title: Photochemical alteration of dissolved organic matter and the subsequent effects on bacterial carbon cycling and diversity.
abstract: The impact of solar radiation on dissolved organic matter (DOM) derived from 3 different sources (seawater, eelgrass leaves and river water) and the effect on the bacterial carbon cycling and diversity were investigated. Seawater with DOM from the sources was first either kept in the dark or exposed to sunlight (4 days), after which a bacterial inoculum was added and incubated for 4 additional days. Sunlight exposure reduced the coloured DOM and carbon signals, which was followed by a production of inorganic nutrients. Bacterial carbon cycling was higher in the dark compared with the light treatment in seawater and river samples, while higher levels were found in the sunlight-exposed eelgrass experiment. Sunlight pre-exposure stimulated the bacterial growth efficiency in the seawater experiments, while no impact was found in the other experiments. We suggest that these responses are connected to differences in substrate composition and the production of free radicals. The bacterial community that developed in the dark and sunlight pre-treated samples differed in the seawater and river experiments. Our findings suggest that impact of sunlight exposure on the bacterial carbon transfer and diversity depends on the DOM source and on the sunlight-induced production of inorganic nutrients.
authors.affiliation: Australian Institute of Marine Science, PMB 3, Townsville MC, QLD 4810, Australia Centre for Sustainable Aquatic Research, College of Science, Wallace Building, Swansea University, Swansea SA2 8PP, UK clonborg@gmail.com.
authors.forename: Christian
authors.initials: C
authors.lastname: Lønborg
authors.affiliation: CSIC, Instituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Nieto-Cid
authors.affiliation: Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36200 Vigo, Spain.
authors.forename: Victor
authors.initials: V
authors.lastname: Hernando-Morales
authors.affiliation: Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36200 Vigo, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Hernández-Ruiz
authors.affiliation: Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36200 Vigo, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Teira
authors.affiliation: CSIC, Instituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain.
authors.forename: Xosé Antón
authors.initials: XA
authors.lastname: Álvarez-Salgado
mesh_terms: D001419:Bacteria / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D057486:Carbon Cycle; D018515:Plant Leaves / Q000737:chemistry / Q000382:microbiology*; D045483:Rivers / Q000737:chemistry* / Q000382:microbiology; D012623:Seawater / Q000737:chemistry* / Q000382:microbiology; D013030:Spain; D013472:Sunlight; D035962:Zosteraceae / Q000737:chemistry / Q000382:microbiology*
chemical_list: D002244:Carbon
keywords: bacterial carbon demand; bacterial diversity; bacterial growth efficiency; dissolved organic matter; solar radiation