Luciane Oliveira Crossetti

Vanishing world: alkaline, saline lakes in Central Europe and their diatom assemblages

Abstract European shallow, alkaline, saline lakes are potential indicators of climate change. Diatoms have often been reported as valuable proxies for different kinds of anthropogenic activities. Diatom assemblages and 14 environmental variables from shallow, alkaline lakes from 2 different regions of the Carpathian basin (Europe) were investigated for 3 years to (1) elucidate the physical and chemical parameters and diatom assemblages of these lakes, (2) select the principle variables affecting the diatom communities, and (3) show the relevance of diatoms as ecological bioindicators. Water chemical characteristics of the lakes in the 2 regions differ significantly in anion concentrations (HCO3−, SO42−, and Cl−), platinum (Pt) units (colour), and oxygen saturation. Dominance by the stress-tolerant, motile diatom ecological guild, represented mainly by Nitzschia and Navicula species, was characteristic in these saline, turbid environments. Indicator species of the 2 regions were found to be different. Diatom assemblage composition was chiefly determined by conductivity and HCO3− and SO42−concentrations. Nutrient loads, extreme weather events, and consequences of habitat maintenance management were unequivocally identifiable by variations in the benthic diatom assemblage composition. Diatoms are valuable indicators for assessment of ecological status of these saline, alkaline lakes. Including these organisms in ecological status assessments of inland saline lakes may improve the effectiveness of directives for conservation management and might be useful in preserving these pristine habitats that depend on natural hydrological processes.

Biovolume de cianobactérias e algas de reservatórios tropicais do Brasil com diferentes estados tróficos

Biovolume of Cyanobacteria and algae from Brazilian tropical reservoirs with different trophic status). The present study aimed at presenting the biovolume of planktonic and periphytic cyanobacteria and algae from reservoirs with different trophic status at Parque Estadual das Fontes do Ipiranga, Sao Paulo, Sao Paulo State, Brazil. The study includes a proposal for determining the biovolume of colonial forms of Cyanobacteria such as Microcystis and Sphaerocavum. The list of biovolume will contribute to algal ecology studies, allowing the application of this information to research in this area of knowledge, besides serving as a comparative model for other tropical ecosystems. The list comprises the biovolume of 568 taxa, including information on their taxonomic classes, maximum linear dimension and surface/volume ratio.

Coherence of phytoplankton and attached diatom-based ecological status assessment in Lake Balaton

Coherence between ecological status assessment by phytoplankton and attached diatoms was analyzed in the littoral zone of Lake Balaton. Sampling of periphytic diatoms, phytoplankton, and water were carried out at ten different littoral sites in the northern and southern shores of the lake for a year. Phytoplankton species were sorted into functional groups and ecological status was assessed by means of the phytoplankton assemblage Q index. The index TDIL was calculated using quantitative attached diatom data. Significant differences were found between the ecological assessments based on phytoplankton and phytobenthos metrics, both seasonally and spatially. The Q index indicated ecological states varying from bad to good, while the average of diatom indices varied from moderate to high conditions. The Q index provided more realistic ecological status of Lake Balaton, compared with trophic status based on TP values, especially in the summer period. Differences in the response-time indication of phytoplankton and attached diatoms suggest that lack of coherence should also be expected between the responses of other BQEs.

Influence of temperature and nutrient content on lipid production in freshwater microalgae cultures

The production of biomass by microalgae is considered a clean alternative compared to other plant crops that require large areas for cultivation and that generate environmental impacts. This study evaluated the influence of temperature and nutrients on lipid contents of cultured species of freshwater microalgae, with a view toward using these lipids for biodiesel production. Two strains of Monoraphidium contortum, a culture containing Chlorella vulgaris and Desmodesmus quadricauda and another strain of Microcystis aeruginosa were maintained in the laboratory for six days, in five culture media: modified ASM-1 (control, with high concentrations of phosphate and nitrate; phosphorus-deficient; non-limiting phosphate; nitrogen-deficient; and non-limiting nitrate). The cultures were then exposed to temperatures of 13°C, 25°C (control) and 37°C for eight days (n=3). Lipids were extracted by the cold-solvent (methanol and chloroform) method. On average, the highest total lipid yields were observed when the strains were maintained at 13°C and in the non-limiting nitrate medium. The lipid percentage varied depending on the concentration of algal biomass. This study showed that manipulation of controlling factors can increase the lipid concentration, optimizing the total production in order to use this raw material for biodiesel.

The influence of environmental variables on spatial and temporal phytoplankton dissimilarity in a large shallow subtropical lake (Lake Mangueira, southern Brazil)

AIM: The uneven distribution of organisms in aquatic ecosystems is generally attributed to environmental heterogeneity in both space and time, reflecting the occurrence of appropriate environmental conditions and the availability of resources to biological communities. The aim of this study was to understand how the dissimilarity of the phytoplankton community in a large subtropical shallow lake is related to environmental dissimilarities. METHODS: Biotic and environmental data were gathered at 19 sites along the 90-km length of Lake Mangueira. Sampling was carried out quarterly during 2010 and 2011, totaling 152 sampling units. The relationship between phytoplankton dissimilarity and the dissimilarity of environmental variables was assessed by the BioEnv analysis. MAJOR RESULTS: There is a significant relationship between phytoplankton dissimilarity and environmental dissimilarity. The model that best explained the dissimilarity of phytoplankton among the sampling units included pH, turbidity and nitrate. CONCLUSIONS: The dissimilarity of phytoplankton was related to the dissimilarity, which were directly associated to the variability of conditions and resources in space and time in Lake Mangueira.

Structure of potamoplankton along a gradient of preservation of riparian vegetation in subtropical streams

Water quality in lotic and lentic systems is greatly influenced by the land use in the adjacent areas. This study was conducted in order to assess whether different degrees of preservation of riparian forest (from well preserved with 30m wide up to degraded with < 5 m wide) influence potamoplankton community structure. The study was conducted in three streams in the upper region of the Rio dos Sinos basin, at four sampling sites, with different width of the forest. Samplings were gathered for abiotic and biological analysis in winter (August 2010) and summer (January/February 2011). The analysis of environmental and biotic variables indicated that seasonality was the main determinant of biomass patterns, regardless of the width of riparian vegetation. The potamoplankton community of the studied streams responded to environmental conditions, although lack of significant difference among the different degrees of riparian vegetation preservation has been observed. Increasing trends on biomass, richness and diversity of species, and higher concentrations of total phosphorus and nitrogen in the non-preserved areas might indicate that the different gradients of preservation of riparian vegetation are related with the water quality in subtropical streams and consequently with the potamoplankton structure.

Environmental dissimilarity over time in a large subtropical shallow lake is differently represented by phytoplankton functional approaches

The aim of the present study was to understand how different phytoplankton functional approaches responded to environmental variability in a large shallow lake, namely Lake Mangueira, in southern Brazil. This coastal lake has a maximum depth of 7m and is ~90km long and ~3–10km wide. Physical and chemical variables, maximum linear dimension, life forms, functional and morphofunctional groups of phytoplankton were analysed. The results showed that the phytoplankton were primarily comprised Cyanobacteria (63.9%), followed by middle-sized algae (21–50μm; 46.7%) and colonial non-flagellated taxa (63%). The highest percentage of total biomass was accounted for by the functional group ‘K’ (as classified by Reynolds et al. 2002; 36.3%), large mucilaginous colonies (46.79%) according to morphologically based functional classification and other large colonies (mostly non-vacuolated; 36.7%) according to morphofunctional classification. Dissimilarity analysis indicated a significant correlation between abiotic data and functional approaches (P=0.001). The dissimilarity in the functional compositions of phytoplankton was related to nutrient and light conditions, especially to silicon content and water transparency, in all functional approaches. The highest correlation with abiotic variables was seen for morphologically based functional group community structure, although the functional group composition of phytoplankton sensu Reynolds et al. seemed to be the most effective system in describing environmental variability in Lake Mangueira over the long term.

Taxonomic and functional nestedness patterns of phytoplankton communities among coastal shallow lakes in southern Brazil

 UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL (UFRGS), INSTITUTO DE PESQUISAS HIDRÁULICAS (IPH), AVENIDA BENTO GONÇALVES, , PORTO ALEGRE, RS -, BRAZIL, UNIVERSIDADE FEDERAL DO RIO GRANDE–FURG, INSTITUTO DE CIÊNCIAS BIOLÓGICAS, AVENIDA ITÁLIA, KM , RIO GRANDE, RS -, BRAZIL AND UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL (UFRGS), DEPARTAMENTO DE ECOLOGIA, INSTITUTO DE BIOCIÊNCIAS, AVENIDA

Everything is not everywhere: a tale on the biogeography of cyanobacteria

Microrganisms such as cyanobacteria have been often considered as exhibiting wide distribution mainly driven by environmental heterogeneity. Recently, however, new findings have evoked the role of previously neglected processes, such as dispersal limitation, determining the distribution of a wide range of microorganisms, including cyanobacteria. Here, we reviewed the biogeographic patterns of cyanobacteria with focus on molecular data and the evidences from the published literature for the processes driving these patterns. Also, considerations are made about concept of species, discordances in the taxonomic concepts, and level of taxonomic resolution, and how these affect the biogeographic study of cyanobacteria. From a overview, it can be observed that both environmental and historical factors are important to structure cyanobacteria diversity across time and space. Moreover, different species may exhibit significant differences in their distribution patterns, from possibly cosmopolitan species to other endemic species. However, distribution patterns are closely dependent on the concept of species, besides the taxonomic resolution, spatial and environmental scales, and the biases of the molecular methodologies applied in the studies. Thus, efforts to broaden sampling and sequencing of unknown and less-known species, as well as geographic regions and habitats poorly exploited, are crucial for a better understanding of cyanobacteria biogeography.