title: In vivo estimation of pigment composition and optical absorption cross-section by spectroradiometry in four aquatic photosynthetic micro-organisms.
abstract: The objective of the present study was to estimate in vivo pigment composition and to retrieve absorption cross-section values, a(∗), of photosynthetic micro-organisms using a non-invasive technique of reflectance spectrometry. To test the methodology, organisms from different taxonomical groups and different pigment composition were used (Spirulina platensis a Cyanophyta, Porphyridium cruentum a Rhodophyta, Dunaliella tertiolecta a Chlorophyta and Entomoneis paludosa a Bacillariophyta) and photoacclimated to two different irradiance levels: 25 μmol photonm(-2)s(-1) (Low Light, LL) and 500 μmol photonm(-2)s(-1) (High Light, HL). Second derivative spectra from reflectance were used to identify pigment in vivo absorption bands that were linked to specific pigments detected by high performance liquid chromatography. Whereas some absorption bands such as those induced by Chlorophyll (Chl) a (416, 440, 625 and around 675 nm) were ubiquous, others were taxonomically specific (e.g. 636 nm for Chl c in E. paludosa) and/or photo-physiological dependent (e.g. 489 nm for zeaxanthin in the HL-acclimated S. platensis). The optical absorption cross-section, a(∗), was retrieved from reflectance data using a radiative transfer model previously developed for microphytobenthos. Despite the cellular Chl a decrease observed from LL to HL (up to 88% for S. platensis), the a(∗) increased, except for P. cruentum. This was attributed to a 'package effect' and to a greater absorption by photoprotective carotenoids that did not contribute to the energy transfer to the core Chl a.
authors.affiliation: LUNAM Université, Université de Nantes, MMS-EA 21 60, 2 rue de la Houssinière, BP 92 208, 44322 Nantes Cedex 3, France; UMR 7266 'LIENSs', CNRS/University of La Rochelle, Institute for Coastal Research and Environment (ILE), 2 rue Olympe de Gouges, 17000 La Rochelle Cedex, France. Electronic address: vona.meleder@univ-nantes.fr.
authors.forename: Vona
authors.initials: V
authors.lastname: Méléder
authors.forename: Martin
authors.initials: M
authors.lastname: Laviale
authors.forename: Bruno
authors.initials: B
authors.lastname: Jesus
authors.forename: Jean Luc
authors.initials: JL
authors.lastname: Mouget
authors.forename: Johann
authors.initials: J
authors.lastname: Lavaud
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Kazemipour
authors.forename: Patrick
authors.initials: P
authors.lastname: Launeau
authors.forename: Laurent
authors.initials: L
authors.lastname: Barillé
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000460:Chlorophyta / Q000378:metabolism* / Q000528:radiation effects; D017377:Diatoms / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D017785:Photons; D010860:Pigments, Biological / Q000737:chemistry* / Q000378:metabolism; D044665:Porphyridium / Q000378:metabolism* / Q000528:radiation effects; D011874:Radiometry; D013053:Spectrophotometry; D053545:Spirulina / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D010860:Pigments, Biological; D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: Absorption cross-section; Cyanobacteria; In vivo absorption bands; Microalgae; Pigments; Reflectance