120
Plankton in Coral-Reef Waters
and final phases of zooplankton migration: during its emergence and during
its descent (Porter 1974b). Actually, as it could be seen from data displayed
in the tables, grazing does not seriously decrease the zooplankton content in
water. The calculated rate of grazing give a value of several tenths of
mgm- 3 or 100-150 sp. m- 3 nighC 1 (Glynn 1973a; Johannes and Gerber
1974), while the size of migration is at least by one order greater: 0.52gm- 3 or 1-3 X 10 3 sp. m- 3 during the same night (Tables 3.18, 3.23).
3.3.2 Microzooplankton
The microzooplankton of reef waters includes planktonic organisms less
than 200 ~ in size: the zooflagellates, the ciliates and the multicellular small
larvae of planktonic and benthic animals. In minor quantities it contains also
small radiolarian sarcodines, the planktonic amoebae and the colorless
dinoflagellates, which together with the zooflagellates form the group of
heterotrophic nanoplankton (sizes 1-20 ~). Among the zooflagellates the
representatives of their naked forms are most numerous. They belong to
their genera common from the orders Protomonadida and Kinetoplastida
(Bodo, Parabodo, Monas, Oicomonas). The zooflagellates feed mostly on
bacteriaplankton and on picoplanktonic cyanobacteria. They are consumed
themselves in turn also by planktonic and benthic filter-feeders and by the
ciliates, forming so an important intermedial trophic link between the
bacterioplankton and the reef animals. The planktonic ciliates of reef waters
include the nake holoplanktonic and benthoplanktonic ciliates and the
loricated tintinnids. For a long time the latter were erroneously considered a
main group of ciliates in reef waters, because their large specimens (100150~) were present even in the net zooplankton samples. They also survived
better the Utremol fixation procedure, used as a main method of
concentration of samples for ciliate counts (Kimor et al. 1981). But even the
use of the sedimentation method resulted in a loss of 90% or more even of
the tintinnids. Their biomass thus counted in reef waters was so small that
this group of reef zooplankton was not deemed to deserve attention. The
use of new methods resulted in proof that the nake ciliates alone comprised
70-90% of the total ciliate populations. Their size is 15-150~, and their
dominating taxa are represented by the spirotrichs Strombidium and
Strobilidium, and by the holotrichs Tiarina and Tontoni.a. The most
numerous among them are usually the different strombidia, among which
the small ones feed on bacteria and the larger ones are phytophages, feeding
on small planktonic algae. The bentho-planktonic ciliates are represented
mostly by a large - up to 150 ~ sized - hypotrichs, like Trachelostyla or
Urostyla, and happen to be numerous in turbulent areas of the reef, where
they are washed out from their native environments: near bottom water
layers, detritus, periphyton and surface layers of soft bottom sediments.
Plankton in Coral-Reef Waters
and final phases of zooplankton migration: during its emergence and during
its descent (Porter 1974b). Actually, as it could be seen from data displayed
in the tables, grazing does not seriously decrease the zooplankton content in
water. The calculated rate of grazing give a value of several tenths of
mgm- 3 or 100-150 sp. m- 3 nighC 1 (Glynn 1973a; Johannes and Gerber
1974), while the size of migration is at least by one order greater: 0.52gm- 3 or 1-3 X 10 3 sp. m- 3 during the same night (Tables 3.18, 3.23).
3.3.2 Microzooplankton
The microzooplankton of reef waters includes planktonic organisms less
than 200 ~ in size: the zooflagellates, the ciliates and the multicellular small
larvae of planktonic and benthic animals. In minor quantities it contains also
small radiolarian sarcodines, the planktonic amoebae and the colorless
dinoflagellates, which together with the zooflagellates form the group of
heterotrophic nanoplankton (sizes 1-20 ~). Among the zooflagellates the
representatives of their naked forms are most numerous. They belong to
their genera common from the orders Protomonadida and Kinetoplastida
(Bodo, Parabodo, Monas, Oicomonas). The zooflagellates feed mostly on
bacteriaplankton and on picoplanktonic cyanobacteria. They are consumed
themselves in turn also by planktonic and benthic filter-feeders and by the
ciliates, forming so an important intermedial trophic link between the
bacterioplankton and the reef animals. The planktonic ciliates of reef waters
include the nake holoplanktonic and benthoplanktonic ciliates and the
loricated tintinnids. For a long time the latter were erroneously considered a
main group of ciliates in reef waters, because their large specimens (100150~) were present even in the net zooplankton samples. They also survived
better the Utremol fixation procedure, used as a main method of
concentration of samples for ciliate counts (Kimor et al. 1981). But even the
use of the sedimentation method resulted in a loss of 90% or more even of
the tintinnids. Their biomass thus counted in reef waters was so small that
this group of reef zooplankton was not deemed to deserve attention. The
use of new methods resulted in proof that the nake ciliates alone comprised
70-90% of the total ciliate populations. Their size is 15-150~, and their
dominating taxa are represented by the spirotrichs Strombidium and
Strobilidium, and by the holotrichs Tiarina and Tontoni.a. The most
numerous among them are usually the different strombidia, among which
the small ones feed on bacteria and the larger ones are phytophages, feeding
on small planktonic algae. The bentho-planktonic ciliates are represented
mostly by a large - up to 150 ~ sized - hypotrichs, like Trachelostyla or
Urostyla, and happen to be numerous in turbulent areas of the reef, where
they are washed out from their native environments: near bottom water
layers, detritus, periphyton and surface layers of soft bottom sediments.