Lorena Villalobos

Trophic parameters and method validation in Lake Riñihue (North Patagonia: Chile) from 1978 through 1997

El lago Rinihue es el ultimo en una cadena de lagos oligotroficos, de origen glacial, en del sur Chile, y fue sujeto de investigaciones limnologicas por el Dr. Hugo Campos y colaboradores de la Universidad Austral de Chile, Valdivia, Chile, desde 1970. El Profesor Campos fallecio en terreno en 1998 y esta publicacion ahora presenta una revision de estos datos con comentarios acerca de la metodologia concerniente a parametros troficos de este lago. Se presentan datos de nutrientes inorganicos, clorofila a, fitobiomasa, productividad primaria y profundidad de Secchi obtenidos a traves de un periodo de 21 anos entre 1978 y 1997, con el objetivo de evaluar cambios potenciales de estos parametros a traves del tiempo. Se utilizaron pruebas no parametricas de Wilcoxon para determinar tendencias temporales y ellas revelaron que: (1) el fosforo total mostro un aumento significativo (TP: 2,7 mg P L-1 a 6,5 mg P L-1), (2) la profundidad de Secchi, el fosforo reactivo soluble y la productividad primaria no cambiaron significativamente, (3) la clorofila a cambio significativamente entre diferentes anos, pero no revela una clara tendencia temporal, (4) el nitrato mostro una tendencia a aumentar e incrementar las concentraciones durante el periodo a inicios de 1990, aunque estos datos se debieron sin duda a anomalias metodologicas, y (5) la fitobiomasa mostro valores significativamente mas altos durante el periodo de 1980. El aumento significativo en el fosforo total y la tendencia a aumentar del nitrato podria reflejar un aumento en el uso de praderas dentro de la cuenca de drenaje. Se detectaron una serie de anomalias en los datos historicos relacionadas a la metodologia los cuales se analizaron y discutieron dentro del contexto de este estudio.

Estado de conocimiento de los crustáceos zooplanctónicos dulceacuícolas de Chile

Chile se caracteriza por presentar un marcado gradiente geografico latitudinal y altitudinal. En el es posible encontrar diferentes cuerpos de agua continentales, cuya diversidad se refleja en la composicion de especies zooplanctonicas. En este gradiente se pueden distinguir cinco zonas principales, en las cuales en las ultimas decadas se ha recolectado informacion ecologica y en menor parte taxonomica. En el norte se distingue la zona de lagos y lagunas localizados en el altiplano chileno-peruano, en donde ha sido posible registrar especies endemicas como Daphnia peruviana y especies del genero Boeckella. Chile central se caracteriza por una serie de cuerpos acuaticos localizados a baja altura y normalmente de baja profundidad, entre los zooplanctontes destaca Tumeodiaptomus vivianae. En esta latitud se encuentran tambien lagos de alta montana de mayor profundidad, los que se caracterizan por la presencia de especies del genero Boeckella. En la zona centro sur, en los lagos denominados Nahuelbutensis, existen pocos registros a este respecto. En la zona de lagos Norpatagonicos se ha recolectado la mayor informacion, y se caracterizan por una baja diversidad de especies. Finalmente en la zona sur de Chile, la region mas tipica en cuanto a riqueza de especies, esta localizada en la region de Torres del Paine, con un alto endemismo (Parabroteas sarsi, Daphnia dadayana, D. commutata).

A study of the river basins and limnology of five humic lakes on Chiloé Island

From November 1996 to October 1997, the river basins of five humic lakes on Chiloe Island were studied monthly: Lakes Natri, Tepuhueico, Tarahuin, Huillinco and Cucao. The objective of this study was to know the catchment area, river basin and the main physical, chemical and biological characteristics of these humic lakes. The trophic status, the actual loading, and the mass balances of phosphorus and nitrogen were determined in relation to anthropogenic activities. Lakes Cucao and Huillinco were characterized by a marine influence. All the lakes had brown coloured waters, caused by humic substances, which limit their transparency. Lake Natri was the deepest (58 m), whereas Lake Tepuhueico had the shallowest depth (25 m). Total phosphorus and nitrogen fluctuated between 23.5 and 35 µg L-1 and 197 and 380 mg L-1 (annual average) in lakes Natri, Tepuhueico and Tarahuin, respectively. Lakes Cucao and Huillinco showed extremely high concentrations of total nitrogen (annual average= 3,000 mg L-1) and total phosphorus (= 223 and 497 mg L-1), and were classified as hyper-eutrophic. Lake Tarahuin registered the greatest diversity of phytoplankton, with 55 species, including Ceratium hirundinella which also occurred in lakes Cucao and Tarahuin. The diversity of the zooplankton community varied across these lakes. The presence of Diaptomus diabolicus (Tumeodiaptomus d. Dussart 1979) (Cucao, Huillinco and Tepuhueico) is noteworthy since this extends its geographical distribution to the south

Two South American endemic species of Daphnia from high Andean lakes

Populations of Daphnia peruviana from several high mountain ponds in southern Peru were compared with Hardings type material from the vicinity of Titicaca Lake and the species re-described. Differential diagnosis for three more morphologically similar species from the region is given. New species Daphnia inca found in a mountain pond near the Peru–Chile border is described and compared with other South American species of the subgenus Ctenodaphnia.

Identification of a Potential Copepod Intermediate Host of Camallanus corderoi (Nematoda: Camallanidae) in Southern Chile

Abstract The nematode Camallanus corderoi infects the intestine of native fishes and introduced salmonids in southern Chile between 39°S and 41°S. Among the 4 most common and widely distributed species of copepods in freshwaters of the region that were challenged, only Mesocyclops araucanus (Cyclopoida) was susceptible to experimental infection with C. corderoi. At temperatures of 20 ± 1°C, free first-stage larvae of C. corderoi had reached the hemocoel by 4 hr after ingestion by the copepods. The first molting of larvae was observed on day 2 postinfection (PI). Unsheathed second-stage larvae were observed in the hemocoel at day 3 PI, and had molted by day 6. Unsheathed third-stage larvae were recovered on day 7 PI. Third-stage larvae had a tail with 3 conical processes and a buccal capsule composed of a single chamber with a basal ring and longitudinal ridges.