74
Plankton in Coral-Reef Waters
First attempts to quantify bacteria in reef bottom sediments were made by
Di Salvo in 1969 on Hawaiian reefs. We have measured the microbial
biomass and its production in waters and sediments of some Pacific reef
systems in 1968-1969 (Sorokin 1971a, 1972). These studies demonstrated an
exclusively rich microflora in reef biotopes, which as for its abundance in
bottom sediments could be compared to fertilized ponds and the water
columns up the reefs - with eutrophic oceanic waters. At the same time it
was shown that filtering reef animals as well as the corals themselves feed on
suspended bacteria. These data proved the important role of bacteria in reef
trophodynamics and metabolism and thus stimulated further investigations
in this field. The main directions of these studies constituted estimations of
the standing stock and production rates of microbial biomass of the stocks
and sources of labile organic matter for microbial production, and of the
availability of bacteria as food for the reef fauna, including fine and crude
filters and sedimentary feeders, detritovores, and sediment-eaters. For estimations of the microbial biomass, the total number of bacteria has been
counted and the size of their cells determined microscopically, first on the
membrane filters stained with erythrosine and cleared in immersion oil after
Rasumov (Sorokin 1971b; Sorokin and Kadota 1972), and later on the black
Nucleopore filters stained by a fluorochrome and analyzed under the
epifluorescence microscope, after Hobbie-Wright (Moriarty 1979; Ducklow
and Mitchell 1979b; Moriarty et al. 1985b). The production of microbial
biomass was first estimated by the use of the 14C-dark assimilation method
by Romanenko (Sorokin 1971a,b, 1978b, 1986b). Later the thymidine
method by Fuhrman and Asam was used (Moriarty and Pollard 1982). The
first method was criticized by the former authors, nevertheless the
production rate values obtained by both methods in general coincided
(Table 3.1). Moreover, after my own experience with intercalibration
methods I have arrived at the following conclusion. The nature of the basic
coefficients, which are used in the formula for recalculation of the
radioactivity of taken up 3H-thymidine remains still indefinite and is selected
by each investigator more or less arbitrarily: such as the ratio between the
thymidine uptake and number of cell divisions (shift between 1 and
16· 10 18 div.nmol- 1 ), content of carbon per cell (shift 3-4 times). Also, the
specific activity of 3H-thymidine preparations in each batch is largely
indefinite and cannot be checked. Thus the thymidine method had to be
calibrated each time it was used after some other method which gave more
direct absolute values of microbial production in carbon units. In my
experience the best method for this purpose appears to be just the dark
uptake 14C method in its modern modified form. Parallel estimations of
microbial production by both methods properly intercalibrated showed no
essential difference (Table 3.2).
The rates of respiration of bacterioplankton (M) were calculated as
follows: M = [p. (1 - K2)]/K2' where P is microbial production, and K2
efficiency coefficient of microbial biosynthesis, which in planktonic bacteria
Plankton in Coral-Reef Waters
First attempts to quantify bacteria in reef bottom sediments were made by
Di Salvo in 1969 on Hawaiian reefs. We have measured the microbial
biomass and its production in waters and sediments of some Pacific reef
systems in 1968-1969 (Sorokin 1971a, 1972). These studies demonstrated an
exclusively rich microflora in reef biotopes, which as for its abundance in
bottom sediments could be compared to fertilized ponds and the water
columns up the reefs - with eutrophic oceanic waters. At the same time it
was shown that filtering reef animals as well as the corals themselves feed on
suspended bacteria. These data proved the important role of bacteria in reef
trophodynamics and metabolism and thus stimulated further investigations
in this field. The main directions of these studies constituted estimations of
the standing stock and production rates of microbial biomass of the stocks
and sources of labile organic matter for microbial production, and of the
availability of bacteria as food for the reef fauna, including fine and crude
filters and sedimentary feeders, detritovores, and sediment-eaters. For estimations of the microbial biomass, the total number of bacteria has been
counted and the size of their cells determined microscopically, first on the
membrane filters stained with erythrosine and cleared in immersion oil after
Rasumov (Sorokin 1971b; Sorokin and Kadota 1972), and later on the black
Nucleopore filters stained by a fluorochrome and analyzed under the
epifluorescence microscope, after Hobbie-Wright (Moriarty 1979; Ducklow
and Mitchell 1979b; Moriarty et al. 1985b). The production of microbial
biomass was first estimated by the use of the 14C-dark assimilation method
by Romanenko (Sorokin 1971a,b, 1978b, 1986b). Later the thymidine
method by Fuhrman and Asam was used (Moriarty and Pollard 1982). The
first method was criticized by the former authors, nevertheless the
production rate values obtained by both methods in general coincided
(Table 3.1). Moreover, after my own experience with intercalibration
methods I have arrived at the following conclusion. The nature of the basic
coefficients, which are used in the formula for recalculation of the
radioactivity of taken up 3H-thymidine remains still indefinite and is selected
by each investigator more or less arbitrarily: such as the ratio between the
thymidine uptake and number of cell divisions (shift between 1 and
16· 10 18 div.nmol- 1 ), content of carbon per cell (shift 3-4 times). Also, the
specific activity of 3H-thymidine preparations in each batch is largely
indefinite and cannot be checked. Thus the thymidine method had to be
calibrated each time it was used after some other method which gave more
direct absolute values of microbial production in carbon units. In my
experience the best method for this purpose appears to be just the dark
uptake 14C method in its modern modified form. Parallel estimations of
microbial production by both methods properly intercalibrated showed no
essential difference (Table 3.2).
The rates of respiration of bacterioplankton (M) were calculated as
follows: M = [p. (1 - K2)]/K2' where P is microbial production, and K2
efficiency coefficient of microbial biosynthesis, which in planktonic bacteria