Abstract

The recruitment success of mangroves is influenced by a variety of factors, including propagule availability, desiccation, herbivory, and hydraulic habitat limitations. Hydrodynamic forces (waves and currents) act as obstacles to mangrove recruitment, restricting the successful colonization of mangrove species. We evaluated the biological and physical limitations to mangrove recruitment through monthly shoreline surveys and lateral pull-tests. Surveys followed mangroves from propagule release through recruitment along the shorelines of De Soto National Memorial (Bradenton, FL), capturing differences in propagule availability and recruitment along natural areas and across differing forms of shoreline stabilization ("living shorelines" and revetments). Propagule densities were highest along "living shorelines", followed by natural areas and revetments. Seedling densities were similar across treatments, mirroring densities found in disturbed mangrove systems in the Philippines ( < 1 seedling per m2). Pull-tests, simulating wave forces, quantified the physical thresholds for uprooting Rhizophora mangle and Avicennia germinans seedlings in both the greenhouse and field. Uprooting susceptibility significantly decreased with increased seedling biomass and age. A. germinans displayed a lower force to removal than R. mangle, but showed a greater increase in uprooting force with increases in size. Surrounding vegetation and canopy cover were not found to significantly affect the uprooting force of either species. Pull-test results were used in conjunction with drag coefficients from the literature to calculate flow velocities where mangroves would become susceptible to dislodgement from hydrodynamic forces. Seedlings tested would become susceptible at velocities of 7.33 ± 2.07 m/s for A. germinans and 5.40 ± 1.59 m/s for R. mangle. The rapid increase in force to removal shows the importance of disturbances, such as erosion, driving seedling dislodgment at the local scale. This research strengthens our understanding of the physical conditions conducive to successful recruitment under hydrodynamic stressors and provides insight into how a common restoration method can influence mangrove recruitment.

Notes

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Graduation Date

2019

Semester

Spring

Advisor

Walters, Linda

Degree

Master of Science (M.S.)

College

College of Sciences

Department

Biology

Degree Program

Biology

Format

application/pdf

Identifier

CFE0007899

URL

http://purl.fcla.edu/fcla/etd/CFE0007899

Language

English

Release Date

November 2019

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

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