Leaf oyster reefs in northern NSW
Prof Kirsten Benkendorff, Director, National Marine Science Centre
There is increasing global recognition for the ecological importance of oyster reefs. Unfortunately, there is also wide spread evidence for significant declines in shellfish reefs, with 99% of these reefs in Australia now considered “functionally extinct”. This has triggered serious restoration efforts with some of the major reef forming species around Australia. However, not much is currently known about our largest reef forming species, the leaf oyster Isognomon ephippium. Leaf oysters can occur on rocks in mixed communities with other oysters but also form reefs in estuaries, on sand, mud and amongst mangroves and are often covered in a layer of silt. We have been investigating their distribution, abundance, condition and water quality tolerance in estuaries in mid-north NSW. Modelling reveals that leaf oyster condition and reef density is influenced by a combination of water quality parameters including salinity, dissolved oxygen and dissolved nutrients. Leaf oyster reefs are healthier in estuarine areas with strong marine influence, good mixing and relatively low nutrient run-off. Our preliminary studies in leaf oyster beds using baited underwater videos have also detected a high diversity of fish species using this habitat. Leaf oyster beds support higher fish diversity and abundance in comparison to adjacent bare substrate. Substantially more information is needed on their, life history, physiology and ecology, to facilitate their future inclusion in shellfish reef restoration programs.
Leaf oyster reef in Woolgoolga Lake
