DISCUSSION

Dissolved constituents in a natural water body, their distribution and

variations in time are known to influence the biotic components inhabiting it.

These dissolved as well as particulate materials in the water, apart from the organisons in it

provide an information of energy turnover in the aquatic ecosystem (Forsberg, 1982).

Temperature is basically important for its effect on certain chemical

and biological reactions occuring in the organisms, inhabiting aquatic DDcdia (Raney and

Menzel, 1969; Brett, 1969; Countant and Proderer, 1973). The monthly stationwise data of

water ten^rature is shown in Appendix-A and the n^an water tenc^rature of the whole

lake (stationwise) is given in table - 13. The data indicates seasonal fluctuations in water

teir^ature of the lake Wadali. It was higher during summer iBonths. It has also been

62

observed that water temperature fluctuates with air temperature showing direct relationship.

Hutchinson (1967) confirmed the same. This is also in agreement with the findings of

Michael (1969); Munawar (1970); Choudhary e/«/,,(1981); Saha and Pandit (1986); Balkhi

et al. (1987); Singbai et al, (1990); Sbarma and Rajput (1994) and Kaur et al., (1995).

Welch (1952) has suggested that smaller the body of water, mote quickly it reacts to the

changes in the atmospheric temperature. During the ninths of rainy season, lowering of

temperature was observed which might be due to the cloudy weather and influx of rain

water. Similarly, during winter months the water ten^rature remained low due to extrenae

cold and shorter sunshine period.

It was observed that periods of high temperatures nearly coincides

with those of low oxygen content but correlation values between water ten^rature and

dissolved oxygen were not significant (Table - 5). However, stationwise correlation values

indicated a significant negative correlation between water temperature and dissolved oxygen

particularly at stations I, IV, V, VI and VII (Tables 6,9,10,11 & 12). This could be

atteibuted to the abundance of zooplanktons and macroinvertebrates at these stations as at

the elevated ten^ratures, the nastabolic activity of the organisms increases requiring more

oxygen. Khalaf and MacD'onald (1975) also observed a negative correlation of water

ten^rature with dissolved oxygen.

j In the present investigation it was also found that water ten^rature has a

significant positive correlation with conductivity and or turbidity and also a significant

negative correlation with transparenc/[at all the sampling stations] This results are weU in

agreement with those of Verma and Shukla ( 1970) and Singhai etal., (1990). This might be

63

due to the absorbance of heat by the dissolved and floating particles in water which might

have radiated the absorbed heat to the surrounding water.

[During the study at the lake Wadali, it was observed that all the biotic

components studied were temperature dependent and there was a fluctuations in the

abundance of biotic con^nents with the variation in ten^rature particularly in the summer

and rainy seasons (plate - 1). While during winter seasons no correlation was seen between

water tenqjerature and the biotic con^nents. The correlation matrix drawn for the whole

lake indicated a singificant positive correlation between water tenqjerature and total

phytoplankton and total zooplankton7(Table-5). However the sampling stationwise results

of correlation between water tenq>erature and total phytoplankton, zooplankton and GPP

indicated an adverse effect on the abundance of total phytoplankton, zooplankton and gross

primary productivity. But it was not much significant except at sampling station-1 where,

there was a significant negative correlation between water tenoperature and total

phytoplankton, total zooplankton and gross primary productivity. These results suggested

that sorm other factors are responsible for the growth of planktons in the lake in addition to

water ten^rature. This could also be due to the fact that a particular species has distinct

temperature requirement. McVea and Boyd (1975) observed a lowering of water

tenqjerature due to aquatic plants. The present results are well in agreenaent with that of

McVea and Boyd (1975).

Transparency gives an idea about the decree of suspended partica|s in

the water of lakes, which in turn affect the light penetration (Verma et al., 1980). The

results of Secchi disc transparency as shown in plate - 2 indicated decreased trasparency

64

during the months of rain season and rising trend from September onward upto December.

Similarly a significant negative correlation was found between transparency and turbidity -

at all the san^ling stations. The lower values of trasparency during rainy season may be

attributed due to the rains which might have brought silt and mud from the catchment area

making the water turbid. This is in the confirmation with the observations made by Zafar

(1964); Kanungo et a!., (1987), Singhai et al, (1990); Kaur et al, (1995). Biswas (1973)

also observed low transparency during rainy season in m ^ - xmAc lake Volta of Ghana. An

increase in transparency was observed from Sepctmber upto December which may be due to

the settling down of silt and sand particals of the bottom while a ((Jccrcasc in trasparency

i 1

was observed after January onwards whieh can be attributed to an increase in phytoplankton * •'• - "i " — • ^ • _ , ..,:,̂ „̂.̂ .. ^ 1 \ ^%'.--lA\\ ' ^ ^ — ^ " '••• "" • • ' -.

populations! (Appendix- B , plates 1 to 17). In the whole lake correlation smdics,

trasparency was showing a significant positive correlation at 1 % level ( r = 0.554) with

dissolved oxygen. This may be due to the higher photosynthetic activity. At the same tin»

a negative correlation was seen with free C02 in the present investigation.

The turbidity of water of lake ranged between 23.6 NTU to 79.5

NTU, being maximum during summer and minimum during winter season. This may be

attributed to the water loss due to evaporation resulting into increases in partical

concentration and increased number of phytoplankton during summer. During rainy season

the turbidity was also found to be more. This type of seasonal variations has also been

reported by Ajmal and Razi-ud-din (1988). Higher turbidity affects the life indirectly

(Verma et al, 1978) by lowering down the penetration of light to be utilized by the aquatic

plants for photosynthesis and thereby depleting the rate of primary productivity and in turn

affects fish food. In the present study a feeble positive correlation was seen between

65

turbidity and GPP, NPP and total phytoplankton (Table-5). Further the total phytoplankton,

zooplankton, GPP and NPP were found to be depleted all of a sudden in the month of June -

95, following the high turbidity values during the preceding ntKjnth i.e. May- 95. The

turbidity of water is caused by the substances which are not present in the form of true

solution. Turbidity of water is actually the expression of optical property in which the light

is scattered by the particles present in the water. Turbidity makes the water unfit for

domestic purposes. The whole lake turbidity was positively correlated with hardness,

calcium, magnesium, nitrates and phosphates (Table-5), indicating the cause of turbidity

during summer months. Similar results were also reported by Verma and Dalela (1975).

Turbid waters can adversely affects fish and fish food populations, by preventing the

successful development of fish eggs and larvae, by modifying natural nwvements and

migration of fish and also by reducing the abundance of food available to the fish.

Settleable materials which blanket the bottom of water bodies damage the invertebrate

population, block gravel spawning beds and if organic, remove dissolved oxygen from

overlyng waters (Edberg and Hofsten, 1973; EIFAC, 1965). Deposition of organic materials

to the bottom sediments can cause imbalances in lake biota by increasing bottom animal

density, principally worm populations and diversity is reduced as pollution sensitive forms

disappear (Mackenthun, 1973). Besides, the near surface waters, are heated because of the

greater heat abosrbancy of the particulate material which tends to stabilized the water

column and prevents vertical mixing (NAS, 1974). As a result decrease in dissolved oxygen

was observed at all the sampling stations with high turbidity which might have not got

dispersed. A weak negative to significant negative correlation between turbidity and

66

dissolved oxygen was reported in the present investigation at all the sampling stations

(Table 6 to 12),

Further a positive correlation was seen between turbidity and water

microbes and faecal coliform in the present investigation at many sampling stations. This

can be attributed to the nutrient rich water due to various suspended and dissolved solids

like nitrates, phosphates and carbonates. The decaying of aquatic plants due to a combined

effect of high water temperature, low dissolved oxygen and high turbidity might have

provided favourable conditions for the microbes.

(Conductivity of water of lake Wadali was found to be fluctuated

between 82.00 ± 0.81(1 mhos/cm and 282.00 ± 0.66 fi mhos/cm. The maximum conductivity

of water was recorded during rainy season, which indicated more concentration of

electrolytes in the water. This may be due to the incoming water in the lake from the

catchment area which might have brought silt and mud along with it during rainy season. It

resulted in increase in turbidity of water. Therefore, in the present investigation the

conductivity values were found to be positively correlated with turbidity of water (Table 5 to

12) and simultaneously conductivity denoted a significant negative correlation with

transparency at 1 % level at all the sait^hng stations (Table 6 to 12). During summer, a

rising trend in water conductivity was seen. This can be attributed to the water evaporations

during summer that resulted into increase in electrolytes concentration of remaining water

lake. Whereas during winter season the water was steady and less disturbed and hence the

salts must have settled down, resulting into lowering down the conductivity of the water?

(plate -4). Similar results were reported by Khalaf and MacDonald (1975) and Trivedi et

67

al, (1985). The conductivity of water of lake is3.,|MiS,iffi.,QtAe^;a£aci5j3f_sub^^

solution to conduct electrical flow. Conductivity is reciprocal of the resistance. The

resistance of an aqueous solution to electrical current or electron flow declines with

increasing ion concentrations. In the present investigation a significant positive correlation

was seen between conductivity and hardness as well as carbonate alkalinity, chlorides,

sulphates, phosphates and magnesium at all the san5>ling stations (Table 6 to 12). These

results are in well agrcmcnt with those of Khalil (1990) and David etal, (1995).

U h e pH of water from lake Wadali was alkaline throughout the

period of investigation ranging between 7,2 to 8.96 (Appendix - A). This may be due to the

abundance of buffering substances brought with rain water and also due to the presence of

sufficient quantities of carbonates^ Zafar (1966) pointed out that pH oi the water is

dependent upon the relative quantities of calcium carbonates and bicarbonates. The water

tend to be more alkaline when it posseses carbonates. It is much less alkaline when it

possesses larger quantities of bicarbonates, carbondioxide and calcium In the present study

a positive correlation between pH and carbonates as well as hardness were observed;

however, a significant to less significant positive correlation were noticed between pH and

bicarbonates, free C02 and calcium content at rrwst all the sampling stations. This might be

due to increased photosynthesis of the algae resulting in to the precipitation of carbonates of

calcium and magnesium from bicarbonates causing higher alkalinity of water. Many other

workers Hkes Rao (1955) ; Zafar (1964); Munawar (l970),Rao (1971); Singhai et al,

(1990); David et al, (1995) have also observed a positve correlation between pH and

carbonates.

68

Throughout the rainy season pH of water of lake Wadali was

comparitively low while it was at higher level during summer (Plate - 5). Similar trend have

been reported by Sreenivasan, (1965); Vijayraghavan (1971); Gupta and Mehrotra (1986).

The increased pH during summer may be the effect of increased photosynthesis. The low

pH during rainy season can be attributed to the inflow of fresh rain water. The pH of water

of lake Wadali remained well within limit throughout the period of investigation and no

trend towards acidity was seen. Beamish et al, (1975) reported that the change in pH of

water to acidic is detrimental. The fluctuation in pH were also observed with reference to

sampling sites. Fluctuation of pH values have also been reported by George (1961); Sahai

et al, (1985). Higher pH was notice during sunouner and lowest pH was recorded in

September -95.

The distribution and abundance and phytoplankton and zooplankton

was found to be unrelated to pH as no constatnt correlation was seen between pH alone and

any other biotic parameter at diffemt sampling stations studied. However, pH in

combination with total alkalinity ( Table - 61 ) favoured the growth of

phytoplankton (r = 0.775 and P<0.05), Again the combinations like DO and pH (Table -61)

and abundance of rotifers and pH (Table -61) showed a positive significant (P<0.05) with

water microbes. Further pH in combination with total alkalinity and nitrate content

(Table-62) have shown highly significant correlation with net primary productivity of the

lake. From these observations it can inferred that pH in combination with other physico-

chemical parameters affect the growth of biota in the aquatic ecosystems. This is well in

agreement with the findings of Zutshi and Vass (1973) and Singh (1986),

69

During present investigation dissolved oxygen ranged between 5.6

mg/1 to 12.6 mg/l in the lake Wadali (Appendix- A). There are two main sources of

dissolved oxygen in water, narittly diffusion from air and photosysthetic acitivity within

water. Diffusion is carried out by physical phenomenons like tenqjerature and water

movert»nts, while photosynthetic acivity is a biological phenomenon carried out by

autotrophs.. Further dissoved oxygen concentrations are an important gauge of existing

water quality and ability of a water body to support a well-balanced aquatic faunaV^

In the present invesitgation, a random distribution of DO showed two

peaks, one during May and another during December. The higher values of DO in

December, April and May would be due to increased phytoplankton, which might have

caused an increase in photosynthetic activity liberating a considarable amount of oxygen

into water. Ganpati (1962) reported increased photosynthetic activity is the main source for

enhancing the oxygen contents. Kajihara (1968) noticed that the contents of DO in shallow

water were affected by the rise in number of phytoplankton and also by the exchange of

oxygen between air and water. Schindler (1971) also observed an increase in photosynthetic

activity causing greater production of oxygen during winter months in Canadian lakes.

Similar observations with respect to DO and phytoplankton were also recorded by Lehn

(1975); Singhai et al, (1990); Subbamma et al, (1992); Kaushik and Sharma (1994) and

Jayacbandran et al, (1995). Lcukowicz (1974) noticed a decrease in oxygen content that

led to the poor growth of phytoplankton. In the present finding, a positive correlation

between DO and phytoplankton was seen in the whole lake correlation studies as well as at

different water sampling stations except sampling station 11 and m which had exhibited

70

comparatively less phytoplankton during April, May aiid December. An increase in oxygen

contents was recorded from the month of August till December. This might be due to a fall

in the ten^rature of water and air. Statistically, dissolved oxygen showed mostly a

negative correlation or very feeble positive correlation with water temperature at all the

sampling stations. However, a positive correlation was found between DO and transparency

at all the stations except station - HI. This could be due to more human activities at station

n i These results are well in agreement with those of Munawar (1970); Rao et ai, (1985);

Kaur et ai, (1995). Ellis et ai, (1946) opined that the state of dissolved oxygen is

dependent on many factors. This was also supported by Southgate (1948) and Sreenivasan

(1969) who observed it as productivity linked phenonmenon. The lower dissolved oxygen

concentration can be attributed to discharge of various domestic sewage channels human

interferences and dying planktons. The dying planktons reliase high amount of chemicals

which are further oxidised by the dissolved oxygen of lake water.

The general level of free C02 of water of lake was negligible during

the maximum months of the year. However, highest level of C02 was observed during

August to October which could be due to the wastes being added to the lake during rainy

seasons. Ganpati (1943); Rao (1955); Saha et ai, (1959) had shown well marked inverse

relationship between dissolved oxygen and carbondioxide but in the present study a definite

inverse relationship could not be establislied. This is in agreement with the findings of

vSingh (1960) and Munawar (1970).

Alkalinity of water is its capacity to neutralize a strong acid. In

natural waters, carbonates, bicarbonates , phosphates and hydroxides are considered as

71

predominant bases, hence alkalinity is expressed as total alkalinity. The alkalinity is

cosidered as an indicator of pond productivity (Davis, 1955).

The ninthly range and mean values of carbonate alkalinity are given

in Appendix -A and Table -13. The increased seasonal trend was noticed form summer to

rainy season reaching a maximum in June. Lower carbonate values were recorded during

winter montlis. Zafar (1966) found higher quantities of carbonates after the rains of July

when large amounts of carbonates got accumulated in the water. In the present study also

the lake was lashed with heavy rain during June resulting into increased carbonates in lake

water. Saran and Adoni (1985) also reported a similar trend in Sagar lake. An inverse

correlation has been observed between carbonates and other physico-chemical parameters,

particularly the bicarbonates. The occurrence of such correlation is in accordance with the

estabUshed carbondioxide cycle in water systems. An inverse correlation between free

carbondioxide and carbonate alklinity was observed at all the sampling stations and also in

the whole lake. Quadri and Shah (1984); Singhai et a/., (1990) also detected a higher

carbonate alkalinity during the period of low free carbondioxide level. During the present

investigation carbonate alkalinity was found to be positively correlated with temperature,

turbidity and conductivity and negatively correlated with transparency and total

phytoplankton.

Bicarbonate alkalinity of the whole lake was found to be nwre during

winter rrKjnths reporting the highest mean values in January -96 (197.91 mg/1), Furhter at

sampling station VI the bicarbonate alkalinity was positively correlated with GPP, NPP,

rotifer population and also with the total phytoplankton. Alkalinity over 150 mg/1 has been

72

found to be conductive to higher production (Ball, 1949) and similarly, Waters (1957)

found higher bicarbonates in water giving higher production. In the present investigation,

the maximum annual average of bicarbonate alkalinity was 197.91 mg/l which reflects the

good productive nature of the lake water. Unni (1982) on Sampana reservoir has reported

higher bicarbonates and very low carbonate alkalinity with pH ranging from 8.4 to 9.2.

Singh et al., (1980) have reported only bicarbonate alkalinity in Riband Dam. Jhingran

(1982) was of the opinion that a mixture of carbonates and bicarbonates is generally found

in water of pH ranging between 8.4 to 10,5. He stated that in waters with pH range of 4.5 to

8.4 carbonate is not present. Verma (1967) has reported only bicarbonate alkalinity in fish

pond with pH ranging between 8.4 to 9.CX). Saha and Pandit (1986) reported very low

carbonate alkalinity in Mukhra pond and bicarbonate alkalinity in Tiwari pond. The pH

recorded by them ranged between 7.2 to 8.1 (Tiwari pond) and 7.2 to 8.6 (Mukhra pond).

In the present investigation the pH of water of lake ranged between 7.2 to 8.96. The review

of literature reveals that pH is not the only governing factor for carbonate and bicarbonate

alkalinity in water, Therefore, it seems that an inverse relationship exists between pH and

bicarboante alkalinity. In the present ivestigation an inverse correlation is seen between

bicarbonate alkalinity and total phytoplankton. This might be due to the precipitation of

calcium and magnesium ions as carbonate that resulted in to lowering down of these ions in

water resulting into an increase in percentage of sodium in the water and hence damaging

the phytoplankton. Alkalinity at sampling station - II was found to be maximum in the

present investigation and the total phytoplankton was also found to be meagre at this station.

Macrophytes were also absent from this region. This could be the effect of precipitation of

irons as hydroxides due to high alkalinity (NAS, 1974) resulting into unavailability of iron

73

to plants. Iron deficiency in soil water and lake water induce chlorosis and plant damage

(NAS, 1974). Fortunately alkalinity values (bicarbonate and total) are found to be moderate

in the lake Wadali throughout the experimental period at stations V, VI and VII and hence it

proved to be productive, as a significant positive correlation was seen between bicarbonate

alkalinity and abundance of total phytoplanktons at stations V, VI and VII.

Hardness of water is the sum of concentrations of alkaline earth OKstal present

in it. In the lake Wadali, it ranged between 112 mg/1 to 447 mg/1 during the months of

October and May respectively. Hardness of water exhibited seasonal pattern with maximum

values in summer season. A significant positive correlation between hardness and calcium

as well as magnesium ions indicated that the hardness was due to calcium and magnesium

ions. Hardness of water also exhibited a significant positive correlation with chlorides at

sampling stations 11, III and V and also an insignificant positive correlations at remaining

sampling stations. Above two findings indicate also that the hardness is due to chlorides of

calcium and magnesium. The hardness values in the present studies also indicate that the

water is hard. The chloride salts of calcium and magnesium in the water might be

responsible for the less abundance of total phytoplanktons in particular the cyanophyceae at

station HI, n and V. However, hardness favoured the growth of molluscs, rotifers,

copepods , total zooplankton, water microbes and faecal coliform. Arce and Boyd (1980)

and Singh (1986) also reported a positive correlation between hardness and chlorides

favouring zooplanktons, in particular the molluscs . This could also be due to the fact that

water hardness reduces tlie toxic effects of poisonous elements (Lioyd, 1960), and that it

keeps the pH in control (Joseph, 1980). Therefore it can be inferred that seasonal variation

in hardness of water seems to be lesser biologically induced, than by the temperature and

74

evaporations of water during summer months. This might have resulted in a high

concentrations of calcium and magnesium, whereas, the dilution caused by rains might

have lowered the hardness during the rest of the period (plate - 11). Similar results were

obtained by Singhai et al, (1990) while studying the physico-chemical characteristics of

Tawa reservoir. Shardendu and Ambasht (1988) also pointed out the level of hardness to

be dependcnd of the water evaporation.

Chlorides are not utilized for plant growth and their presence in large

amounts is regarded as suggestive of pollution by organic matter, chiefly of animal origin

(Munawar, 1970). fjn lake Wadali the chloride concentration varies between 22.86 mg/1 to

107.4 mg/1, however the mean chloride content of water samples of all the stations showed

very less fluctuations. Only higher chloried contents were recorded during rainy season

which can be attributed to the inflow of organic matter of animal origin during rainy season.

Lake Wadali also receives the animal excreta from the Wadali zoo. Similarly, the nearby

human population and the grazing animals might also be responsible for the higher load of

organic matter entering in the lake during rainy season leading to arise in chloride content. I

For rest of the year no definite pattern of chloride fluctuation was seen. The variations may

be accounted for the addtions from precipitations and evaporation and human activities

(especially by washermen ). The present finding coincide with the findings of Zafar (1960);

Lakshminarayana (1965), Venkateshwarlu (1969); Munawar (1970); Singh (1980); Mehra

(1986) and Singhai et al.,(1990). Sreenivasan (1964) and Goel et al, (1980) pointed out

chlorides as an indicator of eutrophication in an aquatic ecosystem. The relationship of

chloride concentrations were studied by calculating correlation coefficients. Chlorides

showed a significant positive correlation ( r= 0.732 ) with total phytoplankton. This is

75

supported by the fiiiduigs of Vemia arid Shukla (1970). In the present studies, a significant

positive correlation was also seen between chloride content and faecal coliform at all the

sampling stations except station VI indicating the bad conditions of the lake from all sides

except at station VI which a less disturbed area of the lake inhabiting the migratory birds.

Nitrates are tlie most oxidised forms of nitrogen and they form an

important nutrient for photo-autotrophic plants. The average nitrate content of the lake

Wadali was comparatively low. Maximum mean nitrate content was recorded during May -

95 (0.32 mg/1) and December- 95 exhibited minimum nitrate values (0.06 mg/1). Nitrates

remained highest during summer and lowest values were obtained during winter (plate- 15).

However, high nitrate values have been suggested in mansoon months by Singh (I960);

Singh(1965); Venkateshwarlu (1969); Munawar (1970); Singhai et aL (1990). Shah (1988)

also reported mininmm nitrates in summer and maximum in winter in the lake water. The

low nitrate contents obtained during present study can be attributed to their utilization by

the pbytoplankton. This is confirmed by the inverse correlation seen between nitrates and

total pbytoplankton at samphng stations II, V and VI and a less effective positive correlation

at stations I, III and IV. Ganpati (I960) |X)inted out that tropical waters, particularly

unpolluted ones, are deficient in nitrates and the concentration beyond 0.15 mg/1 of nitrate-

nitrogen is indicative of eutrophication (vSawycr, 1966; Wetzel, 1975). From this it can be

inferred that the lake Wadali is okgotrophic and also less polluted. However, in the present

studies highest nitrate content was recorded from station III ( Appendix -A ) indicating a

polluted zone. At station III, human activities, were found to be dominant and secondly at

this station, the lake receives the sewage from the Wadali zoo. A signiticmt positive

correlation between nitrates and total pbytoplankton at station VII indicated non- utilization

76

of nitrates by the phytoplaiikton at this station. Most of the nitrates were utilized by faecal

coliform and other water microbes at this samphng station which was evident from the

inverse correlataion seen between nitrartes and these microbes (Table -12). Ecologically

inorganic phosphates are most important as they form the limiting factor for the

productivity. The high concentration of inorganic phosphates indicates the sign of

pollution. They formed the important nutrients, limiting the growth of autrotrophs and also

the biological productivity of ecosystems.

Like nitrates, maximum values of phosphates were recorded in

summer and minimum during rainy and winter seasons. The phosphate contents in the

water of the lake Wadali were found to be comparatively high as compared with the results

of various authors for different lakes (Jana.,1979; Balkhi et al., 1987; Singhai et al., 1990;

Kmtetal., 1995).

Jaiia (1979) reported reduction in phosphate content during monsoon,

while Balkhi etal., (1987) showed a positive relation between phosphate and water column

in their studies on Anchar lake of Kashmir. The present results are well in agreement with

that of Jana (1979). The higher phosphate contents observed during the present

investigation can be attributed to the addition of detergents in the lake and also due to the

release of additional phosphate from dead and decayed phytoplanktonic cells. It may also

be due to the accumulation of excreta of zooplanktons and nmcroinvertebrates. The rising

water temperature in summer might have accelarated the decomposing process of dead

phytoplankton and excreta releasing the phosphate in the water. The released phosphates

favoured the growth of cyanophyceae, most of the zooplankton and also the microbes which

77

is evident from a significant positive correlation observed between the phosphate contents

and various biotic parameters like cyanophyceae, zooplankton and microbes of water

sample from station VI. Similar results were reported at station -V favouring our

interpretation . A positive correlation was seen in between phosphate and nitrate content of

the lake and hence it can be suggested that these nutrients play a vital role in governing the

aquatic ecosystem. This is in confermation with the findings of Zafar (1966); Michael

(1969); Munawar (1970) and Wetzel (1975).

A sudden increase in sulphates was observed from March reaching to

maximum in May. However, during rainy season the sulphate contents in water were found

to be sUghtly decreased but were more than that in the winter season. The higher values of

suphates noticed during summer can be attributed to the evaporation of water during

summer, while the higher values from rainy season could be due to the entry of sulphates

from catchment area of the lake in run off . Similar type of observations have been

reported by Hutchinson (1957). He had also stated that the rain water usually contains 1 to

2 mg sulphates per litre. Tliis is in support to our observation regarding sulphate content in

the water of lake.

Statistically, sulphates showed a significant positive correlation with

magnesium, calcium and hardness indicating that they are responsible for the hardness of

water of the lake Wadali.

/plankton population depend directly or indirectly on different

physico-chemical and biological conditions of the water body (Reid and Wood, 1976),

78

Further Davis (1955) pointed out that biotic aiid abiotic factors act simultaneously to

influence the plankton fluctuation

The pbytoplankton commmunity is a diverse assemblage of members

of chlorophyceae, cyanophyceae and bacillariophyceae. In the present ivestingation

bacillariophyceae accounted for 71.26 % and dominated the pbytoplankton population and

were followed by chlorophyceae (14.84 %) and cyanophyceae (13,90 %),

During present study, two distinct peaks regarding abundance of

population of pbytoplankton were observed i.e. one in April and May and another in

December (plates 1 to 17). Many workers have reported seasonal variations of the

pbytoplankton. Das and Shrivastava (1959) reported a bimodal pattern of pbytoplankton

abundance and recorded peaks in monsoon and spring. Bhowmick (1968) reported

maxunum number of pbytoplankton during monsoon and winter. Pant et at., (1979) also

noticed two distinct peaks i.e. one in August and other in December. While Michael (1969)

has reported a prolonged single peak. Venkateshwarlu (1976) observed that high

temperature and more phosphates were favourable for the growth of pbytoplankton. The

present results are well in agreement with Venkateshwarlu (1976).

The Effect of temperature on pbytoplankton can not be separated from

the effect of light since both factors are interrelated in photosynthesis. The enhanced growth

of pbytoplankton from February to May could be attributed to increased temperature and

light during the longer spring days as observed by Kopcznska (1980). During summer there

79

was a rise in phytoplankton population which could be due to increased mineral nutrients

mainly calcium and magnesium.

The group chlorophyceae was represented by 12 species and they

were abundant at san[q)ling station VI followed by station V. Station I, U and III exhibited

Meagre population of chlorophyceae. The species Mesotaenium was seen predominantly at

station III which is a pollution indicator species, These observations about distribution of

species were found to be dependent upon the mineral status of the sampling station of the

lake, Increase in members of chlorophyceae at station V and VI had resulted in to depletion

of dissolved oxygen and magnesium content which showed a negative correlation with

phytoplankton in the present study. These results confurm the earlier findings of Hutchinson

(1967) and James etal. (1990),

The members of bacillariophyceae dominated the lake and they were

almost found distributed throughout the lake though their abundance was meagre at

sampling station - VII. All the eight species recorded were abundant at sampHng station VI.

Station 11 and III only exhibited pollution indicator species Cymbella, Navicula and

Nitzchia. Multiple correlation studies indicated that the factors like temperature, alkalinity,

pH, C02, calcium and chloride content of the water of lake and their combination in a

particular concentration favoured the growth of phytoplankton and as such from the content

of individual abiotic parameter, no definite conclusion could be drawn.

80

Oscillotoria (Cyanophyceae) was found to be abundant from the

sanipling station II and IE. It is a pollution indicator. Ruttner (1963) and Rai (1974) also

observed this pollution indicator species in pollutc4 water.

Thus, it can be concluded that no single factors was found to be

responsible for the occurrence of phytoplankton but a cumulative effect of noany factors

appeared to govern their growth and occurrence, A significant positive correlation between

total phytoplankton and total zooplankton indicated that the abundance and diversity of

phytoplankton favours the zooplankton.

The seasonal variation in zooplankton is dependent on various

biological and physico-chemical factors. Out of these, temperature, turbidity, pH and

nutrients play a vital role in con^)osition and distribution of zooplankton (Jhingran, 1982).

Zooplankton comprised of protozoons, rotifers, cladoccrans,

copepods, ostracods and worms and larvae. Copepods (36,81%) dominated the zooplankton

population of the lake, followed by rotifers (20.77%), cladocerans (13.22%); worms and

larvae (11.67%); protozoons (9,64%) and ostracods (7.89%). During present study species

belonging to 37 genera were identified. The zooplanktons observed were abundant in

summer but a sharp decrease in their number was noticed on the onset of rainy season

reaching to its minimum in September. During winter, again a slight increase in abundance

of zooplankton was se«n. ITiis type of seasonal fluctuation is in confirmation with the

findings of Seenayya (1973) and Davis (1976).

81

The result of biotk aiid abiotic parameters as indicated in plates 1 to

17, apperently show, a dire :̂t correlation between zooplankton and phytoplankton. In the

month of April and May phytoplanktons were at the peak arid zooplankton established peak

only in May. This anamoly could be due to the feeding habits of the zooplankton. While, a

slight increase in zooplankton popultion during winter was also followed by the peak of

phytoplankton, along with the high nutrient level. This is well in agreement witli the

observataions of Davis (1976); Sharma and Sahai (1988); Adholia and Vyas (1993);Bais

and Agrawal (1995). Minimum density of zooplankton in monsoon months may be due to

the influx of rain water and dilution effect as reported by Chapman (1972) and Davis (1976).

On the otherhand zooplanktons might have consumed by fish population. Turbidity might

have also caused death of zooplankton during rainy season. Similar results were reported by

Michael (1969) and Sharma and Sahai (1988). The low abundance of zooplankton in

December and January might have been resulted due to low water temperature. This

coincides with the findings of Sparrow (1966); Vasisht (1968), who also showed a positive

relationship between zooplankton populatiion and water temperature.

The group rotifera was represented by 22 species of 13 genera.

Rotifers were found to be maximum at station I. 11 and III during May and June (Tables -

36,37,38) from which it may be suggested that higher temperature and less nutrients and low

oxygen contents favoured them to flourish. This is in confirmation with tlie observations of

Arora (1966).. Among observed rotifers five species {Rotararia, Monostyh, Lepadella,

Cephalodella, Brachionus falcatus) were pollution indicators and they were found abundant

at sampling stations I ,11 and III . The distribution of these specise was typical at specific

sampling sites. Lepadella were found abundant at station III, while Rotaria and

82

Branchionus falcatus were totally absent from this sampling station. Staions I and 11

represented all the pollution idicator species. This types of specific distribution indicated

not only the different food habits of the rotiferes but also the type of pollutant in the water.

At sampling station III the depth of water was comparatively less than that of station I and U

and the activities of herbivorous vertebrates and human being with respect to diffemt types

of washing habits were predominant. These specific factors might have developed unstable

conditions and hence the much resistant rotifers i.e. Lepadella were observed from the

sampling station III only. Sudzuki (1964) also observed more resistant species of rotifers at

unstable polluted regions of various lakes in Japan.

pH had no direct bearing effect on the rotifers (Berzins and Pejler,

1987) eventhough it appeared to be important in the distribution of various species. This

factor exhibited feeble positive significance with the total abundance of the rotifers in the

present study. It was also reported by Haque et al., (1988). Most of the observed species

comprised typical planktonic taxa reported to occur in alkaline waters and were known to

tolerate a certain range of pH varitaion Kostc. (1978). The present study is in support with

the findings of Michael (1968); Nayai (1970) and Vasisht and Sharma (1976) relating to

coincidence of rotifer abundance with higher total alkalinity as the total alkalinity exhibited

a significant relationship with total rotifers. However, total hardness of water exhibited an

inverse relationships with rotifer abundance. Further more, quantitative variations of total

rotifer showed an inverse relationships with tiansparency and dissolved oxygen (Table-5)

which might be due to respiratory activity of the rotifers and other zooplanktons and also by

utilization of oxygen for decompositon of algal bloom at higher temperatures. Free

83

carbondioxide was not detected during the periods of abundance rotifers. Its insignificant

correlation with total rotifers was in confirmity with the observation of Deb et al., (1987).

The group cladocexa was represented by eitht species. Phytoplankton

particularly the oaembers of chlorophyceae and bacillariophyceae were found to be

favouring the abundance of the cladocerans. Surprisingly the cladocerans and the members

of chlorophyceae and bacillariophyceae were found to be negatively conelated with total

alkalinity and positively correlated with water ten^rature (Table -5). Accordingly, a high

count of cladocerans was reported in March, April and May from Station III, IV, V and VI

in the present investigation (Tables- 38 to41). This pattern of distribution may be due to the

interaction of various physico-chemical and biotic factors. This is in confirmation with

Nasar and Dutta - Munshi (1974) and Wetzel (1975).

Copepods were represented by eight different species and among

them Cyclops were recorded throughout the year dominating the lake. Copepods exhibited

two peaks i.e one in summer and other in winter (Tables 36 to 42). This is in confirmation

with the findings of George (1969); Chapman (1972) and Govind (1978). The summer

peak may be due to the abundance of diatoms arid blue green algae (Goswami and

Selvakumar, 1977). Winter peak may be attributed to the abundance of phytoplankton in

the present investigation. A decrease in rainy season may be because of predation of

planktonivorous shrimps, prawns and fishes. This is well in agreement with Brandorff and

DeAndrad6(1973).

84

Ostracods were represented by two species belonging to one genus

and they contributed only 7.89 % of ttie total zooplankton population. Most of the species

were observed from sampling stations V and VI. This might be due to ample phytoplankton

and temperature between 19.4 °C to 34.9 °C at these stations.

The protozoons were represented predominantly by seven species and

they were abundant at stations V and VI , They formed 9.64 % of the total zooplankton.

During rainy season particularly July and August no protozoons were recorded from the

lake. This might be because of polluntants entering in the lake along with runoff and the

increased turbidity during these months. They appeared to be the most sensitive

zooplankton as compared to the other zooplanktons recorded. Other species could

withstand the wide range of physico-chemical factors and hence they could be seen through

out the year .

Almost constant pH of lake water towards alkaline side indicates

lesser degree of eutrophication which is further substantiated by the low concentration and

controlled presence of anions in the lake water. On considering total alkalinity, pH ,

nitrates, C02, dissolved oxygen and phosphates together, it becomes quite evident that

phosphates, C02 and dissolved oxygen are negatively correlated and it must the combine

effect of these parameters which would have governed the plankton population of the lake.

The nutrient status of the lake has not attended a stage which could favour the luxurious

water blooms and hence this lake water had never resumed the form of a green soup during

the tenure of this project work. The biological indicators of pollution indicate the degree of

deterioration of water quality. Arora (1961) opined that Rotaria occurs only in polluted

water and is absent in clean water. The occurence of Rotaria Lepadella, Ectocyclops in the

lake water of Wadali alone are sufficient enough as an evidence of deterioration of water

quality of the lake,

Numerous factors arc known to influence the diverse distribution and

abundance of the bacteria.. Bacteria are able to survive in wide limits of temperature. The

water teraparaturc in this investigation varied from 19.3 °C to 34.9 °C (Appendix -A).

Faecal coliform, water microbes and soil microbes grew the best at higher temperature

(Rheinheimer, 1978),

The growth and reproduction of microbes is much affected by

hydrogen ion concdentration of the water. The optimum pH for most microbes is between

6,5 to 8.5 ( Thimann, 1978). In the present investigation the water pH ranged between 7.66

to 8.95 and further a positive significance was seen between the water microbes and pH.

The lowest microbe count was witnessed in winter when dissolved

oxygen content was the highest. Similarly a significant inverse correlation was st&a

between the water microbes and dissolved oxygen (Table -5). This is well in agreerr^nt

with obeservations of Gonzalves and Joshi (1964); Hannan (1979).

The life span of microbes in water was also affected by different

inorganic substances like nitrates, phosphates and sulphates, which, in the productive zone

of water represented the limiting factors for microbial life (Schindler et al, 1971; Staples,

1973). However, the inorganic requirements of bacteria are not yet well understood

86

(Salle, 1972). In oligotrophic lakes, nitrates, phosphates and sulphates are immediatly

utilised by the microbes (Likens, 1972). In the present investigation also with the increase of

microbes, nitrates , sulphates and phosphates were found to be declined which was indicated

by inverse correlation between the microbes and the salts like nitrates, phosphates and

su;phates (Table -5).

JThe lake Wadali was found to be dominated by soil bacteria which

might be because of the nutrients like nitrates, phosphates and sulphates which usually

settle at the bottom enriching the lake soil)/Maximum number of soil bacteria was reported

from the soil of sampling station VI. This could be because of the large number of

phytoplankton and zooplanktons at sampling station VI. The death of plankton make them

settled at the bottom which provides favourable habitat for the soil bacteria. Similarly large

number of faecal coliform at station III indicated the polluted environment in tlie lake at the

sampling station - Illl Godlewaska- Lipowa (1976) observed an increased number of

microbes in the lake water of cities located near human population dwelling and he also

considered it to be as indicator of degree of eutrophication and degradation of lakes.

However,|jTom the bacterial count of the present study, it appears that the oligotrophic

nature of the lake is on the verge of becoming eutrophic in the coming yfejufs.̂ ^^ ^^^^

Primary productivity is the most important biologiocal phenomenon

in nature which involves the trapping of radiant energy of the sun and its transformation into

high biological energy by the process of photosynthis using inorganic materials of low

potential energy. Tlie primary productivity relates to the amount of organic matter

synthesized in a certain space per unit turn. The morphological and geological characters

87

and physico-chemical properties of water show a direct relation with primary production

{Adoni, 1985). Gross primary productivity (GPP) refers to the ovserved changes in the

biomass plus all the predatory and non predatory losses during a unit time. While, net

primary productivity (NPP) is the rate of accumulation of new organic matter per unit time

i.e. gross primary productivity minus all losses.

The average gross primary production and average net primary

production were found to be 8278.44 mg/L/day and 4455.03 mg/l/day during the present

investigation, The values of both GPP and NPP were found maximum in May and the

minimum values were recorded during January and June months. GPP showed a distinct

bimodal pattern with another peak in December.

Singh and Desai (1980) reported high production in early sumnwr and

low values in winter, late summer and rainy seasons. It is believed that during summer the

productivity values decrease due to the death of phytoplankton. However, in the present

investigation productivity (Tjoth GPP and NPP) was found to be maximum. This could be

becaues of abundance of phytoplankton, increased transparency and nutrient rich water of

the lake. The decrease in productivity reported in June was probably due to high turbidity

and minimum transparency. This production rate was found to be increased during post

rainy season when the transpamcy was found to be increase slightly.

Singh and Desai (1980) reported the net productivity of Rihand

reservoir ranging between 130.84 to 636.62 mgfUdzy ; while Saltero and Wright (1974)

obtained 571.92 to 1318.66 mg/l/dm productivity of Bighorn lake which was described as

88

moderately productive by theiix Thosai and Das (1984) have reported the productive nature

of differnt lakes of Nagpur. They reported gross productivity ranging between 87.47 to

137.47 mg C/m /̂h and net productivity ranging between 62.47 to 75 mgC/m^/h of the

Gorewara, Ano^bazhari and Telenkhedi reservoirs. They categorized these resevoirs as

oligotrophic where as Gandhisagar as autotrophic lake. The GPP and NPP values of

Gandhisagar lake wear reported as 1549.9 nagC/m /̂h and 1112 mg C/m /̂h respectively by

Krishnamurthy and Abdulappa (91972). From this data it can be inferred that the lake

Wadali is Oligotrophic.

In the present investigation statistical analysis was carried out to find

possible relationship of producctivity with physico-chemical variables. Singh (1986)

reported a highly significant positive relationship of primary productivity and temparature.

Pillai etai, (1975) stated that water temperature did not show any significant impact on the

productivity of ecosystem. Qasim et al.,(1972) have also reported that water temperature has

no direct imact an GPP and NPP. Nair et a/.,(1983,1984) clearly mentioned that the

correlation coefficient did not reveal any significant relationship between primary

production and water temperature. In the present investigation we have also noticed an

insignificant positive correlation between productivity (GPP and NPP) and water

ten^rature (Table 5). The winter values of GPP and NPP were also higher (Plate 1) when

the water t6nq>6rature was low and hence it can be inferred that the productivity is

independent of temperature fluctuations in water .

Light is an important factor for the photosynthetic activity of

phytoplankton. Penetration of light is checked by the presence of seuspcnded particles at the

89

surface affecting the photosynthesis in sub-surface water (Singh and Desai, 1980). They

have reported that light pentration acts as a limiting factor for plankton aabundance

(Sreenivasam, 1967, Funk and Gauffin, 1971; Salterao and Wright. 1974; Jana et al., 1978;

Sahai and Shanna, 1988; Bhaumik, 1994; Bixasal,1996). Recently, Subbamma (1993)

reported a significant positive correlation between primary productivity and transparency. In

the present study we have also observed a significant positive correlation between

transparency and GPP as well as NPP at sampling stations HI, V and VU, At san^ling

station IV, NPP was found to be positively correlated with water ten^rature. The

correlation was significant at 1% level. But at the same time an insignificant negative

correlation was observed between NPP and transparency as well as DO. But at the same

time NPP also exhibited a significant positive correlation with mg-H-, nitrate contents and

pH of water. Saha and Chaudhary (1985); Khalil (1990) and Varghese (1992) also reported a

negative relationship between plankton density and dissolves! oxygen. A number of workers

have reported direct correlation between alkalinity and productivity (Banerjee, 1967;

Jhingran, 1982; Khalil ,1990; Bhaumik, 1994). But in the present investigation, a significant

to less significant negative correlation was noticed between productivity ( GPP, NPP) and

alkalinity. However, at sampling station VI, our results are well in agreement with tliat of

Jhingran (1982). This might be because of the availability and utilization of nitrates and

phosphates by the phytoplanktons (Table VI) leading to an increase in GPP and NPP. Singh

(1986) has reported a poor relationship between hardness and primary productivity. In the

present investigation when the whole lake is considered as one integrated unit, then gross

primary productivity was found to be positively correlated with hardness of water at 5%

90

level, however when productivity at different sanjpling stations was estimated it was found

that primary productivity did not depend on water hardness.

From the present study it can be generalized that net primary

productivity is dependent on nitrates present in water and its pH.

In the limnological study greater stress is usually given to correlation

studies, as the structure and function of any aquatic ecosystem are interdependent (Ganpati,

1966; Lewis, 1979; Dimmick et al„ 1982; Kenneth 1990). The simple correlation study is

found to be the primary aspect to show interd6|)cndent relationship which can be confirmed

by multiple correlation studies or cluster analysis. The multiple correlation between more

than two variables help in better understanding among the biotic and abotic factors and also

in the assessment of quality of water (Tiwaii et al., 1986). The values of correlation

coefficient(r) lie between +1 (perfect positive correlation } and -1 (perfect negative

c correlation ),

In the present investigation multiple correlation studies were carried

out between the hnked variables as well as between non-correlated physico-chemical and

biotic parameters. The results are shown in table 60 and 61 respectively.

Total alkalinity and pH when considered simultaneously, they

showed a significant positive correlation with total phytoplankton, pH alone had no

significant effect (R = 0.103) on total phytoplankton and rising alkalinity alone had an

91

adverse effect on total phytoplaiiktoii but with rising total alkalinity and pH favoured the

abundance of total phytoplankton ( p < 0.05),

Similarly, a large negative correlation (r = -0.773) between total

phytoplanton and total alkalinity showed that with decrease in alkalinity, total phytoplankton

was found to be increased and this increase was moderately significant (p < 0.1), but when

a correlation between total phytoplankton, total alkalinity and calcium content was studied,

abundance of total phytoplankton was found to be highly significant ( p <0.01). Similar,

results were also obtained when a multiple correlation between total phytoplankton, total

alkalinity and chlorides was taken into consideration (Table - 61). The multiple correlation

between water temperature, calcium content and total phytoplankton indicated much more

favourable condition for tlie abuandance of total phytoplnkton (p < 0,01).

A large negative correlation ( R = - 0,665) between rotifers arjd DO

showed that inciese in the rotifer count reflected in lowering down the dissolved oxygen of

the lake. But the multiple correlation between rotifers, DO and free C02 content indicated a

favourable condition for rotifers (p < 0.1), Similarly a result of multiple correlation between

total zooplankton, water temperature and total alkalinity was found to favourable for rotifer

abundance at 5% level (Table - 61), Increasing hardness alone or increase in sulphate

content alone could not show any significant effect on rotifers (Table - 5) but the

simultaneous rise in both these parameters have significantly favoiu-ed the rotifers.

Total phytoplankton were seen positively correlate^l with chloride

content of the lake water at 10% level (R = 0.732), and the relation between phytoplankton

92

and C02 was found to be insignificant. However a multiple correlation between total

phytoplankton, C02 and chloride was found to be significant at 1% level. Chloride on

getting dissolved in lake water, the free chlorine forms HOCI. This ondissociated form is

bactericidal agent and kills the bateria developing on the decaying plant parts and as a

results the phytoplankton starts using available C02 and thus might have flourished and

hence the multiple correlation between these three might have obeserved as significant

(p <0.01).

The correlation between NPP and total zooplankton as well as the

correlation between NPP and total phytoplankton was found to be insignificant even at 10%

level but when both total zooplankton and total phytoplnakton abundance was collectively

considerd, then the correlation was found to be significant at 1% level indicating that a net

primary productivity depends upon botli phytoplankton and zooplankton population.

From the multiple correlations as considered in the present studies, it

can be suggested that tfie productivity depends on the variables like phytoplankton,

zooplankton, sulphate, nitrates, and also on the pH and alkalinity of the lake water.

Macrophytes, as components of freshwater ecosystem, perform a kfty role in

determining the structure and functions of lake ecosystems (Kaul et al, 1978; Parparov,

1990).The lake Wadali sustained moderate growth of microphytes. Which were mainly

found to be submerged, floating and marginals, 22 different spc<-ies of macrophytes were

recorded from the lake and its chatchment area. The macrophytes from the cachment are a

were also given thought as they come under water, during rainy season. Maximum number

93

of macrophytes were sees) at and around sampling stations IV,V and VL Hydrilla,

Vallisnaria, Ceratopftylum and chara dominated the lake.

The macrophytes derive nutrients from the bottom sediment nutrient

poor affecting the productivity of the lake (Trisal, 1981; Paiidit, 1984). However, the

consumption of nutiients helps in maintaining the algal bloom under control, otherwise the

growth of algal blooms usually decrease the dissolved oxygen content. In the present

invetigation maximum zooplanktons and phytoplanktons were seen at stations IV, V and VI,

though these stations were also rich in macrophytes. The macrophytes might be responsible

for the luxurient growth of planktons, by maintaining the ecological balance. Further, Pandit

(1984) suggested that macrophytes help to fight pollution. The submerged species of

macrophytes found at the margins also at as gre^n manure which might have favoured tlie

abuandance of zooplankton in the lake Wadali. Besides food, the marginal and submurged

macrophytes also provided suitable breeding and sheltering places for the

macroinvertebrates and fishes. Pandit(1984) and Pandit et at., (1985) recorded leaves and

stems of submergeii and marginal plants, as the breeding fishes for many

macroinvertebrates including the insects. The summer migrants and resident birds obseved

in the present investigation were found to built their nest in the zones of the lake and thus

macrophytes observed in the lake Wadali and its catchment area were of use to the birds,

particularly the babblers. The nests of babblers were also later on found to be used by the

migratory bird, pied crested cuckoo, for egg laying.

Macrophytes, especially the submerged species, Ipomoea aquatica

94

observed at sampliug stahoas, V aiid VI fomid to give support to large qoaiHities of

epiphytic algae and also periphytou at these sampling stations, which might have also

formed the favouralble environment for molluscs juid fishes and hence a large numer of

these animals were seen at these sampUng stations during the period of investigation. Pandit

(1984) also reported similar type of ovservatiions in Dal lake of Kashmir,The macrophytes

growing in the lake also constitutes the principle source of food in the food chains of fishes

and water-birds like ducks. Lemna sp.. formed the favourable food of ducks. Kaul and

Pandit (1980) and Pandit and Fotedar (1982) have emphasized the relative importance of

Polygonum, Typha and Lemna as the potential food plants of aqutic birds. All these

macrophytes were found to be abuandant at sampling stations V and VI where the migratory

aquatic birds and resident ducks were seen abundant during the period of this investigation,

Hence, it is suggested that macrophytes forms integral part of fresh water ecosystem.

They are of great importance and hence need special attention as regards to their

exploitation and manageiBent.

jTherefore, it can be concluded that the biotic components of the

water of lake Wadali investigated were, thus foutsd to be dependent on large number of

abiotic parameters in different combinations and these combinations and their abundance

was also found to be dependent on food habits and macrophytes found in lake water and

also in ttie catchment area. However, the results of ttie present study indicated the

ohgotrophic nature of the lake Wadali. Enviornmental variables like water temperature,

alkalinity, pH, chloride, dissolved oxygen, ;ind the nutrients like sulphates, nitrates,

phosphates etc. were also found to be most important of all with resjiect to the productivity

of tlie lake. The pollution indicator plant and animal species were predoaunantly found - at

95

certain regions of the lake where human activites were more, confirming the water to be

unsafe for drinking and also for intensive fish culture. Hence, it is concluded that, the

present water body of Wadali lake is becoming polluted! Looking towards the large

number of visiting migratory birds, proper measures are essential to avoid the pollution of

water of lake so that still more migratory birds may visit in the coming years and similarly,

this may lead to an increase in the fishery activities and proper use of water of the Wadali

lake of Amravati for the welfare of the society.

96