Appendix F
Executive Summaries of State Pilot Studies

The following includes executive summaries from three states (Maine, Vermont and Wisconsin) that performed and completed pilot studies based upon the Lake and Reservoir Bioassessment and Biocriteria Technical Guidance Document. These pilot studies are distinct from the case studies incorporated throughout this document and, thus, are presented separately. The purpose of each pilot study was not to evaluate individual state sampling field methods but rather to test the utility of the data analysis and biocriteria development guidance in this manual. Each state adapted its study to incorporate its available data. All three states reported favorably on the usefulness of this guidance manual and indicated the various stages of their own biocriteria development. For more information regarding these studies, please contact the state's project leader as listed in each executive summary.

Geographic Analysis and Categorization of Maine Lakes: A Trial of the Draft Lake Bioassessment and Biocriteria Technical Guidance

Maine's test of the Draft Lake Bioassessment and Biocriteria Technical Guidance focused on lake classification, selection of reference sites and metric evaluation from extant data. Dataset limitations prevented the creation of a lake biocriteria program for the entire state; instead, various aspects of the guidance were 'spot tested.'

Classification of Lakes

Although Maine lakes are quite diverse, it was decided that delineating 10 or fewer lake classes would be most practical. The classification effort focused on 451 lakes which had complete datasets, utilizing cluster analysis on a combination of morphometric and chemical variables including surface area, flushing rate, maximum depth, mean depth, drainage area, elevation, color, alkalinity and specific conductance. The ecoregion approach suggested in the guidance resulted in 3 'modified' ecoregions (based on Omernik 1987) each having two lake classes. Clustering was primarily based on surface area and depth variables.

In this portion of the test, the biggest constraints were related to the difficulties of doing statistical analysis with available software. Three other concerns were evident: (1) how to handle outlier lakes (i.e., very large lakes), ( 2) how to incorporate additional lakes as data becomes available, and (3) the selection bias represented by monitored lakes in the datasets.

Selection of Reference Lakes

Each of the lakes in the dataset had a development ranking assigned from 1990 Census Data. Rankings from a subset of these lakes were found to be similar to rankings derived from the examination of United States Geological Service (USGS) topographic maps. Lakes having low development rankings were screened by professionals to eliminate lakes impacted by activities unrelated to population. Box and whisker plots were used to compare trophic status of reference lakes to non-reference lakes in each lake class. These comparisons often showed little separation between reference and non-reference lakes. This may be partially explained by the disproportionate number of reference and non-reference lakes. The technique used to choose reference lakes may need refinement but appears to be compatible with the guidance emphasis on using readily available information.

Biological Parameters

Maine examined metrics from Tier 2B level biological data (phytoplankton and zooplankton) to evaluate their potential utility. Some metrics were suggested in the guidance, others had basis in current scientific literature and a few were suggested by the nature of the dataset. Forty-six phytoplankton metrics were examined; the thirteen metrics showing potential utility were reduced to four after the elimination of redundant metrics: total cell volume, % volume Cyanophyta, % volume chrysophytes and the ratio of volume of Cyanophyta to desmids. Seven out of nineteen zooplankton metrics showed potential utility in screening for trophic increases. Metrics were eliminated with inherent redundancy and scoring was developed for two: total abundance and the ratio of cladocerans to copepods. Cumulative distribution plots for reference sites and non-reference sites were utilized to determine scoring levels for the two metrics. A multimetric index was not developed due to the low number of lakes and the overlap of the Tier 2B biological data.

The guidance provided a reasonable framework for the development of the biological metrics. However, the literature suggests that rotifers respond to trophic changes as well as crustacean zooplankton, a point previously overlooked in the guidance. Potential phytoplankton metrics should not only be based on count data, but also total cross-sectional area and/or volume measures. The variation in phytoplankton cell size is so great that cell numbers do not approximate standing crop as well as volume or area. Although a multimetric index was not developed, it appears that reasonable guidance is provided in the draft to accomplish this.

General Comments and Applicability within Maine's Lake Management Strategy

There are some concerns that this experience will be extrapolated to the rest of the country. For example, Maine has a large number of lakes and most are of glacial origin. Maine has only 3 lakes receiving point source discharges; Maine's lake management focus continues to be on trophic status and NPS pollution control. The test of this document was from this perspective, and other states may have other or additional management priorities. Another concern is whether or not the gain is worth the additional cost of obtaining biological (phytoplankton and zooplankton) data. One aspect that may be beyond the scope of the guidance document is the lack of reference lakes for atmospheric deposition impacts (in particular, Hg accumulation). If one assumes that atmospheric deposition is somewhat uniform over regions, it becomes nearly impossible to select unimpacted reference lakes and strong reliance must be placed on the term "minimally impaired" as used in the guidance.

Overall, this test has been considered a success despite some limitations of the dataset, and Maine has shifted from 'test' mode to 'development' mode. Biological samples have been collected from 100 potential reference lakes (1996) which are currently being analyzed and similar samples from 100 lakes of unknown status (1997) which will be analyzed and used as a test dataset in the future. The development of biocriteria for Maine's lakes will be an ongoing process over the next few years as time and funding permits. It is anticipated that the results will be useful to concerned citizens at the local level as well as biologists at the state level.

Biocriteria Development for Vermont Lakes-Pilot and Field Phases

Project Summary, April, 1998

The development of test biocriteria by the Vermont Department of Environmental Conservation (VTDEC) was conducted in order to evaluate methods presented in this Lake and Reservoir Bioassessment and Biocriteria Technical Guidance Document. Methods for conducting each phase of the project were taken directly from the document, and a comprehensive Pilot Phase final report is available. The Pilot Phase of this project was completed during 1995, using existing information contained in the Vermont Lakes and Ponds Database. Following this effort, a field program was initiated to develop reference level biocriteria beginning in 1996. Results and lessons learned from the Pilot Phase and results from the Field Phase (1996-1997) are presented in this summary. Movement towards implemen-tation of fully developed lake biocriteria for Vermont is discussed.

Field Phase

Taking the lessons learned from the Pilot Phase, a comprehensive bioassessment project was designed using this Guidance. To avoid the difficulties of classification, a regional approach to definition of lake biological reference conditions was adopted by planning assessments of both Vermont and New Hampshire lakes. To date, this cooperative Field Phase has evaluated 29 lakes. Ten additional lakes are scheduled for assessment during 1998. Data results from 1996 and 1997 are available, and an over-view of analyses conducted with these data to date is presented below. The reader should note that trial criteria presented below are provisional, and should be considered in development. The present study lake set contains 23 candidate reference lakes, and six known impaired or test lakes. The test lakes are either culturally eutrophied, anthropogenically sedimented, or have perpetually anoxic hypolimnia. The geographic distribution of 1996-1997 study lakes is presented in Figure F-1.

Bioassessment Assemblages, Metrics, and Methods

Following recommendations from the Pilot Phase, the trophic state, phytoplankton, benthic macroinvertebrate, and macrophyte assemblages were selected for assessment. Trophic state parameters (Secchi disk transparency, chlorophyll a, algal bio-volume) were collected bi-weekly at a central location in the lake. Phytoplankton were enum-erated from a season-wide, whole lake com-posite, consisting of composited, bi-weekly, depth-integrated samples of the photic zone acquired from a fixed station network. Discrete bi-weekly composites were retained in archive for future analysis if necessary. Profundal and sublittoral benthic macroinvertebrate samples were collected as triplicate composites using an Ekman dredge, from a fixed station network on each lake. Triplicate composited samples of benthic macroinvertebrates from rocky-cobbled, littoral-mud, and macrophyte bed habitats were collected using a sweep net. A timed collection period of 20 minutes total per composite sample per habitat was employed to ensure quantitative data comparability among lakes. The entire lit-toral zone was surveyed for macrophytes, whereby species were identified and abundances classified using the Braun-Blanquet scale. Benthic macroinvertebrates and macrophytes were assessed during the mid-late summer index period (approximately August 1- August 31). Habitat quality was assessed at the time of the macrophyte survey. A quality assurance program was employed to ensure the precision, accuracy, comparability and representativeness of data collected. Table F-1 presents selected metrics under evaluation for the Field Phase of this bioassessment project.

Preliminary Lake Classification

In selecting candidate reference and test lakes, the same classification metrics were used as for the Pilot Phase. An a-priori classification was adopted using alkalinity as a classifying variable. A cutoff of approximately 15mg/l was used to classify lakes as poorly buffered ( 15 mg/l as CaCO3), or well-buffered (> 15mg/l as CaCO3). Existing lake assessment data suggests that these two lake classes correspond to tannic and clear water lakes (one exception being the clear, but lower-alkalinity Hatch Pond, NH). Thus for ease of presentation, low-alkalinity, poorly buffered lakes are called tannic, while higher-alkalinity, well buffered lakes are called clear. Table F-2 provides the range of physico-chemical attributes for each of these classes.

This proposed classification was validated with phyto-plankton data using canonical correspondence analysis (Figure F-2). The position of clear and tannic lakes is well separated along the second axis, as are the relative positions of the algal orders. Test lakes with increased blue-green algae in the community separate along the first axis. This ordination suggests that there is variability in the phytoplankton assemblage biometrics which can be explained by the proposed classification.

Criteria Development, Phytoplankton

All phytoplankton data were examined using Tukey box plots to identify metrics which discriminate between reference and test lakes. Metrics thus 'appearing' discriminatory were tested by calculating interquartile coefficients. To avoid 'double counting' of impairments, the selected metrics were examined for covariance. A high degree of covariance was noted between the percent composition of cyanobacteria and percent composition of Aphanizomenon flos-aquae, Anabaena flos-aquae, and Anacystis marina (r=0.85, p<0.05). The latter metric was retained as it more accurately defines occurrences of undesirable blue-green algal blooms in test lakes.

A total of five metrics were selected for each lake class to construct a phytoplankton index. Trial criteria were developed by scoring the metric ranges using the 'bi-section' method presented in this Guidance. Trial criteria are presented in Table F-3. Lakes were scored using these criteria, and the distribution of scores is presented in Figure F-3. For tannic lakes, both test lakes met reference criteria. None of the clear test lakes met reference criteria.

Criteria Development, Littoral Zone Macrophytes

The methods by which macrophyte data were collected do not permit calculation of a Shannon-Weiner index of diversity, yet this is an important measure describing the macrophyte assemblage. To provide an alternate measure, a relative species dominance metric is proposed where impairment is indicated by metric values increasing above reference. This metric is calculated as:

% cover - littoral zone
—————————
No. of species

An alternate way of assessing macrophyte communities is to determine the relative contri-bution by different structural groups. Analogous to relative percent composition by algal divisions in the phytoplankton, or by function in the macroinvertebrates, relative percent occurrence by structural grouping can affect other biological assemblages and vary with impair-ments to lake water quality. To evaluate this for the study lakes, seven structural groupings were proposed (Table F- 4).

Interquartile coefficients for macrophyte metrics were calculated, and many metrics were found to be insensitive. The most discriminating metrics were nevertheless retained for trial criteria development in the interest of assessing test lakes against a reference condition. The criteria presented in Table F-5 are at best draft, and should be considered in development pending the acquisition of additional data. Reference and test lake scoring is presented in Figure F-4.

Criteria Development, Trophic State Indices

Trophic state indices were calculated for Secchi disk transparency and chlorophyll a, using Carlson's algorithms, and for total algal biovolume using Sweet's algorithm. This latter index is calculated as:

(Log2 (B+1)) x 5

where B=0.001 x algal biovolume in um3/ml.

Trophic state indices are useful in regions where there exists a wide range of trophic conditions. In this study lake set, even lakes which are considered impaired by eutrophication score only at the low range of eutrophy, with no lake exceeding 62 on the unitless trophic state index scale. Therefore, the calculated scoring ranges for criteria developed from this study set are extremely narrow. Interquartile coefficients and draft trophic state criteria are presented in Table F-6.

The trophic state index calculated from algal biovolume is presented in this section to assess whether this metric has greater discrimination than its untransformed analogue, algal biovolume (presented in the phytoplankton section above). Comparison of the interquartile coefficients for algal biovolume, and for the calculated algal biovolume trophic state index suggests that this metric is most discriminating in the phytoplankton assemblage biocriteria, (interquartile coefficient of 0.89 and 0.09 vs. 0.27 and 1.18 for tannic and clear lakes respectively). Accordingly, algal biovolume should best be retained in the phytoplankton assemblage criteria in refinements of these trophic state criteria. The distributions of reference and test lakes, scored by trophic state indices, are shown in Figure F-5.

Results, Benthic Macroinvertebrates

As of this writing, taxonomic data have been validated only for the 1996 study lakes. A wide variety of macroinvertebrate metrics have been calculated from these data, and it appears that the macroinvertebrates could provide highly discriminating metrics (Table F-7). It is anticipated that a lake macroinvertebrate index will have metrics from each of the five habitats evaluated. Based upon review of the 1996 taxonomy, and observations from the 1997 samples currently in taxonomy, it is believed that profundal zone samples may not provide useful data. Indeed, profundal zone samples are comprised almost entirely of Chironomidae, Chaoboridae, and Oligochaeta, and variation in overall density is dependent on hypolimnetic oxygen conditions. If these observations hold true, profundal zone macroinvertebrate assessments will likely be dropped from Vermont's bioassessment protocols.

Moving Toward Implementation

Vermont's efforts toward developing useful biocriteria are by no means complete. The Field Phase outlined above was designed to provide the States of Vermont and New Hampshire with the baseline experience and information needed to move forward with a long-term sustainable bioassessment program. The trial criteria presented herein should be reevaluated and further refined in conjunction with that longer term program. The present Field Phase provides a large volume of useful data, but it may not be sustainable over the long-term. Using results from the 1996 to 1998 study lakes, the need for robust data to develop (and assess compliance with) criteria will be balanced with the fixed personnel and operating expenses of a small State agency.

Presently, the classification of study lakes is provisional. The reference condition for poorly-buffered (tannic) lakes is well characterized, though a group of poorly buffered and clear lakes might need to be characterized separately. Also there exists the need to assess the reference condition for a variety of well buffered (clear) lake types. Progress on this will be made during the 1998 field season.

This cooperative Vermont/New Hampshire initiative carries with it a paleolimnological component designed specifically to determine the historical condition of candidate reference lakes. Application of paleolimnological models to the sediments of selected candidate reference lakes will ensure that the underlying biological information used to develop criteria is indeed of reference quality.

Vermont has already seen the benefits of biological assessment as a tool for evaluating lakes. Data from this Field Phase have been used to refine and update Aquatic Life Use Support in Vermont's 305(b) inventory for every Vermont study lake bioassessed to date. While numeric criteria are not yet ready for inclusion into Vermont's Water Quality Standards, it is anticipated that subsequent revisions to Standards will contain lake biological criteria.

Readers of this Guidance are encouraged to communicate with the Project Contact directly for information regarding Vermont's bioassessment program.

An Evaluation of the Draft Lake and Reservoir Bioassessment and Biocriteria Technical Guidance Document Using Wisconsin Lakes

Wisconsin's test of the Draft Lake Bioassessment and Biocriteria Technical Guidance focused on the development of a multimetric index for Wisconsin lakes. Such an index would provide a more accurate determination of use impairment for the biennial 305(b) water quality assessment, and changes as a result of watershed best management practices under the nonpoint priority watershed program. This index would also allow more informed permitting decisions, as well as proactive management by rapidly detecting emerging pollutant threats to lakes.

Background

Although bioassessment could detect changes from a broad range of anthropogenic sources, this study only involved lakes that have been impaired by eutrophication. While it would be beneficial to include other pollutants, e.g., acid precipitation and mercury, there was not sufficient information in our data set from lakes impacted by such pollutants. All of the lakes in our data set have experienced some degree of impairment from anthropogenic sources. As such, the reference lakes would be classified as "least impaired." Better reference sites could be selected if they had been chosen prior to data collection.

This study examines the trophic variables: total phosphorus, chlorophyll, Secchi depth and the biotic communities of phytoplankton, zooplankton, sedimented diatoms, and macrophytes. Analysis involved a comparison of index development using Tier 1A (single visit) Tier 1B (multiple visits) as well as Tier 2A and 2B. Macroinvertebrates and fish were not used in the analysis.

Data used for this analysis was largely collected under the Long Term Lakes program of the Wisconsin Department of Natural Resources. Collection began in 1986 and continues through the present. Samples are collected five times annually: late winter, June, July, August, and during fall turnover. Parameters that are analyzed from these collections include Secchi depth, chlorophyll, total phosphorus, phytoplankton, and zooplankton. In addition, the macrophyte assemblage was surveyed occasionally during this time period. Not all of the samples are available for this analysis. Trophic variables (Secchi, chlorophyll, and P) were available for the years 1986-1994 while phytoplankton from 1986 were used and zooplankton from 1986 and 1988 were used. As part of another project, sediment samples were collected from the main basin of most of these lakes in 1991 for diatom analysis. Seven reservoirs of varying trophic characteristics were sampled in 1994 for trophic variables, phytoplankton, and macrophytes.

Classification

The lakes sampled covered three ecoregions, but not all regions contain reference quality lakes. Therefore, lakes were not separated into three ecoregions. In fact, all but two of the reference lakes were found in the northern lakes and forests ecoregion. The reference lakes were chosen based upon low levels of development in their watersheds. All of the lakes had some development on the shoreline but most were summer homes and the density was relatively low. A criteria that was not used in the selection of the reference lakes was their known trophic status. It was felt that lakes that may have naturally had higher nutrient levels but low development should be included in the reference lakes. Since all of the lakes had some degree of disturbance in their watersheds the reference condition was calculated using the tri-section method.

The reference lakes, test lakes, and reservoirs exhibited a wide range of morphological conditions and watershed size (Table F-8). These data were used to determine how robust various metrics were in assessing unknown lakes. When possible, metrics were constructed based upon multiple visits as well as single visits during an index period. August was chosen as the index period.

Metric Development

At least 4 metrics were developed for each biological entity (Table F-9). Trophic variables of the lakes were described using Carlson's Trophic Status Index (TSI), modified for Wisconsin lakes. Trophic status for chlorophyll, phosphorus, and Secchi depth was described using the equations:

WTSIsd = 60 -(32.2 Log SD)

WTSItp = 60 -(33.2(0.96 - .054 log TP)

WTSIchl = 60 - (33.2(0.76 - 0.52 log Chl)

Reference metrics are unusable if they are excessively variable. Variability of the metrics was measured by determining the ratio of the interquartile range to the scope of detection. The scope of detection was defined as the distance from the lower quartile to the minimum value possible when reference values were higher than the test cases. When the reference values were lower than the test cases, the scope of detection was defined as the distance from the upper quartile to the maximum value possible. An interquartile coefficient greater than one generally indicates the metric is too variable to detect impairments.

Some of the metrics had an interquartile coefficient greater than one, but each of the biological units had at least one metric with a coefficient less than one (Table F-9). For metrics to be useful there must also be good separation between the reference and test lakes. Each biological unit also had at least one metric that fulfilled this condition. The list of metrics that were judged to be robust and useful are listed in Table F-10.

Discussion

This study has formulated a draft bioassessment index for Wisconsin lakes using biocriteria metrics. Different metrics were not formulated for individual lake classes or for separate ecoregions largely because of the lack of sufficient reference lakes. Instead, the lakes for all the regions were combined. The Wisconsin Lake Index was tested on 13 lakes using all of the metrics and tested independently for Tiers 1A, 1B, 2A, and 2B. A comparison was made of each lake's classification at the four different levels. All the lakes received the same classification ("departing from reference conditions") under Tier 1A and 1B. Tier 2 appeared to be more descriptive of lake condition than Tier 1. In fact, two lakes classified as "departing from reference conditions" under Tier 1, were categorized as "impaired" using Tier 2 sampling techniques.

This analysis has allowed us to make some recommendations concerning which metrics are useful for developing a Wisconsin Lakes Index. Since all the lakes received the same score under Tier 1A and 1B it is suggested that only a single visit during the index period (August) is necessary if lakes are to be classified using Tier 1 only. In addition, we suggest that the macrophyte metrics be expanded under Tier 1. All of the macrophyte metrics, with the exception of density, can be determined with little or no extra effort under the suggested Tier 1 metrics in the draft document. Density should be included as a Tier 2 metric for macrophytes.

Although there was not complete agreement between Tier 2A and 2B they were similar enough to suggest that only one sampling trip is sufficient. In addition, it is suggested that the zooplankton metrics be eliminated until it is better understood how these metrics relate to the lake's impairment.

The diatom metrics tested were not as useful as expected. The only metric that proved robust enough to use was the percentage of Stephanodiscus. Although this metric was useful there was a great deal of variability across the test lakes. In the 13 lakes where the index was tested, the diatom metric tended to indicate that the lake was less impaired compared with most of the other metrics. This metric may not be as robust as some others. We recommend its usage but with reservations. The diatom metrics likely would be more useful if TSI values were calculated using the entire diatom assemblage but this would entail considerably more work, including detailed taxonomic knowledge.

A summary of the recommendations are:

Tier 1 Only one sampling trip (during August). Metrics: trophic state variables, macrophyte metrics except density.

Tier 2 Only one sampling trip (during August). Metrics: trophic state variables, macrophytes, phytoplankton, diatoms.

It is evident from this analysis that lake assessment using biocriteria is a more robust technique than using the traditional indices: phosphorus, Secchi depth, and chlorophyll by themselves. The additional information from the biota gives a much more accurate picture of a lake's health, especially its biological integrity.

Improvements could be made in developing a Wisconsin Lake Index if better reference conditions were used to define the metrics. Since most of the reference lakes used in this study had some lakeshore development they were not ideal choices. Another ongoing study has identified sufficient reference lakes in each of the major ecoregions in the state, and will develop metrics for sedimented diatoms.

Home ~ Preface ~ Chapter 1 ~ Chapter 2
Chapter 3 ~ Chapter 4 ~ Chapter 5 ~ Chapter 6
Chapter 7 ~ Chapter 8 ~ Chapter 9 ~ Chapter 10
Appendix A ~ Appendix B ~ Appendix C ~ Appendix D
Appendix E ~ Appendix F ~ Appendix G

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