As a result, there are also big changes in fishes resources that can be caught in each country.
In Korea, fish species change significantly, especially in the East Sea. This is because in the East Sea, the Kuroshio Current flowing from the South Pacific Ocean and the North Korean Cold Current flowing from the north meet to form a water temperature front. According to the National Institute of Fisheries Research and Development, marine warming caused by climate change will not only cause a surge in animal plankton, but also cause changes in water resource distribution and fish species replacement.
According to the Korea Environmental Technology Consulting Hotline, three unusual phenomena appeared in the change of fishing resources, which is related to the progress of marine warming. First, the distribution of turbulent fish species is moving northward. Second, the fishing season in winter is being extended. Third, in winter, the increase in catch of fish is evident. The following table shows the output of major fish species in the coastal waters in 2021 of the Ministry of Oceans and Fisheries' statistical system.
Anchovies' growth stagnated during the July-August period, the main spawning season for fish, due to higher water temperatures of 2 to 4℃ on the South Sea and the West Sea coast. Also, the initial survival rate was lowered. Therefore, the production has fallen dramatically.
In the case of mackerel, it recorded higher catches than usual. Since the amount of resources flowing to the southern part of the West Sea and around Jeju Island increased significantly due to the strengthening the Tsushima Warm Current.
The catch of squid surged in the spring-summer 2021. The squid in the south moved northward to the fishing area of the Korea as the water temperature on the west coast rose 0.5 to 1.5℃. However, since November, squid catches on the east coast have decreased as they were dispersed due to abnormal high water temperatures in the northern waters.
In the case of blue crab, the population increased because of the better growth conditions for young individuals such as nutritional salts and plankton increased due to the long rainy season in 2020, and as a result, the catch increased. In particular, due to a 0.8 to 1.5℃ increase in coastal water temperature, blue crabs stayed for a long time, leading to a phenomenon in which fishing season continued until December, unlike previous years.
3) Increasing the risk of fish disease
Marine warming is also expected to have an effect on diseases. Changes in the marine environment change the metabolism and physiology of marine life, and are closely related to the distribution and appearance of pathogens.
According to the National Institute of Fisheries Science, fish diseases occur due to the balance destruction between the environment, pathogens, and resisting power against disease. In the past, bacterial diseases mainly occurred during the high water temperature in summer, but now viral diseases are found to occur all year round. Also, single infections of bacterial and parasitic diseases accounted for 93% in the past, but over the years, single infection cases became less.
For example, in Korean rockfish, the Scuticociliatosis which was mostly in atumn to early spring was discovered in May. In case of flatfish, Trichodinosis and Scuticocillatosis were detected regardless of season. For bacterial diseases, Edwardsielosis which is mainly detected in higher than 20℃ water temperatures was observed. Also in Korea, vibrio sepsis was usually first detected from May to June, however in 2022, it was first detected in April. The Korea Institute of Health and Environment said this year is the first time that vibrio sepsis has been confirmed in April, and that changes in the marine environment are the cause.
The viral diseases are increasing as water temperatures rise, and the rate of mixed infection with bacterial and parasite is increasing, also the rate of parasitic diseases, parasitic and bacterial infections, and nutritional diseases that are resistant to high water temperatures is expected to increase steadily.
