COS 206-1 - Shifts in the thermal affinity of a Gulf of Maine intertidal community over 35 years

Thursday, August 18, 2022

8:00 AM – 8:15 AM EDT

Location: 513C

Presenting Author(s)

JL

Jake Lawlor

McGill University, Canada

Coauthor(s)

AH

Amelia Hesketh

The University of British Columbia, Canada
AB

Andrea Brown

MSc candidate
McGill University
Longueuil, Quebec, Canada
AP

Alexis Pereira

University of Guelph, Canada
JB

Julien Beaulieu

Université du Québec à Montréal, Canada
EB

Ellen Bledsoe

University of Arizona, United States
JB

Joseph Burant

CIEE Living Data Project; McGill University; Université de Montréal, Canada
NK

Nicole Knight

McGill University, Canada
JM

Jenny Muñoz

University of British Columbia, Canada
TP

Tianna Peller

postdoctoral fellow
Eawag
KS

Kate Sheridan

McGill
Montreal, Quebec, Canada
LS

Laura Super

University of British Columbia
Vancouver, British Columbia, Canada
KB

Kylla Benes

University of Montana, United States
JB

Jarrett E.K. Byrnes

University of Massachusetts Boston, United States

Background/Question/Methods

Anthropogenic warming has caused widespread changes in species abundance across habitats, and can differentially affect organisms depending on their species-specific thermal tolerance. Effects of warming, both lethal and sublethal, can vary in direction and magnitude across space, with increasing temperatures positively affecting performance near the cold edges of species’ distributional ranges, and negatively affecting performance at warm edges. For this reason, when viewing effects of climate change in one location over time, we might expect warmer-affinity species to increase in performance, and colder-affinity species to decrease, altering the composition of the community, and thus, the functions it can provide. Here, we use a dataset of intertidal species assemblages on Appledore Island in the Gulf of Maine from 1982-2017 to analyze changes in abundance of intertidal species in relation to the species' occupancy-derived thermal preferences. Then, we use the Community Thermal Index, an abundance-weighted average of species thermal affinities, to describe community-level thermal affinity changes over time. Finally, we compare the rate of community thermal change to the rate of climate change in the region to assess the extent to which biological changes are responding to the environment.

Results/Conclusions

Overall, we tracked changes in abundance in the Appledore Island intertidal community for over 70 species, which had occupancy-derived thermal affinities ranging from 7.6 to 18.9°C, relative to the average 10.2°C sea surface temperature around the island. We found a positive relationship between abundance change and thermal preference such that species with lower temperature thermal preferences ('cold-affinity') are more often decreasing in abundance in survey sites, and species with higher temperature thermal preferences ('warm-affinity') are more often increasing. However, we also observed many species with thermal preferences close to the mean sea surface temperature of the region, which increased or decreased in abundance for reasons that cannot be explained by thermal preference alone. We found that the Community Thermal Index of the intertidal community increased over 35 years of sampling (~ .04°C per decade), but considerably more slowly than the rate of warming in the region (~ .4°C per decade). These results indicate that intertidal communities in the Gulf of Maine are responding to temperature change, but not as quickly as it is occurring, suggesting a lagged biological response, or that additional factors may better explain species abundance changes in the region.