Drivers of Pontocaspian biodiversity RIse and DEmise

Scientists studying molluscs and other small creatures from the great lakes around the Caucasus have not only created a new understanding of a little-known biota and the threats it faces in a key region where Eastern Europe meets Central Asia. They have also pioneered an integrated approach to modelling which could help us better understand the risks of human activity causing entire ecosystems to collapse.

Various factors make the Black Sea and Caspian Sea an excellent place to study the Pontocaspians – unique species that evolved in the strange salinities of the lakes. “The Caspian Basin is an isolated basin which allows you to look at evolutionary pathways and natural stresses,” says Dr Frank Wesselingh, senior researcher in marine biology at Leiden’s Naturalis Biodiversity Center in the Netherlands and project coordinator of PRIDE. “You have a great geological archive and a self-contained natural laboratory all in one.”

Response to stress

This outstanding geological record provides an account of how the region’s climate and environment changed over 3 million years and how biota responded. The scientists have used it to gauge how the Pontocaspians are coping with today’s harsh conditions.

They came up with some dramatic predictions. “We got a really good grip on what drives lake-level variation and what impact this has on the entire system. There is a good probability that the level of the Caspian Sea will drop 18 metres in the next 80 years,” Dr Wesselingh says. Should this occur, vast extensions currently covered by the waters of the Caspian Sea will become dry steppe, as has already happened with the Aral Sea to the east. “That will have a lot of effect on biodiversity but will also have a devastating impact on coastal infrastructures in those areas,” Dr Wesselingh adds.

Biota ups and downs

The PRIDE team were able to map when and where the biota changed during the Quaternary period, giving a chronicle of the ups and downs of the Pontocaspians through time. Combining palaeontology, molecular biology and geology allowed them to pinpoint the origin and timing of several species, establishing pathways leading back to some surprising parts of the globe. “We did this for two mud snails, Ecrobia, which have a common ancestor in an Arctic-North Atlantic species,” says Dr Wesselingh.

The work allowed the PRIDE team to create a taxonomic information platform on the Pontocaspian biota and an information system on climate data, anthropogenic pressures and biodiversity in the Caspian Sea–Black Sea region.

It also allowed them to make a first estimation of the devastating effects that human activity – invasive species, habitat destruction, pollution – is having on the Pontocaspians. “Half to three quarters of species are either threatened, highly threatened or even extinct and this has happened in the last 50 years,” says Dr Wesselingh.

At a time when reports such as the recent UN report on biodiversity are charting unprecedented rates of extinction, the PRIDE study homes in on how robust one biota is under stress.

“You always hear that nature can deal with anything and it is true that nature can deal with a lot of things but not forever. If you go beyond a certain boundary, a system can collapse into a new state where there is no turning back. So our question is what does it take to get a system like the Pontocaspians over the tipping point?” asks Dr Wesselingh.

This research was undertaken with the support of the Marie Skłodowska-Curie programme.

Keywords
PRIDE, Pontocaspian, biodiversity, molluscs, Caspian Sea, Black Sea, evolutionary pathways, ecosystem collapse, extinction

Reference source:
Drivers of Pontocaspian biodiversity RIse and DEmise