Influence of environmental heterogeneity on the distribution of micro-zooplankton community along the tropical coastal waters.

This study mainly focused on the water quality variability and distribution of micro-zooplankton (MZP) along the coastal waters of Tamil Nadu. Dendrogram analysis using water quality data categorized the study area into three regions: North (Chennai), Central (Puducherry), and South (Karaikal). The MZP consists of 40 ciliates and 8 dinoflagellates, with spirotrichea (52.4 %) significantly dominant, followed by dinophyceae (21.1 %), phyllopharyngea (14.7 %), and others (11.8 %). Paracyrtophoron tropicum, a new report in the coastal waters of India, was identified by comparing its molecular phylogeny (18S rRNA accession no: MT500569) to previously reported species. Statistical analysis revealed a positive correlation between P. tropicum abundance and water temperature, PO4, SiO4, TP, Chl-a, and Trichodesmium erythraeum, suggesting that they might not directly control the growth of P. tropicum but indirectly influence it via food availability, i.e., T. erythraeum. However, to understand these species interactions and ecological pathways, further long-term monitoring studies are required.

Microbial community structure and exploration of bioremediation enzymes: functional metagenomics insight into Arabian Sea sediments.

Deep-sea sediments provide important information on oceanic biogeochemical processes mediated by the microbiome and their functional roles which could be unravelled using genomic tools. The present study aimed to delineate microbial taxonomic and functional profiles from Arabian Sea sediment samples through whole metagenome sequencing using Nanopore technology. Arabian Sea is considered as a major microbial reservoir with significant bio-prospecting potential which needs to be explored extensively using recent advances in genomics. Assembly, co-assembly, and binning methods were used to predict Metagenome Assembled Genomes (MAGs) which were further characterized by their completeness and heterogeneity. Nanopore sequencing of Arabian Sea sediment samples generated around 1.73 tera basepairs of data. Proteobacteria (78.32%) was found to be the most dominant phylum followed by Bacteroidetes (9.55%) and Actinobacteria (2.14%) in the sediment metagenome. Further, 35 MAGs from assembled and 38 MAGs of co-assembled reads were generated from long-read sequence dataset with major representations from the genera Marinobacter, Kangiella, and Porticoccus. RemeDB analysis revealed a high representation of pollutant-degrading enzymes involved in hydrocarbon, plastic and dye degradation. Validation of enzymes with long nanopore reads using BlastX resulted in better characterization of complete gene signatures involved in hydrocarbon (6-monooxygenase and 4-hydroxyacetophenone monooxygenase) and dye degradation (Arylsulfatase). Enhancing the cultivability of deep-sea microbes predicted from the uncultured WGS approaches by I-tip method resulted in isolation of facultative extremophiles. This study presents a comprehensive insight into the taxonomic and functional profiles of Arabian Sea sediments, indicating a potential hotspot for bioprospection.

Factors regulating phytoplankton biomass along the Indian coast: elucidation with long-term data.

Long-term variations in phytoplankton biomass from nine coastal states along the Indian coast were studied and co-related with biotic and abiotic factors. Surface water temperature, dissolved inorganic nutrients (nitrogen and phosphorous), and plankton (phytoplankton and zooplankton) biomass data were collected between 1992 and 2015. Linear regression analysis showed a considerable increase in dissolved inorganic nutrients. A substantial increase in the frequency and intensity of phytoplankton blooms (> 3 mg/m3) was observed along the Indian coast. The considerable increase in dissolved inorganic nutrient concentrations could be the major reason for an increase in phytoplankton bloom occurrences. Availability of light and periodicity in zooplankton population were also regulating phytoplankton biomass. Our results revealed that multiple factors are influencing phytoplankton biomass along the Indian coast; particularly, the increase in nutrient concentrations is promoting plankton biomass. Moreover, significant increase in zooplankton biomass can have substantial impact on the biogeochemical cycling and energy transfer to higher trophic levels.

Environmental gradients along the tropical coast drive plankton biomass and alter food web interactions.

Traditionally, the Bay of Bengal is considered as a less productive basin when compared with the neighbouring Arabian Sea. However, limited information is available for a comparative study between these two basins on plankton with relation to environmental properties of inshore waters. In order to understand the spatial variability in plankton biomass along tropical coastal waters, the analysis was carried out by collecting samples from 8 locations, covering both east and west coasts of India during dry and wet periods during 2011. Salinity showed considerable seasonal variability along west coast of India (WCI) and east coast of India (ECI); it has highly fluctuated during wet period along ECI. Suspended solids (SSC) and nitrate showed their concentrations along ECI than WCI. Phosphate and silicate exhibited significant seasonality along WCI, whereas insignificant along ECI. Inconsistency in the monsoonal runoff, physical processes and anthropogenic and terrestrial sources seems to be the major driving forces for these parameters. Nearly 3-fold higher phytoplankton biomass was noticed along WCI than ECI due to low SSC in the former region. Though the zooplankton population also followed the same pattern as phytoplankton, the difference between WCI and ECI is lesser than phytoplankton. Zooplankton abundance showed significant relation with phytoplankton and SSC along WCI and ECI, respectively. The present study reveals irrespective of nutrient concentrations; phytoplankton was dominantly constrained by light availability followed by grazers. Moreover, mesozooplankton was supported by not only phytoplankton but also alternative carbon sources; hence, variability in phytoplankton biomass and SSC leads to alterations in trophic interactions.

Composition and distribution of planktonic ciliates with indications to water quality in a shallow hypersaline lagoon (Pulicat Lake, India).

Planktonic ciliate composition and distribution together with physicochemical variables were investigated in a shallow hypersaline lagoon, Pulicat, India, during three seasons, i.e., pre-monsoon (PRM), monsoon (MON), and post-monsoon (POM). The low freshwater inflow, evaporation, and closure of the lake mouth were the main factors for the hypersaline conditions in Pulicat Lake. The average depth and salinity were 1.8 ± 0.12 m (0.8 to 2.8 m) and 35.3 ± 1.68 (12.5 to 61), respectively. A total of 29 ciliate taxa belonging to 18 genera and five classes were identified. Strombidium conicum (24%) was the dominant species followed by Euplotes sp. (10.7%) and Stenosomella sp. (7.02%). Spirotrichea (84%) was the dominant class followed by Oligohymenophorea (9.6%) and Heterotrichea (5.8%). Fabrea salina, a typical species in hypersaline systems, was abundant at locations where the salinity was more than 35. Multivariate analysis using the Bray-Curtis similarity, followed by SIMPROF (Similarity Percentage Analysis), on ciliate abundance data revealed three ciliate assemblages characterizing south, central, and north of the lake at 40% similarity (SIMPROF, cophenetic correlation = 0.622, P = 5%). Both ciliate abundance and chlorophyll-a were positively correlated with salinity. Species richness and evenness were higher in the south sector when compared with those in the other two sectors. Biotic-environmental interaction through canonical correspondence analysis (CCA) inferred that the combined effects of salinity, chlorophyll-a, and nutrient levels are the key factors responsible for the distribution of the ciliate species, suggesting that ciliates can be considered to be potential bioindicators of water quality.

Role of cyanobacteria in agricultural and industrial sectors: an outlook on economically important byproducts.

Cyanobacteria are potential organisms, which are used as food, feed and fuel. The unique characters of cyanobacteria include short generation times, their ubiquitous presence and efficient nitrogen fixing potential. Cyanobacteria are unique organisms performing photosynthesis, bioremediation of wastewater, high biomass and biofuel productions etc. They are also used in the treatment of industrial and domestic wastewaters for the utilization or removal of ammonia, phosphates and other heavy metals (Cr, Pb, Co, Cu, Zn). Biomasses of cyanobacteria are used as biofertilizers for the improvement of nutrient or mineral status and water-holding capacity of the soil. The secondary metabolites of cyanobacteria are used in pharmaceuticals, nutraceutical and chemical industries. In the industrial sector, value-added products from cyanobacteria such as pigments, enzymes and exopolysaccharides are being produced in large scales for biomedical and health applications. Age-old applications of cyanobacteria in agroecosystems as biofertilizers (Anabaena sp; Nostoc sp.) and in industrial sectors as food products (Spirulina) have motivated the researchers to come up with much more specific applications of cyanobacteria both in agricultural and in industrial sectors. Therefore, considering the effectiveness and efficiency of cyanobacteria, the present review has enlisted the standout qualities of cyanobacteria and their potential applications in agricultural and industrial sectors for the benefit of human beings and environment.