Trophodynamic structure of a swampy Bog at the climax stage of limnological succession IV. Vertical migration and demersal behaviour of large zooplankton

Abstract

The diel vertical migration and the demersal behaviour of crustacean zooplankton were studied throughout the year at Matsumi-ike Bog. Population densities of the predominant species of crustacean zooplankton within the water column were much smaller during the morning than during the night. Most of their migration was directed to the bottom layer during the morning unlike at night. The population density of zooplankton inside the ooze sediment increased significantly in the morning. In a shallow area where the diel vertical migration of zooplankton is insufficient to escape from the predation of visually oriented planktivorous fish, demersal behaviour appears to be an important adaptation for the survival of zooplankton.