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Marine Ecology Progress Series

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MEPS 165:31-43 (1998)  -  doi:10.3354/meps165031

Dynamic behaviour of photosynthesis-irradiance curves determined from oxygen production during variable incubation periods

M. F. Macedo1,*, J. G. Ferreira1, P. Duarte2

1Dept of Environmental Sciences & Engineering, Faculty of Sciences and Technology, New University of Lisbon, P-2825 Monte de Caparica, Portugal 2Dept of Sciences & Technology, Fernando Pessoa University, Praça 9 de Abril 349, P-4200 Porto, Portugal

Production and consumption of oxygen were analysed in phytoplankton populations using a fast biomass-concentration technique. The variation of productivity with irradiance was studied using different incubation periods, from minutes to hours. The influence of the exposure time on the photosynthesis-irradiance (P/I) curve parameters was analysed. The results show that dissolved oxygen concentration in the water does not increase linearly with time and that PBmax (maximum biomass-specific production rate and Iopt (optimal light intensity) are time-dependent. Exponential and linear expressions were proposed to describe PBmax and Iopt as a function of time. A model was built to investigate the importance of static (steady-state) vs dynamic (time-dependent) simulation in the prediction of phytoplankton production under different light intensities. The results show the importance of using dynamic expressions for the P/I relationship, especially in a mixed water column.

Biomass concentration · Phytoplankton productivity · Short incubation periods · Oxygen method · Ecological model

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