Vembanad Lake Research Articles

Ecological impact of artificial barrage on calanoid copepods in the Vembanad Lake, Southwest Coast of India

The Vembanad Lake (VL) is a brackish water lagoon, an integral part of Ramsar site, Vembanad Kol Wetland ecosystem on the southwestern coast of India. VL faces escalating anthropogenic impact, notably worsened by the establishment of the Thanneermukkom barrage (TMB) in 1976. This study hypothesizes that the TMB has led to significant ecological changes in VL, specifically altering the distribution and abundance of calanoid copepods, which are vital as a food source for higher trophic levels, particularly fish. To test this hypothesis, zooplankton samples were collected from various sites along the lake, and environmental parameters such as salinity and chlorophyll-a concentration were measured. This investigation reveals a distinct limnetic zone in the southern region, in contrast to the oligo-mesohaline zone in the north, attributed to the TMB. The study identifies the prevalence of calanoid copepod species such as Heliodiaptomus cinctus, Allodiaptomus mirabilipes, and Acartiella gravelyi in the TMB-South region, reflecting a freshwater-dominated ecosystem. The low salinity and high chlorophyll-a content in this area create an optimal environment for these species. In contrast, the dominance of Acartia (Odontacartia) spinicauda, Pseudodiaptomus serricadatus, and Paracalanus sp. in the TMB-North indicates higher salinity levels, with species in this region adapting to a different ecological niche. Thus, the installation of the TMB has significantly altered the ecological balance of VL by dividing the water body into two distinct salinity zones. This separation has led to changes in the distribution and abundance of calanoid copepods, which are essential for energy transfer to higher trophic levels in the VL food web, consequently affecting fish populations and overall biodiversity.

Large scale screening and quantification of micropollutants in fish from the coastal waters of Cochin, India: Analytical method development and health risk assessment

Urban estuarine and coastal water receive several micropollutants through industrial and agricultural influxes. The bioaccumulation of these micropollutants in fish and their entry into the coastal population's food chain raises significant food safety concerns. Hence, a comprehensive analytical method was developed for ultra-trace level quantification of 345 micropollutants in fish. The optimized sample preparation method could extract compounds suitable for both GC–MS/MS and LC-MS/MS analysis simultaneously. The target list of contaminants included 278 agricultural pesticides and also 102 endocrine disruptors covering polyaromatic hydrocarbons, polychlorinated biphenyls, organochlorines, and endocrine-disrupting pesticides. The GC–MS/MS with large volume injection (LVI) technique, and LC-MS/MS operating in MRM mode, achieved an LOQ of <2.00 ng/g for most of the analytes. The extraction strategy involved tri-phase partitioning between water, acidified acetonitrile, and hexane, followed by salting out. Dispersive solid phase cleanup (dSPE) with C18, Z-Sep+, CaCl2, and MgSO4 was able to reduce the matrix influence, and the method achieved satisfactory recovery in the range of 70.0–120.0 % for all the target analytes. The repeatability and reproducibility relative standard deviation values of the measured analytes were <20.0 %, and the Horwitz ratio values were well below 2. The method was used to accurately measure the target micropollutants in fish from the Cochin estuary, the highly urbanized portion of the Vembanad Lake, and an important Ramsar site. At least one or more of the 41 different micropollutants were identified and quantified in about 90.7 % of the 108 samples analyzed. The importance of large-scale screening and trace-level quantification methods in environmental monitoring and risk assessment is underscored by the results. The risk assessment showed a moderate risk of exposure to the nearby coastal population through the food chain.

Application of GIS in Evaluating Suitable Clam Farming Site in Vembanad Lake, India

The present study identifies and quantifies appropriate sites for black clam farming in the Vembanad Lake using a geographical information system (GIS). The black clam, Villorita cpyrinoides, is the most important clam landed in India. Despite being a candidate species for aquaculture, the trials on farming of clams are very limited. The aim of this study was to select the most suitable sites for clam farming in Vembanad Lake based on the use of GIS-based models. For this, the importance of soil quality, water quality and infrastructure facilities were accessed using an analytical hierarchical process. The site suitability map was prepared using each attribute and divided into four classes, such as most suitable, moderately suitable, least suitable and poor. Water quality is found to play a major role (54%) compared to soil quality (24%) and infrastructure facilities (22%) for development of clam farms in Vembanad Lake. Salinity registered the highest importance (0.21) for the water quality suitability map as compared to other parameters like pH and dissolved oxygen. The total area covered under this study was 6471 ha out of which, 3121 ha (48%) was identified as most suitable and of the remaining 3350 ha, 1804 ha (28%) was identified as moderately suitable, 946 ha (15%) was identified as least suitable and 600 ha (9%) was identified as the poor site for clam farming in Vembanad Lake.

Ichthyofaunal Diversity and Physico-chemical Analysis of Water in the Middle Stretch of Vembanad Lake, Kerala, India

The status of finfish and shellfish diversity and monthly variation in their distribution and abundance were investigated in the middle stretch of Vembanad Lake at 4 selected sites in Kerala. The study was carried out for a period of 7 months from December 2022 to June 2023. In total 31 species of finfishes and shellfishes belongs to 8 orders, 23 families and 29 genera were recorded from the study areas. Calculated values of Biodiversity indices were Shannon Weiner diversity index highest at Vaikom (3.4022), Simpson diversity index highest at Manakunnam (0.9538), Margalef’s richness index highest at Manakunnam (4.346) and Pielou’s evenness index was highest at Thaneermukkom (0.8573). Etroplus suratensis and Villorita cyprinoides were the most abundant species from all four study sites. Three species are under the category of threatened they are Oreochromis mossambicus, Horobagrus brachysoma and Hyporhampus xanthopterus. The result of the present study indicates that the Northern part of Thaneermukkom barrage is endowed with rich edible fish fauna. The physicochemical parameters of water were analyzed during the pre-monsoon and monsoon periods. Salinity was higher on the Northern side of the barrage. During the pre-monsoon period temperature, EC, TDS, alkalinity and salinity were high and during the monsoon period hardness, DO, BOD, Phosphate and Nitrate were high when compared with pre-monsoon but all are within the recommended limit.

A Comparative Analysis of Water Quality Parameters of Vembanad Lake, Kerala and Its Primary Inflows Based on the Seasonal Variations

The ecology of lakes is largely dependent on rivers. However, because research has frequently concentrated on rivers and lakes independently, the interconnectivity between them is poorly defined. During the present study, hydrochemical investigation of surface water from the Vembanad Lake and its primary inflows, Periyar, Muvattupuzha, Manimala, Meenachil, Pamba and Achenkovil were carried out. This study describes the quality and suitability of lake and river water for consumption and irrigation purposes. It also aids in determining the influence of six rivers over the Vembanad lake water quality. Total 80 samples were collected during pre-monsoon and post monsoon seasons. Various physico-chemical parameters such as Temperature, Turbidity, Total Dissolved Solids (TDS), Conductivity, pH, Alkalinity, Total Hardness, Calcium, Magnesium, Sodium, Potassium, Chloride, Bicarbonate and Sulphate were analysed. The chemical classification using Piper trilinear diagram reveals that sodium is the predominant cation in both seasons. The Water Quality Index value of the Vembanad Lake is found to be higher in the pre-monsoon season compared to the postmonsoon. Sodium hazard (Sodium Adsorption Ratio- SAR), Residual Sodium Carbonates (RSC), Sodium Percentage (Na%), Magnesium Hazard (MH), Kelly's Ratio (KR) and Permeability Index (PI) are the parameters used to identify the irrigation water quality. Based on the irrigation water quality parameters it can be concluded that water from southern portion of the lake and six inflows are suitable for irrigation purpose. The U.S. Salinity diagram indicates that the northern portion of the lake occupies the high sodium hazard zone. The water quality of the southern portion of the Vembanad Lake is chiefly controlled by its primary freshwater in flows and the northern portion by the saline water from the Arabian Sea. Keywords: Hydrogeochemistry, Water Quality, Sodium Adsorption Ratio,Vembanad Lake Kerala

Untargeted metabolomics reveals potential health risks associated with chronic exposure to environmentally relevant concentrations of 2-Phenylphenol

Chronic exposure to endocrine-disrupting chemicals through foods of aquatic origin, at levels that are commonly found in the environment, can affect metabolic health and lead to metabolic diseases. One such chemical is 2-phenylphenol (2-PP), a suspected endocrine disruptor that is used extensively in agriculture and industry, and has become a widespread pollutant in aquatic environments. This study evaluated the risk of exposure to 2-PP through foods of aquatic origin from Vembanad Lake, using a Target Hazard Quotient (THQ) and an untargeted metabolomics approach. The study found that 2-PP content was higher in samples from areas with intense industrial, tourism, and agricultural activities. The average concentration of 2-PP in fish, crustaceans, and mollusks from the Vembanad estuary ranged from 0.012 to 0.017 mg/kg. The mean concentration of 2-PP was used to assess the THQ of exposure to the coastal population. The results showed that the THQ value was <1, indicating a low to moderate health risk for both adults and children. Furthermore, an untargeted metabolomics approach using HPLC-Q-Orbitrap MS was used to study the metabolome changes associated with chronic exposure to 2-PP (at the environmentally relevant concentration) over 60 days in the Wistar albino rat model. The findings indicated significant alterations in the phospholipid, fatty acid, sterol lipid, and amino acid profiles, suggesting that chronic exposure to 2-PP at environmentally relevant concentrations could affect purine, phenylalanine, tyrosine, and cholesterol metabolism.

Characteristics and risk assessment of microplastic mediated heavy metal transport in black clam Villorita cyprinoides from a Ramsar wetland of South India

The synergetic and interactive effects of microplastics (MPs) as potential carriers of pollutants and pathogens have a manifold impact on human health and aquatic biota. The present study delineates the role of MPs in transporting heavy metals to the black clam, Villorita cyrpinoides of Vembanad Lake in South India. MPs in water (3.41 ± 1.87 items/L), sediment (154.6 ± 45.4 items/kg) and within clams (0.87 ± 0.34 items/g tissue) showed considerable variation based on their physical and chemical characteristics, which in turn reflected its differential potential to carry heavy metals. Though the levels of heavy metals (Al, Fe, Mn, Zn, Cr, Pb) within the clam and those carried by MPs were less than the hazardous limits, the concentration of Cd within the clam and MP was found to have a positive correlation. Though the present levels of heavy metal pollution in the lake do not pose a direct threat to humans, anthropogenic interventions and reduced water flow have turned the lower reaches of the lake into a sink of heavy metals. Hence with MP concentration increasing it is worth investigating how their future interactions with heavy metals and other pollutants would pose a risk to living organisms.

Gillnet colour affects catch efficiency in pearlspot (Etroplus suratensis) tropical estuary fishery

Gillnets are one of the most commonly used fishing gears in both marine and inland waters. Different colour filament nettings are often used in gillnets. However, the effect of gillnet colour on catch efficiency is unclear for most fisheries. Therefore, in this study we investigated the effect of gillnet colour on the catch efficiency in pearlspot (Etroplus suratensis) fishery in Vembanad lake, India. Gillnet colours tested were transparent, green and blue. Results showed that in this fishery, the catch efficiency of gillnets of the three colours tested differed significantly. The highest catch efficiency of pearlspot was shown by green gillnets compared to transparent or blue netting. Specifically, green gillnets on average were estimated to be 74% more efficient compared to transparent gillnets. For the green compared to the blue gillnets, the catch efficiency was estimated to be higher by 81%. These results demonstrate that gillnet colour can be an important factor significantly affecting the catch efficiency of this fishing gear.

Spatial Mapping of Flood Susceptibility Using Decision Tree–Based Machine Learning Models for the Vembanad Lake System in Kerala, India

Spatial Mapping of Flood Susceptibility Using Decision Tree–Based Machine Learning Models for the Vembanad Lake System in Kerala, India

Distribution and abundance of microplastics in the water column of Vembanad Lake–A Ramsar site in Kerala, India

The study focuses on the occurrence, abundance and characteristics of microplastics (MPs) in the subsurface and bottom waters of Vembanad Lake, a Ramsar site in the state of Kerala. Even though several studies elucidate the prevalence of microplastic pollution in the surface waters of aquatic ecosystems, a little is known about the vertical distribution of MPs in the water column. Vembanad Lake water is greatly affected by microplastic pollution compared to other Indian lakes as it receive discharges from six rivers; a number of sewage canals and run-off. Ubiquitous distribution of MPs was found in the lake with a mean abundance of 26.79 ± 3.74 items L−1 and 52.70 ± 5.43 items L−1 in subsurface and bottom waters respectively. Fibers, constitute more than half of the total MPs in both subsurface and bottom waters. The dominance of polyamide and polypropylene with most of the MPs being fibers indicate that they originate probably from fishing activities and laundry wastewater. The particles with in the size range 100–500 μm were in excess in the water samples. Further fragmentation, increasing the number of MPs in the lake water was envisaged from the SEM images of MPs showing cracks and crevices. These MPs along with adsorbed contaminants upon ingestion by the aquatic organisms become a threat to the food web of the lake. The local population which depends mainly on the fishes and mussels of the lake for their dietary needs would be greatly affected by the contamination of the lake with MPs. Further research on MPs contamination in edible biota would give more insights on the extent and risks of MPs pollution in the lake.

Spatiotemporal variation in the water quality of Vembanad Lake, Kerala, India: a remote sensing approach.

Water quality is one of the essential parameters of environmental monitoring; even a slight variation in its characteristics may significantly influence the ecosystem. The water quality of Vembanad Lake is affected by anthropogenic effects such as industrial effluents and tourism. The optical parameters representing water quality, such as diffuse attenuation (Kd), turbidity, suspended particulate matter (SPM), and chlorophyll-a (Chl-a), are considered in this study to evaluate the water quality of Vembanad Lake, Kerala, India. As this lake is regarded as of ecological importance by the Ramsar Convention and has faced severe concerns over recent years, there was a substantial change in the water quality during the lockdowns of the COVID-19 pandemic. This research is aimed at examining the change in water quality using optical data from Sentinel-2 satellites in the ACOLITE processing software from 2016 to 2021. The analyses showed a 2.5% decrease in the values of Kd, whereas SPM and turbidity show a reduction of about 4.3% from the year 2016 to 2021. The flood and the COVID lockdown had an impact on the improvement in the quality of water from 2018 to 2021. The findings indicated that the reduction in industrial activities and tourism had a more significant effect on the improvement in the water quality of the lake. There was no substantial change in the Chl-a until 2020, whereas an average decrease of 12% in Chl-a values was observed throughout 2021. This decrease can be attributed to the reduction in the lake's hydrological residence time (HRT). Thus, these findings will be a valuable reference to help the government and non-government organizations (NGO) during strategic planning.

Environmental and human facets of the waterweed proliferation in a Vast Tropical Ramsar Wetland-Vembanad Lake System.

The Vembanad Lake and its associated low-lying areas and network of canals (hereafter VBL) form the major part of India's second-largest Ramsar wetland (1512 km2) located in Kerala State alongIndia's southwest coast. The extensive VBL has a large fishery, inland waterways, and popular tourist attractions that support the livelihoods of thousands of people. Over the last several decades, the proliferation of water weeds in the VBL has alarmingly increased, causing many adverse ecological and socioeconomic effects. This study based on a review and synthesis of long-term data introduced the environmental and human dimensions of water weed proliferation in the VBL. Eichhornia (= Pontederia) crassipes, Monochoria vaginalis, Salvinia molesta, Limnocharis flava, Pistia stratiotes, and Hydrilla verticillata are the most troublesome water weeds in the VBL, with the first three being the most widespread. They were mostly imported to India long ago before becoming a part of the VBL.These weeds harmed water quality, waterways, agriculture, fisheries, disease vector management, as well as the vertical and horizontal shrinkage of the VBL through increased siltation and faster ecological succession. The inherently fragile VBL was harmed by extensive and long-term reclamation, the construction of saltwater barrages, and many landfill roads that crisscross water bodies serving as coastal dams, creating water stagnation by blocking natural flushing/ventilation by periodic tides from the adjacent southeastern Arabian Sea. These ecological imbalances were exacerbated by excessive fertiliser use in agricultural areas, as well as the addition of nutrient-rich domestic and municipal sewage, which provided an adequate supply of nutrients and a favourable habitat for the expansion of water weeds. Furthermore, because of recurrent floods and a changing ecology in the VBL, the water weed proliferation has become a more significant problem, with the potential to disrupt their current distribution pattern and spread in the future.

Simple pot modification improves catch efficiency and species composition in a tropical estuary mud crab (Scylla serrata) fishery

Pots are widely used fishing gear type for targeting different crustacean and fish species. Pot entrance size and design are among the most important technical parameters that influence the catch efficiency of certain species. An optimal pot entrance design should allow an efficient entry for the target species while preventing subsequent escape. The tropical estuary pot fishery targeting mud crab (Scylla serrata) in Vembanad Lake, India, employs rectangular pots with rectangular-shaped entrances. Low catch rates for target species and high bycatch rates are observed in this fishery. This study was carried out to investigate if a simple pot modification by extending the entrance of the traditional pots, can improve the catch efficiency of mud crab. Further, we estimated and compared the catch composition in this small-scale fishery using the traditional and modified entrance pots. The results showed that the catch efficiency for all sizes of mud crab is on average more than six times higher with the modified entrance pots compared to the traditional pots (622% (CI: 344–1867%)). However, significant quantities of juvenile crabs are caught in modified pots. Further, the bycatch ratio was significantly reduced for modified compared to the standard entrance pots in this fishery. These results show that such pot modifications have potential to significantly improve the catches in mud crab pot fisheries without increase in capture of bycatch species. However, additional mechanisms for excluding undersized crabs from pot catches should be investigated.

Comparative Analysis of Regression Models for Remote Sensing-based Water Quality Assessment

The 80-kilometer-long Vembanad Lake in Kerala, India, is a Ramsar site. Eutrophication is deteriorating its water quality and threatening its biodiversity. In this study, satellite imageries of Sentinel 2A and Landsat 8 OLI were utilized to determine its water quality. Various data sets of the water quality parameters viz. pH, Electrical conductivity, TSS, TDS, BOD, DO, chloride etc. are analyzed and interpreted. Regression models were developed on the parameters taken up for water quality analysis. The empirical R2 values of the developed models evidenced the accuracy of the developed mdoels. The findings show that remote sensing images are reliable for analyzing surface water quality characteristics. The comparative analysis of the model developed illustrated the effectiveness of using the imaging systems mentioned above for water quality index estimation through remote sensing.

Assessing multi-scale vulnerability of fisheries of Vembanad lake, Peninsular India, due to climate change: a stakeholders-based approach

Assessing multi-scale vulnerability of fisheries of Vembanad lake, Peninsular India, due to climate change: a stakeholders-based approach

The Distribution of Fecal Contamination in an Urbanized Tropical Lake and Incidence of Acute Diarrheal Disease

Aquatic ecosystems of tropical countries are vulnerable to fecal contamination that could cause spikes in the incidences of acute diarrheal disease (ADD) and challenge public health management systems. Vembanad lake, situated along the southwest coast of India, was monitored for one year (2018–2019). Escherichia coli, an indicator of fecal contamination, was prevalent in the lake throughout the year. Multiple antibiotic resistance among more than 50% of the E. coli isolates adds urgency to the need to control this contamination. The high abundance of E. coli and incidence of ADD were recorded during the early phase of the southwest monsoon (June–July), prior to the once-in-a-century floods that affected the region in the later phase (August). The extent of inundation in the low-lying areas peaked in August, but E. coli in the water peaked in July, suggesting that contamination occurred even prior to extreme flooding. During the COVID-19-related lockdown in March–May 2021, fecal contamination in the lake and incidence of ADD reached minimum values. These results indicate the need for improving sewage treatment facilities and city planning in flood-prone areas to avoid the mixing of septic sewage with natural waters during extreme climate events or even during the normal monsoon.

Quality monitoring of inland water bodies using Google Earth Engine

Abstract Regular quality monitoring of inland water bodies is vital for identifying the areas with deteriorating water quality. Satellite remote sensing has been used for obtaining long-term trends that require the processing of many images. The computational load of processing a large number of satellite imageries can be eased by utilizing the cloud computing capabilities of Google Earth Engine (GEE). The present study explores the possibility of using the GEE platform for mapping the Trophic State Index (TSI) of an inland water body. The bottom of atmosphere (BOA) reflectance retrieved by the SIAC algorithm (used in the GEE platform) is assessed for its accuracy. The algorithm could retrieve only BOA reflectance at bands B3 and B4 of Sentinel 2L1C (S2) with reasonable accuracy. The study has identified the Normalized Difference of B3 and B4 bands of S2 (i.e., ND34) as the tool for mapping TSI of a water body using GEE. TSI from six imageries of three lakes was estimated with a mean error &amp;lt;17%. The capability of GEE as a rapid water quality monitoring tool is demonstrated by displaying the temporal and spatial variations of water quality across Vembanad Lake for the period 2016–2021.

Ghost fishing capacity of lost experimental gillnets: a preliminary study from Indian waters.

Abandoned, lost, or otherwise discarded fishing gear contributes considerably to global marine debris. These lost gears, mostly made of non-biodegradable synthetic materials, persist in the marine environment for longer periods of time and pose a great threat to marine life by entangling and killing target fishes and other non-target species such as turtles, birds, and mammals, a phenomenon known as ghost fishing. Other environmental impacts include physical impacts on aquatic habitats, transfer of microplastics into food web, and interference with fishing. Information regarding the catching efficiency and catch rates of lost nets in Indian waters is lacking. Ghost fishing capacity of simulated lost gillnets is being reported for the first time in India. This study investigates the ghost fishing capacity of lost gillnets through an experimental approach at Aroor, Vembanad lake, Kerala, India. Simulation studies using purposefully abandoned shrimp gillnets (32mm mesh size) were conducted to understand the fishing capacity of lost gillnets during two seasons (monsoon and post-monsoon) as separate experiments. The gillnets maintained their catching efficiency until the 15th day during the first experiment and up to the 50th day in the second experiment. Catches showed an exponential reduction over time in both experiments. A total of 251 specimens comprising of 27 species were caught from both sets of experimental nets, and the state of catch in the nets showed different decaying stages from the second day itself along with fresh stages. As the days progressed, particulate matter and detritus began to accumulate on the experimental nets, increasing net visibility and reducing their catching efficiency. The results of the study on ghost fishing capability will contribute to the development of strategies for reducing the effects of lost nets on the aquatic ecosystem and for suggesting improved management strategies.

Economic valuation of gillnet fishing in Vembanad Lake, Kerala, South India, using market price approach

Gillnet is the most widely followed selective and passive fishing gear system in all water bodies, especially in the traditionalfishing sector. Many past studies on gillnet fishing in the Vembanad Lake, Kerala, South India focussed on speciesavailability and gear-wise catch of major fishes and showed that there was a significant reduction in the fish catch.Thepresent study used market-based valuation method to estimate economic value generated through gillnet fishing operationin selected village panchayats spreading across three districts viz., Ernakulum, Alappuzha and Kottayam, bordering theVembanad Lake, during the period in 2019-20. The species-wise quantity and value of finfishes and shellfishes caught inthe gillnets from Vembanad Lake, in the three districts were analysed during the survey period. The total number of gillnetfishers living around the Vembanad Lake is about 6157 and the catch was estimated at 4645.97 t of both finfish and shellfishspecies, out of which shrimps formed around 72%. The maximum quantity of catch was observed for catfishes (Arius spp.)at 278.6 t per annum, which fetched a value ₹4.46 crores, followed by Etroplus maculatus at 149 t (₹3.58 crores in valueterms). The economic value generated through gillnet fishing is estimated at ₹57.94 crores. Keywords: Economic value, Gillnet fishing, Market price method, Vembanad Lake

Flood risk analysis and mapping under compound hazards: A copula approach for tropical coastal district of Alappuzha, India

This study investigates the determination of compound risk under the co-existence of heavy rainfall and water level rise at Alappuzha, a coastal district in Southern Kerala, India using Copulas. In the case of Alappuzha, when the combined action of rainfall and water level rise occurs, the chances of compound flooding is more in and around Vembanad Lake and lower Kuttanad regions. So, the water level and rainfall of three different locations viz. Punnmada, Cherthala, Arookutty are considered for compound flood risk analysis. A joint probability model based on Copula is used to determine the combined risk of flooding. First the marginal distributions of daily rainfall and water level data are developed for each locations and the best fit distribution is used for finding the joint probability. The three most common Archimedean copulas Gumbel–Hougaard (GH), Clayton and Frank are used to find the joint probability of rainfall and water level and the best copula for each location is also identified. Subsequently, the joint and conditional return periods of rainfall and water level are also obtained in an exercise of risk modeling. By using the digital elevation model (DEM) in a Geographic Information System (GIS) platform, the flood prone areas are calculated and represented them graphically, for specific cases of joint return period-water level combinations. This helps as an aid for administrators or policy makers to effectively perform the disaster management at Alappuzha.