Concentrations of methylmercury in game fish from many interior lakes Voyageurs National Park (MN, U.S.A.) substantially exceed criteria for the protection human health. We assessed importance atmospheric and geologic sources mercury to watersheds within identified ecosystem factors associated with variation contamination lacustrine food webs. Geologic were small, based on analyses underlying bedrock C-horizon soils, nearly all O- A-horizon soils was derived deposition. Analyses dated...

We examined effects of dietary methylmercury (MeHg) on reproduction fathead minnows (Pimephales promelas). Juvenile fish were fed one four diets until sexual maturity (phase 1): a control diet (0.06 μg Hg g-1 dry weight) and three contaminated with MeHg at 0.88 (low), 4.11 (medium), 8.46 weight (high). At maturity, male female paired, again the diets, allowed to reproduce 2). To assess during gametogenesis, some phase 2 that differed from those 1. Spawning success pairs same phases 1 was 75%...

Recent laboratory studies have demonstrated that environmentally realistic concentrations of dietary methylmercury can impair reproduction fish. To evaluate relations between reproductive success and biomarkers exposure, we fed juvenile fathead minnows (Pimephales promelas) one three diets contaminated with methylmercury: 0.06 (control), 0.87 (low), 3.93 (medium) μg Hg g-1 dry weight. At sexual maturity, fish were paired, allowed to reproduce, then analyzed for total mercury, plasma...

Threshold concentrations associated with adverse effects of dietary exposure to methylmercury (MeHg) were derived from published results laboratory studies on a variety fish species. Adverse related mortality uncommon, whereas growth occurred only at MeHg exceeding 2.5 µg g(-1) wet weight. behavior had wide range effective concentrations, but generally above 0.5 In contrast, reproduction and other subclinical endpoints that much lower (<0.2 wt). Field lack information exposure, yet available...

The flood-pulse concept (FPC) states that annual inundation is the principal force responsible for productivity and biotic interactions in river-floodplain systems. Somatic growth one component of production, we hypothesized that, if FPC applies, fishes use moving littoral zone should differ among years with differing flood pattern, whereas nonlittoral would show no such response. Growth largemouth bass (Micropterus salmoides) bluegill (Lepomis macrochirus), species exploit resources,...

Methylmercury (MeHg) is a known neurotoxic agent, but the mechanisms by which MeHg may act on reproductive pathways are relatively unknown. Several studies have indicated potential changes in hormone levels as well declines vertebrates with increasing dietary exposure.The purpose of this study was to identify alterations gene expression associated exposure, specifically those previously observed reproduction and biomarkers. Fathead minnows, Pimephales promelas, were fed one three diets that...

Development of the early life stages fishes can be affected adversely by methylmercury (MeHg) transferred from maternal parent to developing egg. We examined transfer MeHg eggs fathead minnows Pimephales promelas and evaluated role burden versus that in dietduring oogenesis on egg concentrations. Juvenile fish were fed one four diets until sexual maturity (phase 1): A control diet (0.06 microg Hg g(-1) dry weight) three contaminated with at 0.88 (low), 4.11 (medium), 8.46 (high). At...

Abstract Previous studies of toxicant effects on fish foraging behavior and predator-prey interactions have taken a strictly empirical approach. The most common observation altered feeding was cessation or reduction in the amount artificial food consumed. Changes number live prey attacked captured, latency to feed capture efficiency also been documented. Predator-prey tests placed major emphasis ability escape predation. Several different test systems, as well model ecosystems, used. It is...

We examined the effects of dietary methylmercury on production testosterone in and reproductive behavior male fish. Juvenile fathead minnows (Pimephales promelas) were fed one three diets contaminated with at concentrations 0.06 (control), 0.87 (low), 3.93 (medium) microg Hg/g dry weight. After attaining sexual maturity, fish paired for mating, behaviors recorded. Carcass mercury plasma also measured. No significant differences found amount time spent by nest preparation or courtship...

This study describes the use of a 15 000 gene microarray developed for toxicological model species, Pimephales promelas , in investigating impact acute and chronic methylmercury exposures male gonad liver tissues. The results show significant differences individual genes that were differentially expressed response to each treatment. In liver, total 650 exhibited significantly ( P &lt; 0·05) altered expression with greater than two‐fold from controls exposure 267 exposure. A majority these...

Summer habitat use and relative abundances of different size classes yellow perch (Perca flavescens) were determined using gill nets set in the main basin, deep bays, shallow bays a lake. Niche overlap indices used to quantify resource patterns. Size spatially segregated into habitats, but not depths within type. Segregation sexes at was observed with females occupying warm, areas, whereas males more common cool, water. Formation an anoxic hypolimnion restricted epilimnion late summer,...

We assessed the utility of larval burrowing dragonflies (Odonata: Anisoptera: Gomphidae) as biosentinels methylmercury (MeHg) contamination. Gomphids were most abundant family sampled during 2008-2010 from 17 lakes in four national parks northwestern Laurentian Great Lakes region. Ten species gomphids sampled; 13 contained 3 or more species, and 2 Gomphus co-occurred 12 lakes. Most total Hg (THg) whole, late-instar larvae was MeHg, with mean percent MeHg exceeding 60% 16 Mean a given varied...

Methylmercury is a bioaccumulative contaminant that biomagnifies in aquatic food webs and adversely affects the health of freshwater fish. Previous studies have documented an inverse relationship between fish condition concentration mercury However, this may be result slow-growing accumulating large amounts methylmercury rather than effects on growth. An evaluation was conducted among condition, growth, northern pike Esox lucius from 26 lakes western region Laurentian Great Lakes...

Standardized test protocols for assessing chemical hazards to aquatic organisms inadequately consider behavioral effects of toxicants; yet, behaving abnormally in the wild have reduced growth, fitness, and high mortality. We determined chronic cadmium (0, 30, 60, 120, 240 μg∙L −1 ) on juvenile bluegill (Lepomis macrochirus) foraging behavior growth rates functional response experiments, each using different sized Daphnia as prey. Bluegill consumption rate increased with prey density....

The effects of four copper concentrations (5 [control], 31, 180, 1710 μg L −1 ) on bluegill (Lepomis macrochirus) foraging behavior were examined with two separate experiments; one experiment assessing the reaction distance to sizes untreated zooplankton and functional response (five tests) treated invertebrate prey. Prey used in these experiments were: Daphnia pulex, D. magna (Cladocera), Hyalella azteca (Amphipoda), Enallagma sp. (Zygoptera). Copper had no effect fish zooplankton. There...