Author ORCID Identifier

0009-0003-3538-5641

Date of Award

12-31-2025

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology/Environmental Biology

First Advisor

Jarrett Byrnes

Second Advisor

Ron Etter

Third Advisor

Luis De León

Abstract

The Gulf of Maine (GOM) has faced many changes over the last 47 years from overfishing of its iconic cod fish stocks to the introduction on non-native species, but no change has been as dramatic as the warming ocean temperatures that began to increase rapidly in the 2010s. This thermal shift is due largely to the northward movement of the Gulf Stream current mixing with Arctic meltwater before entering the GOM. Average summer temperatures jumped by 3.35°C between the periods of 1980-1985 and 2015-2020. This warming trend, combined with an increasing frequency of marine heat wave events, has led to a ramp up in the metabolic demands of one of the GOMs primary grazers, the green sea urchin Strongylocentrotus droebachiensis. Warming in the GOM has also led to temporal turnover in species richness as cold and cool-affinity species largely decline. We also find that warming in the GOM does not increase in parallel with depth and that our deepest sites are warming faster than our shallower sites. This unequal warming led to a shift in some warm-adapted species moving into deeper, slightly colder water to avoid warming surface waters, while cold-adapted species are faced with local extinction. Together this study aims to understand the dynamics of change on subtidal rock walls in the GOM by examining community-level responses to warming ocean temperatures.

Comments

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