Water Resources Research Act Program

Details for Project ID 2020OH202B

Electrochemical sensors for microbial activities in benthic sediments: a sentry for lacustrine P biogeochemistry

Institute: Ohio
Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $35,120 Total Non-Federal Funds: $39,043

Principal Investigators: John M. Senko

Project Summary: Release of P (generally as phosphate) immobilized in benthic sediments poses a remnant threatto induce harmful algal blooms (HAB) despite adequate management of external loads ofphosphate. This process, referred to as internal loading of P, is induced by microbially mediatedalternations of sediment and porewater chemistry. However, the potential for and extent ofinternal loading of phosphate is difficult to constrain, because of the difficulties in tracking andmonitoring small-scale microbial processes in lake-scale systems. To address this problem, wewill test the hypothesis that electrochemical signals associated with contrasting microbialactivities in benthic sediments are indicative of microbiological processes that induce or limit Prelease from sediments. Given that HABs are a pressing water quality concern for Ohio, ourfocus will be Lake Erie sediment microbial processes. We have developed an electrochemicalsplit-chamber zero resistance ammetry (SC-ZRA) technique that has permitted us to detectvarying microbiological activities based on the electrochemical signatures that arise fromcontrasting, microbially-induced redox regimes. The SC-ZRA approach entails deployment ofelectrically connected working electrodes two chambers that are separated by an ion-permeablemembrane. Manipulation of microbial activities can be conducted in either or both chambers,and unique patterns of current and voltage that result from microbial activities can be monitored.Our goal is to use the SC-ZRA approach to determine the microbially-induced signatures ofmicrobiological activities that influence P flux in benthic sediments. The major deliverable ofthis work will be an inventory of signatures of microbial processes that can then be tracked insitu for the detection of P flux from sediments and the potential for internal P loading-supportedalgal blooms. ZRA-based monitoring can determine extents and types of microbial metabolism inthe sediments, be exploited for long-term stewardship of Lake Erie sediments, and serve as an“early-warning system†for internal phosphate loading events. This approach could be an easilydeployable, low power, high resolution, and inexpensive way to monitor microbial activities inbenthic sediments, and may be used for water quality issues in Lake Erie beyond phosphateloading, including the dynamics of metal and organic contaminant transformations in dredgedsediments.