Fjords of the western and northern regions of Svalbard harbour distinct bacterioplankton community structures.

Fjords are highly dynamic ecosystems that are known to be sentinels to climate change due to increased glaciomarine interactions. The convergence and mixing of warm Atlantic water (AtW) and cold Arctic water (ArW) is known to influence the hydrodynamics and ecology of the Arctic fjords. However, most past studies were limited to single-fjord ecosystems, determining the baseline knowledge of inter-fjord comparison on bacterioplankton diversity and distribution patterns. In the present study, we investigated the bacterial diversity and community composition across three Arctic fjords located in the western and northern regions of Svalbard. Our observations show that the bacterial community structure varied significantly among the fjords, while abundant Operational Taxonomic Units (OTUs) were widespread (n = 100) between all the samples and rare OTUs (n = 2221) mainly contributed to these differences. Phylogenetic classification revealed that Alpha (27.3-55%) and Gamma-proteobacteria (16-51.3%), followed by Bacteroidota (17-35.7%) were dominant in the St.Jonsfjorden and Magdalenefjorden, while Verrucomicrobiota (up to 84.19%) and Actinobacteriota (up to 76.5%) were predominant in the Raudfjorden. Temperature, dissolved inorganic phosphate (DIP) and depth were found to significantly influence the community composition of abundant bacterial groups, whereas the rare bacterial groups were affected by temperature, DIP, dissolved inorganic nitrate (DIN), ammonium and depth. A comparative meta-analysis along with Kongsfjorden and Krossfjorden also showed that each fjord had a significantly different bacterioplankton community structure.

Spatial and seasonal trends of trace metals in the surficial sediments from off Kochi - Geochemistry and environmental implications.

Fifty four sediment samples representing pre and post-monsoon seasons were collected along a transect from off Kochi, lying between the latitudes 9°57'59.5″-9°54'30.4″ and longitudes 76°11'7.04″-75°38'50.3″ of the South eastern Arabian Sea. The present study investigates the levels of trace metals (Zn, Cd, Pb, Cu, Fe, Ni, Mn, Co and Cr), total organic carbon (TOC), total inorganic carbon (TIC), elemental composition and grain size to assess the extent of environmental pollution and to discuss the distribution of these trace metals in the surficial sediments. Sediment pollution assessment was done using the Contamination factor (C.F), Geoaccumulation Index (Igeo), Enrichment Factor (EF), and Pollution Load Index (PLI). The majority of trace metals analysed in this study exhibited the highest concentrations at stations 1, 2 and 3 where the land-based anthropogenic input was found to be maximum.

Nutrient concentrations and distribution of phytoplankton pigments in recently deposited sediments of a positive tropical estuary.

Investigation of nutrients in the water column and phytoplankton pigments in recently formed modern sediments (0-5 cm) was carried out in Cochin estuary. The anthropogenic impacts were assessed using nutrients, nitrate, and phosphate in combination with phytopigments in sediments. The nitrate and phosphate concentration during the study ranged from 0.81 to 42.53 µmol/L and from 0.1 to 5.81 µmol/L, respectively. The mean values of the pigment showed the following order: zeaxanthin (791.53 ng/g) > lutein (347.57 ng/g) > fucoxanthin (335.30 ng/g) > pheophytin (308.84 ng/g) > pheophorbide (172.06 ng/g) > chlorophyll a (161.63 ng/g). The increase in the concentration of zeaxanthin indicated the presence of cyanobacteria, associated with eutrophication. Correlation analysis revealed that water column nutrients have a strong relationship between fucoxanthin and lutein, indicating the coexistence of diatoms and prasinophytes in the sampling sites. The principal component analysis showed positive loading of nutrients concomitant with pigment fucoxanthin and lutein, thus establishing that nutrient input controls the phytoplankton biomass of this estuary.

Geochemical fractionation of trace elements in the coral reef sediments of the Lakshadweep Archipelago, Indian Ocean.

Geochemical fractionation of seven trace elements (Cr, Mn, Fe, Cu, Zn, Cd, and Pb) was investigated in the surficial coral reef sediments of three inhabited islands (Kavaratti, Kadmat, and Agatti) belonging to the Lakshadweep Archipelago. The observations indicated that the metals showed their highest contents in the residual fraction of geological origin. The extent of risk, bioavailability, and contamination of trace elements was assessed by risk assessment codes and contamination factors. Based on the results, medium potential adverse effects were observed in the sediments of Kavaratti and Agatti. The concentration of Cd in the exchangeable and carbonate-bound fractions was above its global average shale value in the sediments of Kavaratti and Agatti, suggesting its high mobility and bioavailability and thus an environmental threat to the coral reef ecosystem.

Response of bacterial communities from Kongsfjorden (Svalbard, Arctic Ocean) to macroalgal polysaccharide amendments.

Macroalgae are abundant in coastal Arctic habitats and contain a large amount of polysaccharides. Increased macroalgal productivity due to warmer temperatures and reduced sea-ice cover contribute a significant amount of polysaccharide-rich detritus in the region. To study bacterial degradation of macroalgal polysaccharides and their potential impact on biogeochemical processes we studied the response of bacterial communities from Kongsfjorden, Svalbard (Arctic Ocean) to alginate (AL) and agarose (AG) amendments, using an ex-situ microcosm experiment. Our results show that bacterial communities responded to the increased availability of macroalgal polysaccharides and community shift was congruent with a significant decline in nutrient concentrations. Initially-rare bacterial taxa affiliated with Gammaproteobacteria and Bacteroidia responded to the polysaccharide addition. Each polysaccharide addition incited the growth of certain distinct bacteria taxa. Compared to the un-amended control microcosms (CM), Polaribacter, Colwellia, Pseudoalteromonas, and unclassified Gammaproteobacteria responded to AL addition, whereas Paraglaciecola, Lentimonas, Colwellia, unclassified Gammaproteobacteria, unclassified Alteromonadales, and unclassified Alteromonadaceae responded to the AG addition. These results suggest that polysaccharides shift bacterial community composition towards copiotrophic bacterial taxa, with implications for carbon and nutrient cycling in coastal Svalbard.

Spatial and Temporal Variations of Arsenic Distribution in a Tropical Estuary Along the West Coast of India.

Arsenic (As) contamination was studied and reported for the first time in the sediments of the Cochin estuary. Surface sediment samples were collected from twenty-seven stations encompassing the entire estuary constituting south, central and north estuary. The total As concentration varied from 0.01 mg/kg to 9.28 mg/kg and undetected to 23.37 mg/kg during the pre and post-monsoon. The degree of contamination assessed in terms of geochemical indices such as contamination factor (CF), geoaccumulation index (Igeo) and enrichment factor (EF) unraveled the As contamination to be meager. The application of risk index factor and sediment quality guidelines showed that the As concentration in the estuary is below the background concentration. Pearson correlation analysis of As with iron and TOC exhibited significant weak and poor correlations with these variables.

Spatial variation of trace element concentration and contamination assessment in the coral reef sediments of Lakshadweep Archipelago, Indian Ocean.

Surface sediments were collected from the shore and lagoons of Kavaratti, Kadmat and Agatti islands of Lakshadweep Archipelago and analysed for trace element concentration. The sediment contamination was assessed on the basis of geochemical, biological hazard and ecological risk indices. Except Cd and Pb, all the other trace elements selected for the study were below the contamination level. Compared to Kadmat, Kavaratti and Agatti were more polluted and the pollution was pronounced in lagoons than shore. Population pressure, untreated sewage, diesel based power generation, shipping and tourism activities contribute to sediment contamination. Statistical analysis revealed the association of trace elements with sedimentary characteristics due to anthropogenic sources.