Light pollution is not just the obstruction of the night sky, it is also hundreds of thousands of lights illuminate the sky and that light reflects from the sky causing, “sky glow.” This is a major problem for ecosystems that include nocturnal animals (Longcore and Rich 2004). Responses to light pollution are orientation/disorientation, attraction and repulsion. For a hatchling sea turtle, disorientation is the unfortunate response (Longcore and Rich 2004 & Bourgeois et al. 2009).
(Longcore and Rich Ecological light pollution 2004)
Hatchlings emerge at night on sandy beaches and use the high silhouettes of the dune vegetation, which absorbs light, as an indicator to move in the opposite direction towards the lower brighter horizon (Longcore and Rich 2004 & Bourgeois et al. 2009). The ocean break reflects light and allows hatchlings to seafind (Salmon 2003).
Their cues are mainly associated with light intensity and horizontal elevation (Bourgeois et al. 2009). With lighting on the beachfront, there is no longer the reception of those cues. (Longcore and Rich 2004). Some hatchlings rely on elevation cues over light, but the movement towards the brightest light occurs when the horizon elevation is similar in each direction (Bourgeois et al. 2009).
Their optic orientation systems are adapted to natural illumination and therefore fail to cope with artificial light (Verheijen 1985). This disorientation causes the path to the ocean to elongate, which increases mortality of sea turtles through exhaustion, dehydration, increased predation and human traffic (Bourgeois et al. 2009). Even if they do make it to the ocean, they are more likely to die because of the amount of energy it took them to get there and the high energetic cost of their first days of life is not enough to sustain them (Bourgeois et al. 2009).
Another way anthropogenic light pollution affects sea turtle sensory systems is the disruption of nest-site selection. Brightly lit beaches have shown significantly fewer turtles emerge to nest on their shores (Witherington and Martin 2003).
The white light which contains both long and short wavelengths deters turtles while longer wavelength light does not (Salmon 2003). Female sea turtles lay their eggs at night and the artificial light repels them most likely because it disorients them and makes them think it is day time (Witherington and Martin 2003). This is most likely a survival tactic to protect their eggs from predators that are hunting during the day.
To protect these sea turtles, regulations should be made to either turn the light sources off or reduce the number and wattage of them. Also, if lights are necessary, positioning them so that their light does not reach the beach would help as well (Witherington and Martin 2003). If you are interested in getting involved with sea turtle conservation, check out Caretta Research Project located in Savannah, GA at carettaresearchproject.org
(Hailey Hayes Caretta Research Project July 2018 Savannah, GA)
References
Bourgeois et al. (2009) Influence of artificial lights, logs and erosion on leatherback sea turtle hatchling orientation at Pongara National Park, Gabon. Biological Conservation pp 85-93.
Longcore and Rich (2004) Ecological light pollution. Frontiers in Ecology and the Environment.
Salmon (2003) Artificial night lighting and sea turtles. Biologists pp 163-169
Witherington and Martin (2003) Understanding, Assessing, and Resolving Light-Pollution Problems on Sea Turtle Nesting Beaches. Florida Marine Research Institute Technical Reports.
Verheijen (1985) Photopollution: Artificial light optic spatial control systems fail to cope with. Incidents, causations, remedies. Experimental Biology pp1-18.