The sediment examination showed that the percentage of sand,
silt, and clay fractions have ranged from 82.5 to 91.0%, 5.0 to
15.0%, and 2.0 to 5.0, respectively. Percentage of sand was
high probably because sampling location directly receives material
brought from the sea by the current despite in mangrove
area during tsunami in late December 2004. Nybakken (1992)
mentioned that particle sedimentation depends on the size of
the particle and current. The bigger and heavier particles will
settle faster than the smaller particles and weak current will deposit
material longer than the strong current. Silt fraction was
higher than clay; this condition can be explained because there
was a contribution of litter, especially leaves, from the mangrove
vegetation.
We found that the age of vegetation did not affect the abundance
of Bivalves. However, the higher abundance of Bivalves
was found at study site 3 with 3 years old of mangrove. This
is probably due to the higher density of mangrove (3 ind/m2)
at this site, as it had a lot of root branching used for Bivalves
living on. Mangrove roots represent the area of hard substrate
colonized by massive sponge, oyster (Ostreidae), and barnacle
(Cannicci et al 2008). Moreover, Guerreiro et al (1996) expressed
that sediment textures, tidal elevation and forest type
affect the distribution of macrofauna in mangrove ecosystem.
Cerithidea cingulata was the dominant species in the study
area. We assumed that this species had a good adaptation on
environmental condition at these sites and therefore it won the
competition for food and habitat. In addition, we found three
species of native mollusks in mangrove ecosystem i.e. C. cingulata,
Terebralia palustris and Nerita planospira; three facultative
mollusks i.e. Littorina scabra, C. patulum, and Crassostrea
cucullata and two migrant mollusks i.e. Nerita undata and
Clypeomorus moniliferum.
The sediment examination showed that the percentage of sand,silt, and clay fractions have ranged from 82.5 to 91.0%, 5.0 to15.0%, and 2.0 to 5.0, respectively. Percentage of sand washigh probably because sampling location directly receives materialbrought from the sea by the current despite in mangrovearea during tsunami in late December 2004. Nybakken (1992)mentioned that particle sedimentation depends on the size ofthe particle and current. The bigger and heavier particles willsettle faster than the smaller particles and weak current will depositmaterial longer than the strong current. Silt fraction washigher than clay; this condition can be explained because therewas a contribution of litter, especially leaves, from the mangrovevegetation.We found that the age of vegetation did not affect the abundanceof Bivalves. However, the higher abundance of Bivalveswas found at study site 3 with 3 years old of mangrove. Thisis probably due to the higher density of mangrove (3 ind/m2)at this site, as it had a lot of root branching used for Bivalvesliving on. Mangrove roots represent the area of hard substratecolonized by massive sponge, oyster (Ostreidae), and barnacle(Cannicci et al 2008). Moreover, Guerreiro et al (1996) expressedthat sediment textures, tidal elevation and forest typeaffect the distribution of macrofauna in mangrove ecosystem.Cerithidea cingulata was the dominant species in the studyarea. We assumed that this species had a good adaptation on
environmental condition at these sites and therefore it won the
competition for food and habitat. In addition, we found three
species of native mollusks in mangrove ecosystem i.e. C. cingulata,
Terebralia palustris and Nerita planospira; three facultative
mollusks i.e. Littorina scabra, C. patulum, and Crassostrea
cucullata and two migrant mollusks i.e. Nerita undata and
Clypeomorus moniliferum.
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