Bioassessment of Hollis Creek, Oktibbeha County, Mississippi

Physical, chemical and biological components at five stations on Hollis Creek, Oktibbeha County, Mississippi were evaluated using Rapid Bioassessment Protocols (RBP) and the Sediment Quality Triad (SQT) on August 24-26, 1999, in order to assess potential biological impacts from the Starkville Waste Water Treatment Facility (WWTF) on downstream resources. Two stations were selected above the WWTF and three below. The WWTF discharges treated effluent into Hollis Creek, but during storm events raw sewage may be released. Hollis Creek is a tributary of the Noxubee River that traverses the northern portion of Noxubee National Wildlife Refuge, which is managed as bottomland hardwood forest land for the protection of fish and wildlife resources. Hollis Creek was channelized throughout most of its length, resulting in high, unstable banks, degraded stream channel and unstable substratum. The RBP scores for the habitat evaluations from each station indicated that Stations 1 and 2 had degraded habitat compared to the reference site, Station 5. Benthic macroinvertebrate and fish assemblages also indicated that the biological integrity at Stations 1 and 2 was less than that of the downstream stations. The SQT showed that Stations 1 and 2 were degraded and the most likely causes of the impairment were the elevated concentrations of polycylclic aromatic hydrocarbons and metals in the sediments; Hyalella azteca survival in pore water and growth in solid-phase sediment exposures were reduced at these upstream sites. The source of contaminants to the upper reaches appears to be storm-water runoff. The close concordance between the RBP and SQT in identifying site degradation provided a preponderance of evidence indicating that the upper reaches (Stations 1 and 2) of Hollis Creek were impacted. Biological conditions improved downstream of the WWTF, even though physical degradation steinming from channelization activities were still evident. The increased discharge and stabilized base flow provided by the WWTF appeared to benefit the physically-altered stream system. Impairment attributable to releases from the WWTF on downstream biological resources was not evident from this evaluation, and the potential for degradation in the Noxubee River and National Wildlife Refuge appears minimal.