The average temperature of the world's oceans has risen by 1°C since the start of the Industrial Revolution. To assess the impact of this incessant heat wave on marine species abundance, the British author team marshalled the evidence (including more than 4 million GBIF-mediated occurrence records) on how 304 relatively common marine species from nine taxonomic groups have adapted to warmer seas.
Recognizing that temperature is not the only factor for determining the abundance of marine organisms, the study examined impacts of other critical variables affecting species ranges, including oxygen levels, salinity, storminess and food availability. The use of widely distributed species enabled a hemisphere-wide analysis of latitudinal range shifts across a quarter century, from 1991 to 2016.
Despite some variation in the resulting models as well as variability in the connection between thermal and latitudinal gradients, the results reveal that a species' physiological thermal niche is the strongest predictor of recent changes in abundance.
With populations declining at the equatorward edge of species' ranges and increasing on the poleward side, the study highlights the fact that adaptation alone cannot buffer the negative effects of warmer equatorial seas on species abundance, with major implications for local marine resources and the coastal industries that depend upon them.