The Northern Territory is imagined to be a remote outpost by most Australians, but the 90,000 inhabitants of Darwin enjoy a modern and very liveable environment. It is one of the most pristine urban coastal environments in Australia, with heaps of smartly tended coastal parks, cycleways and beautiful clean beaches. Away from Darwin the roads diminish rapidly in quality and the coast is often covered in mangroves or accessible only with a permit from the local Aboriginal owners.
Most water activity is based around Darwin, where big tides, stingers, crocs and turbid waters should deter marine enthusiasts, but Territorians are pretty much all water mad. This is especially the case with recreational fishing where a good variety of larger species of scale fish make this a fishing mecca. The diving is also worthwhile, offering some unique war wrecks, thanks to the Japanese Imperial Navy. Local reefs are also colourful, especially on the sites more distant from freshwater creeks.
Odd conditions mean odd adaptations. Marine species diversity for Darwin Harbour is high, with more species in various groups (taxon), compared with other ports in Australia. It might be a cloudy swim in adverse tides, but the life that is encountered is unique and definitely worth learning more about. I suspect that most of Darwin’s unique marine life is still to be discovered.
Darwin Harbour is one of Australia’s most pristine urbanised catchments and it still has 78% of its natural vegetation. A lot of this is ecologically important, but difficult to visit. To locals it must seem like there are too many mangroves, but what they see is a large part of all the mangroves there are to see. The NT has 35% of all of Australia’s mangroves, and the mangrove forests of Darwin are very diverse (36 of 50 species). The Darwin Harbour region is a hotspot for odd flora generally, so even with low levels of development 26 rare flora species are listed as threatened or endangered.
The marine life of Darwin Harbour Region is still being described with more than 3000 marine invertebrate species and 415 fish species. Sand Bass and the threadfin pearl perch are often seen inshore along with butterfly cod, sweetlips, greasy cod, batfish, tuskfish and fusiliers. NT waters contain significant populations of threatened species including species of rare sawfish, sea snakes, pipefish, seahorses, sharks and rays.
Inshore reef-forming corals are not large due to the lower light penetration. It still has many patches of brain coral (porites) and finger coral (acropora). Honeycomb corals. (Favites) are also common and come in a variety of primary colours. Occasional basket corals (Turbinaria) are also found on wrecks and offshore reefs. The intertidal platform between Channel Island and the mainland is listed on the Register of the National Estate and has been declared a Heritage Place under the NT Heritage Conservation Act 1991. This declaration was based on the presence of an unusually diverse coral community.
The vast tidal movement ensures rich pockets of filter-feeding life, especially on the local wrecks. An array of colourful seawhips, sea fans and soft corals can be found. There are over 40 species of featherstars and a large variety of nudibranchs. There are even 300 species of sponge, which are not normally numerous in tropical waters. Also uncommon and a bit weird for the tropics are the beds of sargassum and caulerpa seaweed that cover the shallow wrecks and reefs.
Some of this natural diversity isn’t too hard to see for non-divers. Flatback and Olive Ridley Turtles nest on Casuarina Beach, right in the suburbs. Dugongs and Snubfin dolphins are occasional sighted in Darwin Harbour. The mangroves are also home many interesting foreshore animals, fruit bats, fiddler crabs, mudskippers, mud crabs and odd molluscs.
Many animals love the intertidal seagrass beds consisting of Halophila and Halodule species. These quick-growing seagrasses recover well after cyclone damage and are the favourite menu item for dugongs and turtles. Dugong feeding trails can be sometimes seen through the seagrass beds.