Trophic status in coastal waters of the Yucatan Peninsula (SE, Mexico) using water quality indicators

Yucatan Peninsula Coastal ecosystems are being subjected to increasing anthropogenic stresses such as recreational tourism, port development, overfishing, aquaculture as well as population growth, which are affecting coastal water quality. In order to establish a base-line of the trophic status of different zones along the Yucatan littoral, several seasonal surveys were conducted between 2000 and 2001 in 12 localities, four coastal zones, five bays or coastal lagoons and three ports. Water quality variables analysed were salinity, dissolved oxygen, transparency, dissolved inorganic nitrogen, silica and phosphorus, Chlorophyll-a (Chl-a) as well as various indexes were determined. Results indicate different expression of symptoms. The ports and some coastal lagoons are in eutrophic conditions as shown by high Chl-a concentrations (>20 mg/m^-3) and the levels of dissolved oxygen (<2 mg/l), while other areas with low urban development the symptoms of low Chl-a (<2 mg/m^-3) and high levels of dissolved oxygen (>5 mg/l) suggesting oligotrophic condition. These results highlight the need for a comprehensive regional strategy to address this potential problem. We recommend a study of trophic condition together with information on nutrient sources and land use as a tool to provide a basis for setting regional priorities for management, monitoring and research.