Comparative bioaccumulation kinetics of trace elements in Mediterranean marine sponges

While marine organisms such as bivalves, seagrasses and macroalgae are commonly used as biomonitors for the environment pollution assessment, widely distributed sponges received little attention as potential helpful species for monitoring programmes. In this study, the trace element and radionuclide bioaccumulation and retention capacities of some marine sponges were estimated in a species-comparative study using radiotracers technique. Six Mediterranean species were exposed to background dissolved concentrations of ^110mAg, ²⁴¹Am, ¹⁰⁹Cd, ⁶⁰Co, ¹³⁴Cs, ⁵⁴Mn, ⁷⁵Se and ⁶⁵Zn allowing the assessment of the uptake and depuration kinetics for selected elements. Globally, massive demosponges Agelas oroides, Chondrosia reniformis and Ircinia variabilis displayed higher concentration factor (CF) than the erectile ones (Acanthella acuta, Cymbaxinella damicornis, Cymbaxinella verrucosa) at the end of exposure, suggesting that the morphology is a key factor in the metal bioaccumulation efficiency. Considering this observation, two exceptions were noted: (1) A. acuta reached the highest CF for ^110mAg and strongly retained the accumulated metal without significant Ag loss when placed in depuration conditions and (2) C. reniformis did not accumulate Se as much as A. oroides and I. variabilis. These results suggest that peculiar metal uptake properties in sponges could be driven by specific metabolites or contrasting biosilification processes between species, respectively. This study demonstrated that sponges could be considered as valuable candidate for biomonitoring metal contamination but also that there is a need to experimentally highlight metal-dependant characteristic among species.     

Brominated flame retardants,a cornelian dilemma

Environmental Chemistry Letters -     

Effect of cropping and tillage on the dissipation of PAH contamination in soil

This study examined the effect of regular tillage and cropping on the dissipation rate of PAHs in contaminated soil. Lysimeters were placed under natural climatic conditions for 2 years and designed to measure the concentration of PAHs in soil and leachates and their toxicity. The soil initially contained 2077 microg PAHs g(-1). The largest decrease in PAHs concentration occurred during the first 6 months. No further significant decrease was observed after this time. The surface soil layer always contained significantly less PAHs than the deeper layer, regardless of the treatments. Less than 8.4 x 10(-8)% of the PAH initially present in the soil (e.g. less or equal to 33 microg PAHs per lysimeter) were leached from the soils during the experiment and the leachates presented no toxicity (as measured by the Microtox test). The toxicity of the soils decreased with time and was significantly lower on the cropped soil compared to the other treatments, despite the residual concentration of PAHs being the highest in this soil. This study demonstrated that the dissipation rates of PAHs were slow after using natural attenuation even when tillage and cropping were performed at the soil surface.     

Comparison and development of dynamic flux chambers to determine odorous compound emission rates from area sources

Two dynamic flux chambers for direct measurement of odorous compound emissions from quiescent liquid surfaces were investigated under simulated conditions in the laboratory. Initially, a flux chamber built according to the model recommended by French standard NF X 43-104 was studied. This chamber was used in two different ways. The first led to a lack of precision concerning emissions rates from the sampled liquid surface, whereas the second led to an overestimation of the measurements. The second part of the study was devoted to an improved dynamic flux chamber, built according to the feedback from the results obtained using the normalised sampling system. Laboratory tests showed good accuracy and precision. This work underlines the importance of the aerodynamic performances of a dynamic sampling system.     

Potential effects of UV-B on the chemical environment of marine organisms: a review

An increase in ultraviolet-B (UV-B) due to depletion of stratospheric ozone may affect growth of marine phytoplankton by altering the chemistry of their environment. Production of bioactive free radicals, photodecomposition of organic matter, and availability of trace metals are likely to be altered by increased UV-B flux. Such changes to the chemical environment may be both deleterious and beneficial to marine phytoplankton. Extracellular free radicals such as OH, Br(2)(-), and CO(3)(-) are predicted to have a negligible impact, but superoxide and its decomposition product hydrogen peroxide may react rapidly with cell surfaces and destroy membrane function and integrity. Increased UV-B will enhance the bioavailability of the redox active trace metals Fe and Cu. Thus, in the Fe-limited high latitude ocean, increased Fe availability may promote phytoplankton production, while in other parts of the ocean increased Cu availability may be toxic. Overall, the interdependent direct and indirect effects of UV-B on phytoplankton may compensate for each other and account for the ability of marine ecosystems to be subjected to widely variable UV-B flux without apparent damage.