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Bloom of Trichodesmium (Oscillatoriales, Phormidiaceae) and seasonality of potentially harmful phytoplankton in San Pedro Bay, Leyte, Philippines

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  • University of the Philippines Visayas-Tacloban College, Tacloban, Leyte

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Since 1983, San Pedro Bay in the Philippines had been reported to be the site of episodic Pyrodinium bahamense var. compressum blooms that caused paralytic shellfish poisoning in its nearby coastal communities. This bay is also subjected to numerous storms; the strongest was super typhoon Haiyan in November 8, 2013. For the first time, the seasonal dynamics of potentially toxic and harmful phytoplankton in this bay is elucidated. This is also the first record of a bloom of the cyanobacteria, Trichodesmium erythraeum that reached 70 000 colonies/L in April 2013 in this area. There were other 19 potentially toxic and harmful phytoplankton encountered during the sampling period. These consisted of a haptophyte, Phaeocystis globosa, the diatom Pseudonitzschia and 17 dinoflagellates. Seven of these harmful algae had densities high enough to be traced through time. Normally, diatoms abound during the dry season. But Pseudo-nitzschia increased in abundance during the wet season of 2012 and 2013. The dinoflagellates and Phaeocystis globosa behaved as expected and exhibited a relative increase in cell density during the rainy season of both years too. High nutrient availability during this season must have influenced the behavior of the phytoplankton despite differences in temperature and light intensity among seasons. Other notable but rare harmful species found only in plankton net tows during the study were Pyrodinium bahamense var. compressum, Alexandrium tamiyavanichii, Cochlodinium polykrikoides, and Noctiluca scintillans.
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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 64 (2): 897-911, June 2016
Bloom of Trichodesmium (Oscillatoriales, Phormidiaceae) and seasonality
of potentially harmful phytoplankton in San Pedro Bay, Leyte, Philippines
Leni G. Yap-Dejeto & Haide S. Batula
Division of Natural Science and Mathematics, University of the Philippines in the Visayas-Tacloban College,
Magsaysay Ave., Tacloban City, 6500 Leyte, Philippines; leny.yap@upou.edu.ph, llenigy@yahoo.com,
haidebatz@yahoo.com
Received 03-VI-2015. Corrected 18-I-2016. Accepted 16-II-2016.
Abstract: Since 1983, San Pedro Bay in the Philippines had been reported to be the site of episodic Pyrodinium
bahamense var. compressum blooms that caused paralytic shellfish poisoning in its nearby coastal communities.
This bay is also subjected to numerous storms; the strongest was super typhoon Haiyan in November 8, 2013.
For the first time, the seasonal dynamics of potentially toxic and harmful phytoplankton in this bay is elucidated.
This is also the first record of a bloom of the cyanobacteria, Trichodesmium erythraeum that reached 70 000
colonies/L in April 2013 in this area. There were other 19 potentially toxic and harmful phytoplankton encoun-
tered during the sampling period. These consisted of a haptophyte, Phaeocystis globosa, the diatom Pseudo-
nitzschia and 17 dinoflagellates. Seven of these harmful algae had densities high enough to be traced through
time. Normally, diatoms abound during the dry season. But Pseudo-nitzschia increased in abundance during the
wet season of 2012 and 2013. The dinoflagellates and Phaeocystis globosa behaved as expected and exhibited
a relative increase in cell density during the rainy season of both years too. High nutrient availability during
this season must have influenced the behavior of the phytoplankton despite differences in temperature and light
intensity among seasons. Other notable but rare harmful species found only in plankton net tows during the study
were Pyrodinium bahamense var. compressum, Alexandrium tamiyavanichii, Cochlodinium polykrikoides, and
Noctiluca scintillans. Rev. Biol. Trop. 64 (2): 897-911. Epub 2016 June 01.
Key words: Trichodesmium, Pseudo-nitzschia, harmful dinoflagellates, HAB, nutrients, storm, San Pedro Bay,
Leyte, Philippines.
Episodes of Pyrodinium bahamense var.
compressum blooms that cause paralytic shell-
fish poisoning (PSP) have been reported in San
Pedro Bay since 1983. In January 1983, toxic
bloom of Pyrodinium bahamense var. compres-
sum affected 300 km of coastlines of Samar and
Leyte including this bay. The red-tide repeated
in 1987 and 1988 (Bankoff, 2003; Gonzales,
1989). Human fatalities accompanied some of
these blooms historically. The latest recorded
bloom was in October 2007 (LMBTC, 2007).
Laboratory analyses of shellfish samples at
that time from Cancabato Bay showed positive
results for saxitoxin beyond the regulatory limit
of 40 micrograms saxitoxin equivalent/100
grams meat (LMBTC, 2007). Last November
2012, all coastal waters in Eastern Visayas
region including San Pedro Bay covering Palo
and Tanauan, and Cancabato Bay in Tacloban
City, were declared free from this toxic red tide
(BFAR, 2012).
There are two other harmful algae previ-
ously recorded in the bay. Nitzschia navis-
varingica was detected in San Pedro Bay in
2004 and was found to produce the major
toxins, domoic acid and isodomoic acid B
(Kotaki et al., 2005). Pseudo-nitzchia spp. were
also present (Yap-Dejeto, Cobacha, & Cinco,
2008; Yap-Dejeto, Omura, Cinco, Cobacha, &
Fukuyo, 2013).
It is not clear until now how species
of phytoplankton behave annually in tropical
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marine waters. Recent studies have proven
that changes and successions of phytoplank-
ton communities do occur in coastal tropical
areas seasonally (Franco-Herrera, Castro, &
Tigreros, 2006). Harmful phytoplankton are
few; however, these species can cause small
or large-scale shellfish and fish kills (Sell-
ner, Doucette, & Kirkpatrick, 2003) and even
human deaths when they form blooms. Hence,
monitoring of phytoplankton composition is
important to understand their formation and
to predict occurrences of harmful algal bloom
incidents that directly affect commercial shell-
fish production, mariculture industries and
overall food safety.
San Pedro Bay is located in the center of
the Philippines and confined within the coast-
lines of Leyte and Samar islands. It includes
the narrow San Juanico Strait and a shallow
U-shaped embayment, Cancabatoc Bay. It then
spreads out through the Pacific Ocean. A char-
acteristic feature of this bay is its relatively
shallow depth averaging only 20 m. Its total
area is 625 km2 (Campos, 2003); and parts of
the bay are mariculture zones for fish and shell-
fish, and is also an important fishing ground
for people in its coastal communities. Thus,
updated information on the water quality of the
bay is important.
The Philippine Atmospheric Geophysical
Astronomical Services Administration (PAG-
ASA) classifies Leyte Island under Type IV
of the Corona system of classification. This
is characterized by even distribution of rain-
fall throughout the year and short dry season
from February to March (DOST-PAGASA,
2011). This bay is also subjected to numerous
typhoons; the strongest was typhoon Haiyan in
November 8, 2013. Ecological studies of this
bay will thus provide a glimpse of possible
effects of climate change in phytoplankton
ecology in a marine ecosystem.
This paper aims to elucidate the seasonal
succession of harmful phytoplankton in San
Pedro Bay, Leyte, Philippines from 2012-2013;
and to conduct a thorough search of potential
harmful phytoplankton in the system. This is
the first study of this kind that has been done in
this Philippine region (Visayas).
MATERIALS AND METHODS
Sampling strategy: Three representative
stations in San Pedro Bay were established.
Station 1 (11°13’270’ N - 125°02’471’’ E)
at 8-10 m depth was located near Dio Island,
Station 2 (11°15’46’ N - 125°04’5’’ E), 2.3-4
m deep, located within Cancabato Bay and Sta-
tion 3 (11°17’22’ N - 124°58’30’’ E), 11-15 m
deep, located along the San Juanico Strait (Fig.
1). A GPS unit (Handheld Garmin 76) was used
to record the coordinates of the stations which
were then traced and plotted using Manifold®.
Station 1 is located near Dio Island, far from
coastal settlements. Station 2 is located within
the shallow and restricted Cancabato Bay near
residential and mangrove areas. Station 3 is
along the San Juanico Strait, which harbors a
mariculture area and a number of fish cages.
A quantitative data of phytoplankton was
recorded to represent the three (3) climatic
seasons in the Philippines i.e., the rainy season
(June-November), the cold dry season (Decem-
ber-February) and hot dry season (March-May).
Monthly collections were done from January to
March 2012, and August to December 2012.
Bimonthly collections were done from April
to December in 2013. Samples for qualitative
assessment were taken 1-m below the surface
using a 20 µm mesh size (aperture diameter:
30 cm, length: 1m) plankton net, while that for
phytoplankton counts were from a 2-L vertical
alpha water sampler (WILDCO).
Physico-chemical analysis: Physical vari-
ables were assessed in situ. Temperature, salin-
ity, light intensity and depth readings were
recorded using a mercury-filled centigrade
field thermometer, ATTAGO refractometer,
EXTECH light meter and a calibrated rope,
respectively. Current velocity was estimated
through drift method using a fabricated Holey
Sock drogue. Secchi Disc Transparency (SDT;
turbidity of the water column) was estimated.
Measurements for pH and amount of dissolved
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oxygen were taken using a EUTECH Multipa-
rameter Handheld Meter (PCD 650).
For nutrient analyses, water samples were
filtered using 47-mm Whatman GF/C glass-
fiber filters (1.2 µm pore size). The filtered
samples were stored in acid-washed bottles and
were frozen. The prepared samples were then
sent to the Chemical Oceanography Labora-
tory of the Marine Science Institute of Univer-
sity of the Philippines, Diliman for analysis.
Nitrate, nitrite and phosphate concentrations
were measured by the use of SKALAR SANS
++ segmented flow analyzer D5000 following
Strickland and Parsons (1972).
Phytoplankton species identification: Phy-
toplankton samples were settled for at least 48
hours with two settling phases of at least 24
hours. The 1L samples for quantitative analysis
were fixed with Lugol’s solution and settled
for at least 24 hours to obtain about 200 mL
sample. These were then transferred to 250 mL
graduated glass cylinders to settle for at least
another 24 hours. Capillary tubing’s were used
to siphon upper layers of each settling phase
Fig. 1. The inner portion of San Pedro Bay showing the location of the three sampling stations.
7.0000º 11.0000º 15.0000º 19.0000º
11º00’00” N 112º00’00” N
119.0000º 124.0000º 125º00’00” E
124º59’15” E 125º00’09” E 125º01’03” E 125º01’57” E 125º02’51” E
11º12’18” N 11º12’45” N 11º13’12” N 11º13’39” N 11º14’06” N 11º14’33” N 11º15’00” N 11º15’27” N 11º15’54” N 11º16’21” N 11º16’48” N 11º17’15” N 11º17’42” N 11º18’09” N
Station 3
Station 2
Station 1
San Juanico Strait
Cancabata Bay
San Pedro Bay
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to finally obtain about 50 mL final concen-
trated phytoplankton sample (USEPA, 1994
with modifications). One (1) mL of the 50 mL
concentrated sample was then dispensed into
a gridded Sedgwick-Rafter counting chamber
and was examined in triplicate under a light
compound microscope at 40x-400x magni-
fication. The harmful phytoplankton species
present were identified using identification
guides and keys of Omura, Iwataki, Borja,
Takayama and Fukuyo (2012), Larink and
Westheide (2006), Botes (2003), Tomas (1997)
and Yamaji (1984). The number of cells count-
ed in three replicates was averaged in order to
calculate cell density per species. Cell density
was obtained by multiplying the averaged cell
density counted in one-mL to the concentrated
volume of sample.
Data treatment: Monthly cell densities
and physico-chemical parameters from the
three stations were averaged to obtain the
mean monthly data. Pearson’s correlation coef-
ficients and p-values were calculated using
Windows Excel 2013 and Pumpkin Helmet©
package (2014) in R version 3.1.2.
RESULTS
Physico-chemical parameters: The month-
ly and seasonal variation of the physical param-
eters obtained during the two year study period,
2012 and 2013, is shown in figure 2. Mean
monthly water temperatures varied over a rela-
tively narrow range during the two consecutive
years from 26.8 to 31.0 °C. Lowest tempera-
tures were recorded during the cold dry season
of both sampling years while highest tempera-
tures were recorded during the rainy months of
June and August 2013. Salinity varied from 29
to 35 ppt within small amplitude, with the high-
est value recorded during the cold dry season of
2012 and 2013. pH values were all relatively
alkaline and did not vary much across all the
sampling months of both years.
Dissolved Oxygen (DO) concentrations
of most sampling months were greater than
the minimum value of 4 mg/L set by ASEAN
water quality criteria (ASEAN, 2008). The
least current velocity (0.2 m/s) was in Station 1
in December 2013 and greatest current veloc-
ity (0.78 m/s) was in Station 3 in January 2012.
Mean light intensity measurements ranged
from 691 to 1 216 µmol photons/m2.s. High
temperatures and light intensities were during
the rainy season of both years. Transparency
measurements, on the other hand, fluctuated
between 0.19 to 4.6 m.
Mean soluble inorganic nitrogen (NO2;
NO3) and soluble reactive phosphate (PO4)
concentrations in selected months of 2012 and
2013 are shown in figure 3. Concentration of
nitrates (4.36-5.5.43 µm) and phosphates (3.09
µm) were high during the rainy season of 2012
particularly in the months of August and Octo-
ber. In contrast, nitrite concentration during the
same months was low (0.4 µm).
Toxic and harmful phytoplankton compo-
sition and seasonal cell density: A total of 20
potentially toxic and harmful phytoplankton
taxa were identified during the study period
(Table 1) which consists of one cyanobac-
terium, one diatom, one haptophyte and 15
dinoflagellates belonging to the following divi-
sions: (17) Dinophyta, (1) Bacillariophyta, (1)
Cyanophyta and (1) Haptophyta. Dinophy-
sis spp., Prorocentrum spp, Protoperidinium
spp., Pseudo-nitzschia spp., and Trichodes-
mium erythreaum were the most abundant taxa
observed over the 2-year period leaving the
other phytoplankton taxa recorded rare and in
low cell numbers. General phytoplankton num-
ber in 2012 increased during the rainy season
with an average total cell density of 30 000
cells/L, contrary to year 2013 in which the total
phytoplankton number increased substantially
during the hot dry season (average of 75 000
colonies & cells/L) dominated largely by Trich-
odesmium (70 000 colonies/L). Dinoflagellates
increased during the rainy season of both years.
Shown in figure 4 are the seasonal fluctua-
tions in abundance of harmful microalgae that
were found in San Pedro Bay over the last two
years. As observed, these apparent upturn in
abundance of the recorded harmful diatoms and
cyanobacteria occurred during the rainy sea-
son for both years. Low diatom cell densities
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occurred during the rest of the years. But for
the month of April 2013, Trichodesmium esca-
lated into a peak reaching an average total of
70 000 colonies/L.
Shown in figure 5 is the graphic represen-
tation of the seasonal fluctuations in abundance
of dinoflagellates which frequently occurred
in the samples obtained from 2012 to 2013.
By August, the density of the harmful dino-
phytes that were frequently recorded in most
stations and sampling months (Dinophysis
spp., Gymnodinium sp., Prorocentrum spp.,
and Protoperidium spp.) increased remarkably
(highest at 3 300 cells/L) as compared to their
previous and succeeding recorded cell numbers
(undetected to 50 cells/L). Dinophytes that
were found rare and in very few cell numbers
(Alexandrium tamiyavanichii, Cochlodinium
polykrikoides, Noctiluca scintillans, and Pyro-
dinium bahamense var. compressum) were
spotted mostly during the rainy season espe-
cially during the months of June and August
Fig. 2. Mean temporal variations of physico-chemical parameters obtained during 2012 and 2013 sampling months in San
Pedro Bay in al. Bars indicate the standard error of each mean. Transparency is from Secchi disk depth. Unavailable data
values are indicated by broken lines.
12
6
Current (m/s) pH Temperature (ºC)
DO (mg/L) Salinity
Light Intensity
Transparency (m)
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Nitrite (NO2) μM
Nitrate (NO3) μM
Phosphate (PO4) μM
Fig. 3. Mean concentrations of Nitrates, Nitrites and Phosphates during selected sampling months of 2012 and 2013 in San
Pedro Bay. Standard error of each mean is represented by vertical error bars. Unavailable data values for Nitrite are indicated
by blank spaces in the graphs. The ASEAN water quality criteria for aquatic life protection for nutrient concentration is
indicated by black dashed line.
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(Table 1). Station 2 harbored the most dense
potentially harmful algae, followed by station
3, then station 1 (Fig. 4 and Fig. 5).
DISCUSSION
In tropical and subtropical areas, diatoms
usually dominate or form blooms during the
summer season where there is relatively high
temperature and light intensity (Philips et al.,
1997). However, in this study, higher tempera-
tures and light intensities were observed during
the rainy season of both years. This was accom-
panied by peaks in abundance of the diatom
Pseudo-nitzschia spp. during this season. There
was even a moderate negative relationship
calculated between Trichodesmium erythraeum
and light intensity (Pearson’s r= -0.3, p= 0.03).
Studies indicated that this diazotroph is inhib-
ited by intense light (Ho, Chu, & Hu, 2013;
Bell & Fu, 2003). This could mean that light
was too strong for phytoplankton in this area
during these years.
Instead of diatoms, a cyanobacterium
bloomed during the hot dry season of 2013.
There was a sudden increase in abundance
of Trichodesmium erythraeum particularly in
April which contributed to the high nitrite con-
tent of the water body during the same month.
A strong positive relationship (Pearson’s r= 0.6,
p= 0.009) was shown with nitrite concentration
and Trichodesmium density. Trichodesmium
TABLE 1
Potentially toxic and harmful phytoplankton species found in San Pedro Bay from year 2012-2013
(S=Sept, O=Oct, D=Dec, F=Feb M=Mar)
Genus/Species Months/Year Stations Impact
Dinophyceae
Alexandrium tamiyavanichii Aug-13 1 & 2 PSP (GEOHAB, 2010)
Cochlodinium polykrikoides Aug-13 1, 2 & 3 Fish mortality (Gárate-Lizárraga, Lopez-
Cortes, Bustillos-Guzman & Hernandez-
Sandoval, 2004)
Dinophysis spp.1Aug S D Jan F M-12
Jun Aug D-13
1, 2 & 3 DSP (Le, Nguyen & Fukuyo, 2012)
Gymnodinium sp.Aug S O M-12
Jun Aug D-13
1, 2 & 3 PSP (Larsen & Nguyen, 2004)
Noctiluca scintillans Apr Jun Aug-13 1 & 2 Fish mortality (Cardoso, 2012)
Prorocentrum spp.2Aug S O D Jan F M-12
Apr Jun Aug O D-13
1, 2 & 3 Fish mortality (Aligizak, Nikolaidis, Katikou,
Baxevanis & Abatzaopoulos, 2009)
Protoperidinium spp.3Aug S O D Jan F M-12
Apr Jun Aug O D-13
1, 2 & 3 Azaspiracid Poisoning (AZP) (Gribble, Nolan
& Anderson, 2007)
Pyrodinium bahamense
var. compressum
Aug-13 1 PSP (Usup, Ahmada, Matsuoka, Lim & Leaw,
2012)
Bacillariophyceae
Pseudo-nitzschia spp.Aug M F-12
Jun Aug O-13
1, 2 & 3 ASP, toxic substance (Anderson et al., 2010)
Cyanophyceae
Trichodesmium erythraeum Aug O M-12
Jun Aug O D Apr-13
1, 2 & 3 Harmful to marine fauna (Sheridan et al.,
2002)
Haptophyceae
Phaeocystis globosa Aug O M D Jan-12
Aug O D-13
1, 2 & 3 Haemolysis, Foam-forming (Smith et al.,
2013)
1D. tripos, D. oblongum, D. miles, D. caudata; 2P. minimum, P.micans, P. sigmoides, 3P. pellucidum, P. pallidum, P.
divergens, P. depressum, P. conicum
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is a filamentous and colonial nitrogen fixing
cyanobacteria, pervasive in tropical and sub-
tropical regions of the world’s oceans. Its pres-
ence is more prominent in nitrogen poor water
and easily seen during blooms (Capone, Zehr,
Paerl, Bergman, & Carpenter, 1997). These
blooms release carbon, nitrogen and other
nutrients into the environment which contrib-
utes to nutrient loading (Capone et al., 1998).
Generally, Trichodesmium is dangerous
as a food source for other organisms. Only
few specialized animals feed on it actively.
Some strains of Trichodesmium produce tox-
ins causing mortalities in some copepods,
oysters and fish. Some blooms were found
to produce toxins leading to clupeotoxism in
humans after ingestion of fish contaminated
by Trichodesmium-toxins (Post, 2005). There
were no reports of fish mortalities in the bay
however. The bloom was more pronounced
in the semi-enclosed Cancabatoc Bay (Station
2) where 70 000 colonies/L were noted. Mari-
culture areas were found in Station 1 which
harbored less cyanobacteria (2 300 colonies/L).
Fig. 4. Seasonal dynamics of the potentially toxic and harmful haptophyte, Phaeocystis sp. (x102 cells/L), the diatom,
Pseudo-nitzschia sp. (x103 cells/L) and cyanobacterium, Trichodesmium sp. (x104 colonies/L) in San Pedro Bay from 2012
to 2013.
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Fig. 5. Seasonal dynamics of potentially toxic and harmful dinoflagellates with higher cell
densities in San Pedro Bay from 2012 to 2013.
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Anthropogenic activities in the area partly
resulted in phosphate loading through fertil-
izer pollution, waste disposal and aquaculture
activities, reducing growth limitations from
limited phosphate, and brought the increase
Trichodesmium bloom occurrences (Bergman,
Sandh, Lin, Larsson, & Carpenter, 2012). The
increased nitrite concentration in April must
have resulted from this bloom. Nitrogen fixa-
tion process by Trichodesmium in daytime
is still partially understood (Bergman et al.,
2012). Nitrogen fixation converts dinitrogen
(N2) to ammonia (NH3) which is then assimi-
lated by the algae, or will be further nitrified
to nitrite and nitrate. Nitrate is preferred by
the cyanobacteria (Qingfeng, Hong, & Post,
2000) and other marine plants, thus leaving
elevated nitrite. Nitrite might have also come
from regeneration of nutrients when the bloom
started to die off. Other sources of nitrite con-
centration in the area might be influenced by
the contribution of nutrients coming from agri-
cultural run-offs, septic and sewage discharges
and decaying fish feed and fish waste.
Intense light did not favor the growth of
dinoflagellates during the dry season which
may be due to effect of high UV radiation
and temperature (Lesser, 1996). In the results,
dinoflagellates showed an increase in abun-
dance during the rainy season of both years
in which relatively lower light intensity and
temperatures were observed. Dinophysis spp.,
Gymnodinium sp., Prorocentrum spp., and Pro-
toperidinium spp. peaked during the rainy
season of 2012 and 2013 with relatively high
cell densities ranging from 400 to 3 500 cells/L.
High nutrient availability during the season
might have a strong influence on both diatoms
and dinoflagellates inducing both groups to
increase in abundance during the same season.
Peaks of nutrient concentrations are accom-
panied by increase in phytoplankton numbers
particularly in August of both years.
High nutrient input in Station 2 within the
Cancabato bay explains the continued high
total cell density of phytoplankton in the area
(Macanip & Yap-Dejeto, 2012; Oracion &
Yap-Dejeto, 2011). The shallow and restricted
morphology of this bay increases contact with
nutrients in the bottom and susceptibility to
nutrient-related algal problems and risk of
bloom formation (Anderson, 2005).
Aquaculture activities such as cage and
fish pen farming present in Station 3, also affect
nutrient loading. These anthropogenic inputs
have changed the nutrient pool in that area
which, in turn, may or may not create a favor-
able environment for HAB species. Inorganic
nutrients released can affect phytoplankton in
upper waters. Fish farming activities contrib-
ute to the release of inorganic nutrients (NH4
and PO4), particulate organic nutrients, and
dissolved organic nutrients (Olsen & Olsen,
2008). One potential threat of aquaculture to
environment is the effect of bio-deposits such
as fish feces and uneaten feed. These impacts
include physiological effects to fish caused by
low dissolved oxygen levels in the water col-
umn, toxic effects of H2S and ammonia from
bio-deposit degradation, and toxic effects of
harmful algal blooms related to eutrophication
(Degefu, Mengistu, & Schagerl, 2011).
Station 3 was second to Station 2 in terms
of potentially toxic and harmful phytoplankton
abundance. In comparison with Stations 2 and
3, Station 1 has relatively low total phyto-
plankton cell density. This station is far from
coastal settlements, there are no fish cages, and
thus low amounts of nutrients are loaded into
the area. Hence it registered the lowest phyto-
plankton abundance among all three stations.
Episodic environmental events, such as
typhoons, induce extensive ocean-atmosphere
interactions which have profound influences
on phytoplankton ecology (Chung, Gong, &
Hung, 2012). The occurrence of typhoon Hai-
yan on November 8, 2013, caused severe dev-
astation in Eastern Visayas including San Pedro
Bay. The sampling for December was conduct-
ed a month after the typhoon and water was
observed to have high transparency, low DO
concentration and low phytoplankton abun-
dance. Total phytoplankton was only 14 000
cells/L. This is contrary to reports of increased
phytoplankton density after a typhoon (Chung
et al., 2012). Accounts of people and based on
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first hand observation, during the onslaught of
Haiyan, a storm surge covered the city. The
water coming in was murky, almost black in
color. This must have been mostly silt and
sewage. It also must have brought inland most
of surface coastal phytoplankton. There was,
however, an increase in nitrate concentration
(1.14 µM) which might be due to the increase
land run-off and mixing of nutrients from the
bottom sediment through the water column.
The high dissolved oxygen concentra-
tions during the rainy season at 189-265 mm
(DOST PAGASA 2000-2012) reflect the high
rate of rainfall experienced this season. Rain-
fall increases interaction of water and air
which increases dissolved oxygen. More inter-
action of water and air was achieved through
increased mixing of water brought by high rate
of river discharge into the ocean due to rainfall
(Wehmeyer & Wagne, 2011). High input of
rainwater, in return, decreased the salinity of
seawater considerably but only during the rainy
season of 2012. In 2013, however, the increase
in salinity suggests that there is low input of
rainwater, 82 mm (DOST PAGASA 2013)
or freshwater in the area and high DO levels
might have been due to wind-assisted surface
mixing, with wind velocities from 4.4-6.7 kph
(WeatherOnline, 2015) or photosynthesizing
algae and not necessarily the inflow of fresh-
water during the season (Ladipo, Ajibola, &
Oniye, 2011).
Usually, in colder waters, there is high
concentration of oxygen since oxygen dis-
solves more easily in cold temperatures (Jones,
2011). However, in the tropics, temperature
is subject to less seasonal variation reflecting
less change of temperatures between sampling
seasons. The lowest temperature recorded in
this bay was only at a relatively warm 26.8 °C.
This explains the low DO concentration during
the cold dry season of both years, specifically
in stations 1 and 3 during the months of Febru-
ary and March 2012, and in all stations during
the month of December 2013 (4.6-4.9 mg/L).
Phytoplankton profiles remained at low lev-
els during this time too. In addition, absence
of mixing brought by little rainfall and flow,
decreases interaction of air and water thereby
decreasing oxygen solubility which happened
here during the hot dry season.
During the rainy season, the relatively
higher transparency (uppermost at 2.96 m) and
current velocity (0.3 m/s) might have influ-
enced the amount of light that penetrated the
water column as well as the DO concentration
during the season. High current velocity induc-
es mixing of the water column, which increases
dissolved oxygen concentrations (Jones, 2011)
while high transparency values indicate high
amount of light, that can penetrate the water
column conducive for diatom growth.
The spike of phosphate (3.1 µM) in August
and October of 2012 was unusual. It should be
noted that in August 2012, an earthquake with
magnitude 7.6, epicenter 10.83 °N, 126.71
°E occurred (PHIVOLCS, 2012). Sediments
must have been resuspended due to the activi-
ties of the seafloor near the Philippine trench.
Increase in phosphate after an earthquake was
also documented in Izmit Bay, Turkey (Okay et
al., 2001). Nitrate (4.3-5.4 µM) also increased
during this time. But by December, this has
been consumed by primary producers and was
back to 0.19 µM. Phosphate, however, was
still at 2 µM in December 2012 and slowly
decreased in the subsequent months ahead.
Then typhoon Haiyan occurred in November
2013 and again phosphate concentrations were
raised to 1.6 µM in December 2013. Other
sources of phosphate in this bay are the pres-
ence of cage and pen fish farming in Station 3,
and influx of municipal wastewaters consisting
of soap and detergent, wastes from mangrove
ecosystems and discharge of raw human and
animal feces in Station 2. These accumulated
factors might have contributed to the release of
wastes that are high in phosphate content.
The toxin-producing P. bahamense var.
compressum was still detected in the bay but
in lower cell densities. In 2011, its Atlantic
counterpart, Alexandrium was first seen in the
bay (Oracion & Yap-Dejeto, 2011). There was
a Noctiluca scintillans bloom during Octo-
ber 2007 in this bay. Noctiluca has also been
reported to bloom in Manila Bay (Furuya et
908
Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 64 (2): 897-911, June 2016
al., 2006). Gymnodinium sp. is common but
never reached bloom proportions. This spe-
cies may be G. catenatum, the same species
found in Manila Bay (Fukuyo et al., 1993).
There are five Pseudo-nitzschia species so far
recorded in the bay: P. brasiliana, P. micro-
pora, P. pseudodelicatissima and P. pungens
(Yap-Dejeto et al., 2013).
The results of this study show that the tax-
onomic composition and abundance of harmful
and potentially toxic phytoplankton in San
Pedro Bay still vary seasonally. The relative
consequence of light, temperature, DO con-
centration, but most importantly, nutrient avail-
ability was found to influence the spatial and
temporal patterns observed in the abundance
and composition of harmful phytoplankton.
Thus, a total of 20 potentially toxic and
harmful phytoplankton taxa were identi-
fied consisting of one cyanobacterium, one
haptophyte, one diatom and 17 dinoflagel-
lates. Trichodesmium erythraeum bloom was
observed during the month of April in Station
2 reaching 70 000 colonies/L. Phaeocystis glo-
bosa had the least cell density (820 cells/L)
this was followed by Protoperidinium spp.
(8 600 cells/L) and Prorocentrum spp. (4 200
cells/L). Other notable but sporadic harmful
species found only in plankton net tows were
Alexandrium tamiyavanichii, Cochlodinium
polykrikoides, Noctiluca scintillans, and Pyro-
dinium bahamense var. compressum. Rainy
season brought in the most number of harm-
ful and potentially toxic phytoplankton due to
high nutrient concentration. Among stations,
Station 2, in Cancabato Bay, showed high
relative abundance of harmful and potentially
toxic phytoplankton.
ACKNOWLEDGMENTS
It is with deep gratitude that we men-
tion James Lloyd Ostrea, Elyrose Kim Ruizo,
Richelle Ignacio and Divine Macanip for
assisting and conducting field work and data
gathering for this research. Transportation was
provided in part by Fisheries Law Enforcement
Team, Tacloban City Chapter and boat rentals
of Ruel P. Robin Jr. This research is funded by
University of the Philippines in the Visayas
Office of the Vice Chancellor for Research and
Extension, UPV-OVCRE SP12-06.
RESUMEN
Proliferación de Trichodesmium (Oscillatoriales:
Euphorbiaceae) y estacionalidad de fitoplancton poten-
cialmente dañino en Bahía San Pedro, Leyte, Filipinas.
Desde 1983, la Bahía de San Pedro en Filipinas ha sido
reportada como un sitio de proliferación de Pyrodinium
bahamense var. compressum que causó intoxicación para-
lítica en sus comunidades costeras cercanas. Esta bahía
también está sometida a numerosas tormentas; entre las
más fuertes se presentó un súper tifón en Haiyan, el 8 de
noviembre 2013. Por primera vez, se explica la dinámica
estacional del fitoplancton potencialmente tóxico y dañino
en esta bahía. Este es también el primer registro en esta
área de una proliferación de cianobacterias (Trichodes-
mium erythraeum) que alcanzó 70 000 colonias/L en abril
2013. Durante el periodo de muestreo se presentaron otras
19 proliferaciones de fitoplancton potencialmente tóxicas
y dañinas. Estos consistían en una haptófita, Phaeocystis
globosa, la diatomea Pseudo-nitzschia y 17 dinoflage-
lados. Siete de estas algas nocivas tenían densidades
suficientemente altas como para ser rastreadas a través
del tiempo. Normalmente, las diatomeas abundan durante
la estación seca. Pero Pseudo-nitzschia aumentó en abun-
dancia durante la temporada de lluvias de 2012 y 2013.
Los dinoflagelados y Phaeocystis globosa se comportaron
como se esperaba y exhibieron un aumento relativo de la
densidad celular durante la temporada de lluvias en los
dos años. La alta disponibilidad de nutrientes durante esta
temporada debe haber influido en el comportamiento del
fitoplancton a pesar de las diferencias en la temperatura y la
intensidad de la luz entre estaciones. Otras especies nocivas
notables, pero raras que se encontraron sólo en las redes de
arrastre de plancton durante el estudio fueron: Pyrodinium
bahamense var. compressum, Alexandrium tamiyavanichii,
Cochlodinium polykrikoides y Noctiluca scintillans.
Palabras clave: Trichodesmium, Pseudo-nitzschia,
dinoflagelados nocivos, HAB, nutrientes, tormenta, San
Pedro Bay, Leyte, Philippines.
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... This is supported by a slight difference in temperature and salinity between the surface and middle water samples in this station at that time. There was no observed fish kill, but it should be noted that during this time the Trichodesmium cyanobacteria bloomed in the bay (Yap-Dejeto and Batula 2016). A patch of this plankton could have died off in that surface which would have depleted the DO while decomposing. ...
... All phosphate concentrations were above the normal range of 0.2 µM (ASEAN, 2008). These elevated phosphate concentrations were already noted since 2012 (Yap-Dejeto and Batula 2016). One reason for the high phosphate concentration could be the presence of fish cages within the sampling stations as in Marabut and Tanauan and siltation which discharge fish wastes and excess fish feeds. ...
... Patches of Trichodesmium bloom was detected since 2012 in the inner portion of the bay. The peak of the bloom reached 70 000 colonies/L in April 2013 (Yap-Dejeto and Batula 2016). The Marabut station is the one nearest to the inner part of San Pedro Bay (Cancabato Bay). ...
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