Professor, Jinan University, China
President, The Association on Harmful Algal Bloom in the South China Sea, China
Professor, Xiamen University, China
Professor, Institute of Oceanology, Chinese Academy of Sciences, China
The “Harmful Algae and Algal Toxins in Coastal Waters of China: Investigation and Database” project (HAATC) 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. Continuous investigation have been carried out more than three years in seven key sea areas, which are HAB&farming zones from south to north coast. Biotic and abiotic processes were observed during harmful red tides and green tides events. It also aims to establish an open database and query platform of harmful algal blooms in China for understanding the long-term evolution of HAB occurrence under the influence of intensified human activity and global change. It is funded (US$2.3 million) by the Ministry of Science and Technology of China for 5 years starting on the 1st Jan 2019. This HAATC research consortium, led by chief scientist Prof. Tian YAN, includes approximately 100 scientists and students. More than 4 years of work have shown the increased distribution of HAB species (including cysts) and algal toxins in coastal waters of China, the increased occurrence of macro-algae blooms (mainly by Ulva prolifera and Sargassum horneri) in the Southern Yellow Sea, increased amount of causative species being identified, and new records of algal toxins such as azaspiracid, cycloimines and neurotoxins β-N-methylamino-l-alanine have been detected. 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.
Chair Professor, Department of Ocean Science, Hong Kong University of Science and Technology, Hong Kong SAR, China
Understanding how marine phytoplankton and their primary consumer (i.e., microzooplankton) will respond to projected warming is critical for enhancing our ability to predict the response of marine planktonic ecosystems to climate changes. This is also critical to our ability to predict the capacity of the ocean in absorbing and storing anthropogenic CO2. To gain more in-depth insights into the response of marine plankton community to warming, we conducted a series of experiments to evaluate their temperature sensitivity through activation energy (Ea) based on the framework of Metabolic Theory of Ecology (MTE). However, the growth of phytoplankton in different parts of ocean is limited by nutrient availability, such as nitrogen, phosphorus and iron. How resource availability affects phytoplankton thermal sensitivities is still not well studied. I will present a few case studies conducted by my team in recent years. Results from these studies provide new insights into the complex nature of trait specific thermal response of plankton and its implication to global carbon cycling in a warming ocean.
Professor Emeritus, University of the Philippines
National Academy of Science and Technology, Philippines
Harmful Algal Blooms (HABs) previously referred to in general as “red tides”, have been reported in the Philippines since 1983 when Samar-Leyte and Sorsogon marine waters were affected by the bloom of Pyrodinium bahamense, a Paralytic Shellfish Poisoning (PSP) causative dinoflagellate species . The 1983 event resulted to almost a thousand cases of human poisoning and since then, monitoring and research have continued with the detection of persistent HAB causative organisms and identification of novel HAB species.
This report/paper is a review of the status of HAB research and monitoring in the Philippines in relation to the management of their hazards and risks. Among others, it is recommended that a thorough review of the monitoring and management of HABs in the Philippines be undertaken by relevant inter-agency committee considering the increase in the number of areas regularly affected by HABs and the apparent effects of climate change on this phenomenon. It should be noted that the general scheme of Philippine “Red Tide “ monitoring and management was developed almost three ( 3) decades ago. A number of specific suggestions to enhance HAB research, monitoring and management to address their continuing and emerging hazards and risks are included.
Professor, Jinan University, China
So
far more than 300 species has been reported responsible for algal blooms. A
statistics from Intergovernmental Oceanographic Commission (IOC) reported that
about 173 species can produce algal toxins or other toxic substances. The
majority of those toxic species in marine are dinoflagellates.
Cells
of dinoflagellates are nano- to micro-sized, some of them are unarmored. The
fragile and high similarities in cell morphology among species make it
difficult to be distinguished. The accurate identification of species is the
basis of harmful algal bloom (HAB) studies, e.g. in diagnosis of toxic or
non-toxic, in decision options of early warning, in operation measures of
prevention.
The
most toxic dinoflagellates in China, which made human intoxication or
aquaculture losses, are species of Karenia,
Alexandrium, as well as some benthic
species. The total of 5 species of Karenia
has been reported so far in Chinese waters, i.e. Karenia mikimotoi, K. brevis, K. longicanalis, K. papilionacea,
and K. selliformis. Karenia mikimotoi
is the most notorious harmful species off the South and East China Sea, which have
caused more than 100 bloom events from 1998 to 2018. In most cases, the
causative species of a Karenia bloom
was not a single dominant species, but coexistence of species in the
genus Karenia or other genus of
family Kareniaceae. It might be the explanation that some of the
blooms were toxic, but others were not.
Five morphotypes of benthic Prorocentrum lima has been identified from the southern Chinese waters. The results from ecophysiological and toxicological studies revealed that there are differences among the morphotypes within the species.
Associate Professor, Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya, Malaysia
Harmful Algal Blooms (HABs) occur due to the proliferation of harmful microalgae in the aquatic environments. Often, HAB causes deleterious effects on the coastal ecosystem. This included the contamination of commercially important shellfish, massive mortality of farmed or wild finfish, and damaging the socioeconomic value of the marine ecosystem. The increasing impacts of HAB on socioeconomic and public health are tremendous, affecting regionally and globally, partly because of the emergence of new HAB events in areas with no prior record and involving novel toxic species. Rapidly growing aquaculture industries in the country has been hindered by frequent occurrence of fish kill and shellfish toxicity events. In this presentation, the emergence of HAB events due to new and unrecorded harmful species in Malaysia will be shared. To allow better assessment of the risk of HABs to the rapid growing aquacultures, studies have been taken to detect the potential harmful species using both advanced microscopy and molecular methods. Dynamic of phytoplankton communities and its related environmental factors in Johor strait, an important aquaculture area, will be elaborated further. This presentation emphasizes on the use of DNA metabarcoding to detect HAB species at different spatial scales covering the South China Sea and Straits of Malacca, and how this approach aids in the inventory of species distribution for monitoring, risk assessment, and early detection of HAB outbreaks. The challenges of this approach and its future perspective in assessing long-term coastal ecosystem changes will be further elaborated.
Chief Scientist, Japan Fisheries Research and Education Agency, Japan
The geographic range of Alexandiurm catenella poisoning appears to be increasing on both regional and global scales. The molecular ecological study of genetic relationships using highly polymorphic genetic markers may reveal the dispersal mechanism of this species. In this study, MIG (multiplexed ISSR Genotyping)-seq was employed to reveal the genetic relatedness among Pacific Rim populations. Loci which were detected in >70% individuals and isolates in which >50% loci were detected were chosen for the further analysis, resulting in detecting 349 SNPs in 165 samples isolated from Akkeshi (eastern Hokkaido), Sendai, Osaka, Hiroshima Bays (Japan), Jinhae Bay (Korea), Bering Sea, Chukchi Sea, Puget sounds (USA) and Chile. Pairwise Fst values showed significant differences among most of the pairwise samples except for between Osaka & Jinhae Bay and Osaka & Hiroshima Bay. In the principal coordination analysis, the samples from Japan and Korea, the Bering Sea, and the Chukchi Sea (7 samples) were positioned closely, but Puget sounds and Chilean samples were plotted quite far away. Also, results of the bar plot analysis by STRUCTURE suggested when K = 3, each cluster was grouped as 1) Japan and Korean except for Akkeshi Bay, 2) Akkeshi Bay and the Bering/Chukchi Sea, 3) Puget sounds and Chilean samples. These data suggested the presence of a large genetic break between the Bering Sea and Puget sounds populations and genetic connectivity between Akkeshi Bay and the Bering/Chukchi Sea populations.
The distribution of Alexandrium pacificum has been increasingly documented worldwide during the last decades. To examine the genetic relatedness of global populations, we conducted a genetic study using a haplotype marker and 7 microsatellite markers. Seawaters or sediment samples were collected from 11 different localities (17 samples) along 10 Japanese, 3 Chinese, 2 Mediterranean Sea, 2 New Zealand coastal waters and 839 clonal strains (temperate Asian clade) were analyzed. The haplotype marker showed high resolution to discriminate the difference of the geological origin in the populations. We could obtain the sequences from 673 clonal isolates. Two haplotypes were predominant of 85 haplotypes. The first one “Haplo01” (n = 316 isolates) and the second one “Haplo02” (n = 122) were predominated by Japanese isolates and Chinese isolates, respectively. Some Japanese isolates also belonged to haplo2. Interestingly, the Sea of Japan population had unique and highly diversified haplotypes derived from haplo2. New Zealand populations were mainly divided into three groups, i.e. the first one belonged to Haplo2, the second one derived from Haplo1, and the third one positioned in the middle of Haplo1 and Haplo2 groups. The half of Mediterranean Sea isolates belonged to Haplo1 and other half isolates had unique haplotypes derived from Haplo2. Microsatellite analysis data showed the significant population differentiation among most of the pairwise populations except for several Japanese pairwise populations. Results of the haplotype analysis well supported those at microsatellites analyses.
Professor, College of Marine Ecology and Environment, Shanghai Ocean University, China
After reviewing the water quality and marine ecological data in Hong Kong from 1975-2020, it is interesting to find that harmful algal blooms (HAB) often generate incidental clean-up of marine environmental conditions in enclosed embankments such as Tolo Harbour. Further analyses showed that the causative organisms of HAB could take up the excessive nutrients such as carbonates, nitrogenous compounds and inorganic phosphate in water bodies that helps to improve water quality. Applying these natural phenomenon in environmental engineering, a research plant in Yuen Long Sewage Treatment Plant was established to study the capability of microalgae in treating wastewater with satisfactory results for industrialization of relevant process. The project was subsequently subsidized by a fund in the Greater Bay Area for cleansing of fish ponds and polluted watercourses. By modification of cultivation tanks, new receipts of seeded algae and enhanced industrial control of production systems, research team found that various challenges in the algal industry including cost-economic issues, environmental shocks of the system and marketing of algal products could be overcome comfortably, that attracts stronger interest from investors. The future of the 'profitable algal blooms' is further brightened by recent urges for carbon-capturing and green finance because of ESG and global climate change.
Professor, Xiamen University, China
Diatoms are well known to produce resting cells when they sink to deeper waters or sediment to endure prolonged periods of unfavorable environmental conditions. Once resting cells return to euphotic layers, they can rejuvenate quickly, functioning as “seed banks” to initiate a new seasonal bloom, which is considered the cornerstone of the ecological success of diatoms. Despite their significance for the survival of diatoms and their contribution to carbon export from surface oceans, the mechanisms of resting cells formation and survive remain elusive. Here, we have applied an integrative analysis based on histology, physiology, biochemistry, and transcriptome profiling to shed light on processes involved in resting-cell formation in the model diatom Thalassiosira pseudonana. Our results have revealed that the formation of RCs in T. pseudonana is characterised by histological changes of organelles and by a marked acidification of the cytoplasm. These physico-chemical changes were accompanied by the catabolism of storage compounds probably required for the development of RCs. The genes expressions associated with antioxidant defenses, DNA/protein repairs, autophagy, and specific transcription factors were enhanced to increase stress resistance and support resting cells survival. Thus, our results suggest that the formation of resting cells in T. pseudonana requires storage compounds and protons, both of which likely contributing to metabolism in quiescence essential to cope with conditions unfavorable for diatom growth in the marine system.
Professor, Hong Kong Metropolitan University, Hong Kong SAR, China
Karenia mikimotoi is a well-known and highly damaging species of harmful algal bloom (HAB)-causing dinoflagellate. Algal blooms caused by this species are widespread and often result in significant fish and shellfish mortality. Extensive research has been conducted on algicidal bacteria targeting HAB species, which could serve as a promising method for HAB control. In this study, we characterized a bacterial strain that exhibited potent algicidal activity against a K. mikimotoi strain. We employed an in-house developed methodology for establishing axenic K. mikimotoi cell cultures. Both the bacterial strain and K. mikimotoi cells were isolated from a K. mikimotoi bloom that occurred in Yim Tin Tsai, Hong Kong in 2016.
Developing axenic cultures for HAB species presents challenges. Although various methods have been reported for establishing axenic cultures of microalgae, there is no universally accepted approach. Many of the reported methods are ineffective and time-consuming. Generating an axenic culture of K. mikimotoi is particularly difficult due to the fragile structure of their unarmed outermost cell surface. Our developed methodology combines three key techniques: Percoll density gradient centrifugation, antibiotic treatment, and serial dilution. Generally, over 99% of the associated bacteria from the K. mikimotoi cell culture can be eliminated through physical separation via density gradient centrifugation and bactericidal action via antibiotic treatment. Instead of focusing on removing the remaining 1% of bacteria from the culture, our objective was to identify and isolate axenic clones of algal cells through serial dilution. The axenic status of the cell culture established from these axenic clones can be sustainably maintained for many generations (at least 50 generations in our study) without the use of antibiotics.
Axenic K. mikimotoi cells were employed to assess the algicidal activity of a novel strain of algicidal bacteria, Maribacter dokdonensis, isolated from a K. mikimotoi-induced HAB. Our results demonstrated that this M. dokdonensis strain exhibits efficient indirect algicidal action against K. mikimotoi. Both the bacterial culture and its supernatant (spent medium) completely lysed all algal cells within 48 hours. However, the algicidal effect of bacterial cells (residues after centrifugation) was negligible. At a 25% v/v dose, the algicidal efficiency of M. dokdonensis was 55% and 100% at 24 hours and 48 hours, respectively. The algicidal efficiency of M. dokdonensis against K. mikimotoi in the stationary phase was considerably higher than that in the log growth phase. This suggests that K. mikimotoi cells in the log phase display greater tolerance to the algicidal effect. Interestingly, the bacterial culture of M. dokdonensis exhibited a higher algicidal efficiency (~90%) against xenic K. mikimotoi than against axenic K. mikimotoi (~50%) after 24 hours of incubation. The enhanced algicidal effect could be attributed to the presence of associated bacteria in the algal culture. Further research is required to unravel the underlying algicidal mechanism of M. dokdonensis against K. mikimotoi.
Associate Professor, Tsinghua Shenzhen International Graduate School, China
The occurrence of harmful cyanobacterial blooms (HCBs) has accelerated and intensified due to the global warming. It is of great significance to explore and investigate green, economical and highly efficient strategies to control the development of HCBs. Programmed cell death (PCD) is a form of suicide that is strictly regulated by gene expressions when cells are exposed to environmental stresses. Induction of cyanobacterial PCD is conducive to suppressing biomass as well as reducing risks of toxin biosynthesis and release. In this study, Microcystis aeruginosa FACHB-905 was exposed to different stresses, including UV irradiation, β-cyclocitral (BCC) and hydrogen peroxide (H2O2). Electron microscopy, flow cytometry and transcriptomics were employed to investigate the growth suppression and PCD forms in M. aeruginosa cells at cellular, molecular and transcriptomic levels, respectively. The aim of this study was to illustrate the suppression efficacy and features of different PCD forms induced by the applied strategies. Results demonstrated that different PCD forms were induced by different stresses imposed on M. aeruginosa cells. Moderate dosages of H2O2 and BCC induced cells into apoptosis characterized by cell shrinkage and lysis. By contrast, higher H2O2 and BCC concentrations led to ferroptosis and mazEF-mediated PCD characterized by membrane rupture and perforation, respectively. Both strategies resulted in ghost cells whose cell structure remained. UV irradiation also resulted in the mazEF-mediated PCD. The identification of different PCD forms in Microcystis aeruginosa cells inspires the combined induction of these PCD forms for highly efficient HCB control.
Associate Professor, Xiamen University, China
Sandy beaches are common in coastal areas, usually with unstable substrates, low nutrients, unfavourable environment and low biodiversity. However, diatoms are well adapted to sandy beaches. In this study, the morphological characteristics and species diversity of epipsammic diatoms in sandy environments along the coast of South China were studied, and 3 new genera, 21 new species, 6 new recorded genera and 40 new recorded species were published, which comprehensively and objectively reflect the diversity and ecological roles of the diatoms in sandy coasts. The study is the first to carry out epipsammic diatom biodiversity research in China, and finds that diatoms are abundant in sandy coasts, changing the views that “sandy ecosystems are low in biodiversity”, and providing a basis for the protection and utilization of marine diatom biological resources. We found a biraphid diatom species with flexed frustules in beach environment on Weizhou Island, Beihai City, Guangxi Zhuang Autonomous Region, China. Yuzaoea sinensis gen. et sp. nov. CH Li, HH Liu, YH Gao & CP Chen (Bacillariophyceae) was described, which was characterized by heterogeneous frustule and complete raphe on both valves. Phylogenetic analyses based on SSU rRNA and rbcL showed that the genus Yuzaoea was the sister group to the clade of Rhoicosphenia (Bootstrap values = 100%), and the clade “Yuzaoea+Rhoicosphenia” was sister to the clade of monoraphid diatoms, in which the genus Achnanthidium, Planothidium and some Cocconeis (Bs = 100%). Morphologically, the genus Yuzaoea shares many morphological features with monoraphid diatoms like genera Achnanthidium and Planothidium and the members within the Rhoicospheniaceae. Therefore, based on a combined morphological studies and phylogenetic results we suggested that this branch may represent the evolution of one kind monoraphid diatoms, from biraphid diatoms (genus Yuzaoea), to incompleted biraphid diatoms (e.g. genera Rhoicosphenia, Campylopyxis), to monoraphid diatoms (e.g. genera Achnanthidium and Planothidium).
Associate Professor, College of Life Science, South China Normal University, China
Pseudo-nitzschia is a cosmopolitan phytoplankton genus that can form blooms and produce a neurotoxin called domoic acid (DA). Identification of Pseudo-nitzschia is generally based on field material or strains followed by morphological and/or molecular characterization, which are time-consuming and laborious. Pseudo-nitzschia taxa with low abundance in the field or potentially unavailable for culturing may easily be overlooked. To understand the complete profile of the Pseudo-nitzschia community, a metabarcoding approach using annotated amplicon sequence variants (ASV) was applied based on a carefully-calibrated reference sequence database for Pseudo–nitzschia and newly designed primers targeting the ITS1 rDNA domain. This approach was used in the Taiwan Strait of the East China Sea during the two cruises in spring and summer 2019. In total, 48 Pseudo-nitzschia taxa/phylotypes including 36 known and 12 novel were recovered, verified by divergence analyses and haplotype networks. The most frequent species were P. multiseries and P. multistriata in spring, and P. calliantha in summer. Redundancy analyses revealed that temperature was a key factor affecting the Pseudo-nitzschia community. Significantly positive correlation was present between particulate DA (pDA) and presence of P. cuspidata Clade III in summer, whereas no correlation was found between pDA and the other Pseudo-nitzschia species in summer, nor in spring. PDA was detected in four strains of P. cuspidata Clade III in summer, implying P. cuspidata Clade III as the main pDA producer. This comprehensive analysis gave new insights into the diversity of Pseudo–nitzschia in the natural environment.
Assistant Professor, Xiamen University, China
Plastic waste in the ocean is an urgent environmental concern and has given rise to a novel habitat, known as the “plastisphere.” Under ocean acidification (OA), changes in plastisphere community composition may alter plastic degradation, deposition, and passage through food webs, but these have not been studied yet. This is the first study about the effects of simulated high CO2 on the plastisphere using a mesocosm. We discovered that after 1 month the beta diversity of prokaryotic communities living on single-use plastic drinking bottles was significantly different under different carbon dioxide concentrations, with more pathogens at high CO2. Based on function prediction analysis, the relative abundance of bacterial taxa involved in nitrogen and nitrate respiration and ureolysis was significantly higher under simulated high CO2. We conclude that OA has significant effects on the plastisphere and its predicted functions.We conducted a mesocosm experiment to examine how ocean acidification (OA) affects communities of prokaryotes and eukaryotes growing on single-use drinking bottles in subtropical eutrophic waters of the East China Sea. Based on 16S rDNA gene sequencing, simulated high CO2 significantly altered the prokaryotic community, with the relative abundance of the phylum Planctomycetota increasing by 49%. Under high CO2, prokaryotes in the plastisphere had enhanced nitrogen dissimilation and ureolysis, raising the possibility that OA may modify nutrient cycling in subtropical eutrophic waters. The relative abundance of pathogenic and animal parasite bacteria also increased under simulated high CO2. Our results show that elevated CO2 levels significantly affected several animal taxa based on 18S rDNA gene sequencing. For example, Mayorella amoebae were highly resistant, whereas Labyrinthula were sensitive to OA. Thus, OA may alter plastisphere food chains in subtropical eutrophic waters.
Algae-based carbon capture and utilization (CCU) is a promising technology for mitigating greenhouse gas emissions from industrial and power plant sources. Algae photobioreactors, which use artificial light and controlled environmental conditions to cultivate algae and support their growth, are a key technology in this field. Our research focuses on optimizing the design of photobioreactors to enhance algae growth and lipid production. We utilize advanced cultivation techniques to control cultivation conditions, such as light intensity, temperature, and CO2 concentration, and thereby optimize carbon sequestration in the biomass. Our closed-loop system minimizes contamination and maximizes resource efficiency, making it an ideal technology for scalable algae cultivation.
Our research also focuses on the development of environmentally friendly solvents and low-energy-intensive methods for effective cell wall breakage. Incorporating pretreatment techniques, such as ultrasound or microwave, enhances the extraction of microalgal lipids to improve the yield of algal oil. Our lab-scale production capacity currently yields 0.8L of algal crude oil per week, which has a high calorific value and can be used for various applications, including biodiesel.
Microalgae are increasingly recognized as the primary feedstock for third-generation biofuels due to their ability to grow rapidly and convert solar energy to chemical energy via CO2 fixation. Biodiesel, one of the most commonly used biofuels, is considered an ideal recyclable energy carrier and a potential primary energy source. Algae biomass can also be used as a feedstock for producing fertilizers, such as nitrogen, phosphorous, and potassium (NPK), while simultaneously sequestering CO2 by burying biomass in sediment.
Our research on algae photobioreactors, algae cultivation, physical cell description, and algae lipid extraction aims to advance the development of algae-based CCU systems and promote the utilization of algae biomass in fertilizer and biodiesel production. The application of algae-based fertilizers has shown promising results in enhancing crop yields and improving soil health. Additionally, algae-based biodiesel has the potential to reduce reliance on fossil fuels and mitigate greenhouse gas emissions. We believe that algae technology has the potential to revolutionize carbon capture and utilization and play a critical role in the transition to a sustainable future.
The concept of circularity is increasingly gaining prominence in the realm of sustainability, necessitating a profound reevaluation of our production systems. The traditional “take-make-dispose” linear model is proving to be unsustainable. This model relies heavily on readily available resources and energy, produces substantial waste, and, over time, contributes to environmental degradation. This approach favors efficiency over sustainability, thereby exposing a critical flaw in our design philosophy. However, an abrupt transition to complete circularity isn’t always feasible. Microalgae can serve as a valuable intermediary in the product cycle, capturing waste that would otherwise be discarded and reintegrating it into the production chain through nutrient recovery. Our technology finds its inspiration in corals, where microalgae are encapsulated to perform key tasks such as carbon capture and wastewater treatment. The biomass generated from this process can be harvested and potentially used in various sectors like agriculture, animal feed production, and the manufacture of high-value bioproducts. As interest in and applications for microalgae continue to emerge, we will demonstrate examples of how microalgae can function as an essential element in circular production systems.
