A Western Australian Marine Science Institution (WAMSI) project is using genetics to see how ocean currents in the Kimberley transport marine organisms from one reef to another.
Bardi-Jawi rangers, Mayala traditional owners and researchers from four WAMSI partner institutions recently conducted field studies along the remote and rugged coastline, collecting samples on exposed reefs at low tide between the 12 metre tidal surges around the Dampier Peninsular and Buccaneer Archipelago.
“We collected seagrasses, corals, fishes and trochus shells that live in the intertidal zone which is exposed at low tide,” CSIRO’s Dr. Oliver Berry said.
“We selected these species to represent the types of organisms that are common in the Kimberley. Some are also commercially, recreationally or culturally important like the trochus shell and stripey snapper, or form key habitats like seagrass and corals.”
Sites sampled Dampier Peninsular and Buccaneer Archipelago
The researchers are using scans of the organisms’ genomes to measure the genetic relationships between different reefs and seagrass beds. The more genetically similar the organisms from different reefs are, the more movement occurs between them.
“When you consider managing a marine resource you have to understand what drives population dynamics,” Dr. Berry said. “For some populations whether they are growing or shrinking is driven locally by births and deaths. But, especially in places where there are strong tides and currents, it’s possible that even populations quite distant from each other are strongly interdependent because organisms move between them a lot.”
“A seemingly large area like the Kimberley can be very linked if hydrodynamics (ocean currents) drive those population linkages. So if there was a disaster at one location, if that population was insular, or locally driven, it may take a long time for it to recover. But if the population was linked to other areas then it may recover more rapidly. What we’re trying to do is to better understand these relationships between populations.
“Of course it’s a difficult thing to study because most movement in marine species occurs when they are tiny eggs, seeds, or larvae. Genetics is a way to indirectly measure movement, and it’s becoming increasingly cost-effective and powerful with the development of genome sequencing technologies,” Dr. Berry said.
The research being undertaken by WAMSI with scientists from Edith Cowan University, AIMS, Department of Fisheries, WA and the Western Australian Museum, is expected to uncover a range of different patterns reflecting the exposure to currents of different reefs and the different life histories of the organisms.
“For example, looking at the patterns in the trochus shell, we know it has a short larval stage and that some fishes have longer ones,” Dr Berry said. “We expect this to mean fish get transported further and that these differences will be reflected in the genetic relationships between populations.”
“This is the first time anyone has attempted anything like this in the Kimberley, and anywhere in the world in such a macro-tidal environment,” he said.
“Now that there is increasing interest in developing the region we need to get a baseline understanding of how the ecosystem works, so that it can be managed effectively,” Dr Berry said. “We expect to have some results by the end of this year.”
[The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.]