AN ENVIRONMENTAL STUDY OF BLACKBURN LAKE

Environment Protection Authority State Government of

February 2000 Environment Protection Authority

AN ENVIRONMENTAL STUDY OF BLACKBURN LAKE

Authors: Anne Deveraux, David Tiller and Leon Metzeling

Acknowledgements: The authors gratefully acknowledge Veronica Lanigan and Manfred Lux (EPA Freshwater Sciences) for assistance in the field, and Russell Brown (EPA South Metro Region), Peter Wise (Blackburn Lake Sanctuary Advisory Committee) and Lisa Dixon (EPA Freshwater Sciences) for their comments on the draft manuscript. We would also like to thank the City of Whitehorse for their cooperation.

Cover Photograph: Blackburn Lake Photographer: Manfred Lux, Freshwater Sciences, EPA

Freshwater Sciences Environment Protection Authority 40 City Road Southbank Victoria 3006 Australia

Printed on recycled paper

Publication 679

© Environment Protection Authority, February 2000

ISBN 0 7306 7571 8

ii An Environmental Study of Blackburn Lake

ABSTRACT

Blackburn Lake is a small urban lake constructed on . This study was conducted in 1993 to gain a better understanding of the ecology of the lake and its level of contamination. The concentrations of nutrients, heavy metals, petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine insecticides were measured in the water, sediments and biota at several locations within the lake. In addition, an assessment of the invertebrate, zooplankton and phytoplankton communities was undertaken. The major problems identified in Blackburn Lake were: very low dissolved oxygen levels in the bottom waters; substantial petroleum hydrocarbon, copper, lead and zinc contamination of the sediments; and high levels of petroleum hydrocarbon in the yabbies. The invertebrate communities were typical of other urban waterbodies.

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CONTENTS

ABSTRACT ...... iii TABLES...... v FIGURES ...... v 1. INTRODUCTION...... 1 2. METHODS ...... 2 2.1 Study area ...... 2 2.2 Sampling sites...... 2 2.3 Biological sampling and sample processing...... 5 2.4 Physical and chemical sampling and analyses...... 5 3. RESULTS...... 7 3.1 Water quality ...... 7 3.2 Sediment characteristics and contamination...... 7 3.3 Biota contamination...... 12 3.4 Macroinvertebrates...... 14 3.5 Zooplankton...... 15 3.6 Phytoplankton ...... 15 4. DISCUSSION ...... 17 4.1 Dissolved oxygen and stratification ...... 17 4.2 Water clarity...... 17 4.3 Nutrients...... 17 4.4 Metals ...... 18 4.5 Petroleum hydrocarbons...... 20 4.6 Biological health ...... 20 5. CONCLUSIONS...... 21 6. REFERENCES...... 22 7. APPENDICES...... 25 Appendix 1: Polycyclic Aromatic Hydrocarbon (PAH) concentrations in Blackburn Lake sediments (mg/g) and biota (ng/g)...... 25 Appendix 2: Invertebrate taxa and their abundances, Blackburn Lake, February 1993 ...... 27

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Tables Table 1: Summary of site descriptions...... 4 Table 2: In situ measurements and concentrations of suspended solids, phosphorus, nitrogen and total organic carbon in waters in Blackburn Lake...... 8 Table 3: Metal concentrations (mg/L) in waters in Blackburn Lake...... 9 Table 4: Sediment particle size distribution (%) in Blackburn Lake...... 11 Table 5: Metal and nutrient concentrations (mg/g dry weight) and organic content (% dry weight) in sediments from Blackburn Lake...... 11 Table 6: Total petroleum hydrocarbon, PAH, PCB and organochlorine insecticide concentrations (mg/g dry weight) in sediments from Blackburn Lake...... 12 Table 7: Metal concentrations (mg/g dry weight) in yabbies and fish collected from Blackburn Lake...... 13 Table 8: EPA criteria for edible fish and crustacea and NH&MRC food standards code ( mg/g wet weight)...... 13 Table 9: Petroleum hydrocarbons and PAH concentrations (mg/g and ng/g wet weight, respectively) in yabbies collected from Blackburn Lake...... 14 Table 10: Total number of macroinvertebrate taxa and individuals collected in sweep samples from Blackburn Lake...... 14 Table 11: Relative abundance of zooplankton collected from Blackburn Lake...... 15 Table 12: Relative abundance of phytoplankton collected from Blackburn Lake...... 16

Figures Figure 1: Location of Blackburn Lake and its catchment and location of sampling sites...... 3 Figure 2: Temperature and dissolved oxygen profiles for sites 1 and 2 in Blackburn Lake ...... 10

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vi An Environmental Study of Blackburn Lake

1. INTRODUCTION

Urban lakes are important assets to the community as they provide environmental, recreational and aesthetic amenities. With increased awareness of the importance of urban lakes has come a growing concern in the community that these qualities are being degraded, as the waters entering the lake are severely contaminated. Lakes in urban areas are of special concern as they are susceptible to problems of eutrophication, odour and bacterial pollution (Phillips et al. 1988). The ecology and contamination of urban lakes are, however, poorly understood. Blackburn Lake is a lake in metropolitan that is viewed locally as a major public asset. In 1973, a pollution survey of Blackburn Lake was undertaken, in order to better understand problems which had occurred as a result of water pollution in the then City of Nunawading (now City of Whitehorse). It found that the streams and drains were significantly polluted, as a result of both domestic and industrial discharges, and that Blackburn Lake was eutrophic, the problems being attributable to high nutrients and the presence of oils and greases in the sediments (Elliot 1973). The present study of Blackburn Lake commenced in 1993 to gain a better understanding of its ecology and to further investigate the level of pollution in the lake. The study is also intended to assess how well the lake complies with the State environment protection policy (SEPP) water quality objectives for waterbodies in the Yarra catchment (Government of Victoria 1984). An important outcome of the study will be to use the information gained to better manage the lake and its inflows.

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2. METHODS

2.1 Study area Blackburn Lake (figure 1) was formed in 1888 by the damming of an upper tributary of Gardiners Creek. The lake was originally formed to control flooding, to provide a water supply to the local township and orchardists, and for recreational use. The lake, and the parklands surrounding it, are now primarily used for recreation. The 25.8 ha of land surrounding the lake is now owned and managed by the City of Whitehorse and is known as Blackburn Lake Sanctuary. Approximately 65% of the catchment of Blackburn Lake consists of residential areas and public open space, the remaining 35% consisting of industrial areas. Most of the industry is located to the north east along Maroondah Highway, along Norcal and Rooks Roads, and in Thornton Crescent, and consists of about one-third light industry (for example, panel-beaters and mechanics) and two-thirds heavy industry. The entire catchment is now sewered and the main stormwater drainage line from the industrial areas to Blackburn Lake is the Lake Road Drain. It is believed that the catchment area was connected to sewer by the late 1950s or early 1960s (pers. comm. Brian Wright, Yarra Water). The catchment area is estimated at 263 ha and the maximum volume of water in the lake at 100 ML

2.2 Sampling sites Five sites were selected in Blackburn Lake. Two sites were chosen in the main body of the lake (sites 2 and 4), two close to the major inflows (sites 3 and 5) and one close to the outflow near the weir (site 1). A description of each site can be found in table 1. Sampling occurred 16–18 February 1993.

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Table 1: Summary of site descriptions

Site No. 1 Site Location: Near dam wall, 20 m from bank Depth: 5.4 m Thermocline: 0.8 m Sediments: Mostly fine, some coarse particles, grey/brown colour Organic Matter: Small amount of detritus Nearby Aquatic Vegetation: Eleocharis sp. Site No. 2 Site Location: Off Duck Point, mid-lake Depth: 3.6 m Thermocline: 1.25 m Sediments: Mostly fine, some coarse particles, grey/brown colour Organic Matter: Small amount of detritus Nearby Aquatic Vegetation: None Site No. 3 Site Location: The Arm Depth: 3.0 m Thermocline: 1.25 m Sediments: Mostly fine, some coarse particles, grey/brown colour Organic Matter: Some detritus Nearby Aquatic Vegetation: Small stands of Eleocharis sp. Site No. 4 Site Location: 50 m upstream of The Arm, mid-lake Depth: 1.2 m Thermocline: None Sediments: Some fine sediment, grey brown colour Organic Matter: Abundant coarse particulate matter Nearby Aquatic Vegetation: Dense stands of Eleocharis sp., some Typha sp. Site No. 5 Site Location : Top end of lake, main input to lake Depth: 1 m Thermocline: None Sediments: Equal proportions of fine and coarse particles, brown colour Organic Matter: Some organic matter Nearby Aquatic Vegetation: Large stands of Typha sp.

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2.3 Biological sampling and sample processing Aquatic invertebrates were collected by sweeping a hand-net (mesh aperture 250 mm) through the water column and aquatic vegetation for 2 minutes at each site. The net contents were preserved in 5% formaldehyde for transfer to the laboratory for sorting and identification of invertebrates. Identifications were made using standard taxonomic keys and reference collections available at EPA. Identifications were made to species level whenever possible, but for some taxonomically difficult groups (such as Oligochaeta), species differentiation was not attempted. Zooplankton trawls were conducted at each of the five sites using a plankton net (mesh aperture 63 mm) with an opening of 0.03 m2. The net was towed 10 metres in the water, giving 0.3 m3 of water sampled. Taxa were identified and relative abundance estimated. Water samples were also collected for algal (phytoplankton) identification. The samples were preserved with Lugols solution. Taxa were identified and relative abundance estimated. Yabbies (Cherax sp.) and fish (Australian Smelt - Retropinna semoni) were collected from close to sites 3 and 4 and analysed for heavy metals and organics. The yabbies were caught using baited yabby nets while fish were sampled by sweeping around nearby aquatic vegetation. These samples were frozen and stored at -25oC until analysed. Yabbies were dissected to separate the flesh and exoskeleton and analysed separately. These two sites were sampled as they provided shallow areas where nets could be easily located and where oxygen levels were high enough to support fish and yabbies. Sites 1 and 2 were mid lake and deep, and site 5 was difficult to access.

2.4 Physical and chemical sampling and analyses

2.4.1 Water The surface waters at each site were sampled for a number of physico-chemical parameters. In situ measurements were obtained for dissolved oxygen, pH, conductivity, Secchi disk depth and temperature. Water samples were analysed for turbidity, suspended solids, nitrate and nitrite, total Kjeldahl nitrogen, total phosphorus, total organic carbon, and metals (cadmium, chromium, copper, nickel, lead, zinc, antimony, mercury, iron and manganese). As sites 1 and 2 were deep (>3 m), temperature and dissolved oxygen were measured at 0.5 m intervals from the surface to the bottom. Water samples were collected from the hypolimnion (bottom waters) and analysed for suspended solids, nutrients and metals. Samples were analysed by Water Ecoscience using the methods described by SWL (1988).

2.4.2 Sediments Sediments were collected from all five sites using a Petite Ponar Grab (Hellawell, 1978). For the metals copper, lead, zinc, arsenic, cadmium, chromium, antimony and mercury, that portion of sample which passed through a 2 mm mesh nylon sieve was retained for analysis. Total petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine insecticides, that portion of sample which passed through a 212 mm mesh brass sieve was retained for analysis. For total Kjeldahl nitrogen, nitrate and nitrite, total phosphorus, and particle size analysis, the whole sample was retained. Samples were analysed for metals and nutrients by Water Ecoscience using the methods described by SWL (1984, 1988) and organics by EPA (EPA Environmental Chemistry Unit, Methods Manual Vol 1, 2 and 7).

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2.4.3 Biota The yabby and fish samples were analysed for heavy metals (copper, lead, zinc, cadmium, chromium, nickel and mercury), as well as total petroleum hydrocarbons, PAHs, PCBs and organochlorine insecticides. No organic analysis of the fish samples was undertaken due to the small size and number of fish collected. Samples were analysed by Water Ecoscience using the methods described for sediments (SWL 1984, 1988) and organics by EPA (Methods Manual Vol 1, 2 and 7).

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3. RESULTS

3.1 Water quality pH and conductivity varied little between sites (table 2). Dissolved oxygen and temperature showed a substantial decrease between the surface and bottom waters at sites 1, 2 and 3, with small decreases at the shallow sites 4 and 5 (table 2). A thermocline was observed at sites 1, 2 and 3 at a depth between 0.8–1.25 m. No thermocline was seen at sites 4 and 5 because they were too shallow at 1.2 m and 1 m, respectively. Temperature and dissolved oxygen profiles for sites 1 and 2 are illustrated in figure 3. The lake was quite turbid. Secchi disk depth for all sites was just 0.25 m, and turbidity and suspended solids were high (table 2) compared to many urban streams. There was a general decrease in suspended solids and turbidity from site 5 through to site 1 (table 2). The nitrate and nitrite concentration in the surface waters was highest at site 5 (table 2). Surface concentrations were considerably higher than bottom concentrations at sites 1 and 2, where the waters were anoxic. Conversely, the total Kjeldahl nitrogen concentrations were much higher at the bottom than at the surface, especially at site 1. The increase in total Kjeldahl nitrogen in the bottom waters is most likely due to the increase of ammonia nitrogen in these anoxic waters. There was little variation between the total nitrogen concentrations (total Kjeldahl nitrogen + nitrate/nitrite) in the surface waters at all sites. Total phosphorus and total organic carbon concentrations in the surface water samples showed little variation between sites (table 2). At site 1, concentrations were much higher at the bottom. Metals in the surface waters showed a slight decrease in concentrations as the waters flowed from site 5 through to site 1 (table 3). The concentrations of iron, manganese and mercury in the bottom waters at site 1 and 2 were higher than in the surface waters.

3.2 Sediment characteristics and contamination The particle size distribution data indicates that there is a settling of finer particles as the waters flow towards the outlet at site 1 (table 4). Metals in the sediments generally decreased in concentration from site 5 through to site 1 (table 5). The only metal which did not show this trend was cadmium, which showed little variation between sites. Nutrients (phosphorus and nitrogen) in the sediments also decreased in concentration from site 5 through to site 1 (table 5). Nitrate and nitrite concentrations were very low (between 500 and 1000 times less than total Kjeldahl nitrogen). The organic content was similar at all sites except site 5 (where it was substantially less than at other sites). The total hydrocarbon concentrations in the sediment samples were very high (3,400 mg/g – 4,300 mg/g) at all sites (table 6). Their gas-chromatographic profiles were characteristic of a mixture of predominantly lubricating oil, with some kerosene and diesel fuel. The concentrations of PAHs in the sediments were very low at all five sampling sites (table 6), when compared to the total hydrocarbon concentrations. No PCBs and only trace amounts of organochlorine insecticides were detected in the sediment samples (table 6).

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Table 2: In situ measurements and concentrations of suspended solids, phosphorus, nitrogen and total organic carbon in waters in Blackburn Lake

Indicator Unit Site 1 Site 2 Site 3 Site 4 Site 5 Depth m 5.4 3.6 3.0 1.2 1.0 Dissolved Oxygen mg/L surface 6.2 5.7 5.9 6.5 4.0 bottom 0.5 0.4 0.5 4.5 2.3 pH pH 7.5 8.0 7.5 8.15 8.0 Conductivity ms/cm 182 182 185 185 168 Temperature oC surface 22.7 22.9 22.7 23.7 23.4 bottom 16.0 16.0 16.0 23.5 23.4 Turbidity NTU 39 46 45 52 73 Secchi disk depth m 0.25 0.25 0.25 0.25 0.25 Depth of thermocline m 0.8 1.25 1.25 - - Suspended Solids mg/L surface 36 48 46 52 110 bottom 36 76 Nitrate and mg/L Nitrite as N 0.071 0.100 0.081 0.110 0.270 surface <0.003 <0.003 bottom Total Kjeldahl mg/L Nitrogen as N surface 1.3 1.3 1.4 1.3 0.8 bottom 6.0 2.0 Total Phosphorus mg/L surface 0.10 0.12 0.10 0.11 0.14 bottom 0.34 0.073 Total Organic mg/L Carbon 5 8 5 8 12 surface 13 8 bottom

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Table 3: Metals concentrations (mg/L) in waters in Blackburn Lake

Indicator Site 1 Site 2 Site 3 Site 4 Site 5 Cadmium surface <0.0002 <0.0002 <0.0002 0.0004 0.0006 bottom 0.001 0.0006 Chromium surface <0.002 0.002 <0.002 0.002 0.004 bottom <0.005 <0.002 Copper surface 0.003 0.006 0.003 0.007 0.013 bottom <0.005 0.004 Nickel surface 0.002 0.003 0.002 0.004 0.005 bottom <0.005 0.003 Lead surface 0.012 0.015 0.007 0.023 0.035 bottom 0.014 0.016 Zinc surface 0.044 0.066 0.036 0.076 0.20 bottom 0.052 0.036 Antimony surface <0.001 <0.001 <0.001 <0.001 <0.001 bottom <0.001 <0.001 Iron surface 2.5 2.7 2.5 2.9 4.7 bottom 16 6.1 Manganese surface 0.04 0.04 0.04 0.04 0.06 bottom 0.55 0.22 Mercury surface <0.00005 <0.00005 <0.00005 <0.00005 <0.00005 bottom 0.00022 0.00016

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Temperature-Dissolved Oxygen Profile - Site 1.

30 Temperature 8 25 Dissolved Oxygen 7 6 20 5 15 4 10 3 (mg/L) 2

5 Dissolved Oxygen

Temperature (deg.C) 1 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Depth (m)

Temperature - Dissolved Oxygen Profile - Site 2

25 Temperature 8 Dissolved Oxygen 7 20 6 15 5 4 10 3 2

Temperature (deg C) 5 1 Dissolved Oxygen (mg/L) 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

Depth (m)

Figure 2: Temperature and dissolved oxygen profiles for sites 1 and 2 in Blackburn Lake

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Table 4: Percent particle size distribution (%) in Blackburn Lake sediments

Sediment type Site 1 Site 2 Site 3 Site 4 Site 5 Clay (<2 mm) 55 51 40 23 11 Silt (2–60 mm) 42 49 58 67 28 Sand (60 mm–2 mm) 3 0 2 10 61

Table 5: Metal and nutrient concentrations (mg/g dry weight) and organic content (% dry weight) in sediments from Blackburn Lake

Indicator Site 1 Site 2 Site 3 Site4 Site 5 Copper 83 3 110 130 110 Lead 100 190 190 200 140 Zinc 560 890 1200 1100 1200 Arsenic 2.8 3.7 4.9 5.2 5.8 Cadmium <1 2 3 2 <1 Chromium 25 39 58 64 54 Antimony 0.52 0.85 1.2 1.4 1.4 Mercury 0.038 0.084 0.13 0.15 0.14 Nitrate and Nitrite 1.9 1.5 1.6 1.7 1.2 Total Kjeldahl Nitrogen 1000 1800 2300 2300 2500 Total Phosphorus 270 380 490 520 640 Organic Content 8.6 8.6 8.5 11.6 3.2

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Table 6: Total petroleum hydrocarbon, PAH, PCB and organochlorine insecticide concentrations (mg/g dry weight) in sediments from Blackburn Lake

Indicator Site 1 Site 2 Site 3 Site 4 Site 5 Total Hydrocarbons 3400 4200 4300 3100 3700 Total PAH* <2 <2 <2 <2 <2 PCB** nd nd nd nd nd Organochlorines*** t t t t t nd – not detected (at greater than 0.2) * complete list of compounds in appendix 1 ** based on Arochlors 1232, 1254 and 1260 *** DDT, DDD, DDE and dieldrin t – trace, but less than detection limit of 0.02 mg/g

3.3 Biota contamination Metals were detected in all fish and yabby samples (table 7). The concentrations of copper, zinc, chromium and mercury were higher in the yabby flesh than in the exoskeleton. Before analysis for heavy metals, the samples were dried. However, the criteria for human consumption are based on wet weights, so a dry to wet ratio of 5:1 has been assumed to estimate wet weight concentrations (table 7). Copper concentrations higher than recommended by NH&MRC (1989) were recorded only in the yabby flesh at site 3. However, these were still lower than recommended by EPA (1983). The hydrocarbons detected in the yabby samples were predominantly in the form of motor oil, including diesel oil (table 9). PAHs were also detected in trace levels in all the yabby samples. Levels of both the motor oil and the PAHs were higher in the yabby flesh than in the exoskeleton. While organochlorine insecticides were below the detection limit (0.02 mg/g), there was some indication of trace levels of organochlorines in the yabby samples. However, these were below both NH&MRC standards and EPA criteria (table 8). PCBs were not detected in the yabby samples.

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Table 7: Metal concentrations (mg/g dry weight) in yabbies and fish collected from Blackburn Lake. Approximate wet weight concentrations given in brackets (the estimated ratio of dry weight to wet weight used was 5:1)

Yabby exoskeleton Yabby Fish flesh (whole) Indicator Site 3 Site 4 Site 3 Site 4 Site 3 Site 4 Copper <1 <1 99 (20) 69 (14) 3.8 (0.8) 7.5(1.5) Lead <5 <5 <5 <5 <5 <14 Zinc 92 (18) 120 (24) 310 (62) 170 (34) 170 (34) 220 (44) Cadmium <1 <1 <1 <1 <1 <3 Chromium <1 <1 2.7 (0.5) 1.7 (0.3) 2.6 (0.5) 12 (2.4) Nickel <2 <2 <2 <2 <2 <6 Mercury 0.011 <0.005 ~0.03 0.032 0.052 0.059

Table 8: EPA criteria for edible fish and crustacea and NH&MRC food standards code ( mg/g wet weight)

NH&MRC EPA criteria standards Indicator Copper 10.0 30 Lead 1.5 2.0 Zinc 150 1 000 Cadmium 0.2 2.0 Chromium - 5.5 Mercury 0.5 0.5 DDT 1.0 1.0 Dieldrin 0.1 0.3 PCB - 0.1

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Table 9: Petroleum hydrocarbons and PAH concentrations (mg/g and ng/g wet weight, respectively) in yabbies collected from Blackburn Lake

Yabby flesh Yabby exoskeleton Indicator Site 3 Site 4 Site 3 Site 4 Motor oil (C14-C16) 180 150 34 6 C17 0.7 0.5 <0.1 <0.1 C18 0.6 0.4 <0.1 <0.1 C19 0.8 0.5 <0.1 <0.1 C20 1.4 0.9 <0.1 <0.1 C21 0.8 0.6 <0.1 <0.1 Total PAH 25 38 7 10

3.4 Macroinvertebrates Worms (Oligochaeta) were by far the most abundant type of animal found in the sweep samples (appendix 2), with large numbers found at site 5. Snails (Gastropoda) were the next most abundant group. Most of the taxa found in the samples are hardy and widespread, being commonly found in lakes, wetlands, or pools within rivers. They include several species of true bug (Hemiptera), damselfly nymphs (Odonata) and fly larvae (Diptera). No rare or otherwise unusual taxa were found.

Table 10: Total numbers of macroinvertebrate taxa and individuals collected in sweep samples from Blackburn Lake

Site 1 Site 2 Site 3 Site 4 Site 5 Total no. of individuals 145 110 196 387 1988 Number of taxa 9 14 18 16 17

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3.5 Zooplankton Six taxa of zooplankton were found in total from the five samples. The most common was the copepod Mesocyclops sp. All other taxa occurred in small numbers, despite the presence of some usually common and widespread species (such as the copepod Boeckella triarticulata) .

Table 11: Relative abundance of zooplankton collected from Blackburn Lake

Taxon Site 1 Site 2 Site 3 Site 4 Site 5 COPEPODA Boeckella triarticulata + Mesocyclops sp. + + + + + + + + + + + + + + + Australocyclops sp. + CLADOCERA Bosmina meridionalis + + + + Moina sp + + + + Diaphanosoma excisum + + 1–10 individuals + + 11–100 individuals + + + >100 individuals

3.6 Phytoplankton The most frequently found taxon was the euglenoid Trachelomonas sp. This is common in many freshwater environments, often in shallow waters or among weed beds near the shores of lakes. Aulocsira granulata, a widespread diatom found in many lakes and rivers, was relatively abundant at site 3. Chlamydomonads (a general term applied to small, green, unicelled algae) were also relatively abundant at site 3. These are ubiquitous, being found in a wide range of aquatic environments. All other phytoplankton were only found in small numbers, but included several additional taxa commonly found in a wide range of aquatic environments. A single sample taken from Blackburn Lake by Water Ecoscience in June 1993 contained eight taxa, four of which were common to our study (Lidston 1993).

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Table 12: Relative abundance of phytoplankton collected from Blackburn Lake

Taxon Site 1 Site 2 Site 3 Site 4 Site 5 CYANOBACTERIA Phormidium + Spirulina + + Coccochloris + + GREEN ALGAE Crucigenia + + + + + + Ankistrodesmus + + + + + + + + + + Diplochloris + + + Scenedesmus + + Staurastrum + + Chlamydomonads + + + + + ++ + + + Botryococcus + Tetrastrum + Ulothrix + OTHER ALGAE Trachelomonas + + + + + + + + + + + + + + + + + + + + + + Navicula (and other pennates) + + + + + + + + + Melosira granulata + + + + + + + + + + + Cryptomonas + + + Gyrosigma + + Euglena + + + + + Phacus + + + + + uncommon + + uncommon to occasional + + + occasional + + + + occasional to frequent + + + + + frequent

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4. DISCUSSION

4.1 Dissolved oxygen and stratification The dissolved oxygen concentrations in the surface waters of the lake at sites 1, 2, 3 and 4 were above the EPA minimum objective of 4.5 mg/L (Government of Victoria, 1984). However, the concentrations at site 5 and on the bottom at all sites were well below this (table 2). The stratification of the lake at about 1 m below the surface at sites 1, 2 and 3 resulted in near-anoxic conditions below the thermocline (that is, in the hypolimnion), whereas above the thermocline (in the epilimnion), the waters were reasonably well oxygenated (table 2, figures 2 and 3). The stratification is likely to only occur during the warmer months, with complete mixing during the cooler months. Lidston (1993) reported no stratification when Blackburn Lake was sampled in winter. At sites 4 and 5, which are around 1 m deep, oxygen levels on the bottom were also considerably lower than near the surface. In winter, Lidston (1993) noted that the oxygen concentration declined gradually to around 2 mg/L towards the bottom. It therefore appears that there is a substantial oxygen demand exerted by the sediments, and that this is leading to extremely low dissolved oxygen concentrations in summer, due to the lack of mixing that results from the thermocline. The low oxygen concentrations in the lake would be a major limiting factor for biota. A large proportion of the bottom is essentially unavailable to the biota, as would a substantial portion of the water column. Dissolved oxygen concentrations for a greater part of the year would preclude biota from all but the shallow edges and within 1 m of the surface of the lake.

4.2 Water clarity Blackburn Lake is perceived to be a very turbid lake. This view is supported by the high levels of suspended solids and turbidity recorded at all sites (table 2). The levels were higher than those reported for the lower and several of the (Metzeling et al. 1993), all of which are perceived to be too muddy. The lake tends to act as a settling pond, particularly for coarse particles. Both suspended solids and turbidity decreased from the major input end to the outlet (table 2), and the particle size distribution data indicate a substantial increase in percentage of finer particles in the sediments between site 5 and the other four sites (table 4). Even though a substantial proportion of the suspended material may drop out of the water column, clarity remains low.

4.3 Nutrients Sources of nutrients and other pollutants entering urban waterways include overflow and leakages from sewerage systems, spills and stormwater runoff (Duda et al. 1982). It is significant that the entire catchment of Blackburn Lake is now occupied by residential and industrial premises. Historic contributions to nutrient loading of the lake included agriculture, and sullage (until the 1960s) from unsewered parts of the catchment. The phosphorus and nitrogen concentrations in the waters of the lake (table 2) were well above those recommended by ANZECC (1992) for lakes (0.05 mg/L maximum total phosphorus and 0.5 mg/L maximum total nitrogen). Above these concentrations, water quality problems (and, in particular, the risk of algal blooms) are likely to arise. The less stringent water quality objectives in the (draft) Yarra Catchment State Environment Protection Policy (SEPP) (Government of Victoria 1999) for urban waterbodies (total phosphorus maximum 0.10 mg/L and total nitrogen maximum 1 mg/L) are also not 17 Environment Protection Authority

met. It was recognised, in setting the SEPP objectives, that they do not provide for the optimal level of protection, since to set objectives that would give adequate protection would be untenable, given the nature of urban aquatic environments (Government of Victoria 1995). The objectives, therefore, were set as a target for nutrient reduction strategies. While the high nutrient concentrations in the water column would suggest a high potential for algal blooms, none have been recorded in the recent past. The poor clarity in the lake (section 4.2) is likely to be inhibiting the growth of algae. There are no objectives or criteria for nutrients in sediments. Moreover, little is known about background concentrations, as very little data have been collected from relatively undisturbed or natural systems. Edwards Lake, an urban lake in the catchment, has nitrogen and phosphorus concentrations (pers. comm. Marsden, EPA unpublished data) similar to Blackburn Lake, while many of the very degraded urban streams, such as Kororoit Creek (Reed 1990) and Yarrawee Creek (EPA unpublished data) have substantially higher concentrations (above 3 000 mg/g nitrogen and 1 000 mg/g phosphorus). Data recently collected from Lake Tarli Karng, a near pristine lake in the Victorian Alps, show similar nitrogen and phosphorus sediment concentrations (around 1 400 and 220 mg/g, respectively) to Blackburn Lake. However, compared to Blackburn Lake, concentrations in the water column of Lake Tarli Karng were very low (<0.1 and 0.01 mg/L nitrogen and phosphorus, respectively). The availability of sediment nutrients is unknown, although in Lake Tarli Karng the indication was that they are substantially unavailable. In Blackburn Lake, the low oxygen concentrations in the bottom waters are likely to lead to phosphorus release from the sediments, which is apparent in the higher concentrations measured in the bottom waters at site 1. There is, therefore, the potential for the sediments to be a major source of nutrients to the water column in Blackburn Lake. In summary, phosphorus and nitrogen concentrations in the waters of Blackburn Lake are indicative of an extremely enriched waterbody. Nutrient concentrations did not appear to be limiting algal blooms in the lake. Low light penetration, due to high turbidities, is likely to be the main factor limiting phytoplankton growth.

4.4 Metals At one or more of the sites in Blackburn Lake, concentrations for each of lead, zinc, cadmium, copper and iron in the water column (table 3) were generally at or somewhat higher than both the ANZECC (1992) guidelines and EPA (1983) criteria for the protection of aquatic ecosystems. Cadmium and mercury, interestingly, were higher in the bottom waters than the surface waters at sites 1 and 2 (table 3). This was probably due to the anoxic conditions in the bottom waters, creating a strong reducing environment and resulting in the mobilisation of metals previously attached to the sediments (Bourg 1988; Hart 1982). The sediments generally contain the major proportion of heavy metals in an aquatic system (Hart 1982). While simple physical sedimentation of particles to which metals have adsorbed is a major reason for the accumulation of metals in sediments, the retention of metals in the sediments is also the result of complex geochemical processes (Bourg 1988).

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The results of this study (table 5) indicate that the sediments in Blackburn Lake are a major repository and, therefore, an important potential source of metals to the water column and biota. The concentrations of copper, lead and zinc at all sites were above concentrations reported in uncontaminated sediments—copper, 6–28.9 mg/g; lead, 12–38.6 mg/g; and zinc 23 mg/g (Smith 1976; Forstner and Wittman 1981; Wilber and Hunter 1979; Hart 1982; Garie and McIntosh 1986). Copper, lead and zinc levels were generally close to the concentrations reported in the sediments of other urban waterbodies in Victoria (EPA unpublished data; Reed 1992; Mitchell & Clarke 1991) and higher than those found in Lake Burley Griffin (Norris 1983). Zinc was between 1,100–2,600 mg/g, copper between 80–180 mg/g and lead between 120–250 mg/g in , Ballarat (EPA unpublished data). According to sediment guidelines established by the United States Environmental Protection Agency for harbours in the Great Lakes (cited in Giesy and Hoke 1990), sediments in Blackburn Lake are heavily polluted with zinc, copper and lead and moderately polluted with chromium. As with nutrients, the highest concentrations of heavy metals in the sediment were generally at the input end of the lake (sites 3, 4 and 5) (table 5), again most likely due to simple physical sedimentation. The bio-available proportion of the metals found in either the water column or sediments cannot be determined. Metals may concentrate in aquatic biota to very high levels depending on many factors, including the concentration of bio-available forms and the ecology and physiology of the organism. The concentration of metals in biota gives the most appropriate indication of metal bio-availability. Freshwater crustaceans, in particular, are useful indicators of metal bio-availability (Lake and Sokal 1986). Copper, chromium, mercury and zinc were detected in yabbies and fish at most sites in Blackburn Lake (table 7). Copper and zinc concentrations in yabby flesh were only slightly above those found in crustaceans collected from two Dutch lakes (Timmermans et al. 1989) which had low sediment levels of copper contamination, compared to Blackburn Lake. Crustaceans have, as a component of their haemolymph, the copper-containing pigment haemocyanin, which would suggest that higher concentrations may be expected, compared to most other invertebrates and fish. Interestingly, following an extensive review of the literature, Lake and Sokal (1986) concluded that, like other crustaceans, the yabby would not accumulate zinc, whereas yabbies did accumulate lead, even at relatively uncontaminated sites, a very different result to that found in Blackburn Lake (table 7). There is no obvious explanation for this result. The concentrations of mercury in yabbies and fish in Blackburn Lake were around background levels and considerably lower than those found in fish and invertebrates from contaminated locations elsewhere (Ealey et al. 1983; Tiller 1990). Humans may be affected if they eat contaminated aquatic organisms. Only copper in yabbies (table 7) was above the standard recommended by NH&MRC, although it was less than the EPA criterion (table 8). While large numbers of yabbies appear to be taken from the lake for human consumption, the copper concentrations are unlikely to be a major human health issue. Nonetheless, their consumption in large quantities should be discouraged. In summary, despite the very high concentrations of heavy metals in sediments in Blackburn Lake, yabbies and fish appear not to be accumulating substantially higher quantities of heavy metals than would be expected in relatively uncontaminated waterbodies. Nonetheless, the relatively heavy contamination of the sediments combined with the obvious potential for uptake by biota highlight the potential ecosystem and human health issues. Heavy metals have previously been identified as the primary pollutants of concern in road runoff (Peterson and Batley 1992), and it would seem reasonable to assume that road runoff is one of the

19 Environment Protection Authority

major ongoing contributors of the metals to Blackburn Lake, particularly as the catchment is now a highly urbanised area and has two of Melbourne’s major arterial roads passing through it.

4.5 Petroleum hydrocarbons The most obvious point that can be made is that the sediments of Blackburn Lake were grossly contaminated with petroleum hydrocarbons. This contamination is likely to have arisen as a result of contaminated road runoff and from spills of petroleum products in the catchment of the lake. Hydrocarbons adsorbed to sediments are available to benthic invertebrates, particularly to those which live and feed within the sediments, such as Oligochaeta and Chironomus spp. As benthic invertebrates have been found to have the ability to accumulate various hydrocarbons (Muller 1987), the concern is that the communities that live and feed in this environment may be subject to bio-accumulation and possible toxic effects. The concentrations of total hydrocarbons in the sediment samples are significantly higher than those measured in sediments in other urban waterways (eg Reed 1990). Petroleum hydrocarbons in yabbies collected from Blackburn Lake (table 9) were at concentrations higher than those found in invertebrates collected from Kororoit Creek, a highly polluted urban stream (15–104 mg/g wet weight—EPA unpublished data). The concentrations of petroleum hydrocarbons in sediments in Kororoit Creek were much lower than Blackburn Lake, never exceeding 385 mg/g dry weight. The types of petroleum hydrocarbons present are important. The toxicity of hydrocarbons increases with increasing concentration of aromatics; so refined products tend to be more toxic than crude oil (Muller 1987). While the concentrations of polycyclic (polynuclear) aromatic hydrocarbons (PAHs) in Blackburn Lake sediments were less than the detection limit of 2 mg/g dry weight, they were detected in yabby flesh (table 9). In the freshwater environment, the bio-degradation of oil has the effect of increasing the oxygen demand due to the elevation of microbial activity (Shales et al. 1989). This may in part explain the low dissolved oxygen concentrations measured in the bottom waters (table 2, figure 2).

4.6 Biological health The total number of invertebrate taxa gives a good indication of the water quality in Blackburn Lake. The numbers of taxa collected at each of the sampling sites were all low and showed little variation between sites, ranging from 9–18 taxa (table 10). This range in numbers of taxa is comparable to ranges found in other studies of urban waterways, such as Lower Kororoit Creek (13–21 taxa) (Reed 1990), the Yarra River at Alphington (8–20) (Pettigrove 1988) and the Darebin Creek (12–33) (Pouliot 1993). Invertebrate communities in Blackburn Lake were typical of many other urban waterbodies—that is, low number of taxa, low abundances and the dominant taxa consisting of the more robust species tolerant to poor water quality. Many species of mayfly (Ephemeroptera) and caddisfly (Trichoptera) are considered sensitive to poor water quality. While fewer species within these two groups live in lakes than in rivers, only one species of each was found in Blackburn Lake, suggesting that water quality is generally poor. The dipteran family Stratiomyidae was found at all sites and was particularly abundant at site 5. These animals rely on collecting oxygen from the air rather than from the water and their large numbers suggest that oxygen may be limiting at times. The true bug Anisops sp. was also a feature at all sites and, like other members of this order, breathes air. All the commonly occurring invertebrate taxa in Blackburn Lake are able to tolerate water of low oxygen content.

20 An Environmental Study of Blackburn Lake

5. CONCLUSIONS

1. The results of water quality sampling suggest that: · dissolved oxygen concentrations were very low in the bottom waters of the lake, · the lake is very turbid, and · nutrient concentrations in the water column were very high, although the high turbidity would substantially reduce the risk of algal blooms. 2. The sediments in Blackburn Lake contain substantial quantities of heavy metals and extremely large quantities of petroleum hydrocarbons. 3. Yabbies and fish in the lake accumulated heavy metals. Copper concentration in yabbies was above the NH&MRC guideline for human consumption, but below the EPA criterion. Yabbies also accumulated large quantities of petroleum hydrocarbons in their flesh. 4. The invertebrate communities were dominated by taxa tolerant of low water quality, and were typical of other urban water bodies. 5. Water and sediment quality of the lake are substantially influenced by runoff from the catchment. In particular, road runoff is likely to remain a major contributor of metals and petroleum hydrocarbons to the lake. 6. While the sediments in the lake contain a substantial store of heavy metals, petroleum hydrocarbons and nutrients, reducing inputs is likely to be of benefit to water quality and the overall environmental status of the lake, particularly in the longer term.

21 Environment Protection Authority

6. REFERENCES

Australia and New Zealand Environment and Conservation Council 1992, National Water Quality Management Strategy, Australian Water Quality Guidelines for Fresh and Marine Waters. Baudo, R., Giesy, J.P. and Muntau, H. 1990, Sediments: Chemistry and Toxicity of In-Place Pollutants, Lewis Publishers, Chelsea. Bourg, A.C.M. 1988, ‘Metals in aquatic and terrestrial systems: sorption, speciation and mobilization’, in Salomons, W. and Forstner, U., Chemistry and Biology of Solid Wastes, Springer Verlag, Berlin. Canadian Council of Resource and Environment Ministers (CCREM) 1991, Canadian Water Quality Guidelines, Inland Water Directorate, CCREM, Environment Canada, Ottawa. Duda, A.M., Lenat, D.R. and Penrose, D.L. 1982, ‘Water quality in urban streams – what we can expect’, Journal of the Water Pollution Control Federation, 54, pp: 1139–1147. Ealey, E., Deacon, G., Coller, B., Bird, G., Bos-Van Der Zalm, C., Raper, W. and Rusden, S. 1983, Mercury in the Food Web of Raspberry Creek, EPA Publication 153 Elliot, B.J. 1973, Blackburn Lake Pollution Survey, Department of Chemical Engineering, Monash University, Environment Protection Authority (Victoria) EPA 1983, Recommended Water Quality Criteria, First Edition, EPA Publication 165. EPA 1991, Construction Techniques for Sediment Pollution Control, EPA Publication 275. Forstner, U. and Wittmann, G. 1981, Metal Pollution in the Aquatic Environment, Springer, Berlin. Garie, H.L.and McIntosh, A. 1986, ‘Distribution of benthic macroinvertebrates in a stream exposed to urban runoff’, Water Resources Bulletin, 22, pp. 447–455. Giesy, J.P.and Hoke, R.A. 1990, ‘Freshwater sediment quality criteria: toxicity bioassessment’, in: Baudo, R., Giesy, J.P. and Muntau, H. (eds), Sediments: Chemistry and Toxicity of In-Place Pollutants, Lewis Publishers, Ann Arbor. Gill, R.A. and Robothom, P.W.J. 1989, ‘Composition, sources and source identification of petroleum hydrocarbons and their residues’, in Green, J. and Trett, M.W. (eds), The Fate and Effects of Oil in Freshwater, Elsevier Applied Science Publishers, London, chapter 2. Government of Victoria 1984, State Environment Protection Policy No. W29 (Waters of the Yarra and Tributaries), State Government of Victoria. Government of Victoria 1995, Protecting the Waters of the Yarra Catchment, State Environment Protection Policy (Waters of Victoria) Draft Schedule F7 (Waters of the Yarra Catchment) and Draft Policy Impact Statement, EPA Publication 471. Government of Victoria 1999, State Environment Protection Policy (Waters of Victoria), Schedule F7. Waters of the Yarra Catchment, State Government of Victoria. Hart, B.T. 1982, Australian Water Quality Criteria for Heavy Metals, Australian Water Resources Council Technical Paper No. 77, Australian Government Publishing Service, Canberra. Hellawell, J.M. 1978, Biological Surveillance of Rivers – A Biological Monitoring Handbook, Water Research Centre, Stevenage, England. Lake, P.S. and Sokol, A. 1986, Ecology of the Yabby Cherax Destructor Clark (Crustacea: Decopoda: Parastcidae) and Its Potential as a Sentinel Animal for Mercury and Lead Pollution, Australian Water Resources Council, Technical Paper No 87.

22 An Environmental Study of Blackburn Lake

Lidston, J. 1993, Victorian Water Quality Network Lakes Program, SWL Report No. WQ-61, State Water Laboratory of Victoria. Metzeling, L., Tiller, D. and Hunter, M. 1993, Inland Water Quality Monitoring Network 1991 Yearly Report, EPA Publication 360, EPA (Victoria). Mitchell, P. and Clark, H. 1991, An Environmental Study of Merri Creek. SWL report No. WQ-44, State Water laboratory, Victoria. NH&MRC 1989, MRL Standard – Maximum Residue Limits in Food and Animal Feedstuffs of Pesticides, Agricultural Chemicals, Feed Additives and Veterinary Medicines, National Health & Medical Research Council, Australian Government Publishing Service, Canberra. Muller, H. 1987, ‘Hydrocarbons in the freshwater environment – A literature review’, Advances in Limnology, 24, Archiv fur Hydrobiologie, Stuttgart. Neff, J.M. 1979, Polycyclic Aromatic Hydrocarbons in the Aquatic Environment—Sources Fate and Biological Effects, Applied Science Publishers Limited, London. Norris, R.H. 1983, Water Quality Monitoring of the Molonglo River and Lake Burley Griffin, Report to the National Capital Development Commission. Peterson, S.M. and Batley, G.E. 1992, Road Runoff and its Impact on the Aquatic Environment: A Review. CSIRO – Division of Coal and Energy Technology, Centre for Advanced Analytical Chemistry, Investigation Report CET/LH/IR076. Phillips, B.C., Lawrence, A.I., and Goyen, A.G. 1988, ‘The act approach to improving urban stormwater quality’, Water, March 1988, pp. 36–39. Pettigrove, V.J. 1988, Biological Monitoring of the Yarra River using Macroinvertebrates, EPA Publication SRS 88/014. Pouliot, A.M. 1993, The Effect of an Urban Drain on the Aquatic Macroinvertebrates in Darebin Creek, EPA Publication SRS 91/016. Power, E.A. and Chapman, P.M. 1992, ‘Assessing sediment quality’, in: Burton, G. Allen (Jr) (ed) Sediment Toxicity Assessment, Lewis Publishers, London, chapter 1. Reed, J.L. 1990, A Biological Assessment of Lower Kororoit Creek, EPA Publication SRS 90/012. Shales, S., Thake, B.A., Frankland, B., Khan, D.H., Hutchinson, J.D. and Mason, C.F. 1989, ‘Biological and ecological effects of oils’, in Green, J. and Trett, M.W. (eds), The Fate and Effects of Oil in Freshwater, Elsevier Applied Science Publishers, London, chapter 4. Smith, J.D. 1976, ‘The occurrence of heavy metals in sediments of Mordialloc Creek’, The Royal Australian Chemical Institute Proceedings, 43, pp. 305–306. SWL 1984, Digestion Procedures for the Determination of Heavy Metals in Sediments by Atomic Absorption Spectrophotometry and ICP Emission Spectroscopy, State Water Laboratory, Armadale. SWL 1988, Chemical Methods, Volume 1 – Routine Water Analysis, 2nd Edition Report No. CE25, State Water Laboratory, Armadale. Tiller, D.G. 1990, Mercury in the Freshwater Environment – The Contamination of Water Bodies in Victoria as a Result of Past Gold Mining Activities, EPA Publication SRS 90/005, EPA (Victoria). Timmermans, K., van Hattum, B., Kraak, M. and Davids, C. 1989, ‘Trace metals in a littoral food web – concentrations in organisms, sediment and water’, Science of the Total Environment, 87/88, pp. 477– 494.

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Wilber, W.G. and Hunter, J.V. 1979, ‘The impact of urbanization on the distribution of heavy metals in bottom sediments of the Saddle River’, Water Resources Bulletin, 15, pp. 790–800.

24 An Environmental Study of Blackburn Lake

APPENDICES

Appendix 1: Polycyclic Aromatic Hydrocarbon (PAH) concentrations in Blackburn Lake sediments (mg/g) and biota (ng/g)

PAHs concentrations in sediments (mg/g)*

PAH Site 1 Site 2 Site 3 Site 4 Site 5 Naphthalene 0.1 0.1 0.05 0.06 0.03 Acenaphthylene 0.07 nd nd nd nd Acenaphthene NM NM NM NM NM Fluorine 0.1 0.1 0.1 0.2 0.2 Phenanthrene 0.1 0.2 0.2 0.2 0.2 Anthracene 0.2 0.2 0.2 0.2 0.1 Fluoranthene 0.1 0.2 0.2 0.2 0.2 Pyrene 0.3 0.3 0.3 0.3 0.2 Benzo(a)anthracene 0.1 0.1 0.1 0.1 0.04 Chrysene 0.2 0.2 0.1 0.1 0.1 Benzo(b)fluoranthene Benzo(k)fluoranthene 0.3 0.3 0.2 0.2 0.1 Benzo(a)pyrene 0.1 0.1 0.1 0.1 0.05 Dibenz(ah)- anthracene Benzo(ghi)perylene 0.2 0.1 0.1 0.1 0.05 Indeno(123cd)pyrene 0.2 0.2 0.2 0.2 0.1 Total PAH < 2 < 2 < 2 < 2 < 2

contd.. nd – not detected (less than 0.05 ppm) NM – not measured due to interference from internal standard. *The levels shown are regarded as being slightly conservative due to the inability of the GC/FID to efficiently quantify the heavier hydrocarbons. The average level was checked by analysing an air-dried composite of the five samples for Total Petroleum Hydrocarbons (TPH) using freon extraction and infrared detection. The value obtained was approximately 6000mg/g. For all samples, the total PAH content was approximately 2 mg/g (dry basis). Individual PAH isomers were quantified as in the table above.

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Polycyclic Aromatic Hydrocarbon (PAH) concentrations in Blackburn Lake sediments (mg/g) and biota (ng/g)

PAHs concentrations in biota (ng/g)

Yabby Flesh Yabby Exoskeleton PAH Site 3 Site 4 Site 3 Site 4 Naphthalene 1 3 <1 4 Acenaphthylene <1 <1 <1 <1 Acenaphthene 1 3 <1 4 Fluorene <1 2 <1 <1 Phenanthrene 6 9 <1 <1 Anthracene <1 <1 <1 <1 Fluoranthene 3 4 <1 <1 Pyrene 7 13 2 2 Benzo(A)Anthracene <1 <1 <1 <1 Chrysene 4 3 <1 <1 Benzo(B)Fluoranthene 1 1 <1 <1 Benzo(K)Fluoranthene <1 <1 <1 <1 Benzo(A)Pyrene <1 <1 <1 <1 Indeno(123cd)Pyrene <1 <1 <1 <1 Dibenz(AH)Anthracene <1 <1 <1 <1 Benzo(GHI)Perylene 2 <1 5 <1 Total PAH 25 38 7 10

26 An Environmental Study of Blackburn Lake

Appendix 2: Invertebrate taxa and their abundances, Blackburn Lake, February 1993

TAXON Site 1 Site 2 Site 3 Site 4 Site 5

GASTROPODA

Ferrissia petterdi 34 19 46 92 6

Austropeplea tomentosa 7 5 15 14

Physa/physastra sp. 8 2 2 1 8

Immature or unidentified 6 5 1 3 117

OLIGOCHAETA sp 72 46 54 224 1725

Branchiura sowerbyi 3

HIRUDINEA 2

TEMNOCEPHALIDEA 1

CRUSTACEA

DECAPODA

Parastacidae sp. (immature) 1

INSECTA

COLLEMBOLA 1 3 5

EPHEMEROPTERA

Tasmanocoenis tillyardi 1

ODONATA

Ischnura heterosticta 2 4 3 1

Ischnura sp. 1 1

Austrocnemis splendida 2 2

Austroagrion sp. 1 1

Zygoptera (immature and unidentified) 1 1 1 1 3

Anisoptera immature 1 12

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HEMIPTERA

Anisops thienmanni 4 9

Anisops EPA sp 1 1 1 1

Anisops EPA sp 3 1 3 8 3

Anisops (female) 2 7 9 8 24

Anisops immature 3 2 6

Micronecta sp 1

Agraptocorica sp 1

Sigara sublaevifrons 1

NEUROPTERA

Sisyra sp 1

COLEOPTERA

Dytisus sternopriscus 1

DIPTERA

Stratiomyidae (immature) 8 5 15 11 43

Ceratopogonidae SRV sp6 2

Ceratopogonidae pupae 3 1

Tipulidae pupa 1

Ephydra sp. (larvae) 4

Ephydra sp. (pupae) 2

Culicidae sp. 4

Chironomidae

Tanypodinae: Procladius sp. 1

Chironomini: Dicrotendipes sp. 2 9 33 7

Chironomini: Polypedilum sp. 1

Chironomini: Chironimus sp. 1

Orthocladiinae: Cricotopus sp. 1 1

Unidentified pupae 1 2

Unidentified pupae 1 1

Unidentified larvae 1 3

TRICHOPTERA

Ecnomus turgidus 2

LEPIDOPTERA

Unidentified larva 1

28 An Environmental Study of Blackburn Lake

29