Date of Award

Fall 12-7-2023

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Ocean Science and Engineering

Committee Chair

Dr. M. Zachary Darnell

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dr. Kelly Darnell

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Dr. Patrick Biber

Committee Member 3 School

Ocean Science and Engineering

Abstract

Seagrass beds support high biodiversity and animal abundance, serve as feeding grounds for a variety of animals, offer shelter from predation, and act as a nursery habitat for juveniles. The species composition of seagrass beds can impact their use as habitat by animals. Two common species of seagrass in the Gulf of Mexico are Ruppia maritima (widgeon grass) and Halodule wrightii (shoal grass). The shallow coastal waters of the Grand Bay National Estuarine Research Reserve (NERR) support both species, but the use of each seagrass as habitat by nekton is poorly understood, which can limit management decision-making. Nekton communities were sampled in May, July, September, and November 2022 in the Grand Bay NERR within R. maritima and H. wrightii-dominated seagrass beds and unvegetated habitat. All nekton were collected, identified to species, weighed, and measured to quantify density, species richness, and species diversity within each habitat. Seagrass cores were also collected to quantify aboveground biomass, root to shoot ratio, and epiphyte density. Juveniles of several commercially fished nekton species including blue crabs (Callinectes sapidus), white shrimp (Penaeus setiferus), and brown shrimp (Penaeus aztecus) were collected, with higher densities and greater species diversity in seagrass beds compared to unvegetated bottom. R. maritima and H. wrightii were marginally different from each other in terms of habitat use by nekton. Percent cover of both species was the most important habitat feature influencing use by nekton, with greater cover hosting more nekton. These results reinforce the importance of seagrass within the Grand Bay NERR as essential habitat and can be used to inform management and long-term planning.

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