Montara: 2011 Shallow Reef Surveys at Ashmore, Cartier and Seringapatam Reefs

Abstract

In response to the triggering of the Coral Reefs (S6) component of the PTTEP Australasia (Ashmore Cartier) Pty Ltd (PTTEPAA)/Dept. of SEWPaC Monitoring Plan for the Montara Well Release Timor Sea, PTTEP commissioned the Australian Institute of Marine Science (AIMS) to conduct surveys of shallow reef benthic habitats in the vicinity of the Montara well head platform in April 2010. Ashmore Reef and Cartier Islet were the principal emergent reefs of interest, as they were closest to the Montara Well Head platform. To provide a control location, the same sampling was conducted at Seringapatam Reef, a similar emergent reef in the same bioregion, but several hundred kilometres to the south-west and well away from modelled spill trajectories.The condition of the benthic communities at Ashmore and Cartier Reefs in the previous survey in 2010 was consistent with surveys conducted before the uncontrolled release. Although there was no evidence of recent major disturbance that could be attributable to any uncontrolled release,there was evidence of a recent coral bleaching event that was most likely caused by elevated water temperatures (Heyward et al. 2010). Notwithstanding the lack of a major impact, more subtle potential effects from hydrocarbons could not be ruled out and there remained knowledge gaps regarding coral reproduction and the recovery or otherwise of the bleached corals. Consequently, a follow up survey was commissioned by PTTEPAA in 2011 (Coral Reefs S6B), and the results of the surveys are presented here.The most recent 2011 survey enabled a repeated assessment of the shallow reef benthos to ascertain the ongoing state of the coral communities. In addition, an extended and more diverse selection of sampling was undertaken to see if processes of ongoing coral population renewal via sexual reproduction and recruitment were occurring. The 2011 surveys were broader in scope than the 2010 assessment, including comprehensive assessment of the fish communities associated withthe benthic sites, as well as a re-sampling of reef sediments to follow up on the status of hydrocarbon detections noted in the 2010 report