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Water: Monitoring & Assessment

Development of Biocriteria for Wetlands in Montana

Last Updated: March 2000

Contact Information

Randall S. Apfelbeck
Montana Department of Environmental Quality
2209 Phoenix Avenue
P.O. Box 200901
Helena, MT 59620-0901
Phone: (406) 444-2709
E-mail: Randall S. Apfelbeck (rapfelbeck@state.mt.us)
Mr. Apfelbeck is the author of Development of Biocriteria for Wetlands in Montana Exit EPA Disclaimer

Purpose(s) of Project

Montana's wetland research objectives are:

  • To determine the status and trends in wetland water quality.
  • To acquire an understanding of how climate, hydrologic controls, and geomorphic settings influence wetland biological communities; in order that they can be classified as required for the development of successful biocriteria.
  • To develop biological measurements that could be used in developing biocriteria to define the extent and degree of anthropogenic impacts to wetland water quality. In an effort to create wetland specific water quality standards, the Montana Department of Environmental Quality is attempting to develop biocriteria which are sensitive and responsive to changes in wetland water quality.

Project History

In 1992, Montana DEQ began developing wetland biological criteria. At that time, there was little information concerning the status or trends of the water quality of Montana's wetlands. Further, Montana's water quality standards were developed to protect the beneficial uses (e.g., aquatic life) of lakes, rivers and streams. Wetlands were not considered state waters when Montana's water quality standards were developed. Since 1992, Montana has had an ongoing program to develop bioassessment protocols and water quality standards that will more adequately evaluate and protect the aquatic life that live in wetlands.

In 1998, as a result of a TMDL lawsuit, Montana DEQ shifted focus from development of biological criteria to the development of guidelines for making beneficial use decisions that apply to all Montana waterbodies. Despite the shift in state agency water program priorities, Montana's wetland bioassessment program is noteworthy and valuable to other states looking to develop a wetland bioassessment program. Below are the details for the numerous wetland biological assessment projects in Montana.

The original Montana DEQ study was designed in 1992 and involved sampling 80 wetlands throughout Montana during 1993 and 1994. The bioassessment project included collection of macroinvertebrate and diatom samples from wetlands in all ecoregions of Montana.

Ecoregions of Montana and the Wetland Sites Sampled by Montana DEQ

In conjunction with Montana DEQ's research program, Montana State University (MSU) designed a study in 1997 that focused on development of vegetation biocriteria for western Montana depressional wetlands. The focus on vegetation biocriteria is key in Montana because wetland vegetation is easier to assess than macroinvertebrates or diatoms for depressional wetlands that are seasonally dry. The MSU study sampled vegetation and also macroinvertebrates and diatoms for 24 depressional wetlands with similar climate, hydrology, and water chemistry. The research included sampling across three levels of human disturbances--minimally impacted, slightly impacted, and moderately impacted. The study also involved two anthropogenic impairments--dryland agriculture and grazing.

The University of Montana is currently designing a study to determine how chemical and physical gradients, and seasonality influence the macroinvertebrate communities of depressional wetlands located in the Ovando Valley of western Montana. Their study design includes the sampling of macroinvertebrates from 33 depressional wetlands of varying alkalinity, salinity, and hydroperiod, with 6 of the wetlands sampled several times throughout the field season. The study will assist DEQ in refining the wetland classification system and will aid in the development of a sampling index period for western Montana depressional wetlands. These wetlands are also being intensively sampled to develop and test a model for assessing depressional wetlands using the Hydrogeomorphology (HGM) functional assessment approach (Federal Register 1996). After this study is completed, researchers could share data and link biological criteria to HGM.

Study Design

Montana DEQ's approach to developing biocriteria involved several study designs aimed at developing tools to help detect human influence on wetland water quality. The original study was designed in 1992 and involved sampling 80 wetlands throughout Montana during 1993 and 1994 (Figure 1). The study design included the collection of samples that represent the wetland's macroinvertebrate (e.g., aquatic insects) and diatom (algae) communities. Sampling methods were designed so that 1-2 hours was sufficient for the data to be collected in the field for each wetland. Samples of each wetland's water column, sediment, and macroinvertebrate and diatom communities were collected. Water-column and sediment samples were collected to document impairments and for classification purposes.

The sites were classified using ecoregions and hydrogeomorphology and several of the wetland classes were further delineated using water-column chemistry variables. A representative number of wetlands from the following Omernik ecoregions were sampled: Rocky Mountains, Intermountain Valleys and Prairie Foothills, Glaciated Plains, and Unglaciated Plains Ecoregions. To reduce seasonality, all wetlands within the same ecoregion were sampled during similar time periods. Wetlands in the Glaciated Plains Ecoregion were sampled from early April through mid-June, wetlands of the Intermountain Valleys and Prairie Foothills Ecoregion from mid-June until early August, and wetlands of the Rocky Mountain Ecoregion from early July through September.

The classification framework was developed by sampling the full spectrum of wetland types in Montana. The study was designed such that approximately 75 percent of the sites were reference and 25 were impaired. This approach was useful because it allowed Montana DEQ to determine the reference condition of a wide variety of wetland types. Also, the design provided the opportunity to test the ability of the biological measurements to detect water quality impairment.

Anthropogenic impacts such as irrigation or logging were included in the study design. If anthropogenic activities such as dryland agriculture, irrigation, feedlots, grazing, silviculture, road construction, hydrologic manipulation, urban runoff, wastewater, mining, and oil and natural gas production occurred in the wetland's watershed, the wetland was considered impaired. Wetlands for sampling were selected based on many variables, including the availability of historical data, special interests by other entities, cooperation by land owners and accessability.


View photographs from the Montana DEQ Study Area and Design. Exit EPA Disclaimer

In order to classify or document impairment, a hydrogeologist for the Montana Natural Heritage Program (MNHP), assisted Montana DEQ in developing a wetland classification system through summarizing and interpreting the physical and chemical data. Using topographic maps, field observations, and information gathered from land management agencies, geomorphic characteristics were interpreted and a hydrogeomorphic database developed. Maps for each wetland were completed using a Geographic Information System (GIS). Map features included hydrologic delineations, land management areas, counties, cities, major transportation corridors, wetland watershed boundaries and sampling locations.

More information on the types of wetland classes, including photographs of each type, is available on the Montana DEQ Lakes and Wetlands Classification site. Exit EPA Disclaimer

Assemblages Monitored

Sampling Methods: Diatoms

Montana DEQ collected diatoms as composite grab samples. The algae was identified to the lowest taxonomic level possible. Samples were collected using a 250-ml plastic container and then preserved with Lugol's solution. Samples were collected from a location determined to best represent the wetland. These locations were restricted to areas that were easily accessible when wearing hip boots. Sampling was done from April through September. Each site was sampled once.

The Academy of Natural Sciences of Philadelphia (ANSP) performed the subsampling, digestion, and mounting of the diatoms.

Analytical Methods: Diatoms

The multivariate approach was used to analyze wetland diatom communities.

Multivariate analysis is a statistical approach used by biologists to determine relationships among biota such as diatoms or macroinvertebrates, and environmental variables such as water-column chemistry. The multivariate approaches that ANSP used to investigate relationships between Montana wetland diatom assemblages and environmental variables (mostly water-column chemistry) was Detrended Canonical Correspondence Analysis (DCCA) and two-way indicator analysis (TWINSPAN). ANSP graphically displayed clusters of diatoms with similar composition using DCCA (Charles et al. 1996). Using DCCA, ANSP displayed and labeled vectors to illustrate the relationship between diatom assemblages and environmental variables. Longer vectors show us a stronger correlation among diatom assemblages and environmental variables (Figure 2). ANSP used envelops to graphically enclose all reference sites using the wetland class delineations (Figure 3).

Figure 2. Correlation among diatom assemblages and environmental variables

Class 1  circle Dilute Closed Basins of the Rocky Mountain Ecoregion
Class 2  disc Riparian Wetlands of the Rocky Mountain and Intermountain Valley Ecoregion
Class 3  plus sign Headwater Wetland of the Rocky Mountain Ecoregion
Class 4  diamond Riparian Wetland of the Plains Ecoregion
Class 5  X Groundwater Supported Closed Basin Wetlands
Class 6  triangle Saline Wetlands
Class 7  solid triangle Surface Water Supported Closed Basin Wetlands of the Plains Ecoregion
Class 8  plus sign with dot Ephemeral Wetlands
Class 9  square Open Lake Wetlands of the Plains Ecoregion
Class 10 solid square Open Lake Wetlands of the Rocky Mountain and Intermountain Valley Ecoregions

Figure 3. Wetland class delineations


Sampling Methods: Macroinvertebrates

Montana DEQ collected macroinvertebrates using a 1 mm mesh D-net in a sweeping motion. Macroinvertebrates were collected from all microenvironments in a sampling location. These locations were restricted to areas that were easily accessible when wearing hip boots and best represented the wetland. Samples were composited with associated materials such as vegetation and sediment and then preserved with ethanol in a 1-liter plastic container. An effort was made to collect 300 organisms from each location using a consistent method of collection. To insure preservation, sample bottles were refreshed with ethanol several days after collection. Sampling was done from April through September, once per site.

A contractor was used to perform the subsampling and sorting of the macroinvertebrate samples. Due to the extensive time required to sort the samples (up to 18 hours), the subsampling protocol was modified to a 200-organism subsample. At 17 of the 80 sites, an insufficient number of organisms were present in the sample to permit subsampling and the entire sample was sorted and identified.

The contractor identified the organisms in the wetland samples and standardized the taxonomic level of identification based on Montana Stream Protocols. Several taxa were eliminated from consideration for metric development as they were determined to be nonbenthic taxa or semi-aquatic surface dwellers and considered uninformative for reflecting water quality. These taxa included Gerridae, Collembola, Dytiscidae, Hydrophilidae, Ostracoda, Anostraca, Copepoda, Cladocera, Notonectidae and Corixidae.

Analytical Methods: Macroinvertebrates

The multimetric approach was used to evaluate wetland macroinvertebrate communities. The multimetric approach incorporates many attributes into the assessment process and has the ability to integrate information from the biological communities to provide an overall indication of biological condition or ecological health.

The project contractor assisted Montana DEQ in developing wetland macroinvertebrate multimetric indices. The proposed metrics and associated environmental data were evaluated in an attempt to develop an understanding of ecological relationships, to test each proposed metric's ability to predict various anthropogenic stressors, and to test redundancy.

The graphed results of classes 1, 8, and 10 may be viewed by selecting the titles below:

Class 1 Dilute Closed Basins and Headwater Wetlands of the Rocky Mountain Ecoregion.

Class 8 Ephemeral Wetlands.

Class 10 Open Lake Wetlands of the Rocky Mountain and Intermountain Valley Ecoregions.

Other Parameters: Water Chemistry and Sediment

Water-column and sediment samples were collected to document impairments and for classification purposes. Each sample was collected from a location determined to best represent the wetland. These locations were restricted to areas that were easily accessible when wearing hip boots. Field chemical measurements, observations and photographs were recorded at each location.

Lessons Learned

  • We found that diatoms and macroinvertebrates were most useful for evaluating the biological integrity of perennial wetlands with open water environments that had relatively stable water levels and were not excessively alkaline or saline.

  • We concluded that multivariate analysis was a useful tool for developing a wetland classification system and that hydrogeomorphology and ecoregions were practical approaches to classifying wetlands for the development of biocriteria.

  • We determined that both the multimetric and multivariate techniques were valuable for developing wetland biocriteria.

  • In most cases, the multimetric and multivariate approaches that we used to assess the macroinvertebrate and diatom communities both identified the same wetlands as impaired.

  • Two wetland types in the arid west (including Montana) are difficult to classify. Wetlands such as potholes are highly complex and difficult to classify due to both spatial and temporal variability. For these wetlands, the hydrology, water chemistry and biology can change dramatically throughout a season or from year to year as a result of climatic change. For example, the biological community of a wetland often changes due to an increase in salinity or a decrease in water content caused by drought.

  • Note: Montana DEQ has developed a set of proposed metrics, proposed metrics calculations and score calculations used for developing wetland macroinvertebrate indices. These are included in the table below.

Table 2. Proposed metrics, proposed metric calculations and score calculations used for developing wetland macroinvertebrate indices.

Proposed Metrics Theorized Direction of Change in Presence of Stressor Proposed Metric Calculation Score Calculation
Number of Taxa decrease count taxa (Number of Taxa)x0.75
Percent Dominance
  Percent 1 Dominant Taxon
  Percent 2 Dominant Taxa
  Percent 5 Dominant Taxa
average of percent 1, 2, and 5 most dominant taxa (100- Percent Dominance)x0.36
POET decrease count Plecoptera, Odonata, Ephemeroptera and Tricoptera taxa (POET)x3
Number of Individuals decrease count individuals in total sample (maximum count of 300) (Number of Individuals)÷33
  Number of Chironomidae
  Percent Chironomidae Taxa
number of Chir taxa x (100-%chir+50)x (((%Orthocladiinae to total Chir)÷100)+0.5) (Chironomidae)÷83
  Number of Crustacea &
    Mullusca Taxa
  Percent Crustacea &     Mullusca Taxa
number of Crustacea and Mollusca taxa x(100-%Crustacea/Mollusca taxa+50) (Crustacea/Mollusca)÷33
Leech/Sponge/Clam decrease count Hirudinea, Porifera and Sphaeriidea taxa (Leech/Sponge/Clam)x3

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