Abstract
AbstractAimThe Baltic Sea forms a unique regional sea with its salinity gradient ranging from marine to nearly freshwater conditions. It is one of the most environmentally impacted brackish seas worldwide, and the low biodiversity makes it particularly sensitive to anthropogenic pressures including climate change. We applied a novel combination of models to predict the fate of one of the dominant foundation species in the Baltic Sea, the bladder wrack Fucus vesiculosus.LocationThe Baltic Sea.MethodsWe used a species distribution model to predict climate change‐induced displacement of F. vesiculosus and combined these projections with a biophysical model of dispersal and connectivity to explore whether the dispersal rate of locally adapted genotypes may match estimated climate velocities to recolonize the receding salinity gradient. In addition, we used a population dynamic model to assess possible effects of habitat fragmentation.ResultsThe species distribution model showed that the habitat of F. vesiculosus is expected to dramatically shrink, mainly caused by the predicted reduction of salinity. In addition, the dispersal rate of locally adapted genotypes may not keep pace with estimated climate velocities rendering the recolonization of the receding salinity gradient more difficult. A simplistic model of population dynamics also indicated that the risk of local extinction may increase due to future habitat fragmentation.Main conclusionsResults point to a significant risk of locally adapted genotypes being unable to shift their ranges sufficiently fast considering the restricted dispersal and long generation time. The worst scenario is that F. vesiculosus may disappear from large parts of the Baltic Sea before the end of this century with large effects on the biodiversity and ecosystem functioning. We finally discuss how to reduce this risk through conservation actions, including assisted colonization and assisted evolution.
Highlights
Owing to the large and densely populated drainage area, the Baltic Sea is one of the most environmentally impacted seas in the world with habitat loss, eutrophication, pollution and overfishing (Diaz & Rosenberg, 2008; Halpern et al, 2008)
A short geological history, low salinity and low temperature compared to nearby coastal waters in the east Atlantic make the Baltic Sea a species-poor ecosystem with key ecosystem functions often provided by single species (Bonsdorff, 2006; Bonsdorff & Pearson, 1999)
Compared to the current climate conditions, the nutrient scenarios BAU and reference scenario (REF) under future climate predicted a reduction of 30% and 33% in the distribution area of F. vesiculosus, respectively
Summary
Owing to the large and densely populated drainage area, the Baltic Sea is one of the most environmentally impacted seas in the world with habitat loss, eutrophication, pollution and overfishing (Diaz & Rosenberg, 2008; Halpern et al, 2008). Genetic variation is considered an essential component for persistence in a changing environment where new genetic combinations or the dispersal of locally adapted genotypes may retard the range shift of a species. Fucus vesiculosus has rather well-defined range margins in the Baltic Sea, and predicted climate-driven changes together with ongoing eutrophication and habitat fragmentation may all modify the present. To explore whether locally adapted genotypes of F. vesiculosus (Ardehed et al, 2016) may track climate change, we applied a biophysical model to simulate dispersal, connectivity and habitat fragmentation at the receding margin where loss of connectivity may further endanger population persistence (Opdam & Wascher, 2004). We discuss potential ecosystem consequences related to shifting patterns in species distribution and connectivity and suggest some management actions to reduce possible ecosystem impacts
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