Epic ocean voyages of baby corals revealed
Press release issued: 21 August 2013
For the first time, scientists have recreated the journeys of millimetre-sized baby coral through the world’s seas, suggesting some of these tiny adventurers may cross entire oceans. The study, by researchers from the Universities of Bristol and Miami, will help predict how coral reef distributions may change in response to changing oceans.
Coral are well known as the colourful plant-like structures which form coral reefs. However, each coral is actually a colony of anemone-like animals, which start out life as tiny, free-floating larvae about the size of a full-stop. Using a computer model, the researchers simulated how these young corals disperse in the world’s oceans.
Sally Wood, a PhD student at the University of Bristol and one of the study's authors, said: "Dispersal is an extremely important process for corals. As they are attached to the seafloor as adults, the only way they can escape harmful conditions or replenish damaged reefs is by releasing their young to the mercy of the ocean currents. Reefs on remote islands may be particularly vulnerable to damage as they are cut off from sources of new recruits."
Where these intrepid explorers end up is an important question for coral reef conservation. However, tracking the movement of such tiny larvae in the vast oceans is an impossible task.
"This is where computer simulation comes in,” Sally continued. "We can use data on ocean currents to predict where larvae released from a certain location, such as the Great Barrier Reef, will end up."
For the first time, the researchers recreated the paths followed by coral larvae worldwide. Whilst the majority of larvae probably settle close to home, a rare few travel much longer distances, even occasionally crossing the daunting 5,000 km of open ocean separating eastern Pacific corals from those on islands of the central Pacific.
Professor Claire Paris of the University of Miami said: "These individuals will be really important as they are thought to contribute to species persistence on vulnerable isolated reefs, as well as range shifts in response to climate change."
Coral reefs, a vital cultural and economic resource for many of the world’s poorest countries, and home to a diverse marine community rivalling that of the tropical rainforests, are under increasing threat from the combined pressures of human activity, natural disturbances and climate change. How corals will respond to these changes will depend, in part, on the ocean currents.
The model captures just the start of the coral larva’s journey to survival, and further work is ongoing to complete the story. Difficult environmental conditions along the larvae’s travels or at its destination, the 'wall of mouths' awaiting it at the reef face, and fierce competition for the space to grow may mean, even if it overcomes the trials of the open ocean, it may never survive to reproduce.
The research is published today in Global Ecology and Biogeography.
‘Modeling dispersal and connectivity of broadcast spawning corals at the global scale’ by S. Wood, C.B. Paris, A. Ridgwell and E.J. Hendy in Global Ecology and Biogeography (2013)
Sally Wood is funded through a NERC postgraduate studentship. Development of the Connectivity Modeling System used in this study was funded through the NSF-RAPID program (OCE-1048697) to C.B. Paris.