TOTAL SOLUTES LOADS AND GEOCHEMICAL YIELDS IN THE SASKATCHEWAN RIVER BASIN1

ABSTRACT: River solute loads have seldom been measured in very large, complex drainage basins, nor have the methods of calculating loads been critically examined. For sites in the Saskatchewan River Basin, Canada, rating curves were poor predictors of solute loads because correlations between discharge and total solutes concentration were weak (R² < 0.05 in most cases) and suffered from hysteresis. In contrast, the interval method produced reliable estimates in all seasons and sites tested, and was little affected by sampling schedule. The limit of precision (SE) for estimates of mean annual or seasonal solute load was 10–15 percent of the mean (5 percent in very small basins), reached with 10 years or more of data. Two-thirds or more of total annual solute load was transported during the open-water season, but the proportion carried during winter increased from 8 percent to 34 percent from the upstream to the downstream end of the basin, due to reservoirs retaining and mixing water. Annual loads of total solutes varied from 6.2 × 10⁴ tonnes in foothills tributaries to almost 4.0 × 10⁶ tonnes in the Saskatchewan River near the mouth. But, on an areal basis, the mountain and foothills region was the dominant solute source, producing 43–97 tonnes/km²/yr, compared with only 3–22 tonnes/km²/yr for prairie rivers. This difference is a consequence of greater rainfall and, hence, more rapid erosion in the mountains.     

Detecting acid precipitation impacts on lake water quality

The United States Environmental Protection Agency is planning to expand its long-term monitoring of lakes that are sensitive to acid deposition effects. Effective use of resources will require a careful definition of the statistical objectives of monitoring, a network design which balances spatial and temporal coverage, and a sound approach to data analysis. This study examines the monitoring objective of detecting trends in water quality for individual lakes and small groups of lakes. Appropriate methods of trend analysis are suggested, and the power of trend detection under seasonal (quarterly) sampling is compared to that of annual sampling. The effects of both temporal and spatial correlation on trend detection ability are described.     

Maintenance of intact sediment box cores as laboratory mesocosms.

Mesocosms consisting of physically and biologically intact segments of natural communities are an ideal compromise between single species tests and ecosystem experiments in the assessment of sediment contamination. Therefore, large intact sediment cores, as mesocosms with naturally co-adapted communities, would allow sediment contamination to be assessed using the replicability and statistical power of laboratory techniques, while retaining much of the ecological realism of field studies. This study investigates the collection and maintenance of such cores, collected from an unimpacted site in Lake Erie. It demonstrates that box cores containing relatively undisturbed freshwater sediments can be brought back to the laboratory and maintained for up to 8 weeks with little change in the resident benthic fauna. Feeding the systems is not required, nor is it deleterious to the indigenous fauna.     

Inactivation of enzyme laccase and role of cosubstrate oxygen in enzymatic removal of phenol from water.

Research was conducted to evaluate the potential use of laccase and its susceptibility to inactivation in an alternative enzyme-based treatment technology to remove parent phenol from buffered distilled water. Enzymatic oxidative polymerization of phenol with laccase was carried out in continuously stirred batch reactors. The reaction products were insoluble polymers, which precipitated out of the solution once their solubility limits were exceeded. The findings demonstrated that the polymeric products had significant effects on enzyme activity consumption and subsequent phenol removal. Enzyme species present in the reaction vessel were classified into enzyme remaining in the solution (type 1) and enzyme adhering to the precipitate polymers (type 2). Type 1 enzyme was more efficient in removal of phenol from solution compared with type 2. Subsequent filtration enhanced the phenol removal by removing type 2 enzyme adhering to the polymer particles and decelerating enzyme inactivation. The study also investigated the effects of available dissolved oxygen, provided through aeration and hydrogen peroxide addition, on phenol removal. Aeration and hydrogen peroxide addition increased the dissolved oxygen concentration, but had no effect on the progress curve for phenol removal.     

Community social capital and individual functioning in the post‐disaster context

Disasters can have severe and long‐lasting consequences for individuals and communities. While scholarly evidence indicates that access to social support can ameliorate their negative impacts, less understood is whether or not neighbourhood social capital can facilitate recovery. This study uses two waves of survey data—collected before and after a significant flood in Brisbane, Australia, in 2011—to examine the relationship between the severity of the event at the individual and neighbourhood level, access to neighbourhood social capital and individual‐level social support, and functioning in the post‐disaster environment. In line with previous research, the results indicate that the severity of the flood is the most salient predictor of post‐disaster functioning. No evidence was unearthed to show that neighbourhood social capital amassed before the flood leads to better functioning subsequently, but the findings do suggest that individual‐level social support can moderate the effect of flood severity on functioning.     

Plant growth rates and seed size: a re-evaluation

Small-seeded plant species are often reported to have high relative growth rate or RGR. However, because RGR declines as plants grow larger, small-seeded species could achieve higher RGR simply by virtue of their small size. In contrast, size-standardized growth rate or SGR factors out these size effects. Differences in SGR can thus only be due to differences in morphology, allocation, or physiology. We used nonlinear regression to calculate SGR for comparison with RGR for 10 groups of species spanning a wide range of life forms. We found that RGR was negatively correlated with seed mass in nearly all groups, but the relationship between SGR and seed mass was highly variable. We conclude that small-seeded species only sometimes possess additional adaptations for rapid growth over and above their general size advantage.     

Invasive species impacts on ecosystem structure and function: A comparison of the Bay of Quinte, Canada, and Oneida Lake, USA, before and after zebra mussel invasion

As invasion rates of exotic species increase, an ecosystem level understanding of their impacts is imperative for predicting future spread and consequences. We have previously shown that network analyses are powerful tools for understanding the effects of exotic species perturbation on ecosystems. We now use the network analysis approach to compare how the same perturbation affects another ecosystem of similar trophic status. We compared food web characteristics of the Bay of Quinte, Lake Ontario (Canada), to previous research on Oneida Lake, New York (USA) before and after zebra mussel (Dreissena polymorpha) invasion. We used ecological network analysis (ENA) to rigorously quantify ecosystem function through an analysis of direct and indirect food web transfers. We used a social network analysis method, cohesion analysis (CA), to assess ecosystem structure by organizing food web members into subgroups of strongly interacting predators and prey. Together, ENA and CA allowed us to understand how food web structure and function respond simultaneously to perturbation. In general, zebra mussel effects on the Bay of Quinte, when compared to Oneida Lake, were similar in direction, but greater in magnitude. Both systems underwent functional changes involving focused flow through a small number of taxa and increased use of benthic sources of production; additionally, both systems structurally changed with subgroup membership changing considerably (33% in Oneida Lake) or being disrupted entirely (in the Bay of Quinte). However, the response of total ecosystem activity (as measured by carbon flow) differed between both systems, with increasing activity in the Bay of Quinte, and decreasing activity in Oneida Lake. Thus, these analyses revealed parallel effects of zebra mussel invasion in ecosystems of similar trophic status, yet they also suggested that important differences may exist. As exotic species continue to disrupt the structure and function of our native ecosystems, food web network analyses will be useful for understanding their far-reaching effects.