Archive for March, 2010

Postdoctoral Research position: Fish ecophysiology & the global marine carbon cycle

School of Biosciences
Postdoctoral Research position (Ref: N2614)
Reporting To: Dr Rod Wilson
Salary will be in the range £26,523 to £31,671 per annum, depending on qualifications and experience
Fixed Term contract for 3 years

The School of Biosciences, Exeter wishes to recruit a Postdoctoral Researcher to work under the supervision of Dr. Rod Wilson on a 3-year grant funded by the Natural Environment Research Council (NERC) to start as early as 1 June 2010. The project concerns the physiological and environmental controls of gut carbonate excretion in marine fish (Wilson et al., 2009 Science 323: 359-362), and the chemistry and fate of these carbonates within the ocean. These data will then be used to improve modelling of the global contribution of fish to the marine inorganic carbon cycle. The successful applicant will form the vital link in a multidisciplinary research team from Exeter, CEFAS (Lowestoft), UEA, Manchester, Southampton, the Met Office Hadley Centre, and Universite Libre de Bruxelles.
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Paleo-perspectives on ocean acidification

The anthropogenic rise in atmospheric CO2 is driving fundamental and unprecedented changes in the chemistry of the oceans. This has led to changes in the physiology of a wide variety of marine organisms and, consequently, the ecology of the ocean. This review explores recent advances in our understanding of ocean acidification with a particular emphasis on past changes to ocean chemistry and what they can tell us about present and future changes. We argue that ocean conditions are already more extreme than those experienced by marine organisms and ecosystems for millions of years, emphasising the urgent need to adopt policies that drastically reduce CO2 emissions.
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EPOCA/EUR-OCEANS data-mining compilation on the impacts of ocean acidification

The uptake of anthropogenic CO2 by the oceans has led to a rise in the oceanic partial pressure of CO2, and to a decrease in pH and carbonate ion concentration. This modification of the marine carbonate system is referred to as ocean acidification. Numerous papers report the effects of ocean acidification on marine organisms and communities but few have provided details concerning full carbonate chemistry and complementary observations. Additionally, carbonate system variables are often reported in different units, calculated using different sets of dissociation constants and on different pH scales. Hence the direct comparison of experimental results has been problematic and often misleading. The need was identified to (1) gather data on carbonate chemistry, biological and biogeochemical properties, and other ancillary data from published experimental data, (2) transform the information into common framework, and (3) make data freely available. The present paper is the outcome of an effort to integrate ocean carbonate chemistry data from the literature which has been supported by the European Network of Excellence for Ocean Ecosystems Analysis (EUR-OCEANS) and the European Project on Ocean Acidification (EPOCA). A total of 166 papers were identified, 86 contained enough information to readily compute carbonate chemistry variables, and 67 datasets were archived at PANGAEA – The Publishing Network for Geoscientific & Environmental Data. This data compilation is regularly updated as an ongoing mission of EPOCA.
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News from the Catlin expedition in the Canadian Arctic

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Ecosystems under threat from ocean acidification

Acidification of the oceans as a result of increasing levels of atmospheric carbon dioxide could have significant effects on marine ecosystems, according to Michael Maguire presenting at the Society for General Microbiology’s spring meeting in Edinburgh this week.

Postgraduate researcher Mr Maguire, together with colleagues at Newcastle University, performed experiments in which they simulated ocean acidification as predicted by current trends of carbon dioxide (CO2) emissions. The group found that the decrease in ocean pH (increased acidity) resulted in a sharp decline of a biogeochemically important group of bacteria known as the Marine Roseobacter clade. “This is the first time that a highly important bacterial group has been observed to decline in significant numbers with only a modest decrease in pH,” said Mr Maguire.
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The emergent effects of ocean acidification

Ocean acidification is considered a threat to global marine ecosystems. It is caused by rising atmospheric carbon dioxide (CO2) concentrations, which reduce seawater pH and drive large-scale changes in the carbonate chemistry. This process of ocean acidification is underway and will accelerate with CO2 emissions. Many marine organisms are sensitive to changes in the carbonate chemistry, and their physiological/behavioral responses to ocean acidification could lead to profound ecological shifts in marine ecosystems. However, the ecosystem responses to ocean acidification are still largely unknown. Most experiments measure the responses of a single species to extreme conditions over short time periods, and may not accurately predict the consequences to ecosystems. Additionally, there is a limited ability to make inferences about ecosystem effects from single species experiments because the responses of marine communities are likely to be complicated by species interactions. Despite these challenges, it is critical that scientists describe the effects of ocean acidification on marine communities and ecosystems to inform effective management.
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Arctic acid test

A team of researchers and explorers have set off to gather vital winter Arctic Ocean measurements. Nigel Williams reports.

Scientists and explorers set out earlier this month on an Arctic expedition to examine the impact of an acidifying ocean on the region’s animals and plants.

The Catlin Arctic Survey will set up base in northern Canada for some of the scientists while a separate team will undertake a 500 km trek across sea ice off Greenland. Both will investigate the impact of ocean acidification on marine life, while the explorers will also measure variations in sea-ice thickness. Last year’s Catlin Arctic survey showed the Arctic ice was thinner than expected.

The expedition is also the first to take water samples from the sea ice in winter, as all previous Arctic measurements have been taken from ships in open water in summer.

As well as taking water samples, the researchers will collect plankton, pteropods — a type of swimming sea snail — and other local marine life and examine their reaction to increasing levels of acidity and also test how much carbon dioxide passes through the sea ice from the air into the sea.

Globally, oceans have seen a 30 per cent increase in acidity on pre-industrial levels that some scientists believe on current projections the pH of the oceans by 2050 could reach levels not seen for 20 million years. The Catlin scientists aim to establish the acidity of the Arctic Ocean, which appears to be acidifying faster than the rest of the world’s oceans because cold water absorbs more carbon dioxide.
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Ocean acidification a threat to local fisheries

The cold waters and currents of the North Pacific Ocean make the ecosystems around the Aleutians more susceptible to ocean acidification. Brad Warren with the Sustainable Fisheries Partnership spoke about the issue at the Western Alaska Interdisciplinary Science Conference Thursday.

“It’s a cross cutting threat to food webs that support fisheries. It affects the physiologies of many species in the marine system – gill function, reproduction, growth rates, blood chemistry, heart functions. The primary cause of death for fish exposed to high CO2 is heart attacks. It’s really a wide band of effectors of harm.”

Ocean acidification is caused by rising carbon dioxide levels in the atmosphere. It’s absorbed into the ocean, which creates carbonic acid. That acid increases the pH of the ocean waters. The most obvious and best understood problem is its affect on calcification of shells. Warren said the acid corrodes the shells of large species, like crabs and oysters, but also the shells of smaller organisms that are important links in the food web.
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Interactive comment on “On CO2 pertubation experiments: over-determination of carbonate chemistry reveals inconsistencies” by C. J. M. Hoppe et al.

Hoppe et al. report very large discrepancies between measured pCO2 and pCO2 calculated from other carbonate system parameters, in natural seawater treated to adjust pCO2. In particular, pCO2 calculated from the DIC (dissolved inorganic carbon) and TA (total alkalinity) pair is approximately 300 µatm lower than measured pCO2 and pCO2 calculated from other pairs, in the high pCO2 manipulations.

We suspect that these important discrepancies can probably be largely resolved by considering DOM (dissolved organic matter)-related alkalinity (TA-DOM), which was suggested to be important in a recent paper (Kim & Lee, 2009). Kim and Lee found large impacts on TA in phytoplankton culture experiments in which large amounts of DOM were generated, including a ratio of ~1:1 between amount of DOC (dissolved organic carbon) produced and increase in TA-DOM (their figure 3).

This could be highly relevant to explaining Hoppe et al’s results, if the source water for Hoppe et al.’s experiments (collected from the North Sea) was preconditioned by biological activity leading to high levels of TA-DOM. High levels of DOC occur in the North Sea, with levels in the central North Sea observed to vary seasonally between an average of about 100 µM C in autumn and an average of about 200 µM C in spring (figure 4 of Suratman et al., 2009).
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CO2 and phosphate availability control the toxicity of the harmful bloom dinoflagellate Karlodinium veneficum

We demonstrated that the toxicity of the harmful bloom dinoflagellate Karlodinium veneficum is regulated by both CO2 concentrations and phosphate availability. Semi-continuous cultures were grown in a factorial experiment under all combinations of 3 CO2 levels (230, 430 and 745 ppm) and 2 phosphate conditions (0.5 and 20 µM). After steady-state acclimation was achieved, karlotoxin cellular quotas and growth rates were determined in all 6 treatments. This strain produced both types of karlotoxin, KmTx-1 and KmTx-2. Chlorophyll a-normalized production of the 2 types of karlotoxins was much higher in P-limited cultures compared with P-replete ones under the same CO2 conditions. Increasing CO2 strongly stimulated production of KmTx-1 and decreased production of KmTx-2 in both treatments, but especially in P-limited cultures. Because the KmTx-1 toxin is an order of magnitude more potent than KmTx-2, total cellular toxicity was increased dramatically at high pCO2, particularly in P-limited cultures. Specific growth rates were accelerated by enriched CO2 in P-replete cultures, but not in P-limited treatments. Growth rates or toxicity of K. veneficum could increase substantially in the future with high CO2 levels in the ocean, depending on P availability, and so interactions between rising CO2 and eutrophication could cause major shifts in present day patterns of harmful algal toxin production. These results suggest that over the coming decades, rising CO2 could substantially increase karlotoxin damage to food webs in the often P-limited estuaries where Karlodinium blooms occur.
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