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map of AMNET sampling sites


  Bureau of Freshwater & Biological Monitoring





In 1992, the Bureau of Freshwater & Biological Monitoring reactivated its Ambient Macroinvertebrate Network (AMNET) which, at the time of its last sampling in 1988, consisted of only 18 sampling sites statewide. The old network was determined to be inadequate to support the department's 305(b) [water quality inventory report], 303(d) [list of impaired waters] and watershed programs, so bureau staff designed a new program.

The new AMNET program established sampling stations in each of the 20 freshwater Watershed Management Areas, statewide, where the health of in stream benthic macroinvertebrate (sometimes called bottom-dwelling "bugs") communities are evaluated using a USEPA-developed statistical methodology referred to as Rapid Bioassessment Protocol (RBP). Under AMNET, each of the State's five major Water Regions is sampled for benthic macroinvertebrates (bottom dwelling organisms visible to the naked eye) on a rotational schedule of once every five years. Visual observations, Stream Habitat Assessments and limited physical/chemical parameters are performed on each site. To date, all of the major drainage basins have been biologically monitored for the third time with over 760 non-tidal sampling sites established.

The AMNET results have been incorporated into the National Environmental Performance Partnership System (NEPPS) as a primary environmental indicator of water quality impairment. Statewide AMNET monitoring is a commitment in the NEPPS PPA with EPA Region 2, and a key element of NJ's Long-term Water Monitoring and Assessment Strategy. Other uses of the AMNET data include:

AMNET reports of results are published by the bureau as analysis of each Water Region is completed; copies are available from this web site. The biological and habitat ratings are also available from this web site for Round 1, Round 2, Round 3, and Round 4 data. The chemical and biological data will also soon be available from STORET, EPA's computerized data system. GIS data shape-files cans be found at this address:

New Indices:

AMNET employs a multimetric index approach for assessment of biological condition, and regulatory thresholds for use attainment. New Jersey benthic macroinvertebrate communities can be statistically grouped into three distinct structures based on geographical regions: high gradient (above the Fall Line), low gradient (Coastal Plain excluding the Pinelands), and Pinelands. To accurately assess biological condition, an index was developed for each distinct region using guidelines outline in USEPA's Rapid Bioassessment Protocols (RBP) for Use in Wadeable Streams and Rivers. The indices assess sites from two perspectives: the condition of the macroinvertebrate community and the regulatory use attainment. An assessment framework was outlined to address both concerns, and a development report was prepared for each index: High Gradient Macroinvertebrate Index (HGMI), Coastal Plain Macroinvertebrate Index (CPMI), and the Pinelands Macroinvertebrate Index (PMI).

A Standard Operating Procedure (SOP) is available for all aspects of the AMNET program including sampling, analysis, assessment, and a summary of the index development and scoring criteria.

Stressor Identification Investigations

The Stressor Identification process , based on USEPA's "Stressor Identification Guidance Document" (2000), is a systematic protocol to determine the likely stressor or stressors causing biological impairments. While biological information, such as benthic macroinvertebrate data, can determine the condition of an aquatic resource, the data do not identify the likely cause(s) of impairments. The ability to accurately identify stressors and support those findings is a critical step in developing appropriate strategies and corrective measures to improve the quality of aquatic resources.

The purpose of a Stressor Identification (SI) investigation is to determine the most likely cause(s) of the impaired benthic macroinvertebrate community, as identified through the AMNET program. AMNET sites, with a rating of "Poor" or "Fair" are considered impaired, and therefore, not supporting the Aquatic Life use goals of the federal Clean Water Act. A cause of impairment can be viewed most simply as a stressor or agent that negatively impacts aquatic life. These causes may include: chemical or physical pollutants (e.g. toxic chemicals, nutrient inputs, oxygen-consuming wastes); habitat degradation (e.g. loss of in-stream structure such as riffles and pools due to sedimentation, loss of bank and root mass habitat due to channel erosion); and hydrologic modifications (e.g. low base flow, flashy stream flow).

Available reports of completed Stressor Identification investigations.



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Last Updated: August 13, 2015