Dec 24, 2010 - The sewage of the ashram is let into the river at this site. The remaining three sites (S5 to S7) are still downstream and are more near to the ...
Lake 2010: Wetlands, Biodiversity and Climate Change
EFFECT OF URBANIZATION ON NUTRIENT LOADING AND PHYTOPLANKTON DENSITIES IN RIVER GADHI AND DEHARANG RESERVOIR, PANVEL, MAHARASHTRA Minakhsi N. Gurav1 and Madhuri K. Pejaver2 1 2
C.K. Thakur A.C.S. College, New Panvel, Maharashtra
B.N. Bandodkar College of Science, Thane, Maharashtra
Abstract The aim of this study was to assess the effects of nutrients accumulation on phytoplankton densities. The relationship between nutrients and phytoplankton density changes depending upon the nutrient load which increases towards city due to urbanization and increasing anthropogenic activities. The present study was carried out for Gadhi River and its reservoir, Deharang, which is located upstream to the river. Urban water bodies are prone to eutrophication because of a number of factors like high nutrient loads from untreated sewage, anthropogenic activities and a high water residence time (slow flushing rate) which is found more often. Attempt was made to study the relation between nutrients and phytoplankton density with respect to urbanization as well as increased nutrient load. The phytoplankton densities of different genera responded differently to increasing load of nutrients as the river approaches the city. Pearson correlation was considered at 0.5 level significance to indicate the relationship between nutrient load and phytoplankton densities. Nitrate showed positive correlation with Cyanophyceae. No significant correlations were seen among phosphate and silicates and the phytoplankton densities. Key words: Urbanizations, nutrient loading, blooming, correlation coefficient, phytoplankton densities Introduction Increasing urbanization is leading to increased pollution stress on water bodies. This stress is due to various anthropogenic activities including sewage disposal. Due to sewage disposal nutrient enrichment takes place which is followed by alterations in the phytoplankton community structure, growth of excessive algal biomass and possible toxic algal blooms; if the accumulated organic matter exceeds system’s carrying capacity, the hypoxia can lead to a decline in fisheries and shellfisheries yields, poor water quality and ecosystems deterioration (Karydis 2009). Few studies are available examining the relationship between phytoplankton and nutrient concentration changes in wastewater treatment plants (Oudra, 1990). Many water bodies in India are still neglected and less attention is paid towards maintenance of these water bodies. The present paper contributes results of an investigation on the nutrient loading due to urbanization and its effect on densities of the phytoplankton community in River Gadhi and Deharang reservoir Panvel. The main nutrients that contribute to algal growth are phosphates, nitrates and silicates. They are let into water stream due to anthropogenic activities. Description of the study area
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Lake 2010: Wetlands, Biodiversity and Climate Change The present study was undertaken at river Gadhi and its reservoir. The river originates from a reservoir in the mountain and flows across Panvel city and meets the creek. Along its stretch of 16 km, 7 sites were selected, out of which four (S1 to S4) are upstream and away from city. Among these, first site (S1) is the reservoir and second site (S2) is on Gadhi river, which is close to reservoir. These sites have less impact of human hindrance. The site S3 is downstream on the river and show moderate impact of human interference. S4 is near Shantivan, a social organization of Babasaheb Amate which treats leprosy patients, provides care and home place to old people, and run many social activities like running small scale industries by the cured patients. The sewage of the ashram is let into the river at this site. The remaining three sites (S5 to S7) are still downstream and are more near to the creek. These sites are the victims of anthropogenic activities. Sit S5 receives untreated sewage of Sukapur village, S6 receives the untreated sewage of New Panvel and S7 has cremation site. Though these sites are very close variation in water characteristics and phytoplankton densities is often noted. The sites are mentioned in Fig.1
Fig. 1 Location of study sites Materials and methods Using a wide mouth container, 500 ml of surface water samples were collected from different spots at every site from near the boundaries of the river and the reservoir. The samples were collected monthly for a period of 16 months and analyzed for the density of phytoplankton. The samples from every station were preserved in separate container for phytoplankton. For immediate fixation, Lugol’s Iodine solution made in formalin was used in the field and later 4% formaldehyde was used for long term preservation. The phytoplankton were concentrated by allowing them to settle for about 15 to 20 days and then the upper water was decanted by using a rubber tube. The phytoplankton were identified by using standard identification keys (Fritsch, 1979; Sarode and Kamat, 1984; Bellinger, 1992). For quantitative estimation, the counting was done by using Lackey’s Drop method (APHA 1985). For study of nutrients, surface water samples from different sites, at the bank of the river were collected monthly, in early morning hours, in clean plastic carboy of 2 litres capacity. The samples could not be taken from the middle as
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Lake 2010: Wetlands, Biodiversity and Climate Change there was no facility to reach the centre of the river. Two to three samples were collected from each site and the data was pooled together. Water analysis was performed as per the methods prescribed in Trivedi and Goel (1984 ) and Standard Methods (APHA,1990) by using following methods. Silicates
Molybdosilicate Method
Nitrates
PhenoldisulphonicAcid Method
Phosphates
Stannous Chloride Method
Results Nutrients During the present study the silicates were found to be in the range of 0-44.8 mg/l from site S1 to S7 (Table 1). Very high concentrations of silicates were noted rarely during the study period. The high concentration of silicates coincides with visually observed sand dredging activities and runoff during rainy season. The average values of silicates ranged between 8.10 – 11.32 mg/l (Table 1, Fig. 2). In an average, site S3 showed highest concentration of silicates, where sand dredging activities were seen most of the time. There were no noticeable increments in the concentration of silicates towards city (Fig. 2). Table 1: Monthly variation in silicates (mg/l) during the study period Sites
S1
S2
S3
S4
S5
S6
S7
Apr-06
6.50
6.20
6.50
6.50
6.50
6.50
6.50
May-06
8.80
14.20
13.80
16.20
14.30
12.30
10.30
Jun-06
0.40
0.40
0.80
0.80
0.00
0.40
0.40
Jul-06
0.60
1.00
1.00
0.60
1.00
1.00
1.00
Aug-06
0.80
5.20
4.10
5.20
5.20
4.20
4.00
Sep-06
10.20
12.80
0.00
1.12
12.60
1.95
11.00
Oct-06
3.60
3.50
4.20
4.80
2.80
4.80
4.80
Nov-06
10.80
6.60
11.20
12.20
15.40
10.40
14.40
Dec-06
4.80
5.20
8.00
8.80
8.20
8.40
5.80
Jan-07
8.40
6.80
7.80
4.80
9.80
7.80
9.20
Feb-07
6.60
18.00
15.00
15.60
10.60
10.70
5.80
Mar-07
12.80
5.20
6.80
6.20
1.95
5.00
5.20
Apr-07
3.60
4.80
44.80
8.00
0.00
5.20
28.20
May-07
24.00
26.30
27.00
37.95
28.00
11.70
20.30
Jun-07
11.20
11.20
10.80
11.20
6.00
4.40
3.40
Jul-07
33.00
8.37
19.25
9.48
35.00
35.00
33.00
Months
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Lake 2010: Wetlands, Biodiversity and Climate Change Average
9.13
8.49
11.32
9.34
9.83
8.11
10.21
Table 2: Monthly variation in nitrates (mg/l) during the study period Sites
S1
S2
S3
Apr-06
0.64
0.89
0.83
0.58
6.00
6.70
6.20
May-06
0.52
1.30
0.78
14.54
18.00
13.50
9.00
Jun-06
0.70
0.50
0.70
0.45
0.70
0.50
0.50
Jul-06
0.28
0.42
0.48
0.34
0.34
0.26
0.40
Aug-06
0.65
0.85
1.10
1.00
1.10
1.00
0.65
Sep-06
1.71
2.60
1.40
1.70
1.80
1.60
1.50
Oct-06
0.00
0.18
0.27
0.00
0.18
0.27
1.30
Nov-06
0.36
2.15
0.90
0.65
0.70
0.80
0.72
Dec-06
0.18
0.00
0.00
0.00
0.00
0.18
0.27
Jan-07
5.60
5.60
6.20
6.20
6.20
6.20
6.20
Feb-07
0.36
0.09
0.09
0.18
0.09
1.50
1.00
Mar-07
0.09
0.09
0.65
0.72
0.36
0.72
0.36
Apr-07
1.50
0.40
2.15
2.50
2.60
2.55
2.15
May-07
0.65
0.54
0.72
0.65
0.81
0.45
0.81
Jun-07
0.34
0.34
0.34
0.34
0.34
0.34
0.50
Jul-07
5.60
5.60
6.20
6.20
6.20
6.20
6.20
Average
1.20
1.35
1.43
2.25
2.84
2.67
2.36
Months
S4
S5
S6
S7
The nitrates concentrations from site S1 to S7 were found to be in the range of 0-18 mg/l (Table 2). The higher concentration was noted at S5 that receives sewage of village Sukapur which is very next to the city. The average nitrate concentration was between 1.20 and 2.84 mg/l (Table 2, Fig. 2). The concentration of nitrates increased toward down stream as the river approached the city. However, the average nitrate concentration was found to be decreasing slightly from S5 to S7 (Fig. 2). Phosphate concentration from S1 to S7 ranged between 0-19.65 mg/l (Table 3). The average concentrations of all sites were between 0.19 to 4.37 mg/l (Table 3, Fig. 2). The concentration of phosphate was very low at upstream and increased at down stream sites showing highest concentration at S6 which receives untreated sewage of Panvel city. Table 3: Monthly variation in phosphates (mg/l) during the study period Sites
22nd-24th December 2010
S1
S2
S3
S4
S5
S6
S7
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Lake 2010: Wetlands, Biodiversity and Climate Change Months Apr-06
0.12
0.06
0.00
0.31
0.19
0.44
0.19
May-06
0.19
0.12
0.38
0.57
1.60
3.40
0.89
Jun-06
0.00
0.00
0.00
0.00
0.12
0.31
0.12
Jul-06
0.00
0.00
0.12
0.12
0.06
1.80
0.19
Aug-06
0.06
0.06
0.06
0.06
0.06
0.12
0.12
Sep-06
0.06
0.06
0.63
0.12
0.25
19.65
0.82
Oct-06
0.06
0.06
0.48
0.10
0.33
10.80
0.82
Nov-06
0.06
0.06
0.12
0.06
0.63
8.03
1.08
Dec-06
0.63
0.70
0.70
0.89
2.40
3.70
1.08
Jan-07
0.12
0.25
0.25
0.25
3.00
2.70
1.20
Feb-07
0.12
0.19
0.25
0.12
0.19
2.70
1.02
Mar-07
0.38
0.38
0.63
1.14
2.70
4.20
0.70
Apr-07
0.19
0.44
0.44
1.20
2.70
1.80
2.70
May-07
0.06
0.12
0.19
1.30
1.70
5.40
1.40
Jun-07
0.86
0.86
0.92
0.92
3.42
4.30
2.60
Jul-07
0.20
0.14
0.14
0.14
0.62
0.62
0.27
Average
0.19
0.22
0.33
0.46
1.25
4.37
0.95
Fig. 2 Sitewise variation in average concentration of nutrients Phytoplankton densities Phytoplankton showed higher densities for sites S4, S5, S6 and S7 which are very near to city ( Fig. 3). The average values of phytoplankton densities showed higher densities of phytoplankton at S4 and S5 (Fig. 4).
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Lake 2010: Wetlands, Biodiversity and Climate Change
Fig.3 Monthly distribution of phytoplankton densities
Fig.4 Sitewise distribution of average
phytoplankton densities Correlation coefficient between nutrients and phytoplankton densities Significant correlation was found between nitrate concentration and the densities of Cyanophyceae at S2 and S5. Chlorphyceae and Bascillariophyceae did not show any correlation with nitrate densities during the present study, even though there is significant increase in the concentration of nitrates towards the city (Table 4). At most of the sites the correlation between nitrates and phytoplankton densities was found to be insignificant. Table 4: Relation between nitrate concentration and phytoplankton densities and correlation coefficient
Site
Nitrat
s
es
Phytoplankton densities
Correlation Coefficient
Cyanophyc
Chlorophyc
Bascillariophy
Cyanophyc
Chlorophyc
Bascillariophyc
eae
eae
cea
eae
eae
eae
S1
0.91
7221
40
70325
-0.2
-0.1
0
S2
1.06
39750
27296
136839
0.5
-0.2
-0.4
S3
1.10
33030
74846
28694
-0.1
-0.06
-0.2
S4
1.99
583614
90278
1341132
0.1
0.3
-0.1
S5
2.61
469599
357888
1070047
0.6
-0.1
-0.1
S6
2.43
436580
288096
243737
-0.1
-0.2
-0.2
S7
2.10
337880
534257
136831
0
-0.1
-0.2
Phosphates showed significant correlation with Cyanophyceae at S4 and S7 and with Bacillariophyceae at S4 (Table 5). Table 5: Relation between phosphate concentration and phytoplankton densities and correlation coefficient
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Lake 2010: Wetlands, Biodiversity and Climate Change
Site
Phospha
s
tes
Phytoplankton densities
Correlation Coefficient
Cyanophyc
Chlorophyc
Bascillarioph
Cyanophyc
Chlorophyc
Bascillariophy
eae
eae
ycea
eae
eae
ceae
S1
0.19
7222
41
65930
-0.1
0.0
0.0
S2
0.22
39750
27296
128287
0.1
0.2
0.2
S3
0.33
33030
74846
28694
0.2
-0.1
-0.3
S4
0.46
583615
90278
1341132
0.7
0.0
0.5
S5
1.25
440250
357888
1003169
0.2
0.2
0.3
S6
4.37
436581
288096
243738
0.0
-0.1
-0.2
S7
0.95
337881
534257
136831
0.5
0.1
0.1
Silicates showed significant correlation at S4 with Cyanophyceae and Bascillariophyceae and at S3 with Cholorophyceae (Table 6). Though silicate is one of the essential nutrients for the growth of diatoms, the insignificant correlation is seen at almost all the sites. Table6: Relation between silicates concentration and phytoplankton densities and correlation coefficient Phytoplankton densities
Correlation Coefficient
Site
Silicat
s
es
S1
9.13
7222
41
65930
0.0
0.0
0.0
S2
8.49
39750
27296
128287
0.1
0.0
0.1
S3
11.32
33030
74846
28694
0.1
0.7
-0.2
S4
9.34
583615
90278
1341132
0.8
0.0
0.8
S5
9.83
440250
357888
1003169
0.4
-0.1
-0.2
S6
8.11
436581
288096
243738
0.0
0.0
-0.2
S7
10.21
337881
534257
136831
0.4
-0.2
0.0
Cyanophyc
Chlorophyc
Bascillariophyc
Cyanophyc
Chlorophyc
Bascillariophyc
eae
eae
eae
eae
eae
eae
Discussion Both phytoplankton and microalgae absorb and utilize silicates, phosphates and nitrates. During the present study, nitrate did not show significant correlation with phytoplankton densities. However, strong positive correlation of Cyanophyceae with phytoplankton densities is seen at S2 and S5, it cannot be correlated with any pollution status as S2 is away from the city and free from anthropogenic activities, where as S5 is highly affected with sewage disposal. According to Meesuko et al. (2007) and Graham and Wilcox (2000) Cyanophyceae is an important nitrogen-fixing planktonic bloom-former in tropical freshwaters around the world. However, no corresponding observation was noted during the present study. Radwan (2005) in his studies found negative correlation of nitrate and the total count
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Lake 2010: Wetlands, Biodiversity and Climate Change of plankton, while the relation was positive in the different months depending on the amount of discharges from the drains and the location of each station from the point of discharge. The same can be applicable during the present studies. The insignificant correlation was seen in the phosphates and phytoplankton densities at most of the time. Meesuko et al. (2007) also had similar observation during his studies on Kaeng Krachan reservoir. Radwan (1994) mentioned that there is strong positive correlation between phosphate concentration and phytoplankton number. Howerver, Radwan (2005) in his statistical studies found that insignificant correlation exists between phytoplankton number and phosphate concentration which is true for the sites during the present study. According to Graneli et al. (1999), phosphorus is essential for all living organisms and is a common growth limiting factor for phytoplankton in lakes and reservoirs as it is often only available in low concentrations with a high turn-over rate. However, higher concentrations of phosphates at down stream sites are owing to the sewage disposal. It may signify that there is more input of phosphate than consumption by algae. Silicon is the second most abundant element in the earth's crust. There are innumerable mineral sources of silica for natural waters, but most are quite resistant to chemical processes (Faust and Aly 1981). Silicates also showed insignificant correlation with phytoplankton densities even though it had shown strong correlation at S4 with Cyanophycea and Bascillariophyceae. The increasing number of diatoms (Bascillariophyceae) might have utilized silicates for their growth leaving varied amounts of silicates in water depending upon the load due to anthropogenic activities. Nutrient load and phytoplankton densities increased downstream though the significant correlation cannot be predicted. However, increased number of phytoplankton densities may lead to liberation of some toxic substances and conditions like hypoxia leading to serious problems like fish kill. Therefore, from the present study it is concluded that due to urbanization the nutrient load increases leading to phytoplankton bloom leaving the nutrients undetectable most of the time or in very high densities. Nutrients are essential phytoplankton for their growth in very trace amounts. Nutrient loading creates excess nutrients and leads to bloom. This bloom may liberate toxic substances most of the time. This means the water quality is under threat from nutrient enrichment, even if the degree of blooming was still low when compared to blooming in temperate regions or nutrients are below detectable levels. Thus, it should be a matter for serious concern and increased awareness regarding the impacts of land use in reservoir and watershed areas. All land use activities around the reservoir need to be managed appropriately and sustainably in order to protect the ecosystem health from adverse algal blooms. References: APHA: (1985) Standard Methods for the examination of water and waster water , 15th edition. APHA, New York, USA.
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Lake 2010: Wetlands, Biodiversity and Climate Change Bellinger, E. E. (1992) A key to common algae. Freshwater, esturine and some coastal species. The Institute of Water and Environmental Management, London. pp: 139. Chapman, A.D. and Schelske, C.L. (1997) Recent appearance of Cylindrospermopsis (Cyanobacteria) in five hypereutrophic Florida Lakes. Journal of Phycology, 33, pp. 191-195. Faust, S.D. and O.M. Aly, (1981) "Chemistry of Natural Waters", Am Arbor Science Publishers. Inc., Michigan. Fritsch, F. E. (1979) The structure and reproduction of algae. Vol. 1 and 11. Vikas Publishing House. Goldman, C.R. and Horne, A.J. 1994. Limnology. McGraw-Hill, New York, pp. 576. Graham, L.E. and Wilcox, L.W. (2000) Algae. Prentice - Hall Inc, London. pp. 987. Graneli, E., Carlson, P. and Leggrant, C. (1999) The role of C, N and P in dissolved and particulate organic matter as a utrient source for phytoplankton growth, including toxic species. Aquatic Ecology, 33,
pp. 17 - 27.
Karydis M. (2009) Eutrophication assessment in coastal waters based on indicators: a literature review. Global NEST Journal, 11(4), pp. 373-390. Meesukko Chatnaree, Nantana Gajaseni , Yuwadee Peerapornpisal and Alexey Voinov (2007) Relationships Between Seasonal Variation and Phytoplankton Dynamics in Kaeng Krachan Reservoir, Phetchaburi Province, Thailand. The Natural History Journal of Chulalongkorn University 7(2), pp:131-143 Oudra, B. (1990) Bassins de stabilization anairobie facultatifpour le traitement des eaux us&es d. Marrakesh: Dynamigue du phytoplankton microplankton et picoplankton) et &valuation de lu biomane primaire. These de 3eme cycle. Univ, Cady Ayyad. Fac. Sci. Marrakesh, pp. 144. Radwan , A.M. (2005) Some factors affecting the primary production of phytoplankton in Lake Burullus. EGYPTIAN Journal Of Aquatic Research Vol. 31 No. 2, pp: 72-88. Radwan , A.M.1994 . study on the pollution of Damietta branch and its effects on the phytoplankton. Ph. D. Thesis Tanta Univ. Faculty of Science. pp. 289. Sarode, S. T. and Kamat N. D. (1984) Freshwater diatoms from Maharashtra. Saikrupa Prakashan, Aurangabad. Trivedy, R. K. and Goel, P.K. (1984) Chemical and Biological methods for water pollution studies. Environmental Publ., Karad, India, pp; 122.
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