HELGOL,/i~NDER MEERESUNTERSUCHUNGEN Helgol6nder Meeresunters. 49, 633-645 (1995)

Pollution effects in Visakhapatnam harbour, India: an

overv iew of 23 years of investigations and monitoring

A. V. R a m a n

Division of Marine Biology, Department of Zoology, Andhra University; Waltair, Visakhapatnam 530 003, India

ABSTRACT: Visakhapatnam Harbour, a semi-enclosed water body on the east coast of India, is subject to a high degree of pollution caused by industrial and urban wastes. Studies carried out during the last twenty years or so at 6 selected stations in the harbour revealed appreciable hydrographic and biotic changes. Over the years, the concentration of nitrites (max. 5 mg/1) and phosphates (9.6 mg/1) has increased. Dissolved oxygen registered all-time-high values (max. 21.6 mg/1) caused by periodic outbursts of phytoplankton, notably, Skeletonema costatum and other species. Benthic conditions have also changed and only certain pollution-tolerant species (e.g. Capitella capitata) inhabited the bottom sediments that contained a heavy load (2.5 %) of organic matter. In the harbour, increased pollution led to the disappearence of stenoecious species and their replacement with other forms known for their tolerance to pollution. The paper describes the major changes which have occurred in water quality and organisms in the harbour as a result of pollution increase during the last two decades.

I N T R O D U C T I O N

G a n a p a t i (1969) and G a n a p a t i & R a m a n (1973) g a v e a br ief accoun t of the topogra -

phy and some aspec t s of pol lu t ion in V i s a k h a p a t n a m harbour , c o n s e q u e n t to the rap id indus t r ia l i sa t ion and u rban i sa t ion of the city. S ince the pub l i ca t ion of the a b o v e papers ,

the h a r b o u r has g o n e th rough a m a s s i v e e x p a n s i o n p r o g r a m m e , i nc lud ing the cons t ruc- t ion of a 2 sq k m ou te r harbour , w h i c h b r o u g h t in its w a k e fur ther r e d u c t i o n in w a t e r

c irculat ion, a c c e n t u a t i n g s tagnat ion . T h e l a n d - l o c k e d s i tuat ion of the h a r b o u r a n d the

c o n s e q u e n t l imi ta t ions of na tu ra l f lush ing p r o c e s s e s h a v e l a rge ly con t r i bu t ed to the e x p o s u r e of p lan t and an ima l c o m m u n i t i e s to e n v i r o n m e n t a l pol lu t ion s t resses f rom a

va r i e t y of indus t r ia l instal la t ions w h i c h h a v e s p r u n g up in the env i rons of t he harbour . A d d e d to this the ha rbou r also r e c e i v e s mos t of t h e ci ty 's domes t i c e f f luents w h i c h are

cons ide rab le , o w i n g to the rap id ly g r o w i n g u r b a n popula t ion . With a v i e w to f ind ing out

t he overa l l c h a n g e s in re la t ion to pol lu t ion , s tud ies on the p h y s i c o - c h e m i c a l a n d b io log i - cal charac te r i s t ics of w a t e r and s e d i m e n t s at s e l e c t e d stat ions in the ha rbou r h a v e b e e n

u n d e r t a k e n s ince 1968. The p r e s e n t p a p e r dea l s w i t h some of these f indings.

M A T E R I A L A N D M E T H O D S

A l t o g e t h e r six stations, l oca t ed a l o n g a d e c r e a s i n g g rada t ion of pol lu t ion, w e r e c h o s e n for the s tudy (Fig. 1). St .Va r e p r e s e n t s t h e mos t po l lu ted area, s ince the b u l k of the

�9 Biologische Anstalt Helgoland, Hamburg

63,~ A. V. Raman

�9

�9 ~ , ii I

nun, ~ ' , .~

, o

i i i ~ . . . . !

- - . - 4 ~

. ~ , I

I |

i --1.-

J \ ~ r n "L" "'4

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,,,:, . - , - ~ = o ,. '~, . . . . . " - . . . , r " - % x ~ ' '"

, , \~o ~,: _ ~ -\ / ~ do_ \ t e'-~ : i~ , l b . .

r %

o ~

I / , ~ ! �9 L t l

Pollution effects in Visakhapatnam harbour 635

city's sewage is emptied here. Stations Vb and Vc are located downstream. St.IIa is in the entrance channel and St.IIb in the outer harbour, midway be tween the inner harbour and open sea. St.I is the cleanest of all stations and is located in the open sea (depth 35-40 m).

All observations were made during low tide. While it was not always possible to study the entire area, two major investigations, one each in 1976 and 1985-1987 were under taken. During these years, observations were made at selected stations at periodic monthly (1976) and fortnightly (1985-1987) intervals. In order to describe the in te rannua l variations, data collected at a single location (St.IIa), based on intensive (tri-weekly), fortnightly and monthly observations, were used. While the surface samples were obtained with the help of a polythene bucket, a reversing Nansen bottle was used for bottom water.

The water-qual i ty parameters included turbidity (Hellige's Turbdimeter), secchi-disc transparency, salinity (Knudsen method), dissolved oxygen (Winkler Azide modification), B.O.D. (Standard Methods, 1971) and inorganic nitrogen, phosphorus and silicate accord- ing to Strickland & Parsons (1968), and Manua l of Methods in Aquatic Envi ronment Research, FAO (1975). In addition, sediment texture (Holme & McIntyre, 1971) and its organic content (Gaudette et al., 1974) were estimated. Biological investigations included an examinat ion of phytoplankton and benthic polychaetes. For phytoplankton, both unit samples (1 litre volume) and net hauls were collected and their densities (nos/ml) de termined according to UNESCO (Sournia lEd.], 1978). In addition, estimations on chlorophyll a, b and c were made, following Richards & Thompson (1952). For sampling benthos, a Petersen grab (0.05 m 2) was used, as well as a metal quadrate (0.01 m 2) for samples collected intertidally.

The climate of Visakhapatnam is governed by its location in the tropics (latitude: 17~ and 17048 ' North; longitude: 83016'25" and 83~ East). The mean monthly values of day-temperature range from a min imum of 27.7~ C (January) to a maximum of 34.0 ~ C (May). The total rainfall exceeds 1000 mm, nearly 80 % of which occurs during the J u n e - N o v e m b e r period.

Tides are chiefly semi-diurnal and have a mean range of 0.9 m. There is considerable freshwater influx into the harbour through a monsoon-fed stream known as "Mehad- rigedda". Mehadr igedda is also the principal source of industrial effluents into the harbour, since this river is used as a conduit for the discharge of wastes. In the harbour, bordering the north and northwest periphery, there are extensive low-lying swampy areas with mangrove and scrub vegetation.

RESULTS AND DISCUSSION

W a t e r q u a l i t y

Investigations on water quality revealed appreciable differences be t w e e n the har- bout env i ronment subject to pollution, and the unaffected open sea location (Table 1). Inside the harbour (Stations Vc, IIa and IIb), where the effects of pollution are re la t ive ly high, the waters are distinctly characterized by an overall r a n g e of (median values) high temperature (27.5-30.0 ~ C), poor t ransparency (0.6-2.5 m); high turbidity (6.75-23.0 ppm), varying salinity (range 1.98-34.74%o), general ly low pH (5.8-8.9), widely f luctuat ing dissolved oxygen (0-21.6 rag/l) and high inorganic n i t rogen (ammonia

Tab

le

1.

Ph

ysi

co-c

hem

ical

cha

ract

eris

tics

of

sur

face

an

d

bott

om w

ater

s of

Vis

akh

apat

nam

ha

rbou

r.

S -

Sur

face

; B

-

Bot

tom

; N

.D.

- N

ot

det

ecta

ble

. F

igur

es i

n p

aren

thes

es d

eno

te m

edia

n v

alue

s

Cha

ract

eris

tics

19

76 (

Ram

an,

1980

) 19

85-1

987

(Pha

nipr

akas

h,

1989

) S

tati

ons

Sta

tion

s V

c Il

a II

b I

Vc

IIa

lib

I

S 25

.0-3

2.8

24.0

-31,

4 24

.0-3

1.0

24,0

-31.

0 26

.4-3

5.5

24.5

-32.

1 25

.0-3

1.5

23.0

-29.

5 T

emp

erat

ure

(~

(2

8.4)

(2

8.0)

(2

4.9)

(2

7.8)

(3

0.0)

(2

9.5)

(2

8.0)

(2

6.7)

B

24.8

-30.

8 24

.0-3

0,4

24.0

-30.

2 24

.0-3

0.2

25.1

-31.

5 23

,5-3

0.5

24.5

-30.

0 21

.6-2

9.7

(28.

0)

(27,

8)

(27.

7)

(27.

7)

(27.

8)

(27.

5)

(27.

5)

(26.

3)

Tra

nsp

aren

cy (

m)

S 0.

5-2.

5 1.

0-5.

0 1.

0-10

.0

2.5-

20,0

0-

2.4

0.4-

5.7

0.65

-9.4

2.

0-12

.0

(1.0

) (1

.5)

(2,5

) (4

,5)

(0.6

) (1

,1)

(1.3

) (6

.8)

S 8.

0-30

,0

7.5-

13.0

6.

0-8.

0 0.

5-1.

5 1.

0-10

0 1.

0-38

1.

9-37

N

.D.-

10

Tur

bidi

ty (

ppm

) (1

8.75

) (1

1.0)

(6

.75)

(1

.25)

(2

3)

(10)

(1

0)

(N.D

.)

B

10.0

-30.

0 10

.0-2

2.0

6.0-

8.0

0.5-

1.5

1.0-

24

1.0-

70

1.0-

22

N.D

.-20

(1

9.0)

(1

5.0)

(6

.75)

(1

.25)

(1

0)

(10)

(1

0)

(N.D

.)

S 7.

92-3

3.84

15

.34-

33.8

4 22

.94-

33,8

4 23

.21-

33,8

4 1.

98-3

2.14

3.

82-3

4.43

14

.05-

34.5

6 24

.25-

34.9

2 S

alin

ity

(%o)

(2

4.29

) (3

0.42

) (3

0.91

) (3

1.18

) (2

6.74

) (3

0.88

) (3

2.27

) (3

3.33

)

B

24.0

2-33

.84

24,0

2-34

.02

24,0

2-34

.02

24.0

2-34

.02

21.8

-34.

44

20.2

5-34

.67

20.4

3-34

.74

25.5

5-35

.0I

(26,

69)

131.

81)

(31.

89)

(31.

89)

(31.

33)

(32.

18)

(32.

54)

(33.

60)

S 7.

4-8.

2 6.

0-7.

2 7.

0-8.

0 7.

2-8.

2 6.

7-8.

9 5.

8-8.

8 7.

0-8.

4 7.

7-8.

1 p

H

- (6

.7)

(7.0

) (7

.6)

(7,5

} (7

.3)

(7.5

) (7

.8)

B

..

..

6.

6-8,

8 6.

8-8.

1 6.

9-8.

5 7.

4-8.

4 (7

.5)

(7.6

) {7

.6}

(7.9

)

S 0.

4-19

.6

4.2-

13.4

4.

8-11

.8

6.0-

8.8

N.D

.-19

.6

0.8-

21.6

3.

8-12

.0

4.2-

8.4

(6.2

) (6

.8)

(7.2

) (7

,4)

(5.6

) (7

,8)

(7,6

) (6

.8)

Dis

solv

ed o

xy

gen

(r

ag/l

) B

4.

2-8.

4 4.

2-8.

0 4~

2-9.

8 6.

0-8.

4 N

.D.-

9.2

2.4-

12.0

4.

6-8,

4 1.

8-8.

0 (6

.2)

(6.7

) (7

.0)

(7.4

) (4

.0)

(6.0

) (6

.4)

(6.6

)

S 12

-50

4-40

3-

18

0.2-

2.0

..

..

B.O

.D.

(rag

/l)

(23)

(1

4)

(9.6

) (1

.2}

B

16-4

8 8-

28

- 0.

2-1.

2 .

..

.

(22)

{1

6)

(0.4

)

<

Tab

le

1 (c

onti

nued

)

Cha

ract

eris

tics

19

76 (

Ram

an,

1980

) 19

85-1

987

(Pha

nipr

akas

h,

1989

) S

tati

ons

Sta

tion

s V

c II

a II

b I

Vc

IIa

IIb

I

Am

mo

nia

-nit

roge

n (m

g/l)

Nit

rite

-nit

roge

n (r

ag/l

)

Nit

rate

-nit

rog

en

(rag

/l)

S 1-

9.8

0.42

-2.3

0.

1-0.

72

0-0.

016

0,07

-1.8

9 0.

07-1

.82

0.08

-0.7

7 0.

04-0

.25

(4.8

) (1

.24)

(0

.38)

(N

.D.)

(0

.47)

(0

.48)

(0

.35)

(0

.07)

B

..

..

0.

11-0

.95

0.03

-1,2

9 0.

08-0

.77

0.03

-0.1

3 (0

.34)

(0

.30)

(0

.29)

(0

.07)

S 0.

012-

0.93

0.

004-

0.55

0.

004-

0.11

2 0.

004-

0.03

2 N

.D.-

4,74

N

,D.-

0.70

N

.D.-

0.42

N

.D.-

0.21

(0

.155

) (0

.1)

(0.0

32)

(0.0

12)

B

0.01

2-0.

2 0.

008-

0.14

8 0.

008-

0.04

8 0.

004-

0.01

8 (0

.098

) (0

.042

) 10

.02)

(0

.008

)

S 0-

0.38

0-

1.16

0-

1.16

0-

0.01

6 (0

.105

) (0

.042

) (0

,02)

(0

.005

)

B

..

..

0.08

-8.0

0,

2 3.

84

0.00

7-0,

076

(3,7

6)

(0.8

8)

(O.O

38)

0.28

-5.6

0.

2-2.

2 0.

007-

0.01

8 (1

.7)

(0.4

) (0

.018

)

S 0.

48-6

.0

Ph

osp

hat

e-

(2.9

4)

ph

osp

ho

rus

(rag

/l)

B

0.48

-6.0

[3

.12)

S

Sil

icat

e-si

lico

n (r

ag/l

) B

-

(0.1

2)

(0.0

9)

(0.0

6)

(0.0

06)

N.D

.-0.

47

N.D

.-0.

35

N.D

.-0.

18

N.D

.-0.

35

(0.0

9)

(0.0

4)

(0.0

20)

(0.0

06)

N.D

.-4.

40

N.D

.-6.

16

N.D

.-2.

17

N.D

.-0.

24

(0.0

1)

(0.0

2)

(0.0

1)

(0.0

12)

N.D

.-0.

27

N.D

.-1.

28

N.D

.-0.

42

N.D

.-0.

13

(0.0

1)

(0.0

1)

(0.0

2)

(0.0

09)

0.18

6.

96

0.03

8.

07

N.D

.-4.

27

0.01

-0.5

9 (1

.77)

(2

.29)

(1

.38)

(0

.03)

0.02

-1,9

4 0.

09-3

.71

N.D

.-1.

58

N.D

.-0,

44

(0.8

9)

(0.9

1)

(0.4

5)

(0.0

3)

N.D

.-7.

83

0.06

-4,6

3 0.

10-3

.2

N.D

.-0.

87

(2.2

6)

(1.2

0)

(0.7

0)

(0.3

6)

N.D

.-2.

26

N.D

.-2.

61

N.D

.-2.

49

N.D

.-1.

45

(0.7

8)

(0.6

0)

(0.5

2)

(0.2

9)

Q

<

~r

r �9

Go

r~

c~

CO

c~

e/ee

&O,O

35.0

30.0

25.0

20.0

15.0

10.0

5-0

0.0 Va

Vb

V

r i

i

29

| |

ST

AT

ION

S

1,1 if

Solinity

12 12

12

mg

/l

8,.0

7.0

6.0

5~0

/~,0

3.0

2.0

1,0

0,I

0,0

Va

Vb

V

c t

=

i

1 i

STATIO

NS

lla lib

I |

!

102

POg P

J

29

i |

i

VQ

Vb

V

c

mgll I'

" "

19.6[- ~ ~

13.0~ 12.0~-

zo

l~176 I- [

6.0

!~.

~

4.0

2.0

0-0 ~ o!g

Ou

t foil

I.la

86

'lb..

D.O

.

24

3v.~ J,!~

7!o D

ista

nc

e

from

th

e

ou

tfall

Vo V b Vc

m~./~)

u.

08

0.6

0.5

0./,

0.3

0.2

0.1 0.0 t

o.~ o.9 O

ut

tall

11o llb

t

NO

2-N

96

Dis

tan

ce

fro

m

the

o

utfa

ll

Fig. 2. Spatial distribution of salinity, dissolved oxygen, phosphate and nitrite in surface waters in 1976

Pollution effects in V i sakhapa tnam harbour 639

0.35-4.8mg/1; nitrite 0.02-0.155mg/1; ni t rate 0 .01-0.105rag/ l ) , phospha te (0.4-3.76 rag/l) and silicate (0.52-2.26 rag/l) as aga ins t nea r -normal condit ions in the open sea (St.I). Here, wa te r t ransparency (median value) is more: 4.5-6.8 m; turbidi ty negl igible , 0-1.25 ppm; pH 7.6-7.9; salinity, 23.21-34.92 %0; dissolved oxygen, 6.6-7.4 rag/l, and inorganic nitrite, phospha te and silicate levels r emain ing compara t ive ly low (< 0.01 mg/1). Figure 2 shows the spat ial distr ibution (range and median) of salinity, d issolved oxygen and inorganic nutr ients in surface waters, observed away from the pollut ion source.

During the study, it was found that the harbour waters are subject to cons iderable seasonal changes. In 1985-1987, surface-dissolved oxygen at St.IIa va r i ed from a min imum of 0.8 to a max imum of 21.6 mg/1; nitrite, 0-0.7 mg/1; nitrate, 0-6.16 mg/1; phosphate , 0-8.07 mg/1 and silicate, 0.16-3.2 mg/l. However , day- to -day variat ions were equal ly marked at this station. For example , b e tw e e n the 4th and 9th of Sep tember , 1985, dissolved oxygen f luctuated be tween 7.6 and 11.4mg/1; nitrite, 0.19-0.60; nitrite, 0.02-0.09 mg/1; phosphate , 2.25-3.39 rag/1 and silicate, 0.98-1.76 mg/1 - sugges t ive of strong an thropogenic effects (Phaniprakash, 1989). The invest igat ions also r evea led that the concentra t ion of nitrites and phospha te increased apprec iab ly over the years (Fig. 3). This is a t t r ibutable to the d ischarge of fertil iser factory wastes (50 mgd) and un t rea ted domest ic sewage containing these subs tances and their pers i s tence clue to i nadequa t e flushing. By 1982, the high nitrite (max. 5 mg/1) and phospha te (9.6 rag/l) obse rved in surface waters in the harbour (St.IIa) were evident ly caused by their accumulat ion. In 1976, the construct ion of the outer ha rbour had comple te ly offset any t idal action, accentua t ing stagnation. This per iod was also m a r k e d by a nea r - s imul taneous rise in dissolved oxygen, the overall range of which increased progress ively (Fig. 3), a t t r ibut ing to per iodic outbursts of phy top lank ton (Ganapat i & Raman, 1979). During la ter years, however , the levels of nitrite and phosphate , as wel l as dissolved oxygen, b e g a n to decrease .

Apprec iab le differences in wate r qual i ty exis ted be tw e e n the 1976 and 1985-1987 studies (Table 1). For example , wa te r t r ansparency has dec reased (overall mean 1.67-1.0 m) since 1976. Turbidi ty inc reased rela t ively (12.17-14.3 ppm), as did salinity (29.84-30.99%0) and pH (6.85-7.5). There was a genera l decrease in dissolved oxygen (6.68-6.23 mg/1) which was cons iderab le in bot tom waters at St.Vc nea r the s ewage outfall (2.2 mg/1). The concentrat ions of ammoniaca l n i t rogen (2.14-0.37 mg/1), nitrite (0.075-0.07 mg/1), ni trate (0.06-0.01 mg/1) and inorganic phospha te (2.13-1.28 mgFl) dec reased compara t ive ly by 1985-1987. Decrease in dissolved oxygen, nitrite or nitrate, or their occasional total d i sappearance , ind ica ted an onset of reduc ing condit ions in the harbour. In the vicinity of the sewage outfall (St.Vb), H2S is found in solution and marsh gas effervesced from the bot tom w h e n dis turbed.

A number of authors emphas i zed chemica l factors, par t icular ly inorganic n i t rogen and phosphorus , as useful for assess ing pollution. In enclosed sea areas, poUution th rough organic sewage enriches waters with nutr ients and, when p resen t in excessive amounts, can result in the r ep l acemen t of normal phy top lank ton popula t ions with noxious species, thus changing the ent ire biotic structure in the process k n o w n as "cultural eut rophicat ion" (Ketchum, 1973). In the harbour under discussion, the p resence of high concentrat ions of n i t rogen and phosphorus ind ica ted eutrophic conditions.

640 A. V. Raman

22-0

.~20.0 E 1~-0 Z 16-0

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1968'70 72 '7t. '76 '78 '80 82 "8t. '156 YEAR

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- (~ -Sarma et at ( 1 9 8 2 )

t'~ Pr=sada Reddy (1986)

| Rama Raiu et a 1 ( 1 9 8 7 ) [ ] Phani Prakash ( 1 9 8 9 )

Fig. 3. I n t e r annua l var ia t ions ( m e d i a n a n d Range) in (A) d i sso lved o x y g e n . (B) i no rgan i c p h o s p h a t e a n d (C) nitri te in su r f ace wa t e r s at

St.IIa. F igures on top deno t e s a m p l e size

P h y t o p l a n k t o n

Ganapa t i & Raman (1979) and U m a m a h e s w a r e Rao & M o h a n c h a n d (1988) repor ted Skeletonema costatum as a dominan t spec ies among the microplankton in the harbour. More recently, the invest igat ions r evea l ed that at St.Vc. close to the s e w a g e outfall, the phy top lank ton consis ted chiefly of f lagellates. Tetraselmis sp. and Dicrateria sp., which toge ther const i tu ted nea r ly 90 % of the popula t ion in the locahty (Raman & Phan ip rakash , 1989a). The other species not iced were DunaBella sp. and Eutreptia sp., a n d cihates. notably Tetrahymena pyrfformis, Protocruzia adhaerens, Stylonychia sp., Amphileptus sp. and Euplotes terricola. At the downs t r eam location (St.IIa), the phy top lank ton con- stated of diatoms. Thalassiosira pseudonana (50.7 %), Chaetoceros diversus 110.2%),

Pollution effects in Visakhapatnam harbour 641

Table 2. Surface chlorophyll and phytoplankton abundance (range and mean) at selected harbour locations in 1985-1986. N.D.: Not detected

Characteristics Stations (Number of samples)

Chlorophyll (mg. m -3} Chl. a

Chl b

Chl c

Phytoplankton abundance

(X 1000 m1-1)

Vc IIa IIb I (23) (23) (22) (10)

8.00-1517.8 0.61-51.18 0.60-43.68 N.D.-6.55 (40.4) (28.61) (16.46) (2.23)

1.10-1096.5 0.98-38.31 0.42-27.18 N.D.-2.23 (18.5) (12.55) (7.82) (0.89)

1.89-15.71 0.69-106.86 N.D.-66.85 N.D.-5.72 (55.6) (18.66) (17.11) (1.25)

0.54-6258 0.12-191.4 0.07-123.0 0.04-3.23 (292.2) (16.2) (8.95) (0.92)

Ske le tonema costatum (7%) and the flagellate Cryptomonas sp. (5.8%). At St.IIb, characterized by its proximity to the open sea, Th. pseudonana (57.3 %) and Ch. diversus (12.2 %) constituted nearly 70 % of the total population. At St.I in the open sea, where the effect of pollution was negligible, the n u m b e r of phytoplankton species was at its maximum (93), of which Th. subtilis (62 %), Ch. socialis (11%) and Asterionella japonica (5.9 %) dominated. Table 2 shows some details of the numerical abundance of phyto- plankton, with information on chlorophyll (a, b and c) in surface waters at selected stations in the harbour noticed during 1985-1986 (Raman & Phaniprakash, 1989b). It is evident that the harbour waters support high numbers of phytoplankton, some of which occur in bloom proportions. For example, on the 8th March 1986, the flagellate Tetrasel- mis sp. was found in exclusive dominance (6 258 000/m1-1) at St.Vc, when the chlorophyll (a+ b + c) reached an all-t ime-high (4185 mg/m 3) (Phaniprakash, 1989). Similarly, data on short-term changes (4thto9th September, 1985) showed that at St. IIa, total chlorophyll fluctuated be tween 20.85 and 94.95 mg/m 3 in response to phytoplankton availability. In the harbour, the presence of high chlorophyll and rich phytoplankton was therefore suggestive of intense eutrophication.

Several studies have shown nanop lank ton dominance to be an indicator of pol lut ion in enclosed sea areas (Eppley & Weiler, 1979; Mahoney & McLaughlin, 1979; Stockner & Cliff, 1979; Tsuruta & Yamada, 1980; Panuko, 1984). In the harbour under discussion, while nanoflagellates, Tetraselmis sp. and Dicrateria sp., were the characteristic inhabit- ants of St.Vc (close to the sewage ouffall), at St.IIa where water quali ty marginaUy improved, they were replaced by Ske le tonema costatum and the cryptomonad Cryp- tomonas sp. At the transit ional outer harbour region (St.IIb), Thalassiosira pseudonana and Chaetoceros diversus were the principal species. At St.I (open sea), where the effects of pollution a re negligible, typically mar ine forms (Th. subtilis, Ch. socialis and Asterionella japonica) were found.

642 A.V. Raman

B e n t h i c c o n d i t i o n s

Raman (1980) carried out a detailed investigation on benthic polychaetes in the harbour in relation to pollution. The studies conducted in 1976 revealed that the polychaetes were not only the most diverse but, in terms of populat ion density, they often formed a high percentage (>80%) of organisms collected. Polychaete species-abun- dance data (cf. Pearson & Rosenberg, 1978) for harbour locations revealed that - whereas away from the outfall (St.Va), the total n u m b e r of individuals decreased after an initial peak of "opportunists", notably the capitellid Capitella capitata - the n u m b e r of species increased as the distance from the source of enr ichment increased. Based on species- similarity-affinity indices, it was possible to distinguish three distinct polychaete assem- blages, each characterizing the (polluted) inner harbour (Stations Vb, Vc and IIa); the transit ional (semi-polluted) outer harbour (St.IIb) and the unaffected (unpolluted) open sea (St.I) environments (Raman & Ganapati , 1983). At St.Va, located in the immediate vicinity of a sewage source, the sediments turned septic (highly-polluted) to the extent that they killed all bottom life and excluded the introduction of organisms from other areas.

Earlier, Sarma & Ganapat i (1975) listed the occurrence of 38 species of polychaetes in the nor thern arm of the harbour (corresponding to Stations Vb and Vc). They also stated that the mangrove swamp in that locality was "relatively free of pollution", when they carried out their investigation in 1972. Of the 38 forms listed by Sarma & Ganapat i (op. cit.), the author came across only 12 species, when he carried out his study in 1976 (Raman & Ganapati , 1986). The disappearance of other species reported by Sarma & Ganapat i (1975) was considered to be due to an increase in pollution dur ing the in tervening years. More recent findings showed that further changes have occurred (Bismillah. 1986). Of the 11 species of polychaetes encountered during the 1976 study, only 4 forms were found by Bismillah (op, cit.), the others being absent. At St,Vb,

Table 3. Water and benthic characteristics at St.Vb in 1976 and 1985-1986. N.D.: Not detected. Figures in parentheses denote median values unless stated otherwise

Characteristics 1976 1985-1986 (Raman. 19801 (Bismillah, 19861

Dissolved oxygen (mg/1)

Nitrate-nitrogen (mg/1)

Sediment organic matter (%)

Number of benthic species

Numerical abundance [Mean: Nos./0.05 m 2)

Margalef diversity (d)

Shannon-Wiener [H') index

N.D.-ll.4 N.D.-6.2 (5.4) (N.D.)

N.D.-1.1 N.D.-0.271 (0.09} (N.D.)

i. 19-3.90 0.91-11.31 (2.531 (3.721

5 3

23-7 493 10-14295 (879) (925)

0.31 0.24

1.18 0.10

Pollution effects in Visakhapatnam harbour 643

Capitella capitata and Nereis glandicincta that were dominant during the 1976 study

(95 %) had almost d isappeared by 1985-1986 (< 3 %), and a tubificid worm Nlonopy- lephorus sp. now occurs there. Similarly, at St.Vc the two earlier dominants, Diopatra neapolitana and N. glandicincta, have been replaced by C. capitata. Marked changes occurred in water quality and sediments during this t ime (Table 3).

The harbour had also witnessed significant changes in the composit ion and abun-

dance of fouling communities. In 1958, Ganapat i and others reported as many as 43

species of fouling organisms in the harbour. At present, several of these forms have either totally d isappeared from those locahties or now occur in reduced numbers. The examples

include certain serpulid polychaetes, an amphipod, a barnacle, and oyster. These organ-

isms which once flourished have faded out now, evidently due to changes in water quality. Perhaps the most significant finding which em erged during recent years relates

to the introduction, success and spread of an exotic dressinid bivalve Mytilopsis sallei in

the harbour (Satyanarayana Rao et al., 1989). By the nature of its dominance, M. sallei has proved to be a serious competi tor to the many endemic foulers in the harbour.

Pearson (1975) made a detai led invest igat ion on the benthic fauna in Loch Ell,

Scotland, over a period of ten years, in relation to pollution caused by pulp-mill wastes in that area. In the highly polluted Tees estuary, a comparison of surveys carried out in 1935

with others in 1971 and 1973 showed that there was a dramatic reduction in the species of bivalves and polychaetes, caused by pollution (Gray, 1976). More recently, Reish et al.

(1980) discussed results of 28 years of continuous monitor ing of benthic biological

conditions of the Los Angeles-Long Beach harbours, California, in relation to pollution. Local harbour findings have revea led that, prior to the construction of the outer harbour,

the environmental conditions remained comparat ively unpolluted, as indicated by the low nutrient levels and a great diversity of macrobenthic life and other organisms. This is

undoubtedly due to the flushing out of wastes by tides into the sea, result ing in their

quick dispersion. After 1976 there was, however , considerable deteriorat ion in water quality. This was evident from an increase in the concentrat ion of inorganic ni t rogen and

phosphorus. Phytoplankton blooms have become a common feature, as well as mass fish kills. In the harbour, species that, earlier on, inhabi ted unpol luted or semi-pol luted

environments are gradual ly replaced by pollution tolerant forms. In the interior channels, where the effect of pollution is relatively high, the bottom is devoid of any macroscopic

life for some distance from the outfall. To sum up - a combinat ion of factors, including rich nutrient supplies arising from waste discharges, coupled with sluggish circulation

and efficient nutr ient regenera t ion mechanisms have turned Visakhapatnam harbour into a highly eutrophic environment , capable of support ing rich biotic communities. Over

a period of several years, the harbour seems to have acted as a sink for a variety of waste

additives, result ing in the observed changes.

Acknowledgements. Many funding agencies such as INSA, CSIR, DOEn and UGC, New Delhi, enabled me to carry out investigations in Visakhapatnam Harbour over the past several years. Grateful thanks are due to them. I also wish to thank the Visakhapatnam Port Trust Authority for their kind help. Successive Heads of the Department of Zoology in the University have generously extended all facilities. This paper was presented at an International Symposium on "100 years of Biologische Anstalt Hetgoland - A Challenge to Marine Biology in a Changing World", Helgoland, September, 1992. I am grateful to Professor W. Gunkel, Director, and Dr. M. R. Kirchner, Adviser to visiting scientists, of the Biologische Anstalt Helgoland, for their kind assistance.

644 A . V . R a m a n

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