Researchers in Western Australia are testing how different types and intensities of artificial light affect the ability of green turtle hatchlings to find the sea after emerging from their nests, amid growing concern about the ecological impacts of coastal lighting.
Turtle hatchlings typically orient towards the ocean using natural cues such as dark dunes and the starlit horizon, but artificial light at night from towns, resorts and industrial sites can draw them inland or along beaches, increasing the risk of predation, exhaustion and dehydration.
“Our goal is to better understand how green turtle hatchlings – a threatened species – respond to lights of different intensities and types,” said Australian Institute of Marine Science (AIMS) senior lead researcher Dr Michele Thums.
The project, run by AIMS in collaboration with Pendoley Environmental and the WA Department of Biodiversity, Conservation and Attractions, is examining common LED sources as well as the blended glow typical of human settlements. The team says the work builds on decades of research showing different light wavelengths can affect hatchling behaviour, and aims to translate those insights into practical guidance for lighting in coastal areas.
“We hope the findings will guide future lighting decisions that meet the needs of coastal residents, councils and industry, and at the same time, aid in the conservation management of marine turtles,” Dr Thums said.
Over seven nights, the team collected more than 200 green turtle hatchlings from Jurabi Coastal Park near Exmouth to run controlled laboratory trials using a Y‑maze. Each hatchling was exposed up to three times to varying light intensities of several sources, with a darkened maze arm as a control, to identify thresholds at which light begins to draw hatchlings away from darkness. All hatchlings were returned to their nesting beaches the same night.
AIMS postdoctoral researcher and co‑lead Dr Daniel Gomez Isaza said the study is designed to determine the “minimal attraction” levels for different lights. “The aim is to pinpoint the intensity that has minimal attraction of hatchlings for each of the different types of light we tested. ”
“From our early observations, the hatchlings quickly crawled towards the illuminated arm of the Y maze at high light intensities, but the attraction for the lights was reduced as we lowered light intensities. ”
“The next step is for us to analyse the data to pinpoint the intensity when attraction for the lights is not observed. The key new aspect of this research is that we tested how the hatchlings respond to broad-spectrum LED lighting, which are being installed widely across the world. We are hoping to provide guidance on light intensity levels that have minimal impact to the hatchlings.”
Collaborator and turtle expert Dr Kellie Pendoley from Pendoley Environmental said translating the results into risk assessments and guidance for industry, developers and regulators would be critical. “Natural mortality of hatchlings is already high and there is some evidence to suggest that only 1 in 1000 turtle hatchlings make it to adulthood.”
“If artificial lights increase mortality, then turtle populations may be at further risk. As all turtle species are threatened globally, it is important that we understand these processes in order to provide guidance to assist with mitigation of this threat.”
The project is supported by AIMS and Woodside.
