Physiological state of phytoplankton communities in the Southwest Atlantic sector of the Southern Ocean, as measured by fast repetition rate fluorometry

Holeton, Claire L., Nédélec, Florence, Sanders, Richard, Brown, Louise, Moore, C. Mark, Stevens, David P. ORCID: https://orcid.org/0000-0002-7283-4405, Heywood, Karen J. ORCID: https://orcid.org/0000-0001-9859-0026, Statham, Peter J. and Lucas, Cathy H. (2005) Physiological state of phytoplankton communities in the Southwest Atlantic sector of the Southern Ocean, as measured by fast repetition rate fluorometry. Polar Biology, 29 (1). pp. 44-52. ISSN 0722-4060

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Abstract

The majority of the Southern Ocean is a high-nutrient low-chlorophyll (HNLC) ecosystem. Localized increases in chlorophyll concentration measured in the wake of bathymetric features near South Georgia demonstrate variations in the factors governing the HNLC condition. We explore the possibility that the contrast between these areas of high-chlorophyll and surrounding HNLC areas is associated with variations in phytoplankton photophysiology. Total dissolvable iron concentrations, phytoplankton photophysiology and community structure were investigated in late April 2003 on a transect along the North Scotia Ridge (53–54°S) between the Falkland Islands and South Georgia (58–33°W). Total dissolvable iron concentrations suggested a benthic source of iron near South Georgia. Bulk community measurements of dark-adapted photochemical quantum efficiency (F v/F m) exhibited a sharp increase to the east of 46°W coincident with a decrease in the functional absorption cross-section (sPSII). Phytoplankton populations east of 46°W thus displayed no physiological symptoms of iron or nitrate stress. Contrasting low F v/F m west of 46°W could not be explained by variations in the macronutrients nitrate and silicic acid and may be the result of taxon specific variability in photophysiology or iron stress. We hypothesize that increased F v/F m resulted from local relief from iron-stress near South Georgia, east of Aurora Bank, an area previously speculated to be a “pulse point” source of iron. Our measurements provide one of the first direct physiological confirmations that iron stress is alleviated in phytoplankton populations near South Georgia.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Mathematics University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Fluid and Solid Mechanics
Depositing User:	David Stevens
Date Deposited:	01 Dec 2010 14:12
Last Modified:	13 Apr 2023 13:38
URI:	https://ueaeprints.uea.ac.uk/id/eprint/15909
DOI:	10.1007/s00300-005-0028-y

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