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Growth patterns of Mediterranean cold water corals exposed to increased levels of CO2

2010New polyp growth and linear skeletal extension of Mediterranean cold water corals exposed to increased levels of pCO2BERZUNZA SANCHEZ Maria (Mexico)
Organisation: Christian Albrechts University, Kiel (DE)Supervisor :Prof. Dr. Ulrich Sommer & Dr. Cornelia Maier
Summary: Ocean acidification has been recognized as モthe other CO2 problemヤ (in reference to global warming) (Doney et al 2009) affecting marine ecosystems in several ways. The term ocean acidification alludes to a lowering of pH and consequential alteration of seawater chemistry. For calcifying organisms, evidence so far suggests the response to ocean acidification is not universal. Temperate Mediterranean corals for example, do not appear to inhibit calcification at the same rate as shallow water corals (Rodolfo-Metalpa et al 2010). With recent development in deep sea surveying equipment and techniques, exploring the response of cold water corals to ocean acidification is gradually becoming more feasible. Among cold water corals, Atlantic samples of Lophelia pertusa have been shown to decrease calcification rate up to 50% in response to decreased pH (Maier et al 2009). Whether such response is also present in their Mediterranean counterparts however, remains unknown. In this study we assessed potential differences in calcification rates using several proxies of growth (linear extension rate, projected area, buoyant weight) as a function of changes in seawater chemistry created by increasing pCO2. By exposing three different species of corals commonly found but not restricted to the Mediterranean (Lophelia pertusa, Madrepora oculata, Desmophyllum sp), and a range of size classes. this study encompasses potential variation in growth given by species specific or size specific characteristics. The corals were exposed to four treatments of pCO2 (280 ppm, 390 ppm ppm, 750 ppm, 1000ppm) which cover the spectrum of past, present and future levels of pCO2 under the scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC, 2007). Since impaired growth could have negative implications in individual colonyメs fitness, as well as in overall bioherm (deep sea reefs) resilience, it is important to find pCO2 thresholds at which coral growth performance may be compromised. Furthermore, understanding growth patterns of cold water corals under such conditions can help develop preventive conservation measures for this poorly known but nevertheless rich biodiversity ecosystems.