The incubation environment of nests deposited by a genetically distinct group of loggerhead sea turtles in Northwest Florida

Abstract

The warming climate presents a challenge to conservation of all threatened and endangered species but particularly to those that exhibit temperature-dependent sex determination such as sea turtles. Changes in temperature may result in changes in the sex ratio of the population which can directly affect reproductive rate, abundance and population dynamics. The NW Atlantic loggerhead turtle population is listed as threatened under the U.S. Endangered Species Act, and one of the smallest subpopulations in this assemblage nests in the northern Gulf of Mexico. Here, we describe the incubation environment of northern Gulf of Mexico loggerheads nesting at several different beaches in Northwest Florida. Temperature dataloggers were placed inside and adjacent to nests on different nesting beaches across Northwest Florida. In addition, incubation durations were recorded from nests deposited on those same beaches. Internal nest temperatures were higher than those in the sand, however sand temperatures were correlated with incubation durations. Sand temperatures differed along the vertical beach profile and according to depth. Temperatures also differed along a geographic gradient across Northwest Florida and in relation to distance from the Apalachicola River. Incubation durations followed a similar pattern. Mean monthly temperatures at all sites were at or lower than 29 °C (range 23.1 °C–29.6 °C at the dunes; 23.8 °C–29.4 °C at mid-beach) which suggests nests in Northwest Florida may be producing a significant number of males, in contrast to the large number of females being produced on Florida’s Atlantic coast. The temperatures and incubation durations on these nesting beaches may be regulated by differing sources of sand and beach orientations across Northwest Florida.