Edaphic factors affecting the toxicity and accumulation of arsenate in the earthworm Lumbricus terrestris

The toxicity and accumulation of arsenate was determined in the earthworm Lumbricus terrestris in soil from different layers of a forest profile. Toxicity increased fourfold between 2 and 10 d. Edaphic factors (pH, soil organic matter, and depth in soil profile) also affected toxicity with a three fold decrease in the concentration that causes 50% mortality with increasing depth in soil (from 0-70 mm to 500-700 mm). In a 4-d exposure study, there was no evidence of arsenic bioconcentration in earthworm tissue, although bioaccumulation was occurring. There was a considerable difference in tissue residues between living and dead earthworms, with dead worms having higher concentrations. This difference was dependent on both soil arsenate concentration and on soil type. Over a wide range of soil arsenate concentrations, earthworm arsenic residues are homeostatically maintained in living worms, but this homeostasis breaks down during death. Alternatively, equilibration with soil residues may occur via accumulation after death. In long-term accumulation studies in soils dosed with a sublethal arsenate concentration (40 μg/g dry weight), bioconcentration of arsenate did not occur until day 12, after which earthworm concentrations rose steadily above the soil concentration, with residues in worms three fold higher than soil concentrations by the termination of the study (23 d). This bioconcentration only occurred in depurated worms over the time period of the study. Initially, depurated worms had lower arsenic concentrations than undepurated until tissue concentrations were equivalent to the soil concentration. Once tissue concentration was greater than soil concentration, depurated worms had higher arsenic residues than undepurated.

What defines a geochemical map? Implications for environmental assessment.

The environmental quality of land is often assessed by the calculation of threshold values which aim to differentiate between concentrations of elements based on whether the soils are in residential or industrial sites. In Europe, for example, soil guideline values exist for agricultural and grazing land. A threshold is often set to differentiate between concentrations of the element that naturally occur in the soil and concentrations that result from diffuse anthropogenic sources. Regional geochemistry and, in particular, single component geochemical maps are increasingly being used to determine these baseline environmental assessments. The key question raised in this paper is whether the geochemical map can provide an accurate interpretation on its own. Implicit is the thought that single component geochemical maps represent absolute abundances. However,because of the compositional (closed) nature of the data univariate geochemical maps cannot be compared directly with one another.. As a result, any interpretation based on them is vulnerable to spurious correlation problems. What does this mean for soil geochemistry mapping, baseline quality documentation, soil resource assessment or risk evaluation? Despite the limitation of relative abundances, individual raw geochemical maps are deemed fundamental to several applications of geochemical maps including environmental assessments. However, element toxicity is related to its bioavailable concentration, which is lowered if its source is mixed with another source. Elements interact, for example under reducing conditions with iron oxides, its solid state is lost and arsenic becomes soluble and mobile. Both of these matters may be more adequately dealt with if a single component map is not interpreted in isolation to determine baseline and threshold assessments. A range of alternative compositionally compliant representations based on log-ratio and log-contrast approaches are explored to supplement the classical single component maps for environmental assessment. Case study examples are shown based on the Tellus soil geochemical dataset, covering Northern Ireland and the results of in vitro oral bioaccessibility testing carried out on a sub-set of archived Tellus Survey shallow soils following the Unified BARGE (Bioaccessibility Research Group of Europe).

Mercury in feral fish: distribution, accumulation and toxicity

O principal objectivo desta dissertação foi estudar a acumulação de mercúrio em vários tecidos de peixes marinhos, a sua relação com factores biológicos e as respectivas respostas bioquímicas. O trabalho realizado permitiu obter novos conhecimentos sobre a acumulação de mercúrio em peixes, possibilitando avaliar a influência da biodisponibilidade do elemento e as suas possíveis implicações no ambiente. O trabalho foi desenvolvido na Ria de Aveiro (Portugal), uma zona costeira onde existe um gradiente ambiental de mercúrio, o que oferece a oportunidade de estudar a sua acumulação e os seus efeitos tóxicos em condições realísticas. As amostragens foram efectuadas em dois locais considerados críticos em termos de contaminação por mercúrio – Largo do Laranjo (L1 e L2) e num local afastado da principal fonte de poluição, usado como termo de comparação (Referência; R); L1 e L2 corresponderam a locais moderadamente e altamente contaminados, respectivamente. Foram escolhidos juvenis de duas espécies ecologicamente diferentes e representativas da comunidade piscícola local, a tainha garrento (Liza aurata) e o robalo (Dicentrarchus labrax). Em cada local foram recolhidas amostras de água e de sedimento para determinação de mercúrio. Foram quantificadas as concentrações de mercúrio total (T-Hg) e orgânico (O-Hg) em vários tecidos dos peixes, escolhidos tendo em conta a sua função relativamente à toxicocinética e toxicodinâmica de metais. As respostas antioxidantes (Catalase- CAT, glutationa peroxidase- GPx, glutationa reductase- GR, glutationa –S-transferase- GST e conteúdo em glutationa total- GSHt), o dano peroxidativo (LPO) e o conteúdo em metalotioninas (MTs) foram também avaliados. A acumulação de T-Hg foi semelhante para as duas espécies de peixes estudadas, embora D. labrax tenha apresentado concentrações tendencialmente maiores. Ambas as espécies demonstraram capacidade de reflectir o grau de contaminação ambiental existente, indicando claramente que a acumulação depende da concentração ambiental. A acumulação revelou-se específica de cada tecido. O padrão da acumulação em L. aurata foi rim > fígado > músculo > cérebro > guelras > sangue e em D. labrax foi fígado > rim > músculo > cérebro ≈ guelras > sangue. Relativamente à acumulação de OHg, verificou-se que D. labrax exibiu concentrações mais elevadas que L. aurata. Todos os tecidos foram capazes de reflectir diferenças entre R e L2. Os níveis de O-Hg no fígado, músculo e nos conteúdos intestinais foram diferentes entre espécies, sendo mais elevados para D. labrax. As guelras e o intestino foram os tecidos onde se obtiveram os valores mais baixos de O-Hg e observaram-se valores idênticos para as duas espécies. Com excepção das guelras, as concentrações de O-Hg variaram em função do valor observado nos conteúdos intestinais, indicando que a alimentação é a via dominante da acumulação. As concentrações de O-Hg nos conteúdos intestinais revelaram ser uma informação relevante para prever a acumulação de O-Hg nos tecidos, pois verificou-se uma razão praticamente constante entre o teor de mercúrio no fígado, no músculo e nos conteúdos intestinais. A percentagem de O-Hg no músculo e no fígado variou de acordo com o grau de contaminação ambiental e com o tipo de assimilação preferencial do elemento (alimentação vs. água), sugerindo que o fígado exerce um papel protector em relação à acumulação de mercúrio nos outros órgãos. Ambas as espécies de peixes demonstraram ser boas sentinelas da contaminação ambiental com mercúrio (T-Hg e O-Hg), sendo o cérebro e o músculo os tecidos que melhor reflectiram o grau de acumulação com o elemento. A análise conjunta dos dados de bioacumulação e de respostas ao stress oxidativo permitiram estabelecer uma relação entre as concentrações de mercúrio nas guelras, fígado, rim e cérebro e a sua toxicidade. As respostas do cérebro aos efeitos tóxicos do mercúrio revelaram ser específicas de cada espécie. Enquanto que para o cérebro de L. aurata se verificou um decréscimo de todos os parâmetros antioxidantes estudados nos locais contaminados, sem haver evidência de qualquer mecanismo compensatório, no D. labrax observaram-se respostas ambivalentes, que indicam por um lado a activação de mecanismos adaptativos e, por outro, o decréscimo das respostas antioxidantes, ou seja, sinais de toxicidade. Embora em ambas as espécies de peixe fosse evidente uma condição pró-oxidante, o cérebro parece possuir mecanismos compensatórios eficientes, uma vez que não se verificou peroxidação lipídica. As respostas antioxidantes do cérebro de D. labrax foram comparadas em diferentes períodos do ano - quente vs. frio. O período quente mostrou ser mais crítico, uma vez que no período frio não se verificaram diferenças nas respostas entre locais, ou seja, a capacidade antioxidante do cérebro parece ser influenciada pelos factores ambientais. As guelras revelaram susceptibilidade à contaminação por mercúrio, uma vez que se verificou uma tendência para o decréscimo da actividade de CAT em L2 e ausência de indução em L1. O fígado e o rim demonstraram mecanismos adaptativos face ao grau de contaminação moderada (L1), evidenciados pelo aumento de CAT. O rim também demonstrou adaptabilidade face ao grau elevado de contaminação (L2), uma vez que se verificou um aumento GST. Embora o grau de susceptibilidade tenha sido diferente entre os órgãos, não se verificou peroxidação lipídica em nenhum. A determinação do conteúdo em MTs em D. labrax e em L. aurata revelou que este parâmetro depende não só da espécie, mas também do tecido em causa. Assim, em D. labrax foi observado um decréscimo de MTs no cérebro, bem como a incapacidade de síntese de MTs no sangue, guelras, fígado, rim e músculo. Em L. aurata observou-se um aumento do conteúdo em MTs no fígado e no músculo. Estes resultados indicam que a aplicabilidade das MTs como biomarcador de exposição ao mercúrio parece ser incerta, revelando limitações na capacidade de reflectir os níveis de exposição ao metal e por consequência o grau de acumulação. Este trabalho comprova a necessidade de se integrarem estudos de bioacumulação com biomarcadores de efeitos, de modo a reduzir os riscos de interpretações erróneas, uma vez que as respostas nem sempre ocorrem para os níveis mais altos de contaminação ambiental com mercúrio.

Effect of water chemistry on the physiology and toxicity assessment in Daphnia

Todos os sistemas aquáticos estão potencialmente expostos a alterações nos parâmetros da água em consequência de fenómenos ambientais tais como deposição ácida, lixiviação de iões dos solos e alterações climáticas. Dado que os parâmetros químicos da água estão geralmente correlacionados, é pertinente estudar os seus efeitos combinados para o biota aquático. Assim, o principal objetivo desta tese é avaliar a importância ecológica da variação simultânea dos principais parâmetros fisico-químicos da água nos parâmetros de história de vida dos crustáceos tanto na ausência como na presença de metais. Foram estudados os seguintes parâmetros: dureza (0.5 - 3.5 mM), alcalinidade (0.3 - 2.3 mM), pH (5.7 - 9.0) e temperatura (13 - 30ºC). A Daphnia magna foi usada como espécie modelo representando os crustáceos aquáticos. A variação simultânea da dureza e alcalinidade afetou significativamente o crescimento, reprodução e crescimento populacional de Daphnia; no entanto, os efeitos da dureza excederam os efeitos da alcalinidade. Pareceu haver interação entre a dureza e alcalinidade na reprodução dos dafnídeos, o que sugere que os efeitos da variação da dureza para Daphnia e provavelmente outros crustáceos poderão depender do nível de alcalinidade. O pH e dureza da água exerceram efeitos combinados para Daphnia, sendo os efeitos do pH mais pronunciados do que os efeitos da dureza. A diminuição do pH reduziu a sobrevivência, crescimento, reprodução, taxa de ingestão e crescimento populacional dos dafnídeos. No entanto, os efeitos do pH baixo foram mais adversos a baixa dureza, o que sugere uma interação entre estes parâmetros. Assim, a diminuição do pH em lagos de água mole pode ser um estressor determinante para os crustáceos sensíveis à acidez, ameaçando a sua sobrevivência e, consequentemente, afetando a estrutura das cadeias alimentares aquáticas. A temperatura e a química da água (dureza e alcalinidade) interagiram entre si nos parâmetros de história de vida de Daphnia; no entanto, os efeitos da temperatura excederam os efeitos da química da água. De um modo geral, temperaturas extremas reduziram o crescimento, reprodução e, consequentemente, o crescimento populacional de Daphnia. Os efeitos do aumento da temperatura foram mais adversos a baixa dureza e alcalinidade, aumentando a preocupação com os efeitos ecológicos do aquecimento global em águas moles. A dureza e alcalinidade da água também desempenharam um papel importante na toxicidade aguda e subletal (inibição da ingestão) dos metais para Daphnia. A diminuição da dureza aumentou a toxicidade aguda do zinco. Por outro lado, a diminuição da alcalinidade aumentou a toxicidade aguda e subletal do cobre, mas reduziu a toxicidade subletal do zinco, tornando evidente o importante papel da alcalinidade na toxicidade subletal dos metais para Daphnia. Globalmente, os parâmetros fisico-químicos da água parecem interagir entre si, afetando os parâmetros de história de vida e o crescimento populacional de Daphnia e também afetam a toxicidade dos metais. Em particular, a baixa dureza agrava os efeitos adversos da diminuição do pH, aumento da temperatura e toxicidade dos metais, o que aumenta a preocupação com os efeitos ecológicos da sua variação simultânea sobre os crustáceos e, portanto, sobre as cadeias alimentares aquáticas.

The role of environmental stress on protein synthesis fidelity

Estudos recentes estabelecem uma ligação entre erros na tradução do mRNA e cancro, envelhecimento e neurodegeneração. RNAs de transferência mutantes que introduzem aminoácidos em locais errados nas proteínas aumentam a produção de espécies reactivas de oxigénio e a expressão de genes que regulam autofagia, ribofagia, degradação de proteínas não-funcionais e protecção contra o stress oxidativo. Erros na tradução do mRNA estão portanto relacionados com stress proteotóxico. Sabe-se agora que o mecanismo de toxicidade do crómio está associado à diminuição da fidelidade de tradução e à agregação de proteínas com malformações que destabilizam a sua estrutura terciária. Desta forma, é possível que os efeitos do stress ambiental ao nível da degeneração celular possam estar relacionados com a alteração da integridade da maquinaria da tradução. Neste estudo procedeu-se a uma avaliação alargada do impacto do stress ambiental na fidelidade da síntese de proteínas, utilizando S. cerevisiae como um sistema modelo. Para isso recorreu-se a repórteres policistrónicos de luciferase que permitiram quantificar especificamente a supressão de codões de terminação e o erro na leitura do codão AUG em células exposta a concentações não letais de metais pesados, etanol, cafeína e H2O2. Os resultados sugerem que a maquinaria de tradução é na generalidade muito resistente ao stress ambiental, devido a uma conjugação de mecanismos de homeostase que muito eficientemente antagonizam o impacto negativo dos erros de tradução. A nossa abordagem quantitativa permitiu-nos a identificar genes regulados por uma resposta programada ao stress ambiental que são também essenciais para mitigar a ocorrência de erros de tradução, nomeadamente, HSP12, HSP104 e RPN4. A exposição prolongada ao stress ambiental conduz à saturação dos mecanismos de homeostase, contribuindo para a acumulação de proteínas contendo erros de tradução e diminuindo a disponibilidade de proteínas funcionais directamente envolvidas na manutenção da fidelidade de tradução e integridade celular. Ao contrário de outras Hsps, a Hsp12p adopta normalmente uma localização membranar em condições de stress, que pode modular a fluidez e estabilidade membranar, sugerindo que a membrana plasmática é um alvo preferencial da perda de fidelidade da tradução. Para melhor compreender as respostas celulares aos erros de tradução, células contendo deleções em genes codificadores das Hsps foram transformadas com tRNAs mutantes que introduzem alterações no proteoma. Os nossos resultados demonstram que para além da resposta geral ao stress, estes tRNAs induzem alterações a nível do metabolismo celular e um aumento de aminoacilação com Metionina em vários tRNAs, sugerindo um mecanismo de protecção contra espécies reactivas de oxigénio. Em conclusão, este estudo sugere um papel para os erros de tradução na gestão de recursos energéticos e na adaptação das células a ambientes desfavoráveis.

Effect assessment of nanoparticles toxicity in the terrestrial compartment

Over 11 million tons of nanomaterials (NMs) have been produced in 2012 and predictions point the increase in production. Despite predictions and extended usage via consumer products and industry, the understanding of the potential impact of these materials on the environment is virtually absent. The main aim of this thesis is to understand how a selected group of nanomaterials (metal based particles) may impact soil invertebrates, with special focus on the mechanisms of response. Since a case-by-case Environmental Risk Assessment (ERA) of all the emerging contaminants (particularly NMs) is impossible, among others due to time and cost reasons, to gain understanding on the mechanism of action and response is very important to reach a common paradigm. Understanding the modes of action provides predictive characters in cross particle extrapolation. Besides, it also provides insight for the production of new and sustainable materials. Overall, the effects of the selected NMs (Copper and Silver, Titanium and Zirconium oxides) and the respective salt forms, were investigated at the gene expression (using high-throughput tools, microarray and qPCR technology), biochemical (using enzymatic assays for analysis of oxidative stress markers) and organism (survival and reproduction as in OECD test guidelines) levels, this using standard soil species (Enchytraeus albidus, Enchytraeus crypticus, Eisenia fetida). Gene expression analysis provided valuable information on the mechanisms affected by each of the NMs. The gene expression profile highlighted a (nano)material signature and the effect of the duration of exposure. The functional analyses integrated with the biochemical and organism data, revealed a good understanding power. The biochemical parameters (oxidative stress related) were distinct across the materials and also influenced by duration of exposure and concentration. The standardized organismal responses differed the least between the various materials. The overall outcome is that, in this context of NMs effect assessment, gene expression and enzymatic assays introduced a very important knowledge gap, which could not had been achieved by the standard organismal effects alone. A reoccurring issue with some metal based NMs is the possible dissolution and subsequent release of ions that then causes toxicity e.g. Cu-NPs or Ag-NPs release Cu2+ or Ag+. The oxidation state of the particles was investigated, although this was not the focus of the thesis. The study of fate, e.g. dissolution of NPs, is also only in its beginning and the appropriate techniques are currently being developed. The results showed a specific nanoparticle effect. The UV exposure with titanium dioxide nanoparticles increased its effect.

Assessment of the mineralogenic toxicity of aquatic pollutants

In ecotoxicology a major focus is in the aquatic environment, not only because it presents a great economic value to man but it is an ecosystem widely affected by the growing anthropogenic pollution. Most of the studies performed relate to adverse effects in development, reproductive or endocrine disruption but little is known about the possible effects in bone formation and skeletal development. In this study, we set out to evaluate the effects of 8 aquatic pollutants on the skeletal development using an in vivo system, the zebrafish larvae aged 20 days post-fertilization, through chronic exposure. Several endpoints were considered such as the cumulative mortality, total length, occurrence of skeletal deformities and marker gene expression. We were able to establish LD50 values for some pollutants, like 3-methylcholanthrene, lindane, diclofenac, cobalt and vanadate and found that the total length was not affected by any of the pollutants tested. Cobalt was the most harmful chemical to affect hatching time, severely affecting the ability of the zebrafish embryos to hatch and overall the number of deformities increased upon exposure to tested chemicals but no patterns of deformities were identified. We also propose that 3-methylcholanthrene has an osteogenic effect, affecting osteoblast and osteoclast function and that op levels can act as a mediator of 3-methylcholanthrene toxic stress to the osteoblast. In turn we found naphthalene to probably have a chondrogenic effect. Our results provided new insights into the potential osteotoxicity of environmental pollutants. Future studies should aim at confirming these preliminary data and at determining mechanisms of osteotoxicity.

Environmental exposure to toxicants mixtures from a multi-purpose estuary: perspectives for a biomonitoring study in Portugal

This work was focused on a multi-purpose estuarine environment (river Sado estuary, SW Portugal) around which a number of activities (e.g., fishing, farming, heavy industry, tourism and recreational activities) coexist with urban centres with a total of about 200 000 inhabitants. Based on previous knowledge of the hazardous chemicals within the ecosystem and their potential toxicity to benthic species, this project intended to evaluate the impact of estuarine contaminants on the human and ecosystem health. An integrative methodology based on epidemiological, analytical and biological data and comprising several lines of evidence, namely, human contamination pathways, human health effects, consumption of local produce, estuarine sediments, wells and soils contamination, effects on commercial benthic organisms, and genotoxic potential of sediments, was used. The epidemiological survey confirmed the occurrence of direct and indirect (through food chain) exposure of the local population to estuarine contaminants. Furthermore, the complex mixture of contaminants (e.g., metals, pesticides, polycyclic aromatic hydrocarbons) trapped in the estuary sediments was toxic to human liver cells exposed in vitro, causing cell death, oxidative stress and genotoxic effects that might constitute a risk factor for the development of chronic-degenerative diseases, on the long term. Finally, the integration of data from several endpoints indicated that the estuary is moderately impacted by toxicants that affect also the aquatic biota. Nevertheless, the human health risk can only be correctly assessed through a biomonitoring study including the quantification of contaminants (or metabolites) in biological fluids as well as biomarkers of early biological effects (e.g., biochemical, genetic and omics-based endpoints) and genetic susceptibility in the target population. Data should be supported by a detailed survey to assess the impact of the contaminated seafood and local farm products consumption on human health and, particularly, on metabolic diseases or cancer development.

Impact of excipients in the chronic toxicity of fluoxetine on the alga Chlorella vulgaris

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) widely used in the treatment of major depression. It has been detected in surface and wastewaters, being able to negatively affect aquatic organisms. Most of the ecotoxicity studies focused only in pharmaceuticals, though excipients can also pose a risk to non-target organisms. In this work the ecotoxicity of five medicines (three generic formulations and two brand labels) containing the same active substance (fluoxetine hydrochloride) was tested on the alga Chlorella vulgaris, in order to evaluate if excipients can influence their ecotoxicity. Effective concentrations that cause 50% of inhibition (EC50) ranging from 0.25 to 15 mg L−1 were obtained in the growth inhibition test performed for the different medicines. The corresponding values for fluoxetine concentration are 10 times lower. Higher EC50 values had been published for the same alga considering only the toxicity of fluoxetine. Therefore, this increase in toxicity may be attributed to the presence of excipients. Thus more studies on ecotoxicological effects of excipients are required in order to assess the environmental risk they may pose to aquatic organisms.

Toxicity assessment of refill liquids for electronic cigarettes.

We analyzed 42 models from 14 brands of refill liquids for e-cigarettes for the presence of micro-organisms, diethylene glycol, ethylene glycol, hydrocarbons, ethanol, aldehydes, tobacco-specific nitrosamines, and solvents. All the liquids under scrutiny complied with norms for the absence of yeast, mold, aerobic microbes, Staphylococcus aureus, and Pseudomonas aeruginosa. Diethylene glycol, ethylene glycol and ethanol were detected, but remained within limits authorized for food and pharmaceutical products. Terpenic compounds and aldehydes were found in the products, in particular formaldehyde and acrolein. No sample contained nitrosamines at levels above the limit of detection (1 μg/g). Residual solvents such as 1,3-butadiene, cyclohexane and acetone, to name a few, were found in some products. None of the products under scrutiny were totally exempt of potentially toxic compounds. However, for products other than nicotine, the oral acute toxicity of the e-liquids tested seems to be of minor concern. However, a minority of liquids, especially those with flavorings, showed particularly high ranges of chemicals, causing concerns about their potential toxicity in case of chronic oral exposure.

Environmental assessment of Lake Gibson sediments, water quality, and soils of the Niagara Region

In light of the fact that literature on toxicity of heavy metals in non-acidified freshwater systems is sparse, this project was initiated to conduct an environmental assessment of Lake Gibson. Chemistry of soils from adjacent areas and vineyards in the region provide a comparative background database. Water quality determinations were used to identify and highlight areas of environmental concern within the Lake Gibson watershed. A Shelby Corer was used to obtain 66 sediment cores from Lake Gibson. These were sectioned according to lithology and color to yield 298 samples. A suite of 122 soil samples was collected in the region and vicinity of Lake Gibson. All were tested for metals and some for Total Petroleum Hydrocarbons (TPH). Evaluation of the results leads to the following conclusions: 1. Metal concentrations ofAI, Cd, Cu, Cr, Pb, Ni, Fe and Zn in soils from the Niagara Region are well below background limits set by the Ministry of the Environment and Energy (MOEE) for provincial soils. 2. There is a spatial and depth difference for some of the metals within the various soils. The Cr, Ni and Pb contents of soils vary throughout the region (ptoxicity testing of 11 the sediments is required to assess impact on the aquatic biota. 5. Specifically, effluents and discharges from outfalls, roadways, railways and industrial activities are all degrading the local ecosystem. 6. Mineral oil and greases are a major environmental concern in the sediments of Lake Gibson. Ofthe 240 samples tested for TPH, 200 samples exceed the MOEE Open Water Disposal Guideline of 1,500 mg/kg. 7. Four areas within Lake Gibson are especially degraded with respect to TPH. One area is just downstream from the Old WeIland Canal divergence point and waterfall. Other areas of concern are located just south of Beaverdams Road and just west ofthe Ontario Hydro control pipes; south ofthe Village ofBeaverdams. The fourth area of environmental concern and TPH impact is located between Highway 406 and Merrittville Highway.

Toxicity, accumulation and depuration of heavy metalsin the brown mussel perna indica

In this thesis certain important aspects of heavy metal toxicity have been worked out. Recent studies have clearly shown that when experimental media contained more than one heavy metals, such metals could conspicuously influence the toxic reaction of the animals both in terms of quantity and nature. The experimental results available on individual metal toxicity show that, in majority of such results, unrealistically high concentrations of dissolved metals are involved. A remarkable number of factors have been shown to influence metal toxicity such as various environmental factors particularly temperature and salinity, the condition of the organism and the ability of some of the marine organisms to adapt to metallic contamination. Further, some of the more sensitive functions like embryonic and larval development, growth and fecundity, oxygen utilization and the function of various enzymes are found to be demonstrably sensitive in the presence of heavy metals. However, some of the above functions could be compensated for by adaptive process. If it is assumed that the presence of a single metal in higher concentrations could affect the life function of marine animals, more than one metal in the experimental media should manifest such effects in a greater scale. Commonly known as synergism or more than additivity, majority of heavy metals bring about synergistic reaction .The work presented in this thesis comprises lethal and sublethal toxicities of different salt forms of copper and silver on the brown mussel Perna indica. during the present investigation sublethal concentrations of copper and silver in their dent effects on survival, oxygen consumption, filtration, accumulation and depuration on Perna indica. The results are presented under different sections to make the presentation meaningful .

“Assessment of Heavy Metals in the Environmental Compartments of the Central and Northern Coast of Kerala, India”

The nearshore marine ecosystem is a dynamic environment impacted by many activities, especially the coastal waters and sediments contiguous to major urban areas. Although heavy metals are natural constituents of the marine environment, inputs are considered to be conservative pollutants and are potentially toxic, accumulate in the sediment, are bioconcentrated by organisms and may cause health problems to humans via the food chain. A variety of metals in trace amounts are essential for biological processes in all organisms, but excessive levels can be detrimental by acting as enzyme inhibitors. Discharge of industrial wastewater, agriculture runoff and untreated sewage pose a particularly serious threat to the coastal environment of Kerala, but there is a dearth of studies in documenting the contaminant metals. This study aimed principally to assess such contamination by examining the results of heavy metal (Cu, Pb, Cr, Ni, Zn, Cd and Hg) analysis in seawater, sediment and benthic biota from a survey of five transects along the central and northern coast of Kerala in 2008 covering a 10.0 km stretch of near shore environment in each transect. Trophic transfer of metal contaminants from aquatic invertebrates to its predators was also assessed, by employing a suitable benthic food chain model in order to understand which all metals are undergoing biotransference (transfer of metals from a food source to consumer).The study of present contamination levels will be useful for potential environmental remediation and ecosystem restoration at contaminated sites and provides a scientific basis for standards and protective measures for the coastal waters and sediments. The usefulness of biomonitor proposed in this study would allow identification of different bioavailable metals as well as provide an assessment of the magnitude of metal contamination in the coastal marine milieu. The increments in concentration of certain metals between the predator and prey discerned through benthic food chain can be interpreted as evidence of biotransference.

Is Microtox R toxicity related to potentially harmful algae proliferation in Mediterranean salt marshes?

Mediterranean salt marshes are ecosystems that are highly influenced by sea changes and freshwater inputs from runoff. In these ecosystems, toxic and non-toxic algae blooms often produce large and unpredictable biomasses of phytoplankton. The Microtox R test has been described as a successful, quick method for detecting toxicity in various phytoplankton taxa. Ourstudy sought to test the efficiency of Microtox R in detecting toxic HAB in Mediterranean salt marshes. The results showed that the Microtox R test was able to detect toxic substances in the particulate matter of several lagoons in the Empordà salt marshes. This Microtox R toxicity coincided with periods when potentially harmful cyanobacteria, dinoflagellates and haptophytes had a high biomass. The results suggest that potentially harmful phytoplankton cannot be ruled out as a source of Microtox R