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[Show abstract][Hide abstract] ABSTRACT: Cylindrotheca closterium cells were maintained at low temperature (4+/-1 degrees C) and dark conditions up to 21 weeks to assess the effect on survival and physiological status. From a control culture under standard conditions, three densities were prepared: (A) 2 x 10(4), (B) 10 x 10(4), and (C) 25 x 10(4) cells ml(-1). Weekly, inoculums of each stored density were exposed to continuous light and at 20+/-1 degrees C. Sensitivity to copper for microalgal cultures was evaluated in order to assess possible changes in cells sensitivity due to storage. Concurrently, assays with a control culture were carried out in order to assess the sensitivity of C. closterium to copper and to be able to generate a standard sensitivity control chart with a mean value of EC50-72 h+/-2SD (standard deviation). Density-C presented higher cell yield values, between 40% and 80% relative to control culture. Cell density showed to be important feature that may be taken into account in cell storage experiments. There was an increase in sensitivity of cells submitted to storage; however results always kept in the range established as standard sensitivity with no statistically significant difference with regards to control culture. EC50-72 h mean value for the control culture was 29+/-10 mug Cul(-1), while for densities-A, B and C were 22+/-7; 23+/-9 and 23+/-8 microg Cul(-1), respectively. In spite of drastic changes in the environmental conditions due to storage, it is concluded that C. closterium cells stored during 5 months remained metabolically active and with no significant change in its sensitivity.
[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. DOI:10.1016/j.envint.2010.04.017 · 5.66 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; 408(17-408):3696-3703. DOI:10.1016/j.scitotenv.2010.05.012 · 3.16 Impact Factor