In the 450 million years in which sharks and rays populate the oceans, they have repeatedly benefited from higher temperatures. Global warming, however, is currently increasing the animals threatened by overfishing and habitat loss: because the change is applied too quickly, whether it is unlikely that the new environmental conditions use them, according to Wiener Paleobiologist with colleagues in the specialized magazine “Biology” . They analyzed which environmental factors are decisive.
More than 1,200 species of sharks and rays are currently alive, more than a third of them are acutely threatened by overfishing and the destruction of their habitat. The biodiversity of these animals that belong to cartilage fishing was influenced by a number of events during the Mesozoic (252-66 million years ago).
Fossil shark and ray teeth document biodiversity
An international research team around Manuel A. Staggl and Jürgen Kriwet of the Institute of Paleontology at the University of Vienna has investigated which driving forces have played a role and how climate heating influences its diversity. To do this, they used data on climate fluctuations during the Jura (before 200-143 million years) and the chalk period (143-66 million years ago), the biodiversity estimated them with the help of fossil sharks and shining teeth.
The researchers identified three decisive environmental factors: in the past, higher temperatures are an increase in sea level and more flat coastal waters positive due to a strong split in the land mass. This led to a larger habitat and all year round stable conditions in tropical and subtropical areas that expanded far from the north and south. Because of their adaptability, the cartilage fish could colonize these stable and complex ecosystems quickly and efficiently with large biodiversity.
For the first time, negative effects showed high CO2 values
“For the first time we have shown that higher atmospheric CO2 values have a negative influence on the variety of cartilage fishing,” Kriwet told APA. Because a lot of CO2 in the atmosphere also increases the CO2 content in the oceans, leading to an acidification of the seawater.
“Until now we have always assumed that this acidification does not affect so much vertebrated animals,” said the paleobiologist. This should actually apply to bone fishing, “but it seems to be the case that with cartilage fish that have no bony skeleton, there can be changes in embryonic development.” Corresponding indications of direct physiological effects of higher CO2 concentrations in the water would have delivered laboratory tests.
Mechanisms not yet fully clarified
According to Staggl, the exact mechanisms that had the negative effect of CO2 on the biodiversity of sharks and rays have not yet been fully clarified in a broadcast. The extremely warm climate 80 to 65 million years ago combined with extremely warm seas and high water levels led to a huge increase in diversity in sharks and rays. It must still be clarified why a high CO2 content clearly did not matter.
Due to the negative effects of a higher CO2 content of the oceans combined with the rapid change of ecosystems due to the rapid temperature rise, the researchers consider it “unlikely” that sharks and rays benefit from the current global warming. For this reason, “measures for your protection are urgently required. It is not just about the cartilage fish, but about the preservation of entire ecosystems. “Because without the best robbers the ecosystems would collapse,” Kriwet emphasized in a broadcast.
Source: Krone
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