Revista Chilena de Historia Natural 76 (4): 563-590, 2003
RESEARCH ARTICLE
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 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<sup>-1</sup> and 197 and 380 µg L<sup>-1</sup>
(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<sup>-1</sup>) and total phosphorus (= 223 and 497 µg
L<sup>-1</sup>), 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
