HCNSO Student Theses and Dissertations

Defense Date

12-9-2016

Document Type

Thesis

Degree Name

M.S. Marine Biology

Second Degree Name

M.S. Coastal Zone Management

First Advisor

Bernhard Riegl

Second Advisor

Venetia S Briggs-Gonzalez

Third Advisor

Michael B Robblee

Abstract

Seagrass habitats in South Florida are exceptionally valuable. They play an important ecological role in the coastal environment by stabilizing sediment, providing habitat for other species and supporting a whole food web. The availability of light and nutrients in aquatic ecosystems are the driving factors behind seagrass distribution. Water quality has been known to influence the abundance, distribution and composition of seagrass beds. South Florida has extensive diverse coastal communities. Throughout its human development dramatic changes have occurred in its natural ecosystems. In South Florida, many examples of seagrass habitat loss are documented, with a variety of contributing factors. The present research investigates the spatial and temporal patterns in benthic vegetation of the North Biscayne Bay marine basin, located just south of the heavily urbanized Port of Miami. The area has been altered significantly through dredging projects to widen and deepen the channels around the port facilities in order to accommodate larger vessels. This study focuses primarily on environmental and physical conditions that are likely to alter the distribution of seagrass. The availability of light and nutrients in aquatic ecosystems are the driving factors behind seagrass distribution and therefore one may expect seagrass degradation if any drastic changes occurred in these parameters.

Project data used were collected from the South Florida Fish and Invertebrate Assessment Network project (FIAN), an element of the greater Everglades Restoration Program. Additional Environmental and physical data were obtained from the South Florida Water Management District (SFWMD) and the National Ocean and Atmospheric Administration (NOAA). The FIAN Port of Miami (POM) study location is dominated by three species of seagrass: Thalassia testudinum, Syringodium filiforme, and Halodule wrightii. Analysis has shown that over the seven-year period, 2005 - 2011 the state of the seagrass has been fairly stable with minor perturbances (p > 0.05). There are some seasonal fluctuations evident in seagrass cover-densities, but minimal change was observed between the spring and fall (p > 0.05). Syringodium is the dominant species, followed by Thalassia and Halodule within the POM. Environmental and physical conditions from FIAN (salinity, temperature, sediment depth, turbidity, etc.) varied between years and seasons; however, most measurements remained in the ideal range for seagrass growth. Water depth, sediment depth, and turbidity were significant predictors of seagrass occurrence in the POM; however, water depth was the only major predictor of seagrass cover-density. The available environmental and physical data from the SFWMD showed minimal changes in the environmental and physical measurements across available sample years and are in the ideal range for seagrass. Turbidity has improved since the completion of the port construction and major weather disturbances (hurricanes) in 2005. Minimal changes were detected during the seven year study period (2005-2011) within the seagrass habitat of the heavily urbanized region of POM.

Comments

South Florida Fish and Invertebrate Assessment Network

United States Geological Survey Work Order #19

National Oceanic and Atmospheric Administration Work Order #3

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