HCNSO Student Theses and Dissertations
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Defense Date
6-2007
Document Type
Thesis - NSU Access Only
Degree Name
M.S. Marine Biology
Second Degree Name
M.S. Coastal Zone Management
Department
Oceanographic Center
First Advisor
Curtis M. Burney
Second Advisor
Lou Fisher
Third Advisor
Keith Ronald
Abstract
Many environmental parameters, both physical and anthropogenic, can influence nest site selection. One of the most basic requirements for a suitable nesting habitat is a dark beach. With the increases in coastal development, the beaches of Broward County, Florida are becoming more polluted by artificial light, making dark beaches a rarity. On urban beaches in Boca Raton, Florida, it was found that turtles nested directly in front of tall structures, such as high-rise condominiums and clusters of Australian pine trees (Casuarina equisetifolia), that blocked the sky glow from the city providing darker sections of the beach more suitable to nesting females (Salmon et al., 1995). The goal of this project was to compare the previous four years (2002-2005) of nesting with the heights of the buildings and the sky brightness, in historically high nesting zones of Broward County (Mattison, 2004). Nesting distributions were plotted using GIS (Global Information Systems), and the beach was subdivided into smaller sections according to the buildings in each section. The number of nests in front of a building, in front of a gap between the buildings, and in residential zones were compared. The average nesting density (nests/10m) over all four years, as well as the individual yearly densities were analyzed. Ecological light pollution (sky brightness) was measured in nine different directions and angles. The brightest direction for all three locations was when the meter was pointed directly at the structures and the gaps between them at an elevation of 40° (Building and Gap 40°). There was no evidence of higher light intensities from sky glow above the buildings at an angle of 65o (Building and Gap 65°). There was a difference in sky brightness among the three zones, with the tall buildings and gaps being consistently brighter than the residential zones. Contrary to expectations, the gaps were not brighter than the buildings, and there was no significant relationship between sky brightness and nesting densities (Spearman rank correlation). There was also no relationship between the nesting densities and the heights of the buildings (Spearman rank correlation). There was also no association among nesting density, sky brightness, and height (Kendall’s coefficient concordance). These results are contradictory to the theory that suggests females nest more in front of buildings where the sky brightness is blocked (Salmon et al., 1995). This may be due to the fact the buildings and residences were not incompliance with lighting ordinances, causing very high light levels, or it could be caused by the close spacing of the buildings, which resulted in similar light intensities in front of buildings and gaps. These results could provide valuable insight into appropriate management of light pollution and conservation efforts for sea turtles nesting in Broward County.
NSUWorks Citation
Jessica A. Watters. 2007. The Effects of Ecological Light Pollution and Silhouette Height on the Nesting Densities of Caretta caretta in Broward County, Florida. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, Oceanographic Center. (101)
https://nsuworks.nova.edu/occ_stuetd/101.
Comments
Funding provided by Broward County Environmental Protection Department.