Jascieli Carla Bortolini

Drivers of phytoplankton richness and diversity components in Neotropical floodplain lakes, from small to large spatial scales

Understanding the distribution patterns of species and how spatial and environmental factors drive the structure of communities is crucial to the preservation of biodiversity. We evaluate, during the low and high water periods, the phytoplankton diversity in lakes of four Brazilian floodplain systems (FPs): Amazon, Araguaia, Pantanal, and Paraná. We hypothesized that (i) species variation/replacement among floodplains (β2) is the predominant mechanism in shaping phytoplankton gamma diversity; (ii) the variation in phytoplankton taxonomic composition within each floodplain (β1) is mainly governed by local environmental conditions due to the high dispersal ability of phytoplankton at small spatial scales; and (iii) variation in the phytoplankton taxonomic composition among floodplains (β2) is mainly influenced by dispersal limitation. Variation partitioning was used to evaluate the influence of spatial and environmental factors on species richness. Higher γ diversity was found in the Araguaia and Amazon FPs. The high contribution of β2 (large scale) to γ diversity revealed the high degree of environmental heterogeneity in each floodplain. β1 (small scale) was more influenced by environmental variables, and β2 by both spatial and environmental factors. Our findings showed that γ diversity was explained by the interaction between the two factors, and that these processes influencing variation were scale dependent.

Closterium Nitzsch ex Ralfs (Desmidiaceae) em um lago artificial urbano, Paraná, Brasil

An investigation of the genera Closterium from an artificial lake of Cascavel city, Parana, Brazil was undertaken. The samples were collected from January/2002 to November/2003, in the lake littoral zone. Seventeen taxa of the genera Closterium were identified, where 13 of them were typical and four of them non-typical varieties. C. cynthia De Notaris var. cynthia, represented 25% of total samples, followed by C. moniliferum (Bory) Ehrenberg ex Ralfs var. moniliferum (17%). Taxa such as C. ehrenbergii Meneghini ex Ralfs var. ehrenbergii, C. leibleinii Kutzing ex Ralfs var. leibleinii e C. lunula (Muller) Nitzsch ex Ralfs var. biconvexum Schmidle were less frequent in the analysis representing 3% of the taxon total records.

Phytoplankton functional groups in a subtropical Brazilian reservoir: responses to impoundment

The discontinuity in rivers caused by the construction of reservoirs disrupts the longitudinal gradient and decreases the natural connectivity of lotic systems. We evaluated the dynamics of Reynolds functional groups (RFGs) in response to the formation of a subtropical reservoir, in relation to the environmental changes between the pre- and post-impoundment periods. We hypothesized that the disruption of longitudinal connectivity and the changes in the light and mixing regime after the impoundment would directly influence the phytoplankton functional structure. Significant changes in the light and mixing regimes were observed after the impoundment, with the formation of a lacustrine zone, influencing the dynamics of RFGs. Fourteen RFGs were recorded. RFG C (diatoms) dominated in the pre-impoundment period. In the post-impoundment period, RFGs C, P (diatoms), and J (chlorophyceans) codominated with the highest mean values of biovolume. RFGs MP, N, H1, W2, F, E, A, W1, B, X1, and S1 contributed relatively little to the biovolume, although with higher values in the post-impoundment period. RFGs F and S1 were recorded only after the impoundment. This study revealed the important roles of physical processes and nutrients in the spatial and seasonal gradient, and in the selection of phytoplankton functional groups in a subtropical reservoir.

Desmídias (Zygnemaphyceae) do Rio São João, Parque Nacional do Iguaçu, Paraná, Brasil

Desmids (Zygnemaphyceae) of the Sao Joao River, Iguacu National Park, Parana, Brazil). This paper is a characterization of the desmid florula of the Sao Joao River, Iguacu National Park, Foz do Iguacu, Parana, Brazil. Samples were collected in the period from June 2008 to May 2009 in three sampling stations of the Sao Joao river. The samples were obtained with a 25 µm nylon plankton net was immediately fixed on Transeau solution. 44 taxa were identified distributed among the genera Actinotaenium (1), Bambusina (1), Closterium (7), Cosmarium (11), Desmidium (1), Euastrum (2), Gonatozygon (3), Micrasterias (5), Netrium (1), Octacanthium (1), Pleurotaenium (1), Spondylosium (2), Staurastrum (4), Staurodesmus (2), Teilingia (1), and Xanthidium (1). Cosmarium Corda ex Ralfs was the most representative genus in the study, with 25% of the local documented taxa.

Use of phytoplankton functional groups as a model of spatial and temporal patterns in reservoirs: a case study in a reservoir of central Brazil

We analyzed the temporal (dry and rainy periods) and spatial (zones) phytoplankton biomass variation (FGs—functional groups) in a tropical reservoir, and determined the main drivers. We hypothesized that water flow negatively affects the FG–environment relationship because high flow promotes dispersal stochasticity. Our results indicated that the FG–environment relationship was affected mainly by the rainfall regime. Periods with intermediate precipitation showed greater predictability than periods with extreme precipitation. This suggests that the effect of stochastic processes on the phytoplankton community is more important in both the highest and lowest water flow, and deterministic processes are more important at intermediate flow. The longitudinal gradient of nutrients, light, and water-column mixing influenced the distribution of the FG biomass. The riverine zone showed high nutrient concentrations, low light availability, and a high biomass of organisms related to highly enriched systems (FG J—chlorophyceans) and shade-adapted taxa (FG S1—cyanobacteria). The lacustrine zone showed high light availability and a high biomass of heterocytous cyanobacteria (FGs SN and H1) and meroplanktonic diatoms (FG MP). The functional approach can be applied to understand the processes responsible for species coexistence and for the organization of aquatic ecosystems.

Chlorococcales planctônicas do Rio São João, Parque Nacional do Iguaçu, Paraná, Brasil

This paper represents a floristic survey of the algal species in the order Chlorococcales (Chlorophyceae) from the Sao Joao River, Iguacu National Park, Foz do Iguacu, Parana, Brazil. Samples were collected from June 2008 to May 2009 at three sampling stations along the riverbed. The phytoplankton material obtained with a 25 µm nylon plankton net was immediately fixed on Transeau solution. The qualitative analyses of the samples resulted in the identification of 28 taxa distributed among the families Hydrodictyaceae, Oocystaceae, and Scenedesmaceae. The most representative genus was Desmodesmus An, Friedl & Hegewald, with ten taxa. Chlorococcum Meneghini, nom. cons., Coelastrum Nageli in Kutzing and Sorastrum Kutzing were the genera that least contributed toward the biodiversity, with only one taxon each.

Temporal dynamics of phytoplankton using the morphology-based functional approach in a subtropical river

Phytoplankton functional classification based on simple morphological traits may simplify our understanding of variation in this community as a function of environmental filters. We tested the effectiveness of the morphology-based functional group (MBFG) approach as a model of phytoplankton temporal dynamics in a Brazilian subtropical river. The São João River has an area of approximately 79.10xa0km2, with 28.09xa0km2 located within the Iguaçu National Park, in Foz do Iguaçu, Paraná, Brazil. We collected phytoplankton samples and measured environmental variables in the intermediate river section on a monthly basis between August 2008 and July 2009. We tested for differences between the environmental variables, phytoplankton biovolume and sampled months and identified the environmental variables with the greatest influence on MBFGs. Our results revealed clear temporal variability of environmental conditions in this river. We recorded the presence of seven MBFGs (I, II, III, IV, V, VI and VII) in the lotic environment, with MBFG IV (chlorococcal chlorophyceans and desmids), V (flagellates) and VI (diatoms) being the most frequent and most important groups for phytoplankton biomass. Significant temporal differences were found for MBFGs I, II, IV, V and VI, with a clear seasonal succession, especially among MBFGs V and VI. Temperature, pH, electrical conductivity, transparency and nutrients were the main predictors of MBFGs in the São João River. Approaches based on traits have been increasingly applied in community ecology, and we believe that the MBFG approach can increase our understanding of environmental dynamics as well as improve the assessment of general ecological issues.

The genus Euastrum Ehrenberg ex Ralfs (Desmidiaceae) in a subtropical stream adjacent to the Parque Nacional do Iguaçu, Paraná State, Brazil

This study aimed to document the species of Euastrum (Desmidiaceae) in a subtropical stream adjacent to an important environmental protection area, the Parque Nacional do Iguacu, in the extreme west of Parana State, Brazil. For this purpose, monthly samplings of periphytic material associated to Eleocharis minima Kunth were performed in the period between August 2012 and July 2013. This taxonomic inventory allowed the identification of 12 taxa at specific and infraespecific level. Eight new occurrences were recorded for Parana State: Euastrum attenuatum var. splendens, E. bidentatum var. bidentatum, E. cornubiense var. cornubiense, E. croasdaleae var. croasdaleae, E. denticulatum var. quadrifarium, E. didelta var. quadriceps, E. elegans var. elegans and E. evolutum var. incudiforme.

Drivers of seasonal dynamics of phytoplankton community in subtropical streams: a study case

Despite the importance of phytoplankton as a source of autochthonous organic carbon, only a few studies have explored the ecological determinants of phytoplankton community structure in lotic systems when compared with studies in lakes. Thus, the aim of this study was to assess the seasonal phytoplankton dynamics in two distinct streams located in an area of environmental protection in subtropical Brazil, and to identify the main drivers of community structure. Phytoplankton community and environmental variables were sampled on a monthly basis, between September 2012 and August 2013, in Apepu and Gualberto streams, located in Foz do Iguaçu, Paraná, Brazil. We verified that both streams presented a seasonal distinction regarding the precipitation levels. Regarding the others environmental variables (e.g., nutrients, light, temperature), a temporal similarity was observed in both streams. A high taxonomic diversity was recorded, including Bacillariophyceae, Euglenophyceae, Chlorophyceae and Zygnematophyceae as the most representative groups. Low abundance, richness and diversity were recorded in Apepu and Gualberto streams, while high equitability was recorded in both streams due to the uniform distribution of the species. Low variability of phytoplankton was recorded with high temporal similarity between the two streams. This study shows that the factors determining phytoplankton diversity and dynamics in Apepu and Gualberto streams are related not only to hydrological and limnological conditions, but also to the local characteristics of the streams, such as low depth and small extension.

Mixotrophic species influencing phytoplankton community structuring during the filling phase of a subtropical reservoir

Aiming to evaluate temporal alterations in the dynamics of the phytoplankton community in response to environmental changes occurring during the filling phase of Santa Clara reservoir, samples were taken weekly from April to June 2005 in the region close to the dam, following vertical gradients of light and temperature. Sampling depths comprised the subsurface (sup), upper limit of the euphotic zone (Zeu), lower limit of the epilimnion (Zmix) and near the bottom (Zmax). Low light availability hindered phytoplankton growth throughout the period. Descriptor species (biovolumexa0>xa05%) were classified in 17 functional groups (FGs): X2, Y, D, C, P, Lo, E, B, Na, MP, A, J, K, S1, Ws, F and M. Phytoplankton biovolume was low during the filling phase, and characterized a meso-oligotrophic environment. Mixotrophic species belonging to functional groups X2, Y, Lo and E provided the greatest contribution to total biovolume and dominated throughout the period. Water column thermal structure and a tendency of a decrease in nutrient concentrations influenced the change in the dominance of FGs. Our results suggest that mixotrophic strategy was determinant for phytoplankton production and biomass, representing a competitive advantage over strictly autotrophic phytoplankton, suggesting that during the filling phase of Santa Clara reservoir, the microbial loop played an important role in the flow of energy and carbon to higher trophic levels of the food web. Therefore, our initial hypothesis that the disruption of longitudinal connectivity in the river and alterations in the mixing regime and light availability would change phytoplankton community structure causing a replacement in the dominance of FGs containing turbulence-tolerant species by FGs containing species with a higher demand for water column stability and light availability was not corroborated. Although a species replacement was observed, this was not due to enhanced resource availability, but rather due to the trophic abilities of the FGs.