STUDYING THE ROLE OF MUD TEMPERATURE ON THE HOURLY VARIATION OF THE PHOTOSYNTHETIC CAPACITY OF MICROPHYTOBENTHOS IN INTERTIDAL AREAS

The present study aims at assessing the relationship between in situ m ud temperature and microalgal photosynthetic capacity on intertidal mu dflats. Both mud surface temperature and P-max were measured during lo w tide in different tidal conditions: when low tide occurred either in the morning, at midday or in the afternoon to select presumably known changes in temperature. These measurements were performed at 2 differ ent dates to contrast meteorological conditions (March and September). P-max was always higher when low tide coincided with midday, and most of the time changes of the photosynthetic capacity reproduced changes of the temperature within a single emersion period. So, temperature a ppeared to be a factor determining P-max at the hourly scale and at th e level of the tidal cycle on temperature intertidal mudflats. An expe riment was performed to confirm the exogenous control of temperature o n P-max independently of the influence of light. Finally, as primary p roduction is fundamentally determined by the photosynthetic capacity, it is concluded that temperature of the mud surface is an important fa ctor explaining the dynamics of microphytobenthic primary production.