Year of Graduation


Level of Access

Open Access Thesis

Embargo Period


Department or Program


First Advisor

Barry Logan


Abiotic environmental variation can drive the spatio-temporal variation of macrophyte meadow structure and associated community composition. Temperature directly impacts eelgrass (Zostera marina) meadow structure and epifaunal invertebrate community composition. Marine heat waves (MHW) represent scenarios where temperature may be extreme enough to drive community composition. I conducted a 2-year survey of Gulf of Maine eelgrass meadows across northern and southern sites, repeating the surveys monthly throughout the summer growing season. Sampling coincided with the end of the 2021-2023 Gulf of Maine MHW. During the 2022 MHW, northern meadows were 44.6% more dense, and canopy heights were 156% taller than southern meadows. Southern meadows demonstrated decline and/or die-off throughout the MHW. NMDS analyses revealed that during the MHW, epifaunal communities clustered regionally at all sampling points, while during the recovery period, epifaunal communities were similar in June and diverged by region in July and August. In the post-MHW summer, meadow structure significantly declined across all sites, but northern sites displayed a stronger recovery. Envfit analysis indicated that temperature was not significantly correlated with epifaunal communities, while meadow structure was highly associated with northern epifaunal communities. These results indicate that MHWs may indirectly impact epifaunal communities through decreasing meadow structure and available habitat space. Overall, the effects of warming can have varied impacts for extended periods of time, not only individually impacting species, but impacting the interactions between species. This work shows the need to study global change from an ecosystem-wide scale to help detangle interactive and delayed effects.

Available for download on Wednesday, May 16, 2029