Mark Nicholas | Geology Reports

USGS2020

Brightness of the night sky affects loggerhead (Caretta caretta) sea turtle hatchling misorientation but not nest site selection

Sea turtles in the Gulf of Mexico, which are listed as either threatened or endangered under the US Endangered Species Act, face numerous threats from many sources but are particularly susceptible to the effects of light pollution on nesting beaches. Light pollution affects the distribution, density, and placement of nests on beaches, and disrupts seafinding in hatchlings emerging from nests – often leading to their death. Rapid urban growth near Gulf Islands National Seashore (GUIS) over the last century has contributed to increased light pollution on its beaches, and there is concern that light pollution is causing females to lay nests in at-risk locations subject to erosion and flooding and is causing the observed high rates of hatchling misorientation. In this study our objectives were to measure brightness of the nighttime sky (and other variables) at GUIS at loggerhead (Caretta caretta) nests at the time of laying and hatching, and to assess the effects of brightness on the laying of at-risk nests and hatchling misorientation. In addition, we quantified the effects of relocating at-risk nests on nesting success. We found that the contrast in brightness between the landward and seaward directions at GUIS is at least partially responsible for high rates of hatchling misorientation, and we found a strong moderating influence of lunar fraction and lunar altitude on hatchling misorientation (larger lunar fractions and lower lunar altitudes reduced misorientation). We were unable to document any effects of artificial light, lunar fraction, or horizon altitude on the propensity of loggerheads to lay nests in at risk locations; and we found no evidence that relocating nests at GUIS reduced loggerhead nesting success. Rather, we found nesting success and hatchling misorientation rates were improved for relocated loggerhead nests.

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USGS2017

Sea turtles, light pollution, and citizen science: A preliminary report

Sea turtles are an important ecological resource for Gulf Islands National Seashore’s (Gulf Islands) waters and shorelines. Regionally, sea turtles face anthropogenic threats from situations such as entanglement in fishing gear and ingestion of marine debris, as well as possible changes in sex ratios due to increasing temperatures related to human-induced global warming. Locally, light pollution from residential, commercial, and industrial neighborhoods from nearby cities impacts the entirety of Gulf Islands, which spans 160 miles along the Gulf Coast, from Florida to Mississippi, and includes critical habitat for threatened and endangered sea turtles. Because light pollution has been hypothesized to negatively impact sea turtle nesting and hatchling survival, Gulf Islands undertook an effort to understand the relationship between light pollution and sea turtles and create unique educational and outreach opportunities by launching a citizen science program called Turtle Teens Helping in the Seashore (Turtle THIS). At the onset, the Turtle THIS program had two primary goals: quantify the association between light pollution and sea turtle nesting and hatching events using rigorous scientific methods; and initiate a citizen science volunteer program to provide youth with hands-on science and environmental stewardship roles, where they also gain employable skills and career opportunities. With multiple scientific hypotheses to consider, the development of a citizen science program became crucial. Such circumstances allowed Turtle THIS to grow a volunteer and intern program, quantify hypothesized light effects on sea turtles through developed methods, and begin to gather preliminary findings.

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