Summary Analysing the beta diversity components and spatial patterns of species distribution may provide key insights into how local communities respond to human‐induced environmental changes. Indeed, analysing temporal variation in spatial patterns of species distribution may reveal trends of biotic homogenisation and its likely causes. We used an eight‐year phytoplankton data set generated from to 17 reservoirs in Brazil to analyse the temporal variability in beta diversity and its turnover and nestedness components. This data set was also used to determine metacommunity structures across these subtropical reservoirs. We tested whether there was any long‐term temporal trend in beta diversity that might be indicative of biotic homogenisation or differentiation. We also tested how temporal variation was related to climatic conditions, environmental heterogeneity, productivity and cyanobacterial dominance. Lastly, we verified whether the phytoplankton metacommunity showed non‐random structure. We did not find supporting evidence for biotic homogenisation among the reservoirs. Rather, we did find that nestedness decreased during the study. Environmental heterogeneity was the main variable positively related to phytoplankton beta diversity, while high ammonium concentration and cyanobacterial abundance were negatively correlated with spatial variation among the reservoirs. Despite the noticeable temporal variation in metacommunity structures, the phytoplankton species responded similar to latent environmental gradients. Clementsian patterns found mainly in fall and winter were consistent with differences in species composition between sites, reinforcing the role of environmental filtering in driving changes in these metacommunities. Our results suggest that eutrophication control is essential to prevent biotic homogenisation, at least in our study system. We also highlight that metacommunity patterns detected in snapshot surveys should not be extrapolated temporally.

Intensive growth of aquatic macrophytes interferes with water quality and ecosystem dynamics worldwide. Although mechanically removing macrophytes is the most commonly used method for their eradication, it can also cause undesirable disturbances in aquatic reservoir communities. We performed laboratory incubations of phytoplankton sampled before and after macrophytes were mechanically removed from the Piraquara II reservoir, South Brazil. We analyzed changes in growth and composition of the main phytoplankton groups with respect to nutrient shifting. Prior to removing the macrophytes, the phytoplankton community was dominated by low cell abundances of diatoms and flagellates. In contrast, growth rates of cyanobacteria (mainly Cylindrospermopsis raciborskii, Pseudanabaena sp., and Geitlerinema sp.) and of colonial chlorophytes were favored after macrophyte removal, while the abundances of diatoms and flagellates decreased. Our results suggest that removing macrophytes causes dramatic changes in phytoplankton composition and biomass and selects for toxigenic species of cyanobacteria. These changes were probably associated with the disturbance caused by removing the macrophytes, which immediately created new environmental conditions prone to species competition. These findings indicate that the use of mechanical techniques to manage macrophytes should be carefully considered, along with monitoring of harmful species and changes of limnological parameters.

Microcystins (MCs) are hepatotoxins that have been considered to be a worldwide problem due the effects that they can cause to environmental and human health systems. The Iraí Reservoir, located in the South of Brazil, is used as a water supply and MCs concentrations have been reported in this ecosystem. This study aimed to determine the MCs concentrations in the Iraí Reservoir and to evaluate the MCs depuration time and the health of Geophagus brasiliensis using biomarkers. Water and fish samples were collected in the Iraí Reservoir from August 2015 to May 2016. Phytoplankton and chemical analyses were conducted using water samples and the fish were divided into two groups; the Immediate Group (IMM) and the Depuration Group (DEP). In the IMM group, the blood, liver, muscle, brain and gills were collected, in order to evaluate the genotoxic, biochemical and chemical biomarkers. The DEP group was used in the depuration experiment for 90 days, and after this period the fish were submitted to the same procedure as the IMM group. Our results suggested that fish accumulated MCs and it may have caused oxidative stress, neurotoxicity and molecular damage. Furthermore, MCs concentrations increased during the depuration time and it resulted in molecular damage over the first 30 days. After 90 days, the recovery of the antioxidant system occurred. The depuration started on the 15th day, however, the toxins were still present in the samples. Therefore, the effects and the persistence of MCs are a risk to environmental systems and human health.

Th e toxigenic cyanobacterium Cylindrospermopsis raciborskii previously restricted to tropical latitudes, has been increasingly reported in temperate lakes in recent decades. Th e causes of its biogeographical expansion are under investigation, but effi cient physiological adaptation to changes in temperature and light regimes are likely to be involved. Th e present study evaluated the morpho-physiological responses of a strain of C. raciborskii from southern Brazil to nine light intensities, from 9 to 250 μmol photons m -2 s -1 . Blooms of this cyanobacterium are regularly recorded in the region. Morpho-physiological responses were measured based on growth rate and trichome length. Cylindrospermopsis raciborskii showed slow growth at low light intensities, 9 and 20 μmol photons m -2 s -1, and responded morphologically by increasing the length of trichomes. In turn, the strain displayed constant maximum growth rates at light intensities higher than 50 μmol photons m -2 s -1. Th ese results support the hypothesis that C. raciborskii can survive under low light conditions and continue to produce viable trichomes. Moreover, the strain achieved high growth rates under a relatively wide range of light intensities, a physiological adaptation that can potentially be a competitive advantage in the phytoplankton community.

Latin America embodies countries of special interest for ecological studies, given that areas with great value for biodiversity are located within their territories. This highlights the importance of an evaluation

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) on Podostemum from Santa Catarina, southern Brazil, including new observations on morphology and taxonomy of some rare recorded species.http://dx.doi.org/10.1590/1676-06032014003414Abstract: Eunotia is a highly diverse diatom genus in the Neotropics. Considerable morphological variability of the valve showed in several species of the genus resulted in a quite confused taxonomy. Twelve Eunotia taxa attached to Podostemum spp. were investigated using the light microscopy (LM). Additionally, scanning electron microscopy (SEM) was used in order to investigate the fine morphology of most abundant taxa. Samples were collected from four rivers from the State of Santa Catarina between March 2009 and July 2010. The freshwater diatom flora from this south Brazilian state is poorly known in relation to its neighboring states. Eunotia biseriatoides has intermediate features between Eunotia and Perinotia, and the circumscription of these genera is discussed here. Eunotia odebrechtiana is very similar in morphology to E. biseriatoides, and the synonymy is proposed, as well as the transfer of the variety E. odebrechtiana var. essequiboensis to the species E. biseriatoides. The fine structure of E. epithemioides is showed for the first time in SEM, revealing the unusual position of the rimoportula in this genus. A new variety, E. pseudosudetica var. rotundata var. nov., was proposed and compared with the typical one.Except by E. veneris, all other eleven taxa presented here are new records for the State of Santa Catarina, Brazil. Keywords: Diatom, Eunotiaceae, lotic systems, periphyton, taxonomy.CAVALCANTE, K.P., TREMARIN, P.I., CASTRO, E.C., TIBIRIÇ Á , C.E.J.A., WOJCIECHOWSKI, J., LUDWIG, T.A.V. Eunotia (Bacillariophyceae) epífitas sobre Podostemum em Santa Catarina, sul do Brasil, incluindo novas observações sobre a morfologia e taxonomia de espécies raramente registradas. Biota http://dx.doi.org/10.1590/1676-06032014003414Resumo: Eunotia é um gênero de diatomá ceas altamente diverso na regiã o neotropical. A considerá vel variabilidade morfoló gica encontrada nas valvas de vá rias espécies deste gênero resultam em uma taxonomia muito confusa. Neste estudo, 12 tá xons de Eunotia aderidos a Podostemum spp. foram investigados usando microscopia ó ptica (MO). Adicionalmente, microscopia eletrô nica de varredura (MEV) foi utilizada para investigar a morfologia ultraestrutural de tá xons mais abundantes. Amostras foram coletadas em quatro rios do Estado de Santa Catarina entre março de 2009 e julho de 2010. A diatomofló rula deste estado é pobremente conhecida em relaçã o aos estados vizinhos no sul do país. Eunotia biseriatoides é um taxon com características intermediá rias entre Eunotia e Perinotia e a circunscriçã o destes gêneros é discutida aqui. Eunotia odebrechtiana é muito similar morfologicamente a E. biseriatoides e a sinonimização é proposta, bem como a transferência da variedade E. odebrechtiana var. essequiboensis à espécie E. biseriatoides. A ultraestrutura de E. epithemioides é apresentada pela primeira vez em M...

Reservoirs are important source of power generation, recreation, and water supply. Nevertheless, human activities have favored the bloom of toxic cyanobacteria in many reservoirs, which has resulted in environmental, social, and economic problems. This study aims to evaluate the water quality of a reservoir in South Brazil through the analysis of cyanobacteria and cyanotoxins PSTs (Paralytic Shellfish Toxins) and biomarkers of environmental contamination in fish. For this purpose, water samples and fish (Geophagus brasiliensis) (Perciformes: Cichlidae) were collected from September 2013 to May 2014. The fish G. brasiliensis were separated in two groups. The first one "site group" was euthanized after the sampling and their weight and length were measured. The blood, brain, muscle and liver were collected for chemical, biochemical and genetics biomarkers analysis. The second group "depuration group" was submitted to depuration experiment for 40 days in clean water. After that, the same procedures as for the first group were carried out. Cylindrospermopsis raciborskii was the dominant cyanobacteria found in the reservoir, and it showed a density above the recommended limit by Brazilian legislation of 20,000 cells/mL. Results showed that the fish accumulate PSTs in the Reservoir and these were not eliminated after 40 days. The biochemical and genotoxic biomarkers showed a significant difference between "site groups" and "depuration groups", which suggests a recovery of the antioxidant system and a reduction of cellular damage after 40 days in clean water. In conjunction with results reported earlier by others, Alagados Reservoir, in South Brazil, appears to have a persistent contamination of cyanotoxins. Moreover, the mixture of contaminants which may be present in the water body can explain the seasonal differences in fish at the sampled points.