according to the easily metabolizable carbohydrate compounds which characterize the
water column (Fig. 3) and those within the Posidonia leaves, namely fructose, glucose,
inositol and saccharose (Velimirov et ai, 1981). Additionally, fermentation tests for the
storage and structural carbohydrates starch, cellulose and cellobiose were performed.
Differences were mainly reflected in a higher proportion of rhamnose, saccharose,
arabinose and starch fermenting colonies in February. There were more xylose and
D-fucose fermenters in November while no L-fucose fermentation could be detected
(compare with February). All tests for cellulose fermentation were negative, but moderate
cellobiose digestion in both seasons indicates the presence of a β-glucosidase like enzyme.
Figure 3 : Distribution of free dissolved sugar compounds and total free sugar concentrations in Station 3
(November)
DISCUSSION
Defining the study area as a surface of 600 m (extension of the meadow from 0 to 33 m
depth) by 320 m (from Punta Vico to Pietro del Lacco) we obtain a water wedge 33 m in
height with a volume of 31.69 x 10 5 m 3 . If we consider both the surface water and the water
in the immediate vicinity of the meadow as distinct water bodies of 1 m thickness, we
obtain a surface layer and a bottom layer of nearly equal volume and a large midwater
body in between. In order to estimate bacterial density, DOC and POM per m3 water
above the idealized Posidonia bed, the average data per water body were weighted
according to the water volume to obtain an overall mean per unit (Table. 5). It is evident
that bacterial carbon represents only a minute fraction of DOC standing stock and that
the bacterial contribution to the overall POM, assuming a carbon content of 40% per
gram ash free dry weight, is insignificant. These findings are in agreement with data from
pilot studies in autumn and winter of the previous year (Velimirov, 1984; Velimirov in
prep.). Total number of bacteria per unit within and above the seagrass stands obtained
134
water column (Fig. 3) and those within the Posidonia leaves, namely fructose, glucose,
inositol and saccharose (Velimirov et ai, 1981). Additionally, fermentation tests for the
storage and structural carbohydrates starch, cellulose and cellobiose were performed.
Differences were mainly reflected in a higher proportion of rhamnose, saccharose,
arabinose and starch fermenting colonies in February. There were more xylose and
D-fucose fermenters in November while no L-fucose fermentation could be detected
(compare with February). All tests for cellulose fermentation were negative, but moderate
cellobiose digestion in both seasons indicates the presence of a β-glucosidase like enzyme.
Figure 3 : Distribution of free dissolved sugar compounds and total free sugar concentrations in Station 3
(November)
DISCUSSION
Defining the study area as a surface of 600 m (extension of the meadow from 0 to 33 m
depth) by 320 m (from Punta Vico to Pietro del Lacco) we obtain a water wedge 33 m in
height with a volume of 31.69 x 10 5 m 3 . If we consider both the surface water and the water
in the immediate vicinity of the meadow as distinct water bodies of 1 m thickness, we
obtain a surface layer and a bottom layer of nearly equal volume and a large midwater
body in between. In order to estimate bacterial density, DOC and POM per m3 water
above the idealized Posidonia bed, the average data per water body were weighted
according to the water volume to obtain an overall mean per unit (Table. 5). It is evident
that bacterial carbon represents only a minute fraction of DOC standing stock and that
the bacterial contribution to the overall POM, assuming a carbon content of 40% per
gram ash free dry weight, is insignificant. These findings are in agreement with data from
pilot studies in autumn and winter of the previous year (Velimirov, 1984; Velimirov in
prep.). Total number of bacteria per unit within and above the seagrass stands obtained
134