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Chapter 8. Summary and conclusion The benthic organisms play an important role in the marine food chain. The demersal fishery potential especially in the coastal waters depends mainly on benthic productivity. Small benthic organisms fonn a part of the diet of fishes thus regulating the fishery resources of an area. Benthic organisms have been regarded as the best indicators of environmental changes caused by pollution, because of their constant presence, relatively long life span, sluggish habits and tolerance to differcning stress. Since benthic organisms mainly live on the surface of the bottom terrain, are influenced by the water column, sediment texture and organic matter. Concentration of organic matter also detennines the availability of oxygen. Indian ocean has unique features like northern land locked boundary, seasonal reversal of monsoonal currents, upwelling and the oxygen minimum layer. All these factors may influence the organisms inhabiting the pelagic as well as benthic realms. The present study assesses the biomass, density, and community structure of benthos in relation to the environmental parameters during post monsoon and pre monsoon periods along the northeastern Arabian Sea. Most of the earlier bcnthic studies are for localized areas along the west coast extending up to 20 m depth. The present study on the macro and meiobenthos from the conticontinental shelf of India extending from 30 to 200 m is the first report elucidating the seasonal variations in the distribution, abundance and community structure of benthic population. The benthic production and abundance had been correlated to the environmental conditions. Present study fonns a part of multi disciplinary programme, on Marine Research on Living Resources (MR-LR), which includes the assessment of benthic productivity of the continental shelf of Indian EEZ. Study area extended from 245
Mannagoa to Porbandar located between latitude 14° to 22° N and longitude 68° to 74.5° E and covered an area of - 55000 sq. km. Samples were collected from transects off Mannagoa, Ratnagiri, Mumbai, Veraval and Porbander from 30, 50, 75, 100, 150 and 200 m depths. Water samples for hydrographic parameters were collected using Sea-Bird CTD, and sediment samples were collected using Smith-McIntyre Grab. Statistical interprettation for community structure was done using PRIMER v 5 software, and student's t test was worked out for finding the seasonal difference. Multiple regression analysis was carried out to find the important ecological factors predicting the benthie dictribution and abundance. The fishery potential of the area was calculated from the biomass data obtained and compared with the available literature. Relationship between macro and meiobenthos was also worked out. The thesis is presented in seven chapters. The first chapter gives a general introduction regarding the marine environment, its classification, definition, and importance of benthos, review of previous works, scope and objectives of the present study. The second chapter deals with the materials and methods, which covers the sampling methods, analytical procedures for the estimation of various parameters, collection and processing of benthic organisms and their identification and methods for statistical inference. The third chapter describes with the general hydrographic features of northeastern Arabian Sea. The distribution of environmental features like temperature, salinity and dissolved oxygen. During Third chapter is on the hydrographic features of the study area and salient features are as follows. During post-monsoon, temperature decreased from shallow to deeper depths and transect wise analysis showed a general increase towards northern stations. During pre-monsoon, temperature initially increased from 30 m to 75 m depths and then decreased to deeper stations. It also showed a decrease towards northern latitudes. For salinity no consistent depth wise trend was observed during l46
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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.
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monitoring committee (Atlantic Mari
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Vizakat Lathika, I-Iarkantra, S. N.
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analysed after acidification by tit
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used as stain prior to sorting and
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space. Therefore, it is very essent
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Fig. I - Station locations 32
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affected at high temperature. Most
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layers exhibit different oceanograp
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Transect wise variation in temperat
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3.2.2.3. Dissolved oxygen (DO) Dist
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monsoon temperature initially incre
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opined that limited mixing. high or
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Naqvi, S. W. A., Noronha, R. J., Re
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orr Mormugao orr Vernal 35.36 35.32
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The continental shelf and its adjoi
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sediments (4 stations). Silty sand
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fine sediments with comparatively h
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Narayana, 1991 ). Limited input of
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In general. two ditlerent patterns
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et al., (1980) reported values in t
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organisms living in the water and t
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Hashimi, N. H., Kidwai, R. M., Nair
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Postma, H., 1967. In Estuaries, Lau
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Depths Sand Silt Clay Organic matte
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• PRE'MONSOON SOUTHERN'TRANSECTS
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as the best indicators of the envir
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showed that northern transects have
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decreased from shallow to deeper de
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different depth zones showed that a
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cm 2 with a dominance of nematodes.
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and 6.08 g/m 2 were recorded during
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were located in the nearshore water
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changes in the hydrographical and t
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factor for such a large difference
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Belegvad, H., 1932. Investigations
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Parulekar, A. H., Harkantra, S. N.,
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Savich, M. S., 1972. Quantitative d
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Traosects Polychaetes Crustaceans M
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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
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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
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
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Page 221: the organic rich environment with h
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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 260 and 261: against gastropods during pre- mons
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