Sustaining America's aquatic biodiversity. Aquatic insect biodiversity and conservation

Discussion of aquatic biodiversity and conservation of aquatic insectsVT/1219/420-531(CNRE-81P

Aquatic Insect Biodiversity and Conservation

Provides a description of the structure and appearance of aquatic insects, how they live and reproduce, the habitats they live in, how to collect them, why they are of importance, and threats to their survival; document also includes a brief illustrated summary of the eight major groups of aquatic insects and web links to more information.Part of a 12 part series on sustaining aquatic biodiversity in America

The macrobenthos of a new reservoir, Lake Anna, Louisa County, Virginia

The macrobenthos of a new reservoir in central Virginia, Lake Anna, was studied for the first three years after impoundment, 1972-1975. Prior to this, extensive macrobenthic collections had been made in the river destined for impoundment, the North Anna River. The biota of this river had been seriously affected by acid mine drainage for over 100 years. Macrobenthos consists of the organisms living on the bottom or the solid-liquid interface. The occurrence of these organisms is significant, because they are major items in the diet of many fish, and are thus important in the flow of energy through an ecosystem. The basic objectives of this study were to determine the changes in macrobenthic community structure brought about by impoundment, and then to observe the successional changes which occurred in the following years. This information was then compared to a hypothetical model predicting the productivity of new reservoirs. It was discovered that traditional grab sampling was not reliable in new reservoirs because of the abundant submerged terrestrial vegetation. An original sampling method was developed which involved the use of SCUBA to place and retrieve artificial substrate samplers. This SCUBA method was compared to grab sampling, and found to more reliably estimate macrobenthic community structure. Following impoundment, there was an immediate change in macrobenthic community structure. Colonization of the new reservoir occurred very quickly, especially during the first summer period. The acid mine drainage did not affect the distribution of macrobenthos in the new reservoir, probably because of dilution. Identification of over 525,000 organisms revealed that they could be classified into three groups: first colonizers, omnipresent species, and second colonizers. A review of the food habits of these organisms indicated that there were four trophic functional groups: micropredators, macropredators, collector-microgatherers, and collector-microfilterers. The first colonizers consisted of three species, one of which was completely dominant in each of the first three functional groups the first year. The second colonizers consisted of many additional species, several of which shared dominance in each of the same three functional groups the second and third years. The omnipresent group consisted of midge larvae which were dominant in the fourth functional group, collector-microfilterers, in all three years. This information, in conjunction with analysis of the horizontal, vertical, and temporal distribution, indicated that the development of macrobenthic community structure in Lake Anna followed the general trends expected in ecological succession. These trends are increased number of species, increased equitability of species composition, and better organization of distribution. A comparison of the development of macrobenthos in new reservoirs with a model of expected productivity indicated that the abundance of macrobenthos. may also exhibit the same trends as productivity. These trends are an initial increase in productivity for several years, followed by a sharp decline for several years, to be finally followed by a small increase and stabilization. This sequence of events probably requires at least 15 years for macrobenthos.Ph. D

Environmental factors accounting for benthic macroinvertebrate assemblage structure at the sample scale in streams subjected to a gradient of cattle grazing

Macroinvertebrate assemblages were related to environmental factors that were quantified at the sample scale in streams subjected to a gradient of cattle grazing. Environmental factors and macroinvertebrates were concurrently collected so assemblage structure could be directly related to environmental factors and the relative importance of stressors associated with cattle grazing in structuring assemblages could be assessed. Based on multivariate and inferential statistics, measures of physical habitat (% fines and substrate homogeneity) had the strongest relationships with macroinvertebrate assemblage structure. Detrital food variables (coarse benthic and fine benthic organic matter) were also associated with assemblage structure, but the relationships were never as strong as those with physical habitat measures, while autochthonous food variables (chlorophyll a and epilithic biomass) appeared to have no association with assemblage structure. The amount of variation explained in taxa composition and macroinvertebrate metrics is within values reported from studies that have examined macroinvertebrate metric–sediment relationships. The % Coleoptera and % crawlers had consistent relationships with % fines during this study, which suggests they may be useful metrics when sediment is a suspected stressor to macroinvertebrate assemblages in Blue Ridge streams. Findings from this study also demonstrate the importance of quantitative sampling through time when research goals are to identify relationships between macroinvertebrates and environmental factors

Ecological Monitoring in the New River Gorge National River: Analysis of Environmental Impacts from the Black Fly Pest Management Program

National Park ServiceThis volume donated by Dr. Donald Orth to VT Libraries for digitization

Production of filter-feeding Trichoptera in an impounded and a free-flowing river

Production was estimated (size frequency method) for five species of Hydropsychidae and two species of Philopotamidae at two sites on the impounded North Anna River and two sites on the free-flowing South Anna River. Total production was highest (3250.0 g dry weight (DW)∙ha−1∙year−1 at the site immediately below the dam. At the other sites total production ranged from 94.0 to 515.1 g DW∙ha−1∙year−1. An attempt was made to determine the influence of various factors on production. From an analysis of the trophic dynamics of production, seston energetics, and rates of consumption we conclude that the zooplankton released from the reservoir greatly enriches the seston in a narrow size range (105–864 μm) that corresponds to the size of the zooplankton released from the reservoir and the capture net mesh size of the hydropsychids. The extremely high density of filter feeders below the dam reduces the food quality of the seston and limits production downstream. Ecological interactions also were found to influence production, requiring detailed knowledge of the biology of individual species to understand the dynamics of a system. </jats:p

The Hydropsyche scalaris Group In Virginia Usa With The Description Of 2 New Species Trichoptera Hydropsychidae

Volume: 92Start Page: 837End Page: 86