Comparison of oxygen microgradients, oxygen flux rates and electron transport system activity in coastal marine sediments

Oxygen profiles, actual oxygen uptake and electron transport system activity (ETSA) were studied in 4 intertidal sedirnents at Texel, NW Netherlands. Organic carbon content ranged from 0.02 to 0.4 O/ O dry weight. Profiles of oxygen were recorded with a needle minielectrode and showed that oxygen was present down to 18 mm in the sandy beach sediment with low carbon content, whereas oxygen only penetrated down to 1 to 3 mm in the organically richer sediments. Measured oxygen uptake ranged from 395 to 2315 pm01 O2 m-' h -' and exceeded oxygen uptake estimated on basis of molecular diffusion by 1.4 to 3.2 times. The difference between the 2 methods for measuring oxygen uptake indicates that bottom fauna activity significantly contributes to the sediment-water exchange of oxygen. The ETSA varied from 0.02 to 0.81 pm01 0, g-' h -' The ETSA at the sediment surface was positively correlated to sediment oxygen uptake. Nelther ETSA nor oxygen uptake showed correlation to organic carbon or nitrogen content in the sediment.