microalgae includes only photosynthesizing organisms of microscopic size and
does not include seaweeds.
Microalgae are single-celled algae measuring less than 50 µm in size. They
occasionally exist as colonies of many such cells. The term picoplankton refers to
especially small organisms measuring 2 µm in size or less. Jellyfish has sometimes
been included under the definition of plankton, but the category of zooplankton
typically refers to organisms of sizes between 10 µm and 1 mm. Tiny microalgae
thus serve as a food source for larger zooplankton, just as small fish serve as a food
source for larger fish.
The entire natural world exists in this form of food chain, with organisms
consuming other organisms and being consumed in turn. Many other varieties of
organisms besides microalgae, zooplankton, and fish inhabit the seas; in some
instances, fish consume microalgae directly. The food chain is thus not simple, but
quite complex. It is through this food chain relationship, however, that carbon is
circulated through nature.
The microalgae at the base of the food chain are a form of plant and are thus
capable of surviving on their own through photosynthesis. This means that they can
produce the organic materials they need from light energy and carbon dioxide
(CO 2 ); despite their small size, the organisms are capable of living somewhat
independently.
The question of how much organic matter microalgae are capable of creating in
all the world’s seas has long been the topic of ecological research. According to one
1975 report, net annual primary production of organic matter on Earth was calculated at 115 Â 10
9 ton in dry weight for land and 55 Â 10
9 ton for the seas,
which would mean that the seas account for the equivalent of roughly one-third of
land-based production. Net annual primary production refers to total outward
production minus the amount consumed through respiration.
Reported figures on marine production volumes vary significant from one
researcher to the next. Several factors account for these studies’ failure as yet to
calculate a precise value for total marine primary production, despite their having
taken place well before that production. Perhaps the biggest factor has been the fact
that microalgae, the producers of the seas, are not evenly distributed across all
ocean waters (Pulz and Gross 2004).
Twenty-five percent of total marine production comes from a portion accounting
for less than 10% of total marine area, while 50% of production occurs within a
portion representing 30% of total area. This means that some ocean areas are highly
productive while others are not. Although it may be possible to calculate an actual
volume by measuring at as many sites as possible, there are limits to how many
boats can be sent out onto the waters to investigate production volumes there.
Technology for launching artificial satellites to conduct periodic monitoring has
been continually developed to address this issue. Indeed, an artificial satellite was
launched in the U.S. in the 1970s to measure the amount of chlorophyll at the ocean
surface. Chlorophyll, a green pigment that absorbs light energy and is essential for
photosynthesis, provides a reflection of the concentration of microalgae in a given
area. Under sufficient illuminance, a correlation emerges between microalgae
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7 Microalgae, a Biological Resource for the Future
does not include seaweeds.
Microalgae are single-celled algae measuring less than 50 µm in size. They
occasionally exist as colonies of many such cells. The term picoplankton refers to
especially small organisms measuring 2 µm in size or less. Jellyfish has sometimes
been included under the definition of plankton, but the category of zooplankton
typically refers to organisms of sizes between 10 µm and 1 mm. Tiny microalgae
thus serve as a food source for larger zooplankton, just as small fish serve as a food
source for larger fish.
The entire natural world exists in this form of food chain, with organisms
consuming other organisms and being consumed in turn. Many other varieties of
organisms besides microalgae, zooplankton, and fish inhabit the seas; in some
instances, fish consume microalgae directly. The food chain is thus not simple, but
quite complex. It is through this food chain relationship, however, that carbon is
circulated through nature.
The microalgae at the base of the food chain are a form of plant and are thus
capable of surviving on their own through photosynthesis. This means that they can
produce the organic materials they need from light energy and carbon dioxide
(CO 2 ); despite their small size, the organisms are capable of living somewhat
independently.
The question of how much organic matter microalgae are capable of creating in
all the world’s seas has long been the topic of ecological research. According to one
1975 report, net annual primary production of organic matter on Earth was calculated at 115 Â 10
9 ton in dry weight for land and 55 Â 10
9 ton for the seas,
which would mean that the seas account for the equivalent of roughly one-third of
land-based production. Net annual primary production refers to total outward
production minus the amount consumed through respiration.
Reported figures on marine production volumes vary significant from one
researcher to the next. Several factors account for these studies’ failure as yet to
calculate a precise value for total marine primary production, despite their having
taken place well before that production. Perhaps the biggest factor has been the fact
that microalgae, the producers of the seas, are not evenly distributed across all
ocean waters (Pulz and Gross 2004).
Twenty-five percent of total marine production comes from a portion accounting
for less than 10% of total marine area, while 50% of production occurs within a
portion representing 30% of total area. This means that some ocean areas are highly
productive while others are not. Although it may be possible to calculate an actual
volume by measuring at as many sites as possible, there are limits to how many
boats can be sent out onto the waters to investigate production volumes there.
Technology for launching artificial satellites to conduct periodic monitoring has
been continually developed to address this issue. Indeed, an artificial satellite was
launched in the U.S. in the 1970s to measure the amount of chlorophyll at the ocean
surface. Chlorophyll, a green pigment that absorbs light energy and is essential for
photosynthesis, provides a reflection of the concentration of microalgae in a given
area. Under sufficient illuminance, a correlation emerges between microalgae
198
7 Microalgae, a Biological Resource for the Future