An analysis of benthic invertebrate and water quality monitoring data from the Athabasca River

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  • As a result of industrial development in the Athabasca oil sands area of northeastern Alberta, concerns have been raised regarding potential impacts on surface water quality in the area. It is of particular concern that the cumulative effects of increasing development of the oil sands may create hydrocarbon and metal pollution problems in the Athabasca River. With the aims of evaluating baseline water quality conditions and identifying areas that may have been affected by existing industrial developments, water quality of the Athabasca River within the oil sands area has been monitored since 1976. In addition, several studies of benthic invertebrate communities have been conducted and these provided primarily descriptive information. This report presents a detailed statistical analysis of water quality and benthic invertebrate data from previous studies on the Athabasca River. Benthic invertebrate data were from a study conducted in 1981 on the Athabasca River between Fort McMurray and the Tar River confluence. Water quality data for the same area were obtained from the NAQUADAT water quality data base for the period 1976 to 1983. The study area includes a 75 km section of the Athabasca River extending from the confluence with the Horse River upstream of Fort McMurray, downstream to the confluence with the Tar River, approximately 40 km downstream from the Suncor extraction and upgrading plant. Six water quality monitoring stations and eight benthic invertebrate sampling stations were located within the study area. The relationships among various water quality parameters were examined using the methods of principal component analysis. Principal components were also used to describe associations of benthic invertebrate taxa and for transformation of abundance data prior to making statistical comparisons among sampling stations. The relationships between water quality and benthic invertebrates were examined by determining the correlations of benthic invertebrate principal components with water quality principal components. Strong correlations among several of the water quality parameters were apparent. Most of the major ions (calcium, magnesium, sodium, chloride, sulphate, and bicarbonate) were strongly correlated with each other and with specific conductance, total alkalinity, and filterable residue. Potassium concentrations were independent of the concentrations of other major ions. There were also components of sodium and chloride, attributable to the Clearwater River and other east bank tributaries, that were not strongly related to the concentrations of other ions. All of the metals except lead and mercury were associated with non-filterable residue and total phosphate. With respect to those water quality parameters included in the analyses, there was no evidence that effluent from the Suncor plant had a large or consistent effect on the water quality of the Athabasca River downstream from the development. The suggestion is that any effects on water quality were short-term in nature and did not result in changes that persisted for long periods of time. The major differences in water quality and in benthic invertebrate abundance and community composition within the study area were between the left and right sides of the Athabasca River. These differences were considered to be due primarily to the influences of the Clearwater River and other east bank tributaries. Some observed differences in benthic invertebrate abundance and community composition within the study area may be related to nutrient enrichment from the Fort McMurray sewage effluent. There was no evidence of large differences in benthic invertebrate populations between stations immediately upstream and downstream of the Suncor development that could be attributed to the Suncor effluent. The abundance of a variety of benthic invertebrate taxa appeared to be correlated with several water quality parameters. In most cases, these correlations were with water quality parameters that show differences between the left and right sides of the Athabasca River. The observed correlations therefore may be due to drifting of, and colonization by, invertebrates from the Clearwater River, and possibly other right bank tributaries, rather than to any direct influence of water quality. The results of statistical analyses of the benthic invertebrate data presented in this report must be considered tentative or inconclusive. A non-random selection procedure was used during collection of the benthic invertebrate samples and this adversely affects the validity of statistical analyses. The reliability of the results is therefore questionable.

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