Syré, Stefanie (2011) Calcification, growth and shell microstructure in a Mytilus galloprovincialis population from Australia in response to elevated pCO2 and temperature. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 68 pp.

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Abstract

The aftermath of more than 250 years of fossil burning are acidifying oceans that alter marine ecosystems. Predictions for the end of this century describe a drop of surface ocean pH to values of 7.9 to 7.7. This acidification is more rapid than ever in earth history. In addition, temperature is also rising rapidly. Marine species will face these new perturbations in rapidly changing environments. So far, little is known about the adaptation or acclimation potential of organisms in terms of these rapid changes in the abiotic environment. The blue mussel Mytilus spp. occurs world wide in polar to temperate coastal waters and is a known invader to new habitats. This study aimed to understand the ability of M. galloprovincialis to cope with two stressors the marine ecosystems will experience. Mussels were exposed to ambient pH (8.1) and decreased pH (7.9 and 7.7) and as well to ambient (20 °C) and elevated temperature (22 °C). After six and ten week acclimation to an altered carbonate system, no differences in shell and somatic growth, net calcification and microstructure of shell layers were found in low pH and high temperature treated animals. Degradation of periostracum increased significantly with rising temperature and decreasing pH. As the periostracum is a vital protection structure against biofouling and dissolution of the shell, the progressive loss of this cover may cause severe consequences for mussels. However, the sensitivity of marine bivalves to altered stressor regimes may differ between habitats and populations: especially in coastal, estuarine or transitional waters with already fluctuating seawater chemistry, mussels might be more tolerant of abiotic stress. The results of this study suggest a high adaptation potential of Australian M. galloprovincialis to a realistically altered a biotic regime that could be expected in the next few decades. Future research should address combinations of stressors rather than focusing on single factors as well as investigate whole life cycles and furthermore, multiple generations experiments in order to assess, subtle treatment effects on fitness.

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