Suppression of the dinoflagellate Noctiluca scintillans by algicidal bacteria for improving
shrimp aquaculture
Teeyaporn Keawtawee1, Kimio Fukami1, Putth Songsangjinda2 and Pensri Muangyao3
1
Graduate School of Kuroshio Science, Kochi University, Monobe otsu 200, Nankoku, 7838502, Kochi, Japan. E-mail: [email protected],
2
Trang Coastal Aquaculture Station, Mai Fad, Sikao, 92150, Trang, Thailand,
3
Coastal Aquaculture Research Institute, Kao Seng, Muang, 90000, Songkhla, Thailand
Abstract
For suppressing growth of the dinoflagellate Noctiluca scintillans, which often causes diseases
in shrimp culture and economic losses due to increased shrimp mortality, we tried to isolate
and use algicidal bacteria to assess the possibility for improving shrimp aquaculture. In 260
isolates, 10 strains of algicidal bacteria were isolated from shrimp culture ponds. Among these,
strain BS2 showed the strongest killing activity on N. scintillans. When BS2 was not added to
the culture of two species of shrimp (Penaeus monodon and Litopenaeus vannamei) with N.
scintillans, nearly 80-90 % of shrimp died within 7 days. However, when BS2 was added to
the culture of shrimp with N. scintillans, this strain could inhibit N. scintillans growth in
shrimp culture within 48 hours of incubation and shrimp survival rates increased from 23 to
87 % and 13 to 87% of P. monodon and L. vannamei, respectively. BS2 did not impact on
shrimp condition at all. The results suggest that applying algicidal bacteria for suppressing N.
scintillans in the field would be promising for stable shrimp aquaculture.
Introduction
Blooming of dinoflagellate Noctiluca
scintillans in shrimp culture stresses the
shrimps and results in lower or loss of shrimp
production by the occurring of diseases in
shrimp culture (Songsangjinda et al., 2006).
Algicidal bacteria could behave in
suppressing or killing HABs in coastal areas
(Fukami et al., 1992; Yoshinaga et al., 1997;
Doucette et al., 1998). However, no studies
refer to the role of algicidal bacteria in
shrimp culture ponds. Thus, it is essential to
study the effect of isolated bacterial strains
which inhibit the growth of HABs, in
particular N. scintillans in order to evaluate
the possibility of using algicidal bacteria in
shrimp culture ponds. This is expected to be
an alternative method to maintain and
improve shrimp growth and production.
The aim of this study was to isolate algicidal
bacteria from shrimp culture pond water and
to evaluate the killing activities on N.
scintillans under laboratory condition. The
ICHA14 Conference Proceedings Crete 2010
suppressing effect of algicidal bacteria on the
growth of N. scintillans for improving shrimp
survival was investigated.
Materials and methods
N. scintillans was isolated from Angsila,
Mueang, Chonburi province, Thailand. The
culture was maintained by incubating at 28±1
ºC in SWM III media. under 12:12 h
light:dark cycle with Dunaliella sp. as prey.
Algicidal bacteria were isolated from the
shrimp culture pond during the phytoplankton
bloom in June-July 2008 at Dumrong shrimp
farming, Tepha, Songkhla province, Thailand.
The procedure of bacterial isolation is shown
in Fig. 1. All isolates were screened for
killing effect on N. scintillans and cell change
was observed by light microscopy. A
bacterium BS2, showing the greatest killing
effect on N. scintillans, was used for
estimating its effect on other phytoplankton
species (Heterosigma akashiwo, Chattonella
antiqua,
Chaetoceros
ceratosporum,
Prorocentrum lima and Dunaliella sp.), to
ensure its killing specificity. This strain was
also used for a trial on suppressing growth of
N. scintillans under shrimp culture conditions.
Litopenaeus vannamei (White shrimp) and
Penaeus monodon (Black tiger shrimp) with
a body length about 1.5-1.8 cm (small size)
and about 3.5-4.0 cm (big size) were used.
Initial algal density was 10 cells/ml and
algicidal bacterial density was ~105 cells/ml.
The algal abundance and the shrimp survival
were daily investigated up to 7 days of the
trial.
Fig 1 The procedure of algicidal bacteria
isolation using a 24-wells tissue microplates.
Figure 2. Effects of algicidal bacteria (BS2)
on growth of other phytoplankton (H.
akashiwo, P. lima, C. antique, C.
ceratosporum and Dunaliella sp.) at 0, 24
and 48 hours of incubation time. Control
without BS2 cell. ND is not detected
plankton cells. Data are means of 5 replicates
with standard deviations.
Results and Discussions
In 260 bacterial isolates, 10 strains showed
some killing effect on N. scintillans. Among
these, strain BS2 showed the greatest killing
effect (data not shown). After inoculation of
BS2 to N. scintillans, the normal vegetative
cell became rounded, expanded and finally
bursted. In the present study, we emphasized
the bacterial effects on the growth of another
phytoplankton species. As shown in Fig. 2,
the strongest Noctiluca-killing strain BS2
showed killing effect only on N. scintillans
but no influence on other species of
phytoplankton. So far, most isolates killed
many plankton species and very few were
species-specific (Fukami et al, 1991). Some
bacteria in natural environments were
controlling the growth of HABs (Fukami et
al., 1991; Clinton et al., 2005) and inhibiting
the development and/or terminating of HABs
populations (Fukami et al., 1995; Imai et al.,
1998).
ICHA14 Conference Proceedings Crete 2010
Our results indicate that Noctiluca-killing
bacteria are distributed widely and may
control Noctiluca in the shrimp pond.
Bacterial isolate BS2 was tested in the
treatment against N. scintillans in shrimp
rearing conditions (SNB), along with a
control (SN) (Fig. 3). The result showed that
the N. scintillans cell abundances in treatment
SN, with no adding bacterial BS2, increased
after incubation 48 hours and were about 20
cells/ml at 120 hours of the incubation time.
In contrast, in the treatment to which bacteria
BS2 (SNB) were added, N. scintillans cells
decreased and disappeared after 48 hours of
incubation (data not shown). In treatment
without BS2, nearly 80-90 % of shrimp died
within 7 days (Fig. 3), probably due to
suppression by N. scintillans. The effect of N.
scintillans was stronger on smaller size than
bigger size of shrimp. On the contrary, strain
BS2 could inhibit the N. scintillans growth in
shrimp culture within 48 hours of inoculation
time and small shrimp survival rates (small
size) were improved from 13 to 87% and 23
to 87 % in L. vannamei and P. monodon,
respectively (Fig. 3). In addition, the algicidal
bacteria strain BS2 did not show any impact
on growth and mortality of shrimp. In
conclusion, algicidal bacteria could inhibit
harmful phytoplankton growth and improve
shrimp survival and the algicidal activity
showed no impact on shrimp. Therefore, to
use algicidal bacteria in shrimp culture
conditions is promising and the possibility for
applying algicidal bacteria must be further
studied.
Figure 3. Percentage of shrimp survival
after inoculation of N. scintillans and
algicidal bacteria strain BS2. (S: shrimp,
SB: shrimp+BS2, SN: shrimp+ N.
scintillans,
SNB:
Shrimp
+
N.
scintillans+BS2). WsS: L. vannamei (small
size) WsB: L. vannamei (big size), BsS: P.
monodon (small size) and BsB:
P .monodon (big size).
Acknowledgements
This study was supported by the Ministry of
Education, Culture, Sports, Science, and
Technology (Monbukagakusho), Japanese
Government, JSPS, and Fund of the President
of Kochi University. We are thankful to the
staff of Coastal Aquaculture Research
Institute, Songkhla and Dumrong farm for
their valuable helps with field work and
collecting the samples.
ICHA14 Conference Proceedings Crete 2010
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