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Effects of dry-wet cycles on nitrous oxide emissions in freshwater sediments: a synthesis
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Resumo(s)
Background. Sediments frequently exposed to dry-wet cycles are potential biogeochemical
hotspots for greenhouse gas (GHG) emissions during dry, wet and transitional
phases. While the effects of drying and rewetting on carbon fluxes have been studied
extensively in terrestrial and aquatic systems, less is known about the effects of dry-wet
cycles on N2O emissions from aquatic systems. As a notable part of lotic systems are
temporary, and small lentic systems can substantially contribute to GHG emissions,
dry-wet cycles in these ecosystems can play a major role on N2O emissions.
Methodology. This study compiles literature focusing on the effects of drying,
rewetting, flooding, and water level fluctuations on N2O emissions and related
biogeochemical processes in sediments of lentic and lotic ecosystems.
Results. N2O pulses were observed following sediment drying and rewetting events.
Moreover, exposed sediments during dry phases can be active spots for N2O emissions.
The general mechanisms behind N2O emissions during dry-wet cycles are comparable
to those of soils and are mainly related to physical mechanisms and enhanced microbial
processing in lotic and lentic systems. Physical processes driving N2O emissions are
mainly regulated by water fluctuations in the sediment. The period of enhanced
microbial activity is driven by increased nutrient availability. Higher processing rates
and N2O fluxes have been mainly observed when nitrification and denitrification are
coupled, under conditions largely determined by O2 availability.
Conclusions. The studies evidence the driving role of dry-wet cycles leading to
temporarily high N2O emissions in sediments from a wide array of aquatic habitats.
Peak fluxes appear to be of short duration, however, their relevance for global emission
estimates as well as N2O emissions from dry inland waters has not been quantified.
Future research should address the temporal development during drying-rewetting
phases in more detail, capturing rapid flux changes at early stages, and further explore
the functional impacts of the frequency and intensity of dry-wet cycles
Descrição
Palavras-chave
aquatic-terrestrial interface intermittent inland waters lotic lentic drought flooding
Contexto Educativo
Citação
Pinto R, Weigelhofer G, Brito AG, Hein T. 2021. Effects of dry-wet cycles on nitrous oxide emissions in freshwater sediments: a synthesis. PeerJ 9:e10767
Editora
Peerj