Chemical Oceanographic Studies of the Coastal Waters of Cochin

318 Pages·2011·6.89 MB·English

CHEMICAL OCEANOGRAPHIC STUDIES OF THE
COASTAL WATERS OF COCHIN
THESIS SUBMITTED
TO THE
COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY
FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
IN
MARINE SCIENCE
By
K.K. BALACHANDRAN, M.Se.
NATIONAL INSTITUTE OF OCEANOGRAPHY
REGIONAL CENTRE
COCHIN- 682 014
August, 2001
DECLARATION
I hereby declare that this thesis entitled "Chemical Oceanographic
Studies of the Coastal Waters of Cochin" is an authentic record of research
work carried out by me, in the Regional Centre of National Institute of
Oceanography, Cochin-14, under the supervision of Dr. V.N.Sankaranarayanan,
FormerScientist-in-Charge, National Institute ofOceanography, Regional Centre,
Cochin-14 in partial fulfillment of the requirement of the Ph.D. degree of the
Cochin University of Science and Technology and that no part thereof has been
previously formed the basis for the award ofany degree, diploma or associateship
inany University.
Cochin-682014,
August,2001. K.K.BALACHANDRAN)
CERTIFICATE
•
This is to certify that this thesis entitled "Chemical Oceanographic
Studies of the Coastal Waters of Cochin" is an authentic record of the research
work carried out by Sri. K.K. Balachandran, under my supervision and guidance in
the Regional Centre of National Institute of Oceanography, (Council of Scientific
and Industrial Research), Cochin-14 and that no part thereof has been previously
formed the basis for the award of any other degree, diploma or associateship in
any University.
Cochin-682 014,
August, 2001. Dr. V.N. Sankaranarayanan,
Supervising Guide,
Regional Centre ofNIO,
Cochin-682 014.
ACKNOWLEDGEMENT
I express my deep sense of gratitude to Dr. V.N. Sankaranarayanan, former
Scientist-in-Charge, National Institute of Oceanography, Regional Centre, Cochin
forhis inspirational guidance and encouragement that motivated and strengthened
metocomplete the work successfully.
I am thankful to Dr.E.Desa, Director, National Institute of Oceanography,
Goa, Dr.K.K.C.Nair, Scientist-in-charge, National Institute of Oceanography,
RegionalCentre, Cochin for the encouragement and facilities given. I express my
sincere thanks to Sri.V.Kesava Das and SrLK.Kameswara Rao, for their
cooperation and valuable suggestions. The help rendered by Dr.K.Srinivas and
Dr.K.V.Jayalakshmy in statistical analysis and data interpretation is gratefully
acknowledged.
I am grateful to Dr.S.Muraleedharan Nair, Lecturer, Chemical
Oceanography Division, School ofMarine Sciences, Cochin University ofScience
and Technology, for critically reviewing the manuscript and to Dr. M.
Dileepkumar, Dr.S.W.A.Naqvi, Dr.M.D.George, Dr.S.Prasannakumar and
Dr.T.Pankajakshan, for their valuable suggestions in improving the scientific
findings. I also express my sincere thanks to Dr.K.Saraladevi, in improvising the
biological data interpretation.
I wish to place on record the help rendered by P.R.Vijayan, Tony J.Thottam
andV.N.Mohanan, in preparing the geographical locations ofthe study region and
by Dr.N.Anilkumar, Dr. K. Rasheed, and Ms. Minirani for timely help in
successful completion ofthethesis.
I owe a lot to my colleagues of chemical oceanography division for the
cooperation and help rendered to me throughout the course ofthis study.
Finally, I am thankful to each and every one of my colleagues of this
centerwho helped me directly or indirectly during the course ofmy study.
PREFACE
Cochin is the second largest city along the west coast of India and one of
the finest natural harbours in the country. In recent years, great concern has
been expressed with regard to deterioration of Cochin backwaters and
consequent loss of supportive functions of this wetland system, especially due
to urbanization, industrialization and agricultural activities. The impact of
changes in the backwater system on the coastal waters are however, not fully
known. Considering the economic importance of Cochin, these activities are
expected to increase in future. The resultant increased marine transport of
nutrients and other toxic metals through the backwaters are likely to upset the
coastal ecosystem. Moreover, the Arabian Sea, which has been identified as
one of the highly vulnerable region following its mid-depth oxygen deficiency
and associated denitrification, is bordering this coast. Located between these
two environmentally sensitive zones, the coastal waters are vulnerable to the
changes in the backwaters as well as the Arabian Sea. Thus, the coastal waters
necessitate a critical evaluation of the nature and quantum of inputs to the
Arabian Sea as well as their assimilative capacities.
With a view to delineate environmental changes of such a vulnerable
region, a series of chemical oceanographic studies in the coastal waters of
Cochin covering seasonal signals and also that of the adjoining backwaters
have been carried out. A comparison of the water quality of these two different
entities based on the behaviour of some of the major environmental tracers
such as phosphate and nitrate could provide valuable information regarding
probable changes that may occur in the coastal waters in future .
. The thesis is presented in 6 chapters. The first chapter gives a general
introduction to the topic, coastal environmental issues, background information
on oceanographic investigations carried out along the west coast of India, the
shortfall, the need for an exhaustive study, scope and objective of the present
study. The second chapter is on the materials and methods, which cover
description about the study region and methodology, adopted for sample
collection and analysis of chemical oceanographic parameters of water and
sediment samples.
The third chapter comprises the results and discussion of the hydro
chemical parameters of coastal waters of Cochin during different seasons with
statistical analysis. The parameters dealt with are salinity, temperature, pH,
dissolved oxygen, nitrite-N, nitrate-N, ammonia-N, silicate-Si, phosphate-P,
chlorophyll 'a' and suspended solids, dissolved trace metals and sediment
characteristics including sediment metals. The fourth chapter furnishes an
account of water quality and trace metal levels in the Cochin backwater system
and delineate the environmental conditions of the system.
A long-term scenano of environmental quality of the Cochin
backwaters, coastal waters and the stability of coastal region is presented in
chapter 5.
The sixth chapter gIves the summary of the thesis. This chapter is
followed by the list of references cited in the text and published papers of the
candidate.
CONTENTS
Page No.
CHAPTER 1 INTRODUCTION
1.1. Scope and objective 5
1.2. Coastal waters 6
1.3. Mudbanks of Kerala 12
1.4. Estuarine studies 13
CHAPTER 2 MATERIAL AND METHODS
2.1. Study area 18
2.2. Sampling and analytical procedures 20
2.3. Analytical methods 21
CHAPTER 3 COASTAL WATERS
3.1. Physical Parameters 27
3.1.1. Currents 27
3.1.2. Temperature 28
3.1.3. Salinity 30
3.2. Chemical Characteristics 32
3.2.1. pH 32
3.2.2. Dissolved oxygen 34
3.2.3. Ammonia-Nitrogen 39
3.2.4. Nitrite-Nitrogen 41
3.2.5 Nitrate-Nitrogen 43
3.2.6. Phosphate-phosphorus 46
3.2.7. Silicate-Silicon 48
3.3. Biological Characteristics 50
3.3.1. Chlorophyll 'a' 50
3.3.2. Particulate organic carbon 52
3.3.3. Suspended particulate matter 54
3.4. Conclusion 56
3.5. Dissolved trace metals in the coastal waters 72
3.5.1. Copper 73
3.5.2. Zinc 73
3.5.3. Iron 74
3.6. Sediment characteristics of the coastal region 75
3.6.1. Sand 76
3.6.2. Silt 76
.6.3. Clay 77
.6.4. Organic carbon 77
.7. Trace elements 78
.7.1. Lead 80
.7.2. Nickel 82
.7.3. Cobalt 82
.7.4. Chromium 83
.7.5 . Iron 84
.7 .6. Manganese 85
.7.7. Copper 86
.7.8. Zinc 88
.7.9. Elemental distributions in October 89
.7.10 Elemental distributions in February 90
.7.11. Elemental distributions in November 90
,.7.12. Correlation between different elements 90
1.7.13. Conclusion 94
4 COCHIN BACKWATERS
~HAPTER
.1. Physical Parameters 98
.2. Chemical Parameters 103
.3. Trace elements in Cochin backwaters 112
:HAPTER 5 ENVIRONMENTAL QUALITY OVER THE YEARS
.1. Cochin backwaters 120
,.2. Coastal waters of Cochin 123
,.3. Elemental distribution across the study region 126
,.4. Future concerns
~HAPTER 6 SUMMARY 133
tEFERENCES
'UBLISHED PAPERS
CHAPTER 1
INTRODUCTION
Coastal waters fonn a multi-dimensional system where the dynamic
processes are rarely in equilibrium. Compared to the open ocean systems, the
coastal region exhibits environmental gradients occurring spatially and
temporally on micro or macro-scale. The study of the chemical and physical
aspects of the nearshore environment provides background infonnation
necessary for the understanding of the coastal oceanographic processes.
There is a greater potential in applying the tools of modem oceanography and
chemistry to unravel the geological, biological and anthropogenic coastal
processes.
Bigelow, (1930) initiated studies in this direction by observing
temperature cycle on the continental shelf, Cape Cod to Chesapeake Bay.
Ketchum (1955) examined the interaction of freshwater and seawater in
coastal regions, which was treated as a "gigantic estuary". This approach
must be considered as one of the major advancements in the study of the
coastal ocean environment. Currently the coastal water body is receiving
close attention especially with respect to hydrography, biological production
and fertility. The structure of the physical and chemical environment is
commonly expressed in tenns of water quality parameters such as
temperature, salinity, dissolved oxygen, nutrients, metal concentration,
pigments etc. Hydrogeochemical factors can influence the colour, odour,
taste, temperature and degree of mineralisation of water derived from surface
runoff, underground springs etc. (Clark and Snyder, 1970). Studies on the
distributional and biogeochemical characterisitics of nutrients in coastal
waters can provide satisfactory assessment on the bioavailability of various
nutrients.
The coastal areas of the tropics are productive except turbid near river
mouths, where light penetration is poor. In shallow areas, the high
productivity is accounted by the increased regeneration rate of nutrients due
1