Search

Anthropogenic inputs of nitrogen (N), phosphorus (P) and oxygen-consuming material to aquatic ecosystems can change nutrient dynamics, deplete oxygen, and change abundance and diversity of aquatic plants and animals. The Northern Rivers Ecosystem Initiative required a research and assessment program to establish the contribution of pulp mill and sewage discharges to eutrophication and depressions in dissolved oxygen (DO) in the Athabasca and Wapiti rivers of northern Alberta, Canada and examine the adequacy of existing guidelines for protecting these systems. Analysis of long-term data showed that total N (TN) and total P (TP) concentrations in exposed river reaches exceeded concentrations in reference reaches by ≤ 2 times for the Athabasca River, and by 9.6 (TP) and 2.6 (TN) times for the Wapiti River. Results from nutrient limitation experiments conducted in situ and in mesocosms showed that benthic algal production was nutrient sufficient downstream of pulp mill discharges but constrained in upper river reaches by insufficient P (Athabasca River) or N + P (Wapiti River). Dissolved oxygen (DO) concentrations in both rivers declined during winter such that median concentrations in the Athabasca River 945 km downstream of the headwaters were approximately 8 mg L−1 in mid-February. Although water column DO rarely approached the guideline of 6.5 mg L−1, DO studies undertaken in the Wapiti River showed that pore water DO often failed to meet this guideline and could not be predicted from water column DO. Results from this integrated program of monitoring and experimentation have improved understanding of the interactions between nutrients, DO and aquatic ecosystem productivity and resulted in recommendations for revisions to nutrient and DO guidelines for these northern rivers. [ABSTRACT FROM AUTHOR]

To determine whether existing dissolved oxygen (DO) regulationswere adequate to protect riverine biota, the Northern River Basins Studyrequired a research and assessment program to establish the effect ofpulp mill and municipal sewage discharges on under-ice DO concentrationsand aquatic biota in the Athabasca, Wapiti and Smoky rivers of northernAlberta, Canada. Analysis of monitoring data collected over>30 yearsshowed that pulp mill and municipal effluents have caused “sags” in DObelow their discharges and contributed to an increased rate of declinein DO over 10s of kilometers in the Wapiti-Smoky rivers or 100s ofkilometers in the Athabasca River. To permit forecasting of DO declinesin response to changes in river discharge or effluent biochemical oxygendemand (BOD), a one-dimensional steady-state river water quality modelwas implemented that successfully (r2 =0.74-0.92) predicted DO concentrations over an 820 km reach of theAthabasca River for the 1990-1994 winters. Experiments on nativefish and benthic macroinvertebrate species showed that exposure to lowDO and low temperatures (2-3°C) caused delays in hatch ofmountain whitefish eggs (at 6.5 mg/L DO), reduced mass of bull troutalevins post-hatch (at 5.0 mg/L DO), extended the spawning period ofburbot (at 6.0 mg/L DO), and depressed feeding rates and loweredsurvival of the mayfly Baetis tricaudatus (at 5 mg/L DO).As a result of recommendations from this integrated program of rivermonitoring, modelling and experimentation, effluent BOD loading has beenreduced to the Athabasca and Wapiti rivers and the provincial DOguideline for protection of aquatic life has been increased from 5.0 to6.5 mg/L. [ABSTRACT FROM AUTHOR]

Tailings ponds in northeastern Alberta, Canada contain massive amounts of oil sands process water (OSPW) that cannot currently be released due to the toxicity of some components. Limited space and the need for reclamation of oil sands operation sites will necessitate the release of OSPW in the near future. Knowledge of the composition and toxicity of OSPW is lacking yet is crucial for both risk assessment and management planning. This study examines chronic toxicity of a mixture of OSPW components sodium naphthenate and naphthenic acid (NA) to nymphs of the mayfly Hexagenia spp. in control and polycyclic aromatic hydrocarbons (PAH)-spiked sediment treatments. The objective of this study was to determine whether the addition of the PAH-spiked sediment significantly contributed to or masked responses of these sensitive mayflies to mixtures of NA. Mean survival in nymphs exposed to NA and PAH-spiked sediment treatments was reduced by 48% compared to those exposed to the NA mixture alone. Lethal responses were observed in all of the PAH-spiked sediment treatments. However, within PAH-spiked and control sediment treatments, there was no significant difference in nymph survival due to NA concentration, indicating that changes in survivorship were predominantly a reflection of increased mortality associated with sediment PAHs and not to the NA mixture treatment. Sublethal effects on body segment ratios suggest that mayflies exposed to NA and PAH-spiked sediment, as well as those exposed to the highest NA concentration tested (1 mg/L) and control sediment, made developmental trade-offs in order to emerge faster and escape a stressful environment. These results reveal that the release of OSPW to the surrounding environment could cause a reduction in mayfly populations. Mayflies provide ecosystem services and are an important food source for higher trophic levels in both the aquatic and terrestrial communities. [ABSTRACT FROM AUTHOR]

Since 1997, sediment metal concentrations have been monitored in the Alberta Oil Sands Region (AOSR) of the Lower Athabasca River by the Regional Aquatics Monitoring Program (RAMP; 1997-2002), the Joint Oil Sands Monitoring Program (JOSM; 2012-2014), and the Oil Sands Monitoring Program (OSM; 2015-present). However, it has remained difficult to differentiate industrial sources from natural sources and quantify the extent of pollution due to inadequate knowledge of predevelopment reference conditions. Here, baselines were constructed using predevelopment (i.e., pre-1967) sediment concentrations of US EPA priority pollutants (Be, Cr, Cu, Ni, Pb) and V, an element elevated in bitumen and associated waste materials, normalized to Al concentration in cores from floodplain and upland lakes within the AOSR to characterize the natural range of variability. The Lower Athabasca River sediment metal monitoring data were examined in the context of the predevelopment baselines. Most metals are below the threshold for minimal enrichment (<1.5x baseline) except for chromium (up to 4.8x) in some RAMP samples. The predevelopment baselines for sediment metal concentrations will be of particular importance as the oil sands industry potentially shifts from a no-release policy to the treatment and release of oil sands process waters directly to the Lower Athabasca River.