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Thailand snorkeling: Phang Nga Bay National Park snorkeling tours
Thailand still offers some amazing snorkeling opportunities. Despite many areas being damaged by anchors, the coral around some of the more southern islands is in very good shape. We know many secret spots where we've never seen others snorkeling. Our Phang Nga Bay trip is especially good for off-the-beaten-path underwater exploration. The mass tourism operators all go to a few selected places to snorkel. That leaves very large areas of unexplored reefs all to us.
specializes in snorkeling where other tour companies don't go.
We have located several coral reefs in the bay that are in remarkably
good condition, with a very impressive variety of marine life.
(below) are the most common fish families.
The Coral Reef System
If you have never had the opportunity to view the coral reefs of Thailand, you have missed a world of mystery and wonder. Over 200 species, belonging to 75 genera, have been recorded in the waters around Phuket alone. 60 species have so far been noted in the gulf of Thailand. There are literally thousands of other inhabitants in, on and around the reefs. Thus the first feelings that one gets of a coral reef is that it is pure chaos. It appears to be evolution gone wild, a madhouse of colors, shapes and patterns. The fact is however, that there is organization to all of this. Just as the mangrove forest and its many inhabitants rely on each other, so do the inhabitants of the reefs.
Corals are hollow-gutted flower-like animals with hard exoskeletons into which they can retreat when threatened. They could also be described as tentacles at the top of a tube-like body. The polyps (the actual tentacled coral animals) are attached to the hard mass of the reef by basal disks. The corals are protected by the cup-like cells of calcium carbonate (the actual "rock" which makes up the reef) which they secrete and which over time are deposited one atop the other to build up the reef. The reef may be hundreds of meters thick. The living colony itself, however, is only a thin skin of polyps growing on the matrix of the dead substratum (the calcium carbonate which lie beneath and supports further growth -- the foundation).
An interdependent system
The well-being of the coral reef as a whole depends upon the
well being of the wide range of different organisms. These organisms
in turn are sustained by the reef itself. The entire reef can be interpreted
as a mass of interdependent creatures. We normally think of the hard
coral as one animal, but in reality it is a colony of mutually dependent
organisms. For example, through a network of connecting stomach extensions,
food is shared out all over the colony, with each polyp both contributing
to and sharing in the general welfare. The reef itself then, can be
thought of as a whole creature with its own ways of capturing food
and creating a suitable environment for future generations of inhabitants.
Reproduction & Growth
may sexually reproduce continuously or once a year. Some may only
spawn during the lunar period. Fertilized eggs develop into the free-swimming
plankton called planula larvae. With further development, the larvae
settle, attach to the bottom and change into young adults with 6 tentacles
and a basal disc for attaching to the substrate.
there are many exceptions, most corals feed at night and contract
during the day. Corals feed like sea anemones. The prey size ranges
from small fish down to small zooplankton, depending on the size of
the polyps. Corals continuously feed at night in correspondence to
the vertical migration of plankton. Digestion is rapid. Corals store
their food in the form of fat and glycogen. Armed with stinging cells,
or nematocysts (spring-loaded capsules containing harpoon-shaped barbs
on filaments), the tentacles are employed first to trap, incapacitate,
and finally convey zooplankton to the mouth. Fish dart in to feed
on the exposed polyps when the polyps are feeding on the plankton.
Each polyp is able to communicate with neighboring polyps. This can be seen by touching one polyp in a coral colony, and watching its neighboring polyps contract. This may reflect an interconnecting nerve network within the coral colony.
Various colors appear in coral. This is due to the intensity of the light in the coral reef. Sometimes, corals of the same species differ in color. If you dive deep enough, beyond the range where there is enough light to support photosynthesis, you cease to find living hard corals. The greatest depth at which coral growth can take place is 150 meters. The upper seaward slopes are usually the most productive parts of the system, with most of the basic food production and deposition of the limestone skeleton taking place here. Bytheway, as an interesting little side note, red reef fish are camouflage at night.
Mangrove's role in reef preservation
Corals are acutely sensitive to changes in their environment. Mangrove destruction for charcoal or building material adds sediment to the waters. Coral is extremely sensitive to sediment. Mangrove forests collect the sediments in the water. Scientists are just now beginning to realize how the mangroves do this. They have come to realize that the flood tide (incoming or rising) brings in the sediment. The mangled roots of the trees create areas of water turbulence. The sediment comes in on the rising tide and the sediment is trapped. The settled sediment is not re-entrained at ebb (outgoing or falling) because the high vegetation density (mangled root systems) inhibits currents which are too sluggish to erode the sediment. In other words, the sediment comes in with the tide, is trapped in the root systems, but the ebbing tide is not capable of taking all of the sediment back out to sea. Thus the mangrove forest is an important part of the coral reef by ways of sediment entrapment. Furthermore, the removal of mangrove trees increases the amount of sediment in the sea. All of the sediment that has been trapped by the mangrove in forming the mudflats is then washed into the sea. If you want to see the pretty coral and obtain food from the seas, then protect the mangroves.
An Ending... or the Chance for a New Beginning?
The reef is an amazing
of living organisms. Each creature has its place and, as we saw, corals
actually act for the betterment of the entire by sharing food and
contributing to the growth of the reef itself. There is however, one
creature which is capable of destroying this underwater wonderland
-- humans. Much of what was once a virgin underwater jungle has been
exploited to the point of nearly complete destruction. Longtail boats
take tourist to beautiful beaches then drop their anchor directly
on the coral. Souvenir collecting tourists then forage for goodies
to take home. Run-off from hotels disperse tons of chemicals and waste
into reefs. Various damaging fishing methods such as dynamiting and
poisoning have destroyed more than just the fish population. Vast
areas of brightly colored coral have all but disappeared from many
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