Baltic Sea sediment bacterial communities show asymmetric and incomplete recovery after reciprocal temperature change translocation

Marine coastal systems are important for global biogeochemical cycling and are particularly sensitive to climate change effects due to their shallow depths, which results in rapid heat transfer to the sediments. Here we used one-year reciprocal in situ translocations of sediments between a Baltic Sea long-term (>50 years) warming-influenced bay and a nearby unaffected control bay to predict how the sediments and their associated bacterial communities may respond to future climate change and whether those changes were reversible. Geochemical parameters, methane plus sulfate profiles, and 16S rRNA gene-based bacterial diversity and community composition show partial convergence of the sediment-parameters to the translocated environment, suggesting climate change will rapidly alter bacteria communities of Baltic Sea coastal sediments. However, more pronounced responses in the control to the heated bay translocation direction suggest that while a return toward present-day conditions may be possible if climate change is reversed, such a recovery may be incomplete or require a longer time than one year. Ocean warming will alter bacterial communities of Baltic Sea coastal sediments and associated biogeochemical cycles, according to translocation experiments of Baltic Sea sediment.