East Kolkata Wetlands Research Articles

Strategies to control invasion of Sailfin Armoured Catfish, Pterygoplichthys spp. in wastewater-fed aquaculture bheries of East Kolkata Wetland, India with suggestion of a modified barrier based on the biological and behavioural characteristics

Sailfin armoured catfish ( Pterygoplichthys spp.), an alien invasive species of family Loricariidae has invaded extensively in wastewater-fed large aquaculture ponds (locally called ‘bheries’) of East Kolkata Wetlands (EKW), West Bengal, India. As there is no viable controlling method at present, commonly these fishes are removed by different physical methods and discarded. In the present study, we investigated the effectiveness and suitability of different in-practice Pterygoplichthys spp. control methods, based on on-field sampling, biological and behavioural study of the fish and also response analysis of the stakeholder’s of EKW. The results indicate that in-practice eradication efforts, like ‘repeated seine netting’ with or without removal of Eichhornia sheath of the pond periphery and ‘dewatering of pond’ aiming to reduce or eradicate Pterygoplichthys spp., are not fully effective, because of the capture avoidance ability and burrowing habit of these fishes. We found deep and branching burrows of Pterygoplichthys spp. in aquaculture ponds of EKW, with maximum burrow depth of 58 cm, and water in that burrows even after 12 days of dewatering. Hence, it is suggested stakeholders to keep dewatered pond exposed to sunlight for at least four weeks or above to ensure complete water-out from the burrows in which Pterygoplichthys spp. take shelter or lay their eggs. ‘Multilayer bamboo fencing’ or ‘combination of bamboo fencing and net barrier’ use by the stakeholders of EKW to prevent intrusion or re-intrusion of Pterygoplichthys spp. were found only partially effective, because of the capability of these fishes to damage net-blocking through their hard dorsal and pectoral spines or entry through the holes dug across the barrier in beneath or banks of the sewage intake channel. Based on learning on the biological and behavioural characteristics of Pterygoplichthys spp., we then suggested a modified version of barrier to the stakeholder’s of EKW, incorporating a sewage feeder pipeline, a concrete collection chamber with size separation arrangement made of hard materials like wire mesh and a dam of specific dimensions across the channel, for effective prevention of intrusion of these fishes in their aquaculture bheries.

Temporal variations in bio-indices of Oreochromis niloticus (Linnaeus, 1758) in East Kolkata wetlands, India

Temporal variations in selected bio-indices of length-weight relationships (LWRs) like relative condition factor (Kn), relative length of gut (RLG), hepato-somatic index (HSI), gonado-somatic index (GnSI) and gastro-somatic index (GaSI) of Nile tilapia (Oreochromis niloticus) were carried out in 341 samples collected at fortnightly intervals in East Kolkata wetlands, a Ramsar site. The exponent b value of LWRs was 2.9869, 2.8316 and 2.9163 with r2 value being 0.938, 0.936 and 0.935 for male, female and the pooled sample respectively showing negative allometric growth of the fish. The Kn values ranged 1.01 to 1.09 and 1.05 to 1.12 for male and female samples respectively exhibiting significant difference (p<0.05) between sexes. Monthly mean RLG values fluctuated from 6.55 to 9.01 indicating herbivore feeding habits. Monthly mean GaSI values were in the range from 0.64 to 2.63 and that of HSI values from 0.53 to 1.41. Monthly mean GnSI values ranged from 0.19 to 1.27 and 0.35 to 3.01 for male and female fish respectively exhibiting significant (p<0.05) difference between the sexes, which was attributed to maturity and gradual gonadal development. Key words Oreochromis niloticus, Bio-indices, East Kolkata Wetlands, Ramsar site

Anthropogenic stress on a Ramsar site, India: Study towards rapid transformation of the health of aquatic environment

The East Kolkata Wetlands (EKW) region is an important Ramsar Site (huge provisional, regulatory, cultural and spiritual ecosystem services) which is located at the eastern periphery of Kolkata Metropolitan City (India). But in the recent years, illegal land acquisition, wetlands conversion, aquatic species depletion as well as water pollution related diseases have been experienced in different pockets of EKW region. The main objective is to determine regulating factors and stages of eutrophication. The water samples of consecutive three years 2017, 2018 and 2019 (pre and post monsoon) have been obtained from selective 20 wetlands in EKW. The important physicochemical parameters (temperature, electrical conductivity (EC), turbidity, total alkalinity, pH, total hardness, total dissolved solids (TDS), dissolved oxygen (DO), inorganic nitrogen, total phosphorus, potassium, ammonium-nitrogen (NH4+-N), biological oxygen demand (BOD), Secchi disk depth, chlorophyll - a), trophic status index and statistical techniques (like principal component analysis, hierarchical cluster analysis) have been considered to analyze the water quality of these wetlands. The results portray that the magnification of inorganic nitrogen, total phosphorus, potassium and ammonium-nitrogen accelerates the mechanism of eutrophication in the selective wetlands. The DO level has been diminished during 2019 while the BOD level and chlorophyll concentration have been accelerated amidst 2019.The results reveal that about 40% of wetlands i.e. wetland no. 5, 7, 10, 16, 17 (TSI value – 50–70) and wetland no. 8 and 11 (TSI value – 70–100) come under eutrophic and hyper-eutrophic stages respectively due to higher accumulation of nitrogen and phosphorus contents in the wetlands from various non-point sources and these principal components stimulate the processes of eutrophication of the water bodies. Some relevant mitigation measures have been recommended to protect the “kidney of Kolkata Metropolitan City”.

Bacterial diversity assessment of world's largest sewage-fed fish farms with special reference to water quality: a Ramsar site.

Bacterial community structure is one of the essential components of aquaculture dynamics and plays an important role in maintaining wetland health. The present work is an effort to study the structure of bacterial communities in the world's largest sewage-fed fish farms, the East Kolkata Wetlands (EKWs), along with their predicted functional metabolic pathways and correlation with environmental variables. Sequencing data analysis revealed the abundance of genera such as Arcobacter (0-50%), Pseudomonas (0-15%), Sulfurospirillum (0-9%), Cloacibacterium (0-6%), hgcI clade (7-29%), C39 (0-9%), V6 (3-36%), Fluiivicola (1-6%) and Cyanobium (3-8%) in the EKWs. Further, water quality analysis of three treatment groups, i.e. Sewage, Sewage F-1 and Sewage F-2, revealed that dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD) differed significantly and violated the standard prescribed norms (Central Pollution Control Board, CPCB, New Delhi) for fishery propagation and irrigation in India. Further, the correlation matrix analysis between the abundance of bacterial genera and environmental variables indicated that DO, BOD and COD were mainly responsible for bacterial community structure and their proliferation in the EKWs. Our results indicated that the abundance of genera such as Arcobacter, Pseudomonas, Sulfurospirillum and Cloacibacterium has an inverse relationship with BOD and COD. Our observations based on the bacterial community structure and deteriorated water quality indicate the ineffective functioning and poor management of this man-made constructed wetland.

Assessment of Environmental Water Security of an Asian Deltaic Megacity and Its Peri-Urban Wetland Areas

Achieving urban water security requires sustaining the trade-offs between the exploitation of water/environmental resources and ecosystem services. This achievement not only reduces the pollution and contamination in the environment, level of water stress, but also secures good ambient water quality and future for people’s well-being and livelihoods. Changes in land use and land cover and growth of impervious structures can immediately generate severe ecological and social issues and increase the level of natural or manmade risks, affecting the condition of ecosystem services within and in the vicinity of an urban region. As a result of these transformations and further exploitation, due to the growing anthropogenic pressure, surface water and groundwater quality can be deteriorated compared to ambient water quality standards (for both chemical and biological pollutants). Based on land use and land cover (LULC) data retrieved from remote sensing interpretation, we computed the changes of the ecosystem service values (ESV) associated with the LULC dynamics, water quality and, finally, urban water security during the pre- and post-monsoon periods of 2009, 2014 and 2019 in Kolkata, an Asian deltaic megacity, and its peri-urban wetlands named East Kolkata Wetlands (EKW). The area under wetlands reduced comprehensively in 2009–2019 due to the conversion of wetlands into various other classes such as urban settlement, etc. The quality of surface water bodies (such as rivers, lakes, canals and inland wetlands) deteriorated. The groundwater quality is still under control, but the presence of arsenic, manganese and other metals are a clear indication of urban expansion and related activities in the area. As a result, there was a change in the ESV during this timeframe. In the pre-monsoon period, there was an increase in total ESV from US$53.14 million in 2009 to US$53.36 million and US$59.01 million in 2014 and 2019, respectively. In the post-monsoon period, the ESV decreased from US$67.42 million in 2009 to US$64.13 and US$61.89 million in 2014 and 2019, respectively. These changes can be attributed to the peri-urban wetlands and the benefits or services arising out of them that contribute more than 50% of the total ESV. This study found that the area under wetlands has reduced comprehensively in the past 10 years due to the conversion of wetlands for various other uses such as urban expansion of the Kolkata City, but still, this peri-urban wetland supports the urban water security by providing sufficient ecosystem services. In conclusion, the transformation in extent of the water-related ecosystem is a crucial indicator of urban water security, which also measures the quantity of water contained in various water-related ecosystems. Quantitative analysis of the LULC change, hence, is important for studying the corresponding impact on the ecosystem service value (ESV) and water quality that helps in decision-making in securing urban water future and ecosystem conservation.

Potentially suitable habitat, connectivity and priority conservation areas for White-breasted waterhen (Amaurornis phoenicurus) and Bronze-winged jacana (Metopidius indicus)

Wetlands, like East Kolkata Wetlands (EKW) in present study, are vulnerable to habitat alteration and other anthropogenic threats affecting avifauna. Consequently, prioritizing avifaunal conservation based on suitable habitats and their connectivity is essential. White-breasted waterhen (WBW, Amaurornis phoenicurus) and bronze-winged jacana (BWJ, Metopidius indicus) are two resident birds of EKW. We used MaxEnt for habitat suitability maps; assessed habitat connectivity in Circuitscape and mapped top 10% conservation priority areas in Zonation softwares. Both species had similar niche breadth and high niche overlap. The high suitability and moderate suitability areas for WBW was 0.02 km2 and 13.06 km2 respectively, while high suitability area for BWJ was absent and moderate suitability areas covered 6.73 km2. But, these suitable habitats mostly showed low and least connectivity. Finally, we found banks and dikes of wetlands, small vegetations therein and cropfields are important land-use classes in their projected suitable habitats and also in top 10% conservation priority areas. Use of chemical fertilizers and pesticides in the cropfields and clearing of bushes on the banks and dikes, as well as, the floating and emergent macrophytes in waterbodies with intensive commercial pisciculture are recorded as potential anthropogenic threats. Also ~80% of this top 10% conservation priority area are prone to moderate to high habitat transformation. Protection of remaining suitable habitats and their connectivity identified in this study, as well as, restoration of degraded habitats, and reduction of threats will ensure the conservation of WBW and BWJ in EKW and also in other wetlands in human-dominated landscapes.

NUTRITIONAL COMPOSITION OF THE INVASIVE PTERYGOPLICHTHYS DISJUNCTIVUS FROM EAST KOLKATA WETLAND, INDIA

Pterygoplichthys disjuctivus, native to South America (Armbruster 2001) has spread massively as an exotic fish species in many of the open water systems in India including the East Kolkata Wetland, a Ramsar site in West Bengal, India. Such exotic species compete for food and physical resources with the native species thereby affecting habitat structure and the species diversity. In spite of being caught in very high numbers, option for its utilization has not been explored. In this context, the nutritional composition of Pterygoplichthys disjuctivusin terms of gross chemical composition, amino acid, fatty acid and mineral composition was studied to explore its potential to be used as source of fish meal. Nutritional composition analysis showed that the fish is rich in proteins (16.1%), functional amino acid leucine (15.15%) and macro minerals phosphorous (2220 mg/100 g) and potassium (1780 mg/100g).This study indicates that the fish is rich in protein and minerals and could be utilized as a source of fish meal in fish feed formulations. Key words: Invasive species, Pterygoplichthys disjunctivus, East Kolkata wetland

Spatial changes in soil organic matter and waste elements in contaminated agricultural fields at anthropogenically transformed areas within the east calcutta wetlands ecosystem

Physical and chemical properties of soil were compared between different agricultural fields of multi-metal waste contaminated East Calcutta Wetlands (ECW) sites and uncontaminated control study sites. Soil organic matter (SOM) contents were significantly different between contaminated ECW and control sites. Agricultural fields at ECW sites were characterized by higher contents of SOM, porosity, moisture, particle size (sandy >63 μm) and metals; while the control sites had higher bulk density, pH and electrical conductivity (EC). Metal accumulation in soils of ECW showed the trend Fe>Zn>Mn>Cr>Pb>Cu; while at control sites like Fe>(Zn=Mn)>Cr>(Pb=Cu). Post-Hoc analyses (with Tukey HSD) clearly pointed out site-wise significant differences (at p<0.05) in soil metal contents between ECW and control sites. The results of this study pointed out the importance of chelates like SOM and easily biodegradable organic acids in the waste contaminated soils of ECW to arrest metals in significant amount reducing phytoavailability and, thereby, sustained agricultural practices at the concerned areas without any health hazard for nearly a century.

Carbon sequestration by horticultural plants in East Calcutta Wetlands ecosystem, a Ramsar Site in India

East Calcutta Wetlands (ECW) located at the eastern fringe of Kolkata metropolitan, India designated as a Ramsar Site (No. 1208). ECW receives municipal solid wastes and composite wastewater from the city and local artisans use this for horticulture, agriculture and pisciculture practices. Horticulture designated as ‘green industry’ sequester significant amount of carbon (C) in plant biomass and in soil, therefore, helps to mitigate greenhouse gases and combat against global climate change. Six horticultural plant species commonly cultivated in ECW ecosystems were selected for present study. C sequestration potential of horticultural plants depends on plant biomass and plant density in cultivation fields. Highest amount of C was sequestered (40.76±6.73 ton ha-1) by ixora, a perennial plant in plant biomass. In case of basil, also a perennial plant, significant portion of the living plant biomass was exported from ECW as economically important parts which constitute 5.79±0.96 ton ha-1 C. Highest amount of soil organic carbon (SOC) was recorded from marigold fields (50.36±24.88 ton ha-1) which also constitute highest amount of C (34.37±5.67 ton ha-1) in residual parts (RP). Horticulture practices can sequester more amount of C in the ecosystem either by residual parts or remaining living plant biomass than agricultural practices.

Stress responses of Indian major carps cultured in the East Kolkata Wetland, West Bengal, India

Fish are continuously exposed to multiple environmental stressors that work cumulatively and synergistically. This study assessed the stress responses of Indian major carps (IMCs) cultured in a sewage-fed pond (SP) in the East Kolkata Wetland (EKW), India and compared with the normal carps in situ. The experiment was conducted in two farms that cultured Labeo rohita, Catla catla and Cirrhinus mrigala for seven months, covering the summer and winter periods. Serum biomarkers of primary (cortisol) and secondary (glucose, total protein, creatinine, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH)) stress responses, and oxidative stress (superoxide dismutase (SOD)) were quantified using standard kits. The health status of carps was evaluated as a tertiary response. The biological oxygen demand, hardness, total dissolved solids, ammonia and phosphate levels of both ponds exhibited marked variations. The SP carps had significantly low haemoglobin and total protein, and high serum glucose, creatinine, ALT, AST and LDH levels. The SOD and cortisol levels were comparatively low in SP carps. The winter temperature had a significant effect on serum glucose, cortisol, SOD, creatinine, ALT and AST. Carps had a high degree of ectoparasitic infestation during the winter. Cirrhinus mrigala of the SP had significantly high serum creatinine levels. The increasing levels of serum glucose, creatinine, ALT and AST suggested that these indices, which were more pronounced in the carps of EKW in conjunction with winter temperature, could be useful biomarkers of stress, kidney and liver functioning in carps, respectively.

Eco-dynamics of East Kolkata Wetlands with special reference to biodiversity: Efficacy of the application of GIS and Remote sensing in delineation ecological status

Eco-dynamics of East Kolkata Wetlands with special reference to biodiversity: Efficacy of the application of GIS and Remote sensing in delineation ecological status

Eco-dynamics of East Kolkata Wetlands with special reference to biodiversity: Efficacy of the application of GIS and Remote sensing in delineation ecological status

Eco-dynamics of East Kolkata Wetlands with special reference to biodiversity: Efficacy of the application of GIS and Remote sensing in delineation ecological status

Dynamics of temporal foraging and feeding index of Labeo rohita (Hamilton, 1822) in East Kolkata wetlands, a Ramsar site

Dynamics of temporal foraging and feeding index of Labeo rohita (Hamilton, 1822) in East Kolkata wetlands, a Ramsar site

East Calcutta Wetlands, India: integrating sanitation, engineering and ecology

The East Calcutta Wetlands are an indispensable heritage of the city of Calcutta, India, and globally recognised as a partly natural, partly man-made ecosystem that sets an example in sustainable wastewater reuse. The 2017 UN World Water Development Report emphasised the vital role of the East Calcutta Wetlands in treating the city’s municipal sewage through biological methods, without the aid of a mechanical sewage treatment plant but with the help of the community, whose livelihood is connected to this work. Considering that, globally, only 20% of wastewater is treated, the looming water crisis raging through many Indian cities, increasing calls for conservation and proper utilisation of water sources such as rivers and wise use of water/wastewater, it is relevant to examine the dynamics of these wetlands. They afford timely lessons for urban wastewater management and sustainability of a tropical city with ample sunshine. The wetlands are an outcome of engineering innovation connected to a drainage outfall system. This paper examines the context of that innovation and the lessons they hold out for the urban future.

Wetland conversion risk assessment of East Kolkata Wetland: A Ramsar site using random forest and support vector machine model

East Kolkata Wetland (EKW) is a Ramsar site located adjacent to the Kolkata megacity. EKW is one of the resourceful wetland ecosystems of the world which offers a bundle of direct and indirect ecosystem services to the Kolkata megacity region. The rapid expansion of built-up in the surrounding urban agglomeration of the EKW is putting immense pressure on the EKW and the rate of wetland loss has been highest in recent decades. To ensure that this distinct ecosystem is conserved, an efficient means of identifying wetland conversion risk is needed. This study aims to assess the risk of EKW conversion using two advanced data-driven Machine Learning (ML) models, viz, Random Forest (RF), and Support Vector Machine (SVM). The novelty of the paper is in the fact that ML models have been widely applied to groundwater potential, flood susceptibility, and landslide susceptibility, their applicability to wetland conversion risk assessment has not yet been explored. The advantage of RF and SVM is that both of the ML models can overcome the limitations of pre-assumption based conventional methods of wetland risk assessment. A total of eight factors are selected which can be categorized into ecological, bio-physical, demographic, and physical infrastructure groups. Both results indicate that around 60% area under medium to very high-risk zones. A comparison is also made between these two methods to identify the most precise prediction method for this study area. The results of the models are quantitatively validated applying the Receiver Operating Characteristics (ROC) method, where both of this method identifies SVM as a more precise predictive model for this study with 91.12% accuracy. The spatial pattern of encroachment and shrinkage of EKW triggered by urban expansion is successfully captured by RF and ME. Policy analysts and land-use planners can use the outcome derived from RF and SVM models and associated maps to identify the risk zones, assess the effectiveness of wetland conservation programs, design effective policies to stop further degradation of the wetlands, and adopt long-term sustainable planning for this precious ecosystem.

Seasonal Variation of Culturable Benthic Soil Prokaryotic Microbiota as Potential Fish Pathogens and Probiotics from an Aquaculture Farm in East Kolkata Wetlands, India

Rising demand in the aquaculture sector tends towards finding innovative ways to promote better yield and profitability. Benthic soil microbiota can provide an insight into the potent opportunistic fish pathogens as well as probiotics present in the aquaculture system. This study reports the seasonal diversity and abundance of fifteen culturable pathogenic bacterial strains belonging to the genera of Comamonas, Aeromonas, Providencia, Klebsiella, Escherichia, Acinetobacter, Serratia, Stenotrophomonas, Staphylococcus, and Enterobacter along with nine probiotic strains native to genera of Bacillus and Pseudomonas isolated from an aquaculture farm benthic soil, located in East Kolkata Wetlands, West Bengal, India. Strains are isolated using traditional microbial culture methods and tested for their antimicrobial susceptibility against commonly available antibiotics. 16S rDNA analysis was done for the identification of the strains and the establishment of their phylogenetic relationships. Among the isolates, B. pumilus strain S8 in the pre-monsoon sample, E. coli strain M2aR1 in the monsoon sample, and A. hydrophila strain P6dF1 in the post-monsoon sample were the most abundant having MPN counts of 275±21 x 106 CFU/gram dry soil, 278±18 x 106 CFU/gram dry soil, and 321±28 x 106 CFU/gram dry soil respectively. Data on the temporal diversity, abundance, and drug-susceptibility of prokaryotic fish-pathogens and probiotics can be used to formulate measures for sustainable aquaculture practices with reduced maintenance costs.

Sediment metal contaminations in sewage-fed aquaculture system of East Kolkata Wetland, West Bengal, India

Present work aimed to study the contamination of heavy metals (Copper, Lead, Manganese, and Zinc) in sediment from sewage fed aquaculture system of East Kolkata Wetlands, West Bengal, India from July 2016 to March 2017. Composite sediment samples were collected monthly from three sites (S1, S2, and S3) of the Nalban of the East Kolkata Wetlands. The samples were brought to the laboratory, processed, and analyzed. The concentrations of the metals were in the order Mn&gt; Zn &gt; Pb&gt; Cu at S1; Mn&gt; Zn &gt; Cu &gt;Pb at S2 and Zn &gt; Mn &gt; Pb &gt; Cu at S3. The calculated average values of Contamination Factor (CF) were in the order Pb &gt;Cu&gt;Zn&gt;&gt; Mn at S1, Cu Zn &gt; Pb &gt;&gt; Mn at S2, and Pb &gt; Zn &gt; Cu &gt;&gt; Mn at S3. In general, the wetland was rated as low to moderately contaminated. The estimated Pollution Load Index (PLI) values for the wetland also corroborated the inference. Suitable management practices like the proper waiting period for wastewater intake, continuing general cultural practices of maintaining water hyacinth in the marginal areas of the wetland, etc., should be religiously followed to prevent the wetland from further deterioration due to associated risk of pollution. Key words Heavy metal; Sediment pollution; Contamination factor; Pollution load index.

Summer methane emissions from sewage water-fed tropical shallow aquaculture ponds characterized by different water depths.

Aquaculture practices are steadily increasing to meet the fish demand, especially in tropical countries like India. However, efforts to characterize the contribution of these aquaculture ponds towards greenhouse gas emission like CH4 are still very few. CH4 concentration in water [pCH4(water)] and air-water CH4 fluxes were estimated (during the summer months) in two sewage-fed ponds having different depths situated in the East Kolkata Wetlands, India (a Ramsar site). pCH4(water) in both of these ponds showed significant positive correlation with water temperature (R2 = 0.68 and 0.71, p < 0.05). Daily mean chlorophyll-a, turbidity, biochemical oxygen demand (BOD) and gross primary productivity (GPP) also showed positive correlation with pCH4(water). This indicated that higher primary production and presence of turbid materials acted as substrates for methanogenesis, which favoured air-water CH4 effluxes towards atmosphere. Mean air-water CH4 fluxes in the ponds having depth of 1.1m and 0.6m were observed to be 24.79 ± 12.02mgm-2h-1 and 6.05 ± 3.14mgm-2h-1 respectively. Higher depth facilitated net heterotrophic conditions, which led to lower dissolved oxygen levels, which, in turn, led to lower rate of CH4 oxidation. Moreover, under reduced photosynthetically active radiation (in the pond having greater depth), the pH values were comparatively lower (~7.7), which further facilitated a favourable condition for the methanogens to grow. On the whole, it was inferred that apart from pre-established physicochemical factors, depth was also found to play a decisive role in regulating the air-water CH4 fluxes from these aquaculture ponds. In future, continuous sampling should be carried out (by chamber method) to take into account the ebullition CH4 fluxes, and more number of ponds should be sampled throughout a complete annual cycle to have a more holistic understanding about this cluster of sewage-fed aquaculture ponds.

Effect of nutrient alteration on pCO2(water) and chlorophyll-a dynamics in a tropical aquaculture pond situated within a Ramsar site: a microcosm approach.

Tropical sewage-fed aquaculture ponds of East Kolkata Wetlands (EKW), a Ramsar site, act as deposition center of organic matter and nutrient-rich sewage from the Kolkata metropolis, which in turn is utilized as fish feed in aquaculture ponds. Increasing nutrient load due to multifarious anthropogenic activities usually alters the chlorophyll-a (chl-a) and the partial pressure of carbon dioxide in water [pCO2(water)] dynamics in such aquatic systems. In this regard, the effect of nutrient level alteration [8 times and 24 times, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in addition, respectively] on chl-a and pCO2(water) was tested upon waters of EKW aquaculture ponds in three different seasons by means of microcosm for 8 consecutive days. In both DIN 8× and DIP 8× treatments, an overall increase in chl-a concentrations was observed by the end of experiment; however, in DIN 24× and DIP 24× treatments, chl-a in most of the seasons was found to diminish after a steep rise in its concentration during 4th or 5th day. In all the seasons, the surface waters were supersaturated with CO2 under in situ conditions. The extent of supersaturation enhanced with nutrient addition during monsoon; however, in post-monsoon and pre-monsoon, nutrient addition led to undersaturation of CO2. Though chl-a concentration exhibited substantial variability during the microcosm experiments, the variation in trophic state index was not that much remarkable. In DIN-treated microcosms, uptake rate of DIP was significantly high compared to the reverse scenario, which implied that DIP has a more limiting character than DIN. In P-enriched treatments, the lack of N supplies probably limit production of autotrophic biomass. Thus it can be concluded that the nature of sewage and its DIN/DIP content can significantly alter the primary productivity the CO2 dynamics of such aquaculture ponds in future.

Ecology and plankton diversity of Bhara Haripota bhery, East Kolkata wetland, West Bengal

Ecology and plankton diversity of Bhara Haripota bhery, East Kolkata wetland, West Bengal