Aquatic ecosystems of the Yucatan Peninsula (Mexico), Belize, and Guatemala

This study presents limnological and morphological characteristics, physical and chemical properties of waters, and geochemistry of surface sediments for 63 aquatic ecosystems located on the karst Yucatan Peninsula and surrounding areas of Belize and the Guatemalan highlands and eastern lowlands. Our principal goal was to classify the aquatic systems based on their water variables. A principal component analysis (PCA) of the surface water chemistry data showed that a large fraction of the variance (29%) in water chemistry is explained by conductivity and major ion concentrations. The broad conductivity range, from 168 to 55,300 mu S cm(-1) reflects saline water intrusion affecting coastal aquatic environments, and the steep NW-S precipitation gradient, from similar to 450 to > 3,200 mm year(-1). Coastal waterbodies CelestA(0)n and Laguna Rosada displayed the highest conductivities. Minimum surface water temperatures of 21.6A degrees C were measured in highland lakes, and warmest temperatures, up to 31.7A degrees C, were recorded in the lowland waterbodies. Most lakes showed thermal stratification during the sampling period, with the exception of some shallow (< 10 m) systems. Lakes Chichancanab, Milagros, and Bacalar displayed sulfate-rich waters. Waters of sinkholes had relatively high conductivities (< 3,670 mu S cm(-1)) and a broad range of delta O-18 values (-4.1 to +3.8aEuro degrees). Ca, HCO3, and SO4 dominated the waters of the lowland lakes, whereas Na was the dominant cation in highland lakes. Coastal aquatic ecosystems were dominated by Na and Cl. Cluster analysis based on surface water variables classified aquatic environments of the lowlands and highlands into three groups: (1) lowland lakes, ponds, wetlands, and coastal waterbodies (2) highland lakes, and (3) sinkholes and rivers. A broad trophic state gradient was recorded, ranging from the eutrophic Lake Amatitlan and the Timul sinkhole to oligotrophic Laguna Ayarza, with the highest water transparency (11.4 m). We used major and trace elements in surface sediments to assess pollution of waterbodies. Lakes Amatitlan, Atescatempa, El Rosario, Cayucn, Chacan-Lara, La Misteriosa, rivers Subin and Rio Dulce, the wetland JamolA(0)n, and the sinkhole Pet,n de Monos showed evidence of pollution and urban development. Their surface sediments displayed high concentrations of As, Cu, Fe, Ni, Pb, Se, Zn, and Zr, which suggest moderate to strong pollution.