Development of a short-term in situ caging methodology to assess long-term effects of industrial and municipal discharges on salmon smolts.

Trial experiments to develop an in situ method for determining effects of short-term exposure to contaminants on salmon during the sensitive smolt stage were carried out. Wild Atlantic salmon (Salmo salar) smolts were caged at various estuarine locations in northeast New Brunswick, Canada at different levels of anthropogenic impact in 2000 and 2001. Survival, growth (weight and K), and feeding (delta(13)C and delta(15)N) parameters were measured following summer grow-out at a hatchery. A summary of distributions of the four parameters indicated that smolts caged at locations receiving lower levels of industrial and municipal discharges feed and grow better than those caged at sites receiving higher levels. The findings, however, were not repeatable between the 2 years studied. The observed inconsistency between years may be a consequence of the relatively low concentrations of alkylphenolic contaminants (putative causative agents) and overall steroidogenic potency in river water at the time of caging. Differences in temperature and salinity from 2000 to 2001 may have further confounded comparisons across treatments and between years. In future studies, caging in closer proximity to industrial and municipal discharges or in systems with higher concentrations of waterborne contaminants or impoundments would help further the assessment and applicability of this methodology and allow a more robust comparison of smolt feeding and growth among reference and exposure sites.

Mouthpart deformities and community composition of Chironomidae (Diptera) larvae downstream of metal mines in New Brunswick, Canada.

The effect of metal enrichment on chironomid communities was examined in streams receiving mine drainage from metal mining operations in New Brunswick, Canada. At five sites receiving mine drainage, metal concentrations were significantly (p < 0.05) elevated in water (Zn), periphyton (Cd, Co, Cu, and Zn), and chironomid tissue (Cu, Cd, and Zn) relative to five paired reference locations. Metal concentrations in chironomid larvae were significantly correlated with concentrations in both water and periphyton. Chironomid communities were severely affected at sites receiving mine drainage as demonstrated by reduced genera richness and altered community composition. Sites receiving mine drainage exhibited an increased abundance of metal-tolerant Orthocladiinae and a reduced abundance of metal-sensitive Tanytarsini relative to reference sites. The incidence of mentum deformities was significantly elevated at sites receiving mine drainage (1.43 +/- 0.24%), with the mean percentage approaching a doubling of that observed at reference sites (0.79 +/- 0.22%). Trace metal concentrations at mine-associated streams in New Brunswick significantly affected the benthic community and have the potential to alter the structure and function of these aquatic ecosystems.

Accumulation and depuration of 2,3,7,8-tetrachlorodibenzofuran and octachlorodibenzo-p-dioxin by caddisfly larvae (Hydropsyche bidens (ross)) in miniature laboratory streams.

The uptake and depuration kinetics of [3 H]-2,3,7,8-tetrachlorodibenzofuran ([3 H]TCDF) and [14 C]-1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin ([14 C]OCDD) were studied in the filter-feeding caddisfly Hydropsyche bidens (Ross), using artificial laboratory streams. Dietary and water-borne routes of uptake were compared. Biomagnification factors (BMFs) ranged from 0.003 to 0.08 for TCDF and 0.003 to 0.007 for OCDD. The BMFs were significantly lower at higher exposure concentrations and for an earlier larval instar. Assimilation efficiencies for TCDF and OCDD were estimated to be 9.2 and 4.9%, respectively, based on an estimated feeding rate of 0.09 g/g body weight/d. Depuration of TCDF followed first-order kinetics with t1/2 ≥ 28 d. Depuration of OCDD was biphasic with an initial rapid t1/2 of <2.9 d, followed by a slow rate of depuration. The initial rapid rate of depuration of OCDD could be explained by the loss of the gut contents. Depuration rates of TCDF and OCDD were not affected by a 33% increase in stream velocity from 16 to 24 cm/s or by changing contaminant concentrations in food. Nonfeeding caddisfly pupae accumulated approximately one tenth of the concentration of TCDF and OCDD that was accumulated by filter-feeding larvae under the same conditions. For the nonfeeding pupae, 10-d lipid-normalized bioconcentration factors for TCDF (1.0 3 105 ) were 10-fold higher than for OCDD (9.2 × 103 ).