Microphytobenthos primary production of Tagus estuary intertidal flats (Portugal)

Abstract

The purpose of this study was to measure primary productivity of microphytobenthos of intertidal mudflats of Tagus estuary. Sampling occurred from 1991 to 1992, during low tide of spring waters on 2 stations, each one representative of a typical habitat. Net photosynthesis rates (NP) were measured in undisturbed sediment cores incubated in the laboratory andin situ. The results obtained indicated that NP in the laboratory was similar for the two stations, (mean values of 1.1 and 1.3 mmol O2 m−2 h−1, within a range of 5-fold). A stepwise regression analysis combining biotic and abiotic factors was performed to explain temporal variability, indicating that NP in each site was influenced by different parameters, with the exception of precipitation, which might play an important role in the disruption of sediment-water interface. Photosynthesis-Irradiance curves constructed with the results obtained insitu showed similar photophysiological responses of the two communities. Based on the values of photosynthetic efficiency (α), and of optimal light intensity (lk) measured and on the combination of the photoperiod pattern and the amount of light available for each sampling site, an estimation of total annual productivity is given: 47–178 g C m−2.