HYDROLOGICAL ASPECTS OF THE LAGOONS OF ATASTA AND POM, MEXICO

Abstract

The Lagoons of Pom and Atasta are part of a natural protected area of flora and fauna lagoon of Terminos in the region of Campeche, Mexico. This is an important ecological area since it is a habitat of many native and migratory species. These lagoons have been affected by industrial activities and sewage water discharge. Monitoring of nitrogen, phosphorus and faecal coliform in surface waters were carried out along the length of both lagoons during the dry, rainy and north winds seasons during one year. The highest temperatures in the summer (31°C) and minimum in the north winds (25°C) were associated with values of dissolved oxygen (5.1 and 6.3 mg l-1, respectively) indicating also a probably relation of the phytoplankton activity. The pH (8.0-8.2) and the salinity (0.32 – 3.48 SPU) did not show any significant variation amongst the three climatic seasons. The level of ammonium did not surpass the suggested value to the eutrophication control (0.1 mg l-1), while the levels of phosphorus were of higher concentrations (2.0-3.5 mg l-1) to those considered safe (0.01-0.125 mg l-1) to the environmental. The highest concentration of N and P near the inhabitant areas suggest an important contribution of nutrients stemming from the sewage waters, associated with the decomposition of organic materials. The concentration of faecal coliform during the rains and the north wind season (8.0–26.0 MPN 100 ml-1) was greater than during the dry period (1.3–3.5 MPN 100 ml-1) suggesting an important access for the infiltration of rain water and sewage waters not treated coming from the nearest inhabited areas. The deforestation of the mangroves and uncontrolled agricultural activity would affect the quality of the water in both lagoons in the future.