Browsing by Subject "Diamesa"
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Item Emergence, survival, and longevity of adult Diamesa mendotae Muttkowski (Diptera: Chironomidae) in groundwater-fed streams(2013-06) Mazack, Jane ElizabethGroundwater-fed streams, which remain cold in summer but ice-free in winter, provide ideal habitat for ultra-cold stenotherm insects. Diamesa mendotae Muttkowski (Diptera: Chironomidae) is a winter-active species common to groundwater-fed streams in Minnesota. In order to improve the understanding of the winter dynamics of this species, we studied the influence of temperature on its emergence, survival, and longevity. The winter emergence dynamics of D. mendotae and other winter-active chironomids were documented by collecting surface-floating pupal exuviae samples from 24 groundwater-fed streams in southeastern Minnesota. Early, mid, and late winter samples were collected from each stream, and mean water temperatures during the week preceding sample collection were estimated using air-water temperature regressions. The results of this assessment indicate that D. mendotae are influenced by both thermal stability and water temperature. Abundance of D. mendotae was positively related to air-water temperature regression slope in early and mid-winter; emergence was negatively related to water temperature in late-winter. Emergence patterns of other genera were related to estimated water temperatures, showing significant thermal partitioning within the chironomid community. Field collections of adult D. mendotae were used to determine survivorship under long-term exposure to controlled sub-freezing conditions. Batches of specimens were placed into a controlled treatment chamber at -5°C for between 7 and 70 days. Survivorship at constant sub-freezing temperatures was negatively related to treatment length, although some individuals survived sub-freezing temperatures for 70 days. Additionally, male D. mendotae had a significantly higher rate of survivorship than females within the same treatment. Post-treatment longevity decreased with increased exposure to sub-freezing temperatures; however, total longevity increased with treatment time. These studies indicate that D. mendotae is well adapted to the cold winter-weather conditions across southeastern Minnesota, suggesting that adults may be able to survive long periods of extreme temperature conditions in the winter to increase their ability to successfully reproduce. Groundwater inputs not only influence the thermal regime of streams in southeastern Minnesota's karst landscape, but also significantly impact chironomid community dynamics, which may play a significant role in the broader invertebrate and fish communities of these streams.Item Winter invertebrate dynamics in groundwater-fed streams in southeastern Minnesota, USA(2018-01) Mazack, JaneSoutheastern Minnesota is characterized by Karst geology and trout streams. These groundwater-fed streams remain cool in summer and ice-free in winter, providing ideal habitat for trout and cold-adapted insects. Previous studies of winter-active insects have been localized or laboratory-based; however, the broader winter invertebrate community and its relationships to groundwater input are not well established. The goals of this research were to (1) assess the emergence patterns of winter-active chironomids (Diptera); (2) evaluate the effect of groundwater on the voltinism of the chironomid species Diamesa mendotae Muttkowski; (3) assess overall winter invertebrate community composition and abundance; and (4) describe the winter benthic chironomid community. Invertebrates were collected from 36 groundwater-fed streams over three winters (2010 - 2013). Surface-floating pupal exuviae (SFPE) collections were used to study the emergence patterns of cold-adapted chironomids, and Hess samples were used to evaluate winter benthic invertebrate composition and abundance. A total of 14 chironomid genera emerged from December through February; an additional 16 genera emerged in March. D. mendotae was the most commonly encountered and abundant winter-emerging chironomid, and emerged throughout the winter. Analysis of stream thermal regime indicated that D. mendotae complete multiple generations in a single winter in most streams. Benthic invertebrate communities were dominated by few taxa, with three chironomid genera (Diamesa, Orthocladius (Orthocladius), and Pagastia), two mayfly genera (Baetis and Ephemerella) and one caddisfly genus (Hydropsyche) comprising over 60% of individuals collected. Overall abundance was highest in thermally stable streams. Chironomids were abundant and diverse, with the winter-active species Diamesa mendotae dominating the community. We conclude that groundwater-fed streams (sensu Krider et al. 2013) in southeastern Minnesota support large, winter-active invertebrate communities, which are ecologically important to brown trout.