Protozooplankton characterization of two contrasting sites in a tropical coastal ecosystem (Guanabara Bay, RJ)

Abstract

A B S T R A C TMuch time and resources have been invested in understanding plankton dynamics in Guanabara Bay (Brazil), but no attention has been devoted to the protozooplankton. To fulfill this lacuna, abundance and composition of protozooplankton were investigated from January to December -2000 in fortnightly surface water samplings at two distinct water quality sites (Urca -closer to the bay entrance, more saline and cleaner waters; Ramos -inner reaches, hypereutrophic waters). The density at Urca (10 3 -10 5 cell.l -1 ) was one to three orders of magnitude lower than at Ramos (10 4 -10 5 cell.l -1 ). A seasonal trend for nanoplankton and protozooplankton was more evident at Urca, but both sites had lower densities during the colder period. Small heterotrophic dinoflagellates (20-30 µm) were dominant in over 50% of the samples. The protozooplankton abundance and composition reflected the distinct trophic conditions states found at the bay. During the wet-warm season, non-oligotrich ciliates were representative of Ramos site with Gymnodiniaceae dinoflagellates, while tintinnids and heterotrophic dinoflagellates were predominantly found at Urca mainly during the dry-cold season. This first descriptive study towards the understanding of the intricate relationships among the microbial food web components reveals that protozooplankton can be a good indicator of water quality conditions at the bay. R E S U M OMuito tem sido investido para entender a dinâmica do plâncton da Baía de Guanabara (Brasil), estuário tropical com sérios problemas ambientais, mas pouco se sabe sobre o protozooplâncton. Preenchendo esta lacuna, a composição e abundância do protozooplâncton (ciliados, flagelados heterotróficos) foram investigadas em 2000, por meio de amostragens subsuperficiais, quinzenais, em dois locais com qualidade distinta de água (Urca -entrada da baía, águas mais salinas e limpas; Ramos -região mais interna, águas hipereutróficas e menos salinas). A densidade na Urca (10 3 -10 5 cel.L -1 ) foi inferior à de Ramos (10 4 -10 5 cel.L -1 ), com sazonalidade para o nanoplâncton e protozooplâncton mais evidente, menores valores durante o período mais frio (abril a agosto). Pequenos dinoflagelados (20-30 µm) dominaram mais de 50% das amostras. A abundância e composição refletiram o distinto estado trófico na baía (análise fatorial de correspondência: 56%). Ciliados não oligotríqueos (Vorticellidae, Dysteriidae, Didiniidae) e Gymnodiniaceae foram representativos de Ramos na estação quente-úmida (outubro -março), enquanto tintinídeos (Codonellopsidae, Metacyclididae, Tintinnidae, Undellidae) e dinoflagelados (Oxyphysaceae, Ebriidae, Protoperidiniaceae, Noctilucaceae) representativos da Urca, principalmente na estação fria-seca (abril -setembro). Este primeiro estudo descritivo, fundamental para o entendimento das relações na teia alimentar microbiana, revelou o protozooplâncton como bom indicador das condições da qualidade da água da baía.

Small time scale plankton structure variations at the entrance of a tropical eutrophic bay (Guanabara Bay, Brazil)

“…The reason why this compartment was virtually absent from our samples remains uncertain. If there was a methodological problem, the possible under sampled HN community could be acting as a link between the autotrophic picoplankton and the microzooplankton, as observed in a previous survey at nearby sites in Guanabara Bay (GOMES et al, 2007). On the other hand, if the HN community at the entrance of Guanabara bay is actually absent, the microzooplankton may be grazing directly upon the autotrophic picoplankton, as already pointed out in previous studies worldwide (e.g.…”

“…This variation is due to the balance between terrestrial influence, i.e., inputs of high loads of nutrients and organic material from riverine sources and from domestic and industrial sewage, and oceanic forces, i.e., strong tidal currents (80 -150 cm s -1 ) at the narrow entrance of the bay (JICA, 1994). The plankton communities of Guanabara Bay have been well studied since the beginning of the XXth century on both short and long term scales, providing a relevant array of information about the dynamics of the autotrophic microplankton (VILLAC; TENENBAUM, 2010 and references therein), bacterioplankton (GUENTHER et al, 2008b), auto-and heterotrophic nanoplankton , microzooplankton (GOMES et al, 2007) and mesozooplankton (e.g. WANDERNESS et al, 1997;VALENTIN et al, 1999;GOMES et al, 2004;SCHWAMBORN et al, 2004).…”

Carbon Flow for Plankton Metabolism of Saco do Mamanguá Ría, Bay of Ilha Grande, a Subtropical Coastal Environment in the South Brazil Bight

“…There is a highly diverse grazer nanoplankton community in the southeast Brazilian coastal embayments formed mostly by mixotrophic dinoflagellates (Kutner and Sassi, 1979;Sassi and Kutner, 1982;Domingos and Menezes, 1998;Tenenbaum et al, 2006;Villac et al, 2008;Moser et al, 2017) which are possibly the main consumers of Synechococcus, as reported elsewhere (Jeong et al, 2005, and references herein). Indeed, plankton studies in coastal areas of the SBB reported the dominance of heterotrophic nanoflagellates for the carbon biomass (Gomes et al, 2007;Santos et al, 2007). This planktonic structure reflects the meso-oligotrophic conditions of the coastal zone along the SBB where the usual N to P ratios are around 1, limiting the dominance of the primary producers to small photosynthetic cells such as Synecococcus that may rely on sub-micromolar concentrations of nitrogen (Zwirglmaier et al, 2008).…”

Environmental and Sanitary Conditions of Guanabara Bay, Rio de Janeiro

“…These changes, in turn, are reflected into all the upper trophic levels. Protozooplankton abundance is higher in the inner hypereutrophic parts of the bay (10 3 –10 5 cell l -1 ) with dominance of small heterotrophic dinoflagellates and naked ciliates, while large marine dinoflagellates were only found at the entrance of the bay ( Gomes et al, 2007 ). This confirms the trend of a shift from autotrophic to heterotrophic microorganisms in the bay.…”