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

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Fraser River Action Plan 3rd Research Workshop The Effects of Contaminants and Riparian Zone Integrity on Small Stream Ecosystems in the Lower Fraser Basin J. Richardson Westwater Research Centre and Department of Forest Sciences University of British Columbia Small streams represent an integrator of characteristics of a catchment. They are also most reflective of local conditions because of the tight linkages between land and water and the high ratio of edge-to-volume in small streams. In the lower Fraser basin the heavy influence of human activities on streams is detectable everywhere. It may be that there are no small streams in the alluvial portion of the lower Fraser basin that have not been severely modified by human activities. One of the challenges of our studies was to find appropriate reference conditions with which to compare stream communities of the streams of the lower basin. In these studies, we have combined comparative studies with experimentation and the laboratory bioassays of Dr. Ken Hall (University of British Columbia) to provide an analysis of the state of small streams of the lower Fraser basin. Stream ecosystems can be affected by human activities in a variety of ways including a range of contaminants, changes in hydrology, yield of fine sediments, changes in temperature regime, alteration of riparian vegetation and physical rearrangement. Many such changes would be considered non-point source and are difficult to separate out by their individual effects and difficult to manage. Even where the aggregate effects of a particular factor have been considered, the problem of autocorrelation in space or time by comparing streams within a drainage hinders the ability to empirically test or estimate the effect. The interpretation of differences in biological communities between sites may be confounded by the inability to refute hypotheses that are not independent of each other. For instance, in sites which are heavily impacted by heavy metals, the built-up nature of these areas would also result in reduced water retention and hence, higher peak flows, more people with greater chance of sewage leakage, and greater degree of habitat alteration and riparian vegetation removal. Thus, the coincidence of multiple insults restricts one’s ability to isolate individual perturbations in field studies. Identifying the impacts of non-point sources of perturbation is further confounded by a variety of other factors. Within a given drainage there may be similar land use so that it is difficult to separate out general land use differences from other differences between streams and drainages. For instance, streams within a drainage may be more similar to each other for reasons of common underlying alluvium or other geologic features, access or occurrence of particular species (e.g., salmon), or other climatic or water quality factors. This could mean that drainages may have been historically different, and while this is unlikely, we have no clear means of rejecting it. The point being that drawing comparisons across drainages is fraught with limitations. Another set of difficulties in interpretation of the effect of non-point sources of pollution is that biological communities may have adapted to the perturbation. For instance, studies have shown that in streams chronically affected by heavy metal pollution over the course of the past century have species populations which show higher tolerance levels for heavy metals than the same species in unaffected streams. Communities may have adjusted such that more tolerant species have replaced or expanded in the wake of the disappearance of less tolerant species. However, these substitutions may be within the same genus and, therefore, not be resolvable with the current state of invertebrate taxonomy. There is evidence of the latter from studies in the US midwest. We had several guiding objectives for our studies: • to assess the community structure of small streams as a means of identifying impacts of human land uses — including the degree of riparian modification and water quality measure; Page 121
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 Page 122
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PROCEEDINGS 3rd RESEARCH WORKSHOP F
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TABLE OF CONTENTS Participants ....
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Development of a Citizen’s Monito
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Fraser River Action Plan 3rd Resear
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SESSION 1 PULP MILL EFFLUENT ISSUES
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SESSION 5 BIOLOGICAL INDICATORS
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SESSION 6 ESTUARY ISSUES
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Fraser River Action Plan The Use of
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Fraser River Action Plan Concluding
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