Role of tide and lunar phases on the migration pattern of juvenile Hilsa shad (Tenualosa ilisha) within a meso-macrotidal estuary.

Tide and lunar phases often influence the behaviour and life cycle of different fishes, especially migratory species. In the Hooghly River estuary, Hilsa shad is an anadromous fish species that migrates from the adjacent sea to the estuary and rivers for spawning. After spawning, the juveniles remain in the rivers and estuary for few months then start their downstream migration towards the adjacent sea. However, the pattern of their downstream migration has not been studied in detail so far. This study investigates the role of tide and lunar phases on the juvenile Hilsa shad migration pattern. In this study, we have estimated the rate of juveniles migrating through the river channel (no. m-2  h-1 ) during high tide and low tide in all of the lunar phases. The number of juvenile Hilsa shad fishes is found to be much higher during low tides in most of the observations and there is a significant difference (t = 11.904, P < 0.001) between the high tide and low tide catches in the entire study region. Among the eight lunar phases, the number of juveniles is also observed to be higher during the new moon and full moon, and there is also a significant difference in juvenile catch among the lunar phases (F = 64.372, P < 0.001) in the entire stretch of the study area. These observations enabled us to develop a plausible mechanism of the downstream migration of Hilsa shad juveniles.

Outwelling of total alkalinity and dissolved inorganic carbon from the Hooghly River to the adjacent coastal Bay of Bengal.

The seasonal variability of the lateral flux of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) of the tropical Hooghly estuary is analyzed in this work. In situ observations of water temperature, salinity, dissolved oxygen, TAlk, and pH were measured in four different stations of the Hooghly estuary. It was measured once every month during 2015-2016, and subsequently, DIC was estimated. A carbon budget was constructed to quantify carbon flows through the freshwater-marine continuum of the Hooghly estuary, and plausible impacts on the adjacent coastal ocean, the northern Bay of Bengal, were examined. The biogeochemical mass balance box model was used to compute the seasonal flow of carbon flux, and subsequently, the annual budgeting of lateral fluxes of TAlk and DIC to the adjacent coastal ocean was carried out. The net annual TAlk and DIC flux from the Hooghly estuary to the adjacent coastal ocean were 4.45 ± 1.90 × 1011 mol and 4.59 ± 1.70 × 1011 mol, respectively. The net annual DIC flux of the Hooghly estuary is about 30 to 60 times higher than surface area integrated air-water CO2 flux, which is an indication of promoting acidification in the adjacent coastal ocean. The present study indicates that the lateral DIC flux has increased substantially in the Hooghly estuary during the last two decades. The increase in inorganic carbon load in the Hooghly estuary due to the enhanced discharge of inorganic and organic matter load in the upper reaches of the estuary led to this increase in lateral DIC flux. The results strongly establish the need of having such regional studies for better understanding the estuarine carbon dynamics, and its role in controlling the adjacent coastal ocean dynamics.

Impact of high-fat diet on vasoconstrictor reactivity of white and brown adipose tissue resistance arteries.

Blood flow regulation is a critical factor for tissue oxygenation and substrate supply. Increased reactivity of arteries to vasoconstrictors may increase vascular resistance, resulting in reduced blood flow. We aimed to investigate the effect of a high-fat (HF) diet on stiffness and vasoconstrictor reactivity of white adipose tissue (WAT) and brown adipose tissue (BAT) resistance arteries and also investigated the interconversion of both adipose depots in the setting of a HF diet. Vasoconstrictor reactivity and passive morphology and mechanical properties of arteries from B6D2F1 mice (5 mo old) fed normal chow (NC) or a HF diet (8 wk) were measured using pressure myography. Receptor gene expression in WAT and BAT arteries and markers of WAT and BAT were assessed in whole tissue lysates by real-time RT-PCR. Despite greater receptor-independent vasoconstriction (in response to KCl, P < 0.01), vasoconstriction in response to angiotensin II ( P < 0.01) was lower in NC-BAT than NC-WAT arteries and similar in response to endothelin-1 ( P = 0.07) and norepinephrine ( P = 0.11) in NC-BAT and NC-WAT arteries. With the exception of BAT artery reactivity to endothelin-1 and angiotensin II, the HF diet tended to attenuate reactivity in arteries from both adipose depots and increased expression of adipose markers in BAT. No significant differences in morphology or passive mechanical properties were found between adipose types or diet conditions. Alterations in gene expression of adipose markers after the HF diet suggest beiging of BAT. An increase in brown adipocytes in the absence of increased BAT mass may be a compensatory mechanism to dissipate excess energy from a HF diet. NEW & NOTEWORTHY Despite no differences in passive mechanical properties and greater receptor-independent vasoconstriction, receptor-mediated vasoconstriction was either lower in brown than white adipose tissue arteries or similar in brown and white adipose tissue arteries. A high-fat diet has a greater impact on vasoconstrictor responses in white adipose tissue but leads to altered adipose tissue gene expression consistent with beiging of the brown adipose tissue.

Loss of Angiotensin-Converting Enzyme 2 Exacerbates Diabetic Retinopathy by Promoting Bone Marrow Dysfunction.

Angiotensin-converting enzyme 2 (ACE2) is the primary enzyme of the vasoprotective axis of the renin angiotensin system (RAS). We tested the hypothesis that loss of ACE2 would exacerbate diabetic retinopathy by promoting bone marrow dysfunction. ACE2-/y were crossed with Akita mice, a model of type 1 diabetes. When comparing the bone marrow of the ACE2-/y -Akita mice to that of Akita mice, we observed a reduction of both short-term and long-term repopulating hematopoietic stem cells, a shift of hematopoiesis toward myelopoiesis, and an impairment of lineage- c-kit+ hematopoietic stem/progenitor cell (HS/PC) migration and proliferation. Migratory and proliferative dysfunction of these cells was corrected by exposure to angiotensin-1-7 (Ang-1-7), the protective peptide generated by ACE2. Over the duration of diabetes examined, ACE2 deficiency led to progressive reduction in electrical responses assessed by electroretinography and to increases in neural infarcts observed by fundus photography. Compared with Akita mice, ACE2-/y -Akita at 9-months of diabetes showed an increased number of acellular capillaries indicative of more severe diabetic retinopathy. In diabetic and control human subjects, CD34+ cells, a key bone marrow HS/PC population, were assessed for changes in mRNA levels for MAS, the receptor for Ang-1-7. Levels were highest in CD34+ cells from diabetics without retinopathy. Higher serum Ang-1-7 levels predicted protection from development of retinopathy in diabetics. Treatment with Ang-1-7 or alamandine restored the impaired migration function of CD34+ cells from subjects with retinopathy. These data support that activation of the protective RAS within HS/PCs may represents a therapeutic strategy for prevention of diabetic retinopathy. Stem Cells 2018;36:1430-1440.

Beneficial Effects of Angiotensin-(1-7) on CD34+ Cells From Patients With Heart Failure.

The dysfunctional nature of CD34 cells from patients with heart failure (HF) may make them unsuitable for autologous stem-cell therapy. In view of evidence that the vasoprotective axis of the renin-angiotensin system (RAS) improves CD34 cell functions, we hypothesized that CD34 cells from patients with HF will be dysfunctional and that angiotensin-(1-7) [Ang-(1-7)] would improve their function. Peripheral blood was collected from New York Heart Association class II-IV patients with HF (n = 31) and reference subjects (n = 16). CD34 cell numbers from patients with HF were reduced by 47% (P < 0.05) and also displayed 76% reduction in migratory capacity and 56% (P < 0.05) lower production of nitric oxide. These alterations were associated with increases in RAS genes angiotensin-converting enzyme and AT2R (595%, P < 0.05) mRNA levels and 80% and 85% decreases in angiotensin-converting enzyme 2 and Mas mRNA levels, respectively. Treatment with Ang-(1-7) enhanced CD34 cell function through increased migratory potential and nitric oxide production, and reduced reactive oxygen species generation. These data show that HF CD34 cells are dysfunctional, and Ang-(1-7) improves their functions. This suggests that activation of the vasoprotective axis of the RAS may hold therapeutic potential for autologous stem-cell therapy in patients with HF.

The impact of ageing on adipose structure, function and vasculature in the B6D2F1 mouse: evidence of significant multisystem dysfunction.

The critical influence of the white adipose tissue (WAT) on metabolism is well-appreciated in obesity, but adipose tissue dysfunction as a mechanism underlying age-associated metabolic dysfunction requires elucidation. To explore this possibility, we assessed metabolism and measures of epididymal (e)WAT mitochondria and artery function in young (6.1 ± 0.4 months) and old (29.6 ± 0.2 months) B6D2F1 mice. There were no group differences in average daily oxygen consumption, fasted blood glucose or plasma free fatty acids, but fasted plasma insulin and the homeostatic model assessment of insulin resistance (HOMA-IR%) were higher in the old (∼50-85%, P < 0.05). Tissue mass (P < 0.05) and adipocyte area were lower (∼60%) (P < 0.01) and fibrosis was greater (sevenfold, P < 0.01) in eWAT with older age. The old also exhibited greater liver triglycerides (∼60%, P < 0.05). The mitochondrial respiratory oxygen flux after the addition of glutamate and malate (GM), adenosine diphosphate (d), succinate (S) and octanoyl carnitine (O) were one- to twofold higher in eWAT of old mice (P < 0.05). Despite no change in the respiratory control ratio, substrate control ratios of GMOd/GMd and GMOSd/GMd were ∼30-40% lower in old mice (P < 0.05) and were concomitant with increased nitrotyrosine (P < 0.05) and reduced expression of brown adipose markers (P < 0.05). Ageing reduced vascularity (∼50%, P < 0.01), angiogenic capacity (twofold, P < 0.05) and expression of vascular endothelial growth factor (∼50%, P < 0.05) in eWAT. Finally, endothelium-dependent dilation was lower (P < 0.01) in isolated arteries from eWAT arteries of the old mice. Thus, metabolic dysfunction with advancing age occurs in concert with dysfunction in the adipose tissue characterized by both mitochondrial and arterial dysfunction.

CNS inflammation and bone marrow neuropathy in type 1 diabetes.

By using pseudorabies virus expressing green fluorescence protein, we found that efferent bone marrow-neural connections trace to sympathetic centers of the central nervous system in normal mice. However, this was markedly reduced in type 1 diabetes, suggesting a significant loss of bone marrow innervation. This loss of innervation was associated with a change in hematopoiesis toward generation of more monocytes and an altered diurnal release of monocytes in rodents and patients with type 1 diabetes. In the hypothalamus and granular insular cortex of mice with type 1 diabetes, bone marrow-derived microglia/macrophages were activated and found at a greater density than in controls. Infiltration of CD45(+)/CCR2(+)/GR-1(+)/Iba-1(+) bone marrow-derived monocytes into the hypothalamus could be mitigated by treatment with minocycline, an anti-inflammatory agent capable of crossing the blood-brain barrier. Our studies suggest that targeting central inflammation may facilitate management of microvascular complications.

Dual character of Sundarban estuary as a source and sink of CO2 during summer: an investigation of spatial dynamics.

A comprehensive attempt has been made to evaluate the diurnal and spatial pattern of CO2 exchange between the atmosphere and water along the estuarine track of Indian Sundarbans during the two summer months, April and May, 2011. Rigorous field observations were carried out which included the hourly measurements of total alkalinity, pH, fugacity of CO2 in ambient air and water surface, dissolved oxygen, and chlorophyll a. The estuarine water was found rich in total alkalinity and was oversaturated with CO2 throughout the diurnal cycle in the two stations situated at the inner and middle estuary, respectively, whereas an entirely reverse situation was observed in the outer fringes. The fugacity of CO2 in water ranged from 152 to 657 µatm during the study period. The percentage of over-saturation in inner and middle estuary varied from 103 to 168 and 103 to 176 %, respectively, whereas the degree of under-saturation in the outer estuary lied between 40 and 99 %. Chlorophyll a concentrations were found higher in the outer estuary (12.3 ± 2.2 mg m(-3)) compared to the middle (6.4 ± 0.6 mg m(-3)) and inner parts (1.6 ± 0.2 mg m(-3)), followed by a similar decreasing pattern in nutrient availability from the outer to inner estuary. The sampling stations situated at the inner and middle estuary acted as a net source of 29.69 and 23.62 mg CO2 m(-2) day(-1), respectively, whereas the outer station behaved as a net sink of -33.37 mg CO2 m(-2) day(-1). The study of primary production and community respiration further supports the heterotrophic nature of the estuary in the inner region while the outer periphery was marked by dominant autotrophic character. These contrasting results are in parity with the source characters of many inner estuaries and sinking characters of the outer estuaries situated at the distal continental shelf areas.

Carbon Biogeochemistry of the Estuaries Adjoining the Indian Sundarbans Mangrove Ecosystem: A Review.

The present study reviewed the carbon-biogeochemistry-related observations concerning CO2 and CH4 dynamics in the estuaries adjoining the Indian Sundarbans mangrove ecosystem. The review focused on the partial pressure of CO2 and CH4 [pCO2(water) and pCH4(water)] and air-water CO2 and CH4 fluxes and their physical, biogeochemical, and hydrological drivers. The riverine-freshwater-rich Hooghly estuary has always exhibited higher CO2 emissions than the marine-water-dominated Sundarbans estuaries. The mangrove sediment porewater and recirculated groundwater were rich in pCO2(water) and pCH4(water), enhancing their load in the adjacent estuaries. Freshwater-seawater admixing, photosynthetically active radiation, primary productivity, and porewater/groundwater input were the principal factors that regulated pCO2(water) and pCH4(water) and their fluxes. Higher chlorophyll-a concentrations, indicating higher primary production, led to the furnishing of more organic substrates that underwent anaerobic degradation to produce CH4 in the water column. The northern Bay of Bengal seawater had a high carbonate buffering capacity that reduced the pCO2(water) and water-to-air CO2 fluxes in the Sundarbans estuaries. Several authors traced the degradation of organic matter to DIC, mainly following the denitrification pathway (and pathways between aerobic respiration and carbonate dissolution). Overall, this review collated the significant findings on the carbon biogeochemistry of Sundarbans estuaries and discussed the areas that require attention in the future.

Exploratory modelling of the impacts of sea-level rise on the Sundarbans mangrove forest, West Bengal, India.

In this paper we conduct exploratory simulations of the possible evolution of the Indian Sundarbans mangroves to 2100 under a range of future sea-level rise (SLR) scenarios, considering the effects of both inundation and shoreline erosion. The Sea Level Affecting Marshes Model (SLAMM) is used to simulate habitat transitions due to inundation and these outputs are combined with an empirical model of SLR-driven shoreline erosion. A set of plausible climate-induced SLR scenarios are considered, together with delta subsidence and constrained vertical sediment accretion. Significant mangrove decline is found in all cases: the greater the rise in sea level the greater the losses. By the end of the century, the Indian Sundarbans mangroves could lose between 42 % and 80 % of their current area if current management is continued. Managed realignment could offset these losses but at the expense of productive land and the migration of the human population.

Comparative study of heavy metals in selected mangroves of Sundarban ecosystem, India.

Accumulation and partitioning of eight heavy metals Cr, Pb, Zn, Cd, Ni, Cu, Co and Fe were studied in the root, stem and leaf of mangrove species (Sonneratia caseolaris, Acanthus ilicifolius and Excoecaria agallocha) for comparison and in mangrove sediments for calculation of bio concentration factor (BFC) in Sundarban India. Magnitude of Fe was found highest in the sediments (35371.71 mg kg(-1)) and plant parts of the three species (a maximum of 11428.0 mg kg(-1) in the root of S. caseolaris). For other heavy metals, plants showed exclusion and selection mainly based on utilization, regardless of their level in the sediments. In most of the cases significant variation of absorption was found between the three species (F = 11.48 to 157.37; p < 0.001) and between their plant parts (F = 10.98 to 338.03; p < 0.001). S. caseolaris was found to be a less potential heavy metal accumulator than the other two species, except for Fe and Zn in the root. Irrespective of the magnitude of the heavy metals, other species showed significant correlations (r = 0.509 to 0.961; p < 0.001) between heavy metal accumulations, exclusively due to chemical reason, whereas S. caseolaris showed significant correlations (r = 0.554 to 0.926; p < 0.001) between each and every heavy metal, which signifies similar mode of absorption pattern regardless of their utilization. This nonbiased manner of heavy metal accumulation pattern may help the species to withstand in the polluted areas.

Isolation, Expansion, and Differentiation of Mesenchymal Stem Cells from the Infrapatellar Fat Pad of the Goat Stifle Joint.

The IFP, present in the knee joint, serves as a promising source of MSCs. The IFP is an easily accessible tissue as it is routinely resected and discarded during arthroscopic procedures and knee replacement surgeries. Additionally, its removal is associated with minimal donor site morbidity. Recent studies have demonstrated that IFP-MSCs do not lose their proliferation capacity during in vitro expansion and have age-independent osteogenic differentiation potential. IFP-MSCs possess superior chondrogenic differentiation potential compared to bone marrow-derived MSCs (BMSCs) and adipose-derived stem cells (ADSCs). Although these cells are easily obtainable from aged and diseased patients, their effectiveness is limited. Hence, using IFP-MSCs from healthy donors is important to determine their efficacy in biomedical applications. As access to a healthy human donor is challenging, animal models could be a better alternative to enable fundamental understanding. Large animals such as dogs, horses, sheep, and goats play a crucial role in translational research. Amongst these, the goat could be a preferred model since the stifle joint of the goat has the closest anatomy to the human knee joint. Moreover, goat-IFP can fulfill the higher MSC numbers needed for tissue regeneration applications. Furthermore, low cost, availability, and compliance with the 3R principles for animal research make them an attractive model. This study demonstrates a simple protocol for isolating IFP-MSCs from the stifle joint of goats and in vitro culture conditions for their expansion and differentiation. The aseptically isolated IFP from the goat was washed, minced, and digested enzymatically. After filtration and centrifugation, the collected cells were cultured. These cells were adherent, had MSCs-like morphology, and demonstrated remarkable clonogenic ability. Further, they differentiated into adipogenic, chondrogenic, and osteogenic lineages, demonstrating their multipotency. In conclusion, the study demonstrates the isolation and expansion of MSCs, which show potential in tissue engineering and regenerative medicine applications.

Economic incentives drive the conversion of agriculture to aquaculture in the Indian Sundarbans: Livelihood and environmental implications of different aquaculture types.

Expansion of aquaculture in the Sundarbans Biosphere Reserve (SBR) is irreversibly replacing agricultural land and the drivers of this change are disputed. Based on in-depth interviews with 67 aquaculture farmers, this paper characterizes major aquaculture types in the SBR, their impacts, and identifies drivers of conversion from agricultural land. Aquaculture types included traditional, improved-traditional, modified-extensive, and semi-intensive systems. Extensive capture of wild shrimp larvae is environmentally harmful but constitutes an important livelihood. Semi-intensive aquaculture of exotic shrimp (Litopenaeus vannamei) has much higher unit-area profitability than other types but involves greater financial risk. Profitability is the main driver for the transition from agriculture, but environmental factors such as lowered crop yields and cyclone impacts also contributed. Many conversions from agriculture to aquaculture are illegal according to the stakeholders. Existing legislation, if enforced, could halt the loss of agriculture, while the promotion of improved-traditional aquaculture could reduce the demand for wild seed.

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.

Effects of climate change and management policies on marine fisheries productivity in the north-east coast of India.

The study covers two important deltaic systems of the north-east coast of India, viz. the Bengal and Mahanadi delta that support about 1.25 million people. The changes in potential marine fish production and socio-economic conditions were modelled for these two deltas under long-term changes in environmental conditions (sea surface temperature and primary production) to the end of the 21st century. Our results show that an increased temperature (by 4 °C) has a negative impact on fisheries productivity, which was projected to decrease by 5%. At the species level, Bombay duck, Indian mackerel and threadfin bream showed an increasing trend in the biomass of potential catches under the sustainable fishing scenario. However, under the business as usual and overfishing scenarios, our results suggest reduced catch for both states. On the other hand, mackerel tuna, Indian oil sardine, and hilsa fisheries showed a projected reduction in potential catch also for the sustainable fishing scenario. The socio-economic models projected an increase of up to 0.67% (involving 0.8 billion USD) in consumption by 2050 even under the best management scenario. The GDP per capita was projected to face a loss of 1.7 billion USD by 2050. The loss of low-cost fisheries would negatively impact the poorer coastal population since they strongly depend upon these fisheries as a source of protein. Nevertheless, adaptation strategies tend to have a negative correlation with poverty and food insecurity which needs to be addressed separately to make the sector-specific efforts effective. This work can be considered as the baseline model for future researchers and the policymakers to explore potential sustainable management options for the studied regions.

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 1.1 m and 0.6 m were observed to be 24.79 ± 12.02 mg m-2 h-1 and 6.05 ± 3.14 mg m-2 h-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.

CO2 effluxes from an urban tidal river flowing through two of the most populated and polluted cities of India.

Urbanized rivers flowing through polluted megacities receive substantial amount of carbon from domestic sewage and industrial effluents which can significantly alter the air-water CO2 flux rates. In this regard, we quantified the partial pressure of CO2 in the surface water (pCO2(water)), air-water CO2 fluxes, and associated biogeochemical parameters in the Hooghly River, India, flowing through two of the most polluted cities of the country, Kolkata and Howrah, over a complete annual cycle during spring tidal phase (SP) and neap tidal phase (NP). This urbanized part of Hooghly River was always supersaturated with CO2 having an annual mean pCO2(water) and air-water CO2 flux of ~ 3800 µatm and ~ 49 mol C m-2 year-1, respectively. Significant seasonal variability was observed for both pCO2(water) and air-water CO2 flux (pre-monsoon, 3038 ± 539 µatm and 5049 ± 964 µmol m-2 h-1; monsoon, 4609 ± 711 µatm and 7918 ± 1400 µmol m-2 h-1; post-monsoon, 2558 ± 258 µatm and 4048 ± 759 µmol m-2 h-1, respectively). Monthly mean pH and total alkalinity varied from 7.482 to 8.099 and from 2437 to 4136 µmol kg-1, respectively, over the annual cycle. pCO2(water) showed significant positive correlation with turbidity and negative correlation with electrical conductivity and gross primary productivity (GPP). High water discharge could have facilitated high turbidity, especially during the monsoon season, which led to depletion in GPP and enhancement in pCO2(water) which in turn led to very high CO2 effluxes. The CO2 efflux rate in this urbanized riverine stretch was substantially higher than that observed in previous studies carried out in the less urbanized estuarine stretch of Hooghly. This indicates that the presence of highly urbanized and polluted metropolis potentially enhanced the pCO2(water) and CO2 effluxes of this river. Similar observations were made recently in some Asian and Australian urban rivers.

Assessment of the heavy metal accumulation in the Blue Swimmer Crab (Portunus pelagicus), northern Bay of Bengal: Role of salinity.

This is the first report to assay the heavy metal accumulation in Blue Swimmer Crab in the northern Bay of Bengal. The present study finds that copper (Cu) concentration though has been the highest compared to the other metals, particularly in the gill. Cadmium (Cd) and lead (Pb) have high affinity to be concentrated in Hepatopancreas all through the year. All the metal concentrations were higher during monsoon season (comparatively low salinity) than non-monsoon (high salinity) in the different body parts of Blue swimmer crab i.e. the inverse relationship between accumulation of heavy metals and sea water salinity has been shown. Present study revealed that salinity having the role to accumulate metal in different body parts of Blue Swimmer Crab. In future, microcosm experiments should be done to test the effect of frequent fluctuations of ambient salinity, such as is usual in different seasons in the present study area.

Risk of extreme events in delta environment: A case study of the Mahanadi delta.

Anthropogenic climate change is considered as one of the greatest environmental, social and economic threats to the future world. Low lying deltas all over the world are increasingly subjected to multidimensional risk of sea level rise, cyclone, surges and salinisation. The life and livelihood of the communities of such deltas are endangered due to climate change acting as risk multiplier. The Mahanadi delta in the state of Odisha, India is one of the such populous deltas with estimated 8 million population in 2011 with a density of 613 persons/km2. Over the past decades, it experienced major climatic threats in the form of cyclone, surge inundation and flooding with variable intensities and impacts along and across the coast. The present research assessed the risk of climatic extreme events and their variability in the delta, with an intention of mitigation or adaptation to possible impacts in specific region. Synthetic Aperture Radar (SAR) data and daily rainfall data were used to extract flood inundation. Tropical Cyclone Risk Model (TCRM) along with surge decay function was used to estimate cyclonic wind speed and surge inundation and risk indices were computed using fuzzy logic based approach. The result shows that in the coastal districts, risk of severe cyclones rank above the heavy floods. Agriculture, the main livelihood of these districts (71%) is impacted adversely making the delta community vulnerable to such extreme events. Kendrapara followed by Bhadrak and Jagasinghpur districts appear to be most risk prone segment in the delta making the northern part comparatively more risk prone where focused mitigation and adaptation actions are needed.

Biology and fisheries of Hilsa shad in Bay of Bengal.

Hilsa (Tenualosa ilisha) or river shad is an anadromous fish species widely distributed in the North Indian Ocean, mainly in the Bay of Bengal (BoB). Hilsa is the national fish of Bangladesh and it contributes 10% of the total fish production of the country, with a market value of $1.74 billion. Hilsa also holds a very important place in the economics of West Bengal of India with 12.5% of the catch and also tops the marine capture in Myanmar. During the last two decades Hilsa production from inland waters has been stable, whereas marine yields in the BoB increased substantially. In order to sustainably manage the trans-boundary stock of Hilsa, the taxonomy, distribution, habitat, migration patterns, population dynamics, fisheries and socio-economics aspects of the fishery have been reviewed here. To achieve a successful trans-boundary management for the Hilsa stock, complete ban on undersize fishing, well-targeted temporal and spatial bans, creation of protected areas in strategic points, incentive for Hilsa fishers and ecological restoration of Hilsa habitats and more work on technological development of Hilsa aquaculture are recommended.