The role of microbial biofilms in range shifts of marine habitat-forming organisms.

Species range shifts in response to warming and associated tropicalisation of coastal marine ecosystems are occurring globally, but the rates of change vary geographically and across ecosystems. Range shifts of biphasic habitat-forming species are critical as they can alter the physical and biological structure of habitats and thus change entire reef ecosystems. Microbial biofilms are key in regulating the dynamics of dominant habitat-forming species such as coral and kelps, and climate change is expected to impact this dynamic through two key pathways: (i) direct effects on biofilm composition, and (ii) impacts on the complex feedback loops between biofilms and habitat-forming organisms. Biofilms will therefore likely mediate range shifts of habitat-formers; thus, mechanistic understanding of their role is crucial to better predict ecosystem responses to environmental change. Marine species, such as corals and kelp, are responding to climate change by altering their distributions. Microbial biofilms underpin key processes that affect the establishment, maintenance, and function of these dominant habitat-formers. Climate-mediated changes to microbial biofilms can therefore strongly influence species' range shifts. Here, we review emerging research on the interactions between benthic biofilms and habitat-formers and identify two key areas of interaction where climate change can impact this dynamic: (i) via direct effects on biofilm composition, and (ii) via impacts on the complex feedback loops which exist between the biofilm microbes and habitat-forming organisms. We propose that these key interactions will be fundamental in driving the speed and extent of tropicalisation of coastal ecosystems under climate change. [ABSTRACT FROM AUTHOR]