Episodic nutrient addition affects water column nutrient processing rates in river-to-lake transitional zones

Journal of Geophysical Research: Biogeosciences
By: , and 



Storm-driven nutrient loading from tributaries can fuel eutrophication in nearshore and open water areas of lentic ecosystems. However, nutrient processing in river-to-lake transitional zones can substantially alter the amount and composition of nutrients transported to lakes from upstream surface waters. We measured the removal of nutrients and dissolved organic carbon (DOC) from the water column in the Fox rivermouth (Green Bay, Lake Michigan) to evaluate the response of rivermouth plankton to episodic nutrient enrichment. Light and dark water column incubations (8–12 hr) were conducted on four occasions from April through September to measure changes in dissolved nitrogen (N), phosphorus (P), and DOC concentrations in three locations along the Fox rivermouth. Two incubation experiments were conducted on consecutive days, (a) under ambient nutrient concentrations, and (b) under experimentally enriched N and P concentrations. Spatial and temporal variation was observed in nutrient uptake rates, but light incubations consistently had higher nutrient uptake rates than dark incubations. Nutrient enrichment increased total dissolved P and total dissolved N uptake and DOC release in light incubations, but only increased total dissolved P uptake in dark incubations. Moreover, nutrient uptake ratios (N:P) decreased from ambient to nutrient enriched conditions and indicated preferential P uptake by phytoplankton communities in light conditions. Our study substantiates that rivermouths can process nutrients bound for downstream ecosystems and demonstrates the potential of plankton communities to dynamically increase net uptake rates in response to episodic nutrient enrichment.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Episodic nutrient addition affects water column nutrient processing rates in river-to-lake transitional zones
Series title Journal of Geophysical Research: Biogeosciences
DOI 10.1029/2021JG006374
Volume 126
Issue 11
Year Published 2021
Language English
Publisher American Geophysical Union
Contributing office(s) Upper Midwest Environmental Sciences Center
Description e2021JG006374, 16 p.
Country United States
State Wisconsin
Other Geospatial Fox River
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