Organic Matter in Reef Waters
71
absorbing the microplankton, the skins of crustaceans, the loricas of
photozoans and appendicularians and fine inorganic particles grow to sizes
of 0.3-1 cm forming thus the "marine snow" (Marshall 1968). The mucus
contains proteins, lipids and a significant amount of zooxanthellae (Marshall
1972). It provides so food of high quality from these organic aggregates for
zooplankton and fish which feed on it (Johannes 1967; Hatcher 1983a). The
autochthonous suspended matter, enriched with the proteinaceous
compounds of mucus, pseudoplankton, microplankton and the microbial
populations on the detrital particles, have low CIN ratios: 4-8 compared
with the open ocean (15-30) (Coles and Strathmann 1973; Gerber and
Marshall 1974; Caperon et al. 1976; Crossland and Barnes 1983).
Among the allochthonous sources of particulated matter there should be
mentioned the suspended matter of oceanic waters passing over the reef, as
well as the wind-driven drifting masses of blue-green algae mentioned
above. In waters of barrier and fringing reefs near the continents or near
high islands the particulated material is also supplied by the rivers, which
drive to the reefs the terrigenous material (Wolanski and Pickard 1983a;
Sorokin and Tyapkin 1984). It arrives also from mangroves (Benner and
Hodson 1985). Attempts to quantify the rate of release of suspended matter
from the reef bottom biotopes up to the water column have given very high
values. Over the flat of the atoll Enivetok dominated by living corals this
release was estimated to be 300-400 mg m -2 of dry matter per day
(Johannes 1967). On flats with domination of macrophytes it was
270mgCm- 2 day-1 (Johannes and Gerber 1974), and on flats of the atoll
Kavaratti 2.3 g C m -2 day-I, or about 20% of the primary photosynthetic
production (Quasim and Sankaranarayanan 1970). The release of suspended
matter is most intense in the zone of windward flats which are subjected to
wave action and have a high primary organic production. The suspended
matter elevated up to the water column over the flat is then driven to its
lagoonal back-part (zone of patch reefs) and to the lagoon. At the Enivetok
atoll this outflow of suspended matter from 1 m of the length of the flat has
been evaluated by Johannes and Gerber (1974) and by Johannes et al.
(1972) as follows: 800 g C, 100 g Nand 2 g P per day. At the Kawaratti atoll it
was found to be 600 g m -I, on reefs of Puerto Rico 2.5 kg m -I of dry
material and on the high latitude reefs of Abrolhos, with a rich growth of
macrophytes, it was up to 9kgm- 1 day-1 (Hatcher 1983a).
The above data as well as the energy balance scheme (cf. Fig. 11. 7)
clearly show that the larger part of autotrophic production created in the
coral reef ecosystem passes into the trophic pool via the stage of DOM and
SOM. The suspended matter (SOM) coming to the reef and also produced
within the reef system is readily used by filtering reef-bottom fauna and by
planktonic heterotrophs, including microzooplankton and bacteria. The
energy flows into the food-webs involving these sources dominate in the
balance scheme. This is just the reason why through the intensive use of
the sources of dead organic carbon its contents in reef bottom sediments is
71
absorbing the microplankton, the skins of crustaceans, the loricas of
photozoans and appendicularians and fine inorganic particles grow to sizes
of 0.3-1 cm forming thus the "marine snow" (Marshall 1968). The mucus
contains proteins, lipids and a significant amount of zooxanthellae (Marshall
1972). It provides so food of high quality from these organic aggregates for
zooplankton and fish which feed on it (Johannes 1967; Hatcher 1983a). The
autochthonous suspended matter, enriched with the proteinaceous
compounds of mucus, pseudoplankton, microplankton and the microbial
populations on the detrital particles, have low CIN ratios: 4-8 compared
with the open ocean (15-30) (Coles and Strathmann 1973; Gerber and
Marshall 1974; Caperon et al. 1976; Crossland and Barnes 1983).
Among the allochthonous sources of particulated matter there should be
mentioned the suspended matter of oceanic waters passing over the reef, as
well as the wind-driven drifting masses of blue-green algae mentioned
above. In waters of barrier and fringing reefs near the continents or near
high islands the particulated material is also supplied by the rivers, which
drive to the reefs the terrigenous material (Wolanski and Pickard 1983a;
Sorokin and Tyapkin 1984). It arrives also from mangroves (Benner and
Hodson 1985). Attempts to quantify the rate of release of suspended matter
from the reef bottom biotopes up to the water column have given very high
values. Over the flat of the atoll Enivetok dominated by living corals this
release was estimated to be 300-400 mg m -2 of dry matter per day
(Johannes 1967). On flats with domination of macrophytes it was
270mgCm- 2 day-1 (Johannes and Gerber 1974), and on flats of the atoll
Kavaratti 2.3 g C m -2 day-I, or about 20% of the primary photosynthetic
production (Quasim and Sankaranarayanan 1970). The release of suspended
matter is most intense in the zone of windward flats which are subjected to
wave action and have a high primary organic production. The suspended
matter elevated up to the water column over the flat is then driven to its
lagoonal back-part (zone of patch reefs) and to the lagoon. At the Enivetok
atoll this outflow of suspended matter from 1 m of the length of the flat has
been evaluated by Johannes and Gerber (1974) and by Johannes et al.
(1972) as follows: 800 g C, 100 g Nand 2 g P per day. At the Kawaratti atoll it
was found to be 600 g m -I, on reefs of Puerto Rico 2.5 kg m -I of dry
material and on the high latitude reefs of Abrolhos, with a rich growth of
macrophytes, it was up to 9kgm- 1 day-1 (Hatcher 1983a).
The above data as well as the energy balance scheme (cf. Fig. 11. 7)
clearly show that the larger part of autotrophic production created in the
coral reef ecosystem passes into the trophic pool via the stage of DOM and
SOM. The suspended matter (SOM) coming to the reef and also produced
within the reef system is readily used by filtering reef-bottom fauna and by
planktonic heterotrophs, including microzooplankton and bacteria. The
energy flows into the food-webs involving these sources dominate in the
balance scheme. This is just the reason why through the intensive use of
the sources of dead organic carbon its contents in reef bottom sediments is