Blooms Of Microalgae Research Articles

How heatwaves impact microalgae in the presence of environmentally relevant PFAS concentration: Metabolic shifts and challenges posed

Per- and polyfluoroalkyl substances (PFAS) are widely distributed in the aquatic environment. While increasing studies have investigated the effects of specific PFAS exposure on microalgae, the impact of environmentally relevant PFAS concentrations, particularly during extreme weather events like heatwaves, remains unclear. For Microcystis aeruginosa, a cyanobacteria causing harmful algal blooms, PFAS exposure promoted growth and photosynthesis by accelerating the TCA cycle, intensifying carbon/nitrogen and nucleotide metabolism, and enhancing antioxidant expression. Moreover, although heatwave exposure alone adversely affected algal growth, co-exposure to PFAS and heatwaves paradoxically enhanced algal growth. This co-exposure also enhanced the expression of photosynthetic pigments and metabolites involved in alanine, aspartate and glutamate metabolism, as well as arginine and proline metabolism (compared to PFAS exposure alone). Nevertheless, co-exposure intensified oxidative stress, leading to differential expression of antioxidants, which may consequently affect the synthesis of membrane lipids. In addition, PFAS adsorption and uptake are primarily influenced by the varying strengths of PFAS molecules in binding with proteins and notably boosted by heatwaves. This study highlights the role of diverse PFAS in microalgae blooms and the influence of heatwave events on pollutant responses, providing scientific foundations for aquatic ecosystem protection against climate and pollution challenges.

Bacteria modulate microalgal aging physiology through the induction of extracellular vesicle production to remove harmful metabolites

The bloom and bust patterns of microalgae in aquatic systems contribute massively to global biogeochemical cycles. The decline of algal blooms is mainly caused by nutrient limitation resulting in cell death, the arrest of cell division and the aging of surviving cells. Nutrient intake can re-initiate proliferation, but the processes involved are poorly understood. Here we characterize how the bloom-forming diatom Coscinodiscus radiatus recovers from starvation after nutrient influx. Rejuvenation is mediated by extracellular vesicles that shuttle reactive oxygen species, oxylipins and other harmful metabolites out of the old cells, thereby re-enabling their proliferation. By administering nutrient pulses to aged cells and metabolomic monitoring of the response, we show that regulated pathways are centred around the methionine cycle in C. radiatus. Co-incubation experiments show that bacteria mediate aging processes and trigger vesicle production using chemical signalling. This work opens new perspectives on cellular aging and rejuvenation in complex microbial communities.

Molecular approaches and challenges for monitoring marine harmful algal blooms in a changing world

Harmful algal blooms (HABs) of marine microalgae are a growing concern globally and many studies predict that their occurrence, range, and toxicity may increase with climate change, highlighting the need for responsive and adaptable monitoring techniques. Monitoring programmes for HABs require appropriate sampling techniques, accurate and quantitative identification of potentially toxic taxa, and the ability to respond to novel species or HAB events. These challenges have made it difficult to move past traditional techniques, but research tools are continuing to be developed to bring new opportunities for both monitoring programmes and fundamental understanding of these globally significant organisms within a changing landscape.

The first cultivation of the glacier ice alga Ancylonema alaskanum (Zygnematophyceae, Streptophyta): differences in morphology and photophysiology of field vs laboratory strain cells

AbstractMelting glacier surfaces are unique ecosystems for specialized microbes, frequently harbouring blooms of microalgae with pigments contributing to the darkening of ice surfaces, reducing albedo and enhancing melt rates. The main cause of this phenomenon is algae of the genus Ancylonema. Prior investigation depended on field-collected material because these algae resisted cultivation. To enhance research on how these algae dominate melting ice, we established a strain of Ancylonema alaskanum from an alpine glacier and exposed to temperatures around the freezing point at irradiations of ~10% of full sunlight. The morphology of the culture changed, with the cells becoming longer and turning green by losing their brownish pigmentation, indicating that these dark phenols are crucial for survival in the cryosphere. Photophysiological comparisons of strain and glacial material showed adaptation of the photosynthetic apparatus to prevailing conditions. This laboratorial strain opens possibilities for a wide range of comparative ‘omics’ research.

Responses of bacterioplankton, particle- and colony-attached bacterial communities to Phaeocystis globosa blooms in Mirs Bay, China

Microalgae blooms are a frequent occurrence in coastal waters worldwide. It is reasonable to assume that these blooms have various influences on bacterial communities, which in turn may affect the development and dissipation of the bloom. However, the bacterial community characteristics, particularly of attached bacteria, associated with microalgae blooms remain unclear. In this study, we investigated the community profiles of bacteria using high-throughput sequencing during a Phaeocystis globosa bloom in Mirs Bay, southern China, in January 2021. Bacteria living in three habitats, i.e., bacterioplankton, particle-attached bacteria, and colony-attached bacteria, were studied from the exponential growth phase to the decline growth phase of the bloom. Distinct variations in bacterial community composition existed among the three habitats. Bacteroidota, Proteobacteria, and Cyanobacteria were the dominant phyla of bacterioplankton, particle–attached bacteria, and colony-attached bacteria, respectively. Richness and diversity were significantly highest (p < 0.01) in particle-attached bacteria, followed by bacterioplankton, and lowest in colony-attached bacteria. The community diversities of bacterioplankton and particle-attached bacteria decreased significantly (p < 0.05) as the bloom shifted from the exponential to the decline phase. During the decline growth phase of the bloom, Bacteroidota and Verrucomicrobiota were the dominant remarkably abundant bacteria in the bacterioplankton community, whereas Verrucomicrobiota was dominant in the particle-attached bacteria community. No significant difference was observed in the colony-attached bacterial community between the exponential and decline phases of the P. globosa bloom owing to their complex network. The results of this study suggest that P. globose bloom has a profound impact on marine bacteria, particularly species that can decompose organic matter, which could play a crucial role in the dissipation of algal blooms.

Unexpected growth promotion of Chlorella sacchrarophila triggered by herbicides DCMU

The ecotoxicological effects of herbicide contamination on the autotrophic growth of microalgae in aquatic environments have been major concerns. However, little is known about the influence of herbicides on the mixotrophic growth of microalgae. This study investigated the ecotoxicological effect of 3-(3,4-dichlorophenyl)−1,1-dimethyl-urea (DCMU) on the mixotrophic growth of Chlorella sacchrarophila FACHB 4. Results showed that C. sacchrarophila in mixotrophy was more resistant to DCMU than in photoautotrophy. Moreover, a low content of DCMU (20–80 μg·L−1) promoted the mixotrophic growth of C. sacchrarophila, and the promotion effect was obviously enhanced with the increase in light intensity. The chlorophyll content and glucose absorption rate of C. sacchrarophila were found to increase after incubation with DCMU for 24 h. Transcriptome analyses revealed that the mechanism of DCMU to promote the mixotrophic growth of C. sacchrarophila was probably through accelerating glucose uptake and utilization, which was accomplished by reducing photodamage and increasing the chlorophyll content of C. sacchrarophila. This study not only revealed an unexpected bloom of mixotrophic microalgae triggered by herbicides, but it also shed new light on an effective and low-cost strategy to improve the microalgae productivity for utilization.

Methodology and Results of Satellite Monitoring of Karenia Microalgae Blooms, That Caused the Ecological Disaster off Kamchatka Peninsula

The environmental disaster in Kamchatka in the autumn of 2020 was caused by an extensive bloom of harmful microalgae of the genus Karenia. A spectral shape algorithm was used to detect algae on satellite imagery. The algorithm calibration of in situ species composition data made it possible to identify areas where harmful algae dominated in biomass. The algorithm allowed evaluation of the dynamics of the distribution of the algae. The state of phytoplankton was estimated based on images of the specific capacity of photosynthesis. Specific fluorescence is the ratio of the height of the fluorescence line (flh) to the concentration of chlorophyll-a (chl-a). The parameter was used to recognize the stages of the algal bloom: intensive growth, blooming, and change in the dominant algal species. In addition, an increase in the concentration of harmful substances in the coastal zone due to wind impact was analyzed. After analyzing the available data, the events that caused the ecological disaster can be summarized as follows. After the stage of intensive growth of microalgae, nutrient deficiency stimulated the production of metabolites that have a harmful effect on the environment. The change of the dominant alga species in the second half of September and the past storm contributed to a sharp increase in the concentration of metabolites and dead organic matter in the coastal zone, which caused an ecological disaster. The subsequent mass bloom of alga species of the same genus, and the regular wind impact leading to the concentration of harmful substances in the coastal zone, contributed to the development of this catastrophic phenomenon.

Paralytic Shellfish Toxins in the Gastropod Concholepas concholepas: Variability, Toxin Profiles and Mechanisms for Toxicity Reduction.

Harmful algal blooms of toxin-producing microalgae are recurrent in southern Chile. Paralytic shellfish poisoning (PSP) outbreaks pose the main threat to public health and the fishing industry in the Patagonian fjords. This study aims to increase understanding of the individual and spatial variability of PSP toxicity in the foot of Concholepas concholepas, Chile’s most valuable commercial benthic invertebrate species, extracted from the Guaitecas Archipelago in Chilean Patagonia. The objective is to determine the effect of pigment removal and freezing during the detoxification process. A total of 150 specimens (≥90 mm length) were collected from this area. The live specimens were transferred to a processing plant, where they were measured and gutted, the foot was divided into two equal parts, and pigment was manually removed from one of these parts. The PSP toxicity of each foot (edible tissue) was determined by mouse bioassay (MBA) and high-performance liquid chromatography with fluorescence detection and postcolumn oxidation (HPLC-FLD PCOX). The individual toxicity per loco, as the species is known locally, varied from <30 to 146 μg STX diHCL eq 100 g−1 (CV = 43.83%) and from 5.96 to 216.3 μg STX diHCL eq 100 g−1 (CV = 34.63%), using MBA and HPLC, respectively. A generalized linear model showed a negative relation between individual weight and toxicity. The toxicological profile showed a dominance of STX (>95%), neoSTX and GTX2. The removal of pigment produced a reduction in PSP toxicity of up to 90% and could represent a good detoxification tool moving forward. The freezing process in the muscle with pigment did not produce a clear pattern. There is a significant reduction (p < 0.05) of PSP toxicity via PCOX but not MBA. Furthermore, the study discusses possible management and commercialization implications of the findings regarding small-scale fisheries.

Seasonality of Glacial Snow and Ice Microbial Communities.

Blooms of microalgae on glaciers and ice sheets are amplifying surface ice melting rates, which are already affected by climate change. Most studies on glacial microorganisms (including snow and glacier ice algae) have so far focused on the spring and summer melt season, leading to a temporal bias, and a knowledge gap in our understanding of the variations in microbial diversity, productivity, and physiology on glacier surfaces year-round. Here, we investigated the microbial communities from Icelandic glacier surface snow and bare ice habitats, with sampling spanning two consecutive years and carried out in both winter and two summer seasons. We evaluated the seasonal differences in microbial community composition using Illumina sequencing of the 16S rRNA, 18S rRNA, and ITS marker genes and correlating them with geochemical signals in the snow and ice. During summer, Chloromonas, Chlainomonas, Raphidonema, and Hydrurus dominated surface snow algal communities, while Ancylonema and Mesotaenium dominated the surface bare ice habitats. In winter, algae could not be detected, and the community composition was dominated by bacteria and fungi. The dominant bacterial taxa found in both winter and summer samples were Bacteriodetes, Actinobacteria, Alphaproteobacteria, and Gammaproteobacteria. The winter bacterial communities showed high similarities to airborne and fresh snow bacteria reported in other studies. This points toward the importance of dry and wet deposition as a wintertime source of microorganisms to the glacier surface. Winter samples were also richer in nutrients than summer samples, except for dissolved organic carbon—which was highest in summer snow and ice samples with blooming microalgae, suggesting that nutrients are accumulated during winter but primarily used by the microbial communities in the summer. Overall, our study shows that glacial snow and ice microbial communities are highly variable on a seasonal basis.

Glycoside hydrolase from the GH76 family indicates that marine Salegentibacter sp. Hel_I_6 consumes alpha-mannan from fungi

Microbial glycan degradation is essential to global carbon cycling. The marine bacterium Salegentibacter sp. Hel_I_6 (Bacteroidota) isolated from seawater off Helgoland island (North Sea) contains an α-mannan inducible gene cluster with a GH76 family endo-α-1,6-mannanase (ShGH76). This cluster is related to genetic loci employed by human gut bacteria to digest fungal α-mannan. Metagenomes from the Hel_I_6 isolation site revealed increasing GH76 gene frequencies in free-living bacteria during microalgae blooms, suggesting degradation of α-1,6-mannans from fungi. Recombinant ShGH76 protein activity assays with yeast α-mannan and synthetic oligomannans showed endo-α-1,6-mannanase activity. Resolved structures of apo-ShGH76 (2.0 Å) and of mutants co-crystalized with fungal mannan-mimicking α-1,6-mannotetrose (1.90 Å) and α-1,6-mannotriose (1.47 Å) retained the canonical (α/α)6 fold, despite low identities with sequences of known GH76 structures (GH76s from gut bacteria: <27%). The apo-form active site differed from those known from gut bacteria, and co-crystallizations revealed a kinked oligomannan conformation. Co-crystallizations also revealed precise molecular-scale interactions of ShGH76 with fungal mannan-mimicking oligomannans, indicating adaptation to this particular type of substrate. Our data hence suggest presence of yet unknown fungal α-1,6-mannans in marine ecosystems, in particular during microalgal blooms.

The underlying green biciliate morphology of the orange snow alga Sanguina aurantia

In the summer, blooms of microalgae appear on alpine and polar snowfields, creating expanses of red snow sometimes called 'watermelon snow'1. These blooms are attracting research attention because they decrease snow albedo, thereby accelerating the effects of global warming on snowmelt2. Currently, meltwater from alpine snowfields provides one-sixth of the world's population with water for drinking, agriculture, and the generation of hydroelectric power3. Each spring, the surface of new snow is colonized by microscopic organisms from unknown sources. One possibility is that when the melt begins, ciliated cells swim up from the substrate below to populate the snow surface. However, Sanguina, a cosmopolitan genus that frequently dominates high-alpine and arctic blooms4,5, are thick-walled, red or orange in colour, and immotile. Here, we describe a culture of motile green biciliate cells isolated from a sample of red snow. Using cross-referenced Bayesian and maximum-likelihood phylogenetic methods for two genetic markers, ITS2 and rbcL, we establish the green biciliate as belonging to the genus Sanguina. Compensatory-base-change analysis of ITS2 rRNA structure delimits the green culture as S. aurantia, conspecific with individual, thick-walled immotile orange cells, picked from field samples collected in British Columbia and Svalbard. Using single cells was invaluable for comparing sequences derived from thick-walled red and orange Sanguina cells, which do not exist in culture, with the cultured green biciliates.

Development of environmentally friendly biological algicide and biochemical analysis of inhibitory effect of diatom Skeletonema costatum

Skeletonema costatum is a diatom widely distributed in red tide microalgae blooms and as one of the main algae causing harmful algal blooms, because of their rapid reproduction and production of toxic and harmful substances, often play a negative role in aquatic ecosystems, and human health and wellbeing. Bacillomycin D is a nonribosomal cyclic antifungal lipopeptide in the iturins family. In this study, Bacillomycin D was tested for its ability to inhibit the growth of S. costatum. The EC50 24h of Bacillomycin D on S. costatum was 24.70 µg/mL. The chlorophyll fluorescence parameters Fv/Fm, Fv/Fo, and yield of the diatoms decreased significantly with increasing concentrations of Bacillomycin D. Study of the mechanism showed that Bacillomycin D induced cell death by changing cell membrane permeability, promoting the release of cellular contents. In this study, transcriptomic analysis showed Bacillomycin D significantly inhibited the photosynthesis and metabolism of S. costatum. These findings investigated the inhibitory effect of Bacillomycin D on the growth of S. costatum and provided a theoretical foundation for the development of new environmentally friendly biological algicide.

Photogranulation in a Hydrostatic Environment Occurs with Limitation of Iron.

Filamentous cyanobacteria are an essential element of oxygenic photogranules for granule-based wastewater treatment with photosynthetic aeration. Currently, mechanisms for the selection of this microbial group and their development in the granular structure are not well understood. Here, we studied the characteristics and fate of iron in photogranulation that proceeds in a hydrostatic environment with an activated sludge (AS) inoculum. We found that the level of Fe in bulk liquids (FeBL) sharply increased due to the decay of the inoculum but quickly diminished along with the bloom of microalgae and the advent of the oxic environment. Iron linked with extracellular polymeric substances (FeEPS) continued to decline but reached steady low values, which occurred along with the appearance of granular structure. Strong negative correlations were found between FeEPS and the pigments specific for cyanobacteria. Spectroscopies revealed the presence of amorphous ferric oxides in pellet biomass, which seemed to remain unaltered during the photogranulation process. These results suggest that the availability of FeEPS in AS inoculums-after algal bloom-selects cyanobacteria, and the limitation of this Fe pool becomes an important driver for cyanobacteria to granulate in a hydrostatic environment. We therefore propose that the availability of iron has a strong influence on the photogranulation process.

Monitoring techniques for algae blooms from space

Microalgae blooms are one of the most serious environmental problems that greatly affect the living environment of aquatic organisms. They deplete the oxygen source in the water, seriously depleting the respiratory oxygen source for organisms living in the water body. Some species of microalgae are also capable of producing toxins, typically blue-green algae, poisoning aquatic organisms and causing death, health effects on human life when ingested. This paper presents the results of research on mapping algae concentration distribution to support water quality assessment for Dau Tieng reservoir. Landsat satellite imagery was used for qualitative and quantitative assessment of algae presence in the lake area. Calculation results showed that algae concentration had a linear correlation with the band ratio of the 3-band algorithm (3BDA (2), and was a combination of spectral reflective bands in the green wavelength bands GREEN, RED and near infrared NIR. We simulated the spatial distribution of algae concentrations on the entire lake area on 3 points of time when satellite images had been collected. Result of this study showed that remote sensing technology can be used for monitoring the appearance and change of algae concentration in water, which is an essential measurement for timely providing warnings as well as assisting in monitoring and managing water environment quality to minimize damages to people and the ecosystem.

Emerging harmful algal bloom species over the last four decades in China

The first recorded micro-algae bloom in Chinese coastal waters dates back to 1933 and was caused by a mixture of Noctiluca scintillans and Skeletonema costatum sensu lato along the Zhejiang coast (the East China Sea). While well-documented harmful algal blooms (HABs) appeared to be extremely scarce from the 1950s to 1990, both the frequency and intensity have been reportedly increasing since 1990. Among them, the fish-killing HABs, mainly caused by Karenia mikimotoi, Karlodinium digitatum, Karlodinium veneficum, Margalefidinium polykrikoides, and Heterocapsa spp., have intensified. Karenia mikimotoi was responsible for at least two extremely serious events in the Pearl River Estuary in 1998 and the Taiwan Strait (in the East China Sea) in 2012, which appeared to be associated with abnormal climate conditions and excessive nutrients loading. Other major toxic algal blooms have been caused by the species responsible for paralytic shellfish poisoning (including Alexandrium catenella, Alexandrium pacificum, Gymnodinium catenatum) and diarrhetic shellfish poisoning (including Dinophysis spp., and a couple of benthic dinoflagellates). Consequent closures of shellfish farms have resulted in enormous economic losses, while consumption of contaminated shellfish has led to occasional human mortality in the Bohai Sea and the East China Sea. Expansions of these HABs species along the coastline of China have occurred over the last four decades and, due to the projected global changes in the climate and marine environments and other anthropological activities, there is potential for the emergence of new types of HABs in China in the future. This literature review aimed to present an updated overview of HABs species over the last four decades in China.

Microalgal blooms in the skeletons of bleached corals during the 2020 bleaching event on Heron Island, Australia

Climate change is increasing the frequency of marine heatwaves around the world, causing widespread degradation of coral reefs. Endolithic microalgae inhabiting the coral skeleton have been highlighted as potentially important mediators of the consequences of heatwaves on coral reefs. These microalgae often bloom during heat stress due to greater light availability, theoretically delaying coral starvation by providing photoassimilates. However, these microalgae also dissolve coral skeletons at an accelerated rate during marine heatwaves, affecting the structural complexity of the reef. Despite their ecological role, no studies have examined endolithic algal blooms during a natural bleaching event. We quantified blooms of endolithic microalgae in the skeletons of lagoon corals bleaching on Heron Island in the austral summer of 2020. At the peak of heat stress, 20–30% of bleached corals across 9 genera at 3 sites had blooms. They were predominantly seen in branching Acropora spp. (37.8, 65.7 and 66.7% at three sites), which are primary reef builders at Heron Island. At the end of the bleaching event, the overall prevalence varied between 5 and 42%, and nearly all blooms were observed in acroporids. The relative high frequency of these blooms highlights the ongoing need to understand the role of these microbes during coral bleaching events.

Microalgues tòxiques i canvi global Perquè han incrementat les proliferacions al litoral mediterrani?

The ocean and the continent converge in a very narrow line that is, nonetheless, truly relevant to the health, leisure, and economy of our society. The Mediterranean coastline has undergone major changes over the last fifty years, which is evident in the alteration of its microalgae species. The proliferation of dinoflagellates is now common in microscopic organism communities in this ecosystem as a result of the modifications caused by humans and climate change. The increased frequency with which toxic microalgae blooms are detected has been key to raising awareness of this change.

An approach to assessing ecological quality status due to microalgae bloom using biofilm-dwelling protozoa based on biological trait analysis

Functional diversity/distinctness measure based trait has been proved to be a robust indicator to summarize the description of community structures and to assess water quality in different types of aquatic environment. In this study, for identifying the shielding effect of microalgae against protozoan grazing, a nine-day survey was conducted by exposing protozoan communities to a series of concentration gradients (100 (control), 104, 105, 106 and 107 cells ml−1) of two microalgae, respectively. Our results showed clear resistance of two test microalgae against protozoan grazing in five treatments. The functional distinctness measures commonly represented a decreasing trend along the gradient of concentrations of both microalgae. Ellipse tests based on the paired functional distinctness indices revealed that community functioning represented an uptrend departure from the expected pattern with the concentrations of both microalgae increase. Therefore, we suggest that the functional distinctness measures might be a reliable approach to detect the ecological effect of microalgae against protozoan grazing.

Allelopathic inhibitory effect of the macroalga Pyropia haitanensis (Rhodophyta) on harmful bloom-forming Pseudo-nitzschia species

The blooms of harmful microalgae represent a prominent threat to fisheries, public health, and economies throughout the world. Recent studies have shown that certain macroalgae release allelochemicals that can inhibit the growth of bloom-forming microalgae. In this study, we found that the macroalga Pyropia haitanensis significantly inhibited growth of the harmful bloom-forming microalgae Pseudo-nitzschia pungens and Pseudo-nitzschia multiseries. The inhibitory-effect of the live thali of P. haitanensis was highest, followed by that of dry powder, water-soluble extract, and culture medium filtrate. The Pseudo-nitzschia species died 96 h after exposure to 5–10 g fresh-weight L−1 of P. haitanensis live thalli. Furthermore, an aqueous extract of P. haitanensis suppressed the growth of P. pungens and P. multiseries, thereby indicating that P. haitanensis contains stable allelopathic substances that cause the observed inhibitory-effects. On the basis of these findings, we conclude that the macroalga P. haitanensis would have potential utility in controlling the blooms of Pseudo-nitzschia species.

Effect of iron and phosphorus on the microalgae growth in co-culture.

Iron and phosphorus (P) are the important micro- and macro-nutrient for microalgae growth, respectively. However, the effect of iron and P on microalgae growth in co-culture associating with the formation of dominate algae has not been investigated before. In the current study, Anabaene flos-aquae, Chlorella vulgaris and Melosira sp. were co-cultivated under the addition of different initial iron and P to reveal the effect of iron and phosphorus on the growth of microalgae. The results showed that the mean growth rate of A. flos-aquae, C. vulgaris and Melosira was 0.270, 0.261 and 0.062, respectively, indicating that the A. flos-aquae and C. vulgaris algae are liable to be the dominant algae while the growth of Melosira was restrained when co-cultured. The ratio of Fe to P has a significant impact on the growth of microalgae and could be regarded as an indicator of algae growth. Microalgae showed a much more obvious uptake of iron compared to that of P. The information obtained in the current study was useful for the forecast of water quality and the control of microalgae bloom.