IWRA Proceedings

AbstractLake Petén Itzá (16°54`00”N and 89°41´41” W) is located in the lowlands in the north of Guatemala Republic, at 110 m above sea level, within the Maya Biosphere Reserve. The Lake has an area of 100 Km2 and 160 m maximum depth. The basin (1200 Km2) is located in a Tropical Wet Forest Bioma and Subtropical Wet Forest according to Holdridge Life Zones classification. Lake Petén Itzá has not surface effluents. The Department of Petén has overcome a demographical explosion since the 1960s, registering an increment in population from 25000 people to more than one-half million living nowadays in Petén. This has represented an important pressure on the ecological integrity of the ecosystems, which can be observed in Lake Petén Itzá basin. Forest loss, intensive agriculture, ranching and direct sewage discharges from the main towns in the basin (Flores, San Benito and Santa Elena), have increased the inputs of nutrients and pollutants to the lake. The aim of this study was to evaluate the water quality and trophic state of Lake Petén Itzá in order to provide relevant information for making decisions related with water resources management. Water and sediments were sampled quarterly each year since 2004, in seventeen sites in Lake Petén Itzá. Sampling sites were selected near towns and affluents. Water physicochemical and bacteriological analyses were made according to APHA- AWWA methodology [3]. Toxic metals and organochlorine pesticides were analyzed in individuals of Petenia splendida endemic fish. Nutrients levels found in Lake Petén Itzá corresponded to eutrophic lakes, as N-NO3 was found in mean concentrations above 500 g/L and P-PO4 showed mean concentrations above 50 g/L especially in sites near towns. This was confirmed by the presence of eutrophic and hypereutrophic phytoplankton organisms (cyanophytes, chlorophytes and diatoms). Some pollutants found in Lake Petén Itzá, represents risks for the ecology and human health, as ammonia, which was found in high concentrations in sites near towns. Individuals of the endemic fish species Petenia splendida, showed levels of toxic metals (lead and mercury) and organochlorine pesticides (p,p´-DDT 0.7-1.2 ng/g; p,p´-DDE 5.4-20.2 ng/g and p,p´-DDD 0.8-1.9 ng/g), that should be considered, as this fish is prepared in traditional dishes in Petén. Total and fecal coliforms and Escherichia coli were found in water of all sampling sites. The water quality in Lake Petén Itzá is not apt for human consumption or for recreation. Thus it is important that the government make decisions regarding the wastewater treatment in the short-term, especially in Santa Elena, San Benito and Flores. [1] APHA, AWWA, WPCF., Standard Methods for the Examination of Water and Wastewater (20 ed). (1998) 1193 pp.