Biological Oceanography Division

Patterns of macrofaunal distribution were studied along the western Indian continental margin to distinguish the role of habitat heterogeneity in generating and maintaining community structure. A transect perpendicular to the coast at 14 0 N latitude was selected for seabed sampling. Eight stations were sampled in the depth range 34 m to 2546 m and characterized with respect to macrofaunal composition, abundance, biomass, diversity and feeding type. The sediments in the shelf region (34, 48, 100 m) and upper slope (525 m) were characterized by silty and sandy facies, whereas the mid slope (1001 m), lower slope (1524 m) and basin (2001, 2546 m) consisted of clayey silts. The highest value of sediment chlorophyll-a (Chl-a) and total organic carbon (C org ) were recorded from the mid slope areas. Faunal abundance and biomass increased from the shallow to deeper depths in the shelf region, and decreased in the slope region (525-1001 m) due to the reduced bottom-water oxygen. The community parameters showed an overall increase in both the lower slope and basin areas. A total of 81 macro-invertebrate species belonging to 5 major groups represented the macrofauna of the area. Polychaeta was the major group at all depths. Among polychaete families, species of the Spionidae, particularly Prionospio pinnata, predominated at the oxygen minimum zone (OMZ) core and Cossuridae dominated in the lower part of the OMZ in sediments of the mid slope region (1001 m depth).

New hexactinellid sponges were collected from 2589 m depth on the Carlsberg Ridge in the Indian Ocean during deep-sea dredging. All fragments belong to a new genus and species, Indiella gen. n. ridgenensis sp. n., a representative of the family Aulocalycidae described here. The peculiar features of this sponge, not described earlier for other Aulocalycidae, are: longitudinal strands present in several layers and epirhyses channelization.

Species rich benthic communities have been reported from some seamounts, predominantly from the Atlantic and Pacific Oceans, but the fauna and habitats on Indian Ocean seamounts are still poorly known. This study focuses on two seamounts, a submarine volcano (cratered seamount -CSM) and a non-volcano (SM2) in the Andaman Back-arc Basin (ABB), and the basin itself. The main purpose was to explore and generate regional biodiversity data from summit and flank (upper slope) of the Andaman seamounts for comparison with other seamounts worldwide. We also investigated how substratum types affect the megafaunal community structure along the ABB. Underwater video recordings from TeleVision guided Gripper (TVG) lowerings were used to describe the benthic community structure along the ABB and both seamounts. We found 13 varieties of substratum in the study area. The CSM has hard substratum, such as boulders and cobbles, whereas the SM2 was dominated by cobbles and fine sediment. The highest abundance of megabenthic communities was recorded on the flank of the CSM. Species richness and diversity were higher at the flank of the CSM than other are of ABB. Non-metric multi-dimensional scaling (nMDS) analysis of substratum types showed 50% similarity between the flanks of both seamounts, because both sites have a component of cobbles mixed with fine sediments in their substratum. Further, nMDS of faunal abundance revealed two groups, each restricted to one of the seamounts, suggesting faunal distinctness between them. The sessile fauna corals and poriferans showed a significant positive relation with cobbles and fine sediments substratum, while the mobile categories echinoderms and arthropods showed a significant positive relation with fine sediments only.

The mangrove ecosystem eventually provides an excellent supply of organic detritus matter as food. Benthic organisms continuously restructure or bring about mixing of the sediments by means of locomotion, ingestion, ejection and respiration and recognized as one of the major processes altering the primary structure of sedimentary deposits on millimeter to meter scales. These benthic organisms play an important functional role in estuaries and other aquatic ecosystems. They alter geochemical conditions at the sediment-water interface, promote decomposition and nutrient recycling, and transfer energy to other food web components. So an attempt is made to study vertical distribution of benthic Macrofauna in Mavinhole creek and find out the qualitative and quantitative distribution of biotic community i.e. benthic Macrofauna and some of abiotic factors.

Macrobenthic polychaetes play a significant role in marine benthic food chain. A study was carried out to observe the abundance and diversity of soft bottom macrobenthic polychaetes along the South Indian coast, along with observations on sediment characteristics. The present study indicated an increase in the polychaete diversity as compared to earlier reports. Sixtythree different forms of polychaetes were identified along the coast, which constitute the bulk of the macrobenthic fauna. Thirty-eight species of polychaetes showed higher abundance along the west coast, whereas 25 species showed higher abundance along the east coast. Seabed composition showed a spatial variation in its composition along the coast. Occurrence of Prionospio pinnata and Capitella capitata the deposit feeders and indicators of organic pollution suggesting the sampled area is organically rich. Polychaete abundance was found to be higher along the west coast and was attributed to loose texture of sediment due to high sand and sandy-silt resulting in higher interstitial space for organisms to harbor. Canonical correspondence analysis indicated that majority of polychaete species preferred low organic carbon, sandy silt, or sandy-clay substratum. The lower polychaete abundance at high organic carbon and high silt and clay areas can be attributed to avoidance of organisms to rich organic matter and suboxic levels, being a possible indication that these characteristics adversely affects the polychaete abundance and distribution.

Macrobenthic polychaetes play a significant role in marine benthic food chain. A study was carried out to observe the abundance and diversity of soft bottom macrobenthic polychaetes along the South Indian coast, along with observations on sediment characteristics. The present study indicated an increase in the polychaete diversity as compared to earlier reports. Sixty-three different forms of polychaetes were identified along the coast, which constitute the bulk of the macrobenthic fauna. Thirty-eight species of polychaetes showed higher abundance along the west coast, whereas 25 species showed higher abundance along the east coast. Seabed composition showed a spatial variation in its composition along the coast. Occurrence of Prionospio pinnata and Capitella capitata the deposit feeders and indicators of organic pollution suggesting the sampled area is organically rich. Polychaete abundance was found to be higher along the west coast and was attributed to loose texture of sediment due to high sand and sandy-silt resulting in higher interstitial space for organisms to harbor. Canonical correspondence analysis indicated that majority of polychaete species preferred low organic carbon, sandy silt, or sandy-clay substratum. The lower polychaete abundance at high organic carbon and high silt and clay areas can be attributed to avoidance of organisms to rich organic matter and suboxic levels, being a possible indication that these characteristics adversely affects the polychaete abundance and distribution.

The manner in which fungal endophytes activate host stress response systems is unknown; the occurrence of additional mechanisms involved in symbiotically-conferred stress tolerance in mangrove plants (the primary producers of estuarine food chain) is also an unresolved issue. Here, we report antioxidant potentials of four different mangroves and their endophytic fungi. We elucidated the possible roles of antioxidants in symbiotic association between mangroves and their endophytic fungi. Four different mangrove species and the predominant endophytic fungus Aspergillus fl avus were analyzed using various in vitro assay systems (such as iron chelating capacity, reducing power, and hydroxyl radicals/hydrogen peroxide/l-diphenyl-2-picrylhydrazyl radical scavenging and inhibition of lipid peroxidation using the β-carotene-linoleate model system). In vitro models clearly established the antioxidant potency of extracts of mangrove plants and their respective endophytic fungi, which aids in understanding the mutualistic associations of plant and endophyte against various biotic and abiotic stresses. Re-infection analysis of endophytic A. fl avus in tobacco plants confi rmed the endophytic status of the fungus and its enhancement effect on plant growth.

The infectious hematopoietic necrosis virus (IHNV; Rhabdoviridae, Novirhabdovirus) infects teleost fish, such as salmon and trout, and is responsible for significant losses in the aquaculture industry and in wild fish populations. Although IHNV enters the host through the skin at the base of the fins, the viral adhesion and entry mechanisms are not fully understood. In recent years, evidence has accumulated in support of the key roles played by protein-carbohydrate interactions between host lectins secreted to the extracellular space and virion envelope glycoproteins in modulating viral adhesion and infectivity. In this study, we assessed in vitro the potential role(s) of zebrafish (Danio rerio) proto type galectin-1 (Drgal1-L2) and a chimera galectin-3 (Drgal3-L1) in IHNV adhesion to epithelial cells. Our results suggest that the extracellular Drgal1-L2 and Drgal3

The infectious hematopoietic necrosis virus (IHNV; Rhabdoviridae, Novirhabdovirus) infects teleost fish, such as salmon and trout, and is responsible for significant losses in the aquaculture industry and in wild fish populations. Although IHNV enters the host through the skin at the base of the fins, the viral adhesion and entry mechanisms are not fully understood. In recent years, evidence has accumulated in support of the key roles played by protein-carbohydrate interactions between host lectins secreted to the extracellular space and virion envelope glycoproteins in modulating viral adhesion and infectivity. In this study, we assessed in vitro the potential role(s) of zebrafish (Danio rerio) proto type galectin-1 (Drgal1-L2) and a chimera galectin-3 (Drgal3-L1) in IHNV adhesion to epithelial cells. Our results suggest that the extracellular Drgal1-L2 and Drgal3-L1 interact directly and in a carbohydrate-dependent manner with the IHNV glycosylated envelope and glycans on the epit...

Abstract: The fungi are an exceptionally useful model in elucidating the cell functions under extreme conditions (temperature, salinity, and pH values) and mechanisms underlying adaptation to those extreme environmental conditions. Here, Chaetomium globosum was ...

Techniques for disrupting gene expression are invaluable tools for the analysis of the biological role(s) of a gene product. Because of its genetic tractability and multiple advantages over conventional mammalian models, the zebrafi sh (Danio rerio) is recognized as a powerful system for gaining new insight into diverse aspects of human health and disease. Among the multiple mammalian gene families for which the zebrafi sh has shown promise as an invaluable model for functional studies, the galectins have attracted great interest due to their participation in early development, regulation of immune homeostasis, and recognition of microbial pathogens. Galectins are β-galactosyl-binding lectins with a characteristic sequence motif in their carbohydrate recognition domains (CRDs), which comprise an evolutionary conserved family ubiquitous in eukaryotic taxa. Galectins are emerging as key players in the modulation of many important pathological processes, which include acute and chronic infl ammatory diseases, autoimmunity and cancer, thus making them potential molecular targets for innovative drug discovery. Here, we provide a review of the current methods available for the manipulation of gene expression in the zebrafi sh, with a focus on gene knockdown [morpholino (MO)-derived antisense oligonucleotides] and knockout (CRISPR-Cas) technologies.

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Abstract: The alkaline-tolerant marine-derived fungus Chaetomium globosum was tested for the production of enhanced levels of cellulases and free phenolics under highly alkaline conditions using agro wastes (cotton seed, sugar cane bagasse) as substrates under solid ...

The fungi are an exceptionally useful model in elucidating the cell functions under extreme conditions (temperature, salinity, pH values) and mechanisms underlying adaptation to those extreme environmental conditions. Here, Chaetomium globosum was examined for its adaptation mechanism under alkaline stress using antioxidant properties. The aqueous extracts of C. globosum exhibited different levels of antioxidant activity in all the in vitro tests such as α,α-diphenyl-β-picrylhydrazyl (DPPH •), Hydrogen peroxide, Hydroxyl Radical Scavenging Assay (HRSA), Ferric reducing/antioxidant power (FRAP) assay, Metal chelating assay and β-carotene-linolic acid model system. The antioxidant capacity of marine fungi showed an increase in activity with increase in stress. In addition, the production of intra and extracellular antioxidant enzymes of the fungus at various pH stresses were analyzed and discussed for their possible role in the stress mechanism. The present study elucidates that the scavenging activity is one of the protective mechanisms developed to avoid the deleterious effect of stress. Furthermore, the in vitro assays also clearly indicate that fungal extracts are significant source of natural antioxidant, which might be helpful in preventing the progress of various oxidative stresses.

The alkaline-tolerant marine-derived fungus Chaetomium globosum was tested for the production of enhanced levels of cellulases and free phenolics under highly alkaline conditions using agro wastes (cotton seed, sugar cane bagasse) as substrates under solid state fermentation (SSF) processes. In both the agro wastes used, an increase in cellulases (β-endoglucanase, β-Glucosidase, and β-exoglucanase) production was observed with increase in pH. This enhanced carbohydrate-hydrolyzing enzymes (β-endoglucanase, β-Glucosidase and β-exoglucanase) and thereby enriched the total phenolic release from agro-wastes under SSF conditions of higher pH. A linear correlation was observed between released total phenolic contents of agro-wastes and total antioxidant property. The increased antioxidant activity on free radical scavenging was also observed with the increase in pH. Thus, the present study makes it possible to produce nutraceutical ingredients cost-effectively from agricultural wastes.

In the deep subsurface sediments of the Andaman continental slope, in situ methane generation/oxidation could be coupled to the cycling of Mn, as the fluid flow characterized by high methane and Mn could occur in accretionary wedge sediments by diagenetic and tectonic processes. Laboratory studies on Mn cycling by subsurface sediment microbial communities were therefore undertaken 1) to study, further, possible in situ mechanisms of Mn cycling and 2) to examine how Mn redox reactions might be coupled to methane generation/oxidation. Biotic experiments were conducted with uniformly mixed subsamples amended with 100 µM Mn 2+ in the presence (G +) and absence (G-) of added glucose (55.5 µM). The corresponding abiotic controls included setups poisoned with 15 mM sodium azide. Further, to relate the results of in vitro experiments on Mn cycling, to the methane related processes occurring in the subsurface sediments, pore water concentration of Mn, total cell numbers and the abundance of methanogens, methanotrophs and fermenters were determined. Results of the experiment on Mn cycling showed the immobilization of Mn occurred under oxic conditions and mobilization under suboxic conditions in the absence of added glucose at P ≤ 0.001 with abiotic > biotic. Whereas, in the presence of added glucose, immobilization occurred under both oxic and suboxic conditions at P ≤ 0.001 with biotic > abiotic, oxic > suboxic. The biotic cycling of Mn at 360 mbsf coincided with the total cell numbers (1.53×10 8 cells g-1), increased methane levels (89100 ppm-v) and the abundance of methanogens (1.0×10 3 MPN g-1). Besides, the distribution of aerobic methanotrophs decreased in abundance with depth. Also, the abundance of fermenters (3.5×10 3 cells g-1) at 626.7mbsf coincided with the relatively high concentration of Mn (319.1 µM) in sediment pore water. The results indicate that subsurface sediments harbor microorganisms that partake significantly in the cycling of Mn wherein, the availability of organic carbon dictates the direction in which the reactions occur. Besides, aerobic oxidation of methane and Mn has been reported to occur under reducing conditions. The present findings suggest that Mn redox changes affect the methane oxidation/production rates by serving either as an electron donor and/or an electron acceptor.

Aim: In order to understand the methane biochemistry in the Muthukuda mangrove ecosystem, this study aimed to report on methane production, oxidation, flux, and also to investigate the effect of seasons and environmental variables on methane dynamics. Methodology: Sediment analysis was carried out monthly for a year (2021-2022) from the Muthukuda mangrove, southeast coast of India, which is an unexplored region in terms of methane dynamics. Methane parameters methane concentration, methane oxidation, methane production and methanotrophic enumeration were analysed from the sediment samples collected by a PVC corer from the study site. The methane parameters were analysed using standard methods by gas chromatography. The physiological parameters were analysed on the site using portable probes. Results: The physio-chemical parameters varied with the changing seasons at different depths.The concentrations of organic parameters were higher for carbohydrates, followed by lipids and proteins. LOM was higher in the surface and mid sediments in all the seasons. The concentration of methane was higher during summer in surface sediments. Generally, higher methane oxidation was observed in the mid and bottom sediments during all the seasons. Methanotrophic enumeration 8-1 ranged from 0.4 ±0.7 to 4.8±2.4 x10 g. Interpretation: The results suggest that the bacterial community was involved in both methane oxidation and production, though oxidation of methane was lesser than production contributing to the atmospheric methane, methanotrophic bacteria which oxidizes methane significantly playing a major role in the regulation of methane flux.

Background: Microzooplankton consisting of protists and metazoa <200 μm. It displays unique feeding mechanisms and behaviours that allow them to graze cells up to five times their own volume. They can grow at rates which equal or exceed prey growth and can serve as a viable food source for metazoans. Moreover, they are individually inconspicuous, their recognition as significant consumers of oceanic primary production. The microzooplankton can be the dominant consumers of phytoplankton production in both oligo-and eutrophic regions of the ocean and are capable of consuming >100% of primary production. Results: The microzooplankton of the South Andaman Sea were investigated during September 2011 to January 2012. A total of 44 species belong to 19 genera were recorded in this study. Tintinnids made larger contribution to the total abundance (34%) followed in order by dinoflagellates (24%), ciliates (20%) and copepod nauplii (18%). Foraminifera were numerically less (4%). Tintinnids were represented by 20 species belong to 13 genera, Heterotrophic dinoflagellates were represented by 17 species belong to 3 genera and Ciliates comprised 5 species belong to 3 genera. Eutintinus tineus, Tintinnopsis cylindrical, T. incertum, Protoperidinium divergens, Lomaniella oviformes, Strombidium minimum were the most prevalent microzooplankton. Standing stock of tintinnids ranged from 30-80 cells.L -1 and showed a reverse distribution with the distribution of chlorophyll a relatively higher species diversity and equitability was found in polluted harbour areas.