Auto- and heterotrophic nanoplankton and filamentous bacteria of Guanabara Bay (RJ, Brazil): estimates of cell/filament numbers versus carbon content

Variações do nanoplâncton (2-20µm) e bactérias filamentosas (diâmetro: 0.5-2.0 µm) da Baía de Guanabara (RJ, Brasil) são apresentadas, considerando densidade celular e biomassa de autótrofos e heterótrofos. A meta deste trabalho é contribuir para uma futura modelagem da dinâmica trófica neste sistema. Amostras subsuperficiais de água foram coletadas semanalmente durante um ano em dois pontos: Urca (próximo à entrada, mais salino, eutrófico) e Ramos (no interior, menos salino, hipertrófico). Foi feita análise por microscopia de epifluorescência, com densidade celular convertida para biomassa através do biovolume celular. A concentração do nanoplâncton total foi alta (10(8)cel.l-1) na maioria das amostras (>;57%) e das bactérias filamentosas variou de 10(5) a 10(8)fil.l-1. A densidade de autótrofos em Ramos foi uma ordem de grandeza superior tanto para o nanoplâncton (Md: 10(8)cel.l-1 em Ramos e 10(7)cel.l-1 na Urca) quanto para as bactérias filamentosas (Md: 10(6)fil.l-1 em Ramos e 10(5)fil.l-1 na Urca). A biomassa autotrófica do nanoplâncton (Md: 10³µgC.l-1 em Ramos e 10¹µgC.l-1 na Urca) e das bactérias filamentosas (Md: 28µgC.l-1 em Ramos e 1,4µgC.l-1 na Urca) seguiu o mesmo padrão. A contribuição relativa de autótrofos aumentou após a conversão para biomassa. Uma tendência temporal foi evidenciada para as bactérias filamentosas em ambos os pontos e, para o nanoplâncton autotrófico, em Ramos, com valores máximos no período chuvoso (primavera-verão).Variations of nanoplankton (2-20 µm) and filamentous bacteria (diameter: 0.5-2.0 µm) of Guanabara Bay (RJ, Brazil) are presented, considering cell density and carbon content of auto- and heterotrophs. Our goal is to contribute to future modeling of local trophic dynamics. Subsurface water samples were taken weekly during the year 2000 at two sites: Urca (close to the entrance, more saline, eutrophic) and Ramos (inner area, less saline, hypertrophic). Microscopic analysis was done by epifluorescence and cell density was converted to biomass through cell biovolume. Total nanoplankton was about 10(8) cells.l-1 in most samples (>;57%), and total filamentous bacteria densities varied from 10(5) to 10(8) fil.l-1. Autotroph density was one order of magnitude higher at Ramos, both for nanoplankton (Md: 10(8)cells.l-1 at Ramos and 10(7)cells.l-1 at Urca) and for filamentous bacteria (Md: 10(6) fil.l-1 at Ramos and 10(5) fil.l-1 at Urca). The same was observed for autotrophic biomass (Md: 10³µgC.l-1 at Ramos and 10¹µgC.l-1 at Urca for nanoplankton; Md: 28µgC.l-1 at Ramos and 1.4µgC.l-1 at Urca for filamentous bacteria). The relative contribution of autotrophs increased after conversion to biomass. Seasonal variation was conspicuous for filamentous bacteria at both sites and for nanoplankton only at Ramos, with maximum autotrophic abundances during the rainy period (spring-summer)

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

Muito 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 (10³-10(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 mm) 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.Much 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 (10³ - 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 mm) 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

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

A dinâmica dos vários compartimentos do plâncton foi avaliada durante uma série de curta duração na entrada da baía de Guanabara (SE do Brasil), com o objetivo de estimar suas correlações tróficas. A biomassa e eficiência fotossíntética das três frações do fitoplâncton (picoplâncton: < 2µm, nanoplâncton: 2-20µm e microplâncton: &gt; 20µm), juntamente com a composição e abundância do nano-e microplâncton auto-e heterótrofos e do mesozooplâncton, foram determinadas em uma estação fixa durante 3 dias consecutivos, a intervalos de 3h, nas camadas de superfície e de fundo (20m). A variabilidade de quase todos os compartimentos do plâncton na superfície foi diretamente relacionada à temperatura, indicando forte influência da circulação da entrada da baía na estrutura planctônica. Na camada superficial, o mesozooplâncton parece ser alimentado pelo nano-e picoplâncton autótrofos, esse último sendo sustentado pelo microzooplâncton. Próximo ao fundo, o microplâncton auto-e heterótrofo estão possivelmente sustentando a biomassa mesozooplanctônica. Nossos resultados sugerem, portanto, que na entrada da baía de Guanabara esteja estabelecida uma rede trófica multívora, i.e., uma combinação entre as cadeias microbiana e de pastagem.The dynamics of the plankton compartments at the entrance of Guanabara Bay (SE Brazil) were assessed during a short-term temporal survey to estimate their trophic correlations. Size-fractioned phytoplankton (picoplankton: < 2µm, nanoplankton: 2-20µm and microplankton: &gt; 20µm) biomass and photosynthetic efficiency, composition and abundance of the auto-and heterotrophic nano-and microplankton, and mesozooplankton were evaluated at a fixed station for 3 consecutive days at 3-h intervals, in the surface and bottom (20m) layers. The variability of almost all plankton compartments in the surface layer was directly dependent on temperature, indicating the great influence of the circulation at the entrance of the bay on plankton structure. In the surface layer, the mesozooplankton seems to be sustained by both autotrophic nano-and picoplankton, this last being channeled through the microzooplankton. Near the bottom, both auto-and heterotrophic microplankton are probably supporting the mesozooplankton biomass. Our findings thus suggest that the entrance of Guanabara bay presents a multivorous food web, i.e., a combination of both grazing and microbial trophic pathways

The phytoplankton of Guanabara Bay, Brazil: I. historical account of its biodiversity

This is a historical account of the biodiversity of phytoplankton in Guanabara Bay, Brazil. It is based on 57 publications that refer to sampling carried out between 1913 and 2004. The publications included are those with direct microscopic identification. Although 80% of the studies focus on ecological issues that tend to mention only the most abundant species, 24 publications provide comprehensive check-lists at the species level, especially of taxa > 20 &#956;m. The inventory of species includes, to date, 308 taxa among 199 diatoms, 90 dinoflagellates, 9 cyanobacteria, 5 euglenophyceans, 1 chlorophycean, 1 prasinophycean, 1 silicoflagellate, and 2 ebriids. The most conspicuous species were the dinoflagellate Scrippsiella trochoidea and diatoms from the Skeletonema costatum complex. The first was the theme of the very first publication in the area (Faria 1914) that reported on its bloom associated with the mass mortality of fish due to oxygen depletion; it is still often found in high abundances (10(6) cell.L-1) in more protected areas. The second was long considered in the literature as a cosmopolitan and opportunistic species, until the recent discovery of cryptic species within the genus; taxonomic re-evaluation of local populations is, therefore, needed. Besides these two species, only other 25 species stood out in terms of frequency of occurrence and widespread distribution in the Bay, some known to be implicated in harmful blooms elsewhere. The biodiversity of dinoflagellates, especially within the Gymnodiniales, and that of other unidentified flagellates (Haptophyceae, Cryptophyceae, Prasinophyceae, Raphidophyceae) is largely underestimated because of the use of fixatives that distort/destroy diagnostic characters. From the initial inventory of 124 taxa published in 1917 and the subsequent additions in species numbers, one can have a false perception that the phytoplankton biodiversity has increased throughout the years, despite the overall increase in eutrophication observed in Guanabara Bay. The reason for this may be twofold: 1) it is an artifact caused by our progressively improving technical capability to detect and identify species and 2) the possible effects of eutrophication could be better perceived when the community structure is evaluated, that is, when space-time variations in the abundances of the populations (rather than just number of species) are also taken into account

Auto- and heterotrophic nanoplankton and filamentous bacteria of Guanabara Bay (RJ, Brazil): estimates of cell/filament numbers versus carbon content

Variations of nanoplankton (2-20 µm) and filamentous bacteria (diameter: 0.5-2.0 µm) of Guanabara Bay (RJ, Brazil) are presented, considering cell density and carbon content of auto- and heterotrophs. Our goal is to contribute to future modeling of local trophic dynamics. Subsurface water samples were taken weekly during the year 2000 at two sites: Urca (close to the entrance, more saline, eutrophic) and Ramos (inner area, less saline, hypertrophic). Microscopic analysis was done by epifluorescence and cell density was converted to biomass through cell biovolume. Total nanoplankton was about 10(8) cells.l-1 in most samples (>57%), and total filamentous bacteria densities varied from 10(5) to 10(8) fil.l-1. Autotroph density was one order of magnitude higher at Ramos, both for nanoplankton (Md: 10(8)cells.l-1 at Ramos and 10(7)cells.l-1 at Urca) and for filamentous bacteria (Md: 10(6) fil.l-1 at Ramos and 10(5) fil.l-1 at Urca). The same was observed for autotrophic biomass (Md: 10³µgC.l-1 at Ramos and 10¹µgC.l-1 at Urca for nanoplankton; Md: 28µgC.l-1 at Ramos and 1.4µgC.l-1 at Urca for filamentous bacteria). The relative contribution of autotrophs increased after conversion to biomass. Seasonal variation was conspicuous for filamentous bacteria at both sites and for nanoplankton only at Ramos, with maximum autotrophic abundances during the rainy period (spring-summer)

Variação da composição específica do fitoplâncton de Arraial do Cabo (RJ, Brasil) após enriquecimento com nutrientes

O fitoplâncton natural de Cabo Frio foi cultivado em água do mar coletada a 42m de profundidade e enriquecida com concentrações crescentes de nitrogênio e fósforo. Uma série de culturas de volume igual a 151 foi feita em garrafões de 201, para acompanhar as variações da composição específica da comunidade. Foram utilizadas 6 concentrações de nitrogênio, entre 10 e 100/Ltg-at.l"' e, 9 de fósforo, entre 0,5 e 20/^g-at.l"1. Todos os enriquecimentos provocaram uma simplificação da estrutura da comunidade. A redução do número de espécies em relação ao inóculo e a grande dominância de Chaetoceros sp. e Nitzschia “ delicatissima” durante o período de incubação, reduziram o índice de Shannon. O enriquecimento com nitrogênio provocou a seguinte sucessão de espécies dominantes: Rhizosolenia stolterfothii + Prorocentrum balticum (1.° dia), Chaetoceros costatum + Chaetoceros sp. + Cerataulina pelagica (2.° dia), Chaetoceros sp. -j- N. “ delicatissima” (ou em algumas culturas uma diatomácea penada não identificada) (3.° dia) e N. “ delicatissima” + Chaetoceros sp. (4.° e 5.° dias). Uma dominância alternada entre N. “ delicatissima” e Chaetoceros sp., com subdominância de C. affinis e Nitzschia closterium, foi observada nos experimentos de enriquecimento com fósforo.  Diatomáceas cêntricas e penadas não identificadas ocorreram em todos os enriquecimentos.Water samples of Cabo Frio area were pumped from 42m depth and placed into carboys of 20 liters, in order to study the changes in the specific composition of natural phytoplankton after enrichments with increasing amounts of nitrogen and phosphorus, ranging from 10 to 100 and 0,5 to 20/ig-at.l"', respectively. The enrichments lead to a simplification of the community structure. The Shannon’s index decreased after the reduction of species number in relation to the inoculum, with dominance of Chaetoceros sp. and Nitzschia “ delicatissima” during incubations. Nitrogen enrichment showed a sucessive dominance of Rhizosolenia stolterfothii + Prorocentrum balticum (Ist day), Chaetoceros costatum + Chaetoceros sp. -|- Cerataulina pelagica (2nd), Chaetoceros sp. + N. “ delicatissima” (or in some cultures an unidentified Pennate diatom) (3rd day) and N. “ delicatissima” + Chaetoceros sp. (4,n and 5th days).  N. “ delicatissima” and Chaetoceros sp. dominated alternatively the phosphorus enriched experiments, followed by C. affinis and Nitzschia closterium. Centric and Pennate, unidentified diatoms, ocurred in all the enrichments

Composition, density and size-structure of the autotrophic plankton community in a shallow coastal zone at King George Island, West Antarctic Peninsula (WAP), during early summer 2010

The planktonic microorganism community of Admiralty Bay, Antarctic Peninsula is being monitored since 2002. This study describes composition, size-structure and biomass of the phytoplankton communities observed during early summer 2010/2011 in the area. Organisms were counted by microscopy and scored as belonging to three size classes: &lt;10 µm, 10 - 80 µm and 80 - 400 µm. In terms of density, this phytoplankton community was dominated by cells &lt; 10 µm (~106 - 107 cells L-1), confirming the increasing presence of small planktonic autotrophs in West Antarctic Peninsula waters. Organisms &gt; 10 µm dominated in terms of biomass (&gt; 50% of Chlorophyll a) with densities of up to 1.6 x 104 cells L-1, which is approximately 0.6 times higher than observed for early summer in recent years. Additionally, our results confirm a previously observed phenomenon whereby large-size phytoplankton (&gt; 80 µm), especially pennate diatoms, are replaced by mid-size centric diatoms (10- 80 µm), such as Thalassiosira spp., and small dinoflagellates (e.g. Prorocentrum antarcticum) during warmer early summers