MICROPHYTOBENTHOS PRODUCTION IN A MEDITERRANEAN MUSSEL FARM - THE INFLUENCE OF INCIDENT LIGHT

Microphytobenthic oxygen production was studied at a mussel farm locat ed in the Gulf of Fos (NW Mediterranean) in 3 seasonal experiments. Ou r aim was to establish whether the shading due to the breeding structu res (tables) was the cause of a lowering in microphytobenthic oxygen p roduction. Measurements of net oxygen production in benthic chambers i ndicated that in sediments under the tables, a supplement of light cou ld be responsible for a strong increase in microphytobenthic primary p roduction. This occurred only in March, when temperature was the lowes t suggesting a coupling between temperature and light in the regulatio n of microphytobentic production. In July, as well as in September inc ident light was not the factor limiting microphytobenthic production; respiration rates were maximum and heterotrophic mechanisms prevailed. However, in neighboring sediments beside the tables, the microphytobe nthic population always received their optimum of incident light.