Limnol. Rev., Volume 19, Issue 4 (December 2019) – 4 articles , Pages 149-198

Excessive microalgal blooms can be caused by waste disposal into natural water bodies resulting in the destruction of aquatic life. However, microalgae are also known to efficiently remediate pollutants. After the treatment of wastewater, microalgae absorb specific nutrients and can enhance the production of bioproducts. Growing microalgae as an alternative to wastewater treatment and bioproduct production has received considerable attention due to its rapid growth rate, efficient waste removal, tolerance to stress conditions and ability to accumulate valuable products. In addition, these microorganisms have a high photosynthetic rate of CO₂ fixation, oxygen production and need no arable land for their cultivation. Nevertheless, in spite of these theoretical advantages, the issues surrounding the re-use of naturally existing microalgal strains need further exploration in respect to their isolation, identification and lab growth under stress conditions. The true potential of microalgae regarding wastewater treatment and energy has yet to be fully developed. The current cultivation system does not seem to be economically feasible as most of the strains used are commercially purchased. Indigenous microalgae could be the possible answer. Ammonia, one of the major constituents of most wastewaters, contributing to odor, taste, toxicity, and eutrophication is of utmost concern. The present review focuses on the growth of microalgae under high stress of ammonia in wastewater media. It also aims to present a clear-cut methodology for the isolation of microalgae from its indigenous habitat, its growth strategy under different trophic modes of nutrition, nutrient uptake, lipid, and fatty acid production. In addition, some solutions to the problem of how to make microalgae cost-effective and more sustainable are discussed in detail. Full article

The aim of the work was to describe the variability of a group of meiobenthos inhabiting a tidal flat in Nottinghambukta which is influenced by the diverse conditions of a seasonal as well as multi-annual cyclicity. Samples were collected in five series, i.e., during the Arctic spring (2001), summer (2000 and 2001) and autumn (2001). The material for qualitative analysis was collected from sites with different hydrological characteristics. The following major meiobenthic taxa were found: Metazoa, i.e., Nematoda and Crustacea (Ostracoda and Copepoda-Harpacticoida), and Foraminifera. Unstable conditions in the bay result in a seasonal variability in the species composition as well as an uneven colonisation of the Nottinghambukta area by meiobenthos. The lowest taxonomic diversity occurs in summer, but it increases in autumn when the land runoff ceases. Based on the conducted analysis, it can be concluded that the inflow of seawater in autumn brings on the occurrence of new taxa, which probably inhabit the bay temporarily until the summer season during which the highly variable conditions cause a change in the species composition. For the series of samples collected in July 2000 and 2001, the species composition for Harpacticoida was determined. The taxonomic diversity of the harpacticoid assemblage inhabiting the bay was observed in the two subsequent years. Moreover, during the study duration a considerable decrease was observed in the abundance of Ostracoda in Nottinghambukta. Full article

In river-lake systems, reservoirs significantly affect the formation of water resources in the catchment by reducing the maximum flows and floods as well as increasing the low flows. In lake catchments, the pace of hydrological drought progression is usually slow. However, this phenomenon can be very extreme and destructive for water balance structure as a result of the very slow renewal rate of catchment resources. An estimation of hydrological drought development was conducted in the Biebrza river catchment (6900 km²) on the basis of a daily discharge series for 18 water-gauge stations in the period 1982–2014. The number and location of the gauges allowed reliable results of the spatial pattern of drought to be obtained. The main objective of the research was the construction and assessment of the applicability of indicators which are estimators of drought spatial progression. Comparative analysis of four proposed indices led to two of them being recommended. These characteristics estimate the direction of drought development according to the stream network hierarchy, location of sub-catchments and the direction of river basin area increase. As a result, determinants of the spatial development of hydrological drought as well as its importance in the hydrographical structure were identified. Furthermore, the intensity of drought was evaluated and all investigated indices were applied to a time series analysis. Full article

This study aims to contribute to a better estimation of the density of fractures likely to favour the drainage of surface water in the High Ziz River (HZR) basin. The method adopted consists of the use of different airborne image processing techniques (filtering, enhancement and slope analysis) which allow a good discrimination of image discontinuities (lineaments) that can then be used for producing lineament maps. The influence of these lineaments on the underground flow is then studied. Indeed, it was possible to extract the lineament network, following the exploitation of remote sensing and an objectively completed analog analysis using the PCI Geomatica LINE module and its directional filters (Sobel directional filters by the ACP method), and to extract the hydrographic network of the HZR basin, using the ArcHydro tool. After superimposing these data, their thematic maps (of the lineament and hydrographic network) were developed. In addition, this comparison of the two hydrographic networks and lineament maps showed us very varied flow directions influenced by geological structures, particularly fracturing. The topography of the region also has a secondary impact on flows through the presence of slopes generally oriented towards the SE of the basin. The correlation of the results with the different directions of the orders of the hydrographic network allowed us to identify the potential effects of lineaments on the orientations of surface water circulation. In addition to these results, the realization of the Rose diagram indicated that the dominant trend in lineaments is N90–45N° (NE–SW). Full article