A comparison of chronic cadmium effects on Hyalella azteca in effluent‐dominated stream mesocosms to similar laboratory exposures in effluent and reconstituted hard water

Abstract

Laboratory single-species toxicity tests are used to assess the effects of contaminants on aquatic biota. Questions remain as to how accurately these toxicity tests predict site-specific bioavailability and chronic effects of metals, particularly in streams that are effluent-dominated or dependent on effluent discharge for flow. Concurrent 42-d Hyalella azteca exposures were performed with cadmium and final treated municipal effluent in the laboratory and at the University of North Texas Stream Research Facility (Denton, TX, USA), a series of outdoor lotic mesocosms. An additional 42-d laboratory test was conducted with H. azteca to evaluate Cd toxicity in reconstituted hard water (RHW). Endpoints included Cd body burden, survival, growth, and reproduction. Calculated average bioaccumulation factors were: 2,581 (stream mesocosm test) < 3,626 (laboratory effluent) < 7,382 (laboratory RHW). The 42-d survival lowest-observed-effect concentrations (LOECs) were 0.94, 4.53, and 22.97 microg/L for the laboratory RHW, laboratory effluent, and stream mesocosm exposures, respectively. Baseline growth (dry wt) and reproduction (young female(-1)) among the three exposures followed the relationship: Stream mesocosms > laboratory effluent > laboratory RHW. Differences among response variables in the three tests likely resulted from increased food sources and decreased Cd bioavailability in lotic mesocosms. Our results demonstrate that laboratory toxicity tests may overestimate chronic toxicity responses of H. azteca to Cd in effluent-dominated streams.

Influence of nitrogen and phosphorus concentrations and ratios on Lemna gibba growth responses to triclosan in laboratory and stream mesocosm experiments

“…) from 50-L stock carboys into mixing tanks located at the head of each experimental stream, which was consistent with previous lotic mesocosm studies [50,51]. Nitrogen and P concentrations were sampled approximately every 3 d (6 times in 14 d) in the mixing tanks and pools.…”

“…These flow-through pools received the outflow of the stream channels and maintained an approximate volume of 550 L. The pools were covered by 30% shade cloth to approximate riparian canopies and ambient photosynthetically active radiation of lower order stream (1,000-1,200 mE; R.S. King, unpublished data), and reduce variability of sunlight across experimental units [50,51].…”

Environmental Risks of Inorganic Metals and Metalloids: A Continuing, Evolving Scientific Odyssey

“…At a given dissolved metals concentration, aqueous metals are often (Stanley et al 2005), but not always, more toxic in the laboratory compared to the field because laboratory dilution water does not include metal-binding ligands found in natural waters (this may be less the case for dilution involving soils, e .g., Strandberg et al [2006]). The Water Effect Ratio (WER; USEPA 2001) addresses this reality by conducting duplicate testing: comparing field and laboratory water-the former is generally the most toxic.…”

Effect of diet quality on chronic toxicity of aqueous lead to the amphipodHyalella azteca

“…The DT diet also caused small increases in DOC concentrations relative to the other diets (Table 1), which presumably increased the formation of Pb-organic complexes. Some of these same mechanisms may have contributed to the reduced bioavailability and toxicity of cadmium to Hyalella in nutrient-rich stream waters, compared with tests conducted with low-nutrient laboratory waters [19]. However, differences in filtered Pb and DOC concentrations among our tests with different diets should not affect our comparisons of Pb sensitivity among tests, because differences in filterable Pb concentrations would be reflected in modeled effect concentrations, and differences Pb complexation with DOC would be modeled by the BLM.…”