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Health of an ecosystem is very much important as we depend on its goods and services for our existence. Because of this, we need to continuously monitor its health for human benefit and for identifying areas for improvement of our natural systems. The present study tries to assess the condition of a coastal ecosystem within the Vembanad Lake, Kerala, India, using key water quality parameters at micro-level. Principal component analysis identified the minimum required water quality dataset for further analysis and was scored using linear scoring functions. The weighted additive method was used to integrate the individual scores to arrive at a final score representing the ecosystem health. Spline interpolation was applied to develop the ecosystem health map of the study area. Using this method, 35.8% area of the aquatic ecosystem studied was characterized as good, 32.2% as moderate, 26.2% as fair and 5.8% as poor. The assessment results can help the policymakers/managers to make appropriate decisions for the better management of the coastal ecosystems studied. Moreover, this methodology can be replicated for the assessment of coastal regions with similar ecosystem characteristics.

We investigated the effect of depuration of three naturally contaminated commercially important tropical edible bivalve molluscs by varying temperature, salinity and body-size of animals harvested from Ashtamudi and Vembanad estuaries, India using a static depuration system to ensure microbiological food safety. Before depuration, the levels of faecal indicators and pathogens were above the acceptable limits for live consumption. The depuration water temperature had a significant effect on bacterial elimination. Log reduction of faecal coliforms (FC) and E. coli varied between room-temperature (RTDS) and low-temperature depuration system (LTDS) and it was in the range of 1.39-2.44 and 1.88-2.82 log MPN, respectively under RTDS and LTDS. The elimination of bacterial pathogens such as Vibrio and Salmonella spp. was rapid in RTDS compared to LTDS. The highest elimination of FC and E. coli (2.39 and 2.92 log) was at 35 psμ depuration and the lowest (0.87 and 1.65 log) at 15 psμ depuration. The reduction of FC and E. coli was higher in the medium-sized animals compared to the small animals. Based on the results it is recommended that depuration using the static system under room-temperature (30 ± 1 °C); a salinity range of (25-35 psμ) and using medium-size bivalves (clam30 mm; mussel45 mm, and oyster65 mm length) as optimum conditions for producing microbiologically safe bivalves for live consumption within 36 h.

The effect of temperature, salinity and body-size on depuration of naturally accumulated heavy metals in clams, mussels and oysters harvested from Ashtamudi and Vembanad estuaries of Kerala, India were investigated using a static depuration system. Before depuration, the concentrations of heavy metals such as Ni, Co, Fe, Mn, Cu, Pb and Zn were analysed and it was found that the Fe, Zn, Cu and Pb contents in all the three bivalve molluscs were above the prescribed limit which poses a significant health risk to bivalve consumers. To protect consumer food safety, depuration experiments were conducted at varying temperatures, salinities and body-sizes. The clams, mussels and oysters depurated under the room temperature depuration system (RTDS) showed a better reduction of heavy metals compared with low-temperature depuration system (LTDS). ANOVA showed clams and mussels depurated at RTDS significantly (p 0.05) reduced the heavy metals than LTDS. However, there was no significant (p 0.05) difference in oysters between RTDS and LTDS. Further, clams and mussels depurated at low salinity (15-psμ) showed high resistance against Pb reduction. But, all the heavy metals, particularly, Pb, Fe, Zn and Cu were effectively removed at higher salinity depuration (25-psμ and 35-psμ). Moreover, irrespective of the body-size of clams, mussels and oysters used for depuration, a significant (p 0.05) reduction in all metals (Ni, Co, Fe, Mn, Zn, Pb and Cu) was observed. Relatively, the medium-size bivalves showed higher reductions compared to small-size bivalves. Based on the experiments conducted, we recommend 48 h depuration using the static system under room temperature (30 ± 1 °C) with a salinity range of (25-35 psμ) using medium-size bivalves (clam30 mm; mussel45 mm, and oyster65 mm length) as optimum conditions for producing safe bivalves for consumption in the tropics.

Rapid industrialisation and coastal developmental activities have caused considerable damages to the coastal habitats and their associated fauna and flora of Tuticorin coast. The status of the physicochemical and biological aspects indicating the healthiness of selected seagrass and mangrove habitats of Tuticorin coast was studied during 2013-15. The water and sediment quality parameters and the benthic in-faunal constituents were assessed monthly adopting the standard procedures. Our study indicated that the mangrove habitat was profoundly impacted due to the influence of high saline effluents from neighbouring salt pans. The mean values of most of the water quality parameters like salinity (37.87±1.86ppt); chlorophyll-a (8.2±2.95mg.m-3); TSS (529.6±47.13mg.L-1) ammonia (0.12±0.02µg.L-1); nitrite (1.96±0.92µg.L-1); phosphate (8.67±2.58µg.L-1) were reported abnormal from the mangrove habitats. The seagrass habitat was impacted mainly by the activities of the neighbouring port, causing comparatively higher total suspended solids and dissolved solids in the water. Parameters like, DO, salinity, chlorophyll, TSS, NH3 , NO2 , SiO3 in seawater and coarse and fine sand proportions of sediments were significantly varied between habitats (p

Cage culture of finfish is becoming a popular alternate source of livelihood in Vembanad Lake in Kerala, India. A study was conducted during November to December, 2016 to assess the socio-economic status of the farmers practicing cage culture in Kerala and the resultant economic benefits. Data on demographic features, farming activities, specific culture and farm management practices, economics and problems related to cage farming were collected from 36 active farmers of the Ernakulam District. Etroplus suratensis (Pearl spot), Lates calcarifer (Asian sea bass), and Genetically Improved Farm Tilapia (GIFT) were the major species cultured

Hydrographic conditions such as water level, velocity, adequate water circulation and stratifications have a strong influence on the management of fish cage culture in the estuarine environment. In this study, a 3D hydrodynamic model was used to identify the areas of the mixed and stratified water column and to use this in conjunction with particle tracking models for appropriate site selection for cage culture. A Lagrangian method was used to simulate the instantaneous release of "particles" emulating discharge from fish cages to show the behaviour of waste in terms of water circulation and water exchange. Model simulation at Pizhala cage farm revealed that desirable water exchange is experienced in the monsoon and pre-monsoon period. There have existed strong spring-neap variability in the water level with an average range of 0.7 m with a speed of < 0.12 m/s in pre-monsoon and < 0.24 m/s in monsoon. This consistent flow patterns in the Pizhala region helps in the replenishment of oxygenated water and removal of waste produced beneath the cages, and it is corroborated by the Lagrangian particle transport model experiment coupled with Finite Volume Community Ocean Model (FVCOM) in the study.

Restoration of Rhizophora mucronata stand in the Gurupura Estuary resulted in improved water and sediment quality parameters. Monthly monitoring from 2011 to 2016 indicates that the restored mangroves grew to a height of 61.49 ± 5.76 cm. Principal component analysis (PCA) showed that increased duration of salinity in the estuary aided the growth of barnacles in planted mangroves which reduced survival by 10%. The United States Environmental Protection Agency ratings revealed that natural mangrove site in Shambavi River exhibit the maximum good water quality rating though dissolved inorganic phosphorous was rated highest due to non-point pollution sources. The pH, salinity, dissolved oxygen, silicate, phosphate, ammonia, and rainfall demonstrated significant seasonal differences (P 0.001). Mangrove roots and biomes aided in accumulation of clay and significant difference (P 0.001) was observed yearly. Land use management, efficient waste disposal system along with restoration of diverse mangroves can improve the water quality of estuarine ecosystem.

Recurrent jellyfish blooms and their impacts on ecosystem deliverables of coastal habitats have become a major ecological concern. In view of this, repercussions of a surge in the jellyfish population on the plankton community were studied in Cochin estuary (CE), the largest tropical estuary along the southwest coast of India. Evaluation of hydrographic attributes and plankton community of the CE during early and late pre-monsoon revealed a marked disparity in its hydrography which favoured an increase in jellyfish abundances during late pre-monsoon, eliciting distinct impacts on the plankton community. The escalation in the jellyfish abundance and their subsequent predation on the crustacean plankton released the phytoplankton community from the grazing pressure resulting in a trophic cascade in the planktonic food web. The indiscriminate feeding of jellyfishes on the ichthyoplankton, decapod larvae, and Copepoda, the primary diet component of forage fishes evoked a potent threat to the fishery potential of CE.

Epizootic ulcerative syndrome (EUS), primarily caused by the water moldAphanomyces invadans,is an OIE-notifiable disease, having potential impacts on fisheries. We report EUS epizootics among estuarine fishes of Kerala, India, during 2018, under post-flood conditions 3 decades after its primary outbreak. Six fish species (Mugil cephalus,Platycephalussp.,Scatophagus argus, Ariussp.,Planiliza macrolepisandEpinephelus malabaricus) were infected, including the first confirmed natural case inE. malabaricusandP. macrolepis. Salinity, surface temperature, dissolved oxygen and pH of resident water during the epizootic were Aeromonas veronii,Shewanella putrefaciens,Vibrio vulnificusandV. parahaemolyticus) in tissues of affected fish indicates that EUS-infected fish may pose a public health hazard if not handled properly. Lack of clinical evidence in the region during the last 3 decades, a high number of affected fishes, including 2 new fish species, the severity of skin lesions and very low water salinity (A. invadans. Phylogenetic analysis based on the internal transcribed spacer region of the rRNA gene showed that the same clone of pathogen has spread across different continents regardless of fish species and ecotypes (fresh/estuarine environments). Altogether, the present study provides baseline data which can be applied in EUS management strategies within brackish-water ecosystems. We recommend strict surveillance and development of sound biosecurity measures against the disease.

The stake net fishery of Panambukad in the main channel area of Vemband Lake, Kerala was studied during the first fortnight of August 2014. The observations indicated that the average catch including the marine debris ranged from 1.04 to 2.04 kg net-1 day-1 with an average of 1.34 kg net-1 day-1. The percentage of marine debris in the stake nets ranged from 42.68 to 73.4%. Plastic items formed 97% by weight and 99% by number of the total marine litter. The observed litter stuff was categorized as per UNEP system of classification of marine litter where, they are first identified based on their material composition (litter codeeg. PL) and then by their form (RL classes). Items found in the collection included plastic covers (PL07, RL15), metal cap (ME02, RL01), plastic bottle (PL02, RL02), fishing net (PL20, RL05), plastic cup and food containers (PL06, RL09), thermocol (FP 04, RL13), rubber sheet (RB05, RL28), plastic sacks (PL24, RL23), diaper (OT02, RL18) etc. Among them, plastic covers were most dominant and their average number and weight net-1 day-1 was 28 nos and 985 g respectively. The study also showed positive signs of decline in plastic bottles as a major litter item due to its targeted collection by recycling industry within a span of three years. In a survey conducted among the stake net fishers, there was consensus on the view that plastic litter in Vembanad Lake has increased during the last 10 years and this has affected the resources and the fishery. The stakeholders also expressed their willingness to pay for restoration of the fishery resources of the lake. The study recommends the need to establish proper solid waste management systems in coastal villages, to reduce the use of plastics, and provide facilities for disposal of litter which gets collected in stake nets and to increase the awareness among the public about the impacts of marine debris on ecosystem and resources.

The heterocystous cyanobacterium Richelia intracellularis Schmidt 1901 is well known for its capability to fix atmospheric nitrogen (N2) in oligotrophic waters. Symbiotic associations of Richelia intracellularis with the diatoms Rhizosolenia hebetata, Rhizosolenia clevei, Rhizosolenia cylindrus and Hemiaulus membranaceus is reported for the first time from the coastal waters of South Andaman, India. In these the symbiotic associations, variations were observed in the number of vegetative cells, trichomes, and the shape of the heterocysts. The highest number of trichomes was observed in Rhizosolenia clevei (14) per host. The trichomes consisted of 9–10 vegetative cells and a spherical heterocyst that was orientiated toward one end of the host diatom cell. In Rhizosolenia hebetata, three trichomes of Richelia intracellularis were present, one trichome at one end with 7–8 vegetative cells and two trichomes at the other end. In Rhizosolenia cylindrus, two trichomes of Richelia were observed, with a spherical heterocyst and 5–6 vegetative cells. An association between Hemiaulus membranaceus and Richelia intracellularis was also observed but with less frequency. Trichomes were observed in the centre of the diatom. By using the cell-specific rates, the amount of new N provided by the Diatom-Diazotrophic Associations was estimated. This is the first record of a symbiotic association of Richelia in diatoms from Andaman coastal waters.

Experimental trawl survey cruises covering twelve stations around Lakshadweep archipelago, in southeastern Arabian Sea, caught eleven individuals of the uncommon squid, Histioteuthis miranda. This is the first record from waters around India. These specimens were caught in midwater trawl net operated from research vessel “FV Silver Pompano” at a depth of 200 m during night. Detailed morphometric and meristic measurements and molecular taxonomic studies confirmed the species identity. Assuming daily deposition of statolith rings, analysis of increments revealed that the species had slow growth reaching 24 mm dorsal mantle length (DML) at the age of 83 days with an average daily growth rate of 0.28 mm DML/day. A juvenile specimen with 13 mm DML had 68 increments with growth rate of 0.19 mm DML/day. Aberrant microstructure (additional nucleus and rings) were found in the statolith of a 24 mm DML specimen.

Depuration of naturally contaminated farmed edible oyster Crassostrea madrasensis was evaluated using fill and draw depuration system (FDDS) and flow-through depuration system (FTDS) to ensure food safety in oyster consumption. Depuration conducted at room temperature with seawater salinity ranges 30–35 psu and pH of 7.5–8.0. Prior to depuration, the levels of faecal indicator bacteria (

The influence of salinity on growth, survival and byssal fibre attachment of the blacklip pearl oyster, Pinctada margaritifera spat was assessed. P. margaritifera enjoys a coastal distribution in the intertidal reef flats of Andaman and Nicobar Islands, with maximum density at 5 -10 m depth, where drastic changes in environmental parameters such as salinity, temperature and turbidity occur. Spat showed comparatively good growth in terms of instantaneous growth rates (IGRs) of dorso-ventral measurement (DVM), antero-posterior measurement (APM) and total weight (TWT) in a wide range of test salinities from 19 to 37 psu; IGRs were drastically decreased in spat reared at lower and higher salinities outside of this range. The highlight of the present study was better growth performance and 100% survival of P. margaritifera spat at lower salinity levels (22-28 psu) than in the ambient salinity (31 psu). The study also showed that sudden exposure to a higher salinity (above 40 psu) will be helpful for detachment of P. margaritifera spat from settlement tanks in the hatchery to facilitate stress-free spat transfer to sea farming systems. This will be useful in adopting the Japanese technique on post-operative culture for producing high quality pearls from P. margaritifera.

The marine waters of Kerala state along the southwest coast of India are among the most productive upwelling regions in the southeastern Arabian Sea. Analyses were made to assess the impact of environmental changes on the marine fish catch using motorized and non-motorized craft operating off the coast. The catch per unit effort (CPUE) of total landings, OBGN (outboard gillnet), OBTN (outboard trawlnet), NM (non-motorized) crafts, as well as the catch of 5 major fish resources Indian mackerel, lesser sardines, Stolephorus spp., scads, and penaeid prawns were obtained. Sea surface temperature (SST), chlorophyll, salinity, rainfall, sea level anomaly, multivariate ENSO index, dipole mode index, local temperature anomaly, degree heating month (DHM), degree cooling month (DCM) and surface currents were used as variables to investigate the relationship between environment and fishery. Principal component analysis was used to select the minimum data set and GAM (Generalized additive model) was used to detect the influence of the environment on the fisheries. The adjusted R2 value of the GAM was 0.68, taking the CPUE of the total landings as the response variable. For the case of the selected fish resources, the adjusted R2 value of the GAM was 0.73 for penaeid prawns, followed by Stolephorus spp. (0.44), scads (0.33), lesser sardines (0.31), and Indian mackerel (0.25). Considering the CPUE as the response variable for the GAM also returned high adjusted R2 values for fishing method (OBGN = 0.59, OBTN = 0.53 and NM = 0.31). SST, chlorophyll, rainfall, salinity, yearly DCM and surface currents all had significant influences on the marine fisheries along the Kerala coast. Lower SST, high salinity and rainfall promote the fisheries of both small pelagics and large pelagic groups like scads. Along with the negative relationship between SST and fishery, the present analyses also indicate a positive relationship with yearly DCM, which clearly indicates that the warming of coastal waters has a negative impact on fisheries along the Kerala coast. From these results, we find that ocean currents can play a crucial role in fish recruitment in the coastal waters of Kerala. Primary production, the key factor for marine fishery production, was found to be controlled by environmental factors like SST and currents. These results point to the vulnerability of the small-scale fisheries sector of the tropical upwelling zone to increasing SST and climate change.

Oysters are commercially cultured from the Ashtamudi Lake in India, and support 12,000 tonnes of bivalve fisheries/year. Oysters and oyster growing waters were sampled from July 2012 to June 2013 for analysis of total coliforms (TC), faecal coliforms (FC), Escherichia coli, faecal Streptococci (FS) and total plate counts (TPC). E. coli MPN values in oyster growing waters were below the threshold limits set by the USFDA and EU during the months of December to April. Seasonally, the highest MPN values for E. coli were obtained during the monsoon season (June–September), and this trend gradually decreased during the post-monsoon (October–January) and pre-monsoon (February–May) periods. E. coli displayed a significant (p

Coral reef environments support a great diversity of benthic organisms, of which zoanthids form an integral part. Studies have been carried out regarding the degradation of coral reefs and changes in community structure under the present dynamics of climatic change. Zoanthids are dominant among the observed fauna in these degrading reef ecosystems. Zoanthids are observed at mid and lower intertidal zones beyond 20 m from highest high tide level. In the present study, distribution patterns of zoanthid species along three coastal villages of Saurashtra coast, Gujarat were studied. Line intercept transect method was performed to assess the zoanthid coverage. A total of seven species of zoanthids were recorded during the survey.Palythoa mutukiformed the abundant species in the area with 45.99% coverage, followed byZoanthus sansibaricuswith 33.67% andZoanthuscf.sansibaricuswith 12.26% coverage. Abiotic parameters (sea surface temperature, salinity, dissolved oxygen, pH) and nutrient data (ammonia, phosphate, total suspended solids and nitrate) were also recorded during sampling to determine their influence on zoanthid colonies. Higher levels of DO were found to favour the growth ofPalythoa mutukiandIsaurus tuberculatus, whereas increased SST was tolerated byPalythoa tuberculosaonly. Ammonia and phosphate were negatively impacting the growth ofPalythoa mutukiandZoanthusspp. The study provides new information on quantitative zoanthid distribution and the dynamic changes exhibited by zoanthids in relation to various environmental parameters. Zoanthids could be looked upon as an adaptive species which may support reef resurgence in degraded reefs under stress from climate change effects.

The sources of microbiological contamination in shellfish harvesting areas in the Ashtamudi and Vembanad estuaries were identified through a sanitary survey. Samples of shellfish and waters were tested for faecal indicator bacteria. Both estuaries receive high levels of contamination from septic tank discharges and areas with high numbers of birds and livestock. An assessment to illustrate the classification status of the harvesting areas indicated that 64% of oyster and 58% of clam samples from Ashtamudi and 54% of mussel samples from Vembanad would comply with the lower class B standard of the EU classification system. Most water results would comply with the faecal coliform standard for 'Prohibited' areas under the US classification system. None of the water samples from Ashtamudi were below the standard for 'Approved' areas. Pollution reduction measures and implementation of a sanitation programme according to international best practice would improve consumer health protection.

Consequences of a catastrophic flood on the habitat quality and the concurrent responses of the bentho-pelagic community were studied in Cochin estuary, a eutrophic estuary along the southwest coast of India. The episodic flood in 2018 led to a marked decline in the dissolved nutrients and heavy metal concentrations in water and sediments of the estuary. The pre-flood phytoplankton abundance dominated by a bloom-forming species Cerataulina bicornis experienced a significant drop after the flood. Contrarily, zooplankton and macrobenthos responded favorably towards the flood-imposed habitat alterations. Higher susceptibility to heavy metal pollution and increased grazing pressure from gelatinous carnivores restricted the abundance of Copepoda, the dominant zooplankton taxon during pre-flood. The lower heavy metal concentration in the sediment after the flood favored higher macrobenthic abundance and diversity with a conspicuous change in the community structure from opportunistic polychaetes, indicators of pollution to molluscans and crustaceans, indicators of the healthy benthic zones.

The seagrass meadows of Sethukarai coast are unique in nature, housing high faunal diversity compared to other coastal areas. A rare live specimen of bandtail scorpionfish Scorpaenopsis neglecta was found near a burrow dug by an alpheid shrimp. Taxonomy, morphometric and meristic characters, adaptive, behavioural and colour-switching physiological camouflage trait of the S. neglecta are elaborated in this communication. Visual in situ documentation of feeding habits of scorpaenids and their preying behaviour, especially that of lionfish Pterois volitans preying on goby fish is presented. Mutualism exhibited by goby fish Amblyeleotris gymnocephala with the alpheid shrimp Alpheus rapax and the importance of habitat protection from anthropogenic activities are also discussed.

This study forms the first attempt to assess the health status, studying parasites and pathologies in wild or natural and farmed or cultured populations of the Indian backwater oyster, Magallana bilineata (= Crassostrea madrasensis Preston, 1916), the mainstay of oyster farming in the country. The Condition index, prevalence of infection, intensity, and seasonal variations in parasites and pathological conditions were studied. Wild oyster population was infected/infested with protozoan (Perkinsus beihaiensis, Nematopsis sp., Sphenophrya sp., and Stegotricha sp.), metazoan (cestodes and crustaceans), and shell (Polydora spp. and Cliona spp.) parasites and pathological conditions (digestive tubule atrophy, ceroid bodies, haemocytic infiltration, tissue necrosis, neoplastic disorders, and prokaryotic inclusions). Farmed population exhibited only a single protozoan (P. beihaiensis), a metazoan (Polydora sp.) infection and two pathological conditions (digestive tubule atrophy and ceroid bodies) in the tissues. The occurrence, prevalence and intensity rates for parasites and pathological conditions were significantly lower in farmed population compared to the wild population at the study site. Prevalence for parasites and pathologies were observed to be higher during dry season. The condition index (CI) values, which indicate the general health status of the oysters, were also significantly higher for the farmed population. The exposure period and the location of oysters in the habitat had a significant influence on the condition index and parasitic load in the population. None of the parasites were OIE listed; however the presence of a potential pathogen (P. beihaiensis) and pathological conditions warrants regular monitoring of the stocks and water quality at the culture site.

is a serious problem occurring in ponds or estuaries where fish culture is practised. A possible solution to this problem is to raise oysters in an integrated culture with fish to improve water clarity and to help remove excess nutrients. In order to determine the effects that cultured oysters have on the environment, an experimental study was performed in the Moothakunnam region of the Vembanad lake in the Ernakulam District during February-November, 2012. The study was performed in four cages (1× 1× 1 m) referred to as treatments T1, T2, T3 and T4. The four treatments used fish ( Etroplus suratensis ) and oysters (Crassostrea madrasensis) in the ratio of 1:0.3, 1:0.5, 1:0.7 and 1:0 respectively. Several parameters were measured and compared between the four treatments, and these included temperature, pH, salinity, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, total suspended solids, ammonia, nitrite, nitrate and orthophosphate. Results showed that the parameters, DO, BOD, COD, TSS, ammonia and orthophosphate varied with different treatments and months. However, the contents of nitrite and nitrate showed variation only with respect to months. The eutrophication index (E) values calculated for the four treatments were 9.45 ± 4.41, 5.25 ± 3.23, 11.32 ± 6.17 and 11.52 ± 5.45 respectively. The lower E value obtained was for T2 which supports the conclusion that oysters can control eutrophication in an integrated aquaculture system. The optimal co-cultivation proportion of fish to oysters obtained from the present study was 1:0.5.

A detailed pathological survey was carried out on the commercially important edible oyster, Crassostrea madrasensis (Preston), from two distinct coastal/brackish water ecosystems of south India. Samples were collected twice a year during wet and dry seasons from 2009 to 2012. Bacterial colonies in the form of prokaryotic inclusions, protozoans (Perkinsus beihaiensis, Nematopsis sp. and ciliates Sphenophrya sp. and Stegotricha sp.), metazoans (trematodes, turbellaria, cestodes and crustaceans) and shell parasites (Polydora spp. and Cliona spp.) along with various pathological conditions (digestive tubule atrophy, ceroid bodies, haemocytic infiltration, tissue necrosis and neoplastic disorders) were observed in C. madrasensis collected from two sites. Intensity, spatial and seasonal variations in infection prevalence and pathological effects on the host were studied. The protozoan parasite, P. beihaiensis; shell parasite, Polydora spp. and pathological condition, digestive gland atrophy were most prevalent in occurrence. High-intensity infections with P. beihaiensis, larval trematodes and Polydora spp. were found to cause significant impact on host physiology. All other parasites were observed with low mean prevalence and intensity. Karapad in Tuticorin bay, the site reported with marked pollution levels, exhibited higher number of parasitic taxa and high mean prevalence and intensity for pathological conditions.

The Indian marine environment, consisting of adjoining coastal areas and the exclusive economic zone (EEZ), directly sustains useful habitats and supports the livelihood of 3.9 million fishers. The average marine fisheries production of the country during the period 2010–2015 has been estimated at 3.36 million tons consisting of approximately 667 different fish species inhabiting the neritic zone that depend on the productivity of marine ecosystem and in turn are influenced by the reactive nitrogen (Nr) available in the system. During the past three decades significant advances have been made in industry, agriculture, fisheries, and other sectors and these have resulted in the release of Nr influencing the N-cycle in the coastal and marine ecosystems. Nitrogen assessment of the surface waters carried out in the EEZ and adjoining areas during the years 1998–2007 revealed that the annual concentrations (μM) of NO 2 ranged from 0 to 0.4, 0 to 0.6, and 0 to 0.7 in the Arabian Sea, Bay of Bengal, and Andaman Sea, respectively. The corresponding values for NO 3 (μM) were 0–2.5, 0–3, and 0–3.5, respectively. Nr transfer to the marine environment also influences eutrophication, algal blooms, changes in the ecological processes and habitats affecting ecosystem health. In this chapter, the present status of Nr assessment in the coastal and marine ecosystems in the country has been reviewed, its interaction with marine aquaculture listed, and the need for future research thrusts, especially on prediction of the extent and direction of impacts of altered nitrogen fluxes on the coastal and marine resources including diversity of faunal and floral community structure is discussed.

The efficiency of depuration of the Indian backwater oyster Crassostrea madrasensis (Preston, 1916) using the fill-draw method (static method) with high-loading density was evaluated in this study. Depuration experiments were conducted with cartridge-filtered and UV-treated seawater at a salinity of 30.3‰, a pH of 8.3, and a temperature of 29.5°C. The oysters located in trays on the surface and on the bottom were compared for microbial loads. Samples were taken at 0 h, 8 h, 16 h, 24 h, 36 h, and 48 h of depuration. The results showed that in winter monsoon-sampled nondepurated oysters, the most probable number of fecal coliforms and Escherichia coli were greater than the limits according to NSSP and European Union regulations. The surface held oysters took 24 h to reduce the coliforms and E. coli levels to below safe limits whereas for bottom held oysters it took 48 h. The species Salmonella was never detected in the oysters sampled, whereas Vibrio spp. were present in the nondepurated oysters an...

Global bleaching event of 2016 has caused large scale degradation of coral communities at many reef systems. It is inevitable to understand the post bleaching community changes in the benthic system to estimate the recovery and resilience potential of the reef system. Here, we investigated the response of the benthic communities to the bleaching events across the selected reef sites of Mandapam group of islands and Palk Bay reef sites at May 2017, one year post-bleaching. Benthic surveys were conducted during the March–May months of 2016 (bleaching period) and May 2017 (post bleaching). Bleaching was evident in all surveyed reef sites along Mandapam group of islands and Palk Bay during 2016 with the maximum bleaching of 43 ± 2% in Poomarichan island coinciding with the maximum positive SST anomaly recorded in April 2016. Post bleaching survey revealed reduction of live coral cover followed with an increase in macroalgae cover. Maximum reduction of live coral cover was observed from Olakuda reef site (-2%), while maximum macroalgae outgrowth was observed from Kurusadai island (2.75%). Our results show reduced recovery capability of coral communities in Mandapam group of islands and necessitate the need for continuous observations to assess the recovery capability of corals of this region.

The survival of the tropical edible oyster (Crassostrea madrasensis) was examined under the condition of ice-storage in a rectangular thermocol-transport box for a period of 48 h. A total of 100 two-year old farmed oysters were used for the experimental transportation. Inside the box, all oysters were arranged in four layers covered with wet-gunny bags and lined on the top and bottom with ice. Surface and bottom temperature of the transport box varied from 9.7 to 25.2˚ C and 9.7 to 28.4˚ C respectively during the 48 h exposure. The patterns of changing temperature at both surface and bottom were found to be different. Recoveries of the oysters at every two hours till 48h were monitored by taking random samples from the box. All the oysters recovered within 1 h of being placed back into seawater and there was close to 100% recovery within 2 hours. Survival was more than 90% after 8 days of the experiment.

The pearl oyster, Pinctada fucata (Gould), is a commercially important bivalve distributed in the Gulf of Mannar along the southeast coast of India and had supported a healthy, traditional pearl fishery until the 1950s. But, during the past few decades, the natural pearl oyster beds in the Gulf of Mannar have showed a sharp decline leading to the closure of the traditional pearl fishery and was presumed to be due to overexploitation and pollution. Except for a preliminary report on Perkinsus marinus infection in Crassostrea madrasensis in 1988, no incidence of perkinsosis or other Office International des Epizooties (OIE) notified protozoan infections in mollusks has been reported from the Indian subcontinent and the pathogen profile of P. fucata from the region has not been studied. Since Perkinsus spp. is known to have destroyed many oyster beds worldwide, the present study was taken up to screen the pearl oyster population along the Gulf of Mannar coast for the presence of Perkinsus spp. and examine the probable role of Perkinsus in the decline of the natural pearl oyster beds. Thirty individuals of adult P. fucata were collected from wild populations at three different locations in the Gulf of Mannar and 10 individuals from a pearl farm containing hatchery reared stock at Tuticorin. The tissue samples were subjected to Ray's fluid thioglycollate medium (RFTM) culture, histology and polymerase chain reaction (PCR). All the samples showed enlarged blue-black hypnospores in RFTM, indicating the presence of Perkinsus spp. Perkinsus-like organisms were also observed in the histological preparations. Screening of the tissues using the Perkinsus genus specific internal transcribed spacer (ITS) 85 and ITS 750 primers, amplified the product specific to the genus Perkinsus (ca. 700 base pairs) and further, the specific identity of the parasite was determined by sequencing the amplified PCR products which showed 99% identity to Perkinsus olseni. The pairwise genetic distance values and phylogenetic analysis also confirm that the present isolate from P. fucata is a member of the P. olseni clade. This preliminary investigation suggests a possibility that perkinsosis could be one of the major reasons for the decline of the P. fucata beds in the Gulf of Mannar over a period of time. This forms the first report on the existence of P. olseni, an OIE listed pathogen in the wild and cultured P. fucata populations from the Indian subcontinent.

The technology diffusion process of green mussel, Perna viridis, farming in Kerala, India, was studied by analyzing the adoption pattern, socioeconomic profile of mussel farmers, differences in farming methods, profit variations, development of trade and downstream industries, and the social factors responsible for the growth of this new industry. The farming practice has been adopted by villagers from 1996, and because of its rapid growth, India has risen to one among the top 10 farmed mussel producing nations in Asia, with an annual production of 10,060 tonnes, worth $US1.79 million at farm-gate level. Three types of farm ownerships were observed: individual ownership (IND), family ownership (FAM), and ownerships by self-help groups (SHG). The adoption curves are such that there were only a few adopters initially followed by an increasing rate of adoption in the subsequent years because of the demonstration effect. The study indicated the deep-rooted ‘‘risk aversion’’ attitude widely prevalent among technology adopters. Age could not be significantly related to technology adoption, while education and occupation of the respondents significantly (P , 0.05) influenced the technology adoption process. The biggest outcome of mussel farming in Kerala was the empowerment of women with 87% of the SHG farms owned by women. The successful diffusion of mussel farming is the result of a combination of factors, chiefly, the availability of suitable water bodies; high rate of education; proximity of mussel markets and high degree of mussel consumption in the area; and a unique synergy between technology developers, promoters, and credit advancers. This development scenario can work as a role model for developing nations.

The black-lipped pearl oyster, Pinctada margaritifera, is sporadically distributed in the Indo-Pacific region, where they have been traditionally used for food, ornaments, jewelry, tools, and more recently for the production of black pearls (Lane et al. 2003). During the past two decades, black pearl farming programs have been initiated by several nations and are now at various levels of production

The Indian pearl oyster Pinctada fucata (Gould) is typically capable of producing pearls of 3–5 mm diameter. The feasibility of production of pearls similar to Akoya pearls of 6–8 mm diameter was studied from the southwest coast of India. Along with this, mortality and retention rates of implanted oysters, rate of nacre production, thickness of nacre deposited, quality and type of pearls produced and effect of hydrographic variations on the mortality of implanted oysters were also studied. A total of 706 oysters were implanted, 311 with 5 mm, 395 with 6 mm nuclei and stocked in 30 cages for a period of 317 days. The mortality rates were highest, 0.173±0.22 for the 6 mm nucleus implanted oysters followed by 5 mm nucleus implanted oysters at 0.107±0.025 during the first 30 days after implantation. These rates were significantly different (Pb0.05) from the mortality rate of the control oysters (0.042±0.04). The retention rates based on the surviving oysters, ranged from 33 to 61% (average 45.9 for 5 mm) and 31 to 60% (average 48.9% for 6 mm). The nacre deposition rates on the nuclei were found to be 4.0±1.0 μm day −1 and 3.0±1.0 μm day −1 for 6 and 5 mm nuclei respectively. Of the total 131 pearls obtained, 27.6% were A-grade, 31.3% B-grade, 19.8% C-grade, 7.6% baroques and 13.7% rejects or trash. The total suspended solids (TSS) in the water were found to be positively correlated (Pb0.05) with the monthly mortality rate of the implanted oysters. The study showed that it was possible to obtain relatively thick nacre within a short period of 10 months, the deposition rate being about 9 times higher than that observed in Japanese waters and 2.2 to 2.3 times more than that along the Indian southeast coast.

Comparative studies were made on the growth and biometric relationships of the pearl oyster Pinctada fucata (Gould) Tuticorin stock at (Tuticorin (TST) ^ parent stock) transplanted from the Tuticorin Bay (8.71N;78.21E) in the Gulf of Mannar along the Indian southeast coast to Kollam Bay (8.81N; 76.51E) in the Arabian Sea along the Indian southwest coast (Tuticorin stock at Kollam (TSK) ^ transplanted stock). At the time of transplantation, Kollam Bay did not have a native stock, however, within a year, the transplanted stock spawned and oyster spats were collected from within the farm (Kollam stock (KS) ^ progeny stock). The growth in dorso-ventral measurement and total weight in Kollam Bay was 1.4^1.6 times and 3.1to 6.8 times respectively greater than that observed at Tuticorin. Furthermore, at Kollam Bay, the thickness observed at the end of ¢rst year was similar to that obtained at the end of second year in Tuticorin. Both the TSK and KS had signi¢cantly higher instantaneous growth rates (IGR) than TST. All the stocks displayed signi¢cantly diierent biometric relationships. The increased growth in Kollam Bay is attributed to the almost double productivity in the Arabian Sea compared with the Bay of Bengal. It is concluded that in the case of P. fucata , the site and its interaction with environment are important determinants of growth and shell dimensions. The present study clearly indicates that the environmental conditions prevailing along the southeast Arabian Sea are congenial for the growth, gametogenesis, spawning and settlement of P. fucata larvae. In spite of strong monsoonal in£uences in the hydrology of Kollam Bay, the growth and reproduction of P. fucata stocks indicates its relative hardiness and ability to adapt to a changed environment.

Viewlogic's Chronologic VCS/sup TM/ is an industry standard simulator for Verilog HDL. This paper describes incremental compilation in VCS. Incremental compilation is a general compiler optimization technique that improves turnaround time of the typical develop-test-debug-edit cycle of software development. It provides the user with the ability to make small changes to a design, while guaranteeing that the re-compilation time will be proportional to the change in the design. The compiled code simulation environment in Verilog poses unique challenges and opportunities for incremental compilation. The paper describes the issues in determining whether a design unit is unchanged since the preview compilation, or whether it needs to be re-compiled. It also addresses the specifics of incremental compilation in single-user and multiple-user environments. Finally, results are presented that demonstrate the benefits of incremental compilation in VCS.