[en] Extensive sublethal damage assessments were carried out on Pacific herring larvae following the Exxon Valdez oil spill. Egg masses were collected from oiled and non-oiled areas during 1989 to 1991, and incubated to hatch. The hatched larvae were evaluated for morphological deformities, cytogenetic abnormalities, and histopathological lesions. In 1989, herring larvae from the oiled areas showed high incidence of morphological deformities and cytogenetic abnormalities compared to larvae from non-oiled areas. There was no evidence of histopathological lesions. Identical assessments in 1990 and 1991 revealed no detectable oil-related developmental and genetic effects. In contrast, there was a marked decrease in survival, suggesting that that genetic damage at heavily oiled stations combined with severe morphological malformations mitigated against survival through the stressful larval period. 40 refs., 1 tab.,8 figs

[en] The occurrence of viral hemorrhagic septicemia virus (VHSV) in Pacific herring exposed to crude oil, and encountered after an oil spill, was discussed. Adult Pacific herring of unknown status with regard to infection by VHSV were captured from the wild and exposed to weathered crude oil for 16 to 18 days. Total polynuclear aromatic hydrocarbon (TPAH) concentration in tissue, VHSV prevalence, and mortality were correlated with dosage. Results showed that histopathologic lesions significantly correlated with TPAH concentration and prevalence of VHSV, however, gender or length of exposure did not. Increased hepatocellular necrosis, splenic thrombosis and decreased inflammation of the liver were the most significant lesions observed. 30 refs., 3 tabs., 4 figs

[en] A laboratory study was conducted to determine the assimilation efficiency of methyl[²⁰³Hg]mercuric chloride (CH₃²⁰³HgCl) from food by crayfish (Orconectes virilis) and the subsequent depuration rate of the assimilated CH₃²⁰³HgCl. Mean assimilation efficiency of CH₃²⁰³HgCl) from tadpoles was 96%. For the majority of the 50 experimental crayfish (three size-classes of males and females designated small, medium, and large), no significant loss of assimilated CH₃²⁰³HgCl was evident over the 166-day monitoring period. When a significant loss of CH₃²⁰³HgCl was detected, observed half-lives usually fell within 1000-2000 days (3-5 years). The high assimilation efficiency and slow depuration rate imply that crayfish can biomagnify CH₃Hg from their food. (author). 49 refs., 4 tabs., 3 figs

[en] We report here the first induction of gynogenesis in esocid fish by UV irradiation and heat shock. Optimal dosage of sperm UV irradiation was in the range of 1440-2160 J/m². Eggs fertilized with irradiated sperm at such dosages and not heat shocked yielded 100% abnormal larvae with the fertilization rate at 48.3 ± 8.4% (mean ± SD). There were no significant differences in survival to the eyed stage under the heat shock conditions tested (5-30 min post-fertilization for 5-30 min at 26-30^oC). Gynogens were induced in most of the groups with hatching rates at 0.2-3.3%. Optimal conditions for gynogenetic induction of muskellunge (Esox masquinongy) were the application of 30^oC for 8-10 min beginning 20 min post-fertilization, chromosome preparation, silver staining for nucleolar organizer regions, and flow cytometry measurement of the nuclear DNA content using eyed-stage embryos and larvae. Haploids hatched but died within 1 week. (author). 27 refs., 1 tab., 9 figs

[en] Radiotracer experiments were carried out in 20 enclosures located in two lakes at the Experimental Lakes Area (ELA), northwestern Ontario, to study pathways of trace metal removal from the water column of shallow lakes. Two removal mechanisms were characterized: (1) sorption to and subsequent transport with falling particles and (2) direct adsorption to surface sediments. Our approach was to measure independently the kinetics of radiotracer sorption, fluxes and concentrations for particles, particle settling velocities, and the equivalent stagnant boundary film. Our radiotracer results enabled us to test the sensitivity of the tracer removal rates on these rate-determining processes using a numerical transport model. Acid titrations of whole ecosystems revealed that some trace metals (e.g. Mn, Co and Zn) can diffuse back to the water column as the pH is lowered from 6.5 to 4,8 after 18 d, while others remain tightly bound, (e.g. Sn, Fe, Se, Cr, Ag, and Hg isotopes). Subsequent CaCO₃ additions to bring back the pH to its original value restored the initial removal conditions for acid-sensitive radiotracers, indicating that the pH sensitivity is reversible. Transport parameters for particle-related pathways or diffusive pathways across the sediment-water interface obtained from our enclosure experiments were used to predict the removal rats of particle-reactive ⁶⁰Co and the diffusive pathway tracer ¹³⁴Cs observed in earlier experiments where radiotracers were added to whole lakes or to larger enclosures. (Author) (19 refs., 9 tabs., 11 figs.)

[en] The effects of elevated carbon dioxide on the chemistry and subsequent response of stream microorganisms growing on leaf litter of three riparian tree species (quaking aspen, white willow and sugar maple) were studied. Results showed that the effects were species-specific, i.e. aspen leaves contained high concentrations of lignin, maple leafs contained higher concentrations of soluble phenolic compounds and willow leaves contained higher concentrations of carbohydrate-bound condensed tannins. Initially, the higher concentrations of soluble phenolic compounds in maple leaves were rapidly leached in stream water, but overall, the impact of altered leaf chemistry on riparian trees grown under elevated carbon dioxide was clearly variable; no strongly suppressed microbial activity during stream incubation was observed. Any evidence of suppression observed, was species-specific. 49 refs., 2 tabs., 3 figs

[en] An overview of a three-phase study to evaluate the range of biological, biochemical and chemical methodologies to detect and assess chronic sublethal biological impacts in the vicinity of long-duration activities in the Gulf of Mexico associated with oil and gas exploration and production, was provided. The basic program comprises four activities stretching over a two-year period, and is designed to detect nearfield impacts and contaminant gradients extending out of each of three sites. Sampling design includes a radial pattern with stations at intervals up to 3000 meters distant from the platform. The design employs a dose-response model to test the hypothesis that biological, biochemical and chemical variations are due to platform-derived contaminants. Detailed analysis of the contaminants includes analysis of sediments, pore waters and biological tissue, and assessment of community health based on life history and reproduction studies. 57 refs., 9 tabs., 5 figs

[en] The Alaska Department of Fish and Game (ADF and G) investigated the effects of oil on pink salmon eggs incubating in streams and intertidal zones of Prince William Sound following the spill from the Exxon Valdez in 1989. The investigation concluded that mortality in embryos was higher in oiled than non-oiled streams. These authors question the accuracy of the ADF and G's conclusions, claiming that the sampling by the ADF and G took place shortly after spawning completion, thus failing to account for the shock mortality to which embryos are vulnerable for a period of some 20 days after fertilization. Analysis of a subset of ADF and G data showed that sampling shock was a major source of embryo mortality, hence the reported differences in mortality were likely the result of sampling protocol and unequal distribution of sampling effort over time between oiled and non-oiled streams. The authors further claim that compensating for sample timing removed all statistical evidence for an oiling effect in the data subset. These results also help to explain why differences in mortality continued after the oil left the streams, and why differences occurred in those areas upstream of high tide, beyond the physical presence of oil. 21 refs., 3 tabs., 3 figs

[en] The changes in algal and invertebrate communities resulting from the formation and operation of two water reservoirs in Saskatchewan were studied. Lake Diefenbaker was created in 1967 by flooding a river valley, whereas Buffalo Pound Lake was formed in 1952 by impounding the outflow of a shallow lake. Both lakes were studied using a multiple-indicator paleolimnological approach. Algal community composition is similar between the two reservoirs and biomass is distributed evenly among green algae, diatoms, chrysophyte, dinoflagellates, cryptophytes and cyanobacteria. Crustacean zooplankton are also similar between the two reservoirs. Sediment core was retrieved from both reservoirs and analyzed. It was shown that differences in reservoir formation and hydrological regime resulted in distinct patterns of aquatic community change even though the local geology, vegetation, soils, land use and climate were similar. Comparison of paleoecological records from both lakes have made it possible to compare the mechanisms that regulate community ontogeny and production following formation of reservoirs by novo flooding and lake inundation. It was determined that reservoir ontogeny does not inevitably lead to eutrophication. Fossil records have shown that oligotrophication can result from increased lake level stability, reduced erosion and complex ecological interactions among phytoplankton, grazers, and macrophyte populations. 49 refs., 2 tabs., 6 figs

[en] Adult Pacific herring collected from Prince William Sound waters in 1992, three years after the Exxon Valdez oil spill were examined for evidence of abnormalities, especially in the area of reproductive success and histopathology. Results indicated that the sample population exhibited a lower hatching percentage and produced fewer morphologically normal larvae than fish from a previously unoiled site. Differences in microscopic tissue lesions also have been observed, but considered only marginally significant. Macrophage aggregates in the spleen, liver and kidney were greater in fish from previously oiled sites, especially in males, however, these elevated scores were attributed to age rather than exposure to the oil spill. Splenic granulomatous inflammation and severe congestion were interpreted as good bioindicators for abnormal larval progeny. The overall conclusion was that although histopathological damage did not provide conclusive evidence, the decreased reproductive success of fish from oiled sites suggested that the site's oiling history contributed to reproductive impairment. 21 refs., 3 tabs., 1 fig