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during pre-monsoon) followed by 75 m depth off Porbandar (0.36% of OM changed to 1.31 %). The lowest variation was found at 120m off Mumbai. Likewise in other transects significant variation:; were observed which could be attributed to the seasonal changes. Student's t test showed that significant difference was observed only in the 30 m depth and eventhough variations in deeper depths notivced but were not at a significant level. 4.2.3. Discussion OM showed considerable variation with respect to depth and latitude. In general more OM was retained in the fine sediments in the shallow zones (30 and 50 m). The minimum average values were found at 75 and 100 m depths «I %) and maximum average values were found at 30 and 50 m depths (1.5-2%) during both seasons. In general, OM in the sediment was related to the texture of the sediment. In the present study OM ranged from 0.36 to 3.33% during post-monsoon and from 0.18 to 4.52 % during pre-monsoon season. Low values were found in sandy or sand dominating sediment and high values were found in the finer sediments during both seasons. Affinity of OM towards fine sediment fraction has observed by several workers. Murthy et al., (1969) reported OM off Mumbai ranging from 0.24 to 3.15% (av. 1.93%) in the silt-clay fractions. Kidwai and Nair (1972) reported an OM in the clay and silt ranging between 4 and 8 % in the NW coast of India. Parulekar et al., (1976) studied the OM off Mumbai region and suggested that clay and silty clay retained higher OM than the sand and clayey sand substratum. Hashimi et al., (1978) reported the OM up to 5% in the fine grained sediment of the inner shelf and
et al., (1980) reported values in the range of 0.62 to 2.05% off Goa region with highest value in the outer most station, which was muddy in nature while Harkantra et al., (1980) reported OM varying from 0.47 to 6.18% (av. 3.15%) in the west coast ofIndia. Higher organic carbon in the fine substrata of clay and silt and low values in the sandy substratum also suggested a relationship with the textural characteristics of the sediment. Narayana and Prabhu (1993) recorded the OM ranging between 0.1 and 2.87% with uneven distribution in the Honavar shelf, west coast of India. Joydas (2002) reported a value ranging from 0.24-6.23% with an average of 2.81 which is slightly higher than the present study. One factor favouring the accumulation and preservation of OM in mud was the sediment size. The fine-grained sediments have larger surface area and tend to adsorb more OM than coarse sediments. This may be the reason for high OM in the fine-grained sediment. Once associated with mud, OM remains preserved due to high rate of sedimentation in the near shore region and the reduced condition associated with such rapidly deposited mud. This preservation together with new discharge from rivers increases the OM in the inner shelf region. Present study showed high OM in shallow and deeper regions and a low OM in between. During pre-monsoon and post-monsoon seasons, OM was high in the shallow zones (30 and 50 m). The high OM in the shallow regions may be due to river discharge and high biological productivity in the overlying water (Degens and Ittekott, 1984) and may also be due to the impact of low energy conditions prevailing in the area that accumulate fine sediments which can hold more OM (Hashim et al., 1978). During the coarse of their transportation from the coast, some of the fine sediment gets deposited on the inner shelf and balance bypasses to the outer shelf and gets deposited (Nair et al., 1978). The reason for high OM at 50 m depth especially during post-monsoon, in the present study may also be due to the bypassing of the fine sediment in the shallowest region and getting deposited a little away from the coast. 70
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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
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wonns are the most abundant group a
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leadership of Sir James Clark Ross,
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Ansari et al., (1977b) carried out
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Gopalakrishnan and Nair (1998) cond
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Major objectives:- 1. To understand
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CMFRI (Central Marine Fisheries Res
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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: In general. two ditlerent patterns
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
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
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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
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I ):.2.2.2.4. Dominance (Pie/ou's i
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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)
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7/. /ntroduct ion 7.2. Hydrography
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also showed a similar pattern with
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y most of the organisms. It was als
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with sand of which total density (r
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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
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Icvci (p
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mcioHmna serve primarily as rapid m
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surface chlorophyll a was 0.36mg I
Page 231 and 232:
Devassy, V. P., Achuthankutty, C. T
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Longhrust, A. R., Pauly, D., 1987.
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Sikora, W. B., 1977. The ecology of
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Faunal groups Silty Clayey Mixed Sa
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Mannagoa to Porbandar located betwe
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against gastropods during pre- mons
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