採集器具と深度が異なる太平洋西部亜寒帯海域のプランクトンネット標本群の生物量と種組成の比較

抄録

To standardize the netplankton datasets in terms of sampling gear and sampling depth, previous plankton data obtained from the oceanographic A-line surveys in the western subarctic Pacific were analyzed. Comparable netplankton sampling was carried out using two plankton sampling gears, the mini-Bongo net and the NORPAC (North Pacific Standard) net, installed with 335 µm mesh. Considering the two sampling depths, 0–50 m and 0–150 m, the mean ratio of dry weight (DW) of plankton biomass in unit volume was 2.22±1.19. Using the data of plankton population, the ratio of population at the sampling depths was close to DW, suggesting that the plankton biomass at the sampling depths was comparable. On the other hand, individuals of species/taxa in most samples did not differ significantly in terms of sampling depth and sampling gear. However, plankton populations of some species, mainly distributed below the surface mixing layer, was higher in the layer of 0–150 m than in the layer of 0–50 m. This result indicated the need for careful biomass evaluation for some species at different sampling depths.