Deposit Feeders (mg C m^-2)
Period: 01-Jan-2004 - 31 Dec-2004

Distribution versus food sources

The biomass distributions of the deposit-feeders and the filter feeders appear quite similar, despite the fact that their food sources are different. Filter-feeders mainly take up phytoplankton directly from the water column whereas deposit feeders take up food from the sediment: bacteria and benthic diatoms.

However as the benthic bacterial production mainly depends on the input of detritus from the pelagic system this implies that the deposit feeders are as dependent on input from the pelagic as the filter-feeders. Only where the detritus input from the pelagic is smaller such as on high-lying tidal flats in the shelter of the Wadden islands( such as the area close to Vlieland) differences in the distribution can be seen. There the high biomass of filter-feeders along the large gully (the Vliestroom ) effectively clears the water which passes over them of food particles, leading to a much lower input of phytoplankton and detritus further from the channel. To show the differences clearly we compare (again) two sites: de Waardgronden and the Lutjeswaard.

The rather high simulated deposit-feeder biomass in the Marsdiep is caused by the high benthic bacteria biomass, which means abundant food for the deposit feeders. Despite the low settling-rate per m3, the high local primary production in a relatively deep water column still leads to a high net sedimentation of particulate Carbon per m2, the food source for bacteria. This result appears unrealistic and is probably caused by a too coarse formulation of the processes responsible for sedimentation, deposition and resuspension.

(Adult) Suspension Feeders (mg C m^-2)
Period: 01-Jan-2004 - 31 Dec-2004