REA techniques to determine bio-reference locations
Discussion
For this study, the scientists adopted REA techniques to determine bio-reference locations that could be utilized in monitoring water quality as well as wetland permitting in the future of the Raymondville Drainage Outfall System in Texas. They investigated fish and macroinvertebrate assemblage and other physiochemical parameters to determine the sample areas subject to majority of the Texas regional and standard criteria. During the study researchers adopted a standard criteria modified from the Texas standards of surface water quality for the Rio Grande Basin and other values based on averages of 13181, 15808 and 13664 stations in the region. As for the macroinvertebrates, the eleven metric criteria was based on ecoregion thirty-four while the twelve metric criteria for determining high quality of water followed the TCEQ. By applying these stipulations for high water quality, the researchers determined the sample locations that met a good portion of the criteria and this had a higher potential for high quality water.
This bio-assessment provided the researchers a snapshot of the ecological conditions at a given period that is free from seasonal variance linked to long-term researches. The REA approach used in the study was essential in characterizing the quality of water from the sampled sites. Although no region met all the stipulated regional as well as standard criteria, sites from each segment of the region met the required criteria to support aquatic life with DO and pH values. However, the DO values could be linked to nutrient releases, algal bio-metabolism and sediment thickness. Whereas sixty percent of the locations met the guidelines for total nitrate and phosphate, and every site in the northern segment met the criteria for ammonia no particular site attained the standards for EC and TDs. These figures are illustrated in Table 1. The findings imply that the two drainage segments share the same eastward, that is, downstream, decreasing gradient for salinity, EC and TDS as well as nitrates.
From the overall physiochemical outcomes, three sites the northern segment and ten from the southern end attained five of the standard criteria. That means that these segments contained the highest water quality in the two sections of the canal under study. In like manner to the scoring system created by Ruse in 1998, the REA technique implies that scientists should not assume the metric values recorded for macroinvertebrates to be similar for all drainage systems in southern Texas. The findings indicated that five locations, that is, 3, 4, 6, 9, and 10 exhibited a richness value of seven and above. Thus, based on the TCEQ (2007) stipulation, these sites represent sections of the drainage system with the highest quality of water. Although the researchers found only one specimen of Hydroptilidae and Baetide in sites two and one respectively, these locations could also have high water quality.
The results further indicated that only sites two, four and nine supported Eliminidae. Scientists consider these creatures to intolerant towards pollution which implies that these sites could be having high quality water compared to the other sites studied in the drainage canal system. The outcomes from the study on a sample of non-insect taxa groups indicated that sites three and ten could have a higher quality water along the sampled drainage system. Non-insect taxa groups are typically few in degraded or impaired water bodies in Texas. High tolerant/intolerant ratio reflect minimal pollution and high water quality. Thus, site four could contain a habitat that supports aquatic insects that exhibit the least tolerance towards pollution. The low HBI values recorded also support this conclusion regarding site four.
Since the Chironomidae show ubiquity, that is, wide variety among differing water quality and habitats, sites that had low percentages namely sites four and five reflected that sections of the drainage system with the least pollution. However, it is not advisable to depend on one metric when interpreting water quality. Table three contained those bold metric readings that supported high quality water in the ten drainage canal segments. According to the overall findings on benthic macroinvertebrates, site five in the North segment and site ten in South segment met at least four of the criteria. That indicates that these sections had the highest value of water quality in the drainage system. By applying REA, the values recorded for fish metrics differed and thus one metric cannot be used to account for signs of high water quality. In three sites namely site two, six and eight, all of which had less than seventy percent intolerant species, the scientists added four species of fish assemblage that displayed intermediate tolerance towards pollution plus one tolerant species.
The researchers did not find any pollution-intolerant species nor did they observe any individual with an anomaly or sickness. Table five shows those metric values which suggests high quality water in the ten canal sections. As per the overall fish survey findings, site three and nine in the north and south segments respectively could be having the greatest water quality in the drainage system. The REA technique enabled the researchers to identify the sections of the two drainage sections with the highest quality of water based on the sum amount of TCEQ (2007) criteria achieved. The findings further indicated that the following locations are suitable for future bio-assessment of water (sites three and ten), fish (sites three, five and nine), and macroinvertebrate (sites five and ten).
Overall, the study supports the perception that site ten and sites three and five in the south and north sections respectively have high quality water that met most of the criteria and regional standards. The US state or federal permitting of the Raymondville Drain Project should have considered the baseline information acquired from the two bio-reference sites for future analysis of water quality, fish survey and macroinvertebrate sampling. Thus, the scientists recommended a multiple sites sampling technique and the application of several metric values in carrying out REAs of drainage systems when gathering baseline data for water quality and determining the bio-reference ecological conditions. The findings and interpretations do not suggest that long-term fish, macroinvertebrate as well as water quality surveys are less important or unnecessary for such analyses.
In essence, scientists can utilize the REA approach as a regulatory means to provide information quickly when there are financial and time constraints. Also, this technique us not to be viewed as a replacement for long-term bio-assessment. However, studies indicate that REAs are useful tools when analyzing water quality in large areas and determining pollution resulting from land use, bio-inventories and identifying preferential management sites. There is a need for further study to comprehend the underlying environmental processes linked with the trends or the lack thereof that the researchers reported. For instance, sample sites five and ten near the Laguna Madre reflected transitional habitats. Therefore, these sites require further evaluation. Although out of the scope of this research, lower identification or subfamily of the Chironomidae could provide crucial information for this study.
However, due to time and budgetary constraints, the REA approach adopted by the scientists for this study produced essential findings and interpretations for sampling baseline data, for wetland permitting and for the establishment of the Raymondville Drain Project. This study also complimented other low cost, rapid evaluation approaches for analysis of drainage system physical conditions. The study achieved this complimentary feature through provision of a further approach to the analysis and characterization of drainage system’s ecological conditions. Overall the study was successful in meeting the initial objectives of the researchers and the Texas government goal of controlling floods. The approach applied and the results achieved complimented each other to produce reliable results. Nevertheless, the relevant authorities should avail sufficient time and budget for similar bio-analyses of the prevailing environmental conditions in the future to avoid the constraints that necessitated the REA approach. Also, that would ensure the researchers cover wider regions compared to the sample sites studied in this research.
The research was successful largely to the contribution of the following parties. The S & B Infrastructure company partially sponsored this project through a contract they gave to the University of Texas-Pan American. Also, the following individuals offered the research as well as field assistance to the researchers; they are Mark Iglesias, Deborah C Edwards and Juan Alcazar. The El Sauz Rach and Hidalgo and Willacy County Irrigation Districts provided their properties for the research. Notably, there was no conflict of interests and the results plus the interactions belong to the researchers and were not influenced by the sponsors. Anonymous reviewers offered suggestions that were beneficial towards the improvement of this article. Lastly, Zen Faulkes from the University of Texas-Pan American assisted the researchers with drawing and formatting the figures outlined in the maps. The collaboration mentioned above shows the importance of teamwork when conducting environmental research and other rapid assessments. Also, the study was a success in that it provided further understanding of the application of the REA approach in bio-assessments and the environmental conditions needed for establishment of better drainage systems that emit less pollution to the surroundings.