'Green carpet' from the sea
Teh Jen Lee, The New Paper 26 Mar 09;
WHAT comes in with the tide and is green in colour?
Answer: Sea lettuce.
Seasonally, there is an explosive growth or bloom of this seaweed, which is called Ulva. It is so abundant that a thick soft green carpet will blanket the beach.
The National Environment Agency (NEA) has found large patches of sea lettuce in the coastal waters off Pasir Ris. A spokesman for NEA said: 'It is not uncommon to see seaweed growing in our coastal waters. NEA has removed the seaweed on the beach as part of our daily beach cleansing operations.
'NEA has also collected water samples for testing and the tests have shown that the sea water is normal. NEA will continue to monitor the situation.'
Is the sea lettuce edible?
Certain species like Ulva lactuca, Ulva pertusa and Ulva reticulata, can be eaten by humans as a salad or mixed with other vegetables.
But it's not known whether sea lettuce washed up at Pasir Ris is edible.
Some edible forms of seaweed are said to have anti-bacterial properties. They can be used to treat goitre, gout, burns and other irritants.
In some places, sea lettuce is collected or cultivated as animal feed.
On the sea lettuce, the Wild Singapore website writes: 'It can be slippery and conceal rocks and other things that might trip you or poke you. Also, many animals hide under this seaweed. Try not to step on this green carpet.'
Ms Ria Tan, who set up the website and who frequents Singapore's shores, said: 'I've encountered sea lettuce blooms mostly on northern shores which include Pasir Ris, Changi, Pulau Ubin and Chek Jawa.
'It seems to coincide with freshwater input, for example, when there's a lot of rain from the monsoon.
'It's a natural cycle and the seaweed is part of a larger food chain that involves species of fish, crabs, and creatures like that.'
Sea lettuce can grow rapidly in nutrient-rich water because it is only two cells thick.
Compared to most other seaweeds or sea algae, sea lettuce species can better tolerate being exposed during low tide, so it grows near the shore.
According to AlgaeBase, there are more than 120 current Ulva species, but it's very difficult to tell them apart because their features can change with age, reproductive state and environmental factors such as whether they are being eaten up by predators.
Sea lettuce is one of the seaweeds eaten by the green turtle, an endangered species.
More links
Seaweeds are NOT weeds! on the wild shores of singapore blog with more about the marine food chain supported by seaweeds, marine life at Pasir Ris and some other issues that impact this shore.