A study utilizing macroinvertebrate communities was performed in the Wichita River Basin between September 27, 1996 - October 4, 1996. The goals of this study were to assess the water quality in the basin and secondly to supply valuable information concerning the macroinvertebrate taxa present in the Wichita River Basin, thus providing data for future comparisons in performing trend analysis . There has been minimal biological sampling performed within the Wichita River Basin (as is the case throughout the Red River Basin), therefore through the Clean Rivers Program, the Authority plans to alleviate this deficiency for both macroinvertebrates and nekton.

A modified Rapid Bioassessment Protocol II was used in this study, which used seven metrics to attempt to quantify biological health for streams that were sampled (Plafkin et al., 1989 and Barbour et al., 1992). These biological integrity scores are beneficial in that they integrate water quality over a relatively long period of time (as compared to taking a grab sample for water chemistry analysis). Also, trends in biological health can be determined if these RBA’s are performed periodically.

Descriptions of the sampling sites are below in Table 1 and a map showing these sites can be seen on Figure 1.

Pollution tolerance values for macroinvertebrates were assigned based on values established by the Texas Natural Resource Conservation Commission (handout given by Bill Harrison), the EPA (Plafkin, 1989), or from Lenat, 1993. Functional feeding groups for macroinvertebrate families were assigned based on classifications obtained from Merritt and Cummins (1996). Several insect families have been assigned multiple functional feeding group classifications by Merritt and Cummins (1996). In order to clarify these classifications, organisms were further identified to genus, and when possible, to species (Merritt, R.W.,1996, Parrish R.K., 1975, and Thorp, J.H., 1991). The data thus recorded was used to score seven metrics for a slightly modified Rapid Bioassessment Protocol II (RBP II).

The following metrics were scored in the study:

1. Taxa Richness = total number of taxa collected at the site.

2. EPT Index = number of genera belonging to the Orders Ephemeroptera,            Plecoptera and Trichoptera which were collected.

3. Community Loss Index = (taxa richness at the reference site - taxa common to        reference and sampling sites)/taxa richness at the sampling site.

4. Family Biotic Index (modified) = S (xi ti)/n, where:

xi = number of individuals within a taxa,

ti = tolerance value for the taxa,

n = total number of organisms in the sample.

5. Percent Contribution of Dominant Family = percent contribution of the

6. Ratio of Scrapers/Filtering Collectors = number of scrapers/(number of scrapers + number of filtering collectors).

7. Quantitative Similarity Index = (Functional Feeding Groups or FFG’s) - compares two communities in terms of presence or absence of FFG’s, also taking relative abundance into account.

Each metric value obtained was given a Biological Condition Score of 0, 3, or 6, based on its percent comparison to the metric value obtained from reference station data. Scoring criteria for the Percent Contribution of Dominant Family was expressed as the actual percent contribution, not percent comparability to the reference station. The Community Loss Index and Quantitative Similarity Index (FFGs) were not given a percent comparability to the reference station, because a comparison to the reference station is incorporated into these indices. The metric scores for each sampling site were totaled, and were compared to the total metric score for the reference site to obtain the Percent Comparability to Reference Site value. The reference site in this study was Buffalo Creek, due to it’s superior biological and physical health. It should be noted that Buffalo Creek is not an optimal reference site, due to the influence of anthropogenic activities (i.e. WWTP effluent discharge). However, there are no sites in this region that are not affected substantially by anthropogenic activity.

A habitat assessment matrix was completed for each sampling site using forms taken from Plafkin et al., 1989. The matrices were evaluated to determine percent comparability of habitat between the sampling sites and the reference sites. The percent comparability was used to judge the potential for each sampling site to support a similar level of biological health compared to its reference site.

The sampling methodology for this study consisted of using a D-framed kick net to sweep woody habitat, vegetation, and perform kick samples within riffles. Due to inconsistencies in the amounts and types of habitat between the sampling sites, a perfectly consistent sampling method could not be implemented. Therefore, the sampling method consisted of performing 5 minute sweeps, partitioning the 5 minutes between the most suitable macroinvertebrate habitats. The different habitats are sampled approximately the same percentage as they are present. For example, if the habitat consisted of approximately 60 percent bank woody habitat and 40 percent channel woody habitat, then the bank woody habitat would be sampled for 3 minutes and the channel woody habitat would be sampled for 2 minutes. If less than 100 macroinvertebrates are collected after the 5 minutes, then another 5 minutes of sampling are conducted. Lastly, a submerged log was removed from each stream and the macroinvertebrates were collected. This is also performed for approximately 5 minutes, in an attempt to represent the shredder population, with consistent methodology. The following paragraphs describe the exact methodology for each site in the study.

Two 5 minute sweeps were taken in approximately 40 percent bank woody habitat, 25 percent in overhanging bank vegetation and 35 percent channel woody habitat. Riffles were sampled below the bridge and no invertebrates were found due to deposition/lack of interstitial space. Abundance of invertebrates at this site was quite low. A submerged log was picked for 5 minutes and had no invertebrates apparently due to siltation on the log.

North Fork Wichita River at Hwy 267 10/4/96

Three minutes of kick sampling was performed in riffle habitat, 1 minute of sweeping was performed in bank woody habitat and 1 minute of sweeping was performed in channel woody habitat. Invertebrates from the riffle habitat were kept separate from the invertebrates collected in woody habitat. A submerged log was picked for 5 minutes and had no invertebrates apparently due to siltation on the log.

One 5 minute sweep was performed, approximately 3.5 minutes of the sample time within channel woody habitat and 1.5 minutes in bank woody habitat. A submerged log was picked for 5 minutes.

Buffalo Creek at F.M. 1814 9/27/96

One 5 minute sweep was performed, with approximately 10 percent of the time in riffle habitat, 50 percent in bank woody habitat, 20 percent channel woody habitat, and 20 percent submerged vegetation (grass) at edge of stream. A submerged log was picked for 5 minutes.

Two 5 minute sweeps were performed with approximately 50 percent of the time in overhanging bank vegetation, 20 percent in channel woody habitat, and 30 percent in bank woody habitat. A submerged log was picked for 5 minutes.

RESULTS

The results in this study include the actual metric scores for each site, as well as the overall RBA score obtained, which is displayed in Table 2. Second, a listing of the invertebrates collected and where they were collected is shown in Table 3. Lastly, the RBA scores as compared to the Habitat Assessment scores is important in differentiating low RBA scores due to water quality from those due to habitat quality. This is illustrated in Figure 2.

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Figure 2: Rapid Bioassessment Scores compared to Habitat Assessment Scores.

Table 3: A list of the macroinvertebrates collected and at which sites they were collected

The results of this study illustrate the importance of suitable habitat for a healthy macroinvertebrate population. It also illustrates the effects of harsh water quality conditions (i.e. turbidity and total dissolved solids) on macroinvertebrate populations. Buffalo Creek (T3), which was selected as the reference stream, scored the highest for both the habitat and biological assessment. This stream contains all types of habitat sampled within the Wichita River basin. Water quality is similar as the other sampling sites, but not as high in total dissolved solids as the North Fork and South Fork of the Wichita River. Therefore, Buffalo Creek was the logical choice for a reference stream in this study. However, water quality conditions for the North Fork and South Fork of the Wichita River, as well as differences in the types and amounts of suitable habitat must be addressed.

The North Fork (R2) and South Fork (R3) of the Wichita River scored the least of the 5 sampling sites. This is due to both harsh water quality conditions (i.e. turbidity, sedimentation, and total dissolved solids), as well as lacking suitable habitat. R3 had the least habitat assessment score, as well as the least RBA score. This site contained some woody habitat and overhanging vegetation, however these suitable habitats appeared highly susceptible to silt deposition. This site also had riffle habitat, however, no invertebrates were found in these areas apparently due to the lack of interstitial space caused by fine gravel (i.e. silicon) and clay deposits in between the larger cobble substrate. The abundance of macroinvertebrates at R3 was minimal, taking two five minute sweeps and five minutes of picking organisms from a submerged log to obtain 22 organisms. Therefore, it is obvious that R3 is impaired due to both habitat and water quality factors, in that the limited habitat available was negatively affected by the turbidity of the stream. R2 showed a relatively high abundance, however, the majority (67%) of the macroinvertebrates were collected from riffle habitat, which was suitable for macroinvertebrate colonization (as compared to the insufficient riffle habitat at R3). Also, 50 percent of all the macroinvertebrates collected at R2 (71) were of the family Ceratopogonidae. These Dipteran larvae infested aquatic grasses located within the riffle habitat. Little is known about the family Ceratopogonidae, making it difficult in determining why these organisms would be infested in this particular habitat. The larvae are considered predators. However some are considered herbivores, which is believed for this particular species and explains their great presence in the grasses of the riffle habitat.

The habitat assessment for Beaver Creek (33) and the Wichita River (T5) scored similarly, although Beaver Creek obtained a considerably higher RBA score. Both of these waterbodies exhibit high levels of total dissolved solids, due to natural brine springs (Wichita River) and the seepage of highly saline water originating from petroleum production (Wichita River and Beaver Creek). The Wichita River contains a significant greater concentration of total dissolved solids, which could contribute to the lower RBA score at the Wichita River site (T5). Another possible reason for this lower score could be that 50 percent of the sampling at the Wichita River was performed in overhanging vegetation, which was observed to be less suitable for macrobenthic colonization as compared to stable woody habitat. However, in sampling both overhanging vegetation and woody habitat at T5, a greater taxa richness score was obtained due to the addition of several semi-aquatic species of macroinvertebrates. Abundance of macroinvertebrates was also considerably lower at the Wichita River station, in that it took twice the sampling effort as the sampling at Beaver Creek to get 100+ organisms. This is another indicator of impairment at the Wichita River sampling site (T5).

Lastly, the scarce presence of species belonging to the notably intolerant families, Ephemeroptera, Plecoptera, and Trichoptera was informative. This illustrates that the water quality throughout the Wichita River Basin is unfavorable for the majority of intolerant species of macroinvertebrates. There was sufficient habitat sampled in this study to obtain a good representation of the macroinvertebrates found in this basin, therefore it is believed this lack of intolerant species is limited by water quality (i.e. total dissolved solids and turbidity).

There were families represented within this EPT index, Hydropsychidae, Odontoceridae, and Tricorythidae. No families belonging to these three orders were found at R2 and R3, in which the total dissolved solids is the greatest. This suggests that total dissolved solids may play an important role in limiting the presence of intolerant macroinvertebrates.

The results of this study helped in the evaluation of macroinvertebrate populations in the Wichita River Basin (as well as North Texas Region). However, more studies similar to this study could be conducted for more insight on the macroinvertebrate community. First, seasonal changes in macroinvertebrate populations would be very informative. Secondly, a study targeting areas with a wider range of total dissolved solids would help in understanding the effects of total dissolved solids on the macroinvertebrate populations. Lastly, repetition of this study in years to come during the same time period, would help in an overall trend analysis of the biological integrity of the Wichita River Basin. These multiple datasets will also be helpful in assessing the effects of reducing the total dissolved solids through the Red River Chloride Control Project, if and when the project is completed.

Barbour, M.T., J.L. Plafkin, B.P. Bradley, C.G. Graves, and R.W. Wisseman. 1992. Evaluation of EPA’s Rapid Bioassessment Benthic  Metrics: Metric Redundancy  and Variability Among Reference Stream Sites. Environmental Toxicology and Chemistry. 2:437-449.

Harrison, Bill. 1997. Personal communication through handout. Texas Natural  Resources Conservation Commission.

Lenat, David R. 1993. A Biotic Index for the Southeastern United States: derivation and list of tolerance values, with criteria for assigning water-quality ratings. Journal of North American Benthological Society. 12(3): 279-290.

Merritt, R.W. and K.W. Cummins. 1984. An introduction to the Aquatic Insects of North America. Third Edition. Kendall/Hunt Publishing Company. Dubuque, Iowa. 862 pp.

Parrish, Fred K. 1975. Keys to Water Quality Indicative Organisms of the Southeaster United States. United States Environmental Protection Agency. 2^nd Ed. Cincinnati.

Plafkin, J.L., M.T. Barbour, K.D. Porter, S.K. Gross and R.M. Hughes. 1989. Rapid Bioassessment Protocols for use in Streams and Rivers: Benthic Macroinvertebrates and Fish. EPA/444/4-89-001.

Thorp, J.H. and A.P. Covich. 1991. Ecology and Classification of North American Freshwater Invertebrates. Academic Press, Inc. San Diego. 911 pp.

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