Development of a total dissolved solids (TDS) chronic effects benchmark for a northern Canadian lake.

Laboratory chronic toxicity tests with plankton, benthos, and fish early life stages were conducted with total dissolved solids (TDS) at an ionic composition specific to Snap Lake (Northwest Territories, Canada), which receives treated effluent from the Snap Lake Diamond Mine. Snap Lake TDS composition has remained consistent from 2007 to 2014 and is expected to remain unchanged through the life of the mine: Cl (45%-47%), Ca (20%-21%), Na (10%-11%), sulfate (9%); carbonate (5%-7%), nitrate (4%), Mg (2%-3%), and minor contributions from K and fluoride. The TDS concentrations that resulted in negligible effects (i.e., 10% or 20% effect concentrations) to taxa representative of resident biota ranged from greater than 1100 to greater than 2200 mg/L, with the exception of a 21% effect concentration of 990 mg/L for 1 of 2 early life stage fish dry fertilization tests (wet fertilization results were >1480 mg/L). A conservative, site-specific, chronic effects benchmark for Snap Lake TDS of 1000 mg/L was derived, below the lowest negligible effect concentration for the most sensitive resident taxon tested, the cladoceran, Daphnia magna (>1100 mg/L). Cladocerans typically only constitute a few percent of the zooplankton community and biomass in Snap Lake; other plankton effect concentrations ranged from greater than 1330 to greater than 1510 mg/L. Chironomids, representative of the lake benthos, were not affected by greater than 1380 mg/L TDS. Early life stage tests with 3 fish species resulted in 10% to 20% effect concentrations ranging from greater than 1410 to greater than 2200 mg/L. The testing undertaken is generally applicable to northern freshwaters, and the concept can readily be adapted to other freshwaters either for TDS where ionic composition does not change or for major ionic components, where TDS composition does change.

Effect of Total Dissolved Solids on Fertilization and Development of Two Salmonid Species.

Some studies have shown that the early life stages of salmonids are particularly sensitive to elevated concentrations of total dissolved solids (TDS). We evaluated the effect of TDS released in treated effluent into Snap Lake (Northwest Territories, Canada) by the Snap Lake Diamond Mine on two salmonids native to Snap Lake: Salvenius namaycush (lake trout) and Thymallus arcticus (Arctic grayling). Exposures encompassed the embryo-alevin-fry early life stages and extended to 142 days for lake trout and 69 days for Arctic grayling. Such extended testing is uncommon with these two species. Two exposures were conducted with each species, one initiated prior to fertilization, and the other subsequent to fertilization. Fertilization, survival, and growth were not adversely affected for either species by TDS at concentrations >1400 mg/L, with the exception of survival of lake trout, which produced an LC20 of 991 mg/L in one test, and >1484 mg/L in the second test. For the specific TDS composition tested, which was dominated by chloride (45 %-47 %) and calcium (20 %-21 %), the early life stages of these two fish species were relatively insensitive. Although some authors have suggested lower TDS regulatory limits for salmonid early life stages, our study indicates that this is not necessary, at least for these two fish species and for the specific ionic composition tested.

Development of a fluoride chronic effects benchmark for aquatic life in freshwater.

Canada has an interim water-quality guideline for fluoride for protection of freshwater aquatic life that dates from 2002, and 1 Canadian province has a different interim water-quality guideline for fluoride that dates to 1995. The United States does not have a national benchmark for fluoride in freshwater, and only 1 US state has such a benchmark. There are no other national or regional benchmarks for fluoride chronic toxicity in freshwater. In the present study, available data on the acute and chronic toxicity of fluoride to freshwater aquatic life were compiled and reviewed. Acute toxicity was reported to occur at concentrations ranging from 11.5 to >800 mg/L fluoride (F(-) ). The majority of chronic effects occur at concentrations between 1.8 mg/L and 195 mg/L. A total of 10 chronic studies representing 16 species (5 fish, 7 invertebrates, and 4 algae/aquatic plants) were used to derive a chronic effects benchmark of 1.94 mg/L F(-) , applying the species sensitivity distribution approach.

Development of a strontium chronic effects benchmark for aquatic life in freshwater.

There are no national water-quality guidelines for strontium for the protection of freshwater aquatic life in North America or elsewhere. Available data on the acute and chronic toxicity of strontium to freshwater aquatic life were compiled and reviewed. Acute toxicity was reported to occur at concentrations ranging from 75 mg/L to 15 000 mg/L. The majority of chronic effects occurred at concentrations above 11 mg/L; however, calculation of a representative benchmark was confounded by results from 4 studies indicating that chronic effects occurred at lower concentrations than all other studies, in 2 cases below background concentrations reported for US and European streams. Two of these studies, including 1 reporting effects below background concentrations, were repeated and found not to be reproducible; chronic effects occurred at considerably higher strontium concentrations than in the original studies. Studies with narrow-mouthed toad and goldfish were not repeated; both studies reported chronic effects below background concentrations, and both studies had been conducted by the authors of 1 of the 2 studies that were repeated and shown to be nonreproducible. Studies by these authors (3 of the 4 confounding studies), conducted over 30 yr ago, lacked detail in reporting of methods and results. It is thus likely that repeating the toad and goldfish studies would also have resulted in a higher strontium effects concentration. A strontium chronic effects benchmark of 10.7 mg/L that incorporates the results of additional testing summarized in the present study is proposed for freshwater environments.

Incorporation of 28-d Leptocheirus plumulosus toxicity data in a sediment weight-of-evidence framework.

A series of side-by-side trials were conducted to evaluate the variability of 28-d Leptocheirus plumulosus amphipod toxicity test data using existing and modified test protocols. One modification included examination of the influence of press-sieving on the sediment chemistry and the toxicity data. Press-sieving sediment did not reduce the variability in the toxicity data and also contributed uncertainty to the chemistry data. The second modification involved determining the sex of surviving adult amphipods so that the reproduction data could be measured as offspring/surviving female instead of only as offspring/surviving amphipod. Normalizing reproductive output to the number of adult females was ineffective in reducing the variability. The data from sediment toxicity tests are often interpreted in the context of 20% reductions and/or statistically significant reductions relative to negative controls. High inter-replicate variability makes default application of these decision criteria to the 28-d L. plumulosus toxicity test inappropriate regardless of whether or not samples are press-sieved or the sex of surviving amphipods is determined. This is not to say that the 28-d L. plumulosus toxicity test has no value for a sediment WOE: it provides long-term chronic data that may not otherwise be available. However, test-specific decision criteria must be established as part of the problem formulation based on the overall management goal, the availability of other lines of evidence (other toxicity tests as well as other types of data) and the desired level of certainty with respect to decision-making.

The importance of benthos in weight of evidence sediment assessments--a case study.

Sediment quality in a Texas reservoir subject to point and non-point sources of contaminants was assessed using the Sediment Quality Triad weight of evidence approach. Fifteen stations were sampled plus a reference station which, unfortunately, comprised a different habitat type than the other 15 stations. Accordingly, standard comparisons between reference and exposed stations were inappropriate. Interpretation of potential relationships between benthic community structure and sediment-associated contaminants was also confounded by differences in habitat-related characteristics (e.g., water depth and total organic carbon) within the reservoir. Multivariate analyses of the benthic community identified two station groupings separated primarily by habitat-related differences rather than contaminant-related toxicity. Laboratory toxicity tests and chemical analyses, including measures of bioavailability, did not differ consistently between the two community-based station groupings, indicating that toxicity resulting from chemical contamination was not the primary factor in observed community structure in the reservoir, although alterations to the benthos due to chemical contamination could not be ruled out in the absence of an appropriate reference comparison. Appropriately giving highest weight to resident benthic community structure, followed by the results of laboratory toxicity tests, then chemical analyses, provided the best possible assessment of chemical pollution in the absence of a suitable reference comparison. The alternative approach of relying on only sediment toxicity and chemistry data, without considering the full weight of evidence, would have provided misleading information.

Toxicity of 1,4-dichlorobenzene in sediments to juvenile polychaete worms.

Investigation of sediment contamination associated with a marine sewage outfall in Victoria (BC, Canada) found elevated concentrations of 1,4-dichlorobenzene (1,4-DCB). Juvenile polychaete worm (Neanthes) growth was significantly reduced at or near the outfall, roughly corresponding to elevated 1,4-DCB concentrations. There are few data on 1,4-DCB toxicity to marine organisms and no published literature on its toxicity to benthic marine organisms. To determine whether reduced polychaete growth (measured as dry weight) was due to 1,4-DCB exposure, a laboratory investigation was conducted. Uncontaminated marine sediment was spiked with 1,4-DCB and juvenile Neanthes were exposed in 20-d sublethal toxicity tests. There were no adverse effects on survival at any test concentration; mean survival was 80-100%. Statistically significant decreases in average dry weight only occurred at the highest 1,4-DCB concentration (19,900 microg/kg, dry weight); this represented a 1,4-DCB concentration more than 10 times higher than previously measured at the outfall (1,710 microg/kg, dry weight). There were no adverse effects on survival or dry weight at the range of concentrations previously measured in sediments from the vicinity of the outfall.