Sunlight is vital for mangrove seedlings: Yale-NUS study

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SINGAPORE — Mangroves are coastguards that can protect an area from sea level rise, but only a small proportion of seedlings transplanted to an area survive.

However, the results of new research led by Yale-NUS College scientists could help increase the success rate of such transplants.

On March 31st, the team led by Associate Professor Michiel van Breugel and Professor Taylor Sloey, who has since left the College, published the results of a study on the various factors that can affect the survival of mangrove seedlings in the journal Restoration Ecology.

By monitoring the environmental conditions of more than 900 naturally established mangrove seedlings in Pulau Ubin, the team found that light is the strongest factor predicting the seedlings’ survival once established.

A seedling is considered established when it can produce new shoots such as new leaves.

Prof van Breugel said: “In many mangrove studies, it is often assumed that hydrology is the main limiting variable for seedling survival.”

The hydrology of the area describes, among other things, the level, frequency, duration and type of flooding in an area.

He said, “This makes sense because mangroves live in areas that are often inundated by seawater at high tide.”

At high tide, the roots of these mangrove seedlings are deprived of oxygen. While suffering from a lack of oxygen, the seedlings also have the extra work of excreting salt from their bodies.

This is an energy-intensive process for the seedlings, which can lead to death, Prof van Breugel said.

Under these harsh conditions, less than 50 percent of all naturally established seedlings studied by the team survived after six months.

After another six months, less than 20 percent of them remained standing.

However, the team found that the surviving seedlings had higher mean sunshine than those that died.

Prof. van Breugel said: “A lot of light is required to maintain all the physiological machinery in its roots and to survive under such stressful conditions.”

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