抄録
In food webs between usual zooplankton and phytoplankton, an ecosystem model, which con
tains a microbial loop between bacteria and zooplankton, was developed. Numerical simulations
of the ecosystem in Tokyo Bay were carried out for 1 year using this model.
The observation result for the time series fluctuation of 3 stations of the phytoplankton concen
tration in the bay was compared with the calculation result. The fluctuating range of simulated
values is smaller than that of observed values in winter. Simulated results are in good agreement
with order of phytoplankton cycle throughout 1 year the observations. Primary production in
Tokyo Bay from June 1995 to May 1996 is estimated at 1,600 tonC/y from the simulations. Dia
toms are about 1.4 times dinoflagellate in terms of biomass. This indicates that diatom accounts
for about 58% of phytoplankton standing stock in Tokyo Bay. Carbon flow fluxes to zooplankton
from phytoplankton are 550 tonC/y, and carbon flow fluxes to zooplankton from bacteria through
protozoa are 990 tonC/y, and microbial loop are about 1.8 times grazing food webs. In addition,
nitrogen flow fluxes to phytoplankton from nitrogen pool are 156 tonN/y, and nitrogen flow fluxes
to bacteria from nitrogen pool are 480 tonN/y,and microbial loop are about 3 times grazing food
webs. Thus results suggest that the role was great and very important in carbon and nitrogen
cycle. The horizontal distribution of phytoplankton in the summer season from the classical type
of the ecosystem model showed the stabilized distribution. However, daily variations of horizon
tal distributions of diatom concentration in the present model are revealed. It is considered that
the effect by the advection is strong for the change of the horizontal distribution of phytoplankton.
