HCNSO Student Theses and Dissertations

Defense Date

12-2012

Document Type

Thesis

Degree Name

M.S. Marine Biology

Second Degree Name

M.S. Marine Environmental Sciences

Department

Oceanographic Center

First Advisor

Amy C. Hirons

Second Advisor

Silvia Marcia

Third Advisor

Richard E. Spieler

Abstract

Seagrass beds serve critical functions in coastal Florida ecosystems. The beds serve as nursery habitat for many juvenile reef fish species and provide protection for many types of benthic organisms found in Biscayne Bay. They help stabilize sediment that would otherwise increase turbidity around coral reefs, filter the water of contaminants, and help support an entire food web. Three species of seagrass were found at the study sites in northern Biscayne Bay: Thalassia testudinum, Halodule wrightii, and Syringodium filiforme. This study focused on understanding the organism habitat interaction by determining the species diversity, seasonal densities, and the correlation between population size and individual size for Penaeid shrimp, juvenile fish, and small adult fish at each site over a one year period. Habitat selectivity of various species was determined based on the habitat complexity derived from the various different seagrasses found in each of the beds. Animals predominantly favored H. wrightii habitat (Kruskal-Wallis H test: p< 0.0001) and this was likely the result of a decrease in predation risk due to the increased habitat complexity of the seagrass beds. Species diversity did not vary significantly over the course of a year (p= 0.7790), likely due to the lack of large abiotic disturbances (e.g. boating, hurricanes, and extreme salinity changes) to the seagrass beds. Densities of inhabitants changed significantly on a monthly basis, with the overall epifauna densities greatest at the end of the wet season (p< 0.01). The lack of correlation between individual size and overall population size likely indicated the majority of the species caught did not exhibit ontogenetic migration or live in the seagrass beds for the entirety of their life cycle.

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