386
Biogeochemical Metabolism and Energy Flows in Reef Ecosystems
area. As background of the future model, a simplified food-web scheme was
composed, which contained 13 basic components instead of the 104
mentioned above. While this scheme contained some rather insignificant
components such as, for example, turtles, it omitted several basically
important ones, such as the bacterioplankton, the periphytic and bottom
microflora. The system was supposed to be isolated from the surrounding
ocean, but only insofar as the acquiring of additional suspended matter,
DOM and plankton input. Only their probable loss was taken into account.
Corals were united within one compartment with the benthic algae. Detritus
and DOM were totally excluded from the food web. The herbivorous and
predatory zooplankton were also united within one compartment. The same
was done with the zoobenthos and reef fish. The demersal character of the
reef zooplankton and its use by zoo benthos and bottom fish were ignored.
The mode of construction of the above model, from the viewpoint of the
author, seems to be also too audacious. Besides an arbitrary selection of
components for the main trophic groups, all field material collected at the
atoll, which composed the basis of this model, was represented by results of
random analyses of the gut contents of large predatory fish (sharks,
carangids) and of the approximate evaluations of the standing stocks of top
predators: fish, seals, sea-birds. Further necessary information for the
construction of the model, including the efficiency and the species
production coefficients, was taken from the literature, dealing mostly with
temperate water organisms and communities. Using the standing stocks and
items of information on food spectra, the food demands of the top predators
were thus calculated. Then, assuming that the coefficients of grazed
production in all trophic groups are uniform (0.85), all the necessary
parameters of their biomass, production and food rations were calculated
from the model, including then also the autotrophic ones, assured that the
system is balanced. The chief final result of this model analysis was the size
of the primary energy input into the system, necessary for its functioning.
The primary production, so computed, was found to be 4.3 x
10 6 kg km 2 year-I, or 1.2 g C m -2 day-I. This basic value was used to verify
the model by estimating its actual value in zones of the atoll at different
seasons of the year. The latter was estimated to be 6 x 10 6 kg of wet
biomass, which is not very far from the predicted value. Another result of
the model analysis was the construction of an energy-flow scheme for the
whole atoll ecosystem, in which the food rations of subsequent links within
the food web were expressed in kgm- 2 year- 1 (Fig. 10.6). To make this
scheme more comparable to other such schemes, the above values are given
as kcalm- 2 day-l. The model was over simplified and just for this reason
contained many unacceptable or a piori erroneous prerequisies. But being
successfully verified it was then used to deduce some basic conclusions about
the mechanisms controlling production in coral reef ecosystems. The model
was recommended by the authors to be employed for the development of
monitorig and management strategies concerning the use of resources of the
Biogeochemical Metabolism and Energy Flows in Reef Ecosystems
area. As background of the future model, a simplified food-web scheme was
composed, which contained 13 basic components instead of the 104
mentioned above. While this scheme contained some rather insignificant
components such as, for example, turtles, it omitted several basically
important ones, such as the bacterioplankton, the periphytic and bottom
microflora. The system was supposed to be isolated from the surrounding
ocean, but only insofar as the acquiring of additional suspended matter,
DOM and plankton input. Only their probable loss was taken into account.
Corals were united within one compartment with the benthic algae. Detritus
and DOM were totally excluded from the food web. The herbivorous and
predatory zooplankton were also united within one compartment. The same
was done with the zoobenthos and reef fish. The demersal character of the
reef zooplankton and its use by zoo benthos and bottom fish were ignored.
The mode of construction of the above model, from the viewpoint of the
author, seems to be also too audacious. Besides an arbitrary selection of
components for the main trophic groups, all field material collected at the
atoll, which composed the basis of this model, was represented by results of
random analyses of the gut contents of large predatory fish (sharks,
carangids) and of the approximate evaluations of the standing stocks of top
predators: fish, seals, sea-birds. Further necessary information for the
construction of the model, including the efficiency and the species
production coefficients, was taken from the literature, dealing mostly with
temperate water organisms and communities. Using the standing stocks and
items of information on food spectra, the food demands of the top predators
were thus calculated. Then, assuming that the coefficients of grazed
production in all trophic groups are uniform (0.85), all the necessary
parameters of their biomass, production and food rations were calculated
from the model, including then also the autotrophic ones, assured that the
system is balanced. The chief final result of this model analysis was the size
of the primary energy input into the system, necessary for its functioning.
The primary production, so computed, was found to be 4.3 x
10 6 kg km 2 year-I, or 1.2 g C m -2 day-I. This basic value was used to verify
the model by estimating its actual value in zones of the atoll at different
seasons of the year. The latter was estimated to be 6 x 10 6 kg of wet
biomass, which is not very far from the predicted value. Another result of
the model analysis was the construction of an energy-flow scheme for the
whole atoll ecosystem, in which the food rations of subsequent links within
the food web were expressed in kgm- 2 year- 1 (Fig. 10.6). To make this
scheme more comparable to other such schemes, the above values are given
as kcalm- 2 day-l. The model was over simplified and just for this reason
contained many unacceptable or a piori erroneous prerequisies. But being
successfully verified it was then used to deduce some basic conclusions about
the mechanisms controlling production in coral reef ecosystems. The model
was recommended by the authors to be employed for the development of
monitorig and management strategies concerning the use of resources of the