Holbox Island (with its coastal lagoon, Yalahau Lagoon) located in the littoral zone at the north-eastern tip of the Yucatan Peninsula, Gulf of Mexico, is a relatively undisturbed ecosystem that is currently under threat from unplanned and intensive urban development. Although other ecosystems in this littoral zone have been studied to determine the basic requirements for sustainable development, little information about Holbox Island exists. 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) were 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 lower than 90%, suggesting that the site supports higher consumption than production of oxygen. Nitrogen is mostly 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 proximity of boating and dumping 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 impact on 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.
Association of sardine fishery, Sardinella aurita (Teleostei: Clupeidae) and environmental variability of the coastal upwelling ecosystem of Nueva Esparta, Venezuela. The present research is an analysis of Spanish sardine fishing (Sardinella aurita) associated with some climatic and meteorologic parameters of the ecosystem from El Morro Nueva Esparta, Venezuela. The catch and environmental data from the area were taken in the period 1996-2000. Catch data as a function of wind speed, sea surface temperature, air temperature and rain were analyzed by means of simple lineal regression and multiple models. We found a positive correlation of catch with wind speed, and a negative correlation with sea surface temperature, air temperature, and rain. The multiple regression model with intercept had a poor fit, therefore, we made a model without intercept, which improve greatly the fit. A selection of the variables using the forward procedure verified that the independent variables "wind speed" and "air temperature" have a significant relation with catch (p<0.001) at real time. This method suggests that sea surface temperature and rain have little influence on the catch, and suggests a major availability of resources in the months with low air temperature and the highest wind speed (January-June). Rev.
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