Genetic adaptation likely to have occurred over many generations
Mussels from the Kiel Fjord were
discovered to be able to adapt to ocean acidification. In a comparative
experiment, they were less sensitive to increased carbon dioxide
concentrations than their counterparts from the North Sea.
A team of
scientists from GEOMAR Helmholtz Center for Ocean Research Kiel, Alfred
Wegener Institute, University of Bremen and Senckenberg Institute
studied this long-term genetic adaptation to the evolving environmental
When it comes to the effects of ocean acidification, the Baltic Sea is
a unique open-air laboratory. It is apparently also a “training pool”
for the mussel Mytilus edulis.
Over time, the population in the Kiel
Fjord has adapted to the seasonal acidic content in the western Baltic
In a comparative experiment, the mussel's larvae formed calcareous
shells faster than their counterparts in the North Sea. In addition,
more of the mussels from the Kiel Fjord survived. In addition, a
complementary, three-year multi-generational experiment suggests that
this adaptation was not achieved within a few generations, but over
several decades, perhaps even centuries or millennia.
The results of the two experiments were published in the current issue of the Science Advances journal.
For the comparative experiment, mussels were taken from the Kiel Fjord
in List on Sylt. They were acclimatised to the environmental conditions
in the North Sea. Their larvae, together with the larvae from the North
Sea, were then placed in environments at current carbon dioxide
concentrations (at 390 microatmospheres, with an extreme level of 2,400
The high concentration of carbon dioxide occurs
regularly in the Kiel Fjord, when the wind transports low-oxygen and
carbon dioxide-rich water to the surface. This is expected to occur
more frequently as a result of climate change.
At higher carbon dioxide concentrations, both larval populations
developed their first mussel shell at a slower rate. The shells were
also smaller. The larvae from the Kiel Fjord were more robust and had
higher survival rates.
differences between the Kiel and Sylter mussel larvae suggest that the
long-term genetic adaptation has played a decisive role in their
survival and their ability to construct shells,” said lead author Dr Jörn Thomsen in German. “From previous analysis, we know that the two populations also differ genetically.”
However, it is still unknown when the genetic adaptation took place. “It
could have taken place in recent decades when climate change,
over-fertilization and other factors led to an increase in
acidification and rising fluctuations in acidity,” said co-author Dr. Frank Melzner in German.
“It is also possible that the genetic
differences, from which the Fjord mussels benefitted from, were formed
thousands of years ago. The lower salt content of the Baltic Sea has
always influenced the carbonate level in the same way as acidification
Compared to those from the North Sea, the Baltic
Sea mussels were already exposed to lowered concentrations of dissolved
calcium carbonate, which they needed for shell construction, and hence
they had to adapted accordingly.
Link to the study