Mesozooplankton grazing under conditions of extreme eutrophication in Guanabara Bay, Brazil |
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Authors: | Schwamborn R; Bonecker S L C; Galvao I B; Silva T A; Neumann-Leitao S |
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Institution: | 1 Departamento Oceanografia, Universidade Federal de Pernambuco, 50730-540 Recife, Brazil, 2 Departamento Zoologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil and 3 Institut für Meereskunde, Düsternbrooker WEG 20, 24105 Kiel, Germany |
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Abstract: | The objective of the present study was to quantify mesozooplanktongrazing in the eutrophic waters of Guanabara Bay. Mesozooplankton(>200 µm) was dominated by the copepods Acartia lilljeborgi,Acartia tonsa, Parvocalanus crassirostris and Paracalanus furcatus.Dinoflagellates, specifically the species Prorocentrum triestinum,were an important group for mesozooplankton nutrition, beingingested in significant amounts during all experiments. On average,12.3 ± 2.9 P. triestinum cells were ingested copepod1min1 (other dinoflagellates: 11 ± 8 cells copepod1min1). Filamentous cyanophyceae and nanoplankton wereingested in one experiment each, but the mesozooplankton communitygenerally preferred dinoflagellates to these groups, which werealways abundant in the water column. Euglenophyceae were notingested, although they dominated in one experiment. Mesozooplanktoningested, on average, only 0.2% of the nano- and microplanktonbiomass per day. The results suggest that grazing was not acontrolling process for the nano- and microplankton communityin the study area. Addition of zoeae larvae of Chasmagnatusgranulata (Decapoda: Brachyura: Grapsidae) in one experimenthad a significant effect on the mortality of adult copepods,probably due to a predatorprey relationship. |
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