title: The role of microorganisms in a planktonic food web of a floodplain lake.
abstract: Food webs include complex ecological interactions that define the flow of matter and energy, and are fundamental in understanding the functioning of an ecosystem. Temporal variations in the densities of communities belonging to the planktonic food web (i.e., microbial: bacteria, flagellate, and ciliate; and grazing: zooplankton and phytoplankton) were investigated, aiming to clarify the interactions between these organisms and the dynamics of the planktonic food web in a floodplain lake. We hypothesized that hydrological pulse determines the path of matter and energy flow through the planktonic food web of this floodplain lake. Data were collected monthly from March 2007 to February 2008 at three different sites in Guaraná Lake (Mato Grosso do Sul State, Brazil). The path analysis provided evidence that the dynamics of the planktonic food web was strongly influenced by the hydrological pulse. The high-water period favored interactions among the organisms of the microbial loop, rather than their relationships with zooplankton and phytoplankton. Therefore, in this period, the strong interaction among the organisms of the grazing food chain suggests that the microbial loop functions as a sink of matter and energy. In turn, in the low-water period, higher primary productivity appeared to favor different interactions between the components of the grazing food chain and microorganisms, which would function as a link to the higher trophic levels.
authors.affiliation: Universidade Estadual de Maringá, Nupelia, Av. Colombo, 5790-Bloco G90, CEP 87020-900, Maringá, PR, Brazil, biatsegovia@gmail.com.
authors.forename: Bianca Trevizan
authors.initials: BT
authors.lastname: Segovia
authors.forename: Danielle Goeldner
authors.initials: DG
authors.lastname: Pereira
authors.forename: Luis Mauricio
authors.initials: LM
authors.lastname: Bini
authors.forename: Bianca Ramos
authors.initials: BR
authors.lastname: de Meira
authors.forename: Verônica Sayuri
authors.initials: VS
authors.lastname: Nishida
authors.forename: Fabio Amodêo
authors.initials: FA
authors.lastname: Lansac-Tôha
authors.forename: Luiz Felipe Machado
authors.initials: LF
authors.lastname: Velho
mesh_terms: D000818:Animals; D018533:Biomass; D001938:Brazil; D017753:Ecosystem; D020387:Food Chain; D019015:Geologic Sediments / Q000382:microbiology; D060106:Lakes / Q000382:microbiology*; D010839:Phytoplankton / Q000382:microbiology*; D015048:Zooplankton / Q000382:microbiology*