Journal of the Indian Fisheries Association 47 25, 1995 (Proc.Nat.Symp. Aquacrops), 47-56 MACROBENTHOS OFF MAHIM (BOMBAY), WEST COAST OF IN RELATION TO COASTAL POLLUTION AND AQUACULTURE

P. K. VARSHNEY AND K. GOVINDAN* Central Institute of Fisheries Education, Chinhat Centre, Lucknow - 227 105

ABSTRACT Deterioration of water quality clearly indicated a moderate to severe coastal pollution around Mahim whereas a relatively healthy marine environment towards offshore was noticed. Foraminiferans, polychaetes, crustaceans and pelecypods were the dominant macrofauna! groups encountered in the area. The occassional inhabitants lil{e pennatularians, nemertines, sipunculids, ophiuroids and fish larvae were mostly restricted to offshore regions. Biomass and population density of macrofauna were moderate and showed fluctuating trend. Similarity coefficients of foraminiferans (0.89) and polychaetes (0.81) were high for offshore unpolluted stations (3 and 4) as compared to nE1arshore coastal stations (1 and 2). Faunal diversity was relatively more in unpolluted zone. The I diversity Index (H ) was more at station 3 for polychaetes (1.39) and at station 4 for foraminiferans (0.54). In general, biomass was high during postmonsoon excepting station 1 which was invariably under severe pollution stress throughout the study period. Foraminiferans were abundant at sandy bottom while polychaetes preferred muddy (clayey­ silt) bottom. A noticeable ecological modification associated with faunal abundance and diversity were related to deteriorating marine water quality due to anthropogenic waste disposals. The prevailing water quality around Mahim is unsuitable for any kind of culture practices and also for harvesting economically important marine species.

INTRODUCTION Available information on subtidal Widespread aquatic pollution due to macrobenthos (Parulekar et al., 1976, indiscriminate waste disposals causes Govindan et al., 1988) of Bombay is severe ecosystem modifications and inadequate for a definite impact depletion of fishery resources. The assessment and predictions. The demersal fishery potential and stress - increasing trend in pollution stress of induced ecological modifications due to the coastal system of Bombay; however, anthropogenic waste disposals of an area warrants periodic ecological assessment can be reasonably evaluated by the and pollution monitoring studies. Hence estimation of benthic standing crop. in the present study an attempt was

*National Institute of Oceanography, Regional Centre, - 400 061. 48 VERSHNEY AND GOVINDAN made to assess the distribution and and analysed for benthos (Varshney et abundance of macrobenthos off Mahim, al., 1988) and water quality (Strickland Bombay, in relation to the prevailing and Parsons, 1968). Sediments were coastal pollution and also to evaluate the analysed for organic matter and texture suitability of the nearshore coastal (Holme and Mcintyre, 1971). Biomass waters of Mahim for the development of was estimated on dry weight basis. aquaculture.

RESULTS AND DISCUSSION MATERIAL AND METHODS Results of environmental and Mahim Creek on the east Is biological parameters are presented in connected to the narrow Mahim River Figs 2-4 and Table 1. and on the west it opens into the Mahim Water quality : Bay, which in turn meets the Arabian Sea; Mahim Creek and Bay (Lat. 19° 2' Spatial, temporal and seasonal N; Long. 72° 49' E) together comprise an fluctuations in selected water quality 2 area of about 6 km . The creek receives parameters viz. temperature, salinity, about 313 mld of domestic and 21 mld of pH, DO and nutrients were noticed in industrial wastes (M&E/EEC Report, the study area (Figs. 2 and 3). The DO 1979). Four stations were identified for values of the creek (station 1) were the present study (Fig. 1). Monthly almost nil especially during ebb periods collections (Nov '79 to Dec' 80) were made than flood conditions, whereas DO levels

Fig. 1 : Location of stations. MACROBENTHOS OFF MAHIM 49

FLOOD EBB

0 • \J 'JO w oc :;) t- < 25 25 a: w a. r. w t- 20 20 N 0 J FMAMJASOND N 0 J FMAMJASOND E F 35 35 ~~':--~ 411 . I ...... • " I' 1.. 30 30 I \• ' - ' .A' (I: ',~ rI >- I ~. ~-/Ill z 25 25 ::i -<( \1'1 ~ N 0 J FMAHJJ A S 0 N D N 0 J FMAMJJASONp

7 i 7 1 II ' " lrf\ iC -1/1/ " II" I ~ • :y ·t;: ~'~,· .. ,' •'v A ' \ ,,I• \ I, , ') ~. I ·- I "'E l 3 _. 0 0

N 0 J e.so

8.10

7.70

NDJFMJI.MJJASONO

o----o Stn. 1 ·--· Stn. 11 <>----···<> Stn. Ill ·-----· $tn lV

Fig. 2 Changes in pH (A & B), DO (D & D), salinity (E & F) and temperature (G & H). 50 VERSHNEY AND GOVINDAN

FLOOD EBB '$3 71·S E 40

--I 30

20 z I I 1"'\ 0 z 10

JASOND , I • ..r:- a I I I 'I : I .\ - 4 ~ I ro I en I' :1.

2 I z ,...., .... I , ' \ I I \ N I. '\ z0 .d . NOJ fM,tU-4JJAS0NO

-r§:l~ ...... '~;,'-" -;fo·"»

2l·SS 8 8 .'• . I I I. ,' /\ ', , # ' ' ;' ,/ .... ~ ,·r' ._..,, /-..r- :,' ~ /~>,. , 2 'I ,..... ,, !I ": ,"...... I 1 "'o/ • ---- .. ~~~ N 0 J F M A M J ) A $ 0 N 0 NOJ FMAMJ JASONO

- Stn.l ·--· st"'.ll c-----.. st ~ .m . __ ..... st.... lV

Fig. 3 Changes in phosphate (A & B), nitrite (C & D) and nitrate (E & F). MACROBENTHOS OFF MAHIM 51 of coastal stations were normal and Sediment : comparable. Seasonally, low DO levels Station 1, had a sandy bottom while were observed during October. In stations 2 to 4 clayey silt bottom (Fig 4). contrast, the levels of nutrients (Figs 2 The sediment organic matter was quite and 3) were relatively high at near shore low at station 1, due to a sandy stations ( 1 and 2) especially during ebb substratum, but high and comparable at than flood conditions. In general, the other stations which had muddy bottoms creek (station 1) revealed wide (Fig 4). fluctuations in selected water quality parameters as compared to the offshore Macrofauna : stations indicating an environmental Population and biomass : Faunal stress due to input of anthropogenic density (Table 1) varied from wastes to the nearshore coastal system 0.6x103/m2 to 668.8x103/m2 and biomass off Mahim. from 0.1 to 166.2 g/m2 in the study area.

Other FORAMINIFERA j"t~~ POL YCHAETA BENTHOS

SAND [geaj Sll T DeLAY

-100 100 ~ ...... - ...... Gil t ... :.. ·~ : :: , .. :: •• & "" • - ...... :~· ;~ :· ... 9 " z . .. 0 -50 (f) 501- 1- B 1- z <( w _J 2: ~ 0 0.. L!.1 t[ {/) 1

D POPULATION ~ ORGANIC HATTER DENSITY

4 <( z 0::: O<.!>w -zLL t- -z A <( o­ 2- _J::>:Z.: ~_j<( a..OOC oxo 0.. WLL

:;'ig. 4 : Population density in relation to (A) organic matter and (B) sediments. 52 VERSHNEY AND GOVINDAN

3 2 2 Table 1 : Macrobenthic population density (nox10 1m and biomass (g!m ) off Mahim. Biomass given in parenthesis.

Stations Months 1 2 3 4

November 1979 8.0 39.4 3.5 (3.8) (19.6) (1.2) December II 2.4 (0.2) January 1980 12.9 1.6 15.5 10.1 (0.7) (0.3) (1.0) (2.1) February II 462.0 23.8 3.3 19.6 (18.5) (1.6) (0.9) (1.5) March II 371.0 1.6 17.3 6.0 (14.8) (0.2) (1.4) (3.0) April II 330.4 2.4 3.1 9.2 (13.2) (0.2) (0.9) (0.8) May II 138.8 6.2 5.6 21.4 (5.7) (0.4) (1.8) (1.6) June II 668.8 (20.1) July II 60.4 116.4 5.8 8.5 (2.6) (5.8) (5.5) (0.6) August II 33.6 107.0 3.9 1.1 (1.3) (4.5) (0.6) (0.3) September II 43.2 22.6 8.4 10.8 (1.7) (1.0) (2.1) (0.5) October II 287.0 4.8 12.6 1.4 (11.5) (1.5) (2.8) (0.8) November II 186.2 2.0 1.8 28.3 (7.4) (0.1) (3.4) (39.9) December II 473.2 40.6 0.6 19.4 (18.9) (166.2) (0.5) (7.3) MACROBENTHOS OFF MAHIM 53

The mean faunal densities and biomass creek system as noticed earlier at for stations 1,2,3&4 were 236.1, 28.1, 9.8 Versova (Varshney et al., 1988). An and 11.6x103/m2 and 8.9, 15.5, 3.4 and increase In species diversity of 5.0g/m2 respectively. High population foraminiferans was noticed from creek densities and biomass were observed (0.09) to coastal station (0.54). during postmonsoon. Benthic population Polychaetes : Polychaetes (1. 75%) excluding foraminiferans revealed a were the second dominant group with a significant correlation with sediment mean density varying from 331m2 to organic matter (Fig 4). Foraminiferans 2 1940/m , with the maximum being accounted for higher population counts observed during postmonsoon. while pelecypods and polychaetes (Prionospio pinnata) contributed the Twenty four species belonging to 20 higher biomass structure especially genera were encountered. The creek during postmonsoon period. (station 1) was populated by 3 species namely Paraheteromastus tenuis Monaro, Faunal composition : Fauna, in Maldinella sp. and Protodorvillea general was comparable to that of biarticulata Day, whereas Ancistrosyllis Versova (Varshney et al., 1988) and constricta Southern, Lumbriconereis consisted of foraminiferans, polychaetes, latreilli Aud & M.Ed., Cossura coasta crustaceans, pelecypods and other less Kilamori, Glycera alba Rathke, common groups. Prionospio pinnata Ehlers, P. cirrifera Foraminiferans : Foraminiferans Wiren, Cirratulus cirratus, O.F. Miiler were dominant (97.74%) and represented and Maldinella sp. were the common in all collections from the study area. species encountered outside the creek Results indicated (Fig. 4) a decrease in region (stations 2,3,&4). P.pinnata was population density of foraminiferans the dominant species (79 to 89%) at the from creek to coastal stations. coastal stations like at Versova Foraminiferans obtained from creek and (Varshney et al., 1988) and was nearshore stations ( 1 & 2) were encountered in abundance at Mahim somewhat blackish in colour, due to during postmonsoon. organic pollution as compared to offshore The rare species from this region specimens. Five species of foraminiferans were Syllis gracilis Grube, Nereis sp, namely Antmonia beccarii (Linne), . Neanthes sp, Perenereis cultrifera Grube, Quinqueloculina seminulum (Linne), Nephthys inermis Ehters, N. Discorbis nitida (Williamson), Rotalia polybranchia Southern, Eunice calcer and Elphid~um crispum were antennata Savigny, Diopatra neapolitana recorded from Mahim. The abundance Dellechiage, D.cuprea cuprea Bose, of specific foraminiferans like Ammonia Lumbriconereies pseudobifilaris Fauvel, beccarii and Q.seminulum in the Glycera rouxi Aud & M.Ed., Polydora nearshore regions of Mahim could be ciliata Johnston, and Sternaspis scutata related to high nutrient input to the (Ranzani) .. The species diversity (H') 54 VERSHNEY AND GOVINDAN gradually increased from creek (0.86) to disposal and a high input of organic load, coastal stations (1.39). as also indicated by nil or very low DO level ( <1mgll). Zingde and Desai (1980) Crustaceans : and Sabnis ( 1984) also reported very high Crustaceans were occasional BOD (100 mg/1) and nil DO values in inhabitants (0.1%) of the area, this region. However, a gradual represented by copepods (0.03%), improvement in water quality towards amphipods (0.04%), tanaidaceans offshore as noticed by earlier (<0.01%), macrurans (0.01%) and investigations (Sabnis, 1984) was evident crustacean larvae ( <0. 01%). during the present study.

Pelecypods : Enhanced levels of trace metals like Cr, Ni, Cu, Zn and Pb both in water and The contribution ofpelecypods (0.3%) sediment especially in the creek/bay was very low in the study area. 2 regions, together with a relatively high Maximum density (11625/m ) was concentration of these trace metals in noticed at station 1 (December '80) with zooplankton, benthos and fish/shell fishes a predominance of Pholas bakeri. of the creek/bay regions was reported by Pelecypods in general was increased in Sabnis (1984). Both water and sediment abundance from coastal nearshore (8%) of the creek/bay regions revealed a very to offshore station (41%). Three species high levels of total viable (TV C) and namely Pholas bakeri, Mactra sp. and coliforms (TC) counts especially during Tellina sp. were common. ebb period as also pathogens such as Others: Shigella, Salmonella and Vibrio in the region (NIO, 1993). Rest of the macrofauna consisted of less common group like pennatularians Wide fluctuations in benthic standing (0.03%), nemertines (0.03%), sipunculids stock noticed at the creek system could (0.01 %) ophiuroids (0.01 %), fish larvae be mainly attributed to the dominance (<0.03%) and miscellaneous groups of pollutant tolerant foraminiferans in (<0.01%) which included ostracods, the region and a similar trend was echiuroids, phoronids, hydrozoans etc. earlier reported from Versova (Varshney Distribution of most of these groups was et al., 1988). with moderate irregular and uneven. environmental stress supports very high benthic biomass chiefly contributed by Ecological conditions of the creek/ pelecypods. However, a relative bay/nearshore region off Mahim thus stabilization in benthic standing stock varied significantly depending on the 3 2 2 (10 to 11 x 10 /m ., 4 to 5 g/m ) anthropogenic fluxes (Zingde and Desai, associated with stable environmental 1980) and tidal conditions (Sabnis, 1984). conditions towards offshore as compared The impairment of water quality to nearshore coastal system was noticed. observed in the creek system could have been highly influenced by the wastes The dominance of foraminiferans like MACROBENTHOS OFF MAHIM 55

A. beccarii and polychaetes like productivity of the creek/bay system is Paraheteromastus tenuis, Maldinella sp. not adequately utilised at the tertiary and Protodorvillea biarticulata especially level for the conversion of demersal in the creek system indicates their fishery standing stock (Varshney et al.} tolerance to organic pollution similar to 1985). Hence, the poor trophic conversion the situation in Versova creek (V arshney efficiency (Varshney et al.} 1985) and a et al., 1988). The most dominant poor standing stock of fish eggs and polychaete P.pinnata encountered larvae (Gajbhiye et al.} 1982) indicate outside ·the creek system can be unsuitability of the Mahim Creek/Bay considered as a moderate pollution system for the coastal aquaculture. tolerant species. The absence of minor However, the proposed marine reserve faunal groups may indicate adequate forest/ecological zone off Mahim may alterations in the food chain which in improve the environmental conditions of turn may result in severe imbalance of the bay/creek system in the near future. the coastal marine ecosystem of Mahim.

I Low species diversity index (H) ACKNOWLEDGEMENT associated with rich faunal standing stock especially in the nearshore regions The first author is thankful to Dr. S. (stations 1 & 2) than offshore areas Z. Qasim Member, Planning Commission, (stations 3 & 4) also confirms a severe New Delhi, for his interest in the work environmental stress in the nearshore and Shri M. L. Rustagi, Scientist-in­ regions. Reish (1980) reported a decrease charge, CIFOT, Lucknow, for in diversity associated with increase in encouragement and to Dr. S.D. Tripathi, total benthic productivity in areas of Director, Central Institute of Fisheries acute pollution at South California. Education, Bombay for permission to present the same to this seminar. Macrobenthos, in general, followed a trend very similar to that of polluted coastal system of Versova (Varshney et REFERENCES al.} 1988) and (Varshney, 1983). A gradual decline in the commercial Dwivedi, S. N. and Desai, B. N. 1972. fishery potential of the coastal waters of Marine food resources and Bombay due to pollution was already conservation along the west coast indicated (Dwivedi and Desai, 1972). The of India. J. Indian Fish Ass. 2 bay is suitable for intensive clam/oyster (1&2): 81-89. culture, but the results indicate a Elwakeel, S. K. and Rilay, J.P. 1956. moderate to severe pollution stress in The determination of organic carbon the bay and unsuitability due to high in marine muds. J du conscil levels of trace metal· (Sabnis 1984) and permanent international pour L pathogenic bacterial contamination (NIO, exploration de al mer. 22 : 180. 1993). In fact, the observed high benthic 56 VERSHNEY AND GOVINDAN

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