Projected shifts in loggerhead sea turtle thermal habitat in the Northwest Atlantic Ocean due to climate change

Samir H Patel,Heather L Haas,Ronald J Smolowitz,Joshua M Hatch,Vincent S Saba,Gavin Fay,Megan V Winton

doi:10.1038/s41598-021-88290-9

Abstract

It is well established that sea turtles are vulnerable to atmospheric and oceanographic shifts associated with climate change. However, few studies have formally projected how their seasonal marine habitat may shift in response to warming ocean temperatures. Here we used a high-resolution global climate model and a large satellite tagging dataset to project changes in the future distribution of suitable thermal habitat for loggerheads along the northeastern continental shelf of the United States. Between 2009 and 2018, we deployed 196 satellite tags on loggerheads within the Middle Atlantic Bight (MAB) of the Northwest Atlantic continental shelf region, a seasonal foraging area. Tag location data combined with depth and remotely sensed sea surface temperature (SST) were used to characterize the species’ current thermal range in the MAB. The best-fitting model indicated that the habitat envelope for tagged loggerheads consisted of SST ranging from 11.0° to 29.7 °C and depths between 0 and 105.0 m. The calculated core bathythermal range consisted of SSTs between 15.0° and 28.0 °C and depths between 8.0 and 92.0 m, with the highest probability of presence occurred in regions with SST between 17.7° and 25.3 °C and at depths between 26.1 and 74.2 m. This model was then forced by a high-resolution global climate model under a doubling of atmospheric CO2 to project loggerhead probability of presence over the next 80 years. Our results suggest that loggerhead thermal habitat and seasonal duration will likely increase in northern regions of the NW Atlantic shelf. This change in spatiotemporal range for sea turtles in a region of high anthropogenic use may prompt adjustments to the localized protected species conservation measures.

Highlights

It is well established that sea turtles are vulnerable to atmospheric and oceanographic shifts associated with climate change
Filtering the location estimates from these tags yielded 45,840 daily locations within the NW Atlantic, of which 44,865 daily locations occurred on the continental shelf in the Middle Atlantic Bight (MAB) and were used for model fitting
The overall predicted distribution for each month was consistent with the reconstructed tracks and indicated that the probability of loggerhead presence in the NW Atlantic shelf waters is highest from May through October

Summary

Introduction

It is well established that sea turtles are vulnerable to atmospheric and oceanographic shifts associated with climate change. Our results suggest that loggerhead thermal habitat and seasonal duration will likely increase in northern regions of the NW Atlantic shelf. This change in spatiotemporal range for sea turtles in a region of high anthropogenic use may prompt adjustments to the localized protected species conservation measures. An emerging body of research has documented distribution shifts[2], phenological changes to seasonal migration and reproduction[3], and trophic mismatch[4] in a wide variety of marine taxa. In the Pacific, fisheries interactions with loggerhead sea turtles (Caretta caretta) have resulted in temporary area closures, and vessels must comply with stringent regulations to prevent the incidental capture of this species[13]. We hypothesize that loggerheads will do so as the climate warms

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