| A warming Baltic Sea: can fish populations adapt?
The environmental conditions in the Baltic Sea are expected to undergo drastic changes as a consequence of climate change. There is already evidence for increased sea temperatures, milder winters, increased precipitation and decreased salinity. Concurrently, there are alarming reports about declining coastal fish stocks and associated algal blooms in shallow areas of the Baltic Sea. Still, our knowledge about coastal food-web responses to climate change is very limited. This is a major drawback when designing management strategies aiming to improve the status of coastal fish populations and to ensure functional ecosystems and sustainable commercial and recreational coastal fisheries in a changing climate.
Among the most productive environments in the Baltic Sea archipelago are shallow bays, important for reproduction and early life-history development for fish. This project will investigate the potential for fish populations in shallow bays in the Baltic Sea to adapt to temperature changes associated with global warming. We ask (1) if local fish populations can adapt to elevated temperatures and associated shifts in zooplankton community structure and (2) how shifts in seasonal events in response to rising temperatures affect the coupling between larval fish and zooplankton. By comparing perch (Perca fluviatilis) and zooplankton from a heated enclosure with a population from the surrounding Baltic Sea archipelago with natural temperatures, the potential for adaptation to elevated temperatures can be studied.
We will use a combination of experiments, a comparative field study and compilation of historical time series, focusing on juvenile perch and their zooplankton prey. To study adaptations and zooplankton-fish seasonal dynamics in a climate warming scenario we will manipulate the presence and population-of-origin of perch in experimental mesocosms (“bags”) under contrasting temperature regimes. For high temperature treatments we will use an enclosed bay where discharge of warm water from a nearby nuclear power plant has kept the temperature above that of the surrounding Baltic Sea archipelago for over 30 years.
The proposed research will inform us about the potential for rapid local adaptation of coastal fish populations to rising temperatures and the risk of seasonal mis-matches between larval fish and zooplankton under elevated temperatures, as those expected under further climate change. Expected outcomes from the project will be used to predict changes in recruitment habitats and to design management actions to improve fish recruitment and track climate-induced changes in coastal food webs.
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