Microalgae are a valuable natural resource for a variety of value-added products. The growth of microalgae is determined by the impact of many factors, but, from the point of view of the implementation of autotrophic growth, light is of primary importance. This work presents an overview of the influence of light conditions on the growth of microalgae, the content of lipids, carotenoids, and the composition of fatty acids in their biomass, taking into account parameters such as the intensity, duration of lighting, and use of rays of different spectral composition. The optimal light intensity for the growth of microalgae lies in the following range: 26−400 µmol photons m−2 s−1. An increase in light intensity leads to an activation of lipid synthesis. For maximum lipid productivity, various microalgae species and strains need lighting of different intensities: from 60 to 700 µmol photons m−2 s−1. Strong light preferentially increases the triacylglyceride content. The intensity of lighting has a regulating effect on the synthesis of fatty acids, carotenoids, including β-carotene, lutein and astaxanthin. In intense lighting conditions, saturated fatty acids usually accumulate, as well as monounsaturated ones, and the number of polyunsaturated fatty acids decreases. Red as well as blue LED lighting improves the biomass productivity of microalgae of various taxonomic groups. Changing the duration of the photoperiod, the use of pulsed light can stimulate microalgae growth, the production of lipids, and carotenoids. The simultaneous use of light and other stresses contributes to a stronger effect on the productivity of algae.

Diatoms (Bacillariophyta) are ubiquitous microalgae which produce a siliceous exoskeleton and which make a major contribution to the productivity of oceans and freshwaters. They display a huge diversity, which makes them excellent ecological indicators of aquatic ecosystems. Usually, diatoms are identified using characteristics of their exoskeleton morphology. DNA-barcoding is an alternative to this and the use of High-Throughput-Sequencing enables the rapid analysis of many environmental samples at a lower cost than analyses under microscope. However, to identify environmental sequences correctly, an expertly curated reference library is needed. Several curated libraries for protists exists; none, however are dedicated to diatoms. Diat.barcode is an open-access library dedicated to diatoms which has been maintained since 2012. Data come from two sources (1) the NCBI nucleotide database and (2) unpublished sequencing data of culture collections. Since 2017, several experts have collaborated to curate this library for rbcL, a chloroplast marker suitable for species-level identification of diatoms. For the latest version of the database (version 7), 605 of the 3482 taxonomical names originally assigned by the authors of the rbcL sequences were modified after curation. The database is accessible at https://www6.inra.fr/carrtel-collection_eng/Barcoding-database.

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This paper proposes a new monoraphid genus Gliwiczia Kulikovskiy, Lange-Bertalot & Witkowski, separated from Achnanthes sensu lato. Here we describe four species G. skvortzowii Kulikovskiy, Lange-Bertalot & Witkowski, G. tenuis Kulikovskiy, Lange-Bertalot & Witkowski, G. latarea Kulikovskiy, Lange-Bertalot & Witkowski and G. vixcalcar Kulikovskiy, Lange-Bertalot & Witkowski which all are new to science. In terms of morphology, this group of species closely resembles Achnanthes calcar Cleve. Also proposed is the taxonomic transfer of A. calcar Cleve to Gliwiczia calcar (Cleve) Kulikovskiy, Lange-Bertalot & Witkowski comb. nov. Our taxonomic conclusions about the position of this group of species is based on light microscopic (LM) examination of the type material of A. calcar and on extensive LM and scanning electron microscopic (SEM) studies on material originating from Lake Baikal. This new genus differs from other established monoraphid genera in the of cavum (horse shoe) present on both raphe and sternums valves, uniseriate striae on both valves, and areola occlusions in a form of open circular foramina externally. The raphe valve is only slightly concave, whereas the sternum valves appear flat. Only one of the species belonging in Gliwiczia gen. nov., G. calcar, is known to inhabit oligotrophic and dystrophic freshwater lakes of Eurasia. It seems highly likely that the newly described species are limited in their distribution to the waters of Lake Baikal. None of them have thus far been illustrated in any accessible literature even under provisional names.

Type material of Navicula kotschyi was studied, and this species was transferred to Dorofeyukea gen. nov. as D. kotschyi comb. nov. Dorofeyukea was described on the basis of DNA sequence and morphological data. Additional species assigned to this genus that were previously included in Navicula include: D. ancisa comb. nov., D. grimmei comb. nov., D. ivatoensis comb. nov., D. orangiana comb. nov., D. rostellata comb. nov. & stat. nov., D. savannahiana comb. nov., D. tenuipunctata comb. nov., and D. texana comb. nov. All Dorofeyukea species share the same morphological features, including having a narrow stauroid fascia surrounded by 1–3 irregularly shortened striae, uniseriate, and weakly radiate striae, circular, or rectangular puncta in the striae that are covered internally by dome‐shaped hymenes, presence of a pseudoseptum at each apex and absence of septa. Partial DNA sequences of SSU and rbcL loci show Dorofeuykae belongs to the clade of stauroneioid diatoms together with Stauroneis, Prestauroneis, Craticula, Karayevia, Madinithidium, Fistulifera, Parlibellus, and, possibly, Schizostauron. A new species from the monoraphid genus Madinithidium, M. vietnamica sp. nov., was described based on valve and chloroplast morphology as well as DNA sequence data.

two new Geissleria species from Siberian mountain lakes Baikal and Frolikha are described based on molecular and morphological data. the two new species are Geissleria baicalosimilis Kulikovskiy, gusev, Andreeva & Annenkova sp. nov. and G. frolikhiensis Kulikovskiy, gusev, Andreeva & Annenkova sp. nov. According to partial 18S rdNA and rbcL gene fragment analyses, Geissleria does not belong to the large catch-all genus Navicula as it was previously thought. Morphological features such as slit like areolae without hymenes, presence of one isolated pore near the central nodule and presence of props in areolae and an annulus structure support this conclusion. Plastid morphology of Geissleria species is typical for the Cymbellales, with one large chloroplast divided into two plates lying one against each valve, connected by a broad column. All of our data show that Geissleria is most closely to the genus Placoneis, with which they share naviculoid symmetry. given these results, Geissleria should be included in the order Cymbellales.

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