Common and Rare Taxa of Planktonic Ciliates: Influence of Flood Events and Biogeographic Patterns in Neotropical Floodplains.

After much discussion about the cosmopolitan nature of microbes, the great issue nowadays is to identify at which spatial extent microorganisms may display biogeographic patterns and if temporal variation is important in altering those patterns. Here, planktonic ciliates were sampled from shallow lakes of four Neotropical floodplains, distributed over a spatial extent of ca. 3000 km, during high and low water periods, along with several abiotic and biotic variables potentially affecting the ciliate community. We found that common ciliate species were more associated with environmental gradients and rare species were more related to spatial variables; however, this pattern seemed to change depending on the temporal and spatial scales considered. Environmental gradients were more important in the high waters for both common and rare species. In low waters, common species continued to be mainly driven by environmental conditions, but rare species were more associated with the spatial component, suggesting dispersal limitation likely due to differences in dispersal ability and ecological tolerance of species. We also found that common and rare species were related to different environmental variables, suggesting different ecological niches. At the largest spatial extents, rare species showed clear biogeographic patterns.

Revealing the hidden threats: Genotoxic effects of microplastics on freshwater fish.

New evidence regarding the risks that microplastics (MP) ingestion pose to human and wildlife health are being revealed with progress made in ecotoxicological research. However, comprehensive and realistic approaches that evaluate multiple physiological responses simultaneously are still scarce despite their relevance to understand whole-organism effects. To address this information gap, we performed an experiment to assess the effects of MP on freshwater fish physiology from the molecular to the organismal level. Using a model species of global commercial importance (Cyprinus carpio) and MP type (recycling industry fragments), size (range between 125-1000 µm), and two concentrations of environmental relevance (0.75 and 8.25 µg/L). Experimental design included 5 blocks containing 3 treatment levels each one: control, low, and high MP concentration, with 6 fish each aquarium (5 blocks x 3 treatments x 6 fish per aquarium = 90 fish). Our results suggest that, under the experimental conditions applied, MP exposure did not cause adverse effects at the morphological (variation in size of gut), metabolic (variation of standard metabolic rate), or ecological (growth performance) levels. Nonetheless, we observed an increased frequency of micronucleated cells with increasing MP concentration (df = 42, t-value = 3.68, p-value < 0.001), showing the potential genotoxicity of MP, which can clearly harm fish health in long-term. Thus, despite being a highly resistant species, exposure to MP may generate negative effects in juvenile C. carpio at cellular or subcellular levels. Our findings highlight that the manifestation of MP effects may vary over time, emphasizing the need for future studies to consider longer exposure durations in experimental designs.

Experimental warming promotes phytoplankton species sorting towards cyanobacterial blooms and leads to potential changes in ecosystem functioning.

A positive feedback loop where climate warming enhances eutrophication and its manifestations (e.g., cyanobacterial blooms) has been recently highlighted, but its consequences for biodiversity and ecosystem functioning are not fully understood. We conducted a highly replicated indoor experiment with a species-rich subtropical freshwater phytoplankton community. The experiment tested the effects of three constant temperature scenarios (17, 20, and 23 °C) under high-nutrient supply conditions on community composition and proxies of ecosystem functioning, namely resource use efficiency (RUE) and CO2 fluxes. After 32 days, warming reduced species richness and promoted different community trajectories leading to a dominance by green algae in the intermediate temperature and by cyanobacteria in the highest temperature treatments. Warming promoted primary production, with a 10-fold increase in the mean biomass of green algae and cyanobacteria. The maximum RUE occurred under the warmest treatment. All treatments showed net CO2 influx, but the magnitude of influx decreased with warming. We experimentally demonstrated direct effects of warming on phytoplankton species sorting, with negative effects on diversity and direct positive effects on cyanobacteria, which could lead to potential changes in ecosystem functioning. Our results suggest potential positive feedback between the phytoplankton blooms and warming, via lower net CO2 sequestration in cyanobacteria-dominated, warmer systems, and add empirical evidence to the need for decreasing the likelihood of cyanobacterial dominance.

Plastic debris decrease fish feeding pressure on tropical reefs.

Fish feeding on the benthos mediate important ecological processes in reef ecosystems that are threatened by several anthropogenic activities, including plastic pollution. The impacts of plastic pollution on reef ecological processes, such as herbivory, is still unclear. We experimentally tested in the field how the presence of plastic on the benthos affects fish feeding by using a blocked design to compare fish feeding within 1m2 plastic-free areas and areas with either clean plastic or plastic colonized with biofilm in reefs of NE Brazil. Each area was videoed for 10 min, through which we identified fish species, estimated sizes and quantified the number of bites and feeding frequency. The presence of plastic reduced fish feeding on the benthos, regardless of the biofilm presence, and fish barely interacted with plastic debris. Our results demonstrate that the impact of plastic goes beyond entanglement and ingestion, affecting species behavior and ecological role.

Advances in studies on testate amoebae (Arcellinida and Euglyphida): a scientometric approach / Avanços nos estudos sobre amebas testáceas (Arcellinida e Euglyphida): uma abordagem cienciométrica

Testate amoebae have a great potential for use in scientific researches due to their ecological characteristics such as abundance, wealth, and generation time. In this way, this study aimed to present a scientometric analysis to describe the evolution of the different advances in researches on testate amoebae and identify a temporal pattern in this evolution. The literature review was based on papers indexed by Thomson Reuters (www.isiwebofknowledge.com) and SciVerse Scopus (www.scopus.com). In total 562 papers were examined. Results showed a pattern of evolution in scientific studies, most with ecological approach with descriptive and predictive designs. At the global level, researches on testate amoebae progressed in both the number of articles published as well as in the areas studied, especially in Europe and North America. The low number of experimental studies and review articles can characterize the lack of more knowledge to be acquired, both from particular observations (descriptive studies) as well as the observations noted sufficiently predictive of work. In Brazil, studies with testate amoebae are still developing, concentrated in only some regions, but the increased number of studies in recent years allows the prediction of the same overall patterns of advance for Brazilian researches. Thus, we conclude that these organisms are being increasingly used as a tool response in ecological studies.

Amebas testáceas possuem grande potencial de utilização em pesquisas de caráter científico pelas suas características ecológicas como abundância, riqueza, e tempo de geração. Nesse sentido, o objetivo do presente estudo foi apresentar uma análise cienciométrica, a fim de descrever a evolução das diferentes abordagens nas pesquisas de tecamebas e identificar um padrão temporal nessa evolução. A revisão dos artigos científicos foi realizada com base nos artigos indexados pela base Thomson Reuters (www.isiwebofknowledge.com) e pela base SciVerse Scopus (www.scopus.com). Foram analisados 562 artigos científicos. Os resultados demonstraram um padrão de evolução nos trabalhos científicos, sendo a maioria de cunho ecológico com delineamentos descritivos e preditivos. Em âmbito global, as pesquisas com tecamebas apresentaram evolução tanto no número de artigos publicados bem como nas áreas estudadas, principalmente na Europa e América do Norte. O baixo número de trabalhos experimentais e de revisão pode caracterizar a falta de maiores conhecimentos a serem ainda adquiridos, tanto a partir das observações particulares (trabalhos descritivos) bem como das observações suficientemente constatadas dos trabalhos preditivos. No Brasil, as pesquisas com amebas testáceas ainda estão em processo de desenvolvimento, concentradas em apenas algumas regiões. Entretanto, o aumento no número de publicações nos últimos anos possibilita a previsão dos mesmos padrões de evolução globais para as pesquisas brasileiras. Assim, é possível concluir que esses organismos estão sendo cada vez mais utilizados como ferramenta resposta nos estudos ecológicos.