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Ulva prolifera and Sargassum are two common floating macroalgae in China's coastal algal bloom events. Ulva prolifera frequently emerges concomitantly with Sargassum outbreaks, thereby presenting challenges to the monitoring of algal blooms, thereby presenting challenges to the monitoring of algae. To tackle the challenge of differentiating between Ulva prolifera and Sargassum, this study employs Sentinel-2 MSI data for spectral analysis. Notably, significant disparities in the Remote Top of Atmosphere Reflectance (Rtoa) between Ulva prolifera and Sargassum are observed. This study proposes a random forest-based algorithm for discriminating between Ulva prolifera and Sargassum in the regions of the Yellow Sea and East China Sea. The algorithm introduced in this study attains remarkable accuracy in distinguishing Ulva prolifera and Sargassum within Sentinel-2 MSI data, achieving identical F1 scores of 99.1% for both. Moreover, when tested with GF-1 WFV data, the algorithm showcases outstanding performance; this demonstrates the algorithm's robustness and its ability to mitigate the uncertainty linked to threshold selection. Simultaneously, a comparative analysis of algae distribution was conducted for both 2017 and the period from January to May 2023. Experimental results indicate that the algorithm exhibits high accuracy in distinguishing between Ulva prolifera and Sargassum. This capability will significantly enhance the monitoring of large algae in maritime regions; this holds crucial theoretical significance and offers substantial practical value in the realm of marine ecological conservation. [ABSTRACT FROM AUTHOR]

Green macroalgae bloom (GMB), with the dominant species of Ulva prolifera, has regularly occurred since 2007 along the China coast. Although disaster prevention and control achieved favorable results in 2020, the satellite-observed GMB annual maximum coverage (AMC) rebounded sharply in 2021 to an unprecedented level. The reasons for this rebound and the significant interannual variability over past 15 years are still open questions. Here, by using long-term time-series (2007–2022) optical and Synthetic Aperture Radar satellite observations (1000+ scenes), meteorological data and water quality statistics, the mechanism analysis was performed by exploring effects from natural factors and human activities. Two key determinants for AMC are successfully identified from numerous potential factors which are the macroalgae distribution in a key area (the Subei Shoal) during a critical period (from April to May 20) and the nutrient availability. Furthermore, by using these two parameters, a novel model for AMC prediction (R2 = 0.87, p < 0.01) is proposed and independently validated, which can reasonably explain the significant interannual variability (2014–2021) and agree well with the latest observation in 2022 (percentage difference 12%). Finally, suggestions are proposed for future disaster prevention and alleviation. This work may aid future bloom prediction and management measure optimization. [ABSTRACT FROM AUTHOR]

Seaweed communities perform a variety of ecological services, including primary productivity supply, biological habitat construction, water purification, and acting as marine carbon sinks. The abundance of seaweed is the basis for the assessment of ecological services in communities. The Ma'an Archipelago, adjacent to the Yangtze River estuary in China, is an important and typical island group. In this study, the abundance of seaweed in the typical coastal islands of the Ma'an Archipelago, Zhejiang Province, was evaluated by means of sonar detection and scuba diving sampling methods. The organic carbon content of six dominant seaweed species was measured to estimate the carbon sequestration capacity of the dominant species in the Ma'an Archipelago. The results show that 27 species of Rhodophyta, 10 species of Ochrophyta, and two species of Chlorophyta were found in the Ma'an Archipelago. Seaweed was distributed in the coastal areas of the islands, with a distribution width of 2–60 m. Gouqi Island had the longest shoreline, and there, the distribution depth of the seaweed reached 15 m and the area of the seaweed community was the largest. The slope of the rocks in the Sanheng survey area was large and the width of the seaweed community was small. The distribution area of seaweed in the Ma'an Archipelago was 6.51–13.43 km2 and the organic carbon content of the seaweed was 33.16 ± 3.26%. The biomass of Ochrophyta in the Ma'an Archipelago was the largest, followed by Chlorophyta and Rhodophyta. Among the six dominant species, the carbon sequestration of Sargassum thunbergii was the largest, at 277.91–848.74 t per year, and that of Undaria pinnatifida was the smallest. This study provides scientific guidance for the assessment of the primary productivity supply, carbon sink, and conservation capacity of seaweeds in China. [ABSTRACT FROM AUTHOR]

The aim of this study was to extract the polyphenols from three major seaweed species such as Sargassum miyabei, Undaria pinnatifida suringar, and Sargassum thunbergii, which are found in the coastal province (Guangdong), a longest coastal line in China. It was found that the Sargassum thunbergii produced more polyphenols (34.99 mg) as compared to Sargassum miyabei (23.26 mg) and Undaria pinnatifida suringar (25.34 mg), respectively. The orthogonal method was used for the extraction of phenolic compounds and extraction condition of each seaweed species was optimized. The antioxidant activity of extracted polyphenols from all three species stated that the polyphenols extracted from Undaria pinnatifida suringar demonstrated the highest antioxidative activity. Furthermore, gas chromatography–mass spectrometry (GC‐MS) was used for qualitative analysis of polyphenols, which revealed that the major components of polyphenols extracted from Undaria pinnatifida suringar were gallic acid and arbutin followed by syringate in Sargassum miyabei and phloretin in Sargassum thunbergii. [ABSTRACT FROM AUTHOR]

The freshwater red algal genus Sheathia is one of the most species‐rich genera in the Batrachospermales, containing species with heterocortication (both bulbous and cylindrical cells covering the main axis) and homocortication (only cylindrical cells). The hidden diversity of homocorticated Sheathia species has gained research momentum. Recent studies have revised these taxa and described many new species. In this study, a new homocorticated Sheathia species is described and illustrated from Yunnan, China, based on phylogenetic analyses of DNA sequence data. Sheathia yunnanensis sp. nov is morphologically characterized by having homocortication, carpogonium with bent or slightly constricted lanceolate trichogyne, large carposporophyte and carposporangium. However, it is only distinguishable from other homocorticated species by DNA sequence data. Phylogenetic analyses based on rbcL, COI‐5P, psbA and concatenated rbcL + COI‐5P alignment indicated that Sheathia yunnanensis form an independent clade from other homocorticated Sheathia species with high interspecific divergence (rbcL: 3.9–4.9%/37–54 bp, COI‐5P: 6.1–6.6%/36–39 bp and psbA: 2.2–3.9%/18–32 bp). Sheathia yunnanensis, as the first gametophyte of Sheathia species reported in Yunnan, differs from other Sheathia species reported only as 'Chantransia' sporophyte stage. As a result of this study, the number of Sheathia species recognized in China increased to eight, including one heterocorticate and seven homocorticated including three only known from the 'Chantransia' sporophyte stage. The description of this new species expands the diversity of Sheathia in the world. [ABSTRACT FROM AUTHOR]

Turf-forming Gelidiales frequently occur in tropical coral reef regions. It is challenging to identify species correctly due to their small size and simple morphology. In the present study, we combined morphological and molecular phylogenetics methods to study turf-forming species of the genus Pterocladiella from tropical coral reef areas in southern China. Both COI-5P and rbcL gene analyses revealed a novel species described here, Pterocladiella xiae sp. nov. The species was less than 1 cm in height, with a distinctive slender thallus, compressed percurrent axis with up to two orders of ribbon-like branches, and short warty-like branchlets which usually occurred irregularly on the upper thallus. Pterocladiella bartlettii was also recorded in China for the first time. Additional descriptions of reproductive structure in P. musciformis and P. beachiae were also documented. This study enriches our understanding of the biodiversity of Pterocladiella in China and reveals the potential diversity of small turf-forming species in tropical coral reefs. [ABSTRACT FROM AUTHOR]

A new species of Grateloupia from Wenzhou Nanji Island in Zhejiang province, China, was illustrated based on morphological observation, early development, life history and rbcL gene sequence analysis, and named Grateloupia oligoclora H.W.Wang & Y.Bian sp. nov. The morphological features of this new species can be summarized as upright thalli, solitary or cespitose, dark red in colour, cartilaginous and mucilaginous in texture. The margins of the thalli were smooth, without lateral branches, proliferations, or branched, dichotomously branched or with 3–5 irregular rod-shaped branches. The thalli were consisted of cortex cells (6–9 cell layers) and medulla. The cystocarps were spherical and appeared to be speckled from the surface of the thalli. The carpogonial branch ampullae and auxiliary cell branch were typical Grateloupia-type. During the cruciate dividing of tetrasporangia, some dyads showed asynchronous phenomenon. Type of spore development and life history were typical mediate discal type and isomorphic alternation of generations. Phylogenetic analysis based on rbcL sequence indicated that the new taxon formed an independent clade from other Grateloupia species, and this clade was sister to G. subpectinata Holmes with high interspecific divergence 12 bp (1%), supporting its specific status. Accordingly, G. oligoclora H.W.Wang & Y.Bian sp. nov is proposed as a new species of Grateloupia. This study provides new resource and species diversity of marine Rhodophyta in China. [ABSTRACT FROM AUTHOR]

To develop an effective method to eliminate green macroalgae attached to Neopyropia aquaculture nets, we explored the influence of mixed acid solution on the photosynthetic fluorescence characteristics of Ulva spp. (green macroalgae) and Neopyropia yezoensis (red macroalgae) from Dafeng and Rudong aquaculture areas in Jiangsu Province, China. Treatment with mixed acid solution (0.0475 % hydrochloric acid:citric acid (pH 2.0) at a ratio of 4:3) for 60 s caused death of Ulva spp., but did not affect N. yezoensis. Additionally, a mixed acid solution effectively eliminated green macroalgae from Neopyropia aquaculture rafts and the marine environment remained unaffected. Hence, the application of mixed acid solution treatment has demonstrated significant efficacy in eradicating green macroalgae adhered to Neopyropia aquaculture rafts, thus presenting a promising strategy for mitigating green macroalgae proliferation in Neopyropia aquaculture areas and curbing their contribution to green tides. [Display omitted] • Ulva spp. was completely killed with a mixed acid (4:3 HCl to citric acid). • Neopyropia yezoensis treated with the mixed acid can get back. • This method will not have harmful effects on marine environment. [ABSTRACT FROM AUTHOR]

Summary: The freshwater red alga Nemalionopsis shawii Skuja is first reported for mainland China from specimens collected in Guangdong and Yunnan Province. Morphological observations and molecular sequences of rbcL and cox1 genes were used to identify and analyze the phylogenetic position of the samples. Samples from China formed a monophyletic clade with other N. shawii samples from Japan, Indonesia, and Nepal with robust support values. The pairwise genetic distances for N. shawii between the samples from China and other samples were 0.2–1.5% and 1.0–2.4% for rbcL and cox1, respectively. Both male and female reproductive structures were observed in the specimens from Guangdong, but only monosporangia in the specimen from Yunnan. The samples from China increase the diversity of morphological measurements for N. shawii. The discovery of this genus in mainland China results in a new record of a freshwater red alga for this country. [ABSTRACT FROM AUTHOR]

Two new species of Gesneriaceae, Paraboea myriantha sp. nov. and P. brevipedunculata sp. nov. are described and illustrated with photos. They grow in the Caryota obtusa forests from Yunnan Province of China. P. myriantha is closely related to P. glutinosa (Hand.-Mazz.) K.Y.Pan, but differs mainly in corolla outside glandular-puberulent, adaxial corolla lobes semicordate, corolla tube obliquely campanulate, and filaments glandular-puberulent. P. brevipedunculata is closely related to P. crassifolia (Hemsley) B. L. Burtt, but different mainly in simple dichasia with 1 and 2 flowers, peduncles 0.5-2 cm long and capsules slightly twisted. The geographical relationship between the two new species and their similar species has been discussed. [ABSTRACT FROM AUTHOR]

Large-scale green tide disasters have been occurring for more than 10 years in China, with serious ecological consequences. However, limited research has focused on epiphytes that feed on macroalgae. In this study, amphipods were found living on the surface of Ulva lactuca, a green-tide-forming alga, around Gouqi Island, China. Through morphological and molecular methods, the amphipods were identified as Ampithoe lacertosa Bate, 1858, which has not previously been recorded in China. Sequence information about cytochrome c oxidase subunit I (mitochondrial COI) gene from China was compared to sequences reported from 5 coastal countries around the Pacific region. Network diagrams, phylogenetic trees and other methods of analysis revealed evidence of genetically distinct subspecies in the northeastern and northwestern Pacific. We believe that research on herbivorous amphipods will provide preventative strategies and control measures against green tide algae. International cooperation among Asian and North American biologists within the Pacific region will lead to a better understanding of the family Ampithoidae in the future. [ABSTRACT FROM AUTHOR]

The impacts of harmful algal blooms (HABs) on economies, public health, ecosystems, and aquaculture across the globe have all increased in recent decades, and this has been acutely the case in China. Here, we review the history of HABs and HABs research in China, as well as recent trends in HABs and future prospects of HAB science in China. The most updated analyses demonstrated that the number of HAB events, the number of HAB species, the aerial coverage of HABs, and the impacts of HABs in Chinese waters during the 21st century were all higher than that during the last two decades of the 20th century. The increase in the number of HABs in China has been significantly correlated with the increased discharge of ammonium and total phosphorus into coastal waters (p < 0.01 for both). Notable newly recognized events this century have included chronic HABs caused by Prorocentrum donghaiense and Karenia mikimotoi , a paralytic shellfish poisoning event caused by Gymnodinium catenatum that sickened 80 people, brown tides caused by Aureococcus anophagefferens , green tides caused by Ulva prolifera , golden tides caused by Sargassum horneri , and the disruption of a nuclear power plant caused by a bloom of Phaeocystis globosa. A series of key discoveries regarding HABs has been made this century including documentation of nearly all known HAB toxins in Chinese waters, discovery of novel cyst-formation and/or life stages of multiple HABs-causing species, identification of the chemical and physical oceanographic drivers of multiple HABs including those formed by P. donghaiense, K. mikimotoi , and U. prolifera , and the successful mitigation of HABs via the use of modified clay approaches. Future research prospects highlighted include the use of macroalgae as a means to prevent, mitigate, and control (PCM) HABs and the process by which multi-disciplinary studies involving molecular approaches (omics), remote in situ detection, artificial intelligence, and mega-data analyses might be used to develop refined and realistic HAB forecasting platforms. Collectively, this review demonstrates the significant evolution of HAB science since the 20th century in China and demonstrates that while HABs in China are complex and widespread, recent and on-going discoveries make the development of detailed understanding and effective measures to mitigate the negative effects of HABs a hopeful outcome in the coming years. [ABSTRACT FROM AUTHOR]

Macroalgae aquaculture faces grand challenges from extreme temperature events in the context of global warming. For mapping aquaculture areas and assessing potential risks, it is urgent to evaluate the thermal sensitivity of commercially and ecologically important macroalgae. In the present study, thermal tolerance of commercial macroalgae species in China and sea surface temperature (SST) under current conditions and three Shared Socioeconomic Pathways (SSP1–2.6, SSP3–7.0, SSP5–8.5) scenarios in 2050 were collected for calculating thermal safety margin (TSM), an index of thermal sensitivity, for each species in the aquaculture area. Our results indicated that a few species were particularly sensitive to current conditions, and the kelp Saccharina japonica and Ulva pertusa were the most sensitive species to heat and cold stress, respectively. As indicated by the regional thermal sensitivity (RTS) (i.e., the mean of TSMs for all species in each grid cell), the commercial macroalgae located in southern China (20–25°N) were more sensitive to heat stress, while the commercial macroalgae located in the regions of 27–40°N was more sensitive to cold stress. Commercial macroalgae nearby the Yangtze River Estuary (~30°N) were sensitive to both heat and cold stress. Under the three SSP scenarios, macroalgae aquaculture would be more sensitive to heat stress, and the impacts from cold stress would relatively weaken in 2050. Our findings provide crucial information for the management of macroalgae aquaculture and for climate change mitigation and adaptation in China. • Species-specific and region-specific thermal sensitivity of macroalgae aquaculture in China were evaluated. • The impacts of heat stress will increase while cold stress will decrease in the future in the face of climate change. • Macroalgae farming potentially is running out of traditional geographies. • Effective adaptation and mitigation efforts are urgent for the sustainable development of macroalgae aquaculture. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• An unusual bi-algal bloom occurred in western Yellow Sea during spring to summer of 2017. • Distinct genesis and development of floating U. prolifera and S. horneri were described. • The reasons for the significant shrinkage of the green tide in 2017 were discussed. An unprecedented bi-macroalgal bloom caused by Ulva prolifera and Sargassum horneri occurred from spring to summer of 2017 in the western Yellow Sea (YS) of China, where annual large-scale green tides have prevailed for a decade. The distinct genesis and blooming dynamics of the two seaweed species were detected and described. Unlike the consistent raft-origin of the floating Ulva biomass, the massive pelagic S. horneri was derived from multiple sources (residual seaweeds from the previous winter bloom and those drifting from offshore water in the south). The scale of the green tide in 2017 was found smaller than the previous four years. We then discussed a number of hypotheses attributing to this reduction, including reduced epiphytic green algae from aquaculture rafts and the influences of the massive pelagic S. horneri. However, further research is needed to identify the origin of the pelagic S. horneri in the western YS and any affiliations with the benthic populations, and to elucidate the interactions of this species with the annual green tides and the ensuing consequences. [ABSTRACT FROM AUTHOR]

• Thuja sutchuenensis , an endangered China native plant, has been systematically investigated focusing on secondary metabolites. • Eight novel sesquiterpenes (1 – 8) with diverse skeletons were isolated from the stems and roots of T. sutchuenensis. • Compounds 5 (thujasutchin J) and 9 exhibited considerable antibacterial activities with MIC ranging from 6.25 to 25 μg/mL. Eight new sesquiterpenes with diverse skeletons involving four cuparenes, denominated thujasutchins F-I (1 – 4), one eudesmane and one cedrol, named thujasutchin J (5) and thujasutchin K (6), as well as two thujopsenes thujasutchins L-M (7 – 8) together with three known congener compounds (9 – 11) were isolated from EtOAc soluble fraction of ethanolic extract of the stems and roots of Thuja sutchuenensis. Their structures including absolute configurations were unambiguously established by extensive interpretation of the NMR and mass spectroscopic data, X-ray diffractions, and ECD measurements powered by molecular calculations. The biological assays disclosed that 5 and 9 displayed potent inhibitory effect against Staphylococcus. aureus (CMCC 26003), methicillin-resistant Staphylococcus aureus (JCSC 4744), Bacillus cereus (ATCC 10876), and Staphylococcus epidermidis (ATCC 12228) with MICs ranging from 6.25 to 25 μg/mL. [ABSTRACT FROM AUTHOR]