Bojorquez Lagoon (BL), located on the Mexican Caribbean, has received sewage and dredging impacts as a result of tourism development. The lagoon supports a high diversity of primary producers compared to sheltered adjacent lagoons dominated byThalassia testudinum communities. The Diurnal Curve Method (Odum and Hoskin 1958) was used to measure community metabolism and assess eutrophication in BL by comparing it to the nonimpacted lagoons and to other systems studied with this method. Dissolved oxygen community input to the water column in BL ranged between 8.3 g O₂ m⁻² d⁻¹ and 41.5 g O₂ m⁻² d⁻¹ during 1985 and 1986, and averaged 17.1, whereas dissolved oxygen community consumption ranged from 6.4 g O₂ m⁻² d⁻¹ during 1985 and 1986, and averaged 17.1, whereas dissolved oxygen community consumption ranged from 6.4 g O₂ m⁻² d⁻¹ to 37.6 g O₂ m⁻² d⁻¹ and averaged 15.2. These values are higher than those found for the adjacent lagoons and similar coastal lagoons, and are similar to results from other lagoons with sewage or seafood waste discharge. Net flux of oxygen from the community to the water column averaged 1.9 g O₂ m⁻² d⁻¹ and ranged from −9.8 g O₂ m⁻² d⁻¹ to 8.1 g O₂ m⁻² d⁻¹. These values are low compared to the adjacent lagoons, and close to zero, as in dystrophic environments. Primary productivity, as estimated by oxygen input, increased in BL during the period of study, indicating that eutrophication is proceeding, but the lagoon has not reached yet a level of “critical eutrophication” as defined by Mee (1988). La Laguna Bojórquez (LB), ubicada en el Caribe Mexicano, ha sido objeto de impactos por dragados y descargas cloacales, ocasionados por el desarrollo turistico de Cancún. La laguna presenta una gran variedad de productores primarios en comparación con lagunas cercanas en las que domina una comunidad deThalassia testudinum. Se utilizó el método de la curva diurna de oxígeno para medir el metabolismo comunitario (Odum y Hoskin 1958) y evaluar la eutroficación de la LB, comparandola con las lagunas adjacentes y otros sistemas lagunares estudiados con este método. El oxígeno disuelto liberado por la comunidad hacia la columna de agua en LB osciló entre 8.3 g O₂ m⁻²d⁻¹ y 41.5 g O₂ m⁻² d⁻¹ durante 1985 y 1986, con media de 17.1 g O₂ m⁻² d⁻¹. El cons comunitario de oxígeno disuelto fue en promedio de 15.2 g O₂ m⁻² d⁻¹ y osciló de 6.4 O₂ m⁻²d⁻¹ a 37.6 g O₂ m⁻² d⁻¹. Estos valores son superiores a los encontrados en la laguna adjacente y en otras lagunas similares, pero son parecidos a los observados en lagunas afectadas por descargas diversas. El flujo neto de oxigeno de la comunidad hacia la columna de agua fue en promedio de 1.9 g O₂ m⁻² m⁻¹ d⁻¹ y varió de −9.8 g O₂ m⁻²d⁻¹ a 8.1 g O₂ m⁻² d⁻¹, siendo valores inferiores a los encontrados en las lagunas adyacentes y cercanos a cero, como en ambientes distróficos. Laproducción primaria, estimada mediante el oxígeno producido, aumentó en la LB durante el período de estudio, indicando que el proceso de eutroficacion avanza, pero la laguna no ha alcanzado aún el nivel de “Eutroficación Crítica” definido por Mee (1988).

The differential distribution of diatoms and dinoflagellates in the Bay of La Paz, Gulf of California, Mexico, was analyzed in summer of 2009, when a cyclonic eddy confined in the bay dominated the circulation. An uplift of the nutricline in the eddy drove high concentrations of nutrients to the euphotic layer. A differential phytoplankton distribution was observed to be associated with the eddy: there was an abundance of dinoflagellates close to the center of the cyclonic eddy, whereas diatoms were more abundant at the periphery. A significant inverse correlation (R = −0.62, p < 0.002) was found between the temperature at 25 m depth and the dinoflagellates abundance. Based on the temporal evolution of chlorophyll measured by MODIS satellite images, and a conceptual model proposed for the lifecycle of eddies, the cyclonic eddy may have been an old decaying structure. The effect of the cyclonic eddy on the phytoplankton distribution in this small semienclosed region was apparently similar to that found in larger eddies in the open ocean, but this is the first time such a differential distribution has been found associated to a confined eddy.