Zooplankton
125
upwelling areas (Table 3.25). Thus, their biomass in reef waters is 3-10
times greater than in surrounding oceanic waters. The number of ciliates is
very variable in different reef zones and during the day (Fig. 3.19). In
waters up reef shallows they were less abundant than off the reef edge or in
the lagoon. In the late evening their number was at its maximum, and early
in the morning at its minimum (Fig. 3.20). Among the factors controlling
their number are grazing by migrating zooplankton and by sessile benthic
animals, as well as the variations in their growth rates. Multicellular
microzooplankton is represented mostly by the micro-larvaton (Le Borgne
et al. 1989). It comprises 10-20% of the total microzooplankton biomass
(Tables 3.24, 3.26). Its numbers range within 10-40 sp.l-l, with a biomass
of 3-15mgm- 3 • Total biomass of microzooplankton in reef waters varied
within 20 to 200mgl- 1 (Tables 3.24,3.26). Thus, it is several times less than
the nocturnal biomass of mesozooplankton. But their functional activities
could be commensurable, because the specific production rate of microzooplankton (PIB) is about an by order more than that of mesozooplankton.
The generation time of planktonic ciliates is 10-40 h, and so the coefficients
of PIB per day were 0.4-1.5, and in zooflagellates 1.5-3.2 (Landry et al.
1984; Kopylov 1985; Le Borgne et al. 1989). It means that the protozoan
populations reproduce themselves approximately in 1 day. Thus the production of both these components of coral reef zooplankton appears to be
of the same magnitude, 30-50mgm- 3 of the biomass. The calculated
respiration rates of microzooplankton in reef waters off Vietnam gave
values of 30-100 ml 0 2 1- 1 day-I. So its share in total plankton respiration
could be 20 to 40% (Sorokin and Tyapkin 1984). A point of special importance of microzooplankton in reef trophodynamics consists in its exclusive role as a main source of feeding for early fish larvae, ensuring their
survival at this critical period of their ontogenesis.
3.3.3 Conclusion
The results of studies on coral reef zooplankton prove that it forms its own
communities within the reef ecosystems, which differ from the communities
in the surrounding oceanic waters. The fauna of reef zooplankton includes
endemic reef holoplanktonic, demersal and meroplanktonic species, and
contains also typical oceanic species. Many of the open-sea zooplankters
behave within the reef planktonic communities as typical reefal forms. They
employ the reef refuges to escape daytime grazing, and use the food resources of the reef as well. A bulk of reefal zooplankton is reproduced at
the expense of these recources, and thus the zooplankton brought to the
reef with passing or incoming oceanic waters comprise a minor part of its
nocturnal biomass.
The data on a high density of the nocturnal zooplankton, which could be
expressed by values of 0.5-1.5 g m -3, lead to a conclusion about possible
125
upwelling areas (Table 3.25). Thus, their biomass in reef waters is 3-10
times greater than in surrounding oceanic waters. The number of ciliates is
very variable in different reef zones and during the day (Fig. 3.19). In
waters up reef shallows they were less abundant than off the reef edge or in
the lagoon. In the late evening their number was at its maximum, and early
in the morning at its minimum (Fig. 3.20). Among the factors controlling
their number are grazing by migrating zooplankton and by sessile benthic
animals, as well as the variations in their growth rates. Multicellular
microzooplankton is represented mostly by the micro-larvaton (Le Borgne
et al. 1989). It comprises 10-20% of the total microzooplankton biomass
(Tables 3.24, 3.26). Its numbers range within 10-40 sp.l-l, with a biomass
of 3-15mgm- 3 • Total biomass of microzooplankton in reef waters varied
within 20 to 200mgl- 1 (Tables 3.24,3.26). Thus, it is several times less than
the nocturnal biomass of mesozooplankton. But their functional activities
could be commensurable, because the specific production rate of microzooplankton (PIB) is about an by order more than that of mesozooplankton.
The generation time of planktonic ciliates is 10-40 h, and so the coefficients
of PIB per day were 0.4-1.5, and in zooflagellates 1.5-3.2 (Landry et al.
1984; Kopylov 1985; Le Borgne et al. 1989). It means that the protozoan
populations reproduce themselves approximately in 1 day. Thus the production of both these components of coral reef zooplankton appears to be
of the same magnitude, 30-50mgm- 3 of the biomass. The calculated
respiration rates of microzooplankton in reef waters off Vietnam gave
values of 30-100 ml 0 2 1- 1 day-I. So its share in total plankton respiration
could be 20 to 40% (Sorokin and Tyapkin 1984). A point of special importance of microzooplankton in reef trophodynamics consists in its exclusive role as a main source of feeding for early fish larvae, ensuring their
survival at this critical period of their ontogenesis.
3.3.3 Conclusion
The results of studies on coral reef zooplankton prove that it forms its own
communities within the reef ecosystems, which differ from the communities
in the surrounding oceanic waters. The fauna of reef zooplankton includes
endemic reef holoplanktonic, demersal and meroplanktonic species, and
contains also typical oceanic species. Many of the open-sea zooplankters
behave within the reef planktonic communities as typical reefal forms. They
employ the reef refuges to escape daytime grazing, and use the food resources of the reef as well. A bulk of reefal zooplankton is reproduced at
the expense of these recources, and thus the zooplankton brought to the
reef with passing or incoming oceanic waters comprise a minor part of its
nocturnal biomass.
The data on a high density of the nocturnal zooplankton, which could be
expressed by values of 0.5-1.5 g m -3, lead to a conclusion about possible