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BACKGROUND Vega Island is located off the eastern tip of the Antarctic Peninsula (Maritime Antarctica), in the Weddell Sea. In this study, we used metabarcoding to investigate green algal DNA sequence diversity present in sediments from three lakes on Vega Island (Esmeralda, Copepodo, and Pan Negro Lakes). METHODS AND RESULTS Total DNA was extracted and the internal transcribed spacer 2 region of the nuclear ribosomal DNA was used as a DNA barcode for molecular identification. Green algae were represented by sequences representing 78 taxa belonging to Phylum Chlorophyta, of which 32% have not previously been recorded from Antarctica. Sediment from Pan Negro Lake generated the highest number of DNA reads (11,205), followed by Esmeralda (9085) and Copepodo (1595) Lakes. Esmeralda Lake was the richest in terms of number of taxa (59), with Copepodo and Pan Negro Lakes having 30 taxa each. Bray-Curtis dissimilarity among lakes was high (~ 0.80). The Order Chlamydomonadales (Chlorophyceae) gave the highest contribution in terms of numbers of taxa and DNA reads in all lakes. The most abundant taxon was Chlorococcum microstigmatum. CONCLUSIONS The study confirms the utility of DNA metabarcoding in assessing potential green algal diversity in Antarctic lakes, generating new Antarctic records.

Tetradesmus is a microalgal genus with biotechnological potential due to its rapid production of biomass, which is plenty in proteins, carbohydrates, lipids, and bioactives. However, its morphology and physiology need to be determined to guide better research to optimize the species cultivation and biocompounds processing. Thus, this study describes the biochemistry and morphology of the strain Tetradesmus obliquus BR003, isolated from a sample of freshwater reservoirs in a Brazilian municipality. In the T. obliquus BR003 dry biomass, we identified 61.6% unsaturated fatty acids, and 3.4% saturated fatty acids. Regarding other compounds, 28.50 ± 1.47 g soluble proteins/100 g, 0.14 ± 0.009 g carotenoids/100 g, 0.76 ± 0.013 g chlorophyll a/100 g, and 0.42 ± 0.015 g chlorophyll b/100 g with a chlorophyll a/b ratio of 1.8 were detected. The main chemical elements found were S, Mg, and P. The cells of BR003 were elliptically curved at the ends and without appendages. Histochemical tests showed carbohydrates distributed in the cytoplasm and pyrenoids, some lipid droplets, and proteins. The cytoplasm is rich in vacuoles, rough endoplasmic reticulum, mitochondria, and chloroplasts. The nucleus has a predominance of decondensed chromatin, and the cell wall has three layers. Chloroplasts have many starch granules and may be associated with a spherical central pyrenoid. To the best of our knowledge, this was the first biochemical description combined with ultrastructural morphological characterization of the strain T. obliquus BR003, grown under standard conditions, to demonstrate specific characteristics of the species.

Macrophytes can be crucial for maintaining clear water conditions in temperate shallow lakes. However, their restorative potential and role in regulating phytoplankton remains uncertain in tropical lakes. We investigated the effects of emergent (Ludwigia adscendens and Persicaria barbata) and submerged (Vallisneria spiralis) macrophytes on the phytoplankton community of a turbid tropical reservoir. Through two in situ mesocosm experiments (~ 1000 l capacity) lasting 4 weeks, we (1) determined the effects of macrophyte density on phytoplankton biomass and composition, and (2) compared these effects between emergent and submerged macrophytes. In Experiment 1, macrophyte treatments reduced phytoplankton biomass and increased water clarity in a density-dependent manner. Only the ‘high density’ treatment (300 g/m2 emergent and 650 g/m2 submerged macrophytes) induced a taxonomic and functional shift from an initial community dominated by turbid water-adapted filamentous cyanobacteria to one dominated by clear water-adapted green algae and cryptophytes. In Experiment 2, emergent and submerged macrophytes reduced phytoplankton biomass and distinctly altered taxonomic and functional composition, with submerged macrophytes inhibiting Microcystis and stimulating cryptophyte taxa. Our results indicate that macrophytes can induce substantial phytoplankton community shifts in turbid tropical lakes, demonstrating the potential to assist in the reversal from turbid to clear water states during restoration efforts.

This study describing the morphology of the green algae Geminella protogenita (Kutzing) West, which is a rare species found in the territories of Southern Brazil. Although this taxon is widely distributed worldwide, it is known to rarely occur in the regions where it has been registered previously, which is because little attention is given to its taxonomic characteristics based on the morphology. Photomicrographs and cell morphometric data were obtained to conduct the taxonomic characterization. Here, we also provide data on its global distribution and the type of environments to better contribute in the understanding of the biology of this species.

In green algae and plants, state transitions serve as a short-term light-acclimation process in the regulation of the light-harvesting capacity of photosystems I and II (PSI and PSII, respectively). During the process, a portion of light-harvesting complex II (LHCII) is phosphorylated, dissociated from PSII and binds with PSI to form the supercomplex PSI–LHCI–LHCII. Here, we report high-resolution structures of PSI–LHCI–LHCII from Chlamydomonas reinhardtii, revealing the mechanism of assembly between the PSI–LHCI complex and two phosphorylated LHCII trimers containing all four types of LhcbM protein. Two specific LhcbM isoforms, namely LhcbM1 and LhcbM5, directly interact with the PSI core through their phosphorylated amino terminal regions. Furthermore, biochemical and functional studies on mutant strains lacking either LhcbM1 or LhcbM5 indicate that only LhcbM5 is indispensable in supercomplex formation. The results unravel the specific interactions and potential excitation energy transfer routes between green algal PSI and two phosphorylated LHCIIs. High-resolution structures of the PSI–LHCI–LHCII supercomplex from Chlamydomonas reinhardtii reveal the mechanism of assembly between the PSI–LHCI complex and two phosphorylated LHCII trimers.

Seaweeds are considered a promising ingredient to use in developing novel food products, due to their nutritional composition and richness in bioactive compounds. The aim of this work is to investigate the effect of four seaweeds (Chlorella vulgaris CH, Laminaria ochroleuca KO, Ulva spp. SL, Arthrospira platensis SP) enrichment (1%, 2.5%, 4%, flour basis) on technological performance and nutraceutical prospective of soft wheat bread. To do this, dough rheological properties measured by means of farinograph and consistograph parameters, baking response (loaf volume, colour, and porosity), and nutraceutical potential of bread (total soluble phenolic compounds, pigments, and antioxidant activity) were evaluated. Algae addition significantly decreased water absorption and development time, except to SL, and increased stability up to 2.5%, and tenacity for KO. In terms of bread properties, the specific volume was positively affected by SP addition, while negatively by KO enrichment; the porosity enhanced especially for SP and CH. Then, bread crumbs and crusts showed a darker and greener colour, especially for green algae. All seaweeds enriched breads showed significant higher phenolic compounds, chlorophylls a and b, and yellow pigment. At last, SP, SL, and CH at 4% level pointed out the highest antioxidant capacity. Our results suggested that the four algal biomasses could be a suitable ingredient in bread making, also in a perspective of a healthier and sustainable diet.

In the present study, the bioaccumulation of toxic/harmful pollutants (Fe, Pb, As, Cd, Cr, Ba, and Mn) by Cladophora fracta in mine gallery water was investigated. For this aim, the reactors planted with C. fracta were placed into mine gallery waters. Bioconcentration factor (BCF), metal pollution index (MPI), and accumulation capacity values were determined. According to the obtained results, the highest concentrations of Cr, Mn, Fe, Ba, Pb, Cd, and As were determined as 24.3 ± 1.2, 858 ± 27, 26,290 ± 87, 11.4 ± 0.6, 117.05 ± 5.8, 47.9 ± 1.4, and 2390.3 ± 11 mg/kg, respectively. BCF values were Fe > Pb > As > Cd > Cr > Ba > Mn. The MPI values of toxic/harmful pollutants according to days were determined as day 1 > 5 > 7 > 2 > 6 > 4 > 3, respectively. As a result, it was determined that C. fracta, which was placed in the mine gallery and exposed to the gallery waters, was effective in removing toxic/harmful pollutants. Therefore, C. fracta can be used as an alternative treatment material for the removal of toxic/harmful pollutants in mine gallery waters.

Microalgal contamination in algal culture is a serious problem hampering the cultivation process, which can result in considerable economic and time losses. With the field of microalgal biotechnology on the rise, development of new tools for monitoring the cultures is of high importance. Here we present a case study of the detection of fast-growing green algae Chlorella vulgaris (as contaminant) in a diatom Phaeodactylum tricornutum culture using various approaches. We prepared mixed cultures of C. vulgaris and P. tricornutum in different cell-to-cell ratios in the range from 1:103 to 1:107. We compared the sensitivity among microscopy, cultivation-based technique, PCR, and qPCR. The detection of C. vulgaris contamination using light microscopy failed in samples containing cell ratios

Microalgae pose major problems for drinking water treatment processes either through membrane fouling or through blooming events in source water during the summer months. Disinfection treatments such as chlorination and UV-C treatment of drinking water are designed to remove microorganisms including microalgae and bacteria. In order to treat water efficiently it is critical to understand the effect of UV-C treatment on the viability and vitality of phytoplankton. Moreover, this information can be used to assess the utility of UV-C treatment as a potential pre-treatment option for water clean-up. In this study we tested the population growth of 6 phytoplankton species representing three major taxonomic groups (green algae, diatoms and cyanobacteria), commonly found in freshwater lakes in North America and relevant for water treatment facilities. We exposed these species to UV-C treatment and monitored their post-exposure population growth over a 52–55-day period using a plate-based MPN (most probable number) method. We found the green alga Scenedesmus quadricauda and the cyanobacterium Anabaena flos-aquae to be most tolerant to the treatment, while the cyanobacterium Microcystis aeruginosa and the diatom Asterionella formosa were found to be most sensitive with viability being reduced at comparatively lower doses. No significant delays in growth post treatment (i.e. time lags) were reported within species. Asterionella formosa and Aulacoseira granulata showed the longest time lags of all species, which might be in part correlated with DNA repair mechanisms and other physiological adaptations. This work provides the basis for the assessment of UV-C treatment efficacy on freshwater phytoplankton.

A novel Gram-stain-negative, aerobic, non-flagellated, non-motile, oval-rod-shaped and light pink to light tawny-pigmented bacterial strain (designated 1151T) were isolated from marine green algae obtained from the coastal seawater of Weihai, China. Strain 1151T was found to grow at 15–37 °C (optimum, 33 °C), pH 7.0–9.5 (optimum, 7.5–8.5) and in the presence of 1–6% (w/v) NaCl (optimum, 3%). Cells were oxidase-positive and catalase-positive. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 1151T was a member of the genus Sulfitobacter and exhibited the hightest sequence similarity to Sulfitobacter indolifex DSM 14862T (96.6%), followed by the sequence similarity to Sulfitobacter aestuarii hydD52T (96.5%) and Sulfitobacter profundi SAORIC-263T (96.5%). The average nucleotide identity and digital DDH values between strain 1151T and Sulfitobacter indolifex DSM 14862T were 69.9% and 20.9%, respectively. The average amino acid identity between strain 1151T and Sulfitobacter pontiacus DSM 10014T (type strain of the type species) was 62.3%. Q-10 was detected as the sole respiratory quinone. The dominant cellular fatty acids were sum feature 8 (C18: 1ω7c; 44.1%), C20: 1ω7c (29.7%) and C18: 0 (11.7%). The DNA G + C content of strain 1151T was 51.8 mol%. The polar lipids included phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), and three unidentified lipids (L1, L2 and L3). Based on the phylogenetic and phenotypic characteristics, strain 1151T is considered to represent a novel species of the genus Sulfitobacter, for which the name Sulfitobacter algicola sp. nov. is proposed. The type strain is 1151T (= KCTC 72513T = MCCC 1H00384T).

The genome of green microalgae has rarely been reported. Ulva prolifera is a green microalga that has received much attention. Despite research articles about U. prolifera in recent years, we know very little about its genome. Therefore, the 87.9-Mb haploid genome (containing 10 311 protein-coding genes) of U. prolifera was studied, and the genome was compared with that of U. mutabilis, which is the only published Ulva species. Results showed that the two species are closely related. A phylogenetic tree was constructed among U. prolifera and other green algae available in GenBank, revealing the evolutionary status of U. prolifera in Chlorophyta. To understand why U. prolifera could grow rapidly, we identified some genes related to growth, such as those involved in cell division, phosphorylation, and cell proliferation. In addition, genes related to stress resistance were found, which supports the notion that U. prolifera grows vigorously in nature. These results help to characterize green tides from a new perspective and reveal some important insight into the biology of U. prolifera.

The aim of this study was to evaluate the growth-promoting effects of the combination of magnesium aminoclay (MgAC) and amino-functionalized carbon dots (N(CD)s) on Tetraselmis sp. cultures with an emphasis on N(CD)s. To that end, simply sol-gel-synthesized MgAC and one-pot carbonization-synthesized N(CD)s were utilized. The as-prepared N(CD)s possessed the expected amino-functional groups, exhibited strong blue emission with bright luminescence, and showed a quantum yield (QY) of 5.69%. The maximum specific growth rate and biomass productivity were achieved with the combination of 0.1 g L−1 MgAC and 40 μg mL−1 N(CD)s, which afforded improvements in lipid and protein accumulation relative to the control, whereas carbohydrate accumulation slightly decreased. At low concentrations (0.1 g L−1), MgAC demonstrated growth stimulation. The N(CD) addition to the MgAC-containing medium further supported the Tetraselmis sp. cultures in counteracting the effects of UV radiation and in improving photosynthesis activity. In these ways, increased growth and biomass productivity under UV irradiation and enhanced pigment contents under the light-irradiance condition were obtained. Therefore, use of the MgAC-N(CD) combination as a culture-medium supplement is a promising method for microalgae biorefinery applications.

Synthetic dyes are scattered in untreated or inappropriately treated effluents, and their dangerous items created during the halfway corruption are released into the water bodies that cause a horrendous smell, which prompts anomalous changes in the nature of water. In the present study, green algae and cyanobacteria are considered as a significant hotspot for decolorizing color and material gushing. Chlorococcum sp., Scenedesmus obliquus, Chlorella vulgaris, and Oscillatoria sp. were investigated for degradation and removal of some azo dyes [Reactive Orange 122 (Orange 2RL) and Reactive Red 194 (Reactive Red M-2BF)]. The results showed that the maximum decolorization was spotted at 20 ppm Reactive Orange 122 with Oscillatoria sp. mixed with S. obliquus (98.54%). 20 ppm Reactive Red 194 was decolorized by Oscillatoria sp. mixed with S. obliquus (97.58%) after 7 days of incubation. The decolorization was detected by spectroscopic analysis and Fourier transformed infrared (FTIR) spectroscopy. The suitable factors that accelerated the azo dye decolorization and enhanced the biological treatment methods to be more effective and speedier in decolorization were investigated. At 25 °C and continuous lighting, the highest percentage of the azo dye decolorization was obtained; BG11 was the suitable medium that gives a high percentage of the azo dye decolorization. However, relative to the effect pH on azo dye decolorization, results show pH 11 and pH 9 more effective on azo dye decolorization for Reactive Orange 122 and Reactive Red 194, respectively. A total of 6% of thiamine and ascorbic acid recorded maximum degradation activity at Reactive Orange 122 when treated with Oscillatoria sp. mixed with S. obliquus 79.13% and 77.18%, respectively.

Red snow caused by spherical cysts can be found worldwide, while an orange snow phenomenon caused by spherical cells is restricted to (Sub-)Arctic climates. Both bloom types, occurring in the same localities at Svalbard, were compared ecophysiologically. Using a combination of molecular markers and light- and transmission electron microscopy, cells were identified as Sanguina nivaloides and Sanguina aurantia (Chlorophyceae). In search for reasons for a cosmopolitan vs. a more restricted distribution of these microbes, significant differences in fatty acid and pigment profiles of field samples were found. S. aurantia accumulated much lower levels of polyunsaturated fatty acids (21% vs. 48% of total fatty acids) and exhibited lower astaxanthin-to-chlorophyll-a ratio (2–8 vs. 12–18). These compounds play an important role in adaptation to extreme conditions at the snow surface and within snow drifts. Accordingly, the performance of photosystem II showed that one third to nearly half of the photosynthetic active irradiation was sufficient in S. aurantia, compared to S. nivaloides, to become light saturated. Furthermore, formation of plastoglobules observed in S. nivaloides but missing in S. aurantia may contribute to photoprotection. The rapid light curves of the two species show to a certain extent the shade-adapted photosynthesis under the light conditions at Svalbard (high α-value 0.16 vs. 0.11, low saturation point Ik 59 vs. 86). These results indicate significant physiological and ultrastructural differences of the two genetically closely related cryoflora species, but the reasons why S. aurantia has not been found at conditions outside (Sub-)Arctic climate types remain unknown.

Lichens consisting of a symbiotic association of green algae or cyanobacteria and fungi are found in a variety of environmental conditions worldwide. Terricolous lichens, located in soils, affect the living and lifeless environment of the soil due to their effective secondary metabolite and enzymatic content. Terricolous lichens can increase the biological, chemical, and physical usefulness of soil. However, their effects in ensuring the bioavailability of contaminated soil are not known, especially on soil pollution caused by DDTs (p,p '-DDE, p,p '-DDD, p,p '-DDT). This research focuses on the effect of terricolous lichens on zucchini (Cucurbita pepo spp. pepo) grown in soil contaminated by DDTs, utilizing their secondary metabolite and enzymatic contents. Firstly, Peltigera canina, a terricolous lichen species, was added to soil contaminated by DDTs as powdered and intact thallus. After lichen addition to soil, zucchini was planted in. The oxidative stress and antioxidative enzyme activities of zucchini were measured. According to the results, P. canina treatments have a positive effect on the growth and development of zucchini, although oxidative stress was observed. Also, it was determined that powdered application had more effective results than intact thallus application.

Significant levels of polycyclic aromatic hydrocarbons (PAHs) were detected in lakes. The competition between algae would be disturbed by PAHs resulted in variations of algal growth. For controlling the cyanobacterial blooms, it is important to understand this disturbed competition between Microcystis aeruginosa and other algae. A 6-day cultivation experiment was designed to investigate the responses of M. aeruginosa to PAHs in presence of green algae. A popular green alga Chlorella pyrenoidosa was used as a representative of green algae, and phenanthrene and pyrene were selected as representatives of PAHs. The results showed that M. aeruginosa outcompeted C. pyrenoidosa under PAH contamination, and PAHs and M. aeruginosa significantly inhibited the survival of C. pyrenoidosa. PAHs disturbed the growth of algae by influencing photosynthetic pigments and phycobiliproteins, and the different alteration of Fv/Fm ratios implied that shifted algal community composition would be induced by PAHs. The Fv/Fm of the two algal mixture and individual C. pyrenoidosa was significantly negatively correlated with phenanthrene levels. However, there were no significant correlations between the Fv/Fm of M. aeruginosa and the exposure levels of phenanthrene or pyrene. Remarkably, the Fv/Fm significantly increased in M. aeruginosa at 0.15 mg L-1 pyrene, suggesting that PSII resistance to pyrene was enhanced in M. aeruginosa. Our results pointed out an increasing frequency and intensity of cyanobacterial blooms could be induced by PAHs in contaminated waters.

Various solvent extracts from two marine green algae, Codium bursa and Codium fragile collected from the North Tunisian coasts during spring and summer seasons were used to obtain high dry matter yields. The algal extracts showed the great power of in vitro cell growth inhibition against Hela cells, which was confirmed by MTT test. The comparative efficiency of different polarity solvents showed that methanolic extract with high-polarity composition had significantly more important yield than petrol ether extracts, while the higher inhibition activity was obtained with petrol ether extract from C. bursa (IC50= 115.755 μg/mL). Moreover, it showed a seasonal variation that revealed the most important activity during the season of spring as compared to summer. Flash chromatography of the petrol ether extract and GC-MS analysis of its most active fraction revealed a total of six major compounds well-known in medicinal plants: 6,10,14-trimethyl-2-pentadecanone; 2-dodecanone; 1-dodecanol; dodecyl acrylate; formic acid 3,7,11-trimethyl-1,6,10-dodecatrien-3-yl ester; and bicyclo[4.4.0]dec-2-ene-4-ol 2-methyl-9-(prop-1-en-3-ol-2-yl).

Light plays a crucial role in photosynthetic microalgae, and its quality is a key point for biomass production and the variability of the organisms’ biochemical composition, with blue and red, the light bands being the most effectively absorbed by green algae. Recently, light-emitting diodes (LEDs) have emerged as an alternative that allow a better modulation of algal metabolism. The aim of this work was to study the effects of blue and red LEDs on antioxidant capacity, biomass productivity (Px) and carotenoid and fatty acid content over time in a microalga known to be a producer of antioxidant compounds, Scenedesmus obliquus M2-1. Monochromatic blue (B) and red (R) LEDs and two dichromatic combinations of blue and red (BR (40:60) and BR (50:50)) were tested, and fluorescent lamp (FL) was used as a control. Then, supplementation effects of near-infrared radiation (NIR) LEDs were assessed in the same in parameters. Results show that B induced higher PX and higher content in fatty acids when compared with other LED conditions tested. Scenedesmus obliquus M2-1 under R attained a higher antioxidant capacity and under BR (40:60) a higher carotenoid production, particularly lutein and β-carotene, when compared with that of FL. NIR supplementation in BR (40:60) and R treatments enhanced PX and fatty acid content, changing the profile of antioxidant compound production over time, but keeping the maximum concentration. Additionally, NIR supplementation decreased the total carotenoid production. This study reveals that the use of R and BR (40:60) LEDs are a useful tool to enhance the production of carotenoids in S. obliquus M2-1.

Excessive growth of filamentous green algae in rivers has attracted much attention due to their functional importance to primary production and carbon cycling. However, comprehensive knowledge of how filamentous green algae affect carbon cycling, especially the CH4 emissions from river ecosystems, remains limited. In this study, incubation experiments were conducted to examine the factors regulating CH4 emissions from a eutrophic river with dense growth of filamentous green algae Spirogyra through combinations of biogeochemical, molecular biological, and stable carbon isotope analyses. Results showed that although water dissolved oxygen (DO) in the algae+sediment (A+S) incubation groups increased up to 19 mg L-1, average CH4 flux of the groups was 13.09 μmol m-2 day-1, nearly up to two times higher than that from sediments without algae (S groups). The significant increase of sediment CH4 oxidation potential and methanotroph abundances identified the enhancing sediment CH4 oxidation during Spirogyra bloom. However, the increased water CH4 concentration was consistent with depleted water [Formula: see text] and decreased apparent fractionation factor (αapp), suggesting the important contribution of Spirogyra to the oxic water CH4 production. It can thus be concluded that high DO concentration during the algal bloom promoted the CH4 consumption by enhancing sediment CH4 oxidation, while algal-linked oxic water CH4 production as a major component of water CH4 promoted the CH4 emissions from the river. Our study highlights the regulation of Spirogyra in aquatic CH4 fluxes and will help to estimate accurately CH4 emissions from eutrophic rivers with dense blooms of filamentous green algae. Graphical abstract.

This study includes information about the most common freshwater and marine species from the genusCladophorasuch as classification, taxonomy and morphology, ecology, occurrence and distribution, population and community structure, harvesting and culture conditions, chemical composition, and utilization. Habitat requirements and development optima are different for species belonging to the commonly recorded genusCladophora. The majorityCladophoraspecies are distributed throughout the world, in both the moderate and tropical zones. Of the species noted from Europe, only 15 are characterized for freshwaters, both flowing and standing. In small water bodies, these green algae are very common and occur almost everywhere: in lakes, dam reservoirs, large rivers occur mainly in the coastal littoral zone. A commonly occurring species of macroscopic green algae isCladophora glomerata. Habitat parameters have shown that the distribution pattern of filamentous green algae taxa is determined by two different gradients: (i) depth—temperature, light availability, oxygen concentration; and (ii) trophy—nitrate and orthophosphate concentration. A fast growth rate ofCladophorais very effective under good light condition and high concentration of nutrients. Species of the generaCladophorahave been determined to be early spring or summer organisms. The biomass ofCladophoracan be successfully applied as a raw material for production of value-added products. In this review,Cladophoraspecies are discussed in terms of their chemical composition, as well as potential applications in many areas, for example human and animal health, agriculture (organic fertilizers, biostimulants of plant growth, feed additives), environmental protection (bioindicator of pollution/contamination, sorbent of pollutants from wastewater), renewable source of energy (biogas, bioethanol), and high-tech composite materials.

Heat shock proteins (HSPs) and HSP70-HSP90 organizing proteins (HOPs) are related, and they function together to maintain cellular homeostasis and respond to stress. In the present study, we reported the first molecular characteristics of HSP70 (designated as CeHSP70) and HOP (designated as CeHOP) genes from the freshwater green algae Closterium ehrenbergii and examined the changes in their expression profiles under heat stress and toxic chemicals treatment. CeHSP70 presented the conserved motif patterns and EEVD domain specific to cytosolic HSP70; CeHOP contained a typical domain of TPR repeats. Real-time PCR analysis showed that thermal stress considerably up-regulated both CeHOP and CeHSP70. In addition, the genes were significantly induced by CuCl(2), CuSO(4), and NiSO(4), but not by K(2)Cr(2)O(7), herbicide, and endocrine disrupting chemicals. These results suggest that CeHOP and CeHSP70 function together and play a role in responses to specific stressors and indicate their possible use as sensitive specific biomarkers in risk assessments. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12192-020-01143-8) contains supplementary material, which is available to authorized users.

Restoration of ecosystems on the lands disturbed by the mining industry is very slow. Acceleration of these processes is the main purpose of revegetation measures. The purpose of the current research is to show changes of cyanobacteria and algae diversity and abundance depending on the composition of different reforested stands and technosols qualities of the waste rock dumps in West Donbas coal basin, Nikopol manganese ore basin and Kryvyi Rih iron ore basin (Ukraine) that were revegetated in 1966 and 1975. The main technosols physical and chemical qualities, diversity and abundance of cyanobacteria and algae are identified. It is discovered that abundance and diversity of cyanobacteria and algae depends on qualities of soils and forest-forming tree species. The increase in physical clay in soils (particles

Macroalgae blooms of Ulva prolifera have occurred every summer in the southern Yellow Sea since 2007, inducing severe ecological problems and huge economic losses. Genesis and secular movement of green algae blooms have been well monitored by using remote sensing and other methods. In this study, green algae were detected and traced by using Geostationary Ocean Color Imager (GOCI), and a novel biomass estimation model was developed from the relationship between biomass measurements and previously published satellite-derived biomass indexes. The results show that the green algae biomass can be determined most accurately with the biomass index of green algae for GOCI (BIGAG), which is calculated from the Rsurf data that had been atmospherically corrected by ENVI/QUAC method. For the first time, dynamic changes in green algae biomass were studied over an hourly scale. Short-term biomass changes were highly influenced by Photosynthetically Available Radiation (PAR) and tidal phases, but less by sea surface temperature variations on a daily timescale. A new parameter of biomass changes (PBC), calculated by the ratio of the biomass growth rate to movement velocity, could provide an effective way to assess and forecast green tide in the southern Yellow Sea and similar areas.

Snow in Antarctica is a vast terrestrial ecosystem and plays a key role that has likely been underestimated. Algae are the key primary producers on the coloured snow surface, and they support a microbial community that includes bacteria, fungi and/or invertebrates. We analysed microbial communities that co-exist in green and red snow samples from the Fildes Peninsula by Illumina sequencing, Antarctica, as well as the influence of snow physicochemical properties. We detected several species of green algae from Chlorophyta and Ochrophyta as well as fungi and cercozoans. The three red snow samples (RS1, RS2 and RS3) were represented by mixed eukaryotic microalgae from Sanguina, Chloromonas and Trebouxiophyceae. The green snow sample GS5 exhibited lake-to-snow colonisation composed of Trebouxiophyceae, Ulvophyceae and Chrysophyta representatives. The red snow RS4, predominantly by Chlainomonas sp. from slush layers, which presented a different microbial community from the other red snow samples, was sampled close to green snow sample GS5 near Lake Changhu. The environmental parameters were involved into descriptive differences among these coloured snow samples. The two snow algae Chlainomonas and Sanguina were firstly reported from Antarctica, which indicates distinguished snow algae colonisation that is closely connected with the melting snow at the lake ice-cover. Meanwhile, consistent with previous bacterial community profiles, Proteobacteria and Bacteroidetes were mostly represented in all the coloured snow samples. Polaromonas (Betaproteobacteria) was the most abundant genus, and its presence was reportedly essential for the sustained growth of snow algae. Flavobacterium from Bacteroidetes was the most frequently detected genera in GS5, but the Sphingobacteriia with only a few reads were an interestingly minority in GS5. The snow-algae-associated bacteria were closely related to psychrophilic strains or sequences from low-temperature environments. Many possible factors influence on the coloured snow microbial communities would require attentions, to help understand their occurrence mechanisms, their biogeographic distributions in polar regions.

The colonization of biofouling organisms is a significant problem for the aquaculture installations which affect the economy of the fish farms and wellbeing of the cultured fish. In this study, the colonization of biofouling organisms on cage aquaculture nets submerged near to the existing floating cages was analysed for a period of one year from June 2017 to May 2018. Cage net panels were fitted onto an iron frame and submerged at 1 m depth near to existing aquaculture cages. The biofouling organisms found on the panels mainly consisted of macroalgae, bivalves, bryozoans, hydrozoans and ascidians. Some other epifauna like brittle stars, polychaetes, amphipods, crabs, gastropods were also occurred more occasionally on the nets. Recruitment of green algae and brown algae were observed from the first month of net panel exposure. Bivalves and ascidians were developed from the second month. Hydrozoans and bryozoans appeared on the nets after 7 months of panel deployment. Results also revealed that ascidians and bivalves were the dominant fouling organisms in most of the sampling months during this study period.

The increasing use of pharmaceuticals has become a major environmental issue in China. The presence of antibiotics in water may have deleterious effects on non-target aquatic organisms such as microalgae. In this study, a cyanobacterium and an alga species in surface waters, Microcystis aeruginosa and Chlamydomonas microsphaera, were exposed to 0, 0.1, 0.5, 1.0, 2.0, 5.0, 10.0, and 20.0 mg/L of oxytetracycline dihydrate (OXY) and sulfamethoxazole (SMZ) for 96 h to determine the effects of these antibiotics on the growth and surface morphology. Moreover, the photosynthetic activity and the contents of superoxide dismutase (SOD), malondialdehyde (MDA), and protein were measured to examine the biochemical characteristics of M. aeruginosa and C. microsphaera under OXY and SMZ stress. The effects of both antibiotics on the growth of both species were concentration-dependent and characterized by low-dose stimulation and high-dose inhibition. C. microsphaera was more sensitive to both antibiotics than M. aeruginosa was. The algal cell membranes of both species disintegrated after exposure to a high concentration of OXY. All of the physiological parameters measured in this study were relatively stable at low concentrations of OXY and SMZ. After exposure to high concentrations of OXY and SMZ, photosynthetic activity decreased significantly, whereas lipid peroxidation and the abundance of SOD, MDA, and protein increased significantly. Thus, low-dose antibiotics may increase algal blooms in eutrophic waters.

Microscopic propagules of Ulva species (UMPs) spread on Subei Shoal are believed to play a significant role in the formation of the Yellow Sea green tide. Previous laboratory and ship-based studies indicated that modified clay (MC) can effectively remove UMPs from the water column and restrict their germination. To evaluate the effectiveness of this method under natural conditions, a mesocosm experiment was conducted on the Zhugensha sandbank on Subei Shoal. The results show that the suspended particles on the sandbank would partially disturb the flocculation process between the MC and UMPs. However, the MC at a proper dose could effectively remove UMPs from the water column and decrease the adhesion and germination of UMPs on the nylon ropes that comprised the mariculture rafts by > 75%. This method was proven a potential strategy to restrict the initial biomass accumulation of green algae on Subei Shoal. However, field trials in larger time-space scales are still needed to assess the efficiency of this method when used in the open sea.

An ecofriendly and efficient procedure for the synthesis of silver nanoparticles (AgNPs) was performed using aqueous extract of Enteromorpha intestinalis as reducing, capping, and stabilizing agents. AgNPs were characterized by UV spectroscopy, Fourier transform infrared (FTIR), high-resolution transmission electron microscope (HRTEM), and EDX. Moreover, the optimum conditions for the green synthesis were studied and the antimicrobial activity were estimated by agar well diffusion and broth dilution methods. UV vis spectroscopy confirmed the formation of AgNPs due to their surface plasmon resonance. The optimum conditions for the biosynthesis of AgNPs were using 2.5 g or 5 g/100 ml (w/v) of algal biomasses for extraction, and 1 mM of silver ions within 72 h. Transmission electron micrographs showed that AgNPs were spherical in shape and with a mean average size of 9.17 ± 3.2 nm. FTIR revealed the that protein and polysaccharides are responsible for AgNPs synthesis. Additionally, AgNPs exhibited antimicrobial activity against all tested microorganisms. The minimum Inhibitory concentration for all bacteria and Candida albicans ATCC26555 was 6.25 µg/ml except Klebsiella Pneumoniae ATCC70603 and Staphylococcus aureus ATCC4330 was 12.5 µg/ml. Further studies will be recommended to estimate the cytotoxicity of these AgNPs on the human cell line. The future use of algae as green nanofactory will be important in medical applications.

In this study we analyzed the dynamics of the phytoplankton community in two cascade reservoirs in six sampling periods, to investigate the influence of environmental filters on phytoplankton, and the community concordance with the environmental variability. We addressed several questions, and from phytoplankton biomass data and abiotic variables sampled at the Salto Osorio and Salto Santiago reservoirs, Parana, Brazil, we obtained the answers. A total of 136 taxa distributed in cyanobacteria, diatoms, green algae and mixotrophic flagellates were recorded. Diatoms and mixotrophic flagellated algae contributed most of the phytoplankton biomass in both reservoirs. Environmental filters such as nutrient concentrations, light, pH, depth and temperature had the greatest influence on phytoplankton taxonomic structure, being the community in concordance with the environmental conditions. Although some environmental differences between reservoirs were recorded, the phytoplankton community was similar, probably associated with environmental connectivity, but with differences in biomass, which is possibly associated with seston retention in upstream regions. Our results revealed important drivers that influence the phytoplankton structure and dynamics in reservoirs, and this understanding is of interest, due to the maintenance of ecosystem functions and services.

During the experimental cultivation of the red alga Halymenia floresii under Integrated MultiTrophic Aquaculture (IMTA), the establishment of opportunist green algae and the colonization of sessile invertebrates, which were usually disturbing the cultivation, were not observed. The culture tanks were clean and the surface of the H. floresii was remarkably free from any fouling organisms. This phenomenon could reveal that the presence of H. floresii may prevent biofilm formation by releasing allelopathic active compounds that ultimately interfere with the settlement and growth of competitors. In order to understand this phenomenon, H. floresii was cultivated under controlled environmental conditions and analyzed for its surface chemical defense metabolites. The surface-associated metabolites were extracted using the DIP extraction method, using different solvents with increasing polarity and immersion periods. Using epifluorescence microscopy, n-hexane was found to be the suitable immersion solvent for H. floresii for a period of 10 to 60 s to extract surface metabolites. The whole cell metabolites were extracted exhaustively with the same solvent for a period of 24 h. The chemical profiling of the surface compounds was performed by liquid chromatography mass spectroscopy (LC-MS), followed by a Mass Bank search and compared with those obtained from the whole-cell extracts. The mean concentration of H. floresii surface metabolites was 600 ng cm−2 (c. 60 g of a fresh sample) whereas the whole-cell metabolite concentration was around 4.5 μg mg−1 (400 mg of the lyophilized sample). The bioactivity of the H. floresii surface extracts was studied by evaluating their quorum quenching behavior on the surface-associated bacteria. The cultivable bacteria isolated from the surface of H. floresii were identified as Vibrio owensii (B3IM), Alteromonas sp. (B7CC), Pseudoalteromonas arabiensis (B4BC), Ruegeria sp. (B4CC), Tenacibaculum sp.(B9BC), Maribacter sp. (B9IM) and Aquimarina sp. (B9.1CC). All the isolated strains belonged to Alphaproteobacteria, Gammaproteobacteria and Bacteroides. The results of this bioactivity proved that the surface-associated metabolite extract (DIP) interferes with the communication signals produced by the bacteria isolates with the reporter strain employed. According to the Mass Bank compound analysis, we hypothesized that flavonoids and/or halogenated compounds might have contributed to this activity. This work provides an understanding of the influence of surface-associated metabolites on the associated bacterial community and by which H. floresii manages to control the biofouling on its surface.

Primary plastids originated from a free-living cyanobacterial ancestor and possess their own genomes-probably a few DNA copies. These genomes, which are organized in centrally located plastid nuclei (CN-type pt-nuclei), are produced from preexisting plastids by binary division. Ancestral algae with a CN-type pt-nucleus diverged and evolved into two basal eukaryotic lineages: red algae with circular (CL-type) pt-nuclei and green algae with scattered small (SN-type) pt-nuclei. Although the molecular dynamics of pt-nuclei in green algae and plants are now being analyzed, the process of the conversion of the original algae with a CN-type pt-nucleus to red algae with a CL-type one has not been studied. Here, we show that the CN-type pt-nucleus in the primitive red alga Cyanidioschyzon merolae can be changed to the CL-type by application of drying to produce slight cell swelling. This result implies that CN-type pt-nuclei are produced by compact packing of CL-type ones, which suggests that a C. merolae-like alga was the original progenitor of the red algal lineage. We also observed that the CL-type pt-nucleus has a chain-linked bead-like structure. Each bead is most likely a small unit of DNA, similar to CL-type pt-nuclei in brown algae. Our results thus suggest a C. merolae-like alga as the candidate for the secondary endosymbiont of brown algae.

The epiphytic algae on the bryophytes of Larsemann Hills, East Antarctica, are taxonomically investigated, and sixteen algal species are recognized including ten species of blue–green algae dominated by the species of Nostoc, three species of green algae, a xanthophycean alga and two diatoms. The occurrence of algae on different bryophytes is dependent on water-holding capacity of the bryophytes and sometimes nutrient enrichment in nearby lands through the excretion of resting sea birds. Thus, the bryophyte colonies in Broknes Peninsula, Fisher and Solomon Islands have rich and diverse epiphytic algal populations among the 18 study sites. The present study not only widens our knowledge on polar algal distribution, but can also be preferred as ‘model’ environment for the further studies of plant-adaptive strategies to thrive in the harshest environment.

Ulva are ubiquitous and opportunistic green algae species that easily adapt to various environmental conditions. These algae are responsible for the green tides that cause many environmental and ecological problems in coastal waters. We investigated the physiological responses of Ulva australis under warming, acidification, and eutrophication conditions. The physiological changes in the algae were observed under various combinations of temperature, pH, and NH4+ levels. Combinations of three temperatures (10°C, 20°C, and 30°C), two pH levels (7.80 and 8.20), and two NH4+ concentrations (4 μM and 120 μM) were considered under laboratory conditions. Temperature, NH4+, and pH had significant impact on the photosynthetic and nutrient uptake rates. However, the 12 h observation could not stimulate the seaweed to change the pH in the cultured media. Changes in relative growth rates, photosynthetic efficiency, and variations in tissue C and N were not affected by the interactions between temperature, pH level, and nutrient concentration. It is probable that, due to global warming, the bloom of Ulva australis may continue in warm, acidic, coastal waters with high nutrient levels.

In this study, we estimated extracellular concentrations of algal-derived sulfur species in response to changing photoperiods. Cultures from three algal species (Chlorella vulgaris, Chlamydomonas reinhardtii, Scenedesmus obliquus) were subjected to five different light:dark cycles (12:12, 14:10, 16:8, 18:6, 20:4 h) for a period of 3 days. Sulfur compounds including total reactive thiol concentrations, electroactive reduced sulfur species (RSS), and thiol isomers were measured using qBBr fluorescence, differential pulse cathodic stripping voltammetry (DP-CSV), and high-resolution mass spectrometry (HRMS), respectively. Total reactive thiol concentrations were greater in Scenedesmus than in Chlamydomonas and Chlorella at low light regimes (i.e., 12:12 h) whereas Chlamydomonas produced more RSS than the other two species (p

Chlorella variabilis is a high-efficiency photosynthetic green plant, and its photosynthesis capacity is considerably higher than other plants. With increasing CO2 concentration in the atmosphere C. variabilis may change the metabolism to respond to elevated CO2. To investigate the response of C. variabilis when exposed to increased CO2 concentrations, physiological and transcriptome analyses were carried out on C. variabilis that had been cultivated at 1000 ppm CO2 for long (LT) and short (ST) periods of time and these were compared with samples from the control group (CT). The common responses of the ST and LT C. variabilis included increased pigment levels, and higher Fv/Fm and carbon fixation rates. These results indicated that current CO2 levels could limit C. variabilis growth and photosynthesis. Transcriptome changes in the ST samples were coincident with the observed physiological responses, which suggested that carbon flow to the acetyl-CoA pool from photosynthesis enhanced the production of lipids and fatty acids. This was confirmed by the depressed β-oxidation levels, upregulation of fatty acids and triglyceride synthesis pathways, lower soluble carbohydrate contents, and lipid accumulation. However, we found no change or downregulation of genes involved in cellular metabolism in the LT samples, such as the genes participating in protein, fatty acid, and triglyceride synthesis. The results demonstrated that C. variabilis was generally sensitive to the ST condition, but hardly responded to the LT treatment and failed to evolve any specific adaptations.

Algae have the potential to capture carbon dioxide (CO2) and nitric oxide (NO) from flue gases. However, the effects of high concentrations of these gases on the photophysiology of algae are poorly understood. To that end, we used the techniques of chlorophyll fluorescence to study the effect of industrially relevant levels of CO2 and NO on the photophysiology of two green microalgae, Asterarcys quadricellulare and Chlorella sorokiniana, that are tolerant to these gases. Measurements of maximum quantum yield (Fv/Fm) and maximum relative electron transport rate (rETRmax) show an enhanced performance of photosystem II (PSII) under high CO2 levels. In C. sorokiniana, high CO2 stimulated non-photochemical quenching (NPQ), while the opposite effect was observed in A. quadricellulare. Light-saturated photosynthetic rates (Pmax) of both species were highest at 10% CO2. Further, the tested levels of NO did not show adverse effect on the performance of PSII. OJIP chlorophyll fluorescence transients suggest that in C. sorokiniana, the energetic communication between PSII units declined at 15% CO2. However, in A. quadricellulare, this decline was visible even at 10% CO2 with complete inhibition of cell growth at 15% v/v. Overall, our results suggest that although photosynthesis was regulated differently in the two microalga, both species exhibited enhanced PSII performance under reasonably high levels of CO2 and NO. Thus, the two species are potential candidates for bio-fixation of CO2 and NO from flue gases.

In lakes, suspended inorganic particles and dissolved substance are able to absorb or scatter different light wavelengths, leading to the changes of underwater light spectra which are highly related to the water quality. In turn, such changes could form environmental filtering for phytoplankton community to select particular algal populations via intensive competition for light resources. As an example, eutrophic lakes where underwater light spectra changed dramatically have a result of cyanobacterial blooms. In this study, in order to test the effect of light spectrum on growth and competition of green algae and cyanobacteria, Chlorella pyrenoidosa (a common green alga) and Microcystis aeruginosa (a bloom-forming cyanobacterium) grew and competed under three light colors: white (400–700 nm), red (620–700 nm), and blue (410–490 nm) light. Mono- and co-cultured systems were designed and population dynamics of the two species were monitored. The Lotka-Volterra model was used to quantify interspecific competition. Moreover, their photosynthetic activities were measured in mono-cultures. Results showed that in mono-cultures, red light was more favorable for M. aeruginosa, while blue light promoted the growth of C. pyrenoidosa. In co-cultures, M. aeruginosa won in red light and white light, while C. pyrenoidosa dominated under blue light. Light color mainly affected the absorption flux of reaction center (ABS/RC) in photosynthetic system II (PSII) and its potential photosynthetic capacity (Fv/Fm). Fv/Fm of M. aeruginosa in red light (or C. pyrenoidosa in blue light) was significantly enhanced. This study revealed that light color showed a significant influence on interspecific competition between green algae and cyanobacteria, which offers new insights into the dominance establishment and bloom formation of Microcystis.

Background Biostimulants, such as algae extracts or amino acids, are becoming more common in agriculture because the mentality is to make plants more resistant or tolerant to negative environmental factors, rather than using synthetic chemicals (herbicides, insecticides and fungicides), whose use is decreasing year by year, forcing farmers and companies to develop new environmentally friendly products. Results In a field experiment, green algae and amino acids were tested as biostimulants on three hot pepper cultivars. A large variability was observed between the effects of the two biostimulants on the cultivars. Green algae-treated ‘Somborka’ and ‘Habanero Red Caribbean’ cultivars had 10% and 5% higher dry matter in seeds compared to control treatment. Total sugar content was negatively affected by green algae extract and amino acids in pericarp in cultivars ‘Chili AS-Red’ and ‘Habanero Red Caribbean’. Total organic acids content was positively affected by amino acid treatment in ‘Habanero Red Caribbean’ pericarp and placenta, with an increase of 5.5 g and 2.1 g/100 g DW, respectively. In terms of total phenolics, all three cultivars were positively affected by amino acid treatment, but not in each fruit part. In terms of capsaicinoid content, the greatest effect of the two stimulants was on ‘Somborka’, which varied from four (pericarp, seed) to 16 (placenta) times compared to the control. Amino acid extract decreased ‘Habanero Red Caribbean’ capsaicinoid content in placenta by about 40%. Conclusion Amino acids were found to be superior to algal extract, although the effect of both was mostly cultivar specific. For a wider use of biostimulants, it should first be tested whether they are suitable for the cultivar in order to increase and optimize the results. Graphic abstract

Sea urchins Paracentrotus lividus were harvested monthly from April 2015 to March 2016 from two sites in Sardinia (Italy). The two sites, a Posidonia oceanica meadow and a rocky bottom habitat, were naturally characterized by different food sources and availability, being mainly populated by the sea grass Posidonia oceanica and the brown algae Halopteris scoparia, respectively. Total lipids showed a minimum during winter in mature gonads, and a maximum in the summer (recovery stage). Fatty acid (FA) profiles of gut contents and gonads differed from those of the most available food sources. Levels of C18:3 (n-3) (ALA) discriminated samples from the two sites. Despite the very low amounts of C20:5 (n-3) (EPA) and C20:4 (n-6) (ARA) in P. oceanica, the main FA in gonads and gut contents were EPA and ARA in both sites. Increase in green algae intake prior to gametogenesis, especially C. cylindracea, likely affected EPA and ARA levels in gonads. The results show that P. lividus is able to concentrate lipids in gut contents and also to selectively store EPA, ARA and their precursors ALA and 18:2 (n-6) (LA). Moreover, bioconversion of ALA to EPA and of LA to ARA in P. lividus is suggested.

Amphibian clutches are colonized by diverse but poorly studied communities of micro-organisms. One of the most noted ones is the unicellular green alga, Oophila amblystomatis, but the occurrence and role of other micro-organisms in the capsular chamber surrounding amphibian clutches have remained largely unstudied. Here, we undertook a multi-marker DNA metabarcoding study to characterize the community of algae and other micro-eukaryotes associated with agile frog (Rana dalmatina) clutches. Samplings were performed at three small ponds in Germany, from four substrates: water, sediment, tree leaves from the bottom of the pond, and R. dalmatina clutches. Sampling substrate strongly determined the community compositions of algae and other micro-eukaryotes. Therefore, as expected, the frog clutch-associated communities formed clearly distinct clusters. Clutch-associated communities in our study were structured by a plethora of not only green algae, but also diatoms and other ochrophytes. The most abundant operational taxonomic units (OTUs) in clutch samples were taxa from Chlamydomonas, Oophila, but also from Nitzschia and other ochrophytes. Sequences of Oophila “Clade B” were found exclusively in clutches. Based on additional phylogenetic analyses of 18S rDNA and of a matrix of 18 nuclear genes derived from transcriptomes, we confirmed in our samples the existence of two distinct clades of green algae assigned to Oophila in past studies. We hypothesize that “Clade B” algae correspond to the true Oophila, whereas “Clade A” algae are a series of Chlorococcum species that, along with other green algae, ochrophytes and protists, colonize amphibian clutches opportunistically and are often cultured from clutch samples due to their robust growth performance. The clutch-associated communities were subject to filtering by sampling location, suggesting that the taxa colonizing amphibian clutches can drastically differ depending on environmental conditions.

Green algae and plants rely on light-harvesting complex II (LHCII) to collect photon energy for oxygenic photosynthesis. In Chlamydomonas reinhardtii, LHCII molecules associate with photosystem II (PSII) to form various supercomplexes, including the C2S2M2L2 type, which is the largest PSII-LHCII supercomplex in algae and plants that is presently known. Here, we report high-resolution cryo-electron microscopy (cryo-EM) maps and structural models of the C2S2M2L2 and C2S2 supercomplexes from C. reinhardtii. The C2S2 supercomplex contains an LhcbM1-LhcbM2/7-LhcbM3 heterotrimer in the strongly associated LHCII, and the LhcbM1 subunit assembles with CP43 through two interfacial galactolipid molecules. The loosely and moderately associated LHCII trimers interact closely with the minor antenna complex CP29 to form an intricate subcomplex bound to CP47 in the C2S2M2L2 supercomplex. A notable direct pathway is established for energy transfer from the loosely associated LHCII to the PSII reaction centre, as well as several indirect routes. Structure-based computational analysis on the excitation energy transfer within the two supercomplexes provides detailed mechanistic insights into the light-harvesting process in green algae.

Green algae are dominant primary producers in aquatic environments. Thus, assessing the influences of pollutants such as nanoparticles on the algae is of high ecological significance. In the current study, cadmium selenide nanoparticles (CdSe NPs) were synthesized using the hydrothermal method and their characteristics were determined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR) techniques. Subsequently, the toxicity of synthesized nanoparticles on the green microalga Chlorella vulgaris was investigated. The observations by SEM confirmed that exposure to CdSe NPs had severe impacts on the algal morphology. Furthermore, the obtained results revealed the toxic effect of CdSe NPs by a decrease in the number of cells. Measurement of antioxidant enzymes activity showed an increase in the activity of catalase, and a decrease in the activity of superoxide dismutase (SOD) at high concentrations of CdSe NPs. The exposure of C. vulgaris to CdSe NPs resulted also in a change in algal pigments as well as total phenol content. Taken together, CdSe NPs appeared to have significant cytotoxic effects on C. vulgaris in the applied concentrations.

Microalgae can be cultivated for producing high-valued products through the production of enzymes to offset the cost of CO2 sequestration, providing financial incentives. The viability of algae in the photobioreactor needs to be monitored to ensure biologically active live cells. In this study, we explored a simple fluorometry method for differentiation of live and dead algal cells in photobioreactors by fluorescein diacetate (FDA) and propidium iodide (PI) fluorescence staining. FDA stains fluorescent green to the living cells while PI stains the dead cells, allowing the discrimination of live and dead cells. The method was evaluated using two green algae and two strains of cyanobacteria grown in shake flasks and a continuously stirred photobioreactor. The method was found applicable for Chlorella pyrenoidosa and Synechococcus 7002 but was not applicable for the cultures of Scenedesmus dimorphus and Synechococcus elongatus 7942. We conclude that FDA is a good stain for monitoring live algal cells in photobioreactors but its applicability to individual species of algae must be evaluated.

In the present study, the removal of a cationic dye, methylene blue (MB) with brown (Nizamuddinia zanardinii), red (Gracilaria parvispora) and green (Ulva fasciata) macroalgae was studied. The effects of different parameters such as initial solution pH, initial dye concentration, biomass dosage and contact time were investigated on the biosorption of MB by algae. Biosorption isotherm was modeled using the Langmuir, Freundlich and Temkin models. The highest MB dye removal efficiency onto algae was observed in the range of 5–11. Increasing biosorbent dosage from 80 to 240 mg/L, significantly increased the removal efficiency of MB dye; however, increasing the biosorbent dosage above 240 mg/L up to 400 mg/L did not significantly increase the dye removal efficiency. The biosorption of MB dye onto macroalgae reached equilibrium after about 90 min. Based on the Langmuir model, the uptake of MB by brown, red and green algae was determined as 863.4, 83.08 and 1514 mg/g, respectively. The biosorption kinetic data were successfully described with pseudo-second-order model for three biosorbents. FT-IR spectrum analysis suggested amido or hydroxyl, C=C and C–H groups present on algae surface could take part in MB dye biosorption.

Morphological responses of green algae to submerged macrophytes were rarely studied, and the potential active substances played roles in the interaction were little known previously. In the current work, according to acetone extract experiments, it was demonstrated that submerged macrophytes (Ceratophyllum demersum L.) could allelopathically inhibit the growth of Chlorella vulgaris Beij. and induce its colony formation, the effects of which were concentration dependent. Gas chromatography–mass spectrometry analysis revealed eight kinds of active substances from the C. demersum extracts, namely hexanoic acid, phthalic acid, octanedioic acid, butenoic acid, azelaic acid, palmitic acid, alpha linolenic acid and pentanedioic acid. Standard compound addition test indicated that palmitic acid and alpha linolenic acid might play important roles in the induction of colony formation and growth inhibition of C. vulgaris. This study provided some more new insights into the photosynthetic organism interaction between submerged macrophytes and green algae, in terms of not only growth but also morphological responses.

The aim of our study was to experimentally investigate whether it is possible to reduce nuisance growth of filamentous algae in freshwater ecosystems. We used an experimental set-up mimicking a shallow pond system and performed a field investigation in the eutrophic moat of Krapperup castle (Southern Sweden), which exemplifies an extremely impaired ecosystem with ample growth of filamentous green algae. The indoor experiment tested three treatments: I) reduced nutrient concentrations, II) invertebrate grazers and III) addition of barley straw, which may constitute measures against filamentous algal growth and thereby improve the quality of the ecosystem services provided by water bodies. Our results show a decrease in cyanobacteria and diatom abundances in all mesocosms as filamentous algae biomass increased, suggesting that the microalgae suffered from nutrient and light competition with filamentous algae. A tendency for lower filamentous algae final biomass, as well as coverage, was observed in the treatment where the concentration of nutrients was reduced. Grazers treatment showed a tendency to inhibit filamentous algae growth on artificial macrophytes towards the end of the experiment, suggesting that snails initially fed on their preferred food source (diatoms), until it was almost depleted and then started to feed on filamentous algae. Interestingly, the barley straw treatment was the only treatment promoting macrophytes growth and enhancing diatom biomass, but this did not affect filamentous algae biomass. However, the ratio between filamentous algae and macrophyte final biomasses was significantly lower in the straw treatment. In a broader context, it is likely that in a long-term perspective the positive effect of barley straw on macrophyte growth will promote a shift from dominance by filamentous algae to macrophytes as main primary producer. Moreover, our experiment shows that barley straw may be effective in reducing cyanobacterial growth, which may lead to improved water quality and thereby ecosystem services, such as supporting and cultural ecosystem services, since cyanobacteria may produce potent toxins and pose a serious risk to human and animal health. Altogether, our experimental results have important implications for the challenge of reversing nuisance filamentous algal blooms in highly eutrophic systems.

Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort along the coast. Micro-propagules of the green algae including gametes, spores, micro-germlings and micro-vegetative fragments play an important role in the formation of green tides. They serve as a “seed source” of green macroalgae, and their distributions could reflect and influence the “algae source” of green tides. In this study, monthly surveys in the inshore and offshore areas of the Qinhuangdao coast were conducted from April to September 2016 and in January 2017 to investigate the tempo-spatial distribution patterns and the biomass variations of the green algae micro-propagules. The obtained results show that micro-propagules were mainly distributed in the inshore areas with a significantly decreasing abundance towards offshore areas. Their biomass was highest in July and August, and lowest in winter. The areas that were affected by the green tides showed a remarkably higher abundance of micro-propagules compared to other areas. These micro-propagules could serve as the “seed” source of green tides. Their distribution patterns indicate that the green tide in the coastal areas of Qinhuangdao originated locally.

The fluorochrome JC-1 is mainly used in mammalian cells to estimate mitochondrial membrane potential (MMP) as a stress marker, with far less data being available for plants or green algae. To address this, we have validated the possibility for changes in MMP to be used as a sensitive stress indicator in the green alga Chlamydomonas reinhardtii. To optimize the method, we analyzed the conditions for applicable MMP determination, including the proper buffer, excitation/emission wavelengths, and solvent (dimethyl sulfoxide, DMSO) influence on the fluorescence signal, and evaluated usefulness of the method for toxicological research. Our results have allowed us to develop a complete protocol for the estimation of MMP changes in C. reinhardtii. Statistical analyses have confirmed the reproducibility, sensitivity, and applicability of this method for toxicological studies.

A relatively neglected element of the biota of the Lower Devonian Rhynie chert Lagerstatte are filamentous green algae exceptionally preserved by silicification. Palynological processing of sediments associated with the cherts has yielded palynomorphs that we also interpret as the remains of filamentous green algae and one such taxon is described herein. Cells occur individually, in masses or joined end-to-end as an unbranched filament. The cells are characterised by end walls that form a ‘collar’ structure and inner bodies interpreted as reproductive structures. Because of a lack of preserved characters taxonomic precision is limited, although we suggest the fossils are most likely either zygnematalean or oedogonialean algae that inhabited ponds or lakes and were either attached to substrates and/or free-floating.

In plants and green algae, the core of photosystem I (PSI) is surrounded by a peripheral antenna system consisting of light-harvesting complex I (LHCI). Here we report the cryo-electron microscopic structure of the PSI–LHCI supercomplex from the green alga Chlamydomonas reinhardtii. The structure reveals that eight Lhca proteins form two tetrameric LHCI belts attached to the PsaF side while the other two Lhca proteins form an additional Lhca2/Lhca9 heterodimer attached to the opposite side. The spatial arrangement of light-harvesting pigments reveals that Chlorophylls b are more abundant in the outer LHCI belt than in the inner LHCI belt and are absent from the core, thereby providing the downhill energy transfer pathways to the PSI core. PSI–LHCI is complexed with a plastocyanin on the patch of lysine residues of PsaF at the luminal side. The assembly provides a structural basis for understanding the mechanism of light-harvesting, excitation energy transfer of the PSI–LHCI supercomplex and electron transfer with plastocyanin. This cryo-electron microscopy structure of a photosystem I–light-harvesting complex I supercomplex from Chlamydomonas reveals eight Lhca proteins forming two tetrameric light-harvesting complex I belts on one side, and a Lhca heterodimer on the other.