Marmion

Marmion Marine Park is a 9,612-hectare marine protected area along the metropolitan coast of Perth, stretching from Burns Beach in the north to Trigg in the south. The park protects a diverse marine ecosystem including limestone reef systems, seagrass meadows, sandy seabed habitats, and offshore reefs. Marmion is one of Perth's most accessible marine parks and among the most visited marine protected areas in Australia. The park protects the metropolitan section of the Rottnest Shelf — an ancient limestone platform of significant ecological and geological value. The park is managed by DBCA.

Marmion Marine Park supports exceptional marine biodiversity. Reef fish diversity includes baldchin grouper, western blue groper (a protected species and WA state fish), Australian snapper, and over 300 recorded fish species. Weedy sea dragons (Phyllopteryx taeniolatus) — an Australian endemic and marine emblem — inhabit seagrass and reef habitats. Australian sea lions, dolphins, and occasional whale sharks and humpback whales are recorded. Seagrass meadows (Posidonia australis) provide nursery habitat for juvenile fish and dugong feeding. Rock lobster (Panulirus cygnus — the WA rock lobster) is commercially and recreationally important. Nudibranchs and invertebrates are diverse.

Extensive seagrass meadows of Posidonia australis and Posidonia sinuosa cover sandy seabed areas, among the world's most diverse seagrass habitats. Calcareous algae and crustose coralline algae carpet reef surfaces. Kelp and fucalean algae form algal meadows on shallow reefs. The marine flora includes distinctive assemblages of temperate Australian marine algae not found elsewhere in the world.

The Rottnest Shelf limestone — Tamala Limestone — was deposited during Pleistocene interglacial high sea stands approximately 125,000 years ago and forms the linear reef systems (Garden Island Ridge, offshore reefs) characteristic of the Perth coast. The offshore reefs are limestone bioherm systems. The coast between the reefs consists of Quaternary aeolian calcarenite (coastal dune limestone). Sea level was approximately 5 metres higher than present during the last interglacial.

Warm temperate Mediterranean climate. The Leeuwin Current — a warm surface current flowing southward along the WA coast — maintains sea temperatures warmer than would be expected at this latitude, enabling the extraordinary diversity of subtropical marine species in Marmion. Water temperature 17–24°C. Summer prevailing southerly winds (Fremantle Doctor) create excellent conditions for windsurfing and sailing.

The Marmion coast is part of Whadjuk Noongar boodja. Noongar people have harvested coastal marine resources for thousands of years — fish, shellfish, rock lobster, and marine mammals. European settlement of Perth from 1829 rapidly developed the coast for fishing and recreation. The offshore reefs have been fished commercially since the nineteenth century.

Marmion Marine Park was established in 1987 as one of WA's first marine parks. The park has been progressively zoned to provide a range of protection levels from sanctuary zones (no-take) to general use zones. DBCA manages the park with ranger patrols and community engagement programs.

Snorkelling and diving on Mettams Pool, Longreef, and other shore-access reef sites. Boat diving to offshore reefs for blue grouper and other large reef fish. Sea kayaking along the limestone coast. Whale watching (humpbacks, August–November). Shore fishing. Swimming at sheltered coastal beaches.

Multiple entry points along the northern metropolitan Perth coast. Access via West Coast Drive and Marmion Avenue. No formal park entry fees. Boat ramps at multiple locations. The Hillarys Boat Harbour provides marina facilities, cafes, and DBCA Aquarium of Western Australia (AQWA).

Crown-of-thorns starfish outbreaks periodically affect reef communities. Urchin overgrazing can denude kelp and seagrass beds. Urban stormwater runoff from Perth increases turbidity and nutrients. Boat anchoring damage to seagrass and coral habitats is managed through mooring buoys. Illegal fishing in sanctuary zones requires enforcement. Sea surface temperature increase from climate change is bleaching temperate algal communities.