The Effects of Road Transport on Freshwater and Marine Ecosystems

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96 7. IDENTIFICATION OF ENVIRONMENTAL EFFECTS IN ESTUARINE AND COASTAL ECOSYSTEMS 7.1 Introduction <strong>The</strong> New Zealand estuarine and coastal environment is diverse with stormwater discharges occurring into: Estuaries containing saltmarsh (e.g., Pauatahanui Inlet) and mangroves (e.g., the Waitemata Harbour). Large predominantly intertidal inlets and estuaries (e.g., the Avon-Heathcote, Manukau Harbour, Whangarei Harbour). Large predominantly subtidal Harbours (e.g., Wellington). Open coastal waters with rocky shores (e.g., Takapuna to Long Bay Shoreline in Auckland). This section <strong>of</strong> the report examines the effect <strong>of</strong> stormwater discharges from roadways on estuarine and marine ecosystems. <strong>The</strong> key environmental issues are: <strong>Effects</strong> on water quality. <strong>Effects</strong> on sediment quality. <strong>Effects</strong> on biological resources including toxicity and bioaccumulation. Since the preparation <strong>of</strong> the first edition <strong>of</strong> this report, there have been several specific reviews and reports prepared that provide information in relation to the effects <strong>of</strong> stormwater discharges on the marine environment. <strong>The</strong>se include Pridmore et al. (2000) and Williamson et al. (2001). This section reviews the methods and tools currently used to assess environmental effects within estuarine and marine environments with a view to identifying whether they are sufficient to determine the effects <strong>of</strong> road transport emissions on these environments. This section also examines what we know about the effects <strong>of</strong> motor vehicles contaminants in isolation or as part <strong>of</strong> general urban stormwater run<strong>of</strong>f on the marine environment. 7.2 Habitat Compared to habitat monitoring in the freshwater environment (refer Section 6.2), there has been little work carried out to identify specific methods for the assessment <strong>of</strong> habitat quality in the marine environment. Given the diversity <strong>of</strong> habitat types and the nature <strong>of</strong> the environment, establishing estuarine and coastal benchmarks is not as straightforward as it is for freshwater. Robertson et al. (2002) represents the most comprehensive assessment <strong>of</strong> monitoring (including the examination <strong>of</strong> habitat) in the New Zealand coastal environment. Typical habitat changes in estuarine and coastal marine environments that may be attributable to urban stormwater and other stressors include: Changes in sediment characteristics due to deposition <strong>of</strong> fine sediments. Changes in sediment characteristics due to the deposition <strong>of</strong> coarse sediment and debris. Changes in sediment surface micro-flora due to nutrients and the presence <strong>of</strong> oxygen demanding substances. Kingett Mitchell Ltd Resource & Environmental Consultants
97 Changes in sediment surface macro-flora (e.g., sea-lettuce, Gracilaria due to the presence <strong>of</strong> nutrients. As noted in Section 4, sedimentation <strong>of</strong> particulate material from roads results in the deposition <strong>of</strong> coarse particulate materials around stormwater outfalls. <strong>The</strong>se deposition areas, which <strong>of</strong>ten comprise gritty particulate materials below the outfall (road chips, bitumen and other inorganic material from the road or urban environment such as red brick) are in many cases readily identifiable. <strong>The</strong> extent <strong>of</strong> deposition is dependent upon the volume and source <strong>of</strong> the discharge, and the physical nature <strong>of</strong> the receiving environment. This zone has been described in studies such as Bolton-Ritchie et al. (1999). <strong>The</strong> deposition <strong>of</strong> fine sediments at the point <strong>of</strong> discharge is not typically a feature <strong>of</strong> the discharge <strong>of</strong> stormwater from roads. Discharges capable <strong>of</strong> resulting in fine sediment deposition are typically associated with earthworks. No specific tools have been identified for specifically assessing habitat changes that might be attributable to discharges <strong>of</strong> road stormwater to the marine environment. Stormwater discharges from roads and urban catchments typically discharge material that settles adjacent to the stormwater outfall. <strong>The</strong> presence and extent <strong>of</strong> the distribution <strong>of</strong> this material is dependent upon the hydrodynamics <strong>of</strong> the environment at the point <strong>of</strong> discharge and the characteristics <strong>of</strong> the material discharged. If the physical environment is depositional in nature then material may accumulate adjacent to the outfall. 7.3 Water quality and Toxicity 7.3.1 Water quality data As with freshwaters, marine water quality can be monitored for a wide range <strong>of</strong> specific constituents. This analytical ability allows resource managers to assess the quality <strong>of</strong> a receiving water in relation to the possible effects <strong>of</strong> discharges (such as road run<strong>of</strong>f). <strong>The</strong> implications <strong>of</strong> road run<strong>of</strong>f discharge to coastal environments (estuaries and near-shore areas) is dependent upon the ratio <strong>of</strong> stormwater volume to the physical environment at the entry point <strong>of</strong> the stormwater (e.g., estuary width and length, water depth, tidal currents etc.,). In evaluating the effects <strong>of</strong> motor vehicles on coastal systems, the key constituents <strong>of</strong> concern are contaminants (metals and organic compounds). Other constituents that are linked mainly to road surface wear and activities on and adjacent to the road (e.g., suspended solids, BOD, bacteria etc.) are not considered further. <strong>The</strong> development and dispersal <strong>of</strong> stormwater plumes in coastal environments has been examined in a number <strong>of</strong> studies. In each case, the dispersal <strong>of</strong> stormwater occurs on a site-specific basis. In assessing effects, plume behaviour at the discharge point needs to be considered and is primarily dependent upon whether the discharge point is at the shoreline or <strong>of</strong>fshore, whether the discharge is surface or subsurface and what the volume <strong>of</strong> the discharge is relative to the receiving environment volume/cross-section. Washburn et al. (2003) describe the formation and dispersal <strong>of</strong> stormwater plumes from very large urban catchments in California showing that plumes could in that case be detected over kilometres from the discharge point (refer Section 7.5.3). 7.3.2 Toxicity In New Zealand Hickey et al. (1997) assessed the toxicity <strong>of</strong> stormwater discharged to the marine environment on the following test organisms: 1. Diatom (Minutocellus polymorphus) 48 hour inhibition microplate test. 2. Amphipod (Chaetocorophium lucasi) 96 hour acute mortality test. Kingett Mitchell Ltd Resource & Environmental Consultants
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iv 7. IDENTIFICATION OF ENVIRONMENT
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vi MW Molecular weight N Nitrogen N
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30 Metal Cu Cd Pb Zn Table 4.6 - Su
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32 probably reflect lower traffic d
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34 (1995) provide a general review
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36 Further data can be found in the
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38 by ARC (1994) indicated that TPH
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40 Cations/Anions Common ionic cons
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44 5 PATHWAYS & FATE OF CONTAMINANT
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Page 62 and 63: 52 short (e.g., < 1 day). In water,
Page 64 and 65: 54 5.4.2 Dispersion Dilution and di
Page 66 and 67: 56 5.6 Summary The
Page 68 and 69: 58 6.2 Freshwater Ecosystems 6.2.1
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Page 72 and 73: 62 3. Increasing sediment inputs. 4
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Page 76 and 77: 66 Freshwater macro-invertebrate me
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Page 82 and 83: 72 one factor used to classify orga
Page 84 and 85: 74 Zinc Measurement of</str
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Page 88 and 89: 78 minute; sub-mitochondrial partic
Page 90 and 91: 80 Toxicity tests have undertaken u
Page 92 and 93: 82 High molecular weight PAHs are t
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Page 96 and 97: 86 Although a range of</str
Page 98 and 99: 88 Bioaccumulation can be assessed
Page 100 and 101: 90 Figure 6.2 - metal concentration
Page 102 and 103: 92 6.5.3 Bioaccumulation of
Page 104 and 105: 94 Water Stormwater quality data fr
Page 108 and 109: 98 3. Echinoderm (Fellaster zelandi
Page 110 and 111: 100 trace metals (probably Cu and Z
Page 112 and 113: 102 concentrations of</stro
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Page 116 and 117: 106 A large amount of</stro
Page 118 and 119: 108 A review of se
Page 120 and 121: 110 Samples of man
Page 122 and 123: 112 grazers such as mud flat snails
Page 124 and 125: 114 8. OVERVIEW 8.1 Vehicles as sou
Page 126 and 127: 116 The quality <s
Page 128 and 129: 118 International studies have show
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Page 132 and 133: 122 construction. Center for Resear
Page 134 and 135: 124 Carey, J.; Cook, P.; Ciesy, J.;
Page 136 and 137: 126 Ellis, J. B. 1986: Pollutional
Page 138 and 139: 128 Harrop D. O. 1984: Stormwater r
Page 140 and 141: 130 Kennedy, P. C.; Kjellstrom, T.
Page 142 and 143: 132 Maltby, L. A.; Boxall, D. M.; F
Page 144 and 145: 134 Novotny, V.; Muehring, D.; Zito
Page 146 and 147: 136 Ruck, J. 1998: Evaluation <stro
Page 148 and 149: 138 Terracciano, S. A.; O’Brien,
Page 150 and 151: 140 Webster, J. G.; Brown, K. L.; W
Page 152: 142 10. ACKNOWLEDGEMENTS Thanks to
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