Sammendrag
We will explore patterns and drivers of marine fish diversity, focusing on shallow offshore banks. The project is motivated by island theory and methods developed based on terrestrial ecosystems. We aim to further develop these theories and methods based on offshore banks. Oceanic banks are hot spots of enhanced productivity where interactions among species are strong, suggesting that focusing research efforts on banks within the overall marine landscape will provide an efficient way to address marine biodiversity issues. The enhanced productivity on banks are well known for fisheries, and fishing activities are therefore often targeted on banks. The structure of marine ecosystems varies in time and space, and this variation can be analysed in terms of colonization and extinction of species. Species richness for example depends on the balance between colonization, which will increase richness, and extinction, which will reduce it. Whereas terrestrial ecologists have been studying these processes for decades, such studies have been rare in the marine realm. We argue that by focusing on the drivers of these underlying processes, we can achieve a deeper understanding of variation and change of marine ecosystems. Banks can be seen as underwater islands or mountaintops, with different areas and degrees of isolation, two known drivers of extinction and colonization. We will explore how biodiversity is related to the areas of the banks through the species-area relationship. We will investigate the effects of topography, variation in climate, fisheries and predation on extinction and colonization rates, and how the impacts of drivers vary in space and time and if they interact. We will use oceanographic circulation models to investigate which banks are connected and whether the connected banks are upstream or downstream from one another to aid the interpretation of colonization/extinction and dispersion of species. We will use high quality, spatio-temporal data from the Barents Sea and the Scotian Shelf, Northwest Atlantic to get insights not restricted to one specific ecosystem.
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