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Functional relationships and bio-optical properties derived from phytoplankton pigments, optical and photosynthetic parameters; a case study of the Benguela ecosystem

Published online by Cambridge University Press:  15 December 2006

James R. Fishwick ,
Jim Aiken ,
Ray Barlow ,
Heather Sessions ,
Stuart Bernard  and
Josephine Ras
James R. Fishwick
Affiliation:
Plymouth Marine Laboratory, Prospect Place, Plymouth, Devon, PL1 3DH, UK Centre for observation of Air–Sea Interactions & fluXes (CASIX)
Jim Aiken
Affiliation:
Plymouth Marine Laboratory, Prospect Place, Plymouth, Devon, PL1 3DH, UK Centre for observation of Air–Sea Interactions & fluXes (CASIX)
Ray Barlow
Affiliation:
Marine & Coastal Management, Private Bag X2, Rogge Bay 8012, CapeTown, South Africa
Heather Sessions
Affiliation:
Marine & Coastal Management, Private Bag X2, Rogge Bay 8012, CapeTown, South Africa
Stuart Bernard
Affiliation:
University of Cape Town, Department of Oceanography, Private Bag, Rondebosch 7700, CapeTown, South Africa
Josephine Ras
Affiliation:
Laboratoire d'Océanographie de Villefranche, B.P. 08, 06238, Villefranche-sur-Mer, France
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Abstract

The relationships between phytoplankton pigments, optical properties and photosynthetic parameters for different phytoplankton functional types (derived by diagnostic pigment indices, DPI) were determined from data acquired in the Benguela ecosystem and the offshore region in October 2002. We observed robust inter-pigment relationships: total chlorophyll-a (TChla) was highly correlated with total pigment (TP) and accessory pigment (AP). However, the regression equations for stations dominated by flagellates differed from the equations for stations dominated by diatoms and dinoflagellates. The pigment ratio TChla/TP and the optical ratio a676/a440 were not constant but increased non-linearly with increasing TChla or TP; complimentarily the AP/TP and a490/a676 ratios decreased. There were significant non linear relationships between the photosynthetic parameters Fv/Fm or σPSII measured by Fast Repetition Rate Fluorometry and TChla or TP. Pigment ratios, optical ratios, Fv/Fm and σPSII were all inter-correlated with high significance. We determined the distinctive bio-optical properties associated with dominant phytoplankton functional types (derived by DPI) that conformed to the classical partitioning: flagellates (nano-plankton, comprising several taxa) had low biomass,low TChla/TP fraction and low Fv/Fm and high σPSII; diatoms and dinoflagellates (micro-plankton) had high biomass, pigment ratios, Fv/Fm and low σPSII.

Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 86 , Issue 6 , December 2006 , pp. 1267 - 1280
Copyright
2006 Marine Biological Association of the United Kingdom

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