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Volume 40 ， Issue 6 ， 2022
- Abstract：The "harmful algae and algal toxins in coastal waters of China: investigation and database" project (HAATC) is funded (US.3 million) by the Ministry of Science and Technology of China for 60 months starting on the 1st Jan 2019. Since the 1990s, national projects and other related work have greatly improved harmful algal bloom (HAB) research in China. However, the existing research on HABs is often limited to specific sea areas or specific algal bloom disasters, which is insufficient for understanding the longterm evolution of HAB occurrence under the influence of intensified human activity and global change. The HAATC project intends to determine the overall distribution of marine harmful microalgae and macroalgae, and marine algal toxins (in phytoplankton and shellfish) through a large-scale investigation in the coastal waters of China and continuous investigation in key sea areas. It also aims to observe biotic and abiotic processes during harmful red tides and green tides, and establish an open database and query platform of HABs in China. The research consortium, led by chief scientist Prof. Tian YAN, includes approximately 100 scientists and students. More than 2 years of work have shown the increased distribution of HAB species (including cysts) and algal toxins in China's coastal waters, the increased occurrence of macroalgae blooms (mainly by Ulva prolifera and Sargassum horneri) in the Southern Yellow Sea, increased amount of causative species being identified due to the use of molecular technologies in taxonomy, and new records of algal toxins such as azaspiracid, cycloimines and neurotoxins β-N-methylamino-l-alanine have been detected, which complicates the research in algal toxins and toxicology. Eventually, the project will provide systematic basic data and techniques for the rapid and accurate identification of harmful algae species to support the research, monitoring, and control of harmful algal blooms, as well as seafood safety management in China.Keywords：harmful algae;algal toxins;coastal waters of China;database9|2|0Updated：2023-05-20
- Abstract：Hong Kong has a long historical record of harmful algal blooms (HABs). In the 1980s–1990s, HABs were mainly pollution-related and most of the events happened in estuaries and enclosed embayment such as Tolo Harbour and Port Shelter. The major cause of HABs in 1980s–1990s was closely related to nutrients enrichment; included but not limited to changes in the concentration and ratio of soluble N and P in seawater. The major causative organisms of HABs in Hong Kong by then were meso-plankton such as selected species of diatoms and dinoflagellates. Sometimes, zooplankton was also a cause of red tides (the common name of HABs). There has been gradual change after the 2000s. It is attributed to higher and higher influences from the region, namely the Zhujiang (Pearl) River delta. There are increasing influences from Chinese mainland due to extraordinary social and economic growths during the past 20 years. In the past 10 years, HABs in Hong Kong was mainly subject to regional impacts in the Zhujiang River delta. Both the duration period and covered areas have been enlarged which overwhelmed the localized influences of stream pollution and self-contamination of aquaculture zones. More flagellates of uncommon happening become dominant species in HAB now. Nevertheless, the seasonal impact of Noctiluca scintillans in late winter to mid spring remained.Keywords：harmful algal blooms (HABs);Tolo Harbour;long-term trend;regional eutrophication and environmental impacts15|1|0Updated：2023-05-20
- Abstract：Harmful algal blooms (HABs) in the Southern Yellow Sea (SYS) have shown a trend of increasing diversity and detrimental effects. While the Bohai Sea, East China Sea, and South China Sea have experienced a high incidence of HABs since the 1980s, the Yellow Sea provides a relatively healthy ecological environment in which fewer HABs have been documented before the 21st century. Yet large-scale blooms of the green macroalga Ulva prolifera (so-called pgreen tidesq) have occurred annually since 2007 in the Yellow Sea. Six people were poisoned and one person died in Lianyungang in 2008 due to ingestion of algal toxins. Moreover, the Yellow Sea experienced co-occurrence of harmful red tides, green tides, and golden tides in 2017. This combination of events, rare worldwide, indicates the potential for further deterioration of the marine environment in the Yellow Sea, which may be related to climate change, aquaculture, and other human activities. Using the SYS as an example, we collected data of the frequency and scale of HABs over the years, as well as that of marine algal toxins, and analyzed the trend in the diversity of HABs in the SYS, to explore the causes and impacts of HABs, as well as the interrelationships among different types of HABs, including harmful red tides, green tides, and golden tides. We also attempted to improve our understanding of HAB evolution under the influence of global climate change and intensified human activities.Keywords：marine algal toxins;harmful algal blooms;red tides;green tides;golden tides;Southern Yellow Sea7|0|0Updated：2023-05-20
Review
- Abstract：Benthic dinoflagellates have attracted increasing attention in recent years because of their toxicity and ability to form extensive harmful algal blooms. Ostreopsis producing palytoxin and its analogs, Gambierdiscus producing ciguatera toxins, and Prorocentrum producing okadaic acid and dinophysis toxins, have been concerned as serious human poisonings. We explored the benthic dinoflagellate biodiversity and distribution characteristics of a series of tropical reefs in 20–40-m water depth in wet season in the Zhongsha Islands in South China Sea using morphological, phylogenetic, and cell counting methods. Results show that benthic dinoflagellates in the islands are rich in biodiversity and 15 species from genera Amphidinium, Coolia, Ostreopsis, and Prorocentrum were identified: Amphidinium carterae, A. magnum, A. massartii, A. operculatum, Coolia canariensis, C. malayensis, C. palmyrensis, C. tropicalis, Ostreopsis cf. ovata, Prorocentrum concavum, P. cf. sculptile, P. emarginatum, P. hoffmannianum, P. lima, and P. rhathymum. Among them, A. magnum is reported for the first time in Chinese waters. The abundance of benthic dinoflagellates was relatively low at 88–4 345 cells/100 cm2 on sediment and 10–91 cells/g on macroalgae. Prorocentrum and Amphidinium were the dominant and subdominant genera, respectively. It is speculated that the low abundance of benthic dinoflagellates is closely related to the scarcity of macroalgae and stronger water motion at the depth >15 m in Zhongsha Islands. This study expanded the study in biodiversity of benthic dinoflagellates in Chinese waters, and revealed the distribution characteristics of harmful benthic microalgae in reef habitats.Keywords：benthic dinoflagellates;Zhongsha Islands;South China Sea;biodiversity;distribution9|0|1Updated：2023-05-20
- Abstract：The naked dinoflagellate Takayama acrotrocha was identified as responsible for a bloom in Shenzhen Bay, Guangdong, China, in early spring 2021. The identification was confirmed by light, scanning, and transmission electron microscopy and molecular data based on the LSU ribosomal DNA (rDNA) and ITS rDNA sequences. This is the first record of T. acrotrocha bloom in the South China Sea. The sulcus of T. acrotrocha was wide and extended onto the epicone as a short intrusion in general, sometime the intrusion was not apparent and some were finger-like. The apical groove was deeply sigmoid. The nucleus was large, ovoid to cup-shaped and occupied most of the epicone. A large, rounded pyrenoid surrounded by a starch sheath was located at the left side to the centre of the hypocone. Under epifluorescence illumination, a row of large vesicular knobs was observed on the upper border of the cingulum. The intraspecific morphological variabilities in the clonal cultures of T. acrotrocha were investigated carefully. Cells that share the same diagnostic characters used for the description of Takayama xiamenensis such as the finger-like sulcus, a large nucleus located in the epicone and the similar pyrenoid type were observed. The LSU rDNA sequences of T. acrotrocha and T. xiamenensis only differed in 3 base pairs (bp) for a sequence length of 673 bp (with a similarity of 99.55%). For these reasons, we propose T. xiamenensis as a junior synonym of T. acrotrocha.Keywords：Takayama spp.;harmful algal bloom;morphology;phylogeny;South China Sea6|0|0Updated：2023-05-20
- Abstract：Blooms of Phaeocystis globosa have been reported accountable for massive fish mortality worldwide. The toxigenic mechanisms of P. globosa, however, remain largely unclear due to the multiple structures and/or synergistic or antagonistic effects of hemolytic compounds. External stressors could lead to the regulation of photoprotective or antioxidative defense system, as well as the potential hemolytic activity. Therefore, the light-induced photosynthetic system, including the accessory photosynthetic growth, the relative electron transfer rate (ETR), photosynthetic efficiency (Fv/Fm), quantum yield of photosystem II (Yield), together with the hemolytic activity of P. globosa were investigated under variable environmental conditions in the present study. Results confirmed that hemolytic activity of P. globosa was initiated by the light, but inhibited by low temperature (16 ℃), high light intensity (>100 μmol/(m2·s)), and iron-limited conditions. Interestingly, the hemolytic activity was not impacted by photosynthetic electron inhibitors (Diuron, atrazine, paraquat, and dibromothymoquinone), which significantly inhibited the photosynthetic activity of P. globosa. The correlated response of hemolytic and photosynthetic activity of P. globosa under those environmental factors suggested that the hemolytic compounds of P. globosa would be involved in the photosynthetic process but not in the electron transfer chain of P. globosa.Keywords：Phaeocystis globosa;hemolytic activity;photosynthetic system6|0|0Updated：2023-05-20
- Abstract：To assist the researches of toxic and harmful algae and provide government workers with judgment basis for decision-making related events, we established a biological information management system for toxic and harmful algae in China's offshore to assist relevant research. In this study, Karenia mikimotoi was studied as a typical toxic and harmful algae species, and the basic biological information and biogeographic distribution information of K. mikimotoi were systematically studied and collected. In the part of basic biological information, the name, toxin, and molecular characteristic sequence of K. mikimotoi were sorted out by literature searching and website browsing. Through experimental means, the relevant information of morphological identification, pigment composition, and lipid composition were obtained. In the part of biogeographic distribution information, this study sorted out the information of K. mikimotoi, analyzed the characteristics of its occurrence, and completed the standardized construction of biogeographic distribution information. Through the collation of basic biological information and biogeographic distribution information of K. mikimotoi, the standardization of related information was completed, which provided template and method reference for information collection of other toxic and harmful algae species, which was beneficial to the database analysis and design.Keywords：harmful algae;basic biological information;biogeographic distribution information;information standardization6|0|1Updated：2023-05-20
- Abstract：A large-scale algal bloom, caused by Aureococcus anophagefferens, has plagued the coastal embayment of Qinhuangdao, China since 2009. The bay scallop agriculture industry in this area has been adversely affected. Researchers claimed that the poor nutritional value of brown tide cells might be responsible for the detrimental effects on bivalve mollusks. To verify whether brown tide cells are nutritionally inadequate food sources, the biochemical composition (total extractable lipids, amino acids, fatty acids, and monomeric carbohydrates) of the Chinese strain A. anophagefferens was determined during the late logarithmic growth phase when culturing in different nitrogen sources (nitrate, urea and nitrate-urea mixture). Cells cultured in nitrate contained 39.12% protein, 21.99% total extractable lipid, 10.25% total carbohydrates, and a relatively high amount of polyunsaturated fatty acid (PUFA) (51.98%, percentage of total fatty acids), including eicosapentaenoic acid (EPA) (4.81%) and docosahexaenoic acid (DHA) (14.56%). The gross biochemical composition and PUFA content in A. anophagefferens in nitrate cultivation are comparable with values found in the literature of frequently used species in bivalve feeding. Nine monomeric carbohydrates were significantly reduced when cultivated in urea and nitrate-urea mixture (P < 0.05). The DHA, EPA, and PUFA contents significantly decreased when cultivated in urea (P < 0.05). Although the nutritional value of A. anophagefferens dropped when cultured in urea, it is still comparable with certain favorably used algal species in bivalve feeding (i.e., Skeletonema costatum), indicating that A. anophagefferens is not a nutritionally inadequate food source.Keywords：brown tide;Aureococcus anophagefferens;fatty acid;carbohydrate;nutritional value6|0|0Updated：2023-05-20
- Abstract：Paralytic shellfish poisoning (PSP) microalgae, as one of the harmful algal blooms, causes great damage to the offshore fishery, marine culture, and marine ecological environment. At present, there is no technique for real-time accurate identification of toxic microalgae, by combining three-dimensional fluorescence with machine learning (ML) and deep learning (DL), we developed methods to classify the PSP and non-PSP microalgae. The average classification accuracies of these two methods for microalgae are above 90%, and the accuracies for discriminating 12 microalgae species in PSP and non-PSP microalgae are above 94%. When the emission wavelength is 650–690 nm, the fluorescence characteristics bands (excitation wavelength) occur differently at 410–480 nm and 500–560 nm for PSP and non-PSP microalgae, respectively. The identification accuracies of ML models (support vector machine (SVM), and k-nearest neighbor rule (k-NN)), and DL model (convolutional neural network (CNN)) to PSP microalgae are 96.25%, 96.36%, and 95.88% respectively, indicating that ML and DL are suitable for the classification of toxic microalgae.Keywords：paralytic shellfish poisoning (PSP);machine learning (ML);deep learning (DL);toxic algal classification6|0|1Updated：2023-05-20
Marine harmful microalgae
- Abstract：Lipophilic marine toxins (LMTs) produced by some microalgae in the sea could accumulate in shellfish and pose potential threats to the health of seafood consumers. Phytoplankton and shellfish samples were collected from coastal waters of Weihai in Shandong Peninsula, China in autumn, 2020, and screened for lipophilic marine toxins and their potential producers using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and high throughput sequencing of partial DNA (V4 region of the 18S rRNA gene) extracted from phytoplankton. Pectenotoxin-2 (PTX2), trace amounts of azaspiracid (AZA1 or AZA40), and 13-desmethyl spirolide C (13-DesMe-C) were detected in phytoplankton samples, while PTX2 and gymnodimine (GYM) were detected in shellfish samples. The toxin content in shellfish samples was much lower than the regulatory limit or values reported previously. Results suggest that lipophilic marine toxins should have low risk in coastal waters of Weihai in autumn. Based on the data of high throughput sequencing, the OTUs were assigned to 5 identified species of Alexandrium, including A. ostenfeldii capable of producing 13-DesMe-C and GYM. Two OTUs were found closely related to the toxic species in genus Dinophysis, but it is impossible to assign them to any identified species due to the low resolving power of the V4 region for Dinophysis. The OTUs could not be assigned to any identified species in the genus Azadinium, suggesting the existence of unidentified species in this region.Keywords：harmful algal blooms;phytoplankton;shellfish;lipophilic marine toxins (LMTs);Yellow Sea;liquid chromatography-tandem mass spectrometry8|0|0Updated：2023-05-20
- Abstract：Atotal of 133 shellfish samples were collected in seven cities of Shandong Province, China, from May to October, 2019. The domoic acid (DA) concentrations were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and their distribution characteristics were investigated. DA concentration was detected high in over 1/3 (36.1%) of the samples of four kinds of shellfish in all three seasons in range from 0 to 102 μg/kg. The highest DA concentrations were 102, 101, 36.7, and 10.2 μg/kg in Crassostrea gigas, Chlamys farreri, Mactra veneriformis, and Mytilus edulis, respectively. Geographically, Yantai (22.0 μg/kg) and Weihai (16.9 μg/kg) showed relatively high concentrations of DA, whereas Rizhao and Dongying presented only 0.85- and 1.76-μg/kg DA, respectively. DA concentrations in the shellfish samples were strongly related to seasonal changes, being significantly higher in autumn and summer than that in spring. The DA risk exposure assessments indicate that dietary seafood consumption did not pose a health threat to general human population. In addition, three isomers (isoA, isoD, isoE) and 5'-epimer DA were detected in 3.00%Ƀ15.80% of the shellfish samples. This study is the first to observe DA and its isomers in shellfish samples of Shandong Province. The results demonstrate that DA contamination is very common and should be continuously monitored.Keywords：domoic acid;shellfish;liquid chromatography-tandem mass spectrometry (LC-MS/MS);Shandong Province6|0|0Updated：2023-05-20
- Abstract：Lipophilic marine algal toxins (LMATs) are produced by some toxigenic microalgae, which pose a serious threat to marine ecosystem and even human health. The occurrence and environmental control factors of LMATs in the surface seawater and phytoplankton in spring in Laizhou Bay in which Huanghe (Yellow) River estuary is included, in Shandong, East China were investigated. Okadaic acid (OA), pectenotoxin-2 (PTX2), dinophysistoxin-1 (DTX1), pectenotoxin-2 seco acid (PTX2 SA), DTX2, 7-epi-PTX2 SA, PTX11, and 13-desmethyl spirolide C (SPX1) were detected from the surface seawater samples, and PTX2, 7-epi-PTX2 SA, OA, DTX2, DTX1, PTX2 SA, and PTX11 were discovered in the phytoplankton samples showed a decreasing trend. The concentrations of ∑LMATs in the seawater and phytoplankton ranged 2.03–74.38 ng/L on average of 13.72 ng/L and 0.98–479.27 pg/L on average of 50.20 pg/L, respectively. The joint influence of terrigenous input and internal circulation could promote the growth, toxin production, and toxin release of toxin-producing algae, leading to a higher content of LMATs in the bay nearby the Huanghe River estuary in both seawater and phytoplankton. The concentration of LMATs in spring was higher than that in summer, showing obvious seasonal variation. In addition, no significant correlation between most of the physiochemical parameters and LMAT contents in seawater was revealed by correlation analysis except for the positive correlation between DTX2 and chlorophyll a, OA and NH4-N. However, the increase of dissolved inorganic nitrogen content in seawater could enhance the production of OA, DTX1, and DTX2 in phytoplankton due probably to that the inorganic N input could benefit the growth and stimulate toxin production of toxin-producing algae. The result also proved that some PTX2 may be originated from Procentrum spp. and OA, DTXs and part of PTX2 may be originated from Dinophysis spp.Keywords：lipophilic marine algal toxin;Laizhou Bay;seawater;phytoplankton;environmental factor6|0|0Updated：2023-05-20
- Abstract：To learn the marine phycotoxins (MPTs) contamination status in mariculture areas in the East China Sea (ECS), from May 2020 to October 2021, 80 net-concentrated phytoplankton samples were collected from 12 stations in three typical areas with high incidence of red tides, namely, Gouqi Island, Sandu'ao-Lianjiang, and Zhangzhou-Dongshan Island in ECS, and MPTs of the samples were detected. Six types of toxins were detected in 24 samples from 9 stations. Lipophilic marine toxins (LMTs) were more common and diverse in these areas. Pectenotoxin 2 (PTX2) was the main lipophilic marine toxin (LMT) in the concentrated phytoplankton samples and the occurrence showed seasonal differences from north to south. According to the potential risks of pectenotoxin (PTXs) to seafood safety, it is suggested to execute regular monitoring on PTXs in ECS and a mandatory standard should be formulated based on the comprehensive analysis of in-situ monitoring and lab research. Meanwhile, contamination risks of cyclic imine toxins in the north and domoic acid (DA) in the south of ECS should also be paid with attention to. Only 2 paralytic shellfish toxins (PSTs), N-sulfocarbamoyl toxin C2 (C2), and decarbamoyl gonyatoxin 3 (dcGTX3), were found from spring samples in the north of ECS. As the biggest mussel culture county of China, Gouqi Island showed higher toxin diversity and the toxin detection rate was higher than the other two areas. In Gouqi Island area, PSTs were a serious potential threat in spring, and LMTs instead of PSTs became the main risk in summer-autumn seasons. To ensure the safety of seafood and marine environmental health, it is recommended to conduct long-term targeted tracking and monitoring of MPTs in this and similar mariculture areas.Keywords：marine phycotoxins (MPTs);pectenotoxin 2 (PTX2);mariculture areas;East China Sea;seafood safety6|0|2Updated：2023-05-20
- Abstract：Understanding the risk factors associated with shellfish consumption is a relevant public health concern because of the potential adverse effects of paralytic shellfish toxins (PSTs). This work aims to study the effects of the five most common heating treatments (steaming, boiling, frying, water-bath heating, and microwaving), for different processing times and temperature/power settings, on the content of PSTs in mussels (Mytilus edulis) collected in Qinhuangdao, China. The toxin concentration, removal percentages, and toxin distribution in the cooking liquor and meat were examined. The five processing modes effectively accelerated toxin release into the cooking liquor. The average percentage removal was 73.53%±16.50% from tissues. Microwaving led to the most significant toxin degradation among the methods tested. These findings should facilitate risk assessment of PSTs in mussels.Keywords：processing mode;mussels;removal percentage;toxin distribution6|0|0Updated：2023-05-20
Marine algal toxins
- Abstract：Sediment samples were collected at 17 stations in the central Bohai Sea, China, and the diversity and community structure of eukaryotic microalgae were assessed by metabarcoding the V4 region of 18S rDNA. A total of 930 operational taxonomic units (OTUs) were detected for microeukaryotes, including 98 algal OTUs. The algal communities comprised 42 genera belonging to 19 classes of six phyla, and they were dominated by chrysophytes and dinoflagellates. Dinoflagellates were also the most diverse microalgal group. The nano-sized dinoflagellates Biecheleria halophila and Azadinium trinitatum occurred abundantly in the study area; however, they have not been reported previously, as they may be overlooked or misidentified in light microscopy. Many pico-sized chlorophytes were detected in the sediment samples. Sixteen of the detected OTUs were assigned to potentially harmful and/or bloom-forming microalgae, suggesting some potential risks of harmful algal blooms in the central Bohai Sea. The capacity of metabarcoding to detect morphologically cryptic and small species makes this method a sufficiently sensitive means of detection for assessing eukaryotic microalgae in sediments.Keywords：microalgae;dinoflagellate cysts;high throughput sequencing;marine sediment;the Bohai Sea;resting stages6|0|0Updated：2023-05-20
Dormant cells and cysts
- Abstract：Many marine dinoflagellates can form resting cysts as a part of their life cycle, and the cysts could be buried in sediment and remained viable for as long as over 150 years. However, only a very limited number of cyst species have been revived from long-buried sediments and investigated in regard to a possible shift in the intra-specific genetic structure of a species detected from the historical record at a particular location. Here, we report a successful germination of three species of resting cysts that were sampled from the depth dated back to 1941±18 AD from a 44-cm sediment core from the East China Sea. Seven isolates were established from germination of single cyst isolation or multi-cyst germinations. LSU rRNA gene or ITS sequences of these strains were obtained, then they were identified to be Biecheleria brevisulcata (five strains), Biecheleriopsis adriatica (one strain), and Scrippsiella donghaienis (one strain) in terms of morphology and rRNA gene sequence. Biecheleria brevisulcata strain 1, Bps. adriatica strain 21, and S. donghaienis strain 23 were examined in detail with light microscope (LM) and scanning electron microscope (SEM), and analyzed with high performance liquid chromatography (HPLC) for their pigment compositions, and genetic diversity. We also confirmed the presence of a resting cyst of Bps. adriatica in the field for the first time. The LSU rRNA gene-based genetic distances of Bps. adriatica from that obtained from water sample, single-cell PCR sequencing for the cysts isolated from the surface sediment of the same sea area and that reported from other regions during the recent years, and ITS-based genetic distances of S. donghaienis from that obtained from cysts isolated from the surface sediment of the same location and that reported from other regions during the recent years indicated that the intra-specific genetic structure of each species in the sampling area may have shifted during the last 70 years. Our work confirms that B. brevisulcata, Bps. adriatica, and S. donghaienis, all described as new species around 2010, have inhabited the East China Sea for about 70 years. The present work reports for the first time the revival of dinoflagellate resting cysts long-buried in the coastal sediments of China, which facilitates further study on the historical occurrences of other harmful dinoflagellates and their relevance to the regional climate and environmental changes in China.Keywords：core sediment;dinoflagellate resting cyst;germination;Biecheleria brevisulcata;Biecheleriopsis adriatica;Scrippsiella donghaienis6|0|0Updated：2023-05-20
- Abstract：Dinoflagellate Alexandrium catenella is a cosmopolitan bloom-forming species with complex life cycle, the formation and germination of resting cysts are critical for its bloom dynamics. In the coastal waters of Qinhuangdao, A. catenella has been identified as the major causative agent for paralytic shellfish poisoning, but there is little knowledge concerning its resting cysts in this region. In this study, three surveys were carried out along the coast of Qinhuangdao from 2020 to 2021 to map the distribution of A. catenella resting cysts, using a quantitative PCR (qPCR) assay specific for A. catenella. The resting cysts were detected in surface sediments during all the three surveys, and their distribution patterns were similar. High abundance of resting cysts (maximum 1 300 cysts/g sediment (wet weight)) were found in a region (119.62°E-119.99°E, 39.67°N-39.98°N) northeast to the coastal waters of Qinhuangdao, where surface sediments were mainly composed of clay and silt (percentage above 50%). Prior to the formation of the A. catenella bloom in March 2021, the abundance of A. catenella vegetative cells in seawater had extremely significant positive correlation with the abundance of resting cysts in surface sediments, reflecting the important role of resting cysts in the initiation of A. catenella blooms. As far as we know, this is the first report on the distribution of A. catenella cysts along the coast of Qinhuangdao. The results will offer a sound basis for the future monitoring and mitigation of toxic A. catenella blooms and paralytic shellfish poisoning events in this region.Keywords：harmful algal bloom (HAB);Alexandrium catenella;resting cyst;paralytic shellfish toxin (PST);Qinhuangdao6|0|1Updated：2023-05-20
- Abstract：Surface sediment samples were collected in three different functional sea areas in Qingdao coast, East China, including the inner Jiaozhou Bay, the Laoshan Coast, and the Amphioxus Reserve area. Diversity and community structure of eukaryotic algae especially those of phytoplankton resting stages were assessed by metabarcoding V4 region of the 18S rDNA. Biogenic elements including total organic carbon (TOC), organic matter (OM), total nitrogen (TN), total phosphorus (TP), and biogenic silicon (BSi) were analyzed. A total of 1 496 eukaryotic operational taxonomic units (OTUs) were measured, including 207 algal OTUs, which contributed to 13.84% of the total OTUs. Ninety-eight species in 8 phyla, 24 classes of eukaryotic algae were detected. Among them, 47 species have been reported to form resting stages, and 12 species are firstly recorded in Chinese coastal waters. Dinoflagellates dominated in both DNA reads and OTU richness, which contributed to 73.02% and 61.35% of the eukaryotic algal sequences and OTU richness, respectively. DNA reads, OTU richness and alpha diversity indexes of eukaryotic algae were higher in the Laoshan Coast, and lower in Jiaozhou Bay. Eukaryotic algal community differed in the three sea areas, which was dominated by chrysophytes in Jiaozhou Bay, by dinoflagellates in the Laoshan Coast, and co-dominated by dinoflagellates and chrysophytes in the Amphioxus Reserve area. Clustering analysis showed that the Laoshan Coast and the Amphioxus Reserve area are clustered together, while Jiaozhou Bay is clustered separately. Thirty-six harmful algal bloom (HAB) species were detected, and 10 species have been reported to form blooms in Jiaozhou Bay and the Qingdao coast before. Some of these species occurred widely and dominantly in this study, suggesting high potential risk of HABs in the Qingdao coastal area.Keywords：benthic microalgae;18S rDNA;metabarcoding;resting stages;Jiaozhou Bay;Yellow Sea6|0|0Updated：2023-05-20
Continued from the back cover
- Abstract：Molecular investigations have raised concerns about the ecological risks of green tides caused by alien Ulva species in new habitats. The green tide-forming species U. californica Wille was generally considered to be native to North America, but new records have been widely reported in Europe, Asia, and Oceania in recent decades, indicating a strong dispersal capacity of the species. In this study, the first record of U. californica on the coastline of mainland China was reported, following a combined identification with multi-molecular markers and morphological characterization. It was shown that this species has a discontinuous distribution pattern along the coast of mainland China, with northern populations in the Yellow Sea and southern populations in the East China Sea and South China Sea. According to results of examination for life cycles and identification with mating type (MT) genetic markers, it was indicated that all U. californica samples were male gametophytes, and reproduced themselves through parthenogenesis solely. Combined with the fact that southern and northern populations are highly genetically identical, here we believed that U. californica was a recent alien species to mainland China with a rapid local spread. This finding provided evidences that the ability to reproduce in a variety of ways may play an important role in the spread of Ulva species, as well as essential basic data for marine risk management of green tides in China. In addition, according to the phylogeographic analysis, the possible geographical origin and global dispersal routes of U. californica were also proposed.Keywords：discontinuous distribution;mainland of China;new record;non-indigenous species;parthenogenesis;Ulva californica6|0|0Updated：2023-05-20
- Abstract：The large-scale green tide caused by Ulva has occurred successively in the Yellow Sea since 2007, and new events of green tide also continued to appear in nearby sea areas, indicating an undergoing rapid development of occurrence patterns for harmful macroalgal blooms (HMBs) along coastal China. In August 2021, a green tide occurred for the first time in Bayuquan sea area of Yingkou city, Liaoning Province in the Bohai Sea. In this study, morphological and molecular approaches were used to identify the causative species as U. meridionalis, an alien subtropical alga previously found to dominate green tides in the South China Sea. According to the hydrological data of Bayuquan in summer 2021, combined with morphological and developmental observations for this alga, we hypothesized that the disturbance caused by the typhoon In-Fa might have detached the local U. meridionalis from substrates, especially for those thalli with poorly developed holdfasts, and the ensuing wave-free period with unusually high temperature, which fell in the reported optimum growth temperature for U. meridionalis, might have provided the favorable conditions for the final bloom of the floating seaweeds. This is the first report on the bloom of subtropical U. meridionalis in the north temperate sea zone, indicating that the ecological risk of causing green tides in the future by this rapidly spreading species deserves high attention.Keywords：Bohai Sea;green tide;holdfast;alien species;Ulva meridionalis;Yingkou6|0|1Updated：2023-05-20
- Abstract：Large-scale Ulva-caused green tides has posed various environmental and ecological problems as well as economic consequences. It is important to identify them accurately and quickly. The current universal markers based on ITS, rbcL, and 5S spacer sequences were defective to distinct closely related species in the genus of Ulva. In this study, by investigating the intergenic regions of chloroplast (cp) genome, a novel marker of c15 (based on ycf3- rps7) were reliable for discrimination of Ulva species. Notably, the resolution of c15 was suitable for resolve the closely related species of U. linza and U. prolifera, which may provide tools for deciphering the blooming mechanisms of green tides.Keywords：Ulva;linza-procera-prolifera (LPP) complex;molecular makers;ycf3-rps7 region6|0|0Updated：2023-05-20
- Abstract：The green seaweeds Ulva linza and U. prolifera are closely related species. They usually co-occur widely and have important ecological significance as primary producers thriving in the intertidal zone. In the Yellow Sea, a genetically unique floating ecotype of U. prolifera even bloomed to cause serious green tides. However, there is still a lack of appropriate molecular markers to distinguish these two species, partially due to limited evaluations on the intraspecific variations in U. prolifera among different ecotypes. Since organelle genomes could provide rich genetic resources for phylogenetic analysis and development of genetic markers, in this study, the chloroplast genome from one attached population of U. prolifera was completely sequenced, and comparative genomic analyses were performed with other existing chloroplast genomes from U. linza and the floating ecotype of U. prolifera. The results showed that in spite of the high level of collinearity among three genomes, there were plenty of genetic variations especially within the non-coding regions, including introns and gene spacer regions. A strategy was proposed that only those signals of variation, which were identical between two ecotypes of U. prolifera but divergent between U. linza and U. prolifera, were selected to develop the interspecific markers for U. linza and U. prolifera. Two candidate markers, psaB and petB, were shown to be able to distinguish these two closely related species and were applicable to more attached populations of U. prolifera from a wide range of geographical sources. In addition to the interspecific marker, this study would also provide resources for the development of intraspecific markers for U. prolifera. These markers might contribute to the surveys for Ulva species composition and green tide monitoring especially in the Yellow Sea region.Keywords：chloroplast genome;comparative genomics;intraspecific variation;Ulva linza;Ulva prolifera6|0|0Updated：2023-05-20
Marine harmful macroalgae
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Dynamics of
Phaeocystis globosa bloom and implications for its seed sources in the Beibu Gulf, ChinaAbstract：Algal blooms of haptophyte Phaeocystis globosa have been recorded in the Beibu Gulf, South China Sea (SCS) since 2011. Recent evidence suggests that Type Ⅰ and Type Ⅳ are the two dominant genotypes of P. globosa coexisting in this area, and their marker pigment profiles, colony sizes, and genetic information differ. Two genotype-specific quantitative polymerase chain reaction (qPCR) assays were used to clarify the distribution and dynamics of P. globosa bloom in the Beibu Gulf from November 2018 to February 2019. Results show that the patterns of spatial-temporal distribution of Type Ⅰ and Type Ⅳ were similar, the abundance of Type Ⅳ was higher than that of Type Ⅰ during the algal bloom, and thus Type Ⅳ cells dominated the P. globosa bloom in winter 2018. The relationships between environmental factors and P. globosa abundance indicated that temperature and nitrate were critical to the distribution and dynamics of P. globosa blooms in this area. The distribution of P. globosa cells in different water masses before the bloom revealed that the westward water via the Qiongzhou Strait, the SCS bottom water, and the current in the northwestern waters of Hainan Island could transport P. globosa cells into the Beibu Gulf serving as the seed sources triggering the intense blooms in the Beibu Gulf.Keywords：Phaeocystis globosa;harmful algal bloom (HAB);Beibu Gulf;environmental factor;seed source6|0|0Updated：2023-05-20 - Abstract：Toxic and harmful algal blooms are usually more frequent in mariculture areas due to the abundant trophic conditions. To investigate the relationship between toxic and harmful microalgae and environmental factors, we set up 12 stations near three mariculture regions (Gouqi Island, Sandu Bay, and Dongshan Bay) in the East China Sea. We collected samples from all four seasons starting from May 2020 to March 2021. We identified 199 species belonging to 70 genera, of which 38 species were toxic and harmful, including 24 species of Dinophyceae, 13 species of Bacillariophyceae, and 1 species of Raphidophyceae. The species composition of toxic and harmful microalgae showed a predominance of diatoms in the summer (August), and dinoflagellates in the spring (May), autumn (November), and winter (March). The cell densities of toxic and harmful microalgae were higher in summer (with an average value of 15.34×103 cells/L) than in other seasons, 3.53×103 cells/L in spring, 1.82×103 cells/L in winter, and 1.0×103 cells/L in autumn. Pseudonitzschia pungens, Prorocentrum minimum, Paralia sulcata, and Prorocentrum micans were the dominant species and were available at all 12 stations in the three mariculture areas. We selected 10 toxic and harmful microalgal species with frequency >6 at the survey stations for the redundancy analysis (RDA), and the results show that NO3-, water temperature (WT), pH, DO, and NO3- were the main factors on distribution 2 of toxic and harmful microalgae. We concluded that the rich nutrient conditions in the East China Sea mariculture areas increased the potential for the risk of toxic and harmful microalgal bloom outbreaks.Keywords：phytoplankton;toxic and harmful microalgae;environmental factors;mariculture areas;East China Sea (ECS)6|0|0Updated：2023-05-20
- Abstract：Alexandrium blooms in the northwest area of the Bohai Sea (Qinhuangdao coastal area), China, produce large amounts of toxins that could be enriched in shellfish and consequently harm human bodies. To understand the succession of the phytoplankton community structure during Alexandrium bloom events in the northwest area of the Bohai Sea off Qinhuangdao from April 2 to May 7, 2019, microscopy observations and high-performance chromatography (HPLC)-pigment analysis were performed. Sixty species of phytoplankton were identified, mainly diatoms and dinoflagellates. The abundance of Alexandrium reached the maximum on April 16 (3.3×103 cells/L). HPLC-pigment CHEMTAX analysis showed that the phytoplankton community was composed mainly of diatoms, dinoflagellates, prasinophytes, and cryptophytes. Diatoms were the main contributor to the total Chl-a pool. There was a downward trend for the proportion of diatom biomass to the total Chl-a pool, followed by an upward trend. The proportion of dinoflagellate biomass showed the opposite trend, whereas that of the prasinophyte biomass presented an obvious increasing trend. Temperature, nutrients, and nutrient structures were the main factors on the distribution of different phytoplankton groups in the study area as shown in the redundancy analysis. This work illustrates the succession of phytoplankton community structures during Alexandrium blooms and provided a theoretical basis for studies on the mechanism underlying the outbreak of harmful algal blooms in sea areas.Keywords：Alexandrium bloom;phytoplankton population;environmental factor;high-performance chromatography (HPLC)-CHEMTAX;phytoplankton pigment;Qinhuangdao6|0|1Updated：2023-05-20
- Abstract：With the development of industrialization and aquaculture in Jiangsu and Shandong Provinces along the South Yellow Sea coast, China, eutrophication has greatly intensified in the region, resulting in frequent occurrence of diverse harmful algal blooms. An algal bloom formed by a chain-forming dinoflagellate species was recorded in the Haizhou Bay, South Yellow Sea, in September 2020. The causative species was isolated and studied in morphology, molecular phylogeny, pigment profile, presence of paralytic shellfish toxins, and acute toxicity. The loop-shaped apical groove running anticlockwise around the apex, the presence of peridinin as characteristic pigment, as well as a single phylogenic clade of 28S ribosomal DNA (100% posterior probability), defined this species as Gymnodinium impudicum, a non-toxic species that exhibited no obvious biotoxicity to the rotifer Brachionus plicatilis, the copepod Artemia salina, and the shrimp Neomysis awatschensis. Gymnodinium impudicum is typically distributed in coastal waters with high nitrate concentrations, where it reaches a maximum density of 2.6×105 cells/L. This is the first report of a G. impudicum bloom in the Yellow Sea; however, G. impudicum blooms may have been misidentified or underreported in Haizhou Bay due to the species morphological similarity with G. catenatum. A combination of multiple methods is recommended to accurately identify new algal bloom species.Keywords：Gymnodinium impudicum;harmful algal bloom;Yellow Sea;Haizhou Bay;species identification;eutrophication7|0|0Updated：2023-05-20
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Variations in nano- and pico-eukaryotic phytoplankton assemblages in the Qinhuangdao green-tide area
Abstract：Qinhuangdao coastal waters have been frequently hitting by nano- and pico-eukaryotic phytoplankton (NPEP) blooms and green tides (macroalgal blooms) in the recent decade. However, understanding about the impacts of environmental factors and the green tides on the NPEP assemblages in this area is limited. In this study, the composition of NPEP assemblages and their variations were analyzed via amplicon sequence variants (ASVs) assay based on amplicon high-throughput sequencing data with the 18S V4 region as a targeted gene in the Qinhuangdao green-tide area during the green tide. Consequently, average NPEP effective sequences and ASVs of 178 000 and 200 were obtained from each sample, respectively. Although there were 25 classes, 110 genera, and 97 species of NPEP were identified and annotated, the proportions of annotated ASVs at genus and species levels were only 44.7% and 17.8%, respectively. The NPEP communities had a seasonal succession from diatom-dominated to dinoflagellate-dominated. During the three investigations, Skeletonema, Karlodinium, and Gonyaulax were the most dominant genera in May, August, and September, respectively. Species diversity and the abundance of NPEP communities could be increased by a high content of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) but inhibited by low dissolved inorganic phosphorus content. The outbreak of green tides could alter the composition and content of nutrients and accelerate the succession of the NPEP communities from diatom-dominated to dinoflagellate-dominated under the background of a seasonal increase in seawater temperature. These results preliminarily revealed the impacts of the recurrent occurrences of green tides on the NPEP assemblages in the Qinhuangdao green-tide area exhibiting high DON content and dissolved inorganic nitrogen/phosphorus ratio.Keywords：nano- and pico-eukaryotic phytoplankton;high-throughput sequencing;green tide;eutrophication;Qinhuangdao6|0|0Updated：2023-05-20 - Abstract：Large-scale green tides occur frequently in summer in the Yellow Sea in recent decade. Micropropagules, providing "seeds" for the seaweeds, play an important role in the formation of green tide. We studied the distribution pattern and genetic composition of the Ulva micro-propagules in the Yellow Sea during and after the green tide in 2019. In April, a great amount of Ulva micro-propagules was detected in the Subei Shoal, with the average density of 908 inds./L, being similar to that of previous studies. U. prolifera was found out at a low percentage (4%), and 25% of them were positive when tested by the specific marker for the floating ecotype. The percentage of U. prolifera was obviously lower than that in the same season from 2009 to 2016. Therefore, the quantity of U. prolifera micro-propagules sharply decreased. Significant variation in composition of the micro-propagules in Subei radial sand ridges was revealed in the background of the alternation of macroalgal tides in the Yellow Sea in the latest years. During the green tide in June and July, Ulva micro-propagules were detected from some nearshore sites where the floating seaweeds distributed, and U. prolifera was the dominate species. In September, when the green tide ended, no Ulva micro-propagule was detected from the open sea area of the Yellow Sea. It is indicated that the green algae micro-propagules were unlikely to exist in the open water of the Yellow Sea for a long time according to the large-scale surveys. The mechanism of preserving micro-propagules in Subei radial sand ridges, and the destination of U. prolifera micro-propagules in the open sea area of the Yellow Sea after green tide deserves further study.Keywords：green tide;Ulva prolifera;micro-propagule;Yellow Sea6|0|0Updated：2023-05-20
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Bloom dynamics
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