International Journal of Marine Science 2015, Vol.5, No.27: 1-11
2
shown the capability to degrade petroleum in the
laboratory and under controlled conditions (Aldrett et
al., 1997; Raghaven and Vivekanandan, 1999), and
other study showed no significant result in enhancing
biodegradation rate (Simon et al., 2004). Selected
oil-degrading bacteria from Jakarta Bay have been
shown to enhance oil degradation in the laboratory
(Darmayati, 2009; Hatmanti et al., 2009; Teramoto et al.,
2011). However, the efficacy of bacterial application
(bioaugmentation) in the field was still questionable
for Indonesian marine waters. Laboratory assays
cannot always be extrapolated to the field unless there
are parallel larger-scale outdoor experiments.
Mesocosm experiments are a logical intermediate step
between in-vitro findings and full-scale application
(Santas et al., 1999).
Until now, there has been almost no implementation
of bioremediation techniques at oil-polluted sites on
the coast of Indonesia. Therefore, we investigated
suitable biological remediation approaches for
anticipating oil spills in Indonesian sandy beach.
Cilacap has been used as an experimental site due to
being one of the areas where most oil spills occurred.
Based on data from various sources, during the period
1989-2011, there were 16 cases of oil spills occurred in
Cilacap area. These were 12 cases due to tanker
accidents and 4 cases due to leaked pipes (Mauludiyah,
2012). A locally produced Slow Release Fertilizer and
indigenous bacteria (
Alcanivorax
sp. TE9,
Pseudomonas
balearica
st 101 and RCO/B/08015) from Indonesian
oil-polluted waters have been used for this experiment.
The purpose of the study was to compare the efficacy
of using fertilizer only (F biostimulation), a
combination of a fertilizer and a single strain (FSC
biostimulation-single strain bioaugmentation), also a
combination of a fertilizer and a consortium (FCC
biostimulation-consortium bioaugmentation) for
degrading oil in a mesocosm experiment.
2 Results
2.1 Oil degradation
Cilacap sandy beach exhibited a natural ability to
clean itself from oil spilled at the level of 100.000
mg/kg (
Figure
1). During a 90 day experiment, the oil
has decreased about 60% (60.31+ 3.93 %,). The
oil-depletion percentage increased almost 10 % higher
than the control (69.21+2.36%) when biostimulation
only (F) was applied, at a rate of 68 gr fertilizer/kg
Figure 1 Oil degradation percentage over time for the mean of
each treatment, where Control is oiled sediment only, F is oiled
sediment with fertilizer (15 g N/kg) , FSC is oiled sediment
amended with Fertilizer (7.5 g N/kg) plus single strain (2.5 L,
8 x 10
8
cells/mL) and FCC is oiled sediment amended with
Fertilizer (7.5 g N/kg) plus consortium (2.5 L, 8 x 10
8
/mL).
Standard deviations of the replicates (n = 3) are denoted by the
error bars.
wet weight sediment (15 g N/kg). However,
biostimulation (7.5 g N/kg wet weight sediment)
which was combined with bioaugmentation (single
strain or consortium) showed a better performance
with a degradation percentage at the level of 18.5 -
20 % higher than control (78.51 + 3.86% - 80.08 +
2.6 %). At the 3 months observation, there was no
significant difference between the application of
biostimulation plus the single strain (FSC) and
biostimulation plus the consortium (FCC) in the terms
of the oil-degradation. Though, the addition of
consortium resulted in greater oil depletion than single
strain treatment at the 16
th
days sampling (Figure
1).
The FCC and FSC treatment increased oil degradation
by 2.2 and 1.6 times that of the control, respectively.
The affectivity of biostimulation-bioaugmentation
combination appeared faster and higher than
biostimulation only on oil degradation. It was showed
by the value of decay rate which was expressed as k
value (Table 1) and the percentage of
oil depletion
(Figure 1). The efficacy of biostimulation-
bioaugmen-
tation combination treatment was observed
significantly different from control 16 days after
treatment (Figure
1). There k values at the 16
th
days
were higher than others which were 0.050 day
-1
and
0.085 day
-1
for single strain and consortium,
respectively. Biostimulation only treatment reached
the significantly difference with control at the 90
th
days after treatment. It was when k value of control
