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Decrease in water clarity of the southern and central North Sea during the 20th century

Forster, Rodney M.; Barry, Jon; Capuzzo, Elisa; Silva, Tiago; Stephens, David

Authors

Jon Barry

Elisa Capuzzo

Tiago Silva

David Stephens

Abstract

Light in the marine environment is a key environmental variable coupling physics to marine biogeochemistry and ecology. Weak light penetration reduces light available for photosynthesis, changing energy fluxes through the marine food web. Based on published and unpublished data, this study shows that the central and southern North Sea has become significantly less clear over the second half of the 20th century. In particular, in the different regions and seasons investigated, the average Secchi depth pre-1950 decreased between 25% and 75% compared to the average Secchi depth post-1950. Consequently, in summer pre-1950, most (74%) of the sea floor in the permanently mixed area off East Anglia was within the photic zone. For the last 25+ years, changes in water clarity were more likely driven by an increase in the concentration of suspended sediments, rather than phytoplankton. We suggest that a combination of causes have contributed to this increase in suspended sediments such as changes in sea-bed communities and in weather patterns, decreased sink of sediments in estuaries, and increased coastal erosion. A predicted future increase in storminess (Beniston et al., 2007; Kovats et al., 2014) could enhance the concentration of suspended sediments in the water column and consequently lead to a further decrease in clarity, with potential impacts on phytoplankton production, CO2 fluxes, and fishery production.

Publication Date 2015-06
Journal Global change biology
Print ISSN 1354-1013
Electronic ISSN 1365-2486
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 21
Issue 6
Pages 2206-2214
Institution Citation Forster, R. M., Barry, J., Capuzzo, E., Silva, T., & Stephens, D. (2015). Decrease in water clarity of the southern and central North Sea during the 20th century. Global change biology, 21(6), 2206-2214. https://doi.org/10.1111/gcb.12854
DOI https://doi.org/10.1111/gcb.12854
Keywords Ecology; Global and Planetary Change; General Environmental Science; Environmental Chemistry
Publisher URL http://onlinelibrary.wiley.com/doi/10.1111/gcb.12854/abstract
Copyright Statement © 2015 Crown copyright. Global Change Biology published by John Wiley & Sons Ltd. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Additional Information Citation : Capuzzo, E., Stephens, D., Silva, T., Barry, J. and Forster, R. M. (2015), Decrease in water clarity of the southern and central North Sea during the 20th century. Global Change Biology. doi: 10.1111/gcb.12854

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Copyright Statement
© 2015 Crown copyright. Global Change Biology published by John Wiley & Sons Ltd. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.



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