摘要：The primary objective of this study was to survey the aquatic macroinvertebrate diversity of the St. Francis Sunken Lands in northeast Arkansas. Secondary objectives were a determination of their relative abundance and distributional and seasonal patterns. Sixty semi-annual collections were made from 30 stations by sampling each station 2 times for 1 ½ man-hours with a Turtox Indestructible™ dip net. Totals of 243 taxa and 13,952 organisms were recorded for the sample period (August 1987 - July 1988). Each station was assigned to 1 of 4 associations, distinguished by distinct physical factors within the river channels and the immediate watershed. The Old River Channel-Oxbow Association exhibited the most complex and stable community structures; this was attributed to the relative lack of man's alteration of the habitat. The Channelized Ditches-Point Source Pollution Association demonstrated obvious detrimental effects of man's intervention. The relatively simple community structures of the St. Francis Lake-Open Water Association were attributed to the typically homogeneous substrates of this area. The simplest community structures were in the Channelized Ditches- Intense Agriculture Association and were a direct result of man's multiple alterations within the river channels and immediate watershed. Seasonal species diversity indices and numbers of taxa varied inversely with respect to water level. High values occurred during low-water periods, whereas lower values occurred during high-water periods. This inverse relationship was attributed to flooded habitat, which led to population dilution and diminished collecting success.
