Seasonal phosphorus and carbon dynamics in a temperate shelf sea (Celtic Sea)

Poulton, Alex J.; Davis, Clare E.; Daniels, Chris J.; Mayers, Kyle M.J.; Harris, Carolyn; Tarran, Glen A.; Widdicombe, Claire E.; Woodward, E. Malcolm S.. 2019 Seasonal phosphorus and carbon dynamics in a temperate shelf sea (Celtic Sea). Progress in Oceanography, 177, 101872. https://doi.org/10.1016/j.pocean.2017.11.001

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Official URL: http://dx.doi.org/10.1016/j.pocean.2017.11.001

Abstract/Summary

The seasonal cycle of resource availability in shelf seas has a strong selective pressure on phytoplankton diversity and the biogeochemical cycling of key elements, such as carbon (C) and phosphorus (P). Shifts in carbon consumption relative to P availability, via changes in cellular stoichiometry for example, can lead to an apparent ‘excess’ of carbon production. We made measurements of inorganic P (Pi) uptake, in parallel to C-fixation, by plankton communities in the Celtic Sea (NW European Shelf) in spring (April 2015), summer (July 2015) and autumn (November 2014). Short-term (<8 h) Pi-uptake coupled with dissolved organic phosphorus (DOP) release, in parallel to net (24 h) primary production (NPP), were all measured across an irradiance gradient designed to typify vertically and seasonally varying light conditions. Rates of Pi-uptake were highest during spring and lowest in the low light conditions of autumn, although biomass-normalised Pi-uptake was highest in the summer. The release of DOP was highest in November and declined to low levels in July, indicative of efficient utilization and recycling of the low levels of Pi available. Examination of daily turnover times of the different particulate pools, including estimates of phytoplankton and bacterial carbon, indicated a differing seasonal influence of autotrophs and heterotrophs in P-dynamics, with summer conditions associated with a strong bacterial influence and the early spring period with fast growing phytoplankton. These seasonal changes in autotrophic and heterotrophic influence, coupled with changes in resource availability (Pi, light) resulted in seasonal changes in the stoichiometry of NPP to daily Pi-uptake (C:P ratio); from relatively C-rich uptake in November and late April, to P-rich uptake in early April and July. Overall, these results highlight the seasonally varying influence of both autotrophic and heterotrophic components of shelf sea ecosystems on the relative uptake of C and P.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.pocean.2017.11.001
ISSN:	00796611
Date made live:	26 Jan 2018 10:26 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/519125

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1016/j.pocean.2017.11.001

ISSN:

00796611

Date made live:

26 Jan 2018 10:26 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/519125