title: The pigment composition of Phaeocystis antarctica (Haptophyceae) under various conditions of light, temperature, salinity, and iron.
abstract: The pigment composition of Phaeocystis antarctica was monitored under various conditions of light, temperature, salinity, and iron. 19'-Hexanoyloxyfucoxanthin (Hex-fuco) always constituted the major light-harvesting pigment, with remarkably stable ratios of Hex-fuco-to-chl a under the various environmental conditions. Increased pigment-to-chl a ratios at low irradiance confirmed the light-harvesting function of Fucoxanthin (Fuco), 19'-Hexanoyloxy-4-ketofucoxanthin (Hex-kfuco), 19'-butanoyloxyfucoxanthin (But-fuco), and chl c2 and c3. Increased pigment-to-chl a ratios at high irradiance, low iron concentrations, and to a lesser extent at high salinity confirmed the photoprotective function of diadinoxanthin, diatoxanthin, and ß,ß-carotene. Pigment ratios were not always according to expectations. The consistent increase in But-fuco/chl at high temperature, high salinity, and low iron suggests a role in photoprotection rather than in light harvesting. Low Hex-kfuco/chl ratios at high salinity were consistent with a role as light harvester, but the high ratios at high temperature were not, leaving the function of Hex-kfuco enigmatic. Dedicated experiments were performed to test whether or not the light-harvesting pigment Fuco could be converted into its structural relative Hex-fuco, and vice versa, in response to exposure to light shifts. Rapid conversions could not be confirmed, but long-term conversions cannot be excluded. New pigment ratios are proposed for chemotaxonomic applications. The ratios will improve pigment-based diagnosis of algal species in waters dominated by P. antarctica.
authors.affiliation: Ecophysiology of Plants, Centre for Life Sciences, University of Groningen, PO Box 11103, Groningen, 9700 CC, the Netherlands.
authors.forename: Maria A
authors.initials: MA
authors.lastname: van Leeuwe
authors.affiliation: Dept. Ocean Ecosystems, Centre for Life Sciences, University of Groningen, PO Box 11103, Groningen, 9700 CC, the Netherlands.
authors.forename: Ronald J W
authors.initials: RJ
authors.lastname: Visser
authors.affiliation: Ecophysiology of Plants, Centre for Life Sciences, University of Groningen, PO Box 11103, Groningen, 9700 CC, the Netherlands.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Stefels
keywords: 19′-Hexanoyloxyfucoxanthin; CHEMTAX; HPLC; Phaeocystis; fucoxanthin; irradiance; pigments; salinity; temperature