Synergistic effects of extreme temperature and low salinity on foundational macroalga Fucus vesiculosus in the northern Baltic Sea

Abstract

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.

Gene regulatory response to hyposalinity in the brown seaweed Fucus vesiculosus

“…Climate change is expected to modify all these factors, with the extent of the perturbation varying from one region to another. In general, our current knowledge of the tolerance of marine macroalgae to future climate-change conditions is limited to a few factors, mainly temperature and acidification [7,8], but also salinity [9][10][11]. In the Baltic Sea, a major change induced by climate change will be desalination [12], which will shift the surface water salinity gradient southward and challenge the persistence of marine macroalgae at the low-salinity end of the gradient.…”

Effects of temperature on carbon circulation in macroalgal food webs are mediated by herbivores

“…the modeled trends) illustrates that conclusions on carbon balance differ when considering single species in isolation versus a system perspective. F. vesiculosus is able to withstand a wide range of environmental changes, since the species is exposed to different temperatures along the seasons (Takolander et al 2017). Graiff et al (2015) demonstrated that the temperature for maximum photosynthesis capacity (expressed as maximum relative electron transport rate) was 24 °C.…”

“…Graiff et al (2015) demonstrated that the temperature for maximum photosynthesis capacity (expressed as maximum relative electron transport rate) was 24 °C. Takolander et al (2017) found that temperatures beyond 26 °C jeopardize the photosynthetic activity of the macroalgae. In our study, the rates of NPP did not decrease along the temperature gradient and respiration of the Fucus-epiphytes assemblage increased linearly with temperature ( Fig.…”

Rapid genomic expansion and purging associated with habitat transitions in a clade of beach crustaceans (Haustoriidae: Amphipoda)

“…Bays also have shallow anoxic layers due to densely packed organic matter (Revsbech et al 1980). Temperature and salinity have been shown to have synergistic impacts on oxidative stress, such that species may tolerate high temperatures or low salinity, but not in conjunction (Takolander et al 2017). This may explain why the two GoM shifts to brackish environments are accompanied by body size and genome size reductions, but not the Atlantic shift (i.e., L.…”