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Development of a multimetric index for naturally acidic New Jersey Pineland streams.

Jessup, Benjamin1, Moegenburg, Susan*,1, Bryson, Dean2, Poretti, Victor2, 1 Tetratech, Inc., Montpelier, Vermont2 New Jersey Department of Environmental Protection, Trenton, New Jersey

ABSTRACT- Multimetric indices are combinations of individual biological metrics that represent an ecological community. State and Federal agencies frequently use multimetric indices based on benthic macroinvertebrate communities for bioassessment and monitoring of aquatic resources. We developed a multimetric index for streams in the New Jersey Pinelands, an area ecologically distinct from the rest of New Jersey. Pinelands streams are naturally acidic, colored by tannins, low gradient, and have low specific conductance. The currently used index, the New Jersey Impairment Score (NJIS), effectively discriminates anthropogenically impaired and nonimpaired streams in the majority of New Jersey, but not in the Pinelands. We first used land use cover and water chemistry to identify nonimpaired and impaired stream sites. Then, the Pinelands Multimetric Index (PMI) was developed using data on benthic macroinvertebrates collected in the non-winter seasons of 1995-2002. The index was verified using data collected at the same sites, but on different sampling dates. The sample species lists were used to calculate a series of biological metrics representing benthic macroinvertebrate taxa richness, evenness, composition, tolerance to pollution, feeding mode, and habit. The efficiency of each metric at discriminating nonimpaired from impaired sites was then calculated. Seven metrics with high discrimination efficiencies and that represented a wide range of taxonomic attributes were then scored and averaged into the PMI, which correctly discriminated nonimpaired and impaired sites 94% of the time. The seven metrics in the index were insect taxa, non-insect taxa, percent Plecoptera and Trichoptera, percent Mollusca and Amphipoda, percent Diptera excluding Tanytarsini, Beck's Biotic Index, and percent filterers. This study demonstrates the need to consider ecologically distinct regions when developing multimetric indices for biomonitoring purposes.

Key words: New Jersey pinelands, multimetric index, acidic streams, bioasessment

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