Carlos Bertrán

Seasonal limnetic feeding regime of the robalo Eleginops maclovinus (Valenciennes 1830), in the Valdivia river, Chile

Eleginops maclovinus (Valenciennes, 1830) es un pez comun en el litoral, estuarios y tambien rios, preferentemente donde afectan las mareas, del sur de America del Sur, incluyendo las islas Malvinas. Se conoce su alimentacion en los dos primeros habitats, donde consume principalmente animales de ambiente marino y estuarino, donde se alimenta de fauna autoctona (mejillones, crustaceos, poliquetos, etc.). Sin embargo, se desconoce su alimentacion en ambientes limneticos, suponiendose que deberia consumir presas propias de aquellos lugares. En este estudio se analizaron 114 ejemplares de E. maclovinus, de los cuales 98 poseyeron estomagos con contenido. Se ratifico la tendencia zoofagica de la especie, pero tambien se comprobo que en ambientes limneticos consume animales propios de bajas salinidades o salinidades limneticas. El pez se presenta como una especie extraordinariamente versatil en sus capacidades troficas, con una fisiologia que le permite cubrir un amplio abanico ormorregulatorio a nivel digestivo, probablemente uno de las mas variados en el suborden Notothenioidei, de supuesto origen antartico.

Macrofauna del curso inferior y estuario del río Biobío (Chile): cambios asociados a variabilidad estacional del caudal hídrico

Uno de los sistemas loticos chilenos de mayor importancia de acuerdo a su caudal es el rio Biobio (ca. 37o S). Su estuario es reducido, especialmente en las epocas de maximo caudal. Con el objetivo de poner a prueba la hipotesis de que en verano la disminucion del caudal del rio Biobio, determina una mayor depositacion del material particulado fino y que el aumento del caudal en invierno resulta en el lavado y transporte del material depositado hacia el mar, y consecuentemente en una disminucion de la macrofauna bentonica, se recolectaron muestras para analisis sedimentologicos y faunisticos en el curso inferior y estuario del rio Biobio, durante agosto de 1993 y marzo de 1994. Los analisis sedimentologicos indican que el tamano medio del sedimento correspondio a arenas gruesas. La depositacion del material fino suspendido, que ocurre durante el verano se manifiesta en el mayor porcentaje de finos y materia organica durante este periodo. La macrofauna bentonica estuvo compuesta por 16 taxa en el muestreo de invierno y 42 taxa en el de verano. Durante el invierno, la mayoria de ellas estuvo representada por muy pocos individuos. Durante el verano aumento la riqueza especifica y abundancias totales de la macrofauna. Los taxa mas abundantes fueron un Archiannelida indeterminado y el poliqueto Perinereis gualpensis. El aumento del caudal en la epoca invernal, determina el transporte del material depositado hacia el mar y consecuentemente el arrastre de organismos bentonicos. Aun cuando los valores de abundancia y biomasa de macrofauna durante el verano fueron de un orden de magnitud mayor que en la fase invernal, fueron menores que los citados para otros estuarios del centro-sur de Chile (ca. 39o S). Eso contribuye a confirmar el caracter atipico del estuario del rio Biobio, el que debido a sus cambios estacionales de caudal genera cambios significativos en la estructura comunitaria de la macrofauna bentonica

Determinación del nivel de antropización de humedales como criterio para la planificación ecológica de la cuenca del lago Budi, IX Región de La Araucanía, Chile

The level of human impact on the wetlands of the Lago Budi Basin was established, as a function of the degree of alteration to the basin and the degree of alteration to the wetlands. The former was evaluated on the basis of a spatial analysis of the fragility and stability of the hydrographical basin. The latter through a modified impact model, with a panel of experts who evaluated the fulfilment of the wetlands’ function and their state. Four principal types of wetlands were recognized: estuarine, meadow, waterside and marshy. It was found that 98% of the total surface presents a high degree of alteration, as determined by its instability and fragility. Farm use was weighted as the principal agent of alteration of the wetlands’ functions, with 61% of this showing alteration in the maximum degree. This evaluation makes it possible to differentiate areas and generate base criteria for the conservation of wetlands in the basin.

Benthonic fauna of the Itata river and irrigation canals (Chile)

Abstract Benthonic fauna and substrate in three areas of the Itata river (rhithron riffles, rhitron pools, and potamon) and three irrigation canals at the outtake and about 500 m downstream are analyzed. Benthonic fauna included 56 taxa; of these, 12 were exclusive of the river, 11 were only found in irrigation canals, and 33 were in both environments. The widest distributions were found among the Diptera (Heptagyia annulipes and Orthocladiinae), while Trichoptera (Smicridea chilensis) and Ephemeroptera (Baetidae) were more abundant in the river. The highest biomass contribution corresponded to Gastropoda (Chilina dombeyana) in irrigation canals and in the river, although there was also significant Tipulidae family (Diptera) larval biomass in the latter. Both specific richness and density were higher in the river, while biomass did not show significant statistical differences. The mineralogical composition of the bottom of the canals and the river was different, the former being soil of granitic origin, the latter being sediment of a fluviovolcanic origin. Finally, the canal bottoms showed a higher content of organic matter than in the river.

STUDY OF THE COPPER, CHROMIUM AND LEAD CONTENT IN MUGIL CEPHALUS AND ELEGINOPS MACLOVINUS OBTAINED IN THE MOUTHS OF THE MAULE AND MATAQUITO RTVERS (MAULE REGION, CHILE)

The Cu, Cr and Pb concentrations were determined in Mugil cephalus and Eleginops maclovinus, fish species inhabiting the mouths of the Maule and Mataquito Rivers (Maule Region, Chile) which are consumed by the coastal population in large quantities. Measurements were taken by flame atomic absorption spectroscopy to analyse representative muscle tissue of the two species. The method was validated using certified reference material (DOLT-1). The concentration ranges of Cu, Cr and Pb (mg . kg -1 , dry weight) in Mugil cephalus from the Maule river were: Cu 0.5-36.2; Cr 0.3-6.3; Pb 0.4-11.2 and from the Mataquito river varied between: Cu 0.6-23.2; Cr 0.3-6.0 and Pb 0.4-11.1. For the species Eleginops maclovinus from the Maule river the concentration ranges were: Cu 0.8-13.2; Cr 0.2-5.6; Pb 0.2-9.6 and from the Mataquito river: Cu 0.5-18.4; Cr 0.2-3.2 and Pb 0.3-4.0. The concentration ranges of Cu and Cr recorded in the two species of fish are within the levels permitted by FAO and EPA, however the concentrations of Pb in Mugil cephalus originating from both estuaries exceeds the levels permitted by current legislation. The statistical analysis done with one way ANOVA (p < 0.05) indicated that for each metal there are no significant differences between the species and the two sampling sites; however with two way ANOVA between the species and the two sampling sites a significant difference was found for Cu and Cr, but not for Pb.

Benthic macroinvertebrate assemblages as indicators of water quality applying a modified biotic index in a spatio-seasonal context in a coastal basin of Southern Chile

Se caracterizo la calidad del agua en un rio del sur de Chile a traves de un Indice Biotico, en un contexto espacio-temporal y ademas se analizo la composicion y distribucion de macroinvertebrados bentonicos y su correlacion con 14 parametros fisico-quimicos. La toma de muestras ocurrio durante un ano en 5 estaciones de muestreo en la cuenca del rio Boroa. Se registro un total de 77 taxa, los ordenes mas representativos fueron Ephemeroptera (43,30%), Diptera (24,16%) y Plecoptera (18,03%). Las especies mas abundantes fueron Meridialaris diguillina, Nousia maculata (Ephemeroptera) y Limnoperla jaffueli (Plecoptera). Acordando al IBF modificado (Indice Biotico de Familias) los resultados indicaron excelente, muy buena y buena calidad de agua, la ultima calidad fue registrada principalmente en invierno. Los parametros fisicoquimicos asi mismo indicaron calidad de agua excepcional. Estos resultados indican un bajo nivel de impacto antropogenico en la cuenca. Al aplicar el Indice Biotico de Hilsenhoff modificado basado en macroinvertebrados, la influencia de la estacionalidad sobre la calidad del agua fue evidente.

MICROPOGONIAS MANNI AS A BIOINDICATOR FOR COPPER IN LAKE BUDI (IX REGION, CHILE)

This study determined the concentration of copper in the species Micropogonias manni, a fish found in Lake Budi, which is much consumed by the population of Puerto Dominguez, IX Region of Chile. The determinations were done by atomic absorption spectrometry with flame, taking into account the sex, weight and size of the species, and, as representative samples, liver and muscle tissue. The validation of the methodology was done by using certified reference material (fish muscle), The copper concentration found in the liver fluctuated between 3,1 - 323,4 μg g-1, while for muscle tissue it was between 0,7 - 27,0 μg g -1 , dry weight. The maximum copper values found in muscle tissue, are greater than those found by other authors in various fish species. Statistical analysis showed that in muscle tissue, the sex, length and weight variables have no bearing on copper concentration; however, in the liver, the length and weight variables are significant.

Morphology and biology of Prionospio patagonica (Annelida: Spionidae) from Chile

Prionospio patagonica inhabits temporary silty tubes intertidally and shallow subtidally in brackish water estuarine environments in southern Chile. The species is gonochoristic with the female:male ratio being close to 2:1. Females and males release gametes into water. Pelagic planktotrophic larvae were caught in the plankton in the River Valdivia estuary in October-November and in March. Development of the adult morphology is described and illustrated beginning from the 2-chaetiger larval stage. One pair of lateral eyes first appears in the early larva, and shortly after that the right median eye develops. The left median eye appears after settlement, injuveniles with 10-11 segments. Developed 6-segment larvae have three dark red eyes, short palps of equal length, no nototrochs, one pair of small cells with grasping cilia on the pygidium, a small ciliated pit, gastrotrochs on segments 2-6, long serrated bristles in notopodia, adult capillaries in noto- and neuropodia on segments 2-5, single hooks in both rami on segment 6, and one pair of provisional papillae on the pygidium. A ventral buccal bulb is present below the short oesophagus and two pairs of provisional protonephridia are present in segments 1 and 2. The wall of the anterior part of the midgut has a characteristic brown pigment. The 6-segment larvae, about 400 μm long, settle and undergo gradual metamorphosis. In adults, hooks are gradually lost from noto- and neuropodia but sabre chaetae appear from segment 7 and retain their anterior position as growth proceeds. Up to 14 pairs of cirriform branchiae develop from segment 2, and three adult cirri appear on the pygidium. The afferent and efferent arms of each branchial blood loop are interconnected by capillary loops. A greenish heart body is present in the main dorsal blood vessel in anterior segments. Up to 21 pairs of metanephridia develop in anterior sterile segments, beginning with segment 4. Transparent gonoducts are present in fertile segments.

THE EFFECT OF PHYSICAL AND CHEMICAL PARAMETERS ON THE STRUCTURE AND COMPOSITION OF THE PHYTOPLANKTON COMMUNITY OF LAKE BUDI (IX REGION, CHILE)

ABSTRACTThe chemical characteristics of the waters of Lake Budi (IX Region, Chile), in winter and summer were analysed in order to establish seasonal variations and determine their influence on the various phytoplankton components. On the basis of the results it was possible to indicate that the chemical parameters found in the water body under examination vary in time and space, giving rise to different algal communities. The strong influence of salinity on the phytoplankton communities in both study periods appears to result principally from the influence of the sea, resulting from the intrusion of salt water during certain periods of the year. The predominant chemical characteristic in summer indicates a slight reduction in water quality, due to a rise in temperature and a reduction in the oxygen concentration. Keywords: Lake Budi, salinity, phytoplankton, water quality.INTRODUCTIONPhytoplankton constitutes the most important primary producer, and is a fundamental food source for consumers in many continental aquatic systems [1-2-3]. However the wide spectrum of organisms of which it is made up and the limnological characteristics which may be encountered in each individual system have hindered understanding of the processes involved in population dynamics [4]. In general, it has been established that the determining factors for the structure of phytoplankton communities in lakes result from the relationship which exists between the physical, chemical and biological parameters present in a water body [5]. Several studies carried out in freshwater environments have established that the growth of phytoplankton may be controlled to a large degree by the limitation of nutrients [6-7], the availability of light [8] and the composition and abundance of zooplankton [9]. It has also been determined that in coastal lakes which are subject to marine influence during some period of the year, salinity may also be a factor affecting the growth and distribution of phytoplankton [10-11]. The above is a consequence of the problems in osmotic regulation produced by the intrusion of sea-water, both for freshwater and marine organisms [12]. Under natural conditions, it has been determined that phytoplankton respond in a regular manner to the variations in their environment which occur in an annual cycle [13-14]. This is largely a consequence of changes to the physical characteristics and the stability of the water column. As a result, the varying algal components of the phytoplankton in a lake are a clear indicator of its environmental state. In this respect, an analysis of the composition and presence of species, their abundance and biomass, can provide the information needed to evaluate the ecological state of lacustrine systems. However, phytoplankton communities do not respond only to natural changes into the lakes, but may also present variations as a consequence of human interventions affecting the water body, either directly or through activities carried on in the basin as a whole. These influences affecting the lakes result in modifications to the structure and composition of the phytoplankton, which may take the form of changes in the taxa of which the algal associations are composed, in the abundance of each taxa, the richness and diversity of the associations, and other community parameters. Finally, due to the interdependence existing between the different organisms of which systems are composed, these variations in the phytoplankton communities translate into changes to the trophic chain and the productivity of the lakes [15]. Lake Budi constitutes a coastal lacustrine system where there is a strong marine influence due to the intrusion of salt water during certain periods of the year. Moreover, in recent decades there has been considerable human intervention in the basin. These two characteristics are indubitably determining factors in the physical and chemical conditions of the water column in the lake.As proposed, the aim of this study was to establish the physical and chemical parameters of the water which have the greatest influence, and which determine the algal associations present in the phytoplankton of Lake Budi.EXPERIMENTALArea of the study and sample collectionLake Budi (38o 52’ S; 73o 18’ W) is a coastal lake which is connected sporadically to the sea. Different bio-types may be recognized in the composition of its surroundings: banks, either covered with vegetation or bare; mud-sand beaches; and sediments with a high content of organic material derived from aquatic plants [16].Based on the special characteristics of Lake Budi and the contribution of its principal tributaries (Budi, Temo, Allipen, Comue, Bolleco and Botapulli), nine sampling stations were established: Rio Budi, Temo, Allipen, Comue, Bolleco, Botapulli, Deume 1, Deume 2 and Deume 3 (Fig. 1). To account for the marine influence present in Lake Budi, samples were taken at two times of year, the first in July 2004, representing the state of the lake in winter, and the second in January 2005, reflecting summer conditions. Two samples were taken at each sampling station: a surface sample (20cm) and a deep sample (1 m), with the exception of the Rio Budi station, where only surface samples were taken due to the shallowness of the water at the time of sampling. Chemical Analysis Eight physical and chemical parameters for water quality were established for this study: temperature, pH, salinity, oxygen in solution (OS), biochemical oxygen demand (BOD), total suspended solids (TSS), organic suspended solids (OSS) and nitrates. These were determined by extracting water samples using a Ruttner bottle, with each sample taken in duplicate. Consideration was given to conditions at sampling, the type of container, preservation and the maximum time-lapse between the taking and the analysis of the sample [17-18].e-mail: jtapia@utalca.cl

Alimentación de Micropogonias furnieri (Osteichthyes: Sciaenidae) en el lago costero Budi, Sur de Chile

The aim of this study was to determine the feeding of Micropogonias furnieri (n= 256 of commercial size over 25 cm) during austral summer and winter 2004. Du...