Annual variations in plankton blooming in the upper Gulf of Thailand

Anukul Buranapratheprat, Akihiko Morimoto Atsushi Kaneda, Yoshihisa Mino, Vichaya Gunboa

Pachoenchoke Jintasaeranee, Joji Ishizaka

The upper Gulf of Thailand

South

China

Sea

Gulf of

Thailand

13o N

8o 40 N

4o 20 N

99o 40 E 104o E

100o E 100o30 E 101o E

13o30 N

13o N

0 20 km

1234

5

6

7 8 9 10

11 12 13

14 15

16

17

Chon

buri

Bangpakong R.Bangkok

Thachin R.

Maeklong R.

Chaopraya R.

Petchaburi

Hua Hin Sattahip

2015 Red Tide at Bangsaen Beach

2015 Red Tide at Bangsaen Beach

2015 Red Tide at Bangsaen Beach

Mantis Shrimp

2015 Red Tide at Bangsaen Beach

Razor clam

Seasonal variations of red tides

Lirdwitayaprasit et al. (1994)

Red Tide 1991 - 1993

■ Northeast

■ Southwest

■ Transition

Chl-a [mg/m3]

Oct 28, 2003 Dec 5, 2003

NE

Jul 16, 2005 Aug 8, 2005

SW

Surface Chl-a distributions revealed by MERIS

Buranapratheprat et al. (2009)

Seasonal Circulations 5.0 m/s

Wind field NE Monsoon(Nov. - Jan.) 5.0 m/s

Wind field SW Monsoon(May - Aug.)

1.0 cm/sNE Monsoon(Nov. - Jan.)

Circulation 1.0 cm/s

Circulation SW Monsoon(May. - Aug.)

9

Buranapratheprat et al. (2002)

Red tide usually occurs offshore near the river mouths

BU survey on 21 – 22 Sep 2012

Other effects

จดหมายขาวแนวปะการงไทยกลมวจยความหลากหลายทางชวภาพในทะเลภาควชาชววทยา คณะวทยาศาสตร มหาวทยาลยรามค าแหง

Mortality of coral and benthic organisms near Sichang Island

Aqua-MODIS Chl-a: 2 July 2015

Terra-MODIS Chl-a: 30 June 2015

2015 Red Tide at Bangsaen Beach

Wind Fields in June and July

MODIS Chl-a year-to-year variations

Monthly wind in June 2014 and 2015

2014 2015

Seasonal Circulations 5.0 m/s

Wind field NE Monsoon(Nov. - Jan.) 5.0 m/s

Wind field SW Monsoon(May - Aug.)

1.0 cm/sNE Monsoon(Nov. - Jan.)

Circulation 1.0 cm/s

Circulation SW Monsoon(May. - Aug.)

19

Buranapratheprat et al. (2002)

20

Simulated circulations: Case studies

0 20 km

3.0 m/s

Wind SimulationCase 2

0 20 km

3.0 m/s

Wind SimulationCase 1

100o E 100o30 E 101o E100o E 100o30 E 101o E

13o N

13o30 N

+Wind curl

21

Simulated circulations0 20 km

1.0 cm/s

Current SimulationCase 1

0 20 km

1.0 cm/s

Current SimulationCase 2

0 20 km

1.0 cm/s

Current SimulationCase 3

0 20 km

1.0 cm/s

Current SimulationCase 4

100o E 100o30 E 101o E100o E 100o30 E 101o E

13o N

13o30 N

13o N

13o30 N

Coupled POM – NPZD model

Primary Production

Grazing

Loss Egestion

Urine

Decomposition

Phytoplankton

Loss

NutrientsDIN and DIP

Zooplankton

Detritus

Wind plays 2 important roles

1. Modify residual circulations• Weak wind – current from the river mouths move

directly to eastern shoreline• Strong wind – southern current becomes

stronger2. Modify phytoplankton blooming

• Weak wind – stimulate dinoflagellate blooming• Strong wind – retard dinoflagellate blooming

(may stimulate diatom blooming?)

Sensitivity analysis3 factors were examined to investigate chlorophyll response

Based on CU-5 (Oct 2004) data provided by Matsumura Sensae

Nutrient Discharge Wind

Weak wind (Low turbulence) Strong wind (high turbulence)

CU – 5 (Oct 2004)

Relationship between turbulence and blooming

Field observations

St1 St4 St3 St2 St5 St7 St6

St8 *

St9 St10 St11 St12 St13 St14

10 nm

45 nm

43 nm

6 nm

12 nm

Cruise 1: 20 – 21 March 2009

Cruise 2: 24 – 25 August 2009

Turbulence (Vertical Diffusivity)

Chl-a and Kz

0

50

100

150

200

1.00E-06 1.00E-04 1.00E-02 1.00E+00 1.00E+02

Kz[m2

/s]

Ch

l-a

[mg

/m3]

Chl-a and K z

0

2

4

6

8

10

1.00E-08 1.00E-06 1.00E-04 1.00E-02 1.00E+00

K z [m2

/s]C

hl-

a[u

g/l]

Cruise1 Cruise2

Chl-a and Kz

0

50

100

150

200

1.00E-06 1.00E-04 1.00E-02 1.00E+00 1.00E+02

Kz[m2

/s]

Ch

l-a

[mg

/m3]

Chl-a and K z

0

2

4

6

8

10

1.00E-08 1.00E-06 1.00E-04 1.00E-02 1.00E+00

K z [m2

/s]C

hl-

a[u

g/l]

Cruise1 Cruise2

Correlations of Chl-a and Kz during Cruise1 (19 – 20 March 2009)

and Cruise 2 (24 – 25 August 2009).

Smayda, 1997: Turbulence can negatively influence dinoflagellate blooming by three mechanisms:

• physical damage

• physiological impairment

• behavioral modification

Further Investigations

• Apply ecosystem model to investigate the interactions among environmental factors including wind, discharge, nutrients loads both from river discharge and resuspension from bottom sediment on blooming variability.

• Since hypoxia is important, oxygen module will be embedded into the new modified model.

Further Investigations• Ocean color data will be used to identify Chl-a

variations for each conditions:• Strong and weak winds • High and low river discharges• El Niño and La Nina years• Combine effects

Thank you