Received Date: April 15, 2015; Accepted Date: June 23, 2015; Published Date: June 26, 2015
Citation: Bhat NA, Wanganeo A, Raina R (2015) Variability in Water Quality and Phytoplankton Community during Dry and Wet Periods in the Tropical Wetland, Bhopal, India. J Ecosys Ecograph 5: 160. doi:10.4172/2157-7625.1000160
Copyright: © 2015 Bhat NA, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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The Bhoj wetland, a Ramsar site has been found to be under huge pressure due to burgeoning human population in its catchment area. The present investigation spread across nine stations has revealed higher algal diversity (294 species) during the period of 2008-2009. The phytoplankton diversity belonging to six groups revealed 46% contribution of Chlorophyceae followed by Bacillariophyceae (28%), Cyanophyceae (15%), Euglenophyceae (9%), while Pyrophyceae and Chrysophyceae contributed 1% each, respectively. Closterium sp., Cosmarium sp., Pediastrum sp., Scenedesmus sp., Staurastrum sp. and Tetraedron sp. contributed the bulk of Chlorophyceae was dominated by these various species and from Bacillariophyceae was mostly represented by Achnanthes sp., Cymbella sp., Navicula sp., Gomphonema sp. and Synedra sp. Cyanophyceae was represented by Anabaen sp., Aphanocapsa sp. and Oscillatoria sp., Aphanocapsa sp., Microcystis sp. and Oscillatoria sp. Species like Euglena sp. and Phacus sp. represented euglenophyceae. The higher abundance of (Closterium, Pediastrum, Scenedesmus, Navicula, Anabaena, Microcystis and Phacus) and nutrient concentration (nitrate-nitrogen and phosphorus) during the dry and wet periods reflect higher organic pollution in the Bhoj wetland. There should be strict legislation to protect the wetland from undue exploitation.
Wetland; Wet/dry periods; Water quality; Phytoplankton
Anthropogenic activities have been considered to be the most important factor for the degradation of aquatic environments, over the last centuries [1-5]. The main environmental pressures were thought to be pollution from excess nutrient loading, which resulted from agricultural, urban and suburban runoff, wastewater [6-8]. Phytoplankton communities are important sentinels of environmental changes, since they integrate the effects of increased nutrient loads, and they can be more sensitive to the combined impacts of stressors than a single stressor [9-12].
Wetland ecosystems are particularly vulnerable to eutrophication because freshwater enters these areas via rivers which are highly susceptible to pollution from urban, agricultural and industrial wastewater . The study of both abiotic and biotic components is complementary to each other. The abiotic components give information about the type of a substance or pollutants and its concentration, while biotic components indicate their general effect but no clue to the nature and quality of a substance. Biological components show the degree of ecological imbalance, which has been caused. The changes in the physico-chemical conditions of water can be reflected directly in the biotic community of ecosystem. Biological monitoring based on ecology of flora and fauna has been recognized as an excellent and inexpensive tool for measuring pollution level in water. This study attempts to determine the water quality conditions and phytoplankton composition status during wet and dry periods in Bhoj wetland (a Ramsar site).
Bhoj wetland was credited by Raja Bhoj, the famous Parmar king in 1010AD is now an exemplary case of degradation on account of its excessive use by the fast increasing urban population comprised of multiple stakeholders. The Bhoj wetland is located between latitude 23° 13’-23° 16’ N and longitude 77° 18’-77° 24’ E. It is a shallow water body with a watershed area of 361 sq. Km. and a maximum submergence area of about 37 sq. Km. the attainment of maximum water level (508.04 meters above sea level) of the lake depends on the magnitude of monsoon in its watershed area. As per the topography of the catchment area the north side of the lake is having major thrust of urban and semiurban activities which contribute the solid and liquid waste. On the southern side of the water body a national park and national museum or Manav Sangrahalaya is situated. Although sewage inflow from this area is insignificant but eroded soil gets deposited in to the lake and enriches the water with nutrients. The southwest and northwest of the catchment area of the wetland brings in sizeable amounts of waste water, nutrients and silt. This area is mainly under rural activities, in which agriculture is practiced (Figure 1).
The study was carried out during Feb. 2008 to May 2010. Nine sampling stations were selected based on different human activities such as washing, bathing, fishing and boating etc. The inlets, outlets, morphometric features and growth of aquatic vegetation etc., where other important factors considered during the selection of the sampling sites.
The water samples have been collected in one liter polyethylene canes between 8 AM to 12PM from the selected site of the Bhoj wetland. Air temperature, water temperature, dissolved oxygen and total alkalinity have been determined on the spot and the rest of the parameters have been analyzed in laboratory within time period of 24 h after collection. The various physico-chemical parameters have been analysed according to the standard methods [14-16].
The collection of phytoplankton samples have been done by using plankton net and the samples have been preserved simultaneously by adding formaldehyde (4%) and allowed to stand for 24 hours. The quantitative enumeration of phytoplankton has been done with the help of Sedgwick rafter counting cell (1ml capacity). The identification of aquatic biota (phytoplankton) has been done following the standard works and methods of Desikachary , Edmondson , Needham and Needham , Prescott , and Sinha and Naik . The unicellular algae were counted as unit per liter (unit/l) while in case of filamentous forms of Chlorophyceae and Cyanophyceae one filament of a specific size was taken as single unit while in colonial forms one colony was taken as a unit. Results were expressed as units/1 .
Wetlands exhibit different water quality status depending on the inflow from its general catchment besides wastewater . The dry season values observed for pH, DO, Total Alkalinity, Total Hardness and water temperature were slightly higher than the values observed in the wet season. Electrical conductivity, total phosphorus (PO4-P) and nitrate nitrogen (NO3-N) concentration was higher in the wet season than observed in the dry season (Table 1). The present study confirms that with the increase in water temperature the chemical reaction and biological activity speed up that reduces the solubility of gases in water .The lack of seasonal variation in pH of the waters may be attributed to the relatively high total alkalinity of the waters. Fluctuation in dissolved oxygen is also due to fluctuation in water temperature and addition of sewage waste demanding oxygen . The amount of oxygen dissolved in water is essential for respiratory metabolism of most aquatic organisms and affects the solubility and availability of many nutrients and therefore determine the productivity of aquatic ecosystems .
|First year||Second year|
|Total Dissolved Solids||mg/1||169.26||197.61||182.08||149.26|
Table 1: A Physico-chemical characteristics of Bhoj wetland.
The total alkalinity ranged from 66.61 to 80.48 mg/l in both the years of the wetland (Table 1) which makes the reservoir as nutrient rich and highly productive water body as suggested by Munawar . High hardness of aquatic ecosystem points out towards eutrophication. Rai  and Sawyer  classified water on the basis of hardness into three categories that is, soft (0.00-75 mg/l), moderately hard (75.00- 150.00 mg/l) and hard (151.00-300.00 mg/l). According to this classification, Bhoj wetland falls in the category of moderately hard water body with hardness ranging from 85.93 to 98.67mg/l. The higher electrical conductivity observed in the wet season may be due to inflow of surface runoff. Lashari et al.  while working on Keenjhar Lake reported electrical conductivity range from 320 to 496 μS/cm, during monsoon and summer season. Olsen  classified water bodies having conductivity values greater than 500 μS/cm as eutrophic. According to this criteria, Bhoj wetland water falls under the category of mesotrophic water body. PO4-P and NO3-N act as limiting nutrients for the growth of phytoplankton and other aquatic plants. Below 0.1mg/1and 0.090 mg/1 respectively for NO3-N and PO4-P are expected in natural unpolluted water . The concentrations observed in the present investigation are capable of stimulating algal bloom (Table 1).
During the two years of study period, a total of 294 phytoplankton species were recorded from the two years of dry/wet seasons (Table 2). The total phytoplankton diversity belonged to six groups. This diversity in species was contributed by Chlorophyceae to the tune of (46%) followed by Bacillariophyceae (28%), Cyanophyceae (15%), Euglenophyceae (9%), while Pyrophyceae and Chrysophyceae contributed 1% each, respectively (Figure 2).
|Group and Species||Dry||Wet||Dry||Wet|
|Pediastrum tetras excisum||+||+||+|
|Tetraedron pusillum angolense||+|
|Tetraedron quadratum minus||+|
|Cymbella parva cleve||+|
|Eunotia major indica||+||+|
|Gomphonema lacus rankala||+||+||+|
|Navicula halophila robusta||+||+|
|Synedra acus acula||+||+||+||+|
|Total number of phytoplankton 294|
Table 2: Phytoplankton diversity observed during dry and wet periods in the Bhoj wetland.
A total density of 25495 and 24222 units/1 of phytoplankton was on account of 227 and 225 species recorded during the dry and wet seasons respectively (Tables 3 and 4). A comparison of two years dry season reveals that in first year the diversity was 202 species that declined to 146 species in the second year of dry season, similarly the density in first year was 14788 units/l, which decreased to 8366 units/l in second year. This variation in diversity and density during two years may be attributed to significant hydrological changes encountered in the second year, mainly caused by acute drought conditions.
|Density||First year (2008)||Second year (2009)|
Table 3: Phytoplankton density observed during dry and wet periods of the Bhoj wetland.
|Diversity||First year (2008)||Second year (2009)|
Table 4: Phytoplankton density observed during dry and wet periods of the Bhoj wetland.
An assessment of two years of wet season reveals that in first year the diversity of phytoplankton was 179 species that slightly increased to 183species in the second year, similarly the density of phytoplankton in the first year was 10673 units/l, which increased to 15856 units/l in second year respectively.
General decrease in density of phytoplankton during wet season may be due to dilution from monsoon rains in the first year and in the second year, the density decreased in dry season, mainly due to acute drought conditions. Barone and Flores , Adesalu and Nwankwo , and Rajagopal  also reported that the low value of phytoplankton population in wet season was due to dilution, increased outflow and silting. Rana , and Pundhir and Rana  have observed that rainy season, cloudy weather, low transparency and heavy flood contribute to the decline in phytoplankton density. Henry et al.  in his studies also showed a reduction in phytoplankton population and diversity with drought progression in Coqueiral lake.
Chlorophyceae, the dominant class was mainly represented by Cosmarium (21 sp.), Scenedesmus (18 sp.), Closterium (8 sp.), Pediastrum (8 sp.), Staurastrum (7 sp.) and 11 species of Tetraedron (Table 2). Increased temperature and long photoperiod may explain increased Chlorophycean diversity. Nandan and Aher  and Tiwari and Chauhan , reported that high content of phosphate, calcium and nitrate influence the growth of Closterium and Scenedesmus species. Other workers also suggested that the organisms of this species attain high or low diversity according to their tolerance to environmental conditions [34,41,42] related Closterium sp. to long term organic pollution, which is in agreement with the present study. Under conditions of nitrate and phosphate availability, the green algae (Chlorophyceae) are known to proliferate in freshwater environment . Bacillariophyceae, the second most dominant algal group was primarily represented by 6 species of Achnanthes, 16 species of Cymbella, 18 species of Navicula, 11 species of Gomphonema and 8 species of Synedra (Table 2). Sunkad  reported the maximum population density of diatoms in summer and minimum in monsoon months. Patrick  concluded that many species of diatoms could tolerate a temperature up to 35°C. Zafar  has emphasized the importance of temperature in the distribution of diatoms. Temperature influences the production of diatoms as they seem to grow and colonise during the warmer periods and will have lean population in winter [22,47,48].
The Cyanophycean group as mainly dominated by Oscillatoria (14 species), Anabaena and Aphanocapsa (6 sp’s each) (Table 2). The presence of these species indicates higher nutrient status. Wanganeo and Wanganeo  have emphasized that factors like alkalinity, nitrates and phosphates are responsible for the luxuriant growth of Cyanophyceae, apart from higher pH, temperature, and dissolved oxygen. The nutrient increase due to discharge of agricultural and organic effluents coupled with other anthropogenic activities in the catchment, a shift in biodiversity has probably impacted phytoplankton composition of the Bhoj wetland. Bowling , Wanganeo , and Bhat et al.  reported that the presence of Anabaena sp., Oscillatoria sp., and Microcystis sp., indicate nutrient enrichment as these genera commonly respond to increases in nutrients.
In this study significant relationship of Euglenophyceae with calcium hardness and total hardness could be attributed to the fact that calcium is an important part of plant tissue, increases the availability of other ions  and thus might have played a vital role in the growth of phytoplankton. Further, studies on the Euglena bloom in the present study, similar type of observation were reported by Bowling , and Duttagupta et al.  in flood plain wetlands of Assam, and another study on lake Manasbal of Kashmir valley by Khan and Bhat  emphasized the importance of calcium in stimulating the growth of Euglena. Euglenophyceae group is generally abundant in waters rich in organic matter , therefore presence of Phacus sp. in the present study is a direct indication of higher pollution load in the system, because this species is considered to be dominant genera of polluted waters . Further, high nutrients and favourable physico-chemical characteristics recorded in the Bhoj wetland, may be contributing to the increased Euglenophyceae. Munawar  in his study indicated that more amount of CO2, phosphate, nitrate and low content of dissolved oxygen favoured the growth of euglenoids. Singh  concluded that high organic load, low transparency, low dissolved oxygen, high (alkalinity, chlorides, total hardness, calcium and magnesium) favoured the rich growth of Euglenophyceae. Because of organic pollution, euglenoid members were often found in wetland. Species like Euglena and Phacus from euglenophyceae were dominant organisms (Table 2). It is reported that Euglenophycean members generally develop very well in waters which is rich in organic substances . Abundance of this group, represented by single taxa, Euglena sp. can be attributed to the influx of domestic sewage from the urban catchment (Tables 3 and 4).
The decrease in taxa from dry season towards wet season during first year (Table 5) revealed a different situation during second year of investigation on account of acute drought conditions.
Table 5: Variation of phytoplankton diversity indices in Bhoj wetland.
In the first year study though dominance value was in close proximity to zero for most of the groups indicating that the majority of the species are present with lesser dominance, yet Cyanophyceae group was exception which registered highest dominance values of 0.51 (during dry season) and 0.44 (during wet season). Similarly in the second year it was cyanophyceae and euglenophyceae which recorded high values (0.40 and 0.32) from cyanophyceae and euglenophyceae (0.47 and 0.33). It signifies that some taxa dominate the whole study period (Table 5).
Simpson’s diversity index varied between the values of 0.95 to 0.49. The minimum value was recorded from the group cyanophyceae during dry season and a maximum value from the group chlorophyceae during wet season. While in the second year of study, the diversity varied between 0.95 to 0.54. The minimum value was found from the group euglenophyceae during dry season and a maximum value from chlorophyceae group during wet season (Table 5). Simpson’s index of diversity showed that the index of diversity was significantly higher. The Simpson index (low value) indicates an increase in dominance of fewer species in Baigul water bodies . The index value ranges from 0 and 1, the higher the index value, the higher the diversity.
In the present investigation of study period, Shannon -Wiener diversity index ranged between the values of 3.50 to 1.40 in the first year of period (2008-09). While in the second year the values varied between 3.55 to 1.37. The highest diversity index was found to be from the group chlorophyceae during wet season and a lowest value from the group cyanophyceae during dry season in both the years of the study (Table 5). In general the index reveals that wetland is more diverse. Wilhm and Dorris  found that the value of index decline sharply in polluted zones of the lake.
The evenness components of diversity values were found to range between 0.68 to 0.18. The lowest value was found from the group cyanophyceae during wet season and the highest value of 0.68 was found from euglenophyceae group during dry period (Table 5). While in the second year the values varied between 0.50 (bacillariophyceae) to 0.22 (euglenophyceae) during dry periods.
The encroachment of human settlement around the Bhoj wetland is having a negative impact on the aquatic environment; therefore, a number of interventions are required to halt the continued degradation of the wetland ecosystem. There should be strict legislation to protect the wetland from undue exploitation.
Phytoplankton communities are sensitive to changes in their environment and, therefore, many phytoplankton species are used as an indicator of water quality. It seems this wetland is under stress due to the high nutrient concentration and needs immediate attention for its conservation as it is one of the chief sources of potable water. Therefore, management strategies should be designed to restore wetland’s water quality and biological communities that have been damaged by anthropogenic pressures.