MEPS 192:203-217 (2000)  -  doi:10.3354/meps192203

ABSTRACT: The impact of suspension-feeding Nereis diversicolor and non-suspension-feeding N. virens on C and N dynamics in an organic-poor sediment was investigated in a controlled laboratory study simulating periods of high and low phytoplankton (Rhodomonas sp.) concentration. High phytoplankton concentration resulted in a 30-fold higher deposition (clearance) of particulate C and N to the sediment inhabited by N. diversicolor than to N. virens and defaunated sediment. Concurrently, O₂ consumption and NH₄⁺ + NO₃^- release were increased by a factor of 3 in sediment with N. diversicolor, but only by a factor of about 1.5 in N. virens and defaunated treatments. Steady-state porewater concentrations of TCO₂ and NH₄⁺ decreased exponentially with increasing ventilation activity of nereids. Ventilation activity was highest for suspension-feeding N. diversicolor and lowest for deposit-feeding N. virens. About 30% of the deposited algal C and N in the N. diversicolor sediment were lost rapidly as excess CO₂ or NH₄⁺ + NO₃^- flux to the water column. Incorporation into N. diversicolor tissues accounted for 2/3 of the retained C and N. In the case of N. virens, where no net phytoplankton deposition occurred, organic matter removal due to mineralization resulted in a net loss of both sedimentary C and N. Accordingly, the biology and behaviour of infaunal species are important determinants for sediment biogeochemistry and element cycling in marine areas.

KEY WORDS: Carbon · Deposit-feeding · Fluxes · Nereis diversicolor · Nereis virens · Nitrogen · Sandy sediment · Suspension-feeding