Introduction

Water is the prime and basic necessity of life forms in this earth. It is immensely important to maintain the quality of natural ecosystem and also development of human race. The quality of water plays a major role in plankton growth as well as the biology and production of the cultured aquatic organisms and their yields¹. Fresh water environment comprises of a combination of both biotic and abiotic factors. The important abiotic factors which are mainly used to study the water quality of a perennial aquatic body are temperature, P^H, turbidity, dissolved Oxygen (DO), Chloride, alkalinity and Total hardness². Biotic factors are comprised mainly by the plankton and other aquatic flora and fauna.

Zooplanktons are tiny microscopic animals. They float freely in the surface water column. Their movement as well as distribution is determined by water waves and current. They feed on phytoplankton and smaller zooplankton. Threats for aquatic biodiversity is mainly due to human interference and mismanagement of both biotic resources and the abiotic factors which leads to deterioration of water quality³ . Most of the freshwater bodies are constantly getting polluted due to domestic wastes, sewages, industrial and agricultural effluents.

In aquatic food chains, zooplankton forms a major link in the energy transfer between autotrophs and heterotrophs^4-5. Zooplankton community are important members of aquatic food webs because they serve as an important food item for fishes and invertebrate predators ⁶.

The physicochemical properties and diversity of flora and fauna are two important pillars which determine the healthy status of an aquatic ecosystem. The physical, chemical and microbial characters of a water body determine its nutrient status.. It is not possible to understand the biological phenomenon fully without the knowledge of water chemistry of the aquatic ecosystem⁷ . It is necessary to know the physicochemical properties of water to study the rearing practices of the fishes of water bodies⁸ .

No record about the physicochemical properties and zooplankton density and diversity of the perennial water body, Samudrabundh, of Joypur block of Bankura district, West Bengal is available earlier than this study. So, this study has been conducted to fill that lacuna and to make a quantitative analysis  of the water of the aquatic body so that proper utilization of such a big perennial water body can be made.

Materials  and Methods

The study was conducted by collecting water samples and zooplankton samples from the perennial pond of Samudrabundh, Joypur, Bankura. It is located in 23°2’39.81 N and 87°26’12.45 E. Approximately its water area is 25 hectors. The study was conducted during the period of March.2019 to February, 2020. For the ease of doing the job the study period was divided into four seasons viz. summer (March,2019 to May,2019), monsoon(June,2019 to August,2019), Post monsoon(Sep,2019 to Nov,2019), and Winter (December,2019 to February,2020). Random samples of water were collected in the morning on any three days during each season. Instead of surface water , samples from a depth of 50 cm were collected for the study .For determination of  Dissolved oxygen (DO), Free CO₂, PH, total alkalinity, hardness and salinity standard method of APHA(2008) was followed ⁹ . For determination of Temperature thermometer marked with 0.01 graduated centigrade (⁰C) was used. P^H was measured using a digital PH meter (Systronics model,335).Turbidity was measured in NTU by using a Nephlometer (Systronics,338).

For zooplankton samples, 40 L of water was filtered using plankton net of 50 μm mesh size. Zooplankton samples were preserved in 10% formalin at the site itself. Sample was allowed to settle down for a day. Sedgwick Rafter plankton counting cell was used for counting of zooplankton to find out its density. The detailed study of the plankton was done by using OLYMPUS inverted stereoscopic microscope (Model MLX-B) fitted with a NIKON camera. Identification of plankton was done according to the character mentioned by Battish, 1992¹⁰

Results and Discussion

Temperature

Temperature is an important physical factor that affects the quality of the water and considered as controlling factor for the fluctuation of plankton and functioning of the aquatic ecosystem¹¹. Water temperature in tropical waters in the range between 13.5⁰C and 32⁰C is found to be suitable for the development of the planktonic organisms¹².  In the study site the temperature of water varies from 19.3⁰C in winter to 21.3⁰C in Summer . ( Table 1)

In Samudrabundh water temperature shows positive correlation with pH , turbidity , free CO₂, salinity and total alkalinity. It shows negative correlation with DO, chloride, total hardness and total zooplankton. ( Table 2)

Turbidity

Maximum turbidity value 9.3 NTU has been recorded in monsoon .High turbidity values during monsoon has also been observed by Shinde et al, (2011)¹³ at Harsool –Savangi dam in Aurangabad. This is due to rapid flow of  water in rainy season which bring silt, clay etc along with it while low values in summer is due to low water level ( Table 1).

In Samudrabundh turbidity shows positive correlation with pH, free CO₂, salinity and total alkalinity. It shows negative correlation with, DO, chloride, total hardness and total zooplankton ( Table 2).

pH

pH value ranges between 5.7 to 6.8 ( Table 1). According to (Kurbatova, 2005) pH value between 6.0 and 8.5 is considered as medium productive nature of a reservoir¹⁴ . So the reservoir under study is considered as of medium productive nature.

In Samudrabundh  pH  shows  positive correlation with free CO₂,  salinity and total alkalinity . It shows negative correlation with DO, total hardness and total zooplankton ( Table 2).

Dissolved Oxygen.

Dissolved oxygen (DO) is very crucial limnological parameter whose measurement is vital regarding the culture of any aquatic animal. Dissolved Oxygen (DO) in the study site varies from 3.0 mg/l in summer    to 8.4 mg/l in winter .DO value less than 3.0 mg/l is considered as detrimental for fish growth¹⁵ . So, the DO value reaches its lowest threshold value during summer in the study area  ( Table 1).

In Samudrabundh, DO shows positive correlation with chloride, total hardness and total zooplankton . It shows negative correlation with free CO₂ salinity and total alkalinity ( Table 2).

Free CO₂

Carbon dioxide in water bodies is mainly contributed by the respiratory activites of aquatic animals. In the study area the free CO₂ ranges from 10.2 mg/l in winter to 15.8 mg/l in summer ( Table 1).

In Samudrabundh, free CO₂ shows positive correlation with Salinity and Total alkalinity. It shows negative correlation with chloride, total hardness and total Zooplankton  ( Table 2).

According to Ellis (1937) dissolved free CO₂ should be less than 5mg/l for good fish production in water bodies. If the free CO₂ level is more than 20mg/l then it may cause hindarance with oxygen intake by fishes. In the present study the average free CO₂ varies between 10.2mg/l to 15.8mg/l which may be consider a little higher in context of fish production.

Chloride

Salts of sodium and potassium are mainly responsible for the chloride content of water. The chloride content of water in the study area ranges from 36.7mg/l in summer to 54.7mg/l in winter season ( Table 1).

In Samudrabundh chloride shows positive correlation with total hardness and total zooplankton. It shows negative correlation with alkalinity ( Table 2).

Salinity

In Samudrabundh salinity shows positive correlation with alkalinity. It shows negative correlation with total hardness and total zooplankton  ( Table 2).

Total Alkalinity

.In the study area the total alkalinity ranges from 26.7mg/l in winter to 39.3mg/l in summer (Table 1).

In Samudrabundh alkalinity shows positive correlation with temperature, turbidity, pH, free CO₂ and salinity. It shows negative correlation with D.O., chloride, total hardness and total zooplankton ( Table 2).

Total hardness

The hardness of water is also an important parameter which can  indicates water quality. Sawyer (1960) has catagorised perennial water bodies into three groups according to their degrees of hardness ¹⁶. It is as follows: 0 – 75 mg/L = soft, 75 – 150 mg/L= moderately hard, 150 – 300 mg/L= hard, above 300 mg/L= very hard. As the water of the study area ranges between 30.1 mg/l to 47.1 mg/l, so the water of this perennial water bodies is considered soft in biochemical nature  ( Table 1).

In Samudrabundh total hardness shows positive correlation with D.O., chloride and total zooplankton. It shows negative correlation with temperature, turbidity, pH, free CO₂ and salinity ( Table 2).

Table I: Seasonal variation of hydrological  parameters of Samudrabundh , Joypur, Bankura

Table 2: Pearson Correlation matrix (r) between several hydrological parameter and Total abundance of Zooplankton of Samudrabundh , Joypur, Bankura.

Zooplankton analysis

During the study period we have recorded a total of 26 taxa of zooplankton. Out of which 8 species comprises of Rotifer, 05 species of Copepoda, 10 species of Cladocera and 03 species of Ostracoda. The main dominant group in this pond is contributed by Cladocera. It constitutes 46% of the total zooplankton abundance, followed by Rotifera 43%,  Copepoda 9% and Ostracoda 2%   (Figure 1 and Table 3).

Figure 1: Relative abundance of zooplankton groups of Samudrabundh , Joypur, Bankura Click here to View figure

Table 3: List of Zooplankton Groups obtained from Samudrabundh , Joypur, Bankura during study period   

The density of Cladocera ranges from 361(Ind/L) in summer to 441 (Ind/L )in post monsoon. The density of  Rotifera ranges from 265(Ind/L) in monsoon to 438 (Ind/L) in summer .The density of copepods ranges from 56 (Ind/L) in summer  to 102 (Ind/L) in post monsoon .The density of Ostracoda ranges from 6 (Ind/L) in monsoon  to 24 (Ind/L) in summer ( Figure 2 and Table 4).

Figure 2 : Seasonal Variation of abundance of zooplankton of Samudrabundh , Joypur, Bankura Click here to View figure

Table 4: Density (Ind/L) of  different Zooplankton Groups of Samudrabundh, Joypur Bankura during the study period.

Conclusion

The study of the physicochemical factors of Samudrabundh reveals that   its water turbidity is quite low, its pH value reveals that this water body is of medium productive in nature. The total hardness value suggests that the water body is of soft in nature. In some seasons the dissolved oxygen value remains at the critical level for fish production.  Alkalinity is also quite low to support efficient fish production. Panov et al (1973) has suggested that for efficient fish production the zooplankton density of a water body must be above 1500 (Ind/L) ¹⁷ . But in the present study it has been observed that zooplankton density ranges from 756 (Ind/L) to 957 (Ind/L) which is quiet lower than the desired value. Hence it is concluded that the secondary plankton production in this water body is very less as required for high rate of fish yield. So, the study concludes that though this perennial water body bears a tremendous potentiality of fish culture the limnological features and planktonic abundance of this water body is not satisfactorily good for production of finfishes in them

Acknowledgement

We want to acknowledge Principal, Bankura Sammilani College, Bankura for his  help and support for conducting the field  work. We also want to acknowledge the help received from the local respondents who have actively participated in this field work.

Conflict of interest

Authors have no conflict of interest.

Funding Sources

No funding agency

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