Evaluation of a combined macrophyte–epiphyte bioassay for assessing nutrient enrichment in the Portneuf River, Idaho, USA

Environmental Monitoring and Assessment
By: , and 

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Abstract

We describe and evaluate a laboratory bioassay that uses Lemna minor L. and attached epiphytes to characterize the status of ambient and nutrient-enriched water from the Portneuf River, Idaho. Specifically, we measured morphological (number of fronds, longest surface axis, and root length) and population-level (number of plants and dry mass) responses of L. minor and community-level (ash-free dry mass [AFDM] and chlorophyll a [Chl a]) responses of epiphytes to nutrient enrichment. Overall, measures of macrophyte biomass and abundance increased with increasing concentrations of dissolved phosphorus (P) and responded more predictably to nutrient enrichment than morphological measures. Epiphyte AFDM and Chl a were also greatest in P-enriched water; enrichments of N alone produced no measurable epiphytic response. The epiphyte biomass response did not directly mirror macrophyte biomass responses, illustrating the value of a combined macrophyte–epiphyte assay to more fully evaluate nutrient management strategies. Finally, the most P-enriched waters not only supported greater standing stocks of macrophyte and epiphytes but also had significantly higher water column dissolved oxygen and dissolved organic carbon concentrations and a lower pH. Advantages of this macrophyte–epiphyte bioassay over more traditional single-species assays include the use of a more realistic level of biological organization, a relatively short assay schedule (~10 days), and the inclusion of multiple biological response and water-quality measures.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Evaluation of a combined macrophyte–epiphyte bioassay for assessing nutrient enrichment in the Portneuf River, Idaho, USA
Series title Environmental Monitoring and Assessment
DOI 10.1007/s10661-014-3682-0
Volume 186
Issue 7
Year Published 2014
Language English
Publisher Springer
Contributing office(s) Idaho Water Science Center
Description 16 p.
First page 4081
Last page 4096
Country United States
State Idaho
Other Geospatial Portneuf River