PARTICtTLATE ORGANIC MATTER IN SEA WATER
43
has no practical significance. It would be more interesting to find out
whether other adsorption processes which could operate in situ in the
deep ocean could increase the quantity of particulate matter.
The paper in question had examined a good deal of oceanographic
evidence, direct and indirect, as to probable causes of the lack of a
systematic decrease in particulate matter with depth in the deep sea.
The most reasonable explanation seemed to be a dynamic balance
between utilization by bacteria and other biological processes and
renewal by adsorption from the dissolved fraction. Preliminary
experiments were undertaken to explore the adsorption problem, and
results looked promising. Subsequent work has enlarged this subject
to the point where it deserves a separate subsection later.
Riley et al. (1964) explored the question of whether extracellular
substances produced during phytoplankton growth could be converted
to particulate matter by experimental bubbling. Seven species of
diatoms and one dinoflagellate were grown in pure culture in an artificial
medium in which the only organic additives were minimal quantities of
vitamins which are necessary for growth of most of these forms. They
were grown under varying conditions of light and temperature which
were believed to be optimal for the species in question ; in general the
light intensity was 500 ft. c. or less.
At approximately the end of the log phase of growth the cultures
were filtered through glass fibre filters. The medium, generally one
litre, was bubbled for 24 hours in a pyrex flask using the laboratory
air supply, and then was filtered again. The yield was highly variable,
ranging from 2-75% of cellular carbon. The dinoflagellate was at the
lower end of the range ; the diatoms averaged 20%. The mean carbon
yield in all experiments was 1.16 mg C/litre.
These results are open to criticism on the grounds of possible contamination by the laboratory air supply. However, during the same
period another series of experiments was carried out with natural sea
water and using the same air supply and other experimental equipment,
so that any errors due to artifacts should be about the same in both
series. Results obtained with natural sea water were an order of
magnitude lower than the yield from culture experiments. Thus there
is no evidence that the latter were seriously vitiated by contamination.
Hellebust (1965) described the kinds and amounts of organic excretion obtained from 22 species of algae. His results also were highly
variable, although his maximum yield of 25% was exceeded by about a
third of the experiments listed by Riley et al. (1964). However, Hellebust’s yields represented only a 48-hour experiment rather than the week
or more required for growth to the end of the log phase. Only two species
43
has no practical significance. It would be more interesting to find out
whether other adsorption processes which could operate in situ in the
deep ocean could increase the quantity of particulate matter.
The paper in question had examined a good deal of oceanographic
evidence, direct and indirect, as to probable causes of the lack of a
systematic decrease in particulate matter with depth in the deep sea.
The most reasonable explanation seemed to be a dynamic balance
between utilization by bacteria and other biological processes and
renewal by adsorption from the dissolved fraction. Preliminary
experiments were undertaken to explore the adsorption problem, and
results looked promising. Subsequent work has enlarged this subject
to the point where it deserves a separate subsection later.
Riley et al. (1964) explored the question of whether extracellular
substances produced during phytoplankton growth could be converted
to particulate matter by experimental bubbling. Seven species of
diatoms and one dinoflagellate were grown in pure culture in an artificial
medium in which the only organic additives were minimal quantities of
vitamins which are necessary for growth of most of these forms. They
were grown under varying conditions of light and temperature which
were believed to be optimal for the species in question ; in general the
light intensity was 500 ft. c. or less.
At approximately the end of the log phase of growth the cultures
were filtered through glass fibre filters. The medium, generally one
litre, was bubbled for 24 hours in a pyrex flask using the laboratory
air supply, and then was filtered again. The yield was highly variable,
ranging from 2-75% of cellular carbon. The dinoflagellate was at the
lower end of the range ; the diatoms averaged 20%. The mean carbon
yield in all experiments was 1.16 mg C/litre.
These results are open to criticism on the grounds of possible contamination by the laboratory air supply. However, during the same
period another series of experiments was carried out with natural sea
water and using the same air supply and other experimental equipment,
so that any errors due to artifacts should be about the same in both
series. Results obtained with natural sea water were an order of
magnitude lower than the yield from culture experiments. Thus there
is no evidence that the latter were seriously vitiated by contamination.
Hellebust (1965) described the kinds and amounts of organic excretion obtained from 22 species of algae. His results also were highly
variable, although his maximum yield of 25% was exceeded by about a
third of the experiments listed by Riley et al. (1964). However, Hellebust’s yields represented only a 48-hour experiment rather than the week
or more required for growth to the end of the log phase. Only two species