4 Benthic Microfiora, Periphyton
and Plant Associations
The plant benthic communities and the bottom microftora are responsible
for more than half the total autotrophic production and of beterotrophic
metabolism in coral-reef ecosystems. The plant communities include the
microphytobenthos of soft sediments, the periphytonic overgrowths of the
solid surfaces and rubble, the thallophyte seaweeds and the seagrasses. The
bottom microbial associations are represented by bacteria in soft sediments
(soft sands), by bacteria in the detrital sediments, by periphytonic bacteria
and by bacteria symbiotic to benthic animals (sponges). The relative
importance of each of the components listed varies in different reef zones.
4.1 Bacteria and Microalgae in Reef Bottom Sediments
The first proof of an important role played by benthic microftora in reef
metabolism was demonstrated by Di Salvo (1969) and Di Salvo and
Gundersen (1971). Studying the detrital sediments of Hawaiian recefs, they
obtained extremely high plate-count numbers of heterotrophic bacteria - up
to 10 6 cells g -1. The author made in 1968-1971 estimations of the total
number, biomass and production of bacteria in coral sands and periphytonic
overgrowths in a variety of Pacific reefs (Sorokin 1971a, 1973c, 1978b).
The soft reef sediments are represented mostly by coral sands. The sand
particles, being formed from the skeleton material of reef animals and
calcareous algae, have a porous structure (Fig. 4.1). This heightens the
possibility of their overgrowth by bacteria. Being imbedded into the mucous
cover, which they form around the particle, they comprise a kind of
microbiocoenosis (Weise and Rheinheimer 1978; Sorokin 1981c). Among
bacteria, which inhabit the sand particles, the most numerous are rods which
attach to the particle surfaces with the aid of polysaccharide fibrils (Weise
and Rheinheimer 1978; Fletcher and Marshall 1982). Disk-shaped bacteria
are also attached to the surfaces of sand grains. The coccoid bacteria form
on the surface of the sand particles the mucous microcolonies. Many single
cells in these micro biocoenoses are also within the mucus capsules (Moriarty
and Haywood 1982). Prostecobacteria and Caulobacteria attach to the
surface by means of their stalks. Among the physiological groups recorded
and Plant Associations
The plant benthic communities and the bottom microftora are responsible
for more than half the total autotrophic production and of beterotrophic
metabolism in coral-reef ecosystems. The plant communities include the
microphytobenthos of soft sediments, the periphytonic overgrowths of the
solid surfaces and rubble, the thallophyte seaweeds and the seagrasses. The
bottom microbial associations are represented by bacteria in soft sediments
(soft sands), by bacteria in the detrital sediments, by periphytonic bacteria
and by bacteria symbiotic to benthic animals (sponges). The relative
importance of each of the components listed varies in different reef zones.
4.1 Bacteria and Microalgae in Reef Bottom Sediments
The first proof of an important role played by benthic microftora in reef
metabolism was demonstrated by Di Salvo (1969) and Di Salvo and
Gundersen (1971). Studying the detrital sediments of Hawaiian recefs, they
obtained extremely high plate-count numbers of heterotrophic bacteria - up
to 10 6 cells g -1. The author made in 1968-1971 estimations of the total
number, biomass and production of bacteria in coral sands and periphytonic
overgrowths in a variety of Pacific reefs (Sorokin 1971a, 1973c, 1978b).
The soft reef sediments are represented mostly by coral sands. The sand
particles, being formed from the skeleton material of reef animals and
calcareous algae, have a porous structure (Fig. 4.1). This heightens the
possibility of their overgrowth by bacteria. Being imbedded into the mucous
cover, which they form around the particle, they comprise a kind of
microbiocoenosis (Weise and Rheinheimer 1978; Sorokin 1981c). Among
bacteria, which inhabit the sand particles, the most numerous are rods which
attach to the particle surfaces with the aid of polysaccharide fibrils (Weise
and Rheinheimer 1978; Fletcher and Marshall 1982). Disk-shaped bacteria
are also attached to the surfaces of sand grains. The coccoid bacteria form
on the surface of the sand particles the mucous microcolonies. Many single
cells in these micro biocoenoses are also within the mucus capsules (Moriarty
and Haywood 1982). Prostecobacteria and Caulobacteria attach to the
surface by means of their stalks. Among the physiological groups recorded