Key points are not available for this paper at this time.
The effects of 2 polychaete species, Nereis diversicolor and Arenicola marina, on benthic metabolism and decomposition processes in organic-poor (0.06% POC), sandy sediment were experimentally investigated. Sedvnent O2 uptake and CO2 release were stimulated by 80 to 90% and 260 to 270% for N. diversicolor and A. marina, respect~vely, from basal rates of approximately 30 mm01 m-2 d-'. These enhancements in benthic f l u e s were due to both increased solute exchange due to macrofauna irngation and increases in total benthic metabolism. Although the latter was enhanced by 10 to 35 % and 115 to 123 % by N. diversicolor and A. marina, respectively, both species inhibited anaerobic decomposition as indicated by 66 and 42 % lower sulfate reduction rates. Benthic f l u e s and basal rates of benthic metabolism (without macrofauna) were 2 to 3 times higher in sediments enriched with organic matter compared to unamended sediments. Similarly, sulfate reduction rates were 3 times higher in enriched sedlments. Total benthic metabolism in enriched sediments was stimulated by N. diversicolor to a slrmlar extent (+27 to 34 %) as in unamended sediments, whereas A. marma stimulated total benthic metabolism to a slightly lesser extent (+43 to 55%) in enriched sediments than in unamended sediments. N. diversicolor had little effect on sulfate reduction (-4 %) in enriched sediments, while A. manna reduced sulfate reduction by 85 % in enriched sediments. Porewater profiles reflected the balance between stimulating effects on sediment decomposition processes and removal of porewater solutes by benthic macrofauna. Porewater and sediment profiles of reduced S compounds also showed the effects of these polychaetes on sedimentary S cycling, i.e, lower anaerobic decomposition and increased reoxidation of reduced compounds. Both species affected sediment element cycles, stimulating C cycling and favonng more oxidized species and processes in S cycling. Furthermore, both species affected the fate and distribution of the metabolites produced from decomposition by enhancing the exchange of solutes across the sediment-water interface and porewater flushing. In general, the biogeochemical impact of A. marina was greater than that of N. diversicolor
Banta et al. (Fri,) studied this question.