Estuarine macroalgae are important primary producers in aquatic ecosystems, and often foundation species providing structurally complex habitat. Climate change alters many abiotic factors that affect their long-term persistence and distribution. Here, we review the existing scientific literature on the tolerance of key macroalgal species in the Baltic Sea, the world's largest brackish water body. Elevated temperature is expected to intensify coastal eutrophication, further promoting growth of opportunistic, filamentous species, especially green algae, which are often species associated with intensive filamentous algal blooms. Declining salinities will push the distributions of marine species towards south, which may alter the Baltic Sea community compositions towards a more limnic state. Together with increasing eutrophication trends this may cause losses in marine-originating foundation species such as Fucus, causing severe biodiversity impacts. Experimental results on ocean acidification effects on macroalgae are mixed, with only few studies conducted in the Baltic

Comparing future shifts in tree species distributions across Europe projected by statistical and dynamic process-based models.

Climate change has been identified as one of the biggest current drivers of environmental change. Climate model projections for the Baltic Sea forecast increased frequency and duration of extreme temperatures, together with declines in salinity, which are expected to have impacts on the biota. In this experimental study, the interacting effects of low salinity and short-term (8 days) extreme seawater temperatures, followed by an 11-day recovery period, on the foundational macroalga, Fucus vesiculosus, were investigated. To account for potential variation in the responses at local scale, individuals originating from two different local populations, a warm and a cold site were included. In experiments manipulating temperature (20 o C to 28 o C) and salinity (4 or 6), it was found that even an 8day exposure to 26 o C or higher was detrimental to F. vesiculosus, causing extensive tissue necrosis. Tissue necrosis was enhanced by low salinity. Photosynthesis, measured as the steady-state electron transport rate (ETR) and maximum ETR, declined at 26 o C, and this effect was also enhanced by low salinity. Temperatures above 26 ° C caused declines in light-limited photosynthetic efficiency (α), indicating direct physiological damage to PS II reaction centers. After 11 days of recovery, some photosynthetic parameters recovered in the 26 °C, but not in the 28 °C treatment. It is concluded that Baltic F. vesiculosus populations may be severely affected even by shortterm (8 days) exposure to high seawater temperatures when combined with the synergistic effects of low salinity predicted for the future Baltic Sea.

Aim:We propose a novel approach that considers taxonomic uniqueness, functional uniqueness and environmental uniqueness and show how it can be used in guiding conservation planning. We illustrate the approach using data for lake biota and environment.Location: Lake Puruvesi, Finland. Methods:We sampled macrophytes and macroinvertebrates from the same 18 littoral sites. By adapting the original "ecological uniqueness" approach, we used distancebased methods to calculate measures of taxonomic (LCBD-t), functional (LCBD-f) and environmental (LCEH) uniqueness for each site. We also considered the numbers and locations of the sites needed to protect up to 70% of total variation in taxonomic, functional or environmental features in the studied part of the lake.Results: Relationships between taxonomic (LCBD-t), functional (LCBD-f) and environmental (LCEH) uniqueness were generally weak, and only the relationship between macrophyte LCBD-t and LCBD-f was statistically significant. Overall, however, if the whole biotic dataset was considered, macroinvertebrate LCBD-f values showed a consistent positive relationship with macrophyte LCBD-f. Depending on the measure of site uniqueness, between one-third to one half of the sites could help protect up to 70% of the ecological uniqueness of the studied part of Lake Puruvesi. Main conclusions:Although the dataset examined originated from a large lake system, the approach we proposed here can be applied in different ecosystems and at various spatial scales. An important consideration is that a set of sites has been sampled using the same methods, resulting in species and environmental matrices that can be analysed using the methodological approach proposed here. This framework can be easily applied to grid-based data, sets of islands or sets of forest fragments. We suggest that the approach based on taxonomic, functional and environmental uniqueness will be a useful tool in guiding nature conservation and ecosystem management, especially if associated with meta-system ideas or network thinking.

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