Photosynthetic quotients in the Gulf of California during autumn 1987 in the central region and spring 1989 in Puerto Don Juan

Abstract

In order to study the photosynthetic quotient variability (PQ = O₂/¹⁴CO₂) and to infer the relative contribution of new production in the Gulf of California, simultaneous determinations of photosynthesis were made using the ¹⁴C and oxygen techniques. Additionally, nutrient concentration was determined in the central region during autumn 1987 and during spring 1989 in a coastal lagoon in the same region. In both areas nutrient distribution suggests consumption by photosynthesis within the euphotic zone. The PQ integrated in the water column for single experiments goes from 1.43 ± 0.29 to 4.01 ± 0.33 in the central region and from 1.32 ± 0.22 to 3.08 ± 0.38 in the coastal lagoon Puerto Don Juan and does not differ from the PQ calculated for each depth. Calculated PQ values indicate the presence of NO₃^– during photosynthesis. The global PQ for all the experiments in both study areas was calculated by regression analysis for the central region (1.56 ± 0.45) and Puerto Don Juan (1.68 ± 0.56), suggesting NO₃^– influence during both seasons in both areas. A greater relative contribution of new production than regenerated production in both areas of the Gulf of California is inferred.