The IMOS Autonomous Underwater Vehicle Facility and the IMOS regional Nodes have established an Australia wide observation program to deliver precisely navigated time series of benthic imagery at select reference sites on Australia’s continental shelf.
The survey sites are designed to help characterise changes in benthic assemble composition and cover derived from precisely registered maps collected at regular intervals. These maps provide a baseline ecological data necessary to make quantitative inferences about long term effects of human activities (eg fishing) and climate variability (eg marine heat waves) on the benthos.
The two types of reef environments are temperate and tropical.
A key aspect of the monitoring of temperate reef systems, particularly in Tasmania, NSW, SE Queensland and Western Australia is to determine rates of change of major habitat forming species associated with benthic habitat. Kelp forest habitats on these reefs are predicted to undergo significant change related to changes in boundary current characteristics, contracting at their northern end due to warming and thickening of mixed layer depth, and in the south through the formation of ‘barrens habitat’ as a result of overgrazing by the long-spined sea urchin, Centrostephanus rodgersii.
Repeated and precisely registered AUV surveys at key sites will enable scientists to describe the extent of kelp habitats, from inshore to deep water areas, and determine changes within these habitats over time. Currently, benthic observing programs on temperate reefs are undertaken at four main areas:
- Eastern Australia and the East Australian Current
- South-East Queensland
- Western Australia and the Leeuwin Current
In Australia’s northwest the oceanography is complex and seabed monitoring of offshore and coastal habitats influenced by a mix of regional and local currents has been very limited. At Ningaloo Reef (21º50'S to 23º35'S), where the Leeuwin current is of particular interest on the adjacent shelf, and at Scott Reef (14 º04'S), which is under the influence of the Indonesian Throughflow, long term data exists in the respective shallow reef habitats, but until recently data has been virtually non-existent in the majority of waters (>30 m) because of constraints on scientific diving depths.
Recent deeper-water seabed surveys at Ningaloo Marine Park and Scott Reef, including missions with AUVs have demonstrated that in both areas extensive and diverse benthic habitats exist that contribute significantly to the known biodiversity values of the system. Repeated AUV surveys at key sites will enable monitoring of these habitats but also provide an excellent global reference site to monitor the status of deeper water reef habitats over time in the face of large scale climate related change. Currently, benthic observing programs on tropical reefs occur at two main areas:
- Scott Reef and Ningaloo Reef
- Great Barrier Reef
There have been some opportunities for the AUV to be used in surveys to look at habitats or behaviours of a particular species or to investigate changes in benthic structure at a specific location that is outside of the reference sites.
- Urchins in Tasmania
- Nocturnal camouflage behaviour of cuttlefish in South Australia
- Drowned Reefs along the GBR
- Recovery of reefs following cyclone impact at Lizard Island