Trait-based multimetric indices for diatom assessment of rivers and streams across the conterminous United States

Taxonomic inconsistency in diatom datasets can constrain use of diatoms as biological indicators in rivers and streams assessments in the United States (US). For projects like the USEPA’s National Rivers and Streams Assessment (NRSA), differences in species identification or nomenclature among multiple taxonomy laboratories can render diatom data unusable in large-scale assessments. We address this problem by developing trait-based diatom multimetric indices (MMIs) to assess river and stream condition across the conterminous US, using a separate MMI for the East, Plains, and West ecoregions. Diatom data from the 2008-2009 NRSA were used to develop candidate metrics by assigning taxa to morphological and functional traits based on genus-level attributes. Other metrics were developed from diatom genera. The final trait-based MMI for the East had the greatest precision and ability to discriminate reference from disturbed sites, followed by MMIs for the Plains and West. MMI performances were comparable with NRSA MMIs for other biological assemblages for these ecoregions. Our work shows trait-based diatom indices are effective for large-scale assessments, and because they are less labor-intensive and more immune to taxonomic inconsistencies than species-based indices, they are also more practical and reliable.

Impact/Purpose

Taxonomic inconsistency in diatom datasets can constrain use of diatoms as biological indicators in rivers and streams assessments in the United States (US). For projects like the USEPA’s National Rivers and Streams Assessment (NRSA), differences in species identification or nomenclature among multiple taxonomy laboratories can render diatom data unusable in large-scale assessments. We address this problem by developing trait-based diatom multimetric indices (MMIs) to assess river and stream condition across the conterminous US, using a separate MMI for the East, Plains, and West ecoregions. Diatom data from the 2008-2009 NRSA were used to develop candidate metrics by assigning taxa to morphological and functional traits based on genus-level attributes. Other metrics were developed from diatom genera. The final trait-based MMI for the East had the greatest precision and ability to discriminate reference from disturbed sites, followed by MMIs for the Plains and West. MMI performances were comparable with NRSA MMIs for other biological assemblages for these ecoregions. Our work shows trait-based diatom indices are effective for large-scale assessments, and because they are less labor-intensive and more immune to taxonomic inconsistencies than species-based indices, they are also more practical and reliable.

Citation

Riato, L., Ryan A Hill, A. Herlihy, Dave Peck, Phil Kaufmann, J. Stoddard, AND Steve Paulsen. Trait-based multimetric indices for diatom assessment of rivers and streams across the conterminous United States. To be presented at Society for Freshwater Science, Virtual, OR, May 23 - 27, 2021.