Inventory of fishery resources using participatory research approach in Mandovi Estuary in Central western coast of India

Aim: The fisheries resources of Mandovi Estuary, along the central west coast of India were analysed for taxonomic, functional, feeding and population aspects and also to record and prepare an inventory on fish and shellfish species. Methodology: Finfish and shellfish taxa were monitored for four years (2016 to 2020) through surveys in small and regional markets, fishermen surveys, fishing gear samplings, telephonic interviews and photographs. Results: A total of 318 taxa are counted comprising of 169 (53.1%) demersal, 71 (22.3%) pelagic fish, 37 (11.6%), molluscan and 41 (12.9%) crustacean species. The community was dominated by marine immigrants and the freshwater types contributed least to the composition. In the inventory, majority of the resources were of commercial value and this category contributed 70% of total documented species. Even though detailed analyses were required, nearly 2% of the fauna appeared to be endemic to the region. Further, more than 30% species listed were data deficient. Out of 318 species, 10% were unknown in the Mandovi estuary. Interpretation: This data set comprehensively documents the finfish and shellfish diversity of Mandovi estuary from 2016 to 2020. The type of fish assemblage is briefly discussed focusing on the management of these resources in the estuary.

Chemoautotrophy at the Expense of Thiosulphate: A Supplementary Nutritional Source to the Mangrove Clam-Polymesoda Erosa

Chemolithoautotrophy is a primordial process, where chemical energy converts inorganic carbon to organic. The prevalence of chemosynthesis was examined in the mangrove clam, Polymesoda erosa, and the ambient sediment at Chorao Island, Mandovi estuary, Goa. The sediment system is reducing, organically rich, high in electron donors, acceptors, and inorganic carbon. This clam thrives by immersing 75-90% of its body in sulfidic sediments. Hence, it is hypothesized that it could have an adaptive mechanism like microbially mediated utilization of reduced sulfur compound, S2O32- (model compound) coupled to inorganic carbon uptake. During spawning, maximum carbonate uptake rates of 449 and 594 nmole C g dry wt-1 h-1 were recorded in the gill and foot, respectively. Next generation sequencing revealed that Thiothrix and other sulfur oxidizers gathered from ambient sediment were present in gill, mantle and foot in the ratio 1:3:14 and 1:5:6, respectively. It is inferred that the clam and these associated bacteria could make an important contribution to chemosynthetic carbon fixation. The process could serve as an essential supplementary nutritional source especially during the physiologically feeble spawning phase. To the best of our knowledge, this is the first report of chemolithoautotrophic process in P. erosa of the family Cyrenidae.

Variations of Colored Dissolved Organic Matter in the Mandovi Estuary, Goa, During Spring Inter-Monsoon: A Comparison With COVID-19 Outbreak Imposed Lockdown Period

Colored dissolved organic matter (CDOM) is one of the important fractions of dissolved organic matter (DOM) that controls the availability of light in water and plays a crucial role in the cycling of carbon. High CDOM absorption in the Mandovi Estuary (Goa) during spring inter-monsoon (SIM) is largely driven by both in-situ production and anthropogenic activities. Here we have presented the CDOM variation in the estuary during SIM of 2014–2018 and compared it with that of 2020 when the COVID-19 outbreak imposed lockdown was implemented. During 2020, low CDOM absorption was observed at the mid-stream of the estuary as compared to the previous years, which could be attributed to low autochthonous production and less input from anthropogenic activities. On the other hand, high CDOM observed at the mouth during 2020 is linked to autochthonous production, as seen from the high concentrations of chlorophyll a. High CDOM in the upstream region could be due to both autochthonous production and terrestrially derived organic matter. Sentinel-2 satellite data was also used to look at the variations of CDOM in the study region which is consistent with in-situ observations. Apart from this, the concentration of nutrients (NO3–, NH4+, and SiO44–) in 2020 was also low compared to the previous reports. Hence, our study clearly showed the impact of anthropogenic activities on CDOM build-up and nutrients, as the COVID-19 imposed lockdown drastically controlled such activities in the estuary.

Halomonas Venusta Mediated Detoxification and Biotransformation of Selenite Into Selenium Nanoparticles Exhibiting Various Biomedical Applications

Marine environment is in constant threat due to anthropogenic activities which are involved in disturbing the aquatic flora and fauna due to accumulation of toxic metals and metalloids. The current study involves the use of microbial remediation strategy for reduction of toxic sodium selenite (Na2SeO3) into less toxic elemental Se (Se0) with concurrent synthesis of Se nanoparticles (SeNPs) possessing several biomedical potential. Selenite reducing bacterial strain isolated from Mandovi estuary of Goa, India was identified as Halomonas venusta based on 16S rRNA gene sequence analysis and designated as strain GUSDM4. It's maximum tolerance level for Na2SeO3 was 100 mM. The 2, 3-diaminonaphthalene based spectroscopic analysis clearly demonstrated 93% reduction of 4 mM Na2SeO3 to Se0 during late stationary growth phase of Halomonas venusta. Biosynthesis of SeNPs commenced within 4 h during log phase which was clearly evident from red colour in the growth medium and a characteristic peak at 265 nm revealed by UV-Vis spectrophotometry. The intracellular synthesis of SeNPs was confirmed by transmission electron microscopy (TEM) of these bacterial cells. Characterization of SeNPs by X-ray crystallography, TEM and energy dispersive X-ray analysis clearly demonstrated spherical SeNPs of 20-80 nm diameter with hexagonal crystal lattice. These SeNPs at 50 µg/mL exhibited 90% free radical scavenging activity and also demonstrated anti-biofilm activity at 20 µg/mL against common human pathogens which was evident by SEM analysis. These SeNPs interestingly revealed excellent dose-dependent and selective anti-proliferative activity against A549 cancer cell line and mosquito larvicidal activity against Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi. Therefore, these studies have demonstrated amazing potential of marine bacterium, Halomonas venusta in bioremediation along with biosynthesis of SeNPs and their applications as free radical scavenger, anti-biofilm, chemo-therapeutic and larvicidal agents which is the first report of its kind.

Biofouling Community Structure in a Tropical Estuary of Goa on the West Coast of India

Biofouling community structure was studied in a tropical monsoon-influenced Mandovi estuary in Goa, west coast of India. Monthly, seasonal and yearly observations on biofouling on polyvinyl chloride (PVC) panels immersed at subsurface water level were recorded and photographed from May 2012 to September 2013. The barnacle Balanus amphitrite was the dominant fouling organism followed by calcareous polychaetes. The settlement and recruitment of barnacles took place year-round, with the exception of July 2012 and June 2013 (monsoon months). However, their peak abundance was observed during the later months of monsoon (August and September). Polychaetes were dominant during late post-monsoon and pre-monsoon months (December 2012 to April 2013). Silt and slime were observed throughout the observation period. Comparing the fouling pressure of barnacles in the two monsoon seasons (2012 and 2013), fouling was more intense during the monsoon of 2013, indicating an inter-annual variation in the fouling community.