Sampling Method
Marine benthic macroinvertebrate communities were sampled from randomly selected
points along the littoral zone near Brgy. Simlong (see Fig. ___). A trowel with the
dimension of (25 x 10 x5 cm) was used to collect sediment samples. All samples collected were placed on re-sealable zipper storage bags and were immediately fixed in
formaldehyde (10%) in the field. The macroinvertebrate samples were separated from
the macrophytes and the sediment using sieves (1 mm). The macroinvertebrates were
sorted, identified to the lowest possible taxon (Genus) and counted under a
stereomicroscope (Leica).
The species densities of the collected macroinvertebrates were calculated by dividing
the total number of individuals per species by the total volume of collected sediments.
In order to show the richness and abundance of the benthic macroinvertebrates, the
Shannon-Wiener Index (H’) of diversity was also calculated using the following formula:
Where in ni represents the total abundance of each species while N is the total number
of macrobenthos in the samples. Using the value of the Shannon index, the Shannon's
equitability (EH) was calculated by dividing H by Hmax where in Hmax = lnS, S = total
number of species.
complete evenness.
Equitability assumes a value between 0 and 1 with 1 being
Results and Discussion
Table 1. Relative abundances of the macrobenthic community in Simlong, Bantangas.
Taxon
Mollusca
Oliva sp.
Melanoides sp.
Gyrineum sp.
Collubella sp.
Atys sp.
Turbo sp.
Donax sp.
Iphigenia sp.
Plebidonax
Ostrea sp.
Echinodermata
Diadema sp.
Foraminefera
foramineferans
Total
Density ( m )
Relative
Abundance
600
2000
1200
800
200
400
800
800
1200
1000
0.08
0.28
0.17
0.11
0.03
0.06
0.11
0.11
0.17
0.14
400
0.06
713200
722600
98.70
100
3
Table 1. Shows list the different genera of the benthic macroinvertebrates that were
collected and their respective densities and relative abundance. From the obtained
results, it was observed that the macro benthic community of Brgy. Simlong is
composed of species belonging to Phylum Mollusca, Echinodermata, and Foraminifera.
A community demonstrates a high diversity if many equally abundant species are
present. A total of twelve genera were identified in the sediments samples. Foraminifera
species were the most abundant with a total density of 713,200 per m3. In a particular
community that possess high species richness may indicate that there is a high level of
energy transfer. However, it is highly noticeable that in the samples, there were
relatively few genera were identified were there are certain species that dominates the
system. The dominance of this species may disrupt the equal energy distribution for the
organism that is present in the system.
Table 2. Diversity analyses of macrobenthos in Brgy. Simlong
Genus
Oliva sp.
Melanoides sp.
Gyrineum sp.
Collubella sp.
Atys sp.
Turbo sp.
Donax sp.
Iphigenia sp.
Plebidonax
Ostrea sp.
Diadema sp.
foramineferans
Total
Total no. of
individuals
3
10
6
4
1
2
4
4
6
5
2
3566
LN(Pi)
Pi*LN(Pi)
-7.094
-0.0059
-5.890
-0.0163
-6.401
-0.0106
-6.806
-0.0075
-8.192
-0.0023
-7.499
-0.0042
-6.806
-0.0075
-6.806
-0.0075
-6.401
-0.0106
-6.583
-0.0091
-7.499
-0.0042
-0.013
-0.0129
3613
-0.0987
H'=
0.0987
EH = 0.039703
Based on the collected data, Brgy Simlong has a diversity Index of H’= 0.0987 as shown
in table 2. This only means that there is a low community complexity within the sampling
area. In terms of evenness index, having EH value of 0.0397 means that the sampling
area in barangay Simlong are composed of species that are not equally distributed.
Since equitability assumes a value from 0 to 1 with 1 having complete evenness, we
can say that the macrobenthic community have a number of species that dominates
and makes the system not stable for benthic habitat. It should be noted however that
only two sediment samples were collected for this study which may not be enough to
explain the complexity of the whole study area. It is suggested that in order to show the
real diversity of the benthic macroinvertebrates, more sediments samples should be
collected at different random sampling points.
The presence and absence of species may reflect the present condition of the system.
The low species richness in the system may imply that other organisms specifically
macrobenthos struggle to survive with the condition of water. Domestic waste effluents
may have change the condition of water thus affecting the benthic organisms. The
fact that majority of the organisms collected belongs to phylum Mollusca, a group with
relatively high tolerance on changing environment, may possibly reflect the quality of
water in the area. However, further studies should be done that involve water quality
components in other to have a conclusive explanation on the absence of other
macrobenthic species in Brgy. Simlong.