Limnological and morphometrical data of eight karstic systems 'cenotes' of the Yucatan Peninsula, Mexico, during the dry season (February-May, 2001)

The karstic nature of the Yucatan Peninsula allows the formation of natural sink-holes from the dissolution of calcareous rock. These systems are almost the only epigean source of fresh water available in this region. In spite of their biological importance, little is known about the morphometric and limnologic characteristics of these karstic systems. We measured limnological variables in eight cenotes in central Quintana Roo during February-May, 2001. Zooplankton biomass and chlorophyll a were also measured in order to determine if the behavior of primary and secondary production was related to environmental parameters. Important short-term changes were observed in nutrients (NO^sub 3^^sup -^, NO^sub 2^^sup -^, PO^sub 4^^sup 3-^), biomass, and chlorophyll a. The morphometrically conditioned productivity (MCP), which evaluates the cumulative effect of several morphometric variables on production (area, maximum length, shoreline development, perimeter), showed a negative correlation with respect to zooplankton biomass, as did also both pH and temperature. Conversely, NO^sub 3^^sup -^ and NO^sub 2^^sup -^ had a positive correlation with zooplankton biomass. No correlation was found for chlorophyll a. Significant differences in NO^sub 3^^sup -^ (F = 61.52, p