Interactions between Ciliate Species and Aphanizomenon flos-aquae Vary Depending on the Morphological Form and Biomass of the Diazotrophic Cyanobacterium.

Aphanizomenon flos-aquae can form extensive blooms from freshwater to the brackish environment and, being a diazotrophic species, contribute significantly to the nitrogen and carbon cycle. It occurs as single filaments or aggregates and could be used as an alternative nutrients source for bacteria and ciliates. Ciliates are a group of organisms playing a crucial role in the transfer of nitrogen from primary producers to higher trophic levels in aquatic food webs. The aim of the experiment was to study the effects of the cyanobacterium A. flos-aquae on the community of five ciliate species (Spirostomum minus, Euplotes aediculatus, Strobilidium sp., Vorticella sp. and Paramecium tetraurelia). The response of each species to the presence of a low/high cyanobacterial biomass and to the different morphological forms of A. flos-aquae (single filaments or aggregates) was demonstrated. The results of the experiment showed the variability of interactions between the cyanobacterium A. flos-aquae and ciliates and pointed out the possible benefits that A. flos-aquae provides to the ciliates (e.g., a substrate for the development of bacteria as food for ciliates or as a source of nitrogen and carbon).

A dataset on trophic modes of aquatic protists.

BACKGROUND: An important functional trait of organisms is their trophic mode. It determines their position within food webs, as well as their function within an ecosystem. For the better part of the 20th century, aquatic protist communities were thought to consist mainly of producers (phytoplankton) and consumers (protozooplankton). Phytoplankton cover their energy requirements through photosynthesis (phototrophy), while protozooplankton graze on prey and organic particles (phagotrophy). However, over the past decades, it was shown that another trophic group (mixoplankton) comprise a notable part of aquatic protist communities. Mixoplankton employ a third trophic mode by combining phototrophy and phagotrophy (mixotrophy). Due to the historical dichotomy, it is not straightforward to gain adequate and correct information on the trophic mode of aquatic protists. Long hours of literature research or expert knowledge are needed to correctly assign trophic modes. Additionally, aquatic protists also have a long history of undergoing taxonomic changes which make it difficult to compare past and present literature. While WoRMS, the World Register of Marine Species, keeps track of the taxonomic changes and assigns each species a unique AphiaID that can be linked to its various historic and present taxonomic hierarchy, there is currently no machine-readable database to query aquatic protists for their trophic modes. NEW INFORMATION: This paper describes a dataset that was submitted to WoRMS and links aquatic protist taxa, with a focus on marine taxa, to their AphiaID and their trophic mode. The bulk of the data used for this dataset stems from (routine) monitoring stations in the North Sea and the Baltic Sea. The data were augmented and checked against state-of-the-art knowledge on mixoplankton taxa by consulting literature and experts. Thus, this dataset provides a first attempt to make the trophic mode of aquatic protists easily accessible in both a human- and machine-readable format.

Importance of ciliates as food for fish larvae in a shallow sea bay and a large shallow lake.

We estimated the consumption of planktonic ciliates by fish larvae in the Väinameri Sea (a shallow semi-enclosed bay of the Baltic Sea) and Lake Võrtsjärv (a shallow and eutrophic lake). Our primary hypothesis was that planktonic ciliates constitute a substantial component of the diet of fish larvae in both environments. We also assumed that the contribution of ciliates to larval nutrition is bigger in lacustrine than in marine environment because ciliates are usually more abundant in lakes. The nutrition of field collected larval fish was determined by gut content analysis using epifluorescence microscopy. Our study revealed that ciliates occurred in the alimentary tracts of all fish species examined. We discovered that the consumption of ciliates by first-feeding fish larvae contributed approximately 40 and 60% of their total consumed carbon in the Väinameri and in Võrtsjärv, respectively. Ciliates represent essentially important food for fish larvae and sufficient protozoan food may enhance larval growth in the beginning of the exogenous feeding and shorten the most vulnerable period in larval stage before shifting to larger prey.

Testate amoebae (Protozoa Rhizopoda) in two biotopes of Ubatiba stream, Maricá, Rio de Janeiro State / Amebas testáceas (Protozoa Rhizopoda) de dois biótopos do riacho Ubatiba, Maricá, Estado do Rio de Janeiro

Four samplings were carried out during the dry and rainy seasons in 2014, in two biotopes (plankton and aquatic macrophytes) to assess the composition and species richness of testate amoebae community in a coastal stream in the state of Rio de Janeiro, Brazil. Results showed great representation of Difflugiidae, Centropyxidae, Lesquereusiidae and Arcellidae families. Higher richness was observed in the plankton samples and higher densities of testate amoebae were reported among the aquatic vegetation during the dry season. Current investigation is a pioneer study conducted in the Ubatiba stream. Further researches on these protists, especially in Rio de Janeiro, should be undertaken.

Com o intuito de avaliar a composição e a riqueza de espécies da comunidade de amebas testáceas de um riacho costeiro, localizado no estado do Rio de Janeiro, foram realizadas quatro campanhas em 2014 (estação seca e estação chuvosa), em dois biótopos (plâncton e macrófitas aquáticas). Os resultados mostraram maior representatividade das famílias Difflugiidae, Centropyxidae, Lesquereusiidae e Arcellidae. Maiores riquezas foram registradas no plâncton e maiores densidades de amebas testáceas entre a vegetação aquática, ambos no período seco. O estudo foi pioneiro no riacho Ubatiba e evidencia a necessidade de intensificar as pesquisas sobre estes protistas, sobretudo no Rio de Janeiro.

Longitudinal variation of attributes from flagellate protozoan community in tropical streams / Variação longitudinal dos atributos da comunidade de protozoários flagelados de riachos tropicais

This study verified the existence of longitudinal patterns in species composition, richness, density and biomass of flagellate protozoan in tropical streams and investigated whether the possible zonation patterns are different between two periods of the year. For this, samplings were carried out in three regions from 10 streams, during the summer and winter. The flagellate community may be considered species-rich, because it was represented by 106 taxa, belonging to 8 orders and 1 residual group. The values of density and biomass are greater than those commonly found in other lotic environments, with mean values close to 2.3x104 cels. mL-1 and 150.8 µgC L-1. We did not observe any conspicuous and significant longitudinal pattern of the attributes from flagellates community. Only temporal variations of these attributes were verified. The Pearson Correlation evidenced that this temporal patterns was mainly driven by the nutrients availability, temperature and dissolved oxygen, since, the higher values of species richness, density and biomass were recorded during the winter, when the higher concentrations of nutrients and dissolved oxygen and lower temperatures were registered. In summary, the absence of patterns may be ascribed to the unidirectional and continuous flow from lotic environments.

O presente estudo objetivou verificar a existência de padrões longitudinais de composição, riqueza de espécies, densidade e biomassa da comunidade de protozoários flagelados de riachos tropicais e, ainda, investigar se os possíveis padrões de zonação são diferentes entre dois períodos do ano. Foram realizadas coletas em três regiões ao longo de dez riachos, durante os períodos de verão e inverno. A comunidade de protozoários flagelados pode ser considerada bastante rica, sendo representada por 106 táxons pertencentes a oito ordens e um grupo residual. Os valores de densidade e biomassa registrados encontram-se acima dos valores comumente encontrados em outros ambientes lóticos, com valores médios próximos de 2,3x10 4 cels. mL-1 e 150,8 µgC L-1. Não foi verificado nenhum padrão longitudinal conspícuo e significativo dos atributos dessa comunidade. Foram verificadas apenas variações temporais destes atributos. As correlações de Pearson demonstraram que esse padrão temporal foi governado principalmente pela disponibilidade de nutrientes, temperatura e oxigênio dissolvido, visto que os maiores valores de riqueza, densidade e biomassa foram registrados no inverno, e também foram verificadas as maiores concentrações de nutrientes, de oxigênio dissolvido e as menores temperaturas. Em suma, sugere-se que essa ausência de padrões longitudinais pode ser atribuída ao fluxo unidirecional e contínuo dos ambientes lóticos.

Composition and species richness of flagellate protozoa from environments associated to the Baía river (Mato Grosso do Sul State, Brazil): influence of the hydrological period and the connectivity / Composição e riqueza de espécies de protozoários flagelados de ambientes associados ao rio Baía (Mato Grosso do Sul, Brasil): influência do período hidrológico e da conectividade

Despite flagellate protozoa are important for the metabolism of aquatic ecosystems, researches about the ecology of this community is scarce. Therefore, this study investigated the influence of flood regime and hydrological connectivity on the patterns of composition and species richness of protozoan flagellates from aquatic environments in the upper Paraná river floodplain. To this end, samplings were undertaken in two periods of the hydrological cycle (March 2008 and September 2008), at six lentic environments associated with the Baía river (three are connected to the river, and three are isolated). 120 taxa were identified in the studied area, distributed in 10 orders and one residual group. This high species richness was sustained by the order Euglenida, which contributed with 70% of total species. The species composition was significantly different between periods and environments, as well as species richness, which was higher in connected environments during the high water period. The results evidenced that the flood pulse and hydrological connectivity are relevant factors driving the structure and dynamic of plankton flagellate protozoa community in the upper Paraná river floodplain.

Apesar dos protozoários flagelados serem importantes para o metabolismo dos ecossistemas aquáticos, os estudos sobre a ecologia desta comunidade são escassos. Nesse contexto, este estudo tem por objetivos investigar a influência do regime de inundação e da conectividade hidrológica sobre os padrões de composição e riqueza de espécies de protozoários flagelados da planície de inundação do alto rio Paraná. Para tal, foram realizadas coletas em dois períodos do ciclo hidrológico (março/2008 e setembro/2008), em seis ambientes lênticos associados ao rio Baia (sendo três conectados ao rio e três desconectados). Foram identificados 120 táxons na área de estudo, distribuídos em 10 ordens e um grupo residual. Essa elevada riqueza de espécies foi sustentada pela ordem Euglenida, que contribuiu com 70% do total das espécies registradas. A composição de espécies foi significativamente diferente entre os períodos e entre os ambientes, assim como a riqueza de espécies, que foi maior nos ambientes conectados e durante o período de águas altas. Esses resultados demonstraram que o regime de inundação e a conectividade hidrológica são fatores relevantes na estruturação e na dinâmica da comunidade de protozoários flagelados planctônicos, na planície de inundação do alto rio Paraná.