10 Biogeochemical Metabolism and Energy
Flows in Reef Ecosystems
The term "metabolism of reef communities" was first used by Odum and
Odum (1955) in their prioneer work on the metabolism of communities at
the Enivetok atoll, based upon the recording of diurnal fluctuations of
oxygen content in waters over the reef. Later, for studies on primary
production and calcification processes in reef communities, the
measurements of fluctuations of CO2, pH, P04-P in diurnal cycle, or
downstream the waters surging up the reef from the ocean, were also
employed. This approach could be called biogeochemical, and the
metabolism of the whole biota of a given reef zone or biotope, the
biogeochemical metabolism. It reflects the balance values of reciprocal flows
of consumption and excretion of elements or compounds by different
components of communities. The evaluations of rates of biogeochemical
metabolism could therefore be also done by measuring them in separate
components of communities, taking into account the relative areas they
occupy on any given reef biotope or zone (Kinsey 1985b).
In the biogeochemical metabolism of coral-reef communities the aerobic
processes predominate, e.g. photosynthesis, respiration, calcification,
nutrients consumption, and nitrogen fixation. Their rates are usually
expressed in units of carbon, CaC03, P, N consumed or released per m 2 of
area of a given bottom biotope. In soft reef sediments anaerobic processes
with the dominance of sulfate reduction and denitrification could also have
taken place (d. Sects. 1.3,4.1).
10.1 Biogeochemical Metabolism of Organic Matter:
Autotrophic Production and Heterotrophic Decomposition
Also, the first measurements of the relationships between photosynthetic
oxygen evolution (P t ) and heterotrophic oxygen consumption (Mt) at some
Pacific atolls testified that reef ecosystems are autotrophic in their diurnal
balance, while functioning in environments poor in nutrients (Odum and
Odum 1955). But subsequent studies on this balance in reef system situated
near high islands, and thus receiving a large organic input from land,
Flows in Reef Ecosystems
The term "metabolism of reef communities" was first used by Odum and
Odum (1955) in their prioneer work on the metabolism of communities at
the Enivetok atoll, based upon the recording of diurnal fluctuations of
oxygen content in waters over the reef. Later, for studies on primary
production and calcification processes in reef communities, the
measurements of fluctuations of CO2, pH, P04-P in diurnal cycle, or
downstream the waters surging up the reef from the ocean, were also
employed. This approach could be called biogeochemical, and the
metabolism of the whole biota of a given reef zone or biotope, the
biogeochemical metabolism. It reflects the balance values of reciprocal flows
of consumption and excretion of elements or compounds by different
components of communities. The evaluations of rates of biogeochemical
metabolism could therefore be also done by measuring them in separate
components of communities, taking into account the relative areas they
occupy on any given reef biotope or zone (Kinsey 1985b).
In the biogeochemical metabolism of coral-reef communities the aerobic
processes predominate, e.g. photosynthesis, respiration, calcification,
nutrients consumption, and nitrogen fixation. Their rates are usually
expressed in units of carbon, CaC03, P, N consumed or released per m 2 of
area of a given bottom biotope. In soft reef sediments anaerobic processes
with the dominance of sulfate reduction and denitrification could also have
taken place (d. Sects. 1.3,4.1).
10.1 Biogeochemical Metabolism of Organic Matter:
Autotrophic Production and Heterotrophic Decomposition
Also, the first measurements of the relationships between photosynthetic
oxygen evolution (P t ) and heterotrophic oxygen consumption (Mt) at some
Pacific atolls testified that reef ecosystems are autotrophic in their diurnal
balance, while functioning in environments poor in nutrients (Odum and
Odum 1955). But subsequent studies on this balance in reef system situated
near high islands, and thus receiving a large organic input from land,