Proceedings - Teaching and Learning Centre - Simon Fraser ...

Fraser River Action Plan 3rd Research Workshop
• to compare fish and invertebrate assemblages across a range of environmental conditions as an index of
ecosystem condition;
• experimentally assess the causal affects of heavy metal inputs in an unpolluted stream as a means of
accounting for the potential impacts of heavy metals from among the other impacts on urban streams;
and,
• interpret benthic community structure in urban and agricultural streams in the context of predicted effects
of heavy metals on constituent taxa.
In this component of the Fraser River Action Plan we have three primary projects in Lower Mainland streams:
1. patterns in the structure of fish assemblages in small streams;
2. patterns in the structure of riffle macroinvertebrates in small streams; and,
3. a mesocosm experiment testing the dose-dependence of biological responses to heavy metals in solution.
All three of these studies are nearing completion and should be in final report form by the end of August, 1996.
Fish
A total of 40 streams have been sampled once for fish assemblages using baited minnow traps. Among these 40
sites were streams in the Brunette, Salmon and Sumas drainages as well as a further 16 sites in areas primarily
on the north shore in areas relatively unaffected by urban and agricultural activities. The sites on the north shore
were used for reference sites, or outgroup comparison, so that we could ascertain whether the relatively
“pristine” sites in the Salmon River watershed could be assumed to be in good condition. Using ordination, most
of the Salmon River sites clustered among those from the north shore sites, indicating that the Salmon drainage is
a valid point of reference for comparison with other Lower Mainland streams.
Twenty-four of the streams referred to above have been sampled three times and are being compared for
community composition relative to assemblages considered “pristine”. The results of preliminary analyses on
these data using ordination showed clear separation between sites which were considered “pristine” and those
affected by urban and agricultural impacts. Clean sites were characterized by higher densities of cutthroat trout,
coho and crayfish, whereas impacted sites were more likely to have higher densities of sticklebacks, carp and
prickly sculpin. Tests of association with the ordination scores and measures of environmental variables, mostly
habitat attributes, showed no significant association suggesting that variables other than strictly habitat (i.e.,
water quality), might be linked to the patterns in fish assemblage. Integration of our results with water quality
data from Drs. Ken Hall and Hans Schreier will test this latter hypothesis.
Benthos
Twenty-four streams were sampled for benthos in riffle substrate during late summer, 1995. Many of these
streams coincide with those for which fish were sampled, mainly in the Brunette and Salmon drainages. Some
additional streams were sampled to increase sample size, represent a broader set of streams, and also to avoid
the spatial autocorrelative problem of having all the urban sites in the Brunette and all the cleaner semi-rural
sites in the Salmon. Processing of these samples is proceeding well and the data will be subject to similar
ordination and clustering analyses as for the fish. Comparisons with the fish assemblages, habitat attributes and
water quality information will be the basis of analysis of those data.
Mesocosm Experiment
Given the difficulty with separating out the signals imposed on biological communities by heavy metal
contamination in a system with multiple, non-point source impacts, we carried out an experimental test of the
separate effects of heavy metal input on a small and pristine stream. The rationale for using a clean site was that
any species sensitive to heavy metals would still be present and their responses would be illustrative of processes
that may have led to their extirpation in urban streams. The experiment was carried out at the Malcolm Knapp
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