ABSTRACT: Live Skeletonema costatum (diatom) cells labeled with ¹⁴C were added to the sediment surface in 10 cores containing intertidal sediment from Saanich Inlet, Vancouver Island, Canada. The water overlying the sediment in 5 cores was sparged with atmospheric air, whereas the other 5 cores were sparged with N₂. Release of ¹⁴CO₂ started immediately in the oxic cores, reaching a maximum at Days 3 to 4, whereas release in the anoxic cores was slower with a maximum after 6 to 9 d. DO¹⁴C (dissolved organic carbon) release also exhibited high rates initially, but with the highest release in the anoxic cores. Degradation to ¹⁴CO₂ and DO¹⁴C could be described by 2 successive exponential decays representing 2 decomposable fractions. After 80 d, 58 and 42% of the added label had been released as ¹⁴CO₂, and 2 and 13% were released as DO¹⁴C in the oxic and anoxic cores, respectively. The porewater contained only small amounts of ¹⁴CO₂ and DO¹⁴C. However, oxic cores showed the lowest concentrations, indicating faunally enhanced solute fluxes in these cores. Between 31 and 37% of the added label remained as PO¹⁴C (particulate organic carbon) in the sediment after 80 d. Similar amounts of dissolved carbon (¹⁴CO₂+DO¹⁴C) were lost from the added algal POC under oxic and anoxic conditions, but the larger amounts of DO¹⁴C released from the sediment in the anoxic cores indicated a slower anaerobic mineralization of DO¹⁴C.

KEY WORDS: Decomposition . Mineralization . Algae . Carbon dioxide

Published in MEPS Vol. 134 (1996) on April 25
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996