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Seasonality, phytoplankton succession and the biogeochemical impacts of an autumn storm in the northeast Atlantic Ocean

Seasonality, phytoplankton succession and the biogeochemical impacts of an autumn storm in the northeast Atlantic Ocean
Seasonality, phytoplankton succession and the biogeochemical impacts of an autumn storm in the northeast Atlantic Ocean
Phytoplankton chemotaxonomic distributions are examined in conjunction with taxon specific particulate biomass concentrations and phytoplankton abundances to investigate the biogeochemical consequences of the passage of an autumn storm in the northeast Atlantic Ocean. Chemotaxonomy indicated that the phytoplankton community was dominated by nanoplankton (2-20 ?), which on average represented 75±8% of the community. Microplankton (20-200 ?) and picoplankton (<2 ?) represented 21±7% and 4±3% respectively with the microplankton group composed of almost equal proportions of diatoms (53±17%) and dinoflagellates (47±17%). Total chlorophyll-a (TCHLa = CHLa + Divinyl CHLa) concentrations ranged from 22 to 677 ng L-1, with DvCHLa making minor contributions of between <1% and 13% to TCHLa. Higher DvCHLa contributions were seen during the storm, which deepened the surface mixed layer, increased mixed layer nutrient concentrations and vertically mixed the phytoplankton community leading to a post-storm increase in surface chlorophyll concentrations. Picoplankton were rapid initial respondents to the changing conditions with pigment markers showing an abrupt 4-fold increase in proportion but this increase was not sustained post-storm. 19’-HEX, a chemotaxonomic marker for prymnesiophytes, was the dominant accessory pigment pre- and post-storm with concentrations of 48-435 ng L-1, and represented 44% of total carotenoid concentrations. Accompanying scanning electron microscopy results support the pigment-based analysis but also provide detailed insight into the nano- and microplankton communities, which proved to be highly variable between pre-storm and post-storm sampling periods. Nanoplankton remained the dominant size class pre- and post-storm but the microplankton proportion peaked during the period of maximum nutrient and chlorophyll concentrations. Classic descriptions of autumn blooms resulting from storm driven eutrophication events promoting phytoplankton growth in surface waters should be tempered with greater understanding of the role of storm driven vertical reorganization of the water column and of resident phytoplankton communities. Crucially, in this case we observed no change in integrated chlorophyll, particulate organic carbon or biogenic silica concentrations despite also observing a ?50% increase in surface chlorophyll concentrations which indicated that the surface enhancement in chlorophyll concentrations was most likely fed from below rather than resulting from in situ growth. Though not measured directly there was no evidence of enhanced export fluxes associated with this storm. These observations have implications for the growing practice of using chlorophyll fluorescence from remote platforms to determine ocean productivity late in the annual productivity period and in response to storm mixing.
autumn bloom, northeast Atlantic, chemotaxonomy, storm-impacts, biogeochemistry, succession
0079-6611
72-104
Painter, Stuart C.
29e32f35-4ee8-4654-b305-4dbe5a312295
Finlay, Madelaine
10e5dd03-985c-49ce-83e5-893cee4a78c1
Hemsley, Victoria S.
a4c30626-eaea-4817-bea2-d48f757b52fe
Martin, Adrian P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Painter, Stuart C.
29e32f35-4ee8-4654-b305-4dbe5a312295
Finlay, Madelaine
10e5dd03-985c-49ce-83e5-893cee4a78c1
Hemsley, Victoria S.
a4c30626-eaea-4817-bea2-d48f757b52fe
Martin, Adrian P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d

Painter, Stuart C., Finlay, Madelaine, Hemsley, Victoria S. and Martin, Adrian P. (2016) Seasonality, phytoplankton succession and the biogeochemical impacts of an autumn storm in the northeast Atlantic Ocean. Progress in Oceanography, 142, 72-104. (doi:10.1016/j.pocean.2016.02.001).

Record type: Article

Abstract

Phytoplankton chemotaxonomic distributions are examined in conjunction with taxon specific particulate biomass concentrations and phytoplankton abundances to investigate the biogeochemical consequences of the passage of an autumn storm in the northeast Atlantic Ocean. Chemotaxonomy indicated that the phytoplankton community was dominated by nanoplankton (2-20 ?), which on average represented 75±8% of the community. Microplankton (20-200 ?) and picoplankton (<2 ?) represented 21±7% and 4±3% respectively with the microplankton group composed of almost equal proportions of diatoms (53±17%) and dinoflagellates (47±17%). Total chlorophyll-a (TCHLa = CHLa + Divinyl CHLa) concentrations ranged from 22 to 677 ng L-1, with DvCHLa making minor contributions of between <1% and 13% to TCHLa. Higher DvCHLa contributions were seen during the storm, which deepened the surface mixed layer, increased mixed layer nutrient concentrations and vertically mixed the phytoplankton community leading to a post-storm increase in surface chlorophyll concentrations. Picoplankton were rapid initial respondents to the changing conditions with pigment markers showing an abrupt 4-fold increase in proportion but this increase was not sustained post-storm. 19’-HEX, a chemotaxonomic marker for prymnesiophytes, was the dominant accessory pigment pre- and post-storm with concentrations of 48-435 ng L-1, and represented 44% of total carotenoid concentrations. Accompanying scanning electron microscopy results support the pigment-based analysis but also provide detailed insight into the nano- and microplankton communities, which proved to be highly variable between pre-storm and post-storm sampling periods. Nanoplankton remained the dominant size class pre- and post-storm but the microplankton proportion peaked during the period of maximum nutrient and chlorophyll concentrations. Classic descriptions of autumn blooms resulting from storm driven eutrophication events promoting phytoplankton growth in surface waters should be tempered with greater understanding of the role of storm driven vertical reorganization of the water column and of resident phytoplankton communities. Crucially, in this case we observed no change in integrated chlorophyll, particulate organic carbon or biogenic silica concentrations despite also observing a ?50% increase in surface chlorophyll concentrations which indicated that the surface enhancement in chlorophyll concentrations was most likely fed from below rather than resulting from in situ growth. Though not measured directly there was no evidence of enhanced export fluxes associated with this storm. These observations have implications for the growing practice of using chlorophyll fluorescence from remote platforms to determine ocean productivity late in the annual productivity period and in response to storm mixing.

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Accepted/In Press date: 9 February 2016
e-pub ahead of print date: 17 February 2016
Published date: March 2016
Keywords: autumn bloom, northeast Atlantic, chemotaxonomy, storm-impacts, biogeochemistry, succession
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 388243
URI: http://eprints.soton.ac.uk/id/eprint/388243
ISSN: 0079-6611
PURE UUID: 5ff41d31-8aea-40b8-a655-9cf2eccc4aa1

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Date deposited: 22 Feb 2016 13:54
Last modified: 08 Jan 2022 12:31

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Contributors

Author: Stuart C. Painter
Author: Madelaine Finlay
Author: Victoria S. Hemsley
Author: Adrian P. Martin

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