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

Abstract

From November 1996 to October 1997, the river basins of five humic lakes on Chiloé Island were studied monthly: Lakes Natri, Tepuhueico, Tarahuín, 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 µg L -1 (annual average) in lakes Natri, Tepuhueico and Tarahuín, respectively. Lakes Cucao and Huillinco showed extremely high concentrations of total nitrogen (annual average => 3,000 µg L -1 ) and total phosphorus (= 223 and 497 µg L -1 ), and were classified as hyper-eutrophic. Lake Tarahuín registered the greatest diversity of phytoplankton, with 55 species, including Ceratium hirundinella which also occurred in lakes Cucao and Tarahuín. 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.Key words: river basin, limnological characterization, humic lakes, Chiloé, southern Chile. RESUMENDurante noviembre de 1996 y octubre de 1997 mensualmente se estudió la cuenca de cinco lagos húmicos localizados en la Isla de Chiloé: Lagos Natri, Tepuhueico, Tarahuín, Huillinco y Cucao. El estudio tuvo como objetivo conocer el área de la cuenca, la cuenca hidrográfica y las principales características físicas, químicas y biológicas de estos lagos húmicos. Se determinó el estado trófico, como también la carga actual y el balance másico de fósforo y nitrógeno total, en relación a actividades antrópicas. Los lagos Cucao y Huillinco se caracterizaron por presentar influencia marina. Todos los lagos tienen aguas de color marrón, causadas por las sustancias húmicas, que limitan la transparencia. El lago Natri es el más profundo (58 m), mientras que el Tepuhueico presentó la menor profundidad (25 m). Concentraciones de fósforo y nitrógeno total fluctuaron entre 23,5 y 35 µg L -1 y 197 y 380 µg L -1 en los lagos Natri, Tepuhueico y Tarahuín. Mientras que los lagos Cucao y Huillinco mostraron para el nitrógeno y fósforo concentraciones extremadamente altas, para el nitrógeno total (promedio anual > 3.000 µg L -1 ) y para el fósforo (223 y 496 µg L -1 ) clasificándolos como hipereutróficos. El lago Tarahuín registró la mayor diversidad fitoplanctónica con 55 especies. En los lagos Cucao y Tarahuín, destaca la presencia de Ceratium hirundinella. La comunidad zooplanctónica mostró diferencias en la diversidades de especies en los l...

The sedimentary record of the 1960 tsunami in two coastal lakes on Isla de Chiloé, south central Chile

“…Lake Cucao is separated from the ocean by a 1.3 km wide and 5 to 6 m high barrier; the maximum lake water depth is 21 m. The lake surface is at sea level and a river channel through the barrier allows exchange of water with the ocean. The marine water inflow during high tide is enough to cause a stable saline bottom-water body throughout the year, despite strong winds and shallow water depth (Villalobos et al, 2003). A barrier 1.1 km wide and 5 to 6 m high separates Lake Huelde from the ocean.…”

“…The catchment-area-tolake-area ratios of Lake Cucao and Lake Huelde are 3.1 (Villalobos et al, 2003) and ~75, respectively.…”

“…26 as a tidal delta due to the water inflow from the ocean at high tide (Villalobos et al, 2003). The size of the tidal delta in Lake Cucao and the megaripples on its surface indicate considerable inflow and sediment transport (Fig.…”

Geographic variations in shell growth rates of the mussel Diplodon chilensis from temperate lakes of Chile: Implications for biodiversity conservation

“…No observed effect concentration (NOEC) value for both survival and reproduction was 970 mg N L À1 , and the lowest observed effect concentration (LOEC) value was 5400 mg N L À1 for survival after 60 days, giving a calculated threshold effect concentration (TEC) of 2300 mg N L À1 . The only systems of which we have an important database of ammonium concentrations, are the lakes of Chiloe Island (see Villalobos et al, 2003). Of these systems, the only one that presents particularly high ammonium concentrations, is the Huillinco Lake with concentrations between 113.8 and 2,782.8 mg N L À1 .…”

Paleotsunami record of the past 4300 years in the complex coastal lake system of Lake Cucao, Chiloé Island, south central Chile

“…Currently, Lake Cucao lies in the intertidal zone (Villalobos et al, 2003;Kempf et al, 2015), 605 with saline water flowing into the lake from the Pacific during high tides. This process has been 606 active at least sporadically since 4300 cal.…”