wetlands
a publication of Sungei Buloh Nature Park

Vol 8 No 3
Dec 2001


chek jawa's
wet wonderland

aqua-tion for life roles of
water in life

where water
meets the lands
fishes of the Park

dispersal by h2o
seeds dispersed by water

some interesting notes on the pacific golden plover

10th international coastal cleanup 2001 and 5th mangrove cleanup

young ecologists@
sungei buloh nature park

an ode to a turtle
 
dispersal
by H2O
ali ibrahim
conservation officer

Walking along the beach especially after high tide can be a learning experience if you were to ponder upon what the eye can spot—fruits, seeds and even seedlings adrift amongst the flotsam and jetsam. Have you ever wondered: "Has this been going on for millions of years?" "Where did this living assortment come from?" and "How did they arrive?" It was Sir Isaac Newton who once said: "I don't know what I may seem to the world, but, as to myself, I seem to have been only like a boy playing on the sea shore, and diverting myself in new and then finding a smoother pebble or a prettier shell than ordinary..." (continued below)

Yes, this regenerative cycle through dispersal has been going on since the dawn of time. These botanical gems on the beach originated not only from our own shores but from the neighbouring archipelago and even ocean-drifted ones. Let's take a look at the amazing mechanism involved.

Besides mangroves, water-dispersed vegetation is confined to the fringes of beaches and inland watercourses. With sufficient buoyancy and a long period of impermeability to water, their propagules can drift as far and no farther than is necessary to stay viable. The classic example is the coconut (Cocos nucifera) which can keep it afloat because its thick fibrous husk contains air. The fruit will travel a long distance, eventually ending up as a sprouted palm on some coast months later.



Api-api bulu
Avicennia rumphiana


Api-api ludat
Avicennia officinalis


Api-api putih
Avicennia alba


Bakau putih
Bruguiera cylindrica


Bakau minyak
Rhizophora apiculata


Bakau kurap
Rhizophora mucronata


Pong-pong
Cerbera odollam
The buoyant propagules of all mangroves are adapted to dispersal by water currents. This period of floating may be as brief as four days, but much longer periods are more usual. The mangrove species belonging to the family of Rhizophoraceae have spongy hypocotyls with air-filled walls to make it light-weight. Seedlings contained in the fruits of Api-api (Avicennia) have dense, fibrous air-filled rootlets that keep themselves water-borne for a period of time. Leathery fruits of Perepat, Berembang and Gedabu (Sonneratia) with persistent calyces are enclosed by water impermeable walls. In addition, within the fleshy pulp their floatable seeds are protected by resistant seed coats.

For any dispersed seedlings to get established, they have to find suitable substrates to grow in and be able to withstand wave action. With other seedlings, they simply develop right on the spot where they drop, within the ambit of their parent trees.

The term 'viviparous' is used to indicate the precocious germination and growth of the embryo while it is still enclosed by the fruit wall and while the fruit is still attached to the mother tree. This is an adaptation to ensure the seedling's higher chances of survival prior to its dispersal and precarious establishment in soft mud and tidal inundation. It is not surprising that in some instances, even wind-dispersed fruits and seeds can be aided by water agent through the principle of flotation.

Amongst the colourful tapestry of living archive on the beach mentioned earlier were the curious but almost similar looking fibrous drupes of the Nipah (Nypa fruticans) and the Sea Screw-pine (Pandanus tectorius). Fruits of Pong-pong (Cerbera odollam) having lost their red peel appeared like worn-out tennis balls. The almond-shaped fruits with lateral ridges belonging to the Ketapang (Terminalia catappa) are green to maroon when fresh but turning brown and woody when aged. The chocolate-brown and smooth Dungun (Heritiera littoralis) fruit actually looked like the hull of a boat with a small keel. The squarish turnip-looking fruit of Putat laut (Barringtonia asiatica) seemed most bizarre when compared to the rest of the scattered fruits. Finally, the community of angular and corky seeds of Nyireh (Xylocarpus granatum) were another odd puzzle when seen with several pieces of thern side by side.

Needless to say, the list goes further! But for the purpose of this article, only plants belonging to either the mangrove or beach habitats were mentioned.

Nyreh
Xylocarpus granatum


Ketapang
Terminalia catappa


Dungun
Heritiera
littoralis



Perepat
Sonneratia alba


Berembang
Sonneratia caseolaris


Putat laut
Barringtonia asiatica



Nipah
Nypa fruticans



Screw-pine
Pandanus
tectorius

(continued from above) ".... whilst the great ocean of truth lay all undiscovered before me." (Newton)
   
© Sungei Buloh Nature Park