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Field Trip Report: Cox’s Bazar and Saint Martin’s Island; From: Md. Golam Maola
(Mahim)
Research · January 2022
DOI: 10.13140/RG.2.2.18501.12008
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Bangabandhu Sheikh Mujibur Rahman Maritime
University,Bangladesh
Report
Field Trip: Cox’s Bazar and Saint Martin’s Island
Submitted From:
Md. Golam Maola (Mahim)
Student Id: 17311027
Registration No: 2301121700027
Session: 2017-2018
Department of Oceanography and Hydrography
Faculty of Earth and Ocean Science, BSMRMU
Date of Submission: 09 January 2022
Course: Field Trip 2021
Course Code: OCN-3213
ACKNOWLEDGMENT
First of all, I would like to thank ALLAH S.W.T the most gracious, the most merciful, and millions
of Darood-O-Salam for HAZRAT MUHAMMAD (S.A.W.W.) who is forever a model of guidance and
knowledge for humanity as a whole.
I would like to thanks Inst Cdre M Jashim Uddin, (H1), BN, Dean, Faculty of Earth and Ocean
Science for give us the opportunity to undergo field visit in Cox’s Bazar and Saint Martin’s Island.
I also want to express my deepest thanks to teachers Professor Dr. Aftab Alam Khan, Assistant.
Prof. Lt. Cdre Kamrul Ahsan and lecturer Md. Al Amin Department of Oceanography,
Bangabandhu Sheikh Mujibur Rahman Maritime University for guiding us through every step of
the field trip.
I apologize all other unnamed who helped me in various ways to have a good field trip.
Lastly, I am thankful to all my friends and classmates who have been always helping and
encouraging me.
Abstract
Field trips can be a valuable tool in making learning more engaging and provide unique
opportunities for learning certain concepts, including legal concepts by putting them into a more
realistic and relevant context. We, 2nd batch of Department of Oceanography & Hydrography
from Bangabandhu Sheikh Mujibur Rahman Maritime University recently finished our 3rd field
trip from Cox’s Bazar and Saint Martin’s islands during 29 November to 3 rd December. This trip
was very important and informative context of Geological Oceanography, Sedimentology,
Hydrocarbon, Natural resources Potentiality of Eastern coastal part of Bangladesh, Geophysical
Fluid Dynamics, Beach morphology, Coastal dynamics of Eastern coastal part of Bangladesh. We
also come to know about different geological event, tectonic process, Anticline. Overall, this field
trip was very much informative and from learning point of view this trip was very important for
us because we learned many things that could not be thought in the classroom.
Table of Contents:
Acknowledgement
Abstract
Chapter One: Introduction ........................................................................................................................... 3
Introduction:............................................................................................................................................. 3
1.1
Location of the Study area ........................................................................................................... 4
1.2
Accessibility: ................................................................................................................................. 6
1.3
Previous Investigation: ................................................................................................................. 7
1.4
Objective of the Study:................................................................................................................. 8
1.4.1
General objectives: ............................................................................................................... 8
1.4.2 Specified Objectives: ................................................................................................................... 8
1.5
Climate change and future of St. Martin Island: ......................................................................... 9
1.6
Population and Culture: ............................................................................................................... 9
Chapter Two: Methodology ....................................................................................................................... 10
2.1
: Field Survey .............................................................................................................................. 10
2.1.1: Day-01 30 december, 2021 ....................................................................................................... 11
2.1.2: Day-02 01 January, 2021 ........................................................................................................... 13
2.1.3: Day-03 02 January, 2021 ........................................................................................................... 14
2.2
: Determination of Sea Level Change......................................................................................... 15
2.3
: Data Processing ........................................................................................................................ 15
Chapter Three: Coastal Morphology and Sea Level Changes ................................................................... 18
3.1
Regional Geological Setting ....................................................................................................... 18
3.2 Coastal Morphology and Features ................................................................................................... 19
3.2.1: Alluvium Cover (Flat Land) ........................................................................................................ 19
3.2.2: Sandy Beach (Sand Flat/ Sand Dune) ........................................................................................ 19
3.2.3: Shale Beach ............................................................................................................................... 20
3.2.4: Low Lands (Inland water bodies, Lagoon) ................................................................................ 20
3.2.5: Spit and Tombolo ...................................................................................................................... 21
3.2.6: Islets .......................................................................................................................................... 21
3.2.7: Cuspate Foreland ...................................................................................................................... 21
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3.3: Beach................................................................................................................................................ 22
3.3.1: Swash & Backwash .................................................................................................................... 22
3.3.2: Erosional Beach ......................................................................................................................... 22
3.4: Evidences of Sea Level Changes along the Eastern Coast of Bangladesh ........................................ 23
3.4.1
: Eustatic sea level changes in the Quaternary ................................................................... 23
3.4.2: Evidences of Sea Level Changes along the Eastern Coast of Bangladesh ................................. 23
Chapter 4 : Sedimentary Deposits ............................................................................................................. 24
4.1 Fan Deposits ...................................................................................................................................... 24
4.2: Sedimentary Structures ................................................................................................................... 25
4.2.1: Ripple Marks ............................................................................................................................. 25
4.2.2 Concretion .................................................................................................................................. 26
Chapter 5 Biodiversity and Environmental Pollution of St. Martin’s Island ............................................... 26
5.1: Biodiversity of the St. Martin’s Island .............................................................................................. 26
Flora: ................................................................................................................................................... 26
Fauna:.................................................................................................................................................. 27
Lutjanus rivulatus ................................................................................................................................ 27
Seaweed: ............................................................................................................................................. 27
Living coral: ......................................................................................................................................... 27
Fish and fisheries: ............................................................................................................................... 27
Dead coral: .......................................................................................................................................... 28
5.2: Pollution Sources ............................................................................................................................. 28
5.3: Impacts of Pollution on Biodiversity ................................................................................................ 28
Chapter Six: Natural Resource Potentiality ............................................................................................... 30
6.1: Geological Resources ....................................................................................................................... 30
6.2: Biological Resources ........................................................................................................................ 31
6.3: Faunal resources .............................................................................................................................. 31
6.4: Seaweed and algae .......................................................................................................................... 32
6.5: Seagrass ........................................................................................................................................... 32
Chapter Seven: Discussion and Concluding Remarks ............................................................................... 32
7.1: Discussion ........................................................................................................................................ 33
7.2: Conclusion ........................................................................................................................................ 33
Reference .................................................................................................................................................... 33
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Chapter One: Introduction
Introduction:
We completed our field trip program considering two sites, one at Cox's Bazar beach and the other at St.
Martin's Island. Cox's Bazar beach of Bangladesh is the world’s longest natural sandy beach, and is located
150 km south of the industrial port of Chittagong. It is bounded to the west by the Bay of Bengal and to
the east by the Chittagong-Tripura folded belt. The latitude and longitude of the study area are 21°5´N to
21°25´N and 92°0ʹE to 92°10´E, respectively.
St. Martin's Island is a small island (area only 3 km2) in the northeastern part of the Bay of Bengal, about
9 km south of the tip of the Cox's Bazar-Teknaf peninsula, and forming the southernmost part of
Bangladesh. There is a small adjoining island that is separated at high tide, called Chera Dwip. It is about
8 kilometres (5 miles) west of the northwest coast of Myanmar, at the mouth of the Naf River. The whole
St. Martin’s Island was selected as study area which lies between latitude 20°34´ and 20°39´N; and
longitude 92°18´ and 92°21´E. There are five distinct physiographic areas within the island. Uttar Para is
the northern part of the island with a maximum length, along the north-south axis, of 2,134 m, and a
maximum width of 1,402 m. Golachipa is a narrow neck of land connecting Uttar Para with Madhya Para.
Madhya Para, directly south of Golachipa is 1,524m long and 518 m wide at its maximum. Dakhin Para,
lies next to the south and is 1,929 m long, with an additional narrow tail of 1,890 m towards the southeast,
and at its maximum is 975 m wide.
Chera Dwip, the southernmost tip of the island and extending south-east from Dakhin Para is a rocky reef
that is about 1.8 km long and between 50 m and 300 m wide. Lately, this area has been declared an
Ecologically Critical Area (ECA). The island is almost flat with an average height of 2.5 m above Mean Sea
Level (MSL), rising to a maximum of 6.5 m high cliffs along the eastern coast (Warrick et al., 1993; Ahmed,
1995).
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1.1 Location of the Study area
Sugondha Point: Sugondha Point
situated from the north of Kolatoli
point. There is a Burmese market
that famous in Cox's bazar. There
were sea food restaurants but
demolished by government. It has
fly dining restaurant too.[1]
Reju Khal: Reju Khal a hilly stream
flows through the southern part of
Cox's Bazar district. It rises from
the hill ranges of North Arakan,
traverses the district in a southwesterly direction and falls into
the bay of bengal. Mostly rocks of
the Tipam sandstone formation
are exposed here. A road bridge
has been constructed over the
Reju Khal to connect Cox's Bazar
and Himchhari sea beaches with
Inani, Nhila and Teknaf sea
beaches. Reju Khal can also be
approached from Court Bazar,
Ukhia through Jaliapalong by a
metalled road.
Patuartek Pathor Rani Sea Beach:
Patuartek is located approximately
Figure 1: Stations of Study Area
30 km from the main Cox's Bazar
city and around 6 km from the Inani
Sea Beach. Although it is a great attraction for tourists, many of the people haven't heard the name of the
beach that much. Hence, it remained unpopular and only few tourists visit this place. However, with the
help of social media, and many other travel organizations, the place is starting to get new tourist at
present and hopefully in future it may even surpass the popularity of the main Cox's Bazar Sea Beach.[3]
Inani Beach: Inani Beach is a part of Cox's Bazar Beach, is an 18-kilometre-long (11 mi) sea beach in Ukhia
Upazila of Cox's Bazar District, Bangladesh. It has a lot of coral stones, which are very sharp. These coral
stones look black and green, and they are found in summer or rainy seasons.
Fringing reef at The Naf River: Naf River is an international river marking the border of southeastern
Bangladesh and western Myanmar. A fringing reef is one of the three main types of coral reef. It is
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distinguished from the other main types, barrier reefs and atolls, in that it has either an entirely shallow
backreef zone (lagoon) or none at all. If a fringing reef grows directly from the shoreline, then the reef flat
extends to the beach and there is no backreef.[4]
St. Martin's Island: St. Martin's Island is a small island (area only 3 km2) in the northeastern part of the
Bay of Bengal, about 9 km south of the tip of the Cox's Bazar-Teknaf peninsula, and forming the
southernmost part of Bangladesh. There is a small adjoining island that is separated at high tide, called
Chera Dwip. It is about 8 kilometres (5 miles) west of the northwest coast of Myanmar, at the mouth of
the Naf River.[7] Chhera Island, also called Chhera Dwip, Cheradia Island or Cheridia Island, is an
uninhabited island and extension of St. Martin's Island at the mouth of the Naf River in the Bay of Bengal,
within the Chittagong Division of southeastern Bangladesh. Chhera Island is the southernmost island of
Bangladesh. During high tides it is divided from St. Martin's Island by the sea. During low tides, the island
can be reached by walking for about 2½ hours from St. Martin's Island.
Table 1: Station of Our Field Study
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Station Number
Geo Location
Local name
1
Latitude:21.41503
Longitude: 91.9820
Sugandha point, Cox's Bazar
2
Latitude:21.295640
Longitude: 92.05457
Sonarpara (Somewhere beside
Reju canal Bridge), Cox's Bazar
3
Latitude:21.2954
Longitude: 92.05609
Dhopapalong (Beside Reju canal),
Cox's Bazar
4
Latitude:21.18191
Longitude: 92.04825
PatuarTak (Inani Beach), Cox's
Bazar
5
Latitude:21.1815
Longitude: 92.04765
PatuarTak (Inani Beach), Cox's
Bazar
6
Latitude:21.04
Longitude: 92.09
Beside Teknaf Wildlife Sanctuary,
Teknaf
7
Latitude:20.6318
Longitude: 92.32777
St. Martin Island (Near the
Island's jetty)
8
Latitude:20.631860
Longitude: 92.32759
St. Martin Island (Near the
Island's jetty)
9
Latitude:20.630430
Longitude: 92.32711
St. Martin Island (East Side)
10
Latitude:20.630430
Longitude: 92.326940
St. Martin Island (East Side)
11
Latitude:20.6272
Longitude: 92.326580
St. Martin Island (Near
Bangladesh Navy Officers Mess)
12
Latitude:20.62619
Longitude: 92.32623
St. Martin Island (Near
Bangladesh Navy Officers Mess)
13
Latitude:20.62621
Longitude: 92.326340
St. Martin Island (Near
Bangladesh Navy Officers Mess)
14
Latitude:20.589130
Longitude: 92.3370
St. Martin Island (South Side)
15
Latitude:20.585630
Longitude: 92.334950
Chera Dweep, St. Martin Island
16
Latitude:20.585180
Longitude: 92.334560
Chera Dweep, St. Martin Island
17
Latitude:20.578010
Longitude: 92.334940
Tidal point of Beach, St. Martin
Island
18
Latitude:20.575840
Longitude: 92.335650
Ending point of Bangladesh
19
Latitude:20.635520
Longitude: 92.326860
Uttarpara, St. Martin Island
1.2 Accessibility:
Cox’s Bazar is the southwest city of the Bangladesh that is located on the coast of Bay of Bengal. Cox’s
bazar is in the part of the mainland of Bangladesh and became amazing destination for tourists. It is almost
400 kilometers away from the Dhaka, the capital city of Bangladesh. Cox’s Bazar is accessible both by land
and air.
Saint Martin’s Island the only coral island and country`s last south area. The only accessible route is water
transportations. There are Ships that ply between the Island and Teknaf and Cox’s bazar. Teknaf And Cox’s
Bazar both routes can be used for reach the island. We used Teknaf route and the ships which we used to
reach the island named MV Sukanto. The only mode of transport on the island is by cycle rickshaw van
and most people walk from place to place as there is no road on which vehicles can travel. Tourists use
speed boats to go to visit Cheradia Island. All the hotels run their generators until 11 PM after which power
is cut off. Thus, they rely on solar power, which is popular throughout the island. There is no electricity
6|Page
supply from the national grid since a hurricane in 1999. Most of our station were visited through walking
and by troller.
1.3 Previous Investigation:
The island has been a tourist destination for many years ago, especially after the publication of a Bangla
film ‘Daruchini Dwip’ covering unique landscape and local culture of island in 2007. But there is no official
statistics on the number of tourists visited the island due to absence of systematic monitoring. The 200506 tourist figures imply an average of about 750 persons per day over a seven-month tourism season, but
the numbers of visitors on some days in the peak season must be higher and the number of tourists also
depends on some factors.
Development activities in the
Saint Martin Island has increased
in the recent years before that it
was almost under investigation.
This island has been studied by
Geologists, Hydrogeologists, and
Environmentalists on different
times. Moreover, Students and
teachers of Department of
Oceanography, Department of
Geology of University of Dhaka,
Jahangirnagar
University,
University
of
Chittangong
Bangabandhu Sheikh Mujibur
Rahman Maritime University and
Figure 2: Land Form of Cox's Bazar Island
many geologists, hydrogeologists
and environmentalists study the island in every year. Dr. Sheikh Mahabub Alam Chairman and Adviser of
the Department of Tourism and Hospitality Management the People's University of Bangladesh, has
studied about “St. Martin’s island - a tourist paradise has landed in the middle of the ocean along the Bay
of Bengal”(2018). IUCN, International Union for Conservation of Nature and Natural Resources has studied
“Survey of St. Martin’s Island: Summary report of resource and socio-economic information Strengthening
national capacity on managing Marine Protected Areas (MPA) in Bangladesh (A follow up phase of the
BOBLME support in developing the framework for establishing MPA in Bangladesh)”(2015).[4]
The current study discovered that there are just 41 coral species on Saint Martin Island, compared to 141
in the 1980s. There were 127 and 66 coral species on the island in 1990 and 2000, respectively. Figure 2
depicts the decline of coral species on the island over time. It is obvious that coral species have been
declining over time, and if this trend continues, coral species might be reduced to 24 by 2030. If no actions
are done to conserve coral species, it is possible that by 2045 there will be no coral species on Saint Martin
Island. Corals and sea turtles are found to be the island's most important bio diversities, and they are both
threatened by uncontrolled tourism, overfishing, and other anthropogenic activity. Tourists are
transported to the island through ship services and power boats. As a result, a massive amount of waste
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oil, plastic, and other non-biodegradable debris is dumped in the ocean near the island. It has long been
acknowledged that, in the lack of comprehensive planning, population demands and economic expansion
have already resulted in significant environmental damage.(Sayed Ahammed et al., 2016).
1.4 Objective of the Study:
1.4.1 General objectives:
❖
❖
❖
❖
❖
❖
❖
❖
Identification of sandstones with possible reservoir quality of the area;
Detailed study of different structural type;
Determination of sand bodies (Lithology, depth, type);
Characterization of conventional anticlinal traps;
Identification of other conventional (Complex trap) Trapping;
Suggesting possible unconventional trapping (Thin bedded play, Synclinal prospect);
Analysis of stratigraphic Trap Prospect (Channel sand, Sheet sand);
Overall prospect analysis of the area. To attain sufficient experience in data collection of
practical field work
❖ To familiarizing with the specialized tools and techniques.
1.4.2 Specified Objectives:
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
Geological observations of the study area
The natural coastal processes occurred by the islands
Observations of flora and fauna of the study area
To observe ecology and biodiversity of Saint Martin’s Island
To learn about and observe several physical and geological features of the study area
To measure water and Sediment’s quality like pH and Electrical Conductivity of the Saint
Martin’s coast.
To learn about coastal engineering processes and both natural & artificial protections
To monitoring several oceans features like waves, tides, various zones of the onshore areas.
To understand practical visualization of the macro-paleontology and also micro- paleontology.
To know and familiar with the natural resources
Physical, socio-economic and cultural aspect of the study area.
To identify the land use patterns of the area
To observe the corals
To trace out local environments and their living conditions, cultures, livelihoods etc.
To identify environmental profile of Saint Martin’s Island.
To estimate the availability of mollusk and crustacean in Saint Martin’s coast.
To find prospect of local communities.
To find out important finfish and shellfish.
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1.5 Climate change and future of St. Martin Island:
The island land height is almost similar to mean sea level. Due to global warming sea level is rising up
gradually, which will affect island someday. Therefore, the water level of the Bay of Bengal is fluctuating
and submerging surrounding landmass of island wherein sometimes it is also observed that new land is
formed in other side. So the impact of global climate change is a great threat for the future long term
existence of Island (Feeroz, 2009; Rahman, 2009; Warricket al., 1993; Maruf, 2004; Brammeret al., 1993).
[5] Climate data for cox’s bazaar district of Bangladesh is related to the Bay of Bengal. Here some figure
shows recent climate stages of Cox’s bazaar district –
Figure 3: Precipitation, Humidity, Temperature of Chittagong District
1.6 Population and Culture:
Table 2: Population increment status of St. Martin Island (BBS, 2011)
Year
1996
2000
2005
2012
Households
535
791
818
1100
Total population
3,700
4,766
5,726
6000
Population growth rate is comparatively high in island due to early marriage and polygamy culture is still
dominant. Therefore, population size is growing up rapidly which is triggering by illegal Rohingya
(Muslims) entrance from nearby Myanmar. Moreover, during tourist season, short time stay of tourists
within island creates population pressure because of its limited capacity. Contrary, people practice
anthropocentrism among themselves which is liable for population growth and consequently, over
9|Page
consumption and depletion of resources cause environmental degradation. Besides, due to lack of
education, people can’t understand or realize about the impact of population growth. But spreading
education amid mass people and growing non-anthropocentrism amidst them can be helpful for
controlling population growth. Moreover, early marriage, polygamy and illegal Rohingya entrance should
be stopped immediately otherwise it will become threat for future existence.[6]
Chapter Two: Methodology
The methods and field techniques that are used in a particular fieldwork depends on the type of
work to be undertaken. Methodology is the systematic, theoretical analysis of the methods
applied to a field of study. It, typically, encompasses concepts such as paradigm, theoretical
model, phases and quantitative or qualitative techniques.
The overall methods that we followed to make the report successfully is given in the figure:
First step
Planing &
preparation
• Site selection
• Instrument
taking
• Background
information
Second step
Third step
Data collection
• Groupwise
sample
• collections by
using
instrument
• Taking GPS
locations
• Geological &
physical
Features
identifications
Data
manipulation
Four step
Data analysis
Species
identifications
• Map making
• literature
review
•
Figure 2.1: Overall methodology at a glance
2.1 : Field Survey
10 | P a g e
• Report
writing
• Report
submission
The field work has been carried out in the Cox’s Bazar and Saint Martin’s Island. The field work continued
from 29-11-2021 to 03-12-2021. First day we stay in the cox’s bazar and went some station. We reached
in the island on 01’st November and begin our investigation at that day. Two days were fixed for
investigating geological condition and various sample collection, measuring differing parameters like pH,
temperature around the island. Last days we studied biodiversity of this island and collect samples from
the beach.
2.1.1: Day-01 30 december, 2021
Sugandha Beach: Cox's Bazar beach of
Bangladesh is the world’s longest natural
sandy beach, and is located 150 km south
of the industrial port of Chittagong. It is
bounded to the west by the Bay of Bengal
and to the east by the Chittagong-Tripura
folded belt. The latitude and longitude of
the study area are 21°5´N to 21°25´N and
92°0ʹE
to
92°10´E,
respectively.
Matamuhuri and Boghkhali are the two
rivers draining from northern part of the
Chittagong-Tripura folded belt and feeding
sediments to the beach area. Sugandha is
the sand beach points that is closer to the
Cox's Bazar town.
Tidal Deposition
Figure 4: Depositional Feature
Rezu Khal: Rezu Khal estuary is located
(21°17'35.42''N to 21°18'28.34''N and
longitude 92°2'27.15''E to 92°4'30.90''E) in
Cox’s Bazar, southeastern coast of
Bangladesh. Sources of Rezu Khal lie on the
north Arkan Mountain and flows over the
Bandarban district before flowing into the
Bay of Bengal. The intertidal estuarine
mudflat is occupied with mangrove and
salt marshes. The Reju Khal River has two
streams that join together near Jaliapalong
and finally reach to the Bay of Bengal. The
entire sampling was carried out near
Jaliapalong Bridge of the Reju Khal estuary
(21°17ʹ21.06″N and 92°3ʹ36.40″E;). The
study area Reju Khal estuary on the south
eastern coast of Bangladesh represents
Figure 5: Fan Deposition
typical subtropical estuaries and is among
the major estuarine systems in Bangladesh. It is regarded as an important estuarine system both
11 | P a g e
ecologically and economically [19]. In this location a stream's sediment load is typically deposited, eroded,
and redeposited many times in a stream channel, especially during climatic variations such as flooding.
Sediments are deposited throughout the length of the stream as bars or floodplain deposits. At the mouth
of the stream, the sediments are usually deposited in alluvial fans or deltas, which represent a lower‐
energy, more “permanent” depositional environment that is less susceptible to changes in the stream
flow.
Patuartek pathor rani sea beach: Patuartek pathor
rani sea beach is an 18-kilometre-long (11 mi) sea
beach in Ukhia Upazila of Cox's Bazar District,
Bangladesh.[14][15] It has a lot of concretion stones,
which are very sharp. Beside the beach at 41 degree
of southwest located nila anticline. Where by the
subsidence this basin is created and lithification with
thousand of years deform the structure that is
synclinal toward the sea. It was a adrift subsidence
along the fault plane and form highly lithified
deposition.
Jaliadwip, Teknaf: This island is situated in between
Figure 6: Zonation of Beach
Bangladesh and Myanmar border in Naf River basin.
It is an oval shaped island as per seen on satellite
images. As it is situated in between two major
orogenic belt, it is known as basin. And this basin has
got some extensional space from the fault line
created beneath it. this process has been occurring
during the divergence, where mantle plume
generation begins and a basin forms. But in this case,
it stopped at the rifting stage and the vertical
components has been seized due to several tectonic
activities. After that, there was huge shale intrusion
in the basin where shale had a dominancy over other
components. That’s why a lot of shale diapir and
Figure 7: Fringing reefs
deposits have seen in the river bank. This area is yet
to study for more details. This area is induced with mangrove trees, as the water is brackish. Tolerance
level is up to the mangrove trees only.
12 | P a g e
2.1.2: Day-02 01 January, 2021
East Beach, St. Martin (Beside Jetty), and East
Beach Officers mess, St. Martin: We have
observed the wreck line and swash zone in
these particular stations. Alongside, we have
observed the sand dunes on berm. The berm is
a diagenetic structure present on the
uppermost (high tide) section of the strata of
MSGB. The formation of berms on MSGB is
directly tied to swash asymmetry, with high
penetration during uprush leading in reduced
effluence and sediment deposition (López-Ruiz
et al., 2020). We have denoted in the figure.
Figure 8: Wrack Line, Saint Martin's Beach
The swash zone creates the land-ocean barrier
at the landward edge of the surf zone, when waves runup the beach face. It is likely the section of the
ocean most frequently utilized by leisure beach users and, being quite visible, is the region of the littoral
zone most related with coastal erosion and the implications of changing climate (Swash Zone Dynamics,
n.d.). Same as we have observed the beach face in these stations.
We have also used diluted HCl on the corals which indicated the existence of the dead coral rocks on the
beach. Even there were some concretion found on beach. These have shown some reaction too but
because of the shell intrusion inside it. That means there is some similarity in the Inani beach and Saint
Martin Island.
Dead Coral and shell intrusion region south-east:
There was a huge colony of dead corals under water and
beyond water. Most of them went under bleaching
process. Coral bleaching occurs when corals lose their vivid
hues and become white (Lorin Hancock, n.d.).
Figure 8: Dead Coral
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2.1.3: Day-03 02 January, 2021
Cheradwip west part, Cheradwip southern part, Western
Cheradwip: We have observed the dip angle in that region.
The dip angle is 1°. The dip direction is at North 26° West.
We have observed a fault plane and back lagoon is a
marking of this fault plane.
Chera Dwip is elevated at about 3.6 meter above the sea
level and populated by about 4,000 inhabitants the 7.315
kilometer long island is almost flat consisting of alluvial
sands mixed with shells of mollusks. In addition to the main
island, there are a number of tiny islets locally known as
‘Chera dwip’, which means separated island. Visitors will
miss something great if they don’t glimpse at a shallow
lagoon in the northern part of the island which gets
connected to the sea during high tide by a narrow channel
on the western coast.
Researchers have recorded 182 species of wildlife of which
4 species are amphibians, 130 birds, 20 mammals, and a
fossilized coral 33,238 years old on this very island we can
boast about. A huge number of migrated birds come to this
island in winter season enhancing its beauty and holy
ambiance.
Figure 9: Living Shell deposition
Figure 10: Highly Lithified Bedding plane
Tourists can book their trip either from Chittagong or from
Cox’s Bazar. The surrounding coral reef of the St Martin
island has an extension named CheraDwip. A small bush is
there, which is the only green part of CheraDwip, enhancing
the beauty of this island. People do not live on this part of
the island, so it is advisable for the tourists to go there early
and come back by afternoon.[7]
Figure 11: Keya Tree of Saint Martin Island
14 | P a g e
2.2 : Determination of Sea Level Change
On Station 1, dolphin Point, Cox’s Bazar. we
determined the approx sea level change by foot
step measurement. We took a time period of 20
years and consider a position of sea coast at high
tide 20 years back and measure the present sea
coast on 30 december ,2021 at high tide.
The process to determine the sea level change is
Figure 12: Determination of Sea Level Changes
we start walking from a point whare previous
coast existed. The previous coast line was determined by our senior honorable Professor Dr.
Aftab Alam Khan as he visited the place 20 years back. When we start walking the distance
between two foot were 1.75 m approx. The present-day coastline took 44 long footsteps. So, we multiply44 × 1.75 = 75m approx.
So, 75 ÷ 20years = 3.75m
So, it is determined that sea level is retreating 3.75 m in these 20years time span horizontally.
And 1.75 ÷ 20 = 0.1875m
In these 20 years sea level is retreating 0.1875 m per year or 18.75cm per year or 187,5 mm per year.
2.3 : Data Processing
As our field work was to gain practical knowledge of theoretical study So we found few data to
process to form this report.
During our field survey all our geolocation was determined by android software called GPS
status and tool box. The water parameter that was collected real time through Hanna
multiparameter equipment. For beach zonation in St Martins Island, we took average points in
google earth to draw lines of beach zones.
15 | P a g e
16 | P a g e
Figure 13.1: Field Station
East Side, Sain
Martin’s Island:
Chhera dwip:
17 | P a g e
Figure 13.2: Field Station
Chapter Three: Coastal Morphology and Sea Level Changes
3.1 Regional Geological Setting
St Martin’s Island falls into the fold belt region of Bengal basin. St. Martin’s island is close to Myanmar in
the east, Chittagong in the north, to the west and south it is open sea. A small island in the northeast of
the Bay of Bengal located close to the Rakhain coastal area. It is a part of the anticline Chittagong fold belt
which is at least 84 km long and 22 km wide. The island is structurally controlled and its present landform
has been shaped by four major processes, such as sea-level change, tectonic activities, geomorphic
processes and anthropogenic activities. The shelf topography and the geomorphic characteristics
of innumerable offshore islands of Bangladesh are predominantly delineated by the sediment
influx from the upstream and also reworking of sediments from the tide, tidal surge, wave, and ocean
current. As a result, erosion and reworking of marine deposits have developed a complex depositional
environment in this island. Basin development started with the separation of India from Antarctica in the
early Cretaceous. The basin had its origin during the collision of India with Eurasia and Burma, building
the extensive Himalayan and Indo Burma ranges. Gani and Alam (1999) have reviewed the tectonic
concepts of Southeast Asia and have offered a somewhat modified tectonic setting for the ChittagongTripura Fold Belt (CTFB). They proposed that the CTFB is a westward extension of the easterly subduction
of the Indian plate in an arc-trench tectonic setting, sedimentation in the Bengal basin has been controlled
by the uplift and erosion of Himalayan mountain chains as well as the Indo-Burma ranges. The CTFB region
in the very early Neogene was a remnant ocean basin that received sediment from two directions –
1) Collision- derived sediment from the Barail and the Naga hills entering the basin from the north along
the trench axis. And
2) Indo-Burma arc – derived sediment shed transversely to the trench from the east. The island lies on
the western flank of the anticline.
The structure is simple and is represented by an
anticlinal uplift. A little of the axis of the anticline
is traceable along the west coast of Dakshinpara.
The exposed portion of the axis runs from NNW
to SSE, approximately parallel to the island. There
is a fault along the northwestern shoreline with a
trend nearly parallel to the axis. The fault seems
to be a reserve in nature with the eastern side as
an upthrown block. The anticline is slightly
asymmetrical with a monoclonal swing on the
eastern flank. The bedrock on the eastern flank
near the axis dips very gently at an angle of 3° to
5° towards the east, increasing eastwards to 10°
to 12°. The monoclonal swing gives a high dip of
18 | P a g e
Figure 14: Nila Anticline
30° and above at CheraDwip. Very little of the western flank which dips at 6 degrees west is exposed
above the sea. The monoclonal swing gives the anticline a box-like shape. The birth of the island is related
to the regional tectonics of Southeast Asia during the middle Miocene.
3.2 Coastal Morphology and Features
The general topography of the island is almost flat and is occupied by fine to medium grained alluvial
deposits. Overlaying the bedrock, these alluvial deposits of less than two meters thick, have developed
good soil horizons and an extended alluvial plain has been formed. This plain landform occupies 33% of
total area of the island and mostly been used for crop cultivation. At the southern part of Dakshin Para,
the plain land is sub-basin in shape and become shallow inundation at Spring High Tide. The Saint
Martin’s Island presents a variety of geomorphic features, namely; alluvium cover (Flatland), sandy
beach (sandy flat/ sand dune), shale beach, low lands (Inland water bodies, lagoon), spit, tombolo,
cuspate foreland, islets, and a beach covered with concretions.
Figure 15: Coastal Morphology
3.2.1: Alluvium Cover (Flat Land)
The general topography of the island is almost flat and is occupied by fine to medium grained alluvial
deposits. Overlaying the bedrock, these alluvial deposits of less than two meters thick, have developed
good soil horizons and an extended alluvial plain has been formed. This plain landform occupies 33% of
total area of the island and mostly been used for crop cultivation. At the southern part of Dakshinpara,
the plain land is sub-basin in shape and become shallow inundation at Spring High Tide.
3.2.2: Sandy Beach (Sand Flat/ Sand Dune)
19 | P a g e
Encircling the island, particularly in the northeast, the zone between the Spring High and Low Tides can
be characterized by an accumulation of marine sands and has developed an extensive sandy beach. This
beach system has also been well developed surrounding the center of the island. Differential beach
sloping clearly indicates micro-scale spatial variation of sand accumulation along the beach. At the
Figure 16: Wind Generated
Figure 17: Wave Generated
northeast corner, the gentle gradient results a wide emergence of land at low tide; whereas, on the west
side, particularly at the middle, the beach slope is steeper. The sandy beach in the North and North-east
stretches around 400 m into the sea. The Western beach is mainly sandy but the sub-tidal area consists
of a bed of boulders. The beach is the breeding habitat for globally threatened turtles and a wintering
habitat for shorebirds.
Coastal dunes are developed in widespread immediately above the beach and along the shoreline. Such
dune system has well developed surrounding the middle parts of the island. Dunes of the St. Martin's are
of two types: high and low dunes. High dunes are up to 6 m in height and are mostly found on the western
side of Galachipa. Dunes along northwest and southwest corners of the island are lower in height,
undulating and are broadly extended. Dune system of the St. Martin’s Island acts as a natural defense
against storm and tidal surges, and save lives and properties.
3.2.3: Shale Beach
Along the west and east sides of Dakshinpara, beach materials have overwhelmingly been composed ci
medium to coarse shale fragments and broken coral debris. This unique shale beach landform is light grey
to light purple in color, rarely includes any minerogenic composition and is extended up to the lower tidal
limit of the island.
3.2.4: Low Lands (Inland water bodies, Lagoon)
At the southern part of Dakshinpara, the plain land is sub-basin in shape and become shallow inundation
at Spring High Tide. This lowland area is mostly been covered by planted mangrove Sotuietaiia spp. There
are three lagoons on the Island. The lagoons of Uttar Para and Dakhin Para have now become muddy
20 | P a g e
swamps with shallow water. These are only connected to
the sea at high tide through shallow creeks. But the
lagoon that lies between the Southern end of Dakhin
Para and the three small islands comprising Cheradia
retains shallow water and is protected by widespread
boulders and stone corals. The lagoons in the North are
older in origin and show a longer sequence of evolution,
while the lagoon in the South is much younger and is
under the active marine influence (Kabir, 2006). Since
the 1960s, the two Northern lagoons have gradually
been converted into paddy fields. This conversion has
eliminated most of the original wildlife found in these
lagoons.
Figure 18: Lagoon
3.2.5: Spit and Tombolo
A unique geomorphic feature of St. Martin’s Island is the development of a spit bar in its south. This typical
spit bar landform of about 2 km long and less than 100 m wide connects the mainland with Cheradia. This
bar has been formed due to deposition and movement of fine to medium grained sand materials by a
wave and tidal currents.
3.2.6: Islets
Cheradia in the south consists of three small islets of which the middle one is the largest and the
southernmost one is possibly the oldest. The peaks of these islets are less than 3 m in height from the
MSL and become disconnected from the mainland by nearly 1 m deep water at high tide. These are
composed of relatively coarser sand particles with frequent shale fragments, broken coral debris, and
foraminifera, and are overlaid nearly all sides by stony corals and boulders. The middle islet has an
undulating surface feature, has a sub-basin on its top and is under shallow water depth at the extreme
high tide. From its southeast corner, a horn like a landform is exposed seaward. All these islets are covered
by key (Pandanas) plants and some bushes, although some mangroves are also grown in the middle islet.
3.2.7: Cuspate Foreland
Cuspate forelands are created primarily by longshore drift formed by accretion and progradation of sand
and shingle, they extend outwards from the shoreline in a triangular shape. This geomorphic feature
located on the northeast side of the island.
21 | P a g e
3.3: Beach
A beach is a landform alongside a body of water which consists of loose particles. The particles composing
a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources,
such as mollusc shells or coralline algae. Sediments settle in different densities and structures, depending
on the local wave action and weather, creating different textures, colors and gradients or layers of
material.
Figure 19: Beach
3.3.1: Swash & Backwash
Swash is when the waves come towards the beach/land. Backwash is the opposite - it moves away from
the beach/land. They create a steep narrow beach. When swash is stronger than their backwash causing
them to deposit material on the beach.
3.3.2: Erosional Beach
Coastal erosion is the loss or displacement of land, or the
long-term removal of sediment and rocks along the
coastline due to the action of waves, currents, tides, winddriven water, waterborne ice, or other impacts of storms.
When backwash is stronger than swash causing erode the
beach. We observed erosional beach at Golachipa where
beach slope is relatively steep and backwash is stronger
than swash.
Figure 20: Erosional Beach
22 | P a g e
3.4: Evidences of Sea Level Changes along the Eastern Coast of Bangladesh
3.4.1 : Eustatic sea level changes in the Quaternary
The key reason for sea level changes is the changes are due to ice melting during inter-glacial phase or
built up of ice on the land surface during glacial phase. During the glacial phase, sea water is lost
progressively by precipitation as snow, as a result, sea level drops. On the other hand, sea level rises as
the ice melts during the interglacial phase. This process is called glacier eustasy. The climatic
determination which marks the onset of the quaternary period culminated in the sequence of glacial and
inter-glacial events which occurred at fairly regular intervals of 10,000 years for about 2 million years. The
last of this glacial ended some 10,000 years BP. The period from the beginning of the quaternary to the
end of the last glacial has been called the Pleistocene series.
The last two million years of earth's history, which is the Quaternary period, is characterized by strong
climatic variation. The beginning is marked first, by a major glacial stage succeeded by alternating glacial
and interglacial stages. Alternating cold and arid, warm and humid conditions represents the glacial and
interglacial stages in the tropic. The most important phenomenon related to such variation. Observable
all over the globe. Was that of glacio-eustatic sea level changes? The glacial stage marked by fall of sea
level. interglacial by high sea level. The Quaternary climatic history has been subdivided on the basis of
drift deposits in the river Danube and its various tributaries in the Alps, and five major glaciation events
separated by transgressed deposits of warmer interglacial periods have been recognized. Further studies
(Shackleton & Opdyke. 1973; Moore 1982. Chapel & Shackleton 1986) have established that sea level
fluctuated many more times than envisaged by earlier workers. Kukla (1977) correlated original Alpine
units with oxygen isotope results and recognized 17 glacial and interglacial period in Europe over the last
1.7 million years. There is little agreement among the researchers about the actual values of high and low
sea level. It is observed by some workers (Fairsbridge 1961) that sea level attained a highest strandline
position at +220 m during the Calabrian transgression. Though correlation between regression and low
sea level has been generally agreed upon. Doubts have been expressed about very high transgression
Seastrand (Curry 1961. Shepard 1963, Moore 1982). Erosional terraces and coastal deposits occurring at
higher levels do not necessarily indicate the high sea level position. Tricart (1974) has contradicted the
older concept of the very high sea level strand. He suggested that Quaternary sea level never rose beyond
+40 m of the present level and inferred only +1.5 mm rise during the last Flandrian transgression.
Cumulative evidence from different coastal areas (Curray 1969. Gulicher 1969) indicate a Holocene
transgression of +1 m to +6 m between 6.000 to 2,000 BP at least in the Indian Ocean (Merh, 1987).
3.4.2: Evidences of Sea Level Changes along the Eastern Coast of Bangladesh
Bangladesh has a long shoreline having coastal plain, estuaries, barrier bars and a number of the
Nearshore Island. The elevation of Bengal plain with coastal island is very close to the high tide level of
the Bay of Bengal. A significant part of the coastal region is covered with beautiful mangrove vegetation
23 | P a g e
named Sundarbans. The coastal region of Bangladesh is densely populated having a number of small
towns and two major cities - Chittagong and Khulna.
In the previous chapter of this report we found that Sea is retreating and the rate of retreating is 0.1875
m per year or 18.75 cm per year or 187,5 mm per year. We also detect a presence of stream that was
flowing in our study area few years back where prominent stratification of channel fill deposit and tidal
deposit (sand and mud). There is a relation between channel activities and tide. When sea is not retreating
there is tidal influence going on coast and carbonaceous mud deposited on high tide time. As sea is
retreating there is only channel fill deposit dominance can be seen. This is the proof of sea level change
in Eastern Coast of Bangladesh.
Chapter 4 : Sedimentary Deposits
4.1 Fan Deposits
Generally there are two types of fan: Submarine fan and
Alluvial fan. As our field work is on oceanographic purpose so
in this report we focus on our study to submarine fan and its
deposits. A submarine fan is a body of sediment on the
seafloor produced by mass-flow processes. It can be fanshaped, but it's also typical to see more elongate, lobate
geometries. The composition of the material provided,
particularly the quantities of gravel, sand, and mud present,
has a profound influence on the shape and depositional
nature of submarine fan systems. Submarine fan refers to fanshaped bodies deposited by mass-flow processes, primarily
turbidity currents. Submarine fans may be made of any clastic
material, but the bigger ones are all made of terrigenous
clastic material brought in by huge river systems. Submarine
fan systems are commonly divided into upper fan (inner fan),
mid-fan and lower fan (outer fan) areas: in these schemes the
upper fan is dominated by channel and levee complexes, the
mid-fan by depositional lobes and the lower fan by sheets
Figure 21: Reju Khal
(Nichols, 2009). We found fan deposits in Station 2 which was
consists of mud and sand strata. This is why the fan deposit was a mixed sand–mud depositional
submarine system. This type of system forms when a river/delta system delivers considerable amounts of
both sandy and muddy material; these systems are classified as having between 30% and 70% sand. In
the inner and mid-fan sections of the channels, there are lags of coarse sandstone, sandy, high-density
turbidite beds, and muddy turbidite channel in abandonment facies (Reading & Richards, 1994).
24 | P a g e
4.2: Sedimentary Structures
Sedimentary structures are large scale features of
sedimentary rock for example:: parallel bedding, cross
bedding, ripples, and mudcracks that are best examined
in the field and are produced by different sedimentary
process like Fluid movement, sediment-gravity flow,
soft sediment deformation, and biogenic activity. It is as
a tool for interpreting such aspects of ancient
sedimentary environments as sediment transport
mechanisms, paleocurrent flow directions, relative
water depth, and relative current velocity. Primary
sedimentary structures are generated by four
fundamental kinds of processes: (1) mainly deposition
Figure 22 Patuartek Sea Beach
(depositional structures), (2) processes that involve an
episode of erosion followed by deposition (erosional
structures), (3) deposition followed by physical soft-sediment deformation (deformation structures), and
(4) biogenically mediated deposition or nonbiogeneic deposition followed by biogenic modification
(biogenic structures) (Boggs, 2006).
In our study area the most prominent sedimentary structure was ripple marks and concretion which are
described as follows.
4.2.1: Ripple Marks
Ripples are undulations on a sand surface or a
sandstone bedding plane that are evenly
spaced. the distance between them is generally
less than 0.5m, and the relief is rarely more than
3 cm. Ripples can be caused by water flow over
a sandbed as unidirectional currents, oscillatory
waves, or a combination of both (Collinson,
Mountney, & Thompson, 2006). Most of the the
beach we studied on our field survey contained
ripple marks. There were unidirectional ripple
which formed by current action and
bidirectional ripple which is also called
symmetric ripple formed ripple which is also
called symmetric ripple formed by wave
action(Inani Beach).
Figure 23: Ripple Marks
25 | P a g e
4.2.2 Concretion
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within
the spaces between particles, and is found in sedimentary rock or soil. The original occurrence of the
Figure 24: Concretion
concretion was within the Bokabil formation of Surma group, which was tilted (easterly dip) due to
tectonic activity. During the time of last marine transgression, the whole area was subjected to erosion.
All the soft materials (sand, silt, clay) were eroded away. However, the heavy concretions could not be
carried away and directly fall on beds that are foreign to the concretions. Coral mainly build in hard rock
such as concretion and sand blocks. It is seen on top of Surma and recent deposit in the Northwestern
coastline of St. Martin's Island.
Chapter 5 Biodiversity and Environmental Pollution of St. Martin’s Island
5.1: Biodiversity of the St. Martin’s Island
Flora: We have observed these species on spot at Cheradwip.
Sample no.
Scientific Name
Local Name
Location
01.
Caesalpinia crista L.
None
Cheradwip
02.
Cocos nucifera L.
Narikel
Cheradwip
03.
Pandanus tectorius
None
Cheradwip
26 | P a g e
04.
Casuarina equisetifolia L.
None
Cheradwip
Fauna: We have observed these species at Saint Martin fish market.
Sample no.
Scientific name
Local name
Location
01.
Pampus argenteus
Palichanda
Saint Martin
02.
Lutjanus rivulatus
03.
Euthynnus affinis
Saint Martin
Tuna
Saint Martin
Seaweed: We have observed these species in the southern part of Saint martin.
Sample no.
01.
02.
Scientific Name
Padina tetrastromatica
Caulerpa racemosa
Local name
Brown seaweed
Green seaweed
Location
Southern tip
Southern tip
Living coral: A total of 36 species in 16 genera of 7 reef-building coral families (OrderScleractinia)
were recovered and recognized from the island. Nevertheless, Tomascik identified 65 species of 22 genera
in 10 groups from St. Martin's Island. According to Tomascik the genera Porites, Favites, Cyphastrea
Goniopora, and Gonlastrea were most numerous (Hossain & Islam, 2006). But it was 16 years back. Now,
there are just 0.38% coral left in the island.
Sample no.
Scientific Name
Local name
Location
Status
01.
Goniastrea aspera
None
Golachipa/Cheradwip
Living/Dead
02.
Leptastrea pruinosa
None
Cheradwip
Living/dead
03.
Platygyra sinensis
None
Cheradwip
Living/dead
04.
Acropora hyacinthus
None
Cheradwip
Living/dead
Fish and fisheries: A total of 234 species of fish in 85 families covering 14 orders and 2 classes have been
found, of which only 16 are freshwater species, (excavated ponds, number of open wells, a freshwater
swamp and a substantial floodplain region in the island) of the fishes, 98 species are coral linked. The most
27 | P a g e
numerous coral or reef linked fish include damselfish, parrotfish, surgeonfish, dogfishes, groupers,
snappers, emperors, and butterfly fish (Hossain & Islam, 2006).
Total of 301 mollusks along the Bangladesh section of the coastline of the Bay of Bengal of which 154
species in 74 genera, 42 families and 11 orders under 3 classes were recorded from the St. Martin's Island.
A total of 9 species belonging to eight genera in four groups of phylum Echinodermata were reported
from the island.
Dead coral: A number of 19 species in 9 genera and 4 families of fossil (dead) corals were gathered
and recognized from the island. The genera are: Acropora, Cyphastrea, Favia, Favites, Galaxea,
Goniastrea, Goniopora, Montipora and Porites. However, many of them do not reflect the true reef
producing species (Khan, 1985). A group of researchers in a study for the Ocean Science Journal last year
found that the coral cover of the island shrunk from 1.32 sq km to just 0.39 sq km, while the number of
coral species dropped from 141 to 40 between 1980 and 2018.
5.2: Pollution Sources
There are several resorts on the north shore. The majority of visitors to those resorts discard their trash
on the beach. A group of volunteers has gathered tons of plastic, but there is still more. The beach is
becoming increasingly susceptible as a result of resorts' dumping.
The removal of bleaching corals from the ocean is also causing problems for the environment. People are
entering everywhere since the limitations are so bad. As a result, turtle breeding habitats have become
extinct. Despite its location on Bangladesh's southernmost edge, St. Martin's Island has grown in
popularity as a tourist destination in recent years. Hundreds of travelers flock to the island every year
because of its stunning scenery, clean seawater, and coral colonies. At the same time, being one of the
only surviving breeding sites in the vicinity for many species of globally fragile sea turtles, as well as a
wintering habitat for migrating birds, it is of critical ecological importance. However, the island's unique
vegetation and animals have seen drastic changes in the last two decades (Thompson, P.M. and Islam,
2010).
5.3: Impacts of Pollution on Biodiversity
Poorly managed agricultural lands transport large amounts of sediments, fertilizers, and pesticides into
coastal areas, resulting in high levels of nutrients in coastal seas, contamination of the groundwater table,
and eutrophication, which causes algal blooms and hypoxic conditions, which kill fish species (Hossain &
Islam, 2006). Climate change raises water temperatures, harming the zooxanthellae algae that hard corals
28 | P a g e
rely on. Sediment discharge from terrestrial sources turbidizes the water, making it impossible for coral
to thrive. Trash in the water obstructs sunlight, which destroys coral reefs. Plastic may be mistaken for
jellyfish by sea turtles and other marine species, resulting in death. Thousands of marine creatures are
strangled every year by tangled fishing nets on the reefs (Moudud, 2010). As the island's population grows
and it becomes a potential tourist destination, deforestation occurs, as does waste from construction and
fertilizer, pesticides from cultivable land, and sediments from construction, all of which degrade
biodiversity by destroying habitat for various flora and fauna. Physical devastation of corals and other
marine species has been documented as a result of anchor damage, destructive fishing, small boat
grounding, and uncontrolled tourism development (Hossain & Islam, 2006). Uncontrolled garbage
disposal on the island might have a significant impact on ground water quality and increase solid waste
loads. Long-term effects include the use of TBTO (tri-butylinoxide), the presence of antifouling agents
(Resorts, Hotels, and Marine Operations), the release of pollutants such as gas and oil from marine supply
sources and operating boats, and the release of nutrients and toxic compounds during dredging and
subsequent maintenance (Tomascik, 1997).
5.3.1: Biodiversity
Crabs
Fish and Fishery
Mollusks
Name of
Species
Relative
Abundan
ce
Very
Common
Echinoder
ms
154 species of Mollusks in 74 Ocypoda
genera, 42 families and 11
ceratopthalm
orders under 3 classes were
a
A total of 9
reported from the St. Marin's Portunes
Common
species
Island. Tomascik (1997)
sanguinolentu
belonging
recorded all these and a
s.
to eight
fourth unidentified species
Thalamita
Common
genera in
from the island. The total
crenata
four classes
number of recorded mollusk
Charybdis
Fairly
of phylum
species from the St. Martin's cruciata
Common Echinoder
Island stands at 187 species
Dotilla
Fairly
mata were
of 93 genera, 51 families,
myctiroides
Common
rec
11 orders and 3 classes.
Paramelthora Few
orded from
Nevertheless, it appears that x aculeatus
the island
both the lists are incomplete Atergatis
Few
and many more molluscan
integerrimus.
taxa await discover.
A total of 66 scleraclinian coral species were recorded belonging to 22 genera. The subtidal rocky habitat
also supports a low diversity coral reef-associated fauna and flora;
A total of 234 species of
fish in 85 families
representing 14
orders and 2 classes have
been identified, of which
only 16 are freshwater
species of the fishes, 98
species are coral
associated. The most
abundant coral or reefassociated fish are
damselfish, parrotfish,
surgeonfish, dogfishes,
groupers, snappers,
emperors, and butterfly
fish.
Fossil Corals (Dead corals)
29 | P a g e
Living Corals
Soft Corals
A total of 19 species in 9
genera and 4 families of fossil
(dead) corals were collected
and identified from the island.
The genera are: Acropora,
Cyphastrea, Favia, Favites,
Galaxea,
Goniastrea,
Goniopora, Montipora and
Porites. However, many of
them donot represent the real
reef forming species.
A total of 36 species in
16 genera of 7 reefbuilding coral families
(Order. Scleractinia)
were collected and
identified from the
island.
However,
Tomascik
(1997)
found 65
species of 22 genera in
10 families from St.
Martin's
Island.
According to Tomascik
(1997) the genera
Porites,
Favites,
Cyphastrea Goniopora,
and Gonlastrea were
the most abundant.
Soft corals belong to the Subclass
Octocorallia. Taxonomy of soft corals is
difficult and needs specialist attention.
Presence of acommunity off the east coast of
St. Martin's Island is a unique feature of the
island. The dominant families of soft corals
on the island are the following sixfamilies.
A. Gorgonian sea fans:
Acanthogorgidae,
Malithaeidae,Plexauridae
Suberogorgidae
and
B. Small sea fans:
Anthothelidae
C. Sea whips
Chapter Six: Natural Resource Potentiality
6.1: Geological Resources
The geological structure of the island is basic, with an anticlinal uplift as its main feature. Along
Dakshinpara's west shore, a small section of the anticline's axis may be traced. From NNW to SSE, the axis'
exposed portion runs virtually parallel to the island (Chowdhury, 2021)
Anticlines are key kinds of "structural traps" in petroleum geology because petroleum travelling up the
dip along one side of the fold gets caught at the crest. It won't be able to proceed much higher up the
tilted strata or back down the opposite flank until the fold is full with oil and/or gas. As a structural trap,
St Martins Island has a lot of petroleum potential.
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6.2: Biological Resources
We
learn
about
the
biodiversity of St Martin's
island in the previous chapter.
Based on the facts from the
previous chapter, the island
has a lot of potential for
fishery
resources.
Curstaceans, fish, and other
sea creatures are valued in
both the domestic and foreign
markets. Furthermore, fishery
resources can fulfill our
country's growing protein
requirement. Because St.
Martin Island has the
potential to become a turtle
breeding and nesting site,
turtles can help to protect the
Figure 25: Sea Eagle
maritime environment by
eating hazardous jellyfish. As a
result, a tourist-friendly beach has emerged. Sea grasses are important for sea bottom stabilization, water
purity, and as a nursery place for other species. They also work as food source and habitat for the marine
species of the island. Seaweed is an important main producer for the island's aquatic region. Other marine
animals benefit from the nutrients and energy they give. They can be utilized for medical, chemical, and
food purposes. For these objectives, the island's 14 species can be removed. Land animals serve as
biological resources as well. Their excrement, which flows into the ocean, is an important source of
nutrients for the marine ecosystem.
6.3: Faunal resources
Among the reported 4 amphibians, 24 reptiles, 19 mammals, 120 birds, and 6 species of butterflies, a
preliminary survey by the FEJB (2000) on the land-based faunal resources of St. Martin's Island shows
that 2 species of amphibians, 11 species of reptiles, and 18 species of birds are threatened locally.
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6.4: Seaweed and algae
Around St. Martin's Island, 1500 MT of red
sea weed biomass is expected to be
available. The island is home to some of
Bangladesh's most distinctive benthic
community associations, which are found
nowhere else in the region. The island's
economy is mainly on fishing. Annually, it is
expected that roughly 1650 MT of fish are
caught.
Biomass of'red seaweed' is available on St.
Martin's Island. According to published
reports, there are 185 species of benthic
marine algae on the Bangladesh coast,
divided into 80 genera, with 56 species and
Figure 26: Sea Weed And Algae
40 genera belonging to the red algae group
(Rhodophyta). However, many seaweed species have yet to be discovered. According to Rahman (1999),
a total of 14 species (5 Chlorophyta species, 5 Phaeophyta species, and 4 Rhodophyta species) were found
in the examined region of St. Martin's Island, with 9 species classified at the species level and the
remainder at the genus level.
6.5: Seagrass
Seagrasses are blooming plants that grow in the sea, although they are not real grasses (family Poaceae).
There are roughly 50 species documented worldwide, divided into 12 genera, and they grow totally
submerged (hydrophytic adaptions). Halodule uninervis has been found in the littoral zone around St.
Martin's Island in Bangladesh.
Chapter Seven: Discussion and Concluding Remarks
St. Martin's Island is a submerged hill, similar to the Teknaf Range, on top of which it has a record of
certain corals from the Holsin source. Bangladesh's lone coral-bearing island, St. Martin's Island, is located
off the coast of the country. The trip was quite educational. Day by day, the number of visitors grows. The
increasing number of tourists has the potential to harm the coral and its surrounding environment. St.
Martin Island is dealing with both natural and man-made environmental issues. The most pressing
environmental challenges should be addressed right away.
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7.1: Discussion
The Saint Martin’s Island is the only coral island of Bangladesh and has too many biodiversity because of
its coral ecosystem. Though many of the corals has been bleaching out but it is high time to act from the
authority and also from the people to save the ecosystem of coral island. We, as an oceanography student,
of course should conduct a better research on the island and take in part for the economic and ecological
development of Bangladesh. The geological and geomorphological can lead us to the formation and
characteristics of the island that will help us for a better and clear research on the St. Martin’s Island. The
biodiversity of course should not be hampered as without the biodiversity and the ecosystem the island
will be useless and no more value will be given for the island. This trip is just the initiative to encourage
us for further research on Saint Martin’s Island and with a successful ending we learnt a lot from our
beloved nature.
7.2: Conclusion
Oceanography is a multidisciplinary, applied branch of science that requires a lot of practical knowledge.
This trip has helped us understand the only coral bearing island of Bangladesh – the St Martin’s Island &
cox’s bazar from geo-environment, ecosystem and biodiversity perspective. The practical exposure
always helps us understand what we have been taught in the classroom. I think this type of trips will also
help us know our field of interest which may shape our career as the trip is designed such a way that it
covers multiple disciplines. However only three and a half days is not sufficient to fully study this
beautiful island. It is recommended that the duration of this trip should be extended to at least 5 days.
Overall this was a successful trip.
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