Baby turtles leave behind fleeting oases on beach dune deserts

Beaches are important for turtles, and turtles are important to beaches

All Canada Photos/Alamy Stock Photo

By Maria Bolevich

Baby turtles that fail to make it to the sea help fuel __life on otherwise deserted sandy beaches in the tropics.

The remains of turtle eggs that have been attacked by predators lead to a short pulse of __life in what are normally deserts, boosting the abundance of small invertebrates fourfold, a study has found.

These bursts peak seven days after the broken eggs become available and are all but gone in just 20 days.

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“This discovery affirms the role of sandy beaches as unique ecosystems,” says Ronel Nel at the Nelson Mandela Metropolitan University in South Africa, whose team studied the Maputaland beaches in the iSimangaliso Wetland Park, in Kwa-Zulu-Natal. “They are not deserts, as many seem to think.”

Traditionally, we think of beaches being important to the fate of turtles, but these findings highlight the importance of turtles to beaches, she says. Her team sampled sand in naturally predated nests and set up experiments to track changes in microscopic life, known as meiofauna, as compared with control sites nearby that didn’t have broken eggs.

The boost in meiofauna was especially pronounced in the abundance of nematode worms. Their densities increased from a single worm to 10,000 worms per cubic centimetre in just 10 days. Other creatures that benefited included mites, springtails and insect larvae.

Feeding and breeding

“Meiofaunal organisms are vital contributors to ecosystem functions, including nutrient cycling and the provision of energy to higher trophic levels,” says Daniela Zeppilli, from the French Research Institute for the Exploitation of the Sea. They frequently feed on detritus and act as food for bigger organisms. “They are an often-neglected component of marine biodiversity.”

But Zeppilli says it’s not clear that the seasonal boost in nutrients is necessarily a good thing for meiofaunal communities.

She says that after an event such as a pulse of organic matter, a few species, often nematodes, can dominate over all other meiofauna. “So you have a lot of individuals, but very low diversity.”

Nevertheless, such pulses of nutrients might play an important role in these often overlooked marine ecosystems.

“This is interesting because sea turtles in general migrate between feeding grounds and breeding beaches, so energy is transferred between widely-separated ecosystems,” says John Davenport of the University College Cork, in Ireland.

For example, he says, leatherbacks transfer energy from food, such as jellyfish, collected off Nova Scotia, in Canada, to clutches of eggs on nesting beaches in the Caribbean, thousands of kilometres away.

“The authors have shown experimentally that smaller animals also benefit from this energy,” he says. “Sandy beaches are generally energy-poor systems, so the regular seasonal inputs of turtle eggs are important to the microscopic and macroscopic animals that live there.”

Journal reference: Journal of Experimental Marine Biology and Ecology, DOI: 10.1016/j.jembe.2016.11.017

Read more: Why baby turtles work together to dig themselves out of a nest