The cyanobacteria Planktothrix agardhii and Cylindrospermopsis raciborskii are bloom-forming species common in eutrophic freshwaters. These filamentous species share certain physiological traits which imply that they might flourish under similar environmental conditions. We compared the distribution of the two species in a large database (940 samples) covering different climatic regions and the Northern and Southern hemispheres, and carried out laboratory experiments to compare their morphological and physiological responses. The environmental ranges of the two species overlapped with respect to temperature, light and total phosphorus (TP); however, they responded differently to environmental gradients; C. raciborskii biovolume changed gradually while P. agardhii shifted sharply from being highly dominated to a rare component of the phytoplankton. As expected, P. agardhii dominates the phytoplankton with high TP and low light availability conditions. Contrary to predictions, C. raciborskii succeeded in all climates and at temperatures as low as 11 °C. Cylindrospermopsis raciborskii had higher phenotypic plasticity than P. agardhii in terms of pigments, individual size and growth rates. We conclude that the phenotypic plasticity of C. raciborskii could explain its ongoing expansion to temperate latitudes and suggest its future predominance under predicted climate-change scenarios.

Although reservoirs are similar to natural lakes in many respects, such driving forces as water retention time and watershed features can play important roles in the limnology of manmade lakes. With the goal of investigating how these factors influence the limnology of tropical reservoirs, physical and chemical variables were measured at four sampling sites in two reservoirs in southern Brazil, from June 2002 to June 2003. Funil Reservoir is located in one of the most-populated areas in the country, in the Paraíba do Sul river basin, which drains and drastically influences the water quality of the reservoir. In contrast, Lajes Reservoir is located in a well-preserved area, with its water retention time varying from six to 30 times longer than for Funil Reservoir. Funil Reservoir is a turbid (median euphotic zone = 4.3 m), eutrophic reservoir (median total phosphorus (TP) = 3.1 μM), with a high phytoplankton biomass (median chlorophyll-a concentration = 10.0 μg L -1 ). In contrast, Lajes Reservoir is a transparent (median euphotic zone = 9.2 m), mesotrophic water system (median TP = 1.0 μM), with a low phytoplankton biomass (median chlorophyll-a = 1.9 μg L -1 ). Both reservoirs were stratified during the summer months, but isothermy was only observed in Funil Reservoir. Because of its short water retention time, Funil Reservoir is a much more dynamic system than Lajes Reservoir, with a pronounced temporal pattern related to changes in its water column and its phytoplankton biomass. Spatial heterogeneity is more evident in Lajes Reservoir, mainly as a consequence of its location in a preserved area, long water retention time and the presence of net cages for fish culture in the waterbody. The typical spatial zonation found in reservoirs, related to nutrient sedimentation and light availability, however, is more evident in Funil Reservoir than in Lajes Reservoir. Despite the similarities between these two water systems, which are in the same geographical region with similar climate, and are comparable in size, the distinct watershed features and water retention time are responsible for marked differences between these reservoirs.

Potamoplankton attracts little research attention worldwide and this also holds true in Brazil, despite its numerous river systems. The origin and maintenance of phytoplankton populations in these systems have not been well studied. We analysed biological, physical and chemical parameters of the Paraibuna and Pomba rivers to identify the main driving forces behind temporal and spatial phytoplankton patterns. Both systems are located in the southeast, the most populated region. These rivers are similar in climate and geomorphology, and have become eutrophic due to the increase in the human population of the region, especially in Paraibuna River catchments. Twelve and eleven stations were, respectively, sampled during the dry and rainy seasons in the Paraibuna and Pomba rivers. The seasonal pattern of abiotic and biotic variables was related to the increase in the discharge and dilution caused by the rainy period. However, human influences such as the presence of a reservoir and sewage inflow were important to distinguish the rivers. The phytoplankton community of Paraibuna River was influenced by Chapéu D'Uvas Reservoir, which was dominated by a toxic population of Cylindrospermopsis raciborskii. Pomba River phytoplankton was typical of the lotic tropical systems. Phytoplankton functional groups in both rivers were those commonly found in turbid and turbulent shallow lakes. Although the functional group approach was originally described for lentic environments, our data support this approach for lotic community patterns. PHYTOPLANKTON DYNAMICS IN TROPICAL RIVERS Figure 5. Principal Component Analysis based on data from the Paraibuna and Pomba rivers during the dry and rainy periods. WT ¼water temperature, Cond: electrical conductivity, Turb ¼ turbidity, DO: dissolved oxygen, TP: total phosphorus, SRP: soluble reactive phosphorus, SRSi: soluble reactive silica, DIN: dissolved inorganic nitrogen, Chlo: chlorophyll -a, Bact: bacterioplankton. Numbers indicate sample sites

Trends in recent years have indicated that cyanobacterial blooms in tropical reservoirs are increasing in frequency, magnitude and geographical distribution. Funil Reservoir in southeastern Brazil has experienced eutrophication in the recent decades, resulting in lasting and intense toxic cyanobacterial blooms. As input of nutrients is high during the year, the aim of the present study was to evaluate the role of other variables related to changes in cyanobacterial biomass and composition. The dominant group found over the entire study period was Cyanobacteria (97% of total biomass), which contributed to low diversity. A shift of nitrogen-fixing (Anabaena circinalis and Cylindrospermopsis raciborskii) and non nitrogen-fixing (Microcystis aeruginosa) cyanobacteria was observed. Redundancy analysis indicated that physical factors such as temperature, changes in the mixing zone and light intensity were the main driving factors of the seasonal succession. Nitrogenfixing cyanobacteria dominated in periods of low light in the deepest mixing zone, and also seemed to have experienced stronger grazing effects as the density of the large zooplankton group was related to cyanobacteria biomass. M. aeruginosa bloomed in warm stratified waters, high water levels and during months with more daylight, when the zooplankton density was drastically reduced. Although the long-standing dominance of cyanobacteria may be related to high nutrient availability, the present study showed that under high and constant input of nutrients, other factors, especially physical variables, present a more plausible explanation to promote changes in species composition.KEY WORDS: Cyanobacterial bloom · Cylindrospermopsis · Microcystis · Anabaena · Zooplankton Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 57: [137][138][139][140][141][142][143][144][145][146][147][148][149] 2009 reports of surface scum have become much more numerous since the mid-20th century. Harmful algal blooms caused by cyanobacteria (CyanoHABs) are one of the most severe problems in freshwater ecosystems nowadays. These often-toxic blooms and the dense surface scums are indicative of water quality deterioration and food-web changes, and can be responsible for the mortality of fish, domestic animals and even humans (Paerl & Huisman 2009).Cyanobacteria blooms occur in waters during calm stratified conditions with high temperatures and adequate nutrient supplies (Huszar et al. 2000). Cyanobacterial dominance is mostly related to favourable bottom-up factors (Briand et al. 2002, Marinho & Huszar 2002, since they are widely known for their ability to minimize grazing pressure, through different effects on zooplankton community: mechanical interference (difficulty in manipulating and ingesting large colonies or filaments), assimilation (low amounts of essential nutrients) and toxicity (De Bernardi & Giussani 1990). However, some zooplankton species have developed physiological resistance to cyanotoxins (Fulton & Paerl 1988...

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Abstract. Abundant research has been devoted to understanding the complexity of the biogeochemical and physical processes that are responsible for greenhouse gas (GHG) emissions from hydropower reservoirs. These systems may have spatially complex and heterogeneous GHG emissions due to flooded biomass, river inflows, primary production and dam operation. In this study, we investigated the relationships between the water-air CO 2 fluxes and the phytoplanktonic biomass in the Funil Reservoir, which is an old, stratified tropical reservoir that exhibits intense phytoplankton blooms and a low partial pressure of CO 2 (pCO 2 ). Our results indicated that the seasonal and spatial variability of chlorophyll concentrations (Chl) and pCO 2 in the Funil Reservoir are related more to changes in the river inflow over the year than to environmental factors such as air temperature and solar radiation. Field data and hydrodynamic simulations revealed that river inflow contributes to increased heterogeneity during the dry season due to variations in the reservoir retention time and river temperature. Contradictory conclusions could be drawn if only temporal data collected near the dam were considered without spatial data to represent CO 2 fluxes throughout the reservoir. During periods of high retention, the average CO 2 fluxes were 10.3 mmol m −2 d −1 based on temporal data near the dam versus −7.2 mmol m −2 d −1 with spatial data from along the reservoir surface. In this case, the use of solely temporal data to calculate CO 2 fluxes results in the reservoir acting as a CO 2 source rather than a sink. This finding suggests that the lack of spatial data in reservoir C budget calculations can affect regional and global estimates. Our results support the idea that the Funil Reservoir is a dynamic system where the hydrodynamics represented by changes in the river inflow and retention time are potentially a more important force driving both the Chl and pCO 2 spatial variability than the in-system ecological factors.

Considering that scarce data are available on disease progression of feline mammary carcinoma (FMC), this study aimed to analyze the clinical, pathological, and immunophenotypic features collected from 61 queens with FMC and to compare the concordance ratios of the expression levels of five molecular markers (ER, PR, fHER2, CK5/6, and Ki-67) between primary tumors (PT) and metastatic lesions. The results showed that cats with luminal A mammary carcinomas (MC) had higher overall survival (924.6 days, p = 0.001) and longer disease-free period (385.4 days, p = 0.005) compared to the ones with other MC subtypes. In fact, queens with triple negative/basal-like MC showed the lowest survival (mean 156.2 days) and the shortest disease-free survival (mean 28 days) among the molecular subtypes of MC. The lung was the organ most frequently affected by metastases, and animals with lung and/or pleural metastases were more likely to display metastases at three or more locations (p = 0.039). A large heterogeneity in protein expression levels was found between PT and paired metastases, with both estrogen and progesterone receptors more likely to be downregulated in metastases. Paired metastases frequently had higher Ki-67 index than PT, whereas fHER2 overexpression was seen in 46 samples (30 %) and CK5/6 expression was found in 50.7 % of metastases (36/71). Results also revealed that disease progression leads to a high percentage of triple negative/basal-like metastases (9/23; 39.1 %) associated with the absence of luminal A subtype in distant metastases (0/23). This study highlights the prognostic importance of immunophenotyping of MC in cats, although the modified protein expression identified in metastases contributes to justify why possible targeted therapies may fail in some animals with metastatic disease. Altogether, the results obtained also demonstrate that FMC can be used as a model to study human breast cancer.

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