Sediment-associated microalgal biomass expressed as chlorophyll a concentration, total organic matter concentration expressed as ash-free dry weight, and hourly rates of net community primary production and community oxygen consumption were measured at monthly intervals at medium sand, fine sand, and silt sites between 0.5 and 2.0 m above MLLW during an entire year at Netarts Bay, Oregon, USA. Estimated mean annual rates of net primary production were 38 g C/sq m in sand, 53 g C/sq m in fine sand, and 21 g C/sq m in silt. The authors tested the hypotheses that benthic algal primary production dynamics were controlled by sediment type, tidal height, and season. The results show that although there is a relationship between these physical factors and benthic algal production dynamics, this relationship is neither as simple nor as linear as had been previously suggested in published studies.