Thermal affinities and temperature gradients explain how warming changes ocean community composition: Burrows et al. 2019, Nature Climate Change

Figure 1, c-f (Burrows et al. 2019) Thermal characteristics in simulated pools of species varying in thermal diversity (high: c and d; low: e and f) and species’ thermal ranges [STR] (narrow: c and e; wide: d and f), showing subsets forming communities at a mean annual sea temperature of 15 °C.

A new paper published in Nature Climate Change by Dr. Michael Burrows et al., with contributions from Dr. Ryan Batt (former Pinsky Lab postdoc) and Dr. Malin Pinsky, used 29 years of fish and plankton survey data to assess how warming is changing marine communities’ composition and structure. They found that “warm-water species are rapidly increasing and cold-water species are decreasing” as ocean waters warm. Informed by species’ incidence, and changes in sea surface temperature (SST), the team created measures of species’ thermal affinities, community composition, and other summary metrics. They used these to measure community-level change in thermal affinity and composition.

Regions with relatively stable temperatures (e.g. the Northeast Pacific and Gulf of Mexico) showed little change in structure, while areas that warmed (e.g. the North Atlantic) shifted strongly towards warm-water species dominance. They also found that communities whose species pools had diverse thermal affinities and a narrower range of thermal tolerance showed greater sensitivity to change.

Next, they found that communities in regions with strong temperature depth gradients changed less than expected. In these regions, rather than moving horizontally through the water, species can instead move deeper to maintain their preferred temperature.

They concluded that this evidence strongly supports temperature as a fundamental driver of change in marine systems, and that metrics based on species’ thermal affinities are useful tools to predict and provide prognoses for community dominance shifts.

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