Luciana de Souza Cardoso

Hydrodynamics-driven plankton community in a shallow lake

Canonical correspondence analysis (CCA) was used to test the hypothesis that the wind-governed hydrodynamics of a shallow coastal lake is responsible for the spatial and temporal gradients of biotic and abiotic variables. Certain environmental variables, such as turbidity, suspended solids, and water level, formed seasonal spatial gradients in Itapeva Lake, southern Brazil, in response to wind action. Physical variables formed gradients more easily than did most of the plankton community, although the densities of certain species did respond to wind-driven oscillations. The results of this analysis indicate that the spatial and temporal gradients experienced by the physical, chemical, and biological descriptors displayed a characteristic property of this type of wind-driven environment. Moreover, CCA revealed that water dynamics may govern the plankton community of Itapeva Lake.Canonical correspondence analysis (CCA) was used to test the hypothesis that the wind-governed hydrodynamics of a shallow coastal lake is responsible for the spatial and temporal gradients of biotic and abiotic variables. Certain environmental variables, such as turbidity, suspended solids, and water level, formed seasonal spatial gradients in Itapeva Lake, southern Brazil, in response to wind action. Physical variables formed gradients more easily than did most of the plankton community, although the densities of certain species did respond to wind-driven oscillations. The results of this analysis indicate that the spatial and temporal gradients experienced by the physical, chemical, and biological descriptors displayed a characteristic property of this type of wind-driven environment. Moreover, CCA revealed that water dynamics may govern the plankton community of Itapeva Lake.

Rate of change of the phytoplankton community in Itapeva Lake (North Coast of Rio Grande do Sul, Brazil), based on the wind driven hydrodynamic regime

The rates of change of the phytoplankton community in Itapeva Lake distinguish periods of rapid change of phases and greater stability in the community. These rates were calculated on a spatial and temporal scale for the purpose of finding changes in response to wind action. In a spatial analysis, the rates of change of the phytoplankton presented a broader range in the North. This upper limit was recorded in spring (0.38 h−1). The rate of change in the phytoplankton community was very high on average (≥0.10 h−1) indicating the occurrence of intense, rapid environmental changes. Sudden changes in the rates occurred in a point form, due to population substitution. These substitutions resulted from wind action, alternating periods of strong sediment resuspension with periods of quiet.The rates of change of the phytoplankton community in Itapeva Lake distinguish periods of rapid change of phases and greater stability in the community. These rates were calculated on a spatial and temporal scale for the purpose of finding changes in response to wind action. In a spatial analysis, the rates of change of the phytoplankton presented a broader range in the North. This upper limit was recorded in spring (0.38 h−1). The rate of change in the phytoplankton community was very high on average (≥0.10 h−1) indicating the occurrence of intense, rapid environmental changes. Sudden changes in the rates occurred in a point form, due to population substitution. These substitutions resulted from wind action, alternating periods of strong sediment resuspension with periods of quiet.

Structure of the zooplankton community in a subtropical shallow lake (Itapeva Lake – South of Brazil) and its relationship to hydrodynamic aspects

The structure of the zooplankton community in Itapeva Lake was formed by four groups and more than 127 zooplankton species, in which microplankton was the predominant size structure. The largest richness recorded was of the protists group and in autumn seasonal campaign. Protists were characteristic of the lake, regarding density, except during spring at the Center point (copepods) and autumn at the South point (rotifers). The seasonal distribution revealed that during summer, mean density increased in the zooplankton community, exactly the opposite of phytoplankton (that blooms during the cold season). However, the maximum density was recorded during autumn. High density was recorded for the ciliate Codonella sp. at all points and during all seasons. The abundance of the tecamoeba Difflugia tuberculata was strongly associated with the maximum effects of fetch in the lake. Rotifers were generally the second most representative groups in terms of density. Rotifers and Cladocera were more abundant in summer, whereas copepods were in spring and winter/98. The Shannon–Wiener index showed that the smallest zooplankton diversity average occurred during the winter/98 (H=1.44), while in autumn the largest zooplankton diversity average (H=2.36) was observed. Correlations (r-Pearson, p<0.05) with wind velocity were significant for zooplankton density (groups and/or abundant species), diversity, and richness. The analysis of variance (ANOVA) showed a seasonally significant spatial-temporal variation for the factors sampling point, day and shift (p<0.01). Temporal alterations in density, diversity and richness were closely dependent on the hydrodynamic action induced by the wind on the spatial distribution of the zooplankton community in the Itapeva Lake.

Hydrodynamic Control of Plankton Spatial and Temporal Heterogeneity in Subtropical Shallow Lakes

During the last 200 years, many lakes have suffered from eutrophication, implying an increase of both nutrient loading and organic matter (Wetzel, 1996). An aspect that has often been neglected in freshwater systems is the fact that phytoplankton is often not evenly distributed horizontally in space in shallow lakes. Although the occurrence of phytoplankton patchiness in marine systems has been known for a long time (e.g., Platt et al., 1970; Steele, 1978; Steele & Henderson, 1992), phytoplankton in shallow lakes is often assumed to be homogeneously distributed. However, there are various mechanisms that may cause horizontal heterogeneity in shallow lakes. For example, grazing by aggregated zooplankton and other organisms may cause spatial heterogeneity in phytoplankton (Scheffer & De Boer, 1995). Submerged macrophyte beds may be another mechanism, through reduction of resuspension by wave action and allopathic effects on the algal community (Van den Berg et al., 1998). For large shallow lakes, wind can be a dominant factor leading to both spatial and temporal heterogeneity of phytoplankton (Carrick et al., 1993), either indirectly by affecting the local nutrient concentrations due to resuspended particles, or directly by resuspending algae from the sediment (Scheffer, 1998). In the management of large lakes, prediction of the phytoplankton distribution can assist the manager to decide on an optimal course of action, such as biomanipulation and regulation of the use of the lake for recreation activities or potable water supply (Reynolds, 1999). However, it is difficult to measure the spatial distribution of phytoplankton. Mathematical modeling of a phytoplankton can be an important alternative methodology in improving our knowledge regarding the physical, chemical and biological processes related to phytoplankton ecology (Scheffer, 1998; Edwards & Brindley, 1999; Mukhopadhyay & Bhattacharyya, 2006). Over the past decade there has been a concerted effort to increase the realism of ecosystem models that describe plankton production as a biological indicator of eutrophication. Most

The influence of hydrodynamics on the spatial and temporal variation of phytoplankton pigments in a large, sub-tropical coastal lake (Brazil)

This study evaluated the spatial and temporal distribution of phytoplankton pigments in Itapeva Lake and its relationship with hydrodynamic aspects. Regarding spatial distribution, a decreasing N→S gradient was generally observed for the pigments, except in summer. This inversion observed during the summer was influenced by the predominant fetch (N-E). The horizontal heterogeneity was proved (ANOVA) for all seasons of the year, except spring. Spatially in spring, the vertical variance was much more significant (p<0.05) than the horizontal one. The sampling shifts presented a permanent degree of variability among the seasons of the year, showing the existence of a diurnal cycle in the concentration of chlorophyll a. This behavior was related to the fetch, mainly from the NE and SW quadrants, disturbing the system because it is a shallow lake. This confirmed the influence of the Itapeva Lake’s hydrodynamic regime on the spatial-temporal distribution of the phytoplankton pigments.

First record of expansive Ceratium Schrank, 1793 species (Dinophyceae) in Southern Brazil, with notes on their dispersive patterns in Brazilian environments

Ceratium Schrank is a planktonic dinoflagellate ubiquitous in temperate and subtropical freshwater environments from Northern Hemisphere. Over the past two decades, Ceratium species have been recorded in South American water bodies, with expansive behavior and fast colonization. This study registered C. furcoides (Levander) Langhans and C. hirundinella (O. F. Muller) Dujardin for the first time in South Brazil. Ceratium furcoides was found in samples from States of Parana and Rio Grande do Sul and C. hirundinella occurred only in the southernmost Brazil. No co-occurrence of these species was detected on samples. The morphological variation, as well as the dispersal patterns of these species in Brazilian environments, is discussed based on LM and SEM analyses.

Dinoflagelados em diversos habitats e hidroperíodos na zona costeira do sul do Brasil

Data on richness, density, diversity and distribution of dinoflagellates in aquatic habitats (open and closed lagoons, channels, reservoirs and wetlands) during high and low water periods are presented. The study was based on 23 point samples, located on the eastern (Lagoa do Casamento area) and western (Butiazal de Tapes area) shores of Laguna dos Patos, in 2003. Eleven taxa were identified; taxon distribution was more homogeneous during the high-water period. Durinskia baltica (Levander) Carty & Cox was the only taxon whose distribution was the same for both hydroperiods. Peridinium gatunense Nygaard was a high-water indicator species and P. umbonatum Stein was an indicator of habitats associated with the Butiazal de Tapes area. This area had higher Dinophyceae diversity than the Lagoa do Casamento area, regardless of hydroperiod, due to the higher diversity and specificity of aquatic habitats. Habitat type significantly (p <0.01) influenced richness, density and diversity of dinoflagellates, and density was significantly influenced (p <0.01) by hydroperiod. Cluster analysis showed that pH and water temperature were the abiotic variables that had greater influence on the dinoflagellate populations in this study.

Towards a comprehension of Ceratium (Dinophyceae) invasion in Brazilian freshwaters: autecology of C. furcoides in subtropical reservoirs

Ceratium species are not a common component of freshwater phytoplankton in South America. However, these dinoflagellates have often been observed in many water bodies over the past two and a half decades. We investigated Ceratiumfurcoides’ abundance and morphological variation during its initial phase of colonization (2012–2013) in two subtropical reservoirs in southern Brazil in order to explore which environmental factors were related to the occurrence, persistence and bloom formation of this dinoflagellate in those environments. Biomass of C. furcoides showed a strong seasonal pattern, in which warm seasons led to an increase in population density, resulting in cell-size reduction, while in the cold seasons cells increased in volume. Maximum densities over 2,500 cells ml−1 were observed in spring–summer periods in both reservoirs. C. furcoides’ abundance in the studied reservoirs was associated, primarily, with a combination of optimal conditions of temperature, organic matter, and pH, and secondarily, with nutrient availability. The possible factors for the successful colonization performed by C.furcoides across distinct Brazilian waterbodies include good swimming performance, low herbivory pressure, and ability to form dense blooms, as strategies that allow maintenance of populations and effective dispersal.

Spatial and temporal variations of Dinophyceae in subtropical reservoirs in southern Brazil

Knowledge of dinoflagellate diversity in Brazilian reservoirs is limited, especially in subtropical environments. We investigated as to how nutrients and other environmental variables influenced the biomass of Dinophyceae species in three subtropical ecosystems. The reservoirs Samuara, Faxinal, and São Miguel were sampled fortnightly from 2002 to 2006, and eight dinoflagellate taxa were identified. High temperature was a determining factor for the occurrence of Peridinium africanum Lemmermann. Peridinium umbonatum Stein and P. willei Huitfeld-Kass required high concentrations of nutrients. P. willei was inversely related to temperature and directly related to nutrients. P. umbonatum Stein var. umbonatum Stein showed the largest range of tolerance toward resources. Durinskia baltica Carty & Cox and Peridinium gatunense Nygaard could be opportunistic, since they did not show any spatial or temporal pattern.

Periphytic diatoms show a longitudinal gradient in a large subtropical shallow lake

Some limnological differences among 3 areas in Mangueira Lake, Brazil, a large shallow oligo-mesotrophic system under continuous wind influence, were related to the wind action and influenced diatom community structure. Our goal was to investigate if wind and precipitation influence the attached communities, producing a heterogeneous diatom distribution along the lake. Sampling was performed in summers 2006 and 2008 at the North, Center, and South points of the lake. Biofilms were scraped from natural substrata for quantitative analyses; 17 species were considered abundant. The South is characterized by high transparency and high pH and is influenced by continuous wind perturbation (NE direction), both in frequency and intensity. The diatom community was characterized by low-profile guild and pioneer life-forms, which are resistant to physical disturbances. The North is shallow with high humic acids because of its proximity and interaction with the wetland, and it was characterized by high-profile and motile guilds. Interannual spatial variation was registered due the influence of continuous precipitation before the 2008 sampling date, which made the lake more homogeneous than it was in 2006. The Center acted as a transition point, which was more similar to the North in 2006 and more similar to the South in 2008. The longitudinal gradient was generated due to abiotic characteristics of the North and the South. The diatom community exhibited a longitudinal gradient N→S, and the diatom life-forms and ecological guilds were a useful tool for examining spatial heterogeneity.Abstract Some limnological differences among 3 areas in Mangueira Lake, Brazil, a large shallow oligo-mesotrophic system under continuous wind influence, were related to the wind action and influenced diatom community structure. Our goal was to investigate if wind and precipitation influence the attached communities, producing a heterogeneous diatom distribution along the lake. Sampling was performed in summers 2006 and 2008 at the North, Center, and South points of the lake. Biofilms were scraped from natural substrata for quantitative analyses; 17 species were considered abundant. The South is characterized by high transparency and high pH and is influenced by continuous wind perturbation (NE direction), both in frequency and intensity. The diatom community was characterized by low-profile guild and pioneer life-forms, which are resistant to physical disturbances. The North is shallow with high humic acids because of its proximity and interaction with the wetland, and it was characterized by high-profile and motile guilds. Interannual spatial variation was registered due the influence of continuous precipitation before the 2008 sampling date, which made the lake more homogeneous than it was in 2006. The Center acted as a transition point, which was more similar to the North in 2006 and more similar to the South in 2008. The longitudinal gradient was generated due to abiotic characteristics of the North and the South. The diatom community exhibited a longitudinal gradient N→S, and the diatom life-forms and ecological guilds were a useful tool for examining spatial heterogeneity.