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Toxic metal content were measured in samples of mollusc Concholepas concholepas obtained from the Chilean coast. Samples were collected during two periods, one before and one after the earthquake-tsunami which occurred in the Maule Region, Chile, February 27th, 2010 as a result of an earthquake with a magnitude of 8.8. Quantification of toxic metals in samples of hepatopancreas and muscle tissue was performed using flame atomic absorption spectroscopy. The analytical methodology was validated with certified reference material. The content means measured in muscle tissue for January 2010 were Cu: 10.3; Cr: 0.7; Cd: 0.1; Mn: 3.6 and Zn: 38.6 µg g

Land-use change is a principal factor affecting riparian vegetation and river biodiversity. In Chile, land-use change has drastically intensified over the last decade, with native forests converted to exotic forest plantations and agricultural land. However, the effects thereof on aquatic ecosystems are not well understood. Closing this knowledge gap first requires understanding how human perturbations affect riparian and stream biota. Identified biological indicators could then be applied to determine the health of fluvial ecosystems. Therefore, this study investigated the effects of land-use change on the health of riparian and aquatic ecosystems by assessing riparian vegetation, water quality, benthic macroinvertebrate assemblages, and functional feeding groups. Twenty-one sites in catchment areas with different land-uses (i.e. pristine forests, native forests, exotic forest plantations, and agricultural land) were selected and sampled during the 2010 to 2012 dry seasons. Riparian vegetation quality was highest in pristine forests. Per the modified Macroinvertebrate Family Biotic Index for Chilean species, the best conditions existed in native forests and the worst in agricultural catchments. Water quality and macroinvertebrate assemblages significantly varied across land-use areas, with forest plantations and agricultural land having high nutrient concentrations, conductivity, suspended solids, and apparent color. Macroinvertebrate assemblage diversity was lowest for agricultural and exotic forest plantation catchments, with notable non-insect representation. Collector-gatherers were the most abundant functional feeding group, suggesting importance independent of land-use. Land-use areas showed no significant differences in functional feeding groups. In conclusion, anthropogenic land-use changes were detectable through riparian quality, water quality, and macroinvertebrate assemblages, but not through functional feeding groups. These data, particularly the riparian vegetation and macroinvertebrate assemblage parameters, could be applied towards the conservation and management of riparian ecosystems through land-use change studies.

Although Caligus rogercresseyi negatively impacts Chilean salmon farming, the metabolic effects of infection by this sea louse have never been completely characterized. Therefore, this study analyzed lactate responses in the plasma, as well as the liver/muscle lactate dehydrogenase (LDH) activity and gene expression, in Salmo salar and Oncorhynchus kisutch infested by C. rogercresseyi. The lactate responses of Atlantic and Coho salmon were modified by the ectoparasite. Both salmon species showed increasing in plasma levels, whereas enzymatic activity increased in the muscle but decreased in the liver. Gene expression was overexpressed in both Coho salmon tissues but only in the liver for Atlantic salmon. These results suggest that salmonids need more energy to adapt to infection, resulting in increased gene expression, plasma levels, and enzyme activity in the muscles. The responses differed between both salmon species and over the course of infection, suggesting potential species-specific responses to sea-lice infection.

Cu, Mn, Fe, Zn, Cd and Pb levels were measured in liver and muscle samples of Rainbow Trout Oncorhynchus mykiss collected from three watersheds with different land-uses: native forest, exotic plantation, and agriculture in Chile, during January, April, July, and October 2012. Cd and Pb levels were not detected in the liver and muscle, probably since they are under the detection limits. Higher metal concentrations (liver-muscle tissues) were detected in samples from agriculture and exotic plantation streams, whereas trout from native forest streams had lower metal concentrations. Higher metal concentrations were detected in liver tissue compared to muscle tissue, and both negatively correlated to the length and weight of the fish. This suggest the liver had higher ability to accumulate Cu, Mn, Fe and Zn compared to muscle tissue. The concentration range of Fe and Zn recorded in the muscle are within the range reported by other authors, whereas Mn and Cu concentrations are higher than reported in the literature. However, at all sites the concentration of selected metals were below the limits permitted by current legislation (FAO), and therefore did not put the human population at risk, suggesting that is eating wild rainbow trout safe in Chile.

In this study we assessed the influence of three different environmental salinities (5, 15 and 31 psu during 90 days) on growth, osmoregulation, energy metabolism and digestive capacity in juveniles of the Notothenioid fish Eleginops maclovinus. At the end of experimental time samples of plasma, liver, gill, intestine, kidney, skeletal muscle, stomach and pyloric caeca were obtained. Growth, weight gain, hepatosomatic index and specific growth rate increased at 15 and 31 psu and were lower at 5 psu salinity. Gill Na(+), K(+)-ATPase (NKA) activity presented a "U-shaped" relationship respect to salinity, with its minimum rates at 15 psu, while this activity correlated negatively with salinity at both anterior and posterior intestinal portions. No significant changes in NKA activity were observed in kidney or mid intestine. Large changes in plasma, metabolite levels and enzymatic activities related to energy metabolism in liver, gill, intestine, kidney and muscle were generally found in the groups exposed to 5 and 31 psu compared to the 15 psu group. Only the pepsin activity (digestive enzymes) assessed enhanced with environmental salinity, while pyloric caeca trypsin/chymotrypsin ratio decreased. This study suggests that juvenile of E. maclovinus presents greater growth near its iso-osmotic point (15 psu) and hyperosmotic environment (31 psu). Acclimation to low salinity increased the osmoregulatory expenditure as seen by the gill and anterior intestine results, while at high salinity, branchial osmoregulatory activity was also enhanced. This requires the mobilization of lipid stores and amino acids, thereby holding the growth of fish back. The subsequent reallocation of energy sources was not sufficient to maintain the growth rate of fish exposed to 5 psu. Thus, E. maclovinus juveniles present better growth efficiencies in salinities above the iso-osmotic point and hyperosmotic environment of this species, showing their best performance at 15 psu as seen by the main osmoregulatory and energy metabolism enzymatic activities.

Changes in land use which directly or indirectly affect freshwater fauna constitute one of the principal anthropic factors which have caused world biological diversity to disappear rapidly during recent decades. This fauna includes aquatic benthic macroinvertebrates, organisms presenting temporal and spatial variation due to a variety of factors, one of which is the diverse food resources available in the rivers. To assess the effect of anthropic activities on this fauna, the distribution, abundance and characterisation of the functional feeding groups of aquatic macroinvertebrates were analysed, together with the physical and chemical variables in the environments of four coastal river basins of southern south-central Chile. A total of 104 taxa of macroinvertebrates were recorded, the principal component of the community being the Diptera (26 taxa). The abundance and richness of taxa were greater in summer and lower in winter. The most abundant species belong to the order Ephemeroptera and Plecoptera. Macroinvertebrates were affected by different land use: stations with less anthropic activity and greater altitude had higher macroinvertebrates abundance, while the lowest abundance was found at the lowest stations. The functional feeding groups which were most abundant spatially and temporally were the collector-gatherers and the shredders. The physical and chemical water quality variables proved to be of exceptional quality in all the stations. These results suggest that policies governing changes in land use in central and southern Chile should take into account the dramatic alterations that these changes impose on the macroinvertebrates community. Policies for biodiversity conservation should therefore focus on these small but important organisms in the north Patagonian region of South America, which is a hotspot of world diversity.

Pinguipes chilensis, Cheilodactylus variegatus y Aplodactylus punctatus son especies comunes de ser registradas a lo largo de la costa chilena, no obstante informacion sobre su alimentacion es escasa para la zona sur de nuestro pais. Por ello, se analizo la composicion y sobreposicion dietaria de estas especies para la costa Valdiviana. Los resultados senalan que para el periodo primaveral del ano 2010, en P. chilensis (n=41) se identificaron 20 presas, todas caracterizadas por ser invertebrados de gran tamano, principalmente crustaceos (55%) y moluscos (40%), siendo la especie Homalaspis plana la mas representativa (IRI 70%). En Ch. variegatus (n=38) se identificaron 37 presas, mayoritariamente pequenos invertebrados, principalmente crustaceos (49%), moluscos (31%) y anelidos (10%). Dentro de estos ultimos dominaron los poliquetos de la Familia Nereidae (IRI 23,2%). En A. punctatus (n=32) la diversidad de algas rojas (50%) predomino sobre las pardas (41%) y verdes (9%), siendo identificadas 34 especies presa, donde Colpomenia sp. (Phaeophyta) fue la mas representativa (IRI 32,4%). El analisis de sobreposicion de dieta entre las tres especies mostro una baja similitud entre las dietas. Las tres especies analizadas en este estudio, se caracterizan por compartir un mismo habitat. P. chilensis y Ch. variegatus se muestran ambas como depredadores carnivoros generalistas, ya que las dos especies presentan un amplio espectro alimentario sin embargo la morfologia y el tamano de su boca influirian en el tamano de la presa que consumen. En cambio, A. punctatus se confirma como una especie herbivora especialista, ya que consume preferentemente algas rojas.

The aim of this study was to evaluate immunological, metabolic and osmoregulatory secondary stress responses in Eleginops maclovinus specimens submitted to three different stocking densities: i) low (3.1 kg m(-3)), medium (15 kg m(-3)) and high (60 kg m(-3)) during 10 days, alone or in combination with a previous treatment of a protein extract of the pathogen Piscirickettsia salmonis (0.5 μg g weight body(-1)). Plasma, liver, gill and kidney samples were obtained at the end of both experiments. Plasma cortisol and amino acid levels increased, while plasma glucose, triglyceride and lactate levels decreased at higher stocking densities. However, no effects were observed on serum Immunoglobulin type M (IgM anti P. salmonis level) values. Gill Na(+), K(+)-ATPase activity enhanced under these experimental conditions, suggesting an osmotic imbalance. Energy metabolism changes, assessed by metabolite concentrations and enzyme activities, indicated a reallocation of energetic substrates at higher stocking densities. Specimens inoculated with a protein extract of P. salmonis and maintained at different stocking densities showed primary stress response, as all groups enhanced plasma cortisol concentrations. Serum IgM levels increased after treatment with P. salmonis extract but a negative influence of high stocking density on IgM production was observed when immune system was activated. Furthermore, treatment with P. salmonis protein extract evoked deep changes in the metabolite stores in all tissues tested, indicating a mobilization of energy substrates in response to infection. The results show that stocking density induced immunological, metabolic and osmoregulatory secondary stress responses in E. maclovinus specimens and that previous treatment with P. salmonis compromise these changes.

El área costera de la Región de La Araucanía destaca por la presencia de humedales con vegetación boscosa de temu y pitra, de la asociación Blepharocalyo-Myrceugenietum exsuccae. Actualmente estas formaciones se encuentran afectadas por actividades antrópicas. En este estudio se determinó la flora vascular y se evaluó el nivel de degradación y estado de conservación de estos bosques en seis cuencas hidrográficas del borde costero (Imperial, Comúe, Chelle, Boroa, Boldo y Toltén) de la Región de La Araucanía. Para determinar el estado de conservación se emplearon variables florísticas y territoriales, como la valoración de la influencia de los ecosistemas adyacentes sobre el bosque, la relación superficie/ cuenca y el grado de intervención antrópica. Se utilizó información cartográfica sobre la distribución y superficie de los bosques pantanosos, estableciéndose de esta forma el mosaico vegetacional y la diversidad de los principales usos de los suelos. Los resultados muestran que los principales uso del área son agrícola, ganadero y silvícola. La flora vascular de los bosques la componen 94 especies, de las cuales el 14,9% son introducidas, y el mayor porcentaje corresponde a nativas (64,9%) y endémicas del país (20,2%). Once especies se encuentran con problemas de conservación. Asimismo, todos los rodales presentan algún grado de degradación, siendo los ubicados en el curso inferior de la cuenca del río Imperial los que poseen el nivel más alto de degradación, y los menos intervenidos se encuentran en la cuenca del río Boldo. Se concluye que el estado de conservación promedio de los rodales en toda el área corresponde a "degradado". Como principal causa del deterioro están las actividades humanas realizadas tanto al interior como en la periferia de estos bosques.

La vegetación ribereña comprende la zona ecotonal en la transición entre un cuerpo de agua y el ambiente terrestre contiguo, desempeñando un rol elemental en el funcionamiento de los ecosistemas acuáticos. La cobertura, estructura, y composición de la vegetación influyen de manera fundamental en el control de la entrada de energía al ecosistema acuático. Las múltiples funciones ambientales que cumplen los ecosistemas ribereños, y el flujo de servicios ecosistémicos que directa o indirectamente influyen en el bienestar de la sociedad, hacen que el conocimiento de la calidad ecológica de estas áreas sea considerado como un buen indicador ambiental, útil en la planificación y gestión del territorio, especialmente en ecosistemas costeros. Mediante la aplicación del índice QBR se determinó la calidad de la vegetación ribereña en los ríos Lingue y Chaihuín, ambas cuencas costeras del sur de Chile. Los resultados obtenidos indican que el río Chaihuín presenta una vegetación de mejor calidad en sus riberas, en comparación con el río Lingue, donde los bajos valores de QBR son producto de la sustitución de la vegetación ribereña natural para el establecimiento de terrenos agrícolas y plantaciones forestales. La aplicación de este índice y la experiencia global de su utilización indican que resulta ser un instrumento económico y de rápida aplicación, que entrega resultados confiables y útiles para la toma de decisiones en el diagnóstico territorial, considerando las múltiples funciones y valores que hacen de los ecosistemas ribereños buenos indicadores ambientales, diagnosticando los principales impactos y problemas para proponer medidas de restauración y/o mitigación.

In this study we assessed changes in the osmoregulatory system of juvenile sub-Antarctic Eleginops maclovinus submitted to different environmental salinities (5, 15, 32 and 45 psu) using two different acclimation trials: (1) an end-point experiment (exposure for 14 days) and (2) a time course experiment (specimens were sampled on days 1, 3, 7 and 14 post-transfer). Plasma osmolality, cortisol and metabolites (glucose, lactate and protein) values as well as Na+, K+-ATPase (NKA) activity were assessed in several osmoregulatory tissues (gills, kidney and intestine). In both trials, acclimation to different environmental salinities for 14 days induced changes in plasma metabolites (glucose, lactate and proteins) as well as cortisol values related to salinity challenges. Plasma osmolality and gill NKA activity presented a direct and positive relationship with respect to environmental salinity, while kidney NKA activity showed a “U-shaped” relationship. Anterior intestinal NKA activity increased in response to environmental salinity and apparently did not change in the middle portion of this organ, while it was enhanced in the posterior portion in environmental salinities different than seawater. Plasma metabolite values increased under hypo- and hypersaline conditions, indicating the importance of these energy substrates in extreme environments. The time course study revealed that specimens of E. maclovinus are able to accommodate their osmotic and metabolic system to respond to osmoregulatory challenges by allostatic changes.

Coastal zones are very dynamic and fragile environments, constituting a landscape ever more heterogeneous, fragmented and with increasing levels of complexity due to the changing relationship between man and nature. Integrated coastal zone management therefore requires detailed knowledge of the system and its components, based—to a large extent—on technical and scientific information. However, the information generated must be in line with the political requirements necessary for decision-making and planning. Thus the use of indicators to give a simplified view of the many components of the territory, and at the same time to provide important information about patterns or trends, becomes a tool of the utmost importance. These indicators can be understood as measurable characteristics of the environment, which facilitate comprehension of the processes occurring at different scales and serve as a reference to inform the population and support decision-making. The aim of the present note is to demonstrate briefly the need to develop geographical-environmental and natural risk indicators to facilitate comprehension of the dynamic of spatial and temporal landscape patterns, particularly in coastal environments. This approach offers an historical summary of the natural, socio-economic and political processes which currently make up the territory, and which without doubt will continue to influence it in the future. At the same time, it is proposed that information should be integrated on the basis of this framework with a view to generating spatial decision support systems in a context of planning and integrated management of the coastal zones of Chile.

The purpose of the present study was to investigate the seasonal relationship of macrobenthos richness and abundance with sediment characteristics (i.e. texture and organic material) for the coastal Budi Lagoon in southern Chile. Physicochemical measurements and macrobenthos samples were taken over the course of a year at nine sampling stations. Sandy-muddy sediment was the most common, and high percentages of organic material were registered, varying significantly between seasons and stations. The recorded organic material was related to natural (resident wild birds) and anthropogenic (agriculture) sources. Regarding fauna, 28 benthonic taxa and 7092 individuals were identified, with temporal and spatial variations. The most abundant taxa year-round were the molluscs Littoridina cumingii and Kingiella chilenica and the bristle worm Prionospio patagonica. Together, the obtained results evidence the important impact of organic material on the macrobenthos, with macrobenthic richness and abundance decreasing in conditions of high organic material content. The recorded variations for different taxa may indicate a response to the land use around the Budi Lagoon, which is intensely subjected to agricultural and tourist activities. Resumo O objetivo do presente estudo foi investigar a relação sazonal entre macrobentos e características do sedimento, tais como textura e material orgânico, na lagoa costeira Budi Lagoon, sul do Chile. Medidas físico-químicas e amostragem do macrobentos foram realizadas durante um ano em nove localidades. Sedimento arenoso-lodoso foi o mais comum na lagoa, e percentagens elevadas de material orgânico foram registradas, variando significativamente entre as estações e locais de coleta. Em relação a fauna, foram identificados 28 taxas bentônicos e 7092 indivíduos, que apresentaram variação temporal e espacial. As espécies mais abundantes durante todo o ano foram os moluscos Littoridina cumingii e Kingiella chilenica, e o poliqueta Prionospio patagonica. Os resultados obtidos evidenciaram o importante impacto da matéria orgânica sobre o macrobentos, com riqueza e abundância da fauna diminuindo em presença de alto teor de matéria. As variações encontradas para os diferentes taxons indicaram resposta da fauna ao uso da terra ao redor de Budi Lagoon, que intensamente utilizada para agricultura e atividades turísticas.

Eleginops maclovinus is an endemic, subantarctic Notothenioidei species. This study examined the influence of different environmental salinities (5, 15, and 45 psu; and 32 psu as a control) on energy metabolism in E. maclovinus over a period of 14 days. Metabolite contents and enzymatic activities related to carbohydrate, amino acid, and lipid metabolisms were evaluated in metabolic (liver) and osmoregulatory (gill and kidney) tissues. At extreme salinities (5 and 45 psu), the liver showed a high consumption of energy reserves, mainly as amino acids and carbohydrates. Carbohydrate metabolism in the gills did not change under different salinities, but increased lactate levels were found, suggesting that this tissue may use lactate as an energy substrate. Amino acid metabolism in the gills decreased at 5 psu but increased at 45 psu, and lipid metabolism increased at 5 and 15 psu during the first days of the trial, indicating a possible use of lipids as energy. Kidney carbohydrate catabolism and amino acid metabolism increased after 14 days at 45 psu, while lipid metabolism did not vary in relation to salinity changes. Together, these results suggest that the liver is most affected by salinity changes, probably due to its role as a supplier of energetic substrates. The gills and kidney, osmoregulatory tissues, maintained their energy metabolism levels with minor modifications. In conclusion, E. maclovinus exhibits metabolic adjustments to adapt to different salinities, showing the best responses in isosmotic environmental salinities.

Traumatic brain and spinal cord injuries are major public health issues causing significant death and long-term disability in the United States, with higher incidences in young and older adults. The ThinkFirst National Injury Prevention Foundation is a nonprofit organization focused on injury prevention education and awareness for people of all ages, with a particular focus on educating children, teens, and young adults. ThinkFirst chapters have evaluated the effectiveness of the ThinkFirst programs in both children and teens by demonstrating significant improvement in knowledge regarding high-risk behaviors postintervention. Here, we review the available literature studying the efficacy of the ThinkFirst National Injury Prevention Foundation programs, outline current ThinkFirst activity, and discuss future directions of the program. This review discusses the efforts of a number of ThinkFirst chapters in terms of research, legislation, and public communication. It showcases the success of ThinkFirst interventions and suggests future directions which can help improve national injury prevention efforts.

A study was made of the geographic distribution of swamp forest in the coastal territory of the Araucania Region, Chile. An analysis of maps, aerial photographs, and satellite images was carried out, together with field work, to determine the location, degree of fragmentation, shape of fragments and habitat use of the forest. The results showed a total area of 7675 ha of forest (in a region of 165,168 ha) divided into 427 fragments of highly irregular shapes, set in a farming matrix. This forest type was located principally on alluvial (37%) and fluvial-marine (33%) plains associated with the Tolten and Queule river basins. Land unsuitable for agriculture accounted for 50% of the area of forest (CIREN Classes VII and VIII), while land with a superficial phreatic water table (0–20 cm depth) and poorly drained soils concentrated 47% and 66% of the forest respectively. The majority of the forested area stands on soils with poor drainage (available habitat), as a response to the greater biophysical restrictions which such areas represent for agriculture. Of the forested area, 59% was located on 859 properties belonging to small-holders with up to 200 ha, while 39% was located on 58 medium to large properties (over 200 ha and over 1000 ha respectively). Forty percent of the forest is within 300 m of a road and only 8% is more than 1000 m away. It is concluded that the forest is under severe pressure from human activity (by clearing for agricultural land, grazing and firewood extraction) and that there is an urgent need for a plan giving priority to conservation.

Las principales actividades acuicolas en el estuario de Quempillen son la acuicultura de ostras, Ostrea chilensis, y del alga Gracilaria chilensis. La intervencion antropogenica al interior del estuario genera cambios significativos a nivel del sedimento y de los contenidos de materia organica.

Over the past few decades, land-use changes through conversion of global forest cover to exotic plantations is contributing to both habitat and biodiversity loss and species extinctions. To better understand human influences on ecosystem, we use diet composition from introduced Rainbow Trout Oncorhynchus mykiss as indicator of potential changes in the composition of stream-macroinvertebrates due to land use changes from native to exotic vegetation (eucalyptus plantations) in southern Chile. Water quality variables, aquatic macroinvertebrates and Rainbow Trout diet were studied in 12 sites from mountain streams located in two watersheds including one dominated by native riparian vegetation and the other dominated by exotic vegetation. As expected, richness and abundance of macroinvertebrates were clearly higher at sites in native forest than in those with exotic vegetation. Collector-gatherer was the most abundant functional feeding group, but there was no statistical difference in the functional composition between the two watersheds. Differences in in-stream macroinvertebrate availability was more higher correlated with changes in Rainbow Trout diets. Specifically, taxa consumed from the watershed dominated by native forests was higher than from the watershed with exotic vegetation. Additional environmental variables showed statistical differences between watersheds. The exotic vegetation sites had the highest concentrations of dissolved solids, suspended solids, nitrates, chlorides and sulphates. Our findings show that macroinvertebrate assemblage structure and trout diets can be altered by changes in riparian vegetation. The absence of specific macroinvertebrate taxa in streams with exotic vegetation was captured by the composition of trout diets. This suggest that Rainbow Trout diets can be a good biological indicator of land use practices and thus, diet can be used as a rapid and effective tool for evaluate environmental quality. Our findings provide insights about the design of aquatic monitoring programmes to improve detection of anthropogenic impacts in streams in South America and elsewhere.

Background Marine species have colonized extreme environments during evolution such as freshwater habitats. The amphidromous teleost fish, Galaxias maculatus is found mainly migrating between estuaries and rivers, but some landlocked populations have been described in lakes formed during the last deglaciation process in the Andes. In the present study we use mtDNA sequences to reconstruct the historical scenario of colonization of such a lake and evaluated the osmoregulatory shift associated to changes in habitat and life cycle between amphidromous and landlocked populations. Results Standard diversity indices including the average number of nucleotide differences (Π) and the haplotype diversity index (H) indicated that both populations were, as expected, genetically distinctive, being the landlocked population less diverse than the diadromous one. Similarly, pairwise GST and NST comparison detected statistically significant differences between both populations, while genealogy of haplotypes evidenced a recent founder effect from the diadromous stock, followed by an expansion process in the lake. To test for physiological differences, individuals of both populations were challenged with a range of salinities from 0 to 30 ppt for 8 days following a period of progressive acclimation. The results showed that the landlocked population had a surprisingly wider tolerance to salinity, as landlocked fish survival was 100% from 0 to 20 ppt, whereas diadromous fish survival was 100% only from 10 to 15 ppt. The activity of ATPase enzymes, including Na+/K+-ATPase (NKA), and H+-ATPase (HA) was measured in gills and intestine. Activity differences were detected between the populations at the lowest salinities, including differences in ATPases other than NKA and HA. Population differences in mortality are not reflected in enzyme activity differences, suggesting divergence in other processes. Conclusions These results clearly demonstrate the striking adaptive changes of G. maculatus osmoregulatory system, especially at hyposmotic environments, associated to a drastic shift in habitat and life cycle at a scale of a few thousand years.

Caligus rogercresseyi sea lice negatively impact Chilean salmonid farming, but no complete characterization for the metabolic effects of Caligus infestation currently exists. Therefore, the aim of this study was to analyze the effects of C. rogercresseyi infestation on the metabolic responses of Salmo salar and Oncorhynchus kisutch. Energy metabolism responses to C. rogercresseyi were examined over a time-course infestation of both salmonid species. Plasma metabolite levels and enzymatic activities related to intermediate metabolisms of carbohydrate, amino acid, and lipid were evaluated in the liver and muscle. Plasma glucose levels changed in both salmonid species, increasing at 1–3 days post-infestation. In turn, triglyceride levels increased at days 3 and 7 in O. kisutch and S. salar, respectively, while protein and total α-amino acids increased in O. kisutch but decreased in S. salar during infestation. Amino acid intermediate catabolic metabolism in the liver and muscle of O. kisutch increased during infestation, indicating a higher use of the gluconeogenic pathway than S. salar. Lipid intermediate anabolic metabolism increased in O. kisutch liver, remained unchanged in S. salar liver, and increased 1 day post-infestation in the muscle of both salmonids. Liver and muscle carbohydrate intermediate anabolic metabolism in O. kisutch increased during infestation, suggesting that this species preferentially uses the glycogenolytic-glucolytic pathway, in contrast with S. salar. In conclusion, amino acid and carbohydrate catabolism enzymes in O. kisutch activated soon after initial sea lice infestation, which would allow this species to dispose of energy substrates earlier than S. salar. This physiological data contributes towards the ability of O. kisutch to more adeptly cope with the increased energy demand imposed by C. rogercresseyi infestation.

A coastal-lake wetland is a type of inland water ecosystem that does not occur very frequently in Chile, of which lakes Budi, Huillinco and Cucao are examples. Textural differences were found in the various constituent parts of the coastal lake sediments. Gravel was the smallest fraction and showed significant differences among the three coastal lakes (P < 0.05). Significant differences (P < 0.05) were also recorded for the sand and mud fractions. Lakes Cucao and Huillinco are described as muddy sand, in contrast to Lake Budi, which is described as sandy mud, composed primarily of mud with a smaller percentage of sand. There were statistical differences among the lakes with regard to the contributions of organic matter in each fraction. The macrofauna in these bodies of water belongs to the fauna inhabiting estuary environments in southern Chile. Lake Budi had seven taxa, and lakes Huillinco and Cucao ten species of macrofauna each. There were no significant differences in the number of species captured at the three coastal lakes (P > 0.05), but differences did emerge in comparisons made among the sampling stations. Total abundances showed significant differences (P < 0.05) in comparisons made both among the lakes and the stations. Salinity and grain size could be limiting the density and number of species at the lakes.

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, in juveniles 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.

Se analizó la dinámica geomorfológica de la franja costera de La Araucanía mediante el método propuesto por Tricart (1985), Endlicher (1985) y la clasificación de Francke et al. (2004). En base a patrones morfológicos, morfométricos, mor-fogenéticos y de uso de suelo, las unidades geomorfológicas más representativas fueron el cordón montañoso en roca metamórfica y el cordón montañoso en roca metamórfica con intrusiones graníticas, ambas del Paleozoico, las plataformas en roca metamórfica y la llanura fluviomarina representada por humedales de alto valor ecológico. La erosión hídrica muestra un estado erosivo ligero-moderado en gran parte del área de estudio, asociado principalmente a factores antrópicos como la histórica disminución y cambio de cobertura vegetal, malas prácticas agrícolas y la casi nula aplicación de prácticas de conservación de suelos. This paper describes the geomorphology of the coast of La Araucania, using methods proposed by Tricart (1985) Endlicher (1985) and the classification methods of Francke et al. (2004). Based on morphological, morphometric, morphogenetic and land use patterns, the most representative geomorphic units were the mountain range of metamorphic rock, cord metamorphic rock mountain with granite intrusions, both Paleozoic, the metamorphic rock platform and the fluvial-marine plain represented by wetlands of high ecological value. Water erosion was low to moderate in much of the study area and is mainly associated with human factors, such as the historic reduction and change in vegetation cover, poor agricultural practices and almost no application of soil conservation practices.

The concentrations of Cd, Cu, Mn, Ni, Pb, Fe and Zn were determined in superficial sediments extracted from nine zones of Budi Lagoon, located in the Araucania Region (Chile). The concentrations of these metals were determined by flame atomic absorption spectroscopy and the method was validated using certified reference material (marine sediment). The concentration ranges found for the trace elements were: Pb < 0.5; Cd < 0.2–3.9; Cu 21.8–61.9; Ni 31.2–59.4; Zn 54.5–94.8 mgkg−1 (dry weight). The elements that registered the highest concentrations were Mn 285.4–989.8 mgkg−1 and Fe 4.8–10.6 %. The lagoon cluster analysis of the stations was divided into three groups (Temo station with high Cu and low Mn concentrations, Bolleco, Comue, Allipen and Deume 3 stations presented highest Cd concentration, and another group Botapulli, Rio Budi, Deume 2 and Deume 1 stations presented low levels of Cd). The textural characteristics of the sediment were determined (gravel, sand and mud) and the results were correlated with the concentrations of the metals in the various study zones. The sediments of Budi Lagoon presented high levels of Fe and Mn, which are of natural origin and exceed the maximum values recorded by many authors. With respect to the recorded concentrations for Cd, Cu, Ni and Zn, are within the ranges published by other authors in similar works. The Pb element was not detected. The results were subjected to statistical analysis to evaluate the correlations between the content of the elements and obtain the site of sediment.

The need to expand aquaculture production has led to other fish to be considered as potential species for culture, such as the sub-Antarctic notothenioid Eleginops maclovinus (Valenciennes, 1830). The aim of this study was to determine the cumulative effect of density and pathogen infection by protein extract of Piscirickettsia salmonis on skeletal muscle metabolism. In a first experiment, specimens were submitted to three different stocking densities: (1) 3.1 kg m(-3), (2) 15 kg m(-3) and (3) 60 kg m(-3), for a period of 10 days. In a second experiment, metabolic changes caused by an infection of P. salmonis protein extract (a single injection of 0.5 μL P. salmonis protein extract g body weight(-1) was inoculated in the fish) and its combined effect with stocking density was assessed during a period of 10 days. This study concludes that stress caused by high stocking density led to the reorganization of some metabolic routes to fulfill skeletal muscle energy needs. Furthermore, infection response by pathogen P. salmonis differed when stocking density increased, suggesting an increase of energy needs with density in skeletal muscle of infected fish.

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. During the summer period anchoveta Engraulis ringens was the main prey item in terms of percentage of frequency (%F), percentage of weight (%P) and percentage of Index Relative Prey Importance (%IRI); on the other hand, during winter aquatic plants (i.e. undigested remnants of Myriophyllum aquaticum) were the main prey. Therefore, M. furnieri may act like an opportunistic omnivorous fish similar to that described for population from Río de la Plata (Argentina).

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.

The concentrations of cadmium, lead, manganese and zinc were determined in the fish species Micropogonias manni captured in Budi Lake, Araucanía Region (Chile). The measurements were made by atomic absorption spectroscopy, and the analysis considered the sex, weight and size of the species; the representative samples were taken from the liver and muscle tissue. The method was validated using certified reference material (DOLT-1). The ranges of concentrations found in the muscle tissue were: Cd, not determinate (n.d.)-0.26; Pb, n.d.-1.88; Mn, 0.02-12.17 and Zn, 0.48-39.04 mg kg(-1) (dry weight). The concentrations in muscle tissue were generally lower than those found in the liver. With respect to the average concentrations recorded for each metal in the edible part of the fish (muscle tissue), it was found that the levels of Cd, Pb, Mn and Zn are within the ranges published by other authors in similar works and below the maximum concentration limits permitted by current legislation (FAO/WHO 2004; EU 2001) and do not constitute a health hazard for consumers of this species. The results were subjected to statistical analysis to evaluate the correlations between the content of the various metals and the sex, weight and size of each sample.

We describe the benthic macroinvertebrate associations Budi coastal lagoon southern Chile, salt nature. They relate the abundance and biomass species with or...

The “robalo” Eleginops maclovinus (Valenciennes 1830) is a common fsh in the littoral, estuaries and rivers (under tidal effects zone) of southern South América, including the Falkland islands. The feeding habits of this species is known mainly in the two frst mentioned habitats, where it consumes mostly animals from marine and estuarine origin. However, little is known about its seasonal feeding habits in limnetic environments. It is only assumed that it has to eat preys from freshwater origin. In the present study, 127 specimens of E. maclovinus were analysed, 119 of which had stomach contents. The zoophagic tendency of the species is corroborated, but also animáis from low salinities and limnetic salinities were found to be consumed inthe freshwater environment. Consequently, E. maclovinus appears as an extraordinarily versatile species, in relation to its feeding capacities, with physiologic characteristics allowing a wide osmoregulatory spectrum at the digestive level, probably one of the most variable within the suborder Notothenioidei, which has strong Antarctic links.

The mussels Choromytilus chorus and Mytilus chilensis are the most distinctive bivalves of the subtidal soft bottoms of Queule River estuary, southern Chile (ca. 40 °S). In some artificially farmed areas of this estuary, the semi-buried mussels reach densities as high as 250–300 adult indiv. m-2. We carried out seasonal (1983) and fortnightly samplings (August 1984 to December 1985) to compare abiotic and biotic characteristics (i. e., macroinfaunal community structure) on bottom areas with and without mussels. Biodeposition within the mussel bed area did not result in organic enrichment of the sediments, a situation which is discussed in relation to the breakdown of mussel biodeposits. During most of this study, organic matter (%) was higher in the sediments of this area versus that without mussels. While the sediments of the mussel and control area were dominated by the same macroinfauna (i.e., polychaetes), that of the mussel area generally had lower abundances, number of species, and diversity indices. Several explanations are presented to account for diminished abundance and diversity values here. These include insufficient substrate for settling larvae, space limitation, and negative effects of sediment characteristics. Summary Mussel biodeposition in a mussel bed area at the Queule River estuary did not result in organic enrichment of the sediments. This may be attributed to the high rate of biodeposit disintegration. During most of the study, the percentage of combustibles (i. e., organic matter) was higher in the mussel bed sediments. This was not necessarily the effect of mussel biodeposit accumulation, since field studies (between-site comparisons during flood and ebb tides) showed no significant differences between the amount of organic matter in the near fluid, fecal-rich sediments surface (i. e., 0.5 cm) of the mussel and control area. The macroinfauna of both areas was dominated by the spionid Minuspio chilensis and one capitellid worm. The abundance of the whole macroinfauna and that of the most characteristic taxa peaked during summer-autumn months. No changes were detected in the community structure of either area (e. g., no changes in the rank of dominant species). The abundances, number of species, and diversity indices were generally lower in the mussel bed area. This condition may be related to negative effects of some sort of mussel-macroinfauna interaction such as space reduction, adult-larval interactions, or changes in sediment characteristics.

En esta investigación, se evidencian las implicancias ambientales de los procesos de transformación del paisaje sobre el territorio del borde costero de La Araucanía en Chile, el cual se caracteriza por cinco aspectos: (1) altos niveles de pobreza y de ruralidad, (2) una importante consolidación y expansión de asentamientos agregados, (3) presencia de elementos singulares dados por condiciones naturales (humedales, bosques pantanosos, estuarios), (4) pueblos originarios (mapuche) y (5) procesos de colonización tardía. La investigación muestra inicialmente una revisión exploratoria de los hitos históricos más relevantes que han determinado los procesos de transformación del paisaje. Luego se evalúa geoespacialmente el cambio de uso del suelo entre los años 1980 y 2004, lo que permite precisar las principales categorías de cambio del uso del suelo y el estado actual del paisaje ecológico. Este análisis se complementó con la revisión de indicadores demográficos y socioeconómicos que permite visualizar los efectos del cambio de uso del suelo en la población. Los resultados mostraron que la irrupción de la agroganadería hispano-mediterránea y la posterior desforestación por parte de los colonos tuvo graves efectos en el paisaje. Más recientemente, la dinámica de transformación en la matriz agropecuaria dominante hacia la actividad forestal (pasando de 1% en 1980 a 19% en 2004), ocasionó un retroceso de 8.762 ha de la matriz agropecuaria y una disminución general de todas las coberturas naturales. De este modo, se cuantificó una redistribución de los usos del suelo, aumento de la fragmentación del paisaje y pérdida de conectividad espacial de los sistemas naturales. A su vez, se constató un desplazamiento de la población rural y la consolidación de centros urbanos como Nueva Toltén, Hualpín, Teodoro Schmidt y Saavedra, lo cual se relaciona con la disminución de la natalidad, el incremento de la tasa de envejecimiento y la falta de empleo. Se concluye que la interfaz de relaciones socio-culturales, físico-ambientales y económicas en el área, dan cuenta de la necesidad de nuevos enfoques e instrumentos de planificación que permitan potenciar el desarrollo local. This research makes evident the environmental implications of the process of transforming the landscape in the territory of the coastal strip of La Araucania in Chile, which is characterized by five aspects: (1) high level of poverty and rurality, (2) a major consolidation and expansion of aggregate settlements, (3) the presence of singular elements due to natural conditions (wetlands, swamp forests, estuaries), (4) aboriginal people (mapuche) and, (5) late colonization process. The research shows initially an exploratory revision of the more relevant historical milestones, which have determined the process of transforming the landscape. Then, the change in land use between 1980 and 2004 it is geospatial rated, which allows to specify the main categories of change in land use and the current status of the ecological landscape. This analysis was complemented with the revision of demographic and socioeconomic indicators which permits to view the effects of the change in land use in the population. The results showed that the irruption of the spanish agriculture and and the subsequent deforestation by the settlers had severe effects on the landscape. More recently, the dynamics of transformation in the matrix to the dominant agricultural towards forestry (from 1% in 1980 to 19% in 2004), caused a decrease of 8.762 hectares of the agricultural matrix and a general decline of all natural coverage. Thus, a redistribution of the land use, an increased fragmentation of the landscape and a loss of spatial connectivity of natural systems was quantified. Besides, there was a movement of the rural population and a consolidation of urban centers like Nueva Toltén, Hualpin, Teodoro Schmidt y Saavedra, which it is related to falling of birth rate, increasing of rate of aging and lack of employment. We conclude that the interface of socio-cultural relations, economic and physical environment in the area, reveals the need for new approaches and planning tools for enhancing local development.

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.

El estudio se desarrolla en base a la identificacion y distribucion de Spionidae y su relacion con las caracteristicas abioticas del medio, en la desembocadura del sistema estuarial Valdivia-Tornagaleones (Chile). Se muestrearon cuatro periodos en 2005, identificandose ocho especies, Aquilaspio peruana, Boccardia polybranchia, Carazziella carrascoi, Dipolydora socialis, Minuspio patagonica, Rhynchospio glutaea, Scolelepis quinquedentata y Spiophanes sp. Como es tipico en otros estuarios del centro sur de Chile, los espionidos fueron un componente importante de la macroinfauna del estuario Valdivia. La distribucion de la familia Spionidae en el sistema estudiado mostro una mayor riqueza de especies en la zona exterior del estuario, pero altas abundancias (numero de especies) en las zonas interiores. El patron distribucional no vario a lo largo del ano, pero si mostro una fuerte zonacion espacial, con tres grupos significativamente diferentes. Destaco la contribucion de M. patagonica, A. peruana y C. carrascoi en la similaridad de cada uno de estos grupos y de igual forma dentro del componente general de la macroinfauna. Las variables sedimentologicas y profundidad como tambien la contribucion de la materia organica fueron solamente relacionadas marginalmente con la distribucion de esta familia. Los resultados mostraron que la variable ambiental responsable en diferenciacion espacial de los espionidos en los tres grupos, fue la salinidad de fondo permitiendo diferenciar el grupo mas externo con los ubicados al interior de la zona de estudio. La importante contribucion de los espionidos en el componente total de la macroinfauna de la zona de estudio, permiten establecer que especies de esta familia representan un componente importante de zonas estuarinas y de transicion de las costas del pacifico sudoriental.

The 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

Uno de los sistemas lóticos chilenos de mayor importancia de acuerdo a su caudal es el río Biobío (ca. 37º S). Su estuario es reducido, especialmente en las épocas de máximo caudal. Con el objetivo de poner a prueba la hipótesis de que en verano la disminución del caudal del río Biobío, determina una mayor depositación 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 disminución de la macrofauna bentónica, se recolectaron muestras para análisis sedimentológicos y faunísticos en el curso inferior y estuario del río Biobío, durante agosto de 1993 y marzo de 1994. Los análisis sedimentológicos indican que el tamaño medio del sedimento correspondió a arenas gruesas. La depositación del material fino suspendido, que ocurre durante el verano se manifiesta en el mayor porcentaje de finos y materia orgánica durante este período. La macrofauna bentónica estuvo compuesta por 16 taxa en el muestreo de invierno y 42 taxa en el de verano. Durante el invierno, la mayoría de ellas estuvo representada por muy pocos individuos. Durante el verano aumentó la riqueza específica y abundancias totales de la macrofauna. Los taxa más abundantes fueron un Archiannelida indeterminado y el poliqueto Perinereis gualpensis. El aumento del caudal en la época invernal, determina el transporte del material depositado hacia el mar y consecuentemente el arrastre de organismos bentónicos. Aún 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 carácter atípico del estuario del río Biobío, el que debido a sus cambios estacionales de caudal genera cambios significativos en la estructura comunitaria de la macrofauna bentónica The Biobío river (ca. 37º S) is one of the most important Chilean lotic systems with regard to their water flow. Its estuary is reduced, especially during maximum flow. With the purpose of testing the hypothesis that during summer, the decrease of river flow results in a higher deposition of fine particles, and that the increase in river flow during winter results in the washing and transport of deposited particles, and consequently in a decrease of the benthic macrofauna. Sediment samples were collected for sedimentological and faunistical analysis during August 1993 and March 1994. The sedimentological analyses indicate that mean size of sediment corresponded to coarse sands. During summer, the deposition of suspended particles is facilitated by the decrease in the river flow and results in higher percentage of fine particles and organic matter in the sediment. The benthic macrofauna was composed by 16 taxa during winter and 42 taxa during summer. During winter, that macrofauna was represented by just a few individuals. During summer, the species richness and macrofaunal abundances increased. The most abundant taxa were an archiannelid species and the polychaete Perinereis gualpensis. The increase of river flow during winter determines the transport of the deposited material toward the sea and consequently, the washing of benthic organisms. Even though, values of macrofaunal abundance and biomass during summer were about one order of magnitude higher than during winter, they are still lower than those mentioned for other estuaries of south-central Chile (ca. 39º S). That confirms the atypical character of the Biobío river estuary, which due to its seasonal changes, significantly affects the community structure of the benthic macrofauna