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The Northern Territory is a federal territory of Australia, occupying much of the center of the mainland continent, as well as the central northern regions. It shares borders with Western Australia to the west, South Australia to the south, and Queensland to the east. To the north, the territory is bordered by the Timor Sea, the Arafura Sea and the Gulf of Carpentaria. Despite its large area (over 1,349,129 square kilometres), making it the third largest Australian federal division, it is sparsely populated. With a population of 219,948 (June 2008) it is the least populous division in the country.

Arnhem Land consists of the eastern half of the large peninsula that forms the northernmost portion of the Northern Territory. The region, with a total area of about 95,900 km2, consists of a ruggedly dissected plateau and associated lowlands. The coast of Arnhem Land extends from Van Diemen Gulf and the Cobourg Peninsula eastward to Gove Peninsula, the Gulf of Carpentaria south east to the Roper River, and Groote Eylandt. The climate is characterised by a tropical monsoon with a distinct wet season starting in November/December and lasting for approximately four months followed by a dry season. Cyclonic activity is low to moderate (Ferns 1999).

Although no area on earth is unaffected by human influence, Arnhem Land is located in one of the least impacted regions globally (Halpern et al. 2008). Northern Australia is part of the global centre for marine biodiversity. The drivers of anthropogenic change are mostly much less in northern Australia than in the remainder of the Indo-Pacific. Australia as the only developed country in the region has a global responsibility for the conservation of marine biodiversity.

Local indigenous people hold much of the biological knowledge of Arnhem Land. Very little marine research has been conducted and consequently there is very little known about the distribution and abundance of marine flora and fauna, including seagrasses along the Arnhem Land coastline (Butler & Jernakoff 1999; Coles et al. 2004)). Much of the information has been based on anecdotal evidence from the 1970s (Williams et al. 2000; Green & Short 2003), surveys from fixed wing aircraft in the 1980s (Poiner et al. 1987), and a recent survey of intertidal seagrass meadows by helicopter in November 2004 (Roelofs et al. 2005).

Seagrass has been reported in the past from Nhulunbuy (Halophila decipiens) and along the north coast of the Tiwi Islands. Ten seagrass species have been reported from the waters surrounding Arnhem Land (Poiner et al. 1987; Roelofs et al. 2005): Cymodocea serrulata, Cymodocea rotundata, Enhalus acoroides, Halodule uninervis, Halophila decipiens, Halophila ovalis, Halophila spinulosa, Syringodium isoetifolium, Thalassia hemprichii and Thalassodendron ciliatum. H. uninervis and H. ovalis are by far the most common on the open sand and mud flats. T. hemprichii and T. ciliatum are often found on reef platforms and around rocky islands. E. acoroides often occurs in sheltered bays.

For detailed information on the Seagrasses of North East Arhnem Land, click here for review of current knowledge.



Melville Bay (Nhulunbuy)

Monitoring: ongoing

Principal watchers: Dhimurru Sea Rangers, Neil Smit, Vanessa Walsh
Occasional and past watchers: Seagrass-Watch HQ
Location: Giddy River
Site codes: GR1

GR1 position: S12.26372 E136.65942 (heading 40 degrees)

Best tides: <0.4m (Gove Harbour, port 63480)

Issues: Industrial runoff
Comments: Melville Bay is a large embayment adjacent to Nhulunbuy (pop. 3500), the second largest population in the Northern Territory (Gardner 1991). The water in the Bay is shallow, rarely more than 15m in depth and mostly less than 10m.

Seagrasses are largely Halophila spp. although several other species are reported (Hanley 1996).

Along the northern side of Melville Bay, is the Gove peninsula where the Nabalco alumina refinery is located. The Nabalco bauxite mine at Nhulunbuy lies inland and the ore is transported by conveyor to the Gove peninsula. There have been a number of reports examining Nabalco's operations and potential environmental impacts on the region (Noller 1991; Peerzada et al. 1990a, 1990b; Peerzada & Dickinson 1989; McConchie 1991; Hanley 1993a). Concerns have included the level of sulphur emissions from the Steam Power Station stacks, the discharge of heated seawater into the Bay, occasional spills of caustic soda into the Bay (Noller 1991), and heavy metal contamination of oysters in Melville Bay.

Status (Dec08):

  • monitoring sites ony established in October 2008
  • insufficient data to determine seagrass condition





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Seagrass-Watch HQ
Address: Northern Fisheries Centre
PO Box 5396
Cairns Qld 4870
Phone: [+61][07] 40 350 100