Archive for December, 2007

Calcification morphotypes of the coccolithophorid Emiliania huxleyi in the Southern Ocean: changes in 2001 to 2006 compared to historical data

We conducted a scanning electron microscopic survey of morphological variations in the calcareous nanoplankton species Emiliania huxleyi in Southern Ocean surface water samples collected along a transect from 43 to 64°S and 141 to 145°E during November 2001, October to February 2002/2003, 2003/2004, 2004/2005 and 2005/2006. The results were compared with historical data from a similar transect occupied in December to January 1983/1984 and January to February 1994 and 1995. While E. huxleyi was absent or extremely sparse (0.1 to 1 cells ml–1) south of 60°S in 1983/1984 and 1994/1995, this species was consistently present at about 100 cells ml–1 between 60 and 65°S during 2002 to 2006. The extended geographic range and/or increased southward abundance of this keystone species suggests a significant shift in Southern Ocean ecology over the past 2 decades, analogous to an observed recent range extension into the Bering Sea. Morphotype A ‘overcalcified’ mainly occurred north of the Subantarctic Front and was replaced by the weakly calcified Morphotype B/C between the Subantarctic Front and Southern Antarctic Circumpolar Current Front. This north–south shift in E. huxleyi calcification morphotypes closely tracked the north–south decline in the calcite saturation state as calculated from carbonate system measurements. Based on current evidence, no significant changes are apparent in the calcification status of E. huxleyi in the Southern Ocean during the past 12 yr. All cultured isolates from north of the Polar Front belonged to Morphotype A, while all strains isolated south of the Polar Front belonged to Morphotype B/C and their morphologies appeared conservative in culture. The north–south trend of decreased calcification of E. huxleyi in the Southern Ocean thus reflects the shift in dominance of one ecotype to another, rather than the environmental effect of decreased carbonatre ion concentrations and calcite saturation state on a single, ‘apparently cosmopolitan’, population.

Continue reading ‘Calcification morphotypes of the coccolithophorid Emiliania huxleyi in the Southern Ocean: changes in 2001 to 2006 compared to historical data’

Cayman Islands – Cay Compass News Online – Carbon could kill reefs

Coral reefs could suffer severe structural damage and even death as a result of increasing ocean acidification brought on by rising carbon emissions, a new study has warned.

Published in the Journal Science 14 December, the study warned that in less than 50 years, oceans may be too acidic for coral reefs to grow. The acidification is a result of increasing carbon dioxide emissions, about one–third of which are absorbed by the world’s oceans.

Tim Austin, assistant director of the Department of Environment, said the report is important because it demonstrates that carbon emissions are making coral reefs sick, regardless of whether those emissions are causing climate change through global warming.

Continue reading ‘Cayman Islands – Cay Compass News Online – Carbon could kill reefs’

Global Warming’s Impact on Lobsters Has Scientists in a Stew

ELLSWORTH — Despite the glaze of ice coating much of Downeast Maine and the skepticism of some political leaders, global warming is accepted as an indisputable fact by virtually all responsible scientific opinion.

In a report published in the journal Science recently, a group of scientists, including University of Maine oceanography professor Robert Steneck, offered some dire predictions about the effect of global warming on the world’s coral reefs. According to Steneck and his colleagues, as the Earth’s atmosphere grows warmer and the concentration of carbon dioxide (CO2) continues its increase, global sea temperatures will also rise, and the oceans will become more acidic.

Continue reading ‘Global Warming’s Impact on Lobsters Has Scientists in a Stew’

Reefs in Peril

Dr. Nancy Knowlton is a coral reef scientist who studies their ecology and evolution, including the impact of climate change. The founding director of the Center for Marine Biodiversity and Conservation at the University of California, San Diego, she is also a professor at Scripps Institute of Oceanography. Her contributions have been crucial to the advancement of coral reef science.

Today, Knowlton holds the Sant Chair in Marine Science, recently awarded by the Smithsonian Institute’s National Museum of Natural History in Washington D.C. Occupying the museum’s first funded chair in marine sciences, Knowlton will provide leadership to the Smithsonian’s Ocean Initiative, an interdisciplinary move to foster greater public understanding of ocean issues.

A chat with Knowlton is like opening a trunk of coral knowledge. The conversation revolved around a recently released article Knowlton co-authored in the journal Science entitled “Coral Reefs under Rapid Climate Change and Ocean Acidification.” The piece presented a dire scenario of increasing decline and loss of coral reefs, based on the best available scientific information and the most positive climate change and carbon emission scenarios of the UN’s Intergovernmental Panel on Climate Change (IPCC).

“Ocean acidification” is a recently introduced term for an observed reduction in seawater pH. It is triggered by the absorption of atmospheric carbon dioxide (CO2), which reacts with naturally occurring carbonate ions in the ocean, to produce carbonic acid. The change in chemical conditions affects corals and other organisms that need carbonates to build their calcium carbonate skeletons. The phenomenon, together with climate change, increases ocean temperatures and more frequent bleaching events might be too much for coral reefs to handle.

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Correlation of boron isotopic composition with ultrastructure in the deep-sea coral Lophelia pertusa: Implications for biomineralization and paleo-pH

Using the CRPG-CNRS Cameca 1270 ion microprobe facility, we have measured boron isotopic compositions (11B/10B) in different ultrastructural components of the deep-sea aragonitic scleractinian coral Lophelia pertusa. We observe a systematic difference in B isotopic composition between the Early Mineralization Zone (EMZ) and adjacent fibrous skeleton. In EMZ the measured δ11B values are consistently low. Fibrous aragonite is characterized by systematically higher δ11B values but also displays B isotopic heterogeneity associated with specific growth bands in the calyx wall. The magnitude of the observed B isotopic variations cannot be explained by changes in environmental conditions and is likely caused by biological processes involved in the biomineralization of new skeleton, i.e., “vital” effects. The observed B isotopic variations are opposite to the predictions of geochemical models for vital effects. These models are based on the idea that stable isotopic fractionations (including C and O) in coral skeleton are driven by changes in pH of the fluid from which the skeleton is presumed to precipitate. Our data indicate that pH variations are not responsible for the observed stable isotopic fractionations. Geochemical models therefore do not provide an adequate framework within which to understand coral skeletal formation. Without a better understanding of these processes the use of B isotopic composition to reconstruct paleo-pH variations in the oceans must be considered problematic, at least as far as Lophelia pertusa is concerned.
Continue reading ‘Correlation of boron isotopic composition with ultrastructure in the deep-sea coral Lophelia pertusa: Implications for biomineralization and paleo-pH’

Tiburon center will study future of key phytoplankton

The survival of a phytoplankton species that helps clean the Earth of carbon monoxide will be studied by researchers in Tiburon who have received a $1.2 million grant for the work.

San Francisco State University’s Romberg Tiburon Center for Environmental Studies received the grant from the National Science Foundation to study the future of E. huxleyi, a species of calcifying phytoplankton.

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Consequences of increased temperature and CO2 for phytoplankton community structure in the Bering Sea

Global climate change is predicted to have large effects on the ocean that could cause shifts in current algal community structure, major nutrient cycles, and carbon export. The Bering Sea is already experiencing changes in sea surface temperature (SST), unprecedented algal blooms, and alterations to trophic level dynamics. We incubated phytoplankton communities from 2 Bering Sea regimes under conditions of elevated SST and/or partial pressure of carbon dioxide (pCO2) similar to predicted values for 2100. In our ‘greenhouse ocean’ simulations, maximum biomass-normalized photosynthetic rates increased 2.6 to 3.5 times and community composition shifted away from diatoms and towards nanophytoplankton. These changes were driven largely by elevated temperature, with secondary effects from increased pCO2. If these results are indicative of future climate responses, community shifts towards nanophytoplankton dominance could reduce the ability of the Bering Sea to maintain the productive diatom-based food webs that currently support one of the world’s most productive fisheries.

Continue reading ‘Consequences of increased temperature and CO2 for phytoplankton community structure in the Bering Sea’

RP coral reefs will disappear in 50 years

THE Philippines has 27,000 sq. kms. of coral reefs, the second largest in Southeast Asia and among the finest in the world. Among the best examples are the Tubbataha Reef, Marine Park in Palawan, Apo Island in Negros Oriental, Apo Reef in Puerto Galera, Mindoro, and Verde Island Passage off Batangas.

They will disappear in 50 years.

Continue reading ‘RP coral reefs will disappear in 50 years’

Catastrophe feared as oceans grow acidic

Seven hundred miles west of Seattle in the Pacific at Ocean Station Papa, a first-ofits- kind buoy is anchored to monitor a looming environmental catastrophe.

Forget about sea levels rising as glaciers and polar ice melt, and increasing water temperatures affecting global weather patterns. As the oceans absorb more and more carbon dioxide and other greenhouse gases, they’re gradually becoming more acidic.

Some scientists fear that the change may be irreversible.

Continue reading ‘Catastrophe feared as oceans grow acidic’

Causal or casual link between the rise of nannoplankton calcification and a tectonically-driven massive decrease in Late Triassic atmospheric CO2�

On the basis of a global carbon-climate numerical model, we reconstructed atmospheric carbon dioxide concentrations over the first 60 million years of the Mesozoic. Our analysis indicates that pCO2 declined from more than 3000 ppmv to less than 1000 ppmv, with a drastic drop during the Late Triassic. The fast northward drift of Pangea exposed a large continental surface to warm and humid equatorial climate, thus promoting CO2 consumption through weathering. This massive drawdown of atmospheric CO2 is consistent with sedimentological and geochemical data of the rock record and correlates with the primary radiation of calcareous nannoplankton, a biological revolution shifting the global carbonate sink from shallow water environments to the open oceans. Our numerical model shows that at time, tectonics, via weathering, increased the pH of the oceanic surface waters by 0.3 units, corresponding to a 50% decrease in H+ concentration. This may have provided the ultimate environmental trigger which unlocked the newly oxidized Mesozoic open oceans to pelagic nannobiocalcification.
Continue reading ‘Causal or casual link between the rise of nannoplankton calcification and a tectonically-driven massive decrease in Late Triassic atmospheric CO2�’

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Ocean acidification in the IPCC AR5 WG II

OUP book