5.6 Marine and estuarine water quality and ecosystem health

Coastal NSW has generally good recreational water quality during dry weather. Diffuse pollution sources can cause nutrient and contaminant problems in some estuaries during wet weather.

Outside the metropolitan areas, most nutrient pollution is derived from diffuse sources. Point sources of nutrients are actively and effectively managed under licence. Since 1999 compliance with swimming water quality guidelines has steadily improved. The Beachwatch Partnership Program has extended the monitoring of recreational water quality to the North and South coasts of NSW.

Although the upper reaches of Sydney estuaries have impaired water quality and environmental health, the lower reaches appear to be improving.

There were no major pollution incidents during the reporting period 2002–04.

Marine water quality objectives were agreed by the Government in 2006, complementing the estuarine water quality objectives established in 1999.

NSW indicators

Introduction

Marine and estuarine waters support dynamic ecosystems, contain valuable natural resources, and have important environmental values. The quality of these waters can be affected by pollution from point sources, diffuse sources, spills from shipping accidents, land-based spills that reach coastal waters, and discharges from vessels. Pollution can occur directly or via rivers that flow into these coastal waters. However, oceanographic conditions such as upwellings are the main influence in determining marine water quality.

The concentration of people and industry in coastal NSW means that much wastewater is discharged by sewage treatment plants (STPs) into marine and estuarine environments. Discharges can affect water quality and degrade marine and estuarine environments. Estuaries or coastal lakes are much more sensitive to pollution than the ocean because there is less tidal flushing by clean ocean water.

Urban runoff is another significant source of pollution for estuaries and near-coastal marine environments. Runoff from urban areas is generally contaminated with sediment, nutrients, hydrocarbons, heavy metals, pathogens, and other toxic, and occasionally persistent, chemicals. This contamination originates from roads, sewer overflows, spills, industrial activities, building sites and other sources. Runoff from rural areas may also contain sediments, nutrients, and pesticides and herbicides. The impacts on receiving waters are the same as for point-source discharges – reduced diversity of species, loss of pollution-sensitive species, and high levels of persistent toxicants in sediments and marine species.

River regulation may also affect coastal water quality, particularly estuaries and coastal lakes, by reducing the high flows needed to disperse pollutants and sediment. This can interfere with the chemical, biological and physical interactions between marine and freshwater ecosystems and cause pollutants to accumulate in estuaries.

Algal levels, as measured by chlorophyll-a, had remained stable from the 1980s to 2001 (Ajani et al. 2001a), although reports of visible blooms ('red tides') appeared to be increasing (Ajani et al. 2001b). In NSW coastal waters, algal blooms are natural phenomena that occur when cold, nutrient-rich water from deep areas off the continental slope are forced to the surface by oceanographic processes. Blooms often originate north of Sydney where changes in continental slope topography and orientation promote uplifting and upwelling of water towards the ocean surface. Nutrients from the deep then become available to algae in the surface zone of the otherwise nutrient-poor waters of the East Australian Current. The combination of sunlight and nutrients favours the rapid growth of algal blooms, which are then pushed shoreward by wind or current to converge and form visible blooms on local beaches and within frequently used waterways.

One of the greatest threats to healthy estuaries in NSW is the growth of nuisance algae and the consequent loss of seagrass due to overgrowth and shading. Excessive algal growth and loss of seagrass have been strongly linked to increased nutrient production in coastal catchments. Analysis of past satellite images for Wallis Lake has shown a pattern of less seagrass and more algae as development in the catchment increases (Dekker et al. 2005).

Major pollution incidents have a range of sources. These include shipping accidents resulting in oil or chemical spills, spills on land that drain to marine and estuarine waters, release of sewage from vessels, and ballast-water discharges containing marine pests.

Current status and trends

Pollution sources

Figure 5.6 shows licensed discharges of total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN) to estuarine waters and marine waters. The total number of licences is also shown.

Figure 5.6: Licensed discharges of total suspended solids (TSS) and nutrients – total phosphorus (TP) and total nitrogen (TN) – to NSW estuarine and marine waters, and number of DEC licences

Source: DEC data 2005

The increase in nutrients disposed of to marine and estuarine waters generally reflects population growth as well as the sewering of some small unsewered towns (see Human Settlement 2.2).

The slight increase in TSS discharged to estuarine waters from 2002 to 2004 (Figure 5.6), can be attributed to discharges resulting from increased iron and steel production at Port Kembla steelworks.

Although most marine and estuarine plants (such as seagrasses) respond to increases in nutrients, the available nitrogen commonly limits algal growth. Mapping of the potential for some NSW coastal catchments to generate nutrients, other than in the Sydney Basin, show that the main sources of human-influenced total nitrogen production (and the proportion of nitrogen they generate) are agriculture (50%), urban areas (30%) and transport and communication corridors (20%) (Baginska et al. 2004).

The total annual nutrient loads to marine and estuarine waters in 2001 show that diffuse sources are more significant than point sources in most catchments, with over 4000 tonnes of nitrogen and 800 tonnes of phosphorus from diffuse sources, compared to 2700 tonnes of nitrogen and 620 tonnes of phosphorus from point sources (Baginska et al. 2004). This analysis compares modelled data of diffuse nutrient generation from different land uses with actual licensed (point) discharges.

However, this analysis excludes the Sydney metropolitan area, where ocean sewerage outfalls are the largest point sources of nutrients to coastal waters. In 2001 the five metropolitan ocean outfalls (servicing Warriewood, North Head, Bondi, Malabar and Cronulla STPs) discharged nearly 14,400 tonnes of TN and more than 2600 tonnes of TP (DEC licensing data). These point sources exceed diffuse sources to ocean waters because most nutrient loads from diffuse sources are trapped in estuaries except at times of flood, whereas point-source loads are less variable and represent a higher proportion of the total load when freshwater inputs are low.

Marine and estuarine water quality and waterway health

Recreational water quality

Information on NSW marine and estuarine water quality includes monitoring conducted at 129 beaches in the Sydney, Illawarra and Hunter regions under the Beachwatch and Harbourwatch programs, and monitoring conducted by a number of coastal councils as part of the Beachwatch Partnership Program (Map 5.6). The beaches monitored under the Beachwatch Partnership Program vary from year to year depending on council resources and priorities, with 125 beaches monitored in nine local council areas during the summer of 2004–05.

This recreational water quality data provides the community with information on the risks of sewage and stormwater pollution at beaches. Two bacterial indicators – faecal coliforms (also called thermotolerant coliforms) and enterococci – are used to assess recreational water quality, in accordance with the National Health & Medical Research Council swimming guidelines (NHMRC 1990). Although the monitoring of water for recreational use does not provide an assessment of overall water quality and waterway health, the change in recreational water quality through time enables the effectiveness of stormwater and wastewater management to be assessed.

Results from the Beachwatch, Harbourwatch and Beachwatch Partnership programs indicate that increases in pollution from sewage overflows and stormwater during wet weather, as well as the capacity of water bodies to dilute or flush away pollution, are key determinants of marine and estuarine recreational water quality.

During the 2004–05 summer swimming season, the majority of swimming locations monitored along the NSW coast were found to be suitable for swimming more than 90% of the time (Map 5.6), with increases in bacterial levels recorded only following heavy rainfall. A number of swimming locations had compliances of less than 70%, indicating some sewage contamination during both dry and wet-weather conditions.

Detailed results for each of the 129 sites monitored in the Sydney, Hunter and Illawarra regions can be found in the Beachwatch and Harbourwatch State of the Beaches reports (EPA 2000b; EPA 2001; EPA 2002; EPA 2003; DEC 2004a; DEC 2005b). Detailed results for sites monitored in regional coastal areas in partnership with local councils can be found in the Beachwatch Partnership Program State of the Beaches reports (DEC 2004b; DEC 2004c; DEC 2006).

Water quality has generally improved since the late 1990s (Figure 5.7). For open waters, improved sewage treatment has been a factor. Estuarine beaches tend to be affected more by polluted stormwater runoff (including sewerage overflows) than by treated sewage effluent, and so the dryness of the last few years has limited this impact.

Map 5.6: Compliance with swimming water quality guidelines of beach monitoring sites along the NSW coast, 2004–05 summer swimming season

Source: DEC data 2005

Notes: Beach compliance with guideline levels of faecal coliforms and enterococci during the 2004–05 summer swimming season under the Beachwatch, Harbourwatch and Beachwatch Partnership programs.

Figure 5.7: Percentage of beach monitoring sites in the Sydney, Hunter and Illawarra regions that comply with swimming water quality guidelines more than 90% of the time

Source: DEC data 2005

Notes: This shows the proportion of beaches in each region that comply more than 90% of the time with guideline levels of faecal coliforms and enterococci for summer 1999–2000 to summer 2004–05.

Other marine and estuarine water quality and waterway health

Sydney Water Corporation monitors physico-chemical water quality in the coastal lagoons and estuaries of the Sydney Region. In 2004, nutrient levels exceeded guidelines for over 75% of the time in the Parramatta River, from Homebush Bay to further upstream; in the Lane Cove River; in the Cooks River; in the Georges River upstream from Prospect Creek; and in all of the coastal lagoons on the Northern Beaches, except the lower Narrabeen Lagoon. The lower estuaries, including the Hawkesbury estuary and Wattamolla Lagoon in Royal National Park, showed very low levels of exceedences (less than 25% of the time) for nutrient levels. Sydney Water Corporation also monitors benthic communities (bottom-dwelling macroinvertebrates) in the estuaries. Over the last 10 years (1994–95 to 2004–05), monitoring of benthic communities in Port Jackson, the Georges River and Botany Bay system, and Port Hacking showed that nine sites had improving trends (becoming more like reference sites; see Water 5.1 and Water 5.3), three sites had declining trends, 10 sites (in the lower estuaries and Middle Harbour) were similar in quality to reference (unimpacted) sites, and five sites (in the upper estuaries) had impaired benthic communities. This trend indicates an improvement in estuarine health over this period.

Bacteriological information is presented in Water 5.6. While bacteria are monitored because of the risk to human health, other life forms may be affected by different pathogens, with severe impacts. For example, QX disease affects Sydney rock oysters and is caused by a protozoan parasite that can kill up to 100% of oysters in the worst-affected areas. It has previously affected northern NSW estuaries and the Georges River. Although present in other estuaries, outbreaks causing extensive mortality seem to be triggered by suppression of the oysters' immune system by unknown factors. In 2004, for the first time, there was an outbreak in the Hawkesbury estuary, and further oyster infection and mortality occurred in 2005, but was not detected in the adjacent Brisbane Water. The estuary was subsequently closed to the export of oysters.

Algal blooms

The only blooms recorded are those reported to the Government or the Regional Algal Coordinating Committees, so data collection may be biased to near-shore visible blooms. Noctiluca scintillans and Trichodesmium erythraeum are the most common bloom-forming species within estuaries and in coastal waters of NSW; neither are toxic, but they can be a nuisance to swimmers. Blooms of microalgal species that can be potentially harmful to humans or marine life are relatively uncommon in NSW. Blooms of other species have occurred at Botany Bay, Port Hacking, Newcastle, on the far South Coast at Twofold Bay and Bermagui, and in the north at Ballina. While many microalgae species are always present in NSW waters, they usually occur at concentrations that rarely pose a risk to human health. Significant risk to humans is most likely in conditions when the microalgae bloom and their toxins are concentrated by filter feeders such as oysters, mussels and pipis, which can be consumed by humans. Again, such incidences are rare, and stringent testing for the presence of algal toxins in commercial shell fisheries halts production when toxin-producing algae are detected.

Between 2000 and 2005, there were 51 reports of algal discolourations in Sydney estuaries and marine waters. From Sydney to the Queensland border there were 37 reported discolourations; and between Sydney and the Victorian border there were 18 reported. The majority of the blooms were harmless. There was no clear trend in the number of blooms between years.

Pollution incidents

The detection of marine and estuarine pollution incidents relies on reports from the general public and commercial and government organisations. The frequency and extent of incidents is therefore likely to be under-reported. Because many pollution incidents originate from land-based sources, it can also be difficult to determine their exact cause. For these reasons, identifying trends in pollution incidents is difficult.

The majority of reported pollution incidents (91%, or 369 out of 406 reports) have been minor oil spills and oil slicks, mostly in Sydney Harbour and Botany Bay. However, the cumulative and long-term impacts of these minor spills may be significant. The other reported incidents were spills of chemicals (25 reported incidents between 2002 and 2004) and garbage (12 incidents). The largest incident between 2002 and 2004 occurred when 2000 litres of petroleum spilled into the Parramatta River from a road tanker accident. The potentially most significant incident was the grounding of HMS Nottingham on Lord Howe Island in July 2002; however, its fuel tanks were not damaged and no environmental damage was noted.

Response to the issue

The main responses aimed specifically at improving marine and estuarine water quality by reducing pollution include:

• water quality objectives, and strategies promoting the use of these objectives, in land-use and catchment-planning strategies
• programs to reduce pollution from major point sources
• programs to reduce pollution from diffuse sources
• programs to prevent and manage pollution incidents.

Until recently, water quality assessment and management have had neither a consistent approach nor benchmarks for measuring the adequacy of water quality against agreed goals. The NSW Government has endorsed environmental values (Marine Water Quality Objectives for NSW Ocean Waters) to provide this benchmark for estuaries and marine waters, and has developed guidelines for using these objectives in assessing water quality (DEC 2005c).

The marine water quality objectives apply for State waters up to three nautical miles from the shore. They provide water quality criteria for protecting five environmental values:

• aquatic ecosystem health
• primary contact recreation (such as swimming and surfing)
• secondary contact recreation (such as boating)
• visual amenity (the appearance of the water)
• aquatic foods (such as fish).

These complement the NSW Water Quality and River Flow Objectives for estuaries and coastal rivers as part of the water reform program, agreed in 1999, and will also underpin the Natural Resources Commission's standard and targets for natural resources (see Appendix 2).

Estuary Management Plans have been prepared by council-led community groups with the objective of improving sustainable planning and management practices, and protecting and conserving sensitive estuary ecosystems. Strategies for the protection and improvement of estuarine water quality form part of these plans. Forty estuary management plans are being implemented along the coast.

A number of programs are reducing pollution from point sources, including from licensed discharges. These programs are resulting in improved sewage treatment and reduced discharges from whole sewerage systems (see Human Settlement 2.2). Economic instruments, such as load-based licensing, have moved out of the initial implementation phase and in future are expected to play a more significant role in the management of point-source discharges.

In other developments, Sydney Water Corporation is planning or constructing works to upgrade sewage treatment at STPs discharging to the ocean at North Head and Bondi. The Northside Storage Tunnel has now collected 16,600 megalitres (ML) of diluted untreated sewage since it was commissioned in 2000. During 2004–05, more than 4400 ML was captured and treated at North Head STP. This was equivalent to a 98% reduction of potential overflows into Lane Cove River and Middle Harbour over the same period (SWC 2005).

The framework for managing diffuse-source pollution of marine and estuarine waters is the same as the framework for discharges to fresh waters outlined in Water 5.3. There has been considerable activity in recent years to reduce pollution from urban stormwater runoff (see 'Urban Stormwater Program' below) and runoff from agricultural sources (see Land 4.1): both of these areas need continuing work.

In 2002 the Healthy Rivers Commission (HRC) of NSW released the report An Independent Public Inquiry into Coastal Lakes (HRC 2001). The report presented a strategy for improving the management of coastal lakes and their catchments through the development of Sustainability Assessment and Management Plans. Following the coastal lakes inquiry, the NSW Government released a Statement of Intent for coastal lakes in which it adopted several of the HRC's recommendations (NSW Government 2003). The statement included the commitment to undertake sustainability assessments of eight priority lakes (Cudgen, Myall, Wollumboola, Burrill, Narrawallee, Coila, Merimbula and Back) and to prepare management strategies for each of these lakes.

The Coastal Lakes Sustainability Assessment project, undertaken as part of the NSW Comprehensive Coastal Assessment, has developed decision-support tools such as CLAM (Coastal Lakes Assessment and Management) for conducting sustainability assessments for the priority lakes. The aim is to develop a management strategy for each lake that provides information and an integrated basis for planning and management investment. The CLAM tools will be used to underpin management strategies for the eight lakes and are transferable and applicable to other coastal lake systems. NSW government agencies, local councils, and community groups are currently developing management strategies to ensure that ecosystem processes in the lakes are sustainable and, where necessary, restored.

The NSW Waterways Package, announced in 1997, was a $3-billion program to improve the quality of the State's waterways. The Urban Stormwater Program, administered by the Stormwater Trust and concluded in June 2006, was part of this package. The Urban Stormwater Program included a broad range of activities to improve stormwater management, including grants, improved stormwater management planning, a community education program, a stormwater extension officer program and stormwater guidelines on pollution prevention, water-sensitive urban design, stormwater harvesting for reuse, and stormwater treatment measures.

For major pollution incidents in NSW, there are two plans for the management of marine and estuarine pollution incidents:

• National Plan to Combat Pollution of the Sea by Oil and other Noxious and Hazardous Substances (AMSA no date)
• NSW State Waters Marine Oil and Chemical Spill Contingency Plan (NSW Maritime 2005).

The body responsible for preventing or responding to major pollution incidents varies with each type of incident, but these plans provide for a coordinated response from many organisations to clean up the spill.

The statewide natural resource management target for marine waters is: 'By 2015 there is no decline in the condition of marine waters and ecosystems'. The target for estuaries and coastal lakes is: 'By 2015 there is an improvement in the condition of estuaries and coastal lake ecosystems'. The available data may be used as a baseline measure of this target in some parts of NSW, but there is a need for further data on a statewide basis to provide a full picture of progress towards the target.

Future directions

The poor health of some estuaries suggests that current actions for managing new urban development and improving water quality in existing areas need to be strengthened in order to prevent a decline in estuarine water quality following development.

Most of the responses to water quality management have focused on point sources. The Sydney deep ocean sewage outfalls, for example, have dramatically improved beach recreational water quality. Load-based licensing has considerable potential for further reducing point discharges; however, the fees for ocean and estuarine discharge are too low to make alternative disposal methods, such as reuse, more attractive to polluters.

By contrast, pollution from diffuse sources presents the main challenge to achieving better water quality. Although the management of urban stormwater runoff has improved, diffuse water pollution continues to have significant impacts. The coast is subject to intense development pressure, requiring increased effort to manage water pollution from diffuse agricultural and urban sources. The Government needs to work with land managers to further explore ways of reducing runoff of pollutants. The application of the CLAM tools to other priority estuaries and coastal lakes, and their integration with estuary management and planning processes, would provide better management of developments and reduce impacts on water quality.