Exploring bacterial diversity in Arctic fjord sediments: a 16S rRNA-based metabarcoding portrait.

The frosty polar environment houses diverse habitats mostly driven by psychrophilic and psychrotolerant microbes. Along with traditional cultivation methods, next-generation sequencing technologies have become common for exploring microbial communities from various extreme environments. Investigations on glaciers, ice sheets, ponds, lakes, etc. have revealed the existence of numerous microorganisms while details of microbial communities in the Arctic fjords remain incomplete. The current study focuses on understanding the bacterial diversity in two Arctic fjord sediments employing the 16S rRNA gene metabarcoding and its comparison with previous studies from various Arctic habitats. The study revealed that Proteobacteria was the dominant phylum from both the fjord samples followed by Bacteroidetes, Planctomycetes, Firmicutes, Actinobacteria, Cyanobacteria, Chloroflexi and Chlamydiae. A significant proportion of unclassified reads derived from bacteria was also detected. Psychrobacter, Pseudomonas, Acinetobacter, Aeromonas, Photobacterium, Flavobacterium, Gramella and Shewanella were the major genera in both the fjord sediments. The above findings were confirmed by the comparative analysis of fjord metadata with the previously reported (secondary metadata) Arctic samples. This study demonstrated the potential of 16S rRNA gene metabarcoding in resolving bacterial composition and diversity thereby providing new in situ insights into Arctic fjord systems.

The seasonal distribution and pollution potential of dissolved heavy metals and nutrients in subterranean estuaries in southern India.

In order to better understand the distribution pattern, pollution degree and the submarine groundwater discharge (SGD) of dissolved heavy metals, 15 subterranean estuaries (STEs) along southwest Indian coast were sampled over three contrasting seasons. The average concentration of metals were ranked as, pre-monsoon > monsoon > post-monsoon with 3 to 12-fold higher groundwater metal concentrations than the adjacent seawater. Average SGD derived essential metal fluxes were five times higher than the toxic metal fluxes of which Fe and Zn together contributed >90 %. Using the Single Factor Contamination Index, the majority of sites were minimally contaminated with only two sites indicating moderate ecological risk due to As. Higher fluxes of Fe, Cu and Zn were likely a result of rising anthropogenic activities. The SGD derived nutrient fluxes were an important source of DIP for primary production in coastal waters and represented 30 % and 44 % of the DIN and DIP inputs respectively.

A new Tardigrade species, Stygarctus keralensis sp. nov. (Arthrotardigrada: Stygarctidae) from the intertidal zone of Southwest coast of India.

Stygarctus keralensis sp. nov. (Arthrotardigrada: Stygarctidae), is described from the intertidal sandy sediments of Vadakara beach, Kerala, Southwest coast of India. To a certain extent, this new species shows morphological similarity with Stygarctus gourbaultae Renaud-Mornant, 1981, however it can be differentiated by some significant distinguishable characters like double looped seminal receptacle ducts and the presence of a bow shaped internal thickening in between the opening of seminal receptacles situated below the level of gonopore and above the anus; unsculptured body plates I-III; paired sub-cephalic pore/muscle attachment; shape and structure of caudal processes. Presence of minute spikes on third lateral processes in the new species is another unique character by which it can be easily differentiated from S. gourbaultae.

Assessment of benthic macroinvertebrate response to anthropogenic and natural disturbances in the Kodungallur-Azhikode estuary, southwest coast of India.

Benthic biotic indices are important ecological tools extensively used to understand the ecological quality of coastal wetlands. The present study aimed to assess the ecological status of Kodungallur-Azhikode estuary for the first time by using widely used benthic indices such as species richness (S), Shannon diversity index (H'log2), BENTIX, benthic opportunistic polychaetes amphipods (BOPA), AZTI's Marine Biotic Index (AMBI) and multivariate AMBI (M-AMBI). In the canonical correspondence analysis, salinity, dissolved oxygen, organic matter, sediment Eh, sediment pH and sand were identified as important variance descriptors. A single species of an opportunist, Americorophium triaeonyx, an amphipod belonging to the ecological group (EG) III, significantly contributed to the total macrofaunal density. Other dominant opportunistic species included Obelia bidentata (EGII), Arcuatula senhousia (EGIII), Cirolana fluviatilis (EGII), Prionospio cirrifera (EGIV) and Capitella sp. (EGV). The overall assessment indicated a 'good to moderate' condition in AMBI, 'good to poor' condition in M-AMBI, 'high to moderate' condition in BENTIX, 'high to poor' condition in BOPA and 'moderate to poor' condition in univariate Shannon diversity index. All the multivariate indices tested in the study were correlated with each other except BOPA and M-AMBI. The group of stations dominated with a sandy substrate and a moderate level of organic content indicated high to good conditions while other stations demonstrated moderate to poor conditions. However, no significant variation in indices tested between seasons was observed. The present study recommends long-term monitoring of benthic macroinvertebrate assemblages with proper taxonomic identification and functional trait analysis for better calibration of indices, which is the key factor for getting better results.

Chronic effects of copper and zinc on the fish, Etroplus suratensis (Bloch, 1790) by continuous flow through (CFT) bioassay.

Copper (Cu) and zinc (Zn) play a vital role in the growth and development, however increased uptake causes deleterious effects in normal functioning of organisms. We have demonstrated in this contribution the tolerance limit of Cu and Zn on Etroplus suratensis (pearl spot) by Continuous Flow Through (CFT) bioassay and the biomarker responses. The accumulation for Cu, Zn and selected trace metals (Cr, Cd, Ni and Pb) from field conditions, as well Geo-accumulation index (I geo) and Contamination factor (C.F) suggested moderate to heavy pollution in the Cochin estuarine system. The 96 h LC50 values for Cu was 1.74 ±â€¯0.04 mg L-1and that for Zn was 24.36 ±â€¯0.58 mg L-1 at 95% confidence interval. No observed effect concentration (NOEC) and low observed effect concentration (LOEC) for Cu and Zn were derived based on the survival rates. Chronic toxicity values for Cu and Zn were 0.23 mg L-1 and 2.005 mg L-1 respectively for 30 days period. The histological, biochemical, hematological and behavioral parameters showed significant variations at sublethal concentrations. Lamellar hyperplasia in gills, vacuolation combined with necrosis in liver, increased occurrence of melanomacrophage centres in spleen were noticed at chronic levels for both Cu and Zn. Tissue specific bioconcentration was observed for zinc and copper in gill and liver respectively, with least rate of bioconcentration observed in muscle tissues. Malaonate Dehydrogenase (MDH), Super oxide dismutase (SOD), Nonspecific esterase (EST) activity significantly varied compared to control at NOEC and LOEC values in both the metals. The hematological and genotoxic alterations as decrease in erythrocyte count, lymphocytes, hemoglobin concentration and hematocrit percentage were significantly reduced (p < 0.05) and increased thrombocytes and neutrophils, increased frequency of micronuclei, lobed, blebbed and notched nuclei and binucleate cells were characteristic for the metals at the sublethal concentrations. The frequency of behavioral changes remained significantly higher at chronic level than the control group. Thus such CFT based studies are important for precisely mapping the toxicity changes in organisms and also to develop suitable water quality guidelines.

Taxonomy of myid bivalves from fragmented brackish-water habitats in India, with a description of a new genus Indosphenia (Myidae, Myoidea, Myidae).

A group of small bivalves inhabiting Indian brackish-water estuaries and lagoons (known locally as backwaters), variously assigned to Corbula, Cuspidaria, and Sphenia, are reviewed and, based on shell characters, shown to be congeneric. Molecular (COI) and morphological data indicate that this group belongs to the family Myidae. Furthermore, the combined data suggest that these Indian myids are a sister taxon of the genus Sphenia. The Indian material studied herein exhibits a functional morphology typical of infaunal bivalves, whereas typical Sphenia are nestling and epibyssate. A new genus, Indosphenia, is thus erected for the Indian group and includes five species, one of which is named in this study. Indospheniakayalum Oliver, Hallan & Jayachandran, gen. et sp. n. is described from the Cochin Backwater on the western coast of India. Cuneocorbulacochinensis (Preston, 1916) is transferred to Indosphenia. Additionally, the west coast taxa I.abbreviata (Preston, 1907), I.abbreviatachilkaensis (Preston, 1911) and I.sowerbyi (EA Smith, 1893) are recognised herein. Corbulaalcocki Preston, 1907, Corbulagracilis Preston, 1907, Corbulacalcaria Preston, 1907 and Corbulapfefferi Preston, 1907 are placed in synonymy with I.abbreviata, and Cuspidariaannandalei Preston, 1915 is synonymised with I.abbreviatachilkaensis.

Toxicity effects of zinc on two marine diatoms, under varying macronutrient environment.

Diatoms constitute one of the fundaments in the trophic food chains and are responsible for much of the bioaccumulation of heavy metals, in particular zinc, throughout the web of food chains. Chaetoceros calcitrans and Thalassiosira weissflogii are widely present as a dominant marine diatom in estuarine and coastal waters. The zinc uptake, its fractionation in subcellular structures and macromolecular compartments in two marine diatoms, C. calcitrans and T. weissflogii and trophic transfer under different macronutrient concentrations were investigated. The study reveals a significant interaction between macronutrients and metal uptake by the two diatom species. Increased cellular accumulation of zinc and N, P-limited condition were found to affect N, P and Si assimilation by diatoms negatively. Conversely, nitrogen (N) limitation inhibited the intracellular uptake of zinc. However, at higher concentration of zinc, the difference in zinc uptake between nutrient enriched condition (+NP) and nutrient limited (N or P) condition become smaller, indicating that the zinc uptake by diatoms is less dependent on N containing protein ligands at high Zn concentration. Nitrogen concentration in the medium was also found to affect the relative distribution of zinc in subcellular structures and macromolecular components. However, major portion of zinc was distributed in soluble substance and in the protein of the algal cells. The N limited condition facilitates the accumulation of zinc in cell organelles (insoluble substance) leading to increased toxicity. Trophic transfer of zinc was also measured by calculating percentage of metal retained in mussel, Perna viridis over the experiment period. Regardless of the algal species, the percentage of accumulation of zinc was found to be high in mussels fed with algal cells acclimated to nutrient enriched condition (31 and 38%). Our study therefore suggests that N enrichment may lead to an increase in Zn uptake and transfer in marine plankton.

New species of Victoriopisa Karaman Barnard, 1979 (Crustacea: Amphipoda: Eriopisidae) from Vembanad backwaters, Southwest coast of India.

The new species is the third of genus Victoriopisa from Indian waters.The species is described from the Valanthakad mangrove area of Vembanad backwater. Victoriopisa cusatensis sp. nov differs from other species of Victoriopisa by presenting: (1) a characteristic projection at dorsolateral margin of peduncle article 2 of antenna 1in male while smooth in female; (2) broad, triangular lateral cephalic lobe; (3) posteroventral tooth in epimeral plates; (4) presence of lateral and subapical spines in telson (5) smooth palm of gnathopod 2 without any excavations.