Invasion and toxin production by exotic nostocalean cyanobacteria (Cuspidothrix, Cylindrospermopsis, and Sphaerospermopsis) in the Nakdong River, Korea

Okeanomitos corallinicola gen. and sp. nov. (Nostocales, Cyanobacteria), a new toxic marine heterocyte-forming Cyanobacterium from a coral reef

Cyanobacterial mats supplanting coral and spreading coral diseases in tropical reefs, intensified by environmental shifts caused by human-induced pressures, nutrient enrichment, and global climate change, pose grave risks to the survival of coral ecosystems. In this study, we characterized Okeanomitos corallinicola gen. and sp. nov., a newly discovered toxic marine heterocyte-forming cyanobacterium isolated from a coral reef ecosystem of the South China Sea. Phylogenetic analysis, based on the 16S rRNA gene and the secondary structure of the 16S-23S rRNA intergenic region, placed this species in a clade distinct from closely related genera, that is, Sphaerospermopsis stricto sensu, Raphidiopsis, and Amphiheterocytum. The O. corallinicola is a marine benthic species lacking gas vesicles, distinguishing it from other members of the Aphanizomenonaceae family. The genome of O. corallinicola is large and exhibits diverse functional capabilities, potentially contributing to the resilience and adaptability of coral reef ecosystems. In vitro assays revealed that O. corallinicola demonstrates notable cytotoxic activity against various cancer cell lines, suggesting its potential as a source of novel anticancer compounds. Furthermore, the identification of residual saxitoxin biosynthesis function in the genome of O. corallinicola, a marine cyanobacteria, supports the theory that saxitoxin genes in cyanobacteria and dinoflagellates may have been horizontally transferred between them or may have originated from a shared ancestor. Overall, the identification and characterization of O. corallinicola provides valuable contributions to cyanobacterial taxonomy, offering novel perspectives on complex interactions within coral reef ecosystems.

Ecological Implications in a Human-Impacted Lake-A Case Study of Cyanobacterial Blooms in a Recreationally Used Water Body

This study was aimed primarily at describing the planktonic assemblages with special attention to invasive and toxin-producing cyanobacterial species in the context of ecological and health threats. The second aim was to analyze the aspect of recreational pressure, which may enhance the cyanobacterial blooms, and, as a consequence, the negative changes and loss of planktonic biodiversity. This study was carried out in recreationally used Lake Sztynorckie throughout the whole growing season of 2020 and included an assessment of the abundance and biomass of phytoplankton (cyanobacteria and algae) in relation to environmental variables. The total biomass was in the range of 28-70 mg L^-1, which is typical for strong blooms. The dominant filamentous cyanobacteria were Pseudanabaena limnetica, Limnothrix redekei, Planktolyngbya limnetica, and Planktothrix agarhii, and three invasive nostocalean species Sphaerospermopsis aphanizomenoides, Cuspidothrix issatschenkoi, and Raphidiopsis raciborskii. They can pose a serious threat not only to the ecosystem but also to humans because of the possibility of cyanobacteria producing cyanotoxins, such as microcystins, saxitoxins, anatoxin-a, and cylindrospermopsins, having hepatotoxic, cytotoxic, neurotoxic, and dermatoxic effects. The water quality was assessed as water bodies had bad ecological status (based on phytoplankton), were highly meso-eutrophic (based on zooplankton), and had very low trophic efficiency and low biodiversity.

Assessment of the Appearance and Toxin Production Potential of Invasive Nostocalean Cyanobacteria Using Quantitative Gene Analysis in Nakdong River, Korea

Invasive nostocalean cyanobacteria (INC) were first reported in tropical regions and are now globally spreading rapidly due to climate change, appearing in temperate regions. INC require continuous monitoring for water resource management because of their high toxin production potential. However, it is difficult to analyze INC under a microscope because of their morphological similarity to nostocalean cyanobacteria such as the genus Aphanizomenon. This study calculates the gene copy number per cell for each target gene through quantitative gene analysis on the basis of genus-specific primers of genera Cylindrospermopsis, Sphaerospermopsis, and Cuspidothrix, and the toxin primers of anatoxin-a, saxitoxin, and cylindrospermopsin. In addition, quantitative gene analysis was performed at eight sites in the Nakdong River to assess the appearance of INC and their toxin production potential. Genera Cylindrospermopsis and Sphaerospermopsis did not exceed 100 cells mL⁻¹ at the maximum, with a low likelihood of related toxin occurrence. The genus Cuspidothrix showed the highest cell density (1759 cells mL⁻¹) among the INC. Nakdong River has potential for the occurrence of anatoxin-a through biosynthesis by genus Cuspidothrix because the appearance of this genus coincided with that of the anatoxin-a synthesis gene (anaF) and the detection of the toxin by ELISA.

Evolutionary game analysis of coal enterprise resource integration under government regulation

Resource integration of coal enterprises is conducive to reducing pollution and carbon emissions, thus alleviating environmental problems such as global warming. Government regulation has a great influence on enterprise behavior. Therefore, it is necessary to analyze the strategies of government and coal enterprises in resource integration. Based on the perspective of government regulation, this paper discusses how to guide and restrict coal enterprises to conduct resource integration behavior, and whether the government supervises this behavior. First, through empirical research, government regulations of coal enterprises are given practical policy implications. Second, using evolutionary game and simulation technology, from the perspective of government regulation, we explore the complex behavioral interaction mechanism between the dominant and inferior coal enterprises, the mechanism between the government and coal enterprises, and analyze the impact of key factors on the dynamic evolution process. Finally, the sensitivity analysis of the selected parameters is discussed in details, which provides useful decision-making suggestions for the government and enterprises. In addition, this paper further analyzes the impact of different government policies on coal enterprises' green innovation strategies. Results demonstrate that (1) when the power gap between enterprises is large, the probability of dominant enterprises choosing resource integration converges to 1, while the probability of inferior enterprises converges to 0. Therefore, government regulations are invalid for inferior enterprises; (2) the combination of government regulations can help improve the efficiency of coal enterprises' strategic choices. With the increase in the intensity of government rewards and punishments, the probability of enterprise resource integration evolves from 0 to 1; (3) excessive government regulations make the choice between the government and coal companies tend to swing, because the probability of the two is between 0 and 1. Therefore, excessive government regulations cannot effectively achieve resource integration and government regulation. (4) The government subsidy strategy is less effective than the government's pollution penalty strategy in promoting the green innovation of enterprises. Our research shows that the government should choose different policy combinations and intensities to regulate resource integration according to the market power of coal enterprises, which provides theoretical reference and practical guidance for the government to regulate corporate resource integration behavior.

Development of Genus-Specific PCR Primers for Molecular Monitoring of Invasive Nostocalean Cyanobacteria

The geographical range of invasive cyanobacteria with high toxigenic potential is widening because of eutrophication and global warming, thus, monitoring their appearance is necessary for safe water quality control. Most invasive cyanobacteria are nostocalean species, and their accurate identification by classical morphological methods may be problematic. In this study, we developed polymerase chain reaction (PCR) primers to selectively identify five invasive cyanobacterial genera, namely, Chrysosporum, Cuspidothrix, Cylindrospermopsis, Raphidiopsis, and Sphaerospermopsis, using genetic markers such as rbcLX, rpoB, rpoC1, and cpcBA, and determined the amplification conditions for each pair of primers. The primer performances were verified on single or mixed nostocalean cyanobacterial isolates. The five primers allowed selective identification of all the target genera. In field samples collected during summer, when cyanobacteria flourished in the Nakdong River, the respective PCR product was observed in all samples where the target genus was detected by microscopic analysis. Besides, weak bands corresponding to Sphaerospermopsis and Raphidiopsis were observed in some samples in which these genera were not detected by microscopy, suggesting that the cell densities were below the detection limit of the microscopic method used. Thus, the genus-specific primers developed in this study enable molecular monitoring to supplement the current microscopy-based monitoring.