Publications by authors named "Gopal Bera"

10 Publications

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Tight sorption of arsenic, cadmium, mercury, and lead by edible activated carbon and acid-processed montmorillonite clay.

Environ Sci Pollut Res Int 2021 Feb 2;28(6):6758-6770. Epub 2020 Oct 2.

Veterinary Integrative Biosciences Department, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843, USA.

Heavy metal exposure in humans and animals commonly occurs through the consumption of metal-contaminated drinking water and food. Although many studies have focused on the remediation of metals by purification of water using sorbents, limited therapeutic sorbent strategies have been developed to minimize human and animal exposures to contaminated water and food. To address this need, a medical grade activated carbon (MAC) and an acid processed montmorillonite clay (APM) were characterized for their ability to bind heavy metals and mixtures. Results of screening and adsorption/desorption isotherms showed that binding plots for arsenic, cadmium, and mercury sorption on surfaces of MAC (and lead on APM) fit the Langmuir model. The highest binding percentage, capacity, and affinity were shown in a simulated stomach model, and the lowest percentage desorption (< 18%) was shown in a simulated intestine model. The safety and protective ability of MAC and APM were confirmed in a living organism (Hydra vulgaris) where 0.1% MAC significantly protected the hydra against As, Cd, Hg, and a mixture of metals by 30-70%. In other studies, APM showed significant reduction (75%) of Pd toxicity, compared with MAC and heat-collapsed APM, suggesting that the interlayer of APM was important for Pb sorption. This is the first report showing that edible sorbents can bind mixtures of heavy metals in a simulated gastrointestinal tract and prevent their toxicity in a living organism. Graphical abstract.
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http://dx.doi.org/10.1007/s11356-020-10973-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7855320PMC
February 2021

Measured and predicted acute toxicity of phenanthrene and MC252 crude oil to vertically migrating deep-sea crustaceans.

Environ Sci Pollut Res Int 2020 Dec 12;27(36):45270-45281. Epub 2020 Aug 12.

Geochemical and Environmental Research Group, Texas A&M University, College Station, TX, 77845, USA.

Deep-water column micronekton play a key role in oceanic food webs and represent an important trophic link between deep- and shallow-water ecosystems. Thus, the potential impacts of sub-surface hydrocarbon plumes on these organisms are critical to developing a more complete understanding of ocean-wide effects resulting from deep-sea oil spills. This work was designed to advance the understanding of hydrocarbon toxicity in several ecologically important deep-sea micronekton species using controlled laboratory exposures aimed at determining lethal threshold exposure levels. The current study confirmed the results previously determined for five deep-sea micronekton by measuring lethal threshold levels for phenanthrene between 81.2 and 277.5 μg/L. These results were used to calibrate the target lipid model and to calculate a critical target lipid body burden for each species. In addition, an oil solubility model was used to predict the acute toxicity of MC252 crude oil to vertically migrating crustaceans, Janicella spinacauda and Euphausiidae spp., and to compare the predictions with results of a 48-h constant exposure toxicity test with passive-dosing. Results confirmed that the tested deep-sea micronekton appear more sensitive than many other organisms when exposed to dissolved oil, but baseline stress complicated interpretation of results.
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http://dx.doi.org/10.1007/s11356-020-10436-5DOI Listing
December 2020

A mesocosm experiment to determine half-lives of individual hydrocarbons in simulated oil spill scenarios with and without the dispersant, Corexit.

Mar Pollut Bull 2020 Feb 29;151:110804. Epub 2020 Jan 29.

Geochemical and Environmental Research Group, Texas A & M University, College Station, TX, United States of America; Department of Oceanography, Texas A & M University, College Station, TX, United States of America.

Here, we report results from a 15-day mesocosm experiment examining changes in estimated oil equivalents (EOEs), n-alkanes (n-C to n-C), polycyclic aromatic hydrocarbons (PAHs) and petroleum biomarkers. Water accommodated fractions (WAF) of oil and diluted chemically enhanced WAF (DCEWAF) were prepared and concentrations of oil residues determined on day 0, 3 and 15, respectively. Significant removals of n-alkane and PAHs were observed starting from day 3. The n-C/pristane and n-C/phytane ratios suggested that the n-alkane removal was due to biodegradation in the mesocosms. The ratios of C2-dibenzothiophenes/C2-phenanthrenes (D2/P2) and C3-dibenzothiophenes/C3-phenanthrenes (D3/P3) were found to be stable through the experiment. DCEWAF treatment had longer half-lives for most n-alkanes but shorter half-lives for most PAHs than the WAF treatment. Most petroleum biomarkers were stable throughout the experiment. However, depletion of TAS (tricyclic aromatic steroids) was observed on day 15 of DCEWAF treatment.
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http://dx.doi.org/10.1016/j.marpolbul.2019.110804DOI Listing
February 2020

Biological response to dissolved versus dispersed oil.

Mar Pollut Bull 2020 Jan 20;150:110713. Epub 2019 Nov 20.

Texas A & M University, College Station, TX, USA.

The water-soluble compounds of oil (e.g. low molecular weight PAHs) dissolve as a function of their physicochemical properties and environmental conditions, while the non-soluble compounds exist as dispersed droplets. Both the chemical and physical form of oil will affect the biological response. We present data from a mesocosm study comparing the microbial response to the water-soluble fraction (WSF), versus a water-accommodated fraction of oil (WAF), which contains both dispersed and dissolved oil components. WAF and WSF contained similar concentrations of low molecular weight PAHs, but concentrations of 4- and 5-ring PAHs were higher in WAF compared to WSF. Microbial communities were significantly different between WSF and WAF treatments, primary productivity was reduced more in WSF than in WAF, and concentrations of transparent exopolymeric particles were highest in WSF and lowest in the controls. These differences highlight the importance of dosing strategy for mesocosm and toxicity tests.
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http://dx.doi.org/10.1016/j.marpolbul.2019.110713DOI Listing
January 2020

Inter-laboratory calibration of estimated oil equivalent (EOE) concentrations of a water accommodated fraction (WAF) of oil and a chemically enhanced WAF (CEWAF).

Heliyon 2019 Jan 29;5(1):e01174. Epub 2019 Jan 29.

Texas A&M University at Galveston, Galveston, Texas, USA.

Chemical characterization of the presence of oil in environmental samples are performed using methods of varying complexity. Extraction of samples with an organic solvent and analysis by fluorescence spectrometry has been shown to be a rapid and effective screening technique for petroleum in the environment. During experiments, rapid analysis of oil by fluorescence provides the opportunity for researchers to modify the experimental conditions in real time. Estimated Oil Equivalents (EOE) relies on the fluorescence measurement of the aromatic compounds to estimate the oil concentration. The present intercalibration study was designed to investigate whether different fluorometer instruments can reliably measure EOE and whether the results are intercomparable. Additionally, the need for extraction of oil compounds into an organic solvent was investigated. Three different fluorometers were used in three different laboratories: a Horiba Aqualog, a Turner Trilogy and a Shimadzu Spectrofluorophotometer RF-1501. Results from these different instruments showed excellent agreement for EOE determinations. A very high correlation was found between the EOE results obtained with Aqualog Horiba and Turner Trilogy (r = 0.9999), with no significant differences between the mean EOE results (t-test, p = 0.30), and the Aqualog Horiba and Shimadzu (r = 0.995) fluorometers, with no statistically difference between the EOE results obtained by the two instruments (p = 0.40).
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http://dx.doi.org/10.1016/j.heliyon.2019.e01174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6356114PMC
January 2019

Passive dosing yields dissolved aqueous exposures of crude oil comparable to the CROSERF (Chemical Response to Oil Spill: Ecological Effects Research Forum) water accommodated fraction method.

Environ Toxicol Chem 2018 11 5;37(11):2810-2819. Epub 2018 Oct 5.

Geochemical and Environmental Research Group, Texas A&M University, College Station, Texas, USA.

The Chemical Response to Oil Spill: Ecological Effects Research Forum's water accommodated fraction procedure was compared with 2 alternative techniques in which crude oil was passively dosed from silicone tubing or O-rings. Fresh Macondo oil (MC252) was dosed at 30 mg/L using each approach to investigate oil dissolution kinetics, which was monitored by fluorometry as estimated oil equivalents (EOEs). Subsequent experiments with each dosing method were then conducted at multiple oil loadings. Following equilibration, test media were analytically characterized for polyaromatic hydrocarbons (PAHs) using gas chromatography (GC)-mass spectrometry and dissolved oil using biomimetic solid-phase microextraction (SPME). The results showed that equilibrium was achieved within 72 h for all methods. Measured PAH concentrations were compared with oil solubility model predictions of dissolved exposures. The concentration and composition of measured and predicted dissolved PAHs varied with oil loading and were consistent between dosing methods. Two-dimensional GC compositional data for this oil were then used to calculate dissolved toxic units for predicting MC252 oil acute toxicity across the expected range of species sensitivities. Predicted toxic units were nonlinear with loading and correlated to both EOE and biomimetic SPME. Passive dosing methods provide a practical strategy to deliver and maintain dissolved oil concentrations while avoiding the complicating role that droplets can introduce in exposure characterization and test interpretation. Environ Toxicol Chem 2018;37:2810-2819. © 2018 SETAC.
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http://dx.doi.org/10.1002/etc.4263DOI Listing
November 2018

Whether hurricane Katrina impacted trace metal and dioxin depositional histories in marshes of St. Louis Bay, Mississippi.

Sci Total Environ 2018 May 19;624:517-529. Epub 2017 Dec 19.

Department of Marine Science, The University of Southern Mississippi, United States. Electronic address:

Salt marsh sediments generally undergo steady accumulation over time and thus are widely used to reconstruct the depositional histories of various anthropogenic contaminants derived from atmospheric and fluvial sources. Major hurricanes can significantly affect coastal landscapes by eroding and re-distributing sediment. Thus, each major hurricane can leave distinct signals in coastal wetland sediments. On the other hand, early-diagenetic remobilization of Fe and Mn in organic rich marsh sediment is a common phenomenon. However, remobilization of Fe and Mn across the redox boundary can induce remobilization of other trace elements and thus can disturb their depositional histories. Four short (~1m) sediment cores were collected from the fringing marshes of St. Louis Bay, Mississippi (located ~30km east of Hurricane Katrina's track) during 2010-2011 to investigate possible impacts of Hurricane Katrina (2005), and early-diagenetic remobilization of Fe and Mn, on trace metal and dioxin depositional histories in these sediments. Results from Pb, Cs, stable Cs, particulate organic carbon (POC), sediment bulk density and grain size indicate significant impact of hurricane event layers on anthropogenic stable Cs, while deposition profiles of V, Ni and Cr are impacted by Fe and Mn remobilization to a limited extent.
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http://dx.doi.org/10.1016/j.scitotenv.2017.12.156DOI Listing
May 2018

A method for the production of large volumes of WAF and CEWAF for dosing mesocosms to understand marine oil snow formation.

Heliyon 2017 Oct 10;3(10):e00419. Epub 2017 Oct 10.

Geochemical and Environmental Research Group, Texas A&M University, 833 Graham Road, College Station, Texas 77845, USA.

Marine oil snow (MOS) formation is a mechanism to transport oil from the ocean surface to sediments. We describe here the use of 110L mesocosms designed to mimic oceanic parameters during an oil spill including the use of chemical dispersants in order to understand the processes controlling MOS formation. These experiments were not designed to be toxicity tests but rather to illustrate mechanisms. This paper focuses on the development of protocols needed to conduct experiments under environmentally relevant conditions to examine marine snow and MOS. The experiments required the production of over 500 liters of water accommodated fraction (WAF), chemically enhanced water accommodated fraction of oil (CEWAF) as well as diluted CEWAF (DCEWAF). A redesigned baffled (170 L) recirculating tank (BRT) system was used. Two mesocosm experiments (M1 and M2) were run for several days each. In both M1 and M2, marine snow and MOS was formed in controls and all treatments respectively. Estimated oil equivalent (EOE) concentrations of CEWAF were in the high range of concentrations reported during spills and field tests, while WAF and DCEWAF concentrations were within the range of concentrations reported during oil spills. EOE decreased rapidly within days in agreement with historic data and experiments.
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http://dx.doi.org/10.1016/j.heliyon.2017.e00419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5635956PMC
October 2017

Short-term toxicity of 1-methylnaphthalene to Americamysis bahia and 5 deep-sea crustaceans.

Environ Toxicol Chem 2017 12 22;36(12):3415-3423. Epub 2017 Sep 22.

Halmos College of Natural Sciences and Oceanography, Marine Toxicology Laboratory, Nova Southeastern University, Dania, Florida, USA.

There are few studies that have evaluated hydrocarbon toxicity to vertically migrating deep-sea micronekton. Crustaceans were collected alive using a 9-m Tucker trawl with a thermally insulated cod end and returned to the laboratory in 10 °C seawater. Toxicity of the polycyclic aromatic hydrocarbon 1-methylnaphthalene to Americamysis bahia, Janicella spinacauda, Systellaspis debilis, Sergestes sp., Sergia sp., and a euphausiid species was assessed in a constant exposure toxicity test utilizing a novel passive dosing toxicity testing protocol. The endpoint of the median lethal concentration tests was mortality, and the results revealed high sensitivity of the deep-sea micronekton compared with other species for which these data are available. Threshold concentrations were also used to calculate critical target lipid body burdens using the target lipid model. Environ Toxicol Chem 2017;36:3415-3423. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.
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http://dx.doi.org/10.1002/etc.3926DOI Listing
December 2017

Comparative Genomics and Metabolic Analysis Reveals Peculiar Characteristics of Rhodococcus opacus Strain M213 Particularly for Naphthalene Degradation.

PLoS One 2016 17;11(8):e0161032. Epub 2016 Aug 17.

Soil and Water Science Department, University of Florida, Gainesville, Florida, United States of America.

The genome of Rhodococcus opacus strain M213, isolated from a fuel-oil contaminated soil, was sequenced and annotated which revealed a genome size of 9,194,165 bp encoding 8680 putative genes and a G+C content of 66.72%. Among the protein coding genes, 71.77% were annotated as clusters of orthologous groups of proteins (COGs); 55% of the COGs were present as paralog clusters. Pulsed field gel electrophoresis (PFGE) analysis of M213 revealed the presence of three different sized replicons- a circular chromosome and two megaplasmids (pNUO1 and pNUO2) estimated to be of 750Kb 350Kb in size, respectively. Conversely, using an alternative approach of optical mapping, the plasmid replicons appeared as a circular ~1.2 Mb megaplasmid and a linear, ~0.7 Mb megaplasmid. Genome-wide comparative analysis of M213 with a cohort of sequenced Rhodococcus species revealed low syntenic affiliation with other R. opacus species including strains B4 and PD630. Conversely, a closer affiliation of M213, at the functional (COG) level, was observed with the catabolically versatile R. jostii strain RHA1 and other Rhodococcii such as R. wratislaviensis strain IFP 2016, R. imtechensis strain RKJ300, Rhodococcus sp. strain JVH1, and Rhodococcus sp. strain DK17, respectively. An in-depth, genome-wide comparison between these functional relatives revealed 971 unique genes in M213 representing 11% of its total genome; many associating with catabolic functions. Of major interest was the identification of as many as 154 genomic islands (GEIs), many with duplicated catabolic genes, in particular for PAHs; a trait that was confirmed by PCR-based identification of naphthalene dioxygenase (NDO) as a representative gene, across PFGE-resolved replicons of strain M213. Interestingly, several plasmid/GEI-encoded genes, that likely participate in degrading naphthalene (NAP) via a peculiar pathway, were also identified in strain M213 using a combination of bioinformatics, metabolic analysis and gene expression measurements of selected catabolic genes by RT-PCR. Taken together, this study provides a comprehensive understanding of the genome plasticity and ecological competitiveness of strain M213 likely facilitated by horizontal gene transfer (HGT), bacteriophage attacks and genomic reshuffling- aspects that continue to be understudied and thus poorly understood, in particular for the soil-borne Rhodococcii.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0161032PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4988695PMC
July 2017
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