Merbok and Matang Mangrove Ecology

Posted on April 3rd, 2014 by

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Riding on the boat

We had the opportunity to visit Sungai Merbok and Sungai Sepetang to study the mangrove ecosystem for our tropical ecology class. Mangroves are unique trees because they are adapted to live in saline conditions, as well as with changing tidal levels. They have unique root adaptations that will stabilize them in the soil and also allow for gas exchange. Mangroves are also prime habitat for fish, crabs, prawns, and other animals, because of the availability of shelter. When we arrived at the field site on the Merbok River, we took a boat (it was high tide) to observe the root systems from a distance, and to observe the wildlife of the river. In a series of ten traps, we caught a huge Tiger prawn, ikan gerut-gerut (a fish used in local dishes), juvenile jellyfish, and two horseshoe crabs. Along the river, there are many sustainable floating fisheries, and we stopped at one to feed the fish.

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Knee roots come out of the ground a few inches, are rounded, and give the tree lateral stability as well as stabilizing the silt around the tree.

A second trip later in the afternoon was specifically for exploring the mangrove habitat, because the tide was low. At the first site we visited, there were many knee roots and a few buttress roots, which indicate the particular species of tree. There were small Grapsid crabs everywhere over the silt, and we observed a few other crab species as well, like a Fiddler crab. Getting on and off the boat was an adventure in itself, with no official dock and knee-deep mud on the river banks, but we made it to the second site, which was populated by mangroves of family Rhizophora, as indicated by their stilt roots. In observing the mangroves up close, it felt like we were in a National Geographic spread about exotic, tropical places, and it was amazing to experience them first-hand. Our last stop of the afternoon was at a mangrove replanting site, where the government had clear cut a section of mangroves, and we each got to try planting mangrove seedlings. Because the muddy silt was soft enough, all you had to do was find a big stick, stand it firmly in the ground, and make wide circles to create a hole for the mangrove seedling. Mangroves can be harvested for charcoal (we visited a kiln on our way to Matang), and are also clear cut to establish aquaculture ponds. As Malaysia becomes more developed and more industrialized, it will be interesting to see how this effects mangrove conservation.

It was huge! Almost 10 inches long!

The Tiger prawn was huge! Almost 10 inches long!

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Juvenile jellyfish don’t have tentacles yet, so we could hold them.

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Horseshoe crabs: compare with the size the shoe!

After meeting with the locals at Kampung Sungai Bujang and attending a traditional Malay wedding, we drove south to Perak to see synchronized fireflies on the Sepetang River. The mangroves in this area is the best conserved site in Malaysia, and it has been under protection for many years. I’ve never seen a firefly before, so it was amazing to see so many fireflies at once! They live in a colony, usually in one or two trees. The male fireflies have synchronized flashes to attract the females. From the boat, it looked like dimmer, flashing Christmas lights. We talked about these later in class. The particular species of firefly (actually a beetle, pteroptyx tener) likes to colonize in a particular species of mangrove (sonnaratia caseolaris), which is another reason why habitat conservation is essential for so many species.

 

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