Riverine concentrations and export of dissolved silicon, and potential controls on nutrient stoichiometry, across the land–ocean continuum in Great Britain

Tye, Andrew M.; Jarvie, Helen P. ORCID: https://orcid.org/0000-0002-4984-1607; Spears, Bryan M. ORCID: https://orcid.org/0000-0002-0876-0405; Dise, Nancy B. ORCID: https://orcid.org/0000-0003-0463-6885; Williamson, Jennifer L. ORCID: https://orcid.org/0000-0001-8216-5885; Lapworth, Dan J. ORCID: https://orcid.org/0000-0001-7838-7960; Monteith, Don ORCID: https://orcid.org/0000-0003-3219-1772; Sanders, Richard ORCID: https://orcid.org/0000-0002-6884-7131; Mayor, Daniel J. ORCID: https://orcid.org/0000-0002-1295-0041; Bowes, Michael J. ORCID: https://orcid.org/0000-0002-0673-1934; Bowes, Michael; Burden, Annette ORCID: https://orcid.org/0000-0002-7694-1638; Callaghan, Nathan ORCID: https://orcid.org/0000-0003-0273-6161; Farr, Gareth; Felgate, Stacey ORCID: https://orcid.org/0000-0002-9955-4948; Gibb, Stuart; Gilbert, Pete; Hargreaves, Geoff ORCID: https://orcid.org/0000-0002-4361-6134; Humphrey, Olivier S.; Keenan, Patrick; Kitidis, Vassilis; Jürgens, Monika D. ORCID: https://orcid.org/0000-0002-6526-589X; Martin, Adrian ORCID: https://orcid.org/0000-0002-1202-8612; Pearson, Monty; Nightingale, Philip D.; Gloria Pereira, M. ORCID: https://orcid.org/0000-0003-3740-0019; Olszewska, Justyna ORCID: https://orcid.org/0000-0002-4910-2206; Pickard, Amy ORCID: https://orcid.org/0000-0003-1069-3720; Rees, Andrew P.; Stinchcombe, Mark; Worrall, Fred; Evans, Chris D. ORCID: https://orcid.org/0000-0002-7052-354X. 2024 Riverine concentrations and export of dissolved silicon, and potential controls on nutrient stoichiometry, across the land–ocean continuum in Great Britain. Journal of Hydrology, 640, 131738. 10.1016/j.jhydrol.2024.131738

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Abstract/Summary

Silicon (Si) is an essential nutrient element in freshwater and marine ecosystems, and its abundance relative to macro-nutrients (N, P) can impact phytoplankton communities in eutrophic rivers and estuaries. This study is the first national assessment examining (i) the primary sources (geological, biological, landcover) and controls (geomorphological, precipitation) on the transport of terrestrial dissolved silicon across Great Britain to the ocean, and (ii) the current extent and nature of its interactions with macro-nutrients in these catchments in relation to its potential impacts on phytoplankton community structure. It uses results from a year-long survey of 41 rivers along with historical data. Highest concentrations of dissolved Si (4–5.5 mg L-1) were found in rivers of the chalk- and sedimentary sandstone-based catchments of southern Great Britain and the hard sandstone catchments of Scotland. Catchment yield rates for dissolved Si varied between 0.2 and 2.6 t km−2 yr−1, with highest yields found in catchments with higher precipitation and runoff. Analysis of river N:P and dissolved Si:N ratios suggested that the sampled rivers were typically N enriched, and P limited with respect to dissolved Si. Molar dissolved Si:N ratios < 1, an indicator of river eutrophication, were associated with total nitrogen concentrations exceeding 1.8 mg L-1 or greater. The Indicator of Coastal Eutrophication index was used to assess the potential role of dissolved Si in the eutrophication of coastal waters. Negative values indicating limited eutrophication potential to non-siliceous algae were generally found, although some rivers had annual Indicator of Coastal Eutrophication index values exceeding 0, with values as high as 35 kg C km−2 day−1. In many eutrophic rivers, high dissolved Si concentrations derived from catchment lithology, kept the Indicator of Coastal Eutrophication index values below zero. Results have demonstrated that high N and P export have likely shifted most Great Britain rivers and coastal waters beyond the stoichiometric range where diatoms dominate production and into one where non-siliceous algae maybe increasingly present. Thus, future assessments of macro-nutrient management schemes, such as those involving wetlands should include dissolved Si routinely due to its stoichiometric importance.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.jhydrol.2024.131738
UKCEH and CEH Sections/Science Areas:	Pollution (Science Area 2017-) Soils and Land Use (Science Area 2017-) Water Resources (Science Area 2017-) UKCEH Fellows
ISSN:	0022-1694
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	GroundwaterBGS
NORA Subject Terms:	Hydrology Data and Information
Date made live:	07 Aug 2024 11:31 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/537814

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