Olivier Herlory

Bio: Olivier Herlory is an academic researcher from University of Bordeaux. The author has contributed to research in topics: Diatom & Biofilm. The author has an hindex of 4, co-authored 4 publications receiving 437 citations.

Cadmium Toxicity and Bioaccumulation in Freshwater Biofilms

Abstract: A microcosm study was undertaken to examine the effects of dissolved cadmium at various concentrations (0, 10, and 100 μg · L−1) on biofilm accumulation and diatom assemblages. A natural biofilm sampled from the Riou-Mort River (Southwest France) was inoculated into three experimental systems, where biofilm settled on glass slides. Samples collected after 1, 2, 4, and 6 weeks of colonization were analyzed for metal accumulation (total metal content and intracellular metal content in the biofilm), biomass (as measured through dry weight and ash-free dry matter), and quantitative as well as qualitative analysis of diatom assemblages. There was a positive correlation between cadmium accumulation and dissolved cadmium concentrations and duration of exposure: a linear relationship was found between concentration factors (CFs) of growing biofilms and time (CFs/day = 0.25 and 0.38 under contaminations of 10 and 100 μgCd · L−1, respectively). Biofilm settlement, more than photosynthetic activity, was affected by high cadmium concentrations: we observed for all stages of settlement a drastic and significant (p < 0.05) reduction in biofilm biomass and in diatom densities in the highest cadmium contamination, compared to control and low cadmium concentration units.

Diatom teratological forms and environmental alterations: a review

Abstract: The foremost feature of a diatom is the species-specific ornamentation of the silicon cell wall, which is preserved and faithfully reproduced through the generations. If exposed to different kinds of stress during reproductive processes, the diatom cell outline and striation pattern can change in different ways, producing teratological forms. These modifications can be slight, leading to difficulties in establishing a threshold between normal and teratological cells, or so marked that it is very difficult to recognize whether an unknown form is teratological or whether it belongs to a new species or variety. Teratological forms appear as an accidental effect of environmental stresses, which can be both physical and chemical. Artificial conditions also often lead to the development of teratological forms. Most frequently, diatoms present abnormal valve outline (lack of symmetry, bent, incised, swollen, or notched profile), unusual raphe system (fragmented, displaced, and bifurcated), abnormal striation pattern (irregular, altered, fragmented, and branched), and unusual raphe channel system (distorted, curved, and occasionally doubled back). In this review we analyzed 222 articles, published from 1890 up to 2008, with the aim to correlate the abnormal diatom cell morphology to environmental alterations, in a perspective which can greatly enhance the evaluation of river environmental quality for biomonitoring purposes.

Recent views on river pollution and diatoms

Abstract: The first studies of diatoms and river pollution were carried out 60 years ago, and the suitability of these micro-algae as bioassessment indicators for monitoring river quality was quickly demonstrated. The objective of this review is to describe the state of the art of the study of diatoms and river pollution between 1999 and 2009. The objective was to group the publications homogeneously according to subject and to indicate which subjects never overlap. To this end a lexical analysis was conducted on the abstract structure of these publications and seven K-means clusters were defined. Most of the items in this area were found to have been published in Hydrobiologia. One group (group 6) comprises publications about a discipline (ecotoxicology); several others group publications on the basis of the same approaches, for example species (group 3), basin (group 7), or spatial approaches (group 2). Other publications are brought together because the studies used a common method of using data, namely predictive models (group 1) or biotic indices (group 4). One group of publications was of studies performed in the same area—South Africa (group 5). Several remarks can be made. First, ecotoxicological studies are mostly experimental and restricted to small study areas. To answer society’s demand for new assessment tools for micropollutant assessment, the next step would be to have more in-situ tests on larger spatial scales. Second, diatom biomonitoring uses the word “species” extensively, because this is the basis for establishing the lists of flora which are used extensively in such subject areas. Species is closely related to taxonomy; nevertheless this discipline is very rarely addressed in the papers. Third, phylogeny is never addressed in the publications. This is significant because phylogenetic studies for freshwater macroinvertebrates enable appropriate definition of taxonomic aggregations that can be used as accurate indicators of particular environmental stressors.