19 July 2012

Mandai mangroves, giant clams, coral spawning and more

The beautiful Mandai mangroves shows us how we can understand threats to mangroves in Singapore and beyond. We still have Giant clams and efforts are ongoing to conserve them.
Mega Marine Survey along a stream at Mandai mangroves
Ordinary people helping to survey Mandai mangroves
as part of the Mega Marine Survey
Also, studies of coral spawning in Singapore and venomous fishes on Sentosa's recreational beaches. All this and more can be found in the latest issue of the Raffles Bulletin of Zoology which is a Special Memorial Issue Navjot S. Sodhi (1962–2011)

What can we learn from Mandai mangroves? Lots!

From the abstract: Vital for their diverse ecosystem services, Southeast Asian mangroves are the most biodiverse in the world and are critically threatened, yet they remain woefully understudied. A notable exception is Mandai mangrove in Northwest Singapore, a hotspot of research for decades, with an intensive contemporary research agenda. It provides not only a baseline of mangrove research for the region, but exemplifies the threats facing mangroves across Southeast Asia: changing sediments and currents, insect pests, genetic disconnection from other mangrove patches, land reclamation, and future sea level rise. Many of these threats are unique to mangrove ecosystems, but associated data gaps prohibit informed mangrove conservation across the region. Mandai mangrove is one of Southeast Asia’s few mangrove sites with the baseline and contemporary research capable of elucidating these broad threats to the region’s mangrove systems.
Read more in Mandai mangrove, Singapore: Lessons for the conservation of Southeast Asia’s mangroves. D. A. Friess, J. Phelps, R. C. Leong, W. K. Lee, A. K. S. Wee, N. Sivasothi, R. R. Y. Oh and E. L. Webb.  [pdf, 1.84 MB] Also on the wild shores of singapore blog.

Giant clams in Singapore and how to save them

From the abstract: This review presents the history of giant clams (S.F. Tridacninae) in Singapore as derived from artifacts, primary and grey literature, museum collections, and anecdotal evidence. Archaeological finds from the 14th century include giant clam valves of at least two species: Tridacna crocea (Lamarck, 1819) and T. squamosa (Lamarck, 1819). An 1847 publication lists T. gigas (Linnaeus, 1758) in Singapore, a species that is absent from later inventories. Hippopus hippopus (Linnaeus, 1758) and T. maxima (Röding, 1798) also used to be found on the reefs surrounding Singapore’s Southern Islands, bringing the total number of recorded species to five. Early literature describes how inhabitants of 19th century Singapore relied heavily on fishing and collection of shells for food and trade and that this activity was already impacting clam stocks. Exploitation was probably the main cause of giant clam decline until the 1960s when intense coastal development became an additional contributor. Contemporary surveys of 29 reef sites show very low densities of T. crocea and T. squamosa and a complete absence of H. hippopus, T. gigas, and T. maxima. Very little research was conducted on giant clams in Singapore until 1998 when a mariculture project was initiated. This was succeeded by a programme of basic research that produced papers on mariculture, behaviour, shell morphology, reproduction, and conservation; here we present an outline of some of the more important findings. Finally, we discuss conservation strategies designed to ensure that giant clams will not disappear from Singapore’s reefs altogether.
Read more in Giant clams (Mollusca: Bivalvia: Tridacninae) in Singapore: History, research and conservation. M. L. Neo and Peter A. Todd.  [pdf, 1.07 MB]. Also on the wild shores of singapore blog.

Coral spawning in Singapore!

From the abstract: The gametogenic cycle of Platygyra pini was investigated at three sites around Singapore’s southern islands from Mar.2001 to Apr.2002. Equatorial locations, such as Singapore, typically experience moderate annual environmental variation. This has lead to the suggestion that the amplitude of environmental variation at the equator is insufficient to provide reliable cues to synchronise reproduction in marine invertebrates. However, distinct and predictable seasonal patterns of sea surface temperature and rainfall occur in Singapore as a result of the Southeast Asian Monsoon system. Platygyra pini had a seasonal pattern of gametogenesis, with maturation of gametes and spawning occurring predominantly in April. A second, smaller peak in reproductive activity occurred in November suggesting that some colonies also spawn at this time. The major spawning for this species followed a period of rising sea surface temperatures and occurred after the period of heaviest rainfall. While a correlation between environmental fluctuations and spawning timing is not proof of a causal link, these data do indicate that the amplitude of change in environmental parameters such as temperature in Singapore is sufficient to provide a seasonal cue for reproduction and spawning synchrony.

Read more in Reproductive seasonality of the reef building coral Platygyra pini on Singapore’s reefs. James R. Guest, L. M. Chou and Beverly Goh.  [pdf, 6.40 MB].

How many stonefishes are found on Sentosa? And does culling venomous fishes work?

From the abstract: The effectiveness of culling as a method for population control has received much controversy over the last few decades. A five year study investigating the effectiveness of removing venomous fishes along beaches of a popular resort island to provide improved public safety found that six venomous fish families contributed to 44.6% of total fish abundance, and that siganids and plotosids were the most abundant among venomous fishes. Though no strong correlations were found between venomous fish captures and envenomation occurrences, there appeared to be a significant decrease in venomous fish abundances during the fifth and last year of sampling which coincided with decreased envenomation events. It is suggested that the increasing visitorship over the last five years plays an important factor on incidences and that continued surveys will yield greater insight into the effectiveness of this method.

Read more in Controlled culling of venomous marine fishes along Sentosa island beaches: A case study of public safety management in the marine environment of Singapore. Jeffrey T. B. Kwik.  [pdf, 523 KB]

This is just a selection of the many papers found in the latest issue of the Raffles Bulletin of Zoology which is a Special Memorial Issue Navjot S. Sodhi (1962–2011)

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