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Don W. Schloesser - One of the best experts on this subject based on the ideXlab platform.

  • Distribution and Abundance of Burrowing Mayflies (Hexagenia spp.) in Lake Erie, 1997–2005
    Journal of Great Lakes Research, 2007
    Co-Authors: Kenneth A. Krieger, Michael T. Bur, Jan J. H. Ciborowski, David R. Barton, Don W. Schloesser
    Abstract:

    Burrowing mayflies (Hexagenia limbata and H. rigida) recolonized sediments of the western basin of Lake Erie in the 1990s following decades of pollution abatement. We predicted that Hexagenia would also disperse eastward or expand from existing localized populations and colonize large regions of the other basins. We sampled zoobenthos in parts of the western and central basins yearly from 1997–2005, along the north shore of the eastern basin in 2001–2002, and throughout the lake in 2004. In the island area of the western basin, Hexagenia was present at densities ≤ 1,278 nymphs/m2 and exhibited higher densities in odd years than even years. By contrast, Hexagenia became more widespread in the central basin from 1997-2000 at densities ≤ 48 nymphs/m2 but was mostly absent from 2001-2005. Nymphs were found along an eastern basin transect at densities≤ 382/m2 in 2001 and 2002. During the 2004 lake-wide survey, Hexagenia was found at 63 of 89 stations situated throughout the western basin (≤ 1,636 nymphs/m2, mean = 195 nymphs/m2, SE = 32, N = 89) but at only 7 of 112 central basin stations, all near the western edge of the basin (≤ 708 nymphs/m2), and was not found in the eastern basin. Hexagenia was found at 2 of 62 stations (≤ 91 nymphs/m2) in harbors, marinas, and tributaries along the south shore of the central basin in 2005. Oxygen depletion at the sediment-water interface and cool temperatures in the hypolimnion are probably the primary factors preventing successful establishment throughout much of the central basin. Hexagenia can be a useful indicator of lake quality where its distribution and abundance are limited by anthropogenic causes.

  • distribution and abundance of burrowing mayflies Hexagenia spp in lake erie 1997 2005
    Journal of Great Lakes Research, 2007
    Co-Authors: Kenneth A. Krieger, Michael T. Bur, Jan J. H. Ciborowski, David R. Barton, Don W. Schloesser
    Abstract:

    Burrowing mayflies (Hexagenia limbata and H. rigida) recolonized sediments of the western basin of Lake Erie in the 1990s following decades of pollution abatement. We predicted that Hexagenia would also disperse eastward or expand from existing localized populations and colonize large regions of the other basins. We sampled zoobenthos in parts of the western and central basins yearly from 1997–2005, along the north shore of the eastern basin in 2001–2002, and throughout the lake in 2004. In the island area of the western basin, Hexagenia was present at densities ≤ 1,278 nymphs/m2 and exhibited higher densities in odd years than even years. By contrast, Hexagenia became more widespread in the central basin from 1997-2000 at densities ≤ 48 nymphs/m2 but was mostly absent from 2001-2005. Nymphs were found along an eastern basin transect at densities≤ 382/m2 in 2001 and 2002. During the 2004 lake-wide survey, Hexagenia was found at 63 of 89 stations situated throughout the western basin (≤ 1,636 nymphs/m2, mean = 195 nymphs/m2, SE = 32, N = 89) but at only 7 of 112 central basin stations, all near the western edge of the basin (≤ 708 nymphs/m2), and was not found in the eastern basin. Hexagenia was found at 2 of 62 stations (≤ 91 nymphs/m2) in harbors, marinas, and tributaries along the south shore of the central basin in 2005. Oxygen depletion at the sediment-water interface and cool temperatures in the hypolimnion are probably the primary factors preventing successful establishment throughout much of the central basin. Hexagenia can be a useful indicator of lake quality where its distribution and abundance are limited by anthropogenic causes.

  • Recruitment of Hexagenia mayfly nymphs in western Lake Erie linked to environmental variability.
    Ecological Applications, 2006
    Co-Authors: Thomas B. Bridgeman, Don W. Schloesser, Ann E. Krause
    Abstract:

    After a 40-year absence caused by pollution and eutrophication, burrowing mayflies (Hexagenia spp.) recolonized western Lake Erie in the mid 1990s as water quality improved. Mayflies are an important food resource for the economically valuable yellow perch fishery and are considered to be major indicator species of the ecological condition of the lake. Since their reappearance, however, mayfly populations have suffered occasional unexplained recruitment failures. In 2002, a failure of fall recruitment followed an unusually warm summer in which western Lake Erie became temporarily stratified, resulting in low dissolved oxygen levels near the lake floor. In the present study, we examined a possible link between Hexagenia recruitment and periods of intermittent stratification for the years 1997- 2002. A simple model was developed using surface temperature, wind speed, and water column data from 2003 to predict stratification. The model was then used to detect episodes of stratification in past years for which water column data are unavailable. Low or undetectable mayfly recruitment occurred in 1997 and 2002, years in which there was frequent or extended stratification between June and September. Highest mayfly reproduction in 2000 corresponded to the fewest stratified periods. These results suggest that even relatively brief periods of stratification can result in loss of larval mayfly recruitment, probably through the effects of hypoxia. A trend toward increasing frequency of hot summers in the Great Lakes region could result in recurrent loss of mayfly larvae in western Lake Erie and other shallow areas in the Great Lakes.

  • Distribution and seasonal abundance of trematode parasites (Trematoda: Allocreadiidae: Crepidostomum spp.) in burrowing-mayfly nymphs (Ephemeroptera: Ephemeridae: Hexagenia spp.) from connecting rivers of the Laurentian Great Lakes
    Hydrobiologia, 2005
    Co-Authors: Don W. Schloesser
    Abstract:

    Burrowing-mayfly nymphs such as Hexagenia spp. have been used extensively in North America and Europe as a biomonitoring tool to indicate mesotrophic water quality, yet infestation by associated parasites has not been well documented. We performed laboratory analysis of archived samples of Hexagenia spp. nymphs collected in 1985 and 1986 to provide base-line data on the distribution (1985) and seasonal infestation (1986) of the trematode parasite Crepidostomum spp. in Hexagenia spp. nymphs in connecting rivers between Lakes Superior and Erie of the Laurentian Great Lakes. In May and June 1985, frequency of occurrence of metacercariae was widely distributed throughout the connecting rivers (63% of 203 stations with nymphs), except in areas where nymph densities were relatively low (i.e.,≤69 nymphs/m2). Distribution was probably underestimated in the present study because of low probability (mean = 31%, range = 0–57%) of detecting infestation in a small number of collected nymphs ( ≤10) at nymph densities ≤69/m2. In 1986, seasonal infestation between April and October occurred in 3.3% (627) of 18696 nymphs. Overall prevalence, mean intensity, and mean abundance of parasites at one station in the St. Marys River indicate parasite transmission occurred between June and September. This period of transmission is dependent on the life-cycle of the parasite. In addition, the life-cycle of Hexagenia spp. determines which annual cohort of nymphs is infested and therefore, the duration of infestation. Although, no impacts of infestation on Hexagenia spp. nymphs were observed in the present study, infestation intensities were high enough (≥25 metacercariae per nymph) at one station in the St. Marys River to potentially cause tissue damage in a high proportion (53%) of infested nymphs.

  • Temporal variation of energy reserves in mayfly nymphs (Hexagenia spp.) from Lake St Clair and western Lake Erie
    Freshwater Biology, 2003
    Co-Authors: Joann F. Cavaletto, Thomas F. Nalepa, David L. Fanslow, Don W. Schloesser
    Abstract:

    SUMMARY 1. We analysed changes in energy reserves (lipid and glycogen) and length–weight relationships of burrowing mayflies (Hexagenia spp.) in 1997–99 to compare an established population in Lake St Clair with a recovering population in western Lake Erie of the Laurentian Great Lakes. In addition, we measured changes in water temperature and potential food in both water columns and sediments. 2. Although overall mean values of lipid and glycogen levels of Hexagenia nymphs from Lake St Clair and western Lake Erie were not significantly different, there were differences in seasonal patterns between the two lakes. In Lake St Clair, levels were highest in early spring, declined throughout the year, and reached their lowest levels in fall during all 3 years of study. In contrast, levels in western Lake Erie were lower in spring, increased to a maximum in summer, then declined in fall. Seasonal patterns in length–weight relationships were similar to those for lipid and glycogen. 3. Total lipid as a percentage of dry weight did not increase with developmental stage of nymphs until just prior to metamorphosis and emergence from water. However, the major reserve lipid, triacylglycerols, increased systematically with development stage. In the final stage of development, triacylglycerols declined, probably as a result of energy consumption and its conversion to other biochemical components for metamorphosis and reproduction. 4. Indicators of potential food (algal fluorescence in the water column and chlorophyll a and chlorophyll a/phaeophytin ratio in sediments) suggest that Hexagenia in Lake St Clair have a food source that is benthic based, especially in early spring, whereas in western Lake Erie nymphs have a food source that is water column based and settles to the lake bottom during late spring and summer.

Jan J. H. Ciborowski - One of the best experts on this subject based on the ideXlab platform.

  • J. Great Lakes Res. 29(3):521–528 Internat. Assoc. Great Lakes Res., 2003 Do Tube-dwelling Midges Inhibit the Establishment of Burrowing Mayflies?
    2015
    Co-Authors: Wes Plant, Jan J. H. Ciborowski, L.d. Corkum
    Abstract:

    ABSTRACT. There are some locations in Lake Erie where, despite the presence of suitable habitat, mayfly (Hexagenia) nymphal density is low or absent, and midge (Chironomidae) larval density is high. We conducted laboratory experiments to determine if biotic interactions account for this spatial distribu

  • Spatial and temporal variation in the distribution of burrowing mayfly nymphs (Ephemeroptera: Hexagenia limbata and H. rigida) in western Lake Erie
    Journal of Great Lakes Research, 2013
    Co-Authors: Ellen Green, Jan J. H. Ciborowski, Alice Grgicak-mannion, L.d. Corkum
    Abstract:

    Abstract In the early 1990s, burrowing mayfly species reappeared in sediments of the western basin of Lake Erie after an absence of over 30 years due to episodic hypoxia at the sediment–water interface. Long-term monitoring of adult mayflies at shoreline areas had revealed that Hexagenia rigida was more abundant than Hexagenia limbata during the initial recolonization period, but was gradually replaced by H. limbata . We hypothesized that this shift in dominance would be confirmed by the distribution and abundance of nymphs. We identified nymphs collected each spring throughout western Lake Erie from 1997 to 2004. The relative abundances of H. rigida and H. limbata nymphs exhibited the same temporal sequence as adults. Furthermore, the number of sites in the western basin in which H. rigida occurred decreased as the occurrence frequency of H. limbata increased. H. limbata were dominant in the basin by 2004. Hexagenia limbata nymphs persisted in the center-most part of the basin, whereas H. rigida did not, possibly due to differences in tolerance to hypoxia. There were no significant differences in body size between the two populations. Differences in dispersal distance from source populations and the timing and success of egg hatching likely accounted for the initial colonizing success of H. rigida , but the differential ability of H. limbata eggs to overwinter in sediments and possible tolerance of nymphs to hypoxia has possibly led to its current dominance in the western basin.

  • Distribution and Abundance of Burrowing Mayflies (Hexagenia spp.) in Lake Erie, 1997–2005
    Journal of Great Lakes Research, 2007
    Co-Authors: Kenneth A. Krieger, Michael T. Bur, Jan J. H. Ciborowski, David R. Barton, Don W. Schloesser
    Abstract:

    Burrowing mayflies (Hexagenia limbata and H. rigida) recolonized sediments of the western basin of Lake Erie in the 1990s following decades of pollution abatement. We predicted that Hexagenia would also disperse eastward or expand from existing localized populations and colonize large regions of the other basins. We sampled zoobenthos in parts of the western and central basins yearly from 1997–2005, along the north shore of the eastern basin in 2001–2002, and throughout the lake in 2004. In the island area of the western basin, Hexagenia was present at densities ≤ 1,278 nymphs/m2 and exhibited higher densities in odd years than even years. By contrast, Hexagenia became more widespread in the central basin from 1997-2000 at densities ≤ 48 nymphs/m2 but was mostly absent from 2001-2005. Nymphs were found along an eastern basin transect at densities≤ 382/m2 in 2001 and 2002. During the 2004 lake-wide survey, Hexagenia was found at 63 of 89 stations situated throughout the western basin (≤ 1,636 nymphs/m2, mean = 195 nymphs/m2, SE = 32, N = 89) but at only 7 of 112 central basin stations, all near the western edge of the basin (≤ 708 nymphs/m2), and was not found in the eastern basin. Hexagenia was found at 2 of 62 stations (≤ 91 nymphs/m2) in harbors, marinas, and tributaries along the south shore of the central basin in 2005. Oxygen depletion at the sediment-water interface and cool temperatures in the hypolimnion are probably the primary factors preventing successful establishment throughout much of the central basin. Hexagenia can be a useful indicator of lake quality where its distribution and abundance are limited by anthropogenic causes.

  • distribution and abundance of burrowing mayflies Hexagenia spp in lake erie 1997 2005
    Journal of Great Lakes Research, 2007
    Co-Authors: Kenneth A. Krieger, Michael T. Bur, Jan J. H. Ciborowski, David R. Barton, Don W. Schloesser
    Abstract:

    Burrowing mayflies (Hexagenia limbata and H. rigida) recolonized sediments of the western basin of Lake Erie in the 1990s following decades of pollution abatement. We predicted that Hexagenia would also disperse eastward or expand from existing localized populations and colonize large regions of the other basins. We sampled zoobenthos in parts of the western and central basins yearly from 1997–2005, along the north shore of the eastern basin in 2001–2002, and throughout the lake in 2004. In the island area of the western basin, Hexagenia was present at densities ≤ 1,278 nymphs/m2 and exhibited higher densities in odd years than even years. By contrast, Hexagenia became more widespread in the central basin from 1997-2000 at densities ≤ 48 nymphs/m2 but was mostly absent from 2001-2005. Nymphs were found along an eastern basin transect at densities≤ 382/m2 in 2001 and 2002. During the 2004 lake-wide survey, Hexagenia was found at 63 of 89 stations situated throughout the western basin (≤ 1,636 nymphs/m2, mean = 195 nymphs/m2, SE = 32, N = 89) but at only 7 of 112 central basin stations, all near the western edge of the basin (≤ 708 nymphs/m2), and was not found in the eastern basin. Hexagenia was found at 2 of 62 stations (≤ 91 nymphs/m2) in harbors, marinas, and tributaries along the south shore of the central basin in 2005. Oxygen depletion at the sediment-water interface and cool temperatures in the hypolimnion are probably the primary factors preventing successful establishment throughout much of the central basin. Hexagenia can be a useful indicator of lake quality where its distribution and abundance are limited by anthropogenic causes.

  • Sediment Suspension by Burrowing Mayflies (Hexagenia spp., Ephemeroptera: Ephemeridae)
    Journal of Great Lakes Research, 2005
    Co-Authors: André M. Bachteram, K.a. Mazurek, Jan J. H. Ciborowski
    Abstract:

    Burrowing and ventilation activities of benthic invertebrates can influence water column turbidity, nutrient concentrations, and possibly oxygen balance of lakewide ecosystems. In laboratory experiments, we determined rates of bioturbation-induced suspension of fine Lake Erie sediments caused by the burrowing mayfly Hexagenia of various sizes (lengths 13–28 mm) and multiple densities (70–1,111 larvae/m2) and water temperatures (10–25°C). Larvae were inoculated into 2-L jars containing Lake Erie sediment and water. Bioturbation and sediment settling rates were independently estimated from sediment concentrations in water, measured twice daily for 14–18 d. Nonlinear regression was used to estimate sediment suspension rate for each jar (flux, mg/L/h). Logarithmic transformations of size, density, and temperature best described sediment flux. Separate experiments demonstrated that flux was unaffected by sediment depth, but did vary by sediment type, which was related to location from which Lake Erie sediment had been collected. Sediment suspension rates increased as food became depleted. Sediment suspension by pre-emergent (25 mm long) larvae at densities and water temperature typical for late spring in western Lake Erie (400 larvae/m2 at 22°C) averaged 12 g/m2/h. Although this level of bioturbation by Hexagenia larvae in western Lake Erie likely contributes only a small fraction of the basinwide annual sediment load, sediment suspension is possibly an important epibenthic source of nutrients and sediment-associated contaminants during spring. Such concentrations would exceed the clearance capacity of dreissenid mussels and may partially explain why dreissenids have not become abundant in soft sediments of the western basin.

Mark T. Steingraeber - One of the best experts on this subject based on the ideXlab platform.

  • Bioassessment of contaminant transport and distribution in aquatic ecosystems by chemical analysis of burrowing mayflies (Hexagenia)
    Regulated Rivers: Research & Management, 1995
    Co-Authors: Mark T. Steingraeber, James G. Wiener
    Abstract:

    Burrowing mayfly nymphs (Ephemeroptera) inhabit and ingest fine-grained sediments and detritus that may be enriched with metals and persistent organic compounds. The burrowing nymphs can externally adsorb and internally assimilate these contaminants, providing a link for the food chain transfer of potentially toxic substances from sediments to organisms in higher trophic levels. The emergent adults are short-lived and do not feed, thus their gut contents do not contribute greatly to their total contaminant burden. These characteristics make Hexagenia spp. and certain other burrowing mayflies useful for assessing ecosystem contamination. General protocols are presented for the collection, processing and analysis of emergent mayflies to assess the spatial distribution and bioaccumulation of sediment-associated contaminants in aquatic ecosystems. Two essential components of this bioassessment approach are a network of on-site volunteers with the materials and instructions needed to correctly collect and store samples and quality assurance procedures to estimate the accuracy of chemical analyses. The utility of this approach is demonstrated with an example of its application to the Upper Mississippi River (USA). Determination of cadmium, mercury and polychlorinated biphenyl congeners in emergent Hexagenia bilineata from a 1250km reach of this river revealed (1) several source areas of contaminants and (2) distinct patterns in the bioaccumulation (and apparent sediment-associated transport) of each residue on both small and large spatial scales.

  • Cadmium and mercury in emergent mayflies ( Hexagenia bilineata ) from the upper Mississippi River
    Archives of Environmental Contamination and Toxicology, 1992
    Co-Authors: J. Therese Dukerschein, James G. Wiener, Ronald G. Rada, Mark T. Steingraeber
    Abstract:

    Burrowing mayflies (Hexagenia bilineata) were analyzed to assess longitudinal patterns in their cadmium and mercury content along the upper Mississippi River. Emergent mayflies (subimagoes and imagoes) were collected in 1988 at 34 sites (25 navigation pools), extending 1260 km from Little Falls, Minnesota, downstream to St. Louis, Missouri. Cadmium concentrations in composite samples of whole mayflies ranged from 7 to 219 ng/g dry weight in females and from

L.d. Corkum - One of the best experts on this subject based on the ideXlab platform.

  • J. Great Lakes Res. 29(3):521–528 Internat. Assoc. Great Lakes Res., 2003 Do Tube-dwelling Midges Inhibit the Establishment of Burrowing Mayflies?
    2015
    Co-Authors: Wes Plant, Jan J. H. Ciborowski, L.d. Corkum
    Abstract:

    ABSTRACT. There are some locations in Lake Erie where, despite the presence of suitable habitat, mayfly (Hexagenia) nymphal density is low or absent, and midge (Chironomidae) larval density is high. We conducted laboratory experiments to determine if biotic interactions account for this spatial distribu

  • Spatial and temporal variation in the distribution of burrowing mayfly nymphs (Ephemeroptera: Hexagenia limbata and H. rigida) in western Lake Erie
    Journal of Great Lakes Research, 2013
    Co-Authors: Ellen Green, Jan J. H. Ciborowski, Alice Grgicak-mannion, L.d. Corkum
    Abstract:

    Abstract In the early 1990s, burrowing mayfly species reappeared in sediments of the western basin of Lake Erie after an absence of over 30 years due to episodic hypoxia at the sediment–water interface. Long-term monitoring of adult mayflies at shoreline areas had revealed that Hexagenia rigida was more abundant than Hexagenia limbata during the initial recolonization period, but was gradually replaced by H. limbata . We hypothesized that this shift in dominance would be confirmed by the distribution and abundance of nymphs. We identified nymphs collected each spring throughout western Lake Erie from 1997 to 2004. The relative abundances of H. rigida and H. limbata nymphs exhibited the same temporal sequence as adults. Furthermore, the number of sites in the western basin in which H. rigida occurred decreased as the occurrence frequency of H. limbata increased. H. limbata were dominant in the basin by 2004. Hexagenia limbata nymphs persisted in the center-most part of the basin, whereas H. rigida did not, possibly due to differences in tolerance to hypoxia. There were no significant differences in body size between the two populations. Differences in dispersal distance from source populations and the timing and success of egg hatching likely accounted for the initial colonizing success of H. rigida , but the differential ability of H. limbata eggs to overwinter in sediments and possible tolerance of nymphs to hypoxia has possibly led to its current dominance in the western basin.

  • Delayed egg hatching accounts for replacement of burrowing mayflies Hexagenia rigida by Hexagenia limbata after recolonization in western Lake Erie
    Journal of Great Lakes Research, 2013
    Co-Authors: Claudia Bustos, L.d. Corkum
    Abstract:

    Abstract Egg banking may have played a role in the recolonization of two burrowing mayfly species ( Hexagenia limbata and Hexagenia rigida ), which recolonized western Lake Erie after over 30 years of near extirpation. H. rigida was the first of the two to colonize successfully, but was overtaken by H. limbata (the historically dominant species). To understand mechanisms of species replacement, we compared egg hatching between the two species at 20 °C in the lab under typical hatching temperatures (no incubation) and after cold storage (8 °C) for 2, 6 and 12 months. Prolonged storage at cold temperatures simulates temperature conditions to which embryos are exposed when deposited by late-emerging female imagos. Without incubation, H. rigida (95.4 ± 2.02) exhibited significantly higher egg hatching survivorship than H. limbata (85 ± 3.2) (P = 0.01). First hatch date for H. rigida was one day earlier than H. limbata , but time for 50% to hatch (5 d) and hatching duration (5 d) was the same for both species. After 2 and 6 months of incubation, H. limbata exhibited an earlier hatch date, but there was no significant difference in mean percentage of egg survival (ca 63%) between species. After 12 months of cold storage, hatching success for H. limbata was 44.6 ± 4.17%, but H. rigida eggs did not hatch. Banking of eggs at low temperature increases the chance of successful recolonization, once stressful conditions pass. The viability H. limbata eggs after long quiescence may help to explain the shift in dominance from H. rigida to H. limbata .

  • Timing of Hexagenia (Ephemeridae: Ephemeroptera) mayfly swarms
    Canadian Journal of Zoology, 2006
    Co-Authors: L.d. Corkum, Jan Ciborowski, David M. Dolan
    Abstract:

    Although degree-days can be used to determine when insect emergence begins, peak swarming events in species that exhibit extended emergence periods are difficult to estimate. With the aid of logistic regression, we estimated the prob- ability of adult mayfly swarms (‡50 individuals/m 2 ), occurring on any given night in western Lake Erie, using meteorologi- cal data. We sampled adult Hexagenia Walsh, 1863 from 2130 (sunset) to 2300 on 18 dates in 2000 (2 June - 18 July), with the largest numbers retrieved between 13 June and 2 July. Water temperature (20 8C) was the cue to the onset of swarming (subimagos). Highest mean (±SE) density of all Hexagenia adults (subimagos and imagos) was 24740 ± 8757 individuals/m 2 . Overall, 10-fold more imagos (mostly females) than subimagos were attracted to lights. Of the factors examined (air and water temperature, Julian day, dew point, heat index, humidity, moon phase, wind chill, wind direc- tion, wind speed), onshore wind speed (0-9.2 km/h) on calendar dates for which the water temperature exceeded 20 8C was the most significant factor to account for total adult swarms. Eighty-three percent of the 18 swarming events observed in 2000 were correctly predicted. Validity of the model was confirmed with data collected in 2002, during which 5 of 6 swarming events were correctly predicted from the logistic model. Wind promotes adult aggrega- tion at the land-water interface, the effect of which facilitates mating success and predator swamping. Resume´ : Bien que les degres-jours puissent servir a determiner le debut de l'emergence chez les insectes, il est difficile d'estimer les episodes principaux de formation d'essaims chez les especes qui ont une periode d'emergence prolongee. Al'aide de la regression logistique, nous avons estimela probabilitede la formation d'essaims d'ephemeres adultes (‡50 individus/m 2 ) dans une soiree donnee dans la partie occidentale du lac Eried'apres les donnees meteorologiques.

  • Recolonization and possible recovery of Burrowing Mayflies (Ephemeroptera: Ephemeridae: Hexagenia spp.) in Lake Erie of the Laurentian Great Lakes
    Journal of Aquatic Ecosystem Stress and Recovery, 2000
    Co-Authors: Don W. Schloesser, Kenneth A. Krieger, Jan J. H. Ciborowski, L.d. Corkum
    Abstract:

    Burrowing mayflies of the genus Hexagenia spp. were widely distributed (ca. 80% of sites) and abundant (ca. 160 nymphs/m^2) in the western basin of Lake Erie of the Laurentian Great Lakes in 1929–1930, prior to a period of anoxia in the mid 1950s. Nymphs were absent or rare in the basin between 1961 and 1973–1975. In 1979–1991, nymphs were infrequently found (13–46% of sites) in low abundance (3–40 nymphs/m^2) near shore (

J. Therese Dukerschein - One of the best experts on this subject based on the ideXlab platform.

  • Cadmium and mercury in emergent mayflies ( Hexagenia bilineata ) from the upper Mississippi River
    Archives of Environmental Contamination and Toxicology, 1992
    Co-Authors: J. Therese Dukerschein, James G. Wiener, Ronald G. Rada, Mark T. Steingraeber
    Abstract:

    Burrowing mayflies (Hexagenia bilineata) were analyzed to assess longitudinal patterns in their cadmium and mercury content along the upper Mississippi River. Emergent mayflies (subimagoes and imagoes) were collected in 1988 at 34 sites (25 navigation pools), extending 1260 km from Little Falls, Minnesota, downstream to St. Louis, Missouri. Cadmium concentrations in composite samples of whole mayflies ranged from 7 to 219 ng/g dry weight in females and from