IV. DISCUSSION

DISCUSSION

In recent years, pollution of water has become one of the most significant

environmental problems in the world. Today there is a great concern for rapidly

deteriorating quality of water. Most of the rivers and freshwater streams in India

are badly polluted by industrial wastes or effluents. The effluents produce physical,

chemical or biological changes in water. In order to recognise and predict hazardous

effect caused by human activities, effective and reliable monitoring systems are

required. Biological methods can be applied in predicting the impact of pollutants in

aquatic ecosystem

Algae are potential pollution indicators since they respond either by

stimulation or inhibition or by both to the toxicants affecting water quality (Rajendran

and Venugopalan, 1983). The factors that cause varied responses are concentration

of the toxicant, duration of exposure and sensitivity of the test species.

Algal assays were first proposed by Skulberg (1962) and in recent years,

have been used widely to evaluate nutrient status of a variety of water bodies

(Anon, 1969; Bartsch, 1971; Maloney etal., 1972; Tunzi, 1972; Forsberg, 1972,

Cain and Trainor, 1973; Chiaudani and Vighi, 1974; Miller et a/., 1974; Koltz et a/.,

1975). Since algae are the primary producers in the aquatic food chain and are

more sensitive to contaminants than fish or invertebrates, algal assays have an

indispensable role in water pollution monitoring (Wong, 1995). These assays are

considered as a supplement to chemical analysis in the assessment of pollution

and are more sensitive than Daphnia tests for monitoring toxicity in aquatic

environments (Baun et a/., 1998).

Acute toxicity tests are of short duration, typically representing a small

fraction of the life time of the organisms, hence do not picture the complete

consequences of the toxicants in the culture medium (Patin, 1982). Hence long-

term experiments for a period of 21 days were designed for the algal assays.

The present investigation was undertaken with an objective to assess

the impact of different industrial effluents on the growth and metabolism of selected

phytoplankters. in addition to this, the water quality monitoring of the waterways

that receive the effluent was also conducted. For the present study, the algal species

selected were Chlorella ellipsoidea Gerneck, Ankistrodesmus falcatus (Corda.)

Ralfs, Scenedesmus brjuga (Turp.) Lagerheim, Haematococcus laccustris (Girod.)

Rostafinski and Chlorococcum humicola (Naeg.) Rabenhorst. The effluents taken

were distillery effluent, pulp-paper mill effluent and petro-chemical factory effluent.

4.1 Distillery effluent

Analysis of physicochemical parameters of the distillery effluent revealed

that the pH of the effluent remained in the permissible range (pH 5.5 to 9.0; IS:

2490,1982; MOEF, schedule VI 1993). Ray (1961), David and Ray (1966),

Bhaskaran (1959), Verma and Mathur (1 974) and Gill and Toor (1976) reported low

pH values for distillery effluent. The colour of the effluent was dark brown and was

not according to the standards (MOEF, 1993). Dissolved oxygen (DO) was totally

absent in the effluent. The absence of dissolved oxygen indicates the poor quality

of the distillery effluent.

The biochemical oxygen demand (BOD) of the effluent was very high

1600 mg L-' which was significantly far above the tolerant limit (30 mg L-'; MOEF,

1993; IS: 2490, 1981). Similarly chemical oxygen demand (COD) of the effluent

was also very high (39,360 mg L-'), and was far ahead of the standards (250 mg L-';

MOEF, 1993; IS: 2490, 1981). The sulphate concentration was low in the distillery

effluent (24 mg L-') and was less than the effluent standards (400 mg L-I). The

chloride content, 5048.1 mg L-', was many fold higher than the tolerance limit (600 mg L-';

MOEF. 1993; IS: 2490, 1981; CPCB, 1979). Nitrites and nitrates were totally absent

in the effluent. In addition to nitrogenous compounds, phosphate was also not

detected in the effluent.

The concentration of silicate in the effluent was 9.0 mg L-'. Sodium was

absent in the effluent while 2.8 mg L ~ ' potassium was detected in the sample.

Concentration of magnesium and calcium were very high in the effluent and the

values were 1742.5 mg L ~ ' and 1138.28 mg L-' respectively. The total dissolved

solids estimated in the effluent sample was 56,800 mg L-'. The quantity of organic

carbon was very high and was 3000 mg L-'.

Cell multiplication pattern in the five microalgae recorded growth

stimulation in lower concentrations of the distillery effluent, while higher

concentrations arrested the population growth in all the phytoplankton species.

Among the algal species, Ankistrodesmus falcatus (Corda.) Ralfs exhibited

increased growth in concentrations ranging from 0.05% to 0.5% of distillery effluent,

while in the remaining four members, Chlorella ellipsoidea Gerneck, Scenedesmus

bijuga (Turp.) Lagerheim, Haematococcus laccustris (Girod.) Rostafinski, and

Chlorococcum humicola, (Naeg.) Rabenhorst growth enhancement was noticed up

to 0.25% effluent. The optimum concentration required for growth was 0.1%

concentration in the tested species. The decreased growth rate of test organisms

at higher levels of the effluent may be attributed to its high BOD, COD and other

characteristics that are detrimental to the growth of algae. Verma and Shukla (1969)

reported that high BOD. COD and low level of dissolved oxygen make the undiluted

sugar factory effluent unfit to support any form of life in them.

Presence of various elements viz. K, Mg, Ca, Si etc. can promote the

algal growth in lower concentrations. Magnesium is an important constituent of

photosynthetic pigment and the phytoplankton requires magnesium for the growth

(Venkataraman, 1969). Literature survey revealed that lower concentrations of

magnesium could intensify the growth in different algae (Rodhe, 1948 and Natarajan

1 960).

Another major nutrient present in the distillery effluent was calcium.

Calcium plays an important role in the maintenance of plasma membrane, cell wall

etc. Variations in calcium concentration found to affect the growth of algae (Hutner,

1948; Natarajan, 1960; Groves and Kostir, 1961; Rahimian, 1972; Kong eta/., 1999).

Lower concentrations stimulated the growth, while higher concentrations inhibited

the growth.

The distillery effluent sample was rich in organic carbon. The importance

of organic carbon sources in the algal metabolism has been discussed by Pearsall

and Bengey (l940), Doyle ,(1943); Algues, (1946); Myers, (1951); Fogg and Wotfe*

(1954) and Denforth, (1962). Along with other constituents organic carbon content

in the distillery effluent enhanced the growth in lower concentrations.

Patil (1998) reviewed the impact of spent wash on the growth of the

algae. He reported that lower concentrations of the spent wash stimulated the growth

in Spirulina species and Oscillatoria species while higher concentrations inhibited

the growth. Rao and Vidyakumari (1979) documented that high level of chloride

content adversely affects the algal growth. Earlier literatures indicate the reduced

growth of Chlorella vulgaris exposed to raw cane sugar effluent (Benitez, 1979;

Travieso et a/. 1996).

The enhanced growth of test organisms in lower concentrations of

distillery effluent may be due to the stimulatory effect exerted by the different

ingredients present in the effluent. Travieso et al. (1999) reported a similar result in

Chlorella vulgar~s Tanti-Charoen et a/. (1993) and Thangaraj and Kulandaivelu

(1994) supported the same view. Lefe bvre et a/. (1996) observed that fish farm

effluents stimulated the growth in marine diatoms. Growth stimulation in

phytoplankters with low concentrations of latex concentrate effluent was studied

by Yusoff e l a/. (1996). Studies of Aidar et al. (1997) and Smith et al. (1997) also

145 .-

revealed growth stimulation in algae at lower concentrations of different effluents.ln

a similar report, Gopinathan et al. (1994) recorded the growth enhancement in

Tetraselmis gracilis in the beginning of the assay with lower level of thermal effluent.

Bioassays of fish with distillery effluent confirmed that concentrated

elfluent is toxic to fish because of the low pH, low DO values etc. (Gill and Toor,

1976). Shinde and Trivedi (1983) in their studies on the higher plants noticed the

adverse effect of higher concentrations of distillery effluent on the agronomical

characteristics of Abelmoschus esculentus and Zea mays along with the hazardous

changes in the soil.

The results obtained with the distillery effluent in the present investigation

are in accordance with earlier reports. Chlorella ellipsoidea Gerneck showed initial

growth stimulation up to 1 .O% concentration. Reduction in cell muliplication in higher

levels of effluent might have been due to colour, low pH, low dissolved oxygen and

high concentration of other organic and inorganic components observed in the

distillery effluent.

Phytoplankters are the most important primary producers of aquatic

ecosystem. Considering the fresh water environment, algae carry out 60% of the

total carbon production. Discharge of different effluents alters the productivity of

the receiving water bodies.

Distillery effluents slowed down the carbon production in all the

concentrations in the beginning of the experiment in Chlorella ellipsoidea Gerneck,

Ankistrodesmus falcatus (Corda.) Ralfs and Haematococcus laccustris (Girod.)

Rostafinski. However, an enhancement of carbon production was noticed in the

later part of the studies. An induction in carbon fixation was recorded in

Scenedesmus bijuga (Turp.) Lagerheim and Chlorococcum humicola, (Naeg.)

Rabenhorst in lower concentrations at the early stages itself. In all the tested species

stimulation in carbon production was limited to lower concentrations, while higher

concentration lowered the productivity. Aidar et al. (1997) observed an inhibition of

primary production in phytoplankton at higher concentrations of laundry effluent.

Treatment with latex concentrate effluent showed significantly higher

productivity than the control in lower concentrations (Yusoff et a/., 1996). Laundry

effluent also recorded same trend in primaly production (Aidar et al. , 1997). Schwartz

and Gruendhing (1985) opined that high organic carbon content could enhance the

productivity of phytoplankton. The distillery effluent selected in the present study

contained high concentration of organic carbon, which in turn might have contributed

thehigh rate of carbon production.

The photosynthesising cells are characterized by the presence of green

pigments. These coloured organic compounds are the most important component

of the chloroplast lamella. The pigment content of the microalgae has great

importance in productivity studies.

Wide variations in the concentrations of chlorophyllous pigments were

revealed by the test algae treated with different concentrations of the effluent during

the present investigation. Lower concentrations of the distillery effluent stimulated

pigment production in the algal cells than the control. In Chlorella ellipsoidea

Gerneck, stimulation in chlorophyll a occurred, after an initial inhibition. Almost

similar pattern of enhancement in chlorophyll a was noticed in Ankistrodesmus

falcatus (Corda.) Ralfs, Scenedesmus bijuga (Turp.) Lagerheim, Haematococcus

laccustris (Girod.) Rostafinski and Chlorococcum humicola, (Naeg.) Rabenhorst.

In all the microalgae reduction in chlorophyll a content was depicted in higher

concentrations of the distillery effluent.

In the present investigation, an enhancement of the accessory pigments

chlorophyll b, chlorophyll c and carotenoids was recorded in lower concentrations,

while higher concentrations imparted reduction.

Smith et al. (1988), Kobbia et a/. (1995), Yusoff et a/. (1996) and Aidar et al.

(1997) reported the enhancement of pigment content in lower concentrations of

latex concentrate effluent. However Benitez,(1979) and Travieso et a/. (1996) noticed

the reduction in chlorophyll content at higher concentrations of cane sugar effluent.

Aidar et a/. (1997) documented the retarding effect of higher concentrations of the

laundry effluent in the synthesis of chlorophyll a. Inhibitory effect of higher level of

calcium on the formation of chlorophyll a was revealed by Zhang and Prepas (1996).

The biochemical compounds vit. the protein and carbohydrate exhibited

varied responses with different concentrations of the distillery effluent. Reduction

in protein content was observed towards the end of the bioassay in Ankistrodesmus

falcatus (Corda.) Ralfs, Scenedesmus bijuga (Turp.) Lagerheirn and Haematococcus

laccustris (Girod.) Rostafinski. Reduction in protein content was not recorded in

Chlorella ell~psoidea Gerneck and Chlorococcum humicola (Naeg.) Rabenhorst.

Carbohydrate content in the microalgae of the control as well as the

treated cells showed increasing trend till the last day in Chlorella ellipsoidea Gerneck,

Ankistiodesmus falcatus (Corda.) Ralfs, Haematococcus laccustris (Girod.)

Rostafinski and Chlorococcum humicola (Naeg.) Rabenhorst. In Scenedesmus

bijuga (Turp.) Lagerheim the carbohydrate content showed reduction on the final day.

: 14%

Both protein and carbohydrate content of the algae showed enhancement

similar to cell number, carbon production and pigment content in lower

concentrations. Protein and carbohydrate content in 1 .O% and 1.5% concentrations

of the distillery effluent showed shoot up in the beginning. Since the distillery effluent

is rich in organic carbon and other minerals, the cells may have showed the tendency

of absorption of more nutrients from the medium quickly after the exposure.

According to Pistocchi et a/. (1997) increased carbohydrate production at higher

concentrations could be attributed to extracellular rather than intracellular

carbohydrate.

4.2 Pulp-paper mill effluent

The physico-chemical analysis of the pulp- paper mill effluent showed

that the effluent was slightly alkaline (pH 7.4), which occupied in the permissible

limit (pH 5.5 to 9.0; IS: 2490, 1981, MOEF Schedule VI, 1993). The effluent was

brown in colour and was against the standards (MOEF, 1993). Dissolved oxygen in

the pulp-paper mill effluent was very low, 2.5 mg L-l and was below the standards

(CPCB, 1979).

The biochemical oxygen demand (BOD) of the effluent sample was 270 mg L-',

which was fairly above the tolerance limit (MOEF 1993; IS: 2490, 1981). The

chemical oxygen demand (COD) recorded was 640 mg L-'. This too was above the

tolerance limit (250 mg L1, MOEF 1993; IS: 2490, 1981). However, the sulphate

content in the effluent was 98 mg L-I and was lower than the permissible liml(400 mg L-',

CPCB, 1979). In the pulp-paper mill effluent the chloride content was 294.2 mg L-'

and below the standards 1000 mg L-' (MOEF, 1993) and 600 mg L-' (CPCB, 1979).

Nitrite and nitrate was not detected in the sample, while the effluent contained

phosphates and silicates. Sodium and potassium were obsewed in the effluent

sample. There are no specific standards for sodium and potassium. The

concentrations of magnesium and calcium in the sample were 26.42 mg L-' and

61.72 mg L 1 respectively. Total dissolved solids was 850 mg L-' that was lower

than the standards. The effluent contained 0.014 mg L-' mercury, which was slightly

above the standard (0.01 mg L-'). The pollution load from the pulp-paper mill was

found to be very high and contained biodegradable organic substances and other

pollutants (Klein, 1957; Todd, 1970; Hunter and Faust, 1971; Yen, 1996).

The pulp-paper mill effluent added to the medium recorded stimulation

as well as inhibition to the microalgae. The five different unialgal cultures tested

with the pulp-paper mill effluent reacted differently with different concentrations of

the effluent. All the algal species exhibited optimum population growth in 0.1% of

the effluent. In the case of Ankistrodesmus falcatus (Corda.) Ralfs and

Scenedesmus bijuga (Turp.) Lagerheim, 0.5% concentration was growth stimulating

while in Chlorella ellipsoidea Gerneck, Haematococcus laccustris (Girod.)

Rostafinski and Chlorococcum humicola, (Naeg.) Rabenhorst, concentrations higher

than 0.25% retarded the growth. Common characteristic feature noticed was the

inhibition of growth in all the test species at higher concentrations of the effluent.

Growth is an orderly increase of all the components of an organism. It

was observed that the microalgal cells with smaller size had the capacity to grow

faster,thus agreeing with the observation of Raymond (1980). The increase in

algal biomass over a particular, usually a period of week or month may be referred

as "growth or new production" (Eppley and Peterson, 1979). Thus growth is the

increase in the pool size of particulate organic carbon tied up in the phytoplankton.

Earlier investigators like Palmer and Maloney (1955), Rachlin and Farran

(1974). Cain et a/. (1979), Anita etal. (1991) and Berman and Chava (1999) proved

the growth stimulation of the algae at lower concentrations of various effluents.

Schmager (1979) commented that lower concentrations of chlorine could induce

growth, while higher concentrations inhibited the growth in a heterogenous algal

culture. Rao and Vidyakumari (1979), Travieso etal. (1996) and Patil(1998) reported

the reduction of algal growth with higher concentrations of distillery effluent.

The pulp-paper mill effluent contains sodium. Allen (1952) found the

need of sodium for the growth of various blue green algae. The phosphate present

in the effluent is also a growth-inducing factor. Rodhe (1948), Lund (1950), and

Goldberg et al. (1951) revealed the luxurious consumption of phosphorus by algae.

An (2003) commented that phosphorus is a potential limiting element for algal growth.

Most of the organic and inorganic components present in the pulp-paper

mill effluent at lower concentrations might have favoured the cell multiplication. But

at higher concentrations of the effluent, the mineral composition of the effluent

increased and these might have reacted adversely with cell multiplication. Verma

and Shukla (1969) too shared this view.

Results of the present investigation made it clear that the pulp - paper

mill effluent has a significant effect on both GPP and NPP of treated algae. In

Chlorella ellipsoidea Gerneck. Scenedesmus bijuga (Turp.) Lagerheim and

Chlorococcum humicola. (Naeg.) Rabenhorst, lower concentrations intensified both

:: 151 ..

GPP and NPP. Simultaneously, reduction in carbon production was recorded in

higher concentrations. This is in accordance with the reports of Asma and Mathew

(1995),Yusoff et a/. (1996), Aidar et a1.(1997) and Valsamma Joseph (2000). 1

Ankistrodesmus falcatus (Corda.) Ralfs and Haematococcus laccustris

(Girod.) Rostafinski exhibited reduction in GPP and NPP in all cocentrations. The

reduction in carbon production may be attributed to the toxic effect developed in

the photosynthetic pigment. Wong et al. (1994) reported structural damages in the

chloroplast of Chlorella fusca treated with the petrochemical factory effluent.

Reduction in carbon production of treated cells was recorded by earlier workers

like Mac farlane etal. (1972), Subramanian et a/. (1979), Rajendran and Venugopbn (1983).

Carbon production showed an increase with the age of culture. This

may be due to the increased cell number in the aged culture. The increased number

of photosynthesising cells could lead to more primary production.

The photosynthesising cells contain large amount of pigments. These

include chlorophyllous pigments like chlorophyll a, chlorophyll b, chlorophyll c and

non- chlorophyllous pigments like carotenoids. Photosynthetic rate per unit

chlorophyll is often used as an indicator of the physiological state of algal

assemblage (Perry et al. 1981). If chlorophyllous and non- chlorophyllous pigments

are altered by the treatment, it will adversely influence the rate of photosynthesis

and will decrease oxygen production of microalgal cultures. Thus changes incur in

the pigment could lead to an unbalanced physiological state.

Great fluctuations in the concentration of the chlorophyllous pigments

were recognrzed throughout the experimental period, in relation to various

152

concentrations of the effluent. In most cases, the lower concentrations of the effluent

displayed an increased pigment content than the control, as noticed in Scenedesmus

bijuga, (Turp.) Lagerheim, Haematococcus laccustris (Girod.) Rostafinski, and

Chlorococcum humicola (Naeg.) Rabenhorst. Stimulation in pigment content was

observed in all concentrations in Chlorella ellipsoidea Gerneck and Ankistrodesmus

falcatus (Corda.) Ralfs.

Non-chlorophyllous pigments like carotenoids may also serve as a

potential light harvesting pigment. These accessory pigments in algae and higher

plants increase the absorption spectrum over wider wavelength, than would exist if

chlorophyll was the sole absorbing pigments (Harris, 1978). Changes in the

caroteniod content of the microalgae will affect the photosynthetic process.

The treated cells showed inhibition of pigment content and photosynthetic

rate. In some cases the activity of the pigment was inhibited. Abou-waly et al.

(1991 b) reported that chlorophyll activity was inhibited more than the chlorophyll

content when treated with the toxicant. In the present study, the quantity of pigment

was estimated in all cases and in some cases decrease in the carbon production in

contrary to the increased chlorophyll content was observed in some cases. This

suggests the detrimental effect of the effluent on the chlorophyll activity than on its

production.

Gopinathan et al. (1994) documented colinearity between carbon

production and photosynthetic pigments. The colinearity in pigment content and

primary productivity was observed in Chlorella ellipsoidea Gerneck and

Scenedesmus bijuga (Turp). Lagerheim. It was not noticed in Ankistrodesmus

falcatus (Corda.) Ralfs and Naematococcus laccustris (Girod.) Rostafinski.

The protein and carbohydrate content of the five different algal species

exhibited wide variations with different concentrations of pulp-paper mill effluent.

The biochemical compound, protein enhanced in most of the concentrations tried.

After an initial inhibition in protein production, Chlorella ellipsoidea Gerneck showed

stimulation in all treated cells. In Ankistrodesmus falcatus (Corda.) Ralfs,

Scenedesmus bijuga (Turp.) Lagerheim, Haematococcus laccustris (Girod.)

Rostafinski and Chlorococcum humicola (Naeg.) Rabenhorst higher concentrations

inhibited the protein content. Decrease in protein content was noticed on 21stday,

in control as well as in treated cells

Carbohydrate content enhanced in lower concentrations of pulp - paper

mill effluent in Chlorella ellipsoidea Gerneck, Haematococcus laccustris (Girod.)

Rostafinski and Chlorococcum humicola. (Naeg.) Rabenhorst, while higher

concentrations reduced it. In Ankistrodesmus falcatus (Corda.) Ralfs and

Scenedesmus bijuga (Turp.) Lagerheim the carbohydrate content accelerated in

all concentrations. The effluent may undergo biodegradation and and the resulting

compounds may act as nutrients in the medium. Naturally, the treated algal cells

may have absorbed more nutrients that resulted in high carbohydrate content in

the treated cells

4.3. Petrochemical factory eff luent

Analysis of physico-chemical parameters of the petrochemical factory

effluent revealed that the effluent was alkaline with a pH of 8.33, which was within

the permitted range (IS: 2490, 1981, MOEF 1993, Schedule VI). The effluent was

colourless. The dissolved oxygen in the petrochemical factory effluent was 8.7 mg k'

which was better than the other two effluents, and was above the standards

(CPCB, 1979).

The biochemical oxygen demand (BOD) of the effluent was 10.4 mg L-'

and below the tolerance limit (30 mg L-', MOEF 1993; IS: 2490, 1981). The chemical

oxygen demand of the petrochemical effluent was also very low 48 mg L-', and was

lower than the tolerance limit (250 mgL-l, MOEF 1993; IS: 2490, 1981). Though

BOD and COD of the effluent were low, the concentration of sulphate was very

high in the effluent sample. The sulphate content was 2420 mg L-', which exceeded

the tolerance limit (1000 mg L-l; MOEF, 1993; 600 mg L-l; CPCB, 1979). The chloride

and phosphate content in the effluent were 49.63 mg L-I and 0.4 mg L-1 respectively.

The quantity of silicate was found to be 0.04 mg L-l.

The sample contained 1.38 mg L-I nitrate, while nitrite was not detected

in the sample. Sodium and potassium were also present in the effluent. The amount

of total dissolved solids in the sample was higher than the permitted limit (2100 rng L-',

MOEF, 1993, IS: 2490, 1981). Mercury was present in the sample and it recorded

0.013 mg L ' which was above the permissible limit (0.01 mg L-l, MOEF, 1993). The

presence of phenol was detected in the sample and was 0.85 mg L-' that was below

the tolerance limit (1 .O mg L-', MOEF, 1993; 2.0 mg L-l, CPCB, 1979).

Growth pattern in the five test species indicated a negative impact with

higher concentrations of the effluent. The algal assays revealed that the lower

concentrations could stimulate the growth in the test species. The most appropriate

growth was observed in 0.1% of the effluent. Chlorella ellipsoidea Gerneck was the

most tolerant species, while Haematococcus laccustns (Girod.) Rostafinski was

susceptible to petrochemical factory effluent, which showed growth stimulation only

upto 0.25% concentration. In Chlorella ellipsoidea Gerneck growth stimulation was

observed even in 0.75% of effluent, where as 0.5% concentration was the highest

concentration which showed growth enhancement in other test species viz.

Ankistrodesrnus falcatus (Corda.) Ralfs and Chlorococcum humicola (Naeg.)

Rabenhorst. The higher concentrations, 1 .O% and 1.5% inhibited cell multiplication.

Walsh and Garnas (1979) opined that the stimulation of algal growth by

the petrochemical effluent is due to its organic content. Industrial effluents can

cause stimulation or toxicity and structural damages to algae (Walsh etal., 1980;

Wong et a/., 1994, 1995). Low molecular weight hydrocarbons were found to

stimulate phytoplankton growth depending upon the species (Dunstan, 1975).

Decrease in growth with increasing concentrations of the petrochemical factory

effluent was recorded by Soto et a/. (1977), Dahl etal. (1983), Zachleder et al.

(1983), Vandermeulen and Lee (1986), El-Dib et a1 (1 997) and Joseph and Joseph

(2001). Ghosh (1983) studied the toxic effect of phenol on fish. Phenols have a

highly variable effect on aquatic plants. Some phenolic compounds may actually

stimulate the growth at low concentrations, where as others are consistently toxic

(Moore and Ramarnoorthy, 1984). In OscIllatoria quadripuctulata. and Chlorella

pyrenoidosa lower concentrations of phenol stimulated the growth,however higher

concentrations were reported to be inhibitory to the algae (Valsamma Joseph, 2000).

Tadros et a1 (1994) suggested that the growth in Chlorella ellipsoidea Gerneck

was affected by 0.5%, 01% and 0.2% of phenol.

The present investigation also supports the view that lower

concentrations of petrochemical effluent have a growth stimulatory effect.

The high algal biomass formation was reported with refinery effluent.

The stimulatory effect is due to its organic fraction (Walsh and Garnas, 1979).

The petrochemical factory effluent altered the carbon production in all

the treated algal species. All the treated cells of Chlorella ellipsoidea Gerneck,

Scenedesmus bijuga (Turp.) Lagerheim and Chlorococcum humicola (Naeg.)

Rabenhorst exhibited enhanced gross and net carbon production in all treated

concentrations ranging from 0.05% to 1.5%. Carbon production in Ankistrodesmus

falcatus (Corda.) Ralfs and Haematococcus laccustris (Girod.) Rostafinski showed

enhancement in lower concentrations of petrochemical factory effluent. Higher

concentrations retarded the carbon production.

The Increase in carbon production observed in the higher concentrations

of the effluent in Haematococcus laccustris (Girod.) Rostafinski may be due to

acclimation. In a study on the acclimation of algal community to zinc toxicity, it was

concluded that the acclimation of the test organism to a toxicant has an important

effect on its response to toxicity (Wang, 1986). The tolerance of algae to

petrochemical factory effluent was found to be species specific. The mechanism

involved may be e~ther storage or metabolic utilization (Karydis, 1979).

Decrease in gross and net carbon production in Ankistrodesmus falcatus

(Corda.) Ralfs and Haernatococcus laccustris (Girod.) Rostafinski showed similarity

with the investigations of Asma and Mathew (1995) Yusoff ef a/. (1996) and Aidar

et a/. (1997).

The photosynthetic pigments, chlorophyll a and chlorophyll c retarded

in Chlorella ellipso~dea Gerneck on exposure to higher concentrations, while

chlorophyll b and carotenoids recorded enhancement. Higher concentrations of

the effluent lowered the photosynthetic pigments in Ankistrodesmus falcatus (Corda.)

Ralfs, Chlorococcum humicola (Naeg.) Rabenhorst, Scenedesrnus bijuga (Turp.)

Lagerheim and Haematococcus laccustr~s (Girod.) Rostafinski.

The observed toxicity in the pigment production may be explained by

the bioavailable contaminants absorbed by the algal cells from the effluent. Wong

et al. (1994) recorded that the stress effect of organic toxicants on the fine structure

of algae is the abnormal build up of large starch grains and mass destruction of

organelles. The interference with the oxidative phosphorylation, photosynthesis,

respiration, protein and nucleic acid synthesis were detected in Chlorella cells when

exposed to toxicants such as DDTor PCB (Fedtke, 1982; Hoagland and Duke, 1982).

The decrease in chlorophyll a pigment of phytoplankton with the increase

in concentration of the toxicant was reported by Bharati et a/. (1979), Tukaj (1987),

Morales-Loo and Goutz (1990), Herman ef a1 (1991) and El-Dib eta/. (1997). Lemee

et al. (1997) suggested that ecotoxicity could reduce chlorophyll a content. Contrarily

Hein and Rieman (1995) noticed that chlorophyll a pigment remained unchanged in

the higher concentrations of toxicants. At higher concentration of the effluent the

mineral contents will increase considerably and this may interact adversely with

the physiological condition necessary for the synthesis of chlorophyll.

The blochemica1 compounds protein and carbohydrate content showed

variations when treated with petrochemical factory effluent. Lower concentrations

stimulated the protein content in Chlorella ellipsoidea Gerneck, Ankistrodesmus

falcatus (Corda.) Ralfs and Scenedesmus bijuga (Turp.) Lagerheim. All the

concentrations administered enhanced the protein content in Haematococcus

laccustris (Girod.) Rostafinski and Chlorococcum humicola. (Naeg.) Rabenhorst.

Carbohydrate content showed higher values in the lower concentrations exposed

Chlorella ellipsoidea Gerneck, Scenedesmus bfjuga (Turp.) Lagerheim,

Haematococcus laccustris (Girod.) Rostafinski and Chlorococcum humicola (Naeg.)

Rabenhorst cells. All the concentrations stimulated the carbohydrate content in

Ankistrodesmus falcatus (Corda) Ralfs.

The effluent may undergo biodegradation and the resulting compounds

may act as nutrients in the medium. Naturally, the treated cells may absorb more

nutrients during the exponential growth phase resulting in the increased protein content.

Cochrane (1958) reported that the increase in total protein- nitrogen is

a real sign of increase in cytoplasm. Collyer and Fogg (1955), Lewin and Guillard

(1963) were of the opinion that the decrease in protein level was caused by an

insufficient nitrogen level in the nutritive medium. In the present investigation, protein

content in Chlorella ellipsoidea Gerneck, treated with higher concentrations showed

reduced protein content though the control and the treated cultures were provided

with same quantity of nutrients. At higher concentrations, perhaps due to external

stress treated algal cells might not have performed well in the medium. This might

be resulted in the reduction of protein and carbohydrate content.

Inverse relationship between concentration of effluent and biochemical

compounds in algae was investigated by Tukaj (1987). The effects of petroleum

hydrocarbons on the modification of physiological and biochemical processes were

reported by Zachleder et a/. (1983), Vander meulen and Lee (1986).

The present investigation revealed that the effect of effluents on the

algae was highly different. The three effluents affected the growth in the five species

which varied with the concentration of the effluent as well as with the age of the

phytoplankton. The perturbation of the aquatic environment by a variety of pollutants

causes disturbances to the abiotic as well as biotic characters. Since algae are

representing the lower trophic level, these disturbances could be reflected in the

whole ecosystem.

4.4 Muvattupuzha river

Muvattupuzha river is one of the major perennial rivers in Central Kerala.

Muvattupuzha river empties into Cochin estuary which has a permanent opening,

Cochin bar mouth, through which tides affect the inland water courses. The pulp-

paper mill factory, Hindustan Newsprint Limited situated on the bank of the

Muvattupuzha river, discharges its effluents into the river.

The pulp-paper mill effluents carry heavy load of biodegradable organic

substances (Hunter and Faust, 1971) and other pollutants (Klein, 1957; Todd, 1970).

The major by-products of this industry consist of the breakdown products of lignin

and some amount of cellulosic material (Dugan, 1972). The effluents from the pulp

paper factories cause water pollution and affect the riverine biota.

Temperature values were minimum during post-monsoon season and

maximum during pre-monsoon period. The temperature fluctuation observed was

mainly due to the discharge of effluents and atmospheric variations. Menon et a/.

:: 160 ::

(1977) and Ramesha et a/. (1992) reported the temperature fluctuations in the

surface waters of Mangalore. The variations in temperature affect the rate of reactions.

In all the four stations, fluctuations in pH were observed. pH was \OW

during post monsoon season. pH variation in Muvattupuzha river was investigated

by Balchand and Nambisan (1986) who reported that these fluctuations in pH

occurred due to the discharge of effluent. Desirable public water supply should

have a pH as close to 7 as possible (Nelson, 1978). Webb (1982) commented the

undesirable nature of both acidic and alkaline wastewaters from paper mills for

recreation and rearing of fish and other aquatic life.

Hardness in the river water in all the stations showed low values during

monsoon. Alkalinity in station I was lower than the other stations. High values for

alkalinity at station 11, Ill, and IV were due to the impact of the elT?uents.

Salinity values were high during pre-monsoon period and low during

monsoon period. According to Abe eta/. (1996) salinityvariations in the downstream

showed correlation with tides, while upstream showed less correlation with tidal

fluctuations in Muvattupuzha river.

Free carbon dioxide produced in the natural unpolluted water can cause

acidity. In the present investigation, the concentration of free CO, was low.

Comparatively higher values were observed during post-monsoon period. Total

solids, both the suspended and dissolved solids were low in the river water as

compared to standard values. Total dissolved solids were higher during pre-monsoon

period and high values for totakuspended solids were observed in post-monsoon period.

Dissolved oxygen in all the sampling stations exhibited decreased values

and was comparatively higher during monsoon. Balchand and Nambisan (1986)

reported the same trend in Muvattupuzha river. The effluents discharged into the

river had low dissolved oxygen content, which in turn lowered the dissolved oxygen

of the river water. The current observations are in accordance with that of Votintsev

(1993) who noticed that effluents from pulp paper plants lower the oxygen content

of water. The concentration of dissolved oxygen in natural water depends on various

factors such as temperature, partial pressure of oxygen in the atmosphere, salinity,

biological processes like oxidation and reduction, degradation of organic matter,

respiration etc. Rate of depletion of oxygen has been used to investigate the quality

of water bodies Wahby et a/., 1978). In the opinion of De Sousa and Sen Gupta, (1986)

studies on salinity dependent oxygen solubility may help to elucidate the various

physical, chemical and biological processes taking place in estuarine waters.

The carbon production in the river water fluctuated seasonally. Both grass

and net production revealed higher values during monsoon period, while the values

were low during pre-monsoon period. Seasonal variations in productivity were

reported by Schallenberg and Bums (1997), Postma (1954) and Tillmann et a/. (2000).

Biochemical oxygen demand (BOD) in thesampling stations 11. Ill and IV

were comparatively higher than station I. BOD was minimum during monsoon months

and was higher during pre-monsoon period in these sites. The high BOD recorded

in the sampling stations indicates the pollution intensity of the effluent. High BOD

values in Muvattupuzha river, as a result of effluent discharge were earlier noticed

by Balchand and Nambisan (1986).

162 , .

Chemical oxygen demand (COD) values were lower during monsoon

season and higher during pre-monsoon season in all the sampling stations. The

high values of COD recorded in the Muvattupuzha river were due to the effluent

discharge from the pulp-paper mill. During monsoon month, the rainwater diluted

the effluents and it resulted in the decreased COD values from June to December.

The silicate values exhibited fluctuations during the present study. Wide

variations in salinity were also noticed during the period of study.

Nitrate and nitrite contribute about 65% of soluble form of nitrogen

(Martin, 1970). Thermodynamically nitrate is considered as the most stable form of

nitrogen in seawater (Sillen, 1961; Grasshoff. 1983). In the present investigation,

the concentration of nitrite was found to be low while higher values were noticed in

the case of nitrate. However, increased nitrite and nitrate concentration was

observed in Muvattupuzha river by Balchand and Nambisan (1986).

Phosphate content in all sampling stations showed higher values. The

increase in phosphate content observed in the river water was mainly due to effluent.

Another factor that contributed to the enhanced phosphate content was the inputs

from detergents. Balchand and Namb~san (1986) reported four, eight and three

fold increase in nitrate, nitrite and phosphate respectively in Muvattupuzha river

before and after the installation of pulp-paper mill factory. Hydrolysis of condensed

phosphates such as polyphosphates and metaphosphates produces

monophosphates. Production of monophosphates from hydrolysis is expected in

estuaries as a result of pollution from detergents (Koroleff, 1983 b).

4.5 Chitrapuzha river

Industrial effluents are one of the important sources of water pollution.

The disposal of industrial effluents without affecting the biota of the surrounding

system has become a serious concern. The limits of use and abuse of rivers and

estuaries, which supply freshwater and receive effluents from industries, are

determined by biogeochemical cycles, which can affect the water quality. Chitrapuzha

river, a subsidiary of Periyar river is a part of Cochin estuary. It receives effluents

from a major fertilizer plant, an oil refinery, and a petrochemical factory.

Analysis of physical parameters of Chitrapuzha river revealed the lowest

temperature during post monsoon period followed by monsoon period. Temperature

values were high during pre-monsoon period. Similar observations in temperature

were made by Pillai et a/. (1975) and Balakrishnan and Shynamma (1976). The

variation in temperature was mainly due to the atmospheric temperature and due

to the influence of effluents.

The pH at all the four stations showed low values during post monsoon

and pre-monsoon period. Variations in pH of any water body depend on

photosynthetic activity, discharge of industrial effluents, nature of dissolved

materials, rainfall etc. Changes occurring in pH due to chemical and other industrial

effluents render a stream unsuitable not only for recreational purpose but also for

the rearing of fish and other aquatic life (Webb, 1982). The major factor which

altered the pH in Chitrapuzha river is the discharge of effluents from the major

factories located on the banks of the river. Close monitoring of pH values enables

the identification of zones of pollution (Clark eta/., 1977). Under extreme conditions

survival of the aquatic biota becomes a serious problem. Since the tolerance level

of most organisms to alterations in the pH is quite narrow (George, 1979), the

extreme conditions would cause serious problems to the survival of the biota.

Hardness of the water exhibited high values during pre-monsoon period, compared

to other seasons, but it was not too high to cause adverse impact on the biota.

Determination of alkalinity of water is significant in many of its uses and

treatment of natural waters and wastewaters. Alkalinity showed higher values during

post-monsoon season. In all stations it was lower than 100 mg L-I, which is the

desirable limit in drinking water.

Salinity in all the stations showed increased values during pre-monsoon

season. Similar variations in salinity due to monsoon and influxes of seawater were

reported by Gopinathan (l972), Quasim and Sankaranarayanan (1972) and Mathew

and Nair (1980).

Free carbon dioxide which is formed mainly due to the activity of

microbes, was found to be low during pre-monsoon period in Chitrapuzha river.

The total suspended and dissolved solids alter the water quality, for the suspended

solids cut down the light transmission, while total dissolved solids elevate the density

of water and also retard the palatability of water. The river exhibited increased

values for total dissolved and suspended solids during pre-monsoon season.

Dissolved oxygen in fresh water is low and only 10.66 mg L-' at 30°C

under normal atmospheric pressure. The depletion of oxygen content in water leads

to the undesirable obnoxious odour in the aquatic system (Doudoroff Shumway

.- 165 ~,

and Peter, 1970; Nelson, 1978) and damage to aquatic life. Adequate dissolved

oxygen is necessary for the survival of flora and fauna. The decomposition of organic

waste and oxidation of inorganic waste may reduce the dissolved oxygen to

extremely low levels, which may prove harmful to organisms in the aquatic

environment. Johannessen and Dahl (1996) have reported a decline in dissolved

oxygen as a result of nutrient load.

In the present investigation the dissolved oxygen was low in all Stations

during pre-monsoon due to the combined effects of temperature, photosynthetic

action and biochemical oxidation of wastes entering the environment. Similar

observations were made by Babu Jose (2000) in Chitrapuzha river. Bandyopadhyay

and Dutta (1986) and De Sousa and Sen Gupta (1986) noticed the decreasing

solubility of oxygen in water with increasing salinity and temperature. The results of

the present investigation also tally with the earlier observations.

Productivity in the present work showed variations with changing

seasons. Productivity was high during post monsoon period and low during pre

monsoon period. Increased primary production during post monsoon was reported

by Chellappa (1990). Two specific features which promote high and stable

photosynthetic production are incident solar radiation and light saturation for

photosynthesis (Lewis, 1978) and high water temperature that enhanced the specific

production at optimum depth (Harris. 1978).

Eventhough BOD of the effluent discharged by petrochemical factory

remained in the tolerance limit, the high BOD values were observed in all the

sampling stations. This increased BOD values may be due to the adverse effect of

the effluent released from a major fertilizer plant and the refinery situated nearby

the petrochemical factory. The increased BOD values indicate the high degree of

pollution of the aquaticsystem.

Similar to BOD, chemical oxygen demand in four stations showed

enhanced values. The COD values were comparatively low during monsoon period

indicating the dilution occurred as a result of rainwater.

The nutrients in Chitrapuzha river showed greater values during the

present work. The silicate concentration showed higher values during pre-monsoon

and lower values were observed in post monsoon period. Fluctuations in silicate

concentrations by effluent were reported by Krishnamoorthi (1985) and Katti et al.

(2001). Similar results were obtained in the present investigation too, where silicate

content in all the stations exhibited high degree of variations.

The concentration of various forms of nitrogen is controlled by factors

like input rates, interconversion reactions occurring within the water column,

denlrification, deposition etc. Nitrates enter into the waterway through anthropogenic

sources, fertilizers and some industrial effluents. Nitrate-nitrogen in all the four

stations showed fluctuations. Manikoth and Salih (1974) recorded the variations in

nitrate-nitrogen in Cochin estuarine complex.

Industrial effluents mainly contribute to the changes in the concentration

of nitrite nitrogen. The effluent discharge from the fertilizer factory is the major

cause for the enhancement of nitrogen compounds in Chitrapuzha river. Higher

values of nitrate nitrogen in the sample stations contributed to the abundant

phytoplankton growth in these regions.

- 167

Phosphate availability in water stimulates the growth of phytoplankton.

Phosphate abundance causes phytoplankton boom, a phenomenon known as

eutrophication (Rand et al. 1986). Subsequent decay of phytoplankton causes

oxygen depletion. Relatively high concentration of phosphate during pre-monsoon

period indicates the intensity of pollution. Comparatively lower values were observed

during monsoon in the present investigation. Several workers have made similar

observations in Cochin estuary (Joseph, 1974; Lakshmanan et a/., 1987 and

Anirudhan, 1988). Babu Jose (2000) reported high concentration of phosphate at

certain part of Chitrapuzha river during monsoon period because of leaching from

land drainage.

4.6 Cochin estuary

Cochin estuary, a semi enclosed coastal body of water has free access

with open sea and within which the seawater is measurably diluted with fresh water

derived from land drainage and hence it is in full agreement with the definition of

Pritchard (1967). Cochin estuary is a tropical estuary with a chain of brackish water

lagoons and swamps and is rich in aquatic life. The major sources of fresh water

are Periyar river and its tributaries viz. Chitrapuzha and Kadambaripuzha river in

the South. A channel, about 450 m wide at Cochin gut is a permanent link with

Arabian sea which transmits the tidal energy and saline water into the estuary. The

barmouth at Azhikode also helps the estuary to interact with the sea, though the

influence is only to a lesser extent due to the shallow nature of the channel. Rainfall

and fresh water discharge influence the penetration effect of saline water into the

estuary. During southwest monsoon the estuary is virtually converted into a fresh-

water basin except in areas around the barmouth.

The effluents released into Periyar and Chitrapuzha by most of the

industries situated on their banks finally reach Cochin Estuary. On the southern

part of the estuary, a distillery (Mc Dowells Distillery) is situated, which is emptying

the effluent directly into the estuary. Distillery effluents are having low pH, high

BOD, COD, total dissolved solids and other organic and inorganic components. It

is darkly coloured

Temperature of estuaries affects the physical properties of water and

can cause stratication in ambient water. The distribution of temperature in estuaries

depends on the mixing of tidally influenced sea water (Ramamirthan and Jayaraman,

1963), flow of fresh water from rivers (Sankaranarayanan and Qasim, 1969) and

processes like exchange of heat from atmosphere and other localised phenomena.

In the present study, temperature values were low during postmonsoon

and monsoon periods and high values were observed during pre-monsoon.

Balakrishnan and Shynamma (1976) reported high water temperature in Cochin

estuary during pre-monsoon period. Similar variations in temperature were

documented by Gopinathan (1972), Pillai eta)., (1975) Kumaran and Rao (1975),

Ramamirthan et a/., (1986), Joseph (1988) and Siadasan (1996). Sankaranarayanan

and Qasim (1969) stated that influx of fresh water into the estuarine system is not

the sole factor influencing the water temperature in a estuary, but the influx of cold

water from the sea may also be a significant factor.

Low pH values were noticed in all sampling stations and these decreased

values were in correlation with the discharge of acidic distillery effluent. Earlier

workers noticed pronounced seasonal variations in pH in Cochin estuary. Anirudhan

169 .:

(1988) reported neutral pH values during monsoon months. The pH values increase

seasonally upto post monsoon period and may be attributed to the excessive

photosynthetic activity of the algae. High phytoplankton production during post-

monsoon period in Cochin estuary was recorded by Silas and Pillai (1975). Nair et al.

(1983) observed decrease in pH from marine to freshwater zone in Ashtamudy

estuary.

Hardness and alkalinity in all sampling stations showed higher values

during pre monsoon and lower values in monsoon as well as post monsoon period.

Salinity in all sampling stations exhibited very high values during the present

investigation. A comparative decrease in salinity was noticed in all stations from

June onwards. The high salinity in pre monsoon season was due to closure of the

shutters of Thannermukkam bund on the southern side of the Cochin estuary. The

opening and closing of the shutters of this bund alter many of the physical properties

of the water.

Salinity variations in Cochin estuary were reported by Quasim and

Sankaranarayanan (1972), Haridas et a/. (l973), Gopinathan (1975), Balakrishnan

and Shynamma (1976:I, Sivankutty (1972) and Gopakumar (1991). Maqbool(1993)

reported wide fluctuations in salinity at tropical estuaries due to the extreme

conditions of drought and monsoon affecting the estuarine environment. A distinct

seasonal pattern of salinity in the Ashatamudi during pre monsoon and declining

values from estuarine mouth to the riverine zone were reported by Nair et.al. (1983).

Free CO, values in all the four stations displayed lower values during

monsoon and post monsoon periods. Free CO, values were high during pre-

monsoon. The fluctuation in free CO, was due to the impact of effluents as well as

microbial respiration (Maiti, 2001 ).

Total dissolved and suspended solids were high in all stations during

pre-monsoon period and lower values were observed during monsoon and post

monsoon periods. Dissolved oxygen values highly fluctuated during the sampling

period. Stations 11, Ill and IV showed absence of dissolved oxygen during pre

monsoon season. High concentration of distillery effluent and closure of the shutters

of the Thanneermukam bund resulted in the depletion of dissolved oxygen. Another

major factor, which led to the anoxic condition, was retting of coconut husks in

these areas. According to Aziz and Nandan (1995) and Arjinkit (2000) the hypoxic

as well as anoxic condition can be resulted due to the retting of coconut husks.

Nandan (1996) reported hypoxic and anoxic conditions in the backwaters of Kerala.

Anoxic condition leading to fish death was reported recently in Cochin estuary

(Malayala Manorama. 2004). Reduction in dissolved oxygen during pre-monsoon

season in Cochin estuary was documented by earlier workers like Pillai et.al. (1975)

and Kumaran and Rao (1975).

The gross and net carbon production in all the four stations displayed

seasonal variations. In the present investigation, stations 11, Ill and IV recorded

very low carbon production. Decrease in productivity shows the depletion of biota

in these areas. Destruction of flora and fauna in the backwaters due to organic

pollution was reported by Nandan (1995). Seasonal variations in primary production

were also revealed in the present study.

Silas and Pillai, (1 975) and Nair et a/. (1975) suggested high phytoplankton

production during post monsoon period in Cochin estuary and this agrees with the

current observation. Gopinathan eta/. (1984) reported correlation between primary

productivity and factors such as phosphate, nitrate, dissolved oxygen and

temperature in Cochin estuary.

Seasonal fluctuations were observed in BOD values in the four stations

studied. Higher values were observed during pre-monsoon period. The high BOD

in these sampling stations was contributed by distillery effluent, retting of husk, the

periodical closure of bund shutters, water transport services etc. Pre-monsoon

period recorded higher values for COD and lower values were registered in the

monsoon and post monsoon period. The factors which are contributing high BOD

can promote the COD values also.

Wide fluctuations were observed in silicate concentration, which was

higher during pre-monsoon period and lower during monsoon and post monsoon

period. Gopinathan (1975) reported high silicate concentration during monsoon

period in Cochin estuary.

Nitrite and nitrate concentrations in the stations were high during pre-

monsoon season followed by monsoon and post-monsoon seasons. Increased or

decreased nitrite and nitrate content in Cochin estuary were recorded by

Sankaranarayanan and Quasim (1969), Manikoth and Salih (1974), Gopinathan

(1975), Lakshmanan et a1 (1987), and Anirudhan (1988).

Phosphate concentration in all the sampling stations showed great

variations during the period of investigation. Biogeochemistry of phosphorus in

estuaries is controlled by a combination of physical, chemical and biological processes

like addition of phosphorus to the system, by input, decomposition of particulate

matter, removal of phosphorus from the system by precipitation and up take (Martin 1970).

Rivers are the major source of phosphorus input into estuaries. The

riverine influx of phosphorus in estuaries may be substantially modified by

precipitation or dissolution, causing changes in the concentration of phosphorus

(Fox etal., 1985). The weathering of insoluble calcium and fenic phosphate rocks and

land drainage especially from agricultural run off also deliver phosphorus to estuaries

(Martin 1970). The other sources are domestic sewage and industrial effluents.

Stud~es relating to phosphate content in Cochin estuary were done by

many scholars and they observed marked seasonal variations with high phosphate

content during pre monsoon ( Qasim and Sankaranarayanan, 1972; Joseph, 1974;

Lakshmanan et a/. , 1987; Anirudhan, 1988; and Balchand etal., 1990).

During the present investigation species diversity of phytoplankton

showed considerable seasonal variations. Chlorophycean members were noticed

throughout the period of study. Cyanophycean members dominated in the pre

monsoon period of maximum pollution. In the monsoon and post monsoon seasons,

diatom communitiis predominated and this may be attributed to the increased salinity

of these seasons (Gopinathan.1975).

Dumping off the effluents into the waterbodies could create severe threat

to the aquatic environment. In the present investigation a systematic and

comprehensive study on the physico-chemical characteristics was made to assess

the water quality of Muvattupuzha river, Chitrapuzha river and Cochin estuary. It

was found that the intensity of pollution was higher in Cochin estuary and

Chitrapuzha river compared to Muvattupuzha river.