Assessing coral bleaching and diseases in the ninh hai coastal waters of ninh thuan province under impacts of el nino in 2016

MINISTRY OF EDUCATION AND TRAINING NHA TRANG UNIVERSITY THAI MINH QUANG ASSESSING CORAL BLEACHING AND DISEASES IN THE NINH HAI COASTAL WATERS OF NINH THUAN PROVINCE UNDER IMPACTS OF E

MINISTRY OF EDUCATION AND TRAINING

NHA TRANG UNIVERSITY

THAI MINH QUANG

ASSESSING CORAL BLEACHING AND DISEASES IN THE NINH HAI COASTAL WATERS OF NINH THUAN

PROVINCE UNDER IMPACTS OF EL NINO IN 2016

MASTER THESIS

KHANH HOA – 2017

MINISTRY OF EDUCATION AND TRAINING

NHA TRANG UNIVERSITY

THAI MINH QUANG

ASSESSING CORAL BLEACHING AND DISEASES IN THE NINH HAI COASTAL WATERS OF NINH THUAN

PROVINCE UNDER IMPACTS OF EL NINO IN 2016

MASTER THESIS

and Climate Change Topic allocation Decision: 772/QD-ĐHNT date 20/9/2016

Decision on establishing the

Supervisors:

1 Assoc Prof Vo Si Tuan

2 Prof Sigurd Stefansson

3 Prof Henrik Glenner

Chairman:

1 Assoc Prof Ngo Dang Nghia

Faculty of Graduate Studies:

KHANH HOA – 2017

UNDERTAKING

I undertake that the thesis entitled: “Assessing coral bleaching and diseases in

the Ninh Hai coastal waters of Ninh Thuan province under impacts of El Nino in

2016” is my own work The work has not been presented elsewhere for assessment

until the time this thesis is submitted

Khanh Hoa, April 28, 2017

Thai Minh Quang

ACKNOWLEDGMENT

I would like to express the deepest appreciation to the Institute of Oceanography,

Nha Trang University and Nui Chua Nation Park for helping and giving best conditions

I finish my thesis

My special thanks go to Assoc Prof Dr Vo Si Tuan, Prof Henrik Glenner and

Prof Sigurd Stefansson for the continuous support of my master study and research, for

this patience, motivation, enthusiasm, immense knowledge and suggestions for

completing the report

A very special gratitude goes out to all down at Department of marine living

resource - Institute of Oceanography for helping and providing the funding for the work

With a special mention of Mr Phan Kim Hoang, Mr Hua Thai Tuyen and Mr Mai Xuan

Dat for helping in field survey and collected data

I would like to thank the NORHED project has provided a high quality master

program “Marine Ecosystem Management and Climate Change”

And finally, last but not the least, I would like to thank my family: my parents,

my wife and my young sister for supporting me spiritually throughout writing this thesis

Thanks for all your help!

Khanh Hoa, April 28, 2017

Thai Minh Quang

TABLE OF CONTENTS

UNDERTAKING i

ACKNOWLEDGMENT ii

TABLE OF CONTENTS iii

LIST OF ABBREVIATIONS v

LIST OF TABLES vi

LIST OF FIGURES vii

ABTRACT viii

CHAPTER 1 INTRODUCTION 1

CHAPTER 2 REVIEW 2

2.1 Coral reef 2

2.2 Ninh Hai coral reefs 2

2.3 Coral bleaching phenomenon 3

2.4 El Nino 4

2.5 Forecast of Bleaching Alert Area 4

2.6 Coral bleaching in Vietnam 5

2.7 Coral diseases 6

CHAPTER 3 MATERIAL AND METHOD 8

3.1 Research subjects 8

3.2 Second data and information 8

3.2.1 Sea surface temperature data 8

3.2.2 Coral cover data 8

3.3 Location and time study 8

3.4 Data collection 9

3.4.1 For environmental parameter 9

3.4.2 For biological parameter 9

3.4.2.1 Experimental setting 9

3.4.2.2 Measure techniques 10

3.5 Data analysis 11

3.5.1 Assessment of change coral cover during 2007-2016 11

3.5.2 Assessment ratio of coral bleaching and coral damage 12

3.5.3 Assessment coral disease 12

CHAPTER 4 RESULT AND DISCUSSION 13

4.1 Sea surface temperature (SST) during April and August 2016 13

4.2 Long-term changes in hard corals during 2007-2016 at three reef sites

monitoring 14

4.3 Assessment of coral bleaching and coral disease in 2016 under the influence of El Nino 16

4.3.1 Assessment of coral bleaching 16

4.3.1.1 Ratio of coral bleaching on the benthic substrate 16

4.3.1.2 Coral bleaching response index 18

4.3.1.3 Difference of coral bleaching between 2010 and 2016 19

4.3.2 The status of coral disease in Ninh Hai reefs 20

4.4 Resilience of scleractinian corals after bleaching events in 2016 20

4.5 Comparison the level bleaching among coral reef of Vietnam in 2016 22

CHAPTER 5 CONCLUSION AND RECOMMENDATION 24

LIST OF REFERENCES 25

APPENDICES 28

LIST OF ABBREVIATIONS

NOAA: National Oceanic and Atmospheric

SST: Sea Surface Temperature

ONI: Oceanic Niño Index

BI: Bleaching index

HC: Hard coral

SC: Soft coral

SP: Sponges

RKC: Recent killed corals

DCA: Dead coral with algae

SW: Seaweeds

CA: Coralline algae

TA: Turf algae

LIST OF TABLES

Table 3.1: Reef sites monitoring 8

Table 4.1: Mean coral cover (%) at Hang Rai (HR), Mui Thi (MT) và My Hoa (MH)16 Table 4.2: The change mean cover of some common genus coral 18

Table 4.3: Coral bleaching response index in three sites reef 19

Table 4.4: The rate (%) of common genus coral were bleached in 2010 and 2016 20

Table 4.5: Ratio of coral disease on the reef 20

Table 4.6: The extent of coral damage in three sites 21

Table 4.7: Mean substrate composition on the reef in some Vietnam reefs 22

LIST OF FIGURES

Figure 3.1: Limiting area for analysis SST data in CWS 9

Figure 3.2: Reef sites monitoring 9

Figure 3.3: A transect line of 100 m long for surveys of benthos 10

Figure 3.4: A transect line of 100 m long for coral bleaching and coral disease 11

Figure 4.1: Sea surface temperature data analyzed from satellite 13

Figure 4.2: Sea surface temperature during May to August 2016 14

Figure 4.3: The trend of hard coral cover from 2007 to 2016 15

Figure 4.4: Mean percent cover (%) in June 2016 on the reefs 15

Figure 4.5: Percent coral cover on reef slope (Deep) 17

Figure 4.6: Percent coral cover on reef flat (Shallow) 17

Figure 4.7: Vertical transects of the reef with large reef flat at My Hoa (a) and incipient reefs at Bai Nho (b) and Hang Rai (c) 17

Figure 4.8: Genus Acropora and Montipora were bleached in May 2016 21

Figure 4.9: Genus Acropora and Montipora were bleached in August 2016 21

Figure 4.10: Percent change in coral and macroalgae in Ninh Hai reefs 22

ABTRACT

Coral reefs are one of the highly biodiversity ecosystems distributed in shallow tropical sea waters and an important role in fisheries, shoreline protection and human social economic development However, world coral reefs are facing environmental recession due to the effects of climate change and human activity Climate change is the change of environmental factors that can cause negative or positive impacts on coral reef ecosystems Recent studies show that climate change has increased the frequency of El Niño activity which result increase sea surface temperature and is the main cause make the coral bleaching We are going to assess the reef status in Ninh Hai district at the bleaching time based on the forecast data of NOAA Coral Reef Watch for 2016 The primary objective of this study is to provide the basic understanding of coral bleaching, coral diseases and coral reef resilience of Ninh Hai coral reef during and after the El Niño phenomenon in 2016 Long term monitoring data of Ninh Hai coral reefs (Hang Rai, Mui Thi and My Hoa reef sites) was reviewed for assessment status and trend of coral reef during 2007 to 2016 Field trips were performed in May, June and August

2016 The parameters of coral reef component and number bleaching and disease colonies were recorded in reef flat and reef slope by SCUBA divers The result showed Ninh Hai reefs underwent a mass bleaching event as a result of an increasing anomaly

of sea surface temperature under impacts of El Nino during in May to June 2016 Bleaching occurred most severely in My Hoa reef site (20.69-27.16% coral bleached), while in Hang Rai and Mui Thi suffers very little The coral genera Montipora and Acropora were most bleached However, the severity of coral bleaching mortality (2-17%) was low in August Ninh Hai coral reefs can resistant bleaching event (average coverage of 32-44% on the reef), which could be an activity of the season upwelling in this areas At present, the Ninh Hai coral reef is not impressed by diseases The ratio of coral bleaching in Ninh Thuan was higher than that in Con Dao and Nha Trang, but the lower than that in Phu Quoc Island The conservation of Ninh Hai coral reefs is very important to serve sources of coral larvae for other reefs in the South China Sea

Keywords: El Nino, reefs, coral bleaching, coral disease, Ninh Hai, Vietnam

CHAPTER 1 INTRODUCTION

Coral reefs are one of the highly biodiversity ecosystems distributed in shallow tropical sea waters Coral reefs, like tropical rainforests, play an important part in the formation, nurturing, dispersing and reproducing of fisheries resources, contributing to ensuring food security for humans In addition to its important role in fisheries, coral reefs also help shoreline protection by reducing wave energy before overflowing to the shoreline, to minimize the risk of shoreline erosion However, world coral reefs are facing environmental recession due to the effects of climate change and human economic development

Climate alteration is the alteration of environmental agents that can cause negative or positive impacts on coral reef ecosystems The research on the effects of climate change focus to ocean acidification, sea level rise and the rising of sea water temperatures In the above phenomena, the increase in sea water temperature is the most noticeable impact on coral reefs Coral bleaching is a sign of the coral's response as a loss of color when sea water temperature increase abnormal in the area The level of bleaching and survival of the coral depends on the value and time storage of water temperature in the incident area The relationship between El Nino and coral bleaching became clear when comparing the time series of two events

El Niño was most active in 1998 when the world's coral reefs were severe damaged Therefore, coral reef monitoring program has been intensified since 1998 with the purpose of assessing of the resilience of the corals Therefore, in this study

"Assessing coral bleaching and diseases in the Ninh Hai coastal waters of Ninh Thuan province under impacts of El Niño in 2016”, we are going to assess the reef status in

Ninh Hai district at the bleaching time based on the forecast data of NOAA Coral Reef Watch for 2016 The details of reef benthic substrate and coral bleaching then will be monitored with the concerns on other physical parameters related to coral reef resilience such as water surface temperature or water exchange The study provide the basic understanding of coral bleaching and coral diseases during the El Niño phenomenon in

2016 The secondary objective is divided in two: (1) Assessment of coral bleaching and coral disease in 2016 under the influence of El Niño (2) Assessment of the scleractinian corals resilience under the influence of El Niño

CHAPTER 2 REVIEW

2.1 Coral reef

Coral reefs, the “rainforests of the sea” are among the most biologically rich and productive ecosystems on earth with total area is 284,803 km2 distribute in 17 reefs in the world (Spalding et al 2002; Wilkinson 2008) In many developing countries, they also provide valuable benefits to the livelihood of coastal communities Coral reefs play important roles as reservoirs of biodiversity, for fisheries, and tourist development in the coastal zone (Burke et al 2011) Coral reefs are important habitats in the South China Sea generally and Vietnam particularly As the combined data from UNEP (2007) and Burke et al (2002), the total area of coral reefs in the coastal waters in the South China Sea is approximately 930,000 ha Coral reefs in the South China Sea have extraordinary biodiversity with 571 species of scleractinian reef corals (Huang et al 2015; Huang et

al 2016) and over 3000 species of fish (Randall & Lim 2000) Vietnam coral reef is located in the western South China Sea and considered as the richest of over 350 species

of hard corals distributed on 110,000 ha reefs (Ming Chou et al 2002; Vo et al 2013) However, coral reefs have been threats by “over-fishing, use of destructive fishing techniques, pollution (mainly eutrophication) and increased sedimentation; indirect causes of these threats are unsustainable practices in the fisheries sector, coastal development, deforestation and unsustainable tourism” (Vo et al 2013)

2.2 Ninh Hai coral reefs

The Ninh Hai district of Ninh Thuan Province, is located in south-central Vietnam With a shoreline of more than 40 km, the district includes 3 coastal communes The area receives moderate to high levels of wave energy seasonally, from wind- and typhoon-generated swells, and cool waters (< 24oC) in coastal upwelling during summer (Tuan et al 2014) Ninh Hai Reef has an estimated total area more than 2.300 ha, which

is the largest reef area in Vietnam and belongs to the nature reserve of Nui Chua National Park in Ninh Thuan province, where morphological reef is fringing reef (Tuan et al 2014) There are 334 species of coral, 188 species of seaweed, 147 species of reef fish,

115 species of Mollusk, and 80 species of Crustaceans and 13 species of Echinodermata (Tuấn et al 2005)

The average cover of corals (including hard and soft coral) on the reef is about 21.1-30.5% (Long et al 2013) Coral cover in Ninh Hai waters was significantly reduced

in 2003-2007, but remained relatively stable and tended to increase during 2007-2011 Sustainability of coral cover before and after the bleaching event in 2010 shows that coral reefs are highly adaptable (Long et al 2013) Adaptability of Ninh Hai coral reef may be related to the upwelling phenomenon of cold nutrition rich water in this area during the summer Upwelling phenomena in the region have brought cold water from the deep sea to surface, which will reduce the temperatures of surface water (Dippner et

al 2007) and thereby decrease the bleaching event Resilience of corals at Ninh Hai seems to be higher than in other areas without upwelling

2.3 Coral bleaching phenomenon

Sudden warming of sea temperatures in the long term will seriously impact the reef leading to coral bleaching in the region this phenomenon occurs Coral bleaching is

a stress response that results in the change of abiotic (sea surface temperature, irradiance, salinity, ultraviolet radiation, etc.) and/or biotic factors (diseases) Bleaching is the whitening of reef-building corals due to a reduction in their symbiotic dinoflagellate zooxanthellae and/or loss of the pigments in the symbionts (Brown 1997) Symbiotic algae provide photosynthetic products vital to meeting host energetic requirements for the growth and development of corals The reduced amount of symbiotic algae will be disturbs the metabolism of the coral host and can lead to delayed or reduced reproduction, tissue degradation, reduced growth, and death of the affected tissue (Bahr

et al 2015)

The phenomenon of coral bleaching affecting extensive reef areas across the Pacific was first described by Glynn in 1984 Since that date, coral bleaching has occurred in the Caribbean, Indian, and Pacific Oceans on a regular basis in 1983—84, 1986—87, 1991, 1994 and 1996 (Brown 1997) The acknowledgment of the coral bleaching phenomenon has been noted in other countries in the region since 1998, coral bleaching in many areas including Vietnam (UNEP 2007) Coral bleaching has done significant damage to coral reefs worldwide (16% of damaged reefs in 1998) and decreased coral cover 50-90% (Obura & Grimsditch 2009)

Report on the status of coral in Asia Pacific in 2007, noted in 1999-2004 corals signs of recovery The resilience of the reef north of Southeast Asia have part better than the Gulf of Thailand (UNEP 2007) Repeated bleaching is also a common feature at many sites throughout the Caribbean and Pacific Oceans in 2010 Bleaching was recorded in Southern Caribbean (Alemu I & Clement 2014), In the Southeast Pacific Ocean corals bleached in the Thailand (Sutthacheep et al 2013) and Vietnam (Long &

Vo 2013; Tun et al 2010) Reports from these countries showed the more severe bleaching in 2010 than in 1998 (Tun et al 2010) The most affected area is the Gulf of Thailand and the Andaman Sea (Sutthacheep et al 2013; Tun et al 2010)

2.4 El Nino

El Niño and the Southern Oscillation, also known as ENSO is a periodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean (NOAA 2016)

El Niño is the abnormal warming of sea surface layer in the central region and eastern equatorial Pacific Ocean, a change of one side will cause the reaction of the other side

El Nino an oscillation of the system interact with large-scale to complex between the atmosphere and ocean in the tropical Pacific El Nino strongest before Christmas (December each year) then may last until next year (NOAA 2016) NOAA has used Oceanic Niño Index (ONI) become de-facto standard for identifying El Niño and La Niña events in the tropical Pacific Years with the ONI exceeds 0.5, the year will occur

El Niño phenomenon, and its intensity depends on the magnitude of the ONI with four categorized as Weak (0.5 ÷ 0.9), Normal (1.0 ÷ 1.4), Strong (1.5 ÷ 1.9) and Very Strong (> 2.0) (GGWS 2017)

2.5 Forecast of Bleaching Alert Area

Studies on the model for predicting levels and areas of bleaching potential were developed by the U.S National Oceanic and Atmospheric Administration’s Coral Reef Watch (NOAA CRW) (Heron et al 2016) Bleaching Alert Area was localized by analysis data from satellite sea surface temperature (SST) When SST exceeded forecasts for a time long enough to observe a bleaching event, it became possible to provide four level forecast maps of areas likely bleach (“Watch”, “Warning”, ”Alert Level 1” and

“Alert level 2”) (Liu et al 2013; Heron et al 2016)

Forecast results of NOAA showed that the Vietnamese coral reef had an Alert level 1 for bleaching at the Phu Quoc Island and south central Vietnam (from Nha Trang

to Ninh Thuan province) in June 2010 Comparisons between the results predicted by NOAA and the survey results of Nguyen Van Long et al (2013), indicated a 10,8% risk for Alert level 1 bleaching event in the Ninh Thuan coral reef The hard coral coverage

of the Ninh Hai reef were reduced in the period 2003-2007 but remained stable in the period 2007-2009 After that bleaching event 2010 made for the mean coral cover decrease on the reef According to a forecast by NOAA in February 2016 the risk of bleaching along Vietnamese reefs between May and June 2016 is at Alert level 1 in the South West sea, and at Warning level in the central part of the country (Ninh Thuan province to Con Dao Island)

2.6 Coral bleaching in Vietnam

The coral bleaching in Vietnam in 1998 was first recorded in Con Dao Island (October 1998) and Cu Lao Cau Island (May to August 1998) In the Con Dao reef was bleaching 37% (0-74% between 11 survey stations) (Tuan 2000) In the Cu Lao Cau Island, coral bleaching was recorded in May, but was not considered serious However, the survey results at September 1998 at Cu Lao Cau showed no bleaching, but many reefs were found dead and covered by algae This suggests that coral bleaching happened between May and August (Tuan 2000) Coral reefs in Con Dao were bleached 20-100%

of it killed in 2005, because of sea water temperature increase combined with a decrease

of salinity over a period of 7 consecutive days (Bền et al 2008)

The coral bleaching in 2010 were submitted in the reports of coral reef monitoring

in Khanh Hoa province, Ninh Thuan province and the Kien Giang province by Long et

al (Long 2010; Long et al 2010; Long et al 2013) The time when bleaching occured were different in Phu Quoc Island, Van Phong bay, Nha Trang bay, Cam Ranh bay and Ninh Hai reefs with different damage levels

Coral reef had a bleaching average of 56.6% (24.6-91.6% between the stations)

in May 2010 at Phu Quoc Islands where hard coral covered from 2.5% to 40.3% of the stations (Long et al 2010) The bleaching average of the Ninh Hai coral reef was 10.8% (2.4-40% between the stations) with hard coral covering between 21.1 and 30, 5% at the ten monitored station in June 2010 (Long et al 2013) In waters around Khanh Hoa, the

assessment results from six fixed stations monitored in August 2010 showed that hard coral covered from 6.3 to 41.9% of the shore and 3% (0-8.4% between the stations) of the corals were bleached (Long 2010)

2.7 Coral diseases

Corals are colonial animals that belong to the phylum Cnidaria that form polyps with stinging cells Hard (Scleractinian) corals secrete a skeleton of calcium carbonate whereas soft corals, polyps secrete a proteinaceous skeleton (Work & Meteyer 2014) Hard (Scleractinian) corals can be infected by bacteria, viruses and are influenced by the shocks from the environment such as temperature, nutrients and toxins Coral diseases have been named as ‘‘coral disease, white syndrome, white plague, black band, yellow blotch, yellow band, sea fan aspergillosis, dark spot, coral bleaching, white pox coral, coral ciliate, coral fungus and coral virus (Work & Meteyer 2014) After infection, the coral tissue will become inactive In addition, the disease also changes the reproductive rate, the rate of growth, community structure, species diversity and abundance of other organisms in the reef (Raymundo et al 2008) A number of studies indicate that disease prevalence in areas of the Indo-Pacific region, American Samoa and Hawaii is currently quite low (ICRI/UNEP-WCMC 2010) Some common coral diseases on the reefs of tropical waters are: black band disease (BBD); Brown band disease (BRB); White syndrome (WS); Ulcerative white spots (UWS); Skeletal eroding band (SEB)

Black band disease (BBD) is caused by bacteria, mainly Phormidium

corallyticum and bacteria species of the genus Beggiatoa (ICRI/UNEP-WCMC 2010)

These are most active when the water temperature rises to 28oC The temperature increases the severity of the disease since the nutrient content when the water temperature decreases (Singer & Richardson n.d.) Recent studies by Garren et al (2014)

on the correlation when corals are stressed by heat, the mucus releases DMSP around the environment about five times higher, this high concentration of DMSP has a chemotaxis that attracts (Garren et al 2014)

The cause of Brown band disease (BRB) is still not determined, but researchers have noted the emergence of single-celled organisms, ciliates, in the samples (Bourne et

al 2008) White syndrome (WS) is the common name of the disease White Patches (WP) and the White Band Disease (WBD) White Patches (WP) disease has two type: White

Patches type 1, type 2 The differences of the two types are based on the rate of infection,

or disease patterns affecting the species (Raymundo et al 2008) White plague II in

Monastraea coral is caused by Gram-negative bacteria Aurantimonas coralicida (Denner

et al 2003) White Band Disease type 1, type 2, it is recognized more in the Caribbean (Raymundo et al 2008) Acroporid white band I (White band I) has not been identified (Bythell, J & Sheppard 1993), while white band II (white band II) appears in many

species of corals and is known to be caused by Vibrio charcharvina (Ritchie & Smith 1998) Skeletal eroding band (SEB) induced by Halofolliculina corallasia was first

recorded in the Indo-Pacific (Page & Willis 2008)

The spread of the diseases in high biodiversity reefs with high coverage are higher than in reefs that have low coverage The health of corals after bleaching are very weakened and susceptible to infections An increase in coral diseases in the Great Barrier Reef (GBR) were recorded after the bleaching events in 2002 The same was reported from US Virgin Islands in 2005 and 2010

CHAPTER 3 MATERIAL AND METHOD

3.1 Research subjects

Coral Bleaching and Coral Disease

3.2 Second data and information

3.2.1 Sea surface temperature data

The average water temperature data of the sea floor to the surface and standard deviation (SD) is calculated from the NOAA satellite image source by Coast Watch Software V 3.3.0 (CWS) limited in range 109oE-110oE and 11oN-12oN (Fig 3.1) The satellite images used from April 4, 2016 to August 31, 2016

3.2.2 Coral cover data

Coral coverage data in three survey stations were referenced from the primary coral reef monitoring data (2007-2014) made by Department of Marine Living Resource of Institute of Oceanography Data was reviewed from framework on monitoring coral reefs of project's Ninh Thuan province and project's UNEP

3.3 Location and time study

The study was implemented during May, June and August, 2016 at Hang Rai, Mui Thi and My Hoa reef sites (Table 3.1 and Fig 3.2):

Table 3.1: Reef sites monitoring

Figure 3.1: Limiting area for

analysis SST data in CWS

Figure 3.2: Reef sites monitoring

3.4 Data collection

3.4.1 For environmental parameter

Water environment parameters including the sea water temperature (oC) and salinity

(‰) were recorded by the ultimate handheld sampling instrument HIROBA The values

measured in two layer: surface (1 m) and bottom (>3 m depending on the depth of reef)

3.4.2 For biological parameter

3.4.2.1 Experimental setting

Two transects were laid parallel to the depth contours (100m/transect); the shallow

contour located on the reef flat (2 - 5 m deep) and the deep contour on the reef slope

(from 6 - 10 m) The transect are divided into four individual 20 m transect lines (0 – 20

m, 25 – 45 m, 50 – 70 m, 75 – 95 m) (Fig 3.3) The 5 m gap between each individual 20

m transect, allows independence of samples, avoiding replication and ensuring more

precise statistical analysis These four segments are considered as replicates for each of

shallow or deep transect at each site Methodology and selected parameters are assessed

using standard methods based on the Global Coral Reef Monitoring Network (GCRMN) (English et al 1997), Reefcheck protocols (Hodgson et al 2006) and Coral disease

handbook (Raymundo et al 2008)

Figure 3.3: A transect line of 100 m long for surveys of benthos

3.4.2.2 Measure techniques

Benthic substrate: Components are recorded at each 0.5m interval of the 20 m

long of each segment flowing the point-intercept survey method to record parameters of coral reef component (Hodgson et al 2006) Parameters of coral reef components recorded including hard corals none-bleaching (HC), Coral Bleaching (BL), soft corals (SC), recent killed corals (RKC), dead coral with algae (DCA), fleshy seaweeds (FS), coralline algae (CA), turf algae (TA), sponges (SP), rock (RC), coral rubble (RB), sand (SD), silt/clay (SI) and others (OT) were recorded Total score recorded for each segment is 40 points touch section Additionally, coral genera recorded along transects were used for estimating abundant level Percentage of cover of each genus were calculated based on records of their touch to 0.5m point as for benthic component cover

Coral bleaching index: Bleached colonies were counted for more quantitative

survey in the twenty 1m2 quadrats along the 100m length of each transects (Figure 3.4) There was an interval of 5 m between two quadrats The total of 40 quadrats were monitored including 20 of them at the reef flat and 20 others at the reef slope In addition, photos of each quadrat was be taken for further analysis

1 st Section

(20m)

2nd Section (20 m)

3rd Section (20m)

4th Section (20m)

Figure 3.4: A transect line of 100 m long for coral bleaching and coral disease

Coral bleaching was recorded and estimated per hard coral colonies at each quadrat and assigned to one of seven categories: (1) nomarl, (2) 1-10% of the suface bleached, (3): 11-30% bleached, (4) 31-50% bleached, (5) 51-75% bleached, (6) 76-100% bleached, (7) dead

Similar to coral bleaching level, coral damage also was surveyed at six levels (Level 1: normal; Level 2: 1-10%; Level 3: 11-30%; Level 4: 31-50%; Level 5: 51-75%; Level 6: 76-100%)

Coral diseases: Diseases colonies were counted for more quantitative survey in

the twenty 1m2 quadrats along the 100m length of each transects (Figure 3) There was

an interval of 5 m between two quadrats (0; 5; 10; 15; 20 … 95) The total of 40 quadrats were monitored including 20 of them at the reef flat and 20 others at the reef slope The disease was recorded including Black band disease (BBD); Brown band disease (BRB); White syndrome (WS); Ulcerative white spots (UWS); Skeletal eroding band (SEB) The coral disease was photographed and described

3.5 Data analysis

3.5.1 Assessment of change coral cover during 2007-2016

Benthic substrate coverage and ratio coral bleached during 2007-2014 and June

2016 were calculated according to the rate of individual components for each section 20

m (Formula 1) After that percent cover of each benthic substrate was estimated average for 4 section flowing transect and sites

3rd transect (20m)

4th transect (20m)

3.5.2 Assessment ratio of coral bleaching and coral damage

Coral bleaching data was analyzed in two directions: (A) Ratio of coral bleached

on benthic substrate (B) The number coral colonies were bleached in quadrat 1m2

The ratio of coral gets bleached on benthic substrate was calculated according to the formula (2)

𝑅𝑎𝑡𝑖𝑜 𝑜𝑓 𝑐𝑜𝑟𝑎𝑙 𝑏𝑙𝑒𝑎𝑐ℎ𝑒𝑑 =𝑃𝑒𝑟𝑐𝑒𝑛𝑡 𝑐𝑜𝑟𝑎𝑙 𝑏𝑙𝑒𝑎𝑐ℎ𝑖𝑛𝑔 𝑐𝑜𝑣𝑒𝑟 (𝐵𝐿)

𝑃𝑒𝑟𝑐𝑒𝑛𝑡 𝑡𝑜𝑡𝑎𝑙 𝑐𝑜𝑟𝑎𝑙 𝑐𝑜𝑣𝑒𝑟 (𝑇𝐻𝐶) 𝑥 100% (2) Ratio of coral bleaching and mortality were estimated for each categories in each quadrat 1m2 In which the ratio of each categories is calculated from the number of coral colonies divide total colonies (formula 3 & 4)

After that, the average of ratio of each categories coral bleaching and mortality were estimated for transect and sites Total have 20 reification of each category in each transect, 40 reification for each site

𝑅𝑎𝑡𝑖𝑜 𝑜𝑓 𝐶𝑎𝑡𝑒𝑔𝑜𝑟𝑖𝑒𝑠 (𝐶𝑖) = 𝑛𝑖

𝑁 𝑥 100% (3)

Ci: The percent of each bleached category (i = 1-7)

ni: The number colonies of each categories

N: Total colonies were recoded in quadrat

𝑅𝑎𝑡𝑖𝑜 𝑜𝑓 𝑚𝑜𝑟𝑡𝑎𝑙𝑖𝑡𝑦 (𝑀𝑖) =𝑎𝑖

𝑁 𝑥 100% (4)

Mi: The percent of each damage category (i = 1-6)

ai: The number colonies of each damage categories

N: Total colonies were recoded in quadrat

Coral beaching index (BI) value was modify from formula of McClanahan et al (2005, 2007) (McClanahan et al 2005; McClanahan et al 2007) c1-7 were estimated from formula 3

𝐵𝐼 = (0𝑐1+1𝑐2+2𝑐3+3𝑐4+4𝑐5+5𝑐6+6𝑐7)

3.5.3 Assessment coral disease

Percentage of each disease was calculated according to the formula 6 from the ratio of the number of disease colonies and the total number of coral disease colonies 𝑅𝑎𝑡𝑖𝑜 𝑜𝑓 𝑒𝑎𝑐ℎ 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 = 𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑒𝑎𝑐ℎ 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑐𝑜𝑙𝑜𝑛𝑖𝑒𝑠

𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑜𝑟𝑎𝑙 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑐𝑜𝑙𝑜𝑛𝑖𝑒𝑠𝑥 100% (6)

CHAPTER 4 RESULT AND DISCUSSION

4.1 Sea surface temperature (SST) during April and August 2016

Sea surface temperature values (SST) by analysis of satellite images and field survey showed SST increase during April to May of 2016 (from 29 to 31oC) After that SST reduced to 23-24°C at both layers of water at the time of reef monitoring in June, 2016 (Fig 4.1 & 4.2) During the August 2016 seawater temperature changes among from 27

to 29oC The difference of temperature among site, time study were about 0.5oC (Appendix 3) There was no signification among sites, in surface and bottom layers for each field survey with P value >0.05 The salinity of seawater remained stable at over

34 ‰ at three sites, indicating that the study area was not affected by fresh water (Appendix 2) Therefore, Thermal stress is the cause of the bleaching phenomenon

Figure 4.1: Sea surface temperature data analyzed from satellite

Figure 4.2: Sea surface temperature during May to August 2016

4.2 Long-term changes in hard corals during 2007-2016 at three reef sites

monitoring

The average pattern of coral cover did not vary greatly from 2007 to 2010 Mean coral cover is almost maintained at an average of 37.53% on reefs from 2007-2009, and declined to 35.31% in 2010 by bleaching events The historical data show that bleaching events occurred between May and July 2010 that reduced the hard coral cover range 5-10% in each site monitoring (Fig 4.3) After that coral recover on the reef in 2011, mean coral recover higher than one year ago (Mean±SE: 44.79±3.07%) (Fig 4.3) The results monitoring in 2011 at Hang Rai, Mui Thi and My Hoa showed that the corals were high adaptable and resilient (increasing from 10-20% of hard coral cover in each region compared to 2010) From 2011 to 2012, coral cover was reduced to 35% on reefs at all three monitoring stations (Fig 4.3) After that coral recover on the reefs in the period from 2012 to 2014 This fluctuations increased the coral cover from 35.52% to 55% From 2014 to 2016 the coral cover decreased 40.94%

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