The Effects of Road Transport on Freshwater and Marine Ecosystems

88
Bioaccumulation can be assessed through the measurement <strong>of</strong> contaminants in organisms collected from
the field. It can also be assessed through the use <strong>of</strong> organisms, typically fish or mussels which are
placed in cages. Caged organism (such as fish) usually only respond to water borne contaminants.
Assessment <strong>of</strong> the effects <strong>of</strong> sediment-associated contaminant requires other strategies (in-situ chambers
or laboratory studies using sediment). In New Zealand freshwater mussels have been used to monitor
metal and organic compound bioaccumulation in the Waikato River (Hickey et al. 1995, 1997; Nipper et
al. 1995).
6.5.2 Bioaccumulation <strong>of</strong> Trace Elements
6.5.2.1 Invertebrates
Bioavailability <strong>of</strong> metals in aquatic ecosystems is dependent upon the form <strong>of</strong> the metal within the
particular environmental compartment. <strong>The</strong> key factors that need to be considered in relation to potential
uptake include, the chemistry <strong>of</strong> the metal if in solution (and the nature <strong>of</strong> the environment), the size and
the nature <strong>of</strong> the particulate the contaminant is associated with.
In New Zealand, Nipper et al. (1995) examined the uptake <strong>of</strong> contaminants in stormwater by placing
caged New Zealand freshwater mussels (Hyridella menziesi) in the inlet, outlet and in the stormwater
pond at UNITEC (Mt Albert Auckland). <strong>The</strong> mussels were examined for condition index and uptake <strong>of</strong>
metals after three months and organic contaminants after one month. Mussel condition index showed no
significant difference between stormwater pond inlet and outlet mussels. Metal concentrations were
found to be lower in the mussels from the outlet compared to the inlet reflecting the removal <strong>of</strong>
bioavailable metals by the treatment pond. Increases in concentration in mussel tissue were observed for
Cd, Pb and Zn but not for Cu and Hg.
Macaskill et al. (2003) examined bioaccumulation by whole freshwater mussels near stormwater
discharge points from Rotorua City. <strong>The</strong> study also conducted transplant uptake experiments using
mussels (gill tissue analysed) and snails (Potamopyrgus antipodarum). <strong>The</strong> examination <strong>of</strong> mussel metal
concentrations did not reveal any clear trends <strong>of</strong> concentration <strong>of</strong> metals with distance from contaminant
source. To assist in interpretation, bioaccumulation in mussels was compared using the average Ca
normalised concentrations. <strong>The</strong> concentrations <strong>of</strong> Cu, Pb and Zn were elevated at the Government
Gardens and Utuhina locations compared to the Waiteti location reflecting the influence <strong>of</strong> stormwater
discharges. This was most marked for Pb. <strong>The</strong> authors note that the strong signal for Pb may be an
artefact <strong>of</strong> its long half-life in biological tissues especially as freshwater mussels are known to have long
half-lives. . <strong>The</strong>refore the concentrations <strong>of</strong> Pb measured may reflect its presence in petrol prior to 1995.
<strong>The</strong> concentrations <strong>of</strong> Cu and Zn were also elevated (but not statistically so) at locations close to
stormwater outfalls. Transplanted mussels did not show any bioaccumulation in gill tissue over a 70 day
deployment period. No exposure gradient was evident in mussel gill tissue or in the whole snails (s<strong>of</strong>t
body). <strong>The</strong> authors concluded that the results reflected the lack <strong>of</strong> fine particulate settlement in the areas
in proximity to the stormwater discharges.
Goodyear & McNeill (1999) reviewed the bioaccumulation <strong>of</strong> metals by freshwater macro-invertebrates.
Most information in the literature is for the uptake <strong>of</strong> the key elements Cd, Cu, Pb and Zn. Goodyear &
McNeill (1999) found that for Cd, Cu, Pb and Zn displays a unique relationship between metal
concentrations in sediments or waters with different feeding guilds that indicates the relative importance
<strong>of</strong> different sources <strong>of</strong> metals to different feeding groups. <strong>The</strong> authors concluded that biomagnification
did not occur between the guilds. Work by Perdikaki & Mason (1999) did not shown any significant
changes in macroinvertebrate Cd, Pb or Zn concentrations that could be attributable to motorway
discharges. No relationship between stream sediment concentrations <strong>of</strong> metals and invertebrate
concentrations was identified.
Rauch & Morrison (1999) and Moldovan et al. (2001) examined the uptake <strong>of</strong> the PGEs by the freshwater
isopod (Asellus aquaticus) in freshwater rivers, a stormwater detention pond and under experimental
exposure. Rauch & Morrison (1999) found that concentrations ranged from 0.04 to 12.4 mg/kg and 0.16-
4.5 mg/kg after depuration. Sediments were considered to be the main source <strong>of</strong> Pt for the isopods.
Platinum speciation is very important in relation to uptake. <strong>The</strong> authors reported 60-90% <strong>of</strong> the Pt was
Kingett Mitchell Ltd
Resource & Environmental Consultants