Surveys of the marine habitats of southern Melville Bay, Northern Territory, using towed video (Towvid) and aerial photography

Towed underwater video, supported by sophisticated real-time data capture, geo-referencing and classification software (TOWVID) was used to survey and map benthic habitats throughout Southern Melville Bay and waters adjacent to and seaward of Gove Peninsula. The field work was carried out towards the end of the dry season (30 October to 8 November), in light to moderate sea conditions and neap tides after the full moon.A total of 36.117 km of seafloor were mapped from 63 camera tows at an average spatial resolution of 1.5 m. Camera tows were conducted in the following locations: Gove Harbour (5 tows, 4.097 km); Wharf (6 tows, 1.855 km); Wanaka Bay (1 tow, 1.476 km); Inverell Bay (2 tows, 1.642 km); Halftide Bay (3 tows, 0.657 km); Middle Bay (5 tows, 2.447 km); Drimmie Arm (11 tows, 2.577 km); NoName Bay (3 tows, 3.385 km); Melville Bay (19 tows, 8.387 km); West Woody Island (3 tows, 2.955 km); and Northern Beaches (5 tows, 6.639 km). The low visibility and turbid water conditions constrained surveys in many areas to relatively shallow (Classification of habitat included one schema for the abiotic substrate components and another for the overlying benthic organisms. A limited suite of individual organisms were also recorded as point events. The percentage cover of benthic communities was also subjectively quantified.Maps of mangrove areas surrounding the Bay were to be extracted from aerial survey images provided by CDU. However, these images were found to be incorrectly rectified and for this reason were not included in the GIS database. The aim of this study was to support the establishment of a monitoring program to address potential impacts of the cooling water discharge of the Alcan Gove refinery on the marine environment in Melville Bay. The study was designed to address this issue by providing baseline mapping of marine habitats within and around Melville Bay. These baselines will allow the establishment of a long term monitoring program that can document any changes in sensitive habitats such as mangroves, seagrasses and corals.