Vertical distribution of zooplankton biomass in the Sea of Japan

Vertical distribution of total zooplankton biomass and major taxonomic groups are investigated by layers to depths of 2500-3400 m on the basis of three series of net plankton collections. Zooplankton is most abundant above 1500-2000 m. Since true deep-water species do not occur in the Sea of Japan, biomass drops much more sharply at greater depths than it does in the ocean. Since few carnivores inhabit the deep layers, abundant remains of planktonic organisms fall to the bottom, and carnivorous detritovores feeding on these remains are dominant in deep water bottom fauna.

Vertical distribution of zooplankton biomass in the Sea of Japan at Station VITYAZ7519

Vertical distribution of common zooplankton species is examined on the base of two series of layer-by-layer net catches down to depth of 3400 m. Differences between the series are significant for most species only near the surface, whereas in deeper layers character of distribution remains the same. Great depths in the Sea of Japan are populated most actively by species performing intensive daily migrations, and less actively by species continuously confined to a definite depth range. Different character of nutrition of the animals apparently determines extent of utilization of deep layers, which are usual for the species.