Monitoring coral bleaching by satellite thermal products a case study in the a case study in the southern east sea

MONITORING CORAL BLEACHING BY SATELLITE THERMAL PRODUCTS: A CASE STUDY IN THE SOUTHERN EAST SEA, VIETNAM A Thesis presented to the Faculty of the Graduate School at the University of Missouri In Partial Fulfillment Of the Requirements for the Degree Master of Arts by NGAN THUY LE Dr Cuizhen Wang, Thesis Supervisor MAY 2012 The undersigned, appointed by Dean of the Graduate School, have examined the thesis entitled MONITORING CORAL BLEACHING BY SATELLITE THERMAL PRODUCTS: A CASE STUDY IN THE SOUTHERN EAST SEA, VIETNAM Presented by Ngan Thuy Le A Candidate for the degree of Master of Arts in Geography And hereby certify that in their opinion it is worthy of acceptance Professor Cuizhen Wang Professor Michael A Urban Professor Robert Sites ACKNOWLEDGEMENTS My thesis would not have been accomplished without the great supports from my professors, my friends and my family First of all, I would like to show my deepest gratitude to my supervisor, Dr Cuizhen Wang, whose encouragement, guidance and support from the initial to the final level enabled me to develop an understanding of the research I will not forget the days Dr Wang working hard on the IDL programming to help me approach the best results Without her contributions, my enthusiasm in studying coral reefs could not be possible I also would like to thank Dr Mike Urban and Dr Robert Sites who were willing to attend my Thesis Committee and gave me an adequate time to finish my thesis as satisfactorily as I expected There is no word can express my appreciation to their patience It is an honor for me to meet and learn from Vietnamese specialists working at the Oceanography Institute in summer 2011 I am heartily thankful to Mr Phan Kim Hoang and Mr.Tong Phuoc Hoang Son, who shared with me their plenty of precious knowledge about the coral reefs in Vietnam Their sharing inspired me and helped me clarify my research questions Particularly, Mr Son did not hesitate to spend his valuable time teaching me working with the remote sensing data I deeply admire his devotion and her passion to share his experiences with me I should also send my thanks to Mr Le Chi Lam, my mentor in Vietnam and Mr Nguyen Thanh Minh at the Department of Natural Resources and Environment in Khanh Hoa Province for their technical supports ii Besides, I offer my regards and blessings to all faculty members and staff in the Department of Geography as well as my friends who supported me in any respect during the completion of my Master program I really appreciate Dr Matt Foulkes who questioned me: “Why did you that?” to force me think deeply about the purpose of my study In addition, special thanks to Dr Joe Hobbs, Chair of the Department and Director of the Vietnam Institute, who gave me opportunity to study at MU and always, cares for me with his kindness heart Moreover, I would not overcome many challenges and depressions without the encouragements from my greatest friends who are working or studying in Vietnam, Europe and at MU I wish I could express completely my love to my “intimate sisters”, Nga Bui and Ha Phan, who are always beside me, understand my obstacles and support me as much as they can Last but not least, I would like to send my honest gratitude to my family for their countless love and confidence on me This thesis is a special gift for my beloved parents iii TABLE OF CONTENTS ACKNOWLEDGEMENTS ii LIST OF FIGURES vii LIST OF TABLES x LIST OF ABBRIVIATIONS AND EQUATIONS xi ABSTRACT xii CHAPTERS INTRODUCTION 1.1 Coral Reefs .2 1.2 Threats to Reefs .5 1.3 Coral Bleaching .6 1.4 Predicting coral bleaching by sea surface temperature 1.5 Research Objectives .12 CASE STUDY .13 2.1 Status of Coral Reefs in Vietnam 13 2.2 Status of Coral Reefs at Con Dao and Phu Quoc Archipelagos 15 2.3.Coral bleaching at Con Dao Archipelago .19 2.4 Coral bleaching at Phu Quoc Archipelago 21 2.5 Global Thermal Anomalies in 2010 .22 MATERIALS AND METHODS 25 3.1 Data Description 25 3.1.1 AVHRR Pathfinder (PF) Version SST Products .25 iv 3.1.2.MODIS Aqua SST Products 27 3.1.3 NOAA Coral Reef Watch Datasets .29 3.1.4.Observation Sites and Mainland Boundary 30 3.2 Data Pre-processing .31 3.2.1 Extracting SST Value From AVHRR and MODIS Products .32 3.2.2 Excluding of Invalid Pixels 33 3.3 Data Processing 37 3.3.1 Calculating SST Climatology and Maximum Monthly Mean (MMM) .37 3.3.2 Calculating Bleaching HotSpot 39 3.3.3 Calculating Degree Heating Week (DHW) 39 3.3.4 Generating of Bleaching Alert 40 3.3.5 Statistic analysis of MODIS- and AVHRR-derived SST Value 41 RESULTS AND DISCUSSIONS .43 4.1 Comparison of MODIS- and AVHRR-derived SST Value 43 4.1.1 Results of Correlation Analyses 43 4.1.2.Results of Paired Comparisons 46 4.2 Comparison of SST in the Southwestern and Southeastern Areas of the East Sea49 4.3 Thermal Stress in Bleaching Years 54 4.3.1 Thermal stress in 1998 56 4.3.2 Thermal Stress in 2005 .61 4.3.3 Thermal Stress in 2010 .65 4.4 Comparison of the 50 km and km Bleaching Prediction Products 68 4.4.1 Bleaching Threshold and Weekly SST Products 69 v 4.4.2 Mapping HotSpots and Bleaching Prediction .70 CONCLUSIONS 74 5.1 Major Findings 74 5.2 Limitations 75 5.3 Future Envisions 77 APPENDIX A Outputs from Linear Regression of the 2005 Weekly SST Data 79 B Outputs from Paired Comparison of the 2005 Weekly SST Data 86 BIBLIOGRAPHY 93 LIST OF FIGURES vi FIGURES PAGE Figure 1.1: Anatomy of a coral polyp Figure 1.2: Major coral reef sites are red dots on the world map .4 Figure 1.3: Coral bleaching process Figure 1.4: Trends in coral bleaching, 1980 – 2010 Figure 2.1: Reef distribution in the coastal waters of Vietnam .14 Figure 2.2: Location of observed sites at Con Dao in 1994-2004 17 Figure 2.3: Location of observed sites at Phu Quoc in 1994-2007 17 Figure 2.4: The percentage of hard coral cover observed at Con Dao in 1994-2004 .18 Figure 2.5: The percentage of hard coral cover observed at Phu Quoc in 1994-2007 18 Figure 2.6: Coral bleaching was observed in the southwestern of Con Dao archipelago in October, 2005 20 Figure 2.7: Bleaching alert graph (based on the 50 km spatial resolution data set) at Con Dao in 2010 21 Figure 2.8: Coral bleaching was observed at Phu Quoc archipelago in May (a) and August (b), 2010 22 Figure 2.9: Global temperature anomalies since 1880 23 Figure 2.10: Coral bleaching alert areas in Western Pacific in summer 2010 24 Figure 3.1: Locations of the three Virtual Stations in the Southern areas of East Sea 30 Figure 3.2: Location of the case study in East Sea 32 Figure 3.3: Example of Mean Sea Surface Temperature derived from AVHRR products34 Figure 3.4: The weekly SST in 2010 before S-Golay Smoothing 35 Figure 3.5: The weekly SST in 2010 after S-Golay Smoothing .36 vii Figure 3.6: The one-year SST climatology curve of one pixel 38 Figure 3.7: Distribution of the 2005 weekly SST samples .42 Figure 4.1: Scatter plot of the 2005 SST (degree Celsius) data overlaid with the regression line, and 95% confidence and prediction limits 44 Figure 4.2: Concordance of SST values derived from NASA MODIS and NOAA AVHRR products for Heron Island in 2005-2006 44 Figure 4.3: Scatter plot of the SST data in winter months (January to April and November to December of 2005) overlaid with the regression line, and 95% confidence and prediction limits 45 Figure 4.4: Scatter plot of the data in summer months (May to October of 2005) overlaid with the regression line, and 95% confidence and prediction limits .46 Figure 4.5: Comparison of weekly SST values derived from AVHRR PF and MODIS products in January and May 2005 48 Figure 4.6: Sea surface temperature climatology from January to June 50 Figure 4.7: Sea surface temperature climatology from July to December .51 Figure 4.8: 12 months sea surface climatology at Phu Quoc 53 Figure 4.9: 12 months sea surface climatology at Con Dao .53 Figure 4.10: Location of Observed Reefs and relative SST pixels at Phu Quoc .55 Figure 4.11: Location of Observed Reefs and relative SST pixels at Con Dao 55 Figure 4.12: Thermal stress at Phu Quoc in 1998 .57 Figure 4.13: Thermal stress at Con Dao in 1998 58 Figure 4.14: Degree Heating Week from April to July 1998 60 Figure 4.15: Degree Heating Week from April to October 1998 .60 viii Figure 4.16: Degree Heating Week in October 1998 .61 Figure 4.17: Thermal stress at Phu Quoc in 2005 .62 Figure 4.18: Thermal stress at Con Dao in 2005 63 Figure 4.19: Degree Heating Week from May to October 2005 65 Figure 4.20: Thermal stress at Phu Quoc in 2010 .66 Figure 4.21: Thermal stress at Con Dao in 2010 67 Figure 4.22: Degree Heating Week from April to October 2010 68 Figure 4.23: Comparison of SST and bleaching threshold between the 50km (a) and the 4km (b) product .69 Figure 4.24: The 50km spatial resolution HotSpot map at East Sea in June and July 2010 71 Figure 4.25: The 4km spatial resolution HotSpot map in June 2010 71 Figure 4.26: The 4km spatial resolution HotSpot map in July 2010 72 Figure 4.27: The 50km spatial resolution Bleaching Alert map in July 2010 72 Figure 4.28: The 4km spatial resolution Bleaching Alert map in July 2010 73 LIST OF TABLES TABLES PAGE ix 83 CORRELATION ANALYSIS FOR THE 2005 SUMMER DATA Number of Observations Read 2373 Number of Observations Used 2373 Descriptive Statistics Uncorrected Standard SS Variance Deviation Variable Sum Mean Intercept 2373.00000 1.00000 2373.00000 0 AVHRR 71412 30.09336 2150662 0.69520 0.83379 MODIS 71026 29.93068 2128869 1.27596 1.12958 Analysis of Variance Source Sum of Squares DF Model 128.68164 128.68164 Error 2371 2897.89805 Corrected Total 2372 3026.57969 Root MSE Dependent Mean Coeff Var Mean Square F Value 105.28 |t| -17.59 |t| -22.04 |t| -6.30