An eco-narrative of Huon Marine Park - South-east marine region

This report is one in a series of eco-narrative documents that synthesise our existing knowledge of individual Australian Marine Parks. This series is a product of the National Environmental Science Program Marine Biodiversity Hub Project D1, which seeks to collate, synthesise and visualise biophysical data within the parks. These documents are intended to enable managers and practitioners to rapidly ascertain the ecological characteristics of each park, and to highlight knowledge gaps for future research focus.

Huon Marine Park is characterised by a diversity of seabed habitats, ranging from low profile reefs and sediment plains on the continental shelf to a cluster of seamounts on the continental slope and low gradient plains on the continental rise. The shelf reefs and seamounts are the better documented habitats within the park and are the focus of this initial characterisation of the park.

Recent opportunistic seafloor surveying and accumulated transit data from the Marine National Facility (MNF) has revealed an extensive rocky reef system in the north east corner of the park that extends from the reserve boundary (~53 m depth) to around the 100 m depth contour. Whilst there has been little biological survey effort to characterise these reef systems, some information is available from occasional IMOS Autonomous Underwater Vehicle (AUV) surveys and a small number of video tows. These data indicate a moderate to high-profile reef system that is generally deeper than the photic zone and is predominantly covered in a dense but low-profile mix of sessile invertebrates, including sponges, bryozoans, soft corals and seawhips. This sponge-dominated invertebrate community appears to be heavily “pruned” by the influence of high energy Southern Ocean swells (wave heights more than 10 m) that regularly impact this region which presumably remove the larger invertebrates due to drag and/or sand-blasting. In the shallower northern boundary region of the park there is sufficient light for some red algal growth, however, this is at the margins of photic depth and primarily restricted to a low cover of encrusting coralline algae. Overall, the surface waters of Huon Marine Park are characterised by moderate to high productivity, as shown by satellite-derived measures of chlorophyll-a that show the park is among the top 10 for productivity of all Australian Marine Parks. Satellite data also show the park is experiencing a clear trend of warming within its surface waters and is within the reach of marine heat waves through connectivity with the East Australian Current.

Despite the high wave energy environment, the shelf reef habitats of the Huon Marine Park appear to be quite productive. This productivity is evident on the shelf reefs, where a high-density lobster population is recorded, both from counts in AUV surveys (53-85 m depth) and the regular use by the Tasmanian lobster fishing industry. Less is known about associated fish assemblages on these reefs, although from the limited video footage available, key species include schooling butterfly perch and rosy wrasse.

For the deep water habitats of the seamounts, a series of biodiversity voyages have documented a rich benthic fauna, notably across their upper slopes. The most recent benthic habitat survey was conducted on RV Investigator voyage IN2018-V06 during November-December 2018, titled “Status and recovery of deep-sea coral communities on seamounts in iconic Australian marine reserves” it included areas first surveyed 20 years ago, some of which were subsequently closed to trawling. The voyage found some indications of change among benthic fauna on seamounts that had been previously trawled and are now protected within the park.

Further research is needed to adequately describe the resident fish assemblages on shelf reef and sediments in the Huon Marine Park, as well as improving our understanding of shelf-break habitats and biological assemblages where there is currently very little available knowledge. This additional research could include a re-survey of the seamounts to monitor for recovery of previously trawled areas of the park.

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