The rate of colonization by macro-invertebrates on artificial substrate samplers

The influence of exposure time upon macro-invertebrate colonization on modified Hester-Dendy substrate samplers was investigated over a 60-day period. The duration of exposure affected the number of individuals, taxa and community diversity. The numbers of individuals colonizing the samplers reached a maximum after 39 days and then began to decrease, due to the emergence of adult insects. Coefficients of variation for the four replicate samples retrieved each sampling day fluctuated extensively throughout the study. No tendencies toward increasing or decreasing coefficients of variation were noted with increasing time of sampler exposure. The number of taxa colonizing the samplers increased throughout the study period. The community diversity index was calculated for each sampling day and this function tended to increase throughout the same period. This supports the hypothesis that an exposure period of 6 weeks, as recommended by the United States Environmental Protection Agency, may not always provide adequate opportunity for a truly representative community of macro-invertebrates to colonize multiplate samplers. Many of the taxa were collected in quite substantial proportions after periods of absence or extreme sparseness. This is attributed to the growth of periphyton and the collection of other materials that created food and new habitats suitable for the colonization of new taxa. Investigation of the relationship between ‘equitability’ and length of exposure revealed that equitability did not vary like diversity with increased time of exposure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72073/1/j.1365-2427.1979.tb01522.x.pd

The independent and interactive effects of snail grazing and nutrient enrichment on structuring periphyton communities

We investigated the independent and interactive effects of nutrient enrichment and snail grazing on structuring periphyton communities in a northern temperate lake. Nutrient releasing substrates and grazer enclosures were used to simultaneously manipulate nutrient availability and herbivory. Periphyton was allowed 18 days to accrue before grazers ( Elimia livescens = Goniobasis livescens ) were introduced.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42878/1/10750_2004_Article_BF00006063.pd

Physicochemical and Biological Conditions in Two Oklamhoma Reservoirs Undergoing Artificial Destratification

The purpose of this study was to develop more efficient methods of reservoir reaeration and to determine the environmental effects of reservoir destratification. The Garton pump, a low energy, axial flow device, is designed to pump water from the surface downward to destratify and reaerate lakes and reservoirs. A 1.07-m-diameter version of the device was tested in Ham\u27s Lake (40 ha surface area, 10 m maximum depth) near Stillwater, Okla., in 1973 and 1974, and a 1.83-m-diameter version was operated in 1975. Complete thermal destratification was obtained. A 5-m-diameter version of the Garton Pump was operated in Lake of the Arbuckles (951 ha surface area, 27 m maximum depth) near Sulphur, Okla., in 1974 and 1975. Improvements in the design resulted in substantial perturbation of the physicochemical conditions of Lake of the Arbuckles in 1975. This report describes vertical variations in the two reservoirs of: (1) temperature, dissolved oxygen, and several other physicochemical parameters; (2) species composition and density of the algae populations; (3) species composition and diversity of zooplankton; (4) species composition, diversity, and density of benthic macroinvertebrates; and (5) vertical (bathymetric) distribution and growth of fish. The report also includes recommendations for further research