Living in the shadows
Beneath Tanjung Tuan’s murky seas are coral reefs struggling to survive.
Coral reefs thriving in azure blue waters – that was Tanjung Tuan in Port Dickson, some 30 to 50 years ago.
also known as Cape rachado, it is also called Blue lagoon by the locals and not for nothing – in the 1960s and 70s, its waters were blue. Today, its beach is dirty and its water is turbid.
Studies show that in the mid1970s, the situation took a turn with high sedimentation making the sea turbid. This has affected the coral reefs found there.
Tanjung Tuan and Port Dickson still have coral reefs but the question is this: can they continue to survive or has their threshold been reached? In a recent talk organised by the Malayan Sub aqua Club, coral reef ecologist affendi Yang amri from the Institute of Biological Sciences in Universiti Malaya says the corals are still growing at a constant rate even though there was a 20% loss in coral cover from 1976 to 2014. The percentage of coral cover was 32.9% in 1976 and 11.9% in 2014.
“What marine scientists found recently was that other reef areas in Malaysia have experienced growth declines due to climate change, but not those in Tanjung Tuan. So there could be something unique in the corals there in terms of their resistance level towards climate change.
“In fact, Tanjung Tuan coral species are characterised by their ability to ‘spit out’ sediment through mucus, and their tolerance towards particle deposits. These traits have enabled the reefs to be still viable, though more research is needed to determine what makes them different from reefs elsewhere,” says affendi.
affendi says Port Dickson is one of four sites in the west coast of Peninsular Malaysia which have significant coral reefs. The others are Pulau langkawi, Pulau Payar (off langkawi) and Pulau Pangkor.
The corals in Port Dickson are dominated by the massive type such as the genus. Past surveys show live corals to be confined to shallow waters down to 8m. Beyond that, silt and mud have prevented coral growth.
affendi explains that the sediment is not carried out by sea currents but keeps getting re-suspended. It then buries the corals and cuts off sunlight which they need for photosynthesis.
“Sediments can also increase the coral’s energy output since the corals need to physically get rid of the sediment by producing more mucus and tentacle movements. This also explains why Tanjung Tuan corals are usually full of mucus. as mucus production alone can consume up to 40% of the coral’s energy budget, this interferes with the coral’s normal energy budget needed for its maintenance, growth and reproduction.”
also, sediment-smothered corals will be unable to trap prey and this can eventually cause stress-induced mortality.
Corals are deemed to be stressed if the daily sedimentation rate is above 10mg per sq cm. In 1979, the maximum daily sedimentation rate recorded for Tanjung Tuan was 28.7mg per sq cm. By 2002 it was 46.98mg and in 2007, 90.6mg.
He refers to a 2011 publication which showed the maximum daily sedimentation rate to be 76.83mg per sq cm in Tanjung Tuan. In langkawi it was 49.92mg and in Pulau redang in Terengganu, just 0.54mg.
“What we can infer is that the west coast has higher turbidity and sedimentation rate compared to the east coast, and that corals in Tanjung Tuan are definitely stressed out, though they seem to be more resilient given their stable growth rate,” says affendi.
He contends that the best reefs are likely to be found on the southwest side of Tanjung Tuan, though this remains unconfirmed since no proper scientific survey has been conducted due to the presence of strong currents and whirlpools in the area.
“We hope to rope in more people to help with dive surveys but we lack funding, equipment and qualified personnel.”
The whirlpools appear to be of concern. Some in the audience pointed out that no boatmen will venture near the area. affendi, however, opines that whirlpools are not constantly present and occur only several times through the year.
as a part of Tanjung Tuan has been gazetted as a Fisheries Prohibited area (FPa), it was pointed out that the status could help with reef conservation.
affendi says tropical corals usually spawn twice a year, in the months of april and September. as Malaysia is close to the Equator, there is a high chance that the corals here spawn the same number of times and around the same months.
“While as individuals we can’t do much about the sedimentation, we can aim to minimise the local stresses, like throwing rubbish, stepping on corals and extracting reef organisms. The coral reef situation can only be improved if the area is managed well in line with its FPa status and if visitors put more thought into how their behaviour affect the coral ecosystem,” he says.