learn only 3 things about them ...
is only two cells thick so it grows rapidly when the water
has lots of nutrients.
stepping on the green carpet of sea lettuce. It's slippery
and animals live among the seaweeds.
eat or not? Yes you can if you're a pig. It used to be
fed to pigs.
seen? Sea lettuce looks just like its namesake land plant.
Seasonally, there is an explosive growth or 'bloom' of this seaweed.
It is then so abundant that a thick soft 'green carpet' of washed
up sea lettuce blankets the high shores. Be careful! The seaweeds
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'.
Features: A thin blade
which is only two cells thick! This allows sea lettuce to grow rapidly
in nutrient-rich water as it has a high surface to volume ratio. Compared
to most other seaweeds, sea lettuce species can better tolerate being
exposed during low tide. So it grows near the shore. The blade is
attached with a small holdfast, usually embedded in the sand or attached
to a hard surface. During a 'bloom', large amounts can float freely
and blanket a large stretch of the shore. Usually bright green, sometimes
with a yellowish tint.
Which Ulva? According to
there are more than 120 current Ulva species. Species used
to be determined by the structure of the blade, cells and other tiny
features. However, recent studies show that these can change with
age, reproductive state and environmental factors including being
chewed upon by predators. So it's really tricky trying to determine
species of Ulva.
Some form sheets that are flat, thin and translucent, glossy and smooth.
Usually entire without many holes. The edges are sometimes ruffled.
Can grow to 10cm wide or more. Usually bright green.
Some form flat strips, thin and translucent, glossy and smooth with
many holes. Often crinkled into twists, the strips are narrow (1-
2cm wide) and may be 20cm or longer.
Smell of the sea: When the shores
are covered with sea lettuce, you can smell the distinctive aroma
of seaweed gently toasting in the sun. This is truly the smell of
Sea lettuce babies: Sometimes,
you might come across a sea lettuce blade that is white or transparent.
This could be because the sea lettuce has become fertile and converted
some of its cells into reproductive cells and released these cells.
Often, this happens along the edge of the blade.
Role in the habitat: Sea lettuce
is one of the seaweeds eaten by the Green turtle (Chelonia mydas),
as well as other creatures. The dense tangle of seaweed also provides
plenty of hiding places for the small animals that live in the seagrass
Human uses: Sea lettuce is fed
to pigs and livestock. In the past, they were collected in boatloads
in the Straits of Johor, washed in freshwater then cooked and fed
to pigs. Sea lettuce is cultivated for animal feed in some places.
In some places, it is also eaten by humans, as a salad or mixed with
other vegetables. The species that are used commercially include U.
lactuca, U. pertusa and U. reticulata.
It is also reported to have antibacterial properties, and to be used
to treat goiter, gout, scrofula, burns and other irritants. Sea lettuce
also makes good packing material to cover more valuable Caulerpa
seaweeds during shipping and transport, or to cover fish for sale.
As sea lettuce tends to grow well in polluted waters, it is also used
as an indicator of water quality.
form a thick
green carpet on shores.
Chek Jawa, Jan
Labrador, Mar 05
Labrador, May 05
sea urchin in sea lettuce.
Changi, Jul 08
camouflaged on sea lettuce.
Changi, Apr 05
Some form sheets.
Others are ribbon-like.
lettuce on Singapore shores
are difficult to positively identify without close examination of internal
parts. On this website, they are grouped by external features for convenience
species recorded for Singapore
Pham, M. N.,
H. T. W. Tan, S. Mitrovic & H. H. T. Yeo, 2011. A Checklist of
the Algae of Singapore.
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N., H. T. W. Tan, S. Mitrovic & H. H. T. Yeo, 2011. A
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Museum of Biodiversity Research, National University of Singapore,
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Plants of Australia
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C. Jr., 1997. Field
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Bookmark, Inc., the Philippines. 306 pp.
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