4.5 IMPACTS IN VICTORIA

4.5.1 Port surveys

The CSIRO Centre for Research on Introduced Marine Pests (CRIMP) has developed protocols for port surveys to determine the distribution of exotic species in Australian ports²²¹

Survey sampling concentrates on habitats and sites in the port and adjacent areas that are most likely to have been colonised by the target species including wharves, slipways, deballasting areas, and habitats on the nearby exposed coast²²²
Although there are long term plans coordinated at the national level to survey Australian ports, Victoria has already commenced its own port surveys, largely based on the guidelines developed by CRIMP. The Port of Portland survey has been completed and the Port of Hastings survey is nearing completion. Although the Ports of Melbourne and Geelong have not yet been formally surveyed, in the course of developing the protocols for the port surveys, CRIMP identified a large number of exotic species in Port Phillip Bay²²³ This information is complemented by other studies that have been undertaken in the Bay by various bodies.

4.5.2 Port Phillip Bay - Port of Melbourne and Port of Geelong

Port Phillip Bay is a large, shallow bay, with over half of its waters less than 8 metres deep. Victoria's two largest cities and their ports, Melbourne (the capital of the State), and Geelong, are situated on the Bay, with the Port of Melbourne being Australia's major container and general cargo port²²⁴ Over three million people live in its catchment areas, and the Bay is subject to pressures from commercial and recreational activities, as well as receiving chemical and nutrient runoff from urban and agricultural areas. The largest input comes from the Yarra River which discharges into the Bay, and significant amounts of treated effluent are also discharged into Port Phillip Bay from the Western Treatment Plant at Werribee²²⁵ Despite these pressures, the Bay's ecosystem is healthy, evidenced by clean waters and beaches, and diverse marine flora and fauna. Indeed, Port Phillip Bay is rated first in importance in Victoria and seventh in Australia for the number of migratory birds it supports²²⁶

Port Phillip Bay is the most extensively studied marine system in Victoria. The most recent and comprehensive study, The Port Phillip Bay Environmental Study conducted by the CSIRO, is the largest single study of coastal ecology carried out in Australia²²⁷ The study highlighted the importance of the benthic invertebrate community in maintaining water quality in the Bay. Despite high nutrient inputs into the Bay, and the slow rate of exchange of its waters with those of Bass Strait - over the period of about 1 year - eutrophication has not occurred. The clean water of Port Phillip Bay is attributed to the action of organisms in the Bay sediments which convert organic nitrogen into nitrogen gas, thereby preventing an accumulation of nutrients in the Bay²²⁸ The study found that:

...the biggest threat to the Bay in the future, may well be the introduction of exotic organisms which can change the way the entire Bay functions by competing with local species for food, habitat and oxygen.

A large number of introduced species have been recorded in Port Phillip Bay, including all of the eight species discussed above. In total about 145 exotic species have been identified. The origin of some of these species is, however, not known, nor is the method of their introduction, or their potential impacts²²⁹ A list of known and suspected introduced species in Port Phillip Bay is provided in Appendix D .

The Sabella worm, Corbula, and the Asian mussel and are all abundant in Port Phillip Bay, and have been present in the Bay for more than 10 years. Although their impacts on the Bay are still unknown, it is apparent that the success of these three species, and of the small (25mm) exotic tube worm Euchone sp,. has led to a shift in the relative abundance of species in the benthic community, resulting in more filter feeders and fewer deposit feeders²³⁰ For example, in the deepest waters of Port Phillip Bay, Corbula has the highest biomass of any benthic species, and occurs at densities of up to 6,000 per square metre in the Geelong arm²³¹ Changes in the composition of the benthic community of the Bay could result in disruptions to nutrient cycling processes. The Sabella worm, which is spreading eastward in to Port Phillip Bay from Corio Bay, is of particular concern. The worm intercepts particulate food at some distance from the Bay floor, preventing it from reaching denitrifying bacteria in the sediment, and then excretes nitrogen into the water in the form of ammonia²³² This may increase nutrient loads in the Bay, resulting in eutrophication and algal blooms. The complexity of these interactions means that the impact of Sabella on nutrient cycling in the Bay is difficult to predict. Dr Harris, CSIRO²³³ describes the current situation as:

...a balance between the fact that [Sabella] filter like crazy and are actually able to clean up the water of the Bay, and the fact that they short-circuit the sediment system which is important for removing nutrients.

Sabella may also have indirect effects on commercial species and the overall bio-diversity of marine communities by:

i) affecting the marine food chain;
ii) inhibiting the settling of other invertebrate species; and
iii) competing for food and space²³⁴

Exotic species such as Sabella and Corbula compete with native species of filter feeders such as scallops, oysters, sea squirts and blue mussels. For example, the size and longevity of scallops in Port Phillip Bay has declined, suggesting that they are starved of food²³⁵ For the past five years, the maximum size of scallops in the Bay has been less than the minimum harvesting size allowed in the 1960's²³⁶ Fish such as snapper, which feed upon mussels and scallops, may therefore also decline²³⁷

Toxic algae also pose a serious risk to the ecology, amenity and productivity of Port Phillip Bay. In recent years there have been five public health alerts in the Hobsons Bay area due to outbreaks of Alexandrium catenella. Commercial shellfish operations in the Geelong Arm have also been closed a number of times due to blooms of Alexandrium tamarense and Rhizosolenia cf chunii²³⁸

The Committee notes with great concern the presence in Port Phillip Bay of the recently discovered northern Pacific sea star, Japanese kelp, and Codium. The Committee believes that these species could pose serious threats to the Bay's ecology based on their biological characteristics and their impacts in other locations.

Until 1995 it was thought that the northern Pacific sea star was confined to Tasmanian waters, however, in August and September 1995 two sea stars were found in Port Phillip Bay near Port Arlington by scallop fishers²³⁹ Both specimens were mature females ready to spawn. Two further live, mature sea stars have since been found; one in August 1996 at Point Cook, and another in April 1997 near scallop boats berthed at Victoria Dock²⁴⁰ Despite extensive dives in the vicinity of Victoria Dock at the time, no further sea stars were found²⁴¹ No juvenile specimens have been found to date, and it is believed unlikely that the sea stars came from established local populations in Port Phillip Bay. It is thought that they were transported from Tasmania as adults on hulls or fishing gear ²⁴²

In July 1996, Japanese kelp was identified in Port Phillip Bay, 2km off Point Wilson near the discharge point of the Western Sewage Treatment Plant, covering an area of about 1-2 square kilometres²⁴³ In some locations within that area the kelp has become the dominant species, with plants of various sizes occurring at densities of up to 150 per square metre²⁴⁴ The kelp has the potential to destroy native seagrass beds, to compete with plants that are a food source for abalone, and to change the habitats of other invertebrates and fish²⁴⁵

In August 1997, under the Fisheries Act 1968, quarantine of the area was authorised by the Minister for Agriculture and Resources in order to prevent spread of the kelp on the hulls or gear of recreational and commercial fishing vessels. An educational brochure was released to aid in the identification of the kelp, and a trial hand-pulling of the kelp was undertaken by divers to determine if containment of the kelp is possible. To date, results of the trial are not known. Although the quarantine has been supported by users of the area, including abalone divers and recreational fishing groups²⁴⁶ the kelp has since spread beyond the quarantine zone²⁴⁷

It is believed that the kelp's life cycle, which displays a microscopic and a macroscopic stage, will make its eradication difficult. In Port Phillip Bay, between April and December, the kelp grows at an extremely fast rate, reaching lengths of up to 1m within two months²⁴⁸ The kelp then dies back during the summer months. Before dying off, plants release millions of spores which, following fertilisation, develop into a new generation when conditions are favourable. Although the biology of the kelp is not well understood, it has been predicted that ideal conditions in the Bay could see it become a dominant part of the Bay's marine flora²⁴⁹ The Victoria University of Technology (VUT) is currently studying the population to determine the biology and demography of the population in the Bay. CSIRO is also funding VUT research into the development of biocidal agents to kill the kelp's gametophytes²⁵⁰
During the 1996/97 summer, Codium was discovered in Port Phillip Bay, growing in the area infested by Japanese kelp. It is believed that Codium had been present in the vicinity for some time, but was thought to have been a similar native species²⁵¹ During the summer when the kelp dies back, Codium thrives in the infested area, retreating as the kelp comes to dominance during the winter months²⁵² It is possible that a biological association has developed between the two species, with an alternation of dominant exotic species depending on season. At this stage no attempts to eradicate or contain Codium have been undertaken.

There are other exotic species in Port Phillip Bay which are not on the Committee's target list, but which are abundant in the Bay. These species include Euchone sp., a small tube worm which thought to have originated in Japan²⁵³ a small bivalve from the Pacific coast of Asia; and a crab from the eastern Pacific. Knowledge of their biology and their potential impacts is limited. Other introduced species are abundant only in nutrient enriched areas such as intertidal zones near the Werribee sewage treatment farm²⁵⁴

As indicated previously, 172 exotic species have been found in Australian ports, and of these, 145 have been found in Port Phillip Bay. The large number of known introduced species in the Bay may be attributed to a combination of factors which include;

· The Ports of Melbourne and Geelong receive a high number of ship visits (see Chapter 7.7). This is likely to increase the chances of translocation of exotic organisms in ballast water or on ships' hulls²⁵⁵ Corio Bay, which receives much ship traffic and which has confined waters that are flushed particularly slowly, is considered the 'hot spot' in Australia for the introduction of exotic species²⁵⁶

· Many of the international ships which visit Port Phillip Bay are from ports in Asia, particularly Japan, which have similar marine environments to that of the Bay²⁵⁷ This may increase the likelihood of successful establishment of exotic organisms.

· The effects of disturbances such as dredging, high nutrient inputs and the presence of other exotic species may make the Bay more prone to invasion by exotic organisms²⁵⁸

· Port Phillip Bay has been the focus of a large number of surveys, therefore more is known about the flora and fauna in the Bay than in other ports.

Due to the large number of exotic species in Port Phillip Bay, there is a risk that organisms will be translocated from the Bay to other ports. Many ships which visit the Port of Melbourne or the Port of Geelong pick up ballast water before leaving port, and often these ships are bound for other Australian or Victorian ports²⁵⁹ Ships which do not pick up ballast water in the Bay may still translocate exotic organisms on their hulls²⁶⁰

Commercial fishing boats may also be a vector for transfer of organisms between Victorian ports. Fishing vessels are generally divided into two categories - offshore and inshore. The main berths for offshore fishing boats are located at Portland, Lakes Entrance, and San Remo. The boats travel mainly to the south eastern and southern shark fisheries, usually returning to the harbour from which they left²⁶¹ Some offshore fishers, however, have individual contracts with purchasers in other ports. Depending on season, these vessels may travel from Lakes Entrance, Portland, San Remo or Corner Inlet, to Port Phillip Bay and to ports in other states and territories²⁶²

4.5.3 Western Port Bay - Port of Hastings

The Port of Hastings is a deep-water port, situated in Western Port Bay, 60km south east of Melbourne²⁶³ Forty percent of the Bay comprises intertidal mudflats, supporting diverse flora and fauna within a range of habitats including mangroves and salt marshes²⁶⁴ The bay supports 12.3% of the State's coastal wading bird population and is listed under the Ramsar Convention. Many of the migratory birds found in Western Port Bay are protected under CAMBA and JAMBA (see Table 5)²⁶⁵ French Island is located in the centre of Western Port Bay, and Phillip Island, the home of the famous Fairy Penguin Parade, stretches across the Bay's entrance.

Although the Port of Hastings receives the second smallest number of ship visits to Victorian ports, it receives the greatest volume of ballast water²⁶⁶ This is due to the large number of tankers which discharge their ballast to load cargo²⁶⁷ The Port is also visited by many commercial fishing vessels which are licensed to fish in both Port Phillip Bay and Western Port Bay²⁶⁸ Such vessel movements pose a risk of transfer of organisms via hull fouling²⁶⁹

Recently the Port of Hastings was surveyed for exotic species by the Marine and Freshwater Resources Institute (MAFRI) in accordance with CRIMP guidelines. Although a number of floral and faunal surveys have been conducted in Western Port Bay, earlier surveys had not specifically focused on the identification of exotic species. The MAFRI report is not yet complete, but preliminary results indicate that few exotic marine organisms have established populations in the Port of Hastings. This may be attributable to a combination of factors including the limited survey area and the rapid flushing of wharf waters due to strong tidal currents²⁷⁰

Three of the Committee's target species, the European shore crab, the Asian mussel, and Corbula were found in small numbers. Further diver searches in the near future are scheduled to confirm the presence or absence of other target species. Five other introductions, or possible introductions, were identified, including two which may have been present in Western Port for over 20 years²⁷¹

4.5.4 Port of Portland

The Port of Portland is located on an exposed coastline, halfway between Melbourne and Adelaide. It is an artificial harbour, enclosed by two long breakwaters and containing six shipping berths, additional berths for commercial fishing vessels, a marina for recreational vessels and a slipway for small vessels²⁷² Portland Bay contains the only known area of Amphibolis seagrass on the open coast of Victoria, and is one of only two sites of a native, rare brown alga²⁷³

A survey of the Port of Portland was conducted in 1996 by the Marine and Freshwater Resources Institute (MAFRI), based on the CRIMP guidelines. Nine exotic species were found, including three on the Committee's target list -the toxic dinoflagellate Alexandrium tamarense; the Asian mussel; and Corbula. With the exception of Euchone sp., however, no species were abundant enough to have any serious ecological effects. All of the exotic organisms found, except Euchone sp., occur in larger populations in Port Phillip Bay. It is therefore suspected that these species may have been transferred to Portland from Port Phillip Bay²⁷⁴ Conversely, the larger population of Euchone sp. in Portland suggests that Portland could have been the source of the Port Phillip Bay infestation²⁷⁵

Portland has fewer ship visits than other Victorian ports, but receives similar quantities of ballast water²⁷⁶ The relatively low number of exotic species in comparison to Port Phillip Bay may, in part, be attributable to the lower number of ship visits and the exposed coastline surrounding the Port which results in rapid flushing of the harbour. It is believed that hull fouling species which are transported as adult organisms would be the most likely organisms to establish in the Port of Portland. Species transported in ballast water which have long larval periods may be flushed from port waters before they have a chance to develop, and may not be adapted to the exposed conditions just outside the port²⁷⁷

The harbour may also be vulnerable to species with short larval durations transported in vessels with fast transit times, such as woodchip vessels²⁷⁸ Nearly all of the vessels which visit Portland from Japan are woodchip vessels. These arrive empty of cargo, with full ballast tanks that are discharged prior to loading²⁷⁹ It is projected that the number of woodchip vessels visiting Portland is likely to increase over the next five years²⁸⁰ The Committee notes that Euchone sp., which is believed to have originated in Japan, and which has a short larval period of less than 4 days, now occurs in densities of up to 2,000 per square metres throughout the Port of Portland²⁸¹

With a recent increase in the movement of commercial fishing vessels from Port Phillip Bay to Portland for offshore squid fishing, there is also an increased likelihood that organisms such as the Sabella worm will be transferred to Portland on the hulls of boats²⁸²

4.5.5 Summary

The Committee notes that Port Phillip Bay supports a large number of exotic organisms, many of which have established large populations. In comparison, the Ports of Hastings and Portland presently have few recorded exotic species.

Port Phillip Bay may be more susceptible to invasion by exotic species due to the large number of ship visits, the slow flushing of Bay waters, and the fact that various disturbances, including previous incursions by exotic species, may make the Bay more vulnerable to new incursions. That there are fewer exotic species recorded from the Port of Hastings and the Port of Portland may be due to a number of factors including fewer ship visits and faster flushing times. It is also important to note that differences between Port Phillip Bay and the other ports may be attributable to the greater scope and number of surveys that have been conducted in Port Phillip Bay.

The Committee notes with particular concern the potential for exotic organisms such as the Sabella worm and Corbula to disrupt nitrogen cycling processes in Port Phillip Bay, which could lead to nutrient enrichment, or eutrophication, of Bay waters.

Port Phillip Bay is infested by all eight of the species discussed above, and it is necessary to consider ballast water and hull fouling management issues not only in view of preventing further incursions into Port Phillip Bay, but with an understanding of the Bay's role as a source of exotic organisms. The Committee believes it is important to limit the spread of these organisms, both within the Bay and to other ports. In particular the Committee notes the risk of translocation of exotic organisms, particularly the Sabella worm and Japanese kelp, on the hulls of commercial fishing vessels which travel from Port Phillip Bay to other Victorian and Australian ports.