Abstract
Primary production of benthic microalgae was studied in an intertidal sand flat in the Ria de Arosa (NW Spain), where an intensive bivalve aquaculture takes place. Active and degraded pigments, organic matter, and vertical migration of algae were also studied. Total annual production, combining high and low tide values, reached 79 gC m-2, while water column production in the same place was only 6 gC m-2, which suggests that resuspended benthic microalgae can be a major food source for bivalves. Year-round production showed no clear seasonal peaks, probably due to intense sediment disturbance by culturing manipulations, and to high detrital supply: 94 to 98% of organic matter in the sediment is allochtonous non-living material.