Man -made climate change is a challenge for countless living things. This also applies to sharks and rays. You benefit from global warming and the increase in sea level – but not from the increasing CO2 in the oceans, as a new study shows. The current climate change and its consequences therefore recover complex dangers for these cartilage fish and the ecosystems associated with them.
Hairs and rays are among the oldest earth residents: they have been populating the world’s oceans for around 450 million years. Some of her evolutionary flowering times experienced these cartilage fish during the Jura 200 to 143 million years and in the chalk period 143 to 66 million years. At that time, they benefited, among other things, that a wide range of different environmental conditions was available to them. Today this group of animals comprises more than 1200 known sharks and ray types. However, more than a third of the still living species are acute at the moment. A negative effect on the variety of rays and sharks, for example, have overfishing and loss of their habitat due to other human activities. But how big is the influence of current climate change?
A research team around Manuel Staggl from the University of Vienna has now examined this with a look into the past. For this purpose, the paleobiologists analyzed the climate fluctuations 200 to 66 million years ago and determined which environmental factors influenced the biodiversity of sharks and rays at the time. Based on more than 20,000 fossil shark and ray teeth, they determined the biodiversity for the individual age and settled them with the respective climate data. From this they developed possible future scenarios for the current global warming.
Three factors decisive
The evaluation showed that three environmental factors are decisive for shark and ray diversity: higher temperatures and more shallow water areas have a positive effect, but a higher CO2 content of the seas is negative. For the first time, the fossils show that a higher CO2 concentration and the associated acidification of the sea during the Jura and chalk time contributed to the extinction of individual types of sharks and rays. But why? “We cannot completely explain the exact mechanisms that have the negative effect of CO2 on the biodiversity of cartilage fish,” said StaGgl. However, laboratory tests on sharks and rays living today show that higher CO2 values in the water have serious consequences for fish metabolism. Among other things, they influence the senses of animals and change the skeletal development of the embryos.
Since more CO2 is currently dissolving into the oceans and they are exposed, the current, man -made climate change is therefore a great danger to cartilage fish. On the other hand, climate change may also have opportunities for sharks and rays, as the review shows: The increase in sea level during the Jura and the chalk period led to an increase in flat coastal waters and thus offered the bone fishing additional habitat. The higher temperatures also led to a warming of the water in the north and south, which offered stable living conditions with a rich food supply all year round. Both proved to be beneficial for the biodiversity of sharks and rays and could now step in again.
Climate change also harms sharks and rays
Nevertheless, the bottom line is that sharks and rays, like so many living things in climate change, are probably not a golden future, as the researchers emphasize, because the current developments differed from previous climate fluctuations: “At the moment, the environment is currently changing particularly quickly – unfortunately probably too quickly for them Animals and their ecosystems, ”explains Staggl. In view of the simultaneous overfishing, the loss of habitat and the increase in CO2 content in the seas, it is unlikely that these predatory fish will benefit from global warming.
According to the researchers, measures to protect the sharks and rays are therefore urgently required – also in order to obtain the marine ecosystems associated with them. “Because without the top robbers, the ecosystems would collapse,” emphasizes senior author Jürgen Kriwet from the University of Vienna. “By protecting sharks and rays, we invest directly in the health of our oceans and thus also in the people and industry that benefit from these ecosystems.”
Source: University of Vienna; Specialist articles: biology, DOI: 10.3390/Biology14020142