Hydrogeochemical and biological characteristics of cenotes in the Yucatan Peninsula (SE Mexico)

• Published in: Hydrobiologia 2002-01, Vol.467 (1-3), p.215-228
• Main Authors: Schmitter-soto, Jj, Comín, Fa, Escobar-briones, E, Herrera-silveira, J, Alcocer, J, Suárez-morales, E, Elías-gutiérrez, M, Díaz-arce, V, Marín, Le, Steinich, B
• Format: Article
• Language: English
• Subjects: Anaerobic bacteria; Aquatic ecosystems; Aquatic plants; Aquifers; Brackish; Calcium; Carbonate rocks; Caves; Crustaceans; Endemic species; Floating plants; Floats; Freshwater; Hypolimnion; Marine; Meromixis; Organic matter; Rainy season; Saline water; Shellfish; Sinkholes; Stratigraphy; Trophic levels; Water column; Water flow
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1023/A:1014923217206

Cenotes (sinkholes) are the most peculiar aquatic ecosystem of the Yucatan Peninsula (SE Mexico). They are formed by dissolution of the carbonate rock in the karstic platform of the Yucatan Peninsula. A wide morphological variety is observed from caves filled with ground water to open cenotes. In some cenotes, particularly those close to the sea, underneath the fresh water one finds saltwater, where meromixis can take place. This occurs because in the Yucatan Peninsula there is a thin lens (10s of meters thick) that floats above denser saline water. In these cenotes, a relative enrichment of sodium related to calcium is observed while conductivity increases. In contrast, a higher increase of calcium associated to sulfate is observed in cenotes located in SE Yucatan Peninsula. A marked vertical stratification of the water is established during the warm and rainy season of the year (May-October). In cenotes with good hydraulic connection with the rest of the aquifer, the water remains clear during most of the year. However, cenotes with poor hydraulic connection with the aquifer are characterized by turbid waters and very low light transparency. In this group of cenotes, the water column contains a high concentration of chlorophyll (mostly due to chlorophyceans, cyanobacteria, diatoms and dinoflagellates); the hypolimnion and the sediment are rich in organic matter and anaerobic bacteria mediated biogeochemical processes are dominant. The upper part of the cenotes walls is well illuminated and covered by a rich microbial mat. Floating macrophytes may also occupy part of the water surface in oligotrophic cenotes. A great variety of food web paths are represented in the habitats occurring in the cenotes, in which few trophic levels are involved. A few endemic species (crustaceans and fishes) have been reported from cenotes found in the Yucatan Peninsula. Because of the high organic matter input (alochthonous) and production (autochthonous) and the low water flow, cenotes can be considered heterotrophic systems.[PUBLICATION ABSTRACT]