Coral restoration at Double Island 往灣洲

Hong Kong is home to over 80 species of hard coral, a diversity of species considered high even by international standards. This coral not in the form of massive coral reefs as are seen in the tropics, but is clustered in ‘coral communities’ — relatively small patches mostly found in the eastern and north-eastern waters of the territory, growing at shallow depths along the coastline.

healthy coral 1Large Acropora coral colony at Double Island

These coral areas promote the overall health of the local marine ecosystem, but at the same time they are vulnerable to damage. In some areas, the actions of both humans and nature have deteriorated the coral. One local conservation organisation is therefore carrying out a restoration project and last Saturday I joined them as a volunteer.

Why is the coral damaged?

Hong Kong’s corals are fragile and face a variety of threats. Natural threats are compounded by the potential for damage inflicted by humans.

Typhoon damage is a major natural threat — the shallow location of corals in Hong Kong makes them particularly vulnerable to violent wave action. Sediment landing on corals as a result of a storm will also smother them. Corals are also at threat from diseases, bleaching, and bioerioson from other marine organisms which weakens their structures and makes them less resilient. Although these are naturally occurring events, environmental changes and imbalances can increase their gravity.

Add humans in and you immediately increase the damage potential: boat anchors breaking coral through direct impacts, and divers and snorkellers causing damage though carelessness. In fact the surge in popularity of scuba diving is a double-edged sword — on one hand, understanding of marine environmental issues increases, on the other, there are more clumsy underwater humans blundering around causing accidental damage by their presence on reefs (sticks are one of the culprits here!).

coral skeletonsDead coral skeleton. The sea urchins did not kill the coral, they are grazing on the algae that now lives on calcium carbonate remains.

The ERC and the coral restoration project

The Eco-education and Resources Centre (ERC) is a local nonprofit organisation aiming to raise awareness of environmental conservation and protection through various community and education projects. ERC scientist Michelle Cheung explains that although the organisation does not focus exclusively on the marine environment, local coastal and underwater conservation is one of their big priorities due to a lack of awareness among the Hong Kong public regarding what lives under their waters.

Studies have shown that damaged coral communities can recover faster through coral transplantation. The ERC is therefore running a three-year coral restoration project to study the effectiveness of using coral transplantation in Hong Kong. The project is currently in its second year.

The project site, Double Island 往灣洲, is located in the northeast New Territories and is described by the AFCD in its 2005 coral field guide as a ‘biodiversity hotspot’. However, local divers working with the ERC have observed a deterioration of the coral at this site over a number of years. Although coral transplantation cannot reverse damage to corals and is not the solution to the worldwide deterioration of coral reefs, localised re-planting projects may help to mitigate the impact of the damage at specific sites.20150620_101256 (1024x768)Peaceful waters at the project site

Replanting the coral20150620_095234 (1024x768)

The project requires the input of volunteer divers who can help by identifying proper coral fragments, transplanting them and monitoring the results. For this, the ERC has enlisted the help of the HSBC Wayfoong Dive Club. Last Saturday, the club chartered a Diving Adventure boat. We set out from Wong Shek Pier, and conditions were great for the task at hand: calm warm water, hot weather and fair visibility underwater.

20150620_095621 (768x1024)

Before the dive, Michelle briefed us about our task. We needed to swim around the site and identify palm-sized, live fragments of broken coral. Then we would surface (the site is very shallow, 5m or less) where the scientists would come over on a speedboat, check our fragment, confirm it is appropriate, record it, and give us a label and some zip ties. We would then need to redescend and find a suitable solid piece of substrate on which to attach the piece. Apparently quite simple.

However, the task was easier said than done. The challenge was identifying actual live, broken coral. There were plenty of dead bits lying around; these sometimes looked alive since there was algae growing on some of them. There were also stones with patches of young coral. Although small, these were not our target.  We spent a good 30 minutes carefully looking before coming across anything suitable.

From left: the O-shaped fragment found on the sand; young ‘pavona’ corals growing on rocks in foreground (these eventually grow quite massive)

Eventually, my buddy and I found two likely pieces. One looked like a lump of ‘porites’ species (or ‘boulder coral’). The other was a curious, O-shaped fragment which had been identified last year since it had a couple of ties attached. It had come detached from its original spot and was just lying on the sand. It was still alive as the flower-shaped polyps were extended. I think it was a ‘gonipora’ species of coral (or ‘daisy coral’), but I may be completely wrong.

After getting the OK from the scientists, we tagged and secured the two pieces firmly to some large, stable, dead coral skeletons. This too was a bit of a challenge — finding a suitable spot where the fragment could sit neatly and be attached firmly was tricky, not to mention faffing around with zip ties underwater!

Our two fragments secured

The outcome

The day was a success with a number of fragments identified and replanted by volunteers. The ERC team will continue to monitor the health of the replanted fragments over the coming years. It will be interesting to know how they do and whether or not this is a suitable method for restoring damaged coral areas in Hong Kong.

coral volunteers 3

For me, the day was more than just a chance to do something fun and useful. The process of searching the site made me look at corals a lot more closely than I normally would. I had never really noticed ‘young’ corals, for example, or paid much attention to the substrate and its components. Participating in this activity has enriched my understanding of Hong Kong’s coral communities and I’ll definitely take more interest in the hard corals on my local dives now. In the end, perhaps that was the whole point.

Further reading
  • The ERC have published an excellent HK fish ID photo guide book which I often refer to for this blog: (2013) Hong Kong Reef Fish Photo Guide 香港珊瑚魚圖鑑. For more info about the ERC’s activities in Hong Kong, check out their facebook page here.
  • For this post I also referred to AFCD (2005) Field Guide to the Hard Corals of Hong Kong 香港石珊瑚圖鑑. There’s also a small selection of AFCD info about corals here.

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Categories: HK dives, HK marine lifeTags: , , , , , , , , , ,


  1. That’s awesome thing to do. Thanks for sharing your experience, would love to experience it myself someday!

    Liked by 1 person

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