Occurrence and transport of faecal pellets in suspension in a tidal estuary

Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study

“…Because feces and pseudofeces are voided from bivalves as mucus-bound aggregates, they have a higher sinking velocity than nonaggregated particles and settle out at rates up to 40 times that of nonaggregated particles (Kautsky and Evans 1987;Widdows et al 1998). If bottom currents are below the critical erosional velocity, the biodeposits undergo a dewatering process and gradually become incorporated into the sediments (Haven andMorales-Alamo 1966, 1968;Dame 1987;Jaramillo et al 1992) leading to an increase in sediment N content (Kaspar et al 1985;Kautsky and Evans 1987;Deslous-Paoli et al 1992;Hatcher et al 1994). High abundances of bivalves can overenrich sediments with biodeposits, thereby generating high microbial respiration leading to sediment anoxia that both inhibits nitrification and kills bioturbating benthic infauna (Tenore et al 1982;Rodhouse and Roden 1987).…”

“…High abundances of bivalves can overenrich sediments with biodeposits, thereby generating high microbial respiration leading to sediment anoxia that both inhibits nitrification and kills bioturbating benthic infauna (Tenore et al 1982;Rodhouse and Roden 1987). Such local adverse effects can be ameliorated by moderate water currents or wave action that allows biodeposits to be spread across a larger bottom area (Haven and Morales-Alamo 1968;Dame 1987;Dame et al 1991).…”

Transport and breakdown of fecal pellets: Biological and sedimentological consequences1

“…Because fecal pellets are aggregates of particles, pellet sinking rates can be much greater than the rates of their smaller constituents (Haven and Morales-Alamo 1968;McCall 1979). Thus, pellets enhance material fluxes through the water column by increasing sedimentation rates; this can also lead to deposition of particles that, because of hydrodynamic or chemical characteristics, otherwise might not be deposited in a given environment (Haven and MoralesAlamo 1968;Smayda 1969;Small et al 1979;Robison and Bailey 198 1;Silver and Bruland 198 1).…”

“…Diagramatic representations of sediment cycling among benthic animals, fecal pellets, and pellet breakdown and supply of potential food to animals by sediment transport (e.g. Haven and Morales-Alamo 1966;Young 197 1;Risk and Moffat 1977) unfortunately have remained iconic. We have only the most basic quantitative data on responses of a few deposit-feeding species to fluid flows and to sediment transport (e.g.…”

Top-down control of phytoplankton by oysters in Chesapeake Bay, USA: Comment on Pomeroy et al. (2006)

“…Based on the aerial surveys of chlorophyll a concentrations, we conclude that oyster reefs in the Bay, although generally confined to waters < 8 m deep, historically had effective access to a substantial proportion of the estuary's phytoplankton communities and that the complex vertical relief of these reef structures tended to minimize re-filtration, enhancing oyster feeding efficiency. Oysters living in such locations would consume phytoplankton, and undigested organic material in their feces and pseudofeces would be incorporated into the surrounding sediments (Haven & Morales-Alamo 1966, 1968, Newell et al 2005). In such aerobic locations the remaining organic material is subject to metazoan and bacterial decomposition that does not contribute to the development of hypoxia in the bottom waters of the central channel of the Bay.…”