RV Investigator Seamounts Survey Voyage Report

Overview

Australia has gazetted an ambitious national network of Australian Marine Parks that includes the iconic ‘Huon’ and ‘Tasman Fracture’ parks off southern Tasmania where seamounts (‘undersea mountains’) support unique deep-sea coral reefs. These reefs rank among the most bio-diverse globally. Protection of deep-water coral reefs is a high-priority conservation concern nationally and internationally because deep-water corals are very fragile, easily impacted by human activities including bottom trawling, and are believed to recover very slowly. These corals may also be highly vulnerable to climate change because projected changes in water chemistry could limit the ability of corals to build calcareous skeletons. Despite these concerns, and Australia’s significant investment in marine conservation, several fundamental ecological issues remain to be evaluated. These include defining the spatial extent of deep-sea coral communities inside and outside the Tasmanian parks, and evaluating the resilience of the communities to bottom trawling. This information is important to understanding the dynamics of deep-sea communities globally, and for developing and implementing conservation management plans. Investigator voyage V06 aimed to determine the spatial extents of deep-sea coral communities in, and adjacent to, the Huon and Tasman Fracture parks, and quantify changes in the communities by comparing samples taken in 2018 to samples taken, using similar methods on the same seamounts, in 2007 and 1997. The second aim (‘recovery’) was supported by additional sampling on the heavily trawled St. Helens Seamount which was surveyed in 2008. Interpretation of these data will be given additional context through analysis of a comparable data set from New Zealand. Remarkably, these are the only two sets of replicated surveys encompassing areas of contrasting conservation status and impact history in the world’s oceans. The final results will be novel and significant by providing world-first recovery and resilience data to the Australian government and other national and international bodies. The results will help achieve effective monitoring and management actions to enhance the long-term survival probabilities of deep-sea corals.