Initial burial and subsequent degradation of sedimented phytoplankton: relative impact of macro- and meiobenthos

Abstract

The initial burial (transfer through the sediment-water interface) and subsequent degradation of sedimented phytoplankton was examined in the laboratory in sediments containing meiofauna, both with and without macrofauna, over a 10-day period. Burial and degradation were monitored by following changes in vertical profiles of Chl a and phaeopigments in sediment columns with and without an addition of senescent Skeletonema costatum Greville (Cleve) cells to the sediment surface. The macrofauna present in the cores consisted of a subsurface deposit-feeder assemblage typical of organically enriched habitats. Upon diatom addition, the visual redox potential discontinuity (RPD) rose to or near the sediment surface. Chl a and phaeopigment levels increased 6 and 3 days after diatom addition, respectively, with no difference in concentrations in the presence or absence of macrofauna. These increases appeared to be confined to the top 5 mm of sediment. Overall, phaeopigment concentrations were higher in cores containing macrofauna. A minimum of 83 % of the added Chl a was transferred through the sediment-water interface in 10 days. In organically enriched habitats, the initial burial and subsequent degradation of sedimented phytoplankton appears to be a process dominated by the meiofaunal and microbial communities, and unaffected by subsurface deposit-feeding macrofauna.