Transport and breakdown of fecal pellets: Biological and sedimentological consequences1

摘要: Fecal pellets of benthic animals are important in sediment transport processes, yet few quantitative data available on their salient physical characteristics. We measured, directly and independently, the densities (specific gravities), sizes, settling velocities produced by Amphicteis scuphobrunchiata, a deposit-feeding polychaete worm. Pellet density was measured an isosmotic gradient technique. Densities ranged from 1.086 to 1.282 gacm-3 3.03 5.94 cmes-I. Pellets transported as bedload for variable distances; oldest tested (6 h after production) traveled median distance 3.1 m, while freshly egested 9.5 m before disintegrating. Worms would reingest disaggregated pellets, but feeding rates correlated positively with pellet age, consistent previous findings that this species feeds at faster rate energetically more profitable sediment. These results suggest substantial interactions among animals, fecal processes. aquatic organisms affect sedimentary processes two ways. Because aggregates particles, sinking can be much greater than smaller constituents (Haven Morales-Alamo 1968; McCall 1979). Thus, enhance material fluxes through water column increasing sedimentation rates; also lead deposition particles that, because hydrodynamic or chemical characteristics, otherwise might not deposited given environment MoralesAlamo Smayda 1969; Small et al. 1979; Robison Bailey 198 1; Silver Bruland 1). Most interest such vertical has focused planktonic origin. play role operating within boundary layer. Deposit feeders comprise dominant trophic group softbottom environments ingest package ambient during activities. Although it been recognized some time via both suspended load modes (Rhoads