L - Cochin University of Science and Technology

More documents

Recommendations

Info

monsoon temperature initially increased then decreased to deeper depths. Qasim (1982) has also noticed a decrease of temperature from south to north during pre monsoon season in the northern Arabian Sea. The winter is more pronounced in the northern region of the Arabian Sea (AS) than southern region as it is away from the equator (Darbyshire, 1967). This must be the reason for the decrease in temperature from south to north during pre-monsoon season. In general, cooling from south to north and low temperature in the coastal waters (up to 75 m) may be because of the cooling of the land mass in the northern region and a general flow of cold air from the land causing more cooling of the sea close to the land (Sankaranarayanan, 1978). This may be the reason for the low temperature in the shallowest region. Joydas (2002) also noticed a decrease in bottom temperature with depth and latitude. The high values in shallow regions and low values in deeper stations during post monsoon season may be due to the secondary heating during this period. In this season, no cooling of landmasses is taking places as that of pre-monsoon season. Salinity showed a general trend of increase towards north at all depth zones during post-monsoon but during pre-monsoon, northward increase was obvious only in shallow depth zones (30 m and 50 m). In other depth zones, salinity values fluctuated with relatively low values in southern transects and high in northern transects. The high rate of evaporation results in the fonnation of several high saline water masses. The general northward increase during post-monsoon season may be attributed to the presence of Arabian Sea High Saline Water (ASHSW) (Qasim, 1982). The Arabian Sea high saline water, fonned in the northeastern AS, can be traced as a tongue of high saline water towards south (Qasim, 1982). Low surface salinity of the west coast of India south of 20° N might be due to the inflow of low saline water from the south and not due to either rainfall or land run off as no major rivers enter this area and the rainfall in the region is quite low (Qasim, 1982). The southern low saline water indicates the presence of north equatorial current (NEe) which carries the low saline waters along with it from the Bay of Bengal (BOB) and 43
the eastern Indian Ocean into the western AS during this season. During the northeast monsoon (pre-monsoon season of the present study). low saline water from the BOB joins the northward flowing equatorial Indian Ocean water and flows as a northward surface current along the west coast of India (Pankajashan and Ramaraju. 1987). The reduced salinity in the shallow depth zones also shows the presence of BOB waters, which is coming from BOB to AS through the coastal current (Darbyshire, 1967, Wyrtki. 1971). Kumar and Mathew (1997) noticed that the maximum northward extension of this low saline water is upto 12° N in January but could be traced upto 17° N in February- March. It starts retreating from March onwards and coincides with the reversal in the upper layer circulation. Kumar and Prasad (1996) reported a weakly stratified layer of high salinity in the north, thinning towards south in the northern AS. They also added that very low saline water towards the south indicates the influence of BOB waters, being carried along the shelf by the northward flowing coastal current. Joydas (2002) pointed out that the low saline condition in the nearshore region could be attributed to the river discharge. In the present study, deeper waters of southern transects (off Ratnagiri and Mumbai) showed an increase in salinity during both seasons. This increase may be due to the presence of ASH SW. The core of ASHSW seen below the surface in the north deepens while spreading towards south, which may cause the increased salinity in the south. DO was found to increase from south to north in shallow depth zones (30 m and 50 m) and the trend got reversed in deeper zone (I50 m) during pre-monsoon season. DO showed fluctuating trends in between these zones (75 m and 100 m). Generally low values were observed during post-monsoon as compared to pre monsoon. During both seasons DO decreased to deep in all transects. Qasim (1982) reported a distinct decrease from inshore to off shore. Moreover it decreased towards north in the deeper areas of 150 m zone as observed by Joydas (2002). This depletion of oxygen in the shelf edge of northern latitudes may be associated with the oxygen minimum layer described by Gupta et al., (I 976b, 1980) and Qasim (1982). They 44
Page 2 and 3: Certificate I hereby certify that t
Page 4 and 5: 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 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 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
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
Page 179:
150 Taxa 30m 50m 75m lOOm 150 m m D
Page 186:
9% 1% o poIychaete • crustacea o
Page 203 and 204:
a) c) e) g) Plate 5 a) Prinospio sp
Page 205 and 206:
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
Page 213 and 214:
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
Page 219 and 220:
crustaceans and miscellaneous group
Page 221:
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
Page 237:
Faunal groups Silty Clayey Mixed Sa
Page 257:
Mannagoa to Porbandar located betwe
Page 260 and 261:
against gastropods during pre- mons
show all

L - Cochin University of Science and Technology

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?