90
Plankton in Coral-Reef Waters
more than half the total of colony counts of heterotrophic bacteria
(Primakova 1985). Most of them inhabit detritus particles or the surface of
seaweeds. Dense populations of them were found in the intestines of
different reef animals, such as fish and holothurians, as well as on the
surface of living corals. Thus, the luminescent bacteria in reef habitats are
mostly connected with animals and plants.
3.2 Phytoplankton
Phytoplankton is second in its importance as component of microplankton in
coral-reef waters. Correct estimations of its number and biomass, of its
production and even of its species composition meet with methodological
caveats, which we have only recently started to overcome. But then most of
the existing data had been collected with the use of methods which were far
from perfection. Thus, when discussing the results given here we must
consider these realistically. The phytoplankton samples were collected in
reef waters with plankton nets of over 50 mesh (Shirota 1966; Glynn 1973b;
Ricard 1977b), while through the nucleopore filter of 5/l up to 50% of the
total phytoplankton biomass may pass (Sorokin et al. 1977; Legendre et al.
1988). Most phytoplankton data were collected by the Utremol
sedimentation method. But the fixative, which during several months
separates the collection and the processing of samples ruins 70-90% of
planktonic algae, especially the small pennats, naked dinoflagellates, and
coccoliths. This method also drastically underestimates the blue-green algae,
which are floating instead of settling and therefore evade the counts
(Sorokin 1986b). Definite and well-known problems arose around the
interpretation of C 14 -primary production data (Sorokin 1971b; Eppley
1981). Early estimations in reef waters made after the original SteemanNielsen version may have resulted in underestimates by a factor of 2 to 4.
No wonder then that the first estimates of phytoplankton primary
production have led to the opinion that phytoplankton in reef waters was
negligibly little (Doty and Capurro 1956; Jones 1963). But the following
investigations gave quite a different picture (Angot 1968; Sournia 1968;
Ricard 1977c). They showed that at least sometimes during the season
phytoplankton in reef waters could be abundant. But the controversy in
evaluating its role as a functional component of reef ecosystems is still alive
and needs impartial discussion and further investigation.
3.2.1 Taxonomy
The best-studied taxonomic group of phytoplankton in reef waters is the
diatoms. Nevertheless they are not always dominating. But they are the best
Plankton in Coral-Reef Waters
more than half the total of colony counts of heterotrophic bacteria
(Primakova 1985). Most of them inhabit detritus particles or the surface of
seaweeds. Dense populations of them were found in the intestines of
different reef animals, such as fish and holothurians, as well as on the
surface of living corals. Thus, the luminescent bacteria in reef habitats are
mostly connected with animals and plants.
3.2 Phytoplankton
Phytoplankton is second in its importance as component of microplankton in
coral-reef waters. Correct estimations of its number and biomass, of its
production and even of its species composition meet with methodological
caveats, which we have only recently started to overcome. But then most of
the existing data had been collected with the use of methods which were far
from perfection. Thus, when discussing the results given here we must
consider these realistically. The phytoplankton samples were collected in
reef waters with plankton nets of over 50 mesh (Shirota 1966; Glynn 1973b;
Ricard 1977b), while through the nucleopore filter of 5/l up to 50% of the
total phytoplankton biomass may pass (Sorokin et al. 1977; Legendre et al.
1988). Most phytoplankton data were collected by the Utremol
sedimentation method. But the fixative, which during several months
separates the collection and the processing of samples ruins 70-90% of
planktonic algae, especially the small pennats, naked dinoflagellates, and
coccoliths. This method also drastically underestimates the blue-green algae,
which are floating instead of settling and therefore evade the counts
(Sorokin 1986b). Definite and well-known problems arose around the
interpretation of C 14 -primary production data (Sorokin 1971b; Eppley
1981). Early estimations in reef waters made after the original SteemanNielsen version may have resulted in underestimates by a factor of 2 to 4.
No wonder then that the first estimates of phytoplankton primary
production have led to the opinion that phytoplankton in reef waters was
negligibly little (Doty and Capurro 1956; Jones 1963). But the following
investigations gave quite a different picture (Angot 1968; Sournia 1968;
Ricard 1977c). They showed that at least sometimes during the season
phytoplankton in reef waters could be abundant. But the controversy in
evaluating its role as a functional component of reef ecosystems is still alive
and needs impartial discussion and further investigation.
3.2.1 Taxonomy
The best-studied taxonomic group of phytoplankton in reef waters is the
diatoms. Nevertheless they are not always dominating. But they are the best