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The Nanhui-east-tidal-flat (NETF), the largest marginal shoal in the Yangtze River of China, is significantly impacted by human activities. Prior research has not detected the presence of green macroalgae in the NETF, nor has it explored the effects of reclamation on the distribution of macroalgae. However, in 2021, a small-scale aggregated attached algal mats emerged in the NETF, potentially signaling the onset of a green tide and necessitating vigilant monitoring. Morphological and molecular biological identification analysis revealed that all collected green macroalgae were attributed to a single dominant species, Ulva prolifera, characterized by broad blades and prominent air bladders, colonizing various substrates. The attached U. prolifera exhibited continuous growth from March to May 2021, peaking at a wet weight of 373.6229 g/m² and a dry weight of 72.7904 g/m² on May 1, 2021, within the accessible sampling period. The rapid proliferation of the “opportunistic” Ulva was facilitated by high-level eutrophication and favorable environmental conditions. Furthermore, six potential germplasm sources of U. prolifera are summarized. The dominance of Ulva in the intertidal zone often indicates high eutrophication and deteriorating ecological conditions. With long-term reclamation and repeated ecological restoration projects, the intertidal vegetation is subjected to a vicious cycle of growth and destruction. Therefore, it is important to recognize that U. prolifera germplasm (macroalgae and micropropagules) will persist over the long term, and mudflats with monotonous and eutrophic habitats are highly likely to experience future large-scale algal blooms. Notably, a small-scale floating green tide was observed in the sea area near NETF in July 2023, and such concerns are not unfounded. This study conducts foundational scientific research on the attached green tide algae, a type of research that is relatively scarce in other marine areas. Most studies tend to initiate foundational research only after the outbreak of green tides, lacking early background data from the marine environment, thus rendering this study of significant reference value. Concurrently, this study emphasizes that field surveys remain an essential approach for conducting foundational scientific research on green tide algae in the NETF region, with the need to select appropriate research methods based on the occurrence and development of algal mats, as required by the situation. Importantly, this study reflects the stability of marine ecosystems as a prerequisite for modern ocean management and services, provides new perspectives on the occurrence and development of green tides, and highlights potential ecological risk factors that should be considered in the implementation of intertidal construction projects.

Recent years have seen the Ulva green tide and Sargassum golden tide become commonplace in the coastal waters of China. However, little is known on how the combination of ocean warming and eutrophication would affect the interaction of green and golden tides. In this study, we cultured the green tide alga Ulva prolifera and the golden tide alga Sargassum horneri under different temperatures (5, 10, 15, 20, 25, and 30°C) and two nutrient concentrations (Low nutrient, LN: 5 μM-nitrate and 0.5 μM-phosphate; High nutrient, HN: 500 μM-N and 50 μM-P) in both monoculture and coculture systems to investigate the physiological responses and their competitive relationships. In monocultures, the growth of U. prolifera and S. horneri, along with pigment concentrations and photosynthesis, increased with rising temperature, reaching a plateau at 15 - 25°C. However, when the temperature increased to 30°C, the growth of U. prolifera and S. horneri decreased abruptly, with S. horneri even suffering death. In coculture, the growth of both U. prolifera and S. horneri was inhibited compared to the monoculture, with the greatest decline observed in S. horneri at 25°C under two nutrient conditions. Our results show that U. prolifera would outcompete S. horneri under high temperature in coculture, suggesting that ocean warming would enhance the competitive advantage of green tide over golden tide under eutrophication in the future.

Edible mushroom products, encompassing both cultivated and wild varieties, are highly favored by consumers due to their rich nutritional profiles, including significant levels of proteins and amino acids. These mushrooms have extensive applications across the food, pharmaceutical, and cosmetic industries, making the edible mushroom industry a vital component of global poverty alleviation efforts. Taking China as an example, the country produces over 45 million tons of edible mushrooms annually, accounting for 94.01% of the world’s total production, thereby establishing itself as the leading global producer of edible mushrooms. However, alongside the rapid expansion of this industry, concerns have emerged regarding counterfeit products and incidents of poisoning resulting from the consumption of toxic wild mushrooms. As follows, to advance the development and integrity of the mushroom production and processing industry: (1) This study presents the situation of counterfeit edible mushrooms and elucidates the factors contributing to the production of fraudulent products from both subjective and non-subjective perspectives. (2) We provide a detailed introduction to 22 varieties of freshly cultivated edible mushrooms and commonly encountered wild edible mushrooms in the Chinese consumer market, proposing the application of DNA barcoding, environmental DNA analysis, and other technologies for the future authentication of counterfeit mushroom products. (3) Concurrently, we present an overview of mushroom poisoning incidents in China from 2010 to 2023, emphasizing the challenges in mitigating the risks associated with wild mushroom consumption and preventing food poisoning, thereby necessitating heightened consumer caution. (4) Finally, we offer four recommendations aimed at ensuring the healthy, stable, and sustainable growth of the edible mushroom industry.

Integrated Multi-Trophic Aquaculture (IMTA) is growing fast in China, in order for cultivation with this system to continue. Through eDNA approach in able to detect Ostreococcus lucimarinus which include picoeukaryotic in IMTA system at enclosed sea (Hangzhou Bay). Information about this species and their ecological placement in the IMTA system is still very limited. eDNA is an ecological approach that can detect supply down to the species level in monitoring aquatic ecology in the IMTA system. The purpose of this study was to determine the taxonomy and guarantees of Ostreococcus lucimarinus and the role of this species in the IMTA system descriptively. Through high throughput sequencing, the taxonomic results of Ostreococcus lucimarinus and confinement of this picoekaryotic species were highest in winter with a total of 599,632 ind. Based on the sampling location, the highest abundance were in aquaculture areas of 337,165 ind. The approach using eDNA has proven to be capable of detecting up to the species level as well as spatiotemporal abundance dynamics of Ostreococcus lucimarinus.

Abstract Hemibarbus maculatus is a globally important species for its value in fisheries and aquaculture. There is relatively little information available about this species' sexual development genes. Therefore, in this study, we used the technology of high‐throughput RNA sequencing (RNA‐seq), to investigate if the ovary and testis' differently expressed genes (DEGs) during sex differentiation in H. maculatus. Our results revealed a total of 43,468,248 and 39,241,362 qualified reads were generated in the female and male libraries, and 32,127 unigenes were assembled via the annotation analysis. Moreover, 17,808 unigenes were found to be DEGs between males and females, with 12,726 up‐ and 5082 downregulated genes in the ovaries and testes, respectively. The transcriptome analysis revealed there are 23 DEGs between ovary and testes of H. maculatus, which may be involved in sex determination. The expression patterns of these genes were validated by quantitative real‐time PCR (qPCR). The results of qPCR were generally consistent with the RNA‐seq results. This work was the first to annotate genes linked with gonadal development and reproduction in H. maculatus using gonadal transcriptome analysis, which provides useful molecular data for a better understanding of sexual development, as well as functional genomics and population genetics studies of H. maculatus.

Macroalgal biomass blooms, including those causing the green and golden tides, have been rising along Chinese coasts, resulting in considerable social impacts and economic losses. To understand the links between the ongoing climate changes (ocean warming and acidification) and algal tide formation, the effects of temperature (20 and 24 °C), pCO2 concentration (Partial Pressure of Carbon Dioxide, 410 ppm and 1000 ppm) and their interaction on the growth of Ulva prolifera and Ulva lactuca (green tide forming species), as well as Sargassum horneri (golden tide forming species) were investigated. The results indicate that the concurrent rises in temperature and pCO2 level significantly boosted the growth and nutrient uptake rates of U. lactuca. For U. prolifera, the heightened growth and photosynthetic efficiency under higher CO2 conditions are likely due to the increased availability of inorganic carbon. In contrast, S. horneri exhibited negligible responsiveness to the individual and combined effects of the increased temperature and CO2 concentration. These outcomes indicate that the progressive climate changes, characterized by ocean warming and acidification, are likely to escalate the incidence of green tides caused by Ulva species, whereas they are not anticipated to precipitate golden tides.

The extensive outbreak of Sargassum horneri in China has not merely imposed a severe threat to the ecological environment and human life in coastal waters but also impeded the development of waterway transportation and the local economy. Consequently, we isolated polysaccharides from S. horneri, designated as SHP, and evaluated the antioxidant activity of SHP both in vitro and in vivo by investigating the effect of SHP on H2O2-induced African green monkey kidney cells (Vero cells) and zebrafish. The results demonstrated that SHP can enhance the activities of superoxide dismutase, catalase, and glutathione peroxidase in zebrafish. It also effectively inhibits micro malondialdehyde and ROS levels in Vero cells and zebrafish to mitigate the oxidative damage caused by H2O2, thereby achieving the protective effect of SHP on Vero cells and zebrafish. In conclusion, SHP holds the potential as a natural antioxidant. SHP can be contemplated for utilization as a natural antioxidant in the biomedical, cosmetic, and food industries, thereby alleviating the environmental stress caused by S. horneri and achieving resource utilization.

Owing to global climate change or the ever-more frequent human activities in the offshore areas, it is highly probable that an imbalance in the offshore ecosystem has been induced. However, the importance of maintaining and protecting marine ecosystems’ balance cannot be overstated. In recent years, various marine disasters have occurred frequently, such as harmful algal blooms (green tides and red tides), storm surge disasters, wave disasters, sea ice disasters, and tsunami disasters. Additionally, overpopulation of certain marine organisms (particularly marine faunas) has led to marine disasters, threatening both marine ecosystems and human safety. The marine ecological disaster monitoring system in China primarily focuses on monitoring and controlling the outbreak of green tides (mainly caused by outbreaks of some Ulva species) and red tides (mainly caused by outbreaks of some diatom and dinoflagellate species). Currently, there are outbreaks of Cnidaria (Hydrozoa and Scyphozoa organisms; outbreak species are frequently referred to as jellyfish), Annelida (Urechis unicinctus Drasche, 1880), Mollusca (Philine kinglipini S. Tchang, 1934), Arthropoda (Acetes chinensis Hansen, 1919), and Echinodermata (Asteroidea organisms, Ophiuroidea organisms, and Acaudina molpadioides Semper, 1867) in China. They not only cause significant damage to marine fisheries, tourism, coastal industries, and ship navigation but also have profound impacts on marine ecosystems, especially near nuclear power plants, sea bathing beaches, and infrastructures, posing threats to human lives. Therefore, this review provides a detailed introduction to the marine organisms (especially marine fauna species) causing marine biological disasters in China, the current outbreak situations, and the biological backgrounds of these outbreaks. This review also provides an analysis of the causes of these outbreaks. Furthermore, it presents future prospects for marine biological disasters, proposing corresponding measures and advocating for enhanced resource utilization and fundamental research. It is recommended that future efforts focus on improving the monitoring of marine biological disasters and integrating them into the marine ecological disaster monitoring system. The aim of this review is to offer reference information and constructive suggestions for enhancing future monitoring, early warning systems, and prevention efforts related to marine ecological disasters in support of the healthy development and stable operation of marine ecosystems.

The proliferation of large green macroalgae in marine environments has led to the occurrence of green tides, particularly in the South Yellow Sea region of China, where Ulva prolifera has been identified as the primary species responsible for the world’s largest green tide events. Allelopathy among plants is a critical factor influencing the dynamics of green tides. This review synthesizes previous research on allelopathic interactions within green tides, categorizing four extensively studied allelochemicals: fatty acids, aldehydes, phenols, and terpenes. The mechanisms by which these compounds regulate the physiological processes of green tide algae are examined in depth. Additionally, recent advancements in the rapid detection of allelochemicals are summarized, and their potential applications in monitoring green tide events are discussed. The integration of advanced monitoring technologies, such as satellite observation and environmental DNA (eDNA) analysis, with allelopathic substance detection is also explored. This combined approach addresses gaps in understanding the dynamic processes of green tide formation and provides a more comprehensive insight into the mechanisms driving these phenomena. The findings and new perspectives presented in this review aim to offer valuable insights and inspiration for researchers and policymakers.

IntroductionSuaeda salsa (Linn.) Pall. is an important tourist resource and ecological restoration species in coastal wetlands. Environmental factors such as low temperature, darkness, phytohormone, salt stress and seawater flflooding, and light can induce betalain synthesis in S. salsa, which plays an important role in plant adaptation to abiotic stress processes and in shaping the beautiful “red beach” landscape.MethodsIn this study, Illumina sequencing was used to profifile the transcriptome sequence (RNA-Seq) of S. salsa leaves at different temperatures (5° C, 10°C, 15°C, 20°C, 25°C, and 30°C) and to validate differentially expressed genes (DEGs) indicated by real-time PCR (RT-qPCR).ResultsThe betacyanin content was highest in S. salsa leaves at 15°C. Transcription group data showed that compared to the control group (15°C), the “betacyanin biosynthesis pathway” was signifificantly enriched in the fifive different temperature groups. KEGG analysis showed that the DEGs were mainly involved in pathways of phenylpropanoid biosynthesis, carbon fifixation in photosynthetic organisms, flflavonoid biosynthesis, and betacyanin biosynthesis. Among the key enzymes involved in biosynthesis of betacyanin, genes for tyrosinase, CYP76AD1 and 4,5-DOPA dioxygenase were signifificantly upregulated and most abundantly expressed at 15°C. It is possible that the gene for betacyanin synthesis from S. salsa is primarily regulated by the MYB1R1 and MYB1 transcription factor. Four DEGs were randomly selected for quantitative PCR analysis, and DEG expression was generally consistent with the RNA-Seq data, verifying the validity of the transcriptome sequencing data.DiscussionRelative to other temperatures, 15°C was optimum for S. salsa betacyanin synthesis, and this provides a theoretical reference for coastal wetland ecological remediation, reveals mechanisms of S. salsa discoloration, and further mines its potential application for landscape vegetation.

Since 2007, the Yellow Sea has undergone a large-scale outbreak of green tide for 15 years. The large biomass of green tide has caused great economic losses to Shandong and Jiangsu Province. The monitoring data in the recent years indicated that the dominant algae in the Southern Yellow Sea (SYS) was a special ecological type of Ulva species (Ulva prolifera). In order to make rational use of green tide algae and avoid the waste of biological resources, the achievements in the research and technical development on the resource utilization of green tide algae were systematically introduced. Moreover, the utilization and development of U. prolifera, such as food, beauty products, feed or feed additives, fertilizer, energy and papermaking engineering, were summarized. In addition, solutions to reduce the losses caused by the outbreak of green tide algae were also proposed.

Ulva torta (Mertens) Trevisan, 1841 was a global temperate widespread species. Green tide blooms caused by the green algae of the Ulva species occurred frequently in China. As a newly discovered species in the green tide bloom area, it was necessary to explore the relationship between U. torta and other green algae of the Ulva species. The complete chloroplast genome of U. torta was 105,423 bp in size. A total of 100 genes were annotated in the genome, containing 70 protein-coding genes, 27 transfer RNA (tRNA) genes, and three rRNA genes. The chloroplast genome had high AT content (74.76%). Phylogenetic analysis showed U. torta was clustered with Ulva meridionalis. This work could be useful for studying the evolution and genetic diversity of U. torta.

The aim of this study was to provide practical suggestions for land use regulation to mitigate the impacts of intense urbanization using integrated modeling. To achieve effective urbanization management, it is essential to quantify the habitats of critical species and predict their dynamics in response to urbanization impacts in the future. In this study, we developed an integrated bird-habitat modeling that combines maximum entropy and patch-generating land use simulation based on a field survey of bird populations to characterize the habitat dynamics of birds in the Yangtze River Estuary (YRE) under urbanization impacts. Our findings revealed the following: (1) The YRE experienced fundamental fragmentation from 2000. (2) The year 2010 was a turning point, and from 2000 to 2037, habitats for all bird species tended to overlap and fragment, and decreased from 66% to 45%, resulting in a loss of about 4340 km2. (3) The maintenance of a buffer area of 300 m around built-up areas was crucial for preserving bird habitats. Based on the identified variables, the hotspots of birds’ habitats were prioritized and the regulation measures to mitigate urbanization impacts are proposed in YRE.

Many algae respond to the CO2 limitation in seawater by inducing a CO2 concentrating mechanism (CCM) to obtain sufficient inorganic carbon to meet their photosynthetic needs, and Ulva sp. is a model population suitable for studying the ecological adaptability of macroalgae. As the dominant species of green tide disaster, Ulva sp. often faces strong inorganic carbon restriction due to its rapid growth and high population density and must have evolved a variety of carbon acquisition strategies, such as CCM, to overcome these limitations. This paper briefly summarizes the position and function of the important components of CCM (inorganic carbon transporters, carbonic anhydrase, Rubisco, and pyrenoid) and introduces several indexes suitable for evaluating the relative function of CCMs in macroalgae from the aspects of affinity between photosynthesis and Rubisco for CO2, and carbonic anhydrase inhibitor. The methods of judging the carbon sequestration pathway of Ulva sp., the CCM responses of diversity under different carbon sources, and the related genes that may be involved in the operation of CCMs were summarized. This work could provide a reference for revealing the CCMs of macroalgae and lay a foundation for further research on the inorganic carbon utilization strategy of the Ulva sp.

White spot syndrome is an epidemic disease caused by the highly contagious and lethal white spot syndrome virus (WSSV), resulting in huge economic losses to the global aquaculture industry. VP28 is the main structural protein in the capsule of WSSV and is important in the early stage of infection. Under an excitation wavelength of 548 nm, the mOrange fluorescent protein releases a 562 nm emission wavelength, which is different from the autofluorescence of cyanobacteria. Therefore, using this characteristic combined with the receptor system of Synechococcus elongatus PCC 7942, we constructed transgenic S. elongatus to express the recombinant protein VP28-mOrange. In addition, PCR and western blotting were used to confirm the stable expression of the target gene in cyanobacteria. Using mOrange tracer features, we explored the recombinant protein VP28-mOrange in the metabolic cycle of young Litopenaeus Vannamei after feeding. After the young shrimp had stopped consuming transgenic cyanobacteria, the 24 to 33 h fluorescence signal in the intestine was very weak, and almost disappeared after 36 h. We explored the protective effect of transgenic vp28-mOrange S. elongatus within 48 h of being ingested by L. vannamei and set WSSV challenges at 2, 12, 24, and 48 h post-immunization. However, the survival rate of L. vannamei decreased as the time of the WSSV challenge increased. The survival rate on the seventh day was 81%, 52%, 45.5%, and 33.3% for shrimps challenged for 2, 12, 24, and 48 h, respectively. Enzyme activity can also support this conjecture, the enzyme activity indexes of the experimental groups were significantly reduced compared to positive and wild-type controls. Therefore, this immune agent functioned as a preventive agent. Compared with the traditional method, this method was easy to detect and can visualize the digestion of transgenic cyanobacteria in the Litopenaeus vannamei intestine.

Climate change directly influences species composition and distribution of macroalgae on a global scale. Meanwhile, eutrophication and heavy metal pollution continue to be major concerns in coastal areas. The objective of this study was to explore interactive effects of these complex environmental conditions (high temperature, eutrophication and heavy metal pollution) in the bloom forming green alga, Ulva prolifera. This study evaluated the physiological characteristics of two strains of U. prolifera (Korean strain and Chinese strain) at two temperature levels (20 and 25°C), two nutrient concentrations (low nutrient: 50 μM of N and 5 μM of P; high nutrient: 250 μM of N and 25 μM of P) and three copper concentrations [Control (0.03 μM); 0.1 μM; 1 μM]. Under the 20°C and low nutrient condition, the Chinese strain grew significantly slower at 1μM copper group compared to copper control group. Whereas there was no significant change in the growth rate of the Korean strain. High nutrient significantly increased the growth rate, photosynthetic and respiration rates, soluble protein and tissue N in both strains at all copper groups under 20°C compared to copper groups under 20°C and low nutrient condition. Both strains grew significantly slower at 1 μM copper group compare to copper control group under high nutrient and 20°C condition. 25°C significantly reduced the growth rate of both strains at each nutrient condition. Under 25°C and low nutrient condition, 1 μM copper had no effects on growth rate and all photosynthetic parameters of both strains. Meanwhile, under 25°C and high nutrient conditions, 1 μM copper significantly inhibited growth and photosynthetic rates and increased soluble protein content in the Chinese strain compared to copper control treatment. These results suggest that the Korean strain had higher tolerance to the copper stress than the Chinese strain. Higher nutrient levels enhanced the temperature tolerance and the copper stress in U. prolifera. Increased temperature reduced the negative effects caused by copper stress in U. prolifera.

The utilization of allelochemicals to inhibit algal overgrowth is a promising approach for controlling harmful algal blooms (HABs). Quercetin has been found to have an allelopathic effect on algae. However, its responsive mechanism needs to be better understood. In the present study, the inhibitory effects of different quercetin concentrations on M. aeruginosa were evaluated, and the inhibition mechanisms were explored. The results demonstrated that quercetin significantly inhibited M. aeruginosa growth, and the inhibitory effect was concentration-dependent. The inhibition rate of 40 mg L−1 quercetin on algal density reached 90.79% after 96 h treatment. The concentration of chlorophyll-a (chl-a) in treatment groups with quercetin concentrations of 10, 20, and 40 mg L−1 decreased by 59.74%, 74.77%, and 80.66% at 96 h, respectively. Furthermore, quercetin affects photosynthesis and damages the cell membrane, respiratory system, and enzyme system. All photosynthetic fluorescence parameters, including the maximum photochemical quantum yield (Fv/Fm), the actual photochemical quantum yield (YII), the maximum relative electron transfer rate (rETRmax), and light use efficiency (α), exhibited a downtrend after exposure. After treatment with 20 mg L−1 quercetin, the nucleic acid and protein content in the algal solution increased, and the respiration rate of algae decreased significantly. Additionally, superoxide dismutase (SOD) activities significantly increased as a response to oxidative stress. In comparison, the activities of ribulose 1,5-biphosphate carboxylase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) decreased significantly. These results revealed that quercetin could inhibit M. aeruginosa by affecting its photosynthesis, respiration, cell membrane, and enzymic system. These results are promising for controlling M. aeruginosa effectively.

How to control the frequent occurrence of cyanobacteria, especially the outbreak of toxin-producing Microcystis aeruginosa, has been a subject of constant research. This investigation focused on the effect of Moina mongolica on restricting M. aeruginosa blooms under different variables (temperature, light intensity, and salinity) and its growth at the molecular level. The results of batch experiments showed that the range of M. mongolica feeding rates was from 4.02 ± 0.81 × 103~182.23 ± 5.37 × 103 cells/ind·h in the whole experiment, where the highest feeding rates of larva M. mongolica and adult M. mongolica were 133.21 ± 5.24 × 103 vs. 182.23 ± 5.37 × 103 cells/ind·h at 30 °C, 85.88 ± 0.44 × 103 vs. 143.15 ± 14.07 × 103 cells/ind·h at 3000 lx and 88.18 ± 0.32 × 103 vs. 84.49 ± 4.95 × 103 cells/ind·h at 0‰ salinity, respectively. The results of transcriptomics further demonstrated that the response of M. mongolica to M. aeruginosa toxicity was caused by the downregulation of relevant functional genes (cell components, cell processes, metabolic processes, and protein complexes) and related signaling pathways (apoptosis, phagosome, lysosome, ribosome, oxidative phosphorylation, amino and nucleoside sugar metabolism, and PPAR signaling pathways). The findings show that M. mongolica can be released to low-salinity lakes and coastal areas (the subtropic and temperate zones) to prevent and inhibit M. aeruginosa blooms in the early summer phase. Additionally, the results achieved by the investigation will provide the relevant technology for inhibiting cyanobacteria blooms because M. mongolica even resists the produced toxin by M. aeruginosa.

Litopenaeus vannamei is the major farmed shrimp species worldwide. White spot disease due to white spot syndrome virus (WSSV) is severely affecting shrimp worldwide, causing extensive economic losses in L. vannamei culture. This is the first study that applied combined transcriptomic and metabolomic analysis to study the effects on the L. vannamei hepatopancreas after WSSV challenge. Our transcriptomic data revealed differentially expressed genes (DEGs) associated with immunity, apoptosis, the cytoskeleton and the antioxidant system in the hepatopancreas of L. vannamei. Metabolomic results showed that WSSV disrupts metabolic processes including amino acid metabolism, lipid metabolism and nucleotide metabolism. After challenged by WSSV, immune-related DEGs and differential metabolites (DMs) were detected in the hepatopancreas of L. vannamei, indicating that WSSV may damage the immune system and cause metabolic disorder in the shrimp. In summary, these results provide new insights into the molecular mechanisms underlying L. vannamei’s response to WSSV.

Ulva compressa is one of the causal green macroalgae in many countries. In this study, complete chloroplast genome sequence of U. compressa was reported, and the total length of this species was 94,226 bp (GenBank accession number MT916929). The overall base composition of chloroplast genome was A (37.2%), T (37.0%), C (12.7%) and G (13.1%), and the percentage of A + T (74.2%) was higher than C + G (25.8%). U. compressa chloroplast genome encoded 90 genes, including 63 protein-coding genes, 23 transfer RNAs genes, and 4 ribosomal RNAs genes. The maximum likelihood phylogenetic analysis showed that U. compressa is the closest sister species of U. linza. This study will be helpful to understand the genetic diversity of Ulva species.

The growing world population has produced an increasing demand for seafood, and the aquaculture industry is under corresponding pressure to fill this demand. The offshore ecology and environment are under significant threat with the continuous expansion of the scale and intensity of aquaculture. Integrated multi-tropic aquaculture (IMTA) is a healthy and sustainable mariculture model based on ecosystem-level management, and has become popular in recent years. It is an effective way to cope with the significant changes in offshore ecosystems under multiple stressors. Phytoplankton bacteria are essential to maintaining the marine ecosystem’s balance and stability. Investigating the changes in the community structure of marine planktonic bacteria can elucidate the impact of mariculture on the marine ecological environment. This study took the fish-shell IMTA system with natural macroalgae nearby as the object, and monitored the plankton community’s structure in the system’s surface seawater for four quarters from July 2020 to April 2021. The space–time distribution characteristics and influencing factors of the plankton community in the surface water were examined. The results showed no significant difference between the planktonic bacterial communities at different sampling sites. There was also no significant difference in the α-diversity index. However, the dominant species and abundance of planktonic bacteria at the sampling sites differed significantly. Proteobacteria and Bacteroides were the dominant groups of planktonic bacteria. The results of the distance-based redundancy analysis demonstrated that chemical oxygen demand, chlorophyll a, and dissolved oxygen constituted the primary environmental factors affecting the planktonic bacterial community structures. The heatmap also showed that NH4+- N, temperature, and salinity levels were also related to certain planktonic bacteria. This study preliminarily identified the distribution of the surface bacterial plankton community and its response to changes in environmental factors in the sea area near Xiasanhengshan Island. The results provide a preliminary basis for assessing the health and stability of the IMTA system in open sea areas.

With global warming, in recent years, golden tides have frequently occurred off the coasts of China. Sargassum horneri, which attach to aquaculture rafts, can float and form small-scale golden tides after falling off. Temperature will affect the growth and reproduction of algae. In order to explore whether the temperature is the potential influence factor of the golden tide outbreak, in this study, the effects of global warming on the growth and proliferation of S. horneri in the mussel aquaculture area of Gouqi Island will be discussed. Samples of the macroalgae were collected monthly from August 2021 to July 2022 at various stages of its life cycle, and the relationship between algal growth and temperature was analyzed based on the concept of effective accumulated temperature, combined with the parameters of sea surface temperature, photosynthetic rate, growth rate, and growth cycle. Based on the continuous temperature variation observed, the growth cycle could be divided into five stages: the decreasing temperature period (October to November), the low-temperature adaptation period (December), the second suitable low-temperature period (January to February), and the high-temperature decay period (February to May). The effective accumulated temperature stored by S. horneri from 2021 to 2022 was 2772.4 °C·d; compared with previous studies, it decreased by about 800 °C·d. The winter temperature in 2022 was higher than the average temperature in the previous 5 years, allowing the macroalgae to enter the reproductive period in advance. This had a significant impact on the blooming time of golden tides and led to an earlier outbreak and extinction. Therefore, in the future, we can set up a monitoring system for the early warning of golden tides according to the change of SST in winter.

Ulva meridionalis is one of the causal green macroalgae for green tides in Japan and exists in coastal areas of China. In the present study, complete chloroplast (cp) genome sequence of Ulva meridionalis was reported, and the total length of this species was 88,653 bp (GenBank accession number MN889540). The overall base composition of cp genome was A (37.1%), T (39.0%), C (11.4%) and G (12.5%), similar to other Ulva macroalgae within cp genome, and the percentage of A + T (76.1%) was higher than C + G (23.9%). U. meridionalis cp genome encoded 113 genes, including 80 protein-coding genes, 27 transfer RNAs genes and 6 ribosomal RNAs genes. The maximum likelihood phylogenetic analysis shows that Ulva linza is the closest sister species of U. meridionalis.

The main algal species of Ulva prolifera green tide in the coastal areas of China are four species, but after reaching the coast of Qingdao, U. prolifera becomes the dominant species, where the light intensity is one of the most important influencing factors. In order to explore the effects of short-term high light stress on the internal molecular level of cells and its coping mechanism, the transcriptome, proteome, metabolome, and lipid data of U. prolifera were collected. The algae were cultivated in high light environment conditions (400 μmol·m−2·s−1) for 12 h and measured, and the data with greater relative difference (p < 0.05) were selected, then analyzed with the KEGG pathway. The results showed that the high light stress inhibited the assimilation of U. prolifera, destroyed the cell structure, and arrested its growth and development. Cells entered the emergency defense state, the TCA cycle was weakened, and the energy consumption processes such as DNA activation, RNA transcription, protein synthesis and degradation, and lipid alienation were inhibited. A gradual increase in the proportion of the C4 pathway was recorded. This study showed that U. prolifera can reduce the reactive oxygen species produced by high light stress, inhibit respiration, and reduce the generation of NADPH. At the same time, the C3 pathway began to change to the C4 pathway which consumed more energy. Moreover, this research provides the basis for the study of algae coping with high light stress.

Over the past decade, Ulva compressa, a cosmopolitan green algal species, has been identified as a component of green tides in the Yellow Sea, China. In the present study, we sequenced and annotated the complete chloroplast genome of U. compressa (alpha-numeric code: RD9023) and focused on the assessment of genome length, homology, gene order and direction, intron size, selection strength, and substitution rate. We compared the chloroplast genome with the mitogenome. The generated phylogenetic tree was analyzed based on single and aligned genes in the chloroplast genome of Ulva compared to mitogenome genes to detect evolutionary trends. U. compressa and U. mutabilis chloroplast genomes had similar gene queues, with individual genes exhibiting high homology levels. Chloroplast genomes were clustered together in the entire phylogenetic tree and shared several forward/palindromic/tandem repetitions, similar to those in U. prolifera and U. linza. However, U. fasciata and U. ohnoi were more divergent, especially in sharing complementary/palindromic repetitions. In addition, phylogenetic analyses of the aligned genes from their chloroplast genomes and mitogenomes confirmed the evolutionary trends of the extranuclear genomes. From phylogenetic analysis, we identified the petA chloroplast genes as potential genetic markers that are similar to the tufA marker. Complementary/forward/palindromic interval repetitions were more abundant in chloroplast genomes than in mitogenomes. Interestingly, a few tandem repetitions were significant for some Ulva subspecies and relatively more evident in mitochondria than in chloroplasts. Finally, the tandem repetition [GAAATATATAATAATA × 3, abbreviated as TRg)] was identified in the mitogenome of U. compressa and the conspecific strain U. mutabilis but not in other algal species of the Yellow Sea. Owing to the high morphological plasticity of U. compressa, the findings of this study have implications for the rapid non-sequencing detection of this species during the occurrence of green tides in the region.

The world's largest macroalgal blooms caused by Ulva prolifera have occurred in the Yellow Sea for 11 consecutive years. The area covered by blooms has been approximately 500 km2 in previous years, while in 2017, the maximum area decreased significantly to 312 km2. In this study, we concluded that species competition between Ulva and Sargassum (fast rise of the golden tides), extreme high sea surface temperature and harvest for floating Ulva macroalgae were the three critical factors influencing the sharp reduction in covered area for blooms in 2017. In addition, analysis of annual variations of Pyropia aquaculture area in the Southern Yellow Sea over the past two decades revealed that a great expansion in "Sansha" regions was mainly responsible for the initial blooms in 2007, and that this expansion supported the great biomass of the blooms in following years. Based on these findings, we suggest comprehensive utilization of the macroalgal blooms is a feasible way to control them.

Ulva meridionalis, a green macroalgae, is one of the causal species for green tides in Japan and spread into the coast of China. During this research, we sequenced the complete mitochondrial genome of U. meridionalis. The mitogenome is 62,887 bp in length, including 28 encoding genes and 29 tRNA genes. Compared with the Ulva species from mitogenome, the gene order and organization of this mitogenome are similar to most of other determined Ulva mitogenomes, with the nucleotide base composition of A 33.6%, T 32.2%, C 16.2%, and G 18.0%. Phylogenetic analysis shows U. meridionalis is closely related to Ulva flexuosa.

Ulva prolifera is the dominant species of green macroalgal blooms in the Yellow Sea, China. In this study, we sequenced and annotated the complete chloroplast genome of U. prolifera (GenBank accession number: KX342867). The genome of circular chromosomes consists of 93,066 including 66 protein-encoding genes, 26 tRNA genes, and 3 rRNA genes. Compared with the 16 species from Chlorophyta, it has eight genes in expansion and 15 genes in shrink. Phylogenetic analysis shows positioned U. prolifera with U. linza, while Ulva sp.UNA00071828 is closely allied with Ulva fasciata.

Ulva flexuosa, one kind of green tide algae, has outbroken in the Yellow Sea of China during the past ten years. In the present study, we sequenced the chloroplast genome of U. flexuosa followed by annotation and comparative analysis. It indicated that the chloroplast genomes had high conservation among Ulva spp., and high rearrangement outside them. Though U. flexuosa was closer to U. linza than U. fasciata in phylogenetic tree, the average Ka/Ks between U. flexuosa and U. linza assessed by 67 protein-coding genes was higher than those between U. flexuosa and other species in Ulva spp., due to the variation of psbZ, psbM and ycf20. Our results laid the foundation for the future studies on the evolution of chloroplast genomes of Ulva, as well as the molecular identification of U. flexuosa varieties.