Effect of fish and mesozooplankton manipulation on the phytoplankton community in the Patos Lagoon estuary,Southern Brazil |
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Authors: | Paulo C. Abreu Edna Granéli Clarisse Oderbrecht Dione Kitzmann Luis A. Proença Charrid Resgalla |
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Affiliation: | 1. Department of Oceanography-FURG, University of Rio Grande, Caixa Postal 474, 96201-900, Rio Grande, RS, Brazil 2. Department of Marine Ecology, Lund University, Box 124, S-221 00, Lund, Sweden 3. Department of Oceanography-FURG, University of Rio Grande, Caixa Postal 474, 96201-900, Rio Grande, RS, Brazil
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Abstract: | An enclosure experiment in the Patos Lagoon estuary, southern Brazil (32°S, 52°W) investigated the response of phytoplankton to the enhancement of mesozooplankton and fish abundance. Addition of nutrients (NO3 ? and PO4 ?) stimulated the growth of 3–20 μm diameter phytoplankton, especially the diatomCylindrotheca closterium, which, in turn, was heavily grazed by the dominant mesozooplankter, the copepodAcartia tonsa. Acartia did not consume small (2–3 μm) autotrophic flagellates and the cyanobacteriaAnabaena sp., despite their high cell number. Largest grazing ofC. closterium by the copepod occurred only after a decrease of ciliate abundance. The addition of mesozooplankton did not change the levels of primary production, but it significantly increased the phytoplankton assimilation number. Highest chlorophylla concentrations were measured in enclosures stocked with juveniles of the fishXenomelaniris brasiliensis. The large phytoplankton biomass and low mesozooplankton abundance found in this treatment indicates an, effective predator-mediated action on the phytoplankton community. |
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