Beach restoration in Florida: Effects on sea turtle nesting and hatchling physiology

Florida's beaches are constantly being threatened by erosional processes such as hurricanes. When a nearshore habitat is lost, a method commonly employed to restore coastlines is beach nourishment. Beach nourishment methods can vary, and depending on project details such as sand quality, beach slope and sand compaction, newly constructed beaches can cause beneficial or detrimental impacts to sea turtle nesting ecology.My dissertation investigates the physiological consequences different sand physical properties have on incubation gas concentrations of oxygen and carbon dioxide in loggerhead sea turtles. Sand characteristics were summarized for native and nourished beaches, east and west coast Florida beaches, and correlation analyses showed how changes in one sand parameter can influence changes in others. For example, an increase in percentage of smaller sand grains leads to an increase in sand compaction that decreases porosity and reduces the volume of air in beach sand. A reduction in total sand air volume can negatively impact gas diffusion rates between clutch and atmosphere, therefore decreasing clutch survivorship.Two sand physical properties, sand compaction and total calcium carbonate, were identified as most significant in explaining beach sand variability. Their influence on incubation gas exchange and hatchling physiology was researched in two experiments.The first experiment monitored gas concentrations of carbon dioxide and oxygen in sea turtle nests laid in low and high sand compaction. Data showed that diffusion gas rates were compromised in nests located in high sand compaction during the second half of incubation. Metabolism increases during this period and at approximately incubation day 32, the rates of embryonic oxygen demand and carbon dioxide offloading rise. High sand compaction restricts gas diffusion between clutch and atmosphere. This accumulates carbon dioxide in the clutch and prevents oxygen from reaching the eggs. This combination of gases is detrimental to sea turtle development and leads to lower hatching and emerging successes.In the second experiment I found that high concentrations of unbound sand calcium carbonate reduced clutch carbon dioxide concentrations during the second half of incubation. This buffering effect maintained incubation gases within safe physiological levels and reduced clutch mortality. However, hatchlings emerging from these nests had significantly smaller body depths, higher packed cell volumes, higher total protein levels, and higher triglycerides. This physiological data indicate these hatchlings were more dehydrated and metabolized more yolk than controls. Their physiological condition worsened after crawling 10 meters, intended to replicate traversing the beach to ocean.Data show that although clutch carbon dioxide levels can be reduced by unbound sand calcium carbonate, high sand compaction has a consistently negative impact on diffusion of oxygen and carbon dioxide molecules. Differences in atmospheric concentrations, diffusion rates, and solubility of oxygen and carbon dioxide molecules, intensify this effect for the latter.Regulation of specific sand characteristics is paramount for beach nourishment projects. Engineers and regulators should incorporate the information emanating from this dissertation into future beach restoration projects because it relates human needs to the consequences beach sand can have on the incubation of loggerhead sea turtles.