Land Cover Controls the Export of Terminal Electron Acceptors from Boreal Catchments

Marjo Palviainen,Tuija Ruoho-Airola,Petri Ekholm,Pirkko Kortelainen,Jouni Lehtoranta

doi:10.1007/s10021-014-9832-y

Abstract

NO3, Mn, Fe, and SO4 act as terminal electron acceptors (TEAs), modifying mineralization pathways and coupling biogeochemical cycles. Although single TEA concentrations and fluxes have been intensively studied, the factors regulating the simultaneous fluxes and molar ratios of TEAs are poorly elucidated. We studied the mean concentrations, exports, and molar ratios of TEAs from 27 boreal catchments differing in land cover (percentage of agricultural land, peatland, forest, and built-up area) during the years 2000–2011. TEA exports and molar ratios were strongly controlled by land cover and only a little by atmospheric deposition. Fields produced the highest export of TEAs, particularly NO3. Peatland was linked to low NO3 and SO4, but high Fe exports. NO3, Mn, and Fe exports from forests were low, SO4 having proportionally the highest export. Together, the percentages of field and peatland predicted 93, 80, 75, and 67% of the variation in the export of NO3, Mn, Fe, and SO4, respectively. The variable export of TEAs having different availability and physical behavior may create different premises for anaerobic mineralization in downstream systems, which adds a new dimension to the link between terrestrial system, land use, and environmental problems, such as eutrophication and climate change.

Highlights

Linking the ecological status of surface waters to the load of nutrients and organic C may prove to be too narrow a perspective toward understanding and managing aquatic ecosystems
We studied the mean concentrations, exports, and molar ratios of terminal electron acceptors (TEAs) from 27 boreal catchments differing in land cover during the years 2000–2011
We examined numerous boreal catchments differing in land cover, hypothesizing that land cover and atmospheric deposition control the average annual export and the molar proportion of TEAs from the catchments

Summary

Introduction

Linking the ecological status of surface waters to the load of nutrients and organic C may prove to be too narrow a perspective toward understanding and managing aquatic ecosystems. The export of terrestrial organic C and primary production. A generation of toxic sulfides (Wang and Chapman 1999) may block Fe cycling and enhance the release of P from bottom sediments into water (Smolders and others 2006, 2010; Lehtoranta and others 2009). The ecological status of an aquatic system is a function of TEAs, as they partly control mineralization processes and pathways. The fluxes of TEAs and the factors regulating them at the catchment level have remained poorly quantified

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