Polar Biology

, Volume 29, Issue 1, pp 44–52

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

  • Claire L. Holeton
  • Florence Nédélec
  • Richard Sanders
  • Louise Brown
  • C. Mark Moore
  • David P. Stevens
  • Karen J. Heywood
  • Peter J. Statham
  • Cathy H. Lucas
Original Paper

DOI: 10.1007/s00300-005-0028-y

Cite this article as:
Holeton, C.L., Nédélec, F., Sanders, R. et al. Polar Biol (2005) 29: 44. doi:10.1007/s00300-005-0028-y

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 (Fv/Fm) exhibited a sharp increase to the east of 46°W coincident with a decrease in the functional absorption cross-section (σPSII). Phytoplankton populations east of 46°W thus displayed no physiological symptoms of iron or nitrate stress. Contrasting low Fv/Fm 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 Fv/Fm 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.

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Claire L. Holeton
    • 1
  • Florence Nédélec
    • 1
  • Richard Sanders
    • 1
  • Louise Brown
    • 1
  • C. Mark Moore
    • 1
  • David P. Stevens
    • 2
  • Karen J. Heywood
    • 3
  • Peter J. Statham
    • 1
  • Cathy H. Lucas
    • 1
  1. 1.National Oceanography CentreSouthamptonUK
  2. 2.School of MathematicsUniversity of East AngliaNorwichUK
  3. 3.School of Environmental SciencesUniversity of East AngliaNorwichNR4 7TJUK

Personalised recommendations