title: Distribution of chloropigments in suspended particulate matter and benthic microbial mat of a meromictic lake, Lake Kaiike, Japan.
abstract: We investigated the distribution of chloropigments in a small meromictic lake, Lake Kaiike, south-west Japan. In the water-column, concentrations of Chl a related to cyanobacteria, BChl a related to purple sulphur bacteria, and three types of BChl e homologues (BChls e1, e2 and e3) related to brown-coloured green sulphur bacteria, were maximal at the redox boundary. Below the redox boundary, absolute concentrations of Chl a and BChl a gradually decreased with depth, whereas BChls e remained rather constant. Suspended particulate matter (SPM) at the deeper region of the anoxic water-column was enriched in highly alkylated BChl e homologues compared with SPM at the redox boundary. The shift in the relative content of highly alkylated BChl e homologues beneath the boundary was associated with community related adaptation of brown-coloured green sulphur bacteria to changes in light quality/quantity, resulting from the optical absorption and reflectance of SPMs in the overlying water-column. Benthic microbial mats were characterized by high abundances of BChls e, in which highly alkylated homologues were substantially abundant. This suggests that the BChls e in the microbial mat may be derived from the low-light adapted brown-coloured green sulphur bacteria forming the bacterial mat.
authors.affiliation: Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan. ynakaji@jamstec.go.jp
authors.forename: Yoji
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Hisatake
authors.initials: H
authors.lastname: Okada
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Oguri
authors.forename: Hisami
authors.initials: H
authors.lastname: Suga
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitazato
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Koizumi
authors.forename: Manabu
authors.initials: M
authors.lastname: Fukui
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ohkouchi
mesh_terms: D025541:Bacteriochlorophyll A / Q000032:analysis / Q000302:isolation & purification; D001429:Bacteriochlorophylls / Q000032:analysis / Q000302:isolation & purification; D002734:Chlorophyll / Q000032:analysis / Q000302:isolation & purification; D000077194:Chlorophyll A; D002851:Chromatography, High Pressure Liquid; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D006862:Hydrogen Sulfide / Q000032:analysis; D007564:Japan; D010100:Oxygen / Q000032:analysis; D010860:Pigments, Biological / Q000032:analysis* / Q000302:isolation & purification*; D013057:Spectrum Analysis; D014871:Water Microbiology
chemical_list: D025541:Bacteriochlorophyll A; D001429:Bacteriochlorophylls; D010860:Pigments, Biological; C120930:bacteriochlorophyll e; D002734:Chlorophyll; D010100:Oxygen; D000077194:Chlorophyll A; D006862:Hydrogen Sulfide