Abstract

  Holbox Island (with its coastal lagoon, Yalahau Lagoon) located in the littoral zone at the north-eastern tip Yucatan Peninsula, Gulf of Mexico, is a relatively undisturbed ecosystem that is currently under threat '67 unplanned and intensive urban development Although other ecosystems in this littoral zone have been tied to determine the basic requirements for sustainable development, little information about Holbox Island its. Thus far, no data concerning coastal pollution in Yalahau Lagoon have been published. As part of a larger on-going study, this article reports the results of analyses to determine the temporal and spatial variations of standard physical and chemical parameters and to evaluate the relationships among these parameters. Water and sediment samples collected from 42 stations during two seasons of the year (rainy and dry seasons) analyzed using standard methods. The results indicate that, in general, the area is relatively undisturbed by human influence. Dissolved oxygen content was lower than 4 ml l-1 and the percentage of oxygen saturation than 90%, suggesting that the site supports higher consumption than production of oxygen. Nitrogen is present as ammonium and low concentrations of nitrate; nitrite, and phosphate indicate that eutrophication is not widespread in the area. Sediments are mostly sandy, containing less than 10% organic matter at most stations. The redox potential of sediments was negative for all samples. Water quality at stations in the proxim9ating and dun ping activities shows higher degradation than at other stations within the lagoon. These preliminary results provide the opportunity to construct a baseline for coastal water quality prior to impending urban development, and may serve to determine whether the future natural and development processes have the conditions and health of coastal ecosystems around Holbox Island. In addition, because the area is, as yet, relatively undisturbed, the data reported here allow us to take stock of the extent to which other sites in the Yucatan littoral zone have already been degraded by human development activities.

Keywords: water analysis, sediment analysis, GIS mapping