title: Microplankton dynamics under heavy anthropogenic pressure. The case of the Bahía Blanca Estuary, southwestern Atlantic Ocean.
abstract: Quantifying biotic feedbacks in response to environmental signals is fundamental to assess ecosystem perturbation. We analyzed the joint effects of eutrophication, derived from sewage pollution, and climate at the base of the pelagic food web in the Bahía Blanca Estuary (SW Atlantic Ocean). A two-year survey of environmental conditions and microplankton communities was conducted in two sites affected by contrasting anthropogenic eutrophication conditions. Under severe eutrophication, we found higher phytoplankton abundance consistently dominated by smaller sized, non siliceous species, while microzooplankton abundance remained lower and nutrient stoichiometry showed conspicuous deviations from the Redfield ratio. Phytoplankton growth in such conditions appeared controlled by phosphorous. In turn, microplankton biomass and phytoplankton size ratio (<20μm:>20μm) displayed a saturation relationship with nutrients in the highly eutrophic area, although mean phytoplankton growth was similar in both eutrophic systems. The strength of links within the estuarine network, quantified through path analysis, showed enhanced relationships under larger anthropogenic eutrophication, which fostered the climate influence on microplankton communities. Our results show conspicuous effects of severe sewage pollution on the ecological stoichiometry, i.e., N and P excess with respect to Si, altering nutrient ratios for microplankton communities. This warns on wide consequences on food web dynamics and ultimately in ecosystem assets of coastal pelagic environments.
authors.affiliation: Instituto Argentino de Oceanografía, IADO CONICET, Camino La Carrindanga km 7.5, 8000 Bahía Blanca, Argentina. Electronic address: mclabbate@iado-conicet.gob.ar.
authors.forename: M Celeste
authors.initials: MC
authors.lastname: López Abbate
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Marine Ecology/Food Webs, Düsternbrooker Weg 20, 24105 Kiel, Germany.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Molinero
authors.affiliation: Instituto Argentino de Oceanografía, IADO CONICET, Camino La Carrindanga km 7.5, 8000 Bahía Blanca, Argentina.
authors.forename: Valeria A
authors.initials: VA
authors.lastname: Guinder
authors.affiliation: Instituto Argentino de Oceanografía, IADO CONICET, Camino La Carrindanga km 7.5, 8000 Bahía Blanca, Argentina.
authors.forename: M Sofía
authors.initials: MS
authors.lastname: Dutto
authors.affiliation: Instituto Argentino de Oceanografía, IADO CONICET, Camino La Carrindanga km 7.5, 8000 Bahía Blanca, Argentina.
authors.forename: M Sonia
authors.initials: MS
authors.lastname: Barría de Cao
authors.affiliation: Departamento de Ciencias de la Atmósfera y los Océanos, FCEN UBA, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Ruiz Etcheverry
authors.affiliation: Universidad Nacional del Sur, Laboratorio de Ecología Acuática, San Juan 670, 8000 Bahía Blanca, Argentina.
authors.forename: Rosa E
authors.initials: RE
authors.lastname: Pettigrosso
authors.affiliation: Instituto Argentino de Oceanografía, IADO CONICET, Camino La Carrindanga km 7.5, 8000 Bahía Blanca, Argentina.
authors.forename: M Cecilia
authors.initials: MC
authors.lastname: Carcedo
authors.affiliation: Instituto Argentino de Oceanografía, IADO CONICET, Camino La Carrindanga km 7.5, 8000 Bahía Blanca, Argentina; Universidad Tecnológica Nacional, Facultad Regional Bahía Blanca, 11 de Abril 461, 8000 Bahía Blanca, Argentina.
authors.forename: Mónica S
authors.initials: MS
authors.lastname: Hoffmeyer
mesh_terms: D001118:Argentina; D001267:Atlantic Ocean; D018533:Biomass; D002980:Climate; D017753:Ecosystem; D063366:Estuaries; D005068:Eutrophication; D020387:Food Chain; D010758:Phosphorus; D010839:Phytoplankton / Q000254:growth & development; D010933:Plankton; D012722:Sewage; D014876:Water Pollution
chemical_list: D012722:Sewage; D010758:Phosphorus
keywords: Climate; Estuaries; Eutrophication; Microplankton; Nutrient stoichiometry; Path analysis