Date of Award

Spring 5-7-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Biology

Advisor

Carrie Byron

Second Committee Member

Damian Brady

Third Committee Member

Kate Beard

Additional Committee Members

Susan Brawley

Barry Costa-Pierce

Abstract

Commercial seaweed farming efforts are expanding worldwide. The use of new species, ecosystems, and practices present many opportunities for novel research and resource management. The purpose of this project was to evaluate and advance seaweed aquaculture practices in the Western Gulf of Maine. Saccharina latissima (sugar kelp) is the species of focus because it is currently the most farmed macroalga in the Northeastern United States. Fieldwork supporting the empirical studies was conducted January 2016 - May 2019 in Casco and Saco Bays, ME. Growth, yield, morphology, elemental and isotopic composition, and enzymatic activity of S. latissima were quantified across four sites. These observations were used to evaluate the nitrogen bioextraction efficiency of S. latissima farms in this region and the effect of distal-end trimming on the morphology and yield of S. latissima. Additionally, Maine kelp aquaculture was used as a case study to determine if the Ecosystem Approach to Aquaculture was suitable for seaweed farming and to explore the application of a multi-criteria screening model to guide the market-specific siting of seaweed aquaculture. Findings from these studies depict a high variability in ambient environmental conditions between sites and in morphological and compositional variability between individual sporophytes. On a hectare-to-hectare basis, the nitrogen bioextraction by kelp farming in the region far exceeded the nitrogen loading from riverine or atmospheric sources. Distal-end trimming had a significant effect on S. latissima stipe and blade morphology and increased late-season production yields. Furthermore, the Ecosystem Approach to Aquaculture was found to be applicable to the development of kelp aquaculture beyond Asia. Specific attention should be given to maintaining genetic diversity, developing best management practices, and integrating wild and farmed kelp management. Lastly, the screening analysis showed that the application of criteria specific to end-market uses of seaweed biomass results in uniquely optimal areas for cultivation. These findings are novel contributions to the fields of aquaculture research, coastal management, and phycology, and they provide a platform for continued research and development of seaweed aquaculture in the region.

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