In 1995, the West Virginia Department of Environmental Protection (DEP) established the Watershed Assessment Program
to assess and report on the water quality of the State's streams and lakes. Following a period of restructuring
within the agency, the program's name was changed to the Watershed Assessment Branch (WAB). The WAB is comprised of
a staff of biologists and environmental scientists who measure and assess the chemical and physical properties of
water, assess habitat conditions, and collect biological samples in the form of benthic macroinvertebrates and fish
from streams and lakes throughout the state. As of 2017, the WAB has collected 9,330 benthic macroinvertebrate
samples at 6,450 stations, from 3,630 different streams. About 527 fish community samples have been collected at 492
stations, from 404 different streams. Since 1998, the WAB has used the benthic macroinvertebrate data to measure the
biological health of West Virginia streams. Fish community sampling in streams has been part of WAB biological
monitoring since 2006.
Benthic macroinvertebrates (also known as "benthos") are small animals living among stones, logs, sediments and
aquatic plants on the bottom of streams, rivers and lakes. They are large enough to see with the naked eye
(macro) and have no backbone (invertebrate). Insects comprise the largest diversity of the these organisms and
include mayflies, stoneflies, caddisflies, beetles, midges, crane flies, dragonflies and others. Non-insect
members of the benthic macroinvertebrate community are snails, clams, aquatic worms and crayfish. To date, the
WAB has collected and identified 538 different kinds (mostly Genus level identifications) of benthos from 6,202
stations on 5,530 different streams throughout West Virginia. The WAB has found the diversity of some benthos to
be especially high, including mayflies (49 genera) and stoneflies (43 genera). Some benthic genera are fairly
common throughout the state, while others are limited in their distribution to just a few areas. The most
commonly encountered benthos is the midge Polypedilum (Family Chironomidae), found at 81% of collection
stations. The caddisfly Cheumatopsyche (Family Hydropsychidae) and mayfly Baetis (Family Baetidae) have been
found at 77% and 72% of the stations, respectively. The net-winged midge Blepharicera (Family Blephariceridae)
is not common, found at only 1.2% of all collection stations. This sensitive organism is restricted to the
steeper streams in the higher mountains of the state, where oxygen rich water cascades over waterfalls and
tumbles through small rapids and riffles.
For more information about benthic macroinvertebrates, click on a link below.
Benthic Macroinvertebrate and Fish Topics
Cadisfly Family Hydropsychidae
Mayfly Family Baetidae
Midge Family Blephariceridae
Benthic macroinvertebrates live in a wide variety of habitats and can be found from the smallest headwater
streams down to the largest rivers. In West Virginia, benthic macroinvertebrates are especially diverse, having
adapted to the complex array of streams that dissect the mountains and tumble through the narrow valleys. In
general, benthic organisms are most diverse in the fast flowing riffle and run areas of streams. Compared to
pools and glides, riffles and runs are shallower and have higher stream gradients and faster water velocities.
They are composed of rough materials, such as large gravel, cobbles and small boulders that create turbulence
and oxygenate the water, while providing a stable habitat for benthos to live. Many insect benthos spend the
majority of their lives (anywhere from 1 month to 4 years, depending on the species) in the water and only
emerge as adults for a few hours (or up to several days) to reproduce and complete their life cycle. Movement of
benthos larvae includes swimming, crawling around on the stream bottom and drifting with stream currents. After
emerging, adult aquatic insects can fly to new stream locations during their winged terrestrial stage.
Bee Run - Small headwater stream - benthos habitat
Gandy Creek - Mountain trout stream - benthos habitat
Benthic macroinvertebrates have special adaptations that allow them to live in the stream environment. These
adaptations may be unique physical features or even specialized behaviors. For example, many species have flattened
bodies that allow them to hide between boulders and cobbles, thus limiting the stress of fast-moving water and
allowing them to avoid some predators. Others have sharp claws, suction cups, or other grasping mechanisms on their
bodies to prevent them from being swept away in the swift-flowing current. Black fly larvae (Family Simuliidae) have
a silk gland and posterior hooks that are used to anchor them in place while they face upstream actively capturing
food with their fan-like mouth parts. Net-building caddisfly larvae (Family Hydropsychidae) construct funnel-shaped
nets, attach them to stable substrate materials, and then periodically harvest the food caught in the mesh. Some
stonefly species will avoid high water temperatures by burrowing deep into the stream bottom substrate where they
will diapause near the water table. One of the most important adaptations for benthos is the ability to extract
oxygen from the water in which they live. Many aquatic insects accomplish this with external gills that remove
oxygen from the surrounding water, while others rely upon cutaneous respiration to obtain oxygen.
Mayfly Family Heptageniidae - Flattened Body
Black Fly Family Simuliidae - Silk Glands and Hooks
Benthos are often classified based on their feeding strategy. The stonefly Pteronarcys (Family Pteronarcyidae) is in
the shredder functional feeding group. These large stoneflies primarily consume decaying leaves that have fallen
into the stream from trees along the forested riparian corridor. The water penny beetle (Family Psephenidae) is a
scraper and can be observed grazing on algae that covers rocks and logs. The mayfly Family Baetidae is classified as
a collector-gatherer, primarily feeding on fine pieces of organic material on the stream bottom. The most recognized
predator in the aquatic insect world is the larval form of the dobsonfly, more commonly known as the hellgrammite
(Family Corydalidae). Hellgrammites are active predators, crawling around on the large cobble and boulders in the
swifter habitats of streams where they search for other benthic macroinvertebrates to eat.
Beetle Family Psephenidae - Grazing on Algae
Hellgrammite Searching for Prey
Importance in Food Webs
Benthic macroinvertebrates are extremely important in aquatic food webs. In most streams, the energy stored by plants
is available for consumption by benthos either in the form of leaves that fall into the water or in the form of
algae that grows on the stream bottom. The energy derived by eating leaves and algae is then transferred from
benthos to other life forms in and around the stream such as fish, frogs, salamanders, snakes, birds, and even
fishermen. In another sense, benthos are important for recreational purposes, as thousands of trout anglers strive
to "match the hatch" of many species, particularly those of mayflies.
Brook Trout - Preys on Benthic Macroinvertebrates
Mud Salamander - Preys on Benthic Macroinvertebrates
Benthic macroinvertebrates provide reliable and comprehensive information on water and habitat quality and have been
used as biological indicators in many parts of the world for nearly 100 years. In some cases, it may be difficult to
identify pollutants and stressors in streams with chemistry data alone, which only provides information pertinent to
the precise time of sampling. Even the presence of fish may not be indicative of the status of a stream because fish
can swim away to avoid polluted water or unfavorable habitat conditions and then return when conditions improve.
Many benthic macroinvertebrates are not as mobile as fish and cannot move to avoid pollution. Therefore, the
community of benthos living in a stream may indicate the water quality conditions of the past. Additionally, benthos
are excellent tools for assessing water quality because they are extremely diverse, allowing for a wide range of
sensitivity and responses to stressors such as metals, nutrients and sediments. Finally, they are ubiquitous and
relatively easy to collect and identify which makes them attractive to agencies and organizations searching for a
practical means of assessing water quality in streams.
Nutrient Enrichment from Livestock Waste
Sediment Deposition from Constructrion Activity
Collecting Benthic Macroinvertebrates
Streams in West Virginia are primarily high gradient with coarse substrate materials such as boulder, cobble and
gravel. These physical conditions are responsible for the typical riffle/run habitats commonly found in most streams
across the state. The Watershed Assessment Branch samples these riffle/runs for benthos by using a hand-held net,
often referred to as a kick-net. Generally speaking, the net is secured to the stream bottom in a riffle/run while
the cobbles and gravels upstream are cleaned and disturbed ("kicked") causing the benthos to float downstream into
the net. This procedure is used statewide by the WAB in all wadeable streams with riffle/run habitats and is by far
the most common type of benthic sample collected by the agency. All benthos samples are taken to the laboratory
where the organisms are sorted, identified and enumerated in preparation for data analysis and interpretation.
Entities wishing to collect benthic macroinvertebrates from West Virginia streams for basic environmental research
studies or permitting projects will need to obtain a scientific collection permit from the West Virginia DNR, which
requires that the investigator(s) follow the methods established and used by the WAB.
Using Benthic Macroinvertebrates to Assess Biological Conditions
In order to extract and understand the information presented by a benthic macroinvertebrate sample, the WAB uses
a tool commonly called an Index of Biotic Integrity (IBI). An IBI is a summary score that is comprised of
several biological indicators called metrics. A metric is a characteristic of the biological community that
changes in some predictable way with increases in human disturbance. For example, species richness (sometimes
called diversity) generally exhibits a marked decrease as human disturbance increases. Therefore, it is one of
the most commonly utilized component metrics of IBI's.
In 2000, the WAB collaborated with the United States Environmental Protection Agency (EPA) Region III to develop
its own IBI, a multi-metric index for biological assessments called the West Virginia Stream Condition Index
(WVSCI). The WVSCI summarizes family level identifications of benthic macroinvertebrate assemblages to assess
the biological condition of wadeable streams with riffle/run habitats. This index includes six biological
metrics that represent elements of the structure and composition of benthic macroinvertebrate communities. The
WVSCI metrics were selected to maximize discrimination between streams with known stressors and reference
streams. Reference streams have little or no human disturbances, and therefore exhibit good water quality and
habitat conditions (reference document). Many of the streams that the WAB recognizes as reference sites are located on public lands,
such as Monongahela National Forest and the West Virginia State Park system. The WAB used the WVSCI from 2002 to
2014 to assess the biological condition of wadeable streams in the state.
During West Virginia's 2012 legislative session, Senate Bill 562 was passed. This legislation requires the DEP to
develop new assessment methodology that will be subject to legislative approval. The process to develop and evaluate
options for assessing stream health more "holistically" is ongoing, and specifically considers the use of fish
community information, along with benthic macroinvertebrate index scores, as part of the assessment methodology.
Fish community assessments are an important component of many water quality management programs. These assessments
can be useful for making decisions regarding biological integrity and overall stream health. Similar to benthic
macroinvertebrates, samples of fish communities from streams can be assessed using an IBI. Recently (2015) the DEP
collaborated with West Virginia University to finalize the development of fish IBIs specifically applicable to West
Virginia fish communities. It was determined during the IBI development that fish communities varied regionally and
therefore required region specific expectations. The end result is that IBIs have been developed for 3 of the 5
distinct regions in the state.
Human activities have allowed the discharge of chemicals, trace metals and other contaminants into the waters of the
state. Fish and other aquatic organisms may bioaccumulate these contaminants in their tissues to levels much higher
than those in the water and sediments. The WAB collects fish of various species from West Virginia's waterbodies in
order to determine if contaminants are present in their tissues, and to what level. This information is used by the
West Virginia Department of Health and Human Resources, through an interagency agreement with West Virginia's DEP
and Division of Natural Resources, to develop consumption advisories for fish caught in the state. These fish
consumption advisories are reviewed annually and are geared towards helping West Virginia anglers make educated
choices about eating the fish they catch.