HABs: Characterizing Zones of High Potential Nutrient Cycling in Agricultural Catchments

Science Center Objects

River sediments have the capacity to remove nutrients from the water column which lowers the nutrient load to downstream water bodies. The objectives of this project were to characterize rates of sediment nitrogen removal and phosphorus retention in river networks draining agricultural watersheds and to assess how land use and land management actions affect these rates. This information is helpful for managers trying to limit nutrient loading to the Great Lakes.

Fox River, WI and Maumee River, OH

Both the Fox River in Wisconsin and the Maumee River in Ohio transport exceedingly high loads of nitrogen (N) and phosphorus (P) to Lake Michigan. The increased concentration of N and P is causing eutrophication of the lake, creating hypoxic zones and damaging the lake ecosystem. In extreme cases, eutrophication leads to blooms of harmful algae which is a threat to public health. Thus, the Lower Fox River has been identified by the United States Environmental Protection Agency (USEPA) as a priority watershed where action needs to be taken to reduce nutrient loads. Phosphorus loading from these watersheds stimulates the production of algal blooms in the warm, shallow bays where the rivers discharge. USEPA has issued a directive to reduce P run-off from these basins. To decrease loading, best management practices (BMPs) have been implemented in the uplands of the basin. Little work has been done, however, to reduce nutrient concentrations in the river or the tributaries, themselves. Rivers can remove nutrients through biotic uptake and sediment burial and are able to remove N through denitrification. Identifying and managing these locations of increased nutrient cycling known as “hot spots” may be another mechanism for nutrient mitigation.

Scientists determined that the potential to remove nitrogen was high throughout the Fox River network. Scientists also determined that the fine sediments in the Fox River Basin were saturated with phosphorus, which indicates that they may be a source of phosphorus to the water column. Results indicated that streams draining agricultural areas with more implemented nutrient management plans have sediments that are less saturated with phosphorus. These sediments have a higher potential to remove phosphorus from the water column.

Staff member taking water quality samples

Staff collecting water quality samples. 

(Public domain.)

Staff collecting sediment samples

Staff collecting sediments samples. 

(Public domain.)
















Kreiling, R.M., and L.A. Bartsch. 2019. Data Release: Great Lakes Restoration Initiative Project 49 Fox River Basin 2016 and 2017 data. U.S. Geological Survey data release https://doi.org/10.5066/P93RTNVY.

Kreiling, R.M., M.C. Thoms, W.B. Richardson, L.A. Bartsch, and V.G. Christensen. 2019. Complex responses of sediment phosphorus to land use and management within a river network. Accepted. Journal of Geophysical Research: Biogeosciences 10.1029/2019JG005171.

Kreiling, R.M., W.B. Richardson, L.A. Bartsch, M.C. Thoms, and V.G. Christensen. 2019. Denitrification in the river network of a mixed land use watershed: unpacking the complexities.  Biogeochemistry 143:327-346.

Coenen, E.N., V.G. Christensen, L.A. Bartsch, R.M. Kreiling, and W.R. Richardson. 2019. Sediment oxygen demand: a review of in situ methods. Journal of Environmental Quality 48:403-411.

Kreiling, R.M., M.C. Thoms, and W.B. Richardson. 2018. Beyond the edge: linking agricultural landscapes, stream networks, and best management practices. Journal of Environmental Quality 47:42-53.

Kreiling, R.M., M.C. Thoms, L.A. Bartsch, J.H. Larson, and V.G. Christensen. Modeling land use effects on sediment nutrient processes in a heavily modified watershed. Submitted for publication in Ecosystems.


  • Results from this project are needed by decision makers to identify areas in agriculturally dominated watersheds to target for nutrient remediation.
  • This project was funded under the nonpoint pollution impacts on nearshore health focus area.


  • The Natural Resources Conservation Service (NRCS) was instrumental in providing agricultural best management practice data for the study sites which were then used to assess how best management practices can potentially influence in-stream sediment nutrient processing.
  • State and local management agencies provided information that was helpful for site selection.