Grey reef shark's ecological role not to be poo-pooed, new study reveals

Sharks transfer crucial nutrients from their open ocean feeding grounds, to shallower coral reefs via their faeces - according to a pioneering study that is published today in the journal Proceedings of the Royal Society B.

Grey reef shark in Hawaiian coral reefs

Working in the waters surrounding Palmyra Atoll, a remote reef and wildlife refuge south of Hawaii, scientists used acoustic tags to track the movements of the grey reef shark (​Carcharhinus amblyrhynchos​) - a predatory species known to be associated with coral environments, but whose wider ecological role was previously not fully understood.

Combining their existing knowledge about the sharks' feeding habits in open ocean (pelagic) environments, the team were able to estimate the quantities of nitrogen deposited around the reef, via the sharks' faecal material. Astonishingly, they discovered that this specific population of reef sharks - believed to number around 8,300 - contributed to an approximate total of 95.4kg of nitrogen into the reef ecosystem, each day.

This is a substantial amount of nutrients, which contribute to reef primary productivity, "which in turn effectively act as a fertiliser for thousands of other species that call these reef environments home", said Dr David Jacoby, senior co-author from ZSL's Institute of Zoology.

Commenting on this study, Dr David Jacoby went on to say: "While estimating quantities of shark poo may not sound like the most glamorous of pastimes, the findings of this research have fascinating implications for our understanding not only of fragile coral reef ecosystems but also the ecological significance of grey reef sharks - a species currently classified as Near Threatened by the IUCN ​Red List.

"Coupled with their better-known role as predators, our study underlines another, less obvious role played by reef sharks in improving the resilience of these fragile habitats and again underlines the vital importance of conserving these and other wide-ranging predators."

ZSL Scientists inluding Dr Jacoby, will be showcasing their invaluable tracking and monitoring work at the 2018 Royal Society Summer Science Exhibition - a festival celebrating the science shaping our future.

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