Thailand
The Kingdom of Thailand is in Southeast Asia , bordering Laos and Cambodia to the east, the Gulf of Thailand and Malaysia to the south, and the Andaman Sea and Myanmar to the west.
Most of the seagrass meadows are multispecies, located in enclosed or semi-enclosed embayments from the intertidal area ot 5m in depth depending on seagrass species. Among the 12 species of seagrasses found in Thailand, Halophila ovalis is the most widely distributed, because of it’s ability to grow in different habitats. Enhalus acorodies, the largest species, is also common in the major seagrass areas. Seagrasses are more abundant in the Andaman Sea than in the Gulf of Thailand.
The four most important seagrass areas in Thailand are Haad Chao Mai National Park, in Trang province on the southern coast of the Anadaman Sea and just north of Malaysia, Ko Talibong (Talibong Island), also in the Trang Province, Kung Krabane Bay, in Chathaburi province on the eastern coast of the Gulf of Thailand, near Cambodia and Ko Samui (Samui Island), in Surat Thani province, and part of the southern coast of the Gulf of Thailand.
Seagrass-Watch in Thailand
To provide an early warning of change, long-term monitoring has been established in Thailand as part of the Seagrass-Watch, Global Seagrass Observing Network (www.seagrasswatch.org). Establishing a network of monitoring sites in Thailand provides valuable information on temporal trends in the health status of seagrass meadows in the region and provides a tool for decision-makers in adopting protective measures. It encourages local communities to become involved in seagrass management and protection. Working with both scientists and local stakeholders, this approach is designed to draw attention to the many local anthropogenic impacts on seagrass meadows which degrade coastal ecosystems and decrease their yield of natural resources.
Location
Trang
Monitoring: coming soon
Location: Haad Chao Mai National Park
Site code: To be advised
Issues: Benthic push-net fishing
Comments: Trang is the one of the southern provinces (changwat) of Thailand, and is located on the coast of the Andaman Sea, and contains 46 islands together with the mainland area.
The southern coast of the province is protected in the Mu Ko Phetra National Park.
Southern Thailand’s sunny, clear, inshore waters are ideal conditions for the lush seagrass which were ‘pastures’ for fish, crabs, prawns, molluscs, and most importantly, dugongs. The dugong was once abundant in these large expanses of seagrass along Thailand’s southern shores, until pushnets and intrusion by trawlers began to damage the ocean floor. Meanwhile, gill nets, pollution, noise, and habitat destruction have been blamed for the 75 dead dugongs which washed onto the districts’ shores between 1979 and 1998. When a dugong began to frequent the coastal waters along the regenerated sea grass bed of Ban Chao Mai village in 1995, it caused a stir in the media as live dugongs had not been seen in a long time, and most young people had never seen one.
Koh Libong and Koh Muk (Trang)
Data collection: SAN
Principal collectors: Ms.Onanong Sanitmat, Mr.Pathiwat Mueangklang,Mr Chisanupong Juthamat, Ms.Thananporn Jitpakdee, Ms. Korawan Buadoktoom, Ms. Ramita Choongan, Ms Chanyanuch Kongtee, Asst. Prof. Pontep
Area survey and project coordination & management: Prof. Pontep Wirachwong, Ms. Rujinun Palahan, Ms. Kanyanat Pengkasit
Map planning, Data Analysis and Map creation: Seagrass-Watch
Location: Koh Libong and Koh Muk (Trang)
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Koh Libong and Koh Muk (Trang) seagrass mapping results
Seagrass meadows surrounding Koh Libong, Koh Mook, and Mod Ta Noi (Trang, Thailand), were assessed between 13 August 2022 and 12 April 2023. Observers walked, snorkelled or used drop-cameras to collect photoquadrats at mapping points, which were positioned using a restricted random sampling design. Visual estimates of above-ground seagrass percent cover, seagrass species and macroalgae percent cover were recorded at each mapping point from 3 quadrats (50cm x50cm), using globally standardised Seagrass-Watch protocols. Substrate type was assessed at each mapping point by hand, and aided by a Van Veen grab at subtidal points. A differential handheld global positioning system (GPS) was used to locate each mapping point (accuracy ±3m). A total of 607 individual points were examined, of which 145 were collected from drop-camera, 448 from in situ sampling and 250 from Seagrass Spotter.
Seagrass was present at 401 of the mapping points, with percentage cover ranging from 0.2 to 48%, and with an average of 14.9%. Nine seagrass species were identified, with the most frequently encountered being Halophila ovalis, Enhalus acoroides and Cymodocea rotundata (36.3%, 32.6% and 19.0% average cover respectively). Spatially explicit seagrass maps were created from PlanetScope Dove (3.7 m × 3.7 m pixel) imagery, using the field validation point data and a machine-learning model (random forest). A total of 200.3 to 763 hectares of intertidal/shallow seagrass meadows, with an additional 225 hectares in subtidal (turbid) waters was mapped surrounding Koh Libong, Koh Mook and Mod Ta Noi.
Surronding Ko Libong, the seagrass presence map obtained from remote sensing showed seagrass covering between 200.3 to 763.0 ha with an additional 225 ha from subtidal/turbid areas that were manually digitized. The coastal intertidal meadows of the islands southeastern bay were mostly composed of Cymodocea rotundata, Enhalus acoroides and Thalassia hemprichii. Meadows in the western part of bay surrounding Leekpai pier (and dugong viewing tower) were predominantly composed of Enhalus acoroides close to shore and Halophila ovalis in the subtidal offshore areas. Similar species assemblages were found in the subtidal meadows between Koh Libong and Mod Ta Noi on the mainland, with also some Cymodocea rotundata. The seagrass of the northern coast of Koh Libong was scarcer with aggregated patches predominantly composed of Halophila ovalis and Halodule pinifolia.
The coastal seagrass meadows of Mod Ta Noi (mainland Trang) covered approximately 178 ha (from expert driven map digitization) and were composed of mostly Enhalus acoroides, Halophila ovalis and Cymodocea rotundata.
At Koh Mook, seagrass presence was estimated between 36.4 and 71.7 ha by remote sensing. However, the confidence in the output is moderate to low as only Seagrass Spotter data was available and points were concentrated in close proximity. Therefore, the training data used for the remote sensing model was mostly visual interpretation of the imagery without in-situ validation data.
Technical report
Report to Edith Cowen University of activities conducted by Seagrass-Watch for the “Conservation of biodiversity, seagrass ecosystems and their services – safeguarding food security and resilience in vulnerable coastal communities in a changing climate”
How the data was collected
Field validation points were spatially balanced and randomised within the Area of Interest (AOI). All data collected within the AOI was used to ensure mapping of all seagrass meadows present.
At each field validation point, teams conducted a spot-check using either Drop-Cam, in situ observation, or grab.
Photoquadrats were captured (except where only a grab sampler was used) during each spot-check. Photoquadrats were either geotagged or geolocated. Data collected from the photoquadrats (e.g. % cover and species) at each point and the Seagrass Spotter sightings were used to train and validate models for classification of satellite imagery.
Thailand seagrass
Location
Koh Phra Thong Island
Monitoring: ongoing
Principal watchers: Barry Bendell, Pa Nee
Location: Khura Buri District
Site code: PT1, PT2, PT3, Pt4, PT5, PT6
Issues: fishing, run off
Comments: Ko Phra Thong is an island in Khura Buri District, southern Thailand on the Andaman Sea, and is the middle link in a chain of three islands.
On Phra Thong Island, local communities have established protected areas in seagrass meadows where the harvesting of all animals is prohibited.