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Seasonal and inter-annual variability in alkalinity in Liverpool Bay (53.5° N, 3.5° W) and in major river inputs to the North Sea

Seasonal and inter-annual variability in alkalinity in Liverpool Bay (53.5° N, 3.5° W) and in major river inputs to the North Sea
Seasonal and inter-annual variability in alkalinity in Liverpool Bay (53.5° N, 3.5° W) and in major river inputs to the North Sea
A critical factor controlling changes in the acidity of coastal waters is the alkalinity of the water. Concentrations of alkalinity are determined by supply from rivers and by in situ processes such as biological production and denitrification. A 2-year study based on 15 cruises in Liverpool Bay followed the seasonal cycles of changing concentrations of total alkalinity (TA) and total dissolved inorganic carbon (DIC) in relation to changes caused by the annual cycle of biological production during the mixing of river water into the Bay. Consistent annual cycles in concentrations of nutrients, TA and DIC were observed in both years. At a salinity of 31.5, the locus of primary production during the spring bloom, concentrations of NO x decreased by 25?±?4 ?mol kg?1 and DIC by 106?±?16 ?mol kg?1. Observed changes in TA were consistent with the uptake of protons during primary biological production. Concentrations of TA increased by 33?±?8 ?mol kg?1 (2009) and 33?±?15 ?mol kg?1 (2010). The impact of changes in organic matter on the measured TA appears likely to be small in this area. Thomas et al. (2009) suggested that denitrification may enhance the CO2 uptake of the North Sea by 25%, in contrast we find that although denitrification is a significant process in itself, it does not increase concentrations of TA relative to those of DIC and so does not increase buffer capacity and potential uptake of CO2 into shelf seawaters. For Liverpool Bay historical data suggest that higher concentrations of TA during periods of low flow are likely to contribute in part to the observed change in TA between winter and summer but the appropriate pattern cannot be identified in recent low-frequency river data. On a wider scale, data for the rivers Mersey, Rhine, Elbe and Weser show that patterns of seasonal change in concentrations of TA in river inputs differ between river systems.
Seasonality, Total alkalinity, Total dissolved inorganic carbon, Nutrients, Organic alkalinity, Denitrification, Liverpool Bay, Mersey, Rhine, Elbe, Weser
1616-7341
321-333
Hydes, David J.
ac7371d4-c2b9-4926-bb77-ce58480ecff7
Hartman, Susan E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Hydes, David J.
ac7371d4-c2b9-4926-bb77-ce58480ecff7
Hartman, Susan E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481

Hydes, David J. and Hartman, Susan E. (2012) Seasonal and inter-annual variability in alkalinity in Liverpool Bay (53.5° N, 3.5° W) and in major river inputs to the North Sea. Ocean Dynamics, 62 (2), 321-333. (doi:10.1007/s10236-011-0503-7).

Record type: Article

Abstract

A critical factor controlling changes in the acidity of coastal waters is the alkalinity of the water. Concentrations of alkalinity are determined by supply from rivers and by in situ processes such as biological production and denitrification. A 2-year study based on 15 cruises in Liverpool Bay followed the seasonal cycles of changing concentrations of total alkalinity (TA) and total dissolved inorganic carbon (DIC) in relation to changes caused by the annual cycle of biological production during the mixing of river water into the Bay. Consistent annual cycles in concentrations of nutrients, TA and DIC were observed in both years. At a salinity of 31.5, the locus of primary production during the spring bloom, concentrations of NO x decreased by 25?±?4 ?mol kg?1 and DIC by 106?±?16 ?mol kg?1. Observed changes in TA were consistent with the uptake of protons during primary biological production. Concentrations of TA increased by 33?±?8 ?mol kg?1 (2009) and 33?±?15 ?mol kg?1 (2010). The impact of changes in organic matter on the measured TA appears likely to be small in this area. Thomas et al. (2009) suggested that denitrification may enhance the CO2 uptake of the North Sea by 25%, in contrast we find that although denitrification is a significant process in itself, it does not increase concentrations of TA relative to those of DIC and so does not increase buffer capacity and potential uptake of CO2 into shelf seawaters. For Liverpool Bay historical data suggest that higher concentrations of TA during periods of low flow are likely to contribute in part to the observed change in TA between winter and summer but the appropriate pattern cannot be identified in recent low-frequency river data. On a wider scale, data for the rivers Mersey, Rhine, Elbe and Weser show that patterns of seasonal change in concentrations of TA in river inputs differ between river systems.

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More information

Published date: February 2012
Keywords: Seasonality, Total alkalinity, Total dissolved inorganic carbon, Nutrients, Organic alkalinity, Denitrification, Liverpool Bay, Mersey, Rhine, Elbe, Weser
Organisations: Marine Biogeochemistry

Identifiers

Local EPrints ID: 209935
URI: http://eprints.soton.ac.uk/id/eprint/209935
ISSN: 1616-7341
PURE UUID: 0bec9ed4-a61f-4e4e-974a-3d35388c7b72

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Date deposited: 03 Feb 2012 09:50
Last modified: 14 Mar 2024 04:47

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Author: David J. Hydes
Author: Susan E. Hartman

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