James B. Stribling

Stressor tolerance values for benthic macroinvertebrates in Mississippi

Conceptually, tolerance values represent the relative capacity of aquatic organisms to survive and reproduce in the presence of known levels of stressors. Operationally, they represent the relative abundance and co-location of organisms and stressors. These numeric values are then used for calculating tolerance metrics. Defensibility of biological assessments using tolerance metrics is compromised if the origins of the tolerance values or technical foundations of metrics are unknown. To minimize circularity and maximize objectivity, we define stressed conditions using physical and chemical factors. Also, since single, isolated stressors in stream systems are rare, we used an approach that combines multiple physical and chemical characteristics into a single general stressor gradient. In this paper, we describe development of tolerance values for benthic macroinvertebrate taxa collected from 455 wadeable stream sites throughout Mississippi, USA, except the Alluvial Plain. Principal components analysis (PCA) was used to develop a gradient that incorporated direct (instream physical and chemical) and indirect (land use) stressors, which was then scaled from 0 to 10. Weighted averaging of the relative abundance of each taxon was used to assign tolerance values based on the point of greatest relative abundance along the stressor gradient. Tolerance values were derived for 324 of the 567 taxa collected from the study sites, and primarily represented sensitivity to agricultural influences including degradation of physical habitat and nutrient enrichment, the dominant stressors within the state. We suggest that this approach could be used in other areas of the country to develop new tolerance values, refine existing ones, and may be a useful approach for other taxonomic groups.

Precision of benthic macroinvertebrate indicators of stream condition in Montana

Abstract The Montana Department of Environmental Quality (MDEQ) uses 2 forms of benthic macroinvertebrate indicators for detection of stream impairment, a multimetric index (MMI) and a predictive model of observed to expected taxa (O/E), each of which is calibrated to streams across the state. As part of the routine monitoring program, some sample locations were subjected to repeated sampling, i.e., multiple samples were collected from stream reaches in spatial and temporal proximity. Results from repeated sampling allow calculation of precision estimates, which are important for describing a portion of the uncertainty (systematic error) associated with field sampling and site assessments. In this project, we evaluated 131 and 77 repeated-sample pairs for the MMI and O/E, respectively, using 4 different measures of precision: coefficient of variability (CV), 90% confidence intervals, relative % difference (RPD), and % difference for the final assessments. MMI and O/E had similar consistency and repeatability. Segregating the data set and calculations by region or field method yielded generally similar precision estimates for the indicators, although precision was slightly better in the mountains using the Hess field-sampling method than in other regions or with other field methods. Evaluation of RPD showed that assessments (impaired/nonimpaired) on the basis of the MMI differed between samples in 18.3% of repeated-sample pairs and assessments on the basis of O/E differed between samples for 19.5% of repeated-sample pairs. Recommended measurement quality objectives were 10 to 15% for CV and 15 to 20% for RPD for both indicators. Field-sampling precision was the focus of our paper, but we emphasize that detecting the presence of stressors or degraded conditions is the primary objective of the MDEQ stream condition indicators.

Modeling the Factors Controlling Phytoplankton in the St. Louis Bay Estuary, Mississippi and Evaluating Estuarine Responses to Nutrient Load Modifications

AbstractSeveral biochemical and physical factors regulate phytoplankton primary productivity and algal bloom events in estuarine environments. Some of the most important factors include nitrogen, phosphorus and silica availability, light availability, and estuarine flushing potential. A better understanding of these processes is necessary to support sound management strategies that take into account the hydrological, hydraulic, and biochemical connectivity between estuaries and their watersheds. In this paper the factors controlling phytoplankton productivity in a tributary estuary of the northern Gulf of Mexico, the St. Louis Bay estuary, Mississippi, and the system responses to nutrient load alterations are studied. For this purpose a coupled hydrodynamic and water quality model based on U.S. EPA computer models was implemented. The writers present an evaluation of the model predictive capacity, and its implementation to study the processes controlling phytoplankton dynamics, nutrient cycling, and oxyge...

Evaluation of effluent toxicity as an indicator of aquatic life condition in effluent-dominated streams: A pilot study

ABSTRACT The types and quality of data needed to determine relationships between chronic whole effluent toxicity (WET) test results and in-stream biological condition were evaluated using information collected over a 1.5-y period from 6 different sites across the United States. A data-quality-objectives approach was used that included several proposed measurement quality objectives (MQOs) that specified desired precision, bias, and sensitivity of methods used. The 6 facilities used in this study (4 eastern and 2 western United States) all had design effluent concentrations >60% of the stream flow. In addition to at least quarterly chronic Ceriodaphnia dubia, Pimephales promelas (fathead minnow), and Selenastrum capricornutum (green algae) WET tests, other tests were conducted to address MQOs, including splits, duplicates, and blind positive and negative controls. Macroinvertebrate, fish, and periphyton bioassessments were conducted at multiple locations upstream and downstream of each facility. The test acceptance criteria of the US Environmental Protection Agency (USEPA) were met for most WET tests; however, this study demonstrated the need to incorporate other MQOs (minimum and maximum percent significant difference and performance on blind samples) to ensure accurate interpretation of effluent toxicity. More false positives, higher toxicity, and more “failed” (noncompliant) tests were observed using no-observed-effect concentration (NOEC) as compared to the IC25 endpoint (concentration causing ≥25% decrease in organism response compared to controls). Algae tests often indicated the most effluent toxicity in this study; however, this test was most susceptible to false positives and high interlaboratory variability. Overall, WET test results exhibited few relationships with bioassessment results even when accounting for actual effluent dilution. In general, neither frequency of WET noncompliance nor magnitude of toxicity in tests were significantly related to differences in biological condition upstream and downstream of a discharge. Periphyton assessments were most able to discriminate small changes downstream of the effluent, followed by macroinvertebrates and fish. Although sampling methods were robust, more replicate samples collected upstream and downstream of each facility were needed to increase detection power. In general, macroinvertebrate and periphyton assessments together appeared to be sufficient to address project objectives.

Whole Effluent Toxicity Testing:Study Plan for Field Validation

Under the National Pollution Discharge Elimination System (NPDES), many municipal and industrial wastewater treatment facilities must perform Whole Effluent Toxicity (WET) Testing. Regulatory agencies determine the level of compliance of each facility by making inferences about the results of these tests. There has been some concern regarding appropriate ways to integrate WET tests into NPDES permits. The central issue of this concern involves determining the relationship between WET tests and instream biological conditions. Previous research (WERF project 95-HHE-1) has examined this issue using historical data. Because of issues with data comparability, i.e. questionable data quality, and project design, results were inconclusive. This study plan was designed to collect new data on method performance for both WET and bioassessment that would help answer the outstanding question. The study plan was designed using a Data Quality Objective (DQO) approach in which DQOs and MQOs were defined. These DQOs and MQOs were characterized using technical input from many scientists from federal, state, and private organizations. It was through this effort that certain technical design issues arose that needed further investigation before implementing the definitive study. Among these issues were determining if DQOs and MQOs were achievable, and determining appropriate biological assessment methods for various ecoregions (e.g. effluent dependent streams in the arid west). In order to appropriately address these issues, it was determined that a pilot study would be implemented before the definitive study. The pilot study is designed as a one-year study in which participating facilities will perform quarterly WET tests (Ceriodaphnia, P. promelas, Selenastrum) and at least one bioassessment (macroinvertebrate, fish, algae) as well as providing other prescribed data requirements. Results of the pilot will provide answers to technique design issues and will ultimately determine the most appropriate study design for the definitive study. This title belongs to WERF Research Report Series ISBN: 9781843396673 (Print) ISBN: 9781780403182 (eBook)