Diversity of M
27
Part A | 3.1
3. Diversity of Marine Phototrophs
Hideaki Miyashita
Phototrophs transform the energy of solar irradiation into chemical-bond energy in organic
substances. Those organic substances provide biological energy not only for the activities of life
on Earth, but also the formation and maintenance of regional and/or global ecosystems. They
also provide biotechnological resources for materials, energy, and so on. Since their energy
transformation is the starting point of the energy
flow in the marine ecosystem, the understanding of phototrophs is important not only for the
consideration of the homeostasis of the marine
environment, but also for the development of new
marine biotechnologies. Traditionally, diatoms and
flagellates had been understood to be the major primary producers in the ocean. However, the
developments of technologies for phytoplankton
research within the past three decades revealed
a diversity of phototrophs serving as primary producers and contributing to the transformation of
light-energy into the chemical energy. The contribution by those diverse phototrophs to the energy
flow in the ocean seemed much larger than that
by diatoms and flagellates, which indicated the
necessity of reconsidering energy flow or primary
production. In this paper, the author discusses the
3.1 Traditional Understanding of Primary
Producers (1970s) .................................. 27
3.2 Recognition of Picocyanobacteria
Dominance (1970s–2000s) ........................ 28
3.3 Discovery of Ubiquitous
Photoheterotrophs (2000–Current Times) . 29
3.4 Oxygenic Photosynthesis Using Far-Red
Light (1990s–2011) ................................... 30
3.5 Discovery of Picoeukaryotic
Phytoplankton (1990s–2011) ..................... 30
3.6 Strange Phototrophic(?) Microorganisms
(1990–2011) ............................................. 31
3.7 Diversity of Light Energy Transformation
Systems and Reconsideration
of Photosynthesis ................................... 31
3.8 Conclusion .............................................. 33
References..................................................... 33
diversity of planktonic phototrophs that serve as
the primary producers (the starting point of the
energy flow in the marine environments) based on
research results in chronological order.
3.1 Traditional Understanding of Primary Producers (1970s)
Until the mid 1970s, primary production in marine environments was understood to be performed mainly by
diatoms and flagellates [3.1]. It was obvious that they
contribute to primary production, since they are the major organisms that can be collected by a phytoplankton
net (small mesh-size net). Moreover, phytoplankton are
distributed in a wide range of water quality, including
eutrophic and oligotrophic environments. Dinoflagellates are also widely distributed as a major member of
phytoplankton in the oligotrophic ocean. Symbiotic dinoflagellates in corals at tropical reefs play a significant
role as the major primary producer in those oligotrophic
environments. Thus, diatoms and flagellates were understood to be the major primary producers in marine
environments (Fig. 3.1).
The reason why those two microalgae were considered to be the major primary producers was easily
speculated from the approach to phytoplankton sampling and the methods for phytoplankton detection at
the time. Except for phytoplankton bloom such as red
27
Part A | 3.1
3. Diversity of Marine Phototrophs
Hideaki Miyashita
Phototrophs transform the energy of solar irradiation into chemical-bond energy in organic
substances. Those organic substances provide biological energy not only for the activities of life
on Earth, but also the formation and maintenance of regional and/or global ecosystems. They
also provide biotechnological resources for materials, energy, and so on. Since their energy
transformation is the starting point of the energy
flow in the marine ecosystem, the understanding of phototrophs is important not only for the
consideration of the homeostasis of the marine
environment, but also for the development of new
marine biotechnologies. Traditionally, diatoms and
flagellates had been understood to be the major primary producers in the ocean. However, the
developments of technologies for phytoplankton
research within the past three decades revealed
a diversity of phototrophs serving as primary producers and contributing to the transformation of
light-energy into the chemical energy. The contribution by those diverse phototrophs to the energy
flow in the ocean seemed much larger than that
by diatoms and flagellates, which indicated the
necessity of reconsidering energy flow or primary
production. In this paper, the author discusses the
3.1 Traditional Understanding of Primary
Producers (1970s) .................................. 27
3.2 Recognition of Picocyanobacteria
Dominance (1970s–2000s) ........................ 28
3.3 Discovery of Ubiquitous
Photoheterotrophs (2000–Current Times) . 29
3.4 Oxygenic Photosynthesis Using Far-Red
Light (1990s–2011) ................................... 30
3.5 Discovery of Picoeukaryotic
Phytoplankton (1990s–2011) ..................... 30
3.6 Strange Phototrophic(?) Microorganisms
(1990–2011) ............................................. 31
3.7 Diversity of Light Energy Transformation
Systems and Reconsideration
of Photosynthesis ................................... 31
3.8 Conclusion .............................................. 33
References..................................................... 33
diversity of planktonic phototrophs that serve as
the primary producers (the starting point of the
energy flow in the marine environments) based on
research results in chronological order.
3.1 Traditional Understanding of Primary Producers (1970s)
Until the mid 1970s, primary production in marine environments was understood to be performed mainly by
diatoms and flagellates [3.1]. It was obvious that they
contribute to primary production, since they are the major organisms that can be collected by a phytoplankton
net (small mesh-size net). Moreover, phytoplankton are
distributed in a wide range of water quality, including
eutrophic and oligotrophic environments. Dinoflagellates are also widely distributed as a major member of
phytoplankton in the oligotrophic ocean. Symbiotic dinoflagellates in corals at tropical reefs play a significant
role as the major primary producer in those oligotrophic
environments. Thus, diatoms and flagellates were understood to be the major primary producers in marine
environments (Fig. 3.1).
The reason why those two microalgae were considered to be the major primary producers was easily
speculated from the approach to phytoplankton sampling and the methods for phytoplankton detection at
the time. Except for phytoplankton bloom such as red