title: Eutrophication effects on phytoplankton size-fractioned biomass and production at a tropical estuary.
abstract: Size-fractioned phytoplankton (pico, nano and microplankton) biomass and production were estimated throughout a year at Recife harbor (NE Brazil), a shallow well mixed tropical hypereutrophic estuary with short residence times but restricted water renewal. Intense loads of P-PO4 (maximum 14 μM) resulted in low N:P ratios (around 2:1), high phytoplankton biomass (B=7.1-72 μg chl-a L(-1)), production (PP=10-2657 μg C L(-1) h(-1)) and photosynthetic efficiency (P(B)=0.5-45 μg C μg chl-a(-1)), but no oxygen depletion (average O2 saturation: 109.6%). Nanoplankton dominated phytoplankton biomass (66%) but micro- and nanoplankton performed equivalent primary production rates (47% each). Production-biomass models indicate an export of the exceeding microplankton biomass during most of the year, possibly through grazing. The intense and constant nutrient and organic matter loading at Recife harbor is thus supporting the high microplankton productivity that is not accumulating on the system nor contributing to oxygen depletion, but supporting the whole system's trophic web.
authors.affiliation: Instituto de Ciências Biológicas, Universidade de Pernambuco, Recife, PE 50100-130, Brazil; Departamento de Oceanografia, Universidade Federal de Pernambuco, Recife, PE 50670-901, Brazil. Electronic address: mariana.guenther@upe.br.
authors.forename: Mariana
authors.initials: M
authors.lastname: Guenther
authors.affiliation: Departamento de Oceanografia, Universidade Federal de Pernambuco, Recife, PE 50670-901, Brazil.
authors.forename: Moacyr
authors.initials: M
authors.lastname: Araújo
authors.affiliation: Departamento de Oceanografia, Universidade Federal de Pernambuco, Recife, PE 50670-901, Brazil.
authors.forename: Manuel
authors.initials: M
authors.lastname: Flores-Montes
authors.affiliation: Instituto de Estudos do Mar Almirante Paulo Moreira, Arraial do Cabo, RJ 28930-000, Brazil.
authors.forename: Eliane
authors.initials: E
authors.lastname: Gonzalez-Rodriguez
authors.affiliation: Departamento de Oceanografia, Universidade Federal de Pernambuco, Recife, PE 50670-901, Brazil.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Neumann-Leitão
mesh_terms: D018533:Biomass; D001938:Brazil; D063366:Estuaries; D005068:Eutrophication; D010100:Oxygen / Q000032:analysis; D010788:Photosynthesis; D010839:Phytoplankton / Q000378:metabolism; D014329:Tropical Climate
chemical_list: D010100:Oxygen
keywords: Brazil; P%–B% diagrams; Phytoplankton export; Plankton; Size structure; Trophic interactions