Date of Award

8-2025

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Marine Biology and Coastal Sciences

Thesis Sponsor/Dissertation Chair/Project Chair

Colette Feehan

Committee Member

Lisa Hazard

Committee Member

Carla Narvaez

Abstract

Temperate reef ecosystems are experiencing rapid canopy loss of kelp and the proliferation of algal turf. However, the consequences of these changes for crustose coralline algae (CCA)— a key but often overlooked benthic calcifier—are poorly understood. Here, I study CCA recruitment patterns in southern New England, USA, using standardized settlement tiles at two field sites over 12 months (September 2023 – August 2024). I measure CCA accretion rates and the associated biological and environmental correlates of CCA recruitment. At the two sites, CCA accretion rates ranged from 0.0259 to 1.215 mg CaCO3 cm⁻² yr⁻¹, with an average of 0.441 mg cm⁻² yr⁻¹, which is generally much lower than rates on tropical reefs. Generalized least squares regression models indicated that tile orientation (horizontal versus vertical to the seafloor) had no significant effect on accretion, while site had a strong effect. Moreover, limpet abundance showed a weak positive relationship with CCA accretion. In a focused analysis on horizontal tiles at a single site where both kelp and turf recruited to tiles, turf biomass was negatively correlated with CCA accretion, while kelp biomass had no effect. This study suggests cm- to km-scale patchiness in CCA accretion, possibly driven by factors such as local oceanographic regimes, facilitation by grazers/bulldozers, or direct competition with algal turf. Follow-up studies at additional sites will be needed to confirm these patterns and their mechanisms. Given the overlooked status of CCA on many temperate reefs, integrating CCA protection into kelp-forest restoration is likely necessary.

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