Summary of major issues and findings

• Nutrient concentrations in streams are higher in areas with greater agricultural land use or downstream from wastewater-treatment plants than in forested areas. These higher concentrations may result in increased algal growth in streams.

• Nutrient concentrations in ground water are higher in areas with greater agricultural land use than in forested areas. These higher concentrations seldom exceed drinking-water standards.

• Bacteria concentrations in streams are higher in basins with greater agricultural land use (mostly pasture). Fecal coliform bacteria concentrations occasionally exceed State water-quality standards for whole-body contact recreation.

• Nutrient and bacteria concentrations are affected by hydrologic and geologic factors. Stream discharge and the presence or absence of confining geologic layers are two factors that are important in predicting concentrations.

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• In streams and ground water, pesticides were more prevalent in agricultural areas than in forested areas. Concentrations generally were low and seldom exceeded U.S. Environmental Protection Agency drinking-water criteria or standards, or criteria for the protection of aquatic life.

• In bed sediment, the greatest numbers of pesticides and other organic compounds generally were detected at sites downstream from urban areas. No concentrations exceeded U.S. Environmental Protection Agency criteria for the protection of aquatic life.

• In biological tissue, pesticides were detected at 5 of 26 stream sites. Chlordane was detected downstream from Springfield, Mo. DDT, DDE, or dieldrin was detected at four sites in agricultural basins.

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• Concentrations of sulfate and some trace elements in water from streams in areas of active or historical lead-zinc mining tend to be higher than in areas where mining has not occurred. These trace element concentrations decrease with increasing distance downstream from the mining activity. Concentrations usually did not exceed Federal standards or criteria for the protection of drinking water, human health, or aquatic life.

• Concentrations of lead and zinc in bed sediment and fish or clam tissue are substantially higher at sites with mining activities (historical or active) in the basin. Concentrations are high enough to suggest potential adverse biological effects. The State of Missouri has issued a fish consumption advisory for some streams.

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• Radium (a product formed by the radioactive decay of uranium) is present in the confined part of the Ozark aquifer. However, the levels of radium seldom exceeded the U.S. Environmental Protection Agency drinking-water standard.

• Radon (a gas produced by the radioactive decay of radium) levels exceeded a proposed (but withdrawn) U.S. Environmental Protection Agency drinking-water standard in nearly one-half of the samples. Radon can enter homes through their water systems. Homes served by private domestic wells and small public waterworks using ground water can be particularly vulnerable.

• Radon levels are greater in the Springfield Plateau aquifer and the unconfined part of the Ozark aquifer than in the confined part of the Ozark aquifer.

• Several factors can affect aquatic habitats, which then affect biological communities. Many habitat characteristics appeared to be influenced more by basin size than by land use.

• Small streams in agricultural areas generally have fewer trees and other woody plants in the riparian zone than do small streams in forested areas. This results in more sunlight reaching the streams in the agricultural areas. More sunlight and the higher nutrient concentrations probably result in faster growing attached algae in these streams.

• Some other habitat characteristics were different between the agricultural and forested sites studied. Of these characteristics, some are not likely the result of agricultural practices, while others (canopy angle, channel width, and sinuosity) may, at least in part, result from agricultural practices. These characteristics can affect biological communities.

• Although the effects of instream gravel mining in the Ozarks were not studied by the NAWQA Program, some studies suggest that gravel mining has detrimental effects on instream habitat.

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• Stonerollers make up a greater percentage of the fish at agricultural sites than at forested sites. Stonerollers graze on algae attached to rocks and other surfaces. More algae probably grow on these surfaces because of the higher nutrient concentrations and greater amounts of sunlight reaching these streams.

• Sunfish (including the black basses) and darters make up a smaller percentage of fish at agricultural sites than at forested sites. Members of the sunfish family (particularly smallmouth bass) are important game fish. Several species of darters that live in the Ozarks exist nowhere else in the world.

• Fish community composition appears to be related to stream size, canopy angle, substrate, and water chemistry. Some of these factors are affected by human activities.

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