The resilience of marginal populations of Corallina officinalis (Corallinales, Rhodophyta) to climate change
Student thesis: Doctoral Thesis
With increasing severity of climatic implications on, for instance, socio-economy, health and ecosystems due to anthropogenically induced global climate change, the necessity to research the complex interactions and impacts of these changes on organisms is urgent. At present, the impacts of climatic changes on marine coastal ecosystems are poorly understood. Coralline algae were chosen for this study due to their wide global distribution and importance as habitat builders. As critical components of marine shallow water ecosystems and indicator species for climatic impacts, they are alarmingly affected. The species focussed on in this study and representing the traits of coralline algae, is Corallina officinalis. This study aimed at a combined approach of field and laboratory experiments to assess the impacts of climate change across the species distribution in the NE Atlantic ranging from the northern boundary in Iceland to the southern boundary in Spain. Physiological and structural measurements were performed in multiple experiments to determine thermal and chemistry-induced stress responses. These were compared between origins of populations and a distinct vulnerability of the southern marginal populations to increasing temperatures and changing carbonate chemistry were identified. However, northern marginal populations showed a great resilience and adaptation potential to future oceanic conditions. Based on these findings, the generally assumed Centre-to-Margin hypothesis regarding abundance as well as adaptation and resilience potential is not observed in C. officinalis and has to be modified into a North-to-South gradient for this species. Overall, this thesis demonstrates that coralline algae (Rhodophyta, Corallinaceae) are vulnerable to ocean warming and ocean acidification. However, predicting the extent of their susceptibility to these changes is complex as it must be considered together with additional environmental and ecological factors. The studies presented herein highlight the importance of ecological interactions in determining species responses to environmental change.
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