Effects Of Beach Nourishment On Nest Site Selection And Hatchling Fitness In Loggerhead Sea Turtles Caretta Caretta PDF Download

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 ([delta]). For loggerheads, there was a significant difference in [delta] after dune restoration during the years of construction (2005, 2006, 2008, and 2009; p[less than]0.001) and one year post-construction (2007; p[less than]0.05 and 2010; p[less than]0.001). After full-scale restoration, there was a significant difference in [delta] during the years of construction (2005 and 2010; p [less than]0.001) and one year post-construction (2006; p[less than]0.001). For green turtles, there was a significant difference in[delta] after dune restoration during two of the four years of construction (2006; p[less than]0.05 and 2008; p[less than]0.01) and one of the two one-year post-construction years (2010; p[less than]0.05). After full-scale restoration, the significant difference in [delta] lasted every season (2005-2010; p[less than]0.001). There were no significant differences in [delta] 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.