Indian Journal of Marine Sciences
Vol. 32(1), March 2003, pp. 57-66
Effects of industrial wastes on the growth and reproductive stages of
macroalgae of Visakhapatnam coastline, east coast of India
S. B. K. Murthy & M. Umamaheswara Rao
Department of Botany, Andhra University, Visakhapatnam - 530 003, A.P., India
Received 8 January 2002, revised 20 November 2002
Experiments were conducted to understand the effects of effluents and sediment extracts of Hindustan Zinc Smelter and
Alum factory, on the growth and reproductive stages of 9 macroalgae of the Visakhapatnam coast. In fully grown algae,
growth inhibition was minimum at 0.001 or 0.01 % concentrations of HZE-I and II, HZR-I and II and AFE and AFR and
maximum at intermediate concentrations (2.5-25 % HZE and R-I and 0.25-8.0 % HZE and R – II and AFE and AFR). Stationary growth and death of algae was observed at highest concentrations tested. The toxic effects were more in HZE- II and
HZR – II, than in AFE, AFR, HZE-I and HZR-II. Tetraspore production from one brown and 4 red algae and spore germination decreased from 2.0-10.5 % HZE-1 and HZR-I and from 0.1-1.8 % of other wastes. Sporeling growth and survival were
affected at concentration 4-150 times less than those observed for the fully grown algae. Among the 3 classes of algae
tested, green algae were more tolerant to the industrial wastes, than the brown and red algae. These culture experiments indicated the damage caused by industrial wastes to macroalgal communities.
[ Key words : Industrial wastes, toxic effects, marine algae, growth, reproduction, Visakhapatnam coast ]
Studies on pollution effects on marine macroalgae are
very limited in India 1-7 , though the tropical marine
ecosystems are considered to be more sensitive to pollution8 . On the east coast of India, Visakhapatnam
coastline harbours rich algal flora and 96 species have
been reported so far from this area9,10. The macroalgal
community structure of the inshore waters has been
changing since 1970 owing to the discharge of raw
sewage along the coastline and industrial wastes
through the Meghadrigedda stream and harbour 11 . As
benthic algae were found to be more suitable for
evaluating the toxicity of pollutants12 , bioassays were
conducted with macroalgae of Visakhapatnam coast,
to assess the toxic effects and changes in the algal
populations caused by different pollutants. Information obtained on crude oil, petroleum refinery and
fertilizer factory effluents was published earlier13,14.
The present paper deals with the effects of zinc
smelter and alum factory wastes on the growth and
reproductive stages of 9 macroalgae.
Materials and Methods
The Hindustan zinc smelter, located in the vicinity
of Visakhapatnam habour, releases its effluents
through 2 canals (Canal-I,II). Effluents of these canals
and alum factory were collected during 1989 and
1990 near the outfall areas. The concentrations of
heavy metals present in these effluents were
analysed15,16, while working on microalgae. Since
sediments present in the outfall areas act as waste or
heavy metal receivers17 , an attempt has been made to
examine the effects of residues also by collecting the
sediments near the outfalls. Extracts were prepared by
mixing 1 kg of sundried sediment in 1 liter of distilled
water. The water soluble extracts and effluent samples, filtered with Whatman No.1 filter paper, were
used for bioassys. Different working concentrations
were prepared, as given below, treating the 3 effluents
and residues as 100 % conc. and diluting them with
requisite quantities of sterile seawater.
Nine fully grown or mature algae [Chlorophyta:
Ulva fasciata Delile, Chaetomorpha antennina (Bory)
Kuetz.; Phaeophyta: Sargassum polycystum C.Ag.,
Padina tetrastromatica Hauck; Rhodophyta:
Gracilaria corticata J.Ag., Hypnea valentiae (Turn.)
Mont., Jania rubens (Linn.) Lamour, Amphiroa fragilissima (Linn.) Lamour. and Centroceras clavulatum
(C.Ag.) Mont.] were collected during 1989 and 1990
from unpolluted areas of Visakhapatnam coastline
(17° 40′ 30? and 17° 45′ N lat. and 83° 16′ 25? and 83°
21′ 30° E long.) and washed many times with sterile
seawater before conducting experiments on thallus
growth and survival. For growth data, the basal parts
of the filaments of Chaetomorpha antennina; 2.0 mm
diam. discs of Ulva fasciata and 1.0 to 2.0 cm long
apices of the other 7 algae were excised and exposed
58
Indian J. Mar. Sci., Vol. 32, No. 1, March 2003
to effluents and residues as described earlier13,14. Concentrations ranging from 0.001-40 % Hindustan zinc
smelter effluent of Canal-I (HZE-I); 0.001-20 % residue of Canal-I (HZR-I); 0.001-10 % effluent of Canal-II (HZE-II); residue of Canal-II (HZR-II) and
alum factory effluent (AFE) and residue (AFR), were
used for growth experiments with mature thalli. For
survival experiments, HZE-I and HZR-I were used up
to 50 % and the other wastes of Canal-II and alum
factory up to 20 % level. Growth rate and survival of
mature algae were estimated13,14 at 5 day intervals for
25 days. For studies on spores, fertile parts of tetrasporophytic thallai of 5 algae were selected [brown
alga : Padina tetrastromatica; red algae: Gracilaria
corticata, Hypnea valentiae, Jania rubens, Amphiroa
fragilissima] and exposed to 0.05-100 % concentrations of effluents and residues13,14. Tetraspore output
was estimated after 24 h exposure18,19. From the total
output, the number of dividing spores present in petridishes was also counted separately to determine the
percentage of spores germinated. For sporeling
growth experiments, tetraspores of Padina tetrastromatica, Gracilaria corticata and Hypnea valentiae
were allowed to settle and germinate on sterilized
cover glasses and 4 day old sporelings were used to
collect data on their growth and survival in control
and waste concentrations, as described earlier20 . Only
effluents ranging from 0.001-15 % of HZE-I and II
and AFE were used. Twenty five sporelings were
measured at 5 day intervals for 25 days period and
mean growth increase over the initial and survival
percentage of sporelings were estimated.
All the growth and survival experiments with mature thallai and sporelings, were conducted in laboratory at room temperature (28 ± 2°C), using additional
light intensity (1200-1500 lux) during the day time
from 09 00 – 17 00 hrs (8:16 LD cycle). But 800 lux
illuminance was used for spore liberation experiments. The test concentrations of effluents and residues in the petri-dishes were replenished at 5 day intervals. Selected parts of mature algal thalli; reproductive materials and sporelings (settled on coverslips)
were kept in petri-dishes containing sterile seawater
and these petri-dishes with seawater served as controls in all the experiments conducted for growth, survival, spore shedding and sporeling growth13,14. Ten
replicates were run for all the experiments conducted
and mean values were calculated. Taking the differences observed in the growth and survival rates of
algae in control and waste concentrations, data on
median effective/ lethal time (time taken for 50 %
reduction in growth/ mortality) were estimated. Regressions were drawn21 using the median effective
times obtained for mature thallai and sporelings to
estimate the medium effective (EC50 ) and lethal
(LC50 ) concentrations for 72 h duration (3 days exposure). For spore output experiments EC50 values were
estimated for 24 h exposure by graphical interpolation
method22 .
Results
Thallus growth and survival
Data presented in Table 1 show that growth inhibition occurs in mature thalli (except in Chaetomorpha
antennina treated with HZR-I, HZE-II and AFE) even
at lowest concentrations of 0.01 and 0.001 % (10-100
ppm) of the industrial wastes tested. In Chaetomorpha
antennina there was no inhibition at 0.001 % HZE-II
and 0.01 % AFE and HZR-I. The retardation in
growth was, however, observed at higher doses, from
Table 1 — Growth inhibition in mature algae exposed to the lowest concentrations of industrial wastes
Algae
% inhibition in effluents
0.01%
0.001%
0.01%
HZE-I
HZE-II
AFE
% inhibition in residues
0.01%
0.001%
0.01%
HZR-I
HZR-II
AFR
Ulva fasciata
Chaetomorpha antennina
Sargassum polycystum
Padina tetrastromatica
Gracilaria corticata
Hypnea valentiae
Jania rubens
Amphiroa fragilisima
Centroceras clavulatum
3.2*
12.5
12.9*
3.6
1.3
1.5
6.3
5.9
14.3
5.2*
0.0
11.1*
0.4
2.7
2.4
5.9
8.3
8.3
* = 0.25% conc;. + = 0.01 conc.
1.5
0.0
3.0
3.8
1.6
1.3
5.0
7.7
7.1
1.6
0.0
3.2
3.6
8.0
3.4
9.5
4.0
19.0
23.2+
19.1+
41.6+
37.8+
33.3
40.0
33.7
37.7
28.3
40.3
35.4
23.3
25.0
32.8
45.3
21.7
21.2
37.8
59
Murty & Rao : Effects of industrial wastes on macroalgae
0.25% HZE-I and HZR-I in Ulva fasciata and Sargassum polycystum and from 0.01 % HZR-II in the green
and brown algae tested. In general, growth inhibition
was more in the lowest concentrations of HZR-II and
AFR, than in the other wastes tested (Table 1).
Since multicellular algae and animals require
longer periods of exposure23,24 to get sublethal and
lethal responses to pollutant, EC50 and LC50 values
were estimated daily up to 5 days to obtain the optimum time of exposure required for the observable
changes in the growth and survival of macroalgae
tested. Data collected from one green, brown and red
algae exposed to HZE-II for 5 days are shown in Table 2. These values indicate that the median effective
and lethal concentrations (EC50 and LC50 ) did not vary
markedly from 3 days (72 h) exposure to industrial
waste (HZE-II).Based on these observations (Table 2)
the median effective and lethal concentrations were
estimated for 72 h (3 days) duration in all the experiments conducted with 9 algae and 6 industrial wastes
and the results are summarized in Table 3 as 72 h
EC50 and 72 h LC50 values to show the concentrations
of the effluents and residues causing sublethal and
lethal effects on the growth and survival of fully
grown algae tested in this study.
In order to show the general trends of the 3 effluents (HZE-I and II, AFE) and residues (HZR-I and II,
Table 2 — EC50 and LC50 values estimated for three algae
exposed to HZE-II for five days
Ulva fasciata
Days
1
2
3
4
5
EC50
LC50
10.2
7.2
4.5
4.0
3.8
0.2
9.8
9.0
8.4
8.0
Sargassum
polycystum
EC50
LC50
Centroceras
clavulatum
EC50
LC50
6.0
4.6
3.9
3.6
8.4
0.32
0.24
0.20
0.18
0.18
9.2
9.0
8.8
8.4
8.0
1.2
1.1
0.9
0.8
0.8
AFR), one green (Ulva fasciata), one brown (Sargassum polycystum) and 2 red algae (Gracilaria corticata, and Centroceras clavaulatum) were selected out
of the 9 algae and their growth responses observed for
25 days in control and in different concentrations of
HZE-I and HZR-I are presented in Figs. 1-4, together
with the toxicity curves obtained for growth and survival (insets). Similarly the survival data collected on
25th day for these four selected algae are given in
Table 4, to show the rate of survival of algae, exposed
to industrial wastes. In the green algae, Ulva fasciata
(Fig. 1A) and Chaetomorpha antennina, and brown
algae, Padina tetrastromatica and Sargassum polycystum (Fig. 2A) exposed to HZE-I, 80-90 % growth
retardation was observed at 20 or 25 % levels. In these
4 algae 100 % survival was found between 15 and
20 % HZE-I; the mortality rate increased at higher
concentrations and all plants died at 40-50 % HZE-I
(Table 4). The EC50 and LC50 values of the green and
brown algae ranged from 18-20 % and 48-50 % respectively (Table 3). In Gracilaria corticata (Fig. 3A)
and Hypnea valentiae, growth rates declined by 43-60
% at concentrations ranging from 2.5 to 10 % HZE-I,
with 100 % survival up to 15 % level (Table 4). The
survival rate decreased from 20 % (Table 4) and the
EC50 and LC50 values of these two larger red algae
varied from 14-16 % and 30-32 % respectively (Table
3). The effect of HZE-I on the two coralline red algae,
Jania rubens and Amphiroa fragilissima and filamentous Centroceras clavulatum was greater with maximum growth retardation at 10-15 % level in the first
two species and at 5.0 % level in the filamentous alga
(Fig. 4A). The survival of these 3 red algae was also
affected at low concentrations (Table 4) and their
EC50 and LC50 values ranged from 2.5-12.0 % and
20-27 % HZE-I respectively (Table 3). In general, at
higher concentrations of HZE-I and other wastes
Table 3 — 72 h EC50 and72 h LC50 values estimated for fully grown algae exposed to effluents and residues of industrial wastes
Algae
Effluent Concentration (%)
HZE-I
HZE-II
AFE
EC50 LC50
EC50
LC50 EC50
LC50
Residue Concentration (%)
HZR-I
HZR-II
AFR
EC50 LC50 EC50 LC50 EC50 LC50
Ulva fasciata
Chaetomorpha antennina
Sargassum polycystum
Padina tetrastromatica
Gracilaria corticata
Hypnea valentiae
Jania rubens
Amphiroa fragilissima
Centroceras clavulatum
22.0
18.0
20.0
18.0
16.0
14.0
12.0
9.0
2.5
12.0
10.0
10.2
10.0
7.0
4.0
4.0
3.0
1.0
50.0
48.0
50.0
48.0
32.0
30.0
27.0
24.0
20.0
4.5
4.1
4.1
3.0
1.5
1.0
0.6
0.4
0.4
9.0
8.4
8.8
8.0
3.8
3.0
2.5
2.0
0.9
8.0
5.2
5.6
5.2
4.8
4.0
3.2
3.2
2.8
10.0
10.0
10.0
9.8
8.0
7.5
7.2
7.0
6.4
26.3
20.0
24.0
20.0
16.0
9.0
9.0
7.0
3.0
4.0
2.5
3.0
2.5
0.8
0.5
0.4
0.4
0.2
7.0
5.0
6.0
5.0
3.5
3.0
1.2
1.0
0.5
5.0
4.8
4.4
4.0
3.2
2.2
0.3
0.2
1.0
8.4
8.0
8.0
8.0
4.5
3.8
0.8
0.8
0.7
60
Indian J. Mar. Sci., Vol. 32, No. 1, March 2003
Fig. 1 — Effect of HZE-I (A) and HZR-I (B) on the growth of Ulva fasciata [insets show the regressions drawn for estimating EC50 (g)
and LC50 (s) values].
Fig. 2 — Effect of HZE-I (A) and HZR-I (B) on the growth of Sargassum polycystum [insets show the regressions drawn for estimating
EC50 (g) and LC50 (s) values].
Murty & Rao : Effects of industrial wastes on macroalgae
61
Fig. 3— Effect of HZE-I (A) and HZR-I (B) on the growth of Gracilaria corticata [insets show the regressions drawn for estimating
EC50 (g) and LC50 (s) values].
Fig. 4 — Effect of HZE-I (A) and HZR-I (B) on the growth of Centroceras clavulatum [insets show the regressions drawn for estimating
EC50 (g) and LC50 (s) values].
62
Indian J. Mar. Sci., Vol. 32, No. 1, March 2003
tested, growth retardation was maximum before 5th or
10th day and the algae survived till 25th day without
any increase in growth (Figs 1-4). As a result of this
stationary phase in growth, the LC50 values of the 9
algae tested were 2-3 times higher than the EC50 values (Table 3). In the residue of Canal-I (HZR-I),
maximum growth inhibition occurred between 10 and
15 % levels in Ulva fasciata (Fig. 1B), Chaetomorpha
antennina, Sargassum polycystum (Fig. 2B) and
Padina tetrastromatica, with 100 % survival up to
5.0 % (2.5 % in Padina tetrastromatica). Total mortality of these green and brown algae occurred between
15 and 20 % HZR-II (Table 4) and the EC50 and LC50
values ranged from 10-12 % and 20.0-26.3 % respectively (Table 3). Changes in growth were more pronounced in Gracilaria corticata (Fig. 3B), Centroceras clavulatum (Fig. 4B) and other red algae exposed to HZR-I (Tables 3,4) and the EC50 and LC50
values were higher in Gracilaria corticata and Hypnea valentiae, than in the 3 other red algae (Table 3).
All the macroalgae tolerated very low concentrations
of HZE-II, since 88-96 % growth inhibition was found
in the green and brown algae between 0.5 and 5.0 %
level. Cent percent survival of these algae was seen at
2.5 % (1.25 % in Padina tetrastromatica) and their
mortality rate increased at higher doses (Table 4). Plants
of Ulva fasciata, Chaetomorpha antennina, and
Sargassum polycystum died within 1 day at 15 % and
Padina tetrastromatica at 5 % HZE-II. The EC50
values of these green and brown algae varied from
3.0-4.5 % and LC50 values from 8.0-9.0 % (Table 3).
In the 5 red algae maximum growth retardation was
seen between 0.5 and 1.0 % HZE-II and their mortality rate increased from 1.0-2.5 % in Gracilaria
corticata (Table 4) and Hypnea valentiae and from
0.2-0.5 % in Amphiroa fragilissima, Jania rubens and
Centroceras clavulatum. The EC50 values (0.4-1.5 %)
and LC50 values (0.9-3.8 %) are very low for these 5
red algae exposed to HZE-II (Table 3). In the residue
of canal-II (HZR-II), the green and brown algae were
severely affected with 19-41 % growth inhibition at
0.10 % (100 ppm) level (Table 1) and maximum
Table 4 — Percent survival in four selected algae exposed to industrial wastes for 25 days
Algae
Conc. (%)
Survival (%)
HZE-I
HZR-I
Conc. (%)
Survival (%)
HZE-II
HZR-II
Conc. (%)
Survival (%)
AFE
AFR
Ulva fasciata
0-5
10
15
20
35
50
100
100
100
100
64
0
100
78
18
0
0
0
0-0.05
1.25
2.50
5.60
10.00
15.00
100
100
100
34
10
0
100
100
50
40
0
0
0-4
5
6
8
10
15
100
100
100
84
70
0
100
90
68
0
0
0
Sargassum polycystum
0-5
10
20
25
35
40
100
100
100
74
30
0
100
88
0
0
0
0
0-0.05
1.25
2.50
5.00
10.00
15.00
100
100
100
96
50
0
100
70
10
0
0
0
0-2
4
6
8
10
15
100
100
100
96
58
0
100
96
60
0
0
0
0-1.25
2.50
5.00
10.00
20.00
100
100
100
100
90
100
82
14
0
0
0-0.10
1.00
2.50
5.00
7.50
100
100
82
34
0
100
54
0
0
0
0-0.5
2.0
4.0
6.0
8.0
100
100
100
56
0
100
90
50
30
0
0-25
0.5
1.0
5.0
10.0
15.0
100
86
74
56
10
0
100
62
0
0
0
0
0-0.05
0.10
0.20
0.25
0.50
1.00
100
100
96
80
40
0
100
90
40
20
0
0
0-0.05
0.10
0.20
0.40
1.0
5.0
100
100
100
100
92
20
100
90
20
0
0
0
Gracilaria corticata
Centroceras clavulatum
Murty & Rao : Effects of industrial wastes on macroalgae
growth inhibition at 2.5 or 5.0 %. Their survival rate
decreased rapidly from 1.25 or 2.5 % (Table 4). The
EC50 values fluctuated from 2.5-4.0 % and LC50
values from 5-7 % HZR-II (Table 3). The 5 red algae
were more sensitive to HZR-II since lowest EC50
(0.2-0.8 %) and LC50 (0.5-3.5 %) values were obtained
(Table 3) for this residue.
In the effluent of alum factory (AFE), reduction in
growth rate was 80-90 % in Ulva fasciata, Chaetomorpha antennina, Sargassum polycystum and
Padina tetrastromatica between 5 and 8 % concentrations. The survival rate decreased in these green and
brown algae from 7-8 % and total mortality of algae
was seen at 15 % AFE (Table 4). In APE effluent the
EC50 values varied from 5.2-8.0 % and LC50 values
from 9.8-10.0 % (Table 3). The growth and survival
of the 5 red algae were affected at lower concentrations of AFE and the EC50 and LC50 values ranged
from 2.8-4.5 % and 6.4-8.0 % respectively. In the
residue of alum factory (AFR) maximum growth inhibition occurred in green and brown algae at 4-6 %
and in red algae at 0.05-2.0 % levels. The mortality
63
rates were also high (Table 4) and the EC50 and LC50
values of this pollutant varied from 1.0-5.0 % and
0.7-8.4 % respectively for all the 9 algae tested
(Table 3).
Liberation and germination of spores
The effects of only two wastes (HZE-I and AFE)
on shedding and germination of spores of Hypnea
valentiae are shown in Fig. 5. The median effective
concentrations (24 EC50 values) of all the wastes, estimated for the liberation and germination of spores of
5 algae, are given in Table 5. In general, spore output
and germination rate decreased rapidly from
2.0-10.5 % HZE-I and HZR-I and from 0.1-1.8 %
HZE-II, HZR-II, AFE and AFR (Fig. 5, Table 5).
There was no spore discharge after 60-80 % in Padina
tetrastromatica, and Gracilaria corticata and after
20-30 % in Hypnea valentiae, Jania rubens and
Amphiroa fragilissima exposed to HZE-I and HZR-I.
Similarly spore liberation was not seen in 5 algae after
2-10 % HZE-II and HZR-II and after 2-25 % AFE and
AFR. The EC50 values estimated for spore germination
Fig. 5 — Shedding and germination of spores in Hypnea valentiae exposed to HZE-I (A) and AFE (B).
64
Indian J. Mar. Sci., Vol. 32, No. 1, March 2003
were slightly less than those of spore output
(Table 5).
Sporeling growth and survival
Figure 6 shows the growth changes observed for
25 d in sporelings of Gracilaria corticata exposed to
HZE-I. The sporelings of the 3 algae tested, Padina
tetrastromatica, Gracilaria corticata and Hypnea
valentiate, tolerated low concentrations of effluents
and maximum growth retardation was observed at
10 % HZE-I and 0.25-1.0 % HZE-II and AFE. Similarly 100 % sporeling mortality was observed after 5 d
at 15 % HZE-I and 4 % AFE and after 10 d at 0.5 %
HZE-II. Further, the median effective and lethal concentrations of the 3 effluents for growth (0.001-2.5 %)
and survival (0.65-13.2 %) of the sporelings are very
low (Table 6).
Discussion
Literature on the effects of industrial wastes on marine macroalgae is scanty7,25. The chemical composition of Hindustan zinc smelter (HZE-I and II) and
alum factory (AFE)effluents was reported together
with the data collected on diatoms 15,16. These observations reveal that the liquid wastes of these two industries contain a mixture of toxic heavy metals and
Table 5 — 24 h EC50 values estimated for the liberation and germination of spores from fertile thallai of brown and red algae exposed to
industrial wastes
Algae
B
A
Concentration of effluents and residues (%)
AFE
HZR-I
HZR-II
B
A
B
A
B
A
B
10.0
1.4
1.0
1.8
1.5
10.1
8.0
1.0
0.6
1.0
0.8
10.0
8.0
4.0
4.0
1.1
1.0
0.5
0.3
0.8
0.7
0.4
0.2
1.2
1.2
1.2
1.2
1.0
0.9
1.0
0.9
8.2
8.0
4.5
4.0
7.8
7.5
3.5
3.0
0.5
0.4
0.4
0.2
0.3
0.3
0.3
0.2
0.7
0.7
0.5
0.5
0.5
0.5
0.3
0.3
HZE-I
A
Padina
10.0
tetrastromatica
Gracilaria corticata
10.2
Hypnea valentiae
8.2
Jania rubens
5.1
Amphiroa fragilissima 4.6
HZE-II
AFR
A
B
A = Spore liberation; B = spore germination
GRACILARIA CORTICATA
Fig. 6 — Effect of HZE-I (A) and HZE-II (B) on the growth of sporlings of Gracilaria corticata [insets show the regressions drawn for
estimating EC50 values].
Murty & Rao : Effects of industrial wastes on macroalgae
Table 6 — 72 h EC50 and 72 h LC50 values estimated for
sporelings of three algae exposed to Industrial effluents
Algae
Padina
tetrastromatica
Gracilaria
corticata
Hypnea valentiae
Effluent concentration (%)
HZE-I
HZE-II
AFE
EC50 LC50 EC50
LC50 EC50 LC50
2.5
12.0
0.01
0.80
0.20
1.5
2.5
13.2
0.01
0.80
0.25
1.6
2.5
9.0
0.001
0.65
0.20
1.4
nutrients (NO3, NO2 and PO4 varied from 20-350 µ g l–1).
In HZE-I and II, Zn, Mn, Fe, Cu, Cd contents15 varied
from 1.23-106.28 mg l-1 and Pb, Co, Ni and Ch from
0.14-0.81mg l-1 and the concentrations of Zn, Mn, Cu,
Cd, Pb, Co and Ni were highest in HZE-II than in
HZE-I. In alum factory effluent (AFE), the concentrations16 of Cu, Ch, Zn, Mn ranged from 1.06-5.14 mg l-1
and Ni and Co from 0.2-4.0 mg l-1 and these concentrations were more than those of HZE-I. In the present
study on macroalgae of Visakhapatnam coastline,
(Figs 1-4, Tables 1-4) retardation in growth was found
from very low concentrations of the effluents and
residues (Table 1) and from 2.5 to 25 % HZE and R-I
and 0.25-8.0 % HZE and R-II and AFE and R, maximal inhibition (50-90 %) in growth rate was found
and at the highest doses tested, the growth rate slowed
down further and growth stabilization (Figs. 1-4) and
death of the algae (Table 4) occurred. The
72 h EC50 and LC50 values (Table 3) also showed the
critical levels of the two industrial wastes responsible
for causing the sublethal and lethal effects on the fully
grown thalli of the 9 algae tested. These toxic responses observed may be due to the presence of high
concentrations of heavy metals in the zinc smelter and
alum factory wastes15,16. The order of toxicity observed for the 9 algae investigated is HZR-II >
HZE-II > AFR > AFE > HZR-I > HZE-I.
In studies on reproductive activity, tetraspore discharge from 7 algae (Fig.5 and Table 5) declined from
2.5 to 10.5 % HZE-I and HZR-I and from 0.1 to 1.5 %
HZE-II and HZR-II, AFE and AFR, conforming to
the adverse effects observed in other pollution studies
on spore shedding13,14. As observed in growth and
survival experiments of mature algae (Tables 3,4),
HZE-II and HZR-II are more toxic even to the liberation of spores from fertile thalli. The low EC50 values
obtained for germination (Table 5) further indicate
that the division of spores was also affected by the
industrial wastes.
The growth and survival of sporelings were affected (Fig. 6 and Table 6) at concentrations 4-150
65
times lower than those observed for mature plants
(Table 3). Though one must be cautious to extrapolate
the laboratory experiments to field conditions, the
above results on growth and survival of different
stages in the ecological life history of macroalgae reveal that the spores and sporelings are more sensitive
and they are eliminated first from the natural seaweed
growing habitats than the fully grown plants, if exposed to the industrial pollutants.
In pollution studies carried out in India on marine
algal communities3,7 , the green algae were found to be
the most tolerant to pollution, than the brown and red
algae. The sublethal and lethal effects observed in the
present study (Table 3) and in other experimental
studies13,14 agree with the above findings, since the
green algae, Ulva fasciata, and Chaetomorpha
antennina tolerated highest test concentrations, than
the brown and red algae. The brown algae Sargassum
polycystum and Padina tetrastromatica, are moderately tolerant and the calcified red algae Jania rubens
and Amphiroa fragilissima and the filamentous
Centroceras clavulatum are the least resistant to the
industrial pollutants tested. These observations provide evidence for the absence of many brown (Dictyota
dichotoma, Chnoospora minima, Rosenvingea nhatrangensis) and red (Liagora spp., Grateloupia
filicina) algae and reduction in dominance of many
other algae in the coastal habitats of Visakhapatnam
in recent years. These findings also indicate that there
will be a great threat not only to the marine algal
communities, but to other organisms of the Visakhapatnam coast, if the heavy metal levels further increase in the inshore waters and if pollution is continued unabated.
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