A comparative study of the macroinvertebrate communities in three oxbow lakes and the Brazos River in East Central Texas

Abstract

Macroinvertebrate communities of the Brazos River and three of its oxbow lakes, in East Central Texas, were sampled from the summer of 1994 to the spring of 1996. The floodplain for this area is predominantly nutrient-rich forested and agricultural land. All three oxbows were shallow and eutrophic with aquatic vegetation growing along the shores, while the Brazos River was much deeper and vegetation was scarce. Flooding occurred during the winter of 1991-1992 and all three oxbows had connection with the Brazos River. Since then only one oxbow, Big Bend Oxbow, had connection with the Brazos River. This occurred in the late spring of 1995, during the sampling period. Species diversity was found to be the highest in the Brazos River due to fewer individuals of each species found. The total number of individuals found in the three oxbow lakes was at least twice the number of that of the River. Palaemonetes sp., Caenis sp., and Trichocorixa calva were very abundant in the oxbow lakes. Of the 67 species collected, 20 species were predominant in the Brazos River, while 47 species were predominant in the oxbow lakes. Physiochemical parameters that showed the greatest percent of the variance were depth and conductivity. All three oxbows had similar macroinvertebrate communities, which differed from that of the Brazos River. Although the three oxbow lakes were derived from the Brazos River, and occasionally flooded by the river, species composition varied greatly between the oxbows and the Brazos River. Faunal exchange between the oxbows and river is minimal due to the infrequency of flooding and unpredictable precipitation in Central Texas. This study suggests that macroinvertebrates colonizing the oxbow lakes came from other oxbow lakes and artificial ponds and not the river.