Intertidal hyperbenthic populations in the Nanaimo estuary

Samples were pumped from within 5 and 30 cm of the sediment surface in a tidal channel of the Nanaimo estuary and filtered through 100-m mesh plankton nets. Despite homogeneity of the water at these levels, as indicated by salinity and oxygen, there were large persistent differences in population density of small crustaceans. The density at the 5 cm level always exceeds the density at the 30 cm level by a factor of 2 to 20. These results are discussed in relation to Beyer's concept of hyperbenthic plankton populations which is extended to include intertidal areas. It is concluded that hyperbenthic populations are real phenomena and are of considerable importance in trophodynamics. A model for formation and maintenance of hyperbenthic populations is proposed.