CO2 is messing with coral skeletons

An international scientific team has carried out the world’s first analysis of the impact of ocean acidification on every gene in the coral genome, throwing new light on the likely fate of corals under climate change.

This prodigious research undertaking, involving more than 250 million ‘reads’ of genetic material and their detailed interpretation, was carried out by researchers from Australia, France, Netherlands and South Korea using powerful new genetic analysis tools.

In recent years declines in coral calcification have been reported around the world, matching the steady rise in carbon emissions to the atmosphere from human activity.

Whole transcriptome analysis of the coral Acropora millepora reveals complex responses to CO2-driven acidification during the initiation of calcification

The impact of ocean acidification (OA) on coral calcification, a subject of intense current interest, is poorly understood in part because of the presence of symbionts in adult corals. Early life history stages of Acropora spp. provide an opportunity to study the effects of elevated CO2 on coral calcification without the complication of symbiont metabolism. Therefore, we used the Illumina RNAseq approach to study the effects of acute exposure to elevated CO2 on gene expression in primary polyps of Acropora millepora, using as reference a novel comprehensive transcriptome assembly developed for this study. Gene ontology analysis of this whole transcriptome data set indicated that CO2-driven acidification strongly suppressed metabolism but enhanced extracellular organic matrix synthesis, whereas targeted analyses revealed complex effects on genes implicated in calcification. Unexpectedly, expression of most ion transport proteins was unaffected, while many membrane-associated or secreted carbonic anhydrases were expressed at lower levels. The most dramatic effect of CO2-driven acidification, however, was on genes encoding candidate and known components of the skeletal organic matrix that controls CaCO3 deposition. The skeletal organic matrix effects included elevated expression of adult-type galaxins and some secreted acidic proteins, but down-regulation of other galaxins, secreted acidic proteins, SCRiPs and other coral-specific genes, suggesting specialized roles for the members of these protein families and complex impacts of OA on mineral deposition. This study is the first exhaustive exploration of the transcriptomic response of a scleractinian coral to acidification and provides an unbiased perspective on its effects during the early stages of calcification.

CO2 effects on coral ‘complex, disturbing’

Warmer oceans will have both positive and negative effects on coral development, a massive international study has found.

The study, undertaken by scientists from James Cook University (JCU) in Queensland, France, the Netherlands and South Korea, involved 250 million “reads” of coral genetic material and tested the effects of increased carbon dioxide levels.

JCU Professor David Miller says the study found some surprising results about the calcification of coral skeletons.

Recent and upcoming ocean acidification workshops

The NOAA Ocean Acidification Program Office has been working with the University of Washington and the Integrated Ocean Observing System (IOOS) Regional Association, the Northwest Association of Networked Ocean Observing Systems (NA-NOOS), to convene two invitational workshops in 2012, one on integrating ocean acidification (OA) data management for the nation, and one
on defining a global network for OA monitoring. Libby Jewett (NOAA OA), Dick Feely (NOAA PMEL), and Jan Newton (UW & NANOOS) are working with others to plan and conduct these two workshops.