Phaeocystis globosa (Prymnesiophyceae) is a globally dominating phytoplankton species. It plays an important role in both the global sulfur and carbon cycles, by the production of dimethylsulfide (DMS) and the drawdown of inorganic carbon. Phaeocystis globosa has a polymorphic life cycle and is considered to be a harmful algal bloom (HAB) forming species. All these aspects make this an interesting species to study the effects of increasing carbon dioxide (CO2) concentrations, due to anthropogenic carbon emissions. Here, the combined effects of three different dissolved carbon dioxide concentrations (CO2(aq)) (low: 4 μmol kg−1, intermediate: 6–10 μmol kg−1 and high CO2(aq): 21–24 μmol kg−1) and two different light intensities (low light, suboptimal: 80 μmol photons m−2s–1 and high light, light saturated: 240 μmol photons m−2s−1) are reported. The experiments demonstrated that the specific growth rate of P. globosa in the high light cultures decreased with increasing CO2(aq) from 1.4 to 1.1 d−1 in the low and high CO2 cultures respectively. Concurrently, the photosynthetic efficiency increased with increasing CO2(aq) from 0.56 to 0.66. The different light conditions affected photosynthetic efficiency and chlorophyll-a concentrations, both of which were lower in the high light cultures as compared to the low light cultures. These results suggest that in the future, inorganic carbon enriched oceans, P. globosa will become less competitive and feedback mechanisms to global change may decrease in strength.
Archive for December 21st, 2011
Tags: biological response, growth, photosynthesis, phytoplankton
Tags: chemistry, modeling
The acidification of the ocean by anthropogenic CO2 absorbed from the atmosphere is now well-recognized and is considered to have lowered surface ocean pH by 0.1 since the mid-18th century. Future acidification may lead to undersaturation of CaCO3 making growth of calcifying organisms difficult. However, other anthropogenic gases also have the potential to alter ocean pH and CO2 chemistry, specifically SOx and NOx and NH3. We demonstrate using a simple chemical model that in coastal water regions with high atmospheric inputs of these gases, their pH reduction is almost completely canceled out by buffering reactions involving seawater HCO3− and CO32− ions. However, a consequence of this buffering is a significant decrease in the uptake of anthropogenic CO2 by the atmosphere in these areas.
The burning of fossil fuels is causing a rise of acid levels in the ocean, and it may be harming sea life, according to a new study by researchers at Scripps Institution of Oceanography.
Scientists have found ocean water becomes more acidic because about a quarter of the carbon emissions in the air go into the sea.
Jennifer Smith, an assistant professor of Marine Ecology at Scripps Institute of Oceanography, says that affects ocean life.
“As the water becomes more acidic, it becomes more difficult for things that have skeletons and shells, things like mussels and oysters. It makes it more difficult for them to build shells,” she said.