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Biogeographical regions of marine organisms, i.e., their distribution across different habitats, often overlap well with the major global ocean currents. The geological age of the currents plays a major role in this. The ocean circulation patterns are strongly linked to the distribution of the continents.

Many currents, such as land bridges and straits, only emerged a few million years ago. Others date back many millions of years. Their different ages in Earth's history have varying degrees of influence on the distribution areas of today's marine mollusks. This is shown by a new statistical study by SNSB paleontologist Thomas A. Neubauer from the Bavarian State Collection of Paleontology and Geology (SNSB-BSPG).

One example is the closure of the Isthmus of Panama 2.8 million years ago: its relatively young geological age is still visible in the similarity of the mollusk faunas of the tropical East Pacific and West Atlantic. In contrast, the difference between the faunas of the western and eastern Atlantic is much higher, partly because the Atlantic Ocean opened up more than 100 million years ago.

Neubauer and his colleagues have now published new overview maps of the geographical distribution of modern shallow-water mollusks of the world's oceans, such as bivalves and gastropods. The researchers correlated more than 3 million distribution data points for the animals with data on sea temperatures and the course of global ocean currents, particularly with regard to their geological history.

Their analyses show that temperature, ocean currents, and their paleogeographic development have a significant influence on life in shallow marine waters. Both factors are closely intertwined: today's global ocean currents are shaped by the transformation of land and sea over the last million years and thus also affect temperature distribution along the shelf areas.

The authors of the study, in Scientific Reports, also see a major threat in the current rapid pace of climate change.

"Temperature has an immense influence on marine organisms. It controls their metabolic functions, reproduction and the life cycle, as well as evolutionary processes such as speciation and extinction. Rapid global warming is already changing ocean surface temperatures, which in turn is affecting ocean currents. This has consequences for the biology and habitats of marine species and, as a result, for entire ecosystems," says Neubauer, lead author of the study.

The observational data on mollusks used in their work comes from two biodiversity databases: the Global Biodiversity Information Facility () and the Ocean Biodiversity Information System (). Researchers from the Natural History Museum in Vienna and the University of Malaga also participated in the study.