| Popis: |
Short-term variability of primary production was studied during Summer 1986 in Bahia de Los Angeles, Mexico. An 8-day time series of temperature, salinity, nutrients and chlorophyll awas performed. Simultaneously, primary productivity was measured using the14C method. The water column was stratified during the first 3 days, and mixed when the wind speed was up to 10 m s−1. Wind stress played a major role in producing vertical mixing and forcing surface circulation in the Bay. Higher chlorophyll avalues (>3 mg m−3) were recorded at 10 m depth during the first 3 days, and were 2–3-fold greater than those measured on the following days. The inverse relationship between the integrated phytoplankton biomass and the calculated euphotic depth (Zeu) suggests that light penetration in the water column was mainly controlled by the phytoplankton biomass. The photosynthetic assimilation ratio (PB) ranged from 3·7 mgC (mg chla)−1h−1, measured during stratification of the water column, to 9·3 mgC (mg chla)−1h−1, measured with water-mixed conditions.PBvariability was a result of the combined effect of vertical mixing in the water column and the increased light availability. Short-term integrated primary production ranged from 26 to 62 mgC m−2h−1, and its temporal variability was associated with phytoplankton biomass and the light availability. The averaged daily integrated production was related to nitrate concentrations in the water column. These results suggest that limitation of primary production from both light and nutrients occurred simultaneously in Bahia de Los Angeles during Summer 1986. |
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