Transformations in DOC along a source to sea continuum; impacts of photo-degradation, biological processes and mixing

Jones, Timothy G.; Evans, Chris D. ORCID: https://orcid.org/0000-0002-7052-354X; Jones, Davey L.; Hill, Paul W.; Freeman, Chris. 2016 Transformations in DOC along a source to sea continuum; impacts of photo-degradation, biological processes and mixing [in special issue: Carbon cycling in aquatic ecosystems] Aquatic Sciences, 78 (3). 433-446. 10.1007/s00027-015-0461-0

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Abstract/Summary

Peatlands export significant amounts of dissolved organic carbon (DOC) to freshwaters, but the quantity of DOC reaching marine environments is typically less than the input to the fluvial system due to processing within the water column. Key removal processes include photo-chemical degradation, and heterotrophic bacterial respiration. In this study we examined these processes using 14C-labelled DOC to quantify the extent of DOC breakdown and to determine its fate following irradiation under controlled laboratory conditions. We examined the influence of microbial processes occurring within the water column, the potential role of stream-bed biofilms, and the possible modifying effects of downstream mixing, as DOC in water from the peatland encounters runoff from upland mineral soils (“Mountain”), nutrient-rich runoff from agricultural soils, and seawater in an estuary. Our results demonstrated conservative mixing of DOC from Peatland and Mountain waters but interactive effects when Peatland water was mixed with Agricultural and Estuary waters and exposed to solar radiation. The mixing of Peatland and Agricultural waters led to net DOC production, suggesting that DOC was only partially degraded by solar radiation and that the products of this might have fuelled autotrophic microbial growth in the samples. The mixing of Peatland water with saline estuary water resulted in net DOC loss following irradiation, suggesting a role for sunlight in enhancing the flocculation of DOC to particulate organic carbon (POC) in saline environments.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1007/s00027-015-0461-0
UKCEH and CEH Sections/Science Areas:	Emmett
ISSN:	1015-1621
Additional Keywords:	biodegradation, carbon cycling, dissolved organic matter, humic substances, UV radiation
NORA Subject Terms:	Ecology and Environment
Date made live:	02 Feb 2017 12:49 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/514569

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