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The continental shelf and its adjoining land of the study area is bordered by Western Ghats and is influenced by monsoon. The climate is tropical with maximum precipitation during monsoon and the shelf is floored with different types of sediments. According to Stewert and Pilkey (1965) the continental shelf in the study area can be divided into inner shelf and outer shelf marked by the difference in the topography and sediment type. Studics by Nair (1971) and Siddiquie and Rajamanickam (1974) have shown that the inner shelf has smooth featureless topography whereas the outer shelfis fonned by rugged topography. Width of the continental shelf varies from about 100 km off Suarashtra (Off Dwaraka) coast (Gupta, 1979) to 280 -300 km wide off Mumbai (Kidwai and Nair, 1972) and this narrows down to about 100 km off Ratnagiri to a progressive narrowing of 60 km wide shelf off Monnugao (Nair,1975). The shelf off Mumbai is composed of various features like pinnacles with and without adjacent troughs, which are usually 1-2 m deep (Nair,1975). In addition to these features a number of large mound shaped protuberances with a relief of 6 to 8m are also present. In Ratnagiri the pinnacles and troughs are poorly developed as compared to off Mumbai and when it reaches Monnugao pinnacles with relatively gentle depression occur on a slopping shelf. A notable feature is that pinnacles and troughs are most prominent off Mumbai where the shelf is flat and widest and become relatively subdued in profile towards south where the shelf is generally half or less than half of width. Wider shelf OfT Mumbai narrows in Ratnagiri and further narrows southwards. Many workers have studied the substrata of northwestern region and most of them pertain to the regional studies including estuaries and gulf regions and a few studies were carried out in the shelf region to assess the textural characteristics. Kidwai and Nair (1972) studied the sediment texture and distribution of organic matter in the NW coast of India (18-22° N) and later, Nair (1975) described the nature and origin of small-scale topographic prominences on the western continental shelf of India. Parulekar et al., (1976) studied the sediment texture and organic matter 57
distribution off Mumbai region upto 60 m depths. Ansari et al., (1977) Ansari (1978), Hashimi et al., (1978) and Nair et al., (1978) reported the textural characteristics of central west coast (13-16° N) of India. Benthos and sediment characteristics of entire west coast of India were studied by was that of Harkantra et al., (1980) describing the texture and organic matter up to 70 m depth. The other reports were that of Ansari et al., (1980) for Monnugao coast (20-840m) and Setty and Nigam (1982) for west coast (14-22° N). Vizakat et al., (1991) while studying the population ecology and community structure of benthos described the texture and organic matter in the 5-15 m contour off Konkan, west coast of India and Rao (1991) studied the clay mineral distribution in the continental shelf and slope of Saurashtra coast. The other works in the west coast included that of Narayana and Prabhu (1993) who studied the texture and gcochcmistry of sediments of 110navar shelf, Ilarkantra and Parulckar (1994) who studied the benthos and sediment characteristics in the 5-10 m depths of Rajapur Bay, west coast of India (16 0 34' N) and Ingole et al., (2002) worked in the coastal waters of Dabhol, west coast of India. Joydas (2002) gave an account on the sediment texture and macrobenthos of west coast of India. 4.1.2. Results Spatial variations in the sediment characteristics of the northwest continental shelf of India are examined in this chapter. Results are described in 3 parts-first part deals with sediment texture and its spatial variations during post-monsoon and second part deals with the same during pre-monsoon seasons, and seasonal changes are described in the third part. 4.1.2.1. Post-monsoon Six types of texture were observed which include sandy, silty sand, clayey sand, silty clay, clayey and mixed type (where sand, silt and clay in almost equal proportion) (Fig. 9 a & b). Of these silty clay dominated in the study area. Clayey sediment, the second dominant texture, was present at 5 stations followed by sandy 58
Page 2 and 3:
Certificate I hereby certify that t
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Contents Page No. Chapter 1. Introd
Page 6:
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 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 and 76: et al., (1980) reported values in t
Page 77 and 78: organisms living in the water and 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
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factor for such a large difference
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Belegvad, H., 1932. Investigations
Page 118 and 119:
Parulekar, A. H., Harkantra, S. N.,
Page 120:
Savich, M. S., 1972. Quantitative d
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Traosects Polychaetes Crustaceans M
Page 125:
Miscellaneous Transects Nematodes C
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Depths Nematodes Cope pods Foramini
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Wagh, 1975; Parulekar et ai, 1976;
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ones and 17 were included in the 'r
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Nephtydae (2%). Among the 20 sedent
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At 75 m zone, 31 groups/species wer
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Porbandar. At 50 m depth zone, fluc
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otTMumbai and Ratnagiri and low eve
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species richness at each depth zone
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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
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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
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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
Page 221:
the organic rich environment with h
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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
Page 237:
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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