It is extremely important to estimate the
primary production of phytoplankton when considering the carbon cycle in
the ocean. The increase of seawater temperature associated with global
warming in recent years is thought to affect the primary productivity of
the ocean. However, the conventional primary productivity estimation
method uses sea surface temperature as an input variable, and it is
difficult to correctly discuss the change in primary production due to
global warming. Therefore, we designed a method of estimating primary production
using the light absorption coefficient of phytoplankton, which is a
parameter independent of seawater temperatures.
Figure. (a) Basic production estimated by the method
based on the light absorption coefficient, (b) basic production estimated by the
conventional method, and (c) difference between a and b.
In marine ecosystems, the size
structure of phytoplankton is one of the factors that determine the energy
transfer efficiency in the food web. Therefore, spatiotemporal monitoring of the
wide-range phytoplankton-size structure is important for evaluating changes in the
marine ecosystem. Based on previous studies, the light absorption spectrum is
known to differ depending on the size and group of phytoplankton. Therefore, we
designed a method to estimate the phytoplankton-size structure based on the light
Figure. Distributions of (a) CSD slope, which is an indicator of phytoplankton-size structure,
and (b) chlorophyll a (Chl. a).