title: Three-dimensional (3-D) fluorescence spectroscopy analysis of the fluorescent dissolved organic matter released by the marine toxic dinoflagellate Alexandrium catenella exposed to metal stress by zinc or lead.
abstract: We investigated the effects of zinc or lead on growth and on exudation of fluorescent dissolved organic matter (FDOM) by the marine toxic dinoflagellate Alexandrium catenella (Whedon & Kofoid) Balech. The species was exposed to increasing free zinc (1.34 × 10(-7) M-3.98 × 10(-6) M) or lead (5.13 × 10(-9) M-1.82 × 10(-7) M) concentra-tions. Low metal levels ([Zn(2+) ] = 1.34 × 10(-7) M; [Pb(2+) ] = 5.13 × 10(-9) M) had no effect on cell growth. Toxic effects were observed from higher metal contamination ([Zn(2+) ] = 3.98 × 10(-6) M; [Pb(2+) ] = 6.54 × 10(-8) M), as a conversion of vegetative cells into cysts. Analysis of the released FDOM by three-dimensional (3-D) fluorescence spectroscopy was achieved, using the parallel factor analysis (PARAFAC). The PARAFAC modeling revealed four components associated with two contributions: one related to the biological activity; the other linked to the organic matter decomposition in the culture medium. The C1 component combined a tryptophan peak and characteristics of humic substances, whereas the C2 component was considered as a tryptophan protein fluorophore. The two others C3 and C4 components were associated with marine organic matter production. Relea-sed fluorescent substances were induced by low ([Zn(2+) ]= 1.34 × 10(-7) M; [Pb(2+) ] = 5.13 × 10(-9) M) and moderate ([Zn(2+) ] = 6.21 × 10(-7) M; [Pb(2+) ] = 2.64× 10(-9) M) metal concentrations, suggesting the activation of cellular mechanisms in response to metal stress, to exudate FDOM that could complex metal cations and reduce their toxicity toward A. catenella cells.
authors.affiliation: Laboratoire de Cytologie Végétale et Phytoplanctonologie, Faculté des Sciences de Bizerte, Département des Sciences de la Vie, Université de Carthage, Jarzouna, Bizerte, 7021, Tunisie.|Laboratoire Processus de Transferts et d'Echanges dans l'Environnement (PROTEE EA 3819), Equipe Chimie Analytique et Processus de Transferts dans l'Environnement, Université du Sud Toulon - Var, BP 20132, La Garde Cedex, 83 957, France.
authors.forename: Faouzi
authors.initials: F
authors.lastname: Herzi
authors.affiliation: Laboratoire Processus de Transferts et d'Echanges dans l'Environnement (PROTEE EA 3819), Equipe Chimie Analytique et Processus de Transferts dans l'Environnement, Université du Sud Toulon - Var, BP 20132, La Garde Cedex, 83 957, France.
authors.forename: Natacha
authors.initials: N
authors.lastname: Jean
authors.affiliation: Laboratoire de Cytologie Végétale et Phytoplanctonologie, Faculté des Sciences de Bizerte, Département des Sciences de la Vie, Université de Carthage, Jarzouna, Bizerte, 7021, Tunisie.
authors.forename: Asma
authors.initials: A
authors.lastname: Sakka Hlaili
authors.affiliation: Laboratoire Processus de Transferts et d'Echanges dans l'Environnement (PROTEE EA 3819), Equipe Chimie Analytique et Processus de Transferts dans l'Environnement, Université du Sud Toulon - Var, BP 20132, La Garde Cedex, 83 957, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Mounier
keywords: 3-D fluorescence spectroscopy; A
  
  lexandrium catenella; PARAFAC; exudation; fluorescent dissolved organic matter; trace metals