Temperature tracking by North Sea benthic invertebrates in response to climate change JAN G. HIDDINK 1 , MICHAEL T. BURROWS 2 andJORGE GARC  IA MOLINOS 2 1 School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey LL59 5AB, UK, 2 Department of Ecology, Scottish Association for Marine Science, Marine Institute, Oban, Argyll, UK Abstract Climate change is a major threat to biodiversity and distributions shifts are one of the most significant threats to glo- bal warming, but the extent to which these shifts keep pace with a changing climate is yet uncertain. Understanding the factors governing range shifts is crucial for conservation management to anticipate patterns of biodiversity distri- bution under future anthropogenic climate change. Soft-sediment invertebrates are a key faunal group because of their role in marine biogeochemistry and as a food source for commercial fish species. However, little information exists on their response to climate change. Here, we evaluate changes in the distribution of 65 North Sea benthic invertebrate species between 1986 and 2000 by examining their geographic, bathymetric and thermal niche shifts and test whether species are tracking their thermal niche as defined by minimum, mean or maximum sea bottom (SBT) and surface (SST) temperatures. Temperatures increased in the whole North Sea with many benthic invertebrates showing north-westerly range shifts (leading/trailing edges as well as distribution centroids) and deepening. Never- theless, distribution shifts for most species (3.8–7.3 km yr 1 interquantile range) lagged behind shifts in both SBT and SST (mean 8.1 km yr 1 ), resulting in many species experiencing increasing temperatures. The velocity of climate change (VoCC) of mean SST accurately predicted both the direction and magnitude of distribution centroid shifts, while maximum SST did the same for contraction of the trailing edge. The VoCC of SBT was not a good predictor of range shifts. No good predictor of expansions of the leading edge was found. Our results show that invertebrates need to shift at different rates and directions to track the climate velocities of different temperature measures, and are therefore lagging behind most temperature measures. If these species cannot withstand a change in thermal habitat, this could ultimately lead to a drop in benthic biodiversity. Keywords: benthic invertebrate, benthos, distribution shifts, North Sea, sea bottom temperature, sea surface temperature, veloc- ity of climate change Received 25 February 2014; revised version received 12 August 2014 and accepted 12 August 2014 Introduction The long-term persistence of species in the face of cli- mate change depends on the ability of populations to keep pace with moving climates or adapt to changes in situ (Burrows et al., 2011). In particular, shifts in the dis- tributional ranges of populations and communities have been frequently observed in response to these changes (e.g. Parmesan & Yohe, 2003; Helmuth et al., 2006; Dulvy et al., 2008), but only a few studies have examined whether these shifts allow species to keep pace with climate change (e.g. Hiddink et al., 2012; La Sorte & Jetz, 2012; Pinsky et al., 2013). Furthermore, as most marine ectotherms are thermal range conformers, they tend to occupy fully their thermal niche and are therefore more responsive to warming than their terres- trial counterparts (Sunday et al., 2012). For marine spe- cies responding to climate change, rates of distribution shifts are, on average, consistent with those required to track mean ocean surface temperature changes (Polo- czanska et al., 2013). Nevertheless, similar analyses on the tracking of minimum and maximum temperature by species responding to climate change are lacking (Warren & Chick, 2013), yet extremes rather than mean temperatures may be the primary drivers of distribu- tion shifts (Sunday et al., 2012). Improving our current understanding of the factors governing range shifts is crucial for climate change conservation because, by changing the identity of biological communities, they are expected to alter importantly ecosystem function and structure under future anthropogenic climate change (Dawson et al., 2011). The climate variability hypothesis proposes that spe- cies’ latitudinal ranges reflect their thermal tolerance as Correspondence: Jan G. Hiddink, tel. + 44 1248 382 864, fax + 44 1248 716 367, e-mail: j.hiddink@bangor.ac.uk 117 © 2014 John Wiley & Sons Ltd Global Change Biology (2015) 21, 117–129, doi: 10.1111/gcb.12726 Global Change Biology