Fluxes of Terminal Electron Acceptors: Linking Human
Disturbance to the Health of Aquatic Systems
(TEAQUILA)
Background
The TEAQUILA project focuses on the fluxes and behaviour of terminal electron acceptors (TEAs,
i.e. oxygen, nitrate, manganese and iron oxides and sulphate). These compounds are consumed in
the mineralisation of organic matter, and each process affects and changes the surrounding
geochemical environment. Depletion of oxygen leading to anoxia is much more common in
aquatic than terrestrial systems. Anaerobic mineralisation processes consume TEAs especially in
aquatic bottom sediments. These processes affect the cycles of many key elements, which further
contributes to eutrophication and the release of greenhouse gases and harmful substances. The
sources of TEAs, and the factors affecting their transport into water courses and their significance
to aquatic systems, have been poorly elucidated.
Objectives
The aim of the TEAQUILA project is to increase understanding on the following issues:
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how land cover affects the transport of electron acceptors and how runoff and lakes
modify their transport
how anaerobic mineralisation processes driven by organic carbon and electron acceptors
couple biogeochemical cycles
how the coupling of element cycles can be acknowledged in cost-effective water
protection.
Main results
We have shown that land cover is a stronger driver than atmospheric deposition for the export of
TEAs from boreal catchments. Fields, forests and peatlands produce different signatures for the
export of TEAs. The export of all TEAs, especially nitrate, is very high from fields. The land cover
producing variable fluxes of TEAs creates different premises for the aquatic systems to mineralise
organic carbon in the sediments (Palviainen et al. 2015). Moreover, we have shown that a climateinduced change in runoff regime is likely to significantly alter the variability in TEA concentrations
and the timing of the export of TEAs. Increasing runoff has a stronger influence on concentrations
and export in autumn than in spring, and the response is land-cover-specific. The results show that
climate change increases TEA exports in autumn especially in agricultural catchments compared to
the other land-cover classes. The change in timing of exports (i.e. whether the export takes place
before or after the growing season) may affect their processing and the subsequent feedbacks in
the cycling of carbon and nutrients in aquatic ecosystems
We have also simulated how particulate field soil phosphorus behaves when it enters anaerobic
brackish coastal sedimentary systems. In an incubation experiment, the TEAs for the
mineralisation of organic carbon were the field soil manganese and iron oxides and the sulphate
present in the brackish water. The experiment showed that the availability of labile organic carbon
– not anoxia – controls the release of phosphorus from the soil. Additionally, organic carbon
controlled the coupling of iron and sulphur in the incubation units resulting in a different ability to
recapture phosphorus when conditions turn oxic again (Lehtoranta et al. 2015).
The coupling of elements by the mineralisation processes (i.e. consumption of electron acceptors)
is taken into account in the economy studies of the TEAQUILA project. The results indicate that the
TEAs need to be considered in water protection because they may change the cycling of nutrients,
which affects the allocation of cost-efficient measures.
TEAQUILA website and publications www.syke.fi/projects/teaquila