Seventy-one aquatic species including the copepodids and nauplii were identified from Lake Texoma from August 1996 to September 1997. Zooplankton community structure, abundance and spatial and temporal distributions were compared among five lake zones delineated a priori based on chloride concentration. The zones, in order of decreasing chloride concentration, are the Red River zone (RRZ), Red river Transition zone (RRTZ), Main Lake zone (MLZ), Washita River Transition zone (WRTZ) and Washita River zone (WRZ). Bray Curtis Similarity Index showed community structure was most similar in the two Red River arm zones, the two Washita River arm zones and the MLZ. Zooplankton abundance was greatest in the Red River arm (312 org/L), intermediate in the Washita River arm (217 org/L) and least in the Main Lake body (103 org/L). A significant increase in the abundance of a deformed rotifer, Keratella cochlearis, was observed mainly in the Red River arm during a second study from March 1999 to June 1999. Seasonal dynamics, rather than spatial dynamics, were more important in structuring the zooplankton community, especially in the two river arms. Spatial variance was solely attributed to station and zone effects independent of time for a few crustacean species and many of the …

This study describes macroinvertebrate community structure and assesses its potential in detecting point and non-point sources of disturbance associated with rural and urban areas in the Upper Trinity River Basin. Geospatial techniques were used to quantify landuse within the watershed in a GIS. At rural sites near the headwaters of the Trinity River, collector-gathering burrowers that are adapted to minimal flow comprised the majority of taxa. Destinies of taxa compositions at downstream sites increased and shifted toward psammophilic and rheophilic invertebrates, including primarily collector-filtering clingers, that are characteristic of shifting sand habitats in large prairie rivers. Benthic community structure generally benefited from point source impacts including wastewater treatment plant effluents that maintained higher flow. Community indices were negatively associated with forest landuse and positively associated with urban landuse. Partial CCA determined that flow and landuse contributed equally to species dispersions. Comparisons with historical biomonitoring studies in upper Trinity River Basin indicate improved watershed health.