Leilane Talita Fatoreto Schwind

Use of functional diversity to assess determinant assembly processes of testate amoebae community

Abstract Functional diversity is among the main components of biodiversity, by quantifying the characteristics of organisms and by investigating which assembly processes prevail in the organisation of communities. The objective of this study was to assess the functional diversity of testate amoebae in floodplains, verifying whether the determinant assembly process of the community is related to environmental filters or the limiting similarity. We tested the hypothesis that the functional diversity of the testate amoebae would be lower than randomly expected in the hydrological periods, influenced by environmental filters. In addition, the functional diversity of the testate amoebae was expected to be strongly influenced by variables related to the productivity of the environments, since the food resources are the most important environmental factors in the assembly of testate amoeba communities. Sampling was carried out quarterly between 2002 and 2011 on the surface of the pelagic zone in six floodplain environments. Results showed that the values were lower than randomly expected according to the functional diversity indices. In addition, the functional diversity was predicted by the environmental variables related to the productivity of the environments according to multiple regression analyses. Our results highlight that functional diversity was mainly influenced by the environmental filters. The limiting similarity and neutral processes could not be totally discarded, and the three mechanisms of community assembly can occur. The environmental filters were linked to productivity and consequently to food resources, which are determinant in the assembly of the testate amoebae community, corroborating our predicted hypothesis.

Temporal dynamics and environmental predictors on the structure of planktonic testate amoebae community in four Neotropical floodplains

ABSTRACT Understanding the environmental factors that control community structure has become a major focus of ecological research in recent decades. Here, we aimed to analyze the structure of planktonic testate amoebae community and the impact of environmental variables on the diversity of planktonic species in four floodplains of Brazil (Amazonian, Araguaia, Paraná, and Pantanal) over two hydrological periods (2011 and 2012). We hypothesized that biological diversity (richness, abundance, and diversity) of the testate amoebae community is higher during drought periods. Samples were collected from the subsurface of the limnetic region of 72 lakes in the four floodplains during both drought and flood periods in both years. We identified 109 species, belonging to 11 families. Difflugiidae and Arcellidae exhibited higher species composition and abundance. ANOVA results showed noticeable temporal variation in testate amoebae community structure. We confirmed that the highest richness, abundance, and diversity were primarily recorded during drought periods, with significant differences being documented among floodplains and across the two hydrological periods. Multiple regression analysis also indicated that testate amoebae diversity is related to the productivity of the environments in the Amazonian, Araguaia, and Paraná floodplains. Depth of lakes and phosphorus appeared to be limiting factors in the Paraná and Araguaia floodplains, while dissolved oxygen limited species diversity in the Pantanal floodplain. Our results highlight that testate amoebae community exhibit the greatest biological diversity during drought periods, while species diversity is influenced by the environmental conditions (primarily productivity) of each floodplain.

Relationships between environmental conditions and the morphological variability of planktonic testate amoeba in four neotropical floodplains

Planktonic testate amoebae in floodplains exhibit a broad-range of morphological variability. The variation size is already known, but it is necessary to know how this is for morphological variables. This study aimed to identify the relationships between testate amoebae morphology and environmental factors in four neotropical floodplains. We conducted detailed morphometric analyses on 27 common species of planktonic testate amoebae from genera Arcella, Centropyxis, Cucurbitella, Suiadifflugia, Difflugia, Lesquereusia and Netzelia. We sampled subsurface water from each lake in 72 lakes in four Brazilian floodplain lakes. Our goals were to assess: (1) the range of their morphological variability (a) over space within each floodplain, and (b) among the four floodplains, and (c) over time, and (2) which environmental factors explained this variation. Mean shell height and breadth varied considerably among the different floodplain lakes, especially in the Pantanal and Amazonian floodplains. The morphological variability of testate amoeba was correlated to environmental conditions (ammonia, nitrate, phosphate, chlorophyll-a, turbidity, temperature, and depth). Thus, understanding the morphological variation of the testate amoeba species can elucidate many questions involving the ecology of these organisms. Furthermore, could help molecular studies, bioindicator role of these organisations, environmental reconstruction, among others.

Effects of nutrients increase on the copepod community of a reservoir using cages

Abstract Aim: This study investigated changes in copepod abundance and the influence of environmental variables in a reservoir with fish farming using cages, on temporal and spatial scales. We hypothesised that the copepod abundance will increase when influenced by changes in environmental variables due the increase of nutrients originating from fish farming. Methods A 120-day sampling of copepods and environmental variables was carried out in a subtropical reservoir of the Parana River basin (Rosana reservoir), upstream and downstream of three sets of cages with different fish stocking densities. A Principal Component Analysis was conducted to characterise sampling periods and points through environmental variables. The differences between copepod abundance according to sampling periods and points were tested by ANOVA. Results We observed higher maximum values for most nutrient concentrations and dissolved oxygen in the final stage of the experiment and in the location of cages installation. The copepod abundance increased sharply during the first days of the experiment and then decreased during the following periods with a tendency towards returning to the initial conditions at the final stage of the experiment. A significant difference in copepod abundance between the location of cages installation and downstream was showed. In addition, turbidity, chlorophyll-a, and nitrate significantly predicted copepod abundance. Conclusion The results suggested that the changes in copepod abundance over time are influenced by environmental variables, evidenced by the increase in nutrient concentration after the cage installation, related to the increase in the practice of fish farming. The environmental variables related to system productivity were linked to the availability of food resources. Thus, our hypothesis that copepod abundance is increased due the alterations in environmental variables caused by the increase in the practice of fish farming using cages was corroborated.

Chlorophyll-a and Suspended Inorganic Material Affecting the Shell Traitsof Testate Amoebae Community

Shell composition is considered an important functional trait in testate amoebae community. Differences in the composition of shells may represent adaptations of these organisms to changes in the availability of environmental resources. We aimed to evaluate the influence of these environmental resources on the presence of different testate amoeba species, based on observation of one important functional trait (shell composition), in floodplain environments. We hypothesised that species diversity would increase with increased availability of food (chlorophyll-a; a critical environmental requirement). We also predicted that a higher concentration of suspended inorganic material would contribute to the occurrence of species that have an exogenous shell. Testate amoeba samples were taken between 2002 and 2011 in plankton of ten floodplain environments. A significant positive correlation was noted between the concentration of chlorophyll-a and the diversity of testate amoeba species according to a simple regression analysis. Furthermore, non-metric multidimensional scaling showed distinct groups with lower and higher concentration of suspended inorganic material. The occurrence of testate amoeba species with smaller exogenous shells was the most influenced by environments with higher concentrations of suspended inorganic material. Thus, our results emphasised that the evaluated environmental resources are important as assembly factors to shell traits in testate amoebae community.