Assessing background levels of specific conductivity using weight of evidence.

There are many ways to estimate background levels, and many types of evidence may contribute to determining whether a water, air, or soil is at background. As a result, it is important to define background in each case and to weigh the available evidence to determine the best estimate of background. A weight-of-evidence approach is demonstrated that assesses whether the background SC is sufficiently similar in streams of Ecoregion 70 in West Virginia and Ohio.

A field-based model of the relationship between extirpation of salt-intolerant benthic invertebrates and background conductivity.

Field-collected measures of dissolved salts and occurrences of aquatic invertebrates have been used to develop protective levels. However, sufficiently large field data sets of exposures and biota are often not available. Therefore, a model was developed to predict the exposure extirpating 5% of benthic invertebrate genera using only measures of specific conductivity (SC) as the independent variable.

A field-based characterization of conductivity in areas of minimal alteration: A case example in the Cascades of northwestern United States.

The concentration of salts in streams is increasing world-wide making freshwater a declining resource. Developing thresholds for freshwater with low specific conductivity (SC), a measure of dissolved ions in water, may protect high quality resources that are refugia for aquatic life and that dilute downstream waters. In this case example, methods are illustrated for estimating protective levels for streams with low SC.

Field-based method for evaluating the annual maximum specific conductivity tolerated by freshwater invertebrates.

Most water quality criteria are based on laboratory toxicity tests and usually include chronic and acute magnitudes. Field-based criteria are typically based on long-term or continuous exposures, so they are chronic. Biological responses of quantified, short-term aqueous exposures are seldom documented in the field.

A flow-chart for developing water quality criteria from two field-based methods.

Field-based methods increase relevance and realism when setting water quality criteria. They also pose challenges. To enable a consistent process, a flow chart was developed for choosing between two field-based methods and then selecting among candidate results.

Effects of pharmaceuticals on Daphnia survival, growth, and reproduction.

Pharmaceuticals have been globally detected in surface waters, and the ecological impacts of these biologically-active, ubiquitous chemicals are largely unknown. To evaluate the aquatic toxicity of individual pharmaceuticals and mixtures, we performed single species laboratory toxicity tests with Daphnia magna, a common freshwater zooplankton. We conducted acute (6-day) and chronic (30-day) exposure pharmaceutical bioassays and evaluated survivorship and morphology of adults and neonates, adult length, resting egg production, brood size (fecundity), and the proportion of male broods produced (sex ratio).

Human mercury toxicity and ice angler fish consumption: are people eating enough to cause health problems?

Mercury contamination of aquatic ecosystems is a global environmental concern. Bioaccumulation of mercury in fish exposes consumers to risk. We interviewed ice anglers on Monona Bay, Wisconsin during the 2001-2002 ice fishing season to determine risk associated with fish consumption and methyl mercury (MeHg) intake.