Date of Award

Summer 8-18-2023

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Amanda Klemmer

Second Committee Member

Brian Olsen

Third Committee Member

Michael Kinnison

Additional Committee Members

Jessica Muhlin

Robert Steneck

Abstract

Ecosystems at the land-sea interface are subject to a multitude of abiotic and biotic factors that shape which species occupy this habitat. Through my dissertation, I explore how such factors influence coastal communities in the Gulf of Maine. In Chapter 1 I investigate the ability of an intertidal foundation species (rockweed) to dampen local abiotic drivers of community assembly. I found that the influence of site characteristics on meiofaunal community structure was not completely denuded by foundation species presence. Additionally, large scale regional drivers had a strong influence on communities but interact with local abiotic characteristics and foundation species. Chapter 2 examines the role of disturbance intensity and scale on community response to and recovery from foundation species disturbance. I measured invertebrate community composition, before, immediately after, and one year after commercial rockweed harvest. While invertebrate community composition was initially impacted by harvest, even communities with a substantial initial response to harvest were largely able to recover within a year. Moreover, measures of harvest at the small, patch scale predicted invertebrate response to harvest better than regional factors or site level measures of harvest intensity. For Chapter 3, I measure benthic community variation across the rocky intertidal, a model ecosystem for environmental stress gradients, over a span of six years in the Gulf of Maine. I found communities at the high and low ends of the stress gradient were more likely to exhibit changes in composition, while the communities towards the middle largely remained stable. In Chapter 4 I explore the role of rocky intertidal-derived subsidies in consumer community composition in adjacent coastal ecosystems with different in situ productivity. I discovered that communities associated with rockweed subsidies were more similar to the ambient community in the low productivity ecosystem, a sandy beach, than the high productivity ecosystem, a salt marsh. A field experiment showed that consumer abundances were also different between high- and low- quality subsidies in both ecosystems, but the subsidy type that supported the most consumers varied between systems. Together these studies highlight the influence of intrinsic and extrinsic ecosystem characteristics on community composition and variation.

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