Increasing ocean acidity due to climate change will damage the scales of sharks

Long-term stay in the water with the acidity that the oceans is projected to reach the year 2300, leading to partial damage scales Viper South African cat sharks. This conclusion was made by scientists from Germany and South Africa, which contained sharks of this species in water with different acidity for more than two months, and then compared the structure of the scales before and after the experiments. Article published in the journal Scientific Reports.

Industry and other activities of mankind during the last centuries led to a relatively sharp increase in concentration of carbon dioxide in the global atmosphere. According to the latest report of the world meteorological organization, published in November in 2018 averaged 407,8 ppm volume fraction (ppm) — one and a half times higher than in 1750. The most famous consequence of the increase in the concentration of carbon dioxide in the atmosphere is enhancing the greenhouse effect. However, in addition it influences other global climate processes, including the acidification of the oceans.

The fact that about 30 percent of anthropogenic (generated as a result of human activity) carbon dioxide is absorbed by the oceans, resulting in it formed carbon dioxide. Since the beginning of the industrial age largely due to this process, the pH of the oceans has decreased about 0.1, which corresponds to an increase of acidity by 26 percent. In some regions there is a periodic seasonal upwelling and serious decrease in pH from the average of 8.1 to 7.4 to 7.6 for several days.

Inhabiting such regions marine organisms, including kadukova South African cat shark (Haploblepharus edwardsii), able to adapt to changes in pH: this species is able to adjust blood pH under changing pH of the surrounding water. However, projections show that by the year 2300, the average pH may be reduced to 7.3, and the duration and frequency of local changes in pH can grow. Some species, including H. edwardsii, due to high life expectancy and other evolutionary features may not have time to adapt to such changes.

Lutz Auerswald (Lutz Auerswald) from Stellenbosch University and his colleagues from South Africa and Germany experimentally checked, as a relatively long-term changes in pH of the surrounding water affects kadukova South African cat shark. They selected 66 sharks to study short-term changes in pH (32 hours) and 13 for long-term studies with a duration of nine weeks. During the experiments, sharks from different groups were kept in aquariums with water with different levels of 7.31 pH to 8.05.

Blood tests showed that in both cases (short-term and long-term changes in acidity) shark fit good acid-alkaline balance under changes in the environment. However, the study scales showed that in the group that was exposed to the strong decrease in pH for the past nine weeks, the flakes were visibly corroded. The sharks, which included nine weeks under normal pH level, about 9 percent of the scales were damaged, while the shark, which spent nine weeks at a pH level of 7.36, was damaged 25 percent of the scales.

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