Study of Limnological Status of Two Selected Floodplain Wetlands of West Bengal


 Limnology is the study of all aquatic systems, both lentic and lotic fresh, fresh, and saline including lakes, wetlands, marshes, bogs, ponds, reservoirs, streams, rivers, oceans, etc. about their physical, chemical, and biological characteristics. Among this phytoplankton, Zooplankton, periphyton, benthos are a minute aquatic free-floating microscopic organism, which acts as a larger food source of larval and higher vertebrates and invertebrates including carnivorous and omnivorous fishes. They are related to the growth of juvenile fishes and are also play important role in the transfer of energy from the primary phytoplankton to higher trophic levels. The plankton community fluctuates according to the physicochemical parameters and the relative environment of the water body especially the Rotifers as they are known to change immediately along with the change in water quality . Realizing the importance of floodplain wetlands and the paucity of literature on the limnology of this ecosystem present investigation was carried out in two floodplain wetlands having characteristics of open (Kole beel, an ox-bow lake formed near Somra Bazar in Hooghly district), and closed beel Suguna beel situated in Nadia District of West Bengal) system during the period 2011–2013. The physicochemical parameters of the investigated beels' water and soil were, for the most part, favorable for planktonic development. It has an alkaline pH of 7.5–8.4 and is alkaline. The dissolved oxygen content and Secchi Disc transparency values indicate that the water is in excellent condition. The water was moderately hard, with only trace amounts of nutrients present. Seasonal fluctuations in the water column were apparent, and they were mainly attributable to replenished supplies and volume. The plankton population of the studied ecosystem was made up of a mixed and healthy population of diverse fauna. The greatest diversity was observed during the winter season, when favorable temperature, dissolved oxygen, and other physicochemical parameters of water, as well as optimal solar penetration, coincided. In a closed system (Suguna), the richness of planktonic structure resulted in higher fish production (1570.05 kg/ha/yr) than in an open system (Kole) (384.4 kg/ha/yr). The status of floodplain wetlands was determined to be eutrophic based on various Physico-chemical and biological parameters.


Introduction
The status of oodplain wetlands is eutrophic, and during the study period, 6 sh species, 14 phytoplankton genera, and 10 zooplankton genera were reported based on different physicochemical and biological parameters. Variation in rainfall, depth of water body, siltation, and other chemical factors are all factors due to year-to-year variations in plankton content in freshwater impoundments (Welch 1952).
Flood plain wetlands have simultaneously been described as the "kidneys of the Flood landscape" and as "biological supermarkets" (Mitsch, 1995a) illustrating the importance of their role in the ecological functioning of most river systems. River regulation in India has resulted in major changes to the ow regime, including changes to the timing and duration of small to medium-sized oods and alteration of the seasonal pattern of ooding. Such changes have altered lateral connections between the river and its ood plain and are known to affect plant community structure (Casanova & Brock, 2000), macroinvertebrate community composition (Quinn et al, 2000) in ood plain wetlands. As the river and its ood plains are inextricably linked, such change to the ood plain wetlands magni es the effects of ow regulation on the ecological integrity of Australian rivers.
The structure of the oodplain plant community, both emergent and submerged, is an equally important pillar upon which to support sensible management policies. Several important consequential issues are associated with these two principal components. They are inter alia the quality of oodplain water, and the response of the faunal community to changes in the oodplain water, and the response of the faunal community to changes in the oodplain water, as we are aware of the sensitivity of the fauna, both invertebrate and vertebrate, to both insidious and cataclysmic environmental change.
Primary productivity is an important criterion for assessing a water body's productivity. When the nutrient status is low, primary productivity and sh production suffer as well (Singh and Desai 1980), meaning that primary productivity is inversely proportional to the nutrient concentration. Many researchers have studied the primary productivity of water bodies in various locations and at various times of the year, but they have only found one peak of primary production in reservoirs during the summer or early summer (Singh and Desai 1980). Except for the work of Sreenivasan ( , 1968, Ganapati and Sreenivasan (1970), Kaliamurthi (1978), and Natarajan and Pathak (1979), knowledge of primary production in the tropics are still limited (1980). There is almost no detail on the ecological productivity of swamps, oxbow lakes, and other wetlands (Laal 1981 andYadav 1988). This paper aims to investigate the relationship between primary production and planktonic structure in two eco-systems with open and closed characteristics.
Various limnological studies have been carried out in important wetlands of the state. It is evident from above that the limnology of the small oodplain wetlands has been neglected from a study point of view and no action regarding the proper management of these wetlands has been taken. However, the limnology of this wetland has been the subject of interesting studies.

Materials And Methods
Brief description of the study area Saguna beel is a closed system (S) and the basin is solely dependent on rains for a water source. It is almost rectangular with a water spread area of 40 ha and lie between latitude 88º 4' E and longitude 22 º 6' N and located at Kalyani district Nadia, West Bengal. The beel was a defunct watercourse, which earlier had a connection with the river Hooghly.
The Kole beel, an open system, is a shallow saucer-shaped basin of 6-kilometer length having a total area of 81.6 ha. Kole beel lies between latitude 88° 7' E and longitude 23° 2' N and located at Somra Bazar, district Hooghly, West Bengal. The beel is connected with the river Bhagirathi with the braided channel. Water reaction (pH): The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in pH (Table-1

Total alkalinity
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Total alkalinity (Table-1 Total hardness: The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Total hardness (Table-1

Speci c conductivity
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Speci c conductivity (Table-1

Dissolved oxygen:
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Dissolved oxygen (Table-1

Nitrate-Nitrogen
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Nitrate (Table-1

Phosphate-phosphorus:
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in phosphorus (Table-1

Silicate-silica
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in silica (Table-1

Soil pH
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in soil pH (Table-1). The Saguna wetland has shown signi cantly higher values of soil pH in comparison with Kole ( Figure-6b).

Organic carbon
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in soil organic carbon (Table-1

Available nitrogen
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in soil available nitrogen (Table-1

Available phosphorus
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in soil available phosphorus (Table-1 The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in phytoplankton (Table-1

Chlorophyceae
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Chlorophyceae (Table-1). The Saguna wetland has shown signi cantly higher values of Chlorophyceae in comparison with Kole (Figure-9a).
The occurrence of benthic organisms sharply declined from the late winter season reaching the lowest values during the monsoon. The general trend of abundance in the studied lakes followed a sequence of Gastropod > Oligochaete > Chironomids > Bivalves > others.

Gastropod
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Gastropod (Table-1). The Kole wetland has shown signi cantly higher values of Gastropod in comparison with Saguna.

Bivalve
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Bivalve (Table-1). The Kole wetland has shown signi cantly higher values of Bivalve in comparison with Saguna.

Oligochaete
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Oligochaete (Table-1). The Kole wetland has shown signi cantly higher values of Oligochaete in comparison with Saguna.

Chironomids
The analysis of variance revealed that there was a month-wise and wetland type-wise signi cant difference in Chironomids (Table-1 In the present study, the two selected beels were found to have low transparency during the summer period (particularly May-June), which is attributed to the wind action and phytoplankton bloom. Various workers have also reported similar seasonal uctuations in lake water transparency (Michael, 1969;. Temperature  calculated strati ed temperature in a beels eco-system in West Bengal's Nadia district. The water temperature closely matched the temperature of the atmosphere in the beel habitats studied (Tables − 1). Variation in water temperature was quite distinct during different seasons throughout the study. According to , maximum and minimum temperatures in West Bengal beels and baors ranged from 17.5 to 32.0 0C, which is consistent with the current research. Rai and Dutta Munshi (1989) have also reported that the presence of macrophytes profoundly in uences water temperature. The present study also con rms the same. According to ; Jhingran (1989) in water bodies with high organic contents in bottom mud, large-scale mortality takes place in summer months especially after a shower or cold wind.

Dissolved oxygen
The prime life-bearing gas in aquatic media was within the moderate range of 6.4 to 10.8 ppm (Table-1).
The reason for the maximum strati cation of oxygen in monsoon may be attributed to the high rate of surface mixing of atmospheric oxygen due to the showering of a raindrop . It is interesting to mention that the higher concentration of oxygen in the surface water during monsoon was always not in con rmation with the high plankton density whereas Das and Srivastava, (1956) reported that the phytoplankton peak corresponds to the high oxygen values while zooplankton peaks are associated with low oxygen values. Oxygen content observed to be poor during the period of the high temperature such as the summer season (Bhowmik, 1968; conforms with the present study.  also reported similar observations. Dense aquatic vegetation, shallow water depth, and intense shing activities can cause large uctuations in the dissolved oxygen content of water in the beels. .

Water reaction pH
In the present investigation, the hydrogen-ion concentration in the surface water of the beels was 8.0 and above excepting on few occasions. The observed pH as 8.0 and above has been recorded to be productive by various workers (Hutchinson, 1957;. Michael (1969) observed that when pH ranged between 7.3 and 8.4 the water provided optimum conditions for the growth of plankton. The present study bears the agreement of alkaline pH with the study of  where the pH value of the beels and baors of West Bengal was recorded between 6.8 and 9.1.

Alkalinity
Since total alkalinity values are the resultant of the entire biological and chemical process taking place in the water body, as such it is also taken as a rough index of productivity of the water body (Laal, 1981). In the present investigation, the alkalinity of the beels waters was observed to be within the product range. The high alkalinity value was recorded in beels infested with a high density of macrophyte-associated fauna and benthic biomass.  reported similar observations. Free CO 2 Such absence of free CO 2 in water was found to be related to the presence of heavy phytoplankton populations (Michael, 1969). The pronounce absence of the free CO 2 at the subsurface level of the water was in con rmation of the observation made by Reid (1961), who reported that at pH 8 and above the free CO 2 is usually absent. Most sh species will survive waters containing up to 60 ppm (Hart, 1944).

Speci c conductivity
The speci c conductance of water is a measure of the resistance of a solution to electrical ow, which declines with increasing ion content (Wetzel, 2001). The speci c conductivity values recorded from these lakes were in an acceptable range. It has been reported an optimum range as 250-400 µS/cm and opined that speci c conductivity above 400 µS/cm does not limit or favor productivity. The total concentration of solid constituents in natural waters is measured by speci c conductivity.

Nitrate-Nitrogen
In the present investigation, the values of water-soluble nitrate varied from system to system and with seasonal changes. The level of the nutrient was 0.3-1.5 ppm in Kole, while, it was comparatively higher in the range of 0.8 to 1.3 ppm in Saguna (Tables − 1). The uctuation trend in nitrate level indicated mesotrophic to the eutrophic condition of the beels (Goldman and Horne, 1983). The nitrate levels in the studied beels were within the productive range  and ideal for plankton growth, which is consistent with the ndings of the study.

Phosphate-phosphorus
The phosphate cycle of the beels was in correlation with the dissolved oxygen and is known to play important role in controlling the rate of phosphorus release from the sediment to the photic zone (Munawar, 1970). A major distinguishing factor among the water bodies is the difference in frequency and length of river inputs or connectivity (Hamilton and Lewis, 1990;Amoros, 1991). The nutrient enrichment during low water was attributed by Hamilton and Lewis (1987) to turbulence from wind action and sediment resuspension. It was attributed by Boneto et al. (1984) to hypolimnetic anoxic conditions and the release of nutrients from the sediment.

Silicate
Many workers (Bhowmick, 1968) have observed a direct relationship between silicate content and diatom population in the water body. Furch (1984) found a similar phenomenon in Amazonian 'Varzea' ( ood plain) lakes and a oodplain lake in Sao Paulo, Brazil.
During the study period, water temperature, pH, Dissolved Oxygen (DO), Free Carbon Dioxide (FCO 2 ), Total Alkalinity were measured monthly for six months. The limnological parameters of the study site were found to be highest during October 2012. the pH of the Kole was found to be at par during the six months study period. DO and FCO2 were found to be highest during October and lowest during the winter months i.e, December 2011 -January 2013. The water quality, nutrient level, and sh fauna of the Kole beel show change from time to time as it receives different types of water at the different parts of the year. During monsoon, the water from river Ganga enters the beel along with nutrients, shes, and inundates the beel. Again the combined ow from the rivulet upstream along with nutrient and water from the catchment area reverts the ow to the Ganges that continues till the ood receded. Therefore, in both cases, many shes enter the beel along with and against the water current giving a dual bene t to the beel.

Chemical attributes
Soil pH In the present study, the pH values recorded in the soil (6.0-7.0) were thus indicative of high productivity in the investigated beels, which con rms the study. Das (2000) working on the beels of West Bengal has reported a similar pH of soil.

Organic carbon
The uctuation of organic carbon in an aquatic system with the change of places and during different seasons has been reported by various workers (Bhowmick, 1968). The seasonal uctuation indicated a de nite pattern of peaks of organic carbon as observed by Bhowmick (1968).  reported a similar observation where organic carbon values ranged from 3.8 to 4.8 % in beels located at Kalyani.

Available nitrogen
In the present study, available nitrogen in the beels sediment was varying in concentrations. The nitrate and available phosphorus are considered to be limiting factors, being the primary nutrient for ecosystem functions (Carney et al., 1993 andBrown, 1981). The nitrogen levels in beels were within the range of favorable productivity .

Available phosphorus
It is well documented that in shallow lakes, aquatic macrophytes act as a sink for nutrients, both nitrate (N) and Phosphorus (P), during their growth phase withdrawing up to 60% of N & P from the sediment and after their decomposition releases them back to the water as well as to the sediment (Donk et al., 1993). According to , usable phosphorus values were lowest in closed and weedchoked beels (traces to 3.18 mg/100 g of soil), higher in closed but moderately weed-infested beels (traces to 7.6 mg /100 g of soil), and maximum in open beels (traces to 10.08 mg /100 g of soil), in comparison to other nutrient parameters. This observation is based on the study made on a large number of beels of West Bengal and eventually, the present observation is, by and large, in agreement with the ndings and indicative of productive.

Planktonic structure
The plankton population in the beels systems was diverse in respect of species and population density. From the 2 systems, 62 species of plankters belonging to 51 genera and 29 families were identi ed. (Table-1).  found that phyto and zooplankton populations in West Bengal ood plain wetlands were lower during the southwest monsoon, but increased after the ecosystem stabilized and the plankton population formed using inorganic nutrients and organic matter brought in by the incoming ood or run-off water.  also found that phytoplankton dominated the maximum plankton population in the summer, while zooplankton dominated in the winter. In Bihar, Jha (1997) discovered a higher plankton population in closed ood plain lakes.
The beer's phytoplankton was low due to the use of nutrients by a thick growth of macro vegetation. . The wetlands exhibited strong competition between the macrophytes and phytoplankton in respect to sunlight and nutrients (N: P), in uencing the abundance and quality of phytoplankton from one system to another (Wetzel, 2001). Macrophytes being the dominant autotrophs might have used the available nutrients, sunlight more e ciently, as such grow rapidly, almost shadowing the proliferation of phytoplankton (Boyd, 1971 (1961), as the temperature is lowered, the solubility of oxygen in water increases. Cairns (1965) investigated the optimum temperature range (15-30°C) as the most favorable for the growth of diatoms. Copepods were present throughout the year, but there was no discernible trend.
Rotifers have a diverse ability to survive in a variety of habitats, as some feed on phytoplanktons, others on detritus and bacteria, and still others have been identi ed as predatory raptors (Singh, 2000). Rotifers predominate in Indian freshwaters, which is a natural occurrence. (Michael, 1969;Lahon, 1983). Singh (2000) recorded maximum production of rotifers during the summer season. Similar observations have been made by Michael (1966) and Singh (2000). Their growth seemed to be favored by a temperature range of 23.5 to 26.1°C, which is within the optimal temperature range for protozoan growth (Pennak, 1953 Limnology and plankton community of oodplain wetlands The highest phytoplanktonic population is observed during the rising water cycle when limnological changes are most visible as river water reaches the oodplain for the rst time. Water and plankton populations from the pools and depressions are replaced by the ood. Nitrate-nitrogen is abundant in river water, which can be used as a source of nutrients and oxygen. Diatoms and green agellates, Volvocales, are carried in by the ood, and they will spread and take over after the ood. (Pethart, 1995).
The river is a highly complex entity that has a signi cant impact on the limnology of stagnant waters in the oodplain. Even though plankton cannot swim against currents, rivers also have an abundance of it. (Hynes, 1970;Winner, 1975;Rzoska, 1978). Factors in uencing the transport of species from the source region to the water, and factors affecting the growth and reproduction of organisms in the river, are the two types of factors that in uence the abundance of plankton in rivers. (Hynes, 1970). Plankton can be supplied to the river by standing water in contact with the channel.
Many tropical rivers have a wide stretch of the natural oodplain that could be signi cant zooplankton sources (Saunders and William, 1988). Inundation of source areas is caused by changes in water levels, which increases zooplankton abundance.
The timing of a ood is thought to be important in assessing the effects on the water quality of ooded  1994). These properties are closely related to seasonal ood pulse changes in oodplain lakes. (Junk et al., 1989). Sept and Reynolds (1995) discovered that a water level's phytoplanktonic production was affected by temperature, light, and nutrients. Lentic phytoplankton is washed away during the inundation, while riverine species are taken in by oodwaters. Nonetheless, river water causes phytoplankton dilution and wash-out, resulting in a drop in abundance (Talling, 1986). Under insecure environmental conditions, small agellate forms (cryptophytes or green algae) with rapid growth rates (r-selected) often dominate. According to the few studies that have been conducted, open ( oodplain) and closed (depressional) wetlands both sequester similar quantities of organic C and N.
The relatively high rate of soil organic C and N deposition in oodplain soils and possibly other oodplain wetlands is due to slower soil accretion and higher C and N concentrations in the subsoil. As

Macrophyte
Living organisms and their abiotic surroundings are inextricably linked and interact with one another (Odum, 1983). Aquatic plants play an important role in the habitats of lakes, wetlands, rivers, and streams all over the world (Jamil, 1993). Sharma (1995)  . Submerged macrophytes regulate plankton density and primary productivity by providing optimal light quality and quantity, temperature, and total alkalinity (Yadava, 1987). Kole beel had a lower infestation and biomass of macrophytes than the parent river, which was partly due to management action and partly due to contact with the parent river.
The results show that both free-oating and submerged macrophytes have a wide seasonal variation in biomass. Camargo and Florentino (2000) found that the biomass of aquatic macrophytes in tropical water bodies varies greatly from season to season. Junk (1990) found a signi cant difference in water quality parameters during the planktonic and macrophytic phases in Kulia beels (closed beels) in West Bengal. During the macrophyte process, they discovered a lot of Secchi disc visibility (from top to bottom). In the current analysis, however, no direct correlation between macrophytic dominance and transparency could be found. Munawar (1970) claimed that a dense macrophyte population would result in increased photosynthetic activity and, as a result, an increase in pH. The absorption of phosphorus by macrophytes both from the water and sediment is well known (Bristow, 1975;Denny, 1995;Chamber et al., 1989 andGunnison andBarko, 1989). This suggests that nitrate is a more limiting nutrient for macrophyte growth in these lakes than phosphorus.
Aquatic macrophytes play an important role in the dynamics of the Beels' physicochemical and biological properties. Aquatic macrophytes provide nutrition to herbivores while also strengthening the Beel ecosystem's detritus food chain. The primary productivity of the studied beels came from two sources: phytoplankton and macrophytes. The rate of energy transformation by phytoplankton is lower than that of macrophytes, according to Beels. It's a complicated process to transfer energy from the primary producer to sh (carnivores). The sh re ect a fraction of the energy trapped by primary producers as a secondary product of the beels. It's a complicated process to transfer energy from the primary producer to sh (carnivores). The sh re ect a fraction of the energy trapped by primary producers as a secondary product of the beels. In the Open Beel, the average Gross primary output (GPP) by phytoplankton is 1.82 g/m2 per day. The value is 1.68 g/m2 /day in the case of Closed Beel. The phytoplankton of Open Beel produced more gross primary production (GPP) than that of Closed Beel. The Open Beel's Net Primary Production (NPP) is 1 g/m2 per day, while the Closed Beel's NPP is 0.83 g/m2 per day. In the Beels, differences in phytoplankton net primary production (NPP) are 0.17g/m2/day. Despite the drying up of some patches of the wetland beds, some weeds, such as Hydrilla verticillata, Vallisneria spiralis, and Potamageton octundrus, renew their seasonal cycle. Over the winter season, the macrophytes decompose. The availability of water in the wetlands' bed in uences the seasonal variation of biomass.

Ranges of Gross
Despite their immense ability, the Beels only use around 1% of the energy used by sh, and the rest is transformed into a detritus food chain at the bottom of the beels. Because of the two types of productivity sources, the primary productivity of the Beels is higher than the productivity of any other freshwater reservoir. Most of these macrophytes are not speci cally grazed by herbivores, and the unused material is deposited at the bottom as detritus energy, which is generally high in both Beels. Detritus levels in the Open Beel ranged from 0.91 to 4.56 kg/m2/yr/m2, with an average of 2.55 kg/m2/yr.
Detritus levels in Closed Beel ranged from 2.05 to 4.75 kg/m2/yr, with an average of 2.75 kg/m2/yr. In both the Beels, the value of detritus was higher in the winter season (4.45kg/m2/yr.) than in the summer season (1.3kg/m2/yr.). The rich growth of marginal and submerged vegetation in the Brahmaputra oodplain wetlands is a unique feature due to heavy nutrient loading from both allochthonous and autochthonous sources. These macrophytes often supplant the plankton population, hastening eutrophication by replacing the plankton community with macrophytes as the primary producer. This results in a higher rate of evapotranspiration and lake ampli cation. This method, however, can be reversed with good management. Open Beels, which have fewer macrophytes (on average 2142.27 g/m2/yr), are best suited for energy transformation by phytoplankton.
Macrobenthic community  opined that the beels of West Bengal support rich growth of benthos, the average density ranging from 90 to 13,238 nos./m 2 . Parameswaran and Vass (1995) stated benthos of the beels of West Bengal is generally dominated by mollusks, insect larvae, nymphs, and Oligochaetes which agrees with the present investigation.

Conclusion
The limnology and productivity of the two beels are different. Kole and Suguna beels are both shallow and have similar thermal characteristics. Kole beel primary production was poor, ranging from 0.273 to 0.702 g C m-2 day-l.
Rain showers in the forenoon resulted in higher development. This con rms Vcrduin's (1957) hypothesis that phytoplankton exposed to low light during the day can still photosynthesize at high rates in the late afternoon when showers occur earlier in the day. Low photosynthetic concentrations are indicated by alkalinities below 50 ppm (Pleasant, Rand, and Namcrov 1962). The comparison between Ooty Lake and Kodaikanal Lake is striking. Probiotics are recommended for water with a lower tropical temperature. Performance was strong in water with a lower tropical temperature, reaching 8.16 g C m-2 per day. The lake had been highly active, as shown by improvements in oxygen and alkalinity, except in April 1963, when primary production was poor due to persistent cloudy weather. Output was higher when rain showers occurred, according to the carbon dioxide change process.
It can be inferred that the nutrients in water and soil in an aquatic environment play a signi cant role in aquatic production under various temperature regimes. The productivity of relatively regulated water bodies, such as the Suguna beel (closed), is primarily determined by allochthonous nutrient input and management practices. The sources of nutrients in natural open water bodies like the Kole beel, on the other hand, are both allochthonous and autochthonous. Apart from other hydrobiological parameters, the productivity of natural water bodies is affected by several factors such as aquatic vegetation, eutrophication, pollution, and various anthropogenic activities. The abundance of nitrogen and phosphorus in water and soil has a positive association with productivity. However, there was no connection between potassium content and productivity. In contrast to nitrogen and phosphorus, potassium tends to play a smaller role in aquatic production.
In conclusion, phosphorus was released because of repeated drying and wetting. This effect was greater when the drying time was 200 hours rather than 100 hours, suggesting that the degree of drying is a key factor in regulating phosphorus after rewetting.
It is also recognized by the study that human activity remains one of the major ecological elements in the oodplain wetlands and its catchments in both the cases of open and closed oodplain wetlands.
The presence of a good abundance of Cladocera is very much appreciable as they are known to be the staple food of larvae of various culturable shes. But the increasing abundance of Rotifera may be an indication of the increase of pollutants to the water body.
Just like the other wetlands of the state the Kole Beel experience the most dramatic changes in their trophic status and biota. There is a gradual shrinkage in the size of the wetland due to encroachment, agricultural activities, and human settlement within the wetland causing an imbalance in the wetland ecosystem.
Although the Millennium Ecosystem Assessment estimates that wetlands cover seven percent of the earth's surface and deliver 45% of the world's natural productivity and ecosystem services.
The existence of these unique resources in this region of the country is under threat due to differential developmental activities and population pressure. This calls for a long-term planning for the preservation and conservation of these resources.
The water quality of Kole Beel is deteriorating as years are passing by resulting in proli c weed growth, thereby, affecting sustainable food production and potable water for humans and livestock. A large number of people residing in or on the fringe areas of wetlands are partially or entirely dependent upon the aquatic resources of the Beel. The Beel is a habitat of diverse groups of organisms and harbors a vast array of aquatic resources. Therefore, restoration of the Beel is very much important for maintaining bio-diversity.
Fish is an important component in people's diets, providing about 2.9 billion people with almost 20 percent of their average intake of animal protein. Fishery sectors are particularly important in developing countries, for providing both food and livelihoods. The Beel offers immense potential for increasing sh production, employment generation, and several other additional sources of income for the rural population of this area of West Bengal.
Therefore, if we can attract the attention of all the regulating bodies for better scienti c management and maintenance along with the introduction of culture-based shery then the sh production of the beel can be increased 3 fold i.e. up to 668 tonnes of shes per year.
It is our considered opinion that the sh production of the beel can be augmented if the beel is taken under culture-based shery using proper scienti c management framework. This will require support from the Government especially in i. regulating the ow of oodwater from river Ganges, ii. leasing the beel to the co-operative society with traditional (Koiborta, Mahimal) and trained sher, iii. strict enforcement of regulations (Indian Fisheries Act, 1897) regarding shing access, period, time, type, mesh size, gears, encroachment, and free riders, iv. training the sher about the recent scienti c technique.