North Dakota Wetland Bioassessment Program

Last Updated: March 2000

Contact Information

Mike Ell
North Dakota Department of Health
Division of Water Quality
1200 Missouri Avenue
P.O. Box 5520
Bismarck, ND 04333
Office: (701) 328–5214
E-mail: Mike Ell (mell@state.nd.us)

Purpose(s) of Project

The primary purpose of North Dakota's wetland bioassessment program is to develop wetland water quality standards for North Dakota. This currently involves developing biological community metrics and an Index of Biological Integrity (IBI) for temporary and seasonal depressional wetlands. A secondary project goal is to compare the IBI with Hydrogeomorphic (HGM) functional assessments.

Project History

North Dakota Department of Health (NDDH) initiated its wetland bioassessment program in 1993 as a component of the state's strategy to develop wetland water quality standards. NDDH began field sampling in 1995 and is currently analyzing data collected from 1995 through 1999 to develop assemblage metrics, and IBIs for the assemblages, and ultimately biocriteria. The NDDH wetland sampling plan includes vascular plants, macroinvertebrates, and algal assemblages.

Development of a North Dakota sampling protocol for the state's wetland types is ongoing through cooperative work agreements with North Dakota State University, Departments of Animal and Range Sciences and Zoology.

Study Design

North Dakota's study design has continued to expand in scope since the project was initiated. Initial field sampling began in 1995 and 1996 with 13 "least disturbed" temporary and seasonal wetlands. In 1997, the number and range of wetlands was expanded to 20 temporary and seasonal wetlands. Four of the original 13 "reference" wetlands sampled in 1995 and 1996 were sampled in 1997 along with 16 new wetlands. These wetlands captured a larger range of disturbance categories.

In 1998, the number of wetlands again expanded. An additional 16 temporary and seasonal wetlands were added bringing the total number of wetlands sampled to 36 in 1998 and the total number of reference wetlands to six. The 16 wetlands added in 1998 were part of a HGM classification project. These wetlands were added to facilitate a comparison of the two assessment methods. In addition to the 16 HGM wetlands, NRCS personnel conducted a HGM assessment for the 20 wetlands selected by the Department.

During the 1999 sampling season, a second set of 30 temporary and seasonal depressional wetlands, not sampled previously, were sampled for vascular plants. Macroinvertebrates and algae were not sampled in 1999.

Since the inception of the project, temporary and seasonal wetlands have been the focus of IBI development efforts. Further, all wetland study sites have been within the Northern Glaciated Plains and Northwestern Glaciated Plains ecoregions (Figure 1 below), a region commonly referred to as the "Prairie Pothole Region."

Assemblages Monitored

• Macroinvertebrates
• Algae
• Vascular Plants

Sampling Methods: Macroinvertebrates

The NDDH currently uses only the "sweep" or jab net method for macroinvertebrate sampling; however, in the past, activity traps have also been used. Sampling consists of two site visits in June. During each site visit two samples are collected with the emergent vegetative zone.

Sweep Net. The method employs a "D" frame net (0.6 mm mesh size). At each site within the wetland, the substrate (i.e., wetland vegetation and benthos) is "jabbed" for a distance of one meter. The disturbed area is then swept two more times to ensure a representative sample of macroinvertebrates is collected. Each sample collected within the wetland will be placed in a shallow pan where any excess debris or water can be removed. The "cleaned" sample is placed in a jar a preserved with buffered formalin to a concentration of 10 % by volume.

Analytical Methods: Macroinvertebrates

In the laboratory each sample is washed through a 0.6 mm sieve to remove the preservative and cleaned to remove excess debris. The cleaned sample is placed in a shallow white pan divided in quadrants of equal size. Since each sample typically contains a large number of organisms, it is necessary to subsample. A subsample is obtained by randomly selecting a sample quadrant and counting and identifying the organisms in that quadrant. Additional quadrants are selected at random and organisms counted and identified until a subsample of 300 organisms is counted. For samples with less than 300 organisms every quadrant is sampled. All organisms are identified to the lowest taxonomic level practical.

Sampling Methods: Algae (Phytoplankton)

Phytoplankton samples are collected just below the water's surface in the middle or deepest area of the wetland basin. Each wetland is sampled two times in June at the same time macroinvertebrate samples are collected. The sample is collected by submerging a clean 200 mL sample bottle just below the water's surface and filling it. The sample is preserved in the field with M3 fixative to a concentration of 2 % by volume.

Analytical Methods: Algae (Phytoplankton)

Identification and enumeration of phytoplankton is made using the phase-contrast inverted microscope method (Utermohl, 1958). Sample analysis is conducted from a sample aliquot ranging from 2 to 15 mL, depending on turbidity. Phytoplankton greater than 20 micrometer in diameter are enumerated at x125 magnification. (Note: At x125 the entire bottom of the chamber is in view.) Following enumeration at x125 smaller algae are counted at x1250. At least 250 cells of the most numerous algae are counted using the strip count method at x1250 magnification (APHA, 1989). Cell volumes are estimated for dominant taxa by measuring cell dimensions of 50 to 100 individuals using the closest geometric formulas of Wetzel and Likens (1991) and Tikkanen (1986). For rare taxa, volume estimates are made from less than 50 cell measurements. Diatoms will be identified after clearing in 30 % hydrogen peroxide and mounting in Hyrax Mounting Medium.

Sampling Methods: Vascular Plants

Working in cooperation with NDSU, the Department is evaluating three methods to sample the vascular plant community. The first method is more qualitative in nature. It involves a simple inventory of plant species present within each wetland zone, low prairie, wet meadow, and shallow marsh. The other two methods, termed the point and quadrat methods, are quantitative. The inventory is conducted each time the wetland is visited. The point and quadrat methods are done once each, usually in July or August.

In the point method, 200 points are evenly stratified in each wetland zone and the nearest plant species recorded. The quadrat method involves placing fifteen 1 m² quadrats evenly throughout each wetland zone. Each species is recorded within the quadrat and a Daubenmire cover class recorded. With both methods, a secondary species list is made for species encountered, but not sampled.

Note: For specific details on abiotic sampling methods for nutrients, trace elements, general water parameters, and sediment chemistry, directly refer to North Dakota Department of Health.

Lessons Learned

The NDDH has made a great deal of progress within the last five years. Our experience, however, has not been without problems and mistakes. As mentioned previously, the first two years of the program focused solely on "least impaired" or reference condition wetlands. While beneficial in testing sampling methods, the lack of a disturbance gradient in the study design did allow for the testing of attributes and the selection of metrics. Therefore, beginning in 1997 the NDDH chose wetlands across a disturbance gradient, including both reference wetlands and degraded wetlands.

The NDDH has also found it beneficial to stratify wetlands based on ecoregion and wetland class. This minimizes the amount of variation in the biological assemblage and allows more sensitivity in the response of the metrics to the disturbance gradient. Current IBI development efforts are focusing on temporary and seasonal depressional wetlands within the Northern Glaciated Plains and Northwestern Glaciated Plains ecoregions. In 2000 the NDDH will be cooperating in two projects to develop wetland IBIs for semi-permanent depressional wetlands and for flood plain wetlands along the Missouri River.