Ecological preferences and distribution of Aulacoseira species in southeastern Brazilian reservoirs with varying trophic states were studied. One hundred and fourteen plankton samples (winter and summer) from 57 sites located in 16 reservoirs were analysed. Ten water quality parameters were measured. Ten Aulacoseira species were identified using light, scanning and transmission electron microscopy, and new information on their ecological preferences is provided here. Our results indicate that trophic gradient is the main driver of species distribution. Principal components analysis and calculation of weighted average nutrient optima revealed three indicator taxa, Aulacoseira tenella characteristic for oligotrophic waters and two varieties of Aulacoseira granulata (nominate and var. angustissima) typical for eutrophic reservoirs. This is the first ecological study of Aulacoseira in Brazil, adding information on the distribution of this genus in the tropics, and highlighting the need for species-level identification and regional studies to improve the use of diatoms in water quality assessment.

Composition and distribution of diatom assemblages from core and surface sediments of a water supply reservoir in Southeastern Brazil. Biota Neotropica. 16(2): e20150129. http://dx.doi.org/10.1590/1676-0611- BN-2015-0129 Abstract: Fresh water biodiversity is an increasing concern due to growing human impact. Herein, we report a long-term survey (ca. 90 years) of sedimentary diatoms and the modern flora from surface sediments and their biodiversity changes along a eutrophication gradient. Study was carried out in one of the most important water supply reservoirs (Guarapiranga Reservoir) of Sã o Paulo Metropolitan Region, Brazil. Results are based on 75 core subsamples (subfossil assemblages from core) previously dated by 210 Pb and 14 samples from surface sediments (modern assemblages). Overall, 84 taxa were reported, belonging to 30 genera, 71 species and eight non-typical varieties, besides five probable new taxa. Results expanded two new additions for the Brazilian diatom flora (Chamaepinnularia submuscicula and Stauroneis acidoclinata) and 30 infrageneric taxa for the state of Sã o Paulo. 47.6% of total taxa inventoried were accounted exclusively for the subfossil assemblages indicating a significant biodiversity change over time. Access to past oligotrophic conditions and to contemporary mesotrophic regions of the Guarapiranga Reservoir accounted for these new additions representing 25% of the total diatom flora. Decline in the total species number along the trophic state gradient occurred for subfossil and modern assemblages. This pattern was even clearer when considering the changes in species richness over time. Eunotia with 21 taxa was the far most represented genera particularly in the oligotrophic phase. During the transitional period , richness gradually declined. With the onset (in the 1970s) and the major eutrophication period (since ca. 1990) occurred a drastic reduction in richness and the replacement of oligotrophic to eutrophic species. Human management also caused abrupt changes in richness. Marked decline occurred (1933) assotiated with hydrological impacts (water discharge increase) with the initial use of the reservoir as a public water supply. Unlike, sudden increase occurred probably associated with the application of algaecide to control cyanobacterial blooms. Present findings highlight the need for surveying the diatom assemblages in protected environments or in less degraded conditions for biodiversity assessment. Furthermore, reinforce the use of paleolimnological approach as in many cases the only tool to assess biodiversity changes encompassing time scales relevant to human-induced degradation and pre-anthropogenic impacts. Keywords: Bacillariophyta, biodiversity change, eutrophication, Guarapiranga Reservoir, paleolimnology, species richness.FAUSTINO, S.B., FONTANA, L., BARTOZEK, E.C.R., BICUDO, C.E.M., BICUDO, D.C. Composic¸ão e distribuic¸ão das diatomáceas de perfil sedimentar e sedimentos superficiais em reservatório de abastecimento no Sudeste do Brasil. Biota Neotropica. 1...

Th is study represents a taxonomic survey of class Bacillariophyceae diatoms found in samples collected in the Iguaçu River (Iguaçu National Park, municipality of Foz do Iguaçu, in the state of Paraná, Brazil) between August 2007 and July 2008. Two sampling stations were utilized, the fi rst located upstream of Iguaçu Falls (Cais Bananeiras Station) and second downstream of the falls (Cais Macuco Safari Station). Th e study resulted in the identifi cation of 86 taxa, including 74 at the specifi c level and seven taxonomic varieties.

This, study aimed to inventory the diatom flora of tropical reservoirs from southeastern region of Brazil under oligo- to hypereutrophic conditions. We collected diatom samples from the surface sediment and phytoplankton (summer and winter) in 41 sites (ten reservoirs). Seventy-eight taxa, distributed in 28 genera, were identified in the surface sediment and phytoplankton samples. Nizschia was the most representative genus, with nine species. Six taxa represent new records for Brazil and six for São Paulo State; ten taxa were identified at the genus level and probably represent new species. Additionally, this study contributed with data on the ecology of the species and evidenced the necessity of floristic surveys to improve the knowledge about tropical diatom biodiversity.

A taxonomic survey was carried out on Coscinodiscophyceae and Fragilariophyceae found in the Iguaçu River catchment area within Iguaçu National Park, in the state of Paraná, Brazil. Between September 2007 and August 2008, we collected 24 samples from two stations on the Iguaçu River, upstream and downstream of the falls. We identified 37 taxa, including 22 specific and infraspecific taxa of Coscinodiscophyceae, together with 15 specific and infraspecific taxa of Fragilariophyceae. Melosira ruttneri Hustedt and Fragilaria alpestris Krasske ex Hustedt represent new records for Brazil.

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This study investigated the enrichment influence due to fish farming in net cages on the phytoplankton composition, density and diversity in two arms of a subtropical reservoir (Salto Caxias, Paraná). There were no statistically significant differences in the phytoplankton composition and diversity, as well as for concentrations of nutrients among the handled treatment. The density values were higher during the summer. Richness and Shannon diversity values were low during the study period. The equitability values were high during the winter and low in the summer. Variations of phytoplankton community and nutrients were mainly influenced by seasonality. The absence of significant differences between the treatments was probably due to the small number of net cages and fish used, as well as to the hydrodynamics of the studied environments, which are influenced by upstream rivers inflows.Keywords: phytoplankton, community structure, net cages, hydrodynamics's effect.Influência do cultivo de peixes em tanques-rede sobre a estrutura do fitoplâncton: estudo de caso em um reservatório subtropical brasileiro ResumoEste estudo investigou os efeitos do enriquecimento devido ao cultivo de peixes em tanques-rede sobre a composição, densidade e diversidade fitoplanctônica em dois braços de um reservatório subtropical (Salto Caxias, Paraná). Não foram registradas diferenças significativas para a composição e diversidade fitoplanctônica e para as concentrações de nutrientes entre os tratamentos utilizados. A densidade foi maior durante o verão. Os valores de riqueza de espécies e diversidade de Shannon foram baixos durante todo o período de estudo. A equitabilidade foi elevada no inverno e baixa no verão. As variações da comunidade fitoplanctônica e dos nutrientes parecem ter sido influenciadas principalmente pela sazonalidade. A ausência de diferenças significativas entre os tratamentos, provavelmente se devem ao pequeno número de tanques e peixes utilizados, e à hidrodinâmica dos ambientes estudados, os quais são influenciados pelos influxos dos rios à montante.Palavras-chave: fitoplâncton, estrutura da comunidade, tanques-rede, efeitos da hidrodinâmica.