title: Eutrophication and acidification: Do they induce changes in the dissolved organic matter dynamics in the coastal Mediterranean Sea?
abstract: Two mesocosms experiments were conducted in winter 2010 and summer 2011 to examine how increased pCO2 and/or nutrient concentrations potentially perturbate dissolved organic matter dynamics in natural microbial assemblages. The fluorescence signals of protein- and humic-like compounds were used as a proxy for labile and non-labile material, respectively, while the evolution of bacterial populations, chlorophyll a (Chl a) and dissolved organic carbon (DOC) concentrations were used as a proxy for biological activity. For both seasons, the presence of elevated pCO2 did not cause any significant change in the DOC dynamics (p-value<0.05). The conditions that showed the greatest changes in prokaryote abundances and Chl a content were those amended with nutrients, regardless of the change in pH. The temporal evolution of fluorophores and optical indices revealed that the degree of humification of the organic molecules and their molecular weight changed significantly in the nutrient-amended treatment. The generation of protein-like compounds was paired to increases in the prokaryote abundance, being higher in the nutrient-amended tanks than in the control. Different patterns in the magnitude and direction of the generation of humic-like molecules suggested that these changes depended on initial microbial populations and the availability of extra nutrient inputs. Based on our results, it is expected that in the future projected coastal scenarios the eutrophication processes will favor the transformations of labile and recalcitrant carbon regardless of changes in pCO2.
authors.affiliation: ICM-CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain. Electronic address: aparicio@cmima.csic.es.
authors.forename: Fran L
authors.initials: FL
authors.lastname: Aparicio
authors.affiliation: IIM-CSIC, Instituto de Investigaciones Marinas, C/ Eduardo Cabello 6, 36208 Vigo, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Nieto-Cid
authors.affiliation: ICM-CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Encarna
authors.initials: E
authors.lastname: Borrull
authors.affiliation: ICM-CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Calvo
authors.affiliation: ICM-CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain; ICREA, Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain.
authors.forename: Carles
authors.initials: C
authors.lastname: Pelejero
authors.affiliation: ICM-CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Maria Montserrat
authors.initials: MM
authors.lastname: Sala
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar SE-39182, Sweden.
authors.forename: Jarone
authors.initials: J
authors.lastname: Pinhassi
authors.affiliation: ICM-CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Gasol
authors.affiliation: ICM-CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Cèlia
authors.initials: C
authors.lastname: Marrasé
mesh_terms: D005068:Eutrophication; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008522:Mediterranean Sea; D012623:Seawater / Q000737:chemistry*; D013030:Spain; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical
keywords: Acidification; DOM; Eutrophication; Mediterranean Sea; Mesocosms; Optical indices