Émilien Pelletier

Bivalve mollusks in metal pollution studies: from bioaccumulation to biomonitoring.

Contemporary environmental challenges have emphasized the need to critically assess the use of bivalve mollusks in chemical monitoring (identification and quantification of pollutants) and biomonitoring (estimation of environmental quality). Many authors, however, have considered these approaches within a single context, i.e., as a means of chemical (e.g. metal) monitoring. Bivalves are able to accumulate substantial amounts of metals from ambient water, but evidence for the drastic effects of accumulated metals (e.g. as a TBT-induced shell deformation and imposex) on the health of bivalves has not been documented. Metal bioaccumulation is a key tool in biomonitoring; bioavailability, bioaccumulation, and toxicity of various metals in relation to bivalves are described in some detail including the development of biodynamic metal bioaccumulation model. Measuring metal in the whole-body or the tissue of bivalves themselves does not accurately represent true contamination levels in the environment; these data are critical for our understanding of contaminant trends at sampling sites. Only rarely has metal bioaccumulation been considered in combination with data on metal concentrations in parts of the ecosystem, observation of biomarkers and environmental parameters. Sclerochemistry is in its infancy and cannot be reliably used to provide insights into the pollution history recorded in shells. Alteration processes and mineral crystallization on the inner shell surface are presented here as a perspective tool for environmental studies.

Sex alteration in soft-shell clams (Mya arenaria) in an intertidal zone of the Saint Lawrence river (Quebec, Canada).

The purpose of this study was to verify whether any changes in sex ratio might occur in soft-shell clams (Mya arenaria) located in an intertidal harbor zone located at the mouth of the Saguenay Fjord in the Saint Lawrence estuary (Baie Sainte-Catherine (BSC), Québec, Canada) likely to be contaminated by organotin compounds. Bivalves were harvested at the BSC harbor site and from two reference sites. Condition index (weight to length ratio), gonado-somatic index, sex ratio, vitellin-like proteins, organotin concentrations in gonad tissue, maturation stages of the gonads, the number of estradiol-17beta binding sites and the capacity of female gonad extracts to produce estradiol-17beta were determined in collected animals. Results showed that sex ratio in clams was significantly skewed toward males. Moreover, the condition and gonad-somatic indices, vitellin-like proteins in female gonads and the capacity of female gonads to produce estradiol-17beta were significantly reduced at the harbor site with respect to the reference sites. Maturation status of male gonads was clearly delayed at the harbor site. Additionally, gonad tissue contained tributyltin (TBT) at an average level of 109+/-18 ngSn/gdry wt. at the harbor site while organotins were not detected from the reference sites. Finally, female gonads had a higher number of unoccupied estradiol binding sites at the harbor site indicating low levels of this steroid in this tissue. Overall, this paper is first to report that clams collected in the vicinity of a TBT contaminated harbor are subject to masculinizing effects which seems to be consistent with biological effects that organotins are known to exert toward some other marine invertebrates.

Genetic damage induced by trophic doses of lead in the neotropical fish Hoplias malabaricus (Characiformes, Erythrinidae) as revealed by the comet assay and chromosomal aberrations

The effects of clastogenic or mutagenic agents have rarely been studied in neotropical fish species exposed to contaminated water. In this study, the genetic damage caused by lead in the widely distributed South American fish, Hoplias malabaricus, was assessed using the comet (SCGE) assay and by testing for chromosomal aberrations. Eighteen specimens were acclimatized to laboratory conditions and then chronically exposed to contaminated food by feeding prey (Cyprinus sp.) injected intraperitoneally with doses of inorganic lead adjusted to give a contamination level of 21 mg of Pb2+.g-1 net weight of H. malabaricus. Three fish were sampled for chromosomal analysis after four doses (18 days) and another three after eight doses (41 days) of lead and the results then compared with three untreated controls kept under lead-free conditions. An additional six treated fish and three controls were sampled for the comet assay after 13 doses (64 days). Exposure to lead significantly increased the frequency of chromosomal aberrations and the frequency of tailed cell nuclei, the latter indicating DNA damage. These results show that H. malabaricus is a useful biological model for screening the clastogenic effects of lead and possibly other xenobiotics. The genetic damage seen here illustrates the need to investigate the potential effects of heavy metals on fish species in South America.

Highly persistent butyltins in northern marine sediments: a long-term threat for the Saguenay Fjord (Canada).

An exhaustive study of the distribution of butyltin species was conducted in the sediment of the Saguenay Fjord (Canada), a semi-enclosed marine system with sediment permanently submitted to sub-Arctic cold conditions. Concentrations of total butyltins (tributyltin [TBT], dibutyltin, and monobutyltin) ranged from 6 to 288 ng Sn/g dry weight and were typical of those reported for contaminated coastal areas despite limited seasonal traffic of commercial vessels in the fjord. The distribution profiles of butyltin species in four sediment cores clearly indicated the high persistence of TBT that was dominating other species. The particular oceanographic conditions of the Saguenay Fjord (low seawater temperature, anoxic sediments, and low exchange rate of deep waters) combined with a high sediment/pore-water partition coefficient (Kdobs = 1.0 x 10(4) to 1.2 x 10(4) L/kg) and a low sediment/ water diffusive flux of TBT (J1 = 13 x 10(-8) mol/m2/year) are responsible for the burial and preservation of TBT in this marine ecosystem. The half-life of TBT in deep sediment was estimated to be approximately 87+/-17 years (+/-SEM), which implies a much slower degradation rate than any previously reported. Finally, a flood event that occurred five years before the sampling enabled us to calculate a very slow diffusive flux from the preflood to the postflood layer (J2 = 2 x 10(-8) mol/m2/year), indicating an almost permanent sequestration of TBT in the buried layers.

Effectiveness of Bioremediation of Crude Oil Contaminated Subantarctic Intertidal Sediment: The Microbial Response

A field study was initiated in February 1996 in a remote sandy beach of The Grande Terre (Kerguelen Archipelago, 69° 42° E, 49° 19° S) with the objective of determining the long-term effects of some bioremediation agents on the biodegradation rate and the toxicity of oil residues under severe subantarctic conditions. A series of 10 experimental plots were settled firmly into sediment. Each plot received 2L of Arabian light crude oil and some of them were treated with bioremediation agents: slow release fertilizer Inipol EAP-22 (Elf Atochem) or fish composts. Plots were sampled on a regular basis over a 3-year period. A two-order of magnitude increase of saprophytic and hydrocarbon-utilizing microorganisms occurred during the first month of the experiment in all treated enclosures, but no clear differences appeared between the plots. Very high microbial populations were present during the experiment. Biodegradation within treated spots was faster than within the untreated ones and appeared almost complete after 6 months as indicated by the degradation index of aliphatic hydrocarbons within all plots. The analysis of interstitial water collected below the oily residues presented no toxicity. However, a high toxicity signal, using Microtox solid phase, appeared for all oiled sand samples with a noticeable reduction with time even if the toxicity signal remained present and strong after 311 days of oil exposition. As a conclusion, it is clear that the microbial response was rapid and efficient in spite of the severe weather conditions, and the rate of degradation was improved in presence of bioremediation agents. However, the remaining residues had a relatively high toxicity.

Effects of temperature and fertilization on total vs. active bacterial communities exposed to crude and diesel oil pollution in NW Mediterranean Sea

The dynamics of total and active microbial communities were studied in seawater microcosms amended with crude or diesel oil at different temperatures (25, 10 and 4 degrees C) in the presence/absence of organic fertilization (Inipol EAP 22). Total and hydrocarbon-degrading microbes were enumerated by fluorescence microscopy and Most Probable Number (MPN) method, respectively. Total (16S rDNA-based) vs. active (16S rRNA) bacterial community structure was monitored by Capillary-Electrophoresis Single Strand Conformation Polymorphism (CE-SSCP) fingerprinting. Hydrocarbons were analyzed after 12 weeks of incubation by gas chromatography-mass spectrometry. Total and hydrocarbon-degrading microbial counts were highly influenced by fertilization while no important differences were observed between temperatures. Higher biodegradation levels were observed in fertilized microcosms. Temperature and fertilization induced changes in structure of total bacterial communities. However, fertilization showed a more important effect on active bacterial structure. The calculation of Simpsons diversity index showed similar trends among temperatures whereas fertilization reduced diversity index of both total and active bacterial communities.

Effects of nutrient and temperature on degradation of petroleum hydrocarbons in sub-Antarctic coastal seawater

In an attempt to evaluate the potential of petroleum bioremediation at high latitudes environments, microcosm studies using Antarctic coastal seawater contaminated with diesel or crude oil were conducted in Kerguelen Archipelago (49°22′S, 70°12′E). Microcosms were incubated at three different temperatures (4, 10 and 20°C). During experiments, changes observed in microbial assemblages (total direct count, heterotrophic cultivable microorganisms and hydrocarbon-degrading microorganisms) were generally similar for all incubation temperatures, but chemical data showed only some slight changes in biodegradation indices [Σ(C12–C20)/Σ(C21–C32) and C17/pristane]. The complete data set provided strong evidence of the presence of indigenous hydrocarbon-degrading bacteria in Antarctic seawater and their high potential for hydrocarbon bioremediation. The rate of oil degradation could be increased by the addition of a commercial fertilizer, but water temperature had little effects on biodegradation efficiency which is in conflict with the typical temperature-related assumption predicting 50% rate reduction when temperature is reduced by 10°C. Global warming of Antarctic seawater should not increase significantly the rate of oil biodegradation in these remote regions.

Distribution of PAHs in the water column, sediments and biota of Potter Cove, South Shetland Islands, Antarctica

Abstract In order to establish the environmental status of areas close to Antarctic stations it is necessary to document levels of contaminants present in these sites. Several petrogenic and pyrogenic sources have been reported for polycyclic aromatic hydrocarbons (PAHs) in Antarctica. In this work, levels of 25 PAHs were measured in suspended particulate matter (SPM), surface sediment and marine organisms (fish Notothenia coriiceps, bivalve Laternula elliptica and gastropod Nacella concinna) from Potter Cove. Total PAH levels from SPM were low and similar in all sites studied (30–82 ng g-1 dw), phenanthrene being the dominant compound (68–84%). The exception was an area close to the wharf where significantly higher values of light PAHs such as naphthalene, acenaphthylene, 2,3,5-trimethylnaphthalene and fluorene were detected, indicating the influence of recent fuel spills. PAH concentrations in surface sediments were generally low (37–252 ng g-1 dw) except for two sites (1762 and 1908 ng g-1 dw) which suggested an accumulation process associated with the water circulation pattern. Liver tissue of N coriiceps presented significantly higher PAH levels (257 ng g-1 dw) compared with gonads. The pattern of individual compounds from substrates and organisms suggests a petrogenic and low-temperature combustion origin.

Toxic effects of tributyltin and its metabolites on harbour seal (Phoca vitulina) immune cells in vitro.

The widespread environmental contamination, bioaccumulation and endocrine disruptor effects of butyltins (BTs) to wildlife are well documented. Although suspected, potential effects of BTs exposure on the immune system of marine mammals have been little investigated. In this study, we assessed the effects of tributyltin (TBT) and its dealkylated metabolites dibutyltin (DBT) and monobutyltin (MBT) on the immune responses of harbour seals. Peripheral blood mononuclear cells isolated from pup and adult harbour seals were exposed in vitro to varying concentrations of BTs. DBT resulted in a significant decrease at 100 and 200 nM of phagocytotic activity and reduced significantly phagocytic efficiency at 200 nM in adult seals. There was no effect in phagocytosis with TBT and MBT. In pups, the highest concentration (200 nM) of DBT inhibited phagocytic efficiency. A reduction of tumor-killing capacity of adult natural killer (NK) cells occurred when leukocytes were incubated in vitro with 50 nM DBT and 200 nM TBT for 24h. In adult seals, T-lymphocyte proliferation was significantly suppressed when the cells were exposed to 200 nM TBT and 100 nM DBT. In pups, the proliferative response increased after an exposure to 100 nM TBT and 50 nM DBT, but decreased with 200 nM TBT and 100 nM DBT. The immune functions were more affected by BTs exposure in adults than in pups, suggesting that other unsuspected mechanisms could trigger immune parameters in pups. The toxic potential of BTs followed the order of DBT>TBT>MBT. BT concentrations of harbour seal pups from the St. Lawrence Estuary (Bic National Park) ranged between 0.1-0.4 ng Sn/g wet weight (ww) and 1.2-13.4 ng Sn/g ww in blood and blubber, respectively. For these animals, DBT concentrations were consistently below the quantification limit of 0.04 ng Sn/g ww in blood and 0.2 ng Sn/g ww in blubber. Results suggest that concentrations measured in pups are considered too low to induce toxic effects to their immune system during first days of life. However, based on our in vitro results, we hypothesize that BTs, and DBT in particular, could pose a serious threat to the immune functions in free-ranging harbour seal adults.

Phenanthrene Biodegradation in Soils Using an Antarctic Bacterial Consortium

ABSTRACT Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in Antarctic soils is limited by low temperatures, lack of adequate levels of nutrients, low number of PAH-tolerant members in the autochthonous microbiota and low bioavailability of contaminants. In the present work, microcosms systems (performed in 1-L glass flasks containing Antarctic soil supplemented with 1744 ppm of phenanthrene) were used to study (i) the effect of biostimulation with a complex organic source of nutrients (fish meal) combined with a surfactant (Brij 700); (ii) the effect of bioaugmentation with a psychrotolerant PAH-degrading bacterial consortium (M10); (iii) the effect of the combination of both strategies. The authors found that combination of biostimulation and bioaugmentation caused a significant removal (46.6%) of phenanthrene after 56 days under Antarctic environmental conditions. When bioaugmentation or biostimulation were applied separately, nonsignificant reduction in phenanthrene concentration was observed. Microtox test showed a low increase in toxicity only in the most efficient system. Results proved that “in situ” bioremediation process of phenanthrene-contaminated soils is possible in Antarctic stations. In addition, inoculation with a psychrotolerant PAH-degrading bacterial consortium in association with a mix of fish meal and a high-molecular-weight surfactant improved phenanthrene removal and should be the selected strategy when the number of hydrocarbons degrading bacteria in the target soil is low.