ORDINATION OF MACROINVE RTEBRATE COMMUNITIES 751 



flood-control purposes in the early 1920s. The 32-km stretch of the 

 Great Miami River between the intake of the Tait power plant and 

 the final downstream station (14) is subjected to the discharges from 

 two power plants, five municipal sewage-treatment plants, and a 

 number of industrial- wastewater outfalls. 



Physical-Chemical Parameters 



Several physical— chemical parameters were measured for each of 

 the macroinvertebrate sampling periods. Temperature (°C) was 

 measured with a mercury thermometer. Dissolved oxygen (mg/liter) 

 was measured by means of the azide modification of the Winkler 

 method (American Public Health Association, 1975). Alkalinity was 

 titrated with phenolphthalein and bromcresol green— methyl red 

 indicators (Lind, 1974). Conductivity (jumhos) was measured with a 

 YSI conductivity meter; conductivity readings were corrected to 

 values at a standard temperature of 25.0°C. Current was measured 

 with a General Oceanics digital torpedo-type meter. 



The dates for chemical sampling were correlated with the 

 collection dates of macroinvertebrate samplers. Macroinvertebrate 

 samplers and physical— chemical data were collected on the following 

 dates (all dates in 1976): June, macroinvertebrate collection June 21, 

 physical— chemical sampling June 21; August, macroinvertebrate 

 collection August 9, physical— chemical sampling August 16; Septem- 

 ber, macroinvertebrate collection September 21 and 23; October, 

 physical— chemical sampling October 14, Daily river-discharge data 

 were furnished via monitors of the U. S. Department of Interior 

 Geological Survey. 



Macroinvertebrate Sampling and Analysis 



Modified Hestei^Dendy multiplate samplers similar to those 

 described by Fullner (1971) were used for macroinvertebrate 

 sampling. Each sampler consisted of a series of eight Masonite plates 

 separated by a varying number of washers (spacing varied vdthin the 

 samplei^all samplers were of identical configuration and spacing). 

 Each plate measured 10 by 10 cm and was 0.35 cm thick. Three 

 sampling devices were located at each of the 14 stations. Each device 

 consisted of two samplers connected to a v^re suspended from a 

 Styrofoam float. The sampling device was in turn connected to iron 

 and concrete anchors that rested on the river bottom. The samplers 

 were suspended approximately 1 m below the surface at all stations. 

 Sampling devices were placed in quieter waters, i.e., not in riffles, in 

 order to create similar conditions for colonization. The U. S. 



