Effects of Experimental Enrichment with Spartina Detritus on Sediment Community Biomass and Metabolism

Intertidal sediment collected from a silt flat in the Minas Basin (Bay of Fundy) was placed in laboratory aquaria to assess the effects of enrichment with detritus from Spartina alterniflora on chemical fluxes across the sediment water interface and the community within the sediment. Four aquaria enriched with Spartina exhibited increased flux rates of oxygen, carbon dioxide, dissolved organic carbon, nitrates, and ammonia compared to an unenriched control aquarium. Increased bacterial biomass and activity accounted for most of the increased fluxes. Meiofaunal biomass did not increase in the 29 days following the additional of Spartina. Growth of sediment micro-algae was inhibited by the addition of the detritus, possibly owing to antagonistic interactions between algae and bacteria. The metabolic inhibitors sodium azide, sodium molybdate, and the nematocide fenamiphos were added to three of the enriched aquaria to inhibit aerobic and anaerobic respiration, anaerobic sulfate reduction, and meiofaunal metabolism, respectively. The inhibitors were only partially effective initially and apparently became less effective with time. The results indicated that care must be taken when interpreting the results of experiments in natural communities in terms of the effects of selective inhibitors. In other respects, our experiments confirm previous observations on the effects of Spartina detritus on the flux of O 2 , CO 2 , and DOC between sediment and water column but with the important addition that we have described the sediment biological communities associated with these fluxes.