title: Microscale characterization of dissolved organic matter production and uptake in marine microbial mat communities.
abstract: Intertidal marine microbial mats exhibited biologically mediated uptake of low molecular weight dissolved organic matter (DOM), including D-glucose, acetate, and an L-amino acid mixture at trace concentrations.  Uptake of all compounds occurred in darkness, but was frequently enhanced under natural illumination.  The photosystem 2 inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) generally failed to inhibit light-stimulated DOM uptake.  Occasionally, light plus DCMU-amended treatments led to uptake rates higher than light-incubated samples, possibly due to phototrophic bacteria present in subsurface anoxic layers.  Uptake was similar with either 3H- or 14C-labeled substrates, indicating that recycling of labeled CO2 via photosynthetic fixation was not interfering with measurements of light-stimulated DOM uptake.  Microautoradiographs showed a variety of pigmented and nonpigmented bacteria and, to a lesser extent, cyanobacteria and eucaryotic microalgae involved in light-mediated DOM uptake.  Light-stimulated DOM uptake was often observed in bacteria associated with sheaths and mucilage surrounding filamentous cyanobacteria, revealing a close association of organisms taking up DOM with photoautotrophic members of the mat community.  The capacity for dark- and light-mediated heterotrophy, coupled to efficient retention of fixed carbon in the mat community, may help optimize net production and accretion of mats, even in oligotrophic waters.
authors.affiliation: Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City 28557, USA.
authors.forename: H W
authors.initials: HW
authors.lastname: Paerl
authors.forename: B M
authors.initials: BM
authors.lastname: Bebout
authors.forename: S B
authors.initials: SB
authors.lastname: Joye
authors.forename: D J
authors.initials: DJ
authors.lastname: Des Marais
mesh_terms: D000596:Amino Acids / Q000493:pharmacokinetics; D002140:California; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D000458:Cyanobacteria; D003624:Darkness; D004237:Diuron / Q000494:pharmacology; D017753:Ecosystem; D004783:Environmental Microbiology; D005947:Glucose / Q000493:pharmacokinetics; D006540:Herbicides / Q000494:pharmacology; D008027:Light; D008386:Marine Biology; D008800:Mexico; D009584:Nitrogen / Q000378:metabolism*; D009657:North Carolina; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology*; D019346:Sodium Acetate / Q000493:pharmacokinetics
chemical_list: D000596:Amino Acids; D006540:Herbicides; D002245:Carbon Dioxide; D019346:Sodium Acetate; D002244:Carbon; D004237:Diuron; D005947:Glucose; D009584:Nitrogen