POTTER POINT OUTFALL

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Monitoring Results

Indicator Bacteria

Regular monitoring of faecal coliforms at beaches in the vicinity of Cronulla outfall is undertaken by Beachwatch (EPA 1998).

Biological Communities

Roberts (1984)

Found that sewage effluent:

  • effected the depth zonation of organisms compared to a ‘typical’ unpolluted site (Bangalley Head) and that similar zonation patterns were documented close to other outfalls discharging primary treated sewage such as Bondi and Malabar (SPCC 1984).

  • encouraged the development of a unique community with a high tolerance to adverse water quality conditions and turbid waters - microcarnivorous fauna (anenomes and ascidians) dominated the zone between 6 and 12 m depth.

  • affected the structure of species composition and zonation  - due to poor light penetration and unlimited nutrient availability.

Methods:

Roberts (1984) undertook a survey of underwater rocky substrate benthic communities using photo-quadrats. Three different depth zones were randomly sampled along two transects running perpendicular to the shore and three zones (sponge, white rock and kelp) were identified.

Fairweather (1990)

Found that sewage effluent:

  • reduced species diversity with complete dominance of rocky shore biota by ephemeral green algae and the absence of animals.

  • eliminated zonation.

Methods:

Fairweather (1990) investigated rocky intertidal areas around Potter Point, Malabar, Bondi and North Head sewage outfalls and compared them to a number of reference (control) locations.

AWT (1994)

Found that sewage effluent:

  • was linked with higher concentrations of chromium, silver and zinc in some mussels.

General findings (not necessarily related to outfall):

  • organochlorine concentrations were generally below detection limits and levels of heavy metals were generally below the recommended maximum residue limits. The exception was selenium, which appeared to naturally occur in high concentrations in the Sydney region.

  • higher concentrations of mercury were found in mussels deployed near the industrial outfall at Yena Gap on the Kurnell Peninsula and higher levels of chromium and arsenic were found at the other industrial outfall at Tabbigai.

  • lead concentrations were higher in mussels deployed in port Hacking and was considered to be consistent with urban run-off entering Port Hacking.

Methods:

AWT (1994) investigated bioaccumulation of contaminants in live mussels (Mytilus edulis).  These were deployed at various sites around Bate Bay and near Malabar deep ocean outfall.

AWT Ensight (1994 – cited by CEE & Woodward-Clyde 1996)

Found that sewage effluent:

  • increased the cover of the biota adjacent to the outlet with Ulva lactuca and Enteromorpha intestinalis.

  • reduced the abundance (to absent) common low shore organisms such as coralline algae (Corallina officinalis), cunjevoi (Pyura stolonifera) and the limpet Montfortula rugosa within 50 to 100 m of the outlet (but were present 200 m away).

  • increased the abundance of the filamentous brown algae Ectocarpus fasciculatus in the low shore zone near the outlet, along with the green ulvoid algae (Ulva lactuca).  These were absent away from the outlet.

  • had a zone of measurable impact extended between 100 and 200 m north and south of the outfall.

Methods:

AWT (1994) examined the intertidal biota at a number of sites near the existing effluent discharge outlet and at more distant locations of Little Bay and Oak Park (4 – 6 km to the north and south).

Banwell (1996)

Found that sewage effluent:

  • increased the cover of Ulva, Enteromorpha, Littorina and Gelidium at all outfall sites, but not control sites.

  • reduced (to absent) the Corallina, pink crust (encrusting Corallinaceae algae) and Montfortula at the outfall site, but was present at control sites.

Methods:

Banwell (1996) investigated the impact on intertidal flora and fauna of shifting the discharge from Sydney’s major sewage outfalls (at North Head, Bondi and Malabar) from shoreline discharge to offshore (deep water) discharge. The intertidal communities at two of these outfalls (North Head and Malabar) were compared with the intertidal communities at two other outfalls (Potter Point and Bellambi) to see if there was any evidence of a recovery once the sewage at North Head and Malabar was diverted offshore. A number of control locations were also included in Banwell’s (1996) design.

Enteromorpha

Faecal Coliform

Outfall Site

Outfall Site

 

Cunjevoi

Ulva

Outfall Site

Potter Pt. 

  

(Pott_7) Last updated June 2000