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State of the Marine Environment Report for Australia: State and Territory Issues - Technical Annex 3

Edited by Leon P. Zann and David Sutton
Great Barrier Reef Marine Park Authority, Townsville Queensland
Department of the Environment, Sport and Territories, Canberra (1996)
ISBN 0 642 23012 9


Issues in the Western Australian Marine Environment

James A. Stoddart* & Christopher J. Simpson
Kinhill Engineers Pty Ltd.
Victoria Park, WA*, and
Environmental Protection Authority
Perth, WA

Summary

Due to the relatively undeveloped status of most of the Western Australian coast, instances of environmental deterioration of its marine ecosystems are few. For those recorded thus far, the primary pathway of impact has been through the deterioration of water quality, caused by the addition of pollutants. Thus impacts have been most pronounced in waters with restricted mixing and estuaries are seen to be at particular risk.

Extremely low levels of population density outside of Perth and a few coastal centres apparently place little stress on marine systems and, in general, remote systems are considered to be largely pristine. However, the extent and remoteness of these systems also restricts our ability to determine their status. Knowledge of the `natural' state of these systems is too rudimentary to detect any but the most profound impacts on their components and minor impacts may occur without detection.

In most documented cases of severe impacts on Western Australia's marine and estuarine systems, the pollutants implicated are nutrients; although adjacent to the concentration of industry in Cockburn Sound and Princess Royal Harbour, some instances of elevated heavy metals have been detected. Management programs to redress most of these severe instances of pollution at their sources have been initiated. In order of decreasing importance, statewide, these sources are:

Introduction

The Western Australian coastline contains the greatest diversity of marine and estuarine ecosystems of any Australian state. It stretches for over 12 000 km, through some 20 degrees of latitude, from wave-battered cold/temperate kelp beds in the south to low energy, mangrove-fringed mudflats in the north. Outside the metropolitan area, the coast supports an average of less than 30 people/km and most of its ecosystems are regarded as pristine. Nevertheless, human influence has severely degraded some Western Australian ecosystems and without careful management could do so again.

Western Australia is amongst the most urban of the Australian states, with 72% of the population of 1.7 million living within the Perth metropolitan region, and 80% between Geraldton and Esperance. Not surprisingly, it is in the waters adjacent to these populated regions that the major episodes of marine degradation have arisen. In this examination of the state of the marine environment in Western Australia, these episodes receive the greatest treatment. However, they should not obscure the high quality of the majority of the State's waters, nor our lack of information on the baseline conditions prevailing in most of these marine systems.

This treatment follows a geographic theme to allow the consideration of cumulative impacts from diverse sources. The geographic division of the state's waters (Figure 1) follows that described in the Western Australian Government's recent State of the Environment Report (Western Australian Government 1992) with some additions. Within each division, the status of the marine environment is addressed through considering the sum of impacts resulting from the primary human uses of marine and coastal resources. Conclusions drawn in this paper are essentially similar to those of the Western Australian Government report.

Uses are grouped into categories representing the major anthropogenic influences which might, at present, be affecting the Western Australian marine environment. The addition of a natural impacts category recognises that our ability to distinguish perturbations which occur as a result of natural cycles from human-induced changes to normal levels of ecosystem variability, is severely limited. Impacts in this category may require further investigation to determine if human sources have a role in their causation, or may need to be considered in placing human impacts in context.

Figure 1

Western Australia Coastline

In many cases, categories contain references to `concerns raised' on possible impacts. These references are included to provide a comprehensive treatment of issues-by-area and the needs for future research. They should not be viewed as an endorsement of what, in most cases, are unsubstantiated opinions. Locations mentioned in the text are shown in Figure 1.

Regional issues

Offshore North-western Australia (off the Continental Shelf)

Australian territory off the north of Western Australia includes a variety of coral reef habitats, including the platform reefs of Ashmore and Cartier Islands, reefs fringing the volcanic Christmas Island, and the coral atolls of Rowley Shoals and Cocos-Keeling Islands. Several marine protected areas have been declared by Federal and State agencies for the management and conservation of these ecosystems and a number of marine surveys have been carried out, primarily by the Western Australian Museum.

While the Western Australian Museum surveys have provided synoptic information on the biological resources of these areas, little is known of the natural variability of these systems and whether human influences are a significant issue in their present ecology. Unless otherwise referred, the treatment below is sourced from Hatcher (1987).

Tourist and housing developments

Tourism is currently a minor activity: Christmas Island was closed to tourism until 1992. Presently, the tourist potential of Christmas and Cocos Islands is being actively investigated and could increase (Western Australian Tourism Commission, pers. comm. April 1993). On habitable islands, some infrastructure development has occurred, although developments are small and sited inland without marine structures such as wharves or marinas. Boat-based visitation of areas such as the Rowley Shoals by SCUBA divers is increasing in popularity but remains small due to the remoteness of the destination.

Fishing

Illegal fishing by South East Asian fishers , both through subsistence and commercial operations, on offshore coral reefs, such as Ashmore Reef, has been reported to have caused impacts on target species such as trochus, dugong and turtles to the extent where trochus are now described as scarce (Sarti 1983). Although fishing methods such as dynamiting have been used (Hicks 1983) protective surveillance by Federal and State authorities seems to have avoided severe disturbance to the reef habitat. The remoteness of these areas precludes any regular program of resource surveys to support claims of impacts (or their lack).

Recreational fishing and collecting of invertebrates (e.g. shells and corals) is associated with tourist visitation. Should tourism increase further, the potential for local depletion of these stocks may arise.

Aquaculture

There is no reported aquaculture activity in this area, although some proposals to undertake giant clam farming have been raised in the past.

Industry, mining and sewage

The only substantive industry presently operating in these areas is the phosphate mining operation of Christmas Island. Some minor, localised, reef damage has been reported from the anchorage at Flying Fish Cove where phosphate is exported. Spillage of phosphate and discharge of sewage into this area occur without apparent deleterious effects.

Some interest has been shown in petroleum and gas exploration in these areas, although to date production activity has been confined to the more easterly Timor Sea field.

Agriculture

Agricultural activity on these islands is minimal. There is no indication that impacts such as the increased erosion and run-off reported to result from agriculture on many Pacific islands is occurring here.

Natural impacts

Cyclones occasionally cause damage to reefs in this area. Colin (1977) reported the presence of numbers of the crown of thorns starfish, Acanthaster planci, around the Cocos-Keelings and attributes an apparent decline in coral cover around the mid 1970s to predation by them. More recently, Simpson et al. (in press) suggest that the impoverished fauna in the Cocos Lagoon is more likely the result of hypoxia caused by the breakdown of trapped slicks of coral spawn. Hatcher (1987) suggests that the 1982/3 El Nino greatly reduced coral cover in shallow areas around Christmas Island.

Summary

Coral reef ecosystems of the islands off the continental shelf of north Western Australia are largely undisturbed, with the exception of some impacts on species targeted by illegal fishing.

The Kimberly Coast (NT border to Broome)

This macrotidal section of coastline is composed principally of tidal flats and mangroves. Some areas in the West Kimberleys include sections of rocky coast . Sandy beaches are few, being well developed only around Broome. Most of the Kimberley coast is inaccessible from a landward direction and difficult to reach by sea. Thus the coastal waters are known mostly from those sections adjacent to the ports of Wyndham, Derby and Broome.

Tourist and housing developments

The tourist potential of this coastline has been constrained by its remoteness. Significant tourist developments with a marine focus are restricted to the Broome region; attracted largely by the transition from mangrove and mud-flat to sandy beaches in this area. Other developments, such as fishing camps for tourists have been proposed but are yet to eventuate. No assessment of the impacts of functioning operations on the marine environment have been made to date.

Fishing

Commercial: The major fishery in the region is the western extension of the Northern Prawn Fishery, which stretches into Joseph Bonaparte Gulf (JBG), where it seasonally targets banana prawns, Penaeus merguiensis. Some limited trawling for western king prawns, P. latisulcatus, occurs off Broome. The impacts of this fishery on the population ecology of pearl oysters was studied and assessed as minimal before the fishery commenced in 1989. No studies of the impacts on nontarget species of the prawn fleet operations in JBG have been conducted.

Recreational: A growing local population and tourist component targets a restricted set of fish, predominantly by line, with some netting and spear fishing. Around populated areas, mud crabs are fished enthusiastically, resulting in depleted catch rates (assessed from perceptions by Broome and Derby residents).

Little is known about the impacts of recreational fishing on fish stocks.

Aquaculture

The Kimberley hosts an extensive pearl culture operation, which is WA's largest and oldest aquaculture industry. Pearls produced in 1990 were worth about $90 million, largely as exports to Japan (Western Australian Government 1992). Pearl oysters, Pinctada magaritifera, are captured from the wild by divers, with the majority of shell coming from the coast between Broome and Onslow. Some concerns have been raised about the effects of pearl farming, particularly shell dumps, on the benthic habitat immediately beneath operations (Malone et al. 1988). Despite the existence of a number of farms, no specific examples of impacts have been documented.

Industry, mining and sewage

Little industrial development is present on this coast. Meatworks in various centres discharge effluent, mainly into well-flushed estuaries, with no reported adverse impacts.

Agriculture

Concerns exist that modification of catchments by the extensive pastoral industry of the Kimberley is impacting on coastal and estuarine waters through increased sedimentation caused by erosion (Western Australian Government 1992).

Natural impacts

Shallow water ecosystems in this region are prone to the effects of cyclones which occur predominantly in mid summer to early autumn (Lourensz 1981). The strongly seasonal river flow may also cause occasional habitat disturbance through extreme sediment loads deposited on areas under the river plume.

Summary

The marine environment of the Kimberley region is considered largely untouched, although this assessment certainly reflects the rudimentary state of our knowledge of these waters.

The Pilbara Coast (Broome to Exmouth)

Much of this coast is dominated by the large tidal range characterising the Kimberley Coast, although towards the southern parts of this section, tidal range is down to 2m -3m (Easton 1970). In nearshore waters, small to medium stands of mangroves occur shoreward of habitats that commonly include low lying sandy or rocky shores with some coral reefs, usually developed over rocky substrates. Mangroves are best developed around the eastern shores of Exmouth Gulf.

Tourist and housing developments

Marine based tourism in the region is small. That which exists concentrates primarily on recreational fishing. There is little infrastructure associated with tourist developments: some fishing camps exist on islands but support relatively few visitors.

Fishing

Fisheries in the area present a diverse array of target species, fishing methods and size of operation. Examples of the larger operations include prawn trawling in Nickol Bay, trawl, line and trap fisheries targeting finfish, and the deep water trawl fishery for scampi and deep water prawns which extends past the continental shelf (Jernakoff 1988). Pair trawling for demersal fish by international vessels on the North West Shelf has been shown to have caused significant damage to bottom communities. Operations have subsequently been discontinued, although it appears that recovery of these communities will be slow (Sainsbury et al. 1992)

Recreational fishing around centres of population is prevalent although unlikely to be sufficiently intense to alter stocks.

Aquaculture

Despite the presence of many areas of sheltered water, little marine aquaculture has developed, outside of a few small operations targeting winged pearl oysters. Land-based aquaculture is largely constrained by a lack of freshwater sources, high temperatures and the enormous evaporation rate. Some culture of milkfish within the primary ponds of a salt producer has undergone trials.

Industry, mining and sewage

Over the past 10 years, substantial offshore oil and gas reserves have been developed on the North West Shelf and the area is due to become the major supplier of domestic energy within the decade (Fraser 1992). As a result of marine research undertaken by government and private industry in support of managing the impacts of this industry, an extensive knowledge base exists for the region's broad scale oceanography and the distribution of benthic habitats.

To date, there is no record of any oil spill having a significant effect on the area's marine ecosystems. Neither has monitoring associated with oil and gas operations shown widespread impacts on marine communities, although localised mortality of coral and mangroves has occurred. Further increases in exploration, drilling and production are planned for the next decade and will raise the potential for some form of impact. Past experience suggests that the potential for adverse impacts from routine discharges of production water may be of more concern than the effects of accidental oil spills, which are likely to be of limited volume given the high level of technology and management planning of current operations.

The region's substantial focus on the mining of high volume products such as iron ore has led to the development of substantial port facilities at Port Hedland and Dampier. On a tonnage basis, the port of Dampier, which handles iron ore, salt and liquid gas exports, processes the greatest volume of product of any in Australia.

A large solar salt field operates around Dampier. Other than the mortality of mangroves, caused during resumption of areas to create the initial ponds, this operation has not been shown to impact marine ecosystems (Robertson 1993).

Agriculture

Pastoral leases within this area of low rainfall and run-off are not considered to impact on the marine environment.

Natural impacts

With extensive areas of shallow (<10 m depth) waters, habitats on the inner North West Shelf are especially at risk from cyclones. Monitoring studies associated with the oil and gas industry have observed several widespread episodes of coral bleaching, which has been attributed to natural causes similar to other coral reef areas (see Brown 1990 for references). Coral predation by Acanthaster planci has also been documented as a regular feature of reefs within the western section of the Dampier Archipelago (Simpson and Grey 1989; Johnson & Stoddart 1988).

Summary

Despite the presence of a variety of human activities on this broad expanse of continental shelf, few adverse impacts have been recorded. Some localised damage around port facilities has degraded small areas of bottom; the only extensive damage recorded has been caused by demersal trawling for fish which has since ceased.

The Gascoyne Coast (Exmouth to Kalbarri)

Coastal waters of this area are characterised by their clear oceanic nature which results from a narrow continental shelf and low, or very seasonal, run-off from the land. Much of this coast, particularly that to the south of Shark Bay, is comprised of rugged cliffs which make access difficult.

Tourist and housing developments

A tourism industry with a focus on Shark Bay has been under way for some years. A large proportion of this tourism is based on the dolphin viewing area of Monkey Mia where the regular visits of dolphins to beach areas has been developed into a well known attraction. Some impact of visitors and their support facilities has resulted from pressure on nearshore ecosystems from beach-side toilet blocks (WAEPA 1989) and access to stromatolites. Recent incorporation of sensitive areas within marine protected areas could provide the management necessary to mitigate such impacts.

Fishing

Large gill nets for shark have been banned from Shark Bay as a response to perceived risks of entangling and drowning dugong or turtle in this area (Western Australian Government 1992). Trawling for scallops continues to provide good catches, with over 2500 tonnes of meat in 1991 (Western Australian Fisheries Department 1993)

Aquaculture

Aquaculture operations in this area are minimal. A historical pearl farming operation based on Pinctada albina albina in Shark Bay is now represented by a single operator. No environmental impacts of this activity have been raised.

Industry, mining and sewage

Industry along this section of coast is minimal. Some small developments occur at Carnarvon, but have not been implicated in any pollution events.

A large solar salt industry exists within Shark Bay. Recent expansion of this operation met with some opposition on the grounds of excluding fishing operations from some traditional grounds and annexing part of the local fish nursery area. There are no documented impacts of this salt industry outside of pond areas. North of Shark Bay, another salt production facility operates a shipping jetty at Cape Cuvier - also without reported impact. Shipping associated with the industry has caused marine impacts, with the wreck of the Korean Star and associated oil spillage near Cape Cuvier in 1988 (May 1992).

Agriculture

Pastoral leases within this area of low rainfall and run-off are unlikely to impact on the marine environment.

Natural impacts

Disturbance to coral reefs as a result of bleaching and predation by corallivorous snails has caused substantial impacts in some areas (Stoddart 1989). The cyclical nature of this latter impact, which has caused the loss of coral over hundreds of kilometres is yet to be verified. In 1989, corals, fish and many of the reef animals were killed within an area of 3 square kilometres at Coral Bay on the Ningaloo Reef as a result of oxygen starvation caused by the decomposition of slicks of coral spawn trapped within the Bay (Simpson et al. in press).

Summary

Marine impacts of human activities are either minor or nonexistent in this sparsely populated area of coast. Much of the area has now been declared as marine parks and is subject to management.

Temperate West Coast (Kalbarri to Cape Naturaliste)

This section of coast houses the bulk of the state's population and industry. It is also an area of coast which slopes gently to meet the sea at sandy beaches, often protected from the full force of ocean waves by offshore lines of limestone reefs. This physiography acts to increase the potential for anthropogenic impacts by facilitating developments on the fragile dune systems adjacent to the sea.

Tourist and housing developments

Coastal developments within this section are the most intense for the coastline. Marinas predominate as a focus for tourism, housing and fishing harbours. Of 29 marinas listed as planned, under construction or developed, 23 occur here (Western Australian Auditor General 1991). Other than their initial construction in greenfield sites, these marinas are not recorded as causing detrimental impacts to the shallow marine ecosystems in which they are sited.

Fishing

A pot fishery for the Western Rock Lobster dominates fishing in these waters, both in terms of fishing effort and economic value. This fishery is the most valuable single species fishery in Australia (DPIE 1992). The impacts of this fishery have been largely confined to impacts on the target stocks. Some isolated instances of mortality on sea lions and turtles have been noted when these animals are trapped in fishing gear.

Where the fishery extends into coral reef areas at the Houtman Abrolhos Islands, concerns have been raised over the potential for lobster pots to damage sensitive coral communities (Abrolhos Islands Task Force 1989). In most cases, coral communities and preferred fishing sites are spatially separated. A management plan to provide for fishing and conservation is being developed to address areas of potential conflict.

Some impacts of trawling have been suggested for the inshore waters around Geographe Bay. A research program studying the impacts of trawling on nontarget species in this area is due to report in early 1993 (Western Australian Government 1992).

Aquaculture

Aquaculture activities in these waters are limited. Culture of mussels, Mytilus edulis, in waters in and around Cockburn Sound and Warnbro Sound expanded in the late 1980s. These operations have had no apparent environmental or social impacts. Rather, the concern has been with the possible impacts of water of poor quality emanating from Cockburn Sound. Elevated levels of heavy metals and tributyltin (TBT) have been reported from wild mussels occurring in the waters of Cockburn Sound (see below). No such impacts on mussel flesh from farmed mussels have been reported.

Industry, mining and sewage

The major concentration of industry on the west coast occurs in Kwinana, approximately 10 km to the south of Fremantle. A primary consideration in siting industry at Kwinana was its location adjacent to the sheltered waters of Cockburn Sound which provided an excellent (in engineering terms) environment for constructing port facilities and wastewater outfalls, and in some cases, a source of raw materials. The well-studied decline of the ecosystems of Cockburn Sound during the 1960s and 1970s is largely attributable to this sheltered nature, which results in low flushing of waters.

The natural ecosystem of Cockburn Sound and areas immediately adjacent to the north contained dense meadows of seagrass, dominated by species of Posidonia and Amphibolis. Addition of excessive amounts of nutrients, primarily nitrogen, to these waters from industrial effluents and treated sewage resulted in the prolific growth of macroalgae which subsequently caused the loss of more than 75% of a seagrass cover estimated at 4000 ha in 1954 (Western Australian Government 1992). As a result of studies in the 1970s which revealed the extent of seagrass loss and its probable causes, nutrient reduction to the Sound has declined under stringent management guidelines.

Despite the improvement in water quality, it appears that the original seagrass beds are unlikely to return as a result of the poor colonising ability of Posidonia, the major structural component of these beds. This substantial shift in the dominant habitat type may not have had a substantial impact on the Sound's fisheries. Catches from beach and purse seine, gill net, crab net, mussel diving, line and pot fisheries are reported as increasing since 1977 (Western Australian Fisheries Department 1993), although fishery status was not recorded statistically prior to the major habitat perturbation.

Currently, the majority of Perth's domestic wastewater (treated sewage) is discharged to the adjacent marine environment. While there are few obvious effects of this discharge to date, substantial increases predicted to occur over the next 30 years (Figure 2) with a doubling of the population served by this system may exceed the nearshore ecosystem's assimilative capacity. In April 1991, the State Government initiated a comprehensive program of study of the existing and predicted future impacts of this discharge. Joint studies coordinated by the EPA and Water Authority of Western Australia which focus on the cumulative impacts of nitrogenous discharges to coastal waters between Yanchep and Mandurah will provide the information needed to develop a long-term strategy for management of waste discharge. The overall program, due for completion in December 1994, contains a predictive modelling and a comprehensive monitoring approach to avoiding eutrophication within these oligotrophic systems.

Figure 2. Discharge of treated wastewater to Perth coastal waters (2020 projection) Figure 3. Oil input to Cockburn Sound Figure 4: Heavy metals in Cockburn Sound mussels

Heavy metals derived from industrial pollution have also caused problems in Cockburn Sound in the past. However, a recent survey by the Western Australian Environment Protection Authority (WAEPA) shows that levels of all pollutants discharged into Cockburn Sound have decreased dramatically over the last 10 years as a result of better waste treatment and control; oil discharge for instance (Figure 3) has dropped by about 70%. Consequently, WAEPA studies have shown that toxic contaminants (heavy metals, pesticides and hydrocarbons) in mussels and marine sediments have fallen considerably since the late 1970s (Figure 4).

Associated with the concentration of industry within this location is the regular transit of ships carrying a variety of cargoes with potentially significant implications for marine pollution. A recent incident underscoring the potential for pollution derived from shipping occurred in 1991 when the tanker Kirki , carrying 70 000 tonnes of crude oil, lost its bow in heavy seas off the Cervantes area and was taken in tow only a few kilometres off the nearshore reef line. Had the tanker grounded and broken up, the impact on the shallow rock lobster grounds would have been substantial.

A less obvious form of pollution associated with the shipping and boating industry derives from the antifoulant TBT. A recent report (WAEPA 1990a) points to detectable levels of this highly toxic chemical around Cockburn Sound and studies suggest that impacts are occurring in molluscs at least (Kohn & Almasi, in press). It is likely that similar studies in other areas sustaining high boating or shipping use could find similar results. Present regulations prohibit the use of TBT on vessels below 25 m.

Agriculture

Extensive modification of the catchments of streams and rivers in the south-west of Western Australia caused by agricultural clearing and the addition of nutrients, either as fertilisers or animal wastes, has had a severe impact on rivers and estuaries. Of 22 estuaries assessed in the WA State of the Environment Report (Western Australian Government 1992), nine are listed as in poor condition. For eight of these nine, agricultural sources are shown as the primary cause of eutrophication.

Figure 5: Decline in seagrass cover in a nearshore meadow in Geographe Bay

Perhaps the most severe case of estuarine eutrophication in Western Australia involves the Peel-Harvey estuary, a shallow lagoon 70 km south of Perth. The system's natural productivity and restricted flushing predispose it to eutrophication. Symptoms of an increasing phosphorus load within the catchment were first observed in the 1960s as extensive floating accumulations of the alga Cladophora, but escalated steeply in 1973 with the appearance of severe blooms of Nodularia, which are now regular features in late Spring/early Summer (Kinhill 1988).

Poor phosphorus binding capacity in the sandy soils of the coastal plain results in a rapid passage of phosphorus fertilisers applied in agricultural operations into drains and streams within the estuary's catchment. At present, a multifaceted management strategy is under way to reduce the problem through algal harvesting to ameliorate the symptoms of eutrophication, catchment management to reduce inputs of nutrients, and enhancement of flushing through the provision of a more direct connection with the sea.

Another site where eutrophication may be occurring as a result of agriculture and/or urbanisation is Geographe Bay. Preliminary studies of the Bay's seagrasses show a progressive thinning of an inshore meadow near Dunsborough (Figure 5). A recent underwater survey found substantial algal growth on leaves of the seagrasses at this site; a common indication of excessive nutrient loading which may lead to seagrass death.

Summary

As a result of the relatively high population density of this section of Western Australia's coastal waters, the majority of documented impacts have occurred between Kalbarri and Cape Naturaliste. Outside of water bodies with restricted circulations, these impacts have been minor. Most impacts relate to deterioration in water quality due to nutrient loading, although some heavy metal pollution has been apparent from industry. Management of nutrient problems in Cockburn Sound and the Peel-Harvey estuary has largely redressed water quality issues, although the original ecosystems have not been restored to any degree. Investigations of the possible impacts of nutrient loading and TBT in Perth waters are under way.

The South Coast (Cape Naturaliste to the South Australian Border)

Rugged rocky outcrops dominate this high energy coastline which is flanked largely by deep waters supporting extensive temperate kelp ecosystems.

Tourist and housing developments

Coastal developments within this area are few and extremely localised. With the complex physiography of the coast in this region providing a surplus of natural harbours, minimal alteration of coastal structure has been necessary to provide havens for boats or ports.

Fishing

Fishing operations in this region are diverse, ranging from deep offshore trawling in the Great Australian Bight, to purse seining for bait fish, some tuna fishing and a traditional onshore beach seine fishery for Australian salmon. Little is known about the impacts of these fairly remote operations. In general these operations are at a small scale and unlikely to cause substantive perturbations.

Aquaculture

Attempts to establish cage culture of Atlantic salmon at Albany have proven unsuccessful and the cages been removed. Present aquaculture is directed at establishing hatchery and grow-out operations for the flat oyster, Ostrea angasi, at Albany and some interest has been shown in oyster culture in other estuaries. These operations are not expected to lead to adverse environmental impacts.

Figure 6

Figure 6

Industry, mining and sewage

Princess Royal Harbour is a moderate sized embayment adjacent to the town of Albany, with a narrow opening to the sea. Nutrient discharges from industrial and domestic wastes have led to the loss of most of the bay's lush seagrass meadows (Figure 6), which have been smothered by epiphytes and free macroalgae. Industrial discharges have also caused enrichment of heavy metals leading to the contamination of marine biota (Figure 6) to a level where harvesting of fish and shellfish has been banned from some parts of the harbour.

An intensive study by the Western Australian Environmental Protection Authority (WAEPA 1990b) examined the causes of this degradation and made a series of recommendations for controlling pollutant inputs. Many of these recommendations are now in place or planned and metal levels in biota have been reduced to levels which are safe for human consumption. Harvesting of macroalgae has also commenced to reduce recyclable nutrient pools.

Agriculture

Oyster Harbour (Figure 6), an estuary adjacent to Princess Royal Harbour has shown a similar loss of seagrass as a result of nutrient enrichment. In this case, the phosphate loading emanating from farms on the river catchments has been the primary causal agent. Following the WAEPA study cited above, catchment management initiatives are under way to reduce these inputs.

Wilson Inlet near Denmark, to the west of Albany, shows evidence of increasing levels of nutrients, both in sediments and as an increased standing crop of macrophytes (Lukatelich et al. 1987). Although no signs of severe eutrophication have appeared as yet in the biota, it is likely that the system is on the brink of such a change in state.

Summary

The eutrophication of estuaries, and perhaps embayments, resulting primarily from nutrient loading of catchments by agriculture is a common feature in this section of coast. Otherwise, nearshore ecosystems are in near pristine condition.

References

Abrolhos Islands Task Force 1989, Abrolhos Islands Planning Strategy: Final Report, Report to the Abrolhos Islands Consultative Committee, Western Australian Departments of Fisheries, Conservation and Land Management, and Planning and Urban Development, Perth.

Brown, B.E. (ed) 1990, `Coral bleaching', Coral Reefs, vol. 8, pp. 153-232.

Colin, P.L. 1977, `The reefs of Cocos-Keeling Atoll, Eastern Indian Ocean', Proceedings of the 3rd International Coral Reef Symposium, Miami, pp. 63-68.

DPIE 1992, Background Fisheries Statistics, Fisheries Policy Branch, Department of Primary Industries and Energy, Canberra.

Easton, A.K. 1970, `The tides of the continent Australia', Research Paper 37, Horace Lamb Centre for Oceanographic Studies, Adelaide.

Fraser, I. 1992, `WA - An underexploited oil province', in Petroleum - Western Australia, Oil and Gas Australia, Western Australian Department of Mines, Perth.

Hatcher, B.G. 1987, `Australia-Western', in Directory of Reefs of International Importance, vol. 2, Indian Ocean, ed S. Wells, IUCN & Natural Resources, Cambridge, UK.

Hicks, J. 1983, unpubl., Report on Ashmore Reef National Nature Reserve, October 1983 Investigations, Australian National Parks and Wildlife Service, Canberra.

Jernakoff, P. 1988, The Western and North West Shelf Deep-Water Trawl Fisheries: Research Priorities, Bulletin no. 1, Bureau of Rural Resources, Department of Primary Industries and Energy, Canberra

Johnson, D. & Stoddart, J.A. 1988, `Surveys of Acanthaster planci in the Dampier Archipelago, Western Australia', Crown of Thorns Studies Series, Australian Institute of Marine Science, Townsville.

Kinhill 1988, `Peel Inlet and Harvey Estuary Management Strategy', Environmental Review and Management Program - Stage 2, Kinhill Engineers Pty Ltd, Perth.

Kohn, A.J. & Almasi, K.N. (in press), `Imposex in Australian Conus.' Journal of the .Marine Biology Association U.K.

Lourensz, R.A. 1983, Tropical Cyclones in the Australian Region, July 1909 to 1980, AGPS, Canberra.

Lukatelich, R.J., Schofield, N.J. & McComb, A.J. 1987, `Nutrient loading and macrophyte growth in Wilson Inlet, a bar-built southwestern Australian estuary', Estuarine, Coastal and Shelf Science, vol. 24, pp. 141-165.

Malone, F.J., Hancock, D.A. & Jeffriess, B. 1988, Final Report of the Pearling Industry Review Committee, Fisheries Management Paper no. 17, Fisheries Department of Western Australia, Perth.

May, R.F. 1992, `Marine conservation reserves, petroleum exploration and development, and oil spills in coastal waters of Western Australia', Marine Pollution Bulletin, vol. 25, pp. 147-154.

Robertson, A.I. 1993, Study of the impact of Pilbara coastal development on arid zone mangroves, report to the Western Australian Department of State Development, Perth.

Sainsbury, K.J., Campbell, R.A. & Whitelaw A.W. 1992, `Effects of trawling on tropical marine habitat of the North West Shelf of Australia and implications for sustainable fisheries management', in Proceedings of the Sustainable Fisheries Workshop, Bureau of Resource Sciences, ed D. A. Hancock, AGPS, Canberra.

Sarti, N. 1983, (unpubl.), Report to the Chief Fisheries Officer on a Visit to Ashmore Reef, February 1983, Fisheries Department of Western Australia, Perth.

Simpson, C.J. & Grey, K.A. 1989, Survey of Crown-of-thorns Starfish and coral communities in the Dampier Archipelago, Western Australia, Technical Series 25, Environmental Protection Authority, Perth

Simpson, C.J., Cary, J.L. & Masini, R.J. (in press), `Destruction of coral and other reef animals by coral spawn slicks on Ningaloo Reef, Western Australia', Coral Reefs.

Stoddart, J.A. & Johnson, D.B. 1988, Report on surveys of the distribution, abundance and impact of Acanthaster planci on reefs within the Dampier Archipelago (Western Australia), Australian Institute of Marine Science, Townsville.

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WAEPA 1989, Disappearance of Dolphins at Monkey Mia, Bulletin 381, Environmental Protection Authority, Perth.

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