title: Contribution of chemical water properties to the differential responses of bacterioneuston and bacterioplankton to ultraviolet-B radiation.
abstract: The surface microlayer (SML) is characterized by different physicochemical properties from underlying waters (UW). However, whether these differences in abiotic factors underlie the distinct sensitivity of bacterioneuston (i.e. SML bacteria) and bacterioplankton to environmental stressors remains to be addressed. We investigated the contribution of abiotic factors to the UV-B sensitivity of bacterioneuston and bacterioplankton. Nutrients (especially nitrogen and phosphate) emerged as important determinants of bacterial UV-B sensitivity. The role of particles, nutrients, and dissolved organic components on bacterial UV-B sensitivity was further evaluated using dilution cultures. Filtered samples were twofold more UV sensitive than unfiltered samples, suggesting a UV-protective effect of particles. High nutrient concentrations attenuated bacterial UV-B sensitivity (up to 40%), compared with unamended conditions, by influencing bacterial physiology and/or community composition. Suspending cells in natural water, particularly from the SML, also attenuated UV-B sensitivity (up to 23%), compared with suspension in an artificial mineral solution. Bioassays using Pseudomonas sp. strain NT5I1.2B revealed that chemical water properties influence UV-induced oxidative damage. UV-B sensitivity was associated with high cell-specific activities. The chemical environment of the SML and UW influences UV-B effects on the corresponding bacterial communities. Maintaining low cell activities might be advantageous in stressful environments, like the SML.
authors.affiliation: Department of Biology and CESAM, University of Aveiro, Aveiro, Portugal.
authors.forename: Ana L
authors.initials: AL
authors.lastname: Santos
authors.forename: Inês
authors.initials: I
authors.lastname: Baptista
authors.forename: Newton C M
authors.initials: NC
authors.lastname: Gomes
authors.forename: Isabel
authors.initials: I
authors.lastname: Henriques
authors.forename: Adelaide
authors.initials: A
authors.lastname: Almeida
authors.forename: António
authors.initials: A
authors.lastname: Correia
authors.forename: Angela
authors.initials: A
authors.lastname: Cunha
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D064751:Ammonium Compounds / Q000494:pharmacology; D001419:Bacteria / Q000145:classification / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D058491:Bacterial Load; D063366:Estuaries; D007930:Leucine / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology; D010933:Plankton / Q000145:classification / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry; D014871:Water Microbiology
chemical_list: D000596:Amino Acids; D064751:Ammonium Compounds; D010710:Phosphates; D014867:Water; D007930:Leucine
keywords: UV radiation; abundance; activity; surface microlayer; underlying waters