ORDINATION OF MACROI N VE RTEBRATE COMMUNITIES 



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Fig. 4 Diagrammatic representation of similarity matrices (based on 

 coefficient of community) showing strong affinities of macro- 

 invertebrate communities (>0.65) for June, August, and September 

 1976 collection dates, Great Miami River system, Ohio. 



the station-to-station variation in S (temperature explained 26.2%, 

 conductivity 19.0%, and oxygen 11.5%), 



The strongly negative correlations of conductivity and river 

 temperature with number of species per station was indicative of the 

 stressful effect of discharges (sewage-treatment plants, power plants, 

 and industrial wastewater) on the river's macroinvertebrates. Al- 

 though conductivity probably did not affect the macroinvertebrates 

 directly, it served as an excellent marker of pollutional disturbances. 



Though the use of a diversity index and total taxa levels has 

 proved to be useful in this study, the use of similarity matrices, 

 matrix diagrams, and ordination has provided more interesting and 

 insightful information. The presence— absence data for the 14 

 stations (see Beckett, 1977) and the diagrams (Fig. 4) generated by 

 these matrices showed that the macroinvertebrates of stations 10 

 through 14 formed a somewhat continuous association for all three 

 sampling periods. The June similarity matrix diagram also showed 

 marked similarity between various upstream and downstream sta- 

 tions. Stations 1 and 10 and stations 4 and 11 were quite similar in 

 terms of species presence or absence. These distant upstream — 

 downstream affinities were not observed for either the August or 

 September sampling periods. 



