http://sedici.unlp.edu.ar:80/handle/10915/68854 2026-07-21T11:17:59Z 2026-07-21T11:17:59Z Instituto de Limnología "Raúl A. Ringuelet" http://sedici.unlp.edu.ar:80/handle/10915/69005 2019-04-06T04:04:16Z 2012-01-01T00:00:00Z

Edicion de revista VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 Trabajos completos presentados en el "VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos", Santa Rosa, La Pampa, diciembre de 2010. Editores: Santiago A. Echaniz y Alicia M. Vignatti.

2012-01-01T00:00:00Z Trabajos completos presentados en el "VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos", Santa Rosa, La Pampa, diciembre de 2010. Editores: Santiago A. Echaniz y Alicia M. Vignatti. Vignatti, Alicia Paggi, J. C. Echaniz, Santiago Andrés Cabrera, Gabriela Cecilia http://sedici.unlp.edu.ar:80/handle/10915/69004 2019-04-06T04:04:21Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 The zooplankton of the saline lakes of central Argentina includes several native species of crustaceans. Among cladocerans, Daphnia menucoensis Paggi, 1996 and Moina eugeniae Olivier, 1954 are two of the most frequent species in these environments. However, there is no information on their ecophysiological aspects, such as tolerance to different salinities, which may contribute to a better understanding of their geographic and temporal distribution. The aim of this study was to determine the survival of neonates of both species by means of 48-h acute tests (without food or renewal of the medium) at 16 and 18 different salt concentrations. The concentration of total dissolved solids at which the most abundant populations of these species were detected under natural conditions was considered as the “control” or “optimal concentration”. M. eugeniae was more tolerant to increased salinity than D. menucoensis, since 62% of the neonates of the former survived up to 31 g.l-1, whereas more than 50% of the individuals of the latter survived up to 24 g.l-1. In salinities below the “control” concentration, the tolerance limit was different to that recorded in the field, since both species survived at concentrations below 1 g.l-1, whereas in natural conditions they were recorded only as from 7 g.l-1 (M . eugeniae) and 5 g.l-1 (D. menucoensis).

2012-01-01T00:00:00Z The zooplankton of the saline lakes of central Argentina includes several native species of crustaceans. Among cladocerans, Daphnia menucoensis Paggi, 1996 and Moina eugeniae Olivier, 1954 are two of the most frequent species in these environments. However, there is no information on their ecophysiological aspects, such as tolerance to different salinities, which may contribute to a better understanding of their geographic and temporal distribution. The aim of this study was to determine the survival of neonates of both species by means of 48-h acute tests (without food or renewal of the medium) at 16 and 18 different salt concentrations. The concentration of total dissolved solids at which the most abundant populations of these species were detected under natural conditions was considered as the “control” or “optimal concentration”. M. eugeniae was more tolerant to increased salinity than D. menucoensis, since 62% of the neonates of the former survived up to 31 g.l-1, whereas more than 50% of the individuals of the latter survived up to 24 g.l-1. In salinities below the “control” concentration, the tolerance limit was different to that recorded in the field, since both species survived at concentrations below 1 g.l-1, whereas in natural conditions they were recorded only as from 7 g.l-1 (M . eugeniae) and 5 g.l-1 (D. menucoensis). Schwerdt, Marcelo Gabriel López Cazorla, Andrea Cecilia http://sedici.unlp.edu.ar:80/handle/10915/69002 2021-03-24T19:08:23Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 The Cochicó shallow lake is part of the Encadenadas del Oeste system (Buenos Aires province, Argentina). Since 2000, the municipal state has been conducting intensive tasks to supplement silverside (Odontesthes bonariensis) fisheries stock by seeding and furtive fishing control, as part of the strategy to improve and protect the resource, in order to achieve a progressive increase of the silverside stock and quality. The aim of this study was to evaluate the silverside population of the Cochicó shallow lake and, consequently, the management policies that are being implemented on this resource. Sampling was performed on a three-month basis, from April 2007 to March 2008, using gillnets and a trawl net. The relative abundance in number was estimated with gillnet capture. Catch per unit effort (CPUE) in weight was calculated considering the fishing night as the unit effort. The size structure of the dominant species was described and the proportional stock density index (PSD) was calculated. Odontesthes bonariensis was the dominant species, with a relative abundance of more than 92%. The mean CPUE was 201.6 kg/night. This value was higher than that found in previous years (19 to 120 kg/night) using the same methodology. The dominant size ranges were 25-27 and 29-31 cm total length (Lt). The PSD were 71% and 40% for sizes with potential recreational and commercial fishing harvest, respectively. The current quality and abundance of this fishing resource is essential for the Cochicó shallow lake and is the reason why it has emerged as one of the most prestigious silverside recreational fisheries locations in Argentina.

2012-01-01T00:00:00Z The Cochicó shallow lake is part of the Encadenadas del Oeste system (Buenos Aires province, Argentina). Since 2000, the municipal state has been conducting intensive tasks to supplement silverside (Odontesthes bonariensis) fisheries stock by seeding and furtive fishing control, as part of the strategy to improve and protect the resource, in order to achieve a progressive increase of the silverside stock and quality. The aim of this study was to evaluate the silverside population of the Cochicó shallow lake and, consequently, the management policies that are being implemented on this resource. Sampling was performed on a three-month basis, from April 2007 to March 2008, using gillnets and a trawl net. The relative abundance in number was estimated with gillnet capture. Catch per unit effort (CPUE) in weight was calculated considering the fishing night as the unit effort. The size structure of the dominant species was described and the proportional stock density index (PSD) was calculated. Odontesthes bonariensis was the dominant species, with a relative abundance of more than 92%. The mean CPUE was 201.6 kg/night. This value was higher than that found in previous years (19 to 120 kg/night) using the same methodology. The dominant size ranges were 25-27 and 29-31 cm total length (Lt). The PSD were 71% and 40% for sizes with potential recreational and commercial fishing harvest, respectively. The current quality and abundance of this fishing resource is essential for the Cochicó shallow lake and is the reason why it has emerged as one of the most prestigious silverside recreational fisheries locations in Argentina. Sánchez Caro, A. Giorgi, Adonis David Nazareno Doyle, S. Piccinini, M. http://sedici.unlp.edu.ar:80/handle/10915/69001 2021-03-24T18:11:13Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 Luján River rises in the north-eastern part of Buenos Aires Province and flows through a lowland region where it joins the River Plate Estuary. The river’s upper basin comprises a rural area which is mainly used for extensive agriculture and livestock with industrial areas of minor influence. As moving downstream, densely populated urban regions develop and industrial activity increases. Samples were collected seasonally from August 2004 to August 2005 in 12 sampling sites located along the river basin, from its headwater tributaries (Los Leones y El Durazno streams) to the crossing of the national route 9, located in the river’s lower basin. In two out of the four sampling occassions, biofilm samples were taken with the aim of assesing to what extent the biofilm community fitted the degradation level indicated by the measured physical-chemical variables of the river water (particularly BOD; N; P and DO concentrations). The samples were taken with a 3 cm2 brush and piston from submerged surfaces of natural (“tosca”) or artificial substrates (piers; walls). Bacillariophyta generally dominates the biofilm, but there seems to be a relationship between the industrial and urban sewage discharges, the water quality and the relative abundance of the different biofilm groups. In the river reaches where a heavy load of effluents is discharged, an increment of Cyanophyceae is observed. In the reaches of intermediate degradation, associations of cyanophytes and euglenoids appear. Over the course of the river, the algae abundance diminishes along with the water quality degradation, but there are also reaches of recovery due to the river’s own processing capacity where no urban nor industrial wastewaters are discharged.

2012-01-01T00:00:00Z Luján River rises in the north-eastern part of Buenos Aires Province and flows through a lowland region where it joins the River Plate Estuary. The river’s upper basin comprises a rural area which is mainly used for extensive agriculture and livestock with industrial areas of minor influence. As moving downstream, densely populated urban regions develop and industrial activity increases. Samples were collected seasonally from August 2004 to August 2005 in 12 sampling sites located along the river basin, from its headwater tributaries (Los Leones y El Durazno streams) to the crossing of the national route 9, located in the river’s lower basin. In two out of the four sampling occassions, biofilm samples were taken with the aim of assesing to what extent the biofilm community fitted the degradation level indicated by the measured physical-chemical variables of the river water (particularly BOD; N; P and DO concentrations). The samples were taken with a 3 cm2 brush and piston from submerged surfaces of natural (“tosca”) or artificial substrates (piers; walls). Bacillariophyta generally dominates the biofilm, but there seems to be a relationship between the industrial and urban sewage discharges, the water quality and the relative abundance of the different biofilm groups. In the river reaches where a heavy load of effluents is discharged, an increment of Cyanophyceae is observed. In the reaches of intermediate degradation, associations of cyanophytes and euglenoids appear. Over the course of the river, the algae abundance diminishes along with the water quality degradation, but there are also reaches of recovery due to the river’s own processing capacity where no urban nor industrial wastewaters are discharged. Mancini, M. Crichigno, S. Ortiz, M. Haro, José Gustavo http://sedici.unlp.edu.ar:80/handle/10915/69000 2021-03-24T18:28:33Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 Urban lakes are environments with structural and functional features quite different from common lakes. This study aims to present the main results related to the environmental status of Villa Dalcar lake (33°06’25”S, 64°22’31”W, 7 ha), located in the city of Río Cuarto (Córdoba). In this lake, diverse activities as swimming, boating (including motorboat competitions), recreational and for human consumption fishing, removal of bait fish, research and teaching are usually performed. The lake also provides habitat for at least 16 fish species and other communities. However, there has been a significant conflict about the use of water, landscape contamination, fish mortality and different expressions of the trophic state, which was manifested by periods of clear and turbid waters. Different management measures were implemented to control aquatic macrophytes, such as mechanical removal, biomanipulation with fish using Ctenopharyngodon idella and dredging. The results have been variable depending on: the abundance of cyprinids, the activities developed in the basin and the fluctuations in water volume. The lake is a challenge as far as handling is concerned and the latter depends on a number of environmental, social and even political factors.

2012-01-01T00:00:00Z Urban lakes are environments with structural and functional features quite different from common lakes. This study aims to present the main results related to the environmental status of Villa Dalcar lake (33°06’25”S, 64°22’31”W, 7 ha), located in the city of Río Cuarto (Córdoba). In this lake, diverse activities as swimming, boating (including motorboat competitions), recreational and for human consumption fishing, removal of bait fish, research and teaching are usually performed. The lake also provides habitat for at least 16 fish species and other communities. However, there has been a significant conflict about the use of water, landscape contamination, fish mortality and different expressions of the trophic state, which was manifested by periods of clear and turbid waters. Different management measures were implemented to control aquatic macrophytes, such as mechanical removal, biomanipulation with fish using Ctenopharyngodon idella and dredging. The results have been variable depending on: the abundance of cyprinids, the activities developed in the basin and the fluctuations in water volume. The lake is a challenge as far as handling is concerned and the latter depends on a number of environmental, social and even political factors. Mancini, M. Morra, G. Salinas, V. http://sedici.unlp.edu.ar:80/handle/10915/68998 2019-04-06T04:04:35Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 The Quinto river (Popopis) originates in San Luis province and connects by channels to numerous pampean shallow lakes. In the southern region of province of Córdoba, these wetlands provide different ecological services, many of which are linked to fish fauna. However there is little literature base in this regard. In march 2010, water quality and ichthyofauna structure of Onagoity shallow lake (34°46’25 “S, 63°38’37” W, 190 ha) were evaluated. The water was oligohaline (2.30 mg/L), very hard (314 ppm CaCO3) and sulfate-chloride-sodium type. The relationship Ca+Mg/Na+K was 0.23. The average values of pH, temperature, dissolved oxygen and transparency (Secchi disk) were 8.84, 23.5 ºC, 9.7 mg/L and 0.33 m respectively. In connection to the ichthyofauna, 13 species were captured belonging to 5 orders and 9 families: Odontesthes bonariensis, Cyprinus carpio, Jenynsia multidentata, Cyphocharax voga, Astyanax eigenmanniorum, Bryconamericus iheringii, Oligosarcus jenynsii, Cheirodon interruptus, Hoplias malabaricus, Corydoras paleatus, Loricariichthys anus, Pimelodus albicans y Rhamdia quelen. The diversity indexes of Simpson and Shannon-Wiener were 0.84 and 3.04 bits respectively and Pielou equity was 0.82. Considering all of the fishing gear used, silverside O. bonariensis was the most abundant species in number (31.0%), with a length-weight relationship: W = 0.578 E-06 * StL 3,149 (n = 92, R2 = 0.99, 95% CI of b = 3.11 to 3.18) and catch per unit effort (CPUE) of 26.1 kg/net/20 hours and 165 fish/net/20 hours.

2012-01-01T00:00:00Z The Quinto river (Popopis) originates in San Luis province and connects by channels to numerous pampean shallow lakes. In the southern region of province of Córdoba, these wetlands provide different ecological services, many of which are linked to fish fauna. However there is little literature base in this regard. In march 2010, water quality and ichthyofauna structure of Onagoity shallow lake (34°46’25 “S, 63°38’37” W, 190 ha) were evaluated. The water was oligohaline (2.30 mg/L), very hard (314 ppm CaCO3) and sulfate-chloride-sodium type. The relationship Ca+Mg/Na+K was 0.23. The average values of pH, temperature, dissolved oxygen and transparency (Secchi disk) were 8.84, 23.5 ºC, 9.7 mg/L and 0.33 m respectively. In connection to the ichthyofauna, 13 species were captured belonging to 5 orders and 9 families: Odontesthes bonariensis, Cyprinus carpio, Jenynsia multidentata, Cyphocharax voga, Astyanax eigenmanniorum, Bryconamericus iheringii, Oligosarcus jenynsii, Cheirodon interruptus, Hoplias malabaricus, Corydoras paleatus, Loricariichthys anus, Pimelodus albicans y Rhamdia quelen. The diversity indexes of Simpson and Shannon-Wiener were 0.84 and 3.04 bits respectively and Pielou equity was 0.82. Considering all of the fishing gear used, silverside O. bonariensis was the most abundant species in number (31.0%), with a length-weight relationship: W = 0.578 E-06 * StL 3,149 (n = 92, R2 = 0.99, 95% CI of b = 3.11 to 3.18) and catch per unit effort (CPUE) of 26.1 kg/net/20 hours and 165 fish/net/20 hours. Llamazares Vegh, S. Villatarco Vázquez, A. P. Kunert, M. C. Tombari, A. D. http://sedici.unlp.edu.ar:80/handle/10915/68949 2019-04-06T04:04:40Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 The urban wetlands are sites of high biodiversity that are under a great anthropogenic pressure. In the city of Buenos Aires, one of the more important areas of recreation is constituted by Parque Tres de Febrero (well-known as like “Bosques de Palermo”), that conforms a green zone of 25 ha. In this area there are artificial wetlands of diverse physical characteristics. In the present work, the goal is to determine vertebrate’s diversity in these urban aquatic enviroments in order to evaluate the degree of impact of the recreational activity on the conservation of the vertebrates associated to the water bodies. The study was carried out in three artificial lagoons included in the park: Regatas, Rosedal and Planetario. Altogether, seventeen species of fish (Prochilodus lineatus, Oligosarcus jenynsii, Cheirodon interruptus, Bryconamericus iheringii, Hoplias malabaricus, Hypostomus commersoni, Rhamdia quelen, Pimelodus albicans, Pimelodus maculatus, Cyprinus carpio carpio, Cnesterodon decemmaculatus, Gambusia affinis, Jenynsia multidentata, Synbranchus marmoratus, Australoheros facetus, Gymnogeophagus meridionalis and Crenicichla scottii), eighteen species of birds (Podiceps rolland, Podilymbus podiceps, Podiceps major, Phalacrocorax olivaceus, Ardea alba, Egretta thula, Butorides striatus, Nycticorax nycticorax, Anas georgica, Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser, Cairina moschata, Netta peposaca, Aramus guarauna, Fulica armillata, Fulica leucoptera and Chloroceyle amazona), three species of turtles (Phrynops hilarii, Trachemys scripta elegans and Trachemys venusta) and one species of mammal were registered (Myocastor coipo). Among these species, eight are introduced: two fishes (Cyprinus carpio carpio and Gambusia affinis), two turtles (Trachemys scripta elegans and Trachemys venusta) and four birds (Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser and Cairina moschata). Regatas was the site with greater diversity of fishes (n=17) that represents a 10.43% of Río de la Plata’s ichthyofauna (n=163). This site lodges a 13% of the bird species associated to registered water bodies in the City of Buenos Aires (n=107). When comparing the specific richness among lagoons, we found high similarity between Regatas and Planetarium. Also, both sites presented the greatest specific richness of fish during the months of January and February. From this preliminary study it was possible to describe and to differentiate each lagoon by its fauna and physical characteristics, and also it constitutes the base to continue with further studies of communities which allow the development of the necessary guidelines of handling for the protection of Lagos Tres de Febrero.

2012-01-01T00:00:00Z The urban wetlands are sites of high biodiversity that are under a great anthropogenic pressure. In the city of Buenos Aires, one of the more important areas of recreation is constituted by Parque Tres de Febrero (well-known as like “Bosques de Palermo”), that conforms a green zone of 25 ha. In this area there are artificial wetlands of diverse physical characteristics. In the present work, the goal is to determine vertebrate’s diversity in these urban aquatic enviroments in order to evaluate the degree of impact of the recreational activity on the conservation of the vertebrates associated to the water bodies. The study was carried out in three artificial lagoons included in the park: Regatas, Rosedal and Planetario. Altogether, seventeen species of fish (Prochilodus lineatus, Oligosarcus jenynsii, Cheirodon interruptus, Bryconamericus iheringii, Hoplias malabaricus, Hypostomus commersoni, Rhamdia quelen, Pimelodus albicans, Pimelodus maculatus, Cyprinus carpio carpio, Cnesterodon decemmaculatus, Gambusia affinis, Jenynsia multidentata, Synbranchus marmoratus, Australoheros facetus, Gymnogeophagus meridionalis and Crenicichla scottii), eighteen species of birds (Podiceps rolland, Podilymbus podiceps, Podiceps major, Phalacrocorax olivaceus, Ardea alba, Egretta thula, Butorides striatus, Nycticorax nycticorax, Anas georgica, Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser, Cairina moschata, Netta peposaca, Aramus guarauna, Fulica armillata, Fulica leucoptera and Chloroceyle amazona), three species of turtles (Phrynops hilarii, Trachemys scripta elegans and Trachemys venusta) and one species of mammal were registered (Myocastor coipo). Among these species, eight are introduced: two fishes (Cyprinus carpio carpio and Gambusia affinis), two turtles (Trachemys scripta elegans and Trachemys venusta) and four birds (Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser and Cairina moschata). Regatas was the site with greater diversity of fishes (n=17) that represents a 10.43% of Río de la Plata’s ichthyofauna (n=163). This site lodges a 13% of the bird species associated to registered water bodies in the City of Buenos Aires (n=107). When comparing the specific richness among lagoons, we found high similarity between Regatas and Planetarium. Also, both sites presented the greatest specific richness of fish during the months of January and February. From this preliminary study it was possible to describe and to differentiate each lagoon by its fauna and physical characteristics, and also it constitutes the base to continue with further studies of communities which allow the development of the necessary guidelines of handling for the protection of Lagos Tres de Febrero. Galea, María J. Álvarez, S. B. Bazán, Graciela Inés Martínez de Fabricius, A. L. http://sedici.unlp.edu.ar:80/handle/10915/68948 2019-04-06T04:04:43Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 This work presents preliminary taxonomic information of the phytoplankton community of the Colorado river, the natural boundary between the provinces of La Pampa and Río Negro. With the objective to know and categorize the algal communities of phytoplankton, samples were collected in Villa Vieja, on the left bank. The study area is located at 38º 14’ 55’’ lat. S; 67° 11’ 49’’ long. W at 232 msnm, downstream of Embalse Casa de Piedra dam. The results correspond to samples taken in February 2010, the period of maximum flow. The samples were collected with plankton net of 20 microns aperture observed in vivo and then fixed in formalin (4%). For studies of diatoms aliquots of the samples and subsequent treatment for the removal of organic matter and making diatom preparations. The physicochemical and environmental were recorded in situ by using portable sensors and subsequent laboratory techniques. Of all taxa identified to the present functional groups recorded were: 32.7% Bacillariophyceae, Chlorophyceae 44.3%, Cyanophyceae 11.5% and 11.5% other algae remaining partners, including Euglenophyceae.

2012-01-01T00:00:00Z This work presents preliminary taxonomic information of the phytoplankton community of the Colorado river, the natural boundary between the provinces of La Pampa and Río Negro. With the objective to know and categorize the algal communities of phytoplankton, samples were collected in Villa Vieja, on the left bank. The study area is located at 38º 14’ 55’’ lat. S; 67° 11’ 49’’ long. W at 232 msnm, downstream of Embalse Casa de Piedra dam. The results correspond to samples taken in February 2010, the period of maximum flow. The samples were collected with plankton net of 20 microns aperture observed in vivo and then fixed in formalin (4%). For studies of diatoms aliquots of the samples and subsequent treatment for the removal of organic matter and making diatom preparations. The physicochemical and environmental were recorded in situ by using portable sensors and subsequent laboratory techniques. Of all taxa identified to the present functional groups recorded were: 32.7% Bacillariophyceae, Chlorophyceae 44.3%, Cyanophyceae 11.5% and 11.5% other algae remaining partners, including Euglenophyceae. Ferrer, N. C. Cony, Noelia Leonor Fornerón, C. F. Piccolo, M. C. http://sedici.unlp.edu.ar:80/handle/10915/68947 2019-04-06T04:04:47Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 The composition and abundance of the phytoplankton in the Sauce Grande Shallow Lake were studied during the autumn of 2010. Three sampling sites were established: In the output Sauce Grande River (E1), at the entrance of the Sauce Grande River in the water body (E2) and in the deepest sector of the water body (E3). Sixty taxa were identified, belonged to Chlorophyta (50%), Heterokontophyta (27%), Cyanobacteria (20%) and Dinophyta/Euglenophyta (3%). Phytoplankton abundance ranged between 84500 and 340600 ind/ml. No differences were observed in total phytoplankton abundances among sampling stations, but significant differences among sampling dates were found. Planctonema lauterbornii Schmidle (Chlorophyta) was the dominant species with abundances up to 70600 ind/ml. Several salinity indicators (as Chaetoceros muelleri, Cyclotella aff. meneghiniana and Protoperidinium achromaticum) and eutrophication indicators (as Microcystis aeruginosa and Pediastrum boryanum) were registered. Besides, representatives of Cyanobacteria putative toxic-bloom producers (as species of Anabaena, Anabaenopsis, Aphanocapsa and Microcystis) were identified. This shallow lake is classified as eutrophic according to Carlson TSI based on chlorophyll a. The high phytoplankton abundance and the low Secchi disk readings allow defining the Sauce Grande Shallow Lake as “turbid” and phytoplankton dominated.

2012-01-01T00:00:00Z The composition and abundance of the phytoplankton in the Sauce Grande Shallow Lake were studied during the autumn of 2010. Three sampling sites were established: In the output Sauce Grande River (E1), at the entrance of the Sauce Grande River in the water body (E2) and in the deepest sector of the water body (E3). Sixty taxa were identified, belonged to Chlorophyta (50%), Heterokontophyta (27%), Cyanobacteria (20%) and Dinophyta/Euglenophyta (3%). Phytoplankton abundance ranged between 84500 and 340600 ind/ml. No differences were observed in total phytoplankton abundances among sampling stations, but significant differences among sampling dates were found. Planctonema lauterbornii Schmidle (Chlorophyta) was the dominant species with abundances up to 70600 ind/ml. Several salinity indicators (as Chaetoceros muelleri, Cyclotella aff. meneghiniana and Protoperidinium achromaticum) and eutrophication indicators (as Microcystis aeruginosa and Pediastrum boryanum) were registered. Besides, representatives of Cyanobacteria putative toxic-bloom producers (as species of Anabaena, Anabaenopsis, Aphanocapsa and Microcystis) were identified. This shallow lake is classified as eutrophic according to Carlson TSI based on chlorophyll a. The high phytoplankton abundance and the low Secchi disk readings allow defining the Sauce Grande Shallow Lake as “turbid” and phytoplankton dominated. Feijoó, J. Gantes, P. Giorgi, Adonis David Nazareno Rosso, Juan José Zunino, E. http://sedici.unlp.edu.ar:80/handle/10915/68944 2019-04-06T04:04:51Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 An Index of Riparian Quality was applied to a Pampean stream with moderate human impact (Las Flores stream, Luján river basin) to evaluate its degree of conservation. Aquatic macrophyte cover and diversity were also registered in 12 different reaches along the stream to analyze its relationship with the riparian index. In addition, the richness and diversity of the fish community were registered in two reaches with contrasting use of riparian zones and channel morphology. The results of the survey indicate that conservation of the riparian zones is difficult in the stream due to the increase of farming activities, the development of cropland near the margins, the invasion of an alien tree Gleditsia triacanthos (acacio negro) and the development of urban zones. Alteration of the riparian zone also modified the structure of the macrophyte communities and could be associated with a reduction in the richness and diversity of the fish community. We consider that the needs for conservation and recuperation of the riparian zones must be transmitted to the land owners. Activities should be coordinated to maintain the water quality and habitat diversity in order to enhance the basin health.

2012-01-01T00:00:00Z An Index of Riparian Quality was applied to a Pampean stream with moderate human impact (Las Flores stream, Luján river basin) to evaluate its degree of conservation. Aquatic macrophyte cover and diversity were also registered in 12 different reaches along the stream to analyze its relationship with the riparian index. In addition, the richness and diversity of the fish community were registered in two reaches with contrasting use of riparian zones and channel morphology. The results of the survey indicate that conservation of the riparian zones is difficult in the stream due to the increase of farming activities, the development of cropland near the margins, the invasion of an alien tree Gleditsia triacanthos (acacio negro) and the development of urban zones. Alteration of the riparian zone also modified the structure of the macrophyte communities and could be associated with a reduction in the richness and diversity of the fish community. We consider that the needs for conservation and recuperation of the riparian zones must be transmitted to the land owners. Activities should be coordinated to maintain the water quality and habitat diversity in order to enhance the basin health. Echaniz, Santiago Andrés Vignatti, Alicia Pilati, A. Kissner, S. http://sedici.unlp.edu.ar:80/handle/10915/68942 2019-04-06T04:04:57Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 Don Tomás is an urban, turbid and hypereutrophic shallow lake located in the west side of Santa Rosa. As it has an important silverside population (Odontesthes bonariensis) this lake is important for recreational and touristic activities. As many changes in many limnological parameters were observed, including zooplankton composition and abundance between 1995-96 and 2006, the main objective of this research was to compare these parameters with the ones obtained from September 2008 to August 2009. Salinity decreased along the three periods from 1.65 (1995-96) to 0.65 g.l-1 (2008-09) mainly due to the city runoff and the constant water pumping for irrigation. Water transparency also decreased from 0.24 (1995-96) to 0.14 m (2008-09). Zooplankton total richness did not change, but changes in taxonomical composition were observed when groups were separately analyzed (cladoceran richness decreased and rotifers increased during 2006. Cladoceran richness decreased from 9 species in 1995-96 to 4 in 2006, to only 2 species in 2008-2009. The same pattern was observed with copepod richness which decreased from 4 species in 2006 to only 2 species in 2008-09. Rotifer richness, on the other hand, increased from 8 species (1995-96) to 15 (2008-2009). The decreased water transparency could have been due to the lack of Daphnia (observed only in 1995-96) and the increased dominance of rotifers. Total zooplankton abundance showed important inter-annual differences, being the lowest in 2006. The obtained results reveal the wide variability of zooplankton in this type of environment.

2012-01-01T00:00:00Z Don Tomás is an urban, turbid and hypereutrophic shallow lake located in the west side of Santa Rosa. As it has an important silverside population (Odontesthes bonariensis) this lake is important for recreational and touristic activities. As many changes in many limnological parameters were observed, including zooplankton composition and abundance between 1995-96 and 2006, the main objective of this research was to compare these parameters with the ones obtained from September 2008 to August 2009. Salinity decreased along the three periods from 1.65 (1995-96) to 0.65 g.l-1 (2008-09) mainly due to the city runoff and the constant water pumping for irrigation. Water transparency also decreased from 0.24 (1995-96) to 0.14 m (2008-09). Zooplankton total richness did not change, but changes in taxonomical composition were observed when groups were separately analyzed (cladoceran richness decreased and rotifers increased during 2006. Cladoceran richness decreased from 9 species in 1995-96 to 4 in 2006, to only 2 species in 2008-2009. The same pattern was observed with copepod richness which decreased from 4 species in 2006 to only 2 species in 2008-09. Rotifer richness, on the other hand, increased from 8 species (1995-96) to 15 (2008-2009). The decreased water transparency could have been due to the lack of Daphnia (observed only in 1995-96) and the increased dominance of rotifers. Total zooplankton abundance showed important inter-annual differences, being the lowest in 2006. The obtained results reveal the wide variability of zooplankton in this type of environment. Dos Santos, Analía Casco, María Adela Claps, María Cristina http://sedici.unlp.edu.ar:80/handle/10915/68941 2019-04-06T04:05:02Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 In lotic environments, the erosion-sedimentation processes related to the hydrological conditions differ throughout the hydrological cycle, mainly due to rainfall. These processes can produce disturbances in the phytobenthic community. In canals, the current velocity and the water level are the main forcing variables that act on benthic communities, promoting changes in their structure, composition and biomass. Sediment samples were collected in the canal Mercante during two hydrological conditions: 1) at the beginning of spring, during a period of low rainfall (September 2009) and 2) in early autumn after a summer period with heavy rains (March 2010) to determine the content of organic matter, total phosphorus, chlorophyll a, and also the abundance of microphytobenthic individuals and cells. Simultaneously, some variables were measured in the water column. We identified two states of the community that could be associated with the phenomena of erosion / deposition related to the effect of water flow. In September the algal community in sediments showed a vertical architecture, mainly constituted by benthic algae among which several species had an aggregated distribution. In March, a decrease of the proportion and number of benthic algae was observed coinciding with the presence of planktonic species in sediments. Some benthic taxa exhibited similar abundances in the two periods and could be consider as tolerant to changes in flow velocity and as typical members of the canal Mercante. In conclusion, hydrological changes could have a significant role on the structure and dynamic of phytobenthon.

2012-01-01T00:00:00Z In lotic environments, the erosion-sedimentation processes related to the hydrological conditions differ throughout the hydrological cycle, mainly due to rainfall. These processes can produce disturbances in the phytobenthic community. In canals, the current velocity and the water level are the main forcing variables that act on benthic communities, promoting changes in their structure, composition and biomass. Sediment samples were collected in the canal Mercante during two hydrological conditions: 1) at the beginning of spring, during a period of low rainfall (September 2009) and 2) in early autumn after a summer period with heavy rains (March 2010) to determine the content of organic matter, total phosphorus, chlorophyll a, and also the abundance of microphytobenthic individuals and cells. Simultaneously, some variables were measured in the water column. We identified two states of the community that could be associated with the phenomena of erosion / deposition related to the effect of water flow. In September the algal community in sediments showed a vertical architecture, mainly constituted by benthic algae among which several species had an aggregated distribution. In March, a decrease of the proportion and number of benthic algae was observed coinciding with the presence of planktonic species in sediments. Some benthic taxa exhibited similar abundances in the two periods and could be consider as tolerant to changes in flow velocity and as typical members of the canal Mercante. In conclusion, hydrological changes could have a significant role on the structure and dynamic of phytobenthon. Díaz, O. Colasurdo, Viviana Guzmán, L. Grosman, Fabián Sanzano, Pablo http://sedici.unlp.edu.ar:80/handle/10915/68886 2019-04-06T04:05:06Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 In Tapalqué stream, different recreational and farming activities are developed, and on its way through Olavarría city, it receipts rainwater and sewage residues previously treated. The aim of this study is to evaluate the quality of the resource, through the determination of conventional physicochemical and bacteriological parameters, heavy metals and organochloride derivatives. Four sampling stations were monitored each 45 days (2009-2010), before and after the city, after the treatment plant and downstream near Sierra Chica town. The water was classified as oligohaline and sodium bicarbonated. Hypoxia is common at stations 3 and 4. Metals as Pb, Cd and Hg were not detected. Arsenic exceeded the allowed limits for some applications, decreasing its concentration downstream. Organochlorides substances were detected in two points, in one of them Aldrin and in the other Heptachlor and/or its derivates with values above the permitted limits. An important increase in the number of total and fecal coliform organisms in downstream stations was detected.

2012-01-01T00:00:00Z In Tapalqué stream, different recreational and farming activities are developed, and on its way through Olavarría city, it receipts rainwater and sewage residues previously treated. The aim of this study is to evaluate the quality of the resource, through the determination of conventional physicochemical and bacteriological parameters, heavy metals and organochloride derivatives. Four sampling stations were monitored each 45 days (2009-2010), before and after the city, after the treatment plant and downstream near Sierra Chica town. The water was classified as oligohaline and sodium bicarbonated. Hypoxia is common at stations 3 and 4. Metals as Pb, Cd and Hg were not detected. Arsenic exceeded the allowed limits for some applications, decreasing its concentration downstream. Organochlorides substances were detected in two points, in one of them Aldrin and in the other Heptachlor and/or its derivates with values above the permitted limits. An important increase in the number of total and fecal coliform organisms in downstream stations was detected. Bustingorry, José Fernando Escaray, Roberto Ulises Conzonno, Víctor H. http://sedici.unlp.edu.ar:80/handle/10915/68885 2019-04-06T04:05:11Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 Chascomús pond was affected between June-2001 and September-2002 by two periods of flood events (more than 8 m IGM reference) that had two maximum peaks of nearly 9 m. Such events were studied weekly in surface samples taken in three stations: centre and the zones with influence of the tributaries Vitel (affluent) and Arroyo Girado (effluent). The supply of water promoted a dilution that made the salinity to decrease to one third of the mean value of 1,570 mg/l obtained during 1999-2000. In March-2002 it was registered the maximum value of precipitation (538 mm) that caused the beginning of the second flood period. On March 18 differences were detected between the centre with the other two stations of parameters like salinity (222.5 with respect to 324.9 and 304.1 mg/l), specific conductivity (0.38; 0.55 and 0.56 mS/cm), pH (7.71; 7.94 and 8.00) and agar plate count (31,200; 7,260 and 6,600 UCF/ml). These differences were not detected in the next sampling. The phenomena is tried to explain on the basis of the runoff (physical hypothesis) and by the influence of the groundwater (chemical hypothesis). Because of the occasional separation into different quality of waters such phenomena was called “Moises effect”.

2012-01-01T00:00:00Z Chascomús pond was affected between June-2001 and September-2002 by two periods of flood events (more than 8 m IGM reference) that had two maximum peaks of nearly 9 m. Such events were studied weekly in surface samples taken in three stations: centre and the zones with influence of the tributaries Vitel (affluent) and Arroyo Girado (effluent). The supply of water promoted a dilution that made the salinity to decrease to one third of the mean value of 1,570 mg/l obtained during 1999-2000. In March-2002 it was registered the maximum value of precipitation (538 mm) that caused the beginning of the second flood period. On March 18 differences were detected between the centre with the other two stations of parameters like salinity (222.5 with respect to 324.9 and 304.1 mg/l), specific conductivity (0.38; 0.55 and 0.56 mS/cm), pH (7.71; 7.94 and 8.00) and agar plate count (31,200; 7,260 and 6,600 UCF/ml). These differences were not detected in the next sampling. The phenomena is tried to explain on the basis of the runoff (physical hypothesis) and by the influence of the groundwater (chemical hypothesis). Because of the occasional separation into different quality of waters such phenomena was called “Moises effect”. Bohn, V. Y. Piccolo, M. C. Perillo, Gerardo M. E. Pratolongo, P. D. Fornerón, C. F. http://sedici.unlp.edu.ar:80/handle/10915/68884 2019-04-06T04:05:15Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 The aim of this work was to evaluate the optical characteristics and the physical and chemicals parameters in order to determine zones in the Sauce Grande and Chasicó shallow lakes (Buenos Aires province). A portable spectroradiometer was used to obtain the reflectance spectra. The measurements were done in February, 2010. The chlorophyll-a values were obtained in laboratory from surface-derived water samples. A multiparameter probe was used to obtain the in situ parameters. Water transparency was estimated using a Secchi disc. As a result from the statistical analysis by the spectral signature from water, 3 zones were obtained in every lake. In Chasicó lake, the zone 1 represented the center-south area in the lake; the zone 2 was coincident with the NW in the lake whereas the zone 3 was related to the Chasicó river mouth. In Sauce Grande shallow lake, the subzones represented: the NNE area in the lake (zone 1); E and SE of the water body (zone 2) and the Sauce Grande river mouth (zone 3). The maximum depth in the Chasicó lake was 9 m whereas in Sauce Grande shallow lake was 1,50 m. As a consequence, the reflectance values in the Sauce Grande shallow pond surpassed the 8% and in the Chasicó lake the reflectance values did not surpass the 6%. Even though both water bodies are shallow, the effect from the bottom was more evident in the Sauce Grande lake than in Chasicó lake.

2012-01-01T00:00:00Z The aim of this work was to evaluate the optical characteristics and the physical and chemicals parameters in order to determine zones in the Sauce Grande and Chasicó shallow lakes (Buenos Aires province). A portable spectroradiometer was used to obtain the reflectance spectra. The measurements were done in February, 2010. The chlorophyll-a values were obtained in laboratory from surface-derived water samples. A multiparameter probe was used to obtain the in situ parameters. Water transparency was estimated using a Secchi disc. As a result from the statistical analysis by the spectral signature from water, 3 zones were obtained in every lake. In Chasicó lake, the zone 1 represented the center-south area in the lake; the zone 2 was coincident with the NW in the lake whereas the zone 3 was related to the Chasicó river mouth. In Sauce Grande shallow lake, the subzones represented: the NNE area in the lake (zone 1); E and SE of the water body (zone 2) and the Sauce Grande river mouth (zone 3). The maximum depth in the Chasicó lake was 9 m whereas in Sauce Grande shallow lake was 1,50 m. As a consequence, the reflectance values in the Sauce Grande shallow pond surpassed the 8% and in the Chasicó lake the reflectance values did not surpass the 6%. Even though both water bodies are shallow, the effect from the bottom was more evident in the Sauce Grande lake than in Chasicó lake. Biasotti, A. E. Álvarez, S. B. Martínez de Fabricius, A. L. http://sedici.unlp.edu.ar:80/handle/10915/68883 2019-04-06T04:05:18Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 This work is part of a larger project on the study of algal biodiversity of a lotic system in La Pampa province. In this first stage we analyze the algal flora of samples collected during the summer season and autumn of 2010. The study area is located in the floodplain of the Colorado River, the natural boundary between the provinces of La Pampa and Río Negro at its intersection with Provincial Route 11 (Department Lihuel Calel). The methodology used in the collection followed the standard parameters for lotic environments. The samples were fixed with 4% formaldehyde and deposited in the herbarium of the Faculty of Agronomy (UNLPam) under the symbol SRFA. The preliminary results of the algal flora of summer and autumn shows 64 taxa, of which 26.5% corresponds to Cyanophyceae, 36% to Chlorophyceae and Bacillariophyceae, and 1.5% to Dinophyceae. During the summer the class Chlorophyceae species contributed 40% and fall did the Bacillariophyceae with 43.7%. The 37.5% of the registered species were common to both seasons.

2012-01-01T00:00:00Z This work is part of a larger project on the study of algal biodiversity of a lotic system in La Pampa province. In this first stage we analyze the algal flora of samples collected during the summer season and autumn of 2010. The study area is located in the floodplain of the Colorado River, the natural boundary between the provinces of La Pampa and Río Negro at its intersection with Provincial Route 11 (Department Lihuel Calel). The methodology used in the collection followed the standard parameters for lotic environments. The samples were fixed with 4% formaldehyde and deposited in the herbarium of the Faculty of Agronomy (UNLPam) under the symbol SRFA. The preliminary results of the algal flora of summer and autumn shows 64 taxa, of which 26.5% corresponds to Cyanophyceae, 36% to Chlorophyceae and Bacillariophyceae, and 1.5% to Dinophyceae. During the summer the class Chlorophyceae species contributed 40% and fall did the Bacillariophyceae with 43.7%. The 37.5% of the registered species were common to both seasons. Benítez, Hernán Hugo Claps, María Cristina http://sedici.unlp.edu.ar:80/handle/10915/68858 2019-04-06T04:05:21Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 We investigated the vertical and horizontal distributions of zooplankton in the littoral zone of a pampean shallow lake: Lacombe Lake (Buenos Aires, Argentina) throughout the 24-h day in summer. A new methodology that allows to take multiple samples without disturbance and difficulty was employed for sampling sectors with submerged macrophyte beds. This lake is characterized by the presence of littoral and planktivorous ichthyofauna. Lacombe Lake exhibited high transparency owing to the presence of submerged macrophytes (Myriophyllum quitense). We observed little variation at different depths within the horizontal transects with respect to temperature, dissolved-oxygen concentration, conductivity, and pH and recorded statistically significant (ANOVA) horizontal and vertical zooplankton-abundance gradients. The majority of the small-bodied zooplankton (ciliates and rotifers) evidenced no significant variation in their horizontal or vertical distribution. Littoral cladocerans appear to migrate vertically rather than horizontally, whereas Diaphanosoma birgei exhibited significant changes in its horizontal distribution. The presence of emergent and submerged macrophytes in the littoral zone is not sufficient to promote clear differences in diurnal horizontal zooplankton migration. The differences in the diel fluctuations in particular species may be mostly dependent on specific ecological requirements, environmental conditions, and/or fish predation.

2012-01-01T00:00:00Z We investigated the vertical and horizontal distributions of zooplankton in the littoral zone of a pampean shallow lake: Lacombe Lake (Buenos Aires, Argentina) throughout the 24-h day in summer. A new methodology that allows to take multiple samples without disturbance and difficulty was employed for sampling sectors with submerged macrophyte beds. This lake is characterized by the presence of littoral and planktivorous ichthyofauna. Lacombe Lake exhibited high transparency owing to the presence of submerged macrophytes (Myriophyllum quitense). We observed little variation at different depths within the horizontal transects with respect to temperature, dissolved-oxygen concentration, conductivity, and pH and recorded statistically significant (ANOVA) horizontal and vertical zooplankton-abundance gradients. The majority of the small-bodied zooplankton (ciliates and rotifers) evidenced no significant variation in their horizontal or vertical distribution. Littoral cladocerans appear to migrate vertically rather than horizontally, whereas Diaphanosoma birgei exhibited significant changes in its horizontal distribution. The presence of emergent and submerged macrophytes in the littoral zone is not sufficient to promote clear differences in diurnal horizontal zooplankton migration. The differences in the diel fluctuations in particular species may be mostly dependent on specific ecological requirements, environmental conditions, and/or fish predation. Bazán, Graciela Inés Dalmaso, M. G. Álvarez, S. B. Martínez de Fabricius, A. L. http://sedici.unlp.edu.ar:80/handle/10915/68857 2019-04-06T04:05:26Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Santa Rosa, 2010); Biología Acuática; no. 27 This work is part of an overall project that includes the study of the dynamics of algae in aquatic ecosystems in the province of La Pampa (Argentina). The aim of this contribution is to cite the species recorded for the Arocena and determine the saprobic and water quality of the lake. From October 2006 to August 2007 these were seasonal sampled in the Arocena shallow lake (Maracó Department), La Pampa. The samples were collected at six prefixed sites with phytoplankton net opening of 25 microns mesh. The physico-chemical variables (T °C, pH, conductivity, nitrites, nitrates, dissolved oxygen, among others) were obtained using portable sensors and subsequent laboratory techniques. These parameters provided an autecological characterization of the species studied and some of them extended the range of tolerance to the literature. Of all the species listed (251), 40% were Chlorophyceae, 32% Bacillariophyceae, 22% Cyanophyceae, Euglenophyceae 3.5% and 2.5% remaining Chrysophyceae, Xanthophyceae, Cryptophyceae and Dinophyceae. The determined state was β mesosaprobic and the water quality was α mesosaprobic.

2012-01-01T00:00:00Z This work is part of an overall project that includes the study of the dynamics of algae in aquatic ecosystems in the province of La Pampa (Argentina). The aim of this contribution is to cite the species recorded for the Arocena and determine the saprobic and water quality of the lake. From October 2006 to August 2007 these were seasonal sampled in the Arocena shallow lake (Maracó Department), La Pampa. The samples were collected at six prefixed sites with phytoplankton net opening of 25 microns mesh. The physico-chemical variables (T °C, pH, conductivity, nitrites, nitrates, dissolved oxygen, among others) were obtained using portable sensors and subsequent laboratory techniques. These parameters provided an autecological characterization of the species studied and some of them extended the range of tolerance to the literature. Of all the species listed (251), 40% were Chlorophyceae, 32% Bacillariophyceae, 22% Cyanophyceae, Euglenophyceae 3.5% and 2.5% remaining Chrysophyceae, Xanthophyceae, Cryptophyceae and Dinophyceae. The determined state was β mesosaprobic and the water quality was α mesosaprobic. Avigliano, Esteban Tombari, A. Volpedo, Alejandra V. http://sedici.unlp.edu.ar:80/handle/10915/68856 2019-04-06T04:05:30Z 2012-01-01T00:00:00Z

Articulo VI Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Santa Rosa, 2010); Biología Acuática; no. 27 It has been proven that otoliths reflect morphology, morphometry and chemical composition of the environment that fish frequent. However, it has not been established if extreme environmental changes can be reflected by such structure. In this study, we analyze the morphology and morphometry of otolith sagitta of silverside (Odontesthes bonariensis) living in a setting that shows important environmental changes as Chasicó lake in Buenos Aires province (38°37.380’S- 63°4.735’W). We compared physicochemical parameters of water (pH, conductivity, ion concentration Ca2+, Mg2+ y Cl-) measured in the lake in 2010 with bibliographic data of 1999, 2003 and 2004 and different morphometric variables of silverside otoliths captured in 1998 and in 2010. The ion concentration of Ca2+, Mg2+ y Cl- increased between 11% and 90% in the period 1999-2010; the lake reduced its surface 20% in conjunction with a decrease in precipitations. We observed alterations in the distinctive morphological otolith pattern in about 18% of the individuals sampled, like irregular edges and perforations. We found a smaller width-length relation of the otolith for the year 2010 thus, indicating a decrease in its circularity. These morphological variations could be provoked by alterations in calcium carbonate deposition related to an increase in salinity and conductivity due to reduction in the surface of the lake. In conclusion, this study would indicate that morphology and morphometry of otoliths reflect environmental stress.

2012-01-01T00:00:00Z It has been proven that otoliths reflect morphology, morphometry and chemical composition of the environment that fish frequent. However, it has not been established if extreme environmental changes can be reflected by such structure. In this study, we analyze the morphology and morphometry of otolith sagitta of silverside (Odontesthes bonariensis) living in a setting that shows important environmental changes as Chasicó lake in Buenos Aires province (38°37.380’S- 63°4.735’W). We compared physicochemical parameters of water (pH, conductivity, ion concentration Ca2+, Mg2+ y Cl-) measured in the lake in 2010 with bibliographic data of 1999, 2003 and 2004 and different morphometric variables of silverside otoliths captured in 1998 and in 2010. The ion concentration of Ca2+, Mg2+ y Cl- increased between 11% and 90% in the period 1999-2010; the lake reduced its surface 20% in conjunction with a decrease in precipitations. We observed alterations in the distinctive morphological otolith pattern in about 18% of the individuals sampled, like irregular edges and perforations. We found a smaller width-length relation of the otolith for the year 2010 thus, indicating a decrease in its circularity. These morphological variations could be provoked by alterations in calcium carbonate deposition related to an increase in salinity and conductivity due to reduction in the surface of the lake. In conclusion, this study would indicate that morphology and morphometry of otoliths reflect environmental stress.