Description:
<jats:p>Simultaneous measurements of the diel patterns of dissolved O_2, pH—CO_2, dissolved organic nitrogen, ammonia, nitrite, nitrate, dissolved organic phosphorus, phosphate, and silicate were made on four occasions in a shallow salt marsh embayment (Bissel Cove, Narragansett Bay, Rhode Island, USA) that was closed to tidal water exchanges for 24—h periods. In spite of high rates of community photosynthesis and respiration, there appeared to be little diel change in dissolved nutrient concentrations, especially with respect to inorganic nitrogen. During summer and early fall, inorganic nutrients appeared to cycle within the sediment—detritus system of the embayment bottom, rather than being released to the overlying water. This suggests that there would be little export of inorganic nutrients from the marsh during tidal exchanges with the estuary. The behavior of this marsh embayment contrasts with reports from other marsh areas where large net imports or exports of nutrients have been observed. The concentrations of dissolved organic phosphorus and nitrogen were higher than inorganic forms, and showed substantial variation over each diel sampling period. The relationship between photosynthetic or respiratory gas exchange and nutrient cycling in water influenced by benthic community metabolism is subtle and complex, and cannot be adequately approximated by simple models such as the Redfield ratio.</jats:p>