Microphytobenthos production in a Mediterranean mussel farm: The influence of incident light

Microphytobenthic oxygen production was studied at a mussel farm located in the Gulf of Fos (NW Mediterranean) in 3 seasonal experiments. Our aim was to establish whether the shading due to the breeding structures (tables) was the cause of a lowering in microphytobenthic oxygen production. Measurements of net oxygen production in benthic chambers indicated that in sediments under the tables, a supplement of light could be responsible for a strong increase in microphytobenthic primary production. This occurred only in March, when temperature was the lowest, suggesting a coupling between temperature and light in the regulation of microphytobentic production. In July, as well as in September incident light was not the factor limiting microphytobenthic production; respiration rates were maximum and heterotrophic mechanisms prevailed. However, in neighboring sediments beside the tables, the microphytobenthic population always received their optimum of incident light.