Light pollution is confusing baby sea turtles

By Gemma Chilton | May 17, 2016

Artificial lighting not only affects sea turtle hatchlings on the beach, but after they’ve entered the water too, according to new research.

WHEN A SEA turtle hatches on a beach, it’s important that it makes it to the sea as quickly as possible – the shore and shallow waters are notoriously fraught with risk, mainly from predation.

However, researchers in Western Australia have found artificial lighting at sea is interfering with their ability to reach the relative safety of deeper waters as quickly as possible.

While previous studies have found similar results when looking at the journey from nest to the water’s edge, this new research provides the first quantitative evidence that the hatchlings continue to be attracted to artificial light after entering the ocean.

Sea turtle hatchling

Previous studies of the hatchlings have been conducted in the lab, or by observing the turtles from a boat. (Image: Joan Costa)

Tiny trackers

“Until now, the effect of artificial lighting on turtle hatchlings once they entered the sea was unknown, due to a lack of tracking devices small enough for these tiny animals,” said lead researcher Michele Thums from the Australian Institute of Marine Science. Previous studies, she added, have mostly been conducted in the lab, or from an observation boat which could itself disturb the hatchlings.  

This time, the researchers tracked a total of 40 green turtles (Chelonia mydas) after hatching on a beach at Ningaloo by using miniature acoustic transmitters and a network of receivers to track their movements.

The scientists subjected half of the turtles to artificial light on the water, and found the majority of these not only swam towards the light source, but lingered in the risky in-shore waters for longer – increasing their risk of being eaten by predators such as sharks and fish.

All at sea

“Of great concern is that artificial lighting in coastal environments now extends far beyond the shoreline,” said Michele

“Ports, ships and industrial facilities such as oil rigs can increase the footprint of artificial light sources many kilometres into coastal seas, so that in some places turtle hatchlings must deal with the consequences over a significant part of their journey across the shelf to the open ocean,” she said.

The findings are published today in the journal Royal Society Open Science. The research will now be continued by a PhD supervised by Michele, this time looking at flatback turtles and other possible impacts on the hatchlings’ dispersal.

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