Mangrove Swamp

Mangrove is now less seen in Singapore and they have been slowly extinct and maybe they will be gone forever. So, now, we shall try to keep the mangrove in good condition and protect our natural environment.

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Welcome to our IPW mangrove swamp blog by hai sing catholic school students. We would like a comment from you because we can know what good or bad points we had done and if it is a bad comment about us, we will try to change and show the best of us.

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about us

Name- Chan Wee Hong Alvin
Role- Leader
Age- 14
Class- 2E1
Hobbies- Playing computer games and swimming
Email- frozen-arctic@hotmail.com

Name- Thio Chong Jing Cyrus
Role- Co-Researcher and secretary
Age- 13
Class- 2E4
Hobbies- Playing computer games and soccer
Email- cyrusthio@hotmail.com

Name- Chuan Jia Xuan Jeremy
Role- Co Researcher and Assistant leader
Age-14
Class-2E1
Hobbies- Basketball and playing computer games
Email- jcjiaxuan@hotmail.com

Name- Ng Shiuan Jun
Role- Main Researcher
Age- 13
Class- 2E1
Hobbies- Gaming and reading of science books
Email- chaos_killerz@hotmail.com

Name-Quek Hui Juan Emily
Role- Treasurer and Co-researcher
Age- 13
Class- 2E1
Hobbies- Going out with friends and reading
Email- emily_qhj@hotmail.com

[ Jun 6, 2008 ]

14:06

RESEARCH ON THE HISTORY OF MANGROVE

Around 3 years ago, marine researchers in North Queensland discovered ancient mangrove forests crushed and entombed beneath the Great Barrier Reef. After examining those mangroves in their lab, this mangrove forest is found to be 9,000 years old! These mangroves that they have unearthed are said to be from old river channels that were swamped when sea levels rose after the last ice age. Thus it was decided that if the sea level rise happened very fast long ago, it could even be faster after a drastic change in sea level due to climatic change. The mangroves unearthed were quite intact as didn't even have enough time to fully decompose when it was buried, so the marine researchers that discovered these mangroves were able to examine and run test on it.

Based on studies of the mangroves fossils, with evidence from the fossils combined with research from the mangroves we have now, it was suggested that mangroves communities evolved during the Cretaceous which is known as tertiary extinction event which means a large-scale mass extinction of animal and plant species in a short period of time.

These mangroves communities evolved around the border of the Australian and New Gu

inean landmasses, spreading throughout Southeast Asia and the Indian region into the Atlantic through the Mediterranean basin. Thus, the conclusion is this, the centre of origin of mangrove communities are most likely to be the area of Australia and New Guinea.

The distribution of the variety of species of mangroves around the Australian coastline shows that the largest number of species appears at the northern and north-eastern coast. This reason why the diversity of mangrove species and plants in the north-eastern area of Australia is high may be divided into three main factors.

The first factor is that region was one of the centres of origin of mangroves and the point of their dispersal into and out of Australia to its land connections with south-eastern Asia during the various changes in the sea level of the coast. Because of this, it also explains why Australia has other beautiful types of flora.

The second factor is the climatic change of that region is similar to which mangrove vegetation

first developed and consequently, little or no loss of species has even occurred in that area. Scientist have argued that the north-eastern coastline provides refuges for the diverse Australian mangrove flora as it flows northwards with the sea. Thus these north-eastern mangrove forests can be regarded as relics maintained by suitable climatic changes.

The third and last factor is the coastline arrangement in that region, with it numerous sections of a river meeting the sea generally sheltered by the offshore of the Great Barrier Reef, provides large areas of low-energy coastline suitable for mangrove growth and development and because of its climatic suitability, providing a stable area for climate changes during periods when climatic conditions were not favorable.

Research on ancient mangroves

Mangroves have been researched on intensively for many years for it displays amazing effects that affects our world drastically. Now that most mangroves have been discovered around the surface and also studied for many years, mangrove has been quite a dead subject for quite a while. But since the discovery of new mangroves buried or entombed beneath seas or land, scientist has again tried to start anew on this subject and tried to find what has happened a few centuries ago through the topic of mangroves. By so doing they need to compare the now modern mangroves and the ancient mangroves that has been just uncovered.

Mangroves are the interface between the sea and the land. They act as the absorbers of

disasters like severe tide, tsunami or a cyclone. They could withstand the hit of a tsunami because of their wide system of roots and also live in high tide for their roots could reach up high. In the sub-surface, the roots of the typical vegetation of the mangroves perform as a balance between the saline water of the sea and fresh water of the ground. Thus mangrove benefits us in many ways we do not expect. The growth of the mangrove depends upon the number of times and duration of flooding, the nature of soil and the degree of mixture of saline and freshwater at the mouth of the river. These four factors affect most on the growth of a mangrove and thus also affect its survival.

Other than the discovery of extremely old and some decomposing mangroves buried and

entombed beneath the Great Barrier Reef. More discoveries were made at Sunderban of West Bengal. Material evidence from the drill core samples taken from the ground around the area confirms the presence of ancient mangroves 30 to 50 meters below the now present Sunderban. The Ganga – Brahmputra River’s delta is covered by Quaternary sediments. The Quaternary period is the last chapter of the earth’s history spanning about 1.81 million years. A wide area of west Bengal delta at sites thought most susceptible for team which was sent there. They punctured ten boreholes along rising sea-level and land subsidence.

Depending upon the capability of the mangroves there to survive in the brackish waters of the tidal zone and at comparatively higher elevations where salinity is much less, the mangrove habitats are grouped in to two categories, and that is the core mangrove and the back mangrove. The back mangrove is intolerant of the salinity hence it cannot thrive in parts of the delta lashed by the tides where salinity in the water is high. The drill core samples that were taken revealed the presence of ten bio-zones with layers of peat at varying depths typical of mangrove vegetation. Out of these, the lowest two were dated as pre-Holocene which means older than 10,000 years before present and the remaining eight were of the Holocene period. (Holocene means approximately the previous ten thousand years)

The information obtained from the bio-zones is of immense use for obtaining proxy records of

the past climates. It appears that while the northern latitudes of Europe were freezing, the lower Ganga delta remained unaffected by the harsh and freezing climatic changes. Instead through research and the information gathered points towards a tropical wet-humid climate for the region. Because of the presence of something called ‘Kankar’ in the samples points to the in-between of long and dry summers too.

Transgression and regression of the sea is a normal natural phenomenon that occurs rarely. Radiocarbon dating of the sediments of drill cores indicates that since 9000 years before the

present now, the sea has transgressed thrice. Rise of the sea level during transgression causes extensive flooding. The sea level rise during the second transgression 7500 to 7000 years before the present now was much higher than the other two. Evidences show that during this period coastal land was subsiding at a rate of 0.5cm per year. The last transgression 7000 years before present to 6100 years before present recorded a low rise of sea level. This was the period when the growth of the mangrove was at its highest peak. Rich foliage of mangroves finally starts to rot to form a layer of peat. During this period, peat was again formed in the Sunderban mangrove region. Radiocarbon dates have indicated that the sea level in the Ganga delta has never risen beyond the present in the last 6000 years.

The pre-Holocene mangrove that is now buried in deep is also found to be below or overlain with microfossils of marine organisms. These microfossils indicate that there might be a high

possibility that there are more older and ancient mangroves further under the sea. This swamp found at depths of 30 to 50 meters at Diamond Harbor in South Bengal indicates the sudden uplift of coasts. This caused a change in gradient of the stream and slowed the collection of sediments and helped in development and production of yet another mangrove presently buried. Natural phenomenon like sea level changes and vertical displacement of the coast can spell doom for the coasts. World over the coasts at present are subsiding. Combined with impact of global warming, extensive flooding of coastal land can not be ruled out.

Many old Sunderbans lie buried under the present Sunderban like many other countries except that this is an old and ancient mangrove buried beneath the current Sunderban. Anthropogenic

intervention in the nature’s own way of maintaining a balance between land subsidence and the rise of sea level can produce unexpected lethal effects on west Bengal delta. Subsidence and tilting of land along the delta causes increased salinity in the water on the ground. Human inhabitation of mangroves aids in the increase of the salinity levels, which ultimately leads to further reduction of land.

Studies have shown that due to human interference on the mangrove. It has shrunk by more than 50 percent in the past 170 years. The past two decades have been most damaging as human habitation has slowly and painstakingly trespassed upon the mangrove swamps. Hugli, Sattarmukhi, Bulcherry, Matla and Gusuba are some of the streams that crisscross the

mangrove forest. In order to save their dwellings from frequent floods, human population constructs bunds along these rivers, thus making an effort to protect their families. But the bunds collapse frequently as this is a total water regime. Moreover the tube-wells sunk in these habitations draw saline water from the sea or rivers. It is neither potable nor fit for agriculture. Yet the sea of humanity goes on increasing their area year after year.The sea or the delta should never be taken for granted. The studies have shown the prepresence of several mangroves underneath. Nature is always very unpredictable and thus we must always be on our guard against any nature disaster.