Excesso de CO2 já prejudica a vida marinha

[Por Henrique Cortez, do EcoDebate] Cientistas do Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), em recente estudo, demonstram uma relação direta entre a acidificação do oceano e uma diminuição na capacidade de formação de conchas em alguns organismos marinhos.

O estudo “Reduced calcification in modern Southern Ocean planktonic foraminífera”, financiado pelo governo australiano, foi publicado na edição online da revista de 09/03, Nature Geoscience.

Os pesquisadores compararam o peso de o estudo comparou o peso das conchas de animais marinhos microscópicos – chamados forams – com espécimes mais velhos, do período pré-industrial, preservados em sedimentos no fundo do mar.

Os pesquisadores descobriram que os espécimes de hoje, em razão dos oceanos mais ácidos, são menores do que os espécimes do período pré-industrial.

O artigo apenas está disponível para assinantes da revista Nature Geoscience.

Abaixo transcrevemos o abstract e os respectivos links.

Reduced calcification in modern Southern Ocean planktonic foraminifera

Andrew D. Moy, William R. Howard, Stephen G. Bray & Thomas W. Trull
Published online: 08 March 2009 | doi:10.1038/ngeo460

The oceans are becoming more acidic as they absorb anthropogenic carbon dioxide—this may limit the ability of marine organisms to secrete carbonate. A sediment-trap study shows that in the Southern Ocean the shell weights of a surface-dwelling single-celled organism with a calcite shell are lower than pre-industrial values, probably as a result of increasing ocean acidity.

Anthropogenic carbon dioxide has been accumulating in the oceans, lowering both the concentration of carbonate ions and the pH (ref. 1), resulting in the acidification of sea water. Previous laboratory experiments have shown that decreased carbonate ion concentrations cause many marine calcareous organisms to show reduced calcification rates2, 3, 4, 5. If these results are widely applicable to ocean settings, ocean acidification could lead to ecosystem shifts. Planktonic foraminifera are single-celled calcite-secreting organisms that represent between 25 and 50% of the total open-ocean marine carbonate flux6 and influence the transport of organic carbon to the ocean interior7. Here we compare the shell weights of the modern foraminifer Globigerina bulloides collected from sediment traps in the Southern Ocean with the weights of shells preserved in the underlying Holocene-aged sediments. We find that modern shell weights are 30–35% lower than those from the sediments, consistent with reduced calcification today induced by ocean acidification. We also find a link between higher atmospheric carbon dioxide and low shell weights in a 50,000-year-long record obtained from a Southern Ocean marine sediment core. It is unclear whether reduced calcification will affect the survival of this and other species, but a decline in the abundance of foraminifera caused by acidification could affect both marine ecosystems and the oceanic uptake of atmospheric carbon dioxide.

[EcoDebate, 10/03/2009]

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