| |
Coin
seaweed
Halimeda sp.
Family Halimedaceae |
|
| |
The
seaweed grows in shallow waters and sand flats, usually together with
seagrasses and other seaweed. On Chek Jawa, it is more commonly seen
in the coral rubble area, especially on the sand bar that circles
the coral rubble area.
Hard Stuff: This seaweed is also
called the 'money seaweed' and looks somewhat like strings of coins.
Each roundish 'coin' or segment is hard because it is impregnated
with calcium carbonate. This probably helps to make the plant less
tasty to herbivores. The segments are connected to each other with
a more flexible, uncalcified joint. Each plant has a few branches
of these joined segments. The whole plant is anchored to the ground
with a bulbous end that is often buried deep in the sand or clings
to almost any surface. In some species, the segments may be more fan-shaped.
Green Coins: The Coin seaweed
grows by adding new segments. A new segment starts off as a small
white bump that is toxic and lacking in chloroplasts (the green substance
that is used in photosynthesis). The new segment can grow quickly.
Only when it reaches full size are chloroplasts sent into the segment.
In fact, Halimeda seaweeds move their chloroplasts around every
day. At sunset, the chloroplasts are withdrawn deep into the calcium
skeleton and the plant turns pale. The choloroplasts are pumped back
out at sunrise.
Making Money: A segment that breaks
off will quickly produce root-like structures to grip the surface
and begin to grow into a new plant. This seaweed can also reproduce
by releasing male and female reproductive cells into the water. Halimeda
of the same species often do this in synchrony. After this happens,
the whole plant dies.
Role in the habitat: When a Halimeda
seaweed dies, as the tissues disintegrate, fine white calcium carbonate
particles are released. The white sandy beaches of some coral atolls
may be made up mostly of Halimeda remains! In some other places,
sand dollars eat disintegrating Halimeda segments. Halimeda
toxins don't deter some sea slugs that not only eat the plant
but also use the toxins to protect themselves and their eggs.
Human uses: This seaweed is reported
to have antifungal and antibacterial properties. It is also used as
fertiliser to counteract acidic soils. |
|
Coin
seaweed may appear white at night |
|
quick
facts
Each 'coin' segment about
1-2cm in diameter, common in the coral rubble area |
