Relationship Between Environmental Conditions and Recovery of the Coral Reefs in the Andaman Coast of Thailand
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ESEARCH ARTICLE R ScienceAsia 41 (2015): 217–228 doi: 10.2306/scienceasia1513-1874.2015.41.217 Relationship between environmental conditions and recovery of the coral reefs in the Andaman coast of Thailand a a,b, c Nissara Thawonsode , Shettapong Meksumpun ∗, Pattira Kasamesiri a Department of Marine Science, Faculty of Fisheries, Kasetsart University, Chatuchak, Bangkok 10900 Thailand b Centre of Advanced Studies in Tropical Natural Resources, KU Institute for Advanced Studies, Kasetsart University, Bangkok 10900 Thailand c Department of Agriculture, Faculty of Technology, Mahasarakham University, Mahasarakham 44000 Thailand ∗Corresponding author, e-mail: ffi[email protected] Received 13 Oct 2014 Accepted 22 Jul 2015 ABSTRACT: The coral reef ecosystem in the Andaman sea was studied by monitoring aquatic environmental conditions and reef condition from years 2005–2009. Following the Asian tsunami in December 2004, the ammonium-nitrogen concentration in the surface water in Ranong province ranged from 8.45–14.08 µM, while in Phang Nga area, it was between 9.99 and 25.11 µM. Mean sea surface temperatures in Ranong and Phang Nga were 30.6 0.4 °C during ± the dry season. The growth rate of Acropora spp. in Chong Khat bay, Surin Marine National Park, was 1.0 cm/month during the first 5 months after the tsunami. After this five-month period, corals, especially Acropora spp., showed signs of recovery but then faced extensive bleaching in May 2005. Three years after the tsunami, the coral reefs in deep water areas could grow and recover rapidly although they faced serious bleaching while coral reefs in the shallower waters were in a poor condition after serious bleaching in May 2005. This phenomenon revealed that the mass mortality of corals in shallow waters was enhanced by high seawater temperature and high turbidity due to phytoplankton blooms. Overall results indicate that the relationships between environmental conditions and coral reef status in the Andaman sea is an issue of great concern and coastal corals may gradually degrade in the near future unless action is taken to alleviate coastal environmental problems. KEYWORDS: coral bleaching, red tide, tsunami INTRODUCTION results from that study showed that the destructive impact of the tsunami on coral reefs depended Many coral reefs, especially those along the An- on the geographic location of shorelines, islands, daman shoreline and in adjacent narrow channels and reefs. Most of the coral reefs in Ranong and of Thai water, were severely damaged by the gi- Phang Nga were not damaged (less than 30% of gantic tsunami caused by the 9.3 Mw Sumatra- corals were affected). The more severely damaged Andaman earthquake 1 which occurred on 26 De- coral reefs (more than 50% affected) were found cember 2004. To evaluate the impacts of the in Chong Khat bay (Surin Marine National Park, tsunami, an emergency research team led by the De- Phang Nga), Lan, Kam Yai, and Khang Khao islands, partment of Marine and Coastal Resources (DMCR) Ranong (unpublished English-language data). Half of the Ministry of Natural Resources and Environ- of the coral reef in the north-eastern part of Jolly ment (MONRE), including nine educational insti- Buoy island, Andaman and Nicobar islands died due tutions (Burapha University, Chulalongkorn Univer- to the tsunami 2. A few months after the tsunami, sity, Kasetsart University, Mahidol University, Prince Ranong and Phang Nga reefs faced serious problems of Songkhla University, Rajamangala Institute of of coral bleaching and phytoplankton blooms, par- Technology, Ramkamhaeng University, and Walailak ticular during our coastal surveys in May 2005. University) was formed. The assessment of the Coral bleaching is not a new phenomenon in destructive impact of the tsunami on the coral reefs coastal areas with high incidences reported in sev- began within a couple of days after it occurred. The eral regions over the last two decades 3–9. Coral www.scienceasia.org 218 ScienceAsia 41 (2015) 1100000 bleaching in the Andaman sea has also been re- 1 ported 10–12. Extensive coral mortality by coral 3 2 1090000 5 4 bleaching in the Andaman sea was observed in 1991 7 6 11 8 and 1995. Pongsuwan reported that 80% mortal- 1080000 9 ity of Acropora spp. occurred at Surin and Similan is- 11 10 12 1070000 13 lands in 1995. Previous studies have suggested that 14 15 coral bleaching were caused by high temperature or 1060000 13–18 19 irradiance . Fitt suggested that it is caused 16 17 by thermal tolerance limits and thermal thresholds 1050000 18 Ranong in several tropical corals. However, quantitative 19 1040000 and qualitative analysis of these factors, including 20 anomaly excursion, length and exposure timing, has 1030000 410000 420000 430000 440000 450000 460000 18 1040000 not been done . Coral bleaching in the Andaman 22 24 21 20 23 sea seemed to be an annual event . 1020000 26 25 28 27 In addition, coral reef along the Andaman coast 29 32 30 1000000 31 line faced the problem of an increase in turbidity. In 33 34 fact, the Andaman sea has faced problems of nutri- 980000 35 Phang Nga ent loading, red tide, and macroalgal blooms several 960000 36 times after the tsunami in 2004. Since phytoplank- 37 940000 ton bloom increases water turbidity and decreases 38 39 the amount of light available to zooxanthellae in 920000 40 41 42 43 coral polyp, increases phytoplankton levels could 900000 have both direct and indirect effects on the growth 44 890000 rate of corals. Thus to understand the changes in the Phuket 860000 status of coral reefs exposed stressful environmental 380000 400000 420000 440000 460000 480000 500000 conditions, the physicochemical characteristics of Fig. 1 Sampling locations (44 stations) for seawater sea water, degree of coral bleaching, and the growth characteristics in Ranong (March 2005) and Phang Nga of corals were examined from 2005–2009. The goal provinces (March 2006). of this study is to clarify the relationships between the environmental conditions and coral reef status in the study area. The output from this study should contribute to coral reef management of the coastal areas. and Phang Nga provinces. Phayam island is a large island with an area of approximately 35 square kilo- MATERIALS AND METHODS metres. We can find coral reef at both East and West coast of the island. The most beautiful and famous Sampling and site diving site of the near-shore area is Khang Khao This study focused on three topic areas. Firstly, island. Most of the coral reefs of near shore islands seawater characteristic analysis was conducted in in study area are shallow fringing reefs. In our March 2005 (Ranong province) and in March 2006 study area, rainy season span about 8 months (May– (Phang Nga province). Secondly, the incidences of December) each year. High volume of water from red tide were monitored in March 2005, 2006, and rain compensates for the evaporation and results in October 2009. Finally, the coral bleaching incident an average salinity of less than 34 psu 21. Suspended (in May 2005), growth, and recovery of coral (in solids usually affect the water transparency espe- May 2005, February 2007 and October 2009) were cially along the coastal areas during rainy season. examined. One hundred and thirty two sampling The appropriate time for scuba diving is only four stations covered all study areas (near shore and off months during the dry season. shore) were designed as shown in Figs.1 and2. The Andaman sea is generally clean and clear Ranong and Phang Nga are located at the first during the dry season. Surin Marine National Park and second southern provinces, respectively, on the has an aquatic area of 102 square kilometres with Andaman coast of Thailand. The coast along these about 60 km far away from the main land (Phang provinces is submerged with a narrow continental Nga province). The most dominant genus of coral shelf. More than 160 islands belongs to Ranong in this area is Porites followed by Acropora 22. www.scienceasia.org ScienceAsia 41 (2015) 219 1090000 Chemical analysis For nutrient analysis, 20-ml aliquots of water sam- 1080000 Phayam Island ples were filtered through Whatman GF/F filter pa- per. All nutrient samples were kept frozen at 40 °C. 1070000 Concentrations of ammonium-nitrogen, silicate-− 1060000 Khang Khao Island silicon and orthophosphate-phosphorus were then analysed by a nutrient auto-analyser (Skalar San Kam Yai Island Kam Nui Island 1050000 Plus) within one week after sampling. Lan Island For chlorophyll a analysis, approximately 1040000 100 ml of each water sample was filtered through Khai Yai Island Whatman GF F filter paper and chlorophyll a Ranong / 1030000 was extracted from the filters with 90% acetone 420000 425000 430000 435000 440000 445000 450000 455000 460000 solution. Chlorophyll a concentration was then 23 1048000 determined by spectrophotometric method . Surin Marine National Park 1046000 Measurement of coral bleaching 1044000 1042000 Measurement of coral bleaching was conducted Chong Khat Bay along the coastlines of Ranong and Phang Nga in 1044000 May 2005 (Fig. 2). The surveys were performed 1038000 Tao Bay using line transects of 20–60 m in length at Ra- Torinla Island 1036000 Phak Kat Bay nong province with a total of 52 sampling stations 1034000 (15 stations at Phayam island, 18 stations at Kam 368000 370000 372000 374000 376000 378000 380000 382000 384000 Yai and Kam Nui islands, 9 stations at Khang Khao Fig. 2 Map of sampling area around Ranong (52 sampling island, 5 stations at Lan island, and 5 stations at Khai stations (15 stations at Phayam island; 18 stations at Yai island). The length of line transects depended Kam Yai and Kam Nui islands; 9 stations at Khang Khao on the length of the reef flat and reef slope.