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Abstract 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 LC 50 values for Cu was 1.74 ± 0.04 mg L−1and that for Zn was 24.36 ± 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. Highlights • Chronic toxicity values for Cu and Zn on Etroplus suratensis were 0.23 mg L−1 and 2.005 mg L−1 respectively. • Analysis of water and sediment samples from Cochin estuary showed contamination from Cu and Zn. • Tissue-specific pattern of bioaccumulation of Cu and Zn were observed during study. • Evident biomarker changes in Etroplus suratensis were observed on exposure to Cu and Zn. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Ambient N concentration plays a pivotal role in uptake of Zn in C. calcitrans and T. weissflogii. • Increased cellular accumulation of zinc and N/P-limited condition negatively affect N, P and Si assimilation by diatoms. • Zinc uptake by diatoms is less dependent on N containing protein ligands at high Zn concentration. • Varying nutrient condition affects the Zn distribution in the subcellular compartments and macromolecular structures. • Nutrient enrichmnt may lead to an increase in zinc uptake and trophic transfer along the food chain. [ABSTRACT FROM AUTHOR]

Morphological identification of the marine cyclopoid copepodDioithona rigidain combination with sequencing a 645 bp fragment of mitochondrial cytochrome oxidase c subunit I (mtCOI) gene, collected from offshore waters of Kavarathi Island, Lakshadweep Sea, is presented in this study. Kiefer in 1935 classifiedDioithonaas a separate genus fromOithona. The main distinguishing characters observed in the collected samples, such as the presence of well-developed P5 with 2 setae, 5 segmented urosome, 12 segmented antennule, compact dagger-like setae on the inner margin of proximal segment of exopod ramus in P1–P4 and engorged portion of P1-bearing a spine, confirmed their morphology toD. rigida.A comparison of setal formulae of the exopod and endopod ofD. rigidawith those recorded previously by various authors are also presented here. Maximum likelihood Tree analysis exhibited the clustering ofD. rigidasequences into a single clade (accession numbers KP972540.1-KR528588.1), which in contrast was 37–42% divergent from otherOithonaspecies. Further intra-specific divergence values of 0–2% also confirmed the genetic identity ofD. rigidaspecies.Paracyclopina nanawas selected as an out group displayed a diverged array. The present results distinctly differentiatedD. rigidafrom otherOithonaspecies. [ABSTRACT FROM PUBLISHER]

Abstract: The toxicities of the trace metals copper and zinc on the fish Puntius parrah were assessed based on standard renewal bioassay methods, and the 96 h LC50 values for copper and zinc were 0.5 mg/L and 9 mg/L, respectively. The zinc and copper concentrations in water and sediment were high in a highly industrialized area compared with those in non-industrialized zones of the Periyar River. The fish exposed to a sublethal concentration of 0.05 mg/L of Cu and 0.9 mg/L of Zn showed a higher accumulation of both of the metals in the liver than in the kidneys, gills, and muscles. The histological changes induced by copper and zinc on the test organism under sublethal concentrations on the 3rd, 7th, 14th, and 28th -days of exposure were also studied. There was a significant decrease (p < 0.001) in the erythrocyte count after exposure to sublethal concentrations, whereas the hemoglobin, hematocrit, and mean corpuscular hemoglobin concentrations were significantly decreased after 28 days of exposure. Effective management strategies need to be developed and implemented to protect water bodies and aquatic organisms from trace metal pollution and its toxic effects. [Copyright &y& Elsevier]

Abstract: The effects of sub-lethal concentrations of lindane on behavioral, hematological and histological parameters in Etroplus maculatus were investigated. The LC50 value of lindane for E. maculatus was estimated using the Probit method and was found to be 0.028 mg/L. The red blood cell count (RBC) and the hemoglobin (Hb), hematocrit (Ht), mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) were significantly reduced (p > 0.0001) in fish exposed to the toxicant concentrations compared to the control groups. However, the white blood cell count (WBC) was observed to be significantly higher (p < 0.0001). Observations of the tissues showed that lindane had profound destructive effects on the gills, liver and kidney of the fish. The gills showed proliferation of the lamellar epithelium and lamellar fusion, the liver showed necrosis and the kidneys had constriction of the tubular lumen. The frequency of observed behaviors had the same levels of significance throughout the period of study. There was a reduction in the frequency of occurrence between test concentrations, but remained significantly higher than the control. The study shows that lindane is harmful to E. maculatus at sub-lethal concentrations and that the application of this pesticide close to bodies of water is a dangerous threat to aquatic life. [Copyright &y& Elsevier]

• High sediment carbon burial in semi-enclosed mangrove habitat with high NPP. • Low carbon burial in aquaculture converted mangrove habitat. • Biological factors like litterfall and crab density act as primary controls. • Secondary controls were sediment accumulation rates and grain size. Tropical mangrove environments have high carbon sequestration potential and this ecosystem service is currently used in mitigating climate change. However, these environments are declining rapidly in developing countries, diminishing their carbon sequestration potential and may ultimately transforming them as carbon dioxide sources. This study investigated the carbon sequestration potential through sediment burial at three mangrove habitats of Cochin, South-West coast of India. High burial estimates were recorded at two mangrove stations (2.95 ± 0.79–10.41 ± 2.50 t C ha−1 yr−1), but consistent with other tropical mangrove areas. Lower burial rates were estimated at one station (0.57 ± 0.24 t C ha−1 yr−1). Eighty percent of the mangrove net primary productivity through litterfall (NPP L) was stored in the sediment at the station with the highest burial rate, which is demonstrative of a robust carbon sink. However, at a different site, which is subject to aquaculture, only 7.23 % of NPP L was buried in the sediment. A major portion of the fixed carbon at this site is presumably emitted back to the atmosphere or exported to adjacent water bodies. The median total regional mangrove carbon burial rate in this study was 2.95 t C ha−1 yr−1 and the organic carbon burial rate was 1.93 ± 0.75 t C ha−1 yr−1. Biological factors such as mangrove biomass, litterfall and crab density have played a major role in controlling the sediment carbon burial rate. Sediment texture and bulk sediment accumulation acted as secondary controlling factors. The carbon source characterisation in the sediment profile using stable isotope techniques revealed the organic carbon origin as mangrove litter. Gaining a better understanding of carbon sources, burial rates and their controlling factors in mangrove habitats aids in regional climate mitigation efforts and global efforts to increase the carbon sequestration potential of tropical mangrove systems. [ABSTRACT FROM AUTHOR]

The proportion of blue carbon contribution by benthic fauna with regard to climate change issue is a relevant topic recent times. The present study is focusing on the carbon potential and blue carbon contribution of meiobenthic nematodes in the intermediate zone of Arctic Kongsfjord during 2015–2017 and the study is the first of its kind from this region. Foraminifera and Nematoda were the dominant fauna in 2015; whereas it was Foraminifera in 2016 and Tintinnida and Nematoda in 2017. Significant difference was noticed in the community structure of meiofauna in this three consecutive years. Twenty six nematodes were identified from the intermediate zone and their individual carbon potential and total blue carbon during the above-mentioned period is estimated. Parasphaerolaimus paradoxus (7.14 ± 0.05 μg/mg) recorded the highest carbon potential and the lowest value was recorded in Terschellingia longicaudata (0.11 ± 0.3 μg/mg). The sediment factors such as sediment granulometric composition, salinity, pH, Eh and total organic carbon (TOC) were the leading factors influencing the meiofaunal distribution as well as the distribution of nematodes based on carbon potential in the intermediate zone. Investigation of blue carbon deposition by nematodes turned out to be relevant in mitigating the climatic change as the fjord has a tranquil nature. [ABSTRACT FROM AUTHOR]

This study estimated the total ecosystem carbon stock (TECS) and sediment carbon sequestration rate through burial for fragmented mangrove habitats of Kochi, south-west coast of India. The mean TECS of Kochi mangroves was estimated at 335.33 ± 184.47 t C ha−1, with above ground biomass of 171.68 ± 104.42 t C ha−1, belowground biomass of 83.30 ± 41.98 t C ha−1, litterfall carbon as dead biomass of 7.12 ± 2.81 t C ha−1 and soil carbon stock of 73.22 ± 39.40 t C ha−1. The average historical soil carbon sequestration rate of Kochi mangroves was also estimated as 2.95 t C ha−1 yr−1. The study revealed that there was significant variability in TECS and sediment carbon burial rate among riverine, estuarine and marine mangrove habitats and it appears that, the biological factors especially mangrove plant structure, species, age, litterfall production, crab density, mangrove conversion to aquaculture ponds and other urban pressure played major roles in driving the variability in carbon stocks and storage. While the sediment particle size, bulk density and the environmental settings played a secondary role. Very low TECS and soil carbon sequestration rate was found in aquaculture converted mangrove habitat. The CO 2e of ecosystem carbon stock (496311.20 t CO 2 e) and soil CO 2 burial (10.62 t CO 2 e ha−1 yr−1 respectively) of mangroves of Kochi, revealed that even with high urban pressure and anthropogenic activities which resulted in fragmented distribution, they are still potent in long term carbon sequestration unless it is not further disturbed. Therefore, conservation and restoration of mangrove habitats based on understanding of the regional controlling factors of carbon stock and carbon burial is a need for scientific climate change mitigation efforts. The study will also contribute to fill the gaps in global mangrove carbon stock assessments for avoiding uncertainties. [Display omitted] • High total ecosystem carbon stock and sequestration in the mangrove ecosystem. • Observed significant variability in carbon stock and burial. • Major controls include biological factors and geomorphological differentiation. • Aquaculture has an impact on carbon stock and sequestration. • Mangrove destruction negatively impacts coastal economies. [ABSTRACT FROM AUTHOR]

The article reports on a study on the occurrence of mussel Mytilopsis from the southwest coast of India. Using a standard multiparameter instrument, the basic water quality parameters were measured during the study. It refers to the confirmation of bioinvasive occurrence of Mytilopsis in the backwaters in Cochin, India.