Pub Date : 2025-12-01Epub Date: 2025-10-10DOI: 10.1016/j.hal.2025.102999
Hao Chen , Haoluan Wang
Harmful algal blooms (HABs) have emerged as a critical environmental hazard in U.S. coastal waters, posing substantial risks to human health. This study examines six decades of HAB events (1960–2019) across 34 coastal counties in Florida, USA, to evaluate the relationship between HAB exposure and socio-demographic patterns. We further use the Gini coefficient to measure spatial disparities in exposure, with a particular focus on children and seniors, two groups especially vulnerable to environmental hazards. Our analysis reveals that HAB exposure is significantly linked to population decline and a reduced proportion of children in affected counties. In contrast, areas with greater HAB exposure tend to have a higher share of senior residents. Notably, spatial inequality is evident: counties with fewer children generally experience greater exposure, while those with more seniors face disproportionately higher exposure. These findings underscore the importance of addressing environmental justice in policy responses to HABs.
{"title":"Exposure to harmful algal blooms and socio-demographic patterns: Evidence from six decades of analysis in Florida, USA","authors":"Hao Chen , Haoluan Wang","doi":"10.1016/j.hal.2025.102999","DOIUrl":"10.1016/j.hal.2025.102999","url":null,"abstract":"<div><div>Harmful algal blooms (HABs) have emerged as a critical environmental hazard in U.S. coastal waters, posing substantial risks to human health. This study examines six decades of HAB events (1960–2019) across 34 coastal counties in Florida, USA, to evaluate the relationship between HAB exposure and socio-demographic patterns. We further use the Gini coefficient to measure spatial disparities in exposure, with a particular focus on children and seniors, two groups especially vulnerable to environmental hazards. Our analysis reveals that HAB exposure is significantly linked to population decline and a reduced proportion of children in affected counties. In contrast, areas with greater HAB exposure tend to have a higher share of senior residents. Notably, spatial inequality is evident: counties with fewer children generally experience greater exposure, while those with more seniors face disproportionately higher exposure. These findings underscore the importance of addressing environmental justice in policy responses to HABs.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102999"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-10-04DOI: 10.1016/j.hal.2025.102996
Di Jin , Avery Wang , Tracey Dalton
The frequency, intensity, and distribution of sargassum events have been rising in the Caribbean region in recent years causing social and economic disruptions. We develop estimates of the scale of annual economic impacts on local economies of sargassum events using multi-sector economic impact models for Puerto Rico, U.S. Virgin Islands, and coastal Florida. Using field observations from the Sargassum Watch database, we validate the current sargassum forecast in the region. We show that the forecast is performing well and that sargassum season has started earlier and lasted longer in recent years. The high-risk regions for sargassum inundation include Puerto Rico, U.S. Virgin Islands, and southeast coastal areas in Florida. Results of the study show that sargassum events are expected to cause significant negative economic impacts, in multimillion dollars each year, across the study regions, and the impact may be in billions of dollars along Florida’s Atlantic coast. These results provide important input to the planning process in deciding the investments in future sargassum response and cleanup. They can also facilitate targeted data collection and valuation efforts to develop more accurate measures of economic losses.
{"title":"Economic impacts of sargassum events in Puerto Rico, USVI, and coastal Florida","authors":"Di Jin , Avery Wang , Tracey Dalton","doi":"10.1016/j.hal.2025.102996","DOIUrl":"10.1016/j.hal.2025.102996","url":null,"abstract":"<div><div>The frequency, intensity, and distribution of sargassum events have been rising in the Caribbean region in recent years causing social and economic disruptions. We develop estimates of the scale of annual economic impacts on local economies of sargassum events using multi-sector economic impact models for Puerto Rico, U.S. Virgin Islands, and coastal Florida. Using field observations from the Sargassum Watch database, we validate the current sargassum forecast in the region. We show that the forecast is performing well and that sargassum season has started earlier and lasted longer in recent years. The high-risk regions for sargassum inundation include Puerto Rico, U.S. Virgin Islands, and southeast coastal areas in Florida. Results of the study show that sargassum events are expected to cause significant negative economic impacts, in multimillion dollars each year, across the study regions, and the impact may be in billions of dollars along Florida’s Atlantic coast. These results provide important input to the planning process in deciding the investments in future sargassum response and cleanup. They can also facilitate targeted data collection and valuation efforts to develop more accurate measures of economic losses.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102996"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The causes and mechanisms behind the influx of Sargassum in West Africa are poorly understood. The lack of effective management and control measures negatively impacts fishing, tourism, and marine life, leaving coastal communities with insufficient adaptive strategies. Research on Sargassum in the region is limited, which may lead to an underestimation of the socio-economic impacts of the blooms. Regional efforts led by the Abidjan Convention Secretariat and the United Nations Environment Programme (UNEP) have yet to yield significant results. There are considerable gaps in funding, policy prioritization, capacity building, and access to technology for early detection and monitoring, all of which are essential for implementing an effective Sargassum management strategy. Between 2018 and 2023, estimates of stranded biomass across the tropical Atlantic ranged from 2 to 10 million tons annually, with West Africa contributing a smaller yet still significant share. The biochemical composition of West African Sargassum demonstrates some economic potential, though heavy metal contamination and monitoring challenges limit use, necessitating the need for targeted management and detoxification efforts. While Sargassum presents opportunities for innovation and sustainable economic use, resources for developing regional value chains are scarce. West Africa could benefit from a more deliberate collaborative transatlantic partnership, as well as from strengthening an integrated regional strategy to create scalable and sustainable solutions in research, policy, management, and practical applications.
{"title":"Sargassum influxes in West Africa: Impacts, challenges, and prospects for sustainable management","authors":"Abdulwakil Olawale Saba , Kafayat Adetoun Fakoya , Lucette Adet , Hussein Aliu Sule , Akinloye Emmanuel Ojewole , Nimah Folake Osho-Abdulgafar","doi":"10.1016/j.hal.2025.102982","DOIUrl":"10.1016/j.hal.2025.102982","url":null,"abstract":"<div><div>The causes and mechanisms behind the influx of <em>Sargassum</em> in West Africa are poorly understood. The lack of effective management and control measures negatively impacts fishing, tourism, and marine life, leaving coastal communities with insufficient adaptive strategies. Research on <em>Sargassum</em> in the region is limited, which may lead to an underestimation of the socio-economic impacts of the blooms. Regional efforts led by the Abidjan Convention Secretariat and the United Nations Environment Programme (UNEP) have yet to yield significant results. There are considerable gaps in funding, policy prioritization, capacity building, and access to technology for early detection and monitoring, all of which are essential for implementing an effective <em>Sargassum</em> management strategy. Between 2018 and 2023, estimates of stranded biomass across the tropical Atlantic ranged from 2 to 10 million tons annually, with West Africa contributing a smaller yet still significant share. The biochemical composition of West African <em>Sargassum</em> demonstrates some economic potential, though heavy metal contamination and monitoring challenges limit use, necessitating the need for targeted management and detoxification efforts. While <em>Sargassum</em> presents opportunities for innovation and sustainable economic use, resources for developing regional value chains are scarce. West Africa could benefit from a more deliberate collaborative transatlantic partnership, as well as from strengthening an integrated regional strategy to create scalable and sustainable solutions in research, policy, management, and practical applications.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102982"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-09-26DOI: 10.1016/j.hal.2025.102990
Goh Onitsuka , Yutaka Yoshikawa
In the natural oceanic environment, microalgae occasionally form blooms with rates of increase that exceed their growth rates observed under laboratory conditions. We hypothesized that these elevated rates result from the accumulation caused by the combined effects of vertical swimming behavior and physical processes in the upper ocean. To test this hypothesis, we conducted numerical experiments using a Lagrangian particle-tracking model coupled with a hydrodynamic model. In a stratified ocean forced by sea surface winds and waves, we released particles simulating three fish- and shellfish-killing flagellates with different swimming speeds, namely Chattonella marina complex, Karenia mikimotoi, and Margalefidinium polykrikoides. Due to the interplay of diel vertical migration (DVM) and upper ocean turbulence, the particles accumulated vertically, exhibiting peak concentrations in the surface layer in the afternoon. These concentrations were several times higher than those observed at night or in the morning. Strong turbulence resulting from high wind speeds reduced surface accumulation and altered the depth of the maximum particle concentration compared to the still-water case (i.e., DVM only), especially for the slow-swimming Chattonella. Under low wind speeds (U10 = 1.5–2.0 m s−1), particles simulating the fast-swimming M. polykrikoides horizontally accumulated in streaks where surface flow converged, increasing particle concentration by up to one order of magnitude. This horizontal accumulation was caused by the balance between the upward swimming speed of M. polykrikoides and the downwelling associated with horizontal convergence driven by Langmuir circulations. Compared to algal growth, these vertical and horizontal accumulation processes occurred over shorter timescales, highlighting the importance of considering accumulation in monitoring harmful algal blooms.
在自然海洋环境中，微藻偶尔会形成水华，其增长速度超过在实验室条件下观察到的生长速度。我们假设这些升高的速率是由垂直游泳行为和上层海洋物理过程的综合影响引起的积累造成的。为了验证这一假设，我们使用拉格朗日粒子跟踪模型和流体动力学模型进行了数值实验。在受海面风和海浪影响的分层海洋中，我们释放了模拟三种不同游泳速度的杀死鱼类和贝类的鞭毛虫的粒子，即Chattonella marina complex， Karenia mikimotoi和Margalefidinium polykrikoides。由于日向垂直迁移（DVM）和上层海洋湍流的相互作用，颗粒垂直积累，下午在表层达到峰值。这些浓度比夜间或早晨观察到的浓度高几倍。与静水情况（即仅DVM）相比，由高风速引起的强湍流减少了表面积聚并改变了最大颗粒浓度的深度，特别是对于缓慢游动的查通菌。在低风速条件下（U10 = 1.5-2.0 m s−1），模拟快速游动的多角粒藻颗粒水平聚集成条状，使表面水流汇聚，颗粒浓度增加了一个数量级。这种水平积累是由多角藻的向上游动速度与Langmuir环流驱动的水平辐合下移之间的平衡造成的。与藻类生长相比，这些垂直和水平积累过程发生在更短的时间尺度上，突出了在监测有害藻华时考虑积累的重要性。
{"title":"Possible accumulation of harmful flagellates caused by interaction between vertical swimming and upper ocean turbulence","authors":"Goh Onitsuka , Yutaka Yoshikawa","doi":"10.1016/j.hal.2025.102990","DOIUrl":"10.1016/j.hal.2025.102990","url":null,"abstract":"<div><div>In the natural oceanic environment, microalgae occasionally form blooms with rates of increase that exceed their growth rates observed under laboratory conditions. We hypothesized that these elevated rates result from the accumulation caused by the combined effects of vertical swimming behavior and physical processes in the upper ocean. To test this hypothesis, we conducted numerical experiments using a Lagrangian particle-tracking model coupled with a hydrodynamic model. In a stratified ocean forced by sea surface winds and waves, we released particles simulating three fish- and shellfish-killing flagellates with different swimming speeds, namely <em>Chattonella marina</em> complex, <em>Karenia mikimotoi</em>, and <em>Margalefidinium polykrikoides</em>. Due to the interplay of diel vertical migration (DVM) and upper ocean turbulence, the particles accumulated vertically, exhibiting peak concentrations in the surface layer in the afternoon. These concentrations were several times higher than those observed at night or in the morning. Strong turbulence resulting from high wind speeds reduced surface accumulation and altered the depth of the maximum particle concentration compared to the still-water case (i.e., DVM only), especially for the slow-swimming <em>Chattonella</em>. Under low wind speeds (<em>U</em><sub>10</sub> = 1.5–2.0 m s<sup>−1</sup>), particles simulating the fast-swimming <em>M. polykrikoides</em> horizontally accumulated in streaks where surface flow converged, increasing particle concentration by up to one order of magnitude. This horizontal accumulation was caused by the balance between the upward swimming speed of <em>M. polykrikoides</em> and the downwelling associated with horizontal convergence driven by Langmuir circulations. Compared to algal growth, these vertical and horizontal accumulation processes occurred over shorter timescales, highlighting the importance of considering accumulation in monitoring harmful algal blooms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102990"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-09-24DOI: 10.1016/j.hal.2025.102987
Lu Sun , Huixia Geng , Qingchun Zhang , Zhenfan Chen , Chao Liu , Fanzhou Kong , Rencheng Yu
Since 2009, brown tide-causing pelagophyte Aureococcus anophagefferens has recurrently impacted northern Chinese coastal waters. Previous observations suggest elevated abundances of A. anophagefferens occur in specific regions of the Yellow Sea (YS) where the decomposition of Ulva prolifera green tides during late summer, implying supportive role on its growth for green algae decomposition. However, the complex hydrodynamic processes in these areas complicate the disentanglement of the effects of green tide decomposition and hydrodynamic influences. In this study, quantitative PCR and environmental analyses were employed to examine the spatial distribution, interannual variations, and environmental drivers of A. anophagefferens during late summers in 2016, characterized by a high-intensity green tide, and 2017, marked by a low-intensity green tide. A. anophagefferens exhibited a vertically spindle-shaped distribution with peak cell densities at the deep chlorophyll maximum layer, primarily along the Shandong Peninsula and in the eastern YS. Notably, cell abundances in 2016 were significantly higher than those in 2017, linking to increased ammonium, phosphate, and dissolved organic matter resulting from green tide decomposition. Hydrodynamic factors, especially temperature stratification and the Yellow Sea Bottom Cold Water, appeared to significantly affect the distribution of A. anophagefferens. The enhanced nutrient release during the large-scale green tide event in 2016 further promoted the growth of A. anophagefferens, highlighting the link between green tide events and the emergence of other harmful algal blooms in northern Chinese coastal waters.
{"title":"Unique distribution pattern of Aureococcus anophagefferens in the Yellow Sea during late summer influenced by complex hydrodynamics and green tide decomposition","authors":"Lu Sun , Huixia Geng , Qingchun Zhang , Zhenfan Chen , Chao Liu , Fanzhou Kong , Rencheng Yu","doi":"10.1016/j.hal.2025.102987","DOIUrl":"10.1016/j.hal.2025.102987","url":null,"abstract":"<div><div>Since 2009, brown tide-causing pelagophyte <em>Aureococcus anophagefferens</em> has recurrently impacted northern Chinese coastal waters. Previous observations suggest elevated abundances of <em>A. anophagefferens</em> occur in specific regions of the Yellow Sea (YS) where the decomposition of <em>Ulva prolifera</em> green tides during late summer, implying supportive role on its growth for green algae decomposition. However, the complex hydrodynamic processes in these areas complicate the disentanglement of the effects of green tide decomposition and hydrodynamic influences. In this study, quantitative PCR and environmental analyses were employed to examine the spatial distribution, interannual variations, and environmental drivers of <em>A. anophagefferens</em> during late summers in 2016, characterized by a high-intensity green tide, and 2017, marked by a low-intensity green tide. <em>A. anophagefferens</em> exhibited a vertically spindle-shaped distribution with peak cell densities at the deep chlorophyll maximum layer, primarily along the Shandong Peninsula and in the eastern YS. Notably, cell abundances in 2016 were significantly higher than those in 2017, linking to increased ammonium, phosphate, and dissolved organic matter resulting from green tide decomposition. Hydrodynamic factors, especially temperature stratification and the Yellow Sea Bottom Cold Water, appeared to significantly affect the distribution of <em>A. anophagefferens</em>. The enhanced nutrient release during the large-scale green tide event in 2016 further promoted the growth of <em>A. anophagefferens</em>, highlighting the link between green tide events and the emergence of other harmful algal blooms in northern Chinese coastal waters.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102987"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-09-24DOI: 10.1016/j.hal.2025.102986
Yeongji Oh , Min-Sun Lee , Eunbi Lee , Chan-Woo Kwon , Minji Lee , Ho Young Soh , Yoonja Kang
The western Jeju Island region, located on the continental shelf of the northern East China Sea, is influenced by Changjiang Diluted Water (CDW), Yellow Sea Bottom Cold Water, and branches of Kuroshio Current. Due to its proximity to the South Sea of Korea, an area historically subject to annual harmful algal blooms (HABs) but experiencing a recent decline in bloom frequency, we investigated variations in the HAB species occurrence during the CDW intrusion in June 2022 and 2023, when the extent of CDW intrusion drastically differed. Additionally, current flows from the study region toward the South Sea were investigated using a data-assimilative ocean circulation model that integrated multiple satellite and in situ observations. Microscopy and 18S rRNA sequencing analyses and photosynthetic efficiency measurements using Phyto-PAM II revealed that more CDW intrusion increased nutrient stress for diatoms and dinoflagellates, mainly due to extreme phosphorus limitation. However, HAB species such as Pseudo-nitzschia spp. rapidly responded to increased nitrogen availability. In contrast, reduced CDW intrusion mitigated nutrient stress caused by imbalanced stoichiometry, and small-sized HAB species, including Aureococcus anophagefferens, Karlodinium veneficum, Prorocentrum obtusidens dominated under conditions of the DOP availability and light-limitation. Furthermore, ocean current simulations showed strong flows toward the southern coastal waters of Korea during summer. Collectively, our findings suggest that, regardless of the extent of CDW inflow, different types of HAB species can be developed in western Jeju, and ocean currents potentially transport them to the South Sea of Korea.
{"title":"Dynamics of harmful algal bloom species are independent of the extent of the Changjiang Diluted Water Intrusion Off Western Jeju Island in the Northern East China Sea","authors":"Yeongji Oh , Min-Sun Lee , Eunbi Lee , Chan-Woo Kwon , Minji Lee , Ho Young Soh , Yoonja Kang","doi":"10.1016/j.hal.2025.102986","DOIUrl":"10.1016/j.hal.2025.102986","url":null,"abstract":"<div><div>The western Jeju Island region, located on the continental shelf of the northern East China Sea, is influenced by Changjiang Diluted Water (CDW), Yellow Sea Bottom Cold Water, and branches of Kuroshio Current. Due to its proximity to the South Sea of Korea, an area historically subject to annual harmful algal blooms (HABs) but experiencing a recent decline in bloom frequency, we investigated variations in the HAB species occurrence during the CDW intrusion in June 2022 and 2023, when the extent of CDW intrusion drastically differed. Additionally, current flows from the study region toward the South Sea were investigated using a data-assimilative ocean circulation model that integrated multiple satellite and in situ observations. Microscopy and 18S rRNA sequencing analyses and photosynthetic efficiency measurements using Phyto-PAM II revealed that more CDW intrusion increased nutrient stress for diatoms and dinoflagellates, mainly due to extreme phosphorus limitation. However, HAB species such as <em>Pseudo-nitzschia</em> spp. rapidly responded to increased nitrogen availability. In contrast, reduced CDW intrusion mitigated nutrient stress caused by imbalanced stoichiometry, and small-sized HAB species, including <em>Aureococcus anophagefferens, Karlodinium veneficum, Prorocentrum obtusidens</em> dominated under conditions of the DOP availability and light-limitation. Furthermore, ocean current simulations showed strong flows toward the southern coastal waters of Korea during summer. Collectively, our findings suggest that, regardless of the extent of CDW inflow, different types of HAB species can be developed in western Jeju, and ocean currents potentially transport them to the South Sea of Korea.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102986"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-10-09DOI: 10.1016/j.hal.2025.102997
Lei Cui , Yue-Lei Dong , Jian-Le Zhang , Wei-Dong Yang , Song-Hui Lu , Lin-Jian Ou
The coastal waters of Qinhuangdao, Bohai Sea, China, experienced recurrent brown tides caused by Aureococcus anophagefferens from 2009 to 2015, severely impacting scallop mariculture and coastal tourism. While eutrophication is a global phenomenon, A. anophagefferens blooms have been reported only in a small number of isolated ocean regions first in the USA and South Africa, and more recently in the coastal waters of Qinhuangdao, Bohai Sea, China. Mechanisms underlying such few isolated bloom patterns remain to be addressed. This study integrates historical water quality data, socioeconomic statistics, and field observations to investigate how rapid urbanization, industrialization, and agricultural development in the Qinhuangdao region, combined with intensive shellfish mariculture in the adjacent coastal waters, contributed to bloom formation. Increased nutrient loading—particularly dissolved organic nitrogen from land-based runoff and mariculture—together with phosphorus limitation (indicated by high ratios of inorganic nitrogen to phosphorus) and restricted water exchange, created conditions favorable for A. anophagefferens, consistent with global understanding of its bloom ecology. Genetic evidence suggests either ballast water introduction or indigenous activation from dormant sediment populations. Since 2012, comprehensive environmental policies, including wastewater treatment and aquaculture restructuring, have significantly reduced nutrient loads and improved water quality, leading to the cessation of brown tides after 2015 and a ∼95 % reduction in other harmful algal blooms (HABs) by 2018–2020. The Qinhuangdao case underscores the strong linkage between anthropogenic activities and HABs and provides a transferable management framework for other vulnerable coastal systems.
{"title":"From human-driven eutrophication to effective management: Controlling brown tides in the coastal waters of Qinhuangdao, China","authors":"Lei Cui , Yue-Lei Dong , Jian-Le Zhang , Wei-Dong Yang , Song-Hui Lu , Lin-Jian Ou","doi":"10.1016/j.hal.2025.102997","DOIUrl":"10.1016/j.hal.2025.102997","url":null,"abstract":"<div><div>The coastal waters of Qinhuangdao, Bohai Sea, China, experienced recurrent brown tides caused by <em>Aureococcus anophagefferens</em> from 2009 to 2015, severely impacting scallop mariculture and coastal tourism. While eutrophication is a global phenomenon, <em>A. anophagefferens</em> blooms have been reported only in a small number of isolated ocean regions first in the USA and South Africa, and more recently in the coastal waters of Qinhuangdao, Bohai Sea, China. Mechanisms underlying such few isolated bloom patterns remain to be addressed. This study integrates historical water quality data, socioeconomic statistics, and field observations to investigate how rapid urbanization, industrialization, and agricultural development in the Qinhuangdao region, combined with intensive shellfish mariculture in the adjacent coastal waters, contributed to bloom formation. Increased nutrient loading—particularly dissolved organic nitrogen from land-based runoff and mariculture—together with phosphorus limitation (indicated by high ratios of inorganic nitrogen to phosphorus) and restricted water exchange, created conditions favorable for <em>A. anophagefferens</em>, consistent with global understanding of its bloom ecology. Genetic evidence suggests either ballast water introduction or indigenous activation from dormant sediment populations. Since 2012, comprehensive environmental policies, including wastewater treatment and aquaculture restructuring, have significantly reduced nutrient loads and improved water quality, leading to the cessation of brown tides after 2015 and a ∼95 % reduction in other harmful algal blooms (HABs) by 2018–2020. The Qinhuangdao case underscores the strong linkage between anthropogenic activities and HABs and provides a transferable management framework for other vulnerable coastal systems.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102997"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Species diversity of amphidomatacean dinoflagellates belonging to Azadinium and Amphidoma was examined by microscopic observation and ITS- and LSU rDNA-based phylogeny, using 81 culture strains and two uncultured cells from Japanese waters during 2016–2024. In total, 11 species were found in Japanese waters. Of these, Azadinium caudatum, Az. cuneatum, Az. dexteroporum, and Az. spinosum were newly found in the Northwest Pacific, Az. dalianense was the first report in Japan, and Azadinium inconspicuum sp. nov. was a new species described in this study. Azadinium inconspicuum independently branched in the clade of Az. dexteroporum/Az. galwayense/Az. perfusorium but differed from Az. dexteroporum in shape of the Po plate (absent vs. present of the finger-like protrusion), from Az. galwayense in shape of the 2a plate (four- vs. five-sided), and from Az. perfusorium in position of pyrenoid (in the episome vs. at the antapex). It had a close resemblance to Az. luciferelloides in thecal morphology, but differed in detailed position of the ventral pore and shape of the posterior sulcal plate. Azaspiracids (AZAs) were detected in Azadinium poporum and Az. spinosum, but no trace was found in other amphidomatacean cultures, including Az. dexteroporum. Among 81 cultures examined, 47 cultures were assigned to Az. poporum, and belonged to four intraspecific ribotypes. Major AZA components in Japanese Az. poporum strains were AZA-59 (ribotype A1), AZA-2 (ribotype A2), AZA-2, -11, -36, -40 (ribotype B), and AZA-2 (ribotype C1). These results suggested that Az. poporum, particularly in ribotype C1, where high AZA amounts were detected, is the major AZA-producer along the Japanese coastal waters.
{"title":"Diversity of amphidomatacean dinoflagellates in Japan, with a description of Azadinium inconspicuum sp. nov. and azaspiracid components in Azadinium poporum ribotypes","authors":"Koyo Kuwata , Wai Mun Lum , Kazuya Takahashi , Garry Benico , Mayu Ozawa , Hajime Uchida , Satoshi Numano , Ryuichi Watanabe , Ryoji Matsushima , Toshiyuki Suzuki , Mitsunori Iwataki","doi":"10.1016/j.hal.2025.102969","DOIUrl":"10.1016/j.hal.2025.102969","url":null,"abstract":"<div><div>Species diversity of amphidomatacean dinoflagellates belonging to <em>Azadinium</em> and <em>Amphidoma</em> was examined by microscopic observation and ITS- and LSU rDNA-based phylogeny, using 81 culture strains and two uncultured cells from Japanese waters during 2016–2024. In total, 11 species were found in Japanese waters. Of these, <em>Azadinium caudatum, Az. cuneatum, Az. dexteroporum</em>, and <em>Az. spinosum</em> were newly found in the Northwest Pacific, <em>Az. dalianense</em> was the first report in Japan, and <em>Azadinium inconspicuum</em> sp. nov. was a new species described in this study. <em>Azadinium inconspicuum</em> independently branched in the clade of <em>Az. dexteroporum/Az. galwayense</em>/<em>Az. perfusorium</em> but differed from <em>Az. dexteroporum</em> in shape of the Po plate (absent vs. present of the finger-like protrusion), from <em>Az. galwayense</em> in shape of the 2a plate (four- vs. five-sided), and from <em>Az. perfusorium</em> in position of pyrenoid (in the episome vs. at the antapex). It had a close resemblance to <em>Az. luciferelloides</em> in thecal morphology, but differed in detailed position of the ventral pore and shape of the posterior sulcal plate. Azaspiracids (AZAs) were detected in <em>Azadinium poporum</em> and <em>Az. spinosum</em>, but no trace was found in other amphidomatacean cultures, including <em>Az. dexteroporum</em>. Among 81 cultures examined, 47 cultures were assigned to <em>Az. poporum</em>, and belonged to four intraspecific ribotypes. Major AZA components in Japanese <em>Az. poporum</em> strains were AZA-59 (ribotype A1), AZA-2 (ribotype A2), AZA-2, -11, -36, -40 (ribotype B), and AZA-2 (ribotype C1). These results suggested that <em>Az. poporum</em>, particularly in ribotype C1, where high AZA amounts were detected, is the major AZA-producer along the Japanese coastal waters.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102969"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-10-21DOI: 10.1016/j.hal.2025.103005
Haoyu Zhang , Cui Zeng , Xiansheng Zhang , Xiulin Wang , Keqiang Li
Dissolved organic nitrogen (DON) composition critically influences phytoplankton community dynamics, yet the species-specific regulatory mechanisms remain unclear. Combining cultivation experiments and transcriptomics, we reveal distinct growth responses of the diatom Chaetoceros curvisetus and dinoflagellate Prorocentrum minimum to three DON components: plant-derived peptides in labile DON (LDONP) as well as animal manure–derived humic in semilabile DON (SDONH) and fulvic acids in refractory DON (RDONF). Diatoms exhibited superior LDONP utilization via upregulated nitrogen metabolism genes (gdhA, GLT1, glnA) and peptide transporters (PTR), while dinoflagellates dominated SDONH assimilation through endocytosis-associated gene activation (PLD, PIP5K) and enhanced photosystem efficiency. RDONF inhibited both species but triggered energy reallocation to the TCA and Calvin cycles. Fluorescence spectroscopy further linked bioavailability to molecular structure, with diatoms efficiently utilizing protein-like components (T) and dinoflagellates preferentially absorbing humic-like components (E). This study proposed a genomic insight of diatoms and dinoflagellates growth into adaptation to DON regimes. Ecologically, the molecular mechanistic framework might predict phytoplankton succession under shifting DON regimes in coastal ecosystems. These findings provide strategies to mitigate harmful algal blooms in eutrophic coastal waters through DON source management.
{"title":"Differential responses and adaptive mechanisms of diatoms and dinoflagellates to changes in dissolved organic nitrogen components","authors":"Haoyu Zhang , Cui Zeng , Xiansheng Zhang , Xiulin Wang , Keqiang Li","doi":"10.1016/j.hal.2025.103005","DOIUrl":"10.1016/j.hal.2025.103005","url":null,"abstract":"<div><div>Dissolved organic nitrogen (DON) composition critically influences phytoplankton community dynamics, yet the species-specific regulatory mechanisms remain unclear. Combining cultivation experiments and transcriptomics, we reveal distinct growth responses of the diatom <em>Chaetoceros curvisetus</em> and dinoflagellate <em>Prorocentrum minimum</em> to three DON components: plant-derived peptides in labile DON (LDON<sub>P</sub>) as well as animal manure–derived humic in semilabile DON (SDON<sub>H</sub>) and fulvic acids in refractory DON (RDON<sub>F</sub>). Diatoms exhibited superior LDON<sub>P</sub> utilization via upregulated nitrogen metabolism genes (<em>gdhA, GLT1, glnA</em>) and peptide transporters (<em>PTR</em>), while dinoflagellates dominated SDON<sub>H</sub> assimilation through endocytosis-associated gene activation (<em>PLD, PIP5K</em>) and enhanced photosystem efficiency. RDON<sub>F</sub> inhibited both species but triggered energy reallocation to the TCA and Calvin cycles. Fluorescence spectroscopy further linked bioavailability to molecular structure, with diatoms efficiently utilizing protein-like components (T) and dinoflagellates preferentially absorbing humic-like components (E). This study proposed a genomic insight of diatoms and dinoflagellates growth into adaptation to DON regimes. Ecologically, the molecular mechanistic framework might predict phytoplankton succession under shifting DON regimes in coastal ecosystems. These findings provide strategies to mitigate harmful algal blooms in eutrophic coastal waters through DON source management.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 103005"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-10-09DOI: 10.1016/j.hal.2025.102995
Eline Le Moan , Amélie Derrien , Caroline Fabioux , Fred Jean , Malwenn Lassudrie , Aourégan Terre-Terrillon , Hélène Hégaret , Jonathan Flye-Sainte-Marie
Harmful Algal Blooms (HABs) can lead to fishery closures when toxin levels in commercial species exceed regulatory thresholds. Domoic acid (DA), the neurotoxin causing Amnesic Shellfish Poisoning (ASP), is particularly persistent in king scallops (Pecten maximus), a commercially valuable bivalve in France. This species is known for its slow depuration rate compared to other pectinids. This slow depuration rate allows for the calculation of DA dynamics, with the potential to better manage fishery openings in autumn, especially following spring contamination. This study used 20 years of data from the French phycotoxin in-situ monitoring program (REPHYTOX) to characterize decontamination episodes along the French Atlantic and English Channel coastlines. Depuration rates were estimated for 104 events; however, no correlation was found between depuration rate and province, time period, initial DA concentration or environmental conditions. From data, a median depuration rate was estimated and applied in a widely-used exponential decay model. In response to professionals’ needs, we developed a user-friendly predictive tool that estimates DA concentrations in king scallops based upon sampling in spring or summer. We recommend performing DA quantification in scallops whenever DA is detected in other shellfish at the same location, and running the predictive model to anticipate DA content at the opening of the fishery season in autumn. This tool will help fishery managers to anticipate bans, to avoid unnecessary license purchases, or to shift to alternative species. Although developed using French data, the methodology is adaptable to other regions with appropriate adjustments to reflect local ecological, regulatory, and fishery contexts.
{"title":"A 20-year comparative study of domoic acid depuration in the king scallop, Pecten maximus, across French provinces","authors":"Eline Le Moan , Amélie Derrien , Caroline Fabioux , Fred Jean , Malwenn Lassudrie , Aourégan Terre-Terrillon , Hélène Hégaret , Jonathan Flye-Sainte-Marie","doi":"10.1016/j.hal.2025.102995","DOIUrl":"10.1016/j.hal.2025.102995","url":null,"abstract":"<div><div>Harmful Algal Blooms (HABs) can lead to fishery closures when toxin levels in commercial species exceed regulatory thresholds. Domoic acid (DA), the neurotoxin causing Amnesic Shellfish Poisoning (ASP), is particularly persistent in king scallops (<em>Pecten maximus</em>), a commercially valuable bivalve in France. This species is known for its slow depuration rate compared to other pectinids. This slow depuration rate allows for the calculation of DA dynamics, with the potential to better manage fishery openings in autumn, especially following spring contamination. This study used 20 years of data from the French phycotoxin <em>in-situ</em> monitoring program (REPHYTOX) to characterize decontamination episodes along the French Atlantic and English Channel coastlines. Depuration rates were estimated for 104 events; however, no correlation was found between depuration rate and province, time period, initial DA concentration or environmental conditions. From data, a median depuration rate was estimated and applied in a widely-used exponential decay model. In response to professionals’ needs, we developed a user-friendly predictive tool that estimates DA concentrations in king scallops based upon sampling in spring or summer. We recommend performing DA quantification in scallops whenever DA is detected in other shellfish at the same location, and running the predictive model to anticipate DA content at the opening of the fishery season in autumn. This tool will help fishery managers to anticipate bans, to avoid unnecessary license purchases, or to shift to alternative species. Although developed using French data, the methodology is adaptable to other regions with appropriate adjustments to reflect local ecological, regulatory, and fishery contexts.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102995"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号