Influence of water hyacinth floating meadows on limnological characteristics in shallow subtropical waters

The effects of free-floating mats of the water hyacinth Eichhornia crassipes (Mart.) Solms on the limnological characteristics of two lakes located on the fringing floodplain of the lower Paraná River (27˚27´S, 58˚55´W) were studied monthly between April 1998 and April 1999. The mobility of the free-floating vegetation at both locations prevented continual observation. Therefore, to carry out the intensive sampling needed for this study, two experimental ponds (A and B) were filled with water from the Paraná River in 1996. Pond A was designed to reproduce conditions similar to those of lakes vegetated with water hyacinth. Pond B was designed to recreate the limnological conditions of these lakes, such as a high concentration of dissolved and fine particulate organic matter and a peat layer on the bottom; however, pond B lacked acrophytes. Natural lakes covered with free-floating vegetation were very similar to pond A, but these water bodies showed a lower temperature, dissolved oxygen level and pH and a higher conductivity than the non-vegetated pond. Our results indicated that water hyacinth has a strong local influence on the limnological conditions in subtropical shallow lakes. Our results may assist in developing causeconsequence models by demonstrating the relevance of the effect of thermal damping produced by floating meadows.Fil: Casco, Sylvina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura; ArgentinaFil: Carnevali, Romina Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura; ArgentinaFil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura; ArgentinaFil: Neiff, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin

Lagunas periurbanas de Corrientes (Argentina): de la mesotrofía a la eutrofia un camino de ida y vuelta en 20 años

More than 50,000 sub-rounded shallow lakes fed by rain are found on sandy hills fed by rain in Corrientes Province. We selected two lakes near Saladas city as representative of the wetlands prevailing in the region. The aim of this study is to describe the changes in the ecological state of Soto and Sánches lakes, from the use of the basin and recurrence of wet and dry periods. Thirty non periodic samplings were carried out in each lake between 1992 and 2014, during years with different rainfall regime. According to the annual precipitation we distinguish three periods: 1992-1999 (with high rainfalls); 2000-2010 (with prolonged droughts) and 2011-2014 (with heavy rains concentrated in autumn and spring). At both lakes the aquatic plant volume infested differed over the years. In the first period, Soto Lake became eutrophic due to illegal sewage connections from a new neighborhood. The high ratio depth/depth of the photic zone indicates the state of turbid water with dominance of cyanobacteria and high mean and maximum chlorophyll a. After operation of the treatment plant sewage, Soto Lake became characterized as mesotrophic during the dry period and subsequently oligotrophic. During the study period, Sánches Lake had clear water with a high phosphorus concentration, but it had a single bloom of cyanobacteria in the last period. In lakes fed by rain, long-term studies that include dry and wet periods allow for more accurate diagnosis of the ecological state. The use of different indicators, besides the nutrient content is recommended to determine the trophic state.Facultad de Ciencias Naturales y Muse

Lagunas periurbanas de Corrientes (Argentina): de la mesotrofía a la eutrofia un camino de ida y vuelta en 20 años

More than 50,000 sub-rounded shallow lakes fed by rain are found on sandy hills fed by rain in Corrientes Province. We selected two lakes near Saladas city as representative of the wetlands prevailing in the region. The aim of this study is to describe the changes in the ecological state of Soto and Sánches lakes, from the use of the basin and recurrence of wet and dry periods. Thirty non periodic samplings were carried out in each lake between 1992 and 2014, during years with different rainfall regime. According to the annual precipitation we distinguish three periods: 1992-1999 (with high rainfalls); 2000-2010 (with prolonged droughts) and 2011-2014 (with heavy rains concentrated in autumn and spring). At both lakes the aquatic plant volume infested differed over the years. In the first period, Soto Lake became eutrophic due to illegal sewage connections from a new neighborhood. The high ratio depth/depth of the photic zone indicates the state of turbid water with dominance of cyanobacteria and high mean and maximum chlorophyll a. After operation of the treatment plant sewage, Soto Lake became characterized as mesotrophic during the dry period and subsequently oligotrophic. During the study period, Sánches Lake had clear water with a high phosphorus concentration, but it had a single bloom of cyanobacteria in the last period. In lakes fed by rain, long-term studies that include dry and wet periods allow for more accurate diagnosis of the ecological state. The use of different indicators, besides the nutrient content is recommended to determine the trophic state.Facultad de Ciencias Naturales y Muse

Lagunas periurbanas de Corrientes (Argentina)

More than 50,000 sub-rounded shallow lakes fed by rain are found on sandy hills fed by rain in Corrientes Province. We selected two lakes near Saladas city as representative of the wetlands prevailing in the region. The aim of this study is to describe the changes in the ecological state of Soto and Sánches lakes, from the use of the basin and recurrence of wet and dry periods. Thirty non periodic samplings were carried out in each lake between 1992 and 2014, during years with different rainfall regime. According to the annual precipitation we distinguish three periods: 1992-1999 (with high rainfalls); 2000-2010 (with prolonged droughts) and 2011-2014 (with heavy rains concentrated in autumn and spring). At both lakes the aquatic plant volume infested differed over the years. In the first period, Soto Lake became eutrophic due to illegal sewage connections from a new neighborhood. The high ratio depth/depth of the photic zone indicates the state of turbid water with dominance of cyanobacteria and high mean and maximum chlorophyll a. After operation of the treatment plant sewage, Soto Lake became characterized as mesotrophic during the dry period and subsequently oligotrophic. During the study period, Sánches Lake had clear water with a high phosphorus concentration, but it had a single bloom of cyanobacteria in the last period. In lakes fed by rain, long-term studies that include dry and wet periods allow for more accurate diagnosis of the ecological state. The use of different indicators, besides the nutrient content is recommended to determine the trophic state.More than 50,000 sub-rounded shallow lakes fed by rain are found on sandy hills fed by rain in Corrientes Province. We selected two lakes near Saladas city as representative of the wetlands prevailing in the region. The aim of this study is to describe the changes in the ecological state of Soto and Sánches lakes, from the use of the basin and recurrence of wet and dry periods. Thirty non periodic samplings were carried out in each lake between 1992 and 2014, during years with different rainfall regime. According to the annual precipitation we distinguish three periods: 1992-1999 (with high rainfalls); 2000-2010 (with prolonged droughts) and 2011-2014 (with heavy rains concentrated in autumn and spring). At both lakes the aquatic plant volume infested differed over the years. In the first period, Soto Lake became eutrophic due to illegal sewage connections from a new neighborhood. The high ratio depth/depth of the photic zone indicates the state of turbid water with dominance of cyanobacteria and high mean and maximum chlorophyll a. After operation of the treatment plant sewage, Soto Lake became characterized as mesotrophic during the dry period and subsequently oligotrophic. During the study period, Sánches Lake had clear water with a high phosphorus concentration, but it had a single bloom of cyanobacteria in the last period. In lakes fed by rain, long-term studies that include dry and wet periods allow for more accurate diagnosis of the ecological state. The use of different indicators, besides the nutrient content is recommended to determine the trophic state

Lagunas periurbanas de Corrientes (Argentina): de la mesotrofía a la eutrofia un camino de ida y vuelta en 20 años

More than 50,000 sub-rounded shallow lakes fed by rain are found on sandy hills fed by rain in Corrientes Province. We selected two lakes near Saladas city as representative of the wetlands prevailing in the region. The aim of this study is to describe the changes in the ecological state of Soto and Sánches lakes, from the use of the basin and recurrence of wet and dry periods. Thirty non periodic samplings were carried out in each lake between 1992 and 2014, during years with different rainfall regime. According to the annual precipitation we distinguish three periods: 1992-1999 (with high rainfalls); 2000-2010 (with prolonged droughts) and 2011-2014 (with heavy rains concentrated in autumn and spring). At both lakes the aquatic plant volume infested differed over the years. In the first period, Soto Lake became eutrophic due to illegal sewage connections from a new neighborhood. The high ratio depth/depth of the photic zone indicates the state of turbid water with dominance of cyanobacteria and high mean and maximum chlorophyll a. After operation of the treatment plant sewage, Soto Lake became characterized as mesotrophic during the dry period and subsequently oligotrophic. During the study period, Sánches Lake had clear water with a high phosphorus concentration, but it had a single bloom of cyanobacteria in the last period. In lakes fed by rain, long-term studies that include dry and wet periods allow for more accurate diagnosis of the ecological state. The use of different indicators, besides the nutrient content is recommended to determine the trophic state.Facultad de Ciencias Naturales y Muse

Zoo-heleoplankton structure in three artificial ponds of North-eastern Argentina

The aim of the present study was to compare the abundance and species richness of zoo-heleoplankton bigger than 53 µm in an annual cycle under similar climate conditions in three artificial ponds, in order to observe the changes during an annual cycle. Samples were taken monthly from June 1993 to July 1994 in Corrientes, Argentina. The first pond (A) was covered an 80% by Eichhornia crassipes (Mart.), the second one (B) with bloom of Microcystis aeruginosa (Kurtzing) and the last one (C) with organic matter deposited in the bottom. The water was more acidic at pond A, and the water at pond B contained more dissolved oxygen concentration than the water at the other two ponds. The zoo-heleoplankton densities varied between 20-1728 ind.l-1 at pond A, 42-4082 ind.l-1 at pond B and 148-2447 ind.l-1 at pond C. The maximum zoo-heleoplankton abundance was found in the pond with cyanobacteria bloom during Autumn 1994 and the minimum abundance was found in the one with a predominance of E. crassipes. The rank of species richness was pond A > pond B > pond C. Rotifera was the most abundant group in pond A whereas the larval stages of Copepoda were abundant in the other two ponds. Anuraeopsis navicula Rousselt 1910 was the dominant population in the pond with macrophytes prevalence. Brachionus calyciflorus Pallas 1776 and larval stage of Copepoda had variable proportions in the pond with cyanobacteria bloom. Thermocyclops decipiens (Kiefer 1929) was present during the annual cycle only in the pond with organic matter deposited in the bottom. The succession of taxa was observed in the pond with coverage of aquatic macrophytes and with cyanobacteria bloom. Differences in species richness and low similarity in zoo-heleoplankton between ponds were determined by differences in the quality of the water in relation to the presence of macrophytes, cyanobacteria, organic matter deposited in the bottom and fish predation. Multiple regression analysis (stepwise) revealed that water transparency, dissolved oxygen and conductivity were the environmental variables that explained more than 42% of variability in the abundance of the dominant species

Reproductive pattern of the freshwater prawn Pseudopalaemon bouvieri (Crustacea, Palaemonidae) from hypo-osmotic shallow lakes of Corrientes (Argentina)

Pseudopalaemon bouvieri undergoes complete abbreviated development. The reproductive cycle (proportion and size of the sexually mature population and juvenile recruitment), fecundity and egg size of this prawn were examined in three subtropical shallow lakes. The reproductive cycle was seasonal; gonadal maturation occurred during the winter, ovigerous females were abundant in the spring and breeding occurred at the end of spring. Females produced small numbers of eggs (9–55) of relatively large sizes (1.0–2.1 mm). The proportion of ovigerous females with respect to the total number of females, the fecundity and egg size differed among the lakes according to the trophic state of the environments. Pseudopalaemon bouvieri has a reproductive strategy similar to other Palaemonidae species that inhabit nutrient-poor inland waters.Fil: Carnevali, Romina Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Universidad Nacional del Nordeste; ArgentinaFil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Química. Cátedra de Química General E Inorganica; ArgentinaFil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Universidad Nacional del Nordeste; Argentin

Trophic ecology of the freshwater prawn, Pseudopalaemon bouvieri (Decapoda: Palaemonidae) in Northeastern Argentina, with remarks on population structure.

Freshwater decapod crustaceans are important components of food webs in these environments, but little is known about the diet of species that live in tropical waters. We studied the feeding ecology of the prawn Pseudopalaemon bouvieri and its population structure in two different areas with six lagoons, with a different composition and abundance of aquatic macrophytes. At each site of macrophytes banks, 18 prawns sample was collected with a hand net (1mm mesh size) from 1m². In the laboratory, prawns cephalothorax length was measured, sex determined, and a total of 208 stomachs were examined for food items. Our results showed that the population abundance varied between 10 ind/m2 and 1 411 ind/m2. The cephalothorax length ranged between 6mm and 21mm, and the male:female ratio varied between 0.3 and 1.0, with a higher proportion of ovigerous females (21%) in area one than area two. P. bouvieri is omnivorous, and its diet was principally based on algae, plant remains, Protozoa, Rotifera, Oligochaeta, Crustacea, Insecta, detritus and other items. The analysis of the stomach content did not reveal any significant difference in the diet between juveniles and adults, and males and females of both areas consumed a similar diet (Kruskal-Wallis test p=0.8273). We concluded that the dietary items consumed by prawns and the niche breadth were similar between the two areas, although the proportion of items consumed varied between lagoons of both areas. The density of P. bouvieri was different between areas, but the size of cephalothorax (CL) was similarLos crustáceos decápodos de agua dulce son un componente importante de la cadena trófica, pero poco se sabe sobre la dieta de las especies que viven en aguas tropicales. Nosotros estudiamos la ecología alimentaria del camarón Pseudopalaemon bouvieri y la estructura de su población en dos áreas diferentes con seis lagunas, con una diferente composición y abundancia de macrófitas acuáticas. En cada sitio poblado con macrófitas, se tomaron 18 muestras con una red manual (1mm de tamaño de malla) de 1m². En laboratorio, se midió la longitud de cefalotórax de los camarones y se determinó el sexo. Asimismo, fueron examinados un total de 208 estómagos para determinar su alimentación. Nuestros resultados mostraron que la abundancia de la población varió entre 10 ind/m2 y 1 411 ind/ m2. La longitud de cefalotórax osciló entre 6 y 21mm, y la razón macho:hembra varió entre 0.3 y 1.0, con una mayor proporción de hembras ovígeras (21%) en el área 1 que en el área 2. P. bouvieri es omnívoro y su alimentación se basa principalmente en algas, restos de plantas, protozoos, rotíferos, Oligochaeta, crustáceos, Insecta, detrito y otros ítems. El análisis del contenido estomacal no reveló ninguna diferencia significativa en la dieta entre juveniles y adultos, y los machos y hembras de ambas áreas consumieron una dieta similar (Kruskal-Wallis, p=0.8273). Nosotros concluimos que los ítems alimentarios consumidos por los camarones y la amplitud de nicho fueron similares entre las dos áreas, aunque la proporción de ítems consumidos varió entre lagunas de ambas áreas. La densidad de P. bouvieri fue diferente entre áreas, pero el tamaño del cefalotórax (CL) fue similar

Trophic ecology of the freshwater prawn, Pseudopalaemon bouvieri (Decapoda: Palaemonidae) in Northeastern Argentina: with remarks on population structure

Freshwater decapod crustaceans are important components of food webs in these environments, but little is known about the diet of species that live in tropical waters. We studied the feeding ecology of the prawn Pseudopalaemon bouvieri and its population structure in two different areas with six lagoons, with a different composition and abundance of aquatic macrophytes. At each site of macrophytes banks, 18 prawns sample was collected with a hand net (1mm mesh size) from 1m². In the laboratory, prawns cephalothorax length was measured, sex determined, and a total of 208 stomachs were examined for food items. Our results showed that the population abundance varied between 10 ind/m² and 1 411 ind/m². The cephalothorax length ranged between 6mm and 21mm, and the male:female ratio varied between 0.3 and 1.0, with a higher proportion of ovigerous females (21%) in area one than area two. P. bouvieri is omnivorous, and its diet was principally based on algae, plant remains, Protozoa, Rotifera, Oligochaeta, Crustacea, Insecta, detritus and other items. The analysis of the stomach content did not reveal any significant difference in the diet between juveniles and adults, and males and females of both areas consumed a similar diet (Kruskal-Wallis test p=0.8273). We concluded that the dietary items consumed by prawns and the niche breadth were similar between the two areas, although the proportion of items consumed varied between lagoons of both areas. The density of P. bouvieri was different between areas, but the size of cephalothorax (CL) was similar

¿El efecto de los tipos de plantas acuáticas sobre los ensambles de invertebrados cambia en las distintas estaciones en un humedal subtropical?

La complejidad del hábitat es uno de los factores fundamentales que determinan la distribución de los ensambles de invertebrados debido a que las diferentes arquitecturas y formas de crecimiento de las plantas acuáticas afectan su abundancia, riqueza de especies, biomasa y estructura trófica. En este trabajo comparamos la abundancia y riqueza de los macroinvertebrados presentes en dos especies de plantas acuáticas con diferente arquitectura (Salvinia biloba y Egeria najas) en distintas estaciones del año. Las muestras de plantas acuáticas y los invertebrados vinculados fueron recolectadas estacionalmente en un humedal localizado en la provincia de Corrientes (Argentina) con una red de 962 cm2 de área. Para caracterizar los diferentes tipos de hábitats, se seleccionaron 12 rasgos de las plantas acuáticas, incluyendo la dimensión fractal. Un total de 15 225 invertebrados de 13 grupos mayores fueron registrados en ambos tipos de hábitats (41 familias y 24 géneros en S. biloba y 24 familias y 22 géneros en E. najas). Se hallaron diferencias estadísticamente significativas en la abundancia total (número de invertebrados por 1000 g de peso seco de vegetación) y la riqueza de taxones a nivel de familias entre tipos de hábitats. El análisis de Escalamiento Multidimensional No Métrico (NMDS) mostró diferencias en los patrones estacionales de 16 géneros de macroinvertebrados seleccionados entre ambos tipos de hábitat. El análisis de Similaridad mostró diferencias estadísticamente significativas entre tipos de hábitat y estaciones. El hábitat que presentó mayor complejidad estructural (S. biloba) albergó mayor número de taxones y de individuos por peso seco de vegetación. Las diferencias en la abundancia y riqueza de las comunidades de invertebrados entre S. biloba y E. najas fueron mantenidas en las distintas estaciones. La estructuración del hábitat por parte de las macrófitas acuáticas es un factor clave para los ensambles de macroinvertebrados y necesita ser tenida en cuenta cuando se realizan comparaciones entre humedales con diferente vegetación acuática.Habitat complexity is one of the fundamental factors determining the distribution of invertebrate assemblages due to the different architectures and growth forms of aquatic plants, which affect their abundance, species richness, biomass, and trophic structure. In this paper, we compared the abundance and richness of macroinvertebrates associated with two species of aquatic plants with different architectures (Salvinia biloba and Egeria najas) across seasons. Samples of aquatic plants and associated invertebrates were collected seasonally in a wetland located in Corrientes (Argentina) with a net area of 962cm2. To characterize the different habitat types, we selected 12 traits of aquatic plants, including fractal complexity. A total of 15 225 invertebrates from 13 major groups were recorded from both habitat types (41 families and 24 genera in S. biloba and 24 families and 22 genera in E. najas). Significant differences in the total abundance (number of invertebrates per 1000 g plant dry weight) and taxa richness at family level were found between habitat types. Non-metric multidimensional scaling reflected differences in the seasonal patterns of 16 macroinvertebrate genera selected between both habitat types. A similarity analysis showed statistically significant differences between the habitat types and seasons. Structurally more complex habitat (S. biloba) supported a greater number of taxa and the highest number of individuals per plant dry weight. The differences in the abundance and richness of the invertebrate assemblages between S. biloba and E. najas were maintained throughout the seasons. The habitat structuring of aquatic macrophytes is a key factor in macroinvertebrate communities, and it is important to keep in mind when comparing wetlands with different aquatic vegetation.Fil: Gallardo, Luciana Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Carnevali, Romina Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; ArgentinaFil: Porcel, Eduardo A.. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; ArgentinaFil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentin