Archive for November, 2007

Build-up and decline of organic matter during PeECE III

Schulz et al.

Increasing atmospheric carbon dioxide (CO2) concentrations due to anthropogenic fossil fuel combustion currently change the ocean’s chemistry. Increasing oceanic [CO2] and subsequent decreasing seawater pH have the potential to significantly impact marine life. Here we describe and analyze the build-up and decline of a natural phytoplankton bloom initiated during the 2005 mesocosm Pelagic Ecosystem CO2 Enrichment study (PeECE III). We show that processes of inorganic carbon uptake in mixed surface waters and organic carbon export to depth were significantly enhanced at elevated CO2, while ammonium regeneration in deep waters was substantially reduced. This has important implications for our understanding of pelagic ecosystem functioning and future carbon cycling.

Continue reading ‘Build-up and decline of organic matter during PeECE III’

Primary production during nutrient-induced blooms at elevated CO2 concentrations

A CO2 enrichment experiment (PeECE III) was carried out in 9 mesocosms in which the seawater carbonate system was manipulated to achieve three different levels of pCO2. At the onset of the experimental period, nutrients were added to all mesocosms in order to initiate phytoplankton blooms. Primary production rates were measured by in-vitro incubations based on 14C-incorporation and oxygen production/consumption. Size fractionated particulate primary production was also determined by 14C incubation and is discussed in relation to phytoplankton composition. Primary production rates increased in response to nutrient addition and a net autotrophic phase with 14C-fixation rates up to 4 times higher than initial was observed midway through the 24 days experiment before net community production (NCP) returned to near-zero and 14C-fixation rates dropped below initial values. No clear heterotrophic phase was observed during the experiment. Based on the 14C-measurements we found higher cumulative primary production at higher pCO2 towards the end of the experiment. CO2 related differences were also found in size fractionated primary production. The most noticeable responses to CO2 treatments with respect to primary production rates occurred in the second half of the experiment when phytoplankton growth had become nutrient limited, and the phytoplankton community changed from diatom to flagellate dominance. This opens for two alternative hypotheses that the effects are either associated with mineral nutrient limited growth, and/or with a change in phytoplankton species composition. The lack of a clear net heterotrophic phase in the last part of the experiment supports the idea that a substantial part of production in the upper layer was not degraded locally, but either accumulated or exported vertically.
Continue reading ‘Primary production during nutrient-induced blooms at elevated CO2 concentrations’

US Geological Survey, UWI and THA collaborate on Tobago reef study

PORT-OF-SPAIN, Trinidad: In collaboration with researchers at University of the West Indies (UWI) in Trinidad, Buccoo Reef Trust (BRT), and the Tobago House of Assembly (THA), the United States Geological Survey (USGS) has been working to investigate the effects of increased atmospheric carbon dioxide on the Buccoo Reef in Tobago.

This 5-year research project is expected to help determine the impact of ocean acidification on coral reefs. Buccoo Reef is the only site outside the United States where data will be collected.

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Ocean Acidification, the Other Threat of Rising CO2 Emissions

Fossil fuel combustion and industrial processes release over six billion metric tons of carbon into the atmosphere each year. The consequences of these greenhouse gas emissions are often discussed in terms of rising global temperatures, but global warming is not the only threat from increased atmospheric concentrations of carbon dioxide (CO2). Ocean acidification, which occurs when CO2 in the atmosphere reacts with water to create carbonic acid, has already increased ocean acidity by 30 percent (Doney, 2006). Although the chemistry of this effect is well understood and not much debated, the full consequences of ocean acidification for marine ecosystems and human well-being are only beginning to be revealed.

Continue reading ‘Ocean Acidification, the Other Threat of Rising CO2 Emissions’

Oceans face the acid test

Acid oceans are the elephant in the room of global change – an event potentially so massive and profound in its implications for life on Earth that the world media has largely avoided it, governments shunned it and scientists discussed it mostly in muted tones, usually behind closed doors.

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Carbon cycle: Marine manipulations


The effect of increasing levels of atmospheric carbon dioxide on carbon uptake in and export from the upper ocean is one of the big questions in environmental science. But it can be tackled experimentally.

Continue reading ‘Carbon cycle: Marine manipulations’

Enhanced biological carbon consumption in a high CO2 ocean

Riebesell et al.

The oceans have absorbed nearly half of the fossil-fuel carbon dioxide (CO2) emitted into the atmosphere since pre-industrial times, causing a measurable reduction in seawater pH and carbonate saturation. If CO2 emissions continue to rise at current rates, upper-ocean pH will decrease to levels lower than have existed for tens of millions of years and, critically, at a rate of change 100 times greater than at any time over this period. Recent studies have shown effects of ocean acidification on a variety of marine life forms, in particular calcifying organisms. Consequences at the community to ecosystem level, in contrast, are largely unknown. Here we show that dissolved inorganic carbon consumption of a natural plankton community maintained in mesocosm enclosures at initial CO2 partial pressures of 350, 700 and 1,050 muatm increases with rising CO2.

Continue reading ‘Enhanced biological carbon consumption in a high CO2 ocean’

More acidic oceans could profoundly affect plankton

Microscopic ocean plants and animals may consume increasing amounts of carbon as oceans become more acidic, a new experiment carried out in the narrow fjords of Norway suggests. Scientists know that the world’s oceans are becoming more acidic from the absorption of carbon dioxide from power plants, factories, and vehicles. Experiments have already shown that acidity could eat away at the shells of marine organisms and interfere with the physiology of others. But Ulf Riebesell of the Leibniz Institute of Marine Sciences in Germany found that when he exposed waters to the carbon dioxide levels of today and of those projected for 2100 and 2150, plankton – the community of tiny ocean plants and animals – consumed more carbon without consuming more nutrients. However, it’s unclear whether this type of plankton consumption will be able to help lower carbon levels in the ocean, reducing climate change.
Continue reading ‘More acidic oceans could profoundly affect plankton’

Plankton enables enhanced carbon consumption in the ocean, finds study

A study published in the framework of the EU-funded CARBOOCEAN project in Nature reveals that ocean plankton will increase its consumption of dissolved inorganic carbon by up to 39% when CO2 concentration rises.

Continue reading ‘Plankton enables enhanced carbon consumption in the ocean, finds study’

Effects of increased atmospheric CO2 on small and intermediate sized osmotrophs during a nutrient induced phytoplankton bloom

Paulino et al.

We report the transient population dynamic response of the osmotrophic community initiated by a nutrient pulse in mesocosms exposed to different pCO2 levels as well as quantitative variations in phytoplankton and heterotrophic bacteria created by the difference in CO2 exposure.

Continue reading ‘Effects of increased atmospheric CO2 on small and intermediate sized osmotrophs during a nutrient induced phytoplankton bloom’

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Ocean acidification in the IPCC AR5 WG II

OUP book