Archive for June, 2007

The effects of light, macronutrients, trace metals and CO2 on the production of calcium carbonate and organic carbon in coccolithophores—A review

The ratio of calcium carbonate to organic carbon (C) production in the surface ocean is thought to be one of the key marine biotic climate variables, through its effect on ocean C cycling. This ratio is significantly affected by calcification and photosynthetic C fixation in coccolithophores. The abundance of coccolithophores and their rates of calcification and organic C fixation are in turn affected by climate-related changes in the ocean. However, there still exists disagreement on the strength of this feedback mechanism, which is due to the complexity of interactions of the factors regulating phytoplankton growth and ecosystem functioning. This review gives a qualitative overview on experimental and field data of coccolithophores, mainly Emiliania huxleyi, that are most relevant to actual oceanographic conditions and are likely to change in the foreseeable future under a changing climate. The focus is on the bottom-up control factors light, macronutrients, trace metals and carbon dioxide (CO2), which can be of use in modelling studies.

Several trends have been identified that should be considered when attempting to simulate E. huxleyi growth. Light seems to be the central factor determining the occurrence of blooms. At low irradiance the calcite to organic C production ratio increases, but appears to decrease again when irradiance becomes severely limiting. Phosphate and nitrate limitation lead to an increase in the ratio of calcite to particulate organic carbon (POC), which is also shown for zinc but not for iron. This is mainly due to the fact that coccolith formation is generally less dependant on nutrient concentration than is cell replication. Finally, CO2-related effects in E. huxleyi and the other bloom-forming coccolithophore species Gephyrocapsa oceanica have been observed. Under high light conditions, calcification decreases with increasing CO2 concentration. Depending on the nutrient status of the cells, the production of POC strongly increases, or decreases under elevated CO2 concentrations. In contrast, under low light conditions no sensitivity of calcification to CO2 was observed, whereas POC production always strongly increases with CO2 under nutrient-replete conditions. How different growth conditions taken together finally affect coccolithophore calcification and organic C production is discussed for some factors, but needs further investigation.

Zondervan, I., 2007. The effects of light, macronutrients, trace metals and CO2 on the production of calcium carbonate and organic carbon in coccolithophores–A review. Deep Sea Research Part II: Topical Studies in Oceanography 54(5-7): 521-537. Article.

Effect of rising atmospheric carbon dioxide on the marine nitrogen fixer Trichodesmium

Diazotrophic (N2-fixing) cyanobacteria provide the biological source of new nitrogen for large parts of the ocean. However, little is known about their sensitivity to global change. Here we show that the single most important nitrogen fixer in today’s ocean, Trichodesmium, is strongly affected by changes in CO2 concentrations. Cell division rate doubled with rising CO2 (glacial to projected year 2100 levels) prompting lower carbon, nitrogen and phosphorus cellular contents, and reduced cell dimensions. N2 fixation rates per unit of phosphorus utilization as well as C:P and N:P ratios more than doubled at high CO2, with no change in C:N ratios. This could enhance the productivity of N-limited oligotrophic oceans, drive some of these areas into P limitation, and increase biological carbon sequestration in the ocean. The observed CO2 sensitivity of Trichodesmium could thereby provide a strong negative feedback to atmospheric CO2 increase.
Barcelos e Ramos, J., H. Biswas, K. G. Schulz, J. LaRoche, and U. Riebesell (2007), Effect of rising atmospheric carbon dioxide on the marine nitrogen fixer Trichodesmium, Global Biogeochemical Cycles, 21, GB2028, doi:10.1029/2006GB002898. Article.

Climate change movie begins production

OXFORD, England, June 20 (UPI) — Production has started on a British-New Zealand-funded film designed to enable scientists to explain climate change and what can be done about it.

The $1.1 million (600,000 pound) movie is a collaborative effort of Britain’s Oxford University and New Zealand’s Victoria University of Wellington.

The film — with the working title “The Tipping Point” — is being produced and directed by David Sington of DOX Productions and Simon Lamb of Oxford University, who collaborated several years ago to produce the acclaimed 8-hour BBC television series “Earth Story.”

The stars of the new film will be scientists who are involved in studying climate change.

“Al Gore’s ‘An Inconvenient Truth’ has helped increase many people’s awareness of climate change,” said Lamb. “In our film we want the audience to learn about the science of climate change from the scientists themselves and find out how they are tackling the problem.”

The film is expected to be released in 2009, both in theaters and on DVD.

Copyright 2007 by United Press International. All Rights Reserved.

First-of-kind buoy to monitor North Pacific Acidification

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© NOAA

The first buoy to monitor ocean acidification, a result of carbon dioxide absorbed by the ocean, has been launched in the Gulf of Alaska and is a new tool for researchers to examine how ocean circulation and ecosystems interact to determine how much carbon dioxide the North Pacific Ocean absorbs each year. (Click NOAA image for larger view of NOAA image of NOAA scientists and technicians making final adjustments on the first buoy to carry equipment that measures ocean acidification. This buoy was deployed on June 7 in the Gulf of Alaska. Click here for high resolution version. Please credit “NOAA.”)
This buoy is part of a National Science Foundation project awarded to oceanographers at the NOAA Pacific Marine Environmental Laboratory and the University of Washington in Seattle, Wash., in collaboration with Fisheries and Oceans Canada and the Institute of Ocean Sciences in Sidney, B.C.

NOAA press release, 12 June 2007.

Influence of CO2-related seawater acidification on extracellular acid–base balance in the velvet swimming crab Necora puber

We investigated the effect of different levels of hypercapnia-induced acidification (pH = 7.96, 7.31, 6.74 and 6.05) on the extracellular acid base balance of a shallow-water crustacean, the velvet swimming crab Necora puber over a period of 16 days. Any extracellular acidosis incurred was completely compensated by an increase in bicarbonate. Bicarbonate was partly, but not wholly, supplied by dissolution of the exoskeleton. This compensation was sustained for 16 days under all experimental treatments with two exceptions. First there was some evidence of extracellular acidosis in crabs after 16 days at pH = 6.74. Second at the lowest environmental pH (6.05) there was a marked uncompensated acidosis after 24 h. Necora puber appears less sensitive to low pH than many other species examined acutely. However, local acidification as a result of ocean CO2 dispersal or leakage from geological sequestration is likely to compromise even this species.

John I. Spicer, Angela Raffo1 and Stephen Widdicombe, 2007. Influence of CO2-related seawater acidification on extracellular acid–base balance in the velvet swimming crab Necora puber. Marine Biology 151(3): 1117-1125. Article.

A geochemical modelling study of the evolution of the chemical composition of seawater linked to a global glaciation: implications for life sustainability

The Snowball Earth theory initially proposed by Kirschvink (Kirschvink, 1992) to explain the Neoproterozoic glacial episodes, suggested that the Earth was fully ice-covered at 720 My (Sturtian episode) and 640 My (Marinoan episode). This succession of extreme climatic crises induced a stress which is considered as a strong selective pressure on the evolution of life (Hoffman et al., 1998). However recent biological records (Corsetti, 2006) do not support this theory as little change is observed in the diversity of microfossils outcrops before and after the Marinoan glacial interval. In this contribution we address this apparent paradox. Using a numerical model of carbon-alkalinity global cycles, we quantify several environmental stresses caused by a global glaciation. We suggest that during global glaciations, the ocean becomes acidic (pH~6), and unsaturated with respect to carbonate minerals. Moreover the quick transition from ice-house to greenhouse conditions implies an abrupt and large shift of the oceanic surface temperature which causes an extended hypoxia. The intense continental weathering, in the aftermath of the glaciation, deeply affects the seawater composition inducing rapid changes in terms of pH and alkalinity. We also propose a new timing for post glacial perturbations and for the cap carbonates deposition, ~2 Myr instead of 200 kyr as suggested in a previous modelling study. In terms of Precambrian life sustainability, seawater pH modifications appear drastic all along the glaciation, but we show that the buffering action of the oceanic crust dissolution processes avoids a total collapse of biological productivity. In opposite short-lived and large post-glacial perturbations are more critical and may have played a role of environmental filter suggested in the classic snowball Earth theory. Only a permissive life (prokaryotes or simple eukaryotes) may explain the relative continuity in microfossils diversity observed before, during and after Neoproterozoic glaciation events.

G. Le Hir, Y. Goddéris, Y. Donnadieu, and G. Ramstein, 2007. A geochemical modelling study of the evolution of the chemical composition of seawater linked to a global glaciation: implications for life sustainability. Biogeosciences Discussions 4:1839-1876. Article.

A coccolithophore concept for constraining the Cenozoic carbon cycle

An urgent question for future climate, in light of increased burning of fossil fuels, is the temperature sensitivity of the climate system to atmospheric carbon dioxide (pCO2). To date, no direct proxy for past levels of pCO2 exists beyond the reach of the polar ice core records. We propose a new methodology for placing a constraint on pCO2 over the Cenozoic based on the physiological plasticity of extant coccolithophores. Specifically, our premise is that the contrasting calcification tolerance of various extant species of coccolithophore to raised pCO2 reflects an “evolutionary memory” of past atmospheric composition. The different times of evolution of certain morphospecies allows an upper constraint of past pCO2 to be placed on Cenozoic timeslices. Further, our hypothesis has implications for the response of marine calcifiers to ocean acidification. Geologically “ancient” species, which have survived large changes in ocean chemistry, are likely more resilient to predicted acidification.

Henderiks J. & Rickaby R. E. M., 2007. A coccolithophore concept for constraining the Cenozoic carbon cycle. Biogeosciences 4, 323-332. Article.

Exposure to carbon dioxide-rich seawater is stressful for some deep-sea species: an in situ, behavioral study

Since the beginning of the industrial revolution, the concentration of the greenhouse gas carbon dioxide in the atmosphere has increased from 275 to 370 ppm; the increase is thought to have caused much of the rise in global temperature that has occurred during the same period. A means of mitigating its effects is to collect industrial carbon dioxide and sequester it in the deep ocean. Knowledge of effects of such sequestration on deep-sea organisms is crucial to evaluation of the wisdom of deep-ocean sequestration. We therefore tested deep-sea animals for indications that exposure to carbon dioxide-rich seawater is stressful. Our study site was at 3087 m depth off the coast of central California (36°41.91’N, 123°0.14’W). We deployed liquid carbon dioxide in open-topped containers on the sea floor. The carbon dioxide reacted with the carbonate system in the overlying seawater, and carbon dioxide-rich seawater flowed out onto the sediment. We placed inverted-funnel traps near the containers and ~75 m away from them. Measurements of pH confirmed that the area near the containers was exposed to carbon dioxide-rich seawater. As a test taxon, we chose harpacticoid copepods. The traps near the source of the carbon dioxide-rich seawater caught significantly more harpacticoids than those far from it. The harpacticoids apparently attempted to escape from the advancing front of carbon dioxide-rich seawater and therefore presumably found exposure to it to be stressful.
D. Thistle, L. Sedlace, K. R. Carman, J. W. Fleeger, P. G. Brewer, J. P. Barry, 2007. Exposure to carbon dioxide-rich seawater is stressful for some deep-sea species: an in situ, behavioral study. Marine Ecology Progress Series 340:9-16. Article.

CO2-Induced Extinctions of Calcifying Marine Organisms

For some time now the ongoing rise in the atmosphere’s CO2 concentration has been predicted by climate alarmists to raise havoc with earth’s coral reefs and other calcifying marine organisms by acidifying the world’s oceans and thus lowering the calcium carbonate saturation state of seawater, making it ever more difficult for these creatures to produce their calcium carbonate skeletons; and in this regard, Hansen claims “we will be able to avoid acidification of the ocean with its destruction of coral reefs and other ocean life” if we follow his policy prescriptions. However, there is no compelling reason to believe that “coral reefs and other ocean life” will be significantly harmed – much less “destroyed” – by continuing to let technology take its natural course in terms of transitioning from fossil fuel-burning to other forms of energy production; for just like the CO2-induced global warming concept itself, the CO2-induced acidification of the world’s oceans – and especially its deadly consequences concept – is an unproven theoretical construct that ignores many important biological phenomena. Nevertheless, the degree to which this catastrophic concept of CO2-induced death-in-the-oceans has been embraced, even by scientists, is nothing short of astounding, as is indicated by a paper authored by 27 researchers from eight countries that was published in the 29 September 2005 issue of Nature (Orr et al., 2005), in which the group wrote that under a “business-as-usual” scenario of future anthropogenic CO2 emissions, “key marine organisms – such as corals and some plankton – will have difficulty maintaining their external calcium carbonate skeletons,” and where they suggested that these dire conditions “could develop within decades, not centuries as suggested previously.”

CO2 Science, 6 June 2007. Web site.


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