application of alos imageries for monitoring coral health in coastal waters of vietnam

APPLICATION OF ALOS IMAGERIES FOR MONITORING CORAL HEALTH
IN COASTAL WATERS OF VIETNAM.
PI 326
Tong Phuoc Hoang Sơn

Institute of Oceanography – Viet Nam
01 Cau Da street, Vinh Nguyen, Nha Trang – Viet Nam,
Phone number: 84-583590033; Facsimile Number: 84-583-590034; Email Address :



1. ABSTRACT

Coral reef is one of marine habitats have high primary
production but also is high sensitive. Due to comfortable
conditions in humid tropical region, coral reef in coastal
waters of Vietnam sea develop very well with their
distribution stretch along from North to South areas. During
the past several decades, coral reefs in many parts of the
world have been subjected to a series of bleaching events,
including some coral reef areas in coastal waters of Vietnam.
This report present some experiences on the coral mapping in
coastal area of Vietnam and results of application for
detection of evidences of bad status of coral health due to
affect by natural disasters as well as anthropogenic
interventions.

2. INTRODUCTION

Vietnam lie in humid tropical area with coastal habitats
such as coral reef, sea grass bed, mangrove forest, etc,…

develop very well. Coral reefs in Vietnam distribute along
coastal areas from North to South as well as in offshore
waters (Spratly and Paracell Archipelagos). Due to
importance aspect of this habitats, many projects on the
coral mapping have been carried out in coastal area of
Vietnam (Ninh Thuan, Khanh Hoa, Phu Quoc, Da Nang,
Quang Nam,…) but the assessment of natural disasters
that effect to coral reef is still few. Effect of global
warming and ElNino is reasons causing coral bleaching in
Con Dao , Phu Quoc islands in July 1998 (V S Tuan et all
2005) as well as Con Dao island during October 2005 (T.
P. H Son et all 2006 [8] have been discussed in some
papers but how do we monitor and detect the coral
bleaching in coastal waters of Vietnam sea is opened. This
report present some experiences on the coral mapping in
coastal waters of Vietnam and some evidences on affects of
natural disasters as well as human interventions to the coral
health base on the remote sensing techniques. These results
were obtained from ALOS-JAXA project – PI 326 with title
“Application of ALOS and Ocean Color Imageries sources
for monitoring of Coral Health in coastal waters of South of
Viet Nam” .

3. DATA AND METHODOLOGY

3.1 Satellite images:
The remote sensing techniques is main method for detecting
the distribution of coral reefs and assessment the status of
coral health under affect of natural disasters and
anthropogenic intervention. A series of satellite imagery as

well as aerial photography have been used. They include
 ALOS (Japan) imagery from Project “Application of
ALOS imagery for monitoring the coral health in
coastal waters of Vietnam” with 18 scenes AVNIR2
(10m) and PRISM (2.5m) have been used for
detection the distribution in coastal waters in Quang
Tri, Quang Nam, Binh Dinh, Khanh Hoa, Ninh Thuan,
Ba Ria – Vung Tau and Kien Giang provinces
 FORMOSAT2 MS (8m) and PAN (2m): 16 scenes
from SAKE Project have been used for detection the
distribution in coastal waters in Quang Nam, Binh
Dinh, Khanh Hoa, Ninh Thuan provinces.
 Landsat ETM (30m) from USGS (2 scenes) using for
detect distribution coral reef in coastal waters of Ninh
Thuan province and Condao Archipelagos.
 SPOT4 (20m), SPOT5 (10m) from IFREMER project,
National Projects have been used for supplementing
some information on the distribution of coral reef
and related habitats in Con Co, Cu Lao Cham, Nam
Du archipelagos
 The color aerial photograph dataset (include 18
scenes) taking in map scale 1/5.000 that cover whole
of An Thoi Archipelagos – Phu Quoc Island.
3.2 Investigated data:
They include underwater surveyed data by difference
methods on many of coral sites in coastal waters of
Vietnam (figure 1) those are:
 Surveyed data along coastal zone and surrounding the
islands which obtain by manta tow method (an
investigation method use for rapid assessment the

distributed components of coral reefs).
 Surveyed data along coastal zone and surrounding the
islands which obtain by “reef check” method (an
investigation method use for detail assessment the
distributed components of coral reefs along the coast
according to shallow and deep sections)
PI326-1
 Surveyed data on the coral reef distributed in the
cross section by method of “biomass frame” sections.
 Surveyed data used for obtaining “homogeneous
substratum” positions (such as sand, mud, rocky,…)
for building the “Depth Invariance Index” algorithm
use for removing the “water column” in studied area.
On the special term, it is called be method of “water
column correction”. In some case, we re-used the
existed sediment maps instead of underwater
surveyed data (figure 2).
 Positions of key points help for clasification (coral
reef, seagrass beds, bed rock, sand, ) in Cu Lao
Cham obtain from underwater survey during May
2008, as an illustrated samples for obtaining
underwater surveyed data (figure 3)

Figure 1: The studied sites (orange circles) on coral reef
distribution in coastal waters of Vietnam by remote
sensing techniques linking with underwater surveys
1) Tran Island; 2) Co To Archipelago 3) Cat Ba
Archipelago; 4) Long Chau Archipelago; 5) Bach Long Vi
Island; 6) Me Island; 7) Nghi Son Island; 8) Con Co
Island; 9) Coastal water of Thua Thien - Hue Province;

10) Cu Lao Cham Archipelago; 11) Coastal water of
Quang Nam province; 12) Re Archipelago; 13) Xanh
Island; 14) Van Phong Bay; 15) Nha Trang Bay; 16)
Coastal Area of Ninh Thuan province Ninh Thuận; 17) Con
Dao Archipelago; 18) An Thoi Archipelago – Phu Quoc
Island; 19) Nam Du Archipelago; 20) Tho Chu
Archipelago

Figure 2: Positions of sand sites help for calculating the
Depth Invariance Index in the Map of Sediment
Distribution in coastal waters of Quang Nam province

Figure 3: Positions of Ground truthing site help for
clasification (coral reefs, seagrass beds, bed rock,
sand, ) in Cu Lao Cham Archipelago obtain from
survey during May 2008
3.3 Procedure of data processing for detection the
coral reefs and relevance habitats by remote sensing
technique. This procedure have been carry out step by step
as following
 Geometry correction (Geo-Reference): in order to
convert bitmap image co-ordinate to local geography
co-ordinate (UTM project, WGS84 datum)
 Radiance correction: convert Digital Number into
spectral radiance in sensor by the convert formula
appear as following :
Rad = a * DN + b ; when
a: gain and b: offset
 Atmospheric Correction: convert spectral radiance into
reflectance in surface water and filter the atmospheric

affects. In this step we used “Dark Subtract” tool in
ENVI software for processing.
PI326-2
 Water Column Correction: The linear natural logarithm
relationship of water reflectance between i
th
band and
j
th
band is basic formula for calculating the Depth
Invariance Index. It was showed as following
D.I.I
ij
= a * Ln(i) - Ln(j) + b
When
- i, j : are spectral reflectance in water surface of band
pair (i,j) that obtain from atmospheric correction in 128
sand points
- a, b : are slope and intercept in regression line, they
appear strong (or not) relationship between band i and band
j by mean of Standard Deviation (r
2
).
The illustrated results of correlation and regression
analysis in step of “Water Column Correction” (for Cu
Lao Cham case study in ALOS - AVNIR2 date 08 June
2008) show in figure 4.
y = 0.914x + 0.2349
R
2

= 0.8198
2
3
4
2.5 3 3.5 4
Ln (b2)
Ln (b1)

y = 0.5245x + 1.0597
R
2
= 0.8158
2
2.5
3
3.5
2 2.5 3 3.5 4
Ln (b3)
Ln (b2)

y = 2.9959x - 3.9647
R
2
= 0.7822
3
4
5
6
2 2.5 3 3.5
Ln (b4)

Ln (b3)

Figure 4: Some linear natural logarithm relationships of
water surface reflectance between i
th
band and j
th
band,
that is basement for calculating the Depth Invariance
Index (from 128 sandy sites) in AVNIR2 image cover
Cu Lao Cham archipelago date 08 June 2008 (T.P.H
Son, 2009 [12 ])
Equation system of Depth Invariance Index of band pairs
obtain from ALOS-AVNIR2 base on 128 sandy point
taking in Cu Lao Cham case study have been showed as
following:
D.I.I
12
= 0.914* Ln (1) - Ln (2) + 0.2349
D.I.I
13
= 0.4445 * Ln (1) - Ln (3) + 1.1215
D.I.I
14
= 1.5688* Ln (1) - Ln (4) - 0.8333
D.I.I
23
= 0.5245 * Ln (2) - Ln (3) + 1.0597
D.I.I
24

= 1.7562* Ln (2) - Ln (4) – 1.3588
D.I.I
34
= 2.9959* Ln (3) - Ln (4) - 3.9647
The correlation analysis also alow to choose only 5 new
D.I.I bands (cancel D.I.I
13
for processing (r
2
< 0.6) for
next classification
 Mask step: allow to “hide” unstudied area i.e : land,
offshore where don’t exist of coral reef and sea grass bed.
This step will enhance the image quality for
classification.
 Supervised classification: used “Mahalobich Distance”
classification base on survey points in different habitats
for detection the distribution of coral reefs, sea grass beds
and other substratum
3.4 The remote sensing techniques for detection the
evidences causing negative affects to status of the coral
health
 Detection the reasons causing phenomena of coral
bleaching:
The coral bleaching can make the mass mortality of
benthos live in coral reefs. This is a phenomena related
strongly with climate change due to the increasing of sea
water temperature, the decreasing the water salinity, the
increasing the acidification processes,…
By assessment the temporal and spatial variances of sea

surface temperature, water salinity and sediment flux by
ocean color and multi spectral imageries as well as the
finding out especial spectral color spots directly in coral
sites from high resolution image allow us to detect the
phenomena of coral bleaching in somewhere of coastal
water of Viet Nam. .
 Detection some evidences of acidification processes in
offshore water of Vietnam.
Increased fossil fuel burning associated with geothermal
phenomena and industrialization, cement production, land
use changes associated with agricultural activities are
causing atmospheric CO2 concentrations. There is clear
evidence that the carbonate equilibrium of the oceans is
shifting in response to increasing atmospheric CO2
concentrations to rise, and at increasing rates. Even small
changes in CO2 concentrations in surface waters may have
large negative impacts on marine calcifies and natural
biogeochemical cycles of the ocean. For example,
decreased carbonate ion concentration significantly reduces
the ability of corals to produce their calcium carbonate
skeletons (Kleypas et all, 2006 [3])
In Vietnam, the studies on the acidification processes and
the increasing of CO2 emission that affect to coral health
are very restricted.
PI326-3
Our study only record on some evidences of potential
geothermal phenomena in offshore Binh Thuan waters as
one of evidences of acidification processes .
By visual interpretation directly in color composite image
from a scenes of ALOS-AVNIR2 (date, 18 September

2007) allow us found out this phenomena.
 Detection the evidences of sediment and fresh water
plume as well as siltation processes causing the
negative effects to status of coral health.
By fusion technique base on ocean color image merged to
ALOS PRISM one, we found out in some case the fresh
water and sediment from in river can be reach to offshore
waters more 40 km and they caused negative consequence
to coral health in some coral sites.
A very direct approach to image enhancement is the use
of high resolution data, e.g. ALOS AVNIR2 – Band 1
(10m) panchromatic images, to sharpen images of lower
spatial resolution, e.g. MODIS 250 m multis-pectral data.
Once a set of multi-sensor images is placed in register with
a high resolution reference image, the digital numbers
(DNs) of the various multi-spectral bands may be merged
with those for the single band (panchromatic) reference
image using techniques previously described by Cliche et al.
(1985) [2]. These methods may be summarized in the
following equations:

'
i
DN
=
i

*
)(
*

hi
DNDN
+
i

(1)

'
i
DN
=
i

*
 
)(
**
hii
DNiDN


+
i

(2)
Where:
DN
i
and DN
i

' are the DNs for the ith band of the original
and fused multi-spectral image, respectively; DN(h) is the
DN for the high resolution reference image;
i

,
i

are
scaling factors; and
i

and
i

are weighting factors.
In reality condition, we used directly tool “Pan
Sharpness” in SPEAR tools of ENVI 4.4 software for
resolving this problem.
 Detection the evidences of anthropogenic
interventions causing the negative effects to status of
coral health.
The coastal developed activities such as building the
tourism resorts, dredging marine ports, irregular material
dumping,… can causing the negative consequences into
status of coral health.
Base on spectral analysis for detecting the bottom
bathymetry, visual interpretation from color composite
images we saw a lot of cases of siltation can be badly
effected to status of coral health, destroyed and

disappearance of some coral sites in coastal waters of
Vietnam.
RESULTS AND DISCUSSIONS
4.1. - Distribution of coral reefs in coastal waters of
Vietnam sea.
Base on remote sensing techniques linking with underwater
surveys, the distributed scenes of coral reefs in coastal waters
of Vietnam sea have been detected.
Figure 5 is illustrated results on distribution of coral reefs
and related underwater habitats in Cu Lao Cham archipelagos
and surrounding waters (Tong P H S, 2009 [12] ).

Figure 5: Distribution map of coral reefs and sea grass
beds in Cu Lao Cham archipelago obtain from remote
sensing techniques in AVNIR2 (date, 08 May 2008) [12]
Note: HC: Hard coral, SW : Sea weed: SG : Sea grass ;
RK : Rock; SD : Sand , Land Mask
The detail distribution of coral reefs in coastal water of
Vietnam was recored as following
4.1.1 Distribution of coral reefs in Northern side of
Vietnam sea: include coral reefs in Tonkin Gulfs (Co To
archipelago, Tran Island, Cat ba, Bach Long Vi
archipelago,…) and also coastal waters of North of Center
such as Hon me (Thanh Hoa province), Nghi Son (Ha Tinh
province ) and Con Co (Quang Tri)
Until now, we carried out to survey and building the
distributed maps of coral reef in Co To, Bach Long Vi and
Con Co (Thao N.V and Son T P H, 2007 [ ]. The results
present detail in figure 5, and show that:
 In Co To archipelago, live coral distribute scattered in

small islands surrounding of archipelago, such as Co
To Con, Khoi, Ca Chep, Khoai Islands, and also
North West of Thanh Lan Island with total area
estimated about 66.1 ha. Platform reef cover Death
Coral in North of great Co To with area reach to
256.5 ha
 In Bach Long Vi Island, live coral existed in North
and West sides with area reach to 133 ha, remained
area of reefs cover the death coral, with estimated
area is 491 ha.
 In Con Co Island, live coral mainly existed in North
side with estimated area is 72 ha. The southern side
cover the sandy material interpose with rocky cliffs.
4.1.2 Distribution of coral reefs in Central of
Vietnam sea: include coral reefs in Cu Lao Cham and in
PI326-4
coastal waters of Quang nam, Phu Yen, Khanh Hoa, Ninh
Thuan provinces.
 The coral reefs in Cu Lao Cham.
The live coral mainly distributed in western and south-
western sides of Lao Island and other small islets with
estimated area is 165 ha (T.P.H. Son, 2008 [12]. The coral
reefs in these area develop well with genus of Acropora,
Montipora and Goniopora (Nguyen Van Long et all [6 ]).
The North and East of Main Island of Cu Lao Cham
cover mainly of rocky cliffs. The bio resources is very
difficulty existed and developed in these areas.
The southern side of Cu Lao Cham include coral reefs
with high cover level interpose with sand beaches and sea
grass beds exist in Bac, Ong, Chong, Bim, Huong and Nom

grounds.
 The coral reefs in coastal waters of Quang Nam
province.
Include fringing reefs and platform reefs exist
surrounding of An Hoa cape. The platform reefs exist in
the front of An Hoa Gap and “great reef” bank with
predominant genus of Porites, Goniastrea, Platygyra . In
An Hoa cape, the coral reefs cove mainly of “branch” coral
and soft coral with predominant of Acropora. The reef is
narrow and deep.
The total area of coral reefs in this area have been
estimated about 95 ha (T. P. Son, 2007 [11]).
 The coral reefs in coastal waters of Phu Yen Province:
The coral reefs exist in the front of the mouth of Cu
Mong lagoon. They have been met in Nom cape (3.5 ha),
Hoa Thanh (6.9 ha) and Vinh Hoa (4.7 ha).
The coral reefs exist in the front of the mouth of Xuan
Dai lagoon. They have been met in Tu Nham Cape (32.5
ha), Vung La (5.6 ha), Hon Thung ground (10.0 ha), Tuong
ground (2.3 ha), Phu Hoi cape (12.4 ha) and Yen cape ( 3.2
ha).
In coastal waters from O Loan lagoon to An Phu
Commune is region where coral reefs develop very well and
high cover level with main component of soft coral such as
Cu Lao Mai Nha (42.3 ha), Phu Thuong (9.9 ha), Yen Cape
30.2 ha, Go ground - An Chan (39.4 ha), Chua Island – An
Chan (32.7 ha) and Dua island – An Phu (8.3 ha)
In coastal water of Ro gorge, coral reef have been seem
Dien Cape (11.6 ha), Ro Cape (18.8 ha) , Phong So (11.2
ha) và Nua Island (17.4 ha).

 The coral reefs in coastal waters of Khanh Hoa
province have been estimated about 3266 ha, (T.P.H.Son,
2007 [9] they distribute in main regions as following:
Coral reefs in Ben Goi Bay get 584.3 ha area, they main
distribute in Bip, O, Dut, Cum Meo islands, Tuong, Trao
banks Islands and also coastal waters of North West of Bay.
Coral reefs in East coast get 476.6 ha area. They distribute
mainly in Hon Gom penesula , Co Co channel, Great Island,
and some islets in North of Great Island.
Coral reefs in South-West coast get 337.1 ha area. They
distribute mainly in Du cape, Hon Khoi, My Giang, Bai Co
grounds and some underwater banks.
Coral reefs in Binh Cang Bay include coral reefs in Ninh
van, Hon Thi – Nha Phu Lagoon get 142.4 ha. They
distribute mainly in Cay Bang bay, Long beach and Chao
bank.
Coral reefs in Nha Trang Bay get 775.9 ha area. They
distribute mainly in around Hon Tre, Mun, Mot, Tam, Mieu,
Vung and Cau islands as well as in Song Lo and Grand
bank.
Coral reefs in Cam Ranh Bay get 865.7 ha area. They
distribute mainly in Thuy Trieu bank, East coast in Cam
Ranh penesula, Noi, Ngoai, Binh Ba Island.
In coastal waters of Khanh Hoa province have been
characterized by creating of platform reefs in big deep such
as Grand bank – 426 ha, Thuy Trieu Band 800 ha, (figure
6) Ninh Phuoc band 40 ha and Chao Bank – 13 ha

Figure 6. Some typical platform reefs in coastal waters
of Khanh Hoa province – Grand Bank (upper), Thuy

Trieu Bank (lower)
 The coral reefs in coastal water of Ninh Thuan
province: have been estimated about 1277 ha (Son. T.P.H,
2005 [7], they distribute in main regions as following
PI326-5
 The coral reefs in coastal waters of Ninh Thuan
Province:
The narrow non-typical fringing reefs exist in main areas:
Hon Chut to Da Vach Cape - 42 ha, Vinh Hy Gorge - 28
ha , Hon Do – My Tuong – 98 ha
Thai An ground is a The typical fringing reef exist in
many grounds of coastal areas : Thai An - 252 ha, Tu
Thien (151 ha), Son Hai (182 ha).
The platform reef exist in Breda Bank with area of 84 ha
Beside in deep sea, the coral reefs also exist in 30 – 35 m
deep , exist a reef ground that cover mainly by “horn” coral
species with 168 ha area.
4.1.3 Distribution of coral reefs in Southern side of
Vietnam sea.
 The coral reefs in Con Dao archipelago: The coral
reefs get a total area of 743.2 ha and sea grass beds get
a total area 480.8 ha, Son. T.P.H, 2010 [13] with detail
distribution present in table 1
Table 1: The distribution of coral reefs and sea grass
bed in Con Dao archipelago
Coral reef
S (ha)
Sea grass bed
S (ha)
Great lagoon

233.4
Great lagoon
221.8
South ConLon Isl
18.8
South ConLon Isl

Ba Island
31.1
Ba Island
10.3
Ben Dam Lagoon
167.9
Ben Dam Lagoon
78.6
Ong Dun ground
26.7
Ong Dun ground
31.2
OngCuong ground
19.7
OngCuong ground
9.0
Dam Tre Lagoon
35.2
Dam Tre Lagoon
33.8
Dam Tre cape
9.2
Dam Tre cape

14.5
Chim Chim cape
7.8
Chim Chim cape
32.4
Great Tre Island
16.4
Great Tre Island

Small Tre Island
1.5
Small Tre Island

Great Trac island
13.1
Great Trac island

Small Trac island
22.5
Small Trac island

Trac island
6.8
Trac island

Bay canh Island
112.5
Bay canh Island
49.2
Cau Island

20.6
Cau Island

 The coral reefs in An Thoi archipelago and Phu Quoc
Island include 119 ha in North West of Phu Quoc
Island (table 2), 350 ha in An Thoi Archipelagos (table
3) and 9800 ha of sea grass beds in coastal areas of Phu
Quoc (table 4), Son. T.P.H, 2010 [13].
Table 2. The distribution of coral reefs and sea grass
bed in Nouth West of Phu Quoc Island
Sites
S (ha)
Sites
S (ha)
Cua Can cape
50.0
Doi Moi Island
2.1
Ong Quoi Cape
35.0
Thay Boi Island
0.6
Ghenh dau Cape
30.9
Bang Island
0.7
Table 3 : The distributed area of coral reefs in An Thoi
Archipelago
Sites
S

(ha)
Sites
S (ha)
Dam Trong Island
12.5
Xuong Island
24.3
Dam ngoai Island
6.8
Gam Ghi Island
26.2
Dua Island
18.8
Mong tay Island
3.8
Roi Island
30.0
May Rut Ngoai Isl
29.4
Thom Island
44.2
May Rut Ngoai Bank
18.0
Trang island
5.5
May Rut Trong Island
25.6
Kho Island
4.2
Kim Quy Island

9.1
Vang island
39.0
Kim Quy Bank
52

 The coral reefs in Nam Du archipelago have been
estimated about 242 ha with detail distribution in table 4
Table 4 : The distributed area of coral reefs in Nam Du
Archipelago
Sites
S (ha)
Sites
S (ha)
Nam Du Island
71.7
Bo tra island
14.5
Co Loa Island
1.6
Mau Island
17.7
Moc Island
1.3
Nom Ngoai Island
3.0
Giang Island
15.8
Nom giua island
6.9

Truoc Island
10.3
Nom Trong Island
1.5
Dau Island
24.9
Underwater Banks in
West of Nom Island
16.5
Ngang Island
33.6
Underwater Banks in
South of Nom Island
10.9
Dam Island
2.4
Underwater Banks in
South Truoc Island
10.1
 The coral reefs in Tho Chu archipelago:
Total area of coral reef have been estimated 266.1 ha and
sea grass bed with 134.6 ha (table 5) , Son. T.P.H, 2010
[13]
Table 5 : The distributed are of coral reefs in Tho
Chu Archipelago
Coral reefs -
Fringing reef
S
(ha)
Coral reefs – platform

reef
S
(ha)
Tho Chu Isl
66.0
South of Xanh Isl.
99.0
Tu Island
47.9
SW of Cai Ban Isl
12.0
Cau Island
3.1
North of Cau Island
33.6
Xanh Island
4.0


Nhan Island
14.8


Cai ban Island
2.4


Cau Cat Island
4.4

Kho Island
0.7



4.2 The evidences making negative affects to status of
the coral health: include the coral bleaching, acidification
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phenomena, sediment and fresh water flux, siltation and
human intervention.
4.2.1 The coral bleaching event and mass mortality of
benthos in Condao during Mid of October of 2005.
Con dao Islands lie in Southern of Vietnam sea in
geography bounders from 106
o
31’ to 106
0
45’E longitude
and 08
o
37’ – 08
o
45’

N Latitude. Area of coral reef in Con
Dao Island have been estimated about 1,000 ha. They have
high biodiversity with 323 scleractinian species, 202
species of coral fish, 148 mollusk species, 110 crustacean
species, 44 echinoderm species and 125 polychaete species

(Vo S. T et all, 2005) [15]. By mean of previous studies
(Vo. S.T, 2000 [14]), natural disaster is consider as one of
the best important reasons which cause the biodiversity
degradation of coral reef in Con Dao. The typical examples
of effects of Lynda Typhoon (1997) and of El Nino (1998)
with high increasing of sea water temperature and causing
serious coral bleaching in Con Dao have been also recorded
(Vo Si Tuan, 2000) [14].
During Mid October of 2005 an event of mass mortality
of the corals and benthos occurred again in surround waters
of Con Dao Islands, Ben H.X et all, 2008 [1] (figure 7)


Figure 7: Some pictures of coral bleaching and mass
mortality of coral in Condao Island during October
2005 (after Hoang Xuan Ben et all, 2008 [1] )
Base on satellite data (Ocean color and Landsat
ETM+) and also surveyed data from VOS-Nippon vessel,
we found out the reasons causing the coral bleaching in Con
Dao Island during mid of October 2005 (figure 8)
The random coincidence of the extreme increase of
sea surface temperature with lower reducing sea water
salinity as well as high turbidity (mainly due to water plume
from Mekong rivers) during 10-13
th
October 2005 is main
reason causing mass mortality of corals and benthos in Con
Dao Island

Figure 8. The terrestrial, warmer fresh water plume

with high turbid reach more 200 km (from river mouth)
are main reasons causing coral bleaching and mass
mortality of benthos in Condao island (T.P.H Son, et al,
2006 [8].

During March – April of 2010, from survey data we also
recorded the extreme increasing of sea water temperature
and decreasing of water salinity in some places (Van
Phong Bay, Con Dao Island, Tho Chu and Nam Du
archipelagos, )
These results show clearly two periods with extreme
anomaly of highest sea temperature and lowest salinity
occur during October 2005 (light purple line) and second
period of March to June (dot pink line) of 2010 (figure 9).
Latupov and his colleagues [5] by SCUBA surveys from
cooperation Viet – Russian investigation on Oparin
Researcher Vessel during March of 2010 also found out
the coral bleaching in Nam Du and Tho Chu archipelago
with strong rate.
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Regret, by ALOS and any satellite imagery sources we have
not found out this phenomena yet.
24
26
28
30
32
T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12
2002 2003 2004 2005 2006
2007 2008 2009 2010

SST (
°
C)
24
25
26
27
28
29
30
31
32
33
34
35
T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12
2002 2003 2004 2005 2006
2007 2008 2009 2010
S
‰

Figure 9. The monthly variance of Sea Surface
Temperature (upper) and Sea Surface Salinity (lower)
in offshore of Con Dao Island, show that 2005 and 2010
can causing the coral bleaching due to highest water
temperature and lowest sea water salinity.
4.2.2 The oil seep process in geothermal center and
acidification process in Phu Quy Island:
Phu Quy Island or Cu lao Thu island place in center
coordinate about 109

o
58’ E and 10
o
30’ N where exist
many ancient volcanoes.
According to French authors, on 2nd March 1923, there
was an eruption at Tro island (10
o
16 N, 109
o
01 E) which
produced scoriaceous basalt. The eruption stopped on 13th
May 1923, and this island were eroded below sea level (the
recorded material is missing)
The studied results of Pham Van Thom (personal
information) also recognized that, this area is biggest
geothermal center of Vietnam.
When we consider the reason that causing the oil slick
attack on many tourism resorts of Vietnam during 2007, we
searched a lot of AVNIR2 and found out a yellow trace
appear in Phu Quy Island in scene of ALOS - AVNIR2 date
27 July 2007 (figure 10).
Combination all of existed data, we suggest on
phenomena of oil seep in Eastern side of Phu Quy island.
This phenomena will expand the acidification process in
here and effect directly to coral reefs in Phu Quy island


Figure 10. The yellow track from RGB321 color
composite image (AVNIR2 date 17 July 2007) allow to

suggest on formation of natural oil seep and
acidification processes in Phu Quy island

4.2.3 The sediment and fresh water plume from river
after flood events affect badly to status of coral health.
As presented, in section 4.2.1, the terrestrial, warmer fresh
water plume with high turbid from river can cause serious
damage to coral reefs. However, not all of time, we can
search a suitable satellite image with high resolution (e.g,
AVNIR2, SPOT5, Landsat ) for detection the sediment
and fresh water plume after flood events (especial the cloud
cover level in these periods is very high).
By combination between ocean color images and high
resolution satellite images sometime we can overcome
above disadvantage (figure 11)


Figure 11. Inundation area in downstream of Thu Bon
River and sediment plume after Sangsane typhoon
reach to CulaoCham island by fusion techniques
between MODIS (250m) and Band 1 - AVNIR2 (10m)
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The processed data show that the fresh water and sediment
plume from river Thu Bon can reach to North side of Cu
Lao Cham Island (108
o
30 E, 15
o
57’ N) and badly affect to
coral reefs in this area.

4.2.4. The coastal development activities and their
affect to status of coral health.
The coastal developed activities such as building the
tourism resorts, dredging marine ports, irregular dredged
material dumping,… can causing the negative consequences
into status of coral health.
For instance, Nha Trang Bay is not only Marine
Protection Area but also is one of famous tourism sites of
Vietnam. There are a lot of tourism constructors were built
in coastal area where exist coral reef and they destroyed a
part or make disappearance completely coral reefs and
related habitats in these areas.
The Dam Gia ground in North West of Tre Island (Nha
Trang bay) existence a coral reef (21 ha) lie mixing with
sea grass bed (12 ha) in surrounding. Before 2005, this was
an ideal site for snorkeling activities and an excursion site
for tourist but after that VinaPernLand resort was formed
and this reef was destroyed step by step and disappeared
completely during 2008 (figure 12)


Figure 12: Dam Gia Gorge in Nha Trang Bay before
(4/2004) and after (7/2007) build VinaPear Resort. It
make to disappear 50 ha of coral reefs and 12 ha of sea
grass beds. (after, T.P.H. Son, et all 2007 [9])
Some coral sites in coastal waters of Vietnam such as Bai
Tien – Duong De, Tam Island (Nha Trang Bay), My Giang
(Van Phong Bay),… also lie in similar circumstance
The dredging activities in marine ports and dredged
material dumping can also cause the negative effects to

coral reefs in coastal water.
By mean of spectral analysis in an AVNIR2 scenes (date
17 July 2007) for extracting the bottom bathymetry in
South of Nha Trang Bay (T.P.H.Son, et all 2007), we also
fount simultaneously out the underwater “hills” (figure 13).
They appear suddenly (July 2006) and were disappeared
in next year (19 May 2008).


Figure 13. The appearance of underwater “hills” in
South of Nha Trang that formed from dredged
material dumping (extract from AVNIR2 image)
They cause the siltation and server affect directly to
fringing coral reefs in Mun, Mot, Tam Islands and also
platform reef – Thuy Trieu Bank lie on Southern side. The
surveys from sediment traps in Nha Trang Bay (Latupov,
Malyutin, 2006, [4], N.V.Long (cite from Son.T.P.H 2007
[9] also recorgnized these events.
4. CONCLUSIONS
Base on the abundance satellite images include AVNIR2
mainly from JAXA – ALOS project and other sources such
as SPOT4-5, Formosat2, Landsat ETM+ as well as aerial
photographs, the area and distributed maps of almost coral
sites in coastal waters of Vietnam have been detected.
In North side, include coral reefs in Coto archipelago
(256 ha), Bach Long Vi ( 133 ha) and Con Co (72 ha)
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In Central region, include the coral reefs in Cu lao Cham
archipelagos (165 ha), the coastal waters of Quang nam
province (95 ha), the coastal waters of Phu Yen province

(303 ha), the coastal waters of Khanh Hoa province (3266
ha) , the coastal waters of Ninh Thuan province (1000 ha).
In southern side and in Thailand Gulf (only in
Vietnamese territory), include coral reefs in Con Dao
archipelago (743 ha), An Thoi archipelago and Phu Quoc
Island (469 ha), Nam Du archipelago (242 ha) Tho Chu
archipelago (134 ha).
By mean of the remote sensing techniques, we also
detected the series of the evidences causing negative affects
to status of the coral health, those are:
The coral bleaching event and mass mortality of benthos
in Condao archipelago during Mid of October of 2005 and
also at March to June of 2010.
The oil seep process in geothermal center and
acidification process in Phu Quy Island.
The sediment and fresh water plume from river after big
flood event affect badly to status of coral health.
The coastal development activities and their affect to
status of coral health
The reason causing above phenomenon related to
natural disaster, global climate change as well as
anthropogenic intervention.
This report showed big potential for application of ALOS
imagery for monitoring the status of coral health in coastal
waters of Vietnam sea.

6. REFERENCES

[1] H.X. Ben, Vo S T, Hoang P.K, 2008 Mass mortality of
corals and reef living features at Con Dao archipelago

(Vietnam) in October 2005. Journal of marine science and
technology. Seri 8, No 1, 2008: 59-70 [2] Cliche, G., Bonn
and P. Teillet, 1985. Integration of the SPOT Panchromatic
Channel into its Multispectral Mode for Image Sharpness
Enhancement. Photogrammetric Engineering and Remote
Sensing, Vol. 51, No.3, pp. 311-316.
[3] Kleypas, J.A., R.A. Feely, V.J. Fabry, C. Langdon, C.L.
Sabine, and L.L. Robbins, 2006. Impacts of Ocean
Acidification on Coral Reefs and Other Marine Calcifiers:
A Guide for Future Research, report of a workshop held
18–20 April 2005, St. Petersburg, Florida, USA.
[4] Latypov Yu.Ya., Malyutin A.N. 2006. New data on the
distribution of corals on the reefs in Vioetnam // Biology of
the Marine Invertebrates. Vladivostok: FEB, USSR
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[5] Latupov. Ya.Yu et all, 2010 - Reef building coral and
reefs of Vietnam, the scientific report in the Joint Russian-
Vietnamese project of the Institute of Marine Biology RAS
and Institute of oceanography VAST “Biodiversity and
reproduction ability in coral ecosystems of Vietnam”
[6] N.V. Long, Vo,S.T, Hoang P.K, Tuyen H.T, 2006,
Conservation of marine biodiversity: a tool for sustainable
management in Cu Lao Cham Islands, Quang Nam
Province. Proceedings of the 10th International Coral Reef
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[7] T.P.H.Son, 2005. The coral mapping in coastal waters
of Ninh Thuan province. The final report of ICRAN project,
Nha Trang, 2005. 88 pages.
[8] T.P.H Son, Lau Va Khin, Hoang Xuan Ben, Tan Chun

Knee, Joji Ishizaka, Varis Ransi, Sarat Tripathy (2006) .
Discuss on the main reasons causing mass mortality of coral
and benthos in Con Dao Island during October 2005 . In
Proceeding of 2006 NAGISA conference – Kobe – Japan
[9] T.P.H. Son, et all 2007, The status on distribution and
biodiversity on coral reef in coastal water of Khanh Hoa
province. The final report of provincial project, Nha Trang,
2007 (in Vietnamese)
[10] T.P.H. Son and N.V. Thao, 2007, The distribution of
coral reefs in coastal waters of Vietnam sea from remote
sensing data combine with underwater surveys. The final
report on national project 2006-2007, Nha Trang, 2007 (in
Vietnamese)
[11] T.P.H Son, 2008. The distributed coral reef in coastal
watres of An Hoa – Quang Nam province. In the final
report of ICZM project in Coastal Area of Quang Nam
province, Nha Trang, 2007 , pp 114-143 (in Vietnamese).
[12] T.P.H Son, 2009. The distributed coral reef map in Cu
Lao Cham archipelago detect from remote sensing
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DANIDA project, 2009.
[13] T.P.H Son, 2010, “Application of remote sensing
techniques for coral mapping in coastal waters of Vietnam
seas” the scientific report in the Joint Russian-Vietnamese
project of the Institute of Marine Biology RAS and Institute
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ability in coral ecosystems of Vietnam”
[14] Vo S. T, 2000. The corals at Condao Archipelago
(South Vietnam): Before, during and after the bleaching
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th
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[15] Vo S. T (Chief author), Nguyen Huy Yet, Nguyen Van
Long 2005. Coral reefs of Vietnam. Publishing House of
Science and Techniques, Ho Chi Minh City. pp 212 .
Acknowledgments
The authors thank Japan Aerospace Exploration Agency
(JAXA) for supporting the ALOS-AVNIR2 satellite
imageries under ALOS-PI 326 project; the United State
Geological Survey (USGS) for LandSat ETM
+
imagery and
the National Aeronautics and Space Administration
(NASA) for the MODIS imageries which contributed in this
study


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