Coral reef landscape responses to ocean acidification

Principal Investigator: Marc Slattery, University of Mississippi

The consequences of ocean acidification may be the most serious threat facing coral reef ecosystems in the coming decades. Increased atmospheric CO2 crossing the air-sea interface has resulted in about a 30% increase in ocean acidity over pre-industrial era levels. Once CO2 is absorbed by the ocean, a cascade of chemical reactions makes it more difficult for marine organisms to build carbonate shells, calcify, and maintain various physiological processes. Thus, understanding the mechanisms of ocean acidification can help predict future impacts and provide potential mitigation strategies.

While ocean acidification may be the next big problem for coral reefs in general, there are areas within a coral reef landscape that naturally experience slightly acidified conditions. Basic metabolic processes within the confined low-flow crevices of the reef can lead to a build-up of CO2 and a consequent decline in pH. Sponges are relatively common members of these crevice communities, as well as on the open reef, so comparative studies of the same species from acidified crevices and nearby reef surfaces can provide insights into the abilities of these important species to adapt to acidified conditions. For example, prior exposure to acidified conditions might increase the fitness of sponges compared to their relatives from a non-acidic environment. Alternatively, exposure to acidification may increase the susceptibility of these species to other stressors on coral reefs, such as disease or bleaching. Many of these stress responses are manifested at the level of protein expression that directly impacts physiological function. Thus, data acquired from these comparisons can highlight specific biomarkers of stress and/or adaptation that can direct future research and conservation strategies.

Our objectives are to: 1) identify acidified micro-habitats throughout Conch Reef and survey their fauna for physiological differences relative to conspecifics from non-acidified micro-habitats, 2) transplant paired sponges from acidified and non-acidified habitats to sites with additional stressors to assess the impacts of prior acidification exposure on health, and 3) determine the additive effects of climate change stressors, specifically acidification and increased temperature, on sponge and coral physiology. We will utilize state-of-the-art proteomic technologies to examine protein stress biomarkers within these sponges. Furthermore, we will take advantage of the unique test-bed capabilities of Aquarius to evaluate the suitability of novel in situ pH chemo-sensors to perform accurate measurements at ecologically relevant spatial scales over temporal periods of minutes, days, and months. Our results will help determine the roles that ocean acidification will play in the coral reef landscapes of the future, and will aid scientists in efforts to mitigate the impact of this threat to coral reef health.

Aquarius reef base
, July 2011. Mission summary and more information.

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