Corangamite’s coastal waters stretch from west of Peterborough, around Cape Otway, along the Surf Coast, through Port Phillip Heads and around Corio Bay nearly to Point Wilson in the east. There are three Marine National Parks in the region: Port Phillip Heads, Point Addis and Twelve Apostles Marine National Parks. There are also a number of Marine Sanctuaries within the region including The Arches, Marengo Reefs, Eagle Rock, Point Danger and Barwon Bluff. Parts of the Corangamite marine environment are also classified as Ramsar wetlands as part of the Port Phillip Bay (Western Shoreline) and Bellarine site which includes Point Lilias, Limeburners Bay, Swan Bay and Mud Islands.
A healthy marine and coastal environment is biodiverse and dynamic. It contains functioning biological, physical and chemical interactions that support the local environment’s many and varied plants and animals. It is able to operate as a dynamic, constantly changing system.
Ecosystems are in a constant state of flux in response to processes like changing sea and air temperature, nutrient flows and ocean currents. A healthy marine and coastal environment can also be defined by its ability to sustain both its intrinsic value (the value it has in itself regardless of its value to humans) as well as the full range of environmental, social, cultural and economic values that benefit the Corangamite community.
The Marine and Coastal Act 2018 along with the Marine and Coastal Policy provide the overarching statutory and policy frameworks for the management of the region’s marine and coastal environments. The Marine and Coastal Strategy currently being developed will identify key actions and responsibilities for the delivery of the Marine and Coastal Policy.
Wadawurrung Healthy Country Plan says “We see our Dja land and Warre sea Country as all one but we have highlighted it here as it needs some real help. For us it is full of resources, favourite foods and living places along our coast that show how the seas provide so plentifully for generations of Wadawurrung. Fishing, diving, harvesting from the rocky and intertidal reefs”.
Assessment of current condition and trends
The condition of Corangamite’s marine waters is generally good, with low levels of nutrients, turbidity and bio-contaminants, and generally good light conditions. Attention of nutrient and sediment fluxes in the catchments, and appropriate management of stormwater and wastewater in coastal towns is essential to preserve this good condition.
Corangamite’s inshore marine areas are well known and loved by millions of Victorians and visitors, with many different and diverse environments. Both inshore and offshore marine areas also host the activities of several important sectors such as fisheries, ports and shipping.
Within the Corangamite region there are a number of marine sanctuaries and national parks. These include the The Arches, Marengo Reefs, Eagle Rock, Point Danger and Barwon Bluff Marine Sanctuaries. The region also includes the Twelve Apostles, Point Addis and Port Phillip Heads Marine National Parks. South of Cape Otway is the Apollo Commonwealth Marine Park.
Land use within the catchment influences water quality by causing nutrient and sediment pollution that threatens marine ecosystems. High levels of urbanisation such as that within the Geelong City and Bellarine & Surf Coast Landscape systems present issues with discharges from a variety of sources leading to detrimental impacts on the marine environments adjacent to these locations.
The condition of the marine environment is dependent on the land use in the hinterland that adjoins that environment, the impact of extractive uses and industries within that environment and the impacts of of broader issues such as invasive species, climate and pollution. The key role of this strategy is to ensure that terrestrial land and water use impacts on marine systems are minimised.
Major threats and drivers of change
The health of the Corangamite marine environment is under threat from multiple sources, including climate change and growth in towns, cities and industries that interact with their local marine ecosystems. These threats can lead to negative impacts on water quality, pollution and debris, invasive species, marine pests and diseases. Stormwater can contain hydrocarbons, pesticides, detergents, leaves, garden clippings, animal faeces and plastics, along with sewage from leaking, broken or overflowing sewers.
Seagrass beds, estuarine mudflats and mangroves are amongst the most vulnerable habitat types as they require sheltered environments that are at increased risk from nutrients and contaminants transported by storm water. These specialised habitats are critical for all or some life cycle stages of many marine species.
Growth in resident populations and visitor numbers puts pressure on the health of the marine and coastal environment, with direct impacts including:
• habitat loss and degradation
• increased introduction of invasive and pest species
• increased pollution from sources including litter, stormwater runoff and wastewater discharges
• erosion of dunes
• loss of character of coastal towns.
Climate change is increasing the pressure on Corangamite’s marine environment by exacerbating existing threats and introducing new ones, such as:
• rising sea levels, leading to more inundation and erosion
• increased frequency and severity of storms and other extreme weather events
• changes in ocean temperatures, currents and acidification
• changes to waterway flows, levels and regimes
• changes in the range, distribution and abundance of both introduced and native plants and animals, taking advantage of a changed climate
• coastal squeeze, which occurs when coastal ecosystems forced inland by rising sea levels run into human-made barriers such as roads and housing.
More than 160 introduced marine species are now resident in Port Phillip Bay. Those of greatest concern are the northern Pacific seastar (Asterias amurensis), the European fan worm (Sabella spallanzanii), the European green shore crab (Carcinus maenas), Japanese kelp (Undaria pinnatifida), the New Zealand screw shell (Maoricolpus roseus) and the Pacific oyster (Crassostrea gigas). The Asian date mussel (Musculista senhousia), cordgrass (Spartina anglica and Spartina x townsendii sp.), dead man’s finger (Codium fragile ssp.) and red algae (Grateloupia turuturu) are also of concern. Invasive marine species prey on – or outcompete – native species for space, food and light.