Studies show effects of acidification on marine ecosystems
The future of several key marine organisms is severely threatened by the increasing acidification of oceans. Two partly EU-funded studies now published in the open access journal Biogeosciences lend emphasis to previous warnings from scientists worldwide concerning this secondary effect of excessive carbon dioxide (CO2) emissions.
Both studies were supported in part by the EPOCA ('European project on ocean acidification') project, which is funded under the Seventh Framework Programme (FP7). EPOCA brings together more than 100 researchers to study the biological, ecological, biogeochemical, and societal implications of ocean acidification.
The researchers looked at the effects of rising acidification on a critical part of the oceanic food chain and deep sea coral. Both of these areas show dramatic changes to the structure, function and services of polar ecosystems.
The world's oceans have absorbed one third of carbon dioxide emissions since 1800, thereby limiting global warming. However, significant changes in seawater chemistry have occurred, such as a decrease in pH levels, referred to as acidification.
The studies looked at two links in the Arctic marine ecosystem. The first, pteropods, are an abundant species of pelagic mollusc and a favourite food of zooplankton, herring, whales and other predators. Deep sea, cold water coral reefs provide shelter to many species and are an indicator of nearby seawater chemistry.
The other link, the cold water coral Lophelia pertusa is among the first to be affected by rising acidification. The species is also very difficult to gain access to because of its deep ocean habitat. In one of the first studies of its kind, researchers from the French Institut National des Sciences de l'Univers (CNRS-INSU) and the Royal Netherlands Institute for Sea Research teamed up to gather samples.
Pteropod samples were taken near the island of West Spitsbergen, Norway, using a new method which would not stress the animals and would allow them to live in captivity for a period of time. This type of observation is crucial to understanding how pteropods react to increased acidification and changes in aragonite levels.
In order to fully understand the effect of climate change on pteropods, the researchers are looking to extend the amount of time that the animals can be maintained in captivity. This further work will build on the methods used in the research, allowing for a more complete picture of how changing acidification levels may affect this critical link in the oceanic food chain.
Researchers found that coral samples collected in the North Sea were also affected by acidification. Unlike tropical corals, cold water coral reefs are constructed by one or two species. Increased acidification makes them grow at a slower rate, which could threaten the existence of these biological structures. Measuring their exact growth, however, is hampered by the fact that they do not grow in the same way as tropical reefs. By optimising future experiments on the reaction of deep sea coral to increased calcification, the researchers are hoping to extend and broaden the studies to other geographical and depth ranges.
At present, the only known way of controlling ocean acidification is by limiting future levels of CO2 in the Earth's atmosphere. While much attention is focused on the effect that rising temperatures would have, the effect of continued CO2 absorption by the oceans will have potentially dramatic effects on entire ecosystems.
Category: Project results
Data Source Provider: Biogeosciences
Document Reference: Comeau, S. et al. (2009) Biogeosciences (online) 6: 1877-1882. and Maier, C. et al. (2009) Biogeosciences (online) 6: 1671-1680.
Subject Index: Climate change & Carbon cycle research; Coordination, Cooperation; Scientific Research; Resources of the Sea, Fisheries