Studies of macroinvertebrate and fish communities help gauge the health of local watersheds.

By Catherine A. Fox and Charles D. Absher

The ecological goal for the restoration and protection of freshwater ecosystems in the United States is based upon the Clean Water Act and the Great Lakes Water Quality Agreement objectives of "biological integrity." Biological integrity is defined as "the ability of an aquatic ecosystem to support and maintain a balanced, integrated, adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of the natural habitats of a region." Although natural or unimpaired water bodies may no longer exist in a particular study area, expected biological integrity in surface waters may be estimated through the use of a reference site that serves as undisturbed habitat representative of the region. Comprehensive watershed protection programs and carefully designed stream restoration efforts must take into account the results of recent, high-quality, site-specific biological assessments to guide planning efforts so that the ultimate goal of enhancing and preserving our fragile water resources for future generations may be attained.

Macroinvertebrate and fish communities serve as excellent indicators of water quality. They inhabit these areas for most or all of their life cycles (up to 10 years or longer) and, therefore, reflect recent as well as historical environmental conditions. Resident biota in a water body function as continual monitors of environmental quality, capable of detecting both the effects of episodic and cumulative pollution as well as the effects of altering available habitat. Any stress (biological, chemical, or physical) imposed on an aquatic ecosystem manifests its impact on the biological organisms present in that ecosystem such that the organisms might not recover to reestablish their prestress community structure (Loeb and Spacie, 1994). Therefore, the structure and function of resident biota are the only direct measurements of the condition of the aquatic ecosystem.

The purpose of this article is to present a general overview on the fundamental concepts of biological assessment and to show how this critical tool has been used to help guide watershed planning activities in Georgia. This information can assist local governments and all affected stakeholders in identifying specific causes of impairment and developing cost-effective solutions to restore and protect streams, lakes, and rivers for future generations.

The Basics of Biological Assessment

Biological assessments are evaluations of the condition of water bodies using surveys and other direct measurements of resident biological organisms (macroinvertebrates, fish, and plants). Biological assessment results are used to answer the question of whether water bodies support survival and reproduction of desirable fish, shellfish, and other aquatic species—in other words, if the water bodies meet their designated aquatic-life uses. The fact that no pollutants are apparent in the water body does not automatically translate to a viable and robust biological environmental community.

Most states, including Georgia, use biological assessment protocols based on the Environmental Protection Agency's Rapid Bioassessment Protocol (RBP) III (Plafkin et al., 1989). Some modifications were necessary because of varying stream morphologies and in-stream biota characteristic of the different types of habitats found around the country. The monitoring protocols used in Georgia consist of four basic components: in-situ water-quality characterization, physical-habitat assessment, a biosurvey of the aquatic benthic macroinvertebrates, and fish assessment.

In-Situ Measurements

Typically, while the aquatic biologist conducts an investigation, a water-quality meter will be used to assess in-situ parameters, such as temperature, dissolved oxygen, pH, specific conductivity, salinity, and turbidity. Taken alone, these measurements do not give a comprehensive picture of water quality at a particular sample station. However, when combined with the other biological parameters and with other sampling results from efforts conducted as part of an overall watershed assessment, these data become a confirming piece of the puzzle in analyzing biological and water-quality conditions.

Habitat Assessment

An aquatic ecosystem habitat assessment is defined as an evaluation of the physical surrounding habitat as it affects and influences the quality of the water resource and its resident aquatic community. Physical-characterization parameters include estimations of general land use and physical stream characteristics, such as width, depth, water velocity, and channel substrate type. The overall habitat assessment evaluates habitat quality using key structural parameters. If the results of the biosurvey indicate a degraded community, habitat information will aid interpretation of effects relative to the biotic potential of a site. The water quality and physical characterizations provide data on stream quality as well as potential sources and/or causes of impairment.

In Georgia, there are two habitat assessments (riffle/run vs. glide/pool), depending on the characteristics of the stream. In the Ridge and Valley, Blue Ridge, and Piedmont regions of northern Georgia, riffle/run–prevalent streams dominate. Many streams lack this valuable habitat, however. The Coastal Plain streams, south of the Fall Line (a contiguous shoaling boundary across the middle of the state for all Georgia streams and rivers), are glide/pool–prevalent water bodies that lack riffle habitat.

Habitat parameters are evaluated as they relate to overall aquatic-life use and as a potential source of limitation to the aquatic biota (Plafkin et al., 1989). The physical parameters of the habitat assessment are broken into primary, secondary, and tertiary categories. Primary parameters describe those instream physical characteristics that directly affect the biological community. Primary conditions include epifaunal substrate and available cover, embeddedness, velocity/depth combinations, and pool substrate/variability. Secondary parameters (channel alteration, sediment deposition, channel flow status, and frequency of riffles/channel sinuosity) relate to channel morphology, which controls the behavior of stream flow and the sediment deposits the stream collects. The tertiary parameters in the habitat assessment matrix deal with the riparian vegetation and streambank structure. These include bank stability, bank vegetative protection, and the riparian vegetative zone. The stability of a streambank indirectly affects the type of habitat available within a stream. Vegetated banks reduce the amount of sediment that washes from the streambank by absorbing energy from the raindrops, binding soil particles, and reducing the velocity of runoff water. Less sediment to cover rocks and logs results in more habitats available for colonization by invertebrates. The parameters are usually evaluated over the designated sample study reach (100-250 m) of a stream (Plafkin et al., 1989).

The habitat assessment process involves rating the parameters as optimal, suboptimal, marginal, or poor based on a set of specific criteria. A total score is obtained for each biological station and compared to a site-specific control or a regional reference site (unimpacted site). The ratio between the score for the station of interest and the score for the unimpacted site provides a percent comparability measure for each station. The optimal category describes criteria for each parameter that meet natural expectations. The suboptimal category includes criteria that are less than desirable but satisfies expectations in most areas. The marginal category includes judgment criteria describing moderate levels of degradation with severity at frequent intervals in the area. The final category, poor, encompasses criteria for streams having been substantially altered with severe degradation characteristics.

Macroinvertebrate Sampling and Analysis

The timing of a biological assessment sampling event is very important. Reproductive periods and different life stages of aquatic insects are related to the abundance of particular food supplies (Cummins and Klug, 1979). Peak emergence and reproduction typically occur in the spring and fall, although onset and duration vary somewhat across the US. During peak reproduction, approximately 80% of the macroinvertebrates will be too small to be captured in sufficient numbers to accurately characterize the community. Additionally, food-source requirements for early instars are different from those of later instars. Therefore, the biologically optimal sampling season would occur when the habitat is utilized most heavily by later instars and the food resource has stabilized to support a balanced indigenous community (Plafkin et al., 1989). Biologically optimal periods happen between late fall and early winter. Georgia's Index Period for sampling is October through February.

The Georgia Bioassessment Protocol (GBP) recommends use of a D-frame dip net to collect freshwater macroinvertebrates from six different habitat types, including fast and slow riffles, woody debris/snags, sand or bottom substrate, undercut bank/root mats, leaf packs, and macrophytes (DNR, 1999). A total of 20 (+3, depending on the availability of macrophytes) jabs or kicks are taken over the sampling-site area (generally 100- to 250-m stream reach). Organisms are preserved in ethanol (some taxa groups, such as Hirudinea, should be narcotized with club soda prior to preservation) and later identified in the laboratory to the genus level or, if unattainable, the lowest possible taxonomic level using standard taxonomic keys. It is important to recognize the significance of quality-assurance and quality-control procedures throughout this process to ensure the utility of environmental monitoring data to meet the overall sampling program objectives.

To determine the level of impact to the various habitats, it is useful to compare taxa lists for each habitat to the corresponding habitat in the reference/control site, including differences in total taxa, intolerant and/or tolerant taxa, and functional feeding groups. Impaired cobble habitat will have a decrease in macroinvertebrate abundance and a loss of EPT (see below). Impacted sediments will release burrowing mayflies and dragonflies and have a decreased variety of chironomid taxa. Concomitantly, there will be an increase in overall chironomid abundance and tubificid Oligochaetes. Leaves tend to release shredders as impact increases, though this result does depend on the type of impact. Coleoptera and Isopoda usually replace Ephemeroptera and Odonata in streambanks and macrophyte beds as impact increases.

Data analyses, based on community, population, and functional parameters (or metrics), follow EPA RBPs (Plafkin et al., 1989). The metrics include:

Metric 1: Taxa Richness—Reflects the health of the community through a measurement of the variety of taxa present.

Metric 2: EPT Index—This measure is a count of the number of taxa in each order of Ephemeroptera, Plecoptera, and Trichoptera.

Metric 3: Number of Chironomidae Taxa—This metric is a relative measure of the presence and diversity of Chironomidae taxa, similar to the EPT Index.

Metric 4: Percent Contribution of Dominant Taxon—Provides insight to community structure because dominants specialize on the prevailing environmental complex of the aquatic ecosystem.

Metric 5: Percent Diptera—The percent of Diptera taxa present generally increases with exposure to increasing pollution.

Metric 6: North Carolina Biotic Index—The NCBI is a modification of the Hilsenhoff Biotic Index that was developed as a means of detecting organic pollution in benthic macroinvertebrate communities.

Metric 7: Florida Index—Uses key indicator taxa found within coastal-plain streams to assess biological condition.

Metric 8: Percent Filterers—A high percentage of filter feeders indicates healthy coastal-plain streams.

Metric 9: Percent Shredders—Good indicators of toxic effects when the toxicants involved are readily absorbed to the coarse particulate organic matter.

Metric 10: Indicator Assemblage Index (IAI)—Measures the change in the relative abundance of selected tolerant and intolerant taxonomic groups associated with a pollutant source.

For streams classified by the biometric scoring system as poor or very poor, a potential generic cause is established. This involves an examination of biometric scores, habitat assessment data, chemical data, and background information, such as effluent characteristics, treatment processes, discharge monitoring reports, reported fish kills, and land uses. Generic causes are delineated into three major groups: organic, toxic, or physical alteration. Any generic cause might result from point- or nonpoint-source pollution. It is possible for more than one type of generic cause to be responsible for an impact.

Fish Sampling and Analysis

Many state water-quality agencies employ trained and experienced benthic biologists who have accumulated considerable background data on macroinvertebrates and consider benthic surveys a useful assessment tool. However, water-quality standards, legislative mandate, and public opinion are more directly related to the status of a water body as a fishery resource. Fish are good indicators of long-term (several years) effects and broad habitat conditions because they are relatively long-lived and mobile (Karr et al., 1986).

Fish assemblages generally include a range of species that represent a variety of trophic levels (omnivores, herbivores, insectivores, planktivores, and piscivores). They tend to integrate effects of lower trophic levels; thus, fish assemblage structure is reflective of integrated environmental health. For these and other reasons, separate protocols were developed for fish and are based largely on Karr's Index of Biotic Integrity (IBI), which uses the structure of the fish assemblage to evaluate water quality. The integration of functional and structural/compositional metrics, which forms the basis for the IBI, is a common element to the rapid bioassessment approaches.

Seasonal changes in the relative abundance of the fish community primarily occur during reproductive periods and (for some species) the spring and fall migratory periods. Therefore, the preferred sampling season is mid-to-late summer, when stream and river flows are moderate to low and less variable than during other seasons.

Although various gear types are routinely used to sample fish, electrofishing equipment and seines are the most commonly used collection methods in freshwater habitats. Although each method has advantages and disadvantages, electrofishing is recommended for most fish field surveys because of its greater applicability and efficiency. Local conditions might require consideration of seining as an optional collection method. Pulsed direct-current electrofishing is the method of choice to obtain a representative sample of the fish assemblage at each sampling station. However, electrofishing in any form has been banned from certain salmonid spawning streams in the Northwest. As with any fish-sampling method, the proper scientific collection permit(s) must be obtained before commencement of any electrofishing activities. The accurate identification of each fish collected is essential, and species-level identification is required. Field identifications are acceptable; however, voucher specimens must be retained for laboratory verification, particularly if there is any doubt about the correct identity of the specimen.

Composite sampling is the norm for RBP investigations to characterize the reach, rather than individual small replicates. However, a major source of variance can result from taking too few samples for a composite. Therefore, each of the protocols (i.e., for periphyton, benthos, and fish) advocate compositing several samples or efforts throughout the stream reach. The sampling area should be representative of the reach, incorporating riffles, runs, and pools if these habitats are typical of the stream in question. Replication is strongly encouraged for precise evaluation of the methods. Follow-up laboratory analyses are conducted and/or supervised by a fisheries professional trained in fish taxonomy. Quality assurance and quality control must be a continuous process in fisheries monitoring and assessment and must include all program aspects (i.e., field sampling, habitat measurement, laboratory processing, and data recording).

The IBI provides a consistent theoretical framework for analyzing fish assemblage data (Karr et al., 1986). The IBI includes 12 biological metrics based on fish composition and the abundance and condition of fish. Each metric is scored against criteria developed from appropriate regional reference sites. Individual metrics might differ in their relative sensitivity to various levels of biological condition.

Species Richness and Composition Metrics

Metric 1: Total Number of Fish Species—Total number of resident native fish species and salmonid age classes.

Metric 2: Number and Identity of Darter Species—These species are sensitive to degradation resulting from siltation and benthic oxygen depletion because they feed and reproduce in benthic habitats.

Metric 3: Number and Identity of Sunfish Species—These pool species decrease with increased degradation of pools and instream cover.

Metric 4: Number and Identity of Sucker Species—These species are sensitive to physical and chemical habitat degradation and commonly comprise most of the fish biomass in streams.

Metric 5: Number and Identity of Intolerant Species—This metric distinguishes high- and moderate-quality sites using species that are intolerant of various chemical and physical perturbations.

Metric 6: Proportion of Individuals As Green Sunfish—This metric is the reverse of Metric 5. It distinguishes low-quality from moderate-quality waters. Trophic Composition Metrics

Metric 7: Proportion of Individuals As Omnivores—The percent of omnivores in the community increases as the physical and chemical habitat deteriorates.

Metric 8: Proportion of Individuals As Insectivorous Cyprinids—As the invertebrate food source decreases in abundance and diversity due to habitat degradation (e.g., anthropogenic stressors), there is a shift from insectivorous to omnivorous fish species.

Metric 9: Proportion of Individuals As Top Carnivores—The top-carnivore metric discriminates between systems with high and moderate integrity. These species often represent popular sport fish such as bass, pike, walleye, and trout.

Fish Abundance and Condition Metrics

Metric 10: Number of Individuals in Sample—This metric evaluates population abundance and varies with region and stream size for small streams.

Metric 11: Proportion of Individuals As Hybrids—This metric is an estimate of reproductive isolation or the suitability of the habitat for reproduction.

Metric 12: Proportion of Individuals With Disease, Tumors, Fin Damage, and Skeletal Anomalies—This metric depicts the health and condition of individual fish.

Metric 13: Total Fish Biomass (Optional)—The combination of diversity and biomass measures is a useful tool for assessing fish assemblages in larger rivers.

In addition to the IBI, Georgia State protocol utilizes a modified Index of Well-Being (Iwb) to assess the fish community. The IBI is the primary tool used for evaluating the fish community, and the Iwb is used as a secondary assessment to confirm the results of the IBI. The Iwb is a composite index that combines two parameters of fish diversity and fish abundance into a single value reflective of these two components. The four parameters that comprise the Iwb are (1) relative fish density, (2) relative fish biomass, (3) Shannon-Wiener Index of Diversity based on numbers of fish, and (4) Shannon-Wiener Index of Diversity based on biomass of fish.

There are many considerations for the selection of sampling sites, including: (1) the availability of minimally impaired and representative reference site(s), (2) the specific monitoring issue (e.g., short-term impacts or long-term trends), (3) accessibility and safety, (4) the comparability of data from that site with historical information collected by other federal and state agencies, and (5) comparability of habitat. All sampling stations should be as ecologically similar as possible to compare the benthic fauna collected. Sampling locations immediately above or below the confluence of two streams, or a stream and a point-/nonpoint-source discharge, should be avoided. Sampling near the mouths of tributaries entering large water bodies and locally modified sites, such as small impoundments and bridge areas, should be avoided due to possible alterations of the water flow or sediment deposition, which might result in major changes within the macroinvertebrate population diversities.

Reference-Site Selection

To compare changes in community structure and function resulting from a pollutant source, the paired-station approach is a relatively powerful strategy. In the paired-station approach, the potentially impacted stations, established downstream of the pollutant source, are compared to a reference station or to the reference condition based on a composite of sites.

Reference stations should be representative of optimum characteristics expected for the water body under investigation. Compositing data from several reference sites is a better approach than relying on a single site to describe the reference condition. Therefore, the investigator must look for the least impacted area(s): (1) upstream of the impacted areas on the same stream, (2) as close to the impacted area as possible in the same watershed, or (3) an ecoregion reference station to use as the reference site (also referred to as the control station).

Regional reference sites overcome the limitations of assessing impairments that occur and the natural surface-water variations that exist when using site-specific reference sites (Gibson et al., 1994). Regional reference stations allow evaluation of conditions on a larger scale. The ecoregional reference station represents the best attainable conditions for all streams (or other water bodies) with similar physical characteristics for a given ecoregion (Plafkin et al., 1989). The acceptable conditions of a reference site will differ among geographic regions because soil conditions, stream morphology, physiography, vegetation, and dominant land uses are not uniform throughout the regions. Selecting the best available reference sites involves the use of qualitative and quantitative information based on experience and knowledge of potential problems in regional streams.

Factors to be considered when formulating a preliminary list of candidate regional reference sites include the following (Gibson et al., 1994):

• Drainage wholly within an ecological region
• No upstream impoundments
• No known discharges (National Pollutant Discharge Elimination System) or contaminants
• No known spills or other pollution incidents
• No or low human population density
• No or low agricultural activity
• Low or no road and highway density
• Minimal nonpoint-source–pollution impacts

Biological Data Interpretation

States are faced with the challenge of not only developing tools that are both appropriate and cost-effective but also translating scientific analysis into sound management decisions regarding the water resource. Various data analysis strategies involving multimetric and multivariate approaches have been debated in scientific circles over the last five years (Gerritsen, 1996). In general, these approaches involve the evaluation of macroinvertebrate and fish data using the metrics presented previously to formulate an appraisal of biological conditions of the stream under investigation. As presented in the preceding sections, each metric measures a different component of community structure and has a different range of sensitivity to pollution stress. This integrated approach, advocated by EPA, provides more assurance of a valid assessment because a variety of parameters are evaluated.

Five Ecological Condition Categories have been established based on the number of total points earned (see Table 5). The descriptions were extracted and modified from various EPA Rapid Bioassessment Procedures (Plafkin et al., 1989 and EPA, 1990). Very Good is comparable to the best situation to be expected. Species with an endangered, threatened, or special-concern status are present. Exceptional or unusual assemblages of species are present, with sensitive species abundant. Species richness is high, and the stream exhibits outstanding conditions. A stream falling within the Good category has a balanced community with the usual association of expected species. Sensitive species are present, with high richness. Optimum community structure (composition and dominance) for stream size and habitat quality is present. The Fair condition has some expected species absent or in low abundance. Sensitive species are also absent or in very low abundance. Species richness is declining, with tolerant species increasing and beginning to predominate. Community structure and habitat quality are less than desirable but do satisfy expectations in some areas. The Poor category refers to streams with expected species absent or in low numbers. Streams in this category will exhibit low species richness, with tolerant species predominating. Sensitive species are absent. These streams exhibit severe levels of habitat degradation at increasing frequencies. Very Poor is assigned to streams with most expected species absent. Only the most tolerant species remain, and very low species richness is present. The community is lacking organization, having only tolerant organisms present with few or no EPT taxa. Extreme habitat degradation has substantially altered the stream's characteristics.

Many states, including Georgia, are in the process of developing and implementing biological criteria in an effort to apply biological monitoring information to watershed assessment and planning activities. Biological criteria are either narrative or numeric thresholds that are used to determine whether bioassessment results indicate impairment of the aquatic community. The diversity of approaches and programs being pursued among states ranges from exploring the utility of biological criteria to using the concepts of biological assessment and biological criteria for enhancing water-quality programs to developing sophisticated biological assessment methods and incorporating numerical criteria into water-quality standards. It is current EPA policy that all states incorporate biological criteria into their water-quality standards, although very few have done so thus far.

Case Studies in Georgia
Biological/Habitat Assessment of Three Creeks in the City of Griffin

Click here for larger view

Click here for larger view

Analysis of habitat, macroinvertebrate communities, and fish communities was conducted during the summer of 2000. The study area was located in central Georgia, in the Lower Piedmont ecoregion/physiographic province. Present conditions of biotic integrity were assessed at three monitoring stations located in the three major Griffin watersheds, Cabin Creek, Shoal Creek, and Potato Creek in Griffin, Spalding County, GA (see Figure 2). Cabin Creek is in the Upper Ocmulgee watershed, while Shoal and Potato Creeks are in the Upper Flint watershed. Study/monitoring sites were selected to be representative of the watershed inputs into the study area/streams and land use in the drainage area.

At each monitoring station, a stream length of 100-200 m was delineated from which biological sampling occurred. The primary components of biological monitoring included physical habitat assessments and benthic macroinvertebrate and fish sampling. Prior to biological surveys, water quality was assessed via in-situ measurements of the following parameters: water temperature, dissolved oxygen, pH, turbidity, and conductivity.

Click here for larger view

The location of the reference station was Britten Creek, in the vicinity of Greenville, Meriwether County, GA, within the Flint River watershed and the same ecoregion (Lower Piedmont) of the sampling locations. The reference site's selection was based on anthropogenic activities in its drainage basin (least impacted site), physical attributes (stream order, gradient, prevalent type [riffle/run vs. glide/pool], substrate, and so on) similar to the study watershed, and its occurrence in the same ecoregion or physiographic province (Piedmont) as the study sites. A habitat assessment was also conducted at the reference site. In-situ and laboratory water-quality samples were obtained. The purpose of this effort was to provide the "least impacted/impaired" baseline by which to compare study data and represent the "best attainable" conditions for the comparable water bodies under analysis.

It is noteworthy that three constituents (fecal coliform, total suspended solids, and total phosphorus) were found at elevated levels at the reference site. The elevated presence of these constituents at what could be considered a "pristine" site could indicate some impact from agriculture; however, no detailed land-use analysis was conducted for the reference-site watershed. It is fair to assume that the watershed is relatively untouched by urban and suburban development. This means that even a rural watershed is subject to spikes in some key constituents. This indicates that an urban/suburban area is not unique in generating elevated levels of these constituents.

The in-situ water-quality parameters measured at all monitoring stations and the reference site were within state standards and generally within acceptable levels for protection of aquatic biota, although conductivity levels were elevated at the Cabin Creek site. Turbidity levels were relatively low and considered protective of a warm-water aquatic community.

The habitat assessments indicated impairment due to heavy sediment loads at all three monitoring stations and at Potato Creek due to channel alteration, where channelization efforts were noticed. Sediment in waterways has a variety of detrimental effects on aquatic biota, including smothering fish eggs and benthic macroinvertebrates; clogging fish and mussel gills; reducing vision, feeding, and growth; and reducing photosynthetic activity. The habitat assessment score for the reference site indicates that it was of relatively high quality, resembling "least impacted" habitat. The reference site scored "optimal." Potato Creek and Cabin Creek were both rated as having "marginal" habitat conditions, being "dissimilar" to reference conditions; Shoal Creek was rated as having "suboptimal" habitat conditions, being "partially similar" to reference conditions.

Biotic indices (GBP and IBI) rated the three monitoring stations as having Very Poor biotic integrity based on analysis of each site's macroinvertebrate and fish communities. Most likely, biotic integrity is greatly influenced by degraded habitat conditions at all monitoring stations. The low numbers of the macroinvertebrate species of the generally intolerant EPT taxa and their low diversity, as well as the large number of the tolerant chironomid and annelid taxa adversely affected the scoring of these metrics. The most abundant macroinvertebrate identified from the monitoring stations was the highly tolerant Chironomus sp. (Order Diptera: Family Chironomidae). The macroinvertebrate community at the reference site was indicative of its high-quality "least impacted" conditions. The fish community assessment indicated very low numbers and species diversity. As mentioned, the IBI also rated all monitoring stations as having Very Poor biotic integrity, indicating degraded conditions at all monitoring stations. There were no benthic invertivores, native suckers, or sensitive species collected at any of the sites. An overall low occurrence of lithophilic spawners could be a function of the degree of sediment that exists at each monitoring station. Heavy sedimentation can cover up and smother living spaces between rocks, places that lithophilic spawners would use for egg deposition. Approximately 1.5% of the fish collected at this site had some form of an anomaly. A summary of the habitat, GBP, and IBI scores is presented in Table 6. Table 6. Summary of Habitat, Macroinvertebrate, and Fish Assessment in Griffin, GA (Click here to view table 6)

This assessment confirms a portion of the Georgia Environmental Protection Division (EPD) rationale for including Potato Creek and Cabin Creek on the 303(d) List due to biota impairment (in addition to fecal coliform and dissolved oxygen). A recent EPD biomonitoring report for sampling at the same station on Potato Creek essentially yielded the same conclusions. The IBI rank was also Very Poor while the report states, "Fish community impairment in this reach of Potato Creek is probably related to urban impacts from the City of Griffin." Anecdotal reports from sampling crews and field inspections have yielded the conclusion that many of the same type of impaired conditions exist upstream in the watersheds.

Limited Biological/Habitat Assessment in Peachtree City

A screening-level assessment can be conducted by concentrating on quantifying the numbers of benthic macroinvertebrates. A field sampling effort can be conducted consisting of approximately one to three hours spent at each sample location counting the number and types of macroinvertebrates. Figure 3 is a field data sheet developed for the Peachtree City effort. Species can be added based on knowledge of the local biological environment. A quantification of diversity can be estimated by documenting the number of different organisms. A qualitative habitat assessment can be made. A quantitative ranking can be developed using the EPT Index. The EPT Index is calculated as a percentage of these three pollution-intolerant species to the total number of macroinvertebrates sampled for each location. The EPT index is used to determine whether or not there is a good distribution of pollution-intolerant and pollution tolerant species found at each sample location, with no one particular species dominating the sample. A stream is considered healthy if there is a good distribution of these insects found. When there is an imbalance in the insect community (i.e., more pollution-tolerant species than intolerant species), the stream system could be stressed by an excess of loading from organic wastes, sediments, nutrients, metals, and so on.

With the screening-level data, areas can be targeted for more intensive and extensive sampling and assessment. This provides a way for a community to begin to cost-efficiently manage watersheds and begin a process of water-quality, habitat, and biological improvement.

References

Cummins, K.W. and M.J. Klug. "Feeding ecology of stream invertebrates." Annual Review of Ecological Systematics. 10:147-172. 1979.

DNR. Draft Standard Operating Procedures: Freshwater Macroinvertebrate Biological Assessment. Georgia Department of Natural Resources, Water Protection Branch, Atlanta, GA. 1999.

DNR. Standard Operating Procedures for Conducting Biomonitoring on Fish Communities in the Piedmont Ecoregion of Georgia. Georgia Department of Natural Resources, Wildlife Resources Division, Fisheries Section, Atlanta, GA. 2000.

EPA. Biological Criteria: National Program Guidance for Surface Waters. EPA-440/5-90-004. Criteria and Standards Division, Office of Water Regulations and Standards, Washington, DC. 1990.

Gerritsen, J. Biological Criteria: Technical Guidance for Survey Design and Statistical Evaluation of Survey Data, Volume 2, Development of Biological Indices. Prepared for Office of Science and Technology, US Environmental Protection Agency, Washington, DC. 1996.

Gibson, G.R., M.T. Barbour, and J.R. Karr. Biological Criteria: Technical Guidance for Streams and Small Rivers. EPA-822-B-92-002. Office of Science and Technology, Health and Ecological Criteria Division, US Environmental Protection Agency, Washington, DC. 1994.

Karr, J.R., K.D. Fausch, P.L. Angermeier, P.R. Yant, and L.J. Schlosser. Assessing Biological Integrity in Running Waters: A Method and Its Rationale. Special publication 5. Illinois Natural History Survey. 1986.

Loeb, S.L. and A. Spacie. Biological Monitoring of Aquatic Systems. Lewis Publishers, Boca Raton, FL. 1994.

Plafkin, J.L., M.T. Barbour, K.D. Porter, S.K. Gross, and R.M. Hughes. Rapid Bioassessment Protocols for Use in Streams and Rivers: Benthic Macroinvertebrates and Fish. EPA-440/4-89-001. Office of Water, US Environmental Protection Agency, Washington, DC. 1989.

Catherine A. Fox, M.S., is an environmental scientist and principal of FOX Environmental, FBE, DBE, located in Decatur, GA. FOX Environmental provides water-resources policy, planning, and analytical support to government, tribal, corporate, and multidisciplinary consulting firms at the national, regional, and community levels.

Charles D. Absher, P.E., is a water-resources engineer with Integrated Science & Engineering Inc., which serves as program manager for the City of Griffin, GA, Stormwater Utility.

SW - November/December 2002

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