Date of Award

5-2026

Rights

© 2026 Matthew Zachary Mar

Document Type

Thesis

Degree Name

Master of Science in Marine Sciences

Department

Marine Science

First Advisor

Carrie J. Byron

Second Advisor

Thew Suskiewicz

Third Advisor

Cara Blaine

Abstract

Palmaria palmata, more commonly known as dulse, is a North Atlantic red algae that has been of interest to the aquaculture industry for its taste, nutritional content, and economic value. Market demand is higher than what wild harvest can sustainably supply, so it is essential to develop cultivation methods for this species. Line-based farming is an effective method to grow macroalgae at large scales, but has not been implemented for dulse. Limitations in current techniques have made it difficult to produce seeded dulse substrates on a commercial scale due to inefficient spore usage. We tested the viability of a new seeding method for dulse which takes advantage of the passive release of spores within a sporophyte culture to improve spore usage efficiency. Concurrently, we investigated substrate optimization by running five pairwise comparisons of six different twine types, comparing three material types (polyvinyl alcohol, PVA; polyamide, PA; polypropylene, PP), two types of weave (twisted and braided), four diameters, and a range of surface complexities. Data on attached spore density was collected over a nine week nursery period and analyzed to link these substrate properties to spore settlement and adhesion processes.

Passive seeding produced spore densities ranging from 10-100 spores/cm twine on average, comparable to densities reported using other seeding methods for dulse, while eliminating the need for an active release step and lessening the requirements for high fertility sorus material. Twine diameter, weave, and surface texture significantly impacted spore settlement. A 1 mm twine was more space efficient and had higher spore density per unit area than 2 mm twine, while a twisted weave had higher seeding density than a braided one. A highly complex, filamentous texture inhibited spore settlement, producing seeding densities roughly 85% lower than twine with a simpler surface. Wettability and texture had significant impacts on attachment strength, with spores having 30-70% weaker attachment to a hydrophobic PP substrate compared to moderately hydrophilic PA or highly hydrophilic PVA substrates. Spores displayed more intense thigmotropic interactions and interlocked more strongly with a denser, more stable texture than with loosely wound threads, enhancing their attachment strength in response to turbulent flow. We conclude that passive seeding is an effective method to produce seeded dulse substrates, increase spore use efficiency, and improve the scalability of line-based cultivation. Substrate optimization tests indicated that a moderately hydrophilic (contact angle 50-70o), small diameter (~1 mm), twisted twine, with densely connected threads, deep microtopography depth, and no loose filaments would be the ideal substrate to maximize spore settlement, retention, and attachment strength for dulse cultivation.

Comments

Master's Thesis

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