The oyster is a filter feeder, taking plankton, bacteria, and oxygen from the water. It is the filter feeding that leaves the clams (and all filter feeders) susceptible to pollution, and increased silt from dredging can suffocate the animals. This may play havoc with the ecosystem as filter feeders play an integral role in keeping our water ways clean. A single adult oyster can filter FIFTY gallons a water in a single day.