Status of Biotic Integrity, Water Quality, and Physical Habitat in Wadeable East Texas Streams

1 METHODS . 3 Site selection. 3 Water chemistry . 4 Physical habitat . 4 Fish assemblage samples . 5 Mercury in fish tissue . 5 Benthic invertebrate samples. 5 Data analysis. 6 RESULTS. 8 Stream network. 8 Stream condition . 8 Urban, ecoregion, and stream-order influences on water quality . 9 Urban, ecoregion, and stream-order influences on physical habitat . 10 HQI representation of habitat. 10 Urban, ecoregion, and stream-order influences on fish community structure . 10 IBI metric response to water quality and physical habitat. 11 Metric contribution to IBI . 12 Urban, ecoregion, and stream-order influences on invertebrate assemblages. 12 Metric contribution to the invertebrate index. 12 Invertebrate metrics . 12 Invertebrate metric response to water quality and physical habitat. 12 Invertebrate subsample analysis . 13 Prevalence of mercury in fish tissue . 13 DISCUSSION. 14 Stream condition . 14 Evaluation of regional IBIs . 15 Evaluation of invertebrate community index . 15 Spearman rank correlations. 17 Snag versus benthic samples. 18 Benthic subsampling. 18 Water quality data . 18 Physical habitat data and HQI . 19 Mercury in fish tissue . 19 LITERATURE CITED. 20 LIST OF TABLES. 25 LIST OF FIGURES. 58 This page left intentionally blank. Status of Biotic Integrity, Water Quality, and Physical Habitat in Wadeable East Texas Streams LEROY J. KLEINSASSER, TIM A. JURGENSEN, DAVID E. BOWLES, STEVE BOLES, KARIM AZIZ, KENNETH S. SAUNDERS, GORDON W. LINAM, JOSEPH F. TRUNGALE, KEVIN B. MAYES, JASON RECTOR, JACQUELINE RENEE FIELDS, KIP PORTIS, GARY STEINMETZ, AND RANDALL E. MOSS Resource Protection Division, Texas Parks and Wildlife Department, Austin, Texas Abstract. — In an effort to evaluate the overall condition of water quality, physical habitat, and fish and invertebrate communities throughout east Texas and determine if differences in those factors could be observed among ecoregions and stream orders and between urban and nonurban sites, we sampled 91 wadeable streams between 1998 and 2000 in three east Texas ecoregions—Texas Blackland Prairies (TBP), East Central Texas Plains (ECTP), and South Central Plains (SCP). Streams were second through fourth order (1:100,000 map scale) and were selected using a randomized systematic design with probabilities set to ensure roughly equal numbers representing each ecoregion and independently, each stream order, and finally to ensure at least 30 reaches in urban or developed areas. Samples were also collected to evaluate the status of mercury contamination in fish tissue across the region. The sites represented a broad range of condition and based upon fish assemblages from all study sites, >83% of stream kilometers were estimated to have an exceptional or high aquatic life use (ALU) compared to >73% for invertebrate kicknet samples. Biotic indicators exhibited a lower proportion of high or exceptional ratings in urban streams compared to nonurban ones. Dissolved oxygen (DO) concentrations were reflective of high or exceptional ALU’s for an estimated 71.4% of total stream kilometers. No significant differences in DO were found among ecoregions, stream orders, or between urban and nonurban sites. Nutrient concentrations were less than state screening levels at the majority of sites, and demonstrated no significant differences among ecoregions or between urban and nonurban sites, although phosphorus values were higher in higher order streams. Some physical habitat variables differed significantly between urban and nonurban streams, with the former exhibiting less sinuosity, canopy cover, large woody debris, and natural cover than nonurban ones and more nonagricultural riparian disturbance. Fewer significant differences in physical habitat were observed among ecoregions and most differences in stream order were tied to variables relating to channel morphology and stream size. Urban sites had fish assemblages with fewer total, benthic invertivore, sunfish and intolerant species. Invertebrate metrics were highly variable with respect to significance among ecoregions and stream orders, and between urban and non-urban sites. Hilsenhoff Biotic Index (HBI), percent Chironomidae, and percent dominant taxon were all significantly greater at urban sites. In contrast, ratio of intolerant to tolerant taxa, number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, and percent Elmidae were all significantly greater at nonurban sites. Benthic subsampling analysis showed that 100 and 200 specimen subsamples produced results that largely were not significantly different from completely picked benthic samples thus indicating that such subsampling protocols may be economically justifiable when used in conjunction with other metrics such as water quality and fish IBIs. Mercury concentrations in fish tissue demonstrated an increasing trend from west to east. In the ecoregion farthest east (SCP), mercury concentrations in whole fish exceeded a predator protection screening level of 0.1 mg/kg in an estimated 87.2% of stream kilometers. Based upon our analysis, we recommend additional refinement and recalibration of assessment tools for biotic integrity and physical habitat. — In an effort to evaluate the overall condition of water quality, physical habitat, and fish and invertebrate communities throughout east Texas and determine if differences in those factors could be observed among ecoregions and stream orders and between urban and nonurban sites, we sampled 91 wadeable streams between 1998 and 2000 in three east Texas ecoregions—Texas Blackland Prairies (TBP), East Central Texas Plains (ECTP), and South Central Plains (SCP). Streams were second through fourth order (1:100,000 map scale) and were selected using a randomized systematic design with probabilities set to ensure roughly equal numbers representing each ecoregion and independently, each stream order, and finally to ensure at least 30 reaches in urban or developed areas. Samples were also collected to evaluate the status of mercury contamination in fish tissue across the region. The sites represented a broad range of condition and based upon fish assemblages from all