The Effects of Road Transport on Freshwater and Marine Ecosystems

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contamination. However, the assessment dealt with the effects <strong>of</strong> general urban run<strong>of</strong>f and did not
specifically look at the effect <strong>of</strong> road or highway run<strong>of</strong>f.
As part <strong>of</strong> the ARC programme to investigate the effects <strong>of</strong> decreasing sediment quality in low energy
environments, Anderson et al. (2002) reported on the development <strong>of</strong> criteria for assessing the health <strong>of</strong>
benthic faunal communities in s<strong>of</strong>t-shore intertidal environments. Following the development <strong>of</strong> this
community health index ARC have been evaluating further the relationship between benthic health and
sediment quality through an ongoing benthic environmental quality monitoring program (Kingett Mitchell
2003a,b). This continued evaluation is currently being prepared as an ARC report (Dr Shane Kelly ARC
pers comm.).
Overseas, Schiff & Bay (2003) examined the impacts <strong>of</strong> stormwater discharges on the benthic
environment in Santa Monica Bay. Examination <strong>of</strong> sediments <strong>of</strong>f Ballona Creek indicated increased
concentrations <strong>of</strong> metals up to 2 km and 4 km along-shore in either direction from the Creek. <strong>The</strong> authors
utilised the benthic response index (BRI) (Bergen et al. 2002) to evaluate community composition
change. Although the authors identified changes in general physical characteristics <strong>of</strong> sediments, OM
and metal concentrations, they did not observe significant changes in the composition <strong>of</strong> the benthic
community. <strong>The</strong> authors did not that it was possible that the sampling locations may not have been
appropriately positioned in relation to the stormwater plume footprint.
Most studies carried out to-date in New Zealand have dealt with the identification <strong>of</strong> possible effects <strong>of</strong>
urban run-<strong>of</strong>f on coastal ecosystems. <strong>The</strong> studies have indicated that urbanisation as a whole results in
adverse changes to the diversity <strong>of</strong> the biological communities present. Further specific research would
need to be carried out to isolate the potential effects <strong>of</strong> road and highway run-<strong>of</strong>f by carrying out effects
studies in locations where run<strong>of</strong>f from roads and highways was isolated from the confounding effects <strong>of</strong>
general urban run<strong>of</strong>f. If the adverse effects arising from urban run<strong>of</strong>f are attributable to elements such as
Zn, then it is likely that roads and motor vehicles will contribute their proportional share <strong>of</strong> the adverse
effects observed. <strong>The</strong> proportion <strong>of</strong> that effect attributable to vehicles will vary from location to location.
At this stage the proportion <strong>of</strong> any observed effect is not known (even when identified on a contributed
load basis).
A number <strong>of</strong> studies carried out in the Auckland area have shown differences in the quality <strong>of</strong> sediment
benthic invertebrate communities in estuaries with catchments <strong>of</strong> varying intensities <strong>of</strong> urban
development. Recent work undertaken by ARC has indicated that there are good relationships between
macroinvertebrate benthic health in s<strong>of</strong>t muddy sediments and the quality <strong>of</strong> those sediments (as
reflected in the concentrations <strong>of</strong> Cu, Pb and Zn). However, the observed biological response seen in the
field does not necessarily reflect urban stormwater contributions from those catchments. At this point in
time, the available data indicates that the relationship between sediment quality (contaminants derived
from urban run<strong>of</strong>f and biological effects) is somewhat unclear.
7.6 Bioaccumulation
7.6.1 Plants
Salt marsh and mangrove are important coastal biological communities in the coastal environment and
play an important role in the production <strong>of</strong> detritus. Salt marsh and mangroves close to roadways are
exposed to vehicle exhaust emissions. As described in section 6 <strong>of</strong> this report, accumulation <strong>of</strong> trace
element contaminants by terrestrial plants (e.g., grass, sweet corn) has been reported in New Zealand.
As accumulation occurs through both root uptake and probably through airborne stomatal intake, some
uptake by plants growing in intertidal areas would be expected.
Kennedy (unpublished) examined trace element composition <strong>of</strong> Juncus in saltmarsh around Pauatahanui
Inlet adjacent to a road carrying relatively low vehicle traffic. <strong>The</strong> study indicated elevated concentrations
<strong>of</strong> Cu in live and dead tillers and rhizomes, Zn in live tillers and rhizomes and Pb in dead tillers. <strong>The</strong>
elevation occurred close to the roadway.
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