Abstract
Thermo-physical interaction ofphytoplankton with physical flow is studied. The second law ofthermo
dynamics is used to identify the interaction of oceanic living eco-system and its environment. Based on
two facts (one is that phytoplankton exchange materials and energy with oceanic turbulent mixed layer,
and the other is that chemicaland physicalstateof oceanicturbulentmixedlayer is in statisticallystationally
and equilibrium), we showed that material circulationand energycirculation between oceanic living eco
system and external environment is fully expressed thermodynamically by entropy budget for bio-physical
system that has thermodynamical boundaries with spatial structure. Expressing heat ejection ratio
accompanied with photosynthesis in terms ofentropy balance equation, estimated energy circulation ratio
from observed two physical variables is a link between phytoplanktonphysiology and thermodynamics of
living phytoplankton.
Oceanic eco-system is identified by the biota boundary through which solar energy and materials are
transported and used to compose primary production for ocean food web. External environment for the
ocean eco-system is geophysical fluid system that contains no-life. Entropy budget for the eco-system and
its external environment is used for application ofphotosynthesis in the upper ocean turbulent mixed layer.
Entropy production by living phytoplankton contributes most part of free energy for biota food-web and
thus biologically ejected entropy is discarded in the environment.
Ocean general circulation model with surface chlorophyll heating rate incorporates such thermo-physical
interaction between the eco-system and geophysical fluid system (Nakamoto et al., 2000,2001). Ocean
surface biomass specified by surface chlorophyll concentration influences vertical penetration of solar
radiation, resulting in subsurface density gradient, generating geostrophic flow, because surface mixed
layer in the equatorial ocean is thermodynamically sensitive to interaction with living phytoplankton in
rotating earth condition. Ocean circulation system is thus influenced by the ejected entropy associated with
life activity ofoceanic eco-system in addition to entropy flux due to material circulation between the eco
system and physical system. Mean values ofphysical and chemical states thus contain detectable signals
that are reflections ofinteraction ofocean eco-system and physical system.
