| Wrack-beds are composed of marine plants driven ashore and form the world’s largest compost heaps. They are important coastal buffers, sources of marine nutrients, and hence link the marine and terrestrial realms. Despite their importance, wrack ecosystems have received almost no attention in Sweden. This is, however, urgently needed because human activities endanger this ecosystems’ stability. Studies exploring effects of beach clearing elsewhere demonstrate changes of species dependent on wrack beds, such as seaweed flies, which are keystone organisms for wrack turnover. These flies alone contribute up to 50% to the breakdown of carbon and form themselves also important prey for many animals, such as birds.
I plan to investigate the effect of beach clearing on the Swedish intertidal community that depends on wrack-beds by studying the two most important species that facilitate wrack-bed turnover in Europe [1–3], namely Coelopa frigida and C. pilipes. These species are exclusively specialized to live on seaweed wrack-beds, completing their entire life cycle only within beach-cast seaweed [4,5]. The importance of these species has been recognized in the UK, where they have been studied for decades across environmental gradients [1,6,7]. Outside of the UK, these flies have received little attention, and their ability to overcome anthropogenic disturbances, such as beach clearing, is not known.
I propose to compile a dataset on the spatial and temporal distributions of these two seaweed fly species, using existing distribution data for the last six decades. Europe-wide data will be supplemented with detailed data from Sweden collected from disturbed and undisturbed beaches by human beach clearing activities. Subsequently, I will combine this dataset with climatic and environmental variables to identify seaweed fly ecological requirements. The resulting data set, will allow me to model species-habitat relationships over large spatial scales and to identify the key ecological parameters that limit their distribution and contribute to their population dynamics. Furthermore, I will use field and laboratory studies and experiments to determine colonization and total movement rates of the two species in response to various environmental variables and disturbance will be measured. The three specific objectives and aims of the proposed research project are as follows:
• Determine the key ecosystem variables affecting the temporal and spatial distribution and abundance patterns of European seaweed flies;
• Determine the local and regional scale effects of beach clearing and community dynamics on population connectivity in Sweden; and,
• Determine which phenotypic traits limit seaweed fly species adaptive potential in the face of coastal development in Sweden.
From the results we will model various disturbance scenarios in order to develop accurate predictions that can be used in an adaptive management framework to mitigate the consequences of human coastal development. These results from this work will be communicated to stakeholders via peer-reviewed publications, blog reports, and reports submitted directly to communes and country administrative boards.
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