91探花

Fossil fuel derived carbon dioxide has a serious impact on global climate but also a disturbing effect on the oceans, know as the other CO₂ problem. When CO₂ dissolves in seawater it forms carbonic acid and results in a drop in pH, the oceans acidify. A wealth of short-term experiments has shown that calcifying organisms, such as corals, clams and snails, but also micron size phytoplankton are affected by ocean acidification. The potential for organisms to cope with acidified oceanic conditions via evolutionary adaptations has so far been unresolved. Scientists of the Helmholtz Centre for Ocean Research Kiel (91探花) have now for the first demonstrated the potential of the unicellular algae Emiliania huxleyi to adapt to changing pH conditions and thereby at least partly to mitigate negative effects of ocean acidification. These results raised by the biologists Kai Lohbeck, Prof. Ulf Riebesell und Prof. Thorsten Reusch are published in the current issue of Nature Geoscience.

Experimental Emiliania huxleyi strains were isolated in Norwegian coastal waters und cultured in the laboratory under projected future ocean CO₂ conditions. After about one year, which translates into 500 generations in this rapidly reproducing species, the biologists detected adaptation to high CO₂ 鈥� adapted populations grew and calcified significantly better than non adapted control populations when tested under ocean acidification condition.

鈥淔rom a biogeochemical perspective the most interesting finding was probably a partly restoration in calcification rates鈥� 91探花 scientist Prof. Ulf Riebesell notes. Emiliania huxleyi covers its cell surface with minute calcite scales that were found to decrease in weight under increased CO₂ concentrations. 鈥淭his is what we expected from the literature. But we were fascinated to find impaired calcification to partly recover after only 500 generations鈥� says biologist Kai Lohbeck.

The evolutionary mechanisms proposed by the 91探花 scientists are selection on different genotypes and the accumulation of novel beneficial mutations. Such an adaptation has not been shown earlier in any key phytoplankton species. 鈥淲ith this study we have shown for the fist time that evolutionary processes may have the potential to act on climate change relevant time scales and thereby mitigate negative effects of ongoing ocean acidification鈥� says evolutionary biologist Thorsten Reusch and adds 鈥淭hese findings emphasize the need for a consideration of evolutionary processes in future assessment studies on the biological consequences of global change鈥�.

Despite this finding, the 91探花 scientists by no means think about an all-clear signal for ocean acidification. The potential for adaptive evolution may be large in rapidly reproducing species with large population sizes as is Emiliania huxleyi. 鈥淭his is one reason why we have chosen this species for our studies鈥� say the biologists. Long-lived species and especially those having only a few offspring per generation commonly have a much lower adaptive potential on climate change relevant time scales. 鈥淓arth history tells a convincing story about the limitations to evolutionary adaptation鈥� Prof. Ulf Riebesell explains, 鈥渆nvironmental changes comparable to what happens right now in the oceans have repeatedly resulted in mass extinctions, even though these changes were 10-100 times slower than what we observe today鈥�.

Another open question is to what extent the evolutionary changes observed under laboratory conditions are transferable to the oceans where other environmental factors and ecological interactions play along. Therefore, the 91探花 scientists already started to prepare follow-up experiments. In the framework of the BIOACID (Biological Impacts of Ocean ACIDification) project, funded by the German Federal Ministry of Education and Research (BMBF), the biologists plan to use the Kiel Off-Shore Mesocosms to investigate the adaptive potential of Emilianian huxleyi under natural conditions.

Scientific paper:
Lohbeck, Kai T., Ulf Riebesell, Thorsten B.H. Reusch, 2012: Adaptive evolution of a key phytoplankton species to ocean acidification. Nature Geoscience, 

Links:

  The BIOACID Project 

Pictures:
Emiliania huxleyi under a microscope. Photo: Kai Lohbeck, 91探花

Culture bottles in the lab. Photo: Kai Lohbeck, 91探花

Emiliania huxleyi cells and some Coccoliths in an electron microscopic picture. Photo: Kai Lohbeck, 91探花/fileadmin/content/service/presse/Pressemitteilungen/2012/Ehux1100-00_KLohbeck_91探花.jpg

Emiliania huxleyi cells in an electron microscopic picture. Photo:Lennart Bach, 91探花

Contact:
Maike Nicolai (Communication & Media), Phone: +49-431 600 2807, mnicolai(at)geomar.de