Thermal Bias of Marine Fauna: the Latest RLS Article in Nature
Rick D. Stuart-Smith, Graham J. Edgar, Neville S. Barrett, Stuart J. Kininmonth, & Amanda E. Bates
Another study based on the RLS data has been published in Nature. It looks at the distribution of fish and invertebrates on rocky and coral reefs around the world and finds that relatively few species have truly subtropical distributions. Instead they tend to be mostly either tropical or temperate, and that subtropical faunas are largely a mix of these two types of species. Species within these types share similar upper limits to the temperatures they currently live in. The implications of this are that there are locations at which the majority of species are already living close to their upper temperature limits, and others where most species could actually thrive with further warming. Data from RLS surveys show where these locations are, and can show the worst case scenario of how many species may have to move, adapt or die with warming seas. The key measure: if an RLS diver does a survey tomorrow, what proportion of the species they record will still be at that location in 10 and 100 years’ time? The answer differs between locations, but in SE Australia it is surprisingly high compared to other parts of the world. In this location it will be more about how many new species are added.
A critical assumption underlying projections of biodiversity change associated with global warming is that ecological communities comprise balanced mixes of warm-affinity and cool-affinity species which, on average, approximate local environmental temperatures. Nevertheless, here we find that most shallow water marine species occupy broad thermal distributions that are aggregated in either temperate or tropical realms. These distributional trends result in oceanscale spatial thermal biases, where communities are dominated by species with warmer or cooler affinity than local environmental temperatures. We use community-level thermal deviations from local temperatures as a form of sensitivity to warming, and combine these with projected ocean warming data to predict warming-related loss of species from present-day communities over the next century. Large changes in local species composition appear likely, and proximity to thermal limits, as inferred from present-day species’ distributional ranges, outweighs spatial variation in warming rates in contributing to predicted rates of local species loss.
View the full article in Nature