By the middle of the 21st century, many fish species could be reduced by 20-30% due to the lack of oxygen in the oceans caused by global warming.
Climatic changes are reflected in one way or another on all the inhabitants of the Earth. According to paleontologists, previous significant warming led to a decrease in the size of animals. In recent years, scientists have also noted a decrease in the body weight of some species, such as reindeer. According to experts, a similar fate awaits fish. In 2014, scientists announced the simultaneous "weight loss" of several species of the North Sea at once: herring, haddock and sole.
The authors of the new study described the mechanism that causes fish to gradually lose weight. Scientists say that this process will affect not only fish, but also other inhabitants of the sea with gills, including squid and lobsters.
These organisms are ectotherms, their body temperature depends on the ambient temperature. As the ocean gets warmer, fish begin to adapt to the change and their metabolism speeds up. Metabolic rate is related to oxygen uptake. The gas enters the body with water, and then the fish throws the "waste" water through the gills. Fish also require more oxygen as they grow.
Water flows through the gills, enriching the body with oxygen, Global Change Biology.
With the warming oceans, animals face two challenges. The first is that the gills, due to their special shape, do not grow as fast as other organs. The second problem is that because of warming, the oxygen level in the oceans will decrease.
To adapt to a lack of oxygen, fish shrink from generation to generation. According to scientists, at the current rate of warming, the inhabitants of the seas can lose, on average, 20-30% of their body weight over the years. Species such as bluefin tuna - fast and agile fish that need a lot of oxygen - could be reduced by 30% by the middle of the 21st century. Sharks will also "lose weight", especially large species.
Scientists believe that reducing carbon dioxide emissions will help mitigate this effect.
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The study is published in the journal Global Change Biology.
Natalia Pelezneva
