Estimation of cell distribution heterogeneity at toxicological experiments with clonal cultures of benthic diatoms
An increase in anthropogenic pressure on coastal water areas requires regular monitoring of marine ecosystems. The appropriate bioindicators for indirect assessment of the quality of the near-shore environment are benthic diatom algae, which are a key element of coastal communities and are highly s...
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| Format: | Article |
| Language: | English |
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A. O. Kovalevsky Institute of Biology of the Southern Seas of RAS
2020-06-01
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| Series: | Морской биологический журнал |
| Subjects: | |
| Online Access: | https://mbj.marine-research.org/article/view/236 |
| Summary: | An increase in anthropogenic pressure on coastal water areas requires regular monitoring of marine ecosystems. The appropriate bioindicators for indirect assessment of the quality of the near-shore environment are benthic diatom algae, which are a key element of coastal communities and are highly sensitive to environmental impact. Changes in the development of diatoms under the influence of various toxicants may be used as relevant tool for monitoring of marine environment quality. However, scientific and methodological approaches to application of benthic diatom algae as test objects remain unstudied. One of the important methodological problems is the assessment of the significance of the samples in experimental vessels when counting cells abundance at different stages of toxicological test. The study is focused on assessment of the statistical significance of the equality of the initial mean number of cells of clonal culture inoculum placed into each of the replicates, as well as the statistical uniformity of cell distribution over the entire bottom area of Petri dishes. We used clonal cultures of three benthic diatom species belonging to different classes of Bacillariophyta: Thalassiosira excentrica Cleve, 1903 (Coscinodiscophycea), Ardissonea crystallina (C. Agardh) Grunow, 1880 (Fragilariophyceae), and Pleurosigma aestuarii (Bréb. in Kütz.) W. Smith, 1853 (Bacillariophyceae). They significantly differ in valve morphology and life history (floating in water mass, attached to substrate, and motile). The results of statistical comparison of cell number variability in the experiment for all studied species confirmed the absence of significant differences between the mean values of the tested parameter at a standard significance level (0.05). It was shown that despite specific differences in cell growth rate during the experiment, the variability in cell number in the microscope viewing fields varies irregularly. The highest value of the variability coefficient was observed on the 5th day for the small-sized species T. excentrica (Cv = 42…55 %), and the lowest variability – for the large-cell species A. crystallina (Cv = 27…31 %). The absence of significant differences in cell number between three replicates (for each species) was established both during the initial placing of inoculum into the dishes and on the following days of the experiment. The conclusion is applicable for each of diatom species studied, which allows to consider all replicates as subsamples of the replicate sample and to average the results obtained at different stages of the toxicological experiment. The uniformity of cell distribution throughout experimental dishes bottom, which does not depend on species and absolute cell number, was statistically proven. The results obtained allow to statistically reliably estimate the changes in cell number at different stages of toxicological experiment according to replicate sampling, based on cell counting in a limited number of viewing fields.
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| ISSN: | 2499-9768 2499-9776 |