ChifionomtLi) sp. , Endoch'OionomiUi sp. , and JaJiijtanA>(.ii> sp. , are the most 

 prevalent Chirononidae in Beaver Creek. All three prefer slow to standing 

 water, low to medium oxyqen concentrations, and eutrophic waters (Beck 1977). 



i-unnudfviZuA udckemianuA is a common oliqochaete throughout the system. 

 Hiltenun (1970) and Brinkhurst (1974) both state that this species is 

 found under a very wide variety of conditions from extremely productive to 

 oliqotrophic. 



Hilsenoff (1977) has used invertebrates to evaluate the water quality 

 of Wisconsin streams. Each species was assigned a biotic index value on the 

 basis of the quality of streams from which they were collected. values were 

 assiqned to species collected only in unaltered streams of very hiqh water 

 quality and values of 5 assiqned to snecies known to occur in severely 

 polluted or disturbed streams. Intermediate values were assiqned to species 

 known to occur in streams with various deqrees of disturbance or pollution. 

 Hilsenoff s values were applied to the most dominant groups {Chtumatopiijch 

 ChinonomM sp., Hualcl^a <xztzca and Caeiiii sp.) resultinq in an average value 

 of 4.25. This does not necessarily indicate that Beaver Creek is altered 

 or polluted since very adaptable forms can be assigned high values as a result 

 of the fact that they can adapt to many situations and they are tolerant 

 of severe environmental stresses which are coimon in intermittent streams. 



Diversity indices have been calculated for the invertebrates in Beaver 

 Creek and they are presented in Table 6. 



The presence of certain aquatic organisms often provides a good 

 indication of the condition of a stream (Goodnight 1973). However, Wilhm 

 (1970) states that "associations or populations of benthic macroinvertebrates 

 provide a more reliable criterion of organic enrichment than mere occurrence 

 of a given species." Diversity indices have been used to analyze biological 

 cormiunities and provide insight into conmunity structure. Goodman (1975) 

 suggested that diversity does not necessarily indicate stability and 

 Herlbert (1971) and Hilsenoff (1977) question the validity of diversity indices. 

 The attempt to summarize population diversity by two indices (diversity 

 and redundancy) does not seem to have been successful thus far (Hamilton 1975). 

 However, diversity and redundancy included with number of taxa and total 

 number of individuals generally presents valuable information. 



With the limitations of diversity indices in mind, these values along 

 with redundancy have been presented in Table 6. These values can probably 

 be used as a valuable tool in "before and after" studies. They will 

 generally show an effect of severe perturbations on an aquatic community. 



Intermittent prairie streams often support similar invertebrate faunas. 

 The sluqqish water of Beaver Creek, coupled with intermittence during dry 

 years (1977) limits the range of invertebrates. Patrick (1959) found 

 that organisms with a shorter life span are the quickest to establish natural 

 populations. Harrel and Dorris (1968) found that during drought, community 

 structures of several Oklahoma streams were similar. In general, it appears 

 that species which complete their life cycle in one year or less are 

 predominant and species which require more than one year to complete their 

 life cycle are limited to pool dwelling forms. 



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