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The effect of beach nourishment on loggerhead (Caretta caretta) nesting and reproductive success at Sebastian Inlet, FloridaHerren, Richard Michael 01 January 1999 (has links) (PDF)
Beach nourishment has become common in Florida and it occurs on beaches that are major loggerhead (Caretta caretta) nesting grounds. Despite efforts to use beach-quality sand, nourishment sand may be different in grain size, moisture content, shear resistance and temperature when compared to native sand. Two main aspects of loggerhead nesting may be affected by nourishment. First, nourishment may reduce nesting success [(female nesting emergences/ female total emergences) X 100] due to physical barriers (i.e., scarps or steep cliffs) that can impede gravid females. Second, nourishment may reduce reproductive success {i.e., hatching success) by altering the nestsand environment. The objective of this study was to compare loggerhead nesting success, nest placement, slopes at nest sites, nest depths, incubation periods, reproductive success and egg fates among an old renourished beach {"south"), a recently nourished beach ("treatment") and a natural beach ("control") at Sebastian Inlet, Florida in 1996, 1997 and 1998. In all three years, nesting success was significantly different among study sites. After nourishment (1997), nesting success was reduced at the treatment site due to a seaward scarp. A year later (1998), the scarp was leveled and nesting success improved. Nest placement was not significantly different between study sites prior to nourishm_ent of the treatment study site (1996), but it was after nourishment (1997) and one-year post-nourishment (1998). After nourishment, most nests at the treatment beach were placed too close to the water or too close to the dune. There were no significant differences in the slope at nest sites in 1997; suggesting females may have selected similar increases in slope, but at varied cross-shore locations. Nest depths were significantly shallower at the treatment beach after nourishment, probably due to higher compaction of the nourishment sand. In addition, incubation periods were significantly longer on the nourished beaches one year post-nourishment. Loggerhead hatching success was significantly reduced on the nourished beaches in 1996 and 1997. The reduction was seen primarily in a larger proportion of eggs that were arrested early in development. The higher moisture in the nourishment sand may have impeded gas exchange, which resulted in decreased hatching success. One year post-nourishment (1998), there were no significant differences in hatching success. The lack of rainfall in 1998 may have introduced better incubation conditions on the nourished beaches. Researchers at the Florida Institute of Technology continued to show that the nourishment sand exhibited significantly smaller grain size, higher moisture content, lower temperature and higher shear resistance. These attributes were probably responsible for many of the results reported herein. However, other variables such as non-random nest depredation, inlet influences and water table levels may have also contributed to the results.
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Effects Of A Shore Protection Project On Loggerhead And Green Turtle Nesting Activity And Reproduction In Brevard County, FloridaBrock, Kelly 01 January 2005 (has links)
Marine turtle reproductive success is strongly correlated with the stability and quality of the nesting environment. Because females show fidelity to key nesting beaches, the management and physical characteristics of these beaches directly affect future generations of marine turtles and may be essential for the recovery of these threatened and endangered species. The impacts of beach restoration on loggerhead turtles (Caretta caretta) and on green turtles (Chelonia mydas) were investigated. Previous studies concerning beach nourishment projects have focused on loggerhead turtles. I compared data between nourished and non-nourished areas and between loggerhead and green turtles. I found, at one season post-nourishment, negative effects on nesting success and no significant effect on reproductive success for both loggerheads and established the same relationships with green turtles. Physical attributes of the fill sand, which did not facilitate acute scarp formation or severe compaction, did not physically impede turtles in their attempts to nest. Instead, the decrease in nesting success was attributed to an absence of abiotic and or biotic factors that cue nesting behavior. The increase in loggerhead nesting success rates during the second season post-nourishment was attributed to the equilibration process of the seaward crest of the berm. After the beach was restored, both species of turtles placed nests significantly farther from the water in the nourished area than in the non-nourished area. Green turtles nested on or near the dune and loggerheads nested on the seaward crest of the berm. The tendency of loggerheads to nest closer to the water resulted in more loggerhead than green turtle nests being "washed out" by erosion during the equilibration process. There was a significant increase in hatching success only for loggerheads when wash outs were excluded, thus illustrating the importance of nest placement and the detrimental effects of the equilibration process to the reproductive success of loggerheads. A decrease in reproductive output occurred during the first season post-nourishment. The reduction in the estimated total number of hatchlings produced (reproductive output) was a consequence of decreased nesting success lowering nest numbers. This reduction demonstrates that, regardless of similar reproductive success rates, marine turtles incurred net losses during the first season following nourishment. These results further reveal the impacts of decreased nesting success and the importance of minimizing excessive non-nesting emergences associated with beach nourishment.
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