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The coastline and islands at Dampier mostly comprise of exposed Precambrian igneous rocks and Pleistocene limestones. The Precambrian rocks are atypical of the Pilbara coast. The DPA’s management area generally extends only to the high water mark so the DPA is not responsible for land areas beyond this mark.
Water qualityThe tropical open waters of the Dampier Archipelago support an abundance of plankton and pelagic fish, mammals and reptiles. Suspended sediment concentrations are naturally higher in the relatively shallow near-shore regions of the Archipelago and the Port than in the offshore waters. The DPA monitors suspended sediment concentrations in port waters
Intertidal reef platforms occur extensively in the Archipelago but are limited within the port area. They support diverse assemblages of plants and animals that in turn provide feeding grounds for wading birds at low tides and fish, turtles and occasionally dugongs at high tide.
Intertidal sand and mudflats
Sand and mudflats are often associated with mangals and support a large infauna of crustaceans (e.g. fiddler crabs, soldier crabs), molluscs (gastropods and bivalves). These areas are feeding zones for wading birds at low tides and for fish and stingrays at high tides. Primary productivity from cyanobacteria is high in these areas and contributes organic matter and nutrients to near-shore waters.
Beaches
Sandy beaches are not extensive in the Port of Dampier and occur only as small deposits in embayments between rocky headlands. The beaches are typically populated by infaunal polychaete worms, bivalve worms, amphipod crustaceans and ghost crabs. The beaches are used as feeding and nesting grounds by wading birds and as nesting sites by marine turtles.
Rocky shores
Rocky shores of Precambrian igneous rocks are common in the port area and around the archipelago. These provide a habitat for oysters, barnacles, whelks and chitons. At low tide, these areas provide food for seabirds such as oyster catchers, and at high tide for fish.
Mangals
Mangals (mangrove communities) contribute to primary productivity and the nett export of organic matter. They support a diverse array of infauna (inhabiting the sediments), epibenthic fauna (inhabiting the sediment surface), epifauna (inhabiting the mangrove stems and roots), fish (at high tide) and are important feeding and resting areas for turtles. Mangals are not common in the port area.
Seabirds
Seabirds use the terrestrial environment for roosting and breeding and the marine environment for food. Sixteen species of sea and shore birds breed on the islands of the Dampier Archipelago. Migratory species include waders which commute between Australia and Northern Asia and are protected by international agreements (CAMBA and JAMBA).
Seagrasses and macroalgae
Macroalgae occur most extensively on subtidal limestone pavements on the south side of Legendre Island, and between Rosemary Island and Nelson Rocks outside of port limits. Smaller assemblages occur on hard shallow substrates around Eaglehawk, Malus, Enderby and Angel islands. Seagrasses occur within the macroalgal meadows and some shallow sand areas e.g. West Conzinc Island. Thick seagrass beds are not found in the area. Seagrasses are the principle food of dugongs and are also grazed by turtles, which also graze on macroalgae.
Dampier is a region of high coral diversity due to the wide range of environmental conditions that occur. Offshore areas are typified by low turbidity, and low coral diversity and high abundance. Inshore areas are typified by high turbidity, low coral diversity and abundance. Coral locations within the Dampier port have been mapped. The DPA continues to improve this map as new data becomes available.
Deeper hard substrates in channels between islands are typically inhabited by sponges, gorgonians and seawhips, and in some areas dominated by molluscs e.g. oysters.
Subtidal sand and mud
Unconsolidated sediments comprise the majority of the seabed in the Port, consisting of silty muds, coarse sands and gravels. These support a range of burrowing organisms, solitary corals and benthic microalgae. Benthic microalgae contribute to primary productivity, biogeochemical cycling and sediment stability.
Fish
Offshore waters support dense schools of herring, sardines and anchovies. Pelagic fish such as tuna and mackerel feed on these baitfish. Pelagic sharks and billfish also use the bait fish for food. The baitfish are also an important food resource for seabirds such as shearwaters and terns.
Marine reptiles
Four species of marine turtle and twelve species of sea snake occur in open waters of the region. Sea turtles use the sandy beaches of the archipelago for nesting, and feed on marine plants and animals in the area. All marine reptiles are protected.
Marine mammals
Marine mammals occurring in the area include dugongs, humpback whales, and smaller toothed whales and dolphins. All marine mammals are protected.
DPA has a limited tenure of land areas, restricted to the industrial estate of the Burrup Peninsula. Port lands are generally developed.
