Foraminifera and Other Benthic Protozoa
207
The symbiotic forams are one of the main primary producers of organic
matter in coral sands, e.g., in the biotope, which comprises the larger part
of the total area of the reef (Sournia 1976b, 1977). The chlorophyll a
content in coral sands with abundant symbiotic foraminiferan populations is
high and varies within 100 to 900mgm- 2 , and the primary benthic
production is 1.5-4.0gCm- 2 day-1. Per lcm 2 of the shell's surface,
measured by the rate of photosynthesis varied from 5 in Marginopora to
9011g02h-l in calcarines (Smith 1977). The composition of photosynthetic
pigments in Marginopora resembles that in scleractinian corals. The
assimilation number in coral sands dominated by Marginopora is 0.81.2 mg C/mg Chl.a day-I, and the content of Chl.a is 0.3 mg g-l of dry sand.
The large symbiotic forams, being extremely efficient producers of
calcium carbonate, are recognized as third in importance as a source of
biogenic calcite, after corals and calcareous algae (Cushman et al. 1954).
They have a very high growth rate. In young Marginopora it will reach
0.4 mm week- 1 (Ross 1972). The total rate of calcification in sand foram
communities on shallows of flats or in lagoons was estimated to be within
150 to 500 g CaC0 3 m -2 year- 1 (Muller 1974; Ross 1977). This is, on an
average, 10-20% of the values in coral or calcarine algal communities
(Smith 1983). At the Great Barrier Reef they produce 10-15% of the total
biogenic carbonate. Coral sands themselves consist 50-90% of the shells of
forams (Maxwell 1968; Sournia 1976b). Their content in coral sands may
attain 0.6-5 X 10 5 m- 2 with their diameter averaging 2-6mm (Odum and
Odum 1955; Sakai and Nishihira 1981). They are also one of the most
important sources of food for reef benthic animals, and especially of the
holothurians, benthic omnivorous fish, irregular urchins, polychaetes and
shrimps.
Another important group of reef benthic protozoans is the ciliates
(Devaney et al. 1987). The same as the forams many of them harbor algal
symbionts. The most numerous among them are the gastrotrichs and the
predatory suctorians. Available data are still scarce, nevertheless their
probable role in the trophodymamics of reef benthic communities is quite
obvious (Fenchel 1969; Di Salvo 1973). The taxonomic composition of
ciliate communities in coral sands and also in detrital sediments was studied
on the reefs of Belize and of Enivetok atoll (Devaney et al. 1987). The
common genera of benthic ciliates were: Trachelocerca, Tracheloraphis,
Euplotes, Stylonychia, Prorodon, and Uronichia. Some specialized peritrich
and suctorian ciliates live on the surface of corals or in their vicinity and
feed on mucus and on zooxanthellae, which they excrete. Moreover, the
ciliate does not digest instantly the swallowed zooxanthelae, but preserves
them for some time, using them as temporary symbionts, the same as do
some nudibranchs (d. Sect. 5.1.1). We have found such a commensal, the
peritrich ciliate Paramecium sp., which lives in colonies of alcyonacean
Xenia and feeds on its zooxanthellae. In experiments with a culture of these
ciliates grown on grounded tissues of Xenia and literally packed with the
207
The symbiotic forams are one of the main primary producers of organic
matter in coral sands, e.g., in the biotope, which comprises the larger part
of the total area of the reef (Sournia 1976b, 1977). The chlorophyll a
content in coral sands with abundant symbiotic foraminiferan populations is
high and varies within 100 to 900mgm- 2 , and the primary benthic
production is 1.5-4.0gCm- 2 day-1. Per lcm 2 of the shell's surface,
measured by the rate of photosynthesis varied from 5 in Marginopora to
9011g02h-l in calcarines (Smith 1977). The composition of photosynthetic
pigments in Marginopora resembles that in scleractinian corals. The
assimilation number in coral sands dominated by Marginopora is 0.81.2 mg C/mg Chl.a day-I, and the content of Chl.a is 0.3 mg g-l of dry sand.
The large symbiotic forams, being extremely efficient producers of
calcium carbonate, are recognized as third in importance as a source of
biogenic calcite, after corals and calcareous algae (Cushman et al. 1954).
They have a very high growth rate. In young Marginopora it will reach
0.4 mm week- 1 (Ross 1972). The total rate of calcification in sand foram
communities on shallows of flats or in lagoons was estimated to be within
150 to 500 g CaC0 3 m -2 year- 1 (Muller 1974; Ross 1977). This is, on an
average, 10-20% of the values in coral or calcarine algal communities
(Smith 1983). At the Great Barrier Reef they produce 10-15% of the total
biogenic carbonate. Coral sands themselves consist 50-90% of the shells of
forams (Maxwell 1968; Sournia 1976b). Their content in coral sands may
attain 0.6-5 X 10 5 m- 2 with their diameter averaging 2-6mm (Odum and
Odum 1955; Sakai and Nishihira 1981). They are also one of the most
important sources of food for reef benthic animals, and especially of the
holothurians, benthic omnivorous fish, irregular urchins, polychaetes and
shrimps.
Another important group of reef benthic protozoans is the ciliates
(Devaney et al. 1987). The same as the forams many of them harbor algal
symbionts. The most numerous among them are the gastrotrichs and the
predatory suctorians. Available data are still scarce, nevertheless their
probable role in the trophodymamics of reef benthic communities is quite
obvious (Fenchel 1969; Di Salvo 1973). The taxonomic composition of
ciliate communities in coral sands and also in detrital sediments was studied
on the reefs of Belize and of Enivetok atoll (Devaney et al. 1987). The
common genera of benthic ciliates were: Trachelocerca, Tracheloraphis,
Euplotes, Stylonychia, Prorodon, and Uronichia. Some specialized peritrich
and suctorian ciliates live on the surface of corals or in their vicinity and
feed on mucus and on zooxanthellae, which they excrete. Moreover, the
ciliate does not digest instantly the swallowed zooxanthelae, but preserves
them for some time, using them as temporary symbionts, the same as do
some nudibranchs (d. Sect. 5.1.1). We have found such a commensal, the
peritrich ciliate Paramecium sp., which lives in colonies of alcyonacean
Xenia and feeds on its zooxanthellae. In experiments with a culture of these
ciliates grown on grounded tissues of Xenia and literally packed with the