Lagoon Blues: A Reef in Double Jeopardy

A plan to create a coral reef in the lagoon at Pulau Hantu, one of Singapore's southern islands, is being mooted. Many might think this idea sound and even attractive from a conservation perspective, but as island hopper Ria Tan has pointed out, there is much more than meets the superficial eye in Pulau Hantu's muddy seabed.

A briefing with the Singapore Underwater Federation is scheduled tonight at the Nature Society of Singapore's office in Geylang, and I hope that the plan's sponsors may reconsider their project in the light of informed discussion about its ecological viability. The following points (with much input from Ria) are likely to be raised.

While superficially a laudable idea, there is widespread concern amongst local marine conservationists that those involved in Project Noah may have overlooked a number of factors which could weigh heavily on the success, or likely failure of the project.

Census of Pulau Hantu: a double take?
The reports note that a biodiversity census would be done along the perimeter of Pulau Hantu. Does this census include the very lagoon where the planned reef is to be created? Divers may assume that there is little of interest in the intertidal zones between the shore and the deeper waters of a reef. However, an above-water survey of the lagoon (especially at low tide) might make it clear that the lagoon itself and the surrounding flats are rich harbours of marine life that form an integral part of Pulau Hantu’s ecosystem.

At present, volunteers from groups such as the Reef Friends are conducting bi-monthly reef checks on all major local reefs, using established scientific methodologies and the advice of marine biologists familiar with local marine life. This data is available online. One wonders how the new census would be different from such existing efforts?

'Building' a reef: at what cost?
Creating a reef in the lagoon implies replacing an established habitat and ecosystem with one that is not guaranteed to survive and thrive. The potential negative impact is doubled when one considers that corals from other areas will have to be removed in order to build the new reef. 

It would be a shame if the reef plan results in the clearing of the existing ecosystem in the lagoon for the sake of a reef that may not even find optimum conditions for growth in the location. The lagoon serves as a natural link between the mangroves at Pulau Hantu Kecil and Pulau Hantu Besar, and the outlying sea wall. According to Ria, the upper reaches of the lagoon are one of the few locations in our Southern Shores (the other is Pulau Semakau) where common seastars are still plentiful. There are also rich beds of seagrasses which provide food and shelter for creatures from sotongs to dugongs. Closer to the sea walls, one can find an incredible abundance of marine life, from giant clams to myriad fishes, crabs and other invertebrates. In short, the lagoon, as it is, is a stunning example of a man-made habitat that is recovering and replenishing its former biodiversity.

Pulau Hantu may not boast the kind of reefs that blossoms with coral colours and darting Nemos, but the lagoon is itself an equally rich and fragile habitat teeming with species. These sites may not offer the picturesque vision of a crystal clear reef that some divers harbour, but why should this perceived ‘lack’ justify an attempt to turn it into a diving ‘hotspot’ at the expense of the present ecosystem?

One can agree that local marine ecosystems deserve greater appreciation of both their amazing richness as well as the threats that face their survival, in particular sedimentation and pollution caused by reclamation and industrial activities. Members of the local diving community are certainly in a prime position to value, speak up and take part in surveys, projects and drives to highlight the plight of Singapore’s dwindling natural shores and even preserve them for future generations.

But it seems a great shame that a natural and flourishing habitat at Pulau Hantu may have to be scraped away for the sake of a plan that remains questionable, for all its initial appeal. Might not we consider a project such as a boardwalk (akin to the one being constructed at Chek Jawa) across the lagoon that would allow non-divers to view the existing seabed and its marine wealth with minimal impact, while divers continue to explore the outer seawalls for living treasures yet to be (re)discovered?

Each marine habitat is unique and deserves to be valued for what it naturally is. Why should a plain of seagrasses be sacrificed for a coral reef? Sadly, even some nature-lovers mistake aesthetic appeal for natural beauty. A beach of white sand, artificially imposed onto our natural muddy shores, is a desert and wasteland with little life. A man-made garden, for all its creativity and gaudy colours, has not the diversity and deep layers of life (many of which remain undiscovered) that mark the rainforest, which many regard as dank and dangerous. And yet rainforests, like coral reefs, are but one habitat out of the many that sustain the chain of life on this planet and ultimately feed our hunger and cleanse our air. Who mourns for the loss of even less glamorous grounds, such as peat swamps, montane forests, mangrove swamps and seasonal savannahs? Would it make a difference in our epicurean society if more people realise that ugly mangrove swamps and muddy shores provide vital shelter for the fish we love to fry and the crabs that we smother with chilli?

Potential impact on the reef flats outside the seawall
We must also consider the potential impact on the reef flats beyond the Hantu seawall. Not every diver realises that in these deeper (though often murkier) waters, there is already a reef as rich as any other. Here, hard corals grow which can be seen at low tide, along with soft corals, anemones and their associated guests the clownfish. These habitats are already coping with heavy sedimentation and the physio-chemical stresses of nearby industrial sites. Would these reef flats be protected from the impact of clearing the lagoon for a brand new reef? Dare I ask: might the sponsors of the reef plan consider that the entire lagoon, from the shores to the outlying reef flat be regarded as a dynamic and multi-faceted superhabitat that showcases our local marine diversity better than a mere reef?

Coral relocation from other reefs to Hantu
The news that corals from “other reefs” would be relocated to Hantu is probably the most disturbing part of the report. Where are these “other reefs”? Are they pristine habitats or reefs that are already struggling to cope with pollution and sedimentation? Would environmental impact assessments be done on these reefs and measures put in place to ensure that these sites are not degraded or damaged by the extraction of their corals?

How are the corals to be selected and transplanted? A natural reef is not merely a collection of corals – it is the result of centuries of colonisation whereby countless other species of plants, animals and microscopic life build up an intricate ecostructure that keeps the habitat in balance. One does not just plant a grove of trees and call it a rainforest. Does the SUF plan to catch coral fish from other reefs to seed Hantu as well?

Even with the greatest care and devilish planning, transplantation does not have a high survival or success rate. Like trees in a rainforest, corals do not exist in a vacuum, but in a larger environment in which they interact, sustain and receive nourishment from a matrix of other species, the dynamics of which are still little known. Given these risks, it is hard to justify damaging existing reefs simply to provide specimens for the 'created' reef at Pulau Hantu. Existing natural reefs as well as other marine habitats need protection and not additional stresses. In the likely worst case scenario where a large proportion of the transplanted specimens perish, it would be a double sacrifice of both these creatures and those who were evicted on their behalf.

There are other questions that need to be raised. The proposal for a sand filtration system to eliminate sediment deserves careful study on its possible impact on the habitat as well as its very viability given the widespread turbidity of the surrounding waters. Who will be the scientific consultants for this project? Will the views of experienced marine biologists and ecologists be sought and deemed equal to experts in marine engineering and hydrology who may give weight only to the structural and chemical soundness of the project?

In short, the many individuals who study, explore and cherish Pulau Hantu's natural heritage in its totality have good reason to question the ecological basis and eventual sustainability of this reef project. An open and informed public discussion about its merits (or otherwise) would be desirable, lest a plan conceived with the best of intentions suffer the ignominy of failure for want of clearer thinking and ecological foresight. If such were to be the case, both the reefs and all those who root for them would be the losers.

Comments

[Edwin Poh]

Good write up indeed. I learnt more about our fragile marine environment today!

[Hai~Ren]

Nice write-up. I recall at this point in time that corals do actually wage warfare against one another, stinging each other until they withdraw into their own little spaces; I wonder if the relocation plans have taken this into account.

[budak]

Attenborough's Blue Planet series has an episode showing this gory coralistic competition. But somehow I doubt the folks behind this project have as good a grasp of the island's marine ecology and true biodiversity as the people behind the Hantu Blog and the Blue Water Volunteers. The SUF seems to have the notion that a shallow lagoon can be turned into a flourishing crystal clear reef just by throwing in corals from other reefs and adding a filter ala a reef aquarium.

[knightofpentacles]

I do not know anything about marine ecology.

However I fear that the results by the Singapore Environment Council to "preserve" the reef ecology will be not every different from what resulted in URA's attempt to "preserve" cultural heritage by the redevelopment of the Bugis/Chinatown area.

[Jeff]

Coral competition is not very weel know, and may not always be chemical in nature. Another strategy is to just overwhelm the competition by overgrowing them. Acropoa (Staghorn)corals can do this quite fast, which is why some reefs are dominated by such corals. However, these Acropora corals are (usually) impacted by sediment and low light conditions.

Certainly, coral reef biology is a complex ... there are hundreds, if not thousands, of interactions that are unknown.

Cheers, Jeff