AN ENVIRONMENTAL STUDY OF BLACKBURN LAKE Environment Protection Authority State Government of Victoria 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 Gardiners Creek. 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. iii Environment Protection Authority 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 iv An Environmental Study of Blackburn Lake 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 v Environment Protection Authority 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 Melbourne 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