title: Organic matter produced by algae and cyanobacteria: quantitative and qualitative characterization.
abstract: This work aims at characterizing organic matter produced by an alga Euglena gracilis and a cyanobacteria Microcystis aeruginosa and assessing the evolution of its characteristics during growth. A culture medium was optimized. The species growth phases were monitored using both visible spectrophotometry and flow cytometry cell counting. Organic matter fractionation according to hydrophobicity and specific UV absorbance (SUVA) index were used to specifically characterize the produced algal organic matter (AOM). The AOM characteristics were both growth phase and species dependent. However, a similar evolution was observed. The hydrophilic fraction (HPI) was the major fraction whatever the growth phases and was almost the only one produced during lag and exponential phases. It represented around 75% of AOM during exponential phase and then decreased when the stationary phase appeared. It represented 46% and 60% of the AOM during late decline phase for the cyanobacteria and the alga respectively. The hydrophobic (HPO) and transphilic (TPH) fractions started to appear from the beginning of the stationary phase with more hydrophobic compounds coming from intracellular organic material of dying cells. HPO and TPH percentages still increased during the decline phase probably because of two additional processes: photo-dissolution and leaching of particulate organic matter from cells fragments. A comparison of AOM during late decline phase and natural organic matter (NOM) from Glane River (France) underlined that AOM was more hydrophilic and presented a lower SUVA for each fractions than NOM. However, the difference between NOM and AOM hydrophobicity narrowed during decline phase.
authors.affiliation: University of Limoges, EA 4330, Groupement de Recherche Eau, Sol, Environnement (GRESE), ENSIL, Parc d'ESTER Technopôle, 16 rue Atlantis, F-87068 Limoges Cedex, France.
authors.forename: Maud
authors.initials: M
authors.lastname: Leloup
authors.forename: Rudy
authors.initials: R
authors.lastname: Nicolau
authors.forename: Virginie
authors.initials: V
authors.lastname: Pallier
authors.forename: Claude
authors.initials: C
authors.lastname: Yéprémian
authors.forename: Geneviève
authors.initials: G
authors.lastname: Feuillade-Cathalifaud
mesh_terms: D005056:Euglena gracilis / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D046931:Microcystis / Q000378:metabolism*; D009930:Organic Chemicals / Q000378:metabolism
chemical_list: D009930:Organic Chemicals