Cambio diurno y estacional de la clorofila a y algunas variables fisicoquimicas en la Laguna La Cruz, Sonora, Mexico

Chlorophyll a and physical chemical variables were sampled during a diurnal cycle once a month from June 1987 to May 1988, on a fixed location in Laguna La Cruz, Sonora. The purpose of this study was to determine the factors of variability of environmental and sea surface temperatures, disolved oxygen and chlorophyll a (Chla) on a short period basis (diurnal cycles), and seasonal patterns. Also, a midday estimate of primary productivity was done. Diurnal analysis indicated that sea surface temperature is determined by tides and solar radiation heating. Oxygen concentration was associated with sea surface temperature and tides. Chla was determined mainly by tides. Temperature shows a clear seasonal pattern. Two periods were characterized: cold period, from December to April with average temperature of 17°C; and warm period, from June to October, average temperature of 30°C. May and November were transitional periods. In contrast, oxygen variability was opposed to temperature on the annual basis. Chla and primary productivity maximum values were in summer (1.57 mg m^-3 and 1.08 ml l^-1 d^-1, respectively) and minimum values during winter, due to a possible nutrient limitation.