SHORT COMMUNICATION Viable gut passage of cyanobacteria through the filter-feeding fish Atlantic menhaden, Brevoortia tyrannus

We examined the contents of the alimentary tract of juvenile Atlantic menhaden, an obligate filter-feeding fish, with epifluoresence microscopy. All plankton taxa and detrital material observed in plankton samples from the sampling area could also be found in the esophagus of the fish. The corresponding plankton taxa were absent from the pre-feces sampled in the hindgut with the exception of cyanobacteria, which were found intact and fluorescing as they do in nature. The survival of cyanobacteria during gut passage and their presence in menhaden feces may enhance both nutrient availability and the delivery of these cells to the benthos. Additionally, diatoms frustules were found in the pre-feces, which may affect the sequestration of biogenic silica. These results may have bearing on the formation of cyanobacteria blooms, nutrient flow in estuaries and the delivery of material to the sediment.