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Present study also showed high OM in stations beyond 100 m depth during both seasons. Increased OM in the outer regions of Monnugao and off Veraval may be due to the low oxygen content (Carruthers et al., 1959) in these areas preventing degradation, especially off Veraval where the DO was low «0.5ml/l). Nair (1975) also reported inner shelf with high OM (1.9-3.9%) against the outer region (0.88- 0.95%) from the western continental shelf(14-18° N) of India and also attributed this high OM to the reducing environment in the sediment. Joydas (2002) also reported similar results of high OM in the shallow and deeper depths and low values in the 76- 100 m zone. It was suggested that high concentration of organic carbon in the deep sediment layer could be due to the presence of refractory fraction of OM left after the carbon mineralisation (Anon, 1997). High OM in deeper depths may also be a result of the preservation under a reducing environment and in part by the rapid deposition (Kidwai and Nair, 1972). The high OM in the shallow and deeper areas may be attributed to the fine-grained nature of the sediments and to the variation in the benthic productivity (Paropkari et al., 1978). They also have attributed that the grain size and biological productivity are the major contributing factors for the variation in OM content in the area. Kolla et al .. (1978) opined that the factors such as biological productivity, water depth, pressure, turbulance and water chemistry influence the OM distribution. An additional feature relevant to the distribution of OM in marine sediments is the difference in composition of OM. If the OM is proteinaceous in nature it is hydroJyzed during diagenesis (cementation and re-crystallization) and if it contains humic acid and lignitic OM, it survives compaction and diagenesis (Degens et al., (1969). Kidwai and Nair, (1972) suggested that the distribution of OM in a depositional environment might be explained in tenns of its production, destruction and dilution in the environment. A marine depositional environment contains usually allochthonous OM transported to the site of deposition by river discharge and autochthonous OM, which originates at the site of deposition by the degradation of 71
organisms living in the water and the bottom. Rate of production of OM are usually higher in areas of upwelling. Latitudinally, OM decreased to north below 75 m and beyond 75 m, fluctuating values were observed with exceptional high values in the north during post-monsoon. During pre-monsoon, no regular trend was observed, but relatively high values were found in southern transects especially off Ratnagiri. But Joydas (2002) could not observe any latitudinal trend in OM distribution in the west coast. The seasonal difference in the distribution of OM can be attributed to the changes in the texture of the sediment. The amount of riverine input, filtration activities of the rivers and estuaries, strength of the waves and currents, amount of DO in the bottom water together with degradation by microorganisms may be playing a role in the variations in the OM distribution. 72
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Certificate I hereby certify that t
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Contents Page No. Chapter 1. Introd
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the bottom. Ekman (1935) described
Page 9 and 10:
wonns are the most abundant group a
Page 11 and 12:
leadership of Sir James Clark Ross,
Page 13 and 14:
Ansari et al., (1977b) carried out
Page 15 and 16:
Gopalakrishnan and Nair (1998) cond
Page 17 and 18:
Major objectives:- 1. To understand
Page 19 and 20:
CMFRI (Central Marine Fisheries Res
Page 21 and 22:
Joydas, T.V., Damodaran, R., 2001.
Page 23 and 24:
monitoring committee (Atlantic Mari
Page 25 and 26: Vizakat Lathika, I-Iarkantra, S. N.
Page 28 and 29: analysed after acidification by tit
Page 30: used as stain prior to sorting and
Page 33 and 34: space. Therefore, it is very essent
Page 36 and 37: Fig. I - Station locations 32
Page 39 and 40: affected at high temperature. Most
Page 41 and 42: layers exhibit different oceanograp
Page 43: Transect wise variation in temperat
Page 46 and 47: 3.2.2.3. Dissolved oxygen (DO) Dist
Page 48 and 49: monsoon temperature initially incre
Page 50 and 51: opined that limited mixing. high or
Page 52 and 53: Naqvi, S. W. A., Noronha, R. J., Re
Page 56: orr Mormugao orr Vernal 35.36 35.32
Page 62 and 63: The continental shelf and its adjoi
Page 64: sediments (4 stations). Silty sand
Page 68 and 69: fine sediments with comparatively h
Page 70 and 71: Narayana, 1991 ). Limited input of
Page 73 and 74: In general. two ditlerent patterns
Page 75: et al., (1980) reported values in t
Page 79 and 80: Hashimi, N. H., Kidwai, R. M., Nair
Page 81 and 82: Postma, H., 1967. In Estuaries, Lau
Page 85: Depths Sand Silt Clay Organic matte
Page 90: • PRE'MONSOON SOUTHERN'TRANSECTS
Page 96 and 97: as the best indicators of the envir
Page 99 and 100: showed that northern transects have
Page 101 and 102: decreased from shallow to deeper de
Page 103: different depth zones showed that a
Page 106 and 107: cm 2 with a dominance of nematodes.
Page 108 and 109: and 6.08 g/m 2 were recorded during
Page 110 and 111: were located in the nearshore water
Page 112 and 113: changes in the hydrographical and t
Page 114 and 115: factor for such a large difference
Page 116 and 117: Belegvad, H., 1932. Investigations
Page 118 and 119: Parulekar, A. H., Harkantra, S. N.,
Page 120: Savich, M. S., 1972. Quantitative d
Page 123 and 124: Traosects Polychaetes Crustaceans M
Page 125: Miscellaneous Transects Nematodes C
Page 128 and 129:
Depths Nematodes Cope pods Foramini
Page 136 and 137:
Wagh, 1975; Parulekar et ai, 1976;
Page 138 and 139:
ones and 17 were included in the 'r
Page 140 and 141:
Nephtydae (2%). Among the 20 sedent
Page 143 and 144:
At 75 m zone, 31 groups/species wer
Page 145 and 146:
Porbandar. At 50 m depth zone, fluc
Page 148 and 149:
otTMumbai and Ratnagiri and low eve
Page 150 and 151:
species richness at each depth zone
Page 153 and 154:
E2.2.2.!. Richness (Margalef's inde
Page 155:
I ):.2.2.2.4. Dominance (Pie/ou's i
Page 172 and 173:
Tablc 17. Contd .. - Sternaspidae 0
Page 176:
Table 20. contd .. G. alba 20 25 20
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150 Taxa 30m 50m 75m lOOm 150 m m D
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9% 1% o poIychaete • crustacea o
Page 203 and 204:
a) c) e) g) Plate 5 a) Prinospio sp
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a) c) e) Plate 7 a) Cardium sp. d)
Page 207 and 208:
7/. /ntroduct ion 7.2. Hydrography
Page 211 and 212:
also showed a similar pattern with
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y most of the organisms. It was als
Page 215 and 216:
with sand of which total density (r
Page 217 and 218:
muddy bottom of the west coast of I
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crustaceans and miscellaneous group
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the organic rich environment with h
Page 225 and 226:
Icvci (p
Page 227 and 228:
mcioHmna serve primarily as rapid m
Page 229 and 230:
surface chlorophyll a was 0.36mg I
Page 231 and 232:
Devassy, V. P., Achuthankutty, C. T
Page 233 and 234:
Longhrust, A. R., Pauly, D., 1987.
Page 235 and 236:
Sikora, W. B., 1977. The ecology of
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Faunal groups Silty Clayey Mixed Sa
Page 257:
Mannagoa to Porbandar located betwe
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against gastropods during pre- mons
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