RAPID: Are biogeochemical responses linked to the microbial composition of a defined nutrient and microbial input to a large river?

Kansas State University, Manhattan KS

Investigators

Abstract

The goal of this project is to learn how water inputs from a decommissioned fertilizer plant, which carries a large amount of nitrogen (N) and unique microorganisms, affect riverine water quality. The fertilizer plant waste carries microorganisms that grow well in high-N conditions; thus, the concurrent addition of N and unique microbes could enhance microbiological N removal activity within the river, and will advance understanding of the connections between microbial community composition and riverine nitrogen cycling. This is a significant frontier in ecosystem science with high potential to improve mechanistic understanding of future changes in ecosystem structure and function. To accomplish these goals, the research uses two approaches. First, the relationship between changes in river water quality and changes in river water microbial communities will be measured over time and compared to unaffected sections of the river. Second, in order to directly test whether different microbial populations have different effects on water quality, lab experiments will compare N removal in waters inoculated with microorganisms from either the river or fertilizer waste ponds. This project focuses on a uniquely well-defined release of water with distinct chemistry and microbial composition, which enables clear tracking of the effect of altered N input and microbial community composition on river water quality. This research will teach us whether knowing water microbial community composition helps predict water quality in a large river. This project supports direct engagement between research scientists and their local municipality and watershed organization to learn about controls on water quality. It also gives graduate and undergraduate students hands-on experience collecting, synthesizing and interpreting data on river chemistry and microbiology. To reach project goals, the researchers will deploy a suite of sensors (nitrate and dissolved oxygen) and automated water samplers, and collect grab samples to characterize downstream changes in river biogeochemistry and microbial community composition. Also, the researchers will filter live microbial cells from river and fertilizer waste water and use these cells to inoculate replicated lab incubation chambers that contain different N concentrations. Response variables measured in both field and lab activities include: water chemistry, nitrification and denitrification rate potentials, total bacterial and archaeal community composition, nitrification and denitrification functional gene abundance. This work offers a unique opportunity to better understand how large rivers transport and transform nutrients in the face of altered nutrient inputs and microbial loads, a key gap in our understanding of lotic nutrient cycling. Also, because nitrification and denitrification rates are limited by different environmental factors, the work will provide insight on biological versus geochemical controls over two key processes supporting total N removal from aquatic ecosystems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.