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International Journal of Marine Science 2014, Vol.4, No.61, 1-13
http://ijms.biopublisher.ca
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area for these variables (Table 4, 5). In addition, the
scallop also required seabed habitat with higher
current velocity and salinity; lower temperature than
the average study area for these variables.
Furthermore, scallop was relatively more tolerant to
pH (Table 4, 5).
The highest density of plankton in the seabed of
Brebes District was found in the front of the wider
estuary, especially in front of Pemali River in the
eastern part (Figure 3i, 4i). The high density of
plankton was allegedly associated with nutrient input
due to activity on the mainland, where majority of
land use along the coastal of Brebes Districts was
ponds. Whilst in the upper area, the activity was
dominated by agricultural which generally used
fertilizers. Nutrients from those two activities
stimulated the plankton growth.
The high density of plankton in the entire water
column was because the water was relatively shallow
(Figure 3b), therefore it was still part of the euphotic
zone, especially in areas that was distant enough from
the mainland where its suspended solids material
tended to be low (Figure 3d). In the euphotic zone,
plankton could still live because they got the sunlight
allowing them for photosynthesis (Fachrul, 2007).
Plankton was successfully screened using 25 plankton
net classified in micro-plankton, namely plankton with
20-200 µm in size (Omori and Ikeda, 1992). Lucas et
al., 1987) stated that the cumulative weight of
plankton above 20 µm indicated that it was relatively
large, making it easier to sink and become a food
source for filter-feeder organisms, including scallop.
The largest constituent of the phytoplankton
community of seabed in the study area was from the
class Bacillariophyceae (diatoms), with Chaetoceros,
Nitzchia, and Skeletonema were the three genus
commonly found in each observed station. Diatoms
were the largest constituent of plankton in the sea, so
its role as a dominant source of food. Chaetoceros and
Skeletonema were two plankton species widely used
as feed in marine aquaculture.
Scallop habitat required relatively deep waters and a
suitable location was found only in the eastern part of
the study area (Figure 3b, 4b). This depth was
relatively similar to the results reported by Widowati
et al. (1999), where the waters scallop in Pekalongan,
commonly found at depths of 20-30 m. This kind of
habitat preferences was assumed to be related to the
temperature suitability of the seabed waters for a place
to live for scallop. The deeper the water depth was, the
lower temperature would be (Figure 3f, 4f).
Spatially, TSS in Brebes District marine waters had
spread widely, with the highest content was in the
front of Cisanggarung in the western and Pemali River
estuary in the eastern side of the study area. This was
due to the presence of suspended solid flowing in to
the water column through the river stream. In addition,
factors such as physical oceanography and tidal
currents also affected the high turbidity levels in the
area. During the high tide to the low one, the sediment
carried by the flow of the river would be suspended in
to the water column. Thus, it increased the level of
turbidity in the waters around the mouth of the river
(Triatmodjo, 1999).
Scallop were mostly obtained from the location with
very low (< 1.80 mg/L) and low (1.81-3.60 mg/L)
content of TSS indicating that the scallop preferred
areas with low content of TSS as its habitat. The
location was distant from the mainland, especially in
the eastern side of the study area (Figure 3d, 4d).
In general, the seabed at the study area was dominated
by fine substrates (silt and mud), as well as scallop
habitat. Numbers of rivers streaming down into the
coastal around the study area influenced the type of
sediment on the seabed. There were 13 rivers
streaming from the mainland of Brebes District (DKP,
2008). The dominance of these fine substrates
occurred due to deposition of material originated from
weak energy because of the flat riverbed.
Fine-textured sediments such as silt and mud were
generally darker in color because they contained
higher organic materials (Astjario et al., 1990).
Fine-textured sediments were also rich in plankton
such as diatoms (Thomas, 1997), so it became a food
source for benthic consumers (Sukhtankar, 2004)
including for scallop.
Franklin et al. (1980) reported that
Amusium
sp. could
live on the surface of the seabed with varying
substrate types ranging from rocky until muddy
substrate and mostly found in sandy substrates mixed
with shells. However, in the study area, scallop
A.