Archive for October, 2011

Zooplanktivory ameliorates the effects of ocean acidification on the reef coral Porites spp

I tested the hypothesis that the effects of high pCO2 and temperature on massive Porites spp. (Scleractinia) are modified by heterotrophic feeding (zooplanktivory). Small colonies of massive Porites spp. from the back reef of Moorea, French Polynesia, were incubated for 1 month under combinations of temperature (29.3°C vs. 25.6°C), pCO2 (41.6 vs. 81.5 Pa), and feeding regimes (none vs. ad libitum access to live Artemia spp.), with the response assessed using calcification and biomass. Area-normalized calcification was unaffected by pCO2, temperature, and the interaction between the two, although it increased 40% with feeding. Biomass increased 35% with feeding and tended to be higher at 25.6°C compared to 29.3°C, and as a result, biomass-normalized calcification statistically was unaffected by feeding, but was depressed 12–17% by high pCO2, with the effect accentuated at 25.6°C. These results show that massive Porites spp. has the capacity to resist the effects on calcification of 1 month exposure to 81.5 Pa pCO2 through heterotrophy and changes in biomass. Area-normalized calcification is sustained at high pCO2 by a greater biomass with a reduced biomass-normalized rate of calcification. This mechanism may play a role in determining the extent to which corals can resist the long-term effects of ocean acidification.

Continue reading ‘Zooplanktivory ameliorates the effects of ocean acidification on the reef coral Porites spp’

An acidic ocean threatens shellfish farms

For more than two decades, Rob Saunders grew his shellfish larvae in ordinary seawater drawn from the pristine natural environment of Baynes Sound, one of the most productive shellfish farming areas on B.C.’s West Coast.

Now the water in Baynes Sound is so acidic, Mr. Saunders’ fragile seed stock will die unless he artificially adjusts the PH level in his hatchery tanks.

“Because of ocean acidification the only way we can grow any larvae – oysters, clams, mussels, geoducks, you name it – is to take the CO2 out of the seawater,” said Mr. Saunders, CEO of Island Scallops, the largest producer of shellfish seed stock on province’s West Coast.

“We would have been out of business this year if we didn’t figure out how to solve the problem.”

Ocean acidification, a worldwide phenomenon linked to global warming, was identified as a serious threat to the shellfish industry in Oregon and Washington state five years ago.

Caused by the absorption of excess CO2 from the atmosphere, ocean acidification lowers ocean PH levels and reduces the concentration of calcium carbonate, a key building block of seashells and other marine skeletons.

Mr. Saunders is currently taking part in a two-year, $250,000 study of pH levels in the waters between Denman Island and Vancouver Island, about 20 kilometres south of Courtenay.

Funded by the federal Department of Fisheries and Oceans, the study involves rigorous daily testing using an infrared gas analyzer to detect ocean carbon dioxide. DFO officials refused to discuss data that has been gathered so far, saying preliminary results won’t be made public until sometime next spring.

However, Mr. Saunders said there’s no doubt that acidification is affecting the survival of shellfish larvae.

“We grow them under different concentrations of CO2 to see how they live and die,” he said. “And they die if we use the ocean water. Period.”

The changes are not yet severe enough to affect bivalves that have already formed their shells, he added.

Still, ocean acidification is a top priority for biologists at the recently opened Deep Bay Marine Field Station, an $8.5-million shellfish research, development and training centre a few kilometres from Mr. Saunders’s scallop farm.

“It’s a complex issue that could have major repercussions for the west coast shellfish industry, but it’s only come to our attention in the last few years,” said Brian Kingzett, manager of the Deep Bay facility. “We’re just beginning to study it.”

Brennan Clarke, The Globe and Mail, 30 October 2011. Article.

Distinguishing between the effects of ocean acidification and ocean carbonation in the coccolithophore Emiliania huxleyi

The coccolithophore Emiliania huxleyi was cultured under a broad range of carbonate chemistry conditions to distinguish the effects of individual carbonate system parameters on growth, primary production, and calcification. In the first experiment, alkalinity was kept constant and the fugacity of CO2(fCO2) varied from 2 to 600 Pa (1 Pa ≈ 10 µatm). In the second experiment, pH was kept constant (pHfree = 8) with fCO2 varying from 4 to 370 Pa. Results of the constant-alkalinity approach revealed physiological optima for growth, calcification, and organic carbon production at fCO2 values of ∼ 20 Pa, ∼ 40 Pa, and ∼ 80 Pa, respectively. Comparing this with the constant-pH approach showed that growth and organic carbon production increased similarly from low to intermediate CO2 levels but started to diverge towards higher CO2 levels. In the high CO2 range, growth rates and organic carbon production decreased steadily with declining pH at constant alkalinity while remaining consistently higher at constant pH. This suggests that growth and organic carbon production rates are directly related to CO2 at low (sub-saturating) concentrations, whereas towards higher CO2 levels they are adversely affected by the associated decrease in pH. A pH dependence at high fCO2 is also indicated for calcification rates, while the key carbonate system parameter determining calcification at low fCO2 remains unclear. These results imply that key metabolic processes in coccolithophores have their optima at different carbonate chemistry conditions and are influenced by different parameters of the carbonate system at both sides of the optimum.

Continue reading ‘Distinguishing between the effects of ocean acidification and ocean carbonation in the coccolithophore Emiliania huxleyi’

Cold temperatures are all part of the job

Working in temperatures considerably colder than any she had ever experienced in New Zealand became routine for Dr Victoria Metcalf when she spent several summers outdoors undertaking research in the frigid conditions of the Antarctic.

Dr Metcalf, from the Faculty of Agriculture and Life Sciences at Lincoln University, travelled to Scott Base teaming up with other New Zealand and international scientists to study the effect of decreasing pH levels in the Southern Ocean on the survival of the Antarctic bivalve (shellfish), Laternula elliptica.

After her team had collected the shellfish from the mud on the ocean floor Dr Metcalf and the team took them to Scott Base and raised them in purpose built indoor tanks filled with sea water from the local area. The shellfish were then brought back to a New Zealand facility where acidification scenarios were simulated and the effects on the them were analysed.

Continue reading ‘Cold temperatures are all part of the job’

Impact of rapid sea-ice reduction in the Arctic Ocean on the rate of ocean acidification

The largest pH decline and widespread undersaturation with respect to aragonite in this century due to uptake of anthropogenic carbon dioxide in the Arctic Ocean have been projected. The reductions in pH and aragonite saturation state have been caused primarily by an increase in the concentration of atmospheric carbon dioxide. However, in a previous study, simulations with and without warming showed that these reductions in the Arctic Ocean also advances due to the melting of sea ice caused by global warming. Therefore, future projections of pH and aragonite saturation in the Arctic Ocean will be affected by how rapidly the reduction in sea ice occurs. In this study, the impact of sea-ice reduction rate on projected pH and aragonite saturation state in the Arctic surface waters was investigated. Reductions in pH and aragonite saturation were calculated from the outputs of two versions of an earth system model (ESM) with different sea-ice reduction rates under similar CO2 emission scenarios. The newer model version projects that Arctic summer ice-free condition will be achieved by the year 2040, and the older version predicts ice-free condition by 2090. The Arctic surface water was projected to be undersaturated with respect to aragonite in the annual mean when atmospheric CO2 concentration reached 480 (550) ppm in year 2040 (2048) in new (old) version. At an atmospheric CO2 concentration of 520 ppm, the maximum differences in pH and aragonite saturation state between the two versions were 0.08 and 0.15, respectively. The analysis showed that the decreases in pH and aragonite saturation state due to rapid sea-ice reduction were caused by increases in both CO2 uptake and freshwater input. Thus, the reductions in pH and aragonite saturation state in the Arctic surface waters are significantly affected by the difference in future projections for sea-ice reduction rate. The critical CO2 concentration, at which the Arctic surface waters become undersaturated with respect to aragonite on annual mean bias, would be lower by 70 ppm in the version with the rapid sea-ice reduction.

Continue reading ‘Impact of rapid sea-ice reduction in the Arctic Ocean on the rate of ocean acidification’

Coastal fund support EDC ocean acidification project

The Associated Student’s Coastal Fund of UCSB has announced that they will be contributing a $14,000 grant to the Environmental Defense Center (EDC) in support of the Coast and Ocean program.

The grant is specifically to underwrite EDC’s efforts to address the significant environmental impacts of ocean acidification in the Santa Barbara Channel and in oceans throughout the world. The grant will also support a conference at UCSB, which will bring together experts on ocean chemistry issues to educate the University community about ongoing research and decision-making processes, to engender understanding of the roles of the various stakeholders and regulators, and to encourage student and faculty engagement in the policy-making process.

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Ocean acidification and coral reefs: a video research diary with Jack Silverman and Ken Caldeira

Continue reading ‘Ocean acidification and coral reefs: a video research diary with Jack Silverman and Ken Caldeira’

Ocean acidification and coral reefs: a research video diary with Kenny Schneider and Ken Caldeira

Continue reading ‘Ocean acidification and coral reefs: a research video diary with Kenny Schneider and Ken Caldeira’

The Madotz Urgonian platform (Aralar, northern Spain): paleoecological changes in response to Early Aptian global environmental events

Sudden addition of carbon dioxide to the atmosphere can reduce the CaCO3 saturation and weaken the biocalcification potential of marine organisms in shallow water and in open marine settings. In this study, the response of an Aptian neritic carbonate environment to sudden addition of carbon dioxide at the beginning of Oceanic Anoxic Event 1a is investigated. The beginning of the OAE1a was coupled with a major perturbation on the carbon cycle as indicated by a negative carbon isotope excursion in the sedimentary record. This isotope anomaly is regarded as a proxy for massive addition of volcanic or methane-derived CO2 to the atmosphere within only a few 104 years. The impact of a rapid change in atmospheric pCO2 on biocalcifiers in low latitude shallow-water settings can be studied in a well preserved Aptian carbonate shelf succession cropping out today in the Aralar mountains (NE Spain). The Madotz section (N Spain) preserves a continuous shallow water record that was deposited on a mid-latitude, Atlantic-oriented mixed siliciclastic-carbonate ramp. Lower Aptian sediments consist of two neritic limestone successions separated by orbitolinid-rich marlstone enriched in organic matter. The lower neritic limestone succession ends with a submarine hardground and the transition from the lower neritic limestone to the orbitolinid marlstone coincides with a negative spike in the organic carbon isotope record. This negative spike can be correlated with the negative carbon isotope anomaly marking the base of OAE1a. The paleoecological change coinciding with the base of OAE1a occurred at a time of sea level rise and it coincided with a demise of heavily calcified nannoconids in the Tethys and Pacific Oceans. The paleoecological change observed in the Madotz section corresponds to a comparable change seen in the more distal and more expanded carbonate ramp section (Igaratza) at the Aralar Mountains. Ocean acidification caused by sudden increase in pCO2 may explain reduced calcification potential of some shallow water calcifiers. Calcification crisis was amplified by rising sea level, increasing temperatures and increased flux of detrital material and nutrients from continents into coastal seas.

Continue reading ‘The Madotz Urgonian platform (Aralar, northern Spain): paleoecological changes in response to Early Aptian global environmental events’

The abiotic formation of TEP under different ocean acidification scenarios

In view of rising atmospheric CO2 concentrations, the question if the marine biological carbon pump will increase or decrease in efficiency as ocean acidification progresses becomes central for predictions of future atmospheric pCO2. Aggregation and sinking of aggregates contributes significantly to the flux of carbon to depths and changes in aggregation behavior will have far reaching consequences for the biological pump. The abundance and characteristics of Transparent Exopolymer Particles, TEP, are central in regulating aggregation. We investigated the impact of ocean acidification on the abiotic formation of TEP from their precursors. Our results demonstrate that, contrary to earlier suggestions, ocean acidification as expected in the future ocean has no impact on the equilibrium conditions between TEP and their precursors. However, if the carbonate system is altered by adding acid, which does not simulate the future ocean carbonate system correctly, TEP concentration increases with decreasing pH, presumably due to changes in total alkalinity (TA). This implies that abiotic TEP formation is sensitive to changes in TA, but not pH. The discrepancy in results caused by different experimental approaches emphasizes the fact that acidification experiments do not mimic future conditions adequately and may even be misleading.

Continue reading ‘The abiotic formation of TEP under different ocean acidification scenarios’

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Ocean acidification in the IPCC AR5 WG II

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