were duplicated in the two lists. Hellebust obtained a total carbon
excretion of 9% from the diatom Skeletonema costatum and 4.4% from
the dinoflagellate Peridinium trochoideum in the series grown at 3 000
Lux. Figures obtained by Riley et al. (1964) for particle production in
these species were respectively 31 and 2%.
Possibly not all of the particulate matter was formed from dissolved
extra-cellular metabolites. The coarse filtration used in these experiments would perhaps permit fragments of broken or dead cells to pass
through and subsequently become incorporated in the particles. However, the procedure more or less simulated natural conditions in that
surface waters of the sea can be expected to contain an array of dissolved metabolites, cell fragments, and possibly cell sap exuded during
zooplankton grazing. All such phytoplankton products conceivably can
be aggregated and were believed to contribute toward the observed
relationship between phytoplankton concentrations and non-living
particulate matter observed by Riley et al. (1964).
About this time the writer began to find evidence of peculiarities in
yield, depending upon the type of bubbling process used. Several
experiments were designed to explore this situation. The series was
interrupted before sufficient data had accumulated for publication, but
some of the results warrant a brief account here.
One experiment, for example, involved filtration of three lO-lit,re
samples of essentially identical Long Island Sound water through 0.45
p Millipore filters into glass carboys. The first one was bubbled for 3
hours with filtered air from the laboratory compressed air supply and
filtered through a glass fibre filter. The yield was 50 pg C/litre. The
second was passed continuously through a 250 ml bubbling chamber,
entering the bottom and draining off a t the surface into a filter. The
yield was 61 pg C/litre, at least equal to that of the first experiment,
although the mean time in the bubbling chamber was only 12 minutes.
The third one was bubbled for 24 hours, and the yield was 110 pg C/litre.
The first carboy was rebubbled and filtered twice more during the
first 24 hours, with additional yields each time, and the total yield was
184 pg, considerably more than that attained by continuous bubbling.
Six more periods of rebubbling and refiltration for a total of 140 hours
increased the total yield to 474 pg.
Three additional experiments involving alternate bubbling and
filtering were carried out with surface water taken near Bermuda.
These were done in glass carboys, using ambient air introduced with
aquarium pumps. One relatively short experiment of 21 hours duration
gave a total yield of 157 pg C/litre. Two longer ones of 40 and 80 hours,
each involving six periods of bubbling and subsequent filtration yielded
excretion of 9% from the diatom Skeletonema costatum and 4.4% from
the dinoflagellate Peridinium trochoideum in the series grown at 3 000
Lux. Figures obtained by Riley et al. (1964) for particle production in
these species were respectively 31 and 2%.
Possibly not all of the particulate matter was formed from dissolved
extra-cellular metabolites. The coarse filtration used in these experiments would perhaps permit fragments of broken or dead cells to pass
through and subsequently become incorporated in the particles. However, the procedure more or less simulated natural conditions in that
surface waters of the sea can be expected to contain an array of dissolved metabolites, cell fragments, and possibly cell sap exuded during
zooplankton grazing. All such phytoplankton products conceivably can
be aggregated and were believed to contribute toward the observed
relationship between phytoplankton concentrations and non-living
particulate matter observed by Riley et al. (1964).
About this time the writer began to find evidence of peculiarities in
yield, depending upon the type of bubbling process used. Several
experiments were designed to explore this situation. The series was
interrupted before sufficient data had accumulated for publication, but
some of the results warrant a brief account here.
One experiment, for example, involved filtration of three lO-lit,re
samples of essentially identical Long Island Sound water through 0.45
p Millipore filters into glass carboys. The first one was bubbled for 3
hours with filtered air from the laboratory compressed air supply and
filtered through a glass fibre filter. The yield was 50 pg C/litre. The
second was passed continuously through a 250 ml bubbling chamber,
entering the bottom and draining off a t the surface into a filter. The
yield was 61 pg C/litre, at least equal to that of the first experiment,
although the mean time in the bubbling chamber was only 12 minutes.
The third one was bubbled for 24 hours, and the yield was 110 pg C/litre.
The first carboy was rebubbled and filtered twice more during the
first 24 hours, with additional yields each time, and the total yield was
184 pg, considerably more than that attained by continuous bubbling.
Six more periods of rebubbling and refiltration for a total of 140 hours
increased the total yield to 474 pg.
Three additional experiments involving alternate bubbling and
filtering were carried out with surface water taken near Bermuda.
These were done in glass carboys, using ambient air introduced with
aquarium pumps. One relatively short experiment of 21 hours duration
gave a total yield of 157 pg C/litre. Two longer ones of 40 and 80 hours,
each involving six periods of bubbling and subsequent filtration yielded