Date of Award

1-1-2015

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

First Advisor

Eric T. Koepfler

Second Advisor

Kevin S. Godwin

Third Advisor

Scott L. Parker

Abstract

Photopollution present along heavily developed coastlines is known to have a significant negative impact on nesting sea turtle populations by damaging nesting habitat quality, but few studies have explored this relationship on broad spatial scales. The purpose of this study was to characterize the onshore light field along a developed stretch of South Carolina coastline and to quantify how photopollution intensity affects regional loggerhead sea turtle (Carretta carretta) nesting density using historical nesting data. Light measurements were collected using a portable low-light photometer at 74 sites spaced at approximately one km intervals across the study area. At each site, the 360° light field was divided into twelve 30° horizontal intervals. Onshore light measurements were recorded at two inclination angles relative to the horizon at each horizontal interval. NOAA VIIRS satellite imaging was also used to collect photopollution data and to compare results between sampling methodologies. Onshore light intensity at both inclination angles was found to be negatively logarithmically correlated with nesting density. The lower of the two inclination angles was consistently brighter at developed locations, while no significant difference was noted at undeveloped sites. Photometer light intensity data was also moderately correlated with the satellite imaging measurements. Light intensity was found to be highest at central onshore angles relative to peripheral angles in developed regions, while the opposite relationship was observed in undeveloped regions. This study provides a critical baseline for coastal photopollution in the Grand Strand region of South Carolina and demonstrates that loggerhead sea turtle nesting density declines dramatically along beaches exposed to chronic night lighting. In addition, we reveal significant differences in the characteristics of the onshore light field between developed and undeveloped locations that may play a role in nest site selection and could help to inform conservation efforts.

Included in

Biology Commons

COinS