Port Phillip Bay natural events
|
Photo: Basket star on soft coral
|
| Port Phillip Bay is a dynamic marine environment that supports approximately 300 species of fish and several hundred species of crustaceans, jellyfish, corals and sea sponges. Each year a number of natural phenomena occur in its waters and on its beaches.
The Channel Deepening Project has heightened the Victorian community’s interest in the Bay. Events that would otherwise go unnoticed or be of limited public interest are being reported because of their conceivable link to dredging operations.
In some instances the events could be immediately considered natural and dredging as a cause was ruled out.
|
|
|
|
On other occasions, a field investigation was required before a conclusion could be drawn. For all reports, the Office of the Environmental Monitor sought advice from relevant agencies on these events, and based on that advice was satisfied that the events were a result of natural biological or Bay processes.
To assist the community, the Office has published a history of seasonal biological events in the Bay. Table 1 includes details on the events that have already occurred, their cause as well as photos, if available. Table 2 includes some seasonal events that have not yet occurred during the Project, but that may be anticipated in the coming months or years.
|
Table 1: Past Bay events
|
| | Agency that investigated the event
|
| | | Apparent mortality of scallops
|
| | | No evidence of scallop mortality beyond normal conditions
|
|  | Empty mud-filled dead scallop shell on sea bed
Photo courtesy of PoMC
|
| Kelp washed up on foreshore at Pt Lonsdale
|
| | | Result of recent storm activity
|
|  | Kelp washed up on rocks near Pt Lonsdale with the Queen of the Netherlands in the distance
|
| Seastars washed up on a beach at Seaford
|
| | | This introduced marine pest is regularly found on beaches, particularly during the colder months when they move into the shallower waters and are washed ashore during storms
|
|  | Seastar
|
| Spider crabs washed up on a beach at St Leonards
|
| | | The crabs reported to have washed ashore were primarily the shells of Spider Crabs.
Spider Crabs are native to the seawaters of southern Australia and Port Phillip Bay and are known to mate and moult (shed their shells) during the autumn/winter months, particularly during a full/new moon (a full moon had just occurred).
The occurrence of dead Spider Crabs or their shells washing ashore in Port Phillip Bay area is not new or out of the ordinary. The phenomenon is part of the normal life history of these crabs.
|
|  | Spider Crab shells after moulting
|  | Diver collecting samples of Spider Crab shells
|
| Reported spider crab mortality beneath Rye jetty
|
| | | |  | Spider Crabs shells after moulting
|
| Storm surge affects on the north of Port Phillip Bay
|
| | | Storm surges are a natural phenomenon. A storm surge is a rise above the normal water level along a shore that is the result of strong winds pushing on the water's surface and/or reduced atmospheric pressure and that causes the water to pile up higher that what would normally occur.
|
| | Paper nautilus found washed up on Chelsea beach
|
| | | Commonly called the paper nautilus, the Argonauta nodosa has a slender body with arms of unequal length. The egg case is white with nodular radial ridges on the sides and a wide grooved keel around the edge. The species generally inhabits oceanic waters but occasionally move into coastal shallows, such as Port Phillip Bay, in large numbers to release their eggs and die.
|
|  | Paper nautilus
|
| Jelly or Blue Blubbers found washed up on Altona Beach
|
| | | Commonly called the blue or jelly blubber, the Catostylus mosaicus is a native species that is often found in large numbers in Victoria's bays and inlets. It is the most common jelly fish along the eastern Australian coast.
|
The species is not poisonous, but if handled can leave an irritating itch on the skin.
The jelly blubber moves with the tide and strong onshore winds can wash the species onto Port Phillip Bay's beaches.
|
|  | Jelly blubbers on Altona Beach.
Photo courtesy of Hobsons Bay Leader Newspaper
|
| Little Penguins washed up beaches
|
| | DSE and Phillip Island Nature Park
|
| From time to time Little Penguins die at sea and some are washed up on beaches. This can be the result of a natural phenomenon, and researchers estimate that around 15% of the adult penguin population and 80% of fledglings die each year.
Along the Victorian coast, penguins may be washed up following severe winter storms. Very young birds can also be washed up when unsuccessful in hunting for food, particularly between January and April.
|
|  | Dead Little Penguin at Anthony's Nose, Dromana. August 2008. Photo courtesy of Jenny Warfe.
|
| Parasitic worm infestation of snapper
|
| | | Parasites, including roundworms, flukes and tapeworms (scientifically known as nematode, trematode and cestode worms), periodically infect snapper and other recreational finfish species in Port Phillip Bay and Western Port.
These parasites are common in marine finfish, with infections often visible as lesions or actual parasites, inside and/or on the surface of the internal organs of the fish, including the liver and gut.
Typically, these infections cause little harm and infected fish often present as healthy. Infections are usually in response to seasonal changes in environmental conditions and associated fish movements.
|
|  |
|
|
Table 2: Anticipated Bay events
|
| | | | Noctiluca blooms or "red tides"
|
| | Noctiluca is a microscopic, floating species of algae that occurs from tropical to temperate regions worldwide. While it is present in Port Phillip Bay year-round, it can occasionally form dense aggregations known as blooms or red tides. This typically occurs during the warmer months.
|
|  | Noctiluca bloom at Brighton Beach
Photo courtesy of EPA Victoria
|
| Krill washing up on beaches
|
| | Krill are small shrimp-like crustaceans that occur in swarms and are an important food source for fish and some marine mammals and birds. The coastal krill species found in the waters off southeastern Australia (Nyctiphanes australis) swarms during spring and summer. Large swarms are occasionally washed ashore in sheltered coastal bays.
|
| |
|
|
