Atmospheric Deposition, Shelf Sediment Supply, Riverine Input, and Redox Conditions Control Dissolved Manganese in the Indian Ocean
Author(s): Malla, N.; Singh, S. K.
Source: Global Biogeochemical Cycles,vol.39(10);2025;articleno.e2025GB008660
Impact Factor: 5.500
NIO Repository: https://drs.nio.res.in/drs/handle/2264/9556
Abstract: Abstract Dissolved manganese (dMn) is an essential bioactive element required for marine organisms. Redox condition determines its solubility and its solid phase removal from seawater. It displays a typical scavenging type profile in the Indian Ocean with an elevated concentration in the Oxygen Minimum Zone (OMZ) of the Bay of Bengal (BoB). The surface dMn decreases southward in the BoB, and its concentration gradient correlates well with salinity because of the enormous riverine influx. Reductive dissolution of Iron-manganese (Fe-Mn) oxyhydroxides-rich sediments brought by the Ganga-Brahmaputra rivers enriches dMn in the bottom waters of the shelf regions (?25 nM), which gets advected to the open ocean through cross-shelf transport. The atmospheric input is the prominent source of dMn in the BoB. Transport of the Indonesian Through Flow waters supplies high dMn in the surface waters of the Central Indian Ocean Basin. Internal cycling seems to control the dMn distribution in the water column in addition to its external sources. Water column denitrification increases dMn in the OMZ waters of the BoB through the reductive dissolution of sinking Mn oxide particles under the prevailing suboxic conditions. The presence of two sub-surface peaks of dMn associated with nitrite maxima suggests active denitrification in the OMZ waters of the BoB, similar to the Arabian Sea. The interaction of circulating fluid with subducting Fe-Mn-rich crusts enriches the deep water dMn in the Java Sumatra region. Further, the hydrothermal activity over the Southeast and Central Indian Ridges contributes significantly to the dMn budget of the deeper waters.
Unraveling the bacterial composition of a coral and bioeroding sponge competing in a marginal coral environment
Author(s): Mote, S; De, K.; Nanajkar, M.; Gupta, V.
Source: Frontiers in Microbiology,vol.16;2025article no: https://doi.org/10.3389/fmicb.2025.1550446
Impact Factor: 4.500
NIO Repository: https://drs.nio.res.in/drs/handle/2264/9550
Abstract: The newly described bioeroding sponge Cliona thomasi, part of the Cliona viridis complex, is contributing to coral decline in the central eastern Arabian Sea, the West Coast of India. While its morphological and allelopathic mechanisms in coral invasion are well investigated, the role of its microbial communities in spatial competition is underexplored. This study focuses on the coral Turbinaria mesenterina and sponge C. thomasi, both known for their distinct symbiotic associations with Symbiodiniaceae. A 16S rRNA V3 V4 amplicon next-generation sequencing approach, followed by processing through the DADA2 algorithm, was used to analyze the bacterial composition. The results showed higher bacterial richness and diversity in coral samples, identifying 30 distinct phyla, compared to 14 in sponge samples. The coral samples were dominated by Proteobacteria, Actinobacteria, Firmicutes, Cyanobacteria, Planctomycetes, Chloroflexi, and Patescibacteria, while Proteobacteria, Cyanobacteria, Planctomycetes, and Actinobacteria were dominant in the sponge. Enrichment analysis revealed higher dominance of Acidobacteria, Actinobacteria, Chloroflexi, Dadabacteria, Firmicutes, Fusobacteriota, and Patescibacteria in the coral samples, while the sponge samples showed enrichment for Cyanobacteria, Planctomycetes, and Bdellovibrionota. Beta-diversity analysis (PERMANOVA and nMDS) showed significant differences, with an average dissimilarity of 81.44% between sponge and coral samples (SIMPER). These differences highlight variations in microbial profiles between sponges and corals, competing in the same vulnerable environment. Exploring the microbiome aspect, therefore, may elucidate physiological and ecological functions of the holobiont while also representing a health status biomarker for corals, supporting their conservation.
Pre-requisite conditions for the intensification of pre-monsoon cyclones over the Bay of Bengal
Author(s): Maneesha, K.; Patnaik, K. V. K. R. K; Ganapathi, P.; Ratna, S. B.
Source: Scientific Reports, vol.15(1);2025;Article no:33049
Impact Factor: 3.900
NIO Repository: https://drs.nio.res.in/drs/handle/2264/9551
Abstract: Pre-requisite conditions for the intensification of pre-monsoon cyclones over the Bay of Bengal
Sibling species differently distributed around a CO2 vent show transplantation proteomic remodelling, while displaying metabolomic signatures associated with their origin
Author(s): Turner, L. M.; Madeira, D.; Ricevuto, E.; Gallucci, A. M.; Sommer, U.; Viant, M. R.; Dineshram, R.; Gambi, M.-C.; Calosi, P.
Source: Scientific Reports,vol. 15(1);2025; Article no: 33604.
Impact Factor: 3.900
NIO Repository: https://drs.nio.res.in/drs/handle/2264/9555
Abstract: The cellular homeostatic response (CHR) and cellular stress response (CSR) work together to maintain homeostasis. Studying phylogenetically closely-related species inhabiting different environments can help investigate the interplay between the CHR and CSR. We conducted reciprocal in situ transplant experiments in a natural CO2 vent (Ischia, Italy), using the sibling annelid species Platynereis cf.. dumerilii and Platynereis cf.. massiliensis which have been shown to have different preferential distributions around the CO2 vent. Following transplantations, we characterised the response of each individual s proteome, metabolome, and lipidome, to short or long-term exposure to different pCO2 regimes (i.e., high and low), and confirmed its genetic identity. Here we show that different components of the CHR and CSR are utilised at different rates when Platynereis spp. are exposed to different pCO2 regimes, with cellular responses shown to be conserved across species. Metabolome and lipidome responses were dependent on regime of origin, and changed relatively slowly, whereas proteome responses were dependent on transplant type and changed more rapidly. Our results provide new insights to improve our understanding of the interplay between different cellular physiological responses involved in defining the functional phenotype of marine species, and their ability to acclimatise to future projected high pCO2 conditions.



