Blaß, Patrick (2016) Einfluss von Temperaturschwankung auf Herzraten, Filtration und Wachstum der Miesmuschel (Mytilus edulis, Linné 1758). (Master thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 59 pp.

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Abstract

In course of climate change the impact of a rising mean temperature on marine organisms has already been adressed by numerous studies. Climate change is projected to not only shift temperature means but to also increase variability around means and the intensity of extreme events. Marine coastal habitats typically feature strongly varying environmental conditions of numerous biotic and abiotic parameters. These shallow waters in particular are going to be affected by an additional increase in temperature variation. Due to the lack of attention to fluctuating parameters in ecological research, the role of thermal fluctuations as modulators of climate changes impact on marine organisms is virtually terra incognita. Aiming at offering new perspectives in this context, this study represents an approach of differentiating between the two attributes of fluctuations: frequency and amplitude. This study adresses the question if an elevated temperature has different effects on the blue mussel (Mytilus edulis) within a constant or fluctuating temperature regime and if so, whether it is frequency-dependent or not. Blue Mussels (Myilus edulis) of the Kieler Fjord (Baltic Sea) were used for an experiment over the course of seven weeks starting at the end of February. It included four treatments which had different temperature regimes: a) constant 5°C, b) constant 7°C, and with the same mean of 7°C fluctuating (± 2°C) in a frequency of c) 4,5 days and d) 1,5 days. Mortality, growth (in juveniles), condition indexes as well as clearance rates and heartrates were measured. There was a signifcant difference in growth between the treatment with 5°C and all three treatments with a mean temperature of 7°C. The mean of heartrates were lowest at a constant 5°C. Heartrates of the fluctuating treatments were slighty higher than the constant treatment at the same mean temperature of 7°C. The heartrates of the fluctuating treatments also approximately followed the general temperature curves. No significant differences were found between the two fluctuating treatments. Results indicate that smaller fluctuations within winter temperatures (±2°C) at different frequencies only have minor effects on marine organisms like the blue mussel. Minor non-significant trends between the effects of different frequencies suggest the need for further research on climate changes ecological impacts along the projected lines. The Kiel Indoor Mesocosms (KIMs) are capable of simulating any kind of fluctuations within different abiotic parameters. This capacity was used for the first time in course of this study, promising new insights into the role of temperature fluctuations in climate changes impacts on marine ecosystems.

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