Umwelteinflüsse auf Wachstum, Alter und Stoffwechselbudgets der Muschel Arctica islandica

In order to understand the present, environmental knowledge from the past is important. Observational records of environmental data are spatiotemporally incomplete and extremely scarce prior to AD 1860. Large scale environmental variability can be well represented by integrating data from a limited number of geographically scattered indicators or 'proxies' of past climate. This is partly achieved by the analysis of tree rings and of marine sediments cores. Long term environmental reconstruction with high resolution can be achieved by the calcareous skeleton of long lived invertebrates. In the last decade the ocean quahog Arctica islandica has attracted increasing interest among marine biologists owing to its extremely long life span approaching 400 y, and occurrence along the entire North Atlantic Ocean margins. But even more important is that its calcareous shell archives information on past environmental conditions in the morphological growth patterns and biogeochemical properties. The Ocean quahog A. islandica may become an important proxy in environmental change research, although until now the full capabilities of this species have not yet been fully realised.This thesis is an attempt to achieve deeper insight of the environmental proxy A. islandica, in terms of its environment, biology as well as population dynamics and evolutionary history. In order to achieve this goal, a number of approaches targeting six different sites of the North East Atlantic Ocean (i.e. Norwegian coast, Kattegat, Kiel Bay (Baltic Sea), White Sea, German Bight (North Sea) and off North East Iceland) were developed: (i) A general metabolic model which allows calibration of individual metabolic rates of A. islandica from five populations to body mass, water temperature, age and site. (ii) Growth and energy budget models of A. islandica at six different sites allowed a better understanding of the ecological role of the bivalve in its environment and to enable a linkage of the dynamics of A. islandica populations to environmental drivers (iii) Morphological and genetic comparison confirm differences between populations of A. islandica and revealed whether the morphological differences are driven by the environment or underlying genetic differences.Between different populations, environmental temperature is found to be the prime driving force that exerts distinct site specific effects on respiration rate. Respiration of A. islandica is significantly below the average of 59 bivalve species when temperature and mass are taken into account. In addition, growth rates of A. islandica are very low. A. islandica populations differ distinctly in maximum lifespan (40 y Kiel Bay, to 197 y Iceland). Lifespan is the principal determinant of the relationship between energy budget parameters, whereas temperature affects net growth efficiency only. Genetic results indicate a fairly mixed assemblage over the North East Atlantic area. Morphometric and genetic patterns appear to be unrelated and confirm morphological differences between populations of A. islandica, morphometrics appear to be driven by the environment (e.g. temperature and salinity) rather than underlying genetic differences between populations. Therefore this study enhances our understanding of the relationship between environmental conditions and the population biology such as growth, metabolism as well as population dynamics and evolutionary history of A. islandica. In addition, different models may enable the coupling of regional oceanographic temperature models as an environmental proxy of past environmental variabilities. Further, a geographically more extensive data set is necessary to apply A. islandica as a proxy and eliminate uncertainties related to its biological and evolutionary history.