Impacts of recreational boating activities on the seagrass Posidonia in SE Australia

Abstract

In SE Australia, the seagrass Posidonia australis is mostly restricted to isolated populations in estuaries and bays, and meadows in Sydney metropolitan estuaries have recently been listed by the NSW Government as threatened with extinction. While large developments impacting on seagrasses are now mostly controlled by environmental legislation, small-scale impacts remain and can lead to fragmentation across large areas. Here, damage to Posidonia meadows caused by boat moorings, propeller scouring and related recreational boating activities has been investigated using easily accessed aerial photography. While individual impacts were often small, in some locations large areas were affected and significant fragmentation of the seagrass landscape was observed and suggests urgent management action is required. The widespread availability of remote sensed data through tools such as Google Earth (©) should lead to greater community awareness of local changes in seagrassses meadows and could be used to improve the management of these smaller scale impacts.