2019.01.04
Chou Loke Ming, Research Professor at the Tropical Marine Science Institute, National University of Singapore
Ladies and gentlemen, today I will focus on a narrow issue - the reef restoration. But what I try to bring up is that the conditions of coral reefs are very challenging. And urbanization is one very challenging aspect of this. So, what is the significance of reef restoration under such changing conditions? If you are dealing with an environment that is constantly changing, and the question is always: is it worth doing this? I will focus on Singapore itself and the urbanization challenges it is facing.
Chou Loke Ming
As we all know, Singapore’s coastal urbanization, of course, is
based on the reef habitat, and what happens is that the environment keeps
changing. It is just a simple change, but it is a very drastic transformation.
Physical transformation of the environment is so huge that a lot of the natural
habitats get wiped out. And in its place you have this hard structure which
does not encourage growth of natural ecosystem. And this is because of the land
reclamation that Singapore environmental shape has changed. As a result, a lot of the coastal resources have already been demolished. The
impact that we have seen happening on the reefs is that you get a lot of
sedimentation, and what happens is that the growth zone of the corals starts to
get compressed because of insufficient sunlight for lower layer of reef. And,
the substrate is also unstable because of the sediment that has settled down.
Instead of a hard structure, it is now becoming a soft bottom. What has
happened to the environment is that the water visibility has really dropped. It
used to be very clear before. But now it is only about two to three meters of
visibility. Sedimentation is high, and the water is misty all the time.
So under such conditions the management question will be whether the protection is necessary and whether restoration is relevant, seeing that this is a very big challenge. The answer is “yes”, because despite all the damages we have made in the past fifty years and the three periods of bleaching events that the reefs have gone through, there is still a high biodiversity corals, including reef species. These are global events. If reefs were affected for a long time, they would somehow affect us in return. Reefs will have an annual mass spawning during April and other reefs will be self-recruiting because of lava flow, so we do not depend on reefs outside of Singapore for the recruits. It makes a lot of sense, to think about restoration and how to prevent the reefs from diminishing.
Under such conditions of high sediment and unstable substrates, what kind of reef restoration works should we do?
Well, one is to establish coral nursery, some platforms that are raised above the bottom. And on the top would be some mesh netting, which would allow the sediments to fall through so that they do not accumulate around the base that collects coral. Mesh netting can collect small nursery fragments, and the fragments can provide nurtures to the coral. These conditions are good for the development of corals. There would be larvae like this, larvae that have already settled onto rocks.
Another way is to set rubber pieces lying on the floor. And if you take the rubber pieces and stabilize them on the nursery, it will allow a better survival of these recruits. And they can go to a much larger size when you can transfer them onto the reef. This process will not cause the death of corals. And these experiments with the nursery show that if you raise corals on the fragments of nurseries for about six months or so, then they can live longer than those who were taken from the broken reef and transferred to other reefs. And this can ease the pressure on two important corals. So the work still goes on. Most of the other species adapt to the same forms. And then for the unstable substrate where there is just a coating of sediment salt, then you just have to provide something that offers much help, a hard structure for recruits. So we make use of this fiberglass module, which is easy to be transferred, and put it on to the greater part of the reef, then we can have coral community. For the reefs have a sloping surface, so no sediment would accumulate on the surface, allowing the recruits to settle on and grow. But what I need to emphasize is that when you do reverse creation, the long-term monitoring is very important. The process is following: get the project funding first, do a reverse relation, then two years later, put up the results.
All the short-term projects can just tell you the early response of the restoration activities. We followed these fiberglass molecules programs up after about ten years, and then we went back and monitored them. We found that they have developed much better. You have a much greater diversity of corals there. They are all self-recruited. Also, the diversity was not just for corals but also happened in other reef-related species. In fact, they have positive impact on the substrate and they do contribute to ecosystem. After the colonies that have settled on them and grown on the reefs are sexually mature, they can attract many other reef associate cross-species - they go there for the food as well as for habitat.
One of the important things that we wanted to find out is that when
you do this transplantation, you move the corals to a new place, and then how
do you retain the genetic diversity? And we found that if you move about less
than half of the population of that species to a new place, you can actually
retain more than eighty percent of the biodiversity. And there is a difference
between the homosexual species and bisexual species. A lot more researches are
being done on this so we can answer the management question. We do not have to
move the entire coral, we should have a more efficient method.
So now, I would like to say the other challenge in front of us. When we talk about reef restoration it is not just about restoration but creation of reef communities - areas that we have not seen reefs before. So how do we create the communities in non-reef areas? If you look at the four pictures here -- each is one of the species of coral Acropora, full of vitality and very nice, but they are actually grown on one of these nursery tables. We have put fragments onto this nursery table one meter by one meter, and they are almost 3.5 inches. This allows us to create reef communities in bare sandy areas.
Another place that we should look at would be sea walls because
sixty percent of Singapore’s coastline is already surrounded by sea walls. We
look at opportunities of how to make these sea walls more receptive of coral
reef restoration. That is natural colonization of corals, especially in
subtidal areas. But interventions are necessary to increase the diversity,
especially in the intertidal zone. And for the subtidal zone, you can also look
into assisted colonization. And this is way we move transplants on to the
subtidal zone, which would help the reestablishment of the reef community in
such areas. And also there are lots of other things that we should pay
attention to, for example, a lot of the sea walls are sort of vertical --
straight down, and by swapping them, you can increase the surface area of a sea
wall that can be colonized. Another thing is that even if you do just one
stepped terrace, that will increase that space for coral colonization. It would
be better if you do this when you have intertidal pools, so that at high tide,
they will be filled up as tide goes down, and they still can retain water. And
this is the way we are trying to do research. We tried to make full use of sea
walls, so as to push the development of coral communities.
Therefore, we need the restoration, instead of just rehabilitation. I think that we have to look more at how to create reef communities. Restoration is necessary. It helps to mitigate urbanization and climate change. Conventional approach is to restore degraded reefs. But I think we should create new reefs, new areas of reefs, so that we can increase areas of coral reefs. The habitats can be protected for handling climate change. But it has to be a multidisciplinary approach. We need to look at innovative ecological engineering. There are lots of things that we can think about whether we like it or not, for example, developing sea walls for defence against the rising sea level. So if you are going to raise your sea walls for defence, you need to do something that can also retain or enhance marine resources. Thank you very much.