Water quality, hydrology, and invertebrate communities of three remnant wetlands in Missouri, 1995-97

This report presents the results of a study conducted by the U.S. Geological Survey in cooperation with the Missouri Department of Natural Resources from December 1995 through May 1997 to describe the water quality, hydrologic, and invertebrate characteristics of three remnant wetlands. These data may be used to help develop selected water-quality standards for wetlands in Missouri. Wetlands monitored in this study include Spile Lake, Vernon County; Little Bean Marsh, Platte County; and Forker Oxbow, Linn County, Missouri.

Extremes in physicochemical properties in these wetlands were greatly affected by thermal stratification, hydrologic fluctuations, biological activity, and ice formation. The wetlands had dissolved-oxygen concentrations below the 5-milligrams-per-liter State water-quality standard from 40 to 60 percent of a selected 1-year period, corresponding to periods of thermal stratification. Hydrologic fluctuations were common as the water-surface elevation changes in these systems ranged up to 12 feet during the course of the study. Photosynthesis and respiration are likely causes of diurnal fluctuations in pH and dissolved oxygen throughout the study period, but particularly in the summer months. Periods of ice formation were short lived in the wetlands, but corresponded with maximum values of specific conductance and dissolved oxygen in all three systems.

Analyses of invertebrate results using the Jaccard Coefficient of Community Similarity indicated mixed results. Woody snag sample results showed little similarities between sites, while sweep net sample results indicated similarities existed. Most of the families detected at these sites are considered organic tolerant as indicated by the Hilsenhoff Biotic Index. Analysis of the dominant taxon indicates that one or two invertebrate families that are tolerant to organic enrichment generally dominate the wetlands.

The hydrologic, water quality, and invertebrate information analyzed in this study indicate that while there are similarities among wetlands, these are unique systems. The statistical comparisons between water-quality constituents in wetlands and streams indicate dissimilarities are common. Including the presence of thermal stratification in these wetlands, the exclusions and modifications in State standards that are applied to lakes and reservoirs also may be applicable.