[Show abstract][Hide abstract] ABSTRACT: The benthic diatom Cylindrotheca closterium was exposed to whole-sediment spiked with the synthetic surfactant Linear Alkylbenzene Sulphonate (LAS), as commercial mixture or individual homologues (C10-LAS, C11-LAS or C12-LAS). Separately, the diatoms were exposed to C12-LAS in a water-only system. The algal growth was determined after 72 h. The 72-h ErC50 values ranged from <or=4 to 29 mg/kg sediment, suggesting that C. closterium was sensitive to LAS. The outcomes were reproducible with a variation factor lower than 3, showing the reproducibility of the method. The test set up was cost effective, used little bench space and employed a micro-phytobenthos species that fulfilled most of the criteria for a suitable test species in sediment systems. The 72-h ErC50 obtained in a water-only system (0.141 mg/L) was ca. 2 orders of magnitude lower (0.002 mg/L). This was likely due to an indirect effect of the use of fresh sediment.
Ecotoxicology and Environmental Safety 03/2010; 73(3):262-9. · 2.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study checked the suitability of Cylindrotheca closterium (Bacillariophyceae) as a test species for ecotoxicology studies. To date, only limited use has been made of microphytobenthos in ecotoxicology, and C. closterium has been employed as a target organism in this study because the biological group is considered to be very relevant ecologically. The main objective was to assess the response of C. closterium to a contaminant-type (copper) using three different test endpoints (esterase activity, chlorophyll fluorescence and population growth) and two different test methods (Erlenmeyer flasks and microplates), to evaluate which combination of test conditions would provide the most sensitive approach for assessment of effects. Regardless of the endpoints, the response of C. closterium to copper was very similar; however lower sensitivity (EC50 of 27.8 ± 0.7 µg Cu L− 1) was observed when tests were carried out in microplates. Chlorophyll fluorescence measured by flow cytometry as total FL3 was slightly more sensitive (EC50 of 4.7 ± 0.1 µg Cu L− 1) than the other parameters measured, probably because it takes into account the effect on chlorophyll fluorescence and cell density simultaneously. The test method (Erlenmeyer flask or microplate) was the determining factor for the observed differences in sensitivity. These differences found for the two methods are explained by the higher metal adsorption capacity of microplate vessel walls (more than 40%), which decreases the available copper. C. closterium was demonstrated to be a suitable organism for adoption in ecotoxicological studies, given the reliability of the three endpoints and also of the two test methods evaluated here.
Science of The Total Environment 05/2010; · 3.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Contamination in coastal zones is an increasing problem that adversely affects biological diversity and the functioning of coastal ecosystems. Sediment is an important compartment of these zones since large quantities of diverse contaminants can accumulate there. Whole-sediment toxicity assays are of increasing importance, and several assay methods using mainly invertebrates have been developed. However, an important part of the benthic community, the microphytobenthos (represented principally by benthic diatoms and cyanobacteria), has surprisingly been neglected. Recently, comprehensive studies have been conducted using benthic marine microalgae with the object of establishing a toxicity assay method for sediment samples. The main results published to date in the literature and obtained by our own team have been compiled and are discussed in this review. The value and feasibility of using certain organisms of the microphytobenthos group in ecotoxicology studies are also discussed, and a sediment quality guideline based on multivariate procedure has been derived from data obtained in previous studies. Finally, future perspectives for research in this field are discussed.
Environment international 08/2010; 36(6):637-46. · 6.25 Impact Factor
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