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Bioassessments are a primary tool used by the Department of
Environmental Protection's (DEP) ecologists to evaluate the biological
condition of a waterbody. Bioassessments consist of surveys and
other direct measurements of aquatic life (aquatic insects, fish,
crayfish, salamanders, frogs, worms, snails, mussels, etc.) in the
waterbody. Bioassessments, along with other physical
(stream bottom, banks, temperature, and flow) and
chemical (dissolved oxygen, conductivity) assessments, are crucial for
evaluating the health of our streams and waterbodies.
Although instantaneous water chemistry data are collected in County streams, the data cannot tell us much about the long-term, cumulative health of a stream system because the system is constantly evolving and changing as it responds to land use changes, ephemeral pollution, and other influences. Rather, bioassessments reflect the total cumulative impact of all stressors over a period of time on a waterbody on the biological community. Bioassessments are a unique water body response measurement, providing information about a water body that no other measurement can.
Learn more about the design of DEP's biological monitoring program.
Learn more about the presence of various organisms in Montgomery County.
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What is biological monitoring?
Biological monitoring is the study of biological community structure and function to determine water quality. Biological organisms, such as aquatic insects, fish, and stream salamanders, rely on water—normal stream flows and supportive habitat conditions—to survive. Stream ecosystems have numerous biological communities that are interrelated, but some are easier to collect and analyze, and offer a better indicator of water quality, than others.
Using biological indicators includes evaluating the mix of species found, their life-stages, their survival, their reproductive stage, and their health to evaluate the condition of habitat in and around our waterways, as well as the quality of the water itself.
The Environmental Protection Agency (EPA) recommends the use of at least two biological groups to work as indicators of the overall health of any stream.
The County uses benthic macroinvertebrates and fish to assess stream conditions. Amphibians (stream salamanders) have been monitored since 2008 to provide another biological indicator. In addition, Montgomery County collects data on the presence and absence of freshwater mussels, crayfish, and invasive plants to determine the distributions of species in these groups.
Electroshocking is used for stream monitoring.
Ecologists gather tiny aquatic insects in the streambed for biological sampling.
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What does DEP do with biological data?
Assessing waterbody health using biological assessments is fairly complicated. Saying that a water body is healthy because a certain type of organism was found there or that it is unhealthy because it does not support a certain type of organism is overly simplistic. DEP uses biological data in the following ways:
- Data are fed into a multi-metric index
DEP uses a multi-metric index known as the Index of Biological Integrity (IBI) to develop a unitless score rating for a waterbody. This involves taking various raw data on the count and other variables about the species found in the waterbody and using a peer-reviewed methodology to "rate" the data variables with numeric indices. The indices are then combined for an overall IBI score for the individual species (e.g., fish IB score, benthic macroinvertebrate IBI score).
- Data are used to develop an overall score rating for a waterbody
To develop an overall IBI score for a water body, DEP combines two species IBI scores (fish and benthic macroinvertebrates) and expresses the combination as a score whose maximum possible is 100%. Based on thresholds, these scores are classified as Excellent, Good, Fair, and Poor. Starting with raw bioassessment data, the IBI provides both a score and a descriptive assessment of water body health. The IBI scores for individual water bodies in the County are combined for an overall IBI score for a watershed.
- DEP uses data to track trends in watershed health over time
Because the County monitors all watersheds in the County at least once over a 5-year period, an overall snapshot of the condition of the County's watersheds, as measured by bioassessment, can be compiled every five years. This gives the County a good handle on watershed health trends over time.
Stream Conditions: 2001-2005 Monitoring Cycle
This map displays the stream conditions from the County's last monitoring cycle (watersheds monitored 2001-2005). The blue areas are in "Excellent" condition, green areas are "Good," yellow areas are "Fair," and red areas are in "Poor" or impaired condition.
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Organisms That We Monitor
Fish
Learn more about fish found in Montgomery County and how DEP collects and interprets fish data.
Benthic Macroinvertebrates
Learn more about benthic macroinvertebrates found in Montgomery County and how DEP collects and interprets data.
Crayfish
Learn about crayfish found in Montgomery County.
Mussels
Learn about mussels found in Montgomery County.
Amphibians and Reptiles
Learn about monitoring of amphibians and reptiles found in Montgomery County.
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Data Requests
If you're looking for specific types of biological monitoring data, use the links above to view the specific page for the organism. Look through the data fields gathered for that organism. This will help you to make specific data requests. If you're interested in obtaining data, please contact us at askdep@montgomerycountymd.gov and provide the following information:
Name, organization (if applicable), phone number, and/or email address
Type of data requested
Time frame requested
Explanation for use of data (helps to personalize the data request)
Preferred method of data retrieval (email, CD by mail, FTP, pick up CD or materials from DEP offices)
Additional Resources
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