title: Effects of pulse and press additions of salt on biofilms of nutrient-rich streams.
abstract: Chronic and pulse increments of salinity can cause different consequences on the aquatic communities, and its effects are related to factors such as the magnitude, frequency and ionic composition, as well as on the baseline salt concentrations in the water. The aim of this study was to explore the responses of the biofilms from a nutrient-rich stream to both pulse and chronic additions of salt, along with their recovery after the stressor had been removed. For this purpose, a microcosm study was conducted exposing biofilms to water enriched with sodium chloride in two treatments (press and pulse), and comparing the changes in the biofilm with control microcosms without salt additions. The experiment lasted 72h, and the variables measured included bacterial density, chlorophyll-a concentration, community composition, total carbohydrate content, oxygen consumption and the percentage of nuclear alterations in diatoms. Both treatments resulted in a decrease in the bacterial density of the biofilm and in oxygen consumption; the chronic treatment in particular also caused an increased percentage of nuclear abnormalities in the diatom assemblage. The biofilm recovered to control levels after the treatments had been discontinued for 72h. We concluded that the biofilms can be altered significantly under both chronic and pulse additions of salt even after a short-term exposure, and that the community can recover if the stressor is withdrawn.
authors.affiliation: Instituto de Limnología "Dr. Raúl A. Ringuelet", Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 1900 La Plata, Argentina; CONICET, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Argentina. Electronic address: jcochero@ilpla.edu.ar.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Cochero
authors.affiliation: Instituto de Limnología "Dr. Raúl A. Ringuelet", Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 1900 La Plata, Argentina; CONICET, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Argentina; Instituto Nacional de Limnología, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo s/n, CP 3000 Santa Fe, Argentina.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Licursi
authors.affiliation: Instituto de Limnología "Dr. Raúl A. Ringuelet", Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 1900 La Plata, Argentina; CONICET, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Argentina.
authors.forename: Nora
authors.initials: N
authors.lastname: Gómez
mesh_terms: D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D017753:Ecosystem; D004784:Environmental Monitoring; D045483:Rivers / Q000737:chemistry / Q000382:microbiology; D054712:Salinity; D012965:Sodium Chloride / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D012965:Sodium Chloride; D000077194:Chlorophyll A
keywords: Community recovery; Epipelic biofilm; Microcosm; Salinization; Short-term experiment