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\begin{document}

\title{\textbackslash{}cftsetindents

figure0em8em Paleontological and Sedimentological Studies in a modern
dynamic Sedimentary Environment: \textbf{Chandipur-on-sea}}


\author[ ]{Arijit Laik}

\affil[ ]{}
\vspace{-1em}


\date{}

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\textbackslash{}cftsetindents

figure0em8em

Contents: Introduction Introductory Notes Introduction Introductory
Notes

Chandipur is a diversely varied area in terms of the different
sedimentary environments and of different types of biomes. This was
chosen as the field area for M.Sc. 1st semester field to monitor the
variations in the biota in relation to the varied environments.
Sedimentological and organic variations can be well studied from
different locations of the beach. ~Predator- prey relations can also be
studied from the area. Quantitative evaluation of the drill frequency of
the shells of various organisms can reveal important trends in the
prey-predator interaction. Systematic sampling of the shells from the
different regions of the coastal area led to important interpretations
about the interaction between the organisms and different
sedimentological environments. Observations of modern examples of
different sedimentary structures associated with different
sedimentological environments can be further used to determine the
different facies in the rock record. Dominant gastropod species found in
the beach was bivalve species present in the area was habitats of the
organisms can be further used to interpret the paleohabitats of the
organisms from the rock record. Habitat segregation, habitat separation,
resource partitioning, ecological patchiness and the interaction of
those organisms with their biota is clearly evident throughout the
Chandipur beach. Anthropogenic causes initiated the formation of
micro-habitat and hence micro-ecosystems. Easy accessibility of the
different areas and the diversity of the organisms and sedimentological
environments make Chandipur a suitable place for paleontological and
sedimentological fieldwork

\textbackslash{}cftsetindents

figure0em8em

\section*{Scope and Purpose}\label{scope-and-purpose}

\begin{itemize}
\tightlist
\item
  To study the sedimentary facies and sedimentary structures in and
  around Chandipur Beach
\item
  To understand the direction of wave and current.
\item
  The interplay of fluvial, fluvio-marine, marine and Aeolian processes
  has produced a variety of geomorphic features like beach, tidal flat,
  coastal dunes, bars and swamps- this provides an intermixing of
  various environments which we get to study here.
\item
  To study the facies wise distribution of molluscan community.
\item
  To analyse size sorting of the shells across the beach.
\item
  We get to study both the Aeolian action and water action on sediments
  at the same time.
\item
  We get to interpret that present is the key to the past here.
\item
  Walther's law can be proved here.
\end{itemize}

\textbackslash{}cftsetindents

figure0em8em \textbf{`PRESENT IS KEY TO THE PAST'}

followed by the dictum, our main purpose of visit to Chandipur was to
gather knowledge legitimately about geological processes terminology and
products obtained in the modern environment which can be easily
extrapolated to the ancient rock deposits.

Due to the lack of sufficient time we were unable to deal with every
aspect of it, knowing that it was a golden opportunity for us, we did
not want to let it go. Though we have tried to put our best foot
forward, still some aspect of it were left along; our field work was
faithful in lot of ways. This field report exhibits the best possible
works that we could have done in that given time.

\textbackslash{}cftsetindents

figure0em8em

\section*{General Information about the
area}\label{general-information-about-the-area}

\subsection*{LOCATION OF THE STUDY
AREA:}\label{location-of-the-study-area}

\begin{quote}
Chandipur also known as Chandipur-on-sea, is a small town in Baleswar
district, Odisha, India. It is approximately 16 kms from the Balasore
Railway Station.\\
Chandipur is located at at 21\selectlanguage{ngerman}°28'N 87°1'E / 21 °47'N 87°02'E. It has an
average elevation of 3m ( 9.8ft). The town is 51.330 acres (0.20773 sq.
km) in size.
\end{quote}

\subsection*{ACCESSIBILITY:}\label{accessibility}

\subsubsection*{CHANDIPUR BY AIR}\label{chandipur-by-air}

\begin{quote}
The Kolkata Airport at a distance of 204 km and the Bhubaneswar Airport
at a distance of 294 km are the nearest airports to Chandipur.
\end{quote}

\subsubsection*{CHANDIPUR BY ROAD}\label{chandipur-by-road}

\begin{quote}
Road access to Baleswar is via National Highway 5(NH-5).
\end{quote}

\subsubsection*{CHANDIPUR BY TRAIN}\label{chandipur-by-train}

\begin{quote}
The Balasore railway station at a distance of 16 km is the nearest
railway station to Chandipur.\\
The study area is accessible from Kolkata via Balasore. A total number
of 49 trains ply from Howrah to Balasore. The field team reached
Balasore on 2nd January, 2017 by Dhauli Express (TRAIN NO. 12821). Some
other trains from Kolkata to Balasore are listed below:-
\end{quote}

\textbackslash{}cftsetindents

figure0em8em\selectlanguage{english}
\begin{longtable}[]{@{}lll@{}}
\toprule
TRAIN NO. & NAME OF THE TRAIN & DEPARTURE TIME\tabularnewline
\midrule
\endhead
58001 & Howrah Puri Passenger & 00:05 hrs\tabularnewline
12510 & Guwahati- Bengaluru Cantt. (Kaziranga) SF Express (PT) & 01:05
hrs\tabularnewline
12516 & Guwahati- Thiruvananthapuram Central SF Express (PT) & 01:05
hrs\tabularnewline
12703 & Falaknuma SF Express (PT) & 07:25 hrs\tabularnewline
18645 & East Coast Express (PT) & 11:45 hrs\tabularnewline
\bottomrule
\end{longtable}

\textbackslash{}cftsetindents

figure0em8em From Balasore railway station the field team hired cabs to
reach the destination, Chandipur.

\textbackslash{}cftsetindents

figure0em8em

\section*{Climate}\label{climate}

\begin{quote}
From the end of the rainy season to the post winter duration is the best
time to visit Chandipur because of the pleasant breezy and cool weather.
Thus the field team visited the study area from 02.01.2017 to
11.01.2017.\\
The average annual rainfall is 173 mm. The least amount of rainfall
occurs in January. The average in this month is 8mm. The maximum amount
of precipitation occurs in August, with an average of 339 mm.
\end{quote}

\subsection*{SUMMER IN CHANDIPUR}\label{summer-in-chandipur}

\begin{quote}
Summers are hot, and begin in April and extend till May. Mercury point
may rise upto 450\selectlanguage{ngerman}°C .
\end{quote}

\subsection*{MONSOON IN CHANDIPUR}\label{monsoon-in-chandipur}

\begin{quote}
Monsoon begins in may and lasts till June. Chandipur receives heavy
rainfall accompanied by extreme humidity during this time.
\end{quote}

\subsection*{WINTER IN CHANDIPUR}\label{winter-in-chandipur}

\begin{quote}
Winter begins in the month of December and persists till February.
\end{quote}

\textbackslash{}cftsetindents

figure0em8em

\section*{Physiographic setting}\label{physiographic-setting}

The Chandipur coast near the confluence of the river Buribalam with the
Bay of Bengal is characterised by an unusually wide (\textasciitilde{} 4
km) intertidal flat with a narrow (\textasciitilde{} 40 m) beach
skirting on the landward side. It is subjected to semidiurnal tide with
distinct diurnal variability, the mean tidal range varying between 4.89
m (equinoctial, spring) and 1.87 m (equinoctial, neap). Seasonal storm
surges never exceed 1 m (Mukherjee et al., 1987). The sediment in the
beach is commonly of fine to very sand grade while that in the tidal
flat is silt or silty fine sand except where the river Buribalam
debouches onto the tidal flat. Silty mud interlayers deposited from
flood plumes are, however, common both in the beach and the tidal flat.
The coastline is presently undergoing a phase of severe destruction on
account of slow transgression of the sea.. The crest line of the wavecut
berm and the slope break on the beach are aligned NE-SW. The foreshore
is characterised by a plane surface showing current lineations covered
by shore-parallel zones of current crescents and straight crested wave
ripples of long wavelength and very low amplitude. The lateral contact
between the beach and the tidal flat is sharp and stepped, effecting
another abrupt change in gradient. This contact is at a very low angle
with the berm crest line, tending to merge with the latter towards the
river where it enters into the tidal fiat. In the studied stretch a
third break-in-slope thus occurs across the foot of the bar flank.

The geomorphic settings for the coastal tidal flats under study vary
from place to place. Around Chandipur, SW of the estuary of the river
Subarnarekha, the coast can be divided into two broad morphozones: (a) a
landward zone characterized by monotonous lowland modified by fluvial
processes of the main stream, the river Buribalam, and (b) a seaward
zone bordered by a single line of shore-parallel coastal dune lying on
old marine terraces. The line of coastal dune is fronted by the open sea
tidal flat. (a) A sandy sloping shoreward zone with an average width of
30 m, and (b) a wide silty flat matted with ripples, having an average
width of 1.5 km. Near the Buribalam estuary, the silty intertidal flat
is ornamented with clusters of river-mouth bars of varying dimension,
criss-crossed by tidal channels of varying depths. Initiation of
mangrove growth can be seen near the Buribalam estuary. The maximum
temperature at this time hovers around 22°C with minimum going down to
4°C.

\subsection*{VEGETATION}\label{vegetation}

Situated at a distance of 16 km from Balasore, Chandipur has one of the
most beautiful beaches of the world with Casuarina, Tamarix and palm
trees. The coastline of Chandipurharbour mangrove vegetation. Deltaic
swamps are distributed near Chandipur.

Geological Setup

\textbackslash{}cftsetindents

figure0em8em

\section*{GEOMORPHOLOGY}\label{geomorphology}

Chandipur sea beach show interplay of fluvial, fluvio-marine, marine and
aeolian processes which have produced a variety of geomorphic features
like beach, tidal flat, coastal dunes, bars and swamps. The coast
includes a narrow beach (\textasciitilde{}100 m) bordering the land and
a vast expanse of extremely low gradient intertidal flat upfront of it.
Beach is divided into two distinct parts -- the foreshore and the
backshore. The foreshore extends from the lower limit of backshore to
the beach-tidal flat contact. It has a very low dip. The backshore
extends from thefoot of the berm to the uppermost limit of the water
during high tide. The contact between the beach and the tidal flat is
sharp and continuous. Swamps are found behind the aeolian dune field and
in the interbar areas. Near the mouth of the Buribalamriver, a backswamp
has developed behind the bar. The bar is crescent shaped and coalesces
with the beach. The river Buribalam forms meanders near the sea. The two
different banks of the river one has greater slope another has lower
slope refer to depositional bank. River flows by cutting sand bar and
there is lateral migration of the river.

\textbackslash{}cftsetindents

figure0em8em

\section*{Lithology:}\label{lithology}

The entire area of Chandipur is lithologically diverse with distinct
overlapping of different sedimentalogical environments and wide
application of Walter''s Law.The lithology provides a scope for grain
size analysis.

Across the shore starting from the dunes the lithology comprises of fine
grained sand and the sand size becomes coarse on moving towards the
shore.The entire tidal flat area is composed of mixture of silt and
clay.At the bar the sand size is highly coarse with tinge of mud at the
edges of the bar.Near the Buribalam river,the swamp is mainly composed
of mud.

Thus the entire area of Chandipur give a highlight of the vast
intermixing of lithologies across the aeolian , coastal and marine
environments .

Methodology

\textbackslash{}cftsetindents

figure0em8em

\section*{FIELD EQUIPMENTS}\label{field-equipments}

The equipments which were used in the Chandipur field, are as follows-

\subsubsection*{SHOVEL}\label{shovel}

\subsubsection*{COORNI}\label{coorni}

\subsubsection*{MEASURING TAPE (30m \& 5m)}\label{measuring-tape-30m-5m}

\subsubsection*{BRUNTON/CLINOMETER
COMPASS}\label{bruntonclinometer-compass}

\subsubsection*{DIAGONAL SCALE}\label{diagonal-scale}

\subsubsection*{WOODEN STANDS}\label{wooden-stands}

\subsubsection*{STOP WATCH}\label{stop-watch}

\subsection*{SHOVEL}\label{shovel-1}

-It is one of the most important equipment in a sedimentary based field
by which trenches were dug to understand the sedimentary profile
sections in dunes, sand bar and river bank.

\subsection*{TROWEL}\label{trowel}

- It is used for small- scale digging as well as fining up or polishing
the walls of a trench which are dug by shovel.

\subsection*{MEASURING TAPE}\label{measuring-tape}

-

\begin{itemize}
\tightlist
\item
  30 Meters: - It is used for measuring the wavelength of sea wave.
\item
  3 Meters: - It is used for measuring amplitude of sea wave.
\end{itemize}

\subsection*{BRUNTON / CLINOMETER
COMPASS}\label{brunton-clinometer-compass}

It is used to measure the direction of plunge of ripple and also helped
in plane paper mapping.

\subsection*{DIAGONAL SCALE}\label{diagonal-scale-1}

- It is used for measuring the wavelength and amplitude of
ripples(symmetric or asymmetric) and also helped in mapping.

\subsection*{WOODEN STANDS}\label{wooden-stands-1}

- It is used for measuring the wave frequency of the sea water, along
which the 5 meters measuring tapes are attached. The amplitude of sae
wave is measured by those measuring tapes attached to the wooden stand.

\subsection*{STOP WATCH}\label{stop-watch-1}

- It is used for counting the time of wave frequency

\textbackslash{}cftsetindents

figure0em8em

\section*{METHODOLOGY OF SAMPLING:}\label{methodology-of-sampling}

Sampling of specimens were done in order to evaluate the specific
changes in the amount and types of specimens found in different
sedimentary environments as well as in bioms. Specimens of various
species were encountered in the entire region. Sampling was done mainly
to determine the exact relationship between charecteristics and
diversity of the species and the different spacio environmental and
taphonomical changes. These changes were both abrupt and gradual at
different places in the area. The name and charecteristics of the
different species are being enclosed bellow. Following processes were
followed for sampling-

\begin{enumerate}
\tightlist
\item
  Firstly a specific location was chossen where the sampling of
  shell-hashes were done at three different but colinear spots on the
  foreshore,midshore and backshore regions. This location was marked on
  the map by determining the latitude and longitude of the location
  using a hand held GPS device.
\item
  After fixing the correct location and plotting it on the map three
  grids of the dimension 1m x 1m were constructed at the three spots on
  the foreshore,midshore,backshore. These grids were constructed at a
  distance of 5 meters from each other at places where there was a
  abundance of remanant hard parts of the organisms.
\item
  Specimens were collected from the grids using a trowel.
\item
  Sediments from the grids were also collected, and packed in sample
  bags with corresponding names of the places of collection of the
  materials.
\item
  Only the samples with atleast 90\% of the entire, unfragmented shell
  are considered for sampling purpose.
\item
  Now the samples were counted to determine the following parameters-
\item
  Number of species present in the grid
\item
  Total number of individuals present in the grid
\item
  Number of drilled samples
\item
  Number left valve: Number of right valve
\item
  Number of articulated samples
\item
  Percentage of fragmented samples
\item
  Sediment samples were analised to determine the grain size,shorting of
  grains and the grain type present at the area of collection of the
  samples.
\end{enumerate}

\textbackslash{}cftsetindents

figure0em8em

\section*{Sampling Justfication}\label{sampling-justfication}

\begin{enumerate}
\tightlist
\item
  From the changes in the total number of species found in the grids,
  two interpretations can be formulated. The variations may be due to
  changes in the suface slope of the regions concerned, which in turn
  may lead to the differential deposition of the depositing medium. If
  the number of species increases towards the backshore, then it can be
  interpreted that the slope of the surface, over which the deposition
  is taking place, is gradually increasing towards the backshore.
  Differential depositional capability of the medium may be the other
  plausible cause of the variation. If the medium looses a considerable
  amount of energy in between the two sampling spots, then the number of
  species will varry.
\item
  Total number of individuals varry between sampling spots mainly due to
  the changes in the intrinsic charecteristics of the depositing
  medium(type of medium,velocity of the medium,density of the medium
  etc.) as well as due to changes in the amount of the shell materials
  present in the medium. If the type of the medium changes the total
  number of individuals also varies. If the number of individuals
  increases from foreshore to backshore, then it can be interpreted that
  some other medium must had some influence in depositing the shell
  materials, as the energy of the wave decreases towards the backshore,
  making it less capable of depositing considerable number of
  individuals.
\item
  Number of drilled samples indicate the activity of the predator
  organisms in the area of sampling. If the number of drilled samples
  increases towards the backshore that will be the indication of
  increased favourable environments towards the backshore.
\item
  The fourth parameter which was calculated,was the number of ~left
  valve:number of right valve. This parameter indicate the degree of
  transportation by the concerned medium. If the amount of
  transportation is greater, then the ratio gradually approaches unity.
  Type of the two valves, ~whether they were equivalve or not, can be
  interpreted from this parameter. Valves with equal shape show same
  trend of transportation. If the valves are well sorted then they must
  had suffered considerable amount of transportation to attain the
  present sorting.
\item
  The last two parameters indicates the degree of fragmentation of the
  samples, vriation in the percentage of fragmented shells indicate
  variable terbulance or variable amount of transportation. If the area
  of deposition of the samples is close to the source area of the
  samples then the amount of fragmented samples decreases and number of
  articulated samples increases.
\end{enumerate}

\textbackslash{}cftsetindents

figure0em8em

\section*{Mapping}\label{mapping}

The mapping of the beach area was done using plane paper mapping
process. The scale of the map was taken to be 1:2500. This mapping was
carried out to evaluate the boundaries between the different parts of
the shore and tidalflat (both sedimentological and taphonomical
boundaries). The process of plain paper mapping is as follows-

\begin{enumerate}
\tightlist
\item
  Firstly the true north direction is marked on the plain paper. Further
  measurements of the angles are done taking this fixed line to
  represent the north direction.
\item
  Different fixed points of initiation are taken on a line of known
  orientation. These points fall on different boundaries between the
  various parts of the shore. These points are then plotted on the
  paper. Distances between the points are measured by footstep counting.
\item
  Moving along the boundaries from the points of initiation, front
  bearing of the consequtive points are taken. These points of
  frontbearing measurements are taken at certain distances. This
  distances are also measured by the foot-pacing technique.
\item
  Using the frontbearing and the converted distances (converting the
  actual distance to the scale of the map) the points on the boundaries
  are plotted on the plain paper. Line of the converted length along the
  frontbearing direction from the initiation point gives the wanted
  points. These points are then joined by freehand lines on the map.
  This line demarcates the boundary between two parts of the shore.
\item
  This process is repeted to get the complete length of the boundaries.
\item
  After demarcating the boundaries between the parts of the shore,
  boundaries between other major sedimentological environments are
  plotted on the map in the same process.
\item
  Boundaries between two regions of different abundant species, or
  boundaries separating different classes of the same species are
  plotted following the same procedure.
\end{enumerate}

Sedimentological Aspects Sedimentary Facies variations and its
associated structures

Chandipur gives a wide scope to study most of the sedimentological
aspects associated with different environments present in the area. The
presence of a narrow beach striking the vast tidal flat, a marshy land
near to estuary, bars and paleo-swamp create a wide environmental
diversity within a short geomorphic span. Easy distinguish of these
discrete environments and correlation of sedimentary processes as well
as products between them make the area especially favourable for
gathering first-hand knowledge about the environmental control on
sedimentary characteristics a basic requirement for sedimentary facies
analysis. The associated biota along with their traces also differ
drastically along with the changes of the sedimentary environments. In
this report, we attempted to focus on different environmental setup and
their association and relation with each other.

\textbackslash{}cftsetindents

figure0em8em

\section*{Lithological classification}\label{lithological-classification}

There are four facies can be distinguished based on lithology, structure
and biotic remains in Chandipur coastal region and are described
follows:

\textbackslash{}cftsetindents

figure0em8em\selectlanguage{english}
\begin{longtable}[]{@{}ll@{}}
\toprule
Facies & Description\tabularnewline
AEOLIAN FACIES & Aeolian facies was generated due to the wind activity
characterizing high energy condition, resulting in the formation of sand
dunes.\tabularnewline
TIDAL FLAT FACIES & Tidal flat is a seaward planar land where tide
activity is dominant. Depending on tide access the tidal flat is divided
into three zones: 1. Supratidal 2. Intertidal 3. Subtidal\tabularnewline
BEACH FACIES & Beach was formed due to wave reworking in the windward
part of bar.\tabularnewline
SWAMP FACIES & Swamp is a protected zone behind bar. It is a low energy
environment and therefore contains mud.\tabularnewline
&\tabularnewline
\bottomrule
\end{longtable}

\textbackslash{}cftsetindents

figure0em8em

\subsection*{Sedimentary Environment and its
Charactersticts}\label{sedimentary-environment-and-its-charactersticts}

\textbackslash{}cftsetindents

figure0em8em\selectlanguage{english}
\begin{longtable}[]{@{}lll@{}}
\toprule
Environments & Sediment Types & Sedimentary Structures\tabularnewline
Tidal Flat & Grain size very fine, mainly mud, algal mat present. &
Ripple marks(current, wave, lunate, ladder back,
superimposed)\tabularnewline
Aeolian Facies & Sediment grain size comparatively small, light colored,
well sorted. & Setulf structures, Aerodynamic ripple.\tabularnewline
Beach Facies & Both fine and coarse sediments are present. & Swash
ripples, Rhombic ripples, Current crescent,\tabularnewline
Swamp Facies & Dark colored muddy sediments. & Ripple marks, mud balls,
ophiomorpha burrows, Polychaete\tabularnewline
& &\tabularnewline
\bottomrule
\end{longtable}

\textbackslash{}cftsetindents

figure0em8em

Description of Individual Facies with structures

\textbackslash{}cftsetindents

figure0em8em

\section*{Aeolian facies}\label{aeolian-facies}

Aeolian processes in Chandipur are dominantly in the top portions of the
bar and in the backshore region of the beach. By trenching it can be
noticed that the sand layers are showing reverse grading, along with
evidences of grain flow and grain fall.

\subsection*{Dunes or Aeolian dunes}\label{dunes-or-aeolian-dunes}

Immediately landward of the backshore part of the beach are commonly
found large, linear accumulation of unconsolidated sand known as dunes.
They form as the wind carries sediment from the beach and deposits it
under a range of flow conditions. The sufficient sand supply and a
strong wind in the onshore direction are sole reason for formation of
these dunes. Sand dunes are characterized by the presence of steep slip
face and a gentle dipping windward side. Most of the dunes studied are
stabilized due to growth of vegetation on it. Internal structures of
Dune:

\subsection*{Horizontal bedding}\label{horizontal-bedding}

Horizontal bedding of sand dunes is composed of almost horizontal
laminae of sand. Usually, it is found on the windward slopes, flanks and
near the summit of a sand dune, the laminae are very thin and in
fraction of 1- 2 mm thickness. The sand was well sorted and sometimes
heavy mineral poor laminae.

\subsection*{Low angle trough cross
stratification}\label{low-angle-trough-cross-stratification}

It consists of a cross bedding unit in which the lower bounding surface
is curved. The units are trough shaped sets consisting of an elongated
scour filled with curved foreset laminae that commonly have a tangential
relationship to the base of the set. These are mostly low angle trough
cross stratification where the dip of the foreset lies between 10\selectlanguage{ngerman}°to
15°.

\subsection*{Translatent strata}\label{translatent-strata}

As deposition on the stoss side exceeds erosion hence ripples often seem
to climb on each other resulting formation of translatent strata. These
are typically characterized by inverse grading because of concentration
of coarse grains along ripple crests. It is commonly formed on the
windward slopes and flanks. Laminae are very thin and sometimes heavy
mineral rich laminae alternated with sand laminae are found.

\subsection*{Reverse grading}\label{reverse-grading}

An upward increase in grain size within a single bed is known as reverse
grading. This type of reverse grading is formed due to dispersive
pressure.

\subsection*{Normal grading}\label{normal-grading}

An upward decrease in grain size within a single bed is known as normal
grading. This is formed due to turbidity current. \textbf{Figure
\ref{f34}}

\subsection*{Aerodynamic ripples}\label{aerodynamic-ripples}

These are crescent shaped with low relief. These ripples show
concentration of coarse materials at the top. These are formed by the
effect of air to the substrate at a very low angle and energy of air is
so less that it cannot carry the coarse grains, hence accumulated on top
of the ripple Figure \ref{f25}

Setulf: It is a typical Aeolian structure formed by wind action due to
any obstacle present at the way of the wind. It is a structure of
positive relief. Obstacle and current are the two major structure for
the formation of the structure. A narrow ridge of sand is formed behind
any obstacle and gradually tapering away from the obstacle. This
tapering direction indicates the wind direction during the formation of
setulf structures. Larger the obstacles larger will be the ridge behind
it. The length of ridge behind the obstacle is proportional with the
obstacle size.

\textbackslash{}cftsetindents

figure0em8em

\section*{Beach facies}\label{beach-facies}

Beach is the most dynamic of all depositional environments. Wave energy
is the major factor that controls the development and changes in the
beach. The seaward side of the beach is bounded by an extensive tidal
flat, during high tide levels, waves are generated by the shear action
of wind over the water resulting in the formation of this narrow beach.
The beach sediments are mostly those eroded from the Aeolian dune
fields. The general trend of beach is NE-SW. The average width of the
beach is 40-50 m. The contact between beach \& tidal flat is sharp
whereas the contact between the beach \& Aeolian dune field is defined
by an erosional berm.

The beach facies are divided in two sub-facies-Foreshore and Backshore,
having their own

characteristics. Foreshore is characterized mainly by fine grained sand
and the morphology of the surface of foreshore is generally planar and
the slope increases slightly towards the backshore. On the other hand,
the backshore is characterized by relatively coarser grains of sand with
respect to the sand grains of foreshore and is dry, well sorted and well
rounded in nature. Grain size increases further towards the dune field.

The following sedimentary structures are found in the beach enviornment
are:

\subsection*{Current Crescent}\label{current-crescent}

Current crescents are arcuate scours that are preserved on bedding
surface and these are formed, as current flows around an obstacle on the
bed i.e., debris, shells or a single particle. The form of the crescent
reflects the pattern of flow around the obstacle. At the leading edge of
the obstacle, a rolling vortex develops which produces a curved scour
with ``arms'' extending downstream from the sides of the obstacle.
Further downstream sediment that has been eroded from the bed is
deposited in two lobes, on either side of the object (but downstream
from it) forming areas of higher relief than the ambient bed. In
well-developed crescents, a medial ridge separates the two lobes. The
combination of erosional and depositional features collectively make up
the current crescent. The form of a current crescent appears to depend
on the size and shape of the obstacles, the flow conditions and the
duration of time over which the structure forms. In general, when flows
are of short duration or if the obstacle is moved away from the scour
shortly after the current becomes active the structure may resemble a
small, crescent shaped scoured immediately around the upstream edge and
sight of object; there may be little deposition such that the
depositional lobes are difficult to recognize. In contrast, when the
current is of significant duration and the obstacle remains stationary
the depositional lobes may generate two trends of low ripples that can
extend for centimetres to meters downstream, depending on the size of
the obstacle.

\subsection*{Rhombic Ripples}\label{rhombic-ripples}

It is an aqueous current ripple mark characterized by a reticular
arrangement of diamond-shaped tongues of sand, with each tongue having
two acute angles, one pointing upcurrent and the other pointing down
current. These are one of the most common structures that are found on
the beach, formed by swash and the backwash currents. During the swash a
straight crested ripple is formed and during backwash another similar
ripple is formed at an angle to the previous ripple and forms a rhomboid
structure. These ripples develop under very thin layer of water, usually
on the seaward slope of the beaches. The trends of the ripples give us
the direction of the swash and the backwash on the beach.

\textbackslash{}cftsetindents

figure0em8em \textbf{Figures \ref{f31}
\ref{f99} \ref{f100}}

\subsection*{Swash Ripples}\label{swash-ripples}

The front of the dying waves during backwash leave behind a pattern of
tiny imbricating sand ridges with their convexity landward that marks
the line of further encroachment of the waves. They were composed of
very fine sand. Usually coarser but hydrodynamically lighter materials
like broken shells, wooden fragments accumulated along their curved
ridges. These lines in some cases are defined mainly by molluscan
shells. Swash marks are excellent indicators of the shoreline of a sea
or lake. Because of the subtle relief of bed features in the swash zone
the preservation potential of related internal stratification is low.
The most likely internal structures to be preserved are those relating
to beach-slope changes resulting from:

\begin{enumerate}
\tightlist
\item
  Storm erosion and post storm recovery:
\item
  Profile cut-and fill due to tidal translation of the swash zone
\item
  Migration of beach cusps.
\end{enumerate}

Beach deposits are characterized by seaward dipping, Continuous planar
to curved parallel laminae, often with alternating fine and coarse
grained laminae. Coarsening upward sequences of beach laminae occur in
relation to beach cusps. Reverse grading within individual beach laminae
is ubiquitous, and results from dispersive pressure within the highly
concentrated bed load transport layer that is characteristics of swash
and backwash flow. \textbf{Figure \ref{f32}}

\subsection*{Rill Marks}\label{rill-marks}

Rill marks are small dendritic channels or grooves that form on the
beaches by the discharge of pore waters at low tide, or by small streams
debouching onto a sand or mud flat. These are bifurcating dendritic
erosional sculptures. These acquire diverse forms such as branching rill
marks, meandering rill marks, tooth shape rill marks, comb shaped rill
marks, bifurcating rill marks etc.

\subsection*{Biogenic Structures}\label{biogenic-structures}

The burrowing, boring, feeding and locomotion activities of organisms
can produce a variety of trails, depressions and open burrows and
borings in sand. Filling of these depressions and burrows with sediments
of a different type or with different packing create structures that may
be either positive relief features such as trails on the base of
overlying beds, or features that show up as burrow or bore fillings on
the tops of the underlying mud beds. Burrows and borings commonly
extends down into beds therefore these structures are not exclusively
bedding-plane structures.

\textbackslash{}cftsetindents

figure0em8em

\section*{Swamp facies}\label{swamp-facies}

Swamps can be defined as low-lying, vegetated, marshy lands which occur
at a higher level, relative to mean tide level. These are usually
flooded only by the highest spring tides.

Swamp or the marshy-land is the portion between the two bars which
represents calm and quite environment free from the interference of sea
water. Swamp facies is mainly described by the marshy-land, located near
the mouth of the Buribalam river. It is characterised by the huge
concentration of clay with mangroves and grassland.

Several creeks are also present there in which the abundance of one type
of gastropod, \emph{Telescopium sp.} is also seen. Hyper salinity and
anoxic condition prevailing in the swampy area, restrict the generation
of grazer fauna but allows algal mat deposition over a broad area.

In Chandipur, we have encountered both Active swamp and Paleo swamp.

\subsection*{General Characters of Active
Swamp:}\label{general-characters-of-active-swamp}

\begin{enumerate}
\tightlist
\item
  The mud is soft and water laden
\item
  Active population present.
\end{enumerate}

\subsection*{General Characters of Paleo
Swamp:}\label{general-characters-of-paleo-swamp}

\begin{enumerate}
\tightlist
\item
  The mud is thixotropic.
\item
  No active population.
\item
  Knobby surface with dead plant rootlets.
\item
  The ophiomorpha burrows of the paleo-swamp are filled with sand.
\end{enumerate}

\textbackslash{}cftsetindents

figure0em8em \textbf{Sedimentary structures found in the swamp
environment}

\subsection*{Plane Laminated mud}\label{plane-laminated-mud}

Plane laminated mud was seen which indicates the deposition of mud from
suspension.

\subsection*{Mud balls and armoured mud
balls}\label{mud-balls-and-armoured-mud-balls}

The mud is extensively reworked, excavated and deposited in the form of
mud balls on the beach and they are oriented in different directions.
Mud chunks are scooped up by \textbf{wave and during rolling these
become rounded and} \textbf{gather small} fragments of shells etc.,
around them and become armoured mud balls.

\subsection*{Ophiomorpha burrow}\label{ophiomorpha-burrow}

These are the vertical burrows. We encountered such burrows behind the
Cerethium zone of the modern swamp area. Most of the burrows have the
height range of 2.5 to 4cm. We encountered maximum 4.8cm height of
ophiomorpha burrow. Some burrows were found destroyed.

\textbackslash{}cftsetindents

figure0em8em

\section*{Tidal Flat facies}\label{tidal-flat-facies}

Tidal flats are coastal wetlands that form when mud is deposited by
tides. They are found in sheltered areas such as bays, lagoons,
estuaries, etc. It is a transitional environment.

A tidal flat consists of 3 parts:

\begin{enumerate}
\tightlist
\item
  \textbf{Sub-tidal flat:} The area below the low water line is called
  the subtidal flat. The subtidal flat always remains submerged
  underwater. Characterized by: muddy sediments.
\item
  \textbf{Inter-tidal flat:} The area between the high water and low
  water line. It remains submerged during flood tide and is exposed
  during ebb tide Characterized by: Fine silt and mud, herring bone
  cross stratification, desiccation cracks.
\item
  \textbf{Supra-tidal flat:} The area above the high-water line is known
  as supratidal flat. It always remains exposed. Characterized by:
  Evaporates, small-scale bedforms.
\end{enumerate}

The major bedforms observed in tidal flats are ripples of diverse and
complex forms. It is well known that bedforms are controlled by water
depth, bed shear and grain size (Middleton and Southard 1984).

However, the final architecture of bedforms in tidal flats is mainly
governed by the combined influence of variable flow directions
controlled by waves and tides during falling tide level (when shear
velocities decline), wind stress and recession of water level on various
sloping surfaces. As a result, a great variety of bedforms on the
intertidal surface is expected.

Bedforms found in the Tidal flat enviornment

\subsection*{Ripple marks}\label{ripple-marks}

The ripple marks found in the Chandipur tidal flat show a wide variety
of architecture. There is wave generated current ripples, cuspate
ripples, ladder back ripples and interference ripples.

\subsection*{Straight crested ripples}\label{straight-crested-ripples}

These ripples have straight crests, these are symmetrical in nature.
These often show bifurcation of crests. These ripples are formed in
lowest energy condition.

\subsection*{Sinuous ripples}\label{sinuous-ripples}

These ripples have crests which are gently curved (s-shaped in nature).
These ripples are asymmetric in nature. Sinuous ripples are formed under
slightly higher energy condition with respect to the previously
described straight crested.

\subsection*{Lunate ripples}\label{lunate-ripples}

These are curved crested assemblage of asymmetric ripples with up
current closure. Some of them have a lee facing landward near the shore
and some of them have lee facing seaward near the off-shore.

\subsection*{Interference ripples}\label{interference-ripples}

These ripples consist of two sets of ripples at high angle to each
other. Crest of these ripples are sinuous. These are produced because of
interaction of tidal current and wave. In the trough of these ripples
silty sand accumulates in a thin layer. The inter crest areas are called
tadpole nests. Some ripples with three ridges like crest diverging from
a point are observed.

\subsection*{Ladder back ripples}\label{ladder-back-ripples}

At some places in the troughs of the straight crested ripples smaller
ripple are found to occur, giving a ladder like appearance. during ebb
tide as the water level gradually falls some amount of water get
entrapped within the trough of the larger ripples and flow takes place
along these troughs and a second set of smaller ripples are produced
which migrate in the direction normal to that of the larger ripples.

Ladder-back ripples are formed when during ebb tide the water level
gradually falls some water gets entrapped within trough of the larger
straight crested ripples and when flow takes place a second set of
smaller ripples are produced which migrate in a direction normal to that
of the larger ripples.

\subsection*{Flat top ripples}\label{flat-top-ripples}

These ripples are of shallow origin. The crests may be curved or
straight crested but the crest is flattened due to high flow shear.
During ebb tide the ripple crests get liquefied, flattened and deformed.

\subsection*{Bioturbation}\label{bioturbation}

The biotic activity in the tidal flat is noticeable due to presence of
nutrients in appreciable amount. A thin layer of algal-mat is found to
be precipitated from the sea water just after the tide. A lot of
organisms are living on the tidal flat. Bivalve like \emph{Natica sp.,
Cardiam sp., Cerethium sp.} Etc, polychaete burrow, sea-weed, hydrozoas,
hermit-crab occupying dead shells of gastropods A remarkable
concentration of \emph{Cardium sp.} is mainly confined within a thick
mud dominated bed in the subdital zone which is devoid of ripples. In
the zone of paleo-mud the huge abundance of \emph{Cerethium sp.} is
seen. Tracks of different organism are also observed in this area.
Tracks of Natica sp. are broader and deeper than the tracks of
hermit-crab. Tracks of \emph{Cerethium sp.} are narrower and shallow.

Measurement of Wave Parameters

\textbackslash{}cftsetindents

figure0em8em

\section*{Wave Parameters}\label{wave-parameters}

Wave parameters are the group of characteristics that identify a wave.
Both the character and the frequency of wave action have profound
impacts on coastal sediment dynamics. Waves distribute and sort sediment
in direct relationship to the distribution and magnitude of wave forces.
This leads to the development of terrigenous sediment accumulation
patterns in which the coarsest sedimentary particles are in areas
subject to the highest wave forces and fine-grained deposits reside in
regions characterized by low energy waves. The prevailing approaches of
winds and waves leaves an important imprint on sediment transport and,
therefore, coastal type. Because beaches are constructed and modified by
wave processes, they are constantly changing at rates which are
dependent on wave characteristics, tides and ultimately, on
meteorological conditions which control wave formation.

\textbf{Waves} are formed by the frictional drag of wind across the
water surface. There is a process of transfering energy from wind to
water. Water particles are moved from their position by the wind, and
are then returned to the original position by gravity which is a
restoring force. These are called gravity waves. The result is a
circular motion by the water particles. The energy is transported, but
not the water through which the energy travels. The \textbf{size} of the
waves resulting from the energy transfer is governed by the velocity of
the \textbf{wind (W)}, B or distance over which the wind blows, and the
duration (D) of time that the wind blows, summarized as: \textbf{H, P =
function (W,F,D)}

where

\begin{itemize}
\tightlist
\item
  \textbf{wave length (L)} which is the horizontal distance between two
  crests
\item
  \textbf{wave Height (H)} the elevation of the crest above the trough,
  and
\item
  \textbf{wave period (P)} which is the interval of time for two wave
  crests to pass the same position in space
\end{itemize}\selectlanguage{english}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=0.98\columnwidth]{figures/wave/wave}
\caption{{\textbackslash{}cftsetindents
figure0em8em Sine wave pattern and associated parameters in ocean waves.%
}}
\end{center}
\end{figure}

\textbackslash{}cftsetindents

figure0em8em

\section*{Measurement of Wave
Parameters}\label{measurement-of-wave-parameters}

In the field a simple procedure was followed to measure the wave
parameters, the following apparatus were used: Measuring tape, wooden
stands, and stop watches. Two wooden stands were placed at fixed
intervals(30m and 20m).The time and height of the crest when the wave
hit the wooden stand were measured at both stations.Thus the time
period,time required for the crest to travel the distance between the
two fixed stations were obtained. From which the other parameters were
calculated.

\begin{itemize}
\tightlist
\item
  \textbf{Wave Velocity} = Distance between the two stations / time
  taken to travel that distance.
\item
  \textbf{Wave Frequency} = 1/ wave period
\item
  \textbf{Wavelength} = Wave Velocity/Wave Frequency
\end{itemize}

Given the fact that the still water depth was very nominal, as the slope
of the tidal flat is
low(\textbackslash{}(1\textbackslash{}degree-2\textbackslash{}degree\textbackslash{})),
the crest height was considered to be the wave height.

\textbackslash{}cftsetindents

figure0em8em

Table of debis/polutant collected

DEGRADABLE WASTE

FREQUENCY

Cask of green coconut

9

Burnt wood

NON-DEGRADABLE WASTE

FREQUENCY

Plastic paper

45

Ice-cream cup

64

Plastic cup

49

Plastic glass

58

Plastic packet

65

Plastic bottles

34

Glass bottles

16

\textbackslash{}cftsetindents

figure0em8em\selectlanguage{english}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=0.98\columnwidth]{figures/hvt30/hvt30}
\caption{{\textbackslash{}cftsetindents
figure0em8em heights at Station 1 and 2 in meters, and velocity in m/s
vs time%
}}
\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=0.98\columnwidth]{figures/hvt20/hvt20}
\caption{{\textbackslash{}cftsetindents
figure0em8em heights at Station 1 and 2 in meters, and velocity in m/s
vs time%
}}
\end{center}
\end{figure}

\textbackslash{}cftsetindents

figure0em8em

Palaeontological Aspects The Invertrabrate Molluscan Fauna of Chandipur

\textbackslash{}cftsetindents

figure0em8em

\section*{Introduction}\label{introduction}

Chandipur is an area where the sea water regularly traverses nearly 4km
and this makes an expanded scope for studying the biodiversity of
organisms of both the beach and submarine environment.

During the field work a large amount of organism remains in order to
study the biodiversity of area. Specimens are collected from Foreshore,
Backshore, Dune, Distal bar.

Major faunas that are collected from area are:

\begin{itemize}
\tightlist
\item
  Bivalvia.
\item
  Gastropoda.
\item
  Echinoidia.
\item
  Crabs
\item
  Star Fishes.
\item
  Brachiopoda.
\end{itemize}

Chandipur coast supports diverse marine life of which the molluscs are
predominant. Both gastropods and bivalves are equally abundant. It has a
complex outspread of variety in terms of sedimentary facies. Within a
small lateral span of 4km it boasts of an extensive tidal flat, a narrow
beach, some barrier bars, marshy areas behind bars and a palaeo-swamp.
Each area has its own set of characteristic features that determine the
kind of organisms that can survive in them. Thus the entire coastal
province of Chandipur, exhibits an outstanding plethora of invertebrate
fauna, controlled by the existing climate, temperature, salinity,
nutrient supply and intensity of wave action of the area. The diurnal
onset of tidal action, submerge the tidal flat and beach every 12 hours
or so, making the environment here extremely stressful. The organisms
inhabiting here have to get exposed to sun during periods of ebb- tide.
And again gets submerged in water alternately. So here diversity of
organism is less. Most of the organism living here are
\textbf{eurytopic} and \textbf{euryhaline} thus to cope with physico
--chemically stressful habitat. The vast array of morphologic types of
this area is a biological storehouse providing insight about the
different life mode of molluscs.

It shows a great variety of sedimentary aspects as well as serves as a
biological aquarium having a great diversity of life forms sharing the
same room. However our study in field was restricted to benthic fauna
only but even within this restricted study the diversity is clearly
visible which we document in the ensuing pages

We found more or less 18 bivalve species in our total sample collection.
These bivalves also differ in their life mode and habitat. The following
table given below shows the bivalve diversity based on the collected
bivalve species in Chandipur.

\textbackslash{}cftsetindents

figure0em8em

\section*{BIVALVIAN COMMUNITY IN
CHANDIPUR}\label{bivalvian-community-in-chandipur}

\textbackslash{}cftsetindents

figure0em8em\selectlanguage{english}
\begin{longtable}[]{@{}lll@{}}
\toprule
\begin{minipage}[b]{0.32\columnwidth}\raggedright\strut
\textbf{TAXONOMY} \textbf{CLASS BIVALVIA}\strut
\end{minipage} & \begin{minipage}[b]{0.32\columnwidth}\raggedright\strut
\textbf{MORPHOLOGICAL FEATURES}\strut
\end{minipage} & \begin{minipage}[b]{0.32\columnwidth}\raggedright\strut
\textbf{LIFE MODE}\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Donacidae GENUS - Donux SPECIES - scortam\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Equivalved shells, inequilateral, deep pallial sinus, strongly
anisomyarian, small siphonal gape and elongated pedal gape
present.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Deep Burrower (Infaunal)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY -- Mactridae GENUS -- Mactra SPECIES -- luzonica\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Equivalved shell, nearly isomyarian, anterior -posterior line parallel
to hinge line, shallow pallial sinus.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shallow burrower\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY -- Pholadidae GENUS -- Pholas SPECIES --orientalis\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Elongated tube like body, strongly anisomyarian, both concentric and
radial ornamentations present, towards anterior side spinose appearance
helps in excavation.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Mud borer or weathered rock borer (infaunal)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Solenidae GENUS- Solen SPECIES- kempi\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Stream lined body, thin shell, permanent siphonal and pedal gape
present, shallow pallial sinus.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Deep burrowing infaunal\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Ostreidae GENUS- Ostrea SPECIES- sp\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Strongly inequivalved, irregular shell surface, inequilateral,
monomayarian,thick shell.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Cemented\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Veneroidae GENUS- Meritrix SPECIES- meritrix\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Very thick shell\textbf{,} triangular in shape\textbf{,} hinge line
curved\textbf{,} heterodont dentition\textbf{,} shallow pallial
sinus.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shallow burrower\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Arcidae GENUS- Anadara SPECIES- granosa\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Quadrangular shaped\textbf{,} equivalved\textbf{,}
inequilateral\textbf{,} strong radial ridges\textbf{,} fine concentric
elements\textbf{,} nearly isomayarian\textbf{,} straight hinge
line\textbf{,} taxodont dentition.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shallow burrower\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Veneroida GENUS- Sanguinolaria SPECIES- acuminate\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shell elongated, highly compressed, strongly inequilateral, posterior
tapered, anterior rounded, deep pallial sinus, concentric growth line
ornamentation, violate colour.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Rapid deep burrower (infaunal)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Mactridae GENUS- Mactra SPECIES- violacea\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shell large, moderately thin, inequilaterally inflated,umbo prominent
elevated, anterior shorter than posterior, rounded anterior and
posterior margins, sculptured with fine concentric striation, violate in
colour.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shallow burrower\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Myoidea GENUS- Mya SPECIES- sp\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Elongated chalky, mostly burrowing forms with wide posterior gapes,
chondrophore with triangular anterior portion, in front of anterior
ridge.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Infaunal\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Mactridae GENUS- Mactra SPECIES- turgida\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shell large, strong , ovately triangulate, umbo elevated, sculpture with
fine concentric striae, more prominent in umbonal region.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shallow burrower\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Arcidae GENUS- Arca SPECIES- sp\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shell thick, strongly convex, rhomboidal sides, angulated at dorsal
margin, posterior extended, hinge and muscle line parallel, umbo
elevated,ventral almost flat, radially ribbed.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Epifaunal\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Carditidae GENUS- Cardium SPECIES- asiatiicum\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Shell globuse, almost equilateral, lateral teeth and cardinal teeth
present, flattened posterior, anterior is rounded, ventral margin
broadly rounded, pallial line is uninterrupted, deep pallial
sinus.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Infaunal\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Donacidae GENUS- Donax SPECIES- incarnates\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Sub triangular, sharply angular while anterior part rounded, deep
pallial sinus, heart shaped escutcheon present, concentric ridges and
weak radial lines, spines and posterior and external ligament groove,
white in colour.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Deep burrower\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Pholadidae GENUS- Barnea SPECIES- candida\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Large, thin and elongated shell, horizontal ribs crossed by vertical
ribs.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Borer\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Tortricidae GENUS- Sonia SPECIES- scripta\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Pectinidae GENUS- Chlamys SPECIES- sp\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Semi circular, fan shaped, wings or auricles present, anterior ear
larger than posterior ear, orthogyral umbo, internal ligament groove
flanked by two small ridges, monomyarian, and non- siphonate.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Epibyssate\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
FAMILY- Mytilidae GENUS- Mytilus SPECIES- edulis\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Sub triangular shell, anterior highly reduced and pointed, flattened
ventral, byssal notch.\strut
\end{minipage} & \begin{minipage}[t]{0.32\columnwidth}\raggedright\strut
Epibyssate\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

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\begin{center}
\includegraphics[width=0.98\columnwidth]{figures/image19/image19}
\caption{{\textbackslash{}cftsetindents
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\end{center}
\end{figure}

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figure0em8em

\section*{GASTROPODA COMMUNITY IN
CHANDIPUR}\label{gastropoda-community-in-chandipur}

We found more or less 11 gastropod species in our total sample
collection. These gastropods also differ in life mode and habitat. The
following table given below shows the gastropod diversity based on the
collected gastropod species in Chandipur.

\textbackslash{}cftsetindents

figure0em8em\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
\textbf{GASTROPODA} & \textbf{MORPHOLOGICAL FEATURES} & \textbf{Raupian
Parameters} & \textbf{Life Mode}\tabularnewline
\midrule
\endhead
FAMILY-Cerithiidae GENUS-Cerithium SPECIES-cerithium & Conical shell,
Dextral coiling. & T \textgreater{}D\textgreater{}W & SWAMP
ENVIRONMENT\tabularnewline
FAMILY-Potamididae GENUS-Telescopium SPECIES-telescopium & Conical shell
strongly reminiscent of an ice cream cone, the largest of horn snails,
dextral coiling, operculum small and circular. &
T\textgreater{}D\textgreater{}W & SWAMP ENVIRONMENT\tabularnewline
FAMILY-Turitrllidae GENUS-Turritela SPECIES- attenuate & Shell large,
elongated, dextral coiling. & T \textgreater{}D \textgreater{}W &
EPIFAUNAL\tabularnewline
FAMILY-Olividae GENUS-Oliva SPECIES-caerulea & Thick shell, polished,
bullet shell, spire very short, sutural groove narrow and deep, dextral
coiling,ornamented with dark spots. & T\textgreater{}W\textgreater{}D &
EPIFAUNAL\tabularnewline
FAMILY-Olividae GENUS-Amalda SPECIES-ampla & Thick shell, polished,
bullet shell, spire very short, sutural groove narrow and deep, dextral
coiling. & T\textgreater{}W\textgreater{}D & EPIFAUNAL\tabularnewline
FAMILY-Naticidae GENUS-Natica SPECIES-tigrine & Shell relatively thick,
deep umbilicus partly covered by callus, surface with mottled with
closed set of purplish brown dots, body whorl larger than spire. &
W\textgreater{}D\textgreater{}T & EPIFAUNAL\tabularnewline
FAMILY-Naticidae GENUS-Polynesis SPECIES-didyma & Shell relatively
thick, deep umbilicus totally covered by callus, body whorl larger than
spire. & W\textgreater{}D\textgreater{}T & EPIFAUNAL\tabularnewline
FAMILY-Turridae GENUS-Turricula SPECIES-javana & Small shell, brown
coloured, dextral coiling, strong ridges and costae. &
T\textgreater{}W\textgreater{}D & EPIFAUNAL\tabularnewline
FAMILY-Bursidae GENUS-Bursa SPECIES-rana & Large shell, spire conical
and elevated, outer lip denticulated, spiral threads on body whorl
sculptered with prominent varices which bears spines, siphonal canal
short. & T\textgreater{}W\textgreater{}D & EPIFAUNAL\tabularnewline
FAMILY-Tonnidae GENUS-Tona SPECIES-dolium & Thin shell, globular form,
spire turbiniform, well developed long band like basal fasciole. &
T\textgreater{}W\textgreater{}D & EPIFAUNAL\tabularnewline
FAMILY-Muricidae GENUS-Murex SPECIES-tribulus & Fusiform shaped,
siphonal canal elongated and narrowly open, body whorl large bears three
varices, spines present & T\textgreater{}W\textgreater{}D &
EPIFAUNAL\tabularnewline
& & &\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
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\includegraphics[width=0.98\columnwidth]{figures/IMG-0684/IMG-0684}
\caption{{\textbackslash{}cftsetindents
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\end{center}
\end{figure}\selectlanguage{english}
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\includegraphics[width=0.98\columnwidth]{figures/IMG-0687/IMG-0687}
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\end{center}
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\end{center}
\end{figure}\selectlanguage{english}
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\includegraphics[width=0.98\columnwidth]{figures/IMG-0702/IMG-0702}
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\begin{figure}[h!]
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\includegraphics[width=0.98\columnwidth]{figures/IMG-0692/IMG-0692}
\caption{{\textbackslash{}cftsetindents
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\end{center}
\end{figure}

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SPATIO-ENVIRONMENTAL VARIATION IN THE FAUNAL ASSEMBLAGES

\textbackslash{}cftsetindents

figure0em8em

\section*{Other Biota Assemblages}\label{other-biota-assemblages}

The Chandipur coast also supports other variety of faunal assemblages
other than the major molluscan groups which include:

\begin{enumerate}
\tightlist
\item
  Echinodermata.
\item
  Sea anemone.
\item
  Polychaete.
\item
  Ocypode crabs.
\item
  Hermit crabs.
\item
  Horseshoe crabs
\end{enumerate}

\subsection*{Echinodermata}\label{echinodermata}

\textbf{Kingdom} : Animalia\\
\textbf{Sub-kingdom} : Eumetazoa\\
\textbf{Phylum} : Echinodermata

\begin{itemize}
\tightlist
\item
  These are recognized by their radial symmetry, and include such
  well-known animals as starfish, Sea urchins and Regularia.
\item
  Most of the Star fishes and were found at the tidal flat, from the
  intertidal zone to the abyssal zone.\\
\item
  The dead shells of the subclass Regularia were dominantly found in the
  distal bar.
\end{itemize}

\subsection*{Sea anemone}\label{sea-anemone}

\textbf{Kingdom} : Animalia\\
\textbf{Phylum} : Cnidaria\\
\textbf{Class} : Anthozoa

\begin{itemize}
\tightlist
\item
  These are a group of water-dwelling, predatory animals of the order
  Actiniaria.
\item
  They are named for the anemone, a terrestrial flower.
\item
  Sea anemones are classified in the phylum Cnidaria, class Anthozoa,
  subclass Hexacorallia.
\item
  Anthozoa often have large polyps that allow for digestion of larger
  prey and lack a medusa stage.
\item
  Ascnidarians, sea anemones are related to corals, jellyfish,
  tube-dwelling anemones, and Hydra.
\end{itemize}

\subsection*{Polychaetes}\label{polychaetes}

\textbf{Kingdom} : Animalia\\
\textbf{Phylum} : Annelida\\
\textbf{Class} : Polychaeta

\begin{itemize}
\tightlist
\item
  Polychaetes are segmented worms, generally less than 10 cm (3.9 in) in
  length, although ranging at the extremes from 1 mm (0.039 in) to 3 m
  (9.8 ft.). Each segment bears a pair of paddle-like and highly
  vascularized parapodia.
\item
  Polychaetes vary widely from this generalized pattern, and displays a
  range of different body forms. The most generalized polychaetes are
  those that crawl along the bottom.
\item
  The head includes a pair of antennae, tentacle-like palps, and a pair
  of pits lined with cilia, known as ``nuchal organs''. These latter
  appear to be chemoreceptors, and help the worm to seek out food.
\item
  The polychaetes are most common in the Tidal flat environment
\end{itemize}

\subsection*{Ocypode crabs}\label{ocypode-crabs}

\textbf{Kingdom} : Animalia\\
\textbf{Phylum} : Arthropoda\\
\textbf{Class} : Malacostraca\\
\textbf{Order} : Decapoda\\
\textbf{Family} : Ocypodidae\\
\textbf{Genus} : \emph{Ocypode}

\begin{itemize}
\tightlist
\item
  Ocypode is a genus of ghost crabs found in the sandy shores of the
  Candipur beach.
\item
  They have a box-like body, thick and elongated eyestalks, and one claw
  is larger than the other in both males and females. They inhabit deep
  burrows in the intertidal zone.
\item
  They are primarily nocturnal, and are generalist scavengers and
  predators of small animals.
\item
  It constructs simple to complex deep burrows in soft sandy and/or
  muddy substrates.
\item
  They are be found in sandy beaches, sand bars, and in estuarine areas.
\end{itemize}

\subsection*{Hermit crabs}\label{hermit-crabs}

\textbf{Kingdom} : Animalia\\
\textbf{Phylum} : Arthropoda\\
\textbf{Class} : Malacostraca\\
\textbf{Order} : Decapoda

\begin{itemize}
\tightlist
\item
  Most species are aquatic and live in varying depths of salt water,
  from shorelines to deep sea bottoms.
\item
  Tropical areas host some terrestrial species, though even those have
  aquatic larvae and therefore need access to water for reproduction.
\item
  Most hermit crabs are nocturnal.
\item
  A few species do not use a ``mobile home'' and inhabit immobile
  structures left by polychaete worms, vermetid gastropods, corals, and
  sponges.
\item
  Hermit crabs in Chandipur were found in the tidal flat hosted in a
  variety of dead gastropod shells e.g. \emph{Natica, Nassarius,
  Polinices, Turricula, Turritella} to name a few.
\item
  The abundance of the hermit crabs gradually decreased towards the open
  sea.
\end{itemize}

\subsection*{Horseshoe crabs}\label{horseshoe-crabs}

\textbf{Kingdom} : Animalia \textbf{Phylum} : Arthropoda \textbf{Family}
: Limulidae

\begin{itemize}
\tightlist
\item
  The entire body of the horseshoe crab is protected by a hard carapace.
\item
  It has two compound lateral eyes, each composed of about 1,000
  ommatidia, plus a pair of median eyes that are able to detect both
  visible light and ultraviolet light, a single endoparietal eye, and a
  pair of rudimentary lateral eyes on the top. The latter become
  functional just before the embryo hatches.
\item
  Most of the horseshoe crabs found in Chandipur were found in front of
  the palaeo dune in a restricted swampy environment possibly feed by
  water during high surges of tide.
\end{itemize}

\textbackslash{}cftsetindents

figure0em8em

\section*{Facies wise distribution of the faunal
assemblage}\label{facies-wise-distribution-of-the-faunal-assemblage}

A faunal assemblage is a group of associated animal fossils found
together in a given stratum. Faunal assemblage of any environment is
determined by type of `substratum' and `nutrient' present at that
particular environment.

\begin{itemize}
\tightlist
\item
  Factors affecting the faunal assemblage of an area:
\item
  Type of the substratum
\item
  Energy of the environment
\item
  Availability of food
\item
  Types of organisms living in the area
\end{itemize}

Feeding mechanisms is an important factor in the relationship between
substratum and distribution of benthic organisms. In muddy sediments
deposit feeders are more abundant than the suspension feeder as fine
organic matters settles at the bottom in that low energy environment.
Whereas in sandy environment, the suspension feeders dominate. This is
because, deposition of coarse-grained sand occurs in relatively high
energy condition and this greater agitation keeps the food particles in
suspension mode.

\textbackslash{}cftsetindents

figure0em8em

\section*{FAUNAL ASSEMBLAGE OF BEACH}\label{faunal-assemblage-of-beach}

On the beach, numerous dead shells of bivalves and gastropods of various
species were observed. The bivalve shells were mostly disarticulated.
The shells of Mactra were most dominant all along the beach. Apart from
this species, \emph{Mactra violetia, Macoma, Donax scortum, Arca,
Cardium, Solen, Ostre aand} so on were present. In the beach, in front
of the bar, large number of Barnea and towards the estuary, some dead
shells of Meretrix meretrix were also found. The gastropods shells were
\emph{Natica, Cerethidae, Olivagibbosa}, \emph{Turritella, Murex}, etc.
Crabs are present abundantly in the burrows on the backshore regions.

\subsection*{Size sorting of the shells across the
beach}\label{size-sorting-of-the-shells-across-the-beach}

At Chandipur, we have observed different types of molluscan shells in
the beach. These shells are dispersed according to their size in
different parts of the beach. At the uppermost limit of foreshore,
larger shells are found. But near the beach tidal-flat contact, mostly
smaller shells accumulate. This deposition of shells at different zones
of the beach is due to variation of wave energy during swash and
backwash. The swash is much more powerful than the backwash. The swash
brings shells of various size onto the beach. But as the capacity to
move the shells becomes less in backwash, the larger shells only get
disposed along the upper limit of the tide while the smaller sized
shells are moved towards the tidal flat. The slope of the tidal flat
being very less (1-3{[}2070?{]}), the energy of backwash becomes
incapable of even carrying the smaller shells to the flat. So the
smaller shells get dumped in the lower part of the beach i.e., along the
tidal flat -beach boundary. Innumerable small shells and broken
fragments of shells are found dumped in places parallel to each other in
foreshore. They are aligned perpendicular to the shore line and pinch
out away from shore. The shells probably get deposited in that linear
fashion by some vortex action of the wave.

\begin{itemize}
\tightlist
\item
  The larger shells consist of \emph{Mactramera, Mactravioletia,
  Turritella, Donax} The smaller shells consist of- \emph{Natica,
  Mactraluzonica, Arca, Anadara, Cardium}
\item
  The smallest shells consist of- \emph{Anadara, Cardium, Donax,
  Mactraluzonica, Cerethidae, Ostrea} etc.
\end{itemize}

\textbackslash{}cftsetindents

figure0em8em

\section*{FAUNAL ASSEMBLAGE OF BAR}\label{faunal-assemblage-of-bar}

The Bar is dominated mainly by dead shells o\emph{f Mactraviolatia,
Mactraluzonica, Arca, Solen, Glauconome, Mya, Sanguinolariaetc}. Among
gastropods,Tonna, Natica, Turritella, Cerethidaewere common. The
palaeomud in front of the bar wascolonized by mud-boring bivalves like
Mya, Glauconome, Sanguinolariaetc. They werefound in their live in-situ
position. On the bar top, abundant red crabs were seen living in
theirburrows. Interbar area was dominated by the gastropods like
\emph{Cerethidae, Telescopiumtelescopium.} Dead shells of \emph{Murex}
and \emph{Turitellaare} also present in this part.Juvenile shells of
Ostrea are also present.

\textbackslash{}cftsetindents

figure0em8em

\section*{FAUNAL ASSEMBLAGE OF SWAMP}\label{faunal-assemblage-of-swamp}

The organic population of the marsh was not so enriched as the other
sub-environments. Here we found mostly the brackish assemblage. It was
dominated mainly by living gastropod Telescopium telescopium. Besides,
dead shells of \emph{Cerethidae cingulat} aand few fresh water
gastropods were observed in the swamp. Those fresh water shells were
very thin and nearly translucent. Very few gastropod shells were
hermited.

ECOLOGICAL INTERACTIONS ALONG THE COAST OF CHANDIPUR

\textbackslash{}cftsetindents

figure0em8em

\section*{ECOLOGICAL INTERACTION ALONG COAST OF
CHANDIPUR}\label{ecological-interaction-along-coast-of-chandipur}

\textbackslash{}cftsetindents

figure0em8em

\section*{PREDATION BY DRILLING
GASTROPODS}\label{predation-by-drilling-gastropods}

\subsubsection*{INTRODUCTION}\label{introduction}

Evolutionary stasis or stagnancy is broken by organisms to escape
predation, resulting in adaptation, modification and exercise of
necessary precautions.

Predation is a natural behaviour seen in animal communities. It has
major controls in the history of evolution.

Many groups of animals have reduced in numbers and many adopted
different strategies to evolve stronger and proliferate, hence studying
about the predation in details has become an absolute necessity.

In Chandipur several evidences of predation on the molluscan communities
were noticed. Aperture breakage in bivalves and naticid boring in
bivalve and gastropod shells were found.

\begin{quote}
PHYSICAL BORING: In this kind of boring a bore had outer diameter bigger
than inner diameter. (O.B.D\textgreater{}I.B.D). It was done by the
naticid gastropods.\\
CHEMICAL BORING: In that kind of boring the diameter is same throughout
(O.B.D = I.B.D).chemical boring done by muricids only.
\end{quote}

\subsection*{METHODOLOGY OF PHYSICAL
BORING}\label{methodology-of-physical-boring}

The naticids characteristically travel through clean to slightly muddy
sand, both above and below the sediment water interface. They have large
flat foot which facilities their movement within the sediment and with
which they grip their prey tightly. The foot is completely extended and
if large enough, completely envelopes their preys.

\subsection*{COMMON PREDATORS}\label{common-predators}

An event of drilling gets captured in its entirety in a drilled shell
providing a wealth of information about the event such as the identity
of the predator. The holes of naticids are of more parabolic nature than
those compared to of muricid. Apart from the identity of the predator,
the drill holes are also indicative of size of the individual predator
since OBD is correlated with the size of the predator for both naticid
and muricid.

\subsection*{TYPES OF MOLLUSCAN PREY
DRILLED}\label{types-of-molluscan-prey-drilled}

Molluscan prey drilled are usually those molluscs which have thinner
shells. The naticid predator selects its prey in order to maximize net
energy gain.

The type of prey to be chosen by the predator depends on the following:-

\begin{itemize}
\tightlist
\item
  If the predator attacks a prey smaller than that optimal size, the net
  energy gain would be lower than the optimal value. Likewise, if the
  predator attacks a prey larger than the optimal size, it might not be
  able to finish the attack because of its own physiological
  constraints. The net energy gain, therefore, would be zero because of
  a failed attack.
\item
  There exists a ``handling limit'' for a specific size of naticid
  predator beyond which the attacks are more likely to fail. Moreover,
  if the size ratio of a prey to its predator is too large, the predator
  could be overpowered by the prey; the outcome of the attack might be
  fatal for the predator, and therefore yielding a negative energy gain.
\item
  Bivalve predation mortality initially increases with prey size up to a
  maximum that represents the preferred size, beyond which mortality
  progressively decreases towards the maximum prey size attained.
  Naticid predation therefore appears to be most intense on medium-sized
  bivalves.
\end{itemize}

At Chandipur we found \textbf{Mactra, Cardium, Donax, Ostrea} to be
preyed by the naticids. The shells attacked were mostly medium in size.

\subsection*{CALCULATION OF PREDATION
INTENSITY}\label{calculation-of-predation-intensity}

All the specimens in our collection were disarticulated valves.

Hence, the frequency of drilling predation was calculated by dividing
the number of bored valves by the half of total number of valves in the
collection

\begin{quote}
Drilling Frequency (DF) = ND/ (N*0.5)\\
Where,
\end{quote}

ND- Number of valves with complete drill hole

\begin{quote}
N- Total number of valves.
\end{quote}

\subsection*{BEHAVORIAL PARAMETERS OF
PREDATION}\label{behavorial-parameters-of-predation}

\subsubsection*{PREFERRED SITE OF
DRILLING}\label{preferred-site-of-drilling}

\begin{quote}
Among the drilled bivalves, the bivalves like \textbf{Mactra, Cardium,
Donax} are found to be drilled mostly near the umbo region. Irrespective
of whether it is the right valve or left valve, the drilled bivalve
shells bore hole at the umbo region dominantly.\\
The reason behind this is --
\end{quote}

\begin{enumerate}
\tightlist
\item
  The shell is very thin near the umbo region. And hence less energy is
  required for drilling by the naticids.
\item
  The shell bears less ornamentation at the umbo than the peripheral
  part, and hence less hindrance in drilling.
\item
  The soft part inside the shell is more attached to the umbo region
  relative to the periphery. And thus drilling near the umbo paralyses
  the organism within, rapidly.
\item
  The shell is made harder near the periphery for enhancing boring and
  burrowing. Thus drilling at the periphery doesn't serve to be
  fruitful.
\end{enumerate}

holes are observed near the central part of the shell, although it is
not the thinnest part of the shell. However, that is the spot where the
adductor muscle of these monomyarian bivalves situated and thus
attacking the muscle ensures the immediate opening of the valves.
Therefore, naticids drill holes in the central part in \textbf{Ostrea.}

\textbackslash{}cftsetindents

figure0em8em

\section*{INTERACTION AMONG HERMIT CRABS, DEAD/LIVE MOLLUSCAN SHELLS,
HYDROZOA}\label{interaction-among-hermit-crabs-deadlive-molluscan-shells-hydrozoa}

While traversing along the beach of chandipur, we encountered numerous
dead shells of molluscs littering the coast. But often these dead shells
are habitat to a group of living organisms called Hermit Crab. They are
typically marine small decapods crustaceans with no hard parts and a
fully exposed abdomen. So they occupy empty gastropod shells for their
protection against predation, physical and thermal stresses throughout
their lifespan. The entire genus of hermit crab would have been extinct
if these gastropod shells were absent.

When a gastropod shell is occupied by hermit crabs, the apertural margin
continuously gets in direct contact with the sediment surface while
locomotion and becomescorrugated. In contrast, during locomotion of
gastropods, there remains a soft and fleshy layer of foot between the
apertural margin and sand surface resulting in smooth outer lip. This is
the best way to understand whether any hermit crab had inhabited the
shell or not.

Hermit crabs and hydrozoa have a symbiotic relationship, meaning they
live in harmony together. The hermit crab gains protection from
predators by its relationship with the hydrozoa on board.The hydrozoa
not only get a convenient substrate to attach to, but the movement of
the crab provides ample food by both stirring up sediment as the crab
moves, as well as transportation, moving it to different feeding zones
where zooplankton is more plentiful.

Special Problems

\textbackslash{}cftsetindents

figure0em8em

\section*{Sampling Protocol for
Micro-fossils}\label{sampling-protocol-for-micro-fossils}

Microfossils being small and fragile require a skilled hand and
appropriate methods for collection of samples, their separation from
rocks, studies, illustrations, statistical analysis etc.

\textbackslash{}cftsetindents

figure0em8em \textbf{The tidal flat at Chandipur has inferably an
abundance of micro-fossils, for a detailed study and analysis. The
following are the standard processes involved in sampling of
microfossils and their study:}

\subsection*{Collection of samples}\label{collection-of-samples}

\begin{itemize}
\tightlist
\item
  Larger foraminifera may be picked up or sieved out of sediments on
  talus slope.
\item
  Samples may be collected from subsurface borings at a desirable
  interval
\item
  The samples from exposed fossiliferous rocks may be collected as `spot
  samples' in case of predetermined stratigraphic levels and as `channel
  samples' (multiple samples in a row) each litho-unit of large
  stratigraphic sequence with a constant interval varying from 1-3 m
  depending upon the thickness of the sequence.
\item
  Samples may be collected from the sea as core /grab samples (this type
  of sampling methods was applied in our field work at Chandipur).
\end{itemize}

\subsection*{Micro fossil sampling}\label{micro-fossil-sampling}

\begin{itemize}
\tightlist
\item
  Select water stagnant areas as sampling location
\item
  Make a grid (10 cm \selectlanguage{ngerman}× 10 cm × 1 cm) at the location
\item
  Scrap out the whole sample and transfer it to a white plastic
  container and pour equal amount of rose Bengal (for staining)
  solution.
\end{itemize}

\subsection*{Preparation of rose Bengal
solution:}\label{preparation-of-rose-bengal-solution}

\begin{itemize}
\tightlist
\item
  2 gm rose Bengal powder + 1L of distilled water
\item
  Use a magnetic stirrer to mix it for about 15 -- 20 min
\end{itemize}

\subsection*{Use of rose Bengal
solution:}\label{use-of-rose-bengal-solution}

\begin{itemize}
\tightlist
\item
  For bio-monitoring, whether the sample is containing dead or alive
  organisms.
\item
  It stains the cytoplasm of a living cell (pink stain) and does not
  stain a dead cell. For staining a 6 month or older sample, prepare the
  rose Bengal solution using ethanol in place of distilled water.
\end{itemize}

\subsection*{SAMPLE PREPARATION AND SEPARATION OF
MICROFOSSILS}\label{sample-preparation-and-separation-of-microfossils}

The rock types containing different microfossils require different
methods of treatment, but as a rule, less treatment the sample receives
the less it will be damaged and broken during their recovery.

Their separation from the sediment is performed in a lab having washing,

sieving units, oven, hot plates, fume-cupboard, petri-dishes, beakers,
pestel and mortar, filter papers, and a physical balance. A sieve set
with 60, 80 and 115 mm mesh sieves with a pan should suffice of the
variable sizes of the different groups of microfossils.

Since the technique used in sampling the microfossils at Chandipur was
grab sampling, so for the preparation of samples we use washing and
wet-sieving technique.

\subsection*{Washing and wet sieving}\label{washing-and-wet-sieving}

The pulverised fractions of rock are then subject to washing with
distilled water to remove the parts of clay and silt. The material is
passed through sieve set of 60, 80, and 115 mm meshes. The residue of
+60 fraction contains most of the foraminifera an ostracoda while the
+125 fraction is important for pollens and spores, conodonts etc. The
sieved fractions thus obtained are dried in an oven up to 50°C before
sorting of microfossils under a binocular stereoscopic microscope.

\textbackslash{}cftsetindents

figure0em8em

\section*{Morphology of Crab Burrows}\label{morphology-of-crab-burrows}

\subsection*{Methodology of Burrow
Casting}\label{methodology-of-burrow-casting}

Burrow fillings are prepared to evaluate the characteristics of the
habitat of different burrowing organisms. Informations of these burrow
fillings can then be used to determine the type of burrowing organism
from the burrows found in the rock record. Because of the greater
mobility and availability of raw wax, it is used to fill the burrows.

\subsubsection*{Preparation of Burrow
Cast}\label{preparation-of-burrow-cast}

The burrow fillings are prepared by the following process.

\begin{itemize}
\tightlist
\item
  Firstly raw wax is heated and melted in a pan to prepare the melt for
  burrow filling. The wax is heated well above its melting temperature
  so that it remains in the melted form for some time.
\item
  A location is selected with burrows of different organisms.
\item
  Now the melted wax is poured in the burrows through the opening.
\item
  Then the wax is left for some time to solidify inside the burrow, so
  that it can acquire the shape of the burrow.
\item
  After the solidification of the wax, the entire structure is dug out
  carefully from the rock.
\item
  Different characteristics of the burrows are studied from the
  solidified models. Shape and structure of the burrows.
\end{itemize}

\textbackslash{}cftsetindents

figure0em8em

\section*{Problems of Coastal
Pollution}\label{problems-of-coastal-pollution}

Coastal and estuarine ecosystems have been, and still are, heavily
influenced by the human species through pollution and habitat loss
throughout the world. This \textbf{coastal pollution and its impacts}
have resulted in a number of environmental issues including the
enrichment of enclosed waters with organic matter leading to
eutrophication, pollution by chemicals such as oil, and sedimentation
due to land-based activities or sea level rise due to the global change.
Over 80\% of all marine pollution originates from land-based sources
which are primarily industrial, agricultural and urban. Pollution
accompanies most kinds of human activities, including offshore oil and
gas production and marine oil transportation.

\subsection*{Nature and Imapact}\label{nature-and-imapact}

One of the important aspects of environmental management, particularly
of Chandipur coastal region, involves the preservation of its quality.
Because of rapid economic development, the stress on the environment is
increasing. This requires environmental assessment, which would
concentrate on short- or long-term monitoring of pollution resulting
from human settlement, and industrial and agricultural activities. In
addition, the threat of pollution associated with offshore oil and gas
exploitation in the continental shelf has been a major concern in recent
years. Domestic sewage and industrial effluents are recognized as the
most important problems in certain isolated coastal regions.

\subsubsection*{Plastics}\label{plastics}

The only substance that is illegal to dump anywhere in the ocean is
plastic. Plastics are primarily synthetic organic polymers derived from
petroleum. Plastic materials are found to be the major macroscopic
pollutants in this region. Plastics are lightweight, strong,durable and
cheap, characteristics that make them suitable for the manufacture of a
very wide range of products. These same properties happen to be the
reasons why plastics are a grave risk to the surroundings. Since they
are also floating, an increasing load of plastic debris is being spread
over long distances, and when they eventually settle in sediments they
may be kept for centuries.

\subsubsection*{Pesticides Residue}\label{pesticides-residue}

India is predominantly an agricultural country. Large quantities of
pesticides, herbicides, fungicides, etc. are used in agriculture and
disease-vector control. Their residues will ultimately find their way
into the sea. Organophosphorus pesticides will undergo biodegradation,
but the organochlorines and polychlorinated biphenyls are persistent in
the marine environment. Their main transport route to the sea is through
the atmosphere, while a part may also be transported with sewage and
effluents.

\subsubsection*{Sewage and Effluents}\label{sewage-and-effluents}

The oceans are vast and can break down this vile liquid, but it still
causes many adverse effects on marine life. Sewage or polluting
substances flow through sewage, rivers, or drainages directly into the
ocean. This is often how minerals and substances from mining camps find
their way into the ocean. The release of other chemical nutrients into
the ocean's ecosystem leads to reduction in oxygen levels, the decay of
plant life, a severe decline in the quality of the sea water itself. As
a result, all levels of oceanic life, plants and animals, are highly
affected.

\subsubsection*{Oil}\label{oil}

Oil is at the heart of the modern economy in providing a cheap source of
energy and as a raw material for making plastics, etc. It is a mixture
of hydrocarbons and up to 25\% non-hydrocarbons such as sulphur,
vanadium, and metals. Environmental impacts occur at all stages of oil
and gas production and use. They result from prospecting activities
(including seismic techniques), physical impact due to the installation
of rigs, operational discharges when production starts, accidental and
routine spills, and finally combustion.Overall, coastal ecosystems
remain largely affected by direct discharges of oil from offshore
activities and illegal discharges from ships. Operational discharges
consist of production water and drilling cuttings. Although the amount
of oil discharged via production water is increasing as platforms are
getting older, cuttings still account for 75\% of the oil entering the
sea as a result of normal operations.

\subsubsection*{Sediments}\label{sediments}

The role of sediment in chemical pollution is tied both to the particle
size of sediment, and to the amount of particulate organic carbon
associated with the sediment. For phosphorus and metals, particle size
is of primary importance due to the large surface area of very small
particles. Phosphorus and metals tend to be highly attracted to ionic
exchange sites that are associated with clay particles and with the iron
and manganese coatings that commonly occur on these small particles.
Many of the persistent, bio-accumulating and toxic organic contaminants,
especially chlorinated compounds including many pesticides, are strongly
associated with sediment and especially with the organic carbon that is
transported as part of the sediment load in rivers.Unlike phosphorus and
metals, the transport and fate of sediment-associated organic chemicals
is complicated by microbial degradation that occurs during sediment
transport in rivers and in deposited sediment. Organic chemicals
associated with sediment enter into the food chain in a variety of ways.
Toxic compounds bio-accumulate in fish and other top predators both
directly though sediment ingestion and indirectly through the food web.

\subsubsection*{Eutrophication}\label{eutrophication}

Eutrophication results from the increase of nutritional resources to a
particular water body and includes the supply of mineral nutrients
(nitrogen, phosphorus, silicon, trace elements) as well as organic
carbon. Discharges and emissions from land-based sources (industry,
households, traffic, agriculture) provide large inputs of nutrients to
coastal waters via rivers, direct discharges, diffuse sources and
deposition from the atmosphere. However, eutrophication cannot be
defined just in terms of an increase in nutrients concentration, as its
manifestations (very often harmful to ecosystems) occur due to the
existence of natural conditions, such as high temperatures and calm
coastal waters. In the recent past eutrophication has been most
pronounced in the developed world, but it has to be expected that it
will become more and more important in the developing countries of Asia,
Africa and Latin America in the near future.

The effects of eutrophication vary from increased growth of
phytoplankton, benthos and fish to changed species composition at
moderate eutrophication. From blooms of nuisance causing or toxic algae
(Fig. 1) to mass growth of certain species and mortality of others at
severe eutrophication, and ultimately to anoxic conditions and mass
mortality (fishkills). An algal biomass related phenomenon such as
oxygen depletion of the water column and consequent mortality of animals
can be prevented by a general reduction of nutrient discharges. At
present, mathematical models on ecosystem dynamics are reliable enough
to estimate dose-effect relationships. Algal species related harmful
effects are less predictable. There is a general consensus that there is
a global increase in harmful algal blooms. Also, there are reports which
suggest a link between blooms of toxic algae and human activities such
as salmon (or fish) farming.Consequently, alterations in pelagic and
benthic communities are to be expected. Which species is stimulated by
eutrophication is highly dependent on the local environmental
conditions.

\subsection*{Prevention of coastal
Pollution}\label{prevention-of-coastal-pollution}

\begin{itemize}
\tightlist
\item
  Major pollutant being plastic, its use has to be restricted and
  recycling must be entertained. The death of marine species by
  ingestion of plastic is a great loss to nature and the species are
  becoming extinct because of this. Plastic is an epidemic. Virtually
  every piece of plastic that was ever made still exists in some or the
  other form. Some of the compounds found in plastic have been found to
  alter hormones or have other potential human health effects.
  \textbf{So, littering of plastic based materials must be stooped at
  and near the coastal regions, whereas the amount and type of plastic
  pollutants present at the coast must be monitored on regular basis for
  the systematic assessment of the problem.}
\item
  Oil is the fastest source of deterioration to the ocean, being far
  more harmful than trash and waste. Oil spills suffocate marine life to
  death, and leads to behavioral changes and a breakdown in thermal
  insulation to those that do survive. It essentially changes the entire
  ecosystem of an affected area, such as a long coastline or deep ocean.
  \textbf{Therefore, spilling of oil must be stopped by strict usage of
  the prevailing environmental laws and rules {[}The Shore Nuisance
  (Bombay and Colaba) Act, 1853; The Indian Ports Act, 1901; The Inland
  Stream Vessel Act, 1917; The Orissa River Pollution \& Prevention Act,
  1953; The Water (Prevention and Control of Pollution) Cess Act, 1977;
  The Water (Prevention and Control of Pollution) Amendment Act, 1978;
  The Coast Guard Act, 1978{]} .}
\item
  \textbf{Usage of the fertilizers must be controlled so that they do
  not contaminate the waters.}
\item
  Finally social and political will, together with a shift in awareness
  is required so more people respect the environment and are less
  disposed to abuse it. At an operational level, regulations, and
  international government participation is needed. It is often very
  difficult to regulate marine pollution because pollution spreads over
  international barriers, thus making regulations hard to create as well
  as enforce
\end{itemize}

\subsection*{Our Initiative}\label{our-initiative}

The present state of coastal pollution in and around Chandipur beach is
of serious concern. Local economy is solely dependent on the tourism
industry. Deteriorating ecological status of the beach because of the
pollution is posing serious threats to the tourism industry and thereby
effecting the whole economy of the area. So the beautification and
prevention of coastal pollution are becoming serious issues to consider.

\textbackslash{}cftsetindents

figure0em8em

Table of debis/polutant collected

DEGRADABLE WASTE

FREQUENCY

Cask of green coconut

9

Burnt wood

NON-DEGRADABLE WASTE

FREQUENCY

Plastic paper

45

Ice-cream cup

64

Plastic cup

49

Plastic glass

58

Plastic packet

65

Plastic bottles

34

Glass bottles

16

\textbackslash{}cftsetindents

figure0em8em We took a quantitative approach for the better assessment
of the present situation of the problem. We divided our entire team into
smaller groups and selected random working locations along the beach.
Then each team constructed a grid of 1mx1m dimension on the beach at
positions with considerable amount of pollutants. Then the type and
number of pollutants present at the location were calculated. All of the
calculated debris were then disposed at a nearby dustbin. This study
revealed the nature and amount of most abundant pollutant present at the
area. Preventive measures can be taken to reduce the amount of the most
abundant pollutant determined from the above mentioned study.

Maps and Field Photographs Maps\selectlanguage{english}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=0.98\columnwidth]{figures/india/india}
\caption{{\textbackslash{}cftsetindents
figure0em8em \textbf{Map Showing the location of the Field Area}%
}}
\end{center}
\end{figure}

\textbackslash{}cftsetindents

figure0em8em\selectlanguage{english}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=0.98\columnwidth]{figures/fieldsat/fieldsat}
\caption{{\textbackslash{}cftsetindents
figure0em8em \textbf{Satellite imagery dated 10/2016 showing the area
studied in detail, i.e. Chandipur Beach and some landmarks \emph{the
blue line show the infered limit of the tidal flat,data has been
extrapolated from Digital Terrain Data Set (SRTM)}}%
}}
\end{center}
\end{figure}

\textbackslash{}cftsetindents

figure0em8em

Photographs trench in distal bar showing fining upward sequence lunate
ripple in tidal flat, tip of the pen showing flow direction cerithium
rich zone in tidal flat mud ball in sand bar, tip of the pen showing
flow direction mud ball found in sand bar showing shell concentration at
outer surface burrow and trail marks of red crab in sand bar formation
of rhombic ripple at southwestern side of sand bar formation of rhombic
ripple at southwestern side of sand bar process of measuring amplitude
of ripples curved crested bifurcating wave ripple double crested wave
ripple straight crested bifurcating wave ripple formation of ladder back
ripple in between two crests ladder back ripple interference ripple
trail marks of naticids egg coller in tidal flat ripples generated by
wave current interaction in tidal fla point crested (cheron type)
ripples in tidal flat trench section showing coarsenning upward
succession in aeolian dune field trench section showing coarsenning
upward succession in aeolian dune field a prominent erosional surface
found in trench section at dune indicating a strom event trench in back
shore showing coarsening upward succession, also showing organic layer
in between sand layers different shapes of red crab burrow red crab
aerodynamic ripples in sand bar meretrix in life mode found in sand bar
sigmoidal cross stratification at trench section in sand bar, also
showing fining upward succession shellrich layers at cross section in
sand bar mud balls forming current cresent flat topped straight crested
wave ripple in sand bar lunate ripple sowing heavy minerals contration
at trough swash ripple and current cresent at foreshore rhombic ripples,
two pens indicating two arms of rhombus translatent strata found at
vertical section in aeoian dune field cross stratification and speerite
structure at vertical section in aeolian dune

\selectlanguage{english}
\FloatBarrier
\end{document}

