Benthic chambers were used to investigate fluctuations in nutrient fluxes and oxygen changes when comparing two benthic biota. Muddy sediments located under mussel-cultivation ropes were compared with a station outside the mussels' influence. Biodeposition from the mussels results in a drastic increase in the nutrient fluxes. A standard procedure is established in order to give reliable comparisons between stations and seasons: as a rule it should include six-hour periods of incubation with sampling intervals of two hours and at least four benthic chambers - preferably six - at each station.