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Benthic foraminiferal Li/Ca: Insights into Cenozoic seawater carbonate saturation state

Benthic foraminiferal Li/Ca decreases down a Norwegian Sea holothermal depth transect, suggesting that the saturation state of seawater with respect to calcium carbonate influences foraminiferal Li/Ca. Benthic foraminiferal Li/Ca increases by 17% across the glaciation event in the early Oligocene, which likely reflects the increase in seawater saturation state evidenced by the concomitant deepening of the calcite compensation depth. Following the establishment of the Antarctic ice sheet, benthic foraminiferal Li/Ca bears a remarkable resemblance to the estimated oxygen isotopic composition of seawater, suggesting that during this time seawater saturation was largely controlled by glacioeustatically driven changes in shallow-water carbonate accumulation rates.

Lear CH, Rosenthal Y (2006) Benthic foraminiferal Li/Ca: Insights into Cenozoic seawater carbonate saturation state. Geology 34(11): 985–988. Article.

Effects of elevated pCO2 on epilithic and endolithic metabolism of reef carbonates

We investigated effects of elevated partial pressure of CO2 (pCO2) on the metabolism of epilithic and endolithic phototrophic communities that colonized experimental coral blocks. Blocks of the massive coral Porites lobata were exposed to colonization by epilithic and endolithic organisms at an oceanic site in Kaneohe Bay (Hawaii) for 6 months, and then were transported to laboratory tanks. A bubbling system was used to maintain two treatments for 3 months, one at ambient pCO2 (400 ppm) and the second at elevated pCO2 (750 ppm). Net photosynthetic rates of epilithic communities in the high pCO2 treatment, dominated by encrusting coralline algae, decreased by 35% while respiration rates remained constant. In contrast, metabolism of endolithic phototrophs, comprised of cyanobacteria and algae, was not significantly affected by the elevated pCO2 even though endoliths contributed about 63% to block production.

Tribollet A., Atkinson M. J. & Langdon C., 2006. Effects of elevated pCO2 on epilithic and endolithic metabolism of reef carbonates. Global Change Biology 12:2200-2208. Article

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This news stream was launched in July 2006 by Dr Jean-Pierre Gattuso (Research Professor at the Centre national de la recherche scientifique, Laboratoire d’Océanographie de Villefranche-sur-mer). From May 2008 it was maintained by the European Project on Ocean Acidification. Since August 2012, the news stream has been managed by the Ocean Acidification International Coordination Centre (OA-ICC), based at the Environment Laboratories of the International Atomic Energy Agency (IAEA) in Monaco, with the goal of continuing this service to all ocean acidification stakeholders, including the scientific community, decision makers and the general public.

The purpose of this news stream is to centralize information about ocean acidification and its consequences on marine organisms and ecosystems. By no means is it meant to be comprehensive, but we attempt to provide an unbiased view of the literature and media articles.

Disclaimer: The IAEA and its Member States do not endorse the opinions or views expressed in the items that are posted on this news stream, which are posted solely for the purpose of informing the interested audience.

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Ocean Acidification International Coordination Centre (OA-ICC)

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Ocean acidification in the IPCC AR5 WG II

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