Turtle eggs offer lifeline to dunes


By Kurt Kleiner in Baltimore SEA turtles help fertilise the dunes where they lay their eggs, says an ecologist from Florida, who believes their unhatched eggs make an important contribution to the health of the beach. Coastal dunes are notoriously fragile, providing barely enough nutrients to support the animals and plants living on them. According to Sarah Bouchard of the University of Florida in Gainesville, the loggerhead turtles that lay their eggs in the dunes are lifesavers. They provide a net gain of nutrients to the ecosystem’s total energy in two ways: they feed elsewhere, and any of their eggs that fail to hatch decompose and release substantial nutrients. Bouchard monitored 97 turtle nests on Melbourne Beach in Florida containing a total of 10 608 eggs. Only 42 per cent of these eggs hatched successfully. Of the rest, over half were eaten by predators such as racoons and crabs, and the remainder decayed, fertilising the sand and soil. Bouchard estimates that the 21-kilometre beach absorbs nutrients from 1.5 million eggs each year, with a total of 86 kilograms of phosphorous, 2000 kilograms of lipids, and 1000 kilograms of nitrogen. Altogether the turtles import around 250 million kilojoules of energy to the dunes. “By introducing nutrients into the local ecosystem,” she says, “turtles are helping to stabilise their own nesting environment.” Bouchard says it is still uncertain what proportion of the dune’s nutrients the non-hatching eggs contribute. She is now planning experiments to compare dunes where turtles nest with other dunes to work out if the added nutrients make a difference. More on these topics:
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