Karen A Blocksom

• Statistician at United States Environmental Protection Agency

In the coastal plains of southeastern United States, blackwater streams are relatively common. In South Carolina, many naturally occurring blackwater streams have been identified over decades of water monitoring, particularly when they fail to meet water chemistry expectations originally set based on non-blackwater streams. The South Carolina Depar...

Bioassessment indices routinely used in freshwater assessments are calculated using enumeration methods that are often time‐intensive. For diatom assessments that are mainly based on time‐consuming valve counts, little attention has been devoted to optimizing current counting methods, despite the need for cost‐effective bioassessments and biomonito...

Blackwater rivers and streams have stained or tea‐colored water from tannins released by decaying plant matter. Natural conditions in these waters often differ from non‐blackwater systems. For example, the pH and oxygen levels in waters can be very low, but completely natural. We examined an existing USEPA data set and found that blackwaters existe...

The tolerance of aquatic organisms to stressors is widely used to monitor and evaluate the condition of freshwater ecosystems. Tolerance values (TV) derived from analyses of the relationship between species and their environment are considered to be more objective than those that rely on expert opinion. We used principal component analysis (PCA) to...

We assessed the distribution of alien fishes in the Karun River Basin, Iran. Fish were collected from 39 sites during the November–December 2018 low-flow period. In total, 39 fish species from nine orders and 14 families were documented. Among these, 10 species were alien to the basin (986 individuals; 15.7%). Four species were the most abundant al...

We assessed the distribution of alien fishes in one of the most ecologically and economically important aquatic ecosystems in Iran, the Karun River Basin. Fish samples were collected from 35 sites in the Karun River Basin during the low-flow period from November to December 2018. We documented the occurrence of 37 species of fishes from nine orders...

We analyzed spatial variation in fish species richness and community composition in the Karun River basin, Iran. Knowledge about fish diversity in the basin is incomplete and varies widely along spatial and temporal scales: The Karun is the longest river in Iran (950 km) with the largest drainage area (about 67,000 km²). Fish samples were collected...

Large river systems are one of the most important water resources for human societies. However, the ecological integrity of large rivers has been altered greatly by human activities. To monitor and manage these ecosystems, multimetric indices (MMI) are considered as efficient tools. This study aimed to develop and validate a fish-based multimetric...

A physical, chemical and biological characterization of river systems is needed to evaluate their ecological quality and support restoration programs. Herein, we describe an approach using water chemistry, physical structure and land use for identification of a disturbance gradient existing in the Karun River Basin. For this purpose, at each site,...

Length-weight relationships (LWR) for seven species from the Karun River system in Iran were provided. These species include Alburnus doriae, Alburnus sellal, Barbus karunensis, Capoeta coadi, Squalius berak, Turcinoemacheilus saadii and Rhinogobius lindberg. Fishes were collected in November and December 2018 and LWR is based on total length and w...

Nonnative plants are widely recognized as stressors to wetlands and other ecosystems. They may compete with native plant species or communities and alter ecosystem properties, which can affect ecological condition, posing challenges to resource managers. As part of the United States Environmental Protection Agency’s National Wetland Condition Asses...

In 2011, the US Environmental Protection Agency and its partners conducted the first National Wetland Condition Assessment at the continental-scale of the conterminous United States. A probability design for site selection was used to allow an unbiased assessment of wetland condition. We developed a vegetation multimetric index (VMMI) as a parsimon...

Soil concentrations of 12 heavy metals that have been linked to various anthropogenic activities were measured in samples collected from the uppermost horizon in approximately 1000 wetlands across the conterminous US as part of the 2011 National Wetland Condition Assessment (NWCA). The heavy metals were silver (Ag), cadmium (Cd), cobalt (Co), chrom...

Although ecosystem services research has become common, few efforts are directed toward in-depth understanding of the specific ecological quantities people value. The theoretical framework of final ecosystem services focuses attention on such measurable attributes, as a common currency for social-ecological systems research. Environmental communica...

This multi-year pilot study evaluated a proposed field method for its effectiveness in the collection of a benthic macroinvertebrate sample adequate for use in the condition assessment of streams and rivers in the Neuquén Province, Argentina. A total of 13 sites, distributed across three rivers, were sampled. At each site, benthic macroinvertebrate...

United States Supreme Court rulings have created uncertainty regarding U.S. Clean Water Act (CWA) authority over certain waters, and established new data and analytical requirements for determining CWA jurisdiction. Thus, rapid assessment methods are needed that can differentiate between ephemeral, intermittent, and perennial streams. We report on...

Benthic macroinvertebrates are sampled in streams and rivers as one of the assessment elements of the US Environmental Protection Agency's National Rivers and Streams Assessment. In a 2006 report, the recommendation was made that different yet comparable methods be evaluated for different types of streams (e.g., low gradient vs. high gradient). Con...

Benthic macroinvertebrates are sampled in streams and rivers as one of the assessment elements of the U.S. Environmental Protection Agency’s National Rivers and Streams Assessment. In a 2006 report, the recommendation was made that different yet comparable methods be evaluated for different types of streams (e.g., low gradient vs. high gradient). C...

Benthic macroinvertebrates are sampled in streams and rivers as one of the assessment elements of the US Environmental Protection Agency’s National Rivers and Streams Assessment. In a 2006 report, the recommendation was made that different yet comparable methods be evaluated for different types of streams (e.g., low gradient vs. high gradient). Con...

Background/Question/Methods The ecological condition of wetland resources across the conterminous United States is poorly understood. To address this issue, the U.S. Environmental Protection Agency (USEPA), in collaboration with states, tribes, and other federal partners, is conducting the first-ever National Wetland Condition Assessment (NWCA)....

Elutriate bioassays are among numerous methods that exist for assessing the potential toxicity of sediments in aquatic systems. In this study, interlaboratory results were compared from 96-h Ceriodaphnia dubia and Pimephales promelas static-renewal acute toxicity tests conducted independently by two laboratories using elutriate samples prepared fro...

Understanding differences in zooplankton abundance depends on comparing similar data. Scientists employ numerous methods to collect and count freshwater zooplankton, potentially leading to difficulties when comparing studies. As scant information concerning specific biases exists, we quantified how (1) net mesh size and (2) counting techniques infl...

Significant amounts of antibiotics enter the environment via point and nonpoint sources. We examined the temporal dynamics of tetracycline exposure to stream periphyton and associated organisms across a logarithmically dosed-series of experimental mesocosms, designed to mimic natural conditions. Target in-stream tetracycline exposures were based on...

We assessed the North American mid-continent great rivers (Upper Mississippi, Missouri, and Ohio). We estimated the extent of each river in most- (MDC) or least-disturbed condition (LDC) based on multiple biological response indicators: fish and macroinvertebrate, trophic state based on chlorophyll a, macrophyte cover, and exposure of fish-eating w...

As part of the Environmental Monitoring and Assessment Program for Great River Ecosystems (EMAP-GRE), sediment samples were collected from 447 randomly selected littoral sites along the main channels of the Ohio, Missouri, and Upper Mississippi Rivers between 2004 and 2006. Toxicity of these sediment samples was measured using a 7-day Hyalella azte...

Pesticides are nearly ubiquitous in surface waters of the United States, where they often are found as mixtures. The molecular mechanisms underlying the toxic effects of sub-lethal exposure to pesticides as both individual and mixtures are unclear. The current work aims to identify and compare differentially expressed proteins in brains of male fat...

We measured mercury (Hg) concentrations in whole fish from the Upper Mississippi, Missouri, and Ohio Rivers to characterize the extent and magnitude of Hg contamination and to identify environmental factors influencing Hg accumulation. Concentrations were generally lower (80% of values between 20-200 ng g(-1) wet weight) than those reported for oth...

Great rivers of the central United States (Upper Mississippi, Missouri, and Ohio rivers) are valuable economic and cultural resources, yet until recently their ecological condition has not been well quantified. In 2004-2005, as part of the Environmental Monitoring and Assessment Program for Great River Ecosystems (EMAP-GRE), we measured legacy orga...

We describe a simple empirical modeling approach for determining least-disturbed conditions for the great rivers of the Upper Mississippi River basin: Missouri, Upper Mississippi, and Ohio Rivers. We used multivariate analysis to identify reference strata (reaches for which a single reference expectation was appropriate) on each river. Strata inclu...

Large river bioassessment protocols lag far behind those of wadeable streams and often rely on fish assemblages of individual rivers. We developed a regional macroinvertebrate index and assessed relative condition of six large river tributaries to the upper Mississippi and Ohio rivers, Midwest USA. In 2004 and 2005, benthic macroinvertebrates, wate...

The Wisconsin Department of Natural Resources (WDNR), with support from the U.S. EPA, conducted an assessment of wadeable streams in the Driftless Area ecoregion in western Wisconsin using a probabilistic sampling design. This ecoregion encompasses 20% of Wisconsin's land area and contains 8,800 miles of perennial streams. Randomly-selected stream...

Regulatory agencies need rapid indicators of hydrologic permanence for jurisdictional determinations of headwater streams. The study objective was to assess the utility of larval salamanders and habitat variables for determining stream permanence across a large geographic area. We sampled four core forests (61 sites in IN, KY, and OH) in spring (Ap...

The level of sampling effort required to characterize fish assemblage condition in a river for the purposes of bioassessment may be estimated via different approaches. However, the goal with any approach is to determine the minimum level of effort necessary to reach some specific level of confidence in the assessment. In the Ohio River, condition i...

  In 2003, we compared two benthic macroinvertebrate sampling methods that are used for rapid biological assessment of wadeable streams. A single habitat method using kick sampling in riffles and runs was compared to a multiple habitat method that sampled all available habitats in proportion of occurrence. Both methods were performed side-by-side a...

Measurement and estimation of performance characteristics (i.e. precision, bias, performance range, interferences and sensitivity) are often neglected in the development and use of biological sampling methods. However, knowledge of this information is critical in enabling potential users to assess data quality and make comparisons among different s...

Multiple diatom sampling methods exist for the assessment of lotic systems but few comparisons of their application efficacies in monitoring have been conducted. In this study 60 sites were sampled on four large, non-wadeable rivers in Ohio and Kentucky, USA, which varied in depth, flow rate, surrounding land use and hydrologic modification. Four a...

Efforts to develop benthic macroinvertebrate sampling protocols for the bioassessment of lotic ecosystems have been focused largely on wadeable systems. As these methods became increasingly refined and accepted, a growing number of monitoring agencies expanded their work and are now developing sampling protocols for non-wadeable large rivers. Large...

Two United States Environmental Protection Agency (U.S. EPA) macroinvertebrate sampling protocols were compared in the Mid-Atlantic Highlands region. The Environmental Monitoring and Assessment Program (EMAP) wadeable streams protocol results in a single composite sample from 9 transects whereas the Rapid Bioassessment Protocol (RBP) II consists of...

Collection of representative benthic macroinvertebrate samples from large rivers has been challenging researchers for many years. The objective of our study was to develop an appropriate method(s) for sampling macroinvertebrates from the Ohio River. Four existing sampling methods were compared in the Markland Pool of the Ohio River (ORM 436.2 - 531...

Bioassessment of nonwadeable streams in the United States is increasing, but methods for these systems are not as well-developed as for wadeable streams. In this study, we compared six macroinvertebrate field sampling methods for nonwadeable streams adapted from those used by three major programs: the U.S. Environmental Protection Agency's Environm...

Data were collected from 60 boatable sites using an electrofishing design that permitted comparisons of the effects of designs and distances on fish assemblage metrics. Sites were classified a priori as Run-of-the-River (ROR) or Restricted Flow (RF). Data representing four different design options (i.e., 1000 and 2000 m for both single and paired b...

Description: This document describes the approach and results of a study to measure the performance characteristics of a macroinvertebrate sampling protocol recently developed for nonwadeable streams and rivers. The findings in this report will assist monitoring agencies by providing performance information not typically available with bioassessmen...

Data were collected from 60 boatable sites using an electrofishing design that permitted comparisons of the effects of designs and distances on fish assemblage metrics. Sites were classified a priori as Run-of-the-River (ROR) or Restricted Flow (RF). Data representing four different design options (i.e., 1000 and 2000 m for both single and paired b...

Six reaches in each of two large rivers (one each in Kentucky and Ohio) were sampled using a prototype benthic macroinvertebrate sampling technique. The intent was to better understand the relationship between large river macroinvertebrate assemblages and habitat features. This information was to determine an acceptable sampling design to support d...

The Macroinvertebrate Biotic Integrity Index (MBII) was developed from data collected at 574 wadeable stream reaches in the Mid-Atlantic Highlands region (MAHR) by the U.S. Environmental Protection Agency's (USEPA) Environmental Monitoring and Assessment Program (EMAP). Over 100 candidate metrics were evaluated for range, precision, responsiveness...

When biological metrics are combined into a multimetric index for bioassessment purposes, individual metrics must be scored as unitless numbers to be combined into a single index value. Among different multimetric indices, methods of scoring metrics may vary widely in the type of scaling used and the way in which metric expectations are established...

The Mid-Atlantic Highlands Assessment (MAHA) included the sampling of macroinvertebrates from 424 wadeable stream sites to determine status and trends, biological conditions, and water quality in first through third order streams in the Mid-Atlantic Highlands Region (MAHR) of the United States in 1993-1995. We identified reference and impaired site...

In response to the recent focus by the U.S. Environmental Protection Agency on bioassessment of lakes, a multimetric index was developed for New Jersey lakes and reservoirs using benthic macroinvertebrates. Benthic samples were collected from reference and impaired lakes with muck and intermediate sediments in central and northern New Jersey during...

We explored the recent (1969–1996) dynamics of fish communities within Lake Erie, a system formerly degraded by eutrophication and now undergoing oligotrophication owing to phosphorus abatement programs. By merging bottom trawl data from two lake basins of contrasting productivity with life-history information (i.e., tolerances to environmental deg...