Seasonal evaluation of biotic and abiotic factors suggests phosphorus retention in constructed floodplains in three agricultural streams

Matt T Trentman; Jennifer L Tank; Stuart E Jones; Sara K McMillan; Todd V Royer

doi:10.1016/j.scitotenv.2020.138744

Seasonal evaluation of biotic and abiotic factors suggests phosphorus retention in constructed floodplains in three agricultural streams

Sci Total Environ. 2020 Aug 10:729:138744. doi: 10.1016/j.scitotenv.2020.138744. Epub 2020 Apr 27.

Authors

Matt T Trentman¹, Jennifer L Tank², Stuart E Jones², Sara K McMillan³, Todd V Royer⁴

Affiliations

¹ University of Notre Dame, Department of Biological Sciences, Notre Dame, IN 46556, USA. Electronic address: mtrentma@nd.edu.
² University of Notre Dame, Department of Biological Sciences, Notre Dame, IN 46556, USA; University of Notre Dame, Environmental Change Initiative, Notre Dame, IN 46556, USA.
³ Purdue University, Department of Agricultural and Biological Engineering, West Lafayette, IN 47907, USA.
⁴ Indiana University, O'Neill School of Public and Environmental Affairs, Bloomington, IN 47405, USA.

PMID: 32498158
DOI: 10.1016/j.scitotenv.2020.138744

Abstract

Floodplain restoration constructed via the two-stage ditch in agricultural streams has the potential to enhance nutrient retention and prevent the eutrophication of downstream ecosystems. Identifying the role of biotic and abiotic factors influencing soluble reactive phosphorus (SRP) retention in floodplains is of interest given that changing redox conditions associated with floodplain inundation can result in a release of geochemically sorbed SRP to the water column. In three agricultural waterways (Indiana, USA), we conducted seasonal measurements of a suite of biogeochemical pools (total P, bioavailable P and Fe) and processes (SRP flux and microbial respiration) from multiple floodplain transects, along with their adjacent stream sediments, to determine the role of biotic and abiotic processes on floodplain SRP retention or release. Across floodplain soils, organic matter explained a significant amount of variation in soil respiration, and SRP flux from the water column to the floodplain soils was driven by the molar ratio of Fe: P, with values >6 indicating potential SRP sorption due to increased available sorption sites. We developed a mass balance model at a single site to relate seasonal floodplain processes with water column SRP export, above and below the study reach, using measurements in this study combined with data from the literature. Grab sample data suggest that the reach retained 26% of incoming SRP, which the mass balance model attributed to seasonal synergy between plant assimilation in spring and summer (removing P from floodplain soils) and abiotic P sorption during winter and spring inundation (adding SRP to the floodplain). Retention of SRP was higher in floodplain soils compared to stream sediments based on the modeled SRP budget. Thus, we suggest that these constructed floodplains will maximize SRP retention from the water column if they inundate regularly, have floodplain soils with Fe:P > 3-6, and that promote sustained plant life.

Keywords: Agriculture; Floodplains; Phosphorus; Streams; Two-stage ditch.

MeSH terms

Agriculture*
Ecosystem
Indiana
Phosphorus
Rivers
Seasons

Substances

Phosphorus