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Publications

Read publications and other informational products to learn more about USGS science occurring in the Mississippi Basin.

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Feeding chronology of juvenile piranhas, Pygocentrus notatus, in the Venezuelan llanos Feeding chronology of juvenile piranhas, Pygocentrus notatus, in the Venezuelan llanos

During the 1988 rainy season, I studied the 24 h feeding chronology of juvenile (40–68 mm standard length) piranhas, Pygocentrus notatus (Characidae: Serrasalminae) from a natural population inhabiting a small savanna stream in Apure State, Venezuela. Stomach contents analyses, supported by laboratory determinations of digestion rate, showed that these fish are primarily diurnal...
Authors
L.G. Nico

Toxicity of inorganic and organic selenium to Daphnia magna (cladocera) and Chironomus riparius (diptera) Toxicity of inorganic and organic selenium to Daphnia magna (cladocera) and Chironomus riparius (diptera)

Elevated concentrations of selenium (Se) have been previously measured in biota sampled from the Kesterson National Wildlife Refuge (KNWR) in the San Joaquin Valley of central California. We conducted acute and chronic toxicity tests with the cladoceran Daphnia magna and the midge Chironomus riparius to determine the toxicity or bioaccumulation of waterborne Se in a reconstituted water...
Authors
Christopher G. Ingersoll, F.J. Dwyer, T.W. May

Concentrations of boron, molybdenum, and selenium in chinook salmon Concentrations of boron, molybdenum, and selenium in chinook salmon

The concentrations of boron, molybdenum, and selenium in young chinook salmon Oncorhynchus tshawytscha were determined in three partial life cycle chronic toxicity studies. In each study, fish were exposed to a mixture of boron, molybdenum, selenate, and selenite in the proportions found in subsurface agricultural drainage water in the basin of the San Joaquin Valley, California. Tests...
Authors
Steven J. Hamilton, Raymond H. Wiedmeyer

Plant community structure in an oligohaline tidal marsh Plant community structure in an oligohaline tidal marsh

An oligohaline tidal marsh on the northern shore of Lake Pontchartrain, LA was characterized with respect to the distributions and abundances of plant species over spatial and temporal gradients using Detrended Correspondence Analysis (DCA). In addition, the species distributions were correlated to several physical environmental factors using Detrended Canonical Correspondence Analysis...
Authors
J.S. Brewer, J.B. Grace

Homestead tree planting in two rural Swazi communities Homestead tree planting in two rural Swazi communities

Tree planting practices were investigated on a total of 95 homesteads in two communities in rural Swaziland. Information was also collected on socioeconomic characteristics of the homesteads. In both the study areas, Sigombeni and Bhekinkosi, there was considerable variation amongst individual homesteads in size, relative wealth (as indicated by cattle and motor vehicle ownership), and...
Authors
James A. Allen

Partitioning and bioavailability of mercury in an experimentally acidified Wisconsin lake Partitioning and bioavailability of mercury in an experimentally acidified Wisconsin lake

We studied the partitioning of mercury (Hg) among air, water, sediments and fish at Little Rock Lake, a clear water seepage lake in north-central Wisconsin. The lake was divided with a sea curtain into two basins, one acidified with sulfuric acid to pH 5.6 for two years and the other an untreated reference site (mean pH 6.1), to document the effects of acidification. Trace-metal-free...
Authors
James G. Wiener, William F. Fitzgerald, Carl J. Watras, Ronald G. Rada
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