Samples of chamber-enclosed water (50 ml for carbohydrates, protein and dissolved organic carbon analysis; 20 ml for total inorganic carbon analysis) were taken by inserting a needle attached to a syringe through the septa located in the chamber lid, 10 min and 3 h after the start of incubation in chambers in both mudflat and saltmarsh experimental units. Additionally, near-chamber water temperature, and dissolved O2 concentration in chamber-enclosed water were monitored during each sampling period. Water temperature was measured with a hand thermometer, and dissolved O2 was measured in situ by
inserting needle sensors (Unisense A/S) through the septa located in the chamber lid. Oxygen was measured to corroborate that its concentration did not decay more than 20% during incubation (data not shown). If this happened, incubation was excluded from the experiment.