Page 812 - The Toxicology of Fishes

792 The Toxicology of Fishes

180
1993
160 1997
Copper in Hydropsyche (µg/g dw) 120
140

100
80

60
40
20

0
GG DL GC AB TU
Station ID

FIGURE 19.8 Copper concentrations in the bioindicator (larvae of the Hydropsyche sp.), extending from a recontaminated
station below the Warm Springs Ponds (GG) downstream to the Turah station (see Figure 19.1). Before remediation, copper
followed the clear exponential gradient downstream typical of sediment contamination. Remediation reduced bioavailable
copper concentration more upstream than mid-river, changing the spatial distribution trend.

sites or among species (Cain et al., 1995). Cain and Luoma (1999) avoided the ambiguities of external
metal and undigested gut content by analyzing metal concentrations within the cell solution of insects
(the cytosolic material inside cells as isolated by homogenization and ultracentrifugation). Cytosolic
concentrations of copper in the Hydropsyche were approximately 20 to 60% of whole-body concentra-
tions and correlated strongly with whole-body concentrations. This evidence clearly shows that the
copper contamination was assimilated into invertebrate tissues and was available to disrupt biochemical
processes. The metal in cell solution is probably readily available for trophic transfer to predators, as
well (Wallace et al., 2003).
Year-to-year variability in metal contamination was typically greater in insects than in sediments in
the Clark Fork, although conclusions were based on only one collection per year. One result was that
the effects of remediation efforts were more complex to interpret in insects. A trend of declining
concentrations in the Hydropsyche was evident in stations from the Deer Lodge Valley, between 1986
and 2003, but year-to-year variability overwhelmed any trends in the reaches of the river downstream
from Deer Lodge. Higher concentrations were observed in years of high river discharge than in years
of low river discharge (presumably reflecting the greater particulate or dissolved input from runoff in
years of greater discharge). Concentrations of copper and cadmium in the insect larvae correlated
significantly with annual discharge for all the years at the downstream stations. The result was that the
spatial trend in metal concentrations in the Hydropsyche shifted to higher concentrations mid-river than
in the uppermost river, especially in high flow years (Figure 19.8).

Adverse Effects on Invertebrates
Field observations and in situ microcosm studies (Clements, 2004) show that the structure and function
of invertebrate communities change in streams subjected to metal contamination from mine wastes but
recover when metal contamination is remediated. In some cases, the abundance of benthic macrofauna
can be reduced by the contamination, but not always. Insensitive species can be very abundant and show
little sign of stress in some contaminated environments (Lefcort et al., 2000). On the other hand, the
species richness of the benthic community consistently is reduced in the most contaminated areas, but
it is not an especially sensitive measure of effects as contamination declines. Hydropsyche were