TY - JOUR AU - MACEK, Miroslav AU - ALCOCER, Javier AU - LUGO VÁZQUEZ, Alfonso AU - MARTÍNEZ-PÉREZ, María Elena AU - PERALTA SORIANO, Laura AU - VILACLARA FATJÓ, Gloria PY - 2009/08/01 Y2 - 2024/03/28 TI - Long term picoplankton dynamics in a warm-monomictic, tropical high altitude lake JF - Journal of Limnology JA - J Limnol VL - 68 IS - 2 SE - Original Articles DO - 10.4081/jlimnol.2009.183 UR - https://www.jlimnol.it/jlimnol/article/view/jlimnol.2009.183 SP - 183-192 AB - Long term analyses of the microbial loop, centred on the picoplankton dynamics, were carried out over a five-year (1998 to 2002) period in Lake Alchichica (Puebla, Mexico), a high altitude tropical athalassohaline lake. The hydrodynamics of the lake followed a warm-monomictic pattern with mixing at a minimum temperature during the early dry season while the stratification was pronounced in the late dry season and throughout the rainy season; anoxic conditions in the hypolimnion lasted <9 months. The annual mean concentrations of chlorophyll-a were below 4 μg L-1 in 1998, 1999 and 2001, however, 6.1 and 5.2 μg L-1 in 2000 and 2002, respectively. Total picoplankton, TPP, displayed a temporal pattern that followed the mixing-stratification cycle. The highest TPP values (the whole water column ≥5×106 cells mL-1) were found during mixing and early stratification (January-March). The minimum numbers were present during late stratification (October-November). The maximum TPP numbers were observed within the layer 0-20 m, which corresponded to the epilimnion during the stratification period. Neither the thermocline nor the deep chlorophyll maximum showed an elevated TPP concentration. In the hypolimnion, TPP numbers were low (frequently <1×106 cells mL-1) apparently as a result of the long period of anoxia. Notwithstanding autotrophic picoplankton (APP) contributed even ≥30% of TPP (2001 to 2002); no significant correlation was found between TPP and chlorophyll-a. ER -