Monaghan, M.T., S.A. Thomas, G.W. Minshall, J.D. Newbold, and C.E. Cushing. 2001. Limnology and Oceanography 46:1091–1099.
The transport and deposition of particulate organic matter (POM) in streams has received much attention in recent years. As with many ecosystem processes, determining the relative importance of physical and biological mechanisms for POM removal (e.g., sedimentation and filter-feeding) remains an important task. We examined the influence of benthic filter-feeding Hydropsyche and Simuliidae on downstream transport distance (SP) and deposition rate (vdep) of POM in two streams. We conducted five field experiments using radiolabeled (14C) natural detritus and living diatoms (Asterionella) to measure longitudinal loss (kP m−1 = 1/SP) before and after complete removal of filter-feeding benthic macroinvertebrates. kP decreased following filter-feeder removal in each experiment, although meta-analysis indicated no consistent nonzero effect. However, the changes in kP were within the range to be expected from previously published rates of capture by the filter-feeders, indicating limited statistical power. We also examined uptake of radiolabeled POM by filter-feeders in three of the experiments. Simuliidae radioactivity increased significantly during two of the three releases of POM, although uptake accounted for up to 11% of wholestream POM deposition. Our results suggest that transported POM and diatoms are deposited from the water column rapidly and that mechanisms other than filter-feeding by invertebrates are responsible for most of the transfer of POM from the water column to the sediments of streams.