Abstract
A coupled predator-prey chain, starting with bacterivores, was investigated using the minicell recapture technique (MiniCap). Water samples were subjected to size fractionation with decreasing filter pore size, in order to obtain a successive truncation of the microbial food chain. Our results showed that the major bacterivores were flagellates in the size range of 1 to 3 .mu.m. The truncation of the food chain caused increased or decreased predation on the bacteria, depending on whether the bacterivores were released from or subjected to increased predation pressure. We present a model describing trophic interactions between organisms less than 12 .mu.m in size. This model suggests 4 trophic levels to form a regulatory chain, exerting a tight control on major bacterivores.