Lipid nanocapsules for behavioural testing in aquatic toxicology: Time-response of Eurytemora affinis to environmental concentrations of PAHs and PCB

Cellular accumulation of crude oil compounds reduces the competitive fitness of the coral symbiont Symbiodinium glynnii

Oil spill events in the marine environment can have a deleterious impact on the affected ecosystems, such as coral reefs, with direct consequences for their socioeconomic value. The mutualistic relationship between tropical corals and their dinoflagellate symbionts (Symbiodiniaceae) provide structural and nutritional basis for a high local biodiversity in oligotrophic waters. Here, we investigated effects of crude oil water-accommodated fraction on the competitive fitness of the model zooxanthellae species Symbiodinium glynnii. Results of laboratory essays demonstrate that crude oil carbon is incorporated into the cellular biomass with a concomitant change of δ¹³C isotopic value. Carcinogenic/mutagenic polycyclic aromatic hydrocarbons were identified in the culture media and were responsible for a linear reduction in population growth of S. glynnii, presumably related to energy relocation for DNA repair. Additionally, the experiments revealed that physiological effects induced by crude oil compounds are genetically inherited by the following generations under non-contaminated growth conditions, and induce a reduction in the competitive fitness to cope with other environmental parameters, such as low salinity. We suggest that the effects of crude oil contamination represent an imparing factor for S. glynnii coping with anthropogenic drivers (e.g. warming and acidification) and interfere with the delicate symbiont-host relationship of tropical corals. This is especially relevant in the coastal areas of northeastern Brazil where an oil spill event deposited crude oil on shallow water sediments with the potential to be resuspended to the water column by physical and/or biological activity, enhancing the risk of future coral bleaching events.

Promotion of the Development of Sentinel Species in the Water Column: Example Using Body Size and Fecundity of the Egg-Bearing Calanoid Copepod Eurytemora affinis

The development of sentinel species in aquatic ecosystems is mostly based on benthic organisms; however, organisms living in water column such as zooplankton have received less attention, except for some cladocerans. In this paper, a new ecological indicator based on simple measurements of the size and fecundity of egg-bearing calanoid copepods is developed. The well-studied estuarine copepod Eurytemora affinis is used to illustrate this new framework. A large database obtained from laboratory experiments developed under different conditions is used to define a reference regression line between clutch size (CS) and prosome length (PL). The same database allowed one to confirm that the coefficient of variation (CV) of CS is an adequate estimator of the accumulated stress at population level. The CV of PL shows very little variability in all experimental and field conditions. The values of CS and PL obtained from the Seine, Loire, Gironde, Scheldt and Elbe estuaries in Europe are compared to the reference regression line. A quality index (QI) is calculated as a percentage of difference between the observed and the predicted CS. The QI classified 19 samples collected in the Seine estuary between 2004 and 2010 into four classes according to the physiological condition of the copepod female. A single sampling from June 2004 (5.26%) showed a very good condition, whereas 57.9% of the sampling dates confirmed good conditions. On the other hand, four sampling dates were associated to very bad conditions and three sampling dates indicated bad conditions. Seven additional samples obtained from other European estuaries between 2006 and 2009 were also used. Females showing poor conditions were observed in the early spring of 2005 and 2008 as well as during the month of November. These years were characterized by very strong climatic anomalies with a very cold late winter in 2005 and a warm winter in 2008. Therefore, it seems that the QI perfectly reflected the strong stress caused by the sudden change in hydro-climatic conditions that have certainly affected the physiology of copepod females and probably the availability of food. The new indicator is very simple to calculate and can be generalised to several aquatic ecosystems (fresh water and brackish water) by targeting the dominating egg-bearing calanoid copepods. As in the case of E. affinis, the development of sentinel species based on copepods or cladocerans can enrich ecological and ecotoxicological studies given their capacity to integrate the variability of their habitats’ quality at the individual and population levels.

The genome of the European estuarine calanoid copepod Eurytemora affinis: Potential use in molecular ecotoxicology

In this study, we sequenced and assembled the genome of a European estuarine calanoid copepod using Oxford Nanopore PromethION and Illumina HiSeq 2500 platforms. The length of the assembled genome was 776.1 Mb with N50 = 474.9 kb (BUSCO 85.9%), and the genome consisted of 2473 contigs. A total of 18,014 genes were annotated and orthologous gene clusters were analyzed in comparison to other copepods. In addition, genome-wide identification of cytochrome P450s, glutathione S-transferases, and ATP-binding cassette transporters in E. affinis was performed to determine gene repertoire of these detoxification-related gene families. Results revealed the presence of species-specific gene inventories, indicating that these gene families have evolved through species-specific gene loss/expansion processes, possibly due to adaptation to different environmental stressors. Our study provides a new inventory of the European estuarine calanoid copepod E. affinis genome with emphasis on phase I, II, and III detoxification systems.

Short-term exposure to gold nanoparticle suspension impairs swimming behavior in a widespread calanoid copepod

Calanoid copepods play an important role in the functioning of marine and brackish ecosystems. Information is scarce on the behavioral toxicity of engineered nanoparticles to these abundant planktonic organisms. We assessed the effects of short-term exposure to nonfunctionalized gold nanoparticles on the swimming behavior of the widespread estuarine copepod Eurytemora affinis. By means of three-dimensional particle tracking velocimetry, we reconstructed the trajectories of males, ovigerous and non-ovigerous females. We quantified changes in their swimming activity and in the kinematics and geometrical properties of their motion, three important descriptors of the motility patterns of zooplankters. In females, exposure to gold nanoparticles in suspension (11.4 μg L^-1) for 30 min caused depressed activity and lower velocity and acceleration, whereas the same exposure caused minimal effects in males. This response differs clearly from the hyperactive behavior that is commonly observed in zooplankters exposed to pollutants, and from the generally lower sensitivity of female copepods to toxicants. Accumulation of gold nanoparticles on the external appendages was not observed, precluding mechanical effects. Only very few nanoparticles appeared sporadically in the inner part of the gut in some samples, either as aggregates or as isolated nanoparticles, which does not suggest systemic toxicity resulting from pronounced ingestion. Hence, the precise mechanisms underlying the behavioral toxicity observed here remain to be elucidated. These results demonstrate that gold nanoparticles can induce marked behavioral alterations at very low concentration and short exposure duration. They illustrate the applicability of swimming behavior as a suitable and sensitive endpoint for investigating the toxicity of nanomaterials present in estuarine and marine environments. Changes in swimming behavior may impair the ability of planktonic copepods to interact with their environment and with other organisms, with possible impacts on population dynamics and community structure.

Formation of Developmentally Toxic Phenanthrene Metabolite Mixtures by Mycobacterium sp. ELW1

Mycobacterium sp. ELW1 co-metabolically degraded up to 1.8 μmol of phenanthrene (PHE) in ∼48 h, and hydroxyphenanthrene (OHPHE) metabolites, including 1-hydroxyphenanthrene (1-OHPHE), 3-hydroxyphenanthrene (3-OHPHE), 4-hydroxyphenanthrene (4-OHPHE), 9-hydroxyphenanthrene (9-OHPHE), 9,10-dihydroxyphenanthrene (1,9-OHPHE), and trans-9,10-dihydroxy-9,10-dihydrophenanthrene (trans-9,10-OHPHE), were identified and quantified over time. The monooxygenase responsible for co-metabolic transformation of PHE was inhibited by 1-octyne. First-order PHE transformation rates, kPHE, and half-lives, t1/2, for PHE-exposed cells were 0.16-0.51 h-1 and 1.4-4.3 h, respectively, and the 1-octyne controls ranged from 0.015-0.10 h-1 to 7.0-47 h, respectively. While single compound standards of PHE and trans-9,10-OHPHE, the major OHPHE metabolite formed by ELW1, were not toxic to embryonic zebrafish (Danio rerio), single compound standards of minor OHPHE metabolites, 1-OHPHE, 3-OHPHE, 4-OHPHE, 9-OHPHE, and 1,9-OHPHE, were toxic, with effective concentrations (EC50's) ranging from 0.5 to 5.5 μM. The metabolite mixtures formed by ELW1, and the reconstructed standard mixtures of the identified OHPHE metabolites, elicited a toxic response in zebrafish for the same three time points. EC50s for the metabolite mixtures formed by ELW1 were lower (more toxic) than those for the reconstructed standard mixtures of the identified OHPHE metabolites. Ten unidentified hydroxy PHE metabolites were measured in the derivatized mixtures formed by ELW1 and may explain the increased toxicity of the ELW1 metabolites mixture relative to the reconstructed standard mixtures of the identified OHPHE metabolites.

Bioremediation mechanisms of combined pollution of PAHs and heavy metals by bacteria and fungi: A mini review

In recent years, knowledge in regard to bioremediation of combined pollution of polycyclic aromatic hydrocarbons (PAHs) and heavy metals by bacteria and fungi has been widely developed. This paper reviews the species of bacteria and fungi which can tackle with various types of PAHs and heavy metals entering into environment simultaneously or successively. Microbial activity, pollutants bioavailability and environmental factors (e.g. pH, temperature, low molecular weight organic acids and humic acids) can all affect the bioremediation of PAHs and heavy metals. Moreover, this paper summarizes the remediation mechanisms of PAHs and heavy metals by microbes via elucidating the interaction mechanisms of heavy metals with heavy metals, PAHs/PAHs metabolites with PAHs and PAHs with heavy metals. Based on the above reviews, this paper also discusses the potential research needs for this field.

Potential of the small cyclopoid copepod Paracyclopina nana as an invertebrate model for ecotoxicity testing

Aquatic invertebrates contribute significantly to environmental impact assessment of contaminants in aquatic ecosystems. Much effort has been made to identify viable and ecologically relevant invertebrate test organisms to meet rigorous regulatory requirements. Copepods, which are ecologically important and widely distributed in aquatic organisms, offer a huge opportunity as test organisms for aquatic toxicity testing. They have a major role not only in the transfer of energy in aquatic food chains, but also as a medium of transfer of aquatic pollutants across the tropic levels. In this regard, a supratidal and benthic harpacticoid copepod Tigriopus japonicus Mori (order Harpacticoida) has shown promising characteristics as a test organism in the field of ecotoxicology. Because there is a need to standardize a battery of test organisms from species in different phylogenetic and critical ecosystem positions, it is important to identify another unrelated planktonic species for wider application and comparison. In this regard, the cyclopoid copepod Paracyclopina nana Smirnov (order Cyclopoida) has emerged as a potential test organism to meet such requirements. Like T. japonicus, it has a number of features that make it a candidate worth consideration in such efforts. Recently, the genomics of P. nana has been unraveled. Data on biochemical and molecular responses of P. nana against exposure to environmental chemicals and other stressors have been collected. Recently, sequences and expression profiles of a number of genes in P. nana encoding for heat shock proteins, xenobiotic-metabolizing enzymes, and antioxidants have been reported. These genes serve as potential biomarkers in biomonitoring of environmental pollutants. Moreover, the application of gene expression techniques and the use of its whole transcriptome have allowed evaluation of transcriptional changes in P. nana with the ultimate aim of understanding the mechanisms of action of environmental stressors. Whole-animal bioassays and gene expression studies indicate that P. nana may serve as an excellent tool to evaluate the impact of diverse disturbances in the marine environment. With a better understanding of toxicological mechanisms, ecotoxicologists will be able to understand defense mechanisms against toxicants in copepods. In this review, we illustrate the potential of P. nana as an alternative as well as a complementary invertebrate model organism for risk assessment of aquatic pollutants.