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Determining patterns in the composition of dissolved organic matter in fresh waters according to land use and management

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Abstract

In fresh waters, the origins of dissolved organic matter (DOM) have been found to exert a fundamental control on its reactivity, and ultimately, its ecosystem functional role. A detailed understanding of landscape scale factors that control the export of DOM to aquatic ecosystems is, therefore, pivotal if the effects of DOM flux to fresh waters are to be fully understood. In this study we present data from a national sampling campaign across the United Kingdom in which we explore the variability in DOM composition in three broad landscape types defined by similar precipitation, geology, land use and management, hydrology, and nutrient enrichment status. We characterised samples from fifty-one sites, grouping them into one of three major underlying classifications: circumneutral streams underlain by clay and mudstone (referred to as ‘clay’), alkaline streams underlain by Cretaceous Chalk or by Carboniferous or Jurassic Limestone (‘limestone’), and acidic streams in peatland catchments underlain by a range of low permeability lithologies (‘peat’). DOM composition was assessed through organic matter stoichiometry (organic carbon: organic nitrogen; organic carbon: organic phosphorus; C/N(P)DOM) and metrics derived from ultra-violet (UV)/visible spectroscopic analysis of DOM such as specific UV absorption (a254 nm; SUVA254). We found similar SUVA254, C/NDOM and DOM/a254 relationships within classifications, demonstrating that despite a large degree of heterogeneity within environments, catchments with shared environmental character and anthropogenic disturbance export DOM with a similar composition and character. Improving our understanding of DOM characterisation is important to help predict shifts in stream ecosystem function, and ecological responses to enrichment or mitigation efforts and how these may result in species composition shifts and biodiversity loss in freshwater ecosystems.

Journal Article Type Article
Acceptance Date Jul 26, 2022
Online Publication Date Aug 29, 2022
Publication Date May 1, 2023
Publicly Available Date Mar 29, 2024
Journal Biogeochemistry
Print ISSN 0168-2563
Publisher Springer Verlag
Volume 164
Issue 1
Pages 143-162
DOI https://doi.org/10.1007/s10533-022-00964-2
Keywords Nutrient stoichiometry, Carbon, Dissolved organic matter, Nitrogen, Phosphorus
Publisher URL https://link.springer.com/article/10.1007/s10533-022-00964-2

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