Bottom Plant Associations
159
approximately 15 g of wet biomass. The content of chlorophyll per m 2 of
bottom is about equal in plant associations dominated either by corallines or
by thallomic macrophytes (Wanders 1976b).
The highest gross production of photosynthesis in reef communities was
recorded in the seagrass communities - sea grass beds (Odum 1957;
Westlake 1963; Quasim and Bhattathiri 1971; Zieman et al. 1979; Murphey
and Kremer 1983). The gross photosynthesis in these communities could
attain 12-20gCm- 2 day-l. Their average values varied within 5lOgCm- 2 day-l and the P/M ratios 1-1.5 per day. The net photosynthesis
production in reef seagrass communities is relatively low: 1-4gCm- 2 .
Often it is negative because of high respiration rates of the plants themselves
and of the abundant benthic heterotrophs which inhabit the seagrass
biotopes (Table 14.8). The net production of reef seagrass associations was
also estimated by measuring their crops (Zieman 1975; Greenway 1976;
West and Larkum 1983). Its values within 1.2-2.4gCm- 2 day-l have been
obtained in this way. The primary production of mangroves was measured
experimentally (Colley et al. 1962) by the indirect method of calculating
from data on the light energy absorption by leaves and the chlorophyll
content in them (Bunt et al. 1979), and by analyzing the weight of fallen
leaves and branches (Boto et al. 1984). The generalized estimates by Lugo
and Snedeaker (1974) resulted in values of a gross production of 1318gm- 2 day-l of dry organic matter (4-6gC). The data obtained by this
method of calculation in several sites of the Great Barrier Reef of Austrialia
gave ranges of 2-3gCm- 2 day-l. Per lcm 2 of leaves surface it was about
13011 g C day-I, that is several times less than that of the macrophytes. The
direct experimental estimates showed its average level as 8 g C m -2 day-I,
that is about twice as much as the indirect once (Colley et al. 1962). The
fallen-leaves estimates gave range of net primary production of mangrove
forests within 2 to 4 g m -2 day-l of dry weight or around 1-1.5 g C m- 2
(Colley et al. 1962; Pool et al. 1975; Cintron et al. 1980; West and Larkum
1983).
Significant roles in the ecology of benthic plant associations are played by
epiphytes which are harbored by macrophytes, seagrasses, and by air roots
of mangroves as well. The relationships between the host and the epiphytic
plants are often more similar to symbiosis than to those of commensalism or
parasitism. Thus, between them an exchange with the metabolites and
photosynthates (Penhale and Smith 1977) as well as with the nutrients
(Penhale and Thayer 1980) occurs. The epiphytic blue-greens supplying
their hosts with fixed nitrogen, get from them the photosynthetically
produced organic matter (Hanson 1977; Capone et al. 1979; Penhale and
Capone 1981).
The above data demonstrate the important structural and functional roles
of the benthic plant associations in coral reef ecosystems. They provide the
bulk of total autotrophic organic production and of calcareous material. On
an average, their production could be evaluated to be within 30-50% of the
159
approximately 15 g of wet biomass. The content of chlorophyll per m 2 of
bottom is about equal in plant associations dominated either by corallines or
by thallomic macrophytes (Wanders 1976b).
The highest gross production of photosynthesis in reef communities was
recorded in the seagrass communities - sea grass beds (Odum 1957;
Westlake 1963; Quasim and Bhattathiri 1971; Zieman et al. 1979; Murphey
and Kremer 1983). The gross photosynthesis in these communities could
attain 12-20gCm- 2 day-l. Their average values varied within 5lOgCm- 2 day-l and the P/M ratios 1-1.5 per day. The net photosynthesis
production in reef seagrass communities is relatively low: 1-4gCm- 2 .
Often it is negative because of high respiration rates of the plants themselves
and of the abundant benthic heterotrophs which inhabit the seagrass
biotopes (Table 14.8). The net production of reef seagrass associations was
also estimated by measuring their crops (Zieman 1975; Greenway 1976;
West and Larkum 1983). Its values within 1.2-2.4gCm- 2 day-l have been
obtained in this way. The primary production of mangroves was measured
experimentally (Colley et al. 1962) by the indirect method of calculating
from data on the light energy absorption by leaves and the chlorophyll
content in them (Bunt et al. 1979), and by analyzing the weight of fallen
leaves and branches (Boto et al. 1984). The generalized estimates by Lugo
and Snedeaker (1974) resulted in values of a gross production of 1318gm- 2 day-l of dry organic matter (4-6gC). The data obtained by this
method of calculation in several sites of the Great Barrier Reef of Austrialia
gave ranges of 2-3gCm- 2 day-l. Per lcm 2 of leaves surface it was about
13011 g C day-I, that is several times less than that of the macrophytes. The
direct experimental estimates showed its average level as 8 g C m -2 day-I,
that is about twice as much as the indirect once (Colley et al. 1962). The
fallen-leaves estimates gave range of net primary production of mangrove
forests within 2 to 4 g m -2 day-l of dry weight or around 1-1.5 g C m- 2
(Colley et al. 1962; Pool et al. 1975; Cintron et al. 1980; West and Larkum
1983).
Significant roles in the ecology of benthic plant associations are played by
epiphytes which are harbored by macrophytes, seagrasses, and by air roots
of mangroves as well. The relationships between the host and the epiphytic
plants are often more similar to symbiosis than to those of commensalism or
parasitism. Thus, between them an exchange with the metabolites and
photosynthates (Penhale and Smith 1977) as well as with the nutrients
(Penhale and Thayer 1980) occurs. The epiphytic blue-greens supplying
their hosts with fixed nitrogen, get from them the photosynthetically
produced organic matter (Hanson 1977; Capone et al. 1979; Penhale and
Capone 1981).
The above data demonstrate the important structural and functional roles
of the benthic plant associations in coral reef ecosystems. They provide the
bulk of total autotrophic organic production and of calcareous material. On
an average, their production could be evaluated to be within 30-50% of the