Ocean Acidification Hits Young Sea Stars Hardest

Ocean acidification hits young sea stars the hardest compared to their adult counterparts, according to a new study.

Young members of a species are sensitive as it is to environmental stresses compared to their parents, so with juvenile marine life now combating ocean acidification as well, it's taking its toll. That goes for the sea star Asterias rubens from the Baltic Sea, scientists from GEOMAR (Helmholtz Centre for Ocean Research Kiel) have shown.

Described in the journal Marine Ecology Progress Series, researchers simulated three different levels of acidification that could be reached in the Baltic Sea by the uptake of additional carbon dioxide (CO2) within the coming decades. The findings showed that even at slightly increased acidification, the small sea stars grew more slowly and ate less.

"In adult sea stars, we only observed this effect at significantly higher carbon dioxide concentrations in the water," researcher Dr. Jörn Thomsen said in a statement.

And if these young sea stars can't survive amidst ocean acidification, it could have damaging repercussions on the local ecosystem. The sea star Asterias rubens is an important predator, keeping the mussel population in the Western Baltic under control.

"If the sea stars suffer from the effects of ocean acidification, it could affect the entire ecosystem in the long run," explained first author Dr. Yasmin Appelhans. "For example, only a few sea stars live in the Bay of Lübeck, because of the low salinity there. The mussels in this region can spread unhindered and outcompete other species."

One possible explanation for why ocean acidification is most detrimental to young sea stars in particular, researchers say, is that CO2 hinders their ability to store calcium carbonate, which is vital in forming their protective skeletons, as is true of all calcifiers.

All marine life, from the smallest sea star to the biggest predatory shark, is struggling to adapt to climate change. For instance, recent research has shown that ocean acidification is robbing sharks of their predatory senses.