Denis Fichet

Experimental studies of impacts of harbour sediments resuspension to marine invertebrates larvae : Bioavailability of Cd, Cu, Pb and Zn and toxicity

The larvae of three marine species (Artemia salina, Crassostrea gigas, Paracentrotus lividus) reared within the suspended particulate phases of contaminated sediments from harbours were used in bioassays firstly to assess their ability to accumulate four metals (Cd, Cu, Pb, Zn) and secondly to show the toxicity of such rearing media by recording delays in growth and possible abnormal larval development. The results show that resuspension processes of dredged harbour sediments may induce both a release of Cd, Cu and Pb which are bioavailable for larvae (levels of bioaccumulation depending on the species) and biological perturbations, i.e. abnormal development in C. gigas and P. lividus larvae for the more contaminated sediments and growth inhibition in all three larvae for slightly contaminated sediments. The concentrations of Pb reached in the C. gigas D-shaped larvae and the P. lividus pluteus were unusually high; in contrast, Zn was not accumulated by the three species. The impact of dumping operations thus appears to depend both on the metal considered and on the larvae used in such tests. In this context, Pb seems a more worrying metal than Zn and C. gigas and P. lividus are better indicator species than A. salina larvae.

Bioaccumulation and toxicity of four dissolved metals in Paracentrotus lividus sea-urchin embryo

The bioaccumulation of four metals (Cd, Cu, Pb, Zn) dissolved in water was assessed measuring the concentrations recorded within sea-urchin larvae (Paracentrotus lividus, Lmk.) after a 48-h exposure period. Concurrently, the frequencies of abnormalities were evaluated at the 48-h pluteus stage to check the actual toxicity of such contaminants with regards to larval development. Maximum metal concentrations in the larvae reached 43.8 +/- 6.7 micrograms Cd g-1 dry weight (d.w.), 1269 +/- 392 micrograms Cu g-1 d.w., 3106 +/- 679 micrograms Pb g-1 d.w., 534 +/- 62 micrograms Zn g-1 d.w. Bioconcentration factors (BCFs) reached very high values for Pb (maximum value: 16,282 +/- 973) and indicated that the concentrations of Pb and Cd were directly related to the water concentration at least in the range of concentrations tested. Zn appeared to be partially regulated above a certain threshold concentration (between 5 and 25 micrograms l-1). Cu was accumulated with an active uptake at least below lethal threshold level (100 micrograms l-1). Nevertheless, above these thresholds, high mortality of embryos prevent any interpretation of Zn and Cu bioconcentration factors. Concurrent studies carried out on embryotoxicity confirmed the high toxicity of Cu towards sea-urchin pluteus larvae and highlighted the different behaviour of Cd. The internal Cd concentrations were directly related to the external ones, comparable to other non-essential metals, but Cd had little toxic effect on the initial larval development.

Polycyclic aromatic hydrocarbons (PAHs) in surface sediment and oysters (Crassostrea rhizophorae) from mangrove of Guadeloupe: levels, bioavailability, and effects.

Surface sediment and oysters (Crassostrea rhizophorae) from the coastlines of Guadeloupe were analysed for polycyclic aromatic hydrocarbons (PAHs) using GC/MS. Biomarkers of oxidative stress were used to assess the response of these oysters to hydrocarbons exposure. The total concentration of PAHs in the sediment ranged from 49 to 1065 ng/g dw, while concentrations in oyster ranged from 66 to 961 ng/g dw. Molecular indices based on isomeric PAHs ratios characterize the pollution sources and show that most of the contaminations in sediment originate from pyrolytic inputs. Bioaccumulation factors (BAFs) have been related to isomeric ratio calculated for oysters in order to refine PAHs sources. The variations of BAFs observed in the different compounds resulted from different uptake pathways in the mangrove oysters according to the type of inputs. Response of biomarkers showed inhibition of catalase and an increase of lipid peroxidation at the station where PAHs concentrations were the highest. Taken together, data obtained point to the relevance of considering environmental conditions as factors influencing biomarker responses in environmental monitoring programs. These data also indicate the need for regular environmental follow-up studies in Guadeloupe.

Spatio-temporal structure of the nematode assemblages of the Brouage mudflat (Marennes Oléron, France)

The density and species composition of the nematode assemblage was investigated in the Brouage mudflat (Marennes-Oleron, France) at three stations over four seasons in relation to environmental parameters (organic matter percentage, chlorophyll a and heavy metal content). From the 43 species recorded, six dominant genera represented 75% of the assemblage. Fluctuations of these species were mainly in response to the observed temporal patterns. Over the course of a year, epigrowth feeders were the most important trophic group (43%) with three dominant species Metachromadoroides remanei, Chromadora macrolaima and Ptycholaimellus jacobi but some non-selective deposit feeders, notably Daptonema oxycerca, also contributed to the utilisation of primary production. The feeding strategies of the dominant species particularly for epistrate feeders are discussed. An assessment of the influence of nematodes grazing on microphytobenthos biomass and production was then performed. Comparison of nematode species grazing rates based on nematode abundance and ingestion rates and microphytobenthic production are discussed. Using the trophic structure of nematode populations to extend those results, grazing rates represent a significant part of microphytobenthic production in springtime.

Concentration and mobilisation of Cd, Cu, Pb and Zn by meiofauna populations living in harbour sediment: their role in the heavy metal flux from sediment to food web

The bioavailability of Cd, Cu, Pb and Zn was assessed in different harbours of the Atlantic coast (France). The responses of the two dominant meiobenthic groups (nematodes and copepods) to a heavy metal contamination gradient measured in similar subtidal sediments were observed in field surveys. Heavy metal concentrations were measured in nematodes and copepods. Nematodes have higher Cd, Cu, Pb and Zn transfer factors than copepods or other benthic species. The flux of heavy metal through nematodes was estimated and appears to be important compared to plankton in the process of heavy metal transfer to benthic or pelagic food webs.

Macrofaunal community responses to marina-related pollution on the south coast of England and west coast of France

This study evaluates the influence of man-made activities on the benthic environment at two different marinas: Southsea Marina on the south coast of England, and Minimes Marina on the Atlantic coast of France. We assessed the differences in: (1) sediment percentage organic matter, particle size and heavy metal concentration, using copper (Cu), cadmium (Cd), zinc (Zn) and lead (Pb) as contamination indicators; (2) sediment elutriate toxicity (LC 50 ) using algal ( Fucus serratus ) bioassay; and (3) benthic community characteristics (number of species, abundance, most contributing species (SIMPER) and biotic index (AMBI)). Canonical correspondence analysis (CCA) was performed to relate the abundance of species to the environmental variables. At both marinas, we observed an increasing gradient of contamination from outside to the innermost sites. At both marinas, the lowest macrofaunal abundance was recorded at the innermost sites and differences in benthic community structure were observed between sites. At Southsea Marina, the cirratulids Tharyx marioni and T. killariensis and the cossurid Cossura pygodactylata dominated sites outside, while the opportunistic species Capitellides girardi dominated the innermost sites. At Minimes Marina, the cirratulid Streblospio shrubsolii was abundant outside and at the middle sites but was almost absent at the innermost sites. The biotic index—AMBI—indicated that sediments in the innermost sites were heavily disturbed at Southsea Marina and slightly to moderately disturbed at Minimes Marina. In Southsea, the AMBI was positively correlated to the sediment metal concentrations (Cu, Zn and Cd) and elutriate toxicity (LC 50 ), while in Minimes the AMBI was positively correlated to the % of sediment fine particle and elutriate toxicity (LC 50 ).

Vanadium toxicity to three marine invertebrates larvae: Crassostrea gigas, Paracentrotus lividus and Artemia salina

Abstract In this study, the toxicity of vanadium to three invertebrate larvae ( Artemia salina, Crassostrea gigas, Paracentrotus lividus ) was assessed. Two criteria were mainly observed: percentage of normal developed larvae and growth of normal larvae. After short term experiments (2 days), toxic effect of vanadium appears for a concentration of 50 μg l −1 ( C. gigas larvae), 100 μg l −1 ( P. lividus pluteus). A. salina are less sensitive, and toxic effects appear only after 8 days of contact with vanadium concentration of 250 μg l −1 . For the three species tested, growth of larvae was not affected by the introduction of vanadium up to 750 μg l −1 in the rearing medium, but high teratogenic effect occur on the development of sea urchin pluteus. The toxic effect of vanadium appeared at 50 100 μg l −1 for marine larvae, this observation was in contrast with results previously obtained with adult marine organisms.

Extracting massive numbers of nematodes from muddy marine deposits: efficiency and selectivity

Extraction of large numbers of living and debris-free nematodes is based on the active downward migration of nematodes through muddy sediments. This study is an assessment of how representative the extracted nematode population is in comparison to the in situ population. Nematode extraction efficiencies ranged from 20-29%; however, the method yielded 153 000 and 223 000 debris-free nematodes in 48 h (per m2 of mud with nematode population density of 776 000 individuals m–2). Sieve mesh size, migration device mesh size, and size distribution and behaviour of nematode species all influenced the extraction results. The species composition of the extracted nematode populations was significantly different from the in situ population assemblage. Metachromadora remanei and M. vivipara migrated less efficiently than Ptycholaimellus jacobi, Chromadora macrolaima and Daptonema oxycerca. This bias should be monitored in experimental studies using nematode populations extracted by means of sieving and downward migration.