How community interactions amplify response of calcifying phytoplankton species to ocean acidification

Science Daily Posted: 14 Dec 2016 08:51 AM PST  See full article here

Coccolithophores, single-celled calcifying phytoplankton that play a key role in the Earth’s climate system, might lose their competitive fitness in a future ocean. In a field experiment investigating the effects of ocean acidification on the coccolithophore Emiliania huxleyi in its natural environment, the species failed to bloom. A team of researchers concludes, that a small response to ocean acidification was amplified through ecological interactions and causes a massive impact on the ecosystem.

Image result for coccolithophore Emiliania huxleyiPhoto:Dr. Jeremy R. Young Palaeontology Dept. The Natural History Museum LONDON, SW7 5BD, UK

…The uptake of fossil fuel carbon dioxide (CO2) by the ocean increases seawater acidity and causes a decline in carbonate ion concentrations. This process, termed ocean acidification, makes it energetically more costly for calcifying organisms to form their calcareous shells and skeletons. Several studies have shown that this also holds true for Emiliania huxleyi, the world’s most abundant and most productive calcifying organism….

…”In view of Emiliania‘s rather small changes in metabolic performance observed in previous laboratory experiments, we predicted that it would still be able to maintain its ecological niche in an acidifying ocean. What we observed came as a big surprise”…A small reduction in cellular growth due to ocean acidification caused the population size to gradually decline during the pre-bloom phase. “When it was time for Emiliania to start bloom formation, there were so few cells left in the plankton community that it couldn’t outgrow its competitors anymore,” reflects Ulf Riebesell….

The results of this study demonstrate the importance of investigating the effects of ocean acidification in natural communities….”If Emiliania huxleyi fails to maintain its important role, other, possibly non-calcifying, organisms take over. This might initiate a regime shift with far-reaching ecological and biogeochemical consequences,” Prof. Riebesell concludes.

Ulf Riebesell, Lennart T. Bach, Richard G. J. Bellerby, J. Rafael Bermúdez Monsalve, Tim Boxhammer, Jan Czerny, Aud Larsen, Andrea Ludwig, Kai G. Schulz. Competitive fitness of a predominant pelagic calcifier impaired by ocean acidification. Nature Geoscience, 2016; DOI: 10.1038/ngeo2854