Effects of Spartina detritus enrichment on aerobic/anaerobic benthic metabolism in an intertidal sediment

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Abstract
The effect of S. alterniflora detritus on metabolism of a muddy intertidal sediment was studied after burial of plant litter in the sediment. Total CO2 release to overlying water during 3 mo. following detritus enrichment increased 5.9 times while O2 uptake only increased 1.4 times. The ratio between CO2 release and O2 uptake varied between 1 and 5 and was generally 1.6-3 times higher in the enriched area than in the control area. Decomposition of Spartina added to the sediment was rapid: .apprx. 50% of the mass was lost during an initial leaching phase. Loss of ash-free dry weight from the particulate matter after the leaching period was exponential with a half-life of 44.6 d [days] and a decay coefficient of 0.016. CO2 relesed to overlying water after 105 d amounted to 67% of the C lost from the detritus. The release of DOC [dissolved organic C] to overlying water accounted for only 2.8% of the particulate C loss. Aerobic respiration estimated from O2 uptake corrected for chemical oxidation accounted for 21% of the total CO2 production. Thus, 79% of the CO2 originating from the Spartina during detritus decomposition over 3 mo. was produced by anaerobic metabolism. The importance of anaerobic decomposition after enrichment of the sediment with detritus was apparent in the development of a low Eh [oxidation-reduction potential] in the detritus layer.