Biomarker Geochemistry of Core Sediments in the Mangrove Ecosystems along Northern Kerala

258 Pages·2015·6.83 MB·English

Biomarker Geochemistry of Core Sediments
in the Mangrove Ecosystems along Northern
Kerala Coast
Thesis submitted to
Cochin University of Science and Technology
in partial fulfilment of the requirements
for the degree of
Doctor of Philosophy
in
Marine Chemistry
Under the Faculty of Marine Sciences
By
Manju M.N
Reg. No. 3691
Department of Chemical Oceanography
School of Marine Sciences
Cochin University of Science and Technology
Kochi – 682016
April 2015
Biomarker Geochemistry of Core Sediments in the Mangrove Ecosystems along
Northern Kerala Coast
Ph.D. Thesis under the Faculty of Marine Sciences
Author:
Manju M.N
Research Scholar
Department of Chemical Oceanography
School of Marine Sciences
Cochin University of Science and Technology
Kochi - 682016
Email: [email protected]
Supervising Guide:
Dr. N. Chandramohanakumar
Professor
Department of Chemical Oceanography
School of Marine Sciences
Cochin University of Science and Technology
Kochi - 682016
Email: [email protected]
April, 2015
COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY
DEPARTMENT OF CHEMICAL OCEANOGRAPHY
Dr. N. Chandramohanakumar
Professor [email protected]
This is to certify that the thesis entitled “Biomarker Geochemistry of Core
Sediments in the Mangrove Ecosystems along Northern Kerala Coast” is an authentic
record of the research work carried out by Ms. Manju M.N, under my supervision and
guidance at the Department of Chemical Oceanography, School of Marine Sciences,
Cochin University of Science and Technology, Kochi-682016, in partial fulfilment of
the requirements for Ph.D degree of Cochin University of Science and Technology and
no part of this has been presented before for any degree in any University. I further
certify that all the relevant corrections and modifications suggested by the audience
during the Pre-synopsis Seminar and recommended by the Doctoral Committee of
Ms. Manju M. N has been incorporated in the thesis.
Dr. N. Chandramohanakumar
(Supervising Guide)
Kochi - 682016
April, 2015

I hereby declare that the thesis entitled “Biomarker Geochemistry of
Core Sediments in the Mangrove Ecosystems along Northern Kerala
Coast” is an authentic record of the research work carried out by me under the
guidance and supervision of Dr. N. Chandramohanakumar, Professor, Department
of Chemical Oceanography, School of Marine Sciences, Cochin University of
Science and Technology, and no part of this has previously formed the basis of the
award of any degree, diploma, associateship, fellowship or any other similar title or
recognition from any University/Institution.

Kochi-16 Manju M.N
April, 2015

I would like to take this opportunity to thank all the persons who helped me
to commence and complete my research work. I would like to acknowledge them
for their efforts, assistance and collaboration which have worked towards the
success of this study.
I am deeply grateful to my supervising guide, Dr. N. Chandramohanakumar, for
patiently taking me through this difficult task of research. I express my deep and
sincere gratitude to my guide for conceptualisation and implementation of this
research topic, in addition to his peerless guidance and motivation throughout my
research.
I am thankful to Dr. Sujatha C.H., Head, Department of Chemical Oceanography
for her valuable suggestions and encouragement during the tenure of my work. I do
not have words to acknowledge Dr. Jacob Chacko and Dr. S. Muraleedharan Nair,
for their help and encouragement throughout the course of my research.
I am grateful to Dr. Mohan Kumar, K., Director, School of Marine Sciences
and Dr. Sajan, K., Dean, Faculty of Marine Science, for providing facilities for the
research work.
I owe special thanks to my classmate Dr. Ratheesh Kumar C.S, for his
unstinted support all through the course of this research work. I am grateful to Mrs.
Resmi P, for her help and motivation throughout the study. I am thankful to
Dr. Gireeshkumar T.R, Mrs. Nebula Murukesh, Dr. Martin G.D, Ms. Saritha S,
Ms. Movitha Mohandas, Dr. Manju Mary Joseph and Dr. Renjith K.R, for their
assistance in the entire phase of my research work.
I would like to thank Mr. Salas P.M, Mr. Sanil Kumar, Dr. Prasob Peter,
Dr. Deepulal P.M, Mrs. Ragi A.S, Mrs. Leena P.P, Ms. Ramzi A, Dr. Shaiju P,
Mrs. Bindu K.R, Mr. Rahul R, Mr. Udayakrishnan P.B, Mr. Manu Mohan,
Mr. Shameem and Mr. Akhil P Soman, for their inspired advice, continuous
encouragement and support.
I extend my special gratitude towards Dr. Aninda Sarkar, Professor, Department
of Geology and Geophysics, IIT Kharagpur, for stable carbon isotope analysis. I
sincerely acknowledge the help rendered by SAIF Lab, STIC, Cochin University of
Science and Technology for instrumental analysis. I thank staff of Sophisticated
Analytical Instrumentation Facility, CUSAT, for CHNS analysis.
I take this opportunity to thank the non- teaching staff of Department of
Chemical Oceanography and Cochin University of Science and Technology for helping
the administrative work of my thesis.
I would like to thank my father, mother, elder sister and brother- in- law for
their support, patience, and for their continued inspiration over the years. I am
thankful to Dr.Venugopal R, for his valuable advice and encouragement.
I would like to thank almighty (God), to bless me by giving the potential to
complete this enormous task.

MANJU M.N
Preface
Mangroves are diverse group of trees, palms, shrubs, and ferns that share a
common ability to live in waterlogged saline soils exposed to regular flooding, and are
highly specialised plants which have developed unusual adaptations to the unique
environmental conditions. They are sites of accumulation and preservation of both
allochthonous and autochthonous organic matter owing to their strategic loction at
the interface between land and sea and prevailing reducing environment. They are
among the most productive ecosystems and are efficient carbon sinks with most of the
carbon stored in sediments.Mangrove ecosystems play a significant role in global
carbon cycle and hence the knowledge on the processes controlling the delivery of
organic matter to coastal sediments, and how these signatures are preserved in the
sediment is a prerequisite for the understanding of biogeochemical cycles.
The evaluation of nature and sources of organic matter can be accomplished by
the determination of biochemical constituents like carbohydrates, proteins and lipids.
When characterised at molecular level, lipids provide valuable information about the
sources of organic matter, even though they account only small fraction of organic
matter. They are useful for the paleo-environmental reconstruction because of their low
reactivity, high preservation potential and high source specificity relative to other
organic class of compounds. The application of recent analytical techniques has
produced a wealth of useful information but has also indicated the gaps in our
knowledge on cycling of organic matter in the coastal ecosystems. The quantity and
quality of organic matter preserved in sediments vary depending up on the nature of
material delivered to the sediment and on the depositional environment. The input from
both autochthonous and allochthonous sources sharpens the complexity of
biogeochemistry of mangrove ecosystem and hence bulk sedimentary parameters are not
completely successful in evaluating the sources of organic matter in mangrove
sediments. An effective tool for the source characterisation of organic matter in coastal
ecosystems is biomarker approach. Biomarkers are chemical "signatures" present in
environmental samples whose structural information can be linked to its biological
precursor. The usefulness of molecular biomarkers depends on high taxonomic
specificity, potential for preservation, recalcitrant against geochemical changes, easily
analysable in environmental samples and should have a limited number of well-defined
sources.
The thesis entitled “Biomarker Geochemistry of Core Sediments in the
Mangrove ecosystems along Northern Kerala Coast” is an attempt to characterise
the sources of organic matter in the core sediments of mangrove forests providing
special emphasis on lipid biomarkers such as n-alkanes and fatty acids. Core
sediment samples were collected from five mangrove ecosystems along Northern
Kerala coast, Southwest India. In this study, a combination of bulk geochemical
parameters and different groups of molecular biomarkers has been used to define
organic matter sources and thereby identifying various biogeochemical processes
acting in the study region. Core sediments were used in this study because they can
provide long term and continuous past historical records and act as a useful tool for
the effective reconstruction of past environmental conditions.
The thesis is divided into six chapters. Chapter 1 is Introduction and it
contains general aspects of mangrove ecosystems, the aim and scope of the study.
Chapter 2 is Materials and methods. This chapter deals with the nature and
general geographical features of the study area. It also contains the details of the
sampling and analytical methodology. Chapter 3 is Geochemistry of heavy metals,
which includes the down core variations of the general sedimentary parameters,