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The Effects of Road Transport on Freshwater and Marine Ecosystems

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79<br />

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96 hour reproducti<strong>on</strong> inhibiti<strong>on</strong> test (IC50) using the alga Senastrum capricornutum.<br />

15 minute bioluminescence reducti<strong>on</strong> test (EC50) using Microtox system.<br />

Nipper et al. (1995) noted that few <str<strong>on</strong>g>of</str<strong>on</strong>g> the baseflow samples collected from the carpark p<strong>on</strong>d inlet <strong>and</strong><br />

outlet were acutely toxic to Daphnia, algae <strong>and</strong> bacteria. <str<strong>on</strong>g>The</str<strong>on</strong>g> inlet <strong>and</strong> outlet samples caused some<br />

enhancement in algal growth <strong>and</strong> the inlet sample resulted in some enhanced reproducti<strong>on</strong> in Daphnia.<br />

When storm flow samples were examined, no acute toxicity was observed in any <str<strong>on</strong>g>of</str<strong>on</strong>g> the p<strong>on</strong>d inlet <strong>and</strong><br />

outlet tests. <str<strong>on</strong>g>The</str<strong>on</strong>g> s<strong>and</strong> filter inlet sample resulted in acute <strong>and</strong> chr<strong>on</strong>ic toxicity to Daphnia. Moderate<br />

chr<strong>on</strong>ic toxicity to Daphnia was identified in tests utilising the p<strong>on</strong>d inlet sample <strong>and</strong> the s<strong>and</strong> filter outlet<br />

sample. Acute resp<strong>on</strong>ses were observed by Hickey et al. (1997) for Daphnia magna in two <str<strong>on</strong>g>of</str<strong>on</strong>g> the three<br />

storms tested by them. Chr<strong>on</strong>ic resp<strong>on</strong>ses were observed for both algae <strong>and</strong> Daphnia. No significant<br />

differences were observed for filtered <strong>and</strong> unfiltered samples.<br />

Hickey et al. (1997), found that when the measured toxicity data (UNITEC stormwater p<strong>on</strong>ds) was<br />

compared with the toxicity expected based <strong>on</strong> chemical analyses, toxicity was lower than expected.<br />

Hickey et al. (1997) c<strong>on</strong>sidered that acute toxicity could have been expected for the inflow to the UNITEC<br />

p<strong>on</strong>ds <strong>on</strong> most occasi<strong>on</strong>s <strong>and</strong> <strong>on</strong> some occasi<strong>on</strong>s for the outflow based <strong>on</strong> total <strong>and</strong> soluble Cu<br />

measurements. It was noted that some toxicity was measured <strong>on</strong> occasi<strong>on</strong>s when no criteria was<br />

exceeded suggesting that c<strong>on</strong>taminants other than metals may have c<strong>on</strong>tributed to toxicity. Further work<br />

by Hickey et al. (1997) in relati<strong>on</strong> to reference toxicants (zinc) indicated that in that case, the overall<br />

bioavailability <str<strong>on</strong>g>of</str<strong>on</strong>g> Zn in the stormwater examined was low.<br />

Macaskill et al. (2003) undertook toxicity testing <str<strong>on</strong>g>of</str<strong>on</strong>g> stormwater samples collected in April 2002 from<br />

Rotorua City. <str<strong>on</strong>g>The</str<strong>on</strong>g> tests were carried out using algae, water flea <strong>and</strong> amphipod test organisms.<br />

Stormwater from the residential catchment was the least toxic to any <str<strong>on</strong>g>of</str<strong>on</strong>g> the species tested, with<br />

commercial <strong>and</strong> industrial catchment stormwater comparable but having generally greater toxicity.<br />

Samples were most toxic to the freshwater algae followed by minimal toxicity to the water flea <strong>and</strong> were<br />

the least toxic to the freshwater amphipod.<br />

<str<strong>on</strong>g>The</str<strong>on</strong>g> algae used in the toxicity tests by Macaskill et al. (2003) were found to be the most sensitive <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />

test species. <str<strong>on</strong>g>The</str<strong>on</strong>g> authors noted that this, may have in part been due to the short-term chr<strong>on</strong>ic test used.<br />

Based up<strong>on</strong> the results some diluti<strong>on</strong> (116, 83 <strong>and</strong> 5 times) would be required to ensure no adverse<br />

effects occurred <strong>on</strong> algae.<br />

<str<strong>on</strong>g>The</str<strong>on</strong>g> toxicity test results using the water flea (EC50 values) showed that the no toxic resp<strong>on</strong>ses were<br />

received <strong>and</strong> <strong>on</strong>ly minor diluti<strong>on</strong> was required at the discharge point. EC50 values for amphipods were<br />

greater than 100% for stormwater from all catchment l<strong>and</strong>uses. As a result <strong>on</strong>ly minimal diluti<strong>on</strong> (about 2<br />

times) would be required to ensure no acute adverse effects occurring <strong>on</strong> the test species.<br />

<str<strong>on</strong>g>The</str<strong>on</strong>g> work <str<strong>on</strong>g>of</str<strong>on</strong>g> Macaskill et al. (2003) showed that <str<strong>on</strong>g>of</str<strong>on</strong>g> the three test species, algae <strong>and</strong> at least <strong>on</strong>e <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />

invertebrate species showed resp<strong>on</strong>ses to undiluted stormwater samples. <str<strong>on</strong>g>The</str<strong>on</strong>g> stormwater from the<br />

residential catchment was the least toxic to any <str<strong>on</strong>g>of</str<strong>on</strong>g> the species tested, with commercial <strong>and</strong> industrial<br />

catchment stormwaters generally comparable but having greater toxicity.<br />

Macaskill noted that when comparing the test results with a comparis<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> stormwater quality with water<br />

quality guidelines that the test results were slightly more sensitive than comparing water quality directly<br />

with guidelines.<br />

A range <str<strong>on</strong>g>of</str<strong>on</strong>g> toxicity studies have been undertaken using urban stormwater discharging to freshwater<br />

envir<strong>on</strong>ments. Tests undertaken using Microtox have shown that for run<str<strong>on</strong>g>of</str<strong>on</strong>g>f parking areas, 50% <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

samples are toxic <strong>and</strong> for highways (bridge), 20% <str<strong>on</strong>g>of</str<strong>on</strong>g> samples were severely toxic. Studies involving<br />

freshwater algae have shown that nutrients in run<str<strong>on</strong>g>of</str<strong>on</strong>g>f may stimulate growth but that metals in stormwater<br />

may inhibit growth. Work in New Zeal<strong>and</strong> has shown that urban stormwater has chr<strong>on</strong>ic effects <strong>on</strong><br />

growth <str<strong>on</strong>g>of</str<strong>on</strong>g> freshwater algae (in toxicity tests).<br />

Kingett Mitchell Ltd<br />

Resource & Envir<strong>on</strong>mental C<strong>on</strong>sultants

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