Geology topics

M.J. Lydy

Publications and source records attributed to M.J. Lydy.

3 recordsLinked to original sources

USGS2014

A comparison of selected diversity, similarity, and biotic indices for detecting changes in benthic-invertebrate community structure and stream quality

Implementation of advanced wastewater treatment at the two municipal wastewater-treatment plants for Indianapolis, Indiana, resulted in substantial improvement in the quality of the receiving stream and significant changes in the benthic-invertebrate community. Diversity, similarity, and biotic indices were compared to determine which indices best reflected changes in the composition of the biota in the river. None of the indices perfectly reflected the changes in river quality or community structure. Similarity indices, especially percentage similarity, exhibit the most promise of the three classes of indices. Diversity indices were least useful, wrongly indicating that water quality deteriorated after the upgrade of the wastewater-treatment plants. The most descriptive tool in analyzing the data was the percentage of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa present. Using a mixture of indices and other analytical tools, such as EPT, in the analysis of biological data will ensure the most effective investigations of water quality.

Archives of Environmental Contamination and Toxico↗

USGS1996

Assessment of water quality at selected sites in the White River Basin, Indiana, 1993 and 1995 using biological indices

As part of the National Water Quality Assessment (NAWQA) Program, fish communities were sampled at 11 sites in the White River Basin, Indiana, in 1993 and 1995 to help determine water-quality conditions. Ninety-one species of fish with representatives from 18 families were collected in the basin. Total numbers of fish collected at every site increased between collection years. The Index of Biological Integrity (IBI) and Qualitative Habitat Evaluation Index (QHEI) were calculated for all 11 sites in 1995. The QHEI scores indicated six sites had excellent habitat to support fish communities. Only three sites were rated in the “good” to “excellent” IBI water-quality categories, indicating some type of nonhabitat environmental degradation to the fish communities. Eight of the sites were rated in the “fair,” “poor,” or “very poor” IBI water-quality categories.

Indiana↗

USGS1993

Assimilation efficiency for sediment-sorbed benzo(a)pyrene by Diporeia spp.

Two methods are currently available for determining contaminant assimilation efficiencies (AE) from ingested material in benthic invertebrates. These methods were compared using the Great Lakes amphipod Diporeia spp. and [ 14 C]benzo(a)pyrene (BaP) sorbed to Florissant sediment (< 63 µ m). The first approach, the direct measurement method, uses total organic carbon as a tracer and yielded AE values ranging from 45.9~50.4%. The second approach, the dual-labeled method, uses 51 Cr as a non-assimilated tracer and did not yield AE values for our data. The inability of the dual-labeled approach to estimate AEs was due, in part, to the selective feeding by Diporeia resulting in a failure of the non-assimilated tracer ( 51 Cr) to track with the assimilated tracer ([ 14 C]BaP). The failure of the dual-labeled approach was not a result of an uneven distribution of the labels among particle size classes, but more likely resulted from differential sorption of the two isotopically labeled materials to particles of differing composition. The [ 14 C]BaP apparently sorbs to organic particles that are selectively ingested, while the 51 Cr apparently sorbs to particles which are selectively excluded by Diporeia. The dual-labeled approach would be a viable and easier experimental approach for determining AE values if the characteristics that govern selective feeding can be determined.

Aquatic Toxicology↗