Numbers of marine mollusks have fallen in recent decades in parts of the eastern Mediterranean as warming waters have made conditions unsuitable for native species, a new study showed Wednesday.
The waters off the coast of Israel – among the warmest in the Mediterranean Sea – have already warmed by three degrees Celsius within four decades, with water temperatures regularly approaching 30C (86 Fahrenheit) in summer.
The waters off the coast of Israel are among the hottest in the Mediterranean Sea and have already warmed to 3C within four decades.
(Photo: AFP)
An international team of researchers, writing in the journal Proceedings of Royal Society B, studied the effect of these warm waters on local populations of marine mollusks, as well as invasive species. coming from the Red Sea through the Suez Canal.
Paolo Albano, from the Department of Paleontology at the University of Vienna, first tried to compare numbers of local and non – native species on the Israeli shelf on the eastern Mediterranean.
But he quickly realized the extent to which local mollusc numbers had declined.
“I was hoping to find a Mediterranean ecosystem with these‘ newcomers ’,” he told AFP.
“However, after the first dive, I immediately realized that it was another problem: the lack of native Mediterranean species, even the most common ones you would find everywhere in the Mediterranean terrestrial. “
Local ‘species eradication’
Albano and his colleagues compared mollusc numbers identified from more than 100 seabed samples with historical records, finding that only 12 percent of molluscs were historically present. in shallow sediments still present.
Suez Canal
(Photo: AP)
On rocky reefs, that figure stood at just five percent.
The team also estimated that 60 per cent of the remaining mollusc populations do not reach breeding size, giving the region a “demographic sink” for some species.
Albano said that while other factors may play a role in these declining populations, particularly the impact of non-native species and pollution, the overall movement appears to be caused by oceans. warming.
“Temperature tolerance is a key issue here and most of the native Mediterranean species in the easternmost Mediterranean are bordered to the extent that they suffer from temperature, “he said.
Compared to local molluscs, numbers of tropical species entering the Mediterranean Sea through the Suez Canal thrived.
coral reef in Israeli waters
(Photo: Reuters)
This species reversal marks the beginning of a “modern ecosystem,” the authors said, and a massive loss of native species appears to be too important to correct.
Albano described the Eastern Mediterranean as “paradigmatic of what is happening in marine ecosystems as a result of global warming: species respond to warming by shifting their fields and in some of areas this means eradicating species locally. “