Barracuda Koh Tao

Entanglement of marine animals in anthropogenic debris is a hot topic, with man-made materials now being found in every section of the water column from the surface to the bottom of the deepest trenches and the hadopelagic zone with as much as 12.7 million tonnes of plastic estimated to enter the ocean each year. Marine animals engage and interact with debris in many different ways, with major threats reported to be entanglement and ingestion, alongside destruction of habitats such as coral reefs.

This is where our project comes in. Entangled coral colonies can be a common site on the lesser dived spots around Koh Tao, and the direct and indirect effects of coral entanglement in marine debris, notably discarded fishing gear, are widely underreported for the Indo-Pacific region. It is estimated that approximately 11.1 billion plastic items are entangled on reefs across the Asia-Pacific region alone, posing a great threat to corals and their dependents. 

Entanglement can be directly responsible for breakage, as well as inhibiting the growth by restricting access to sunlight, as well as preventing the important cleaning function of grazing fish species. Indirectly, entanglement in plastic debris has been linked to a greater prevalence of disease in coral species in the Pacific region, with the likelihood of bacterial disease outbreak being between 4% and 89% greater in corals that have come into physical contact with debris. Coral species that grow in branching or corymbose forms, such as the Acroporids and the Poccilioporids are thought to be eight times more vulnerable to entanglement in debris due to their complex structures, suggesting that important habitats for juvenile reef fish species as well as invertebrates are most greatly affected.

What are we doing about it at the Roctopus ecoTrust?

As well as organising regular dive clean-ups, Marine Biologist Jade has launched a monitoring program which targets the very specific problem of coral entanglement. Survey dives are conducted on all of the major dive sites of Koh Tao, as well as the less commonly visited areas. Reefs are systematically surveyed, with the frequency of entanglement events recorded, type of debris analysed and species most severely affected investigated. Of course, careful debris removal also forms an integral part of this program. Trainees at the ecoTrust can be expected to get hands-on with this project in all aspects, with survey dives conducted at least twice per month. 

Pelagic Fish Monitoring Koh Tao
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