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Map of 23 collection sites along the coast of Jeju Island in Korea. The collection site numbers are given in bold. Those numbers cross-reference to Table 1 and S1 Table. Names of these sampling sites are given in S1 Table. The number of species found in each site, based on our molecular analyses is shown within parentheses.

Map of 23 collection sites along the coast of Jeju Island in Korea. The collection site numbers are given in bold. Those numbers cross-reference to Table 1 and S1 Table. Names of these sampling sites are given in S1 Table. The number of species found in each site, based on our molecular analyses is shown within parentheses.

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Article
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Species diversity in the genus Ulva remains understudied worldwide. Using molecular analyses we investigated the species composition, diversity, distribution, and relative frequencies of the genus Ulva along the entire coast of Jeju Island, off the southern tip of Korea. Species identification was performed for 215 samples collected from 23 sites,...

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... Jeju Island, which is located approximately 150-200 km off the southern coast of the Korean Peninsula (Fig 2). Jeju Island is known as one of the fastest warming regions worldwide; the sea surface temperature around this region has risen by 1.6˚C-2.1˚C ...
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... species, which included only from the GenBank database, were identified as four clusters. All collected Ulva specimens analyzed in this study were finally grouped into nine Ulva species clusters, which was consistent with the findings of the species identification based on the phylogenetic analyses (Table 2; Fig 2; S3 Table). ...
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... find that there are no sites where all 9 Ulva species co-occurred and no more than four species were observed within each site (Table 1; Fig 2). However, more abundant species tended to distribute geographically more widely. ...
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... Jeju Island, which is located approximately 150-200 km off the southern coast of the Korean Peninsula (Fig 2). Jeju Island is known as one of the fastest warming regions worldwide; the sea surface temperature around this region has risen by 1.6˚C-2.1˚C ...
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... species, which included only from the GenBank database, were identified as four clusters. All collected Ulva specimens analyzed in this study were finally grouped into nine Ulva species clusters, which was consistent with the findings of the species identification based on the phylogenetic analyses (Table 2; Fig 2; S3 Table). ...
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... find that there are no sites where all 9 Ulva species co-occurred and no more than four species were observed within each site (Table 1; Fig 2). However, more abundant species tended to distribute geographically more widely. ...

Citations

... At present, there is still a lack of research on the relationship between nearshore attached green macroalgae, nearshore floating green macroalgae, and large-scale green tides. Previous studies have investigated and analyzed the diversity of nearshore green macroalgae species (Loughnane et al., 2008;Han et al., 2013;Zhang et al., 2017a;Kang et al., 2019). Due to the morphological and phenotypic plasticity of Ulva in different environments (Gao et al., 2016(Gao et al., , 2017b, DNA barcoding is the most widely used method for distinguishing Ulva species. ...
... Zhang et al. (2017a) used internal transcribed spacers (ITS) and the 5S ribosomal intergenic spacer to identify attached and floating green macroalgae in the Neopyropia aquaculture area of Rudong, Jiangsu Province, China. Kang et al. (2019) used tufA and ITS to analyze Ulva diversity, species composition, and distribution along the coast of Jeju Island, South Korea. Liu et al. (2022) used ITS, the 5S ribosomal intergenic spacer, and the mitochondrial interstitial region between the rps2 and trnL region (rps2-trnL) gene spacer sequences to analyze Ulva sp. ...
Article
Green tides have occurred in the Southern Yellow Sea (SYS) for 16 consecutive years, causing widespread concern. Attached and floating green macroalgae have been observed in Binhai Harbor, Jiangsu Province, China, in the SYS. This study used morphological analysis, and internal transcribed spacers and rps2-trnL molecular identification methods, to analyze the species composition and biomass of green macroalgae along the Binhai Harbor coast. Six species of green tide algae (Ulva prolifera, Ulva meridionalis, Ulva linza, Ulva flexuosa, Ulva californica, and Ulva intestinalis) were identified, in addition to Blidingia sp. The discovery of U. californica is the first report of this species off the coast of Jiangsu Province. The floating green macroalgae along the Binhai Harbor coast originated from attached green macroalgae in Binhai Harbor, and a small number of the attached algae were closely related to the large-scale floating U. prolifera in the SYS. Moreover, in December 2021, February 2022, and April 2022, the total biomass of attached green macroalgae in Binhai Harbor was 25.600, 10.767, and 25.867 t, respectively , of which the U. prolifera biomass was 10.697, 8.709, and 4.185 t, respectively. This study proved Bin-hai Harbor may not be an important source of green tide in the SYS.
... As a consequence of the difficulties in morphological identification, the study of the species composition and its importance in the development of these blooms has remained overlooked for long. However, the development of new molecular identification tools allows us to overcome these taxonomic challenges (Kang et al. 2019, Steinhagen et al. 2019, Fort et al. 2021) and suggests that multispecific green tides are more common than previously thought (Nelson et al. 2008, Guidone and Thornber 2013. ...
... persistence and stability of green tides could be enhanced by an increase in the number of opportunistic species able to produce macroalgal blooms, as explained by the diversity-stability hypothesis (McCann 2000). The increasing number of studies reporting the coexistence of several species in green tides (Guidone et al. 2013, Kang et al. 2019, the occurrence of temporal and spatial successions between bloom-forming species as a result of environmental gradients or disturbances (Lavery et al. 1991, Nelson et al. 2008, or the increased extension of macroalgal blooms due to the arrival of alien species (Yabe et al. 2009, Bermejo et al. 2020 also support this hypothesis. The understanding of the biotic interaction, positive and negative, between these species, and the density dependent mechanisms regulating their interactions (e.g., competition for resources, allelopathic compounds, and mutual protection) will be useful for the implementation of effective suitable environmental management strategies or for Ulva aquaculture, as this species is cultivated for commercial or bioremediation purposes (e.g., IMTA). ...
Article
The generalized use of molecular identification tools indicated that multi‐specific green tides are more common than previously thought. Temporal successions between bloom forming species in a seasonal basis was also revealed in different cold temperate estuaries, suggesting a key role of photoperiod and temperature controlling bloom development and composition. According to the Intergovernmental Panel on Climate Change, water temperatures are predicted to increase around 4°C by 2100 in Ireland, especially during late spring coinciding with early green tide development. Considering current and predicted temperatures, and photoperiods during bloom development, different ecophysiological experiments were developed. These experiments indicated that the growth of Ulva lacinulata was controlled by temperature, while U. compressa was unresponsive to the photoperiod and temperatures assayed. Considering a scenario of global warming for Irish waters, an earlier development of bloom is expected in the case of U. lacinulata. This could have significant consequences for biomass balance in Irish estuaries and the maximum accumulated biomass during peak bloom. The observed seasonal patterns and experiments also indicated that U. compressa may facilitate U. lacinulata development. When both species were co‐cultivated, the culture performance showed intermediate responses to experimental treatments in comparison with monospecific cultures of both species.
... Furthermore, rps2-trnL can also effectively distinguish U. prolifera, U. flexuosa, U. compressa, and U. linza, which are commonly found in SYS green tides [17]. While DNA-based approaches provide a better understanding of species boundaries, they are associated with issues such as conflicts between different methods or markers and species-level differences indicated by the level of uncertain sequence divergency [18,19]. In addition to morphology-based taxonomy, crossing experiments have been used to test biological species concepts and refine species boundaries, with considerable application in Ulva. ...
Article
Full-text available
Green tides are a serious global ecological disaster; the largest occur in the Southern Yellow Sea (SYS). Early-stage green tides in the SYS are composed of four species (Ulva prolifera, Ulva flexuosa, Ulva linza, and Ulva compressa). We found that U. aragoensis is a constituent species of green tides in the SYS based on molecular data. Furthermore, this study re-evaluated the proportion of U. aragoensis in green tides and found that it was more prevalent in micro-propagules cultured from surface seawater during an early-stage green tide in 2021. The internal transcribed spacers, tufA, 18S, rbcL, large subunit, psbA, and rps2-trnL gene sequences were compared; the tufA and rbcL gene sequences were the most suitable DNA barcodes for distinguishing U. aragoensis. A haplotype analysis of the sequences of floating U. aragoensis and its micro-propagules was performed to study the correlation between green tide macroalgae and micro-propagules; close haplotype similarities occurred between them. This study further clarified the species composition of SYS green tides and provided a reference for assessing the relationship between micro-propagules and green tide macroalgae.
... The majority of marine Ulva species in Vietnam turn out to be cosmopolitan species, of which U. ohnoi and U. tepida are the most common species found in Vietnam (Fig. S20a, b). Other species, U. spinulosa and Ulva VN sp6, were recorded from the Pacific basin (e.g., Japan (Shimada et al. 2003), South Korea (Kang et al. 2019), Hawaii (O'Kelly et al. 2010 and China (MF139302)). Ulva kraftiorum was, up to now, only known from Western Australia (Kraft et al. 2010). ...
Article
Species diversity of Ulva in Vietnam was investigated using three commonly used genetic markers, the nuclear encoded rDNA ITS region and the plastid encoded rbcL and tufA genes. Single locus species delimitation methods, complemented with morphological and ecological information resulted in the delimitation of 19 species. This diversity is largely incongruent with the traditional understanding of Ulva diversity in Vietnam. Only four species identified in this study, U. lactuca, U. reticulata, U. spinulosa, and U. flexuosa, have been previously reported, and seven species, U. ohnoi, U. tepida, U. chaugulii, U. kraftiorum, U. meridionalis, U. limnetica, and U. aragoënsis, are recorded for the first time from Vietnam. Seven genetic clusters could not be associated with species names with certainty. A new species, U. vietnamensis, is described from marine to brackish coastal areas from southern Vietnam based on its morphological and molecular distinctiveness from the currently known Ulva species. A comparison with recent molecular‐based studies of Ulva diversity showed that species composition in Vietnam is similar to that of adjacent countries, including Japan, China, as well as Australia. Our study emphasizes the importance of molecular data in the assessment of Ulva diversity, and indicates that a lot of diversity may still remain to be discovered, especially in tropical regions.
... californica was initially only found along the Pacifi c coast of North America (Scagel et al., 1989;Hansen, 1997). With the emergence of its new molecular records in Europe (Hayden and Waaland, 2004), Asia (Ogawa et al., 2013;Kang et al., 2014Kang et al., , 2019, and Oceania (Heesch et al., 2009;Kirkendale et al., 2013), U . californica has been reported as a potential alien or non-indigenous species (NIS) in Mediterranean (Wolf et al., 2012), Japan (Kawai et ...
Article
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.
... As their morphological features are very limited and unstable, which are sensitive to various factors such as salinity (Blomster et al., 1998), temperature (Blomster et al., 2002), and associated bacteria (Kessler et al., 2018), the morphological identifi cation for Ulva are always very diffi cult (Blomster et al., 2373 No.6 LIU et al.: Comparative chloroplast genomes of U. prolifera and U. linza 1999). The development of molecular approaches has signifi cantly improved this dilemma, resulting in the reconstruction of genera Ulva (Hayden et al., 2003), and identifi cation of some cryptic species (Hofmann et al., 2010), but some of related species still lack appropriate molecular markers to distinguish them from each other (Kang et al., 2019;Steinhagen et al., 2019). The type locations for U . ...
Article
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.
... In recent years, combining DNA sequences and morphoanatomy has become a standard approach in Ulva diversity studies Hayden and Waaland 2004;Loughnane et al. 2008;Shimada et al. 2008;Heesch et al. 2009;Kraft et al. 2010;Mares et al. 2011;Guidone et al. 2013;Kirkendale et al. 2013;Ogawa et al. 2013;Kiana et al. 2016;Hanyuda and Kawai 2018;Krupnik et al. 2018;Steinhagen et al. 2018b;Kang et al. 2019;Tonatiuh et al. 2019;Fort et al. 2020a;2022;Xie et al. 2020;Melton III and Lopez-Bautista 2021;Tran et al. 2021). Markers that are frequently used include the nuclear ribosomal internal transcribed spacer (nrDNA ITS), the plastid encoded gene ribulose-bisphosphate carboxylase (rbcL), and more recently the plastid translation elongation factor Tu (tufA). ...
... Markers that are frequently used include the nuclear ribosomal internal transcribed spacer (nrDNA ITS), the plastid encoded gene ribulose-bisphosphate carboxylase (rbcL), and more recently the plastid translation elongation factor Tu (tufA). The majority of studies defined species boundaries based on the phylogenetic species concept (i.e., based on topological criteria such as monophyly and distinctiveness from sister species expressed as branch lengths or genetic distances, and concordance between different markers) (Steinhagen et al. 2018a;Kang et al. 2019;Fort et al. 2020a;Tran et al. 2021). Algorithmic methods, developed to assist species delimitation based on DNA information, can reduce investigator-driven bias and have shown to be effective in drawing lines among species in other macroalgal groups and have also been explored in Ulva (Steinhagen et al. 2018a;Kang et al. 2019;Fort et al. 2020a;Tran et al. 2021). ...
... The majority of studies defined species boundaries based on the phylogenetic species concept (i.e., based on topological criteria such as monophyly and distinctiveness from sister species expressed as branch lengths or genetic distances, and concordance between different markers) (Steinhagen et al. 2018a;Kang et al. 2019;Fort et al. 2020a;Tran et al. 2021). Algorithmic methods, developed to assist species delimitation based on DNA information, can reduce investigator-driven bias and have shown to be effective in drawing lines among species in other macroalgal groups and have also been explored in Ulva (Steinhagen et al. 2018a;Kang et al. 2019;Fort et al. 2020a;Tran et al. 2021). DNA-based studies revealed a considerable conflict between traditional and phylogenetic species definitions, including cryptic diversity. ...
Article
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The green seaweed Ulva is important from ecological and economic perspectives, but the identification of species is often problematic. Here we assessed and discussed different perspectives to establish a stable taxonomic framework for Ulva, which will benefit both ecological and applied research. We evaluated (1) the performance of commonly used DNA-barcode markers (ITS rDNA, rbcL, and tufA) using species delimitation methods (PTP and GMYC), (2) the usage of species names in the literature, and (3) the geographic coverage of genetic data to identify poorly sampled regions. Species delimitation employing the tufA gene was the most consistent across methods. Not surprisingly, DNA-based species delimitation was often in disagreement with traditional morphology-based species definitions. Biological species concepts, where tested, proved to be generally narrower than DNA-based species delimitation. Although the use of molecular markers has greatly improved our view of Ulva diversity, the names associated with DNA sequences in public databases are often unreliable, complicating species identification. Recently, sequencing type materials has considerably reduced the gap between DNA sequence data and Linnaean names, but our knowledge on Ulva diversity remains inadequate, especially in tropical regions. Perspectives for Ulva taxonomy include the consistent use of multiple DNA-barcode markers assisted by species delimitation methods, applications of genomic data, and crossing experiments. To arrive at a stable nomenclature, we outline the benefits and shortcomings of adhering to the rules and practices of the International Code of Nomenclature for algae, fungi, and plants, for example, by sequencing name-bearing types and discuss alternative approaches.
... Compared with some previous research results the number of species in these studied sites in Hai Phong is relatively large (Tab 5). Taiwan (1987) 15 Lewis et al., [26] Gujarat Coast-India (2009) 10 Jha et al., [27] Qingdao-China (2011) 8 Du et al., [28] Hainan Island-China (2017) 5 Titlyanov et al., [29] Jeju Island-Korea (2019) 9 Kang et al., [30] Asia (2020) 56 ...
Article
Full-text available
The knowledge of marine algae species composition is imperative not only for understanding the structure, function and biogeographical affinities but also for planning strategies for marine algae conservation and management. This study was carried out to determine the diverse species and evaluate some use-values of green macroalgae from genus Ulva in Hai Phong, where many different habitats such as estuarine floodplains, lagoons or small bays and diverse in the bottom (hard, sandy, sandy-mud bottom). Ulva samples were collected at 11 sites in 5 areas in 2021. Based on the results of species composition, were identified 11 species of the genus Ulva. The species composition of the genus Ulva in Hai Phong accounted for 73.3% of the total species recorded in Vietnam; accounting for 19.6% of the total number of Asian species, and 12.9% of the total number of Ulva species in the world. The Cluster and MDS (Multi-Dimensional Scaling analysis) on the similarity in vertical distribution and geographical distribution among the studied species. Based on the active ingredients and uses value, the studied determined 9 species of genus Ulva in Hai Phong were identified with economic value.
... Since then, some studies argue that the use of temperate and boreal species epithets to name tropical and subtropical Ulva species is inappropriate (O'Kelly et al., 2010) and that the latter often correspond to new cryptic or closely resembling species (Heesch et al., 2009;Kraft et al., 2010). Species identification based on morphology is therefore noted as a source of misidentification, and several authors have highlighted the need for molecular-based species determination (Guidone et al., 2013;Wichard et al., 2015;Kang et al., 2019). The combination of both molecular and morphological species determination allows highlighting species complexes and accurately refining species boundaries, as in the case of the linza-prolifera-procera (LPP) complex (Shimada et al., 2008) and the "European clade" of U. prolifera (Cui et al., 2018). ...
... Through this study, we confirmed that Ulva species show a strong intraspecific morphological plasticity (e.g. size cells difference) that made the morphological identification challenging, and it was difficult to determine clear diagnostic taxonomic characters, as highlighted in previous works (Kraft et al., 2010;Guidone et al., 2013;Kirkendale et al., 2013;Wichard et al., 2015;Kang et al., 2019). For example, the number of pyrenoids, which has long been considered an important discriminatory character (Bliding, 1968;Koeman & van den Hoek, 1981;Coat et al., 1998), was found to be unreliable to accurately delimit Ulva species (Tanner, 1986;Phillips, 1988), as it may fluctuate significantly among seasons for a given species (Malta et al., 1999;on Ulva lactuca). ...
Article
Ulva is a green macroalgal genus with rich species diversity and worldwide distribution. While current knowledge on Ulva diversity focuses on temperate regions, genetic and morphological data in tropical and subtropical areas are scarce and the species richness is not clearly defined. The genus is known for its bloom-forming ability that can induce green tides leading to severe environmental and economic damage. In the last two decades, several important blooms of Ulva spp. have occurred in New Caledonia, requiring further investigations to identify the species involved. As knowledge of New Caledonian Ulva diversity is limited, an update to the Ulva spp. inventory in the area is essential. Based on Ulva specimens collected throughout New Caledonia (Grande Terre, Isle of Pines and Loyalty Islands), we (1) reassessed species diversity using species delimitation methods, (2) analysed morpho-anatomical characters to identify species and/or enrich their diagnosis, and (3) reconstructed a multilocus phylogeny (ITS, rbcL, tufA) of the genus. We found 21 secondary species hypotheses (SSHs) among our dataset, from which five were successfully assigned to U. lactuca, U. ohnoi, U. tepida, U. meridionalis and U. taeniata. Ten SSHs were defined as new species for which we provided taxonomic description, and six other SSHs were singletons that will need to be data-enriched for better interpretation. Our concatenated multilocus matrix included 61 Ulva species. Of these, 15 species were found in New Caledonia and were moderately to strongly supported. Among the Ulva species found in New Caledonia, seven are known to be bloom-forming which highlights the need for strict regulation and regular monitoring of water quality, particularly in areas exposed to strong nutrient input where these species can form green tides.
... Genus Ulva belongs to the family Ulvaceae which is comprised of cosmopolitan and abundant green macroalgae (approximately 100 species) that inhabit freshwater as well as saline shallow environments [7][8][9]. This algal genus is used as a source of traditional food in many Asian countries. ...
Article
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Coronavirus disease 2019 (COVID-19) is the disease caused by the virus SARS-CoV-2 responsible for the ongoing pandemic which has claimed the lives of millions of people. This has prompted the scientific research community to act to find treatments against the SARS-CoV-2 virus that include safe antiviral medicinal compounds. The edible green algae U. lactuca. is known to exhibit diverse biological activities such as anti-influenza virus, anti-Japanese encephalitis virus, immunomodulatory, anticoagulant, antioxidant and antibacterial activities. Herein, four new ceramides in addition to two known ones were isolated from Ulva lactuca. The isolated ceramides, including Cer-1, Cer-2, Cer-3, Cer-4, Cer-5 and Cer-6 showed promising antiviral activity against SARS-CoV-2 when investigated using in silico approaches by preventing its attachment to human cells and/or inhibiting its viral replication. Cer-4 and Cer-5 were the most effective in inhibiting the human angiotensin converting enzyme (hACE)–spike protein complex which is essential for the virus to enter the human host. In addition to this, Cer-4 also showed an inhibition of the SARS-CoV-2 protease (Mpro) that is responsible for its viral replication and transcription. In this study, we also used liquid chromatography coupled to electrospray ionization high-resolution mass spectroscopy (LC–ESI–HRMS) to identify several metabolites of U. lactuca, including metabolites such as fatty acids, their glyceride derivatives, terpenoids, sterols and oxysterols from the organic extract. Some of these metabolites also possessed promising antiviral activity, as previously reported.