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As human health is a reflection of environmental health, aquatic insect communities can be good indicators of the health of Maryland’s watersheds. Starting in 2002 and as part of the state’s responsibilities under the Clean Water Act, the Maryland Department of the Environment (MDE) began using biological indicators, such as fish and benthic (bottom dwelling) invertebrates to report on watershed health. MDE has a staff of aquatic biologists who take samples, count and identify organisms under a microscope, and report the results. The department uses this information to make biennial water quality reports to the Environmental Protection Agency.
The Benthic Bug Barometer
MDE relies on solid scientific data to support regulatory and legislative actions to protect our environment. Staff from the Technical and Regulatory Services Administration’s (TARSA) Ecological Assessment Division (EAD) is responsible for determining how to best use biological data for regulatory decisions. In TARSA’s Baltimore and Annapolis labs, benthic macroinvertebrates (bottom-dwelling organisms that lack a spine, such as insects, mollusks, and arthropods) are analyzed to assess impacts from dredged material disposal activities in Chesapeake Bay.
Sorting Sieved Sediment Samples
To assure that dredging activities are not adversely affecting aquatic communities, EAD staff collects sediment samples near dredged material disposal sites. These locations include Hart-Miller Island, Poplar Island, and the Poole’s Island open-water placement site. The mud/sand samples are rinsed over a half-millimeter mesh screen and preserved for laboratory processing.
In TARSA’s benthic lab, these samples are sorted in trays to remove macroinvertebrates from the debris. EAD taxonomists (person who identifies invertebrates and fish) then identify any organisms found in the sample, record their numbers on a data sheet, and analyze these counts using established biological measurements (metrics).
What Determines Watershed Health?
Lab technicians look at metrics such as species diversity, percent abundance of pollution-sensitive or pollution-indicative organisms, and total abundance to determine if the benthic community shows signs of stress. Any signs of organism stress (poor species diversity, very large abundances of a few organisms, presence of pollution-tolerant organisms) are then further analyzed. Using available water quality parameters and other information, technicians can determine if the stress is the result of natural (salinity, storms, etc.) or human-induced impacts.
TARSA staff also work closely with other agencies, such as the Maryland Department of Natural Resources’ (DNR) Maryland Biological Stream Survey (MBSS) Program, to identify water quality impacts in Maryland’s non-tidal streams and rivers. MBSS monitors both fish and benthic macroinvertebrates communities using specific biological metrics to determine signs of stress. MDE's staff then works closely with DNR biologists to decide if watersheds should be categorized as impaired, or if other natural conditions (beaver dams, bedrock, storms, etc.) are affecting the biological community.
Spotting Stressors
More recently, TARSA is analyzing the habitat, water quality, land use, and other information collected in streams to look for indications of specific biological stressors or pollutants. A statistical model is being developed that uses this information to predict the probability that a given stressor is impairing the aquatic community.
TARSA is also developing methods to identify the magnitude and extent of biological impairments. This information will help the MDE develop Total Maximum Daily Loads and will also allow staff to better target limited monitoring resources and identify priority watersheds for both restoration and protection. These biological assessment methods are part of MDE’s overall strategy to achieve the Clean Water Act goal of preserving the chemical, physical, and biological integrity of the nation’s waters.
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