algal diversity in three freshwater pond ecosystem...

Algal Diversity in Three Freshwater Pond Ecosystem at Tiruvannamalai, TamilnaduRamakrishnan, N., Hariprasath and Sampathkumar, K.Government Arts College, Thiruvannamalai - 606 603, Tamil Nadu, IndiaE-mail: [email protected]

Algal diversity is the key parameter to determine the productive nature of the pond ecosystem. The limnological survey and the algal diversity in three freshwater ponds in Tiruvannamalai (12o 15’ NLand 79o 07’EL) district, Tamil Nadu was undertaken during April 2000 to March 2001. Sampling was done at monthly intervals. Water samples were analysed for the concentration of various physico-chemical parameters (water temperature, free CO2, pH, DO, nitrate, phosphate, silicate and calcium as described in APHA (1995). Phytoplankton of all the ponds was collected by filtration of 10 liters of water through plankton net of bolting silk (mesh size 173 / linear inches). Filtered phytoplanktons were fixed in 4% formalin (Kumar & Singh, 2000). Enumeration of algal density was done by taking 1ml of sub sample in a Sedgwick Rafter chamber from 10ml of the sample. The results have been expressed as units per liter. Identification of algal taxa was done using standard keys.

Phytoplankton standing crop formed two peaks in the present study i.e. during June and December. Lowest standing crop values were recorded during rainy months in the three ponds. The division Cyanophyta registered maximum percent of species (43.90) than other divisions followed by Chlorophyta (29.26), Bacillariophyta (19.51) and Euglenophyta (7.31). Phytoplankton diversity was regulated by various physico-chemical parameters and showed positive as well as negative correlation within themselves and the phytoplankton density. Among the environmental factors, water temperature plays a significant role in affecting the growth and abundance of phytoplankton. Multiple regression analysis was done between phytoplankton density (var 1) and the environmental factors (var 2 to 9), which revealed that more than 96 to 99% of variation in phytoplankton density was influenced by these physico-chemical factors recorded in this study and only 1- 4% by other factors which were not considered in the present study. By means of multiple regression equations embodied in the text, the phytoplankton density may be predicted at any time.

INTRODUCTIONEnvironmental problems are complex and multidisciplinary in nature especially in wetland ecosystem. In general, the importance of the diversity of planktonic and benthic organisms are generally overlooked. The wetlands, generally associated with the rivers, lakes and reservoirs are not only rich in biodiversity but contribute significantly to the maintenance of water quality. Major effect on biodiversity of the aquatic system is the environmental factors and chemical aspects of the water body (Gopal, 1997). Internationally, however, the biodiversity in freshwater environments has started attracting some attention in recent years, for example, the issues related to biodiversity in aquatic ecosystem in the programme of the UNESCO and the International Union of Biological Sciences.

The main aim of this paper is to draw attention to the large proportion of diversity that exists in the freshwater environments, its importance, and the need for its conservation. The floristic component of aquatic biota is dominated by algae in open deepwater (Round, 1977). So, in this aspect the present study was undertaken in three freshwater ponds on their algal diversity and limnological aspects over various months of the year.

MATERIALS AND METHODSThree experimental ponds selected for this study are situated at the Girivalam path around Tiruvannamalai Hill, Tiruvannamalai (12o 15’ NL and 79o 07’ EL). All the ponds are eutrophic in nature. Sampling was done at monthly intervals from April 2000 to March 2001. Water samples were analysed for the concentration of various physico-chemical parameters (water temperature, free CO2, pH, DO, nitrate, phosphate, silicate and calcium) described as in APHA (1995).

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Phytoplanktons of all the ponds were collected by the filtration of ten liters of water through plankton net of bolting silk with standard mesh size (173 per linear inches). Filtered phytoplankton samples were fixed in 4% formalin. Enumeration of algae was done by taking 1ml of sub sample in a Sedgwick Rafter chamber from 10ml of the sample. The results have been expressed as units per liter. Identification of algal taxa was done following the key given by Smith (1950), Desikachary (1959); Randhawa (1959); Philipose (1967) and Gonzalves (1981).

RESULTSA perusal of Figures 1 to 8 reveals that the physico-chemical nature of the three experimental ponds clearly indicates of their eutrophic status. Water temperature recorded maximum value during May for ponds I and II and for pond III in June. Minimum value was registered during November for pond II and in other ponds in January (Fig 1). Free CO2 registered more or less same trend as prevailed in water temperature of all the ponds. Pond III registered the lowest value than other two ponds throughout the study period. Highest value of free CO2 (3.60mg/l) was recorded in pond II during November (Fig 2). Pond III was alkaline throughout the study period, whereas in pond II, acidic pH prevailed in October and November. Pond I registered acidic pH only during January (Fig 3). Pond III registered two peak values during July and November whereas other two sites registered lower value during these months (Fig 3).

Dissolved oxygen (DO) also showed the same trend as pH in all the ponds. Comparing the values of all the ponds, pond I showed higher values than other two ponds throughout the period. Nutrients like nitrates and phosphates registered lower values during June and July. Maximum values were observed during November for all the three ponds, except in pond I, where higher nitrate value was observed during December (Fig 5 & 6). Silicate content of the experimental ponds registered same trend as for nitrate and phosphate (Fig 7). Calcium in pond II and III showed same trend as observed in other nutrients whereas in pond I three peaks were observed in a year cycle (Fig 8).

A total number of 82 algal taxa were identified in three ponds which were distributed over four major divisions like 36 species in Cyanophyta, 24 species in Chlorophyta, 16 species in Bacillariophyta and 6 species in Euglenophyta. Specific distribution of species in each division of algae in three ponds shown in Fig 9a-d, indicated more number of exclusive occurrence of species in Cyanophyta division in pond III (Fig 9a), whereas for other divisions specific and exclusive occurrence of species appeared in pond I (Fig. 9b-d). Maximum number of species occurrence was noticed in the division Cyanophyta (36) in pond III (Fig 9a). Nevertheless, higher diversity of species in other three divisions occurred in pond I (Fig 10). The less polluted pond I registered higher algal diversity than the other two ponds. The total algal standing crop and population density of cyanophyta showed two distinct peaks during June and December in all the ponds (Fig 10 - 12).

Pond I registered greater algal density than the other two ponds (Fig 10), however highest standing crop was observed in pond III during June and December (Fig 12). The divisions like Cyanophyta and Bacillariophyta registered its peak value during summer months, in the other two divisions peak values were observed during winter months (Fig 11). Relationships between variables like total algal standing crop (var 1) with the environmental factors (master variables) like water temperature, free CO2, pH, DO, nitrate, phosphate, silicate and calcium (var 2- 9) were tested with correlation matrix for three ponds. These are presented in Table 1 - 3.

Correlation analysis was carried out between environmental factors (var 2-9) with total standing crop (var 1) and division wise algal standing crop for three ponds (given in Table 4-6). A forward stepwise multiple regression analysis technique was applied to evaluate the effect of all environmental factors like water temperature, free CO2, pH, DO, nitrate, phosphate, silicate and calcium. These were treated as independent variables (var 2 - 9) with algal standing crop (var 1) as dependent variable. The results are presented in Table 7 - 9 for the three ponds respectively. The master variables (var 2-9) were not individually regressed with total algal standing crop (var 1); their influence on the overall equation was more significant in pond II than other two ponds (Fig 13 - 15)

DISCUSSIONThe seasonal distribution of phytoplankton is mainly determined by various environmental factors such as water temperature, pH, free CO2, dissolved oxygen and nutrients of water like nitrogen, phosphate, silicate and calcium (Hamilton et al 1999; Wallace et al; 1999). Distinct low water temperature was noticed during November to January in all the ponds, which may be influenced by North East Monsoon and low atmospheric temperature (Vass & Sachian, 1955; Chow, 1958; Michael, 1969 and Rajendran Nair, 2000). In warmer months i.e. from March to June the increased water temperature was due to increase in atmospheric temperature and longer days. A similar seasonal variation in temperature was reported in most of the Indian deep wetland systems (Srinivasan, 1964; Singhal et al., 1986; Kanshik et al., 1989; 1991; Sobha et al., 2002). Correlation matrix analysis made between environmental factors showed more negative correlation in pond I than in other two ponds. Only water temperature and pH, DO and calcium showed positive correlation. In pond III except pH, DO and silicate all others showed negative correlations (Table 1 - 3).

Free CO2 showed significant negative correlation with pH (Table 1-3). This was inconformity with Ganapathi (1960), Singh (1965), Verma (1969), Vysa (1968), Wetzel (1972) and Kumar (1997). The sharp decline in pH was due to rain water in agreement with decrease in the density of phytoplankton (Bohra, 1977). Higher values of dissolved oxygen (DO) content were recorded in winter months for all the ponds, the period in which the water temperature was lower. This might be due to the fact that the solubility of DO increases with decrease in water temperature. This was in conformity with Kumar (1996 - b). The correlation coefficient (r) values between these two variables (var 2 Vs var 5) showed significant negative correlations (-0.822) (Table -1). Nutrients like nitrate (var 6), phosphate (var 7), silicate (var 8) and calcium (var 9) are the four major nutrients, which control the growth of algae in deep wetland ecosystem. Our earlier results also conformed to the present investigation (Figure 5 - 8). There was negative correlation (r) observed between majority of the nutrients (var 6 - 9) with total algal standing crop in all the ponds (Table 1- 3) except phosphate in pond I (+0.103), calcium (0.548) in pond II and silicate in pond III (+0.123), which showed positive correlation (Singhal et al., 1986).

Greater algal diversity was observed in pond I followed by pond II and III however the density of algae was maximum in pond III than in other two ponds. Excessive growth of certain algal species like Anabaena, Microcystis, Oscillatoria, Scenedesmus, Pediastrum, Navicula and Tabellaria was known to indicate nutrient enrichment of deep wetland ecosystem (Bush and Welch, 1972; Kumar, 1990; Pandey et al 1998 and Ramakrishnan, 2002 a,b). Cyanophyta division was the most significant group contributing above 40% in all the ponds. The sequence of percentage in all the ponds was: Cyanophyta > Chlorophyta > Bacillariophyta > Euglenophyta. The present result was in conformity with Singh and Swarup (1979).

Among the four algal divisions Cyanophyta density was greater in all the ponds and lowest density was observed in Euglenophyta division. An interesting result that was found to exist in the present investigation was an inverse relationship between Cyanophyta and Chlorophyta in pond I (Fig 10) during rainy months and also negative correlation between Cyanophyta and Euglenophyta in pond I. According to Holmes & Whitton (1981) and Tiwari et al (2001) abundance of Cyanophyta and low population of Chlorophyta, Bacillariophyta in the experimental pond is an indication of eutrophic nature of the ponds. This condition prevailed in our present investigations.

Distinct two peaks of total algal standing crop are clearly indicated in the present investigation. Moreover, the seasonal variations of phytoplankton along with temperature changes, may be due to oxygen and carbon-dioxide variations along with other physico-chemical characteristics of water, which also affect the phytoplankton density and diversity (Tripathy & Pandey 1990). Several authors have emphasised the importance of water temperature in the periodicity of BGA (blue-green algae), which was also observed in the present study (Singh Swarup, 1978; Reynolds et al., 1981 and Pandey et al., 1994). Vysa & Kumar (1968) indicate that Euglenoids show their presence during rainy season only, whereas in the present study the species of Euglenoids occurred throughout the period of study, however maximum density was registered during rainy or winter months in pond I and II (Table 4 - 5).

This was in conformity with Pandey et al., (1994). Correlation (r) matrix analysis between Euglenophyta and master variables (environmental factors var 2 - 9) showed there was an inverse relationship established with water temperature and pH (Table 5-6). Nevertheless the other factors showed positive correlation, while in pond II and III majority of the factors showed negative correlations (Laxminarayan, 1965; Munwar, 1970; Rai & Kumar, 1977 and Mathew, 1978).

Correlation analysis between Chlorophyta and environmental master variables (var 2 - 9) showed more positive values, whereas Bacillariophyta division with environmental variables water temperature and pH showed negative correlation in all the ponds. All nutrients (var 6 - 9) showed positive correlation with chlorophyta except nitrate nitrogen in pond III (Table 6). Correlation matrix analysis between Bacillariophyta and environmental variables (var 2-9) in three ponds showed negative correlations except few factors like water temperature, which showed positive correlation in all the ponds. pH showed positive correlation in Pond II and III and calcium showed only positive value in pond II (Table 5 - 6).

Multiple regression analysis (Table 4 - 6) revealed the value of coefficient of determination and clearly indicated that more than 96 to 99% of variation in phytoplankton density was influenced by physico-chemical factors and only 1 - 4% by other factors not considered in the present study. By means of multiple regression equations embodied in the text, phytoplankton density may be predicted at any time. Based on the collective contribution in the overall regression between dependent variable total algal standing crop (var1) with independent variables (Water temperature, free CO 2, pH, DO, N, P, Si and Ca) var 2 to var 9. The results were presented in figure 15-17. These graphs show the observed verses predicted values for total algal standing crop (var 1) with the physico-chemical variables (var 2 to 9).

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Fig 10 Pond -I

Fig 11 Pond –II

Fig 12 Pond –III

Figure 10 - 12. Total algal standing crop and division wise algal density of the experimental ponds

Fig 13. Predicted versus observed graph for total algal standing crop (depedent) regressed (r= 0.8286, p = 0.6354) with master variables (Water temperature, free CO2, DO, N, P, Si, Ca) in pond I.

Fig 14. Predicted versus observed graph for total algal standing crop (depedent) regressed (r= 0.9643, p = 0.10739) with master variables (Water temperature, free CO2, DO, N, P, Si, Ca) in pond II.

Fig 15. Predicted versus observed graph for total algal standing crop (depedent) regressed (r= 0.9207, p = 0.29437) with master variables (Water temperature, free CO2, DO, N, P, Si, Ca) in pond III.

Table 7 : Multiple regression analysis results between environmental factors (var 2-9) with the algal standing crop (var 1) for the Pond I.

Dep. Var : Var 1 Multiple R = 0.82860854 F = 0.8215238 R2 = 0.68659212 df = 8, 3

No. of cases : 12 Adjusted R2 = -0.14916223 p = 0.635461

Standard error of estimate : 1319.3550854

Intercept : 64073.450846 Std. Error = 59048.49 t(3) = 1.0851P < 0.3673

Table 8 : Multiple regression analysis results between environmental factors (var 2-9) with the algal standing crop (var 1) for the Pond II.


No. of cases : 12 Adjusted R2 = 0.74260822 p = 0.107393


Intercept : -5750.233002 Std. Error = 10693.79 t(3) = -0.9377P < 0.6281

Table 9 : Multiple regression analysis results between environmental factors (var 2-9) with the algal standing crop (var 1) for the Pond II.


No. of cases : 12 Adjusted R2 = 0.44144552 p = 0.294371


Intercept : -18911.91458 Std. Error = 26745.20 t(3) = -0.7071P < 0.5305

Figure 9a-d. Venn diagrams depicting the specific distribution of species in four algal division of the three experimental ponds.

Table 1 : Correlation matrix of physicochemical variables (var 2-9) with total standing algal standing crop (var 1) for pond I.

VAR2 VAR3 VAR4 VAR5 VAR6 VAR7 VAR8 VAR9 VAR1Temp. VAR2 1F.CO2 VAR3 -0.5089 1

pH VAR4 -0.5843 -0.8526 1DO VAR5 -0.8224 0.4419 -0.4556 1N VAR6 -0.5579 0.2299 -0.1606 0.8287 1P VAR7 -0.3960 0.1528 -0.0850 0.6132 0.7392 1Si VAR8 -0.0580 0.0889 0.10951 0.3872 0.5361 0.8220 1Ca VAR9 -0.4437 -0.2176 0.11018 0.6193 0.5595 0.5064 0.3845 1

VAR1 -0.1729 0.2119 -0.4660 0.0628 -0.1198 0.1030 -0.1150 -0.2783 1

Table 2 : Correlation matrix of physicochemical variables (var 2-9) with total standing algal standing crop (var 1) for pond II.

VAR2 VAR3 VAR4 VAR5 VAR6 VAR7 VAR8 VAR9VAR

1Temp

.VAR

2 1F.CO2 VAR

3-

0.6652 1pH VAR

4 0.8568-

0.6640 1DO VAR

5-

0.2411 0.5418-

0.2712 1N VAR

6-

0.6631 0.7959-

0.58990.072

8 1P VAR

7-

0.6036 0.7713-

0.44480.127

0 0.9191 1Si VAR

8-

0.4672 0.6109-

0.27690.123

8 0.7437 0.8638 1Ca VAR

9 0.0396 0.4300 0.19170.691

5 0.1010 0.2759 0.3593 1VAR

1 0.5040 0.0016 0.38660.335

2-

0.4162-

0.3489-

0.41040.539

4 1

Table 3 : Correlation matrix of physicochemical variables (var 2-9) with total standing algal standing crop (var 1) for pond III.

VAR2 VAR3 VAR4 VAR5 VAR6 VAR7 VAR8 VAR9 VAR1Temp

. VAR2 1F.CO2 VAR3 -0.6819 1

pH VAR4 0.2747-0.2836 1

DO VAR5 -0.9041 0.6470 -0.5420 1N VAR6 -0.5759 0.4602 0.1916 0.3545 1P VAR7 -0.6757 0.5690 -0.1923 0.6454 0.7279 1Si VAR8 -0.8689 0.5703 -0.1438 0.7521 0.7903 0.8366 1Ca VAR9 -0.4712 0.4409 -0.0177 0.2899 0.6456 0.6595 0.7111 1

VAR1 -0.0414-0.3855 0.0073 0.0872 -0.2431 -0.2239 0.1227 -0.008 1

Correlation coefficient (r) values

Table 4 Pond - I

Total Standing

cropCyanophyta Chlorophyta Bacillariophy

taEuglenophyt

a

Water Temp oC

-0.173 * -0.669 *** -0.827 *** 0.196 * -0.5669 ***

Free CO2 0.202 * 0.443 ** 0.580 *** -0.170 * 0.315 *pH -0.466 ** -0.582 ** -0.663 ** -0.137 * -0.403 **Do mg/l 0.033 * 0.360 * 0.481 ** -0.243 * 0.374 *N - 0.117 * 0.390 * 0.83 ** -0.310 * 0.585 **P 0.103 * 0.388 * 0.575 *** -0.083 * 0.621 ***Silicate -0.115 * 0.125 * 0.274* -0.190 * 0.329*Calcium - 0.278 * -0.680 ** 0.399 ** -0.297 * 0.323 *

Table 5 Pond - II

Total Standing


taEuglenophyt

a

Water Temp oC

0.484 ** 0.659 ** -0.279 * 0.708 ** 0.241 **

Free CO2 --0.028 * -0.219 * 0.664 ** -0.588 *** -0.435 **pH 0.331 * 0.531 ** -0.276 * 0.632 *** 0.189 *Do mg/l 0.382 * 0.024 * 0.874 *** -0.205 * -0.246 *N -0.457 *** -0.513 *** 0.165 * -0.676 *** -0.105 *P -0.385 * -0.455 ** 0.216 * -0.641 *** -0.151 *Silicate -0.394 * -0.451 ** 0.171 * -0.601 *** -0.131 *Calcium 0.548 *** 0.288 * 0.811 *** 0.096 * 0.381 *

Table 6 Pond - III

Total Standing


taEuglenophyt

a

Water Temp oC

-0.041 * -0.006 * -0.342 * 0.290 * 0.473 **

Free CO2 -0.386 * -0.263 * -0.136 * -0.640 *** -0.548 ***pH 0.55 * 0.132 * -0.009 * -0.198 * 0.237 *Do mg/l 0.87 * 0.052 * 0.409 ** -0.253 * -0.593 ***N -0.017 * -0.004 * -0.001 * -0.033 * -0.021 *P -0.224 * -0.173 * 0.024 * -0.490 ** -0.428 **Silicate 0.123 * 0.113 * 0.357 * -0.269 * -0.344 *Calcium -0.017 * -0.194 * 0.159 * -0.107 * 0.243 *

* Not Significant ** Significant at 1% level *** Significant at 5% level

Table 4 - 6. Correlation values between physico-chemical characteristics with total algal standing crop and division wise algal density

Fig 1 Water temperature oC

Fig 2 Free CO2 mg/l

Fig 3 pH

Fig 5 Nitrate mg/l

Fig 4 DO mg/l

Fig 6 Phosphate mg/l

Fig 7 Silicate mg/l

Fig 8 Calcium mg/l

Figure 1 - 8. Physico-chemical characteristics of the experimental ponds

algal diversity in three freshwater pond ecosystem...

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