Limnology, in particular eutrophication processes of tropical high mountain lakes in Ecuador. Ecology of high Andean streams.

 

(German Research Foundation, German Federal Ministry of economic Cooperation and Development).

 

 

Assessment of quality of water and eutrophication tendency of high-altitude tropical lakes, as they occur in the high Andes of South America, was previously hardly possible because there are no sufficient studies on ecology of these waters. Extremely high levels of UV radiation and missing seasons cause that these waters cannot be compared with waters of the temperate climate zone.

  

In cooperation with the Escuela Politecnica Nacional de Quito, Ecuador and the Pontificia Universidad Catolica del Ecuador, the San Pablo Lake, a cold (up to 20 ° C) high mountain lake, located directly on the equator, and its tributary, Rio Itambi, were investigated. The Lagos San Pablo is 600 ha and 35 m deep and is located at 2,700 m above sea level. The inflow takes place over a stream, which drains the surrounding mountain watershed with a height of up to 4,000 m.

Lago San Pablo

 

 The results show that the lake is monomictic with a stratification phase from October to June with only about 2 ° C temperature difference, the epilimnion is 15 m thick and is characterized by nocturnal cooling processes. Nocturnal convergence flows occur and lead to a regular partial mixing of the lake, the so-called atelomixis. Here, a part of the phytoplankton population is shifted to the non-illuminated aphotic zone.

Phosphorus is present in high concentrations in the epilimnion (0.14-0.25 mg / L SRP) year-round.

  • Eutrophication is manifested primarily in the development of macrophytes and the occurrence of a hypolimnic oxygen deficit.
  • Limitation of primary production occurs by nitrogen, only occasionally phosphorus becomes minimum factor.
  • A harmful effect of high UV radiation could not be detected.
  • In addition, however, atelomixis and the associated algae losses of the epilimnion inhibit development of the phytoplankton.
  • Composition of the community of the lake is characterized by an extreme species poverty (with high biomass), the low biodiversity is probably the result of the isolated position of the high mountain lake in the tropics.
Lago San Pablo, Eciador, with enclosures study effects of UV radiation
Lago San Pablo, Eciador, with enclosures study effects of UV radiation

Rio Itambi

 

Depending on altitude, structure of the rivers in Ecuador varies greatly, although the high-altitude waters (2,500 to 4,500 m) have so far hardly been recorded and described ecologically. Data on ecological zonation and hydrological structure, however, form the basis for any monitoring of the waters.

 

Catchment area, water structure and chemical and biological dynamics of Rio Itambi, a typical Andean highland river, have been studied to deepen knowledge of biology of highland waters and to establish a system of river zonation. Essential parameters for the formation of the biocoenosis are the low oxygen concentrations, the lack of allochthonous entry and the high dynamics of erosion associated with regular landslides.

 

Publications

 

Lago San Pablo

  • Casallas Guzmán, J. (2005) Limnological investigations in Lake San Pablo, a high mountain lake in Ecuador. Dissertationsschrift, TU Berlin. 137 p. [download: http://edocs.tu-berlin.de/diss/2004/casallas_jorge.htm]
  • Gunkel, G. & Casallas, J. (2004) El Lago San Pablo (Imbakucha) – Un lago eutrófico? In: Mercure, St., W. Wilson & T. Whillans (eds). Gestión Integral de Cuencas y Asentamientos Humanos, IMBAKUCHA 2002. 413-427. Abya-Yala, Quito, Ecuador.
  • Kiersch, B., Mühleck, R. & Gunkel, G. (2004) Las macrofitas de algunos lagos altoandinos del Ecuador y su bajo potencial como bioindicatores de eutrofización. Revista de Biologia Tropical 52, 829-837.
  • Gunkel, G. (2003) Limnología de un Lago Tropical de Alta Montaña, Lago San Pablo-Ecuador: Características de los sedimentos y tasa de sedimentación. Revista de Biología Tropical 51, 2, 381-390.
  • Gunkel, G. & J. Casallas (2002) Limnological of an equatorial high mountain lake, Lago San Pablo, Ecuador: Limitation of lake productivity by deep diurnal mixing. Proc. Int. Ass. Theoret. Applied Limnol. 28 , 1818-1823.
  • Gunkel, G. & Casallas, J. (2002) Limnology of an Equatorial High Mountain lake, Lago San Pablo, Ecuador: The Significance of Deep Diurnal Mixing for Lake Productivity. Limnologica 32, 33-43.
  • Casallas, J. & Gunkel, G. (2002) Algunos aspectos limnologicos de un lago altoandino: El Lago San Pablo, Ecuador. Limnetica 20, 2, 29-46.
  • Gunkel, G. (2000) Limnology of an equatorial high mountain lake in Ecuador, Lago San Pablo. – Limnologica 30, 113-120.

 

Rio Itambi

  • Carrera, P. & Gunkel, G. (2004) Ecología del Rio Itambi, San Pablo, Otavalo, Ecuador. In: Mercure, St., W. Wilson & T. Whillans (eds). Gestión Integral de Cuencas y Asentamientos Humanos, IMBAKUCHA 2002. 381-403. Abya-Yala, Quito, Ecuador.
  • Carrera Burneo, P. & Gunkel, G. (2003) Ecology of an high Andean strema, Rio Itambi, Otavalo, Ecuador. Limnologica 33, 29-43.
  • Carrera, P. (2002) Beschreibung und Klassifizierung eines kleinen Fließgewässers der Hochandenregion (Rio Itambi) in Hinblick auf Einzugsgebiet, Gewässerstruktur und Dynamik. Dissertation Technische Universität Berlin, 96 S. u. Anhang