naidu_PD_sandhiPriya

1
PRODUCTIVITY VARIATION IN THE EASTERN ARABIAN
SEA DURING LATE HOLOCENE: IMPLICATIONS OF
CLIMATE CHANGE
Dissertation submitted to Doon University in partial fulfillment of the
requirement for the Degree of
“MASTER OF SCIENCE IN ENVIRONMENTAL SCIENCE”
(SPECIALIZED IN NATURAL RESOURCE MANAGEMENT)
BY
SANDHI PRIYA
Department of Environmental Science and Natural Resource Management
DOON UNIVERSITY, DEHRADUN
RESEARCH SUPERVISOR
Dr. P. DIVAKAR NAIDU
CHIEF SCIENTIST
CSIR-National Institute of Oceanography
Dona Paula, Goa 403004, INDIA
UNIVERSITY SUPERVISOR
Dr. V. SHRIDHAR
(09-01-2014 to 18-06-2014)

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PRODUCTIVITY VARIATION IN THE EASTERN ARABIAN
SEA DURING LATE HOLOCENE: IMPLICATIONS OF
CLIMATE CHANGE
BY
SANDHI PRIYA
Dissertation submitted to Doon University for the M.Sc. Environmental Science Degree
(SPECIALIZED IN NATURAL RESOURCE MANAGEMENT)
RESEARCH SUPERVISOR
Dr. P. DIVAKAR NAIDU
CHIEF SCIENTIST
CSIR-National Institute of Oceanography
Dona Paula, Goa 403004, INDIA

3
I would like to dedicate this thesis to my
beloved grandmother…
(For her infallible love)

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DECLARATION
I hereby state that the work slot in this report entitled “Productivity Variation in the
Eastern Arabian Sea During Late Holocene: Implications of Climate Change” is original
and authentic, carried out at the National Institute of Oceanography, Dona Paula, Goa under
the supervision of Dr. P. Divakar Naidu (Chief Scientist) and it has not been submitted in part
or full for any degree in any other university or institute.
Sandhi Priya
M. Sc. Natural Resource Management
Doon University, Dehradun

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ACKNOWLEDGEMENT
This master thesis has been carried out at the Paleoceanography Laboratory, National
Institute of Oceanography, Goa. A number of people deserve thanks for their support and help. It
is therefore my greatest pleasure to express my appreciation to them all in this
acknowledgement.
I thank Dr. S.W.A. Naqvi, Director, National Institute of Oceanography, Goa, for
permitting me in this much known institute where I have achieved such a memorable learning
experience.
I offer my sincerest gratitude to my supervisor, Dr. P. Divakar Naidu, Chief Scientist,
National Institute of Oceanography, Goa, who has supported me throughout my Masters thesis
with his patience and knowledge whilst allowing me the lab to work in my own way. I attribute
the level of my Masters thesis to his encouragement and effort and without him this thesis, too,
would not have been completed or written. One simply could not wish for a better or friendlier
supervisor.
I am thankful to Dr. Ranadhir Mukhopadhyay, Head of H.R.M. Division, Mr. V. Krishna
Kumar, Principle Technical Officer and Mr. Rohit, Project Assitant, NIO, Goa for providing
hostel accommodation and other important necessities.
Besides, I would like to extend my gratitude and appreciation to Dr. Sushant S. Naik,
Scientist, NIO, Goa for his valuable suggestions and good support.
I show gratitude to Dr. Kusum Arunachalam, Professor, Environment and Natural
Resource Management Department, Doon University, Dehradun, for her encouragement and
support.
I would also like to thank Dr. V. Shridhar, Assistant Professor, Environment and
Natural Resource Management Department, Doon University, Dehradun, for his unending
encouragement. His classes on Climate change and policies gave me lot of insight into carrying
out my dissertation programme. All the more, I would like to thank him for having trust and
confidence in me.

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Dr. Ramaswamy, Chief Scientist and Dr. Prakash Babu, Senior technical officer, NIO,
Goa deserves my sincere expression of thanks for providing me experimental hands-on-training
on different analytical instruments.
I am also extremely indebted to my senior Ms. Shital Godad, for providing necessary
knowledge to accomplish my dissertation work. I am very much thankful to her for pampering
and encouraging me within this span of time.
I gratefully acknowledge to all the research scholars and project assistants Champoungam
Panmei, Pallhavi P. Devsekar and Smita Naik for making the lab atmosphere pleasant and
friendly. Thank you for everything.
I expand my thanks to Moushmi. K.S. dissertation student who has always showed great
zeal in helping me.
I take this opportunity to say heartful thanks to Swati Tyagi, my roommate and also a
dearest chum to whom I could always talk about my problems and excitements. She taught me
the real sense of perseverance within my stay at NIO.
I acknowledge all the teaching and non teaching staff, Department of Environmental
Science and Natural Resource Management, Doon University, Dehradun for their co-operation
throughout my academic time.
I owe more than appreciation to my brother Vinayak for always believing in his sister‘s
potential and to make me learn as how one can foster in life. You are my rock.
In the end I would like to thank my parents, for always believing in me, for their
continuous love and their support in my decisions. Without whom I could not have made it here.
I owe everything to them.
As always it is impossible to mention everybody who had an impact to this work,
however there is someone whose spiritual support is even more important. I feel a deep sense of
gratitude for my grandmother who formed part of my vision and taught me good things that
really matter in life. I am also very much grateful to all my family members and friends for their
constant inspiration and encouragement.
Sandhi Priya

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CONTENTS
Serial number Name of the topic Page number
I CERTIFICATE 4
II DECLARATION 5
III ACKNOWLEDGEMENT 6-7
IV CHAPTER I
INTRODUCTION
1.1 BIOLOGICAL
PRODUCTIVITY
1.2 UPWELLING
14-24
V CHAPTER II
LINK BETWEEN MONSOON
AND PRODUCTIVITY
2.1 MONSOON
25-29
VI CHAPTER III
PROXIES USED TO
RECONSTRUCT THE
PRODUCTIVITY
VARIATIONS
3.1 HOW CAN
PALEOCLIMATIC PROXY
METHODS BE USED TO
RECONSTRUCT PAST
CLIMATE DYNAMICS
3.2 OCEAN SEDIMENT
3.3 FORAMINIFERA
3.4 RADIOLARIANS
30-40
VII CHAPTER IV
LITERATURE REVIEW
4.1 CLIMATE CHANGE AT
GEOLOGICAL TIMESCALE
41-45

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4.2 MONSOON AND
UPWELLING RELATION
4.3 CALCIUM CARBONATE
FLUCTUATIONS
4.4 COMPARISION
BETWEEN EASTERN AND
WESTERN ARABIAN SEA
VIII CHAPTER V
MATERIALS AND
METHODS
5.1 STUDY LOCALE
5.2 NAMING OF SAMPLE
5.3 SAMPLE PROCESSING
5.4 COULOMETER
5.5 CNS ANALYZER
46-56
IX CHAPTER VI
RESULTS AND DISCUSSION
56-64
X CHAPTER VII
CONCLUSION
65
XI CHAPTER VIII
REFERENCES
66-68

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CONTENT NAME OF THE FIGURE PAGE NUMBER
LISTOFFIGURES
CH-I: Figure 1: Nested cycles of
carbon associated with ocean
productivity
16
Figure 2: The principle components
of the biological pump
17
Figure 3: Composite global ocean
maps of concentrations of satellite-
derived chlorophyll
18
Figure 4: Temperature variations
with depth
19
Figure 5: World map showing
tropical, temperate, and polar zones
21
Figure 6: Coastal Upwelling 22
Figure 7: Major upwelling areas of
the world. 23
FIGURE 8: Composite image of
ocean color of the Indian Ocean in
September- October, towards the
end of the Indian summer monsoon
24
CH-II: Figure: 1 Seasonality of
Indian Equatorial Currents
25
Figure: 2 South-West Monsoon 27
Figure: 3 Map showing patterns of
ocean current circulation in
different seasons in the Indian
Ocean
29
CH-III: Figure 1: Biogenic oozes in
oceanic sediments
30
Figure 2: Fossil test (shell) of
planktonic foraminifera
(Globigerinoides ruber) that lives
primarily in tropical to subtropical
waters of all the oceans
32
Figure 3: Distribution of different
types of sediment on the seafloor
33
Figure 4: Left: Living
phytoplankton; Right: Living
Zooplankton
35

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Figure5: Planktonic foraminifera: A
potential proxy for paleoclimatic
/paleoceanographicstudies
37
Figure 5: Benthic Foraminifera-
bottom dwellers. They live all along
and beneath the ocean floor in the
sediments.
38
Figure 7: Radiolarians are part of
the marine plankton
40
CH-IV: Figure 1: Satellite imagery of
Arabian Sea
46
Figure 2: Sample location details 47-48
Figure 3: The clay matrix dissolves
and passes through the holes in the
sieves, leaving the tiny fossils
behind.
50
Figure 4: UIC Coulometer 51
Figure 5: Principles of operation 52
Figure 6 (a) KOH trap to reaction
vial (b) Reaction vial to the thin
section of the HNO3trap (c) Main
power to the heating unit
53
Figure 7: Total Carbon- Nitogen
Analyzer
55

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LIST OF GRAPHS
Serial
Number
Name of the Graph Page Number
1 Figure 6.1.1: Percentage of CaCO3
Figure 6.1.2: Faunal assemblage (Planktonic Forams)
Figure 6.1.3: Faunal Assemblage (Benthic Forams)
Figure 6.1.4: Faunal Assemblage (Radiolaria)
58
2 Figure 6.2.1: % Total Calcium Carbonate
Figure 6.2.2: Faunal Assemblage (Planktonic Forams)
Figure 6.2.4: Faunal Assemblage (Radiolarians)
60
3 Figure 6.3.1: % Total Calcium Carbonate
Figure 6.3.2: Faunal Assemblage (Planktonic Forams)
Figure 6.3.4: Faunal Assemblage (Radiolarians)
61
4 Figure 6.4a: % Total Organic carbon (AAS 9/9)
Figure 6.4b: % Total Organic Carbon (AAS 9/10)
Figure 6.4c: % Total Organic Carbon (AAS 9/11)
63-64

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NAME OF THE TABLE PAGE
NUMBER
AAS 9/9 CaCO3 and Coarse fraction
Data
69
Data
70
Data
71
AAS 9/9 Faunal Assemblage Data 72

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CHAPTER I
INTRODUCTION
1.1 BIOLOGICAL PRODUCTIVITY
Primary productivity is the production of organic compounds from inorganic substances
through photosynthesis or chemosynthesis. Photosynthesis is the use of light energy to convert
water and carbon dioxide into energy-rich glucose molecules. Chemosynthesis is the process by
which certain microorganisms create organic molecules from inorganic nutrients using chemical
energy. Bacteria in hydrothermal vents use hydrogen sulfide as an energy source. Acting as
producers, these bacteria support the hydrothermal vent communities.
Two factors influence a region’s photosynthetic productivity: the availability of nutrients
and the amount of solar radiation, or sunlight. Primary producers need nutrients such as
nitrogen, phosphorus, and iron. Lack of nutrients can be a limiting factor in productivity. Thus,
the most abundant marine life exists where there are ample nutrients and good sunlight. Oceanic
productivity, however, varies dramatically because of the uneven distribution of nutrients
throughout the photosynthetic zone and the availability of solar energy due to seasonal changes.
Primary production is the total amount of carbon (C) in grams converted into organic
material per square meter of sea surface per year (gm C/m2
/yr).
• Factors that limit plant growth and reduce primary production include solar radiation and
nutrients as major factors and upwelling, turbulence, grazing intensity and turbidity as
secondary factors.
• Only 0.1 to 0.2% of the solar radiation is employed for photosynthesis and its energy
stored in organic compounds.
• Macronutrients and Micronutrients are chemicals needed for survival, growth and
reproduction.
Ocean productivity largely refers to the production of organic matter by "phytoplankton,"
plants hovering in the ocean, most of which are single-celled. Phytoplanktons are
"photoautotrophs," harvesting light to change inorganic to organic carbon, and they supply this
organic carbon to diverse "heterotrophs," organisms that obtain their energy solely from
the respiration of organic matter. Open ocean heterotrophs include bacteria as well as more
complex single- and multi-celled "zooplankton" (floating animals), "nekton" (swimming

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organisms, including fish and marine mammals), and the "benthos" (the seafloor community of
organisms).The many nested cycles of carbon associated with ocean productivity are revealed by
the following definitions (Bender et al. 1987) (Figure 1). "Gross primary production" (GPP)
refers to the total rate of organic carbon production by autotrophs, while "respiration" refers to
the energy-yielding oxidation of organic carbon back to carbon dioxide. "Net primary
production" (NPP) is GPP minus the autotrophs own rate of respiration; it is thus the rate at
which the full metabolism of phytoplankton produces biomass. "Secondary production" (SP)
typically refers to the growth rate of heterotrophic biomass. Only a small fraction of the organic
matter ingested by heterotrophic organisms is used to grow, the majority being respired back
to dissolved inorganic carbon and nutrients that can be reused by autotrophs. Therefore, SP in the
ocean is small in comparison to NPP. Fisheries rely on SP; thus they depend on both NPP and
the efficiency with which organic matter is transferred up the food web (i.e., the SP/NPP ratio).
"Net ecosystem production" (NEP) is GPP minus the respiration by all organisms in the
ecosystem. The value of NEP depends on the boundaries defined for the ecosystem. If one
considers the sunlit surface ocean down to the 1% light level (the "euphotic zone") over the
course of an entire year, then NEP is equivalent to the particulate organic carbon sinking into the
dark ocean interior plus the dissolved organic carbon is being circulated out of the euphotic zone.
In this case, NEP is also often referred to as "export production" (or "new production" (Dugdale
& Goering 1967), as discussed below). In contrast, the NEP for the entire ocean, including its
shallow sediments, is roughly equivalent to the slow burial of organic matter in the sediments
minus the rate of organic matter entering from the continents.
(Sigman, D. M. & Hain, M. P. (2012). The Biological Productivity of the Ocean. Nature
Education Knowledge)

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Figure 1: Nested cycles of carbon associated with ocean productivity
(Sigman, D. M. & Hain, M. P. (2012) The Biological Productivity of the Ocean. Nature Education Knowledge)
BIOLOGICAL PUMP
On the time scale of thousands of years, the chemistry of the ocean essentially sets the
concentration of CO2 in the atmosphere. Ocean productivity affects atmospheric CO2 by
the export of both organic carbon and calcium carbonate (CaCO3) from the surface ocean to
depth; the former lowers atmospheric CO2, while the latter raises it more modestly (Archer
2003, Sarmiento & Gruber 2006). These opposing effects on CO2 are evident at a simplistic
level from the reactions associated with (1) the formation of organic carbon (as CH2O, sugar)
that consumes dissolved CO2 and (2) the precipitation of CaCO3 that releases it:
Organic carbon: CO2 + H2O → CH2O + O2 (eq. 1)
Calcium carbonate: Ca2+
+ 2HCO3
-
→ CaCO3 + CO2 (eq. 2)
The downward transport of organic carbon extracts dissolved inorganic carbon from the
Surface Ocean and atmosphere, sequestering it in the deep sea. This "biological pump" for
carbon is coupled to the removal of nutrients (e.g., N and P) from surface waters and their

17
accumulation in the deep ocean, as described above. However, in the case of dissolved inorganic
carbon — the sum of three inorganic carbon species: dissolved CO2, bicarbonate (HCO3
-
), and
carbonate (CO3
2-
) — only ~10% of it is consumed from surface waters, while N and P
consumption is often effectively complete. The term "biological pump" is sometimes put back
with the term "soft tissue pump" to openly specify the impact of organic carbon rain out of the
surface ocean and its subsequent degradation in deep waters, to be distinguished from the
"carbonate pump," in which CaCO3 is precipitated in surface waters and exported to depth. A
simplified diagram of the principle components of the biological pump is presented in Figure 2.
Figure 2: The principle components of the biological pump
(http://www.msrc.sunysb.edu/octet/biological_pump.html)

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IMPACT OF CLIMATE CHANGE ON BIOLOGICAL PUMP
The global increase in the average air temperature due to trapping of infrared radiation
leads to rising temperatures in the surface ocean. The increase in water temperatures of the
surface ocean can directly affect the stratification of the ocean, physiological rate processes, and
planktonic community structure. Stratification of the surface ocean can locally be intensified by
predicted changes in precipitation patterns and the melting of sea ice. The resulting changes in
mixing regimes as well as possible changes in allochthonous nutrient inputs affect nutrient and
light availability.
Changes in land use, the combustion of fossil fuels, and the production of cement have
led to an increase in CO2 concentration in the atmosphere. At present, about one third of
anthropogenic emissions of CO2 are believed to be entering the ocean. However, the biological
pump is not believed to play a significant role in the elevation in CO2. This is because the
biological pump is primarily limited by the availability of light and nutrients, and not by carbon.
This is in contrast to the situation on land, where elevated atmospheric concentrations of
CO2 may increase primary production because land plants are able to improve their water-use
efficiency (= decrease transpiration) when CO2 is easier to obtain. However, there are still
considerable uncertainties in the marine carbon cycle, and some research suggests that a link
between elevated CO2 and marine primary production exists.
VARIATIONS OF PRODUCTIVITY IN MODERN OCEANS
Geographic variation
Satellites can measure the color of the surface ocean in order to track the concentration of the
green pigment chlorophyll that is used to harvest light in photosynthesis. Higher chlorophyll
concentrations and in general higher productivity are observed on the equator, along the coasts
(especially eastern margins), and in the high latitude ocean. A major driver of these patterns is
the upwelling and/or mixing of high nutrient subsurface water into the euphotic zone, as is
evident from surface nutrient measurements.

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Figure 3: Composite global ocean maps of concentrations of satellite- derived chlorophyll
(http://www.nature.com/scitable/knowledge/library/the-biological-productivity-of-the-ocean-70631104)
Depth variation
Due to the insolvency of low latitude surface waters in N and P, the productivity of the low
latitude ocean is typically described as nutrient limited. However, limitation by light is also at
work. As one descends from sunlit but nutrient-deplete surface waters, the nutrient
concentrations of the water rise, but light drops off. The cross-over from sunlit and nutrient-poor
to dark and nutrient-rich typically occurs at roughly 80 m depth and is demarcated by the "deep
chlorophyll maximum", a depth zone of elevated chlorophyll concentration due to higher
phytoplankton biomass and/or a higher chlorophyll-to-bulk carbon ratio in the
biomass. Phytoplankton at the DCM is compromising between limitation by light and by
nutrients. Phytoplankton growth at the DCM intercepts the nutrient supply from below, reducing
its transport into the shallower euphotic zone. Thus, the DCM is not only a response to the depth
structure of nutrients and light but indeed helps to set these conditions. On the other hand, in
highly productive regions of the ocean, high phytoplankton density near the surface limits the
depth to which light penetrates, reducing productivity in deeper waters. Such self-limitation of
primary productivity is a common dynamic in the ocean biosphere.

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Figure 4: Temperature variations with depth
(http://www.windows2universe.org/earth/Water/temp.html)
Seasonality
Seasonality in productivity is greatest at high latitudes, driven by the availability of light
(Figure 3a and b). The areal intensity and daily duration of sunlight are much greater in summer,
an obvious direct benefit for photosynthesis. In addition, the wind-mixed layer (or "mixed
layer") of the upper ocean shoals such that it does not mix phytoplankton into darkness during
their growth (Siegel et al. 2002). The mixed layer shoals in the spring partly because increased
sunlight causes warming and freshening (the latter by the melting of ice), both of which increase
the buoyancy of surface waters. Mixed layer shoaling is sometimes also encouraged by generally
calmer spring and summer weather, which reduces wind-driven turbulence. During the "spring
bloom," NPP exceeds the loss of phytoplankton biomass to grazing and mortality, leading to
transient net biomass accumulation and a peak in export production. The population of grazing
organisms also rises in response to the increase of their feedstock, transferring the organic carbon
from NPP to higher trophic levels. In regions such as the North Atlantic, the preceding deep
winter mixed layers may be important in initiating the spring bloom by briefly releasing
growing phytoplankton from grazing pressure (Boss & Behrenfeld 2009). However, the robust
connection of the spring bloom with mixed layer shoaling across many environments argues

21
strongly for the general importance of the mixed layer/light availability dynamic described above
(Siegel et al. 2002).
In some temperate and subpolar regions, productivity reaches a maximum during the spring as
the phytoplankton transition from light to nutrient limitation. In the highest latitude settings,
while the "major nutrients" N and P remain at substantial concentrations, the trace metal iron can
become limiting into the summer (Boyd et al. 2007, Martin & Fitzwater 1988). In at least some
of these polar systems, it appears that light and iron can "co-limit"
summertime photosynthesis (Maldonado et al. 1999, Mitchell et al. 1991).
PRODUCTIVITY IN TROPICAL OCEANS
The tropical region spanning the planet‘s midsection is biologically diverse, providing a
favorable habitat for a large variety of marine creatures. The productivity is low in tropical
regions of the open ocean. Because the sun is more directly overhead, light penetrates much
deeper into tropical oceans than in temperate and polar waters. Solar energy also is available
year-round. However, productivity is low because a permanent thermocline prevents mixing
between surface waters and nutrient-rich deeper waters.
Figure 5: World map showing tropical, temperate, and polar zones
(http://www.gma.org/herring/biology/distribution/comparing_oceans.asp)

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1.2 UPWELLING
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense,
cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually
nutrient-depleted surface water. The increased availability in upwelling regions results in high
levels of primary productivity. Upwelling often happens where wind blows along a coastline.
The wind causes the water at the ocean surface to move perpendicular to it, away from the coast,
because of a process called Ekman transport. When surface water moves away from the coast,
water from deeper in the ocean rises up and takes it place.
Figure 6: Coastal Upwelling
(http://oceansjsu.com/105d/exped_climate/7.html)
The three main drivers that work together to cause upwelling is wind, Coriolis effects and
Ekman transport. They operate differently for different types of upwelling, but the general
effects are the same. In the overall process of upwelling, winds blow across the sea surface at a
particular direction, which causes a wind-water interaction. As a result of the wind, the water is
transported a net of 90 degrees from the direction of the wind due to Coriolis forces and Ekman
transport. Ekman transport causes the surface layer of water to move at about a 45 degree angle
from the direction of the wind, and the friction between that layer and the layer beneath it causes
the successive layers to move in the same direction. This results in a spiral of water movement
down the water column. Then, it is the Coriolis forces that dictate which way the water will
move; in the Northern hemisphere, the water is transported to the right of the direction of the
wind. In the Southern Hemisphere, the water is transported to the left of the wind. If this net

23
movement of water is divergent, then upwelling of deep water occurs to replace the water that
was lost.
Phytoplankton productivity results from two primary input factors: sunlight and
nutrients. Upwelling provides nutrients, primarily nitrate and phosphate, that phytoplankton
utilize for growth. Productivity refers to the amount of organic carbon that the phytoplankton
produces by the process of photosynthesis. Actively growing phytoplankton frequently divides
into new cells, and because each of the phytoplankton cells contains chlorophyll, oceanic areas
with high phytoplankton productivity usually also have high concentrations of chlorophyll which
can be observed with remote sensing.
Figure 7: Major upwelling areas of the world.
(http://www.marinebio.net/marinescience/02ocean/swmovement.htm)
UPWELLING IN INDIAN OCEAN
Upwelling is a seasonal phenomenon in the Indian Ocean because of the monsoon
regime. During the southwest monsoon, upwelling occurs off the Somali and Arabian coasts and
south of Java. It is most intense between 5° and 11° N, with replacement of warmer surface
water by water of about 57 °F (14 °C). During the northeast monsoon, strong upwelling occurs
along the western coast of India. Mid-ocean upwelling takes place at that time at 5° S, where the
North Equatorial Current and the Equatorial Countercurrent run alongside each other in opposite
directions.
The Arabian Sea has a dense, high-salinity layer (37 parts per thousand) to a depth of
about 400 feet (120 metres) because of high evaporation rates at subtropical temperatures with
moderate seasonal variations. Salinity in the surface layer of the Bay of Bengal is considerably
lower, often less than 32 parts per thousand, because of the huge drainage of fresh water from
rivers. High surface salinity (greater than 35 parts per thousand) is also found in the Southern

24
Hemisphere subtropical zone between 25° and 35° S; while a low-salinity zone stretches along
the hydrological boundary of 10° S from Indonesia to Madagascar. Antarctic surface-water
salinity generally is below 34 parts per thousand.
FIGURE 8: Composite
image of ocean color of
the Indian Ocean in
September- October,
towards the end of the
Indian summer monsoon
(http://www-
das.uwyo.edu/~geerts/cwx/n
otes/chap11/phyto.html)

25
CHAPTER II
LINKS BETWEEN MONSOON AND PRODUCTIVITY
2.1 MONSOON
Traditionally, the terminology ―monsoon‖ was used for climate that has an obvious
seasonal shift of prevailing winds between winter and summer, particularly in tropical Asia,
Australia, Africa, and the Indian Ocean. The term also increasingly refers to regions where there
is a clear alternation between winter dry and summer rainy seasons. According to this definition,
the monsoon region is distributed globally over all tropical continents, and in the tropical oceans
in the western North Pacific, eastern North Pacific, and the southern Indian Ocean. Monsoon
systems represent the dominant variation in the climate of the tropics with profound local,
regional, and global impacts.
“Monsoon is a seasonal prevailing wind in the region of South and South East Asia,
blowing from the south-west between May and September and bringing rain (the wet
monsoon ), or from the north-east between October and April (the dry monsoon ).”
Figure: 1 Seasonality of Indian Equatorial
Currents
(Tomczak and Godfrey)

26
Monsoon plays a critical role in activating environmental features such as seawater
temperature, salinity, dissolved oxygen content and nutrient generation which in turn become
responsible for production of phytoplankton and zooplankton. Environmental features such as
monsoon, upwelling, temperature, salinity and dissolved oxygen and nutrients play vital role in
the production, initially at the primary and subsequently at the secondary and the tertiary levels.
Among these, southwest monsoon in India is of critical importance in the production of phyto
and zooplankton especially in the inshore upwelling areas. It has been known that an intense
monsoon triggers of strong upwelling along the southwest coast of India.
South west Monsoon
The southwest monsoon brings rain towards the end of summer as the high pressure built in
the Indian Ocean pushes the wind masses towards the low pressure formed on land. It is the
temperature variation between the sea and the landmass- sea air being cooler and land being
warmer- that causes the action. Also we have to take an important factor called Temperature
Gradient into consideration. It is the temperature variation between the landmass and the
surrounding sea.
Action of southwest monsoon in India
The southwest monsoon arrives in two branches: the Bay of Bengal branch and the Arabian
Sea branch. The latter extends toward a low-pressure area over the Thar Desert and is roughly
three times stronger than the Bay of Bengal branch. The southwest monsoon typically breaks
over Indian Territory by around 25 May, when it lashes the Andaman and Nicobar Islands in the
Bay of Bengal. It strikes the Indian mainland around 1 June near the Malabar coast of Kerala. By
9 June, it reaches Mumbai; it appears over Delhi by 29 June. The Bay of Bengal branch, which
initially tracks the Coromandal Coast northeast from Cape Comorin to Orissa, swerves to the

27
northwest towards the Indo-Gangetic Plain. The Arabian Sea branch moves northeast towards
the Himalayas. By the first week of July, the entire country experiences monsoon rain; on
average, South India receives more rainfall than North India. However, Northeast India receives
the most precipitation. Monsoon clouds begin retreating from North India by the end of August;
it withdraws from Mumbai by 5October. As India further cools during September, the southwest
monsoon weakens. By the end of November, it has left the country.
The western Arabian Sea is characterized by large seasonal variations in current direction,
upwelling intensity and mixed layer characteristics such as temperature, nutrient content and
productivity (Wyrtki 1971, 1973). These seasonal changes are the oceanic response induced by
the large scale monsoonal winds. The monsoon, driven by the strong atmospheric pressure
gradient between land and ocean, causes a biannual reversal of the current patterns due to
changing direction of monsoon wind. The summer monsoon is driven by differential (land–sea)
sensible heating and tropospheric latent heating (Clemens et al 1991) which results in a distinct
atmospheric circulation system with seasonally changing wind directions. Monsoonal winds drag
sea surface waters of the northwest Arabian Sea influencing the surface circulation. The
prevailing clockwise surface circulation during the SW monsoon causes coastal upwelling off
Oman as well as open-ocean upwelling associated with the low level Findlater Jet, a northeast-
trending stratospheric wind that crosses the Arabian Sea about 400 km off the coast of Arabian
Figure: 2 South-West
Monsoon
http://moonwrites.wordpress.com/2
010/03/09/south-west-monsoon-in-
india/

28
peninsula (Find later 1974; Anderson and Prell 1991, 1993; Brock et al 1992; Lee et al 2000).
This seasonal upwelling brings deep nutrient-rich, oxygen-poor and cold waters to the surface
and increases the productivity in the euphotic zone (Krey and Bauered 1976; Nair et al 1989).
Surface productivity has its annual maximum during the summer monsoon (Nair et al 1989;
Haake et al 1993).
North-East Monsoon
The wind regime of the NW Indian Ocean is governed by the Asian monsoon. The monsoon,
driven by the atmospheric pressure difference between land and ocean, induces a biannual
reversal of the current regime due to changes in monsoon wind directions. During the winter
months, between December and February, the NE winds generate a northern anticlockwise gyre
(Wyrtki, 1973; Molinary et al., 1990). This system is replaced during the boreal summer from
June through October by the SW monsoon, which forms a large-scale clockwise current system.
Summer monsoon winds over the western Arabian Sea cause strong upwelling off the coasts of
Oman and Somalia. Advection of cold nutrient-rich waters leads to a significant increase in
primary productivity (Wyrtki, 1971; Swallow, 1984; Nair et al., 1989; Brock and McClain, 1992;
Rixen et al., 1996).
With the reversal of the wind direction following the onset of the NE monsoon during the
winter months, the water cools and the sea surface temperature is nearly 25˚C (Wyrtki, 1971;
Van Couwelaar, 1997; Rixen et al., 1996). During this period due to surface water cooling, the
mixed layer deepens to ~ 100m, and nutrient-rich water is injected to euphotic zone. Carbon
productivity reaches some 1.0- 1.3g cm-2
d-1
, which is more than twice the productivity of the
summer months (Van Couwelaar, 1997). Wind- speed seems also to play an important role in the

29
extent of the surface water cooling and the amount of deepening of the mixed layer during NE
monsoon period.
Figure: 3 Map showing patterns of ocean current circulation in
different seasons in the Indian Ocean
http://www.yourarticlelibrary.com/geography/oceanography/ocean-currents-factors-
influencing-and-general-characteristics/32216/

30
Chapter iii
PROXIES USED TO RECONSTRUCT THE PRODUCTIVITY
VARIATIONS
3.1 HOW CAN PALEOCLIMATIC PROXY METHODS BE USED TO RECONSTRUCT
PAST CLIMATE DYNAMICS
Paleoclimatic reconstruction methods have developed greatly in the past decades, and
range from direct measurements of past change (e.g., ground temperature variations, gas content
in ice core air bubbles, ocean sediment pore-water change and glacier extent changes) to proxy
measurements involving the change in chemical, physical and biological parameters that reflect –
often in a quantitative and well-understood manner – past change in the environment where the
proxy carrier grew or existed. In totaling to these methods, paleoclimatologists also use
documentary data (e.g., in the form of specific observations, logs and crop harvest data) for
reconstructions of past climates. While a number of qualms remain, it is now well accepted and
verified that many organisms (e.g., trees, corals, plankton, insects and other organisms) amend
their growth and/or population dynamics in retort to changing climate, and that these climate-
induced changes are well recorded in the past growth of living and dead (fossil) specimens or
assemblages of organisms. Tree rings, ocean and lake plankton and pollen are some of the best-
known and best-developed proxy sources of past climate going back centuries and millennia.
Past distributions of pollen and plankton from sediment cores can be used to derive quantitative
estimates of past climate (e.g., temperatures, salinity and precipitation) via statistical methods
calibrated against their modern distribution and associated climate parameters.
Figure 1: Biogenic oozes in oceanic
sediments
(http://geology.uprm.edu/Morelock/dpseabiog
enic.htm)

31
The chemistry of several biological and physical entities reflects well-understood
thermodynamic processes that can be transformed into estimates of climate parameters such as
temperature. Key examples include: oxygen (O) isotope ratios in coral and foraminiferal
carbonate to infer past temperature and salinity; magnesium/calcium (Mg/Ca) and
strontium/calcium (Sr/Ca) ratios in carbonate for temperature estimates; alkenone saturation
indices from marine organic molecules to infer past sea surface temperature (SST); and O and
hydrogen isotopes and combined nitrogen and argon isotope studies in ice cores to infer
temperature and atmospheric transport. Lastly, many physical systems (e.g., sediments and
aeolian deposits) change in predictable ways that can be used to infer past climate change. There
is ongoing work on further development and refinement of methods, and there are remaining
research issues concerning the degree to which the methods have spatial and seasonal biases.
Therefore, in many recent paleoclimatic studies, a combination of methods is applied since
multi-proxy series provide more rigorous estimates than a single proxy approach, and the multi-
proxy approach may identify possible seasonal biases in the estimates. No paleoclimatic method
is infallible, and knowledge of the underlying methods and processes is required when using
paleoclimatic data.
3.1.1 FORAMINIFERA AS A SUBSTITUTE
Foraminifera (figure 2) are single-celled animals which construct tests. They are among
the most abundant organisms in the world's ocean. There are two major groups of foraminifera,
benthic and planktonic foraminifera. Benthic foraminifera live in the sediments on the sea floor.
Planktonic foraminifera live in the upper several hundred meters of the ocean. Foraminifera are
sensitive to environmental conditions in the ocean and, therefore, are good indicators of climate.
By studying characteristics of foraminifera assemblages, paleoclimatic information can be
inferred. Foraminifera are also important to paleoclimate studies because their calcium carbonate
often tests preserve a record of past stable isotope compositions.

32
3.2 OCEAN SEDIMENT
Marine sediments instigate from a variety of sources, including continental and oceanic
crust, volcanoes, microbes, plants and animals, chemical processes, and outer space. Though,
identifying the source of a particular deposit of marine sediments often proves difficult.
Sediments may be altered from their unique condition by any of a number of physical, chemical,
and biological transformations that take place after the sediment is formed. Sedimentologists
make use of a number of different classification and analysis techniques to characterize
sediments. Visual analysis of the texture and composition of a sediment sample, or descriptive
classification, is often the first step in differentiating sediments. Size classification, based on
visual, mechanical, or laser-based sizing of sediments, aids in understanding physical and
chemical changes in sediments that occur during transport and deposition. Genetic classification
includes a more complete description of the physical, chemical, and biological properties of
sediments.
The sediments in the ocean consist of 3 major components: detrital, biogenic and
authigenic based on their origin. Conversely, it must be kept in mind that there are no pure
detrital, authigenic or biogenic sediments; sediments are always mixtures of different
components. Figure 2 shows different types of Ocean sediment on the sea floor.
Detrital: brought into the ocean from outside, consists of terrigenous, volcanic, and
cosmogenic material.
Figure 2: Fossil test (shell) of
planktonic foraminifera
(Globigerinoides ruber) that lives
primarily in tropical to
subtropical waters of all the
oceans.
(http://earth.usc.edu/classes/geol150/stott/v
ariability/proxy.html)

33
Terrigenous sediments are those where the ultimate source is weathering and erosion of
rocks on land. The materials composing these sediments are introduced to the ocean by water,
wind or ice. Terrigenous sediments are more abundant close to the continents, specifically near
river mouths and in the very deep areas of the oceans. These sediments are most abundant on
continental margins where rivers come in (Atlantic > Pacific). The smaller, windblown
terrigenous particles are present everywhere in the oceans and they are the major component of a
large fraction of the sediment in the deep Pacific basin, mostly because the biogenic components
are not preserved there. Terrigenous sediments enclose information about river fluxes, sources of
the weathered material (provenance), weathering processes on land, wind stress and direction, as
well as glacial extent and glaciers location (ice rafted debris).
Volcanic sediments are composed of minerals brought into the ocean mostly by wind, as
dust and ash from volcanic eruptions. They are typically in the size range of 1m. Their
abundance gives information about periods and locations of intensive volcanic activity. These
sediments are more abundant close to volcanic islands but also globally distributed after big
eruptions. These deposits are easy to date by radioactive age determination and because of their
global and instantaneous distribution can be used for global correlation.
Figure 3: Distribution of different types of sediment on the seafloor
(http://ocean.stanford.edu/courses/bomc/chem/lecture_14.pdf)

34
Cosmogenic particles are those that arrive from outer space and survive the Earth‘s
atmosphere to enter the sedimentary record. About 4-6 x104 tons of these particles accumulate
each year; they range in size from 0.1 to 1mm and have a typical spherule shape. They have
distinct geochemical signatures (high 3 He, Ir, Os and Os isotopes and organic compounds not
typical to Earth) and provide information about possible changes in the rate of cosmogenic
bombardment as well as catastrophic impacts (K-T). They could also be a mean of estimating
sedimentation rate if we assume constant accumulation.
Authigenic components are oceanic inorganic minerals that precipitate directly from the
seawater, either in the water column or in the sediment after burial. These minerals make up only
a small fraction of deep-sea sediments today, but in special environments and certain geological
times, they comprise the bulk of the sedimentary sequence.
Biogenic Sediments are one of the most important constituents of marine sediments. As
the name implies, these form directly or indirectly through biological activity. They are made of
a variety of delicate and intricate structures mostly of skeletal remains of marine phytoplankton
and zooplankton. The life span of most of these organisms is on the order of weeks, so there is a
slow continuous ―rain‖ of their remains down through the water column to build successive
layers of sediment. The distribution of these sediments would depend on the abundance of
organisms precipitating these phases and dissolution at depth.
Carbonate Sediments are composed principally of skeletal remains of calcite or
aragonite secreting organisms. Foraminifera (figure 3) are protists that produce calcite
exoskeletons, or tests. They can be planktonic (float on the surface) or benthic (live at the
bottom) and range in size from ~ 30m to 1mm. The spiny ones have symbionts and live in the
photic zone where light is available; these spiny species are very delicate and more soluble. Non-
spiny forms are better preserved in sediments.
Silica Secreting Organisms include: Radiolarians are large zooplankton in the range
of 50-300 micron. They secrete very intricate shells structures. They are usually abundant in low
latitudes.

35
3.3 FORAMINIFERA
Kingdom: Protista
Subkingdom: Protozoa
Class: Granuloreticulosea
Superclass: Rhizopoda
Order: Foraminiferida
The Foraminifera ("hole bearers", or forams for short) are a phylum or class
of amoeboid protists. They are characterized both by their thin pseudopodia that form an external
net for catching food, and they usually have an external shell, or test, made of various materials
and constructed in diverse forms. Most forams are aquatic, primarily marine, and the majority of
species live on or within the seafloor sediment (benthos) with a small number of species known
to be floaters in the water column at various depths (plankton).
Figure 4: Left: Living phytoplankton; Right: Living
Zooplankton (Rachel Carson, The Sea Around Us.)

36
Planktic Foraminifera:
Planktic foraminifers are a major marine calcareous microfossil group. Their shells are
abundant in most oceanic sediments. Planktic foraminifera are very sensitive to environmental
variations and their distribution through passive transport, as well as their high relative
abundances and good preservation potential make them ideal proxies to interpret marine
sediments and oceanic conditions (figure 4). Their preservation potential is high and their test is
made up of calcium carbonate. The environmental changes in surroundings get recorded in the
calcareous tests of the foraminifera. As the soft part gets disintegrated after death, the hard part
remains intact as fossil in sediments. Foraminifers are microscopic in size and abundant in
almost all marine environments. Considering its size, abundance and diversity, it is very much
feasible to use foraminifera as a proxy; small amount of sample contains hundreds and thousands
of foraminifera while their ability of adaptation to environment lead the diversity of foraminifera.
They are omni-present thus can be recovered from every marine environment from lowest to the
high latitude. Their diversity is a function of changing environment thus different environments
are characterized by different and typical assemblages. Their test is capable for being preserved
and mainly used as a basis for the classification. Any change in the environment is visible in the
form of a morphological manifestation such as changes in size, coiling direction and deformation
of the test (Nath, B. N.; Planktic foraminifera: A potential proxy for paleoclimatic /paleoceanographic
studies).

37
Benthic Foraminifera
Benthic foraminifera are single-celled organisms similar to amoeboid organisms in cell
structure. The foraminifera differ in having granular rhizopodia and elongate filopodia that
emerge from the cell body. They are commonly referred to as the bottom dwellers (figure
5). They live all along and beneath the ocean floor in the sediments. Benthic organisms live in a
wide array of environments, ranging from marshes to abyssal plains. They are able to move and
feed by use of pseudopodia. The type of pseudeopodia varies for each species. They are
excellent indicators of ocean depth and serve as the primary biostratigraphic indicators for
paleontologists. In just a handful of sediment, thousands of forams can be found (B. Sen Gupta,
Louisiana State University). Their small size is key in how important they are to
research. Benthic foraminifera occupy a wide range of marine environments, from brackish
estuaries to the deep ocean basins and occur at all latitudes. Many species have well defined
salinity and temperature preferences making them particularly useful for reconstructing past
trends in ocean water salinity and temperature.
Figure5: Planktic foraminifera: A
potential proxy for paleoclimatic
/paleoceanographic
studies(http://www.dailymail.co.uk/sciencetech/artic
le-2389820/Planktonic-foraminifera-Ancient-fossils-
size-sand-grains-insight-evolution.html)

38
The life position and depth distribution of deep water benthic foraminifera at the
sediment water interface has been a major field of ecological research since the importance of
epifaunal of and infaunal habitats and species-specific microhabitat preferences for isotope and
trace element studies and paleoenvironmental reconstructions were recognized (Corliss, 1985;
Jones and Charnock, 1985; Altenbach and sarnthein ,1989).
Application of foraminifera
Planktonic foraminifera continue to play a central role in paleoceanography, providing the
science with robust and reliable proxies, and will continue to do so for some time.
1- PastMonsoonVariations
Among the micropaleontological proxies, planktic foraminifera are widely used as sensitive
monsoon indicators because they respond directly to oceanographic conditions.
2- PastProductivityReconstruction
Planktic foraminiferal assemblages and their isotopic composition are frequently studied for
reconstructing paleoceanography and paleoproductivity (e.g. Niebler et al., 1999; Lea et al.,
2000; Meggers et al.,2002). Abundance of benthic foraminifera in marine sediments has been
used to reconstruct the paleoproductivity of the oceans (Herguera and Berger, 1991).
3- PastSeawaterTemperatureReconstruction
Planktic foraminifera are widely used for past SST estimation by transfer function and also
for oxygen isotope studies of shells of Planktonic foraminifera. Planktonic foraminifera provide
important clues on estimating the SST, the difference in species composition contain clues to the
temperature of the waters in which they lived (Broecker, 1986).
Figure 6: Benthic Foraminifera- bottom dwellers.
They live all along and beneath the ocean floor in
the sediments.
(https://microbewiki.kenyon.edu/index.php/Foraminifera)

39
4- Indeterminingchemistryofoceanwaters:
The chemistry of the shell is useful because it reflects the chemistry of the water in which it
grew. For example, the ratio of stable oxygen isotopes depends on the water temperature,
because warmer water tends to evaporate off more of the lighter isotopes.
5- Sea level changes
Eustatic sea level fluctuated significantly in accordance with the waxing and waning of
continental ice sheets (Chappell and Shackleton, 1986). Foraminifera are widely used
for reconstructing sea level changes mainly understanding the bathymetry of the different
species.
6- Biostratigraphy
Biostratigraphy is mainly based on index fossils, first and last appearance datum and acme
zone of a species in a sedimentary formation. Foraminifera provide evidence of the relative ages
of marine rocks. There are several reasons that fossil foraminifera are especially valuable for
determining the relative ages of marine rock layers. They have been around since the Cambrian,
over 500 million years ago. They show fairly continuous evolutionary development; so different
species are found at different times. Forams are abundant and widespread, being found in all
marine environments, very small and easy to collect, even from deep oil wells hence widely
applied in biostratigraphy.
7- For Petroleum exploration:
Planktic foraminifera are good index fossil for oil and natural gas exploration. It is often
used in determining the particular geological period, when the decay of organic matters occurred
under anaerobic conditions in marine rock. Usually formation of petroleum occurs in typical
environment especially marine and their assemblages are good indicator of particular
environment condition and helpful in determine the oil-bearing horizon. Because of this oil
industry has been an important employer of paleontologists who specialize in these microscopic
fossils. Stratigraphic control using foraminifera is so precise that these fossils are even used to
direct sideways drilling within an oil-bearing horizon to increase well productivity.

40
3.4 RADIOLARIANS
Radiolaria (figure 6) are protozoa distinguished 1) by segregation of their soft anatomy
into the central capsule, containing the endoplasm, and the surrounding ectoplasm (or calymma),
and 2) by their siliceous (opaline) skeletons of the large majority of species. Radiolarians have
existed since the beginning of the Paleozoic era, producing an astonishing diversity of intricate
shapes during their 600 million year history. They take their name from the radial symmetry,
often marked by radial skeletal spines, characteristic of many forms. Nevertheless, many other
forms lack such radial symmetry. Skeletal elements of radiolarians, even the radially
symmetrical ones, do not actually meet at the center of the organism. This distinguishes them
from the superficially similar skeletons of acantharians, which are composed of celestite rather
than opal.
Figure 7: Radiolarians are part of the marine plankton.
They occur in all oceans, including shallow seas, bays,
fjords, etc., but almost invariably at salinities above 30
parts per thousand. They are most abundant in the upper
few hundred meters of the open oceans, but have been
reported at all depths, including deep trenches of the
Pacific, with different species often inhabiting different
depth horizons. Surface and subsurface geographic
distributions of species are influenced by ocean climatic
variables, with biogeographic provinces characteristically
mirroring surface and subsurface water masses.
(http://www.radiolaria.org/what_are_radiolarians.htm)

41
CHAPTER IV
LITERATURE REVIEW
CLIMATE CHANGE AT GEOLOGICAL TIMESCALE
Life on Earth has thrived and evolved for hundreds of millions of years. However, this
doesn‘t mean that the climate has been stable throughout this time. Geological data shows
evidence of large-scale climate changes in the past, caused by factors like the tilt of the Earth‘s
axis and tectonic plate movement. Some of these changes were gradual; others were much more
rapid.
Time Period Climate References
2.6 million
years
Decrease in global temperature (glacial
periods) separated by warm (interglacial)
periods(1)
Periodic glaciations with continental
glaciers moving as far from the poles as 40
degrees latitude
(1)Gibbard,
P.L., S.
Boreham,
K.M. Cohen
and A.
Moscariello,
2007
19-20 kya
Dust levels were as much as 20 to 25 times
greater than at present (1)
The massive sheets of ice locked away
water, lowering the sea level, exposing
continental shelves, joining land masses
together, and creating extensive
coastal plains.(2) This was probably due to a
number of factors: reduced vegetation,
stronger global winds, and less precipitation
to clear dust from the atmosphere(1)
Sea levels went down about 164 feet (50
meters) in 1,000 years.(3)
(1)Cowen, Robert C. "Dust
Plays a Huge Role in Climate
Change" Christian Science
Monitor 3 April 2008
(2) Mithen 2004
(3) Amanda Briney; an
Overview of Global
Glaciation from 110,000 to
12,500 Years Ago

42
CLIMATE DURING THE QUATERNARY PERIOD
The theory of the climatic variations during the Quaternary Ice Age, states that the effect
of an increase in the solar radiation intercepted by the earth is a relatively small increase in the
earth‘s temperature, but a large increase in the evaporation, cloudiness and precipitation. In high
latitudes or on high mountains, where the precipitation is mainly in the form of snow, the first
result is an extension of the ice-sheets and glaciers, but as the radiation increases still further, the
rise of temperature becomes great enough to melt away the ice. If the solar radiation, starting
from a minimum, goes through two complete cycles, the climatic succession would be: cold dry
climate; glacial; warm wet inter-glacial; glacial; cold dry interglacial; glacial; warm wet
interglacial; glacial; cold dry climate. Hence there would be four glacial periods separated by
three interglacials, of which only the first and third would actually be warm. In low latitudes, on
the other hand, the two cycles of radiation would be represented only by two pluvial periods
separated by an interpluvial, the maximum of each pluvial coinciding with a warm wet
interglacial (Dr. G. C. Simpson; Royal Meteorological Society).
CLIMATE DURING HOLOCENE
Climate has been fairly stable over the Holocene. Ice core records show that before the
Holocene there was global warming after the end of the previous ice age and cooling periods, but
climate changes became more regional at the start of the newer dryas. During the transition from
last glacial to holocene, the Huelmo/Mascardi(name given to a cooling event in South
America between 11,400 and 10,200 years BP) Cold Reversal in the Southern
Hemisphere began before the Younger Dry as, and the maximum warmth flowed south to north
from 11,000 to 7,000 years ago. The Holocene warming is an interglacial period and there is no
reason to believe that it represents a permanent end to the present ice age. However, the
current global warming may result in the Earth becoming warmer than the Eemian Stage, which
10-12kya
Global average temperature changes (1)
Slow warming from the last ice age; large
ice melt.(2)
(1)Bond, G.; et al. (2001)
(2)Roberts, Neil (1998). The
Holocene: an environmental
history (2nd ed.)

43
peaked at roughly 125,000 years ago and was warmer than the Holocene. This prediction is
sometimes referred to as a super-interglacial (International Commission on Stratigraphy).
4.2 MONSOON AND UPWELLING RELATION
Holocene records from the monsoon domains of India and East Asia provide evidence for
the existence of short-term climate fluctuations, indicating the general instability of monsoonal
climate system even after the global climate system had calmed down (Gasse and Van Campo,
1994; Wang et al., 1999).
Time Monsoon Productivity Records References
HOLOCENE
(Intact)
Intense monsoon
SW Monsoon intensity
decreased in 3.5-1.2ka- it
can be interpreted as a
result of the onset of arid
climate in general
throughout the tropics and
in particular in the Asian
tropics.
Greater value of
upwelling indices
Lowest upwelling
indices
Fluxes of
total
foraminifera
Naidu P.D.,
Current Science
(1996)
3.5 and 1.2 ka SW monsoon became
weaker during this period
lowest upwelling
indices
Naidu P.D.,
Current Science
(1996)
10 to 5 ka strongest SW monsoon in
the western Arabian Sea
the most intense
upwelling
Naidu and
Malmgren, 1996
12 ka (13.1 cal
kyr B.P.)
intensification of SW
monsoon winds
Increase in the
upwelling indices.
This increase in
upwelling coincides
with the initiation of
glacial melt-water
discharge in the
northern hemisphere
Naidu and
Malmgren, 1996

44
4.3 CALCIUM CARBONATE FLUCTUATIONS
The pelagic Mid-Atlantic Ridge and terrigenous- rich continental- rise cores that span the
last 130,000 years show identical carbonate fluctuations which accurately reflect climatic
oscillations during the Holocene and Last Interglacial (Damuth, 1975). Numerous studies have
confirmed that in Equatorial Atlantic and Caribbean sediments the carbonate content is relatively
higher in interglacial than in glacial sequences and has fluctuated in response to quaternary
climatic oscillations (Correns, 1937; Wiseman, 1954, 1956, 1965; Olausson, 1965, 1967;
Broecker, Turekian and Heezen, 1958; Turekian, 1965; Needham, Conolly, Ruddiman, Bowles
and Heezen, 1969; Ruddiman, 1971; Hays and Peruzza, 1972; Damuth, 1973; Gardner, 1973;
Prell, 1974).
The carbonate preservation pattern in the Pacific is out of phase with that in the Atlantic.
Carbonate maxima occur during interglacials in the Atlantic but during glacials in the Pacific
(Volat et al., 1980). Calcium carbonate fluctuations in eastern Arabian Sea cores were influenced
by dissolution (Naidu 1991). The quaternary CaCO3 pattern in the Indian Ocean has not been
analyzed in such detail as in the Pacific and Atlantic Oceans. In the Indian Ocean some sites
exhibit a Pacific pattern (Olausson, 1967, 1969, 1971; Oba, 1969; Naidu, 1991, 1994; Berger,
1992), whereas others show both Pacific and Atlantic patterns (Peterson and Prell, 1985; Naidu
et al., 1993).
Three factors controlling the carbonate content at any location in the ocean: (1)
Biogenous input, (2) terrigenous input and (3) carbonate removal by dissolution on the sea floor
inputs (Naidu, 1991). Carbonate is the main component of the total flux (about 65%). It supports
the fact that productivity is the main factor which controls the observed calcium carbonate
fluctuations in the Arabian Sea (Naidu, 1991). Productivity in Arabian Sea is greater during
glacial periods than in interglacial periods. Organic carbon also shows relatively high
percentages in the glacial sections (>0.5%) and low during interglacial sections (<0.4%) (Guptha
et al., 2005).
4.4 COMPARISION BETWEEN EASTERN AND WESTERN ARABIAN SEA
Arabian Sea is a unique area which gets affected by two types of monsoon, Southwest
and Northeast monsoon. During northeast monsoon, sporadic upwelling can be observed in the
eastern Arabian Sea (Colborn, 1975; Cullen and Prell, 1985). A strong branch of the northeast
monsoon current carrying low salinity water from the Bay of Bengal turns north and flows up

45
along the west coast of India, affecting the Eastern Arabian Sea during the Period from
November to January (Wyrtki, 1973).
The western Arabian Sea is characterized by strong southwesterly monsoon winds during
the northern hemisphere summer, which blow across the Arabian Sea, causing offshore Ekman
transport and intense seasonal upwelling along Oman and Somalia margins (Wyrtki, 1973;
Schott, 1983; Shallow, 1984; Bauer 1991). The upwelling process brings cold, nutrient-rich
waters from a few hundred meters depth to the surface and increases the biological productivity
in the euphotic zone. These southwest (SW) monsoon winds and associated upwelling processes
make the Arabian Sea one of the highest productive regions in the world oceans (Qasim, 1982).
This increased productivity due to upwelling is responsible for peaks in total planktic
foraminiferal lists with high abundance of G.bulloides and G.glutinata in the western Arabian
Sea during interglacial intervals (Ishikava and Oda ,2007).During the northeast (NE) monsoon
the upwelling is suppressed (Curry et al, 1992) but there is a convective mixing due to surface
cooling(Madhupratap et al, 1996). However, a comparison of seasonal sea surface temperatures
(SSTs) averaged for the period from 1970 to 2007 showed warmer SSTs during winter compared
to those of the SW monsoon upwelled waters (Takahashi et al, 2009) thus emphasizing the
intensity of upwelling in this study region. Naidu and Malmgren (2005) have also reported that
upwelling intensity in the western Arabian Sea is related to the SST difference between summer
and winter season.

46
CHAPTER V
MATERIALS AND METHODOLOGY
5.1 STUDY LOCALE:
The Indian Ocean is the third largest of the world's oceanic divisions, covering
approximately 20% of the water on the Earth‘s surface (The Indian Ocean and the Superpowers:
Routledge 1986). It is bounded by Asia—including India, after which the ocean is named.
(Mathur, Anand 2003). The climate north of the equator is affected by a monsoon climate.
Strong north-east winds blow from October until April; from May until October south and west
winds overcome.
The Arabian Sea is a region of the northern Indian Ocean bounded on the north by
Pakistan and Iran, on the southwest by northeastern Somalia, on the east by India, and on the
west by the Arabian Peninsula. The Arabian Sea is characterized by the extremes in the
atmospheric forcing which leads to a large Seasonal variation in biochemical process
(Ramaswamy et al., 2005). The monsoon plays important role in the upwelling process. During
SW monsoon produce high upwelling and which result high productivity but during NE
monsoon the productivity is low compared to the SW monsoon which is due to the reversal of
wind during the NE monsoon (Nair et al., 1989). The upwelling plays a significant role in the
productivity.
Figure 1: Satellite imagery of Arabian Sea (http://www.ndmindia.nic.in/recentdisaster/cycarabian.jpg)

47
5.1.1 SELECTION OF CORE
It is well known that the sedimentation along the western continental margin of India is
influenced by the seasonal fluctuations in monsoon, variation in monsoonal intensity during
glacial and interglacial periods and sea-level fluctuations. To understand these fluctuations,
collection of the sediment cores from the western continental slope were planned.
In the present study, we have chosen three cores in a transect with water depths ranging
from 806 to 2010 m.
DETAILS OF THE SAMPLING STATION (Cruise report: A.A. Sidorenko):-
NAME OF
THE CORE
NAME OF
EQUIPMENT
LATITUDE
(N)
LONGITUDE
(E)
WATER
DEPTH
(meters)
9/9 Gravity corer 10˚20.589 75˚00.449 2010
9/10 Gravity corer 10˚19.863 74˚17.873 1247
9/11 Gravity corer 10˚19.531 75˚33.090 806
Figure 2: Representation of core depth
Depth
2010 m
1247 m
806 m

49
5.2 NAMING OF SAMPLE:
The samples of the core were collected from the repository of the National Institute of
Oceanography. The sub-sampling was done at an interval of 3-4 cm and was named accordingly.
ABBREVIATIONS
A.A.S. – A.A. Sidorenko (Cruise name)
9/9 – 9- Cruise number; 9- Station Number
Example- A.A.S. 9/11
A.A.S. 9 11
5.3 SAMPLE PROCESSING
Estimated quantity of dried sediment was taken in a beaker and was curved in water for
disintegration. The sediment was kept overnight in order to crumble down fully. Subsequently,
the samples were being treated with sodium hexametaphosphate (NaPO3)6 and hydrogen
peroxide solutions. Sodium hexametaphosphate is used as a dispersing agent to break down clay
and other soil types. Hydrogen peroxide dissociates the sample quickly by dissolving organic
matter. The negative aspect of hydrogen peroxide is it destroys the chemical composition of
foraminifera if kept for longer time. All the treated samples were then washed through a 150 µm
sieve with a very gentle water pressure so as to foil from foraminiferal test breakage, (figure 5.3).
After washing, the wet residues were kept for drying in the oven at 60˚C.
The dried residues were then weighed and transferred into the labeled vials. A sample
splitter was used to split 150µm sample to the preferred sample amount in order to count the
foraminifera (benthic and planktonic) and siliceous species. The planktonic, benthic foraminifera
and siliceous organisms were identified on the basis of their characteristics number and
arrangement of chamber (e.g. spherical, hemispherical, cylindrical, flask shaped, lenticular,
conical, biconical), nature and position of aperture, and Ornamentation. Total number of
planktonic, benthic foraminifera and siliceous species was counted and computed the abundance
of planktonic, benthic foraminifera and siliceous species per gram sediment.
Name of
the cruise
Cruise
number
Station
Number

50
Simultaneously, 6-7 gram of core sample was taken and kept for drying in the oven for
few hours at 60˚C. The samples were pulverized by the help of motor and pestal. The powdered
sample was then transferred into a labeled vial for the coulometer analysis.
5.4 COULOMETER
A coulometer is a device used to determine electric charges. The term comes from the unit
of charge, the coulomb. There can be two goals in measuring charge:
 Coulometers is used to determine an amount of substance by measuring the charges. The
devices do a quantitative analysis. This method is called coulometry, and related coulometers
are either device used for a coulometry or instruments that perform a coulometry in an
automatic way.
5.4.1 CARBON COULOMETRY
Carbon coulometry measures the amount of carbon contained in sediments, either of
organic or inorganic orgin, and thus allows one to examine changes in the chemical makeup of
lake sediments through time. The carbon content of sediments can be related to a number of
factors such as rates of decomposition, productivity, and/or precipitation of carbonate minerals.
The CO2 Coulometer can be used to rapidly determine carbon content from water, gas, or
sediment samples.
Principle
Carbon dioxide gas (evolved from either organic or inorganic constituents) is swept by a
gas stream into a coulometer cell. The coulometer cell is filled with a partially aqueous medium
containing ethanolamine and a colorimetric indicator. Carbon dioxide is quantitatively absorbed
by the solution and reacts with the ethanolamine to form a strong, titratable acid which causes
the indicator color to fade. The titration current automatically turns on and electrically generates
Figure 3: The clay
matrix dissolves and
passes through the
holes in the sieves,
leaving the tiny
fossils behind.
http://paleobiology.si.edu/foss
iLab/projects.html

51
base to return the solution to its original color (blue).
Equipment and Procedure
LRC uses a UIC model 5014 CO2 Coulometer which detects carbon by automatic,
coulometric titration. CO2 gas is swept into the coulometer from either an acidification module
for TIC or from a combustion furnace that combusts all carbon (TC) within the sample. By
subtracting the total inorganic carbon from the total carbon (TC-TIC) one determines the value
for total organic carbon (TOC).
A summary of the chemical reactions occurring in the Coulometer cell follows:
- Absorption of CO2 by cathode solution (cathode reaction)
CO2 + HOCH2CH2NH2 HOCH2CH2NHCOOH.
- Electrochemical generation of OH (cathode reaction).
2 H2O + 2 e-
 H2 (g) + 2OH-
- Neutralization of absorbed CO2 reaction product by electrochemically generated OH
HOCH2CH2NHCOOH + OH-
HOCH2CH2NHCOO-
+ H2O
- Anode reaction.
Ago
Ag+
+ e-
Figure 4: UIC Coulometer (http://www.soest.hawaii.edu/S-
LAB/equipment/slab_coulometer.htm)

52
The current of the reaction (the e− created) is measured by the coulometer. Each electron
counted corresponds to one molecule of CO2 in the sample gas stream, which corresponds to one
atom of carbon in the new sample. In the most fundamental terms, the coulometer counts carbon
atoms.
Figure 5: Principles of operation
Acidification module of Coulometer
Samples are acidified in a heated reaction vessel to evolve forms of inorganic carbon
(including dissolved CO2, carbonate ion, bicarbonate ion and carbonic acid) as carbon dioxide.
CO2 free carrier gases brush the reaction products through a scrubbing system and into the CO2
coulometer for detection. Inorganic carbon levels from ppm to pure carbonates can be
determined when the machine is connected to the coulometer. By using absolute coulometer
detection based on the principles of Faraday‗s law, the instrument system requires no calibration.
Additionally, the machine is capable of analyzing either solid or liquid sample. Solids and liquids
may be weighed directly into the sample flasks. Reaction rates vary with sample type although 5
to 7 minutes analyses are typical. To quicken CO2 evolution, sample heating and magnetic
stirring are used.

53
(a) (b)
(c)
Setting up of acidification module:
The acidification module consists of an acid dispenser, a pre scrubber and a post scrubber.
1N hydrochloric acid is prepared and filled in the container from which it is brought into the
reaction vessel by the acid dispenser.
Potassium hydroxide is used as the pre scrubber which removes carbon dioxide from air
(carrier gas) before it enters the reaction vessel. It is prepared by dissolving 11.5 g of KOH in
25ml distilled water and is then filled in the pre scrubber assembly of the acidification module.
For the preparation of post scrubber 12.5 g of potassium iodide is weighed and dissolved in
25ml distilled water and is acidified to a pH of 3 by adding acetic acid.
 The KI scrubber is used for removing H2S, SO2 or any other unwanted gas which may result
from the acidification of some materials in the sample.
The post scrubber assembly should be changed daily during regular use. Pre scrubber should
be changed if it becomes foamy or else it should be diluted by adding distilled water
Figure 6 (a) KOH trap to reaction vial (b) Reaction vial to the thin section of
the HNO3trap (c) Main power to the heating unit
(http://pubs.usgs.gov/of/2002/of02-371/METHODS/coustart.htm)

54
Cell preparation:
 A clean and dehydrated coulometer cell was taken and a Teflon coated magnetic stirrer was
placed in the cathode compartment.
 The cathode solution is then filled in the individual compartment and is closed with the cell
top on which platinum electrode fixed is in such a way that the electrode is not blocking the light
path in the cell compartment.
 To the anode compartment small quantity of KI was added, filled with carbon anode solution.
The level of anode solution should be made slightly less than the liquid level in the cathode
compartment.
 The silver electrode was then placed properly inside it along with the anode cell top.
 The cell is then placed in the cell compartment of the coulometer and its position is adjusted
such that maximum cell current is obtained. Once the cell is fixed in the cell section it is better
not to change its position until the instrument is put off.
Sample analysis:
Solidify dried, homogenized samples are used for calcium carbonate estimation using
coulometer. The suitable analysis parameters were programmed into the instrument to start the
analysis. Before beginning the measurement of the T.I.C. of the sediment samples, it is required
to make sure the performance of the instrument by running certain standard samples and
comparing obtained data with the recognized correct measurements. Firstly, the instrument was
made to analyze an empty sample tube to obtain the blank value of T.I.C. that is later used to
calculate the T.I.C. of sediment samples. The blank should be less than 10 g C in about 5
minutes. Then, a known amount of standard sediment was put in the sample tube and placed in
the heating apparatus. The sample should have a weight between 20 to 30 mg. About 5 ml of the
acid was pumped into the reaction tube. When all of the CO2 had evolved and titrated
(recognized by a stable Coulometer 17 display and a %T of 29), the value of % carbon was
recorded. This value of the T.I.C. obtained was compared with the known carbon content value
to confirm that the instrument is working properly and giving correct results. Alternatively,
Calcium carbonate standard can also be used wherein; about 20 mg of the standard should give
approximately 11.5 to 12.0 % of carbon. The sample was then removed, the residue was
disposed off and the next analysis was begun. The test tubes were washed in distilled water after

55
every analysis and let arid completely before being used again. Likewise, the sediment samples
were run to determine their carbon content. Sporadically, few duplicates of samples were run to
confirm the proper functioning of the instrument.
TIC analysis result:
The percentage of inorganic carbon in the sample was calculated using the following
basic equation:
%TIC = [(display value as μg C) – (blank value as μg C)] *100
Sample weight in μg C
% CaCO3= % TIC x 100/12, Or
% CaCO3= (X‘) * Carbon %
Where X‘= multiplication factor i.e., 8.33
5.5. TOTAL CARBON-NITROGEN ANALYZER
The CN analyzer (Figure 5.9) is an instrument which is used for the measurement of total
carbon and nitrogen present in the sample. Around 2gms of the dried sample were taken and
grounded. Grounded non-acidified samples were used for CN analysis.
Analysis
The analysis of Carbon and Nitrogen is important in soil, plant, animal feed, food
samples, sediments and sludge samples. The Analyzer combines the analysis of Total Carbon
and Total Nitrogen in one unit using high temperature catalytic combustion.
Figure 7: Total Carbon-
Nitogen Analyzer
http://www.skalar.com/news/the-
primacssnc-total-carbon-total-nitrogen-
analyzer

56
Principle
The samples are introduced into the high temperature combustion oven by the unique
vertical sample introduction system. At 1050Â°C the carbon is completely oxidized to CO2 in
the presence of a catalyst. The CO2 is measured by Non Dispersive Infra Red Detection (NDIR)
for Total Carbon. The analysis of Nitrogen is based upon the well-proven DUMAS technology.
Nitrogen is converted in NxOy which is reduced at 600 Â°C to N2. The N2 gas is measured by
Thermal Conductivity Detection (TCD). The software displays the carbon and nitrogen peaks
simultaneously in real-time and the results can easily be printed or exported to a LIMS system.
Whenever priority samples have to be analyzed, the work list can be extended during the run.
The sample is weighed into a re-usable quartz crucible and the sample weight is automatically
transferred to the work list in the software, which avoids transcription errors.
The analyzer provides an accurate and reliable solution for the automation of Total
Carbon and Total Nitrogen analysis and has been designed as an easy-to-use and low
maintenance analyzer. Due to the unique vertical sample introduction the sample ashes remain in
the crucible after analysis and are taken out of the instrument with the removal of the crucible.
This avoids sample ash build-up in the combustion zone and therefore reduces the maintenance
requirements of the instrument.

57
CHAPTER VI
RESULTS AND DISCUSSIONS
6.1 RESULTS
The calcium carbonate content of deep sea sediments is controlled by three factors: a)
productivity of carbonate secreting organisms; b) dissolution of calcareous tests during and after
deposition; c) dilution by non-calcareous material (Naidu 1989). Cores AAS 9/9, 9/10 and 9/11
document fluctuations of calcium carbonate during late Holocene.
AAS 9/9
Depth CaCO3 Planktonic Forams Benthic Forams Radiolarians
2010m Changeable trend down
the core with maximum
value of 22.82% at the
core-top and decreases till
a depth of 68cm with
certain fluctuation in the
trend (Figure 6.1.1). The
minimum value of 14.16%
is observed at depth of
74cm.
The highest number
is seen at location 56
cm with ~106/g
sediment and the
least at 2cm interval
i.e., 31/g sediment.
There is an increasing
trend amid 41 to
59cm.
The benthic
foraminiferal
records show
distinct changes
in the 9/9 core.
Authorized range
in the respective
core is 490/g
sediment at 45cm
depth of the
sediment (Figure
6.1a). The
graphical
depiction shows
an increasing
trend of
assemblages
along the core
depth.
In this study
(Figure 6.1a),
the total number
of radiolarians
(for 1gm
sediment) is
higher in the
upper core
length ~ 40 cm;
and tends to
show a similar
kind of trend
down the depth
of core.

58
AAS 9/9
0 20 40 60 80 100
0
100
200
300
400
500
0 20 40 60 80 100
0
20
40
60
80
100
120
0 20 40 60 80 100
0
100
200
300
400
500
600 AAS 9/9
#Silicioustests#PlankticForams#BenthicForams
Depth (cm)
Figure 6.1a: Faunal Assemblage AAS 9/9
10
15
20
25
0 10 20 30 40 50 60 70 80 90 100
%TotalCalciumcarbonate
Depth (cm)
CaCO3 %
Figure 6.1.1 Percentage of CaCO3

59
AAS 9/10
AAS 9/11
DEPTH CaCO3 PLANKTONIC
FORAMS
BENTHIC
FORAMS
RADIOLARIAN
1247 m
In AAS 9/10, the
total calcium
carbonate shows
maximum values at
the core pinnacle
while the values
around 32cm show a
decreasing trend
(Figure 6.2.1). The
maximum and
minimum Percentage
of calcium carbonate
is 32% at 0cm and
13.16 at 95cm
respectively.
The assemblage
is more at a
depth of 12cm
i.e., ~4872/gm
sediment.
An unusual peak is
seen at a core depth of
95 cm i.e., 32978/gm
sediment. The faunal
assemblage increases
from 42 to 95cm in the
core.(Figure 6.2a).
The percentage of
radiolarian is more at
the surface. It shows a
stable trendline in the
graphical form (Figure
6.2a).
DEPTH CaCO3 PLANKTONIC
FORAMS
BENTHIC
FORAMS
RADIOLARIANS
806m
In AAS 9/11 the
percentage of total
calcium carbonate
shows a maximum
value at surface of
the core 24.57%
and values decrease
till a depth of 27cm
to 19.92%.
Thereafter it shows
an increasing trend
(Figure 6.3.1).
The assemblage
increases along the
core depth. Highest
number counted is
670/gm sand at
9cm.
(Figure 6.3a)
Benthic foraminifera
abundance in Core
AAS 9/11 document
greater fluctuations
throughout the length
of the core with
maximum ~1740 and
minimum ~433/gm
sediment (Figure
6.3a)
The percentage
increased at the top
core depth where as it
became stable down
the depth.
(Figure 6.3a)

60
AAS 9/10
0 20 40 60 80 100
0
5000
10000
15000
20000
25000
30000
35000
0 20 40 60 80 100
0
5000
10000
15000
20000
25000
30000
35000 0 20 40 60 80 100
-50
0
50
100
150
200
250
300
350
Depth (cm)
AAS 9/10
#Silicioustests#Plankticforams#Benthicforams
10
15
20
25
30
35
0 20 40 60 80 100
%TotalCalcium
Carbonate
Depth (cm)
CaCO3%
Figure 6.2.1: Percentage of CaCO3

61
AAS 9/11
0 20 40 60 80 100
0
500
1000
1500
2000
2500
0 20 40 60 80 100
0
100
200
300
400
500
600
700
0 20 40 60 80 100
0
20
40
60
80
100 AAS 9/11
#Silicioustests#Plankticforams#Benthicforams
Depth (cm)
17
18
19
20
21
22
23
24
25
0 20 40 60 80 100
%TotalCalciumCarbonate
Depth (cm)
CaCO3%
Figure 6.3.1: Percentage of CaCO3

62
6.2 DISCUSSION
The three cores recovered from the Eastern Arabian Sea are from decreasing water depths
in the following order; AAS9/9, 9/10, 9/11. The core contiguous to the coast, AAS9/11 having a
water depth of 806 m and lying in the present day Oxygen Minimum Zone (OMZ) which is
found at a water depth between 150 and 1200 m (Von Stackelberg, 1972). The core AAS9/10
from a water intensity of 1247 m might descend within the current day OMZ while the core
AAS9/9 is from a deeper water depth of 2010m. The core locations are ideal to understand the
productivity variations and the extent of terrestrial or terrigenous inputs to the south-eastern
Arabian Sea. These three sediment cores are very close to the location of Core GC-5 (10°23‘N &
75°34‘E) (Thamban et al., 2001) and hence the sedimentation rates should be alike. By
assuming the constant sedimentation rate of ~18cm/kyr we estimate the present studied cored
covers a time span of last 5-6 ka BP, calendar age, which represent the mid to late Holocene
period.
6.2.1 FLUCTUATIONS IN CALCIUM CARBONATE
In the eastern Arabian sea cores (9/9 and 9/10) the calcium carbonate content is
maximum (32%) in the top 0-26cm interval which gradually decreases along with the interval,
excluding core 9/11 showing opposite kind of feature. It is noticeable that the calcium carbonate
peaks are matching with each other. The highest abundance of planktonic and benthic
foraminifera coincides with a high percentage of calcium carbonate in the three cores. As three
factors i.e.: 1) Biogenous input, 2) terrigenous input and 3) carbonate removal by dissolution on
the sea floor controls the CaCO3 content in the marine sediment. In all these cores planktic
foramifera are well preserved therefore dissolution factor is ruled out. Therefore, the observed
carbonate fluctuations in the eastern Arabian Sea sediment cores seems to result mainly due to
productivity variation in the water column or dilution of terrigenous inputs. Though AAS 9//9,
AAS9/10 and AAS 9/11 are from different water depths the percentage of calcium carbonate in
these cores varies from 32 to 14.07%. This suggests that the influence of terrigenous dilution is
not depth related in the eastern Arabian Sea.

63
6.2.2 PRODUCTIVITY VARIATION DURING LATE HOLOCENE
In order to understand productivity variations, organic carbon (OC) variations (Figure
7.4) in these cores were observed (CN Analyzer; Moushmi, 2014). The OC content in the residue
is often closely related to the face water productivity. The OC content of sediments as well
depends upon factors like sedimentation rates; oxygen exposure times and organic matter
composition. Supplementary, only a small fraction of the organic matter produced in the ocean is
preserved in the bottom sediments (Meyers, 1994). OC values are greatest in the core AAS9/11
which is closer to the coast. The higher OC values in the OMZ (oxygen minimum zone) core
9/11 is most likely related to high productivity as well as enhanced preservation of organic
matter. The core top OC values in all the three cores are high and decrease sharply in the upper
10 cm of the core. Subsequently the values generally increase but the fluctuation patterns in the
three cores are not similar. Better age constraints will help in understanding the reasons for these
variations.
1
1.5
2
2.5
3
3.5
4
0 20 40 60 80 100
%TotalOrganicCarbon
Depth (cm)
AAS 9/9
1.5
2
2.5
3
3.5
4
0 20 40 60 80 100
%TotalOrganicCarbon
Depth (cm)
AAS 9/10
Figure 6.4a: % Total
Organic carbon (AAS 9/9)
Figure 6.4b: % Total Organic
Carbon (AAS 9/10)

64
6.2.3 DIVERSITY OF RADIOLARIANS
The abundance of radiolarians in this study is less when compared with other previous
studies; here it varies from 200 to 250 tests per gram sediment. Radiolarian abundance is low in
the area despite the fact of high productivity and may be up to some extent due to the dissolution
of the radiolarian tests. In the study area, higher values of silica are observed in the surface
sediments. By comparing the results with the X-Ray Fluorescence data it is found that silica
percentage is more at the core top (AAS 9/10) and then show an abrupt decrease in the upper 10
cm of the core (Moushmi, 2014). However towards the lower portion of the core the variations
are dissimilar to OC variations. This could be due to lower Si content in the south-eastern
Arabian Sea (Nair et al., 1979). Si enters the naval environment mostly through riverine influx,
submarine volcanism and glacial weathering. Quartz, biogenic Silica and alumino-silicate
detritus, all add to the concentration of Si in marine sediments. Overall the contribution of
siliceous organism to the total biogenic component along the eastern Arabian Sea is not
significant.
6.2.4 BENTHIC FORAMINIFERA ABUNDANCE VARIATIONS
Benthic foraminifera accumulation rates (BFAR) has been used as productivity proxy in
the open ocean environments in the Pacific Ocean (Herguera and Berger, 1991). Subsequently it
has been suggested that BFAR would not represent the biological productivity in the regions
where dissolved oxygen concentrations are lower (Naidu and Malmgren, 1995). AAS9/11 is
from the intense OMZ region document lesser abundance of benthic foraminifera than in AAS
9/10, which is almost outside OMZ. Therefore it is evident from the present study also that the
abundance of benthic foraminifera along the eastern Arabian Sea is also controlled by the
dissolved oxygen concentrations.
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
0 20 40 60 80 100
%TotalOrganicCarbon
Depth (Cm)
AAS 9/11
Figure 6.4c: % Total
Organic Carbon (AAS 9/11)

65
Chapter vii
CONCLUSIONS
 The profusion of planktonic, benthic and radiolarians, and the high calcium carbonate and
organic carbon values found in these samples evidently show the record of upwelling in
the sediments.
 Major biogenic components to the sediment in these three cores are planktonic and
benthic forams, minor contribution from siliceous organisms. All three cores devoid of
pteropods.
 The calcium carbonate content along the eastern Arabian Sea are controlled by the
biological productivity and terrigenous dilution, however the terrigenous dilution along
the western margins of India are not depth related.
 Organic carbon content along the depth transect in the eastern Arabian Sea appears
largely controlled by the euphotic zone productivity.
 It is evident from the present study also that the abundance of benthic foraminifera along
the eastern Arabian Sea is also controlled by the dissolved oxygen concentrations.

66
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69
SAMPLE Depth CaCO3 % Coarse Fraction (1gm)
0-3 0 19.32 0.00188
3-5 3 22.74 0.0000971
5-7 5 21.99 0.00073
7-9 7 22.82 0.0018
9-11 9 20.49 0.0011
11-13 11 19.65 0.00081
13- 15 13 19.65 0.0044
15-17 15 20.15 0.0034
17-19 17 19.49 0.0054
19-21 19 16.24 0.0039
21-23 21 17.49 0.00056
23-25 23 16.24 0.00344
25-27 25 15.57 0.00246
27-29 27 17.07 0.0011
29-31 29 16.24 0.0009
31-33 31 15.07 0.00212
33-35 33 14.91 0.0011
35-37 35 15.91 0.00185
37-39 37 17.82 0.00177
39-41 39 17.49 0.00108
41-43 41 15.07 0.0025
43-45 43 17.49 0.00293
45-47 45 17.9 0.00475
47-50 47 17.74 0.00177
50-53 50 17.57 0.0084
53-56 53 15.82 0.00325
56-59 56 14.66 0.00515
59-62 59 14.57 0.00582
62-65 62 14.74 0.00163
65-68 65 16.9 0.00351
68-71 68 14.57 0.00371
71-74 71 14.41 0.00204
74-77 74 14.16 0.003
77-80 77 16.99 0.0034
80-83 80 14.74 0.0023
83-86 83 16.32 0.0076
86-89 86 16.41 0.00324
89-92 89 16.9 0.00522
92-96 92 18.24 0.00739
96-100 96 16.99 0.00626
AAS 9/9
TABLES PREPARED DURING THE STUDY

70
SAMPLE DEPTH CaCO3% Coarse Fraction(1gm)
0-3 0 32 0.096
6-9 6 25 0.058
9-12 9 20.5 0.0317
12-14 12 26.6 0.08083
14-17 14 28.6 0.08529
20-23 20 20.8 0.0216
23-25 23 18.07 0.0215
25-29 25 19.74 0.0269
29-32 29 18.49 0.0319
32-35 32 15.99 0.0254
35-38 35 15.99 0.03
38-41 38 16.68 0.0274
42-44 41 17.4 0.0278
44-47 44 16.74 0.0338
47-50 47 16.68 0.0984
50-53 50 17.9 0.0326
53-56 53 17.4 0.0258
56-59 56 16.66 0.029
59-62 59 17.15 0.0316
62-65 62 17.07 0.0331
65-68 65 15.16 0.0262
68-71 68 14.91 0.0242
71-74 71 15.41 0.017
74-77 74 14.74 0.019
77-80 77 15.07 0.0363
79-80 79 19.24 0.0295
80-83 80 14.91 0.0325
83-86 83 14.07 0.034
86-89 86 14.57 0.0328
89-92 89 12.74 0.0445
92-95 92 15.32 0.042
95-100 95 13.16 o.04
AAS 9/10

71
SAMPLE DEPTH CaCO3% Coarse Fraction (1gm)
0-3 0 20.17 0.0122
0-6 3 18.91 0.0087
6-9 6 18.53 0.005
9-12 9 18.4 0.0105
12-15 12 18.19 0.0072
15-18 15 19.75 0.0102
18-21 18 18.06 0.0075
21-24 21 18.97 0.007
24-27 24 19.92 0.008
27-30 27 19.17 0.009
30-33 30 21.78 0.01
33-36 33 22.97 0.0078
36-39 36 21.79 0.0105
42-45 42 20.9 0.013
45-48 45 21.15 0.0125
51-54 51 22.52 0.0129
54-57 54 23.22 0.032
57-60 57 21.01 0.0181
60-63 60 22.74 0.013
63-66 63 22.57 0.015
66-69 66 24.57 0.017
72-75 72 23.15 0.02
75-78 75 21.4 0.0326
78-81 78 21.65 0.014
84-87 84 23.82 0.019
87-90 87 23.74 0.015
90-93 90 24.07 0.015
93-96 93 23.15 0.0119
96-100 96 24.15 0.016
AAS 9/11

72
#benthic #planktons #silicious Depth
144.7933884 47.60330579 156.6942149 0
120.3821656 33.12101911 138.2165605 3
35.13957307 5.582922824 21.67487685 5
50.07824726 7.198748044 40.6885759 7
128.7356322 26.92939245 76.19047619 9
125.7318952 26.50231125 65.33127889 11
200.6779661 17.62711864 65.08474576 13
277.3333333 39.33333333 34.66666667 15
175.0286369 50.40091638 55.44100802 17
239.2092257 22.40527183 61.28500824 19
259.0769231 25.23076923 60.30769231 21
95.04373178 55.97667638 66.47230321 23
281.9047619 99.68253968 548.5714286 25
284.1059603 39.07284768 45.03311258 27
177.9160187 17.41835148 57.23172628 29
98.74125874 2.797202797 33.84615385 31
117.7743431 8.964451314 18.85625966 33
133.4448161 13.04347826 4.013377926 35
149.7093023 6.104651163 38.95348837 37
282.0338983 12.20338983 126.1016949 39
74.18263811 9.695603157 21.4205186 41
239.3984962 4.812030075 31.87969925 43
382.7272727 39.09090909 43.63636364 45
256.3685637 52.03252033 74.79674797 47
307.8369906 65.830721 78.36990596 50
300.8849558 31.26843658 58.40707965 53
85.26315789 106.3157895 77.89473684 56
268.8757396 88.99408284 36.92307692 59
208 22.66666667 42 62
423.7337192 30.10130246 54.41389291 65
169.0621194 20.9500609 29.71985384 68
262.305296 6.230529595 22.42990654 71
293.3333333 12.17391304 13.33333333 74
179.9373041 43.26018809 114.1065831 77
200.6472492 12.29773463 7.766990291 80
490.6946265 30.40629096 18.87287025 83
324.8796148 50.7223114 78.97271268 86
336.8421053 69.98577525 105.8321479 89
193.9393939 43.03030303 53.93939394 92
132.4137931 23.72413793 6.620689655 96
AAS 9/9- Faunal Assemblage

73
#benthic #planktic #silicious depth
17062.6 4431.843 0 0
1308.287 769.0608 17.67956 6
4617.722 3341.772 0 9
6334.772 4872.902 324.8601 12
18903.17 30932.47 0 14
3749.628 3313.625 0 20
2066.087 956.5217 0 23
4026.754 1205.873 0 25
2202.585 1116.804 0 29
4495.569 2247.785 0 32
6553.521 3114.085 0 35
5721.938 2232.952 0 38
7373.7 6620.183 0 42
19840.34 12209.44 0 44
4573.228 1792.913 51.9685 47
1337.853 786.4407 27.11864 50
6762.74 5135.342 0 53
2755.741 1791.232 0 56
5005.505 3929.052 0 59
2308.861 1488.608 0 62
1014.634 1242.777 0 65
549.2119 243.7828 0 68
6403.113 5033.463 34.24125 71
517.1271 371.2707 4.41989 74
2512.999 1999.591 0 77
6584.323 3072.684 0 80
16057.76 7533.268 0 83
596.6102 433.8983 0 86
3803.015 2476.382 0 89
13612.5 6600 0 92
32978.36 14101.86 222.0765 95

74
#benthic #planktic #silicious depth
693.0876 148.6943 43.01075 0
514.5497 71.13164 9.237875 3
1764.337 365.1926 86.73324 6
2361.039 670.1299 10.38961 9
1001.117 200.2235 0 12
795 151.25 7.5 15
626.3904 120.3926 0 18
545.8023 158.1296 7.651435 21
520.2094 133.1937 1.675393 24
433.4867 92.73229 0 27
621.6561 99.36306 5.095541 30
2229.841 322.5397 7.619048 33
494.2774 105.5286 0 36
1486.435 156.4669 0 39
1696.433 253.8745 0 42
954.2416 187.1465 0 45
1213.423 210.4698 12.88591 48
931.0288 227.8189 0 51
1313.838 131.5927 0 54
1451.669 379.7281 0 57
1717.677 293.1613 0 60
743.8043 142.6993 0 63
345.2217 111.133 0 66
1205.505 139.4495 0 69
685 132.5 0 72
1900.717 523.3859 0 75
352.0913 73.0038 0 78
523.1162 73.56322 0 81
739.577 107.5529 0 84
1365.02 388.785 0 87
918.2309 146.7098 0 90
1066.667 209.8361 0 92
1740.479 386.7731 0 96

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