Revista de Biología Tropical ISSN: 0034-7744 [email protected] Universidad de Costa Rica Costa Rica Donato, Jhon; Jimenez, Paola; Reynolds, Colin Limnology in El Dorado: some surprising aspects of the regulation of phytoplankton productive capacity in a high-altitude Andean lake (Laguna de Guatavita, Colombia) Revista de Biología Tropical, vol. 60, núm. 3, septiembre, 2012, pp. 967-980 Universidad de Costa Rica San Pedro de Montes de Oca, Costa Rica Available in: http://www.redalyc.org/articulo.oa?id=44923907002 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Limnology in El Dorado: some surprising aspects of the regulation of phytoplankton productive capacity in a high-altitude Andean lake (Laguna de Guatavita, Colombia) Jhon Donato1, Paola Jimenez2 & Colin Reynolds3 1. Departamento de Biología, Universidad Nacional de Colombia, Av (Cra.) 30 No. 45-03, Bogotá, Colombia; jcdona- [email protected] 2. Departamento de Biología, Universidad Nacional de Colombia, Av (Cra.) 30 No. 45-03, Bogotá, Colombia; paola- [email protected] 3. CEH Lancaster, Library Avenue, Bailrigg, GB-LA1 4AP Lancaster UK; [email protected] Received 29-VII-2011. Corrected 30-I-2012. Accepted 29-II-2012. Abstract: High-altitude mountain lakes remain understudied, mostly because of their relative inaccessibility. Laguna de Guatavita, a small, equatorial, high-altitude crater lake in the Eastern Range of the Colombian Andes, was once of high cultural importance to pre-Columban inhabitants, the original location of the legendary El Dorado. We investigated the factors regulating the primary production in Laguna de Guatavita (4°58’50” N - 73°46’43” W, alt. 2 935m.a.s.l., area: 0.11km2, maximum depth: 30m), during a series of three intensive field campaigns, which were conducted over a year-long period in 2003-2004. In each, standard profiles of tempera- ture, oxygen concentration and light intensity were determined on each of 16-18 consecutive days. Samples were + collected and analysed for chlorophyll and for biologically-significant solutes in GF/F-filtered water (NH4 , - - NO3 , NO2 ; soluble reactive phosphorus). Primary production was also determined, by oxygen generation, on each day of the campaign. Our results showed that the productive potential of the lake was typically modest (campaign averages of 45-90mg C/m2.h) but that many of the regulating factors were not those anticipated intuitively. The lake is demonstrably meromictic, reminiscent of karstic dolines in higher latitudes, its stratifica- tion being maintained by solute- concentration gradients. Light penetration is poor, attributable to the turbidity owing to fine calcite and other particulates in suspension. Net primary production in the mixolimnion of Laguna de Guavita is sensitive to day-to-day variations in solar irradiance at the surface. However, deficiencies in nutrient availability, especially nitrogen, also constrain the capacity of the lake to support a phytoplankton. We deduced that Laguna de Guatavita is something of a limnological enigma, atypical of the common anticipation of a “mountain lake”. While doubtlessly not unique, comparable descriptions of similar sites elsewhere are suf- ficiently rare to justify the presentation of the data from Laguna de Guatavita that our studies have revealed so far. Rev. Biol. Trop. 60 (3): 967-980. Epub 2012 September 01. Key words: chlorophyll a, photosynthetic rate, stratification, meromictic structure, sacred lakes. High-altitude mountain lakes remain rela- potentially narrow ranges of annual tempera- tively under-researched, mostly because of ture variation seem likely to generate only their remoteness and relative inaccessibility modest seasonal effects on phytoplankton pro- render them logistically difficult locations for duction, at least when compared to the cyclic, sustained research programmes. The popular seasonal variability detected among temperate assumption that they are usually highly trans- lakes (Lewis 1996). On the other hand, as at parent, oligotrophic and nutrient-poor has been all other latitudes, short-term variability in scarcely challenged. When mountain lakes insolation, in hydrological exchanges, in wind- are simultaneously located at low latitudes, induced vertical mixing and in their various small annual fluctuations in day length and impacts on the underwater availability of light Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 60 (3): 967-980, September 2012 967 and nutrients, in the intensity of planktivores necessarily undertaken in a series of intense activity, is as potentially pervasive in influ- 16-18 day field campaigns that were designed encing phytoplankton dynamics and period- to obviate a large number of distant sampling icity (Talling 1969, Lewis 1996, Hubble & expeditions. However, as we shall demon- Harper 2001). Nevertheless, lakes situated in strate, almost every aspect of the limnology of mountainous regions may well be subject to Laguna de Guatavita was substantially outside fluctuating local microclimates and weather our expectations. Our findings showed that the conditions, introducing extremes of cloud and environmental factors that substantially control precipitation, including snow, that leave habi- the biological productivity of the lake were tats as vulnerable to short-term variability in sufficiently counterintuitive to persuade us to irradiance, nocturnal cooling, mixed depth and share our observations with a wider audience light availability, as they do in the trophogenic of limnologists. layers of lakes at higher latitudes. It is relevant to mention that there was Whereas the photosynthetic responses of another factor influencing our selection of phytoplankton to short-term variations in light Laguna de Guatavita as a study site and it has intensity are now well documented (Marra less to do with limnology and rather more to 1978, Yoder & Bishop 1985, Kroon et al. 1992, its significance in the long history of the pre- Mallin & Paerl 1992), longer-term adaptive Columbian settlement of the central Andes by adjustments –in swimming behaviour, pigmen- indigenous people. At least one tribe of Indians, tation, and growth rates– eventually affect- the Muiscas, flourished here until the 16th Cen- ing changes in species composition - are still tury. They belonged to the Chibcha linguistic being resolved (Reynolds 2006). The case for family that settled mainly in the basins of the investigating phytoplankton assemblages, in the former Pleistocene lakes, between Bogotá and context of a wide range of well-characterized Tunja (Reichel-Dolmatoff 1997). Indeed, lakes habitat conditions, remains strong. The desire to figured importantly in Muiscan culture: life include information on the environmental con- and death were regarded as transitions between ditions and dynamic responses of phytoplank- terrestrial activity and aquatic dormancy. The ton in high-altitude, low-latitude lakes requires various high-altitude lagoons were treated as no further justification. The choice of suitable sacred places, dedicated to the gods and where locations in the high mountains of the Andean they were worshiped and were paid tributes in Cordillera and close to the equator seems, ret- the form of figurines, fashioned from wood, cot- rospectively, self-selecting: there are numerous ton, stone and, especially, gold, called “tunjos”, small lakes, of various origin (orogenic, volca- and emeralds. The famous legend of El Dorado nic and glacial), located in the Cundinamarca originated from the Muiscan practice of anoint- and Boyacá departments of Colombia, and not ing new chiefs with turpentine and gold dust, excessively distant from the National University from forehead to feet, so that they resembled in Bogotá, that offer prima-facie sites for inves- a shaft of radiant light. The new chief became tigation of the influences of low latitude and purified by bathing in the limpid waters of the high altitude on fundamental hydrobiological Guatavita lagoon, from which activity, he drew processes. Even in this particular region, there the strength and wisdom necessary to govern are inevitable logistic difficulties in organizing his people with due justice (Perdomo 1989). It and sustaining relevant systematic field studies. was the ablutions that became of interest to the In the end, the results of an earlier survey of one post-Columban conquistadores. of these lakes (Zapata 2001, Rivera et al. 2005, Donato 2010) were decisive in selecting Laguna MATERIALS AND METHODS Guatavita as the site for the present study. The first purpose of this paper is to con- Laguna de Guatavita is one of a series vey the results of this investigation. It was of heterogeneous lakes located in the Eastern 968 Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 60 (3): 967-980, September 2012 Range of the Colombian Andes, supposed to Vertical profiles of dissolved oxygen con- have been formed towards the end of the Pleis- centration, temperature, conductivity and light tocene glaciation, 10 000-12 000 years before at the deepest point of the lake were also present (Psenner & Catalan 1994). The lakes constructed each day. Temperature and dis- vary in their morphometry, hydrology, chemi- solved oxygen were measured using a YSI cal composition and stratification, as well as Model 57 probe (Yellow