Schäfer, Susanne (2016) Effects of elevated water temperatures on the invasive sea anemone Aiptasia diaphana from Madeira Island. (Master thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 42 pp.

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Abstract

In times of climate change, sea water temperatures are predicted to increase. However, the strength of warming varies over different latitudes, causing diverse reactions in marine organisms. This study provides experimental information on how sea anemones are affected by global warming. For this purpose, Aiptasia diaphana were kept for 43 days at five different temperature regimes in order to determine the upper thermal tolerance limit and changes in weight and size close to this maximum. The sea anemones survived temperatures of up to 33°C for 6 weeks showing declines in weight and size with increasing temperatures. Survival analysis revealed an abrupt end of the thermal tolerance within only 2° C of warming. This study indicates that - in addition to survival - weight and size are both suitable characteristics to investigate warming effects in A. diaphana. This thesis was part of the GAME project 2015, an experimental study at a global scale, investigating whether latitudinal differences influence the upper thermal tolerance of sea anemones. The maximum temperature the anemones survived differed between sites substantiating the hypothesis that sea anemones from lower latitudes live closer to their upper thermal tolerance limit than those from higher latitudes. However, the discrepancy between the temperature increase predicted by climate models and the maximum deviation tolerated by the sea anemones varied considerably between locations. In order to make reliable predictions about future distributions of species, the necessity of combining global trends and local characteristics has to be emphasized.

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