Semester of Graduation

Fall 2023

Degree

Master of Science (MS)

Department

The School of Renewable Natural Resources

Document Type

Thesis

Abstract

Oysters are declining globally, resulting in an increase in oyster reef restoration, with many efforts prioritizing maintenance of reef-associated biodiversity. Understanding the role that reef-specific characteristics play in supporting biodiversity and how sampling gear influences measurements of biodiversity can inform design and management of restoration projects. I examined the relationship between live oyster volume and reef-associated benthic and nekton assemblages (hereafter reef assemblages) and how sampling gears influence our understanding of biodiversity on intertidal Crassostrea virginica reefs near Cocodrie, Louisiana. I quantified substrate characteristics, assemblages via trays, and water-column characteristics across four reefs and four seasons in 2022-2023, and compared two sampling gears, suction sampler and trays, during summer 2022. Reef assemblage taxa abundance, Pielou’s evenness, Shannon-Wiener diversity, and taxa richness (hereafter biodiversity metrics) were related to live oyster volume, but these patterns varied across seasons and by biodiversity metric. Diversity and evenness decreased with increasing live oyster volume across seasons driven by smaller macrofauna taxa that numerically dominated the assemblages. Taxa abundance patterns varied by season; increasing with increasing live oyster volume in the spring and fall with no significant patterns in the winter and summer. Taxa richness patterns also varied by season; decreasing with increasing total substrate volume (i.e., live and dead oysters) in the winter and spring, when overall richness was lower, and fewer unique taxa were found, and increasing in the summer and fall with increasing total substrate volume, when more unique taxa were sampled. Overall, live oysters are associated with the presence of unique taxa and play a role in assemblage structure beyond providing structural habitat. Additionally, I found that most biodiversity metric outcomes differed by gear type and did not result in the same patterns across reefs and gear types. Abundance and richness were higher, and evenness was lower in trays compared to suction samples. Shannon-Wiener diversity was similar in suction and tray samples at two out of three reefs. The selection of different sampling gears may result in different conclusions of biodiversity trends, ultimately impacting conservation decisions. Live oyster volume is a key reef characteristic influencing reef assemblage, but differences in results by gear type directly influences our understanding of foundation species’ impacts on reef assemblages.

Date

8-11-2023

Committee Chair

La Peyre, Megan K.

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