Community Structure of Benthic Macroinvertebrates in an Intermittent Stream Receiving Oil Field Brines

Abstract

Physicochemical conditions and community structure of benthic macroinvertebrates in an oil-field-brine-polluted stream in Oklahoma were studied from October 1963 to September 1964. Turbidity varied inversely with conductivity and was lowest where brines were more highly concentrated. Seventy-nine species of benthic macroinvertebrates were collected during this study. Numbers of species varied from 31 at stations below the outfall to 55 at the farthest downstream station. Faunal assemblages were dominated by three families of insects: Tendipedidae, Simulidae, and Hydropsychidae. Maximum numbers of individuals occurred at stations in middle reaches where turbidity was lowest. Maximum numbers of species occurred at the extreme downstream station. Information theory methods were used to evaluate community structure of benthic macroinvertebrates. Diversity per m2 (H) was minimal in upper reaches during summer and maximal in middle reaches during winter. Redundancy (R) was minimal in middle reaches during spring and maximal in upper and middle reaches during winter. Diversity per individual (H) was minimal during winter in middle reaches and maximal in the lower reach during summer. INTRODUCTION Benthic organisms have been used by a number of investigators for evaluating stream conditions (Gaufin and Tarzwell, 1952, 1956; Beck, 1954; Hynes, 1958, 1963; Beak, 1964; Wilhm & Dorris, 1966). Because they are relatively immobile, quantitative sampling methods may be employed in obtaining estimates of community structure. Traditionally, stream pollution investigators have attempted to categorize aquatic organisms according to pollutional tolerance (Patrick, 1949; Beck, 1955; Wurtz, 1955; Gaufin, 1958; Beak, 1964). All of these methods suffer from the fact that pollution is varied because effluents produce different effects in different streams. As a result, efforts to classify organisms as to pollutional tolerance have tended to be somewhat subjective. Margalef (1957, 1958) suggested using information theory methods for the formulation of an index that would express diversity. Patten (1962) and Wilhm and Dorris (1966) have utilized this approach. In the present study, indices derived from information theory were applied in the analysis. of benthic macroinvertebrate community structure in a brine-polluted stream. DESCRIPTION OF STUDY AREA Black Bear Creek, a tributary of the Arkansas River, is located in Garfield, Noble and Pawne.e counties in north central Oklahoma ' Contribution 415 from the Zoology Department, Oklahoma State University. 428 This content downloaded from 157.55.39.104 on Sun, 19 Jun 2016 06:42:04 UTC All use subject to http://about.jstor.org/terms 1968 MATHIS AND DORRIS: COMMUN4ITY STRUCTURE 429 (Fig. 1). The main channel is approximately 169 km long and it has an average gradient of 0.9 m/km. Meanders are common, especially in the lower reaches. A method of drainage analysis based on the degree of branching (Horton, 1945; Strahler, 1957) ranks Black Bear Creek as a seventh order stream. Seven stations were selected for study. Station numbers were designated on the basis of distance in kilometers below the stream origin. Stream sediments ranged from cobble to silt in size. Silts and fine sands were found in marginal areas of pools. Coarse sand occurred in mid-pool areas. Riffle areas consisted of coarse sand and pebbles except for Station 125 where cobbles were present. Riffle and pool areas of Station 43 consisted of coarse sand. The riffle area of Station 125 was located on bedrock. Stream discharge and depth varied throughout the year. Riffles were sometimes absent from the two upper stations, but pools persisted even during driest parts of the year. Generally, riffles were abundant in the upper reaches while pools dominated the lower stretches. Maximum depth observed was 1.5 m. Stream discharge increased downstream but was maximum at Station 125. Velocity varied from station to station and was correlated with stream width, the more narrow stations having the greatest velocity. Oil wells in this region produce a mixture of oil and brines. Brines are removed by mechanical separators and either stored in an evaporation pit or allowed to escape into a nearby stream. A major source of brines is the Garber oil field, located in the western third of the basin. This field has numerous oil wells, tank batteries, and separators and many of them are located along Black Bear Creek 24 to 35 km from the origin. Oil installations not included in the Garber field are thinly scattered along the main channel to 65 km downstream. A few / t --Refinery i5 Kilometers Riverkna ~Garber' r ..OlField