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Inland capture fisheries in many parts of the world, especially in developing nations, receive relatively low governance priority, thereby raising concerns about their sustainability. Consequently, most inland capture fisheries are data‐limited, which renders conventional capture fisheries assessment methods inapplicable for making science‐based monitoring and management decisions. Three recent data‐limited approaches for marine fish stock assessments using length frequency and catch data (Length‐Based Indicators [LBI], Growth‐Type Groups Length‐Based Spawning Potential Ratio [GTG‐LBSPR] and Catch Maximum Sustainable Yield [CMSY]), were explored for applicability to assess stock status of three commercially exploited finfish species, Daysciaena albida, Eleutheronema tetradactylum and Mugil cephalus, in Chilika lagoon, an inland water body along the east coast of India. The LBI and GTG‐LBSPR approaches are based on catch length‐frequency data, while the CMSY is based on catch‐only data. The LBI provided insight into current exploitation status of the three species in relation to sustainable fishing, the GTG‐LBSPR provided reference points (RP) for the unfished portion of spawning biomass and relative yield in relation to selectivity, and the CMSY provided RPs for MSY, biomass and fishing pressure that yield MSY, to assess stock status and fishery management decisions. All three approaches suggested that the three species were overfished in terms of catch length and quantity, which agreed with expert knowledge of the fishery in the lagoon. All three approaches can support management and policy decisions in inland fisheries and fishery management recommendations. Future research should explore and standardise such approaches to overcome data limitations in assessing and managing inland capture fisheries. [ABSTRACT FROM AUTHOR]

The present paper reports the site of attachment preference, overlapping and partitioning of niche among different life stages of parasitic isopod Cymothoa indica Schiöedte and Meinert, 1884 in the Gobiidae fish Glossogobius giuris (Hamilton 1822) collected from the Chilika lagoon, India. Out of 2113 host fishes, 176 were found to be infected by the parasites. Out of the 233 different life stages of the parasites examined, 89 were female, 104 were male, and the rests were juveniles. 100% of the females, 84.6% of the male and 72.5% of the juveniles were found to be attached to the buccal cavity, while the rest of the males and juveniles were attached to the branchial cavity. In most cases, there was niche overlapping, leading to competition for the resources. Females preferred more specialized niches as compared to males and juveniles. In a few instances, there is niche partitioning, as shown by the male and juveniles. There is a negative correlation between the number of parasites found in the body of the fishes and the weight of the host fishes. This manuscript also provides a brief description of the different life stages of this parasite in the above-mentioned host collected from the same lagoon. [ABSTRACT FROM AUTHOR]

The Holocene arid events and related societal responses are important scientific inquiries due to concerns about their reoccurrences in the future. In the Indian subcontinent, significant number of studies have focussed on understanding the Holocene aridification events at 8.2 and 4.2 ka. Despite these studies, high resolution palaeoclimatic records from the eastern India during Holocene, particularly around the above-mentioned aridification events are lacking. In this study, we present high resolution Holocene palaeoclimate records reconstructed based on geochemical and isotopic data from the Chilika Lagoon located in the east coast of India. A 130 cm long sediment core, retrieved from the southern end of the lagoon, revealed a continuous sedimentation history between 8.49 and 0.99 ka. The variations in organic carbon isotopic compositions, total organic carbon contents, along with major and trace element abundances suggested a strong effect of 8.2 dry event and a shift in chemical weathering at around 4.2 ka in the eastern coast of India. Additionally, a strong warm climate anomaly was observed at 1.2 ka. Interestingly, higher sedimentation rates were observed post 4.2 ka, which potentially indicated a significant change in settlement dynamics and human interventions. It appears that the eastern coast of India experienced human migration and surge in agricultural practices similar to that in northwest India after the 4.2 ka climatic event. It is likely that people relocated themselves, which eventually increased the pastoral activities in newly occupied lands. Consequently, enhanced land use and land cover changes accelerated soil erosion in the region leading to higher sedimentation rate in the lagoon. [ABSTRACT FROM AUTHOR]

Coastal lagoons are high value productive and important systems for different projects. For example, aquaculture, fisheries and tourism are few of them. The quality of coastal waters in the ecosystems of lagoons can be greatly influenced by the growth of unwanted elements, e.g., excessive fisheries, tourism, etc. In this paper, a mathematical model is proposed and analysed to study the general and simplified form of an ecosystem of Chilika Lake, India. Chilika Lake (19°28′N–19°54′N and 85°06′E–85°36′E) is the largest wintering ground for migrating water fowl found anywhere on the Indian sub-continent. These migratory birds utilize the Chilika Lake for feeding, resting and breeding. The interaction of birds and small fish in the Chilika Lake is considered to be Leslie–Gower Holling type II. Since big fish are being sourced as income for local fishermen and the population of big fish is highly variable, and hence birds and small fishes are mainly the two types of biomass considered for this study. It must be noted that, in this study, we have considered the case of Chilika lake theoretically only and no practical data is collected for this study, and the name of Chilika is used only for better ecological understanding. Therefore, this theoretical study maybe linked to any such ecosystem. Their interaction is found mathematically, a two-dimensional continuous-time dynamical system modeling a simple predator–prey food chain. The dynamical system is represented in the form of two nonlinear coupled ordinary differential equation (ODE) systems. The main mathematical results are given in terms of boundedness of solutions, existence of equilibria, local and global stability of the coexisting interior point. An ecosystem in Indian coastal lagoons may suffer immediate environmental perturbations, such as depressions, tropical cyclones, earthquakes, epidemics, etc. To model such situations, the ODE model is further extended to a stochastic model driven by L e ́ $\check{d}{e}$ vy noise. The stochastic analysis includes the existence of the unique global solution, stability in mean, and extinction of the population. The proposed model is numerically simulated with the help of an assumed set of parameters for the possible pictorial behavior of the theoretical model. The proposed model may be used for planning purposes by using the data on meteorological and weather shocks such as heavy rainfall, heat-waves, cold-waves, depressions, tropical cyclones, earthquakes, etc. from India Meteorological Department (IMD). [ABSTRACT FROM AUTHOR]

We present bulk organic carbon isotopic composition (δ13C), total organic carbon (TOC) content, and total organic carbon to total nitrogen (C/N) ratio along with major and trace element geochemistry of an AMS radiocarbon-dated Holocene sediment core collected from Chilika Lagoon, India. The data are used to understand changes in the organic matter (OM) sources and the strength of the Indian summer monsoon (ISM). Our results indicate that during early to middle Holocene (10.4–4.9 ka), terrestrial (23–65%) and macrophyte (24–32%) sources were significant contributors to the sediment OM; marine component contributed ≤23%. An abrupt shift in the OM sources was observed at ~4.0 ka, marked by a significant decrease in OM contributions from the terrestrial (5%) and macrophyte (14%) end-members, and an increase in the marine end-member source (70%) into the lagoon. The period from ~4.0 to 2.1 ka recorded the lowest and highest contribution from the terrestrial (5–11%) and marine (50–70%) sources, respectively. This was followed by a gradual increase in the terrestrial and decrease in the marine contribution to 21% and 25% till the present, respectively. During this period, phytoplankton became the major source (31–40%) of OM to the lagoon. This period also experienced increasing anthropogenic activities in the catchment. In this study, proxy records show a strong ISM during early Holocene (10.4–9.0 ka), which was followed by a gradual weakening until 4.9 ka. At ~4.0 ka, an abrupt and pronounced weakening of ISM occurred that was followed by an amelioration of ISM precipitation towards 1.1 ka. Later, the ISM gradually weakened to the present-day condition. Overall, Chilika Lagoon core records exhibit that changes in the Northern Hemisphere summer insolation regulate the long-term trend of ISM during the Holocene. [ABSTRACT FROM AUTHOR]

A yellow-colored, Gram-stain-positive, rod shaped, non-motile bacterium, designated as strain JC619T, was isolated from the sediment of Chilika lagoon, India. Strain JC619T shows highest 16S rRNA gene sequence similarity (99.08%) with Isoptericola chiayiensis KCTC 19740T followed by Isoptericola halotolerans KCTC 19046T (98.6%) and other members of the genus Isoptericola (< 98%). NaCl is required for growth of strain JC619T and tolerates up to 18% (w/v) and pH up to 10. Strain JC619T grows optimally at temperature 30 °C, NaCl concentration of 3% (w/v), and at pH 7.5. The genome size of strain JC619T is 3.2 Mb with G+C content of 73.0 mol%. ANI scores of strain JC619T are 81.9% and 80.1% and dDDH values are 24.4% and 22.7% with I. chiayiensis KCTC 19740T and I. halotolerans KCTC 19046T, respectively. Respiratory quinones are MK-9(H4) and MK-9(H2). Predominant fatty acids (> 10%) are anteiso-C15:0, iso-C16:0, and iso-C15:0. Major polar lipids of strain JC619T are phosphatidylglycerol, phosphatidylinositolmannoside, diphosphatidylglycerol, and phosphatidylinositol. Strain JC619T is catalase positive but cytochrome oxidase negative and reduces nitrate. The genomic distinction of strain JC619T with its nearest related species of the genus Isoptericola is well supported with chemotaxonomic characteristics and differential physiological properties. Therefore, strain JC619T represents a new species under the genus Isoptericola for which Isoptericola sediminis sp. nov. is proposed. Type strain is JC619T (=KCTC 49244T =NBRC 114063T). [ABSTRACT FROM AUTHOR]

A shiny dark yellow pigmented, Gram-stain-negative, rod-shaped, non-motile bacterium, designated as strain JC631T, was isolated from the sediment ecosystem of Chilika lagoon, India. Strain JC631T tolerates up to pH 10 and NaCl up to 3% (w/v). MK6 is the only respiratory quinone. Predominant (> 10%) cellular fatty acids are anteiso-C11:0, anteiso-C13:0, and anteiso-C15:0. Major polar lipids are phosphatidylethanolamine, phosphatidylcholine, a few unidentified phospholipids, and a few unidentified aminolipids. 16S rRNA gene sequencing showed that strain JC631T shared the highest sequence identity (98.7%) with Arenibacter latericius KMM 426T followed by Arenibacter certesii CCUG 48006T (98.6%) and other members of the genus Arenibacter (< 97%). The genome size of strain JC631T is 4.16 Mb with a GC content of 40.8 mol%. Strain JC631T has ANI scores of 78.3% and 78.1%; dDDH values of 22.2% and 21.8%, respectively, with the type strains of A. latericius and A. certesii. The genomic distinction is well supported by chemotaxonomic characteristics and differential physiological properties. This supports strain JC631T to be described as a new species of the genus Arenibacter, named as Arenibacter lacus sp. nov. The type strain is JC631T (= KCTC 72002T = NBRC 114071T). [ABSTRACT FROM AUTHOR]

The distribution and fractionation of heavy metals in the sediment cores from five locations and their impacts on ecological health of Chilika lagoon were investigated. The heavy metals Cu, Zn, Pb, Cd, Co, Ni, Mn and Fe were determined in the cores. In general the average concentration of heavy metals in different cores are found in the following order Fe > Mn > Cu > Pb > Zn > Ni > Co > Cd. The cores (C1, C3 and C5) collected near the major fishing villages and jetties have higher metal concentration when compared with cores collected from relatively pristine regions. Correlations between the trace metals and Organic Carbon (OC), Total Nitrogen (TN), Total Phosphorus (TP) and silty clay fraction, suggests that these elements and grain size play a role in controlling the abundance of heavy metals in the sediments. Metals like Pb, Cu, Zn are positively correlated to OC, TN and TP and grain size. Significant enrichment for Pb (EF = 5–20) and moderately significant enrichments for Cu (EF = 2–5) is observed in almost all the cores. Co and Ni are moderately enriched in cores C1 and C2. Extremely severe enrichment for Cd (EF > 40) is observed in core C1. Runoff from the agricultural fields, untreated sewage discharge and boat traffic are the major heavy metal sources. Roadway runoff, fuel discharge and atmospheric deposition are the dominant source of elevated Pb levels. The fractionation profiles of metals in different cores found them to be associated mostly with residual phase followed by Fe-Mn oxides and organic bound metals. Risk Assessment Code (RAC) reveals significant pollution by Mn in almost all the cores, whereas Pb, Cu and Zn are also present in bioavailable form to some extent in the sediments. In general, Fe-Mn oxides and organic bound metal fraction phases would contribute metals accumulation into the food-chain (i.e plant and fishery resources) consumed by the population create human health hazards. [ABSTRACT FROM AUTHOR]

Abstract Inland and coastal water bodies around the world are susceptible to eutrophication due to inputs of anthropogenic nutrients, such as nitrogen (N) and phosphorus (P). Studies related to quantification of uptake rates of these nutrients and the factors governing these rates are limited in tropical aquatic systems, leading to inadequate understanding of N and carbon (C) cycling in these environments. Here, we report the rates of dissolved inorganic N (DIN) uptake and N 2 fixation along with N isotopic composition of particulate organic matter (δ15N POM) in Asia's largest brackish water lagoon (Chilika, India). The experiments were carried out at sixteen different locations in the lagoon where NO 3 − and NH 4 + uptake rates varied from 0.004 to 1.42 μmol N L−1h−1 (average ∼ 0.51 ± 0.51 μmol N L−1h−1) and 0.19–1.76 μmol N L−1h−1 (average ∼ 1.11 ± 0.43 μmol N L−1h−1), respectively. In general, NH 4 + was preferred substrate in the lagoon as depicted from relative preference index (RPI NH4+ >1). Despite higher DIN concentrations, the lagoon showed diazotrophic activity as evidenced by considerable N 2 fixation rates at majority of stations. Preliminary calculations of the lagoon-wide N budgeting indicate N 2 fixation and atmospheric deposition to be significant sources of new N to the lagoon. δ15N POM in the lagoon ranged from 1.34 to 8.31‰ (average ∼ 3.99 ± 1.68‰) indicating contributions from marine and terrestrial sources along with N 2 fixation to the organic matter pool. [ABSTRACT FROM AUTHOR]

Abstract Astronomic tides and nonlinear tidal dispersion were assessed for the Indian River lagoon system, a tropical coastal estuary (located in central east Florida) with engineered features (causeways). The four inlets, which choke the tides entering the system, together with the expansive size and shallowness of the estuary (and the associated energy dissipation) are the prominent mechanisms leading to the microtidal environment of the lagoon. Inside the shallows, there are 12 causeway abutments that cause a compartmentalization of the waters into separate basins, whereby the causeway openings act mechanistically as acceleration-inducing throttles to promote local regions of high kinetic energy (velocities). The causeways lead to a furthered decay of tidal amplitudes, phase lags in the tides and an enhanced generation of harmonic overtides and tidal residuals relative to the natural domain (i.e., fully open—no causeways). Numerical modeling of astronomic tidal flows (Advanced Circulation—ADCIRC) employed an unstructured, triangular mesh that resolved the entire scale of the lagoonal system with element sizes of 10–100 m and captured its many intricate domain features, including: the causeways in Indian River lagoon proper and Banana River lagoon; over 150 km of sinuous channels in Mosquito lagoon; and the hydraulic connections of the individual lagoons—one of which, Haulover Canal, is only 55 m wide. The model performed well with an index of agreement of (on average) 94% when compared with tidal data from 23 stations located throughout the system. Tides in the shallows are small at just millimeters in range; the model captured the tidal signal at the stations located there with an index of agreement of (at worst) 79%. Considering previous tidal studies of the Indian River lagoon system and tropical coastal estuaries in general, this level of domain definition and model validation of astronomic tide behavior is unprecedented and provides a benchmark for numerical simulation of lagoonal tidal flow. [ABSTRACT FROM AUTHOR]

Assessing wildlife tourism sustainability in developing countries is crucial, but few studies analyse the sustainability of dolphin-based wildlife tourism in this context. We measure multiple indicators within the human dimensions of wildlife tourism, including tourist visitation numbers, satisfaction, preferences, perceptions, background and specialisation, to ascertain the extent to which the dolphin-watching industry at Chilika Lagoon, in rural India might be considered sustainable. Our methods included participant observation, tourist surveys, and the use of secondary data on visitation over 10 years. We found that the growth rate of tourist visitation over 10 years was beginning to decline. Tourists were mostly inexperienced, and dissatisfied with their dolphin-watching experience. Tourist preferences and perceptions showed useful insights and shortcomings in the way in which the industry was being conducted and managed, and reflected the expectations of non-specialist visitors. Our study highlights drawbacks in the way that wildlife tourism is managed in a rural, developing world context, which draws the sustainability of the dolphin-watching industry in Chilika into question. Future development of an early warning system that addresses combined governance or managerial, social, economic and ecological indicators, and an integrated management plan for conservation and wildlife tourism could contribute to the sustainable management of such industries. [ABSTRACT FROM AUTHOR]

Length–weight relationships (LWRs) of six finfish species under two families of the order Perciformes collected from Pulicat lagoon (India) are presented in this study. The fish specimens were collected weekly from the catches of shore seine net (with a mesh size of 50mm at the main webbing and 10 mm at the cod end) operated in the lagoon at an average depth of 2.5 m by the local fishermen during the period from July 2018 to April 2019. This study reports the LWRs for five gobiid and one siganid fish species which have no earlier reports on LWRs. The calculated 'b' value ranged from 3.538 (Favonigobius reichei) to 2.677 (Oxyurichthys microlepis) and 'a' value varied from 0.0041 (Favonigobius reichei) to 0.0199 (Acentrogobius cyanomos). This study also reports the new maximum total length (TLmax) for the gobiid fish species Oxyurichthys microlepis. [ABSTRACT FROM AUTHOR]

During our routine ecological survey conducted at Pulicat Lagoon, the most diverse class Gastropods comprised of 26 families with 34 species and Bivalvia with 13 families and 17 species were recorded. The most abundant molluscs species was Crassostrea madrasensis, captured between October 2013 - September 2015. Quite a good number of molluscs were washed ashore. The economic value of the shells in the field of cosmetics was raised high recently. Both in terms of aquaculture and market value the attention should be diverted towards their conservation. With few exceptions, the majority of these molluscs were ornamental. [ABSTRACT FROM AUTHOR]

The spatial distribution of the C/N ratios and variations in δ13C and δ15N of suspended particulate matter were used to characterise their source in Asia’s largest brackish water lagoon, Chilika, India. In addition, the significance of re-mineralised nutrients in the primary productivity of the shallow lagoon was also determined through quantification of the subsurface nitrogen uptake conditions at two relatively stable locations in the lagoon. The results indicated that the influence of terrestrial organic matter was the maximum in the northern sector and was relatively limited at the central and southern part of the lagoon.In situ15N uptake experiments (daytime) under biogeochemically stable conditions revealed that the N uptake by phytoplankton ranged between 0.24 and 1.01 mM m−3 h−1during pre-monsoon and post-monsoon seasons. New production and regenerated production in the shallow lagoon was also estimated by calculatingf-ratios (ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation, have been estimated), which varied from 0.52 in the post-monsoon to 0.38 in the pre-monsoon. Lowering of thef-ratio from post- to pre-monsoon indicated a dominance of mineralisation over the new production. [ABSTRACT FROM AUTHOR]

• Monsoonal changes triggered the Holocene denudation of Eastern Ghat. • The denudation rate was high during the early to mid-and late Holocene. • Degree of chemical weathering gradually increased towards the late Holocene. • Aridification was intense during the late Holocene. A Holocene sediment record from Chilika Lagoon, India, suggests that changes in climate control denudation and weathering rate change. We assessed climate variability in the region and through time using multiproxy data comprising biotic and abiotic proxies. Mangrove and its associate assemblages suggest a backwater estuarine environment between ∼7.8 and 6 ka B.P. Depleted δ13C org values during ∼7.8 to 5.5 ka B.P. indicate dominance of C 3 vegetation, suggesting a warmer climate and strengthened monsoon. Enhanced δ13C org and absence of pollen/spores are observed in the sediment layers deposited after ∼5 ka B.P., indicating arid climatic conditions with a dominance of C 4 photosynthesizing plants and a relative lowering of sea level. Paleodenudation rates estimated using 10 B e (m e t e o r i c) / 9 Be ratios varied between 556 ± 35 to 242 ± 15 t.km−2.yr−1. Phases of intense denudation occurred during 7.8–6.7 and 2.2–1 ka B.P., corresponding to Holocene Climatic Optimum and Medieval Climatic Anomaly, respectively. The degree of chemical weathering appears to have gradually increased from the early to late Holocene and correlates well (negatively) with the denudation rate. A gradual increase in the degree of chemical weathering from the early to late Holocene suggests an increase in the residence time of minerals in the weathering zone as the monsoon weakened. [ABSTRACT FROM AUTHOR]

The environmental factors contributing to the Microcysti s aeruginosa bloom (hereafter referred to as Microcystis bloom) are still debatable as they vary with season and geographic settings. We examined the environmental factors that triggered Microcystis bloom outbreak in India's largest brackish water coastal lagoon, Chilika. The warmer water temperature (25.31–32.48 °C), higher dissolved inorganic nitrogen (DIN) loading (10.15–13.53 μmol L−1), strong P−limitation (N:P ratio 138.47–246.86), higher water transparency (46.62–73.38 cm), and low-salinity (5.45–9.15) exerted a strong positive influence on blooming process. During the bloom outbreak, M. aeruginosa proliferated, replaced diatoms, and constituted 70–88% of the total phytoplankton population. The abundances of M. aeruginosa increased from 0.89 × 104 cells L−1 in September to 1.85 × 104 cells L−1 in November and reduced drastically during bloom collapse (6.22 × 103 cells L−1) by the late November of year 2017. The decrease in M. aeruginosa during bloom collapse was associated with a decline in DIN loading (2.97 μmol L−1) and N:P ratio (73.95). Sentinel-3 OLCI-based satellite monitoring corroborated the field observations showing Cyanophyta Index (CI) > 0.01 in September, indicative of intense bloom and CI < 0.0001 during late November, suggesting bloom collapse. The presence of M. aeruginosa altered the phytoplankton community composition. Furthermore, co-occurrence network indicated that bloom resulted in a less stable community with low diversity, inter-connectedness, and prominence of a negative association between phytoplankton taxa. Variance partitioning analysis revealed that TSM (16.63%), salinity (6.99%), DIN (5.21%), and transparency (5.15%) were the most influential environmental factors controlling the phytoplankton composition. This study provides new insight into the phytoplankton co-occurrences and combination of environmental factors triggering the rapid onset of Microcystis bloom and influencing the phytoplankton composition dynamics of a large coastal lagoon. These findings would be valuable for future bloom forecast modeling and aid in the management of the lagoon. [Display omitted] • Cooccurence network and environmental factors were examined in a Microcystis bloom. • Microcystis bloom occurred during high DIN loading with strong P–limitation. • Cyanophyta Index using Sentinel 3- OLCI data were well corroborated with field data. • Bloom caused low diversity and inter-connectedness in community network. • TSM, salinity, DIN, and transparency were drivers of phytoplankton composition. [ABSTRACT FROM AUTHOR]

Chilika, a lagoon along the east coast of India, is undergoing transformation due to frequent shoreline change near inlet(s). Shoreline change near inlet includes change in position and shape of inlet, inlet channel length, and spit growth/erosion. These variable features of lagoon inlet(s) critically depend on alongshore sediment transport (LST) and discharge (water and sediment) from the lagoon to the sea. The LST and the processes responsible for sand spit growth/erosion, considered as important attributes of inlet stability, are the subject matter of the present investigation and hence the study assumes importance. The study includes integration of observational and modeling framework. Observations include nearshore wave, bathymetry, beach profile, shoreline and sediment grain size of spits while numerical modeling includes simulation of the wave using MIKE 21 Spectral Wave model and LST simulation using LITtoral DRIFT. The results indicate that the predominant wave directions as S and SSE, which induces round the year south to north alongshore transport with significant seasonal variation in magnitude. The estimated LST closely matches with previous studies near Chilika inlet and for other locations along the Odisha coast. Besides temporal variability, the study reveals spatial variability in alongshore transport near Chilika inlet and considers it as one of the important attributes along with northward spit growth for inlet migration/closure/opening. [ABSTRACT FROM AUTHOR]

Extent of heavy metal contamination in Chilika Lake was assessed to conserve the eco-dynamics of the lake. Distribution of heavy metals, cations and total organic carbon were analysed in the sediment samples collected from three sites that represent a salinity gradient. Analysis of environmental indices, viz. enrichment and contamination factors, geo-accumulation (Igeo) and pollution load indices showed that the concentrations of Cd and Hg were significantly high with geoaccumulation index being greater than one in all three stations. Levels of Pb and Co were also found to be elevated with Igeo value of 0.025 and 0.048 respectively. Among the three sampling stations, Kaluparaghat witnessed the highest pollution load index followed by Balugaon and Rambhartia. Principal component analysis revealed that the high-salinity zone was associated with high concentration of Hg and decreased concentration of other toxic metals, indicating that source of pollution of Hg is different from that of other metals. [ABSTRACT FROM AUTHOR]

The net ecosystem metabolism in lagoons has often been estimated from the net budget of dissolved nutrients. Such is the case of the LOICZ estuarine biogeochemistry nutrient budget model that considers riverine dissolved nutrients, but not riverine detritus. However the neglect of detritus can lead to inconsistencies; for instance, it results in an estimate of 5–10 times more seaward export of nutrients than there is import from rivers in Chilika Lagoon, India. To resolve that discrepancy the UNESCO estuarine ecohydrology model, that considers both dissolved nutrients and detritus, was used and, for Chilika Lagoon, it reproduced successfully the spatial distribution of salinity, dissolved nutrients, phytoplankton and zooplankton as well as the fish yield data. Thus the model suggests that the riverine input of both detritus and dissolved nutrients supports the pelagic food web. The model also reproduces well the observation of decreased fish yield when the mouth of the lagoon was choked in the 1990s, demonstrating the importance of the physics that determine the flushing rate of waterborne matter. Thus, both farming in the watershed by driving the nutrient and detritus inputs to the lagoon, and dredging and engineering management of the mouth by controlling the flushing rate of the lagoon, have a major influence on fish stocks in the lagoon. [ABSTRACT FROM AUTHOR]

Weaver, R.J.; Johnson, J.E., and Ridler, M., 2016. Wind-driven circulation in a shallow microtidal estuary: The Indian River Lagoon. Studying wind-driven fluctuations in the surface elevation along the Indian River Lagoon (IRL) allows researchers to better understand the best methods for managing sustainable water quality in a microtidal estuary. Water quality has a direct effect not only on the marine life, but also on tourism. This study improves the knowledge of circulation and surge in a shallow, microtidal estuary while enabling validation of numerical modeling efforts. Two submersible pressure sensors were deployed in the IRL for 7 months. Data collected from these gauges is analyzed in conjunction with data from permanent gauges at Haulover Canal and Sebastian Inlet, with an emphasis placed on the relationship between surface elevation and meteorological forcing. A time series analysis was employed to correlate periods of harmonic oscillations with wind events. Analysis focused on the direction of the wind with respect to the along-estuary and cross-estuary orientation of the lagoon. Results indicate that the water rises or falls uniformly in the cross-estuary direction and is transported to the south during Nor'easter events, piling up at the constriction south of Sebastian Inlet. Study results will be used to provide a better understanding of circulation in shallow-water estuaries, as well as improve numerical models to better predict wind-driven circulation in the IRL. [ABSTRACT FROM AUTHOR]

Water quality analysis is prime important to understand the wealth of living organism and environmental condition in water bodies. In GIS, ordinary Kriging interpolation method has been applied for surface analysis of water quality parameters such as temperature, salinity, pH, chlorophyll-a (Chl-a) and suspend sediment (SS), to carried comparison analysis between monsoon and summer season in lagoon at Vedaranyam wetland. Kriging is an approach to mapping the water quality parameters for analyzing the dispersion patterns. The results of the spatial distribution analysis has been indicated in lagoon around salt pan and aquaculture area have high saline condition reach about 36 parts per thousand (ppt) and in monsoon seasons suspended sediment reach maximum due to river runoff in the study area. [ABSTRACT FROM AUTHOR]

An effort has been made for the first time in Asia's largest brackish water lagoon, Chilika, to investigate the spatio-temporal variability in primary productivity (PP), bacterial productivity (BP), bacterial abundance (BA), bacterial respiration (BR) and bacterial growth efficiency (BGE) in relation to partial pressure of CO2(pCO2) and CO2air–water flux and the resultant trophic switchover. Annually, PP ranged between 24 and 376 µg C L−1d−1with significantly low values throughout the monsoon (MN), caused by light limitation due to inputs of riverine suspended matter. On the contrary, BP and BR ranged from 11.5 to 186.3 µg C L−1d−1and from 14.1 to 389.4 µg C L−1d−1, respectively, with exceptionally higher values during MN. A wide spatial and temporal variation in the lagoon trophic status was apparent from BP/PP (0.05–6.4) and PP/BR (0.10–18.2) ratios. The seasonal shift in net pelagic production from autotrophy to heterotrophy due to terrestrial organic matter inputs via rivers, enhanced the bacterial metabolism during the MN, as evident from the highpCO2(10,134 µatm) and CO2air–water flux (714 mm m−2d−1). Large variability in BGE and BP/PP ratios especially during MN led to high bacteria-mediated carbon fluxes which was evident from significantly high bacterial carbon demand (BCD >100% of PP) during this season. This suggested that the net amount of organic carbon (either dissolved or particulate form) synthesized by primary producers in the lagoon was not sufficient to satisfy the bacterial carbon requirements. Lagoon sustained low to moderate autotrophic–heterotrophic coupling with annual mean BCD of 231% relative to the primary production, which depicted that bacterioplankton are the mainstay of the lagoon biogeochemical cycles and principal players that bring changes in trophic status. Study disclosed that the high CO2supersaturation and oxygen undersaturation during MN was attributed to the increased heterotrophic respiration (in excess of PP) fuelled by allochthonous organic matter. On a spatial scale, lagoon sectors such as south sector, central sector and outer channel recorded “net autotrophic,” while the northern sector showed “net heterotrophic” throughout the study period. [ABSTRACT FROM PUBLISHER]

Magnetotactic bacteria (MTB) are aquatic prokaryotes that orient themselves to earth's magnetic field with the help of intracellular organelle magnetosomes. Although many species of MTB have been identified, the isolation of MTB is a challenging task due to the lack of systematic isolation procedure and/or commercial media. In this study, we are reporting the isolation of magnetotactic spirillum from the Pulicat lagoon, India using a systematic and selective procedure. Sampling site was chosen on the basis of physicochemical properties of the ecosystem and the catalysed reporter deposition fluorescence in situ hybridization (CARD-FISH) analysis of sediment samples. In the current study, a combination of techniques including 'capillary racetrack' Purification and gradient cultivation resulted in the isolation of magnetotactic spirilla from aquatic sediments. Based on the 16S rRNA gene sequence analysis, the strain was identified as Magnetospirillum and was designated as Magnetospirillum sp. VITRJS1. The genes responsible for magnetosome formation ( mamA, B, E, F, K, M, O, P, Q, T) were successfully detected using PCR amplification. The presence of cbbM gene confirmed that the isolate is chemolithoautotroph and utilises reduced sulphur as an electron source. Furthermore, magnetosomes extracted from VITRJS1 found to be cubo-octahedral in shape and 45 nm in size. Our results indicate that the systematic procedure using sediment analysis, CARD-FISH, and a combination of isolation methods enables the selective and rapid isolation of MTB from aquatic sediment sample. [ABSTRACT FROM AUTHOR]

• Euphotic zone depth (Z eu) estimated from absorption coefficient data for the Chilika lagoon. • Sentinel S2A/S2B MSI data for large-scale characterization of underwater light environment shown. • Spatio-temporal dynamics of Z eu in the Chilika lagoon linked to macrophyte growth. Euphotic zone depth (Z eu) is a key indicator of underwater light environment that regulates different biogeochemical and physical processes in aquatic ecosystem. Remote sensing approaches offer a unique opportunity to frequently monitor Z eu , although its estimation from diffuse attenuation coefficient (K d) requires depth profiles of the down-welling irradiance (E d). Measuring E d values at different water depths (i.e., E d profiling) in shallow waterbodies is a challenging task with the available profiling equipment. In this study, K d values were estimated from measured absorption coefficient (a) data at multiple locations in the Chilika lagoon, which is a shallow waterbody located in the eastern coast of India and is a prestigious Ramsar site. Specifically, remote sensing reflectance (R rs), a values (wavelength: 400–715 nm at 4 nm interval), Secchi disc depth (Z SD), suspended particulate matter (SPM) and chlorophyll- a (Chl- a) contents were measured during Oct. 07–08, 2018 and Feb. 02–08, 2019 in the Chilika lagoon. Atmospherically corrected Sentinel 2A/2B (S2A/S2B) MSI- R rs data (level 2A) were then used to develop algorithms for mapping Z eu for the entire lagoon. Modeling results showed that R rs values at band 4 (665 nm) or band 5 (704 nm) extracted from the S2A/S2B MSI data may be used to estimate K d of photosynthetically active radiation (PAR) (observed range: 1.29 m−1 to 10.74 m−1) with the root-mean-squared error (RMSE) as low as 0.81 m−1. However, uncertainties associated with atmospheric correction of S2A/S2B MSI-single band R rs values are high when compared with in situ R rs. Thus, a multivariate modeling approach was adopted with R rs - band ratio and band difference variables selected by stepwise, forward, and backward variable selection method with p < 0.05. Modeling results showed that the band differences between band 2 and band 4 and band 3 and band 5 may be used to estimate K d (PAR) with improved mean absolute percentage difference (MAPD) while ensuring low uncertainty associated with atmospheric correction. Spatio-temporal dynamics from S2A/S2B MSI for 85 different dates during Jan. 2017 to June 2021 provided seasonal patterns for Z eu in the Chilika lagoon. [ABSTRACT FROM AUTHOR]

• Euphotic zone depth (Z eu) estimated from absorption coefficient data for the Chilika lagoon. • Sentinel S2A/S2B MSI data for large-scale characterization of underwater light environment shown. • Spatio-temporal dynamics of Z eu in the Chilika lagoon linked to macrophyte growth. Euphotic zone depth (Z eu) is a key indicator of underwater light environment that regulates different biogeochemical and physical processes in aquatic ecosystem. Remote sensing approaches offer a unique opportunity to frequently monitor Z eu , although its estimation from diffuse attenuation coefficient (K d) requires depth profiles of the down-welling irradiance (E d). Measuring E d values at different water depths (i.e., E d profiling) in shallow waterbodies is a challenging task with the available profiling equipment. In this study, K d values were estimated from measured absorption coefficient (a) data at multiple locations in the Chilika lagoon, which is a shallow waterbody located in the eastern coast of India and is a prestigious Ramsar site. Specifically, remote sensing reflectance (R rs), a values (wavelength: 400–715 nm at 4 nm interval), Secchi disc depth (Z SD), suspended particulate matter (SPM) and chlorophyll- a (Chl- a) contents were measured during Oct. 07–08, 2018 and Feb. 02–08, 2019 in the Chilika lagoon. Atmospherically corrected Sentinel 2A/2B (S2A/S2B) MSI- R rs data (level 2A) were then used to develop algorithms for mapping Z eu for the entire lagoon. Modeling results showed that R rs values at band 4 (665 nm) or band 5 (704 nm) extracted from the S2A/S2B MSI data may be used to estimate K d of photosynthetically active radiation (PAR) (observed range: 1.29 m−1 to 10.74 m−1) with the root-mean-squared error (RMSE) as low as 0.81 m−1. However, uncertainties associated with atmospheric correction of S2A/S2B MSI-single band R rs values are high when compared with in situ R rs. Thus, a multivariate modeling approach was adopted with R rs - band ratio and band difference variables selected by stepwise, forward, and backward variable selection method with p < 0.05. Modeling results showed that the band differences between band 2 and band 4 and band 3 and band 5 may be used to estimate K d (PAR) with improved mean absolute percentage difference (MAPD) while ensuring low uncertainty associated with atmospheric correction. Spatio-temporal dynamics from S2A/S2B MSI for 85 different dates during Jan. 2017 to June 2021 provided seasonal patterns for Z eu in the Chilika lagoon. [ABSTRACT FROM AUTHOR]

Temperature change scenarios over the Chilika Lagoon of India for 200 years (1901-2100) were quantified by the observational data sets of the Climate Research Units (CRU) of UK as well as 39 numbers of GCMs simulations from the Couple Model Inter-comparison Project Phase 5 (CMIP5) through Mann Kendall trends analysis. Long-term trend during 1901-2005 over Chilka Lake indicates the highest warming in the pre-monsoon season (1.79°C) and lowest warming (1.09°C) was shown in both the winter and post-monsoon seasons while opposite warming trends i.e., the lowest warming was observed in pre-monsoon season and highest warming was shown in the winter season for recent four decades (1969-2009) data. The performance of the CMIP5 GCMs was evaluated over a target point of Chilika Lake. Twelve numbers of models were considered as a group of "better performing GCMs" on the basis of their ability to simulate the long-term trends as well as the mean seasonal correlation with observation. Quantile mapping technique is used for adjusting the bias for the selected GCMs. Improvement in the multi-model ensemble (MME) of bias corrected better performing models compared to MME of 39 GCMs was judged with the help of Taylor plot as well as using four different conventional statistical indices viz. correlation (r), index of agreement (d index), Nash-Sutcliffe efficiency (NSE) and root mean square error (RMSE). All the ensemble members commonly available in the four Representative Concentrations Pathways (RCPs) from the better performing selected models show a temperature change of 0.27-3.61°C, 0.38-3.98°C, 0.28-3.72°C, 0.33-3.41°C and 0.22-2.50°C in annual, winter, pre-monsoon, monsoon and post-monsoon seasons respectively at the end of 21st century over Chilika Lagoon. [ABSTRACT FROM AUTHOR]

Occurrence of fluid mud (mud banks) in the southwest coast of India is an enigma for the scientific community. Over the years, several multi-disciplinary studies were conducted and various hypotheses were postulated on the occurrence and sustenance of fluid mud. Nevertheless, none of them could be proved or disproved with field data. In the present study, an attempt was made to assess the validity of some of the prevailing hypothesis on its occurrence such as subterranean conduit flow of mud/water from a coastal lagoon, submarine groundwater discharge, river flows etc. by integrating field surveys, refining the hydrogeological understanding of the area and application of environmental isotopes ( 222 Rn, δ 18 O, δ 2 H and 3 H) in the ‘Alappuzha mud bank’ region, Kerala, during its formation in the southwest monsoon period. In-situ 222 Rn monitoring survey in the coastal waters of Pallana showed that 222 Rn activities in the fluid mud region were negligible compared to the suspected continental end members such as Pamba River, Vembanad Lagoon, shallow and deep groundwater indicating that there was no freshwater inputs from these sources. Comparison of the characteristic stable isotopic signatures of δ 18 O and δ 2 H in the samples from the fluid mud region and the suspected continental end members implied that there was no mixing of these water sources with the seawater. 3 H results indicated that the shallow groundwater is modern and recharged annually from precipitation while deep groundwater in the Warkali aquifer within the study area is old (>50 years). It also indicated that there is no vertical interconnection between the Vembanad Lagoon and the deep Warkali aquifers. Hence, from the study, it appears that river flows, submarine groundwater discharge or subterranean (conduit flow) flow from the Vembanad Lagoon may not be responsible for the occurrence and sustenance of fluid mud in Pallana coast, Alappuzha. [ABSTRACT FROM AUTHOR]

Current study provides basic information on Length-weight relationship ( LWR) and length-length relationship ( LLR) of three fish species of genus Thryssa (Clupeiformes: Engraulidae) i.e., Thryssa purava (Hamilton, 1822), Thryssa polybranchialis Wongratana, 1983 and Thryssa mystax (Bloch & Schneider, 1801) from Chilika Lagoon, India. Samples were collected during the monsoon (July) and post-monsoon (November) seasons in 2016 and during the pre-monsoon season (May) in 2017, using screen barrier nets (mesh size 8-18 mm) and gill nets (mesh size 14 and 16 mm). The b values were determined from LWRs as 3.026 for Thryssa purava, 3.326 for Thryssa polybranchialis and 3.081 for Thryssa mystax. [ABSTRACT FROM AUTHOR]

Monitoring habitat fragmentation (HF) for economically significant species at close-ranges can provide crucial data for deriving the indicators of the Sustainable Development Goals (SDG) 14.4 for complex socio-ecological systems such as coastal lagoons. However, exclusivity of local-scale processes causing fragmentation, differences in the monitoring approaches, differential interpretations of resilience to disasters, as well as mismatches in reporting outcomes of scientific studies indicate the need for a focussed monitoring framework for transitional ecosystems. Using the example of penaeid prawns (Peneaus sp.), an economically important species from Pulicat lagoon, (an intertidal ecosystem on the east coast of India), the present work presents the development of a practical framework using selective but effective indicators of HF. The overall approach involves establishment of baselines, causal loops, triggering transformations as well as adaptive responses as per the scale and magnitude of HF. In the context of deriving baselines (Level 1), in-situ indicators such as salinity, turbidity, chlorophyll-a concentrations and distribution of seagrass which directly influence the habitat selection are proposed. Derived datasets on nutrient budgets, changes in abundances, Representative Concentration Pathways scenarios 4.5 and 8.5 for climate-induced changes are proposed as external forcings to understand the causative parameters (Level 2). Monitoring extents of tidal influence in ecosystem-based approach for disaster risk reduction (EcoDRR) is proposed to evaluate triggers and adaptive responses (Level 3). The EcoDRR based framework presented has the potential to contribute towards policy-targeted transformative approaches relevant to India's National Fisheries Policy 2020 as well as SDG 14, cross-correlated with targets of other SDGs. [Display omitted] • New ecosystem-based modelling framework for transitional coastal lagoon ecosystems • Methodologies to assess evidence and extent of fragmentation at species-level • Eco-DRR and Red List of Ecosystems framework for upscaling to ecosystem-level • Example of Pulicat lagoon ecosystem, South-east coast of India [ABSTRACT FROM AUTHOR]

Variable seasonal interaction of both fresh and marine waters in lagoon ecosystems generally creates salinity gradients, which significantly impact the microhabitat of the benthos. This study assessed the spatial-seasonal abundance and diversity of ostracods along the salinity gradient of Chilika Lagoon (India) by seasonally collecting substrate sediment from twenty-two fixed stations along with the environmental parameters of lagoon-bottom water in Asia's largest brackish water lagoon. The samples were analyzed for living and dead ostracod species abundance, diversity and correlated with environmental parameters. The river mouth proximal region having sandy silt substrate under low energy conditions and high total organic carbon, had a higher abundance of low salinity tolerant ostracod species. The interior region of the lagoon showed a high abundance and diversity of variable salinity tolerant brackish water species, with a high proportion of dead specimens. In the region proximal to the sea mouth that is influenced by high energy conditions and sandy substrate, ostracod abundance and diversity are low, and only a few very high salinity tolerant ostracod species are found. Canonical correspondence analysis in addition to environmental preferences of living ostracod species and articulated valve abundance suggest environment-specific ostracod assemblages, consistent with the traditional use of ostracod species as a proxy to reconstruct paleo coastal ecology and paleoenvironment. • Ostracoda species are distributed according to their salinity tolerance and have an environmental specific response • Low, variable and high salinity tolerant ostracod species associations are found across the Chilika Lagoon • Ostracoda abundance and diversity are high in the interior region, suggesting a preference for calm, stable environments • Ostracoda species are a potential proxy for paleoenvironment reconstruction of coastal lagoon ecosystems [ABSTRACT FROM AUTHOR]

[Display omitted] • The Holocene experienced five major phases of climate variations. • The Indian summer monsoon was stronger during the Early and Late Holocene. • There was a prolonged phase of weak monsoon during the Mid-Holocene. • Spectral analysis of χ lf data suggests solar influence on ISM rainfall. Core sediments from the Chilika Lagoon in the eastern part of the Core Monsoon Zone (CMZ) of India have provided a record of local environmental changes and catchment processes during the past 7800 cal. years B.P. Variations in the rock magnetic parameters (χ lf , χ hf , χ ARM and IRM's at varying field strengths) of sediment samples reflect climate-induced changes in the Chilika Lagoon catchment. The down-core variations in the concentration-dependent magnetic parameters indicate an intensified summer monsoon and enhanced terrigenous input to the lagoon during the Early to Mid-Holocene (∼7.8 ka to ∼ 5.5 ka B.P.). In contrast, the Mid- to Late Holocene period witnessed a weaker Indian Summer Monsoon Rainfall (ISMR) and less terrigenous input to the lagoon, with an intermediate phase of strengthened monsoon around 2 to 1 ka B.P. Spectral analysis of sedimentary magnetic susceptibility (χ lf) data show significant periodicities (at 95 % significance level) of 2523, 573, 147, 93, 59, and 55 years, which are in agreement with the periodicities shown by other paleoclimatic proxies from the region. [ABSTRACT FROM AUTHOR]

The Chilika lake of Odisha is a natural brackish water lagoon of marine origin and it was a part of the Bay of Bengal during the later stages of the Pleistocene period. A 60-km (37 miles)-long barrier beach called Rajhansa, formed by northerly currents in the Bay of Bengal, resulted in the formation of this shallow lake and forms its eastern side. Formation of a barrier spit near Palur due to littoral drift and creation of a sand bar along the eastern shore have transformed the lake gradually to a shallow lagoon. The water spread of the lagoon varies between 1165 sq.km. in monsoon to about 906 sq.km ion pre-monsoon. . The lagoon is divided into four sectors like Northern, Central, Southern and Outer channel. The lagoon supports a unique assemblage of marine, brackish water and fresh water biodiversity. During winter (November-January), a large portion of this lagoon remains submerged and acts as a wetland, which also serves as breeding and nesting grounds for millions of migratory bird species. Lake is designated as a ramsar site since 1981. 28 species of prawn, 38 species of crab, and 400 types of vertebrates are seen in this lake. The vertebrates include 225 species offish, 37 types of reptiles and amphibians, 4 types of crocodiles, 150 migratory and residential species of birds, 24 types of mammals. The lake also harbours many endangered and vulnerable species including Irrawady Dolphin, Sea cow, limbless skink, smooth skinned otter., 726 types of flowering plants, five types of grasses and mangroves are also present here. The. Genetic diversity is also seen here on a wide spectrum. People of 122 villages and 8 towns on the bank of Chilika depend upon its biodiversity for their livelihood. Marine product and tourism activities around the lagoon contribute significantly to the economy of Odisha State. [ABSTRACT FROM AUTHOR]

In human-dominated landscapes, interactions and perceptions towards wildlife are influenced by multidimensional drivers. Understanding these drivers could prove useful for wildlife conservation. We surveyed the attitudes and perceptions of fishers towards threatened Irrawaddy dolphins ( Orcaella brevirostris) at Chilika Lagoon India. To validate the drivers of fisher perceptions, we : (1) observed dolphin foraging behavior at stake nets, and (2) compared catch per unit effort (CPUE) and catch income of fishers from stake nets in the presence and absence of foraging dolphins. We found that fishers were mostly positive towards dolphins, believing that dolphins augmented their fish catch and using culture to express their perceptions. Foraging dolphins were observed spending half their time at stake nets and were associated with significantly higher catch income and CPUE of mullet ( Liza sp.), a locally preferred food fish species. Wildlife conservation efforts should use the multidimensional drivers of human-wildlife interactions to involve local stakeholders in management. [ABSTRACT FROM AUTHOR]

The abundance and distribution of barium (Ba) serve as a reliable proxy for oceanic biogeochemical processes. Its cycling in the coastal regions, however, is complicatedly regulated by multiple sources/sinks. In this study, the spatial distribution of dissolved barium concentrations in a large coastal lagoon (Chilika lagoon, India) and its source waters have been investigated for three different seasons (pre-monsoon (May 2017), monsoon (August 2017), and post-monsoon (January 2018)). Additionally, contents of Ba and other elements in the bed and suspended sediments in their different fractions (bulk, clay, and exchangeable) have also been investigated. These data were used to constrain coastal processes in regulating coastal Ba inventory. The dissolved [Ba] of the Bay of Bengal (median ~ 37 nmol/kg (range: 30–53 nmol/kg)) are lower than that observed for the river (median ~ 319 nmol/kg (range: 256–583 nmol/kg)), and groundwater (median ~ 464 nmol/kg (range: 20–4428 nmol/kg)) samples. The salinity-weighted barium concentrations of the Chilika lagoon for the pre-monsoon (1052 nmol/kg) and monsoon (652 nmol/kg) seasons are higher compared to that during the post-monsoon period (332 nmol/kg). Covariations between salinity and [Ba] confirm the non-conservative behavior of barium during all three seasons. The salinity-[Ba] trends show barium removal in the low-salinity regions, attributable to its authigenic scavenging onto Fe-Mn oxyhydroxides. Mass balance calculations show that the relative contribution of barium via rivers (~18%), (freshwater) submarine groundwater discharge (SGD; ~25%), and desorption from particulate matters (~19%) to the lagoon during pre-monsoon seasons is nearly the same. During the monsoon season, the SGD supply of barium decreases to ~2%, whereas riverine (~20%) and desorption (~24%) contributions remain similar to that observed during the pre-monsoon. The sediment chemistry (Mg, Al, Fe) data and their correlations with Ba concentrations reveal that the desorptive release of barium to the lagoon is mainly via its cationic replacement from the suspended sediments by seawater Mg. In addition to these sources, our results show that about half of the dissolved barium during pre-monsoon and monsoon seasons remains unaccounted and may have been supplied by an additional source, which may be linked to subsurface supply of recirculated seawater and/or organic matter remineralization. Our quantitative approach emphasizes the importance of these additional sources in regulating the coastal barium inventory. • Non-conservative removal/release of Ba was observed in a coastal lagoon. • Release of dissolved Ba at mid-salinity region is observed for three seasons. • Ba release is mainly due to its desorption from particulate phases. • SGD supply of barium is higher during pre-monsoon than monsoon seasons. [ABSTRACT FROM AUTHOR]

Abstract: The palynological studies of a sediment core collected from the northeastern region of the Chilka Lagoon, reveal the history of mangrove vegetation during the last 4165 yrs BP The Chilka Lagoon (a Ramsar Site) is one of the ecologically and socio-economically important wetlands situated in the humid tropical climatic zone along the east coast of India. The palynological results indicate that the mangrove vegetation was well developed between 4165 and 2549 yrs BP, indicating warm and humid climatic conditions; though, they show a degrading trend in the latter phase of this period. After 2549 yrs BP, mangroves again flourished in the area and persisted until 2246 yrs BP, as a result of relative stability of sea-level. The mangroves disappeared since 2246 yrs BP, as inferred from the marked increase of midland taxa, indicating drier conditions. Along with climatic factors, anthropogenic activities have also accelerated the degradation of mangroves in the study site. The present study provides an understanding of mangrove ecosystem in the past and such investigations could also be useful for the regeneration of the mangroves in the region. [Copyright &y& Elsevier]

Six Holocene sedimentary events (ranging in age from 420–890, 890–1560, 2040–2340, 2420–3380, 3890–4330, and 5480–5760yrsBP) have been identified in the lagoon of Rasdhoo Atoll (Maldives; 4°N, 73°W), thereby underlining the importance of atoll lagoons as potential archives of environmental change. Holocene coastal sediments have been studied as archives for past tsunami and storm events but comparable sedimentological studies of mid-ocean atoll lagoons are rare. In ten vibracores covering the past 6.5kyrs that are characterized by mudstone, wackestone, and floatstone background sedimentation, we found two types of event deposits: (1) several cm thick rudstone layers with redeposited corals like Acropora sp. and Seriatopora sp., which derive from the marginal and/or lagoonal reefs and have been transported into the lagoon and (2) thin (several mm) layers of wackestone, floatstone, and rudstone consisting of reef-derived components like coralline red algae, reef foraminifera (e.g., Amphistegina spp., Calcarina sp.), and redeposited coral fragments. Both types of event layers may be correlated among several cores, which we interpret as tsunami deposits. Five of the six events have temporal counterparts identified at the coasts of Thailand, Sumatra, and India. In the Maldives, close to the equator, no category 1–5 typhoons were recorded, but only tropical depressions and storms as potential triggers of event sedimentation have occurred rarely. Major earthquakes off western Indonesia and generated tsunamis, which potentially reach most parts of the Indian Ocean, are common. [ABSTRACT FROM AUTHOR]

Abstract: Chilika, the second largest lagoon of the world was studied for 2 years on monthly basis to understand the dissolved inorganic carbon (DIC) dynamics through mass balance approach. The study revealed that during the low flow period the lagoon is net autotrophic (Net ecosystem production (NEP)=33Mgd−1) resulting in a sink of DIC whereas remains net heterotrophic during the high flow period (NEP=−3099Mgd−1). DIC concentration significantly varied with respect to seasons as well as sectors owing to fresh water discharge and biological activity of both pelagic and benthic communities. Sectoral mixing model showed negative residuals (sink of DIC) in all sectors during low flow, attributable to primary production (PP) as evidenced by strong correlation with residuals (r=−0.51, p<0.05). During high flow, DIC residuals of the entire lagoon (except southern sector) were positive (source of DIC) possibly due to bacterial mineralization as evidenced by δ 13 C DIC isotopic signature. The estimated net community production (NCP) in pelagic compartment was 14mgCm−2 d−1 during the low flow period. and −148mgCm−2 d−1 during high flow indicated dominating community respiration. The lagoon sediment acted as a net source of DIC throughout the study period. [Copyright &y& Elsevier]

A study was conducted in Lakshadweep islands to determine the feasibility of using Indian Remote Sensing (IRS) satellites for detecting changes in the seagrass from other coastal features. IRS ID and IRS P6 LISS III having spatial resolution of 23.5 m with lower cost compared to all other contemporary satellites with the same spatial resolution have not been widely used for monitoring the changes in seagrass cover. In this context, the present study attempted to explore the effectiveness of LISS III data for mapping seagrasses and to inform the international community about the usefulness of these low-cost imageries for coastal resource monitoring. Supervised classification and change detection studies found a significant decrease in seagrass cover of 73.03 ha in the Lakshadweep group of islands. An overall accuracy of 67.5% was obtained for the change maps, and seagrass cover and its changes vary at different islands. [ABSTRACT FROM PUBLISHER]

Abstract: Lyngbya aestuarii is the dominant cyanobacterium in Chilika lagoon occurring in all the seasons irrespective of variation in the salinity regime ranging from 3 to 28ppt. The organism possess the UV screening scytonemin pigment, which was maximum when grown at 56ppt salinity. Three different forms of scytonemin were detected in L. aestuarii with retention time (RT) 1.76, 2.42 and 2.94min, however, occurrence of these forms was influenced by the salinity. Scytonemin with RT 2.42 was sensitive to higher salinity and its maximum concentration was obtained at 28ppt salinity correlated with the highest salinity level of Chilika. Formation of multilayer colored sheath around the trichome was prominently observed at the salinity of the culture from 28 to 56ppt. But at salinity below 7ppt and also at more than 56ppt salinity degradation of sheath with corresponding decrease in scytonemin was observed. [Copyright &y& Elsevier]

Abstract: A 17-year-long δ13C and δ18O record from a scleractinian coral (Porites spp.) of Bangaram island (Lakshadweep Archipelago) is based on a nearly-monthly sample interval. This live coral head of Porites spp. was recovered from the lagoon of Bangaram (Lakshadweep) island at ∼20m water-depth. The skeletal δ13C and δ18O values varied approximately in phase and exhibit a positive relationship with each other. High-density (monsoon) bands are characterized by enriched δ18O values and low-density (non-monsoon) bands by depleted δ18O values. Coral δ13C and δ18O primarily reflects local oceanographic and climatic variability. The high-density bands were formed during the southwest monsoon (June–September) because of increased turbidity and cloud cover, whereas low-density bands were deposited during the non-monsoon months (October–May). Temporal changes in coral-derived sea surface temperature (SST) show a good agreement with instrumental SST record. The δ18O values in monsoon and non-monsoon bands are mainly due to the sea surface temperature (SST) changes, controlled by monsoon-induced upwelling and insolation changes. Coral-derived SST values clearly show warming events during summer 1993 and 1998. Spectral analysis of δ18O data reveals a teleconnection between the local SST and tropical Pacific climate variability. Enriched δ18O values for the monsoon months of 1984, 1985, 1993 and 1997 are probably indicative of cooler surface water due to the stronger upwelling at the studied location. Generally higher δ13C values correlate with enriched δ18O values of the monsoon bands. This increase in δ13C during the southwest monsoon months is attributed to a decrease in endosymbiotic photosynthesis. Alternatively, an increase in biological production, due to monsoon-induced upwelling, may have resulted in the δ13C enrichment of dissolved inorganic carbon (DIC) in surface waters. However, other possibilities, such as higher δ13C values due to coral mass-spawning events during monsoon times cannot be ruled out. A progressive decrease of ∼0.5‰ in δ13C from 1985 to 2001 may be due to the changes in photosynthesis and/or changing food habits from autotrophy to heterotrophy as the coral grew in size. [Copyright &y& Elsevier]

Compounding effects of slow life-history traits and adult-specific overharvesting have caused a range-wide decline of several giant clam populations. Erratic changes in these populations reported at isolated reefs, are attributable to stochastic fluctuations in recruitment and survival rates. These population rate parameters may be adversely influenced by the considerable and increasing human-reef economic interactions in tropical waters. The unsubstantiated knowledge on such influences hinders conservation management of species-habitat linkages particularly for species like the small giant clam (Tridacna maxima). Our study reports small giant clam survival rate, its ecological determinants and stochastic fluctuations from shallow lagoon waters of Lakshadweep Archipelago; a natural habitat not subjected to commercial giant clam harvesting. Survival rate was estimated by monitoring the status of identified individuals in belt-transects through successive years 2005-2009. The role of different factors in explaining the variation in survival rates was investigated at relevant scales: anthropogenic pressure at the population level in the reef, clam density at sub-population level in the belt-transects, and variables related to clams at the individual level. Effects were quantified through univariate regression techniques and Kaplan-Meier estimator coupled with generalized linear (logit link) models. Small giant clam survival rate in the reef decreased and its spatio-temporal fluctuations increased along the increasing gradient of human populations. Survival was density-independent. Size/age specific survival followed Siler distribution characterized by very low early-age survival, increased adult-age survival, and low older-age survival. Anchorage in coral substrate exerted a curvilinear effect, where survival of moderately anchored clams > loosely anchored clams >> deeply embedded clams. Our study recommends regular population monitoring in densely inhabited islands to detect incipient changes, which can subsequently be confronted by scientific lagoon bed management. [ABSTRACT FROM AUTHOR]

In current study an analytical and comparative study of post treatment options for UASB reactor treating municipal wastewater is presented. The two important post treatment alternatives viz. facultative waste stabilization pond and aerated lagoon are considered, lagoon and pond refer broadly to basins constructed in, or on the ground surface, using earthen dikes to retain the wastewater within which natural stabilization process occur with the necessary oxygen coming from atmospheric diffusion, photosynthetic and / or mechanical sources. [ABSTRACT FROM AUTHOR]

The parapseudid tanaidacean Ctenapseudes sapensis (Chilton, 1926) is minutely redescribed and illustrated. The species is very similar to C. chilkensis, described by the same author based on samples from the brackish Chilka Lake in India (Chilton, 1924). C. sapensis was the only apseudomorph tanaidacean found in Upper Songkhla Lagoon, southern Thailand. This species is dominant in this lagoon, and, at the same time, is a major food source for some catfishes (Osteogeneiosus militaris, Arius truncatus and Arius maculatus). [ABSTRACT FROM AUTHOR]

Chilika Lake is situated on the Indian east coast. It is one of the largest lagoons in the world, with a unique assemblage of marine, brackish water and freshwater species. Due to the opening of new connections to the sea in the years 2000 and 2008, an environmental change is expected in the lagoon. The study gives an assessment of sediment contamination by heavy metals on the verge of this change (sampling campaign in 2000). Sediment samples from two surface levels (0–5 and 30–35 cm), and from depth profiles, were analysed for mineralogical composition, main and trace element concentrations, and element bonding forms. Background concentrations from a depth profile were also examined. The profile spans a time of ≈13 500 years. Age determinations by radiocarbon dating and the 137Cs- and 210Pb-method were carried out. The composition of the surface sediments is generally uniform. The heavy metals exhibit slightly decreasing concentrations from NE to SW, thus indicating the supply of contaminants from the Mahanadi River. The anthropogenic portion of the heavy metal supply is mainly bound to Fe-oxide-hydroxides. Phosphorus is enriched in the sediments of the southern lake sector. Changes in element concentrations in the last 13 500 years have occurred mainly in two steps. The long-term variations exceed the anthropogenic changes caused by the Mahanadi River inputs. The very sensitive response of coastal area fabrics on climate changes also causes fast geogenic changes in element concentrations in sediments (similar grain sizes). This prevents the use of element concentrations from deep sediment horizons to define contaminations in those areas. [ABSTRACT FROM AUTHOR]

Studies on biogeochemical cycling of carbon in the Chilka Lake, Asia’s largest brackish lagoon on the east coast of India, revealed, for the first time, strong seasonal and spatial variability associated with salinity distribution. The lake was studied twice during May 2005 (premonsoon) and August 2005 (monsoon). It exchanges waters with the sea (Bay of Bengal) and several rivers open into the lake. The lake showed contrasting levels of dissolved inorganic carbon (DIC) and organic carbon (DOC) in different seasons; DIC was higher by ∼22% and DOC was lower by ∼36% in premonsoon than in monsoon due to seasonal variations in their supply from rivers and in situ production/mineralisation. The DIC/DOC ratios in the lake during monsoon were influenced by physical mixing of end member water masses and by intense respiration of organic carbon. A strong relationship between excess DIC and apparent oxygen utilisation showed significant control of biological processes over CO2 production in the lake. Surface partial pressure of CO2 ( pCO2), calculated using pH–DIC couple according to Cai and Wang (Limnol and Oceanogr 43:657–668, ), exhibited discernable gradients during monsoon through northern (1,033–6,522 μatm), central (391–2,573 μatm) and southern (102–718 μatm) lake. The distribution pattern of pCO2 in the lake seems to be governed by pCO2 levels in rivers and their discharge rates, which were several folds higher during monsoon than premonsoon. The net CO2 efflux, based on gas transfer velocity parameterisation of Borges et al. (Limnol and Oceanogr 49(5):1630–1641, ), from entire lake during monsoon (141 mmolC m−2 d−1 equivalent to 2.64 GgC d−1 at basin scale) was higher by 44 times than during premonsoon (9.8 mmolC m−2 d−1 ≈ 0.06 GgC d−1). 15% of CO2 efflux from lake in monsoon was contributed by its supply from rivers and the rest was contributed by in situ heterotrophic activity. Based on oxygen and total carbon mass balance, net ecosystem production (NEP) of lake (−308 mmolC m−2 d−1 ≈ −3.77 GgC d−1) was found to be almost in consistent with the total riverine organic carbon trapped in the lake (229 mmolC m−2 d−1 ≈ 2.80 GgC d−1) suggesting that the strong heterotrophy in the lake is mainly responsible for elevated fluxes of CO2 during monsoon. Further, the pelagic net community production represented 92% of NEP and benthic compartment plays only a minor role. This suggests that Chilka lake is an important region in biological transformation of organic carbon to inorganic carbon and its export to the atmosphere. [ABSTRACT FROM AUTHOR]

Chilika Lagoon (19°28′-19°54′N, 85°06′-85°36′E), on the Orissa coast, India, is one of the world's unique ecospheres. It is the largest brackish water lagoon with estuarine character. Because of its rich biodiversity and socioeconomic importance, it was designated as a "Ramsar site"--a wetland of international importance--in 1981. Interest in detailed analysis of the circulation, biotic, and abiotic factors affecting the lagoon and its limnology is a result of the opening of the new mouth on 23 September 2000 to resolve the threat to its environment from various factors--eutrophication, weed proliferation, siltation, industrial pollution, and depletion of bioresources. This paper describes the development of a two-dimensional depth-averaged hydrodynamic model for Chilika Lagoon and the resulting simulation of currents and salinity corresponding to (i) the Southwest and Northeast monsoon seasons and (ii) pre- and post-mouth-opening conditions. Numerical experiments are performed to understand the different factors--wind, tides and freshwater influx--and their independent and collective roles. Comparison of results obtained with one or both of the openings is made to quantify and validate the changing salinity pattern, which has improved the productivity of the lagoon. Our study shows the salinity levels to be much lower during the southwest monsoon compared to the northeast monsoon, which is validated by observations. The decrease in salinity is attributed to more freshwater influx during the southwest monsoon. There is a significant increase (14%-66%, depending on the sector) in salinity after opening of the new mouth, the maximum change being observed in the channel that connects the lagoon to the sea. The constriction in the lagoon that blocks the tidal effects entering the lagoon is found to be responsible for maintaining the main body of the lagoon with low salinity. The dynamic model will be an important input for our on going work in seasonal study of the ecology of Chilika Lagoon. [ABSTRACT FROM AUTHOR]

The northeasterly long shore transport (littoral drift) along the east coast of India shifts the mouth of the lagoon northeastwards. It results in lengthening of the outer channel, reduced tidal flux, fall in salinity levels, weed infestation, decline in fishery resources, and overall loss of biodiversity and productivity. The Chilika Development Authority made an artificial mouth near the village of Sipakuda, which was opened on 23 September 2000. The present study focuses on applications of Resourcesat-1 LISS-III and AWiFS data to understand the impact of the new mouth opening on the morphology and water quality of the Chilika Lagoon. Digital image processing of multi-temporal Resourcesat-1 AWiFS, LISS-III, and IRS-1D LISS-III data was carried out. Changes were shown out for pre- and post-opening of the new mouth. The results indicate that the initial cut of 80 m has widened to approximately 676 m and, so far, the process has not attained stability. There has been northward erosion for approximately 376 m and southward erosion for approximately 143 m at the new mouth. The study shows that the strong ebbing tide current from the northwest is responsible for this erosion. The old mouth has been closed completely just three years after the opening of the new mouth. There has been an overall rise in salinity levels in the Chilika Lagoon, in particular during the pre-monsoon period following the opening of the new mouth. This indicates that the tidal flux in the lagoon has increased and the associated circulation is effective in mixing the water masses. After the opening of the new mouth, weeds have reduced by a 172-km2 area, in particular in the northeast part of the lagoon. AWiFS data is extremely useful in identifying changes in morphology and water quality under different tide conditions. Tidal conditions influence the signatures of turbidity, weed cover, shoals, and spits under development. The SWIR channel of AWiFS is found to be extremely useful for detecting aquatic vegetation. The study concludes that large transport of sediments at the new mouth opening, along with predominant erosion of the northern bank, suggests a northward migration of the new mouth in the near future. [ABSTRACT FROM AUTHOR]

India is home to a wide range of water impoundments located in a diversity of climates, stretching from mountain conditions near the Himalayas in the north, to tropical conditions in the south. The impoundments include natural lakes, wetlands and coastal lagoons, as well as constructed reservoirs and tanks. This paper provides an overview of the lake management in India, focusing on wetlands, reservoirs and tanks. While there has never been a thorough survey of the lakes of India, it is possible to discuss the general conditions in which lake management is currently carried out in India. Overall, lakes all over the country are exhibiting varying degrees of environmental degradation caused by encroachments, eutrophication (from domestic and industrial effluents) and siltation. The high population density ensures that many water bodies are under severe and direct pressure from anthropogenic activities in their catchments. Actions to control and prevent these problems are addressed, with a focus on measures such as public interest litigation, the National Lake Conservation Plan, and the Special Purpose Vehicles. The role of national and international institutions is critiqued. Finally, the issues related to gaps in the knowledge base, delays in restoration, lack of coordination, ineffectiveness of legislation, and the general lack of an integrated approach to management are discussed, and possible solutions to these impediments are explored. [ABSTRACT FROM AUTHOR]