You are here

Determining the impacts of beach restoration on loggerhead (Caretta caretta) and green turtle (Chelonia mydas) nesting patterns and reproductive success along Florida's Atlantic coast

Download pdf | Full Screen View

Date Issued:
2012
Abstract/Description:
Artificial beach nourishment, the most common method to mitigate coastal erosion in the United States, is also considered the most ecologically friendly alternative for shoreline stabilization. However, this habitat alteration has the potential to impact nesting marine turtles and developing hatchlings. The first objective of this study was to determine how nourishing beaches with two different design templates affects loggerhead (Caretta caretta) and green turtle (Chelonia mydas) nesting success, the ratio of nests to the total number of nests and non-nesting emergences, and reproductive success, the ratio of hatched and emerged hatchlings to the total number of eggs deposited. Two types of restoration designs exist along the southern Brevard County, FL coastline, which supports some of the highest density loggerhead and green turtle nesting worldwide. Since 2005, approximately 35 kilometers of beach have undergone 1) full-scale restoration (typically called nourishment), where sand was added above and below the mean high tide line (2005, 2010) or 2) dune restoration, where sand was placed on the dune (2005, 2006, 2008, 2009). To quantify the effects of these restoration types, we used a Before-After-Control-Impact-Paired Series (BACIPS) model, which tests for significance between the difference in nesting success rates at the impact (engineered) and control sites (natural beach) before and after restoration (?). For loggerheads, there was a significant difference in ? after dune restoration during the years of construction (2005, 2006, 2008, and 2009; p(<)0.001) and one year post-construction (2007; p(<)0.05 and 2010; p(<)0.001). After full-scale restoration, there was a significant difference in ? during the years of construction (2005 and 2010; p (<)0.001) and one year post-construction (2006; p(<)0.001). For green turtles, there was a significant difference in ? after dune restoration during two of the four years of construction (2006; p(<)0.05 and 2008; p(<)0.01) and one of the two one-year post-construction years (2010; p(<)0.05). After full-scale restoration, the significant difference in ? lasted every season (2005-2010; p(<)0.001). There were no significant differences in ? for loggerhead or green turtle reproductive success rates after either type of restoration. The second objective was to use the different restoration designs to study what beach characteristics function as loggerhead nesting cues to explain why altering the beach decreases nesting success rates. We examined beach elevation and slope, sand moisture content, sand grain size, beach width, and distance traveled. Logistic regression model selection found all variables were important (R2=0.75). Further examination of trends, with each crawl divided into quarters, found beach slope served as a nesting cue. In all study sites except one, when turtles false crawled, the beach flattened out in the final quarter of the crawl. Conversely, in nesting emergences, the final quarter rose at a steeper slope than the previous quarter. Additionally, model selection found variables important in nest site selection were also important in hatching (R2=0.44) and emergence (R2=0.45) success. These results offer new insight into how and why marine turtle nesting patterns change after artificial nourishment, providing information necessary to nourish beaches in a more (")turtle-friendly(") manner. ?
Title: Determining the impacts of beach restoration on loggerhead (Caretta caretta) and green turtle (Chelonia mydas) nesting patterns and reproductive success along Florida's Atlantic coast.
11 views
6 downloads
Name(s): Hays, Allison, Author
Weishampel, John, Committee Chair
Ehrhart, Llewellyn, Committee CoChair
Mota, Mario, Committee Member
Hinkle, Charles, Committee Member
, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2012
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Artificial beach nourishment, the most common method to mitigate coastal erosion in the United States, is also considered the most ecologically friendly alternative for shoreline stabilization. However, this habitat alteration has the potential to impact nesting marine turtles and developing hatchlings. The first objective of this study was to determine how nourishing beaches with two different design templates affects loggerhead (Caretta caretta) and green turtle (Chelonia mydas) nesting success, the ratio of nests to the total number of nests and non-nesting emergences, and reproductive success, the ratio of hatched and emerged hatchlings to the total number of eggs deposited. Two types of restoration designs exist along the southern Brevard County, FL coastline, which supports some of the highest density loggerhead and green turtle nesting worldwide. Since 2005, approximately 35 kilometers of beach have undergone 1) full-scale restoration (typically called nourishment), where sand was added above and below the mean high tide line (2005, 2010) or 2) dune restoration, where sand was placed on the dune (2005, 2006, 2008, 2009). To quantify the effects of these restoration types, we used a Before-After-Control-Impact-Paired Series (BACIPS) model, which tests for significance between the difference in nesting success rates at the impact (engineered) and control sites (natural beach) before and after restoration (?). For loggerheads, there was a significant difference in ? after dune restoration during the years of construction (2005, 2006, 2008, and 2009; p(<)0.001) and one year post-construction (2007; p(<)0.05 and 2010; p(<)0.001). After full-scale restoration, there was a significant difference in ? during the years of construction (2005 and 2010; p (<)0.001) and one year post-construction (2006; p(<)0.001). For green turtles, there was a significant difference in ? after dune restoration during two of the four years of construction (2006; p(<)0.05 and 2008; p(<)0.01) and one of the two one-year post-construction years (2010; p(<)0.05). After full-scale restoration, the significant difference in ? lasted every season (2005-2010; p(<)0.001). There were no significant differences in ? for loggerhead or green turtle reproductive success rates after either type of restoration. The second objective was to use the different restoration designs to study what beach characteristics function as loggerhead nesting cues to explain why altering the beach decreases nesting success rates. We examined beach elevation and slope, sand moisture content, sand grain size, beach width, and distance traveled. Logistic regression model selection found all variables were important (R2=0.75). Further examination of trends, with each crawl divided into quarters, found beach slope served as a nesting cue. In all study sites except one, when turtles false crawled, the beach flattened out in the final quarter of the crawl. Conversely, in nesting emergences, the final quarter rose at a steeper slope than the previous quarter. Additionally, model selection found variables important in nest site selection were also important in hatching (R2=0.44) and emergence (R2=0.45) success. These results offer new insight into how and why marine turtle nesting patterns change after artificial nourishment, providing information necessary to nourish beaches in a more (")turtle-friendly(") manner. ?
Identifier: CFE0004332 (IID), ucf:49447 (fedora)
Note(s): 2012-05-01
M.S.
Sciences, Biology
Masters
This record was generated from author submitted information.
Subject(s): beach nourishment -- dune restoration -- beach restoration -- loggerhead -- green turtle -- nesting success -- reproductive success -- nesting cues -- nest site selection
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0004332
Restrictions on Access: campus 2013-05-15
Host Institution: UCF

In Collections