Red Tide Organism Research Articles

Do red tide events promote an increase in zooplankton biodiversity?

Red tides occurring off the southern coast of Korea impact the marine ecosystem and aquaculture industries. Zooplankton are crucial in the food web, connecting primary producers to higher predators and interact diversely with red tide organisms. This study explores dynamics of the zooplankton community over seven years including three red tide and four non-red tide years in Tongyeong using metabarcoding. In non-red tide years, zooplankton diversity showed typical seasonal patterns, increasing from June to early October. However, during red tide years, diversity remained high, with a shift in species composition-decreased Copepoda and increased Branchiopoda, Echinodermata, Malacostraca, and Annelida. Diversity indices were significantly higher in red tide years across all periods except for the richness in “after” that showed an insignificant higher value. The differences in zooplankton assemblages across periods were influenced by surface temperatures and the density of the red tide-causing alga Margalefidinium polykrikoides. Eight species emerged as indicator species and showed direct correlations with M. polykrikoides and among them, seven species were indicator species for red tide occurrence years. The ecological characteristics of M. polykrikoides blooms and their recurrent occurrences over several decades suggest that zooplankton may adapt to the toxins and use these blooms as spawning cues. Overall, this study provides comprehensive understanding on changes in zooplankton communities during red tide events, offering novel insights into their ecology.

Temporal variations of bacterial and eukaryotic community in coastal waters—implications for aquaculture

Despite increased attention to the aquaculture environment, there is still a lack of understanding regarding the significance of water quality. To address this knowledge gap, this study utilized high-throughput sequencing of 16S rRNA and 18S rRNA to examine microbial communities (bacteria and eukaryotes) in coastal water over different months through long-term observations. The goal was to explore interaction patterns in the microbial community and identify potential pathogenic bacteria and red tide organisms. The results revealed significant differences in composition, diversity, and richness of bacterial and eukaryotic operational taxonomic units (OTUs) across various months. Principal coordinate analysis (PCoA) demonstrated distinct temporal variations in bacterial and eukaryotic communities, with significant differences (P = 0.001) among four groups: F (January-April), M (May), S (June–September), and T (October-December). Moreover, a strong association was observed between microbial communities and months, with most OTUs showing a distinct temporal preference. The Kruskal–Wallis test (P < 0.05) indicated significant differences in dominant bacterial and eukaryotic taxa among months, with each group exhibiting unique dominant taxa, including potential pathogenic bacteria and red tide organisms. These findings emphasize the importance of monitoring changes in potentially harmful microorganisms in aquaculture. Network analysis highlighted positive correlations between bacteria and eukaryotes, with bacteria playing a key role in network interactions. The key bacterial genera associated with other microorganisms varied significantly (P < 0.05) across different groups. In summary, this study deepens the understanding of aquaculture water quality and offers valuable insights for maintaining healthy aquaculture practices.Key points• Bacterial and eukaryotic communities displayed distinct temporal variations.• Different months exhibited unique potential pathogenic bacteria and red tide organisms.• Bacteria are key taxonomic taxa involved in microbial network interactions.

Preliminary investigation on the causes of red tides in Qinhuangdao coastal areas in 2022.

To explore the causes of red tides in Qinhuangdao coastal water, we conducted surveys on both water quality and red tides during April to September of 2022 and analyzed the relationships between main environmental factors and red tide organisms through the factor analysis and canonical correspondence analysis. The results showed that there were eight red tides along the coast of Qinhuangdao in 2022, with a cumulative blooming area of 716.1 km2. The red tides could be divided into three kinds based on the major blooming organisms and occurrence time, Noctiluca scintillans bloom, diatom-euglena (Skeletonema costatum, Eutreptiella gymnastica, Pseudo-nitzschia spp.) bloom, and dinoflagellate (Scrippsiella trochoidea and Ceratium furca) bloom. Seasonal factor played roles mainly during July to September, while inorganic nutrients including nitrogen and phosphorus influenced the blooms mainly in April and July. The canonical correspondence analysis suggested that N. scintillans preferred low temperature, and often bloomed with high concentrations of ammonium nitrogen and dissolved inorganic phosphorus. S. costatum, E. gymnastica, and Pseudo-nitzschia spp. could tolerate broad ranges of various environmental factors, but favored high temperature and nitrogen-rich seawater. C. furca and S. trochoidea had higher survival rate and competitiveness in phosphate-poor waters. Combined the results from both analyses, we concluded that the causes for the three kinds of red tide processes in Qinhuangdao coastal areas in 2022 were different. Adequate diet algae and appropriate water temperature were important factors triggering and maintaining the N. scintillans bloom. Suitable temperature, salinity and eutrophication were the main reasons for the diatom-euglena bloom. The abundant nutrients and seawater disturbance promoted the germination of S. trochoidea cysts, while phosphorus limitation caused the blooming organism switched to C. furca and maintained the bloom hereafter.

Algicidal substances of Brevibacillus laterosporus and their effect on red tide organisms

Herein, the algicidal effects of Brevibacillus laterosporus on typical red tide organisms were investigated. Through comparative analysis of the fermentation solution, sterile filtrate and bacterial body, it was found that this strain mainly exerts its algicidal function by secreting algicidal substances. In this paper, we established a method for extracting the algicidal substances of B. laterosporus and systematically investigated their features and effect on Heterosigma akashiwo. The results showed that the algicidal substances are a mixture of compounds all with molecular weights less than 3500 Da, with those below 100 Da producing 45% of the algicidal effect; these are more polar and best extracted with methanol. The algicidal substances are stable over a range of temperatures (-80.0 to 70.0°C) and pH values (4.0-8.0). The algicidal substances caused most H. akashiwo cells to rupture within 24 h. In the remaining cells, the algicidal substances activated the antioxidant system and reduced their metabolic activity, leading to apoptosis, as observed by cell crumbling and a reduction in membrane potential. The responses of different algal cell surface structures to the algicidal substances were also compared and analysed. It was concluded that these algicidal substances can act on the cell membrane and change its permeability, allowing entry of the algicidal substances to produce an algicidal effect.

The synthesis of an acrylamide copolymer and its synergistic effects on clay flocculation of red tide organisms

The modified clay (MC) method is a common emergency treatment technology for red tides, and the selection of surface modifiers is the key to the MC technology. A cationic polymeric modifier, the copolymer of dimethyl diallyl ammonium chloride and acrylamide (P (DMDAAC-co-AM), PDA) was optimized via a visible-light-induced polymerization technique. The PDA-modified clay (PDAMC) was prepared with strong salt tolerance and achieved efficiencies of 86% at the concentration of 50 mg L−1, and the dose was 90% lower than that of aluminum polychloride-modified clay (PACMC). While polyacrylamide and commercial PDA can achieve efficiencies of only 25 and 67%, respectively, but high doses were required. This is because PDA changed the surface charges of clay particles from negative to positive, which promotes the formation of the polymer-chains bridging network to overcome the difficulties of curling in seawater. According to the analysis of flocculation parameters and spatial conformation of PDAMC, the high salinity tolerance of the PDAMC was attributed to the synergistic processes of charge neutralization and the three-dimensional network bridging. Therefore, this study has developed a highly effective flocculant material used in seawater and provided an important reference for the management of red tide organisms.

The Red Tide Organism Chaetoceros sp. Responding to Exposure to Oil and Dispersant

Laboratory experiments were conducted to study the effects of oil spills and dispersants on the growth of the red tide organism Chaetoceros sp. Crude oil produced from the Chinese Bohai Sea, diesel oil, and the chemical dispersant (GM-2) produced in China were added into Chaetoceros sp. cultures. The results showed that both crude oil and diesel oil could enhance the growth of Chaetoceros sp. Data were analyzed by one-way ANOVA, and the confidence interval was 95%. At a concentration of 20 mg L−1 crude oil and a concentration of 10 μL L−1 diesel oil, Chaetoceros sp. bloomed to 1.57 × 105 cells mL−1 (p &lt; 0.01) at day 14 and 3.55 × 104 cells mL−1 (p &lt; 0.05) at day 10, respectively. A concentration of 10 μL L−1 diesel oil stimulated the specific growth rate for Chaetoceros sp. of 0.49 d−1 over 10 days. The specific growth rate of Chaetoceros sp. with 20 mg L−1 crude oil alone was 0.46 d−1 over 14 days. However, the mixture of oil and dispersant did not enhance the growth of Chaetoceros sp. as significantly as oil alone. These results implied that oil spills in coastal waters can stimulate Chaetoceros sp., and the specific dispersant GM-2 applied following oil spills may be unlikely to further enhance the growth of Chaetoceros sp.

Dosage-effectiveness of modified clay flocculating red tide organisms: Mechanical mechanism and mathematical model

Modified clay (MC) technology is the most widely used method to remove red tide organisms from seawater on a large scale. In recent years, frequent outbreaks of red tides worldwide have led to a sharp increase in MC consumption. However, the efficient application of MC for red tides control lacks theoretical basis. The study explored dosage-effectiveness of MC for microalgae (red tide organism) removal. The results showed that the effectiveness of MC for microalgae removal increased first and then decreased with the increase of MC dosage due to the self-flocculation of MC. The self-flocculation of MC was caused by the strong attractive total interaction energy between MCs at close range in seawater. A mathematical model established based on the extended Langmuir model can simulate dosage-effectiveness of MC well, and the quantitative relationship between the dosage of MC and its degree of self-flocculation was deduced based the mathematical model. These studies will help to enrich the flocculation theory of MC application, and provide significant guidance for the efficient application of MC for red tides control.

Establishment and preliminary study of electrophysiological techniques in a typical red tide species

Electrophysiology studies the electrical properties of cells and tissues including bioelectrical signals and membrane ion channel activities. As an important means to reveal ion channel related physiological functions and the underlying mechanisms, electrophysiological techniques have been widely used in studies of animals, higher plants and algae that are closely related to higher plants. However, few electrophysiological studies have been carried out in red tide organisms, especially in dinoflagellates, which is mainly due to the complex surface structure of dinoflagellate amphiesma. In this study, the surface amphiesma of Alexandrium pacificum, a typical red tide species, was removed by centrifugation, low-temperature treatment and enzymatic treatment. In all three treatments, low-temperature treatment with 4 °C for 2 h had high ecdysis rate and high fixation rate, and the treated cells were easy to puncture, so low-temperature treatment was used as a preprocessing treatment for subsequent current recording. Acquired protoplasts of A. pacificum were identified by calcofluor fluorescence and immobilized by poly-lysine. A modified “puncture” single-electrode voltage-clamp recording was first applied to dinoflagellates, and voltage-gated currents, which had the characteristics of outward K+ current and inward Cl− current, were recorded and confirmed by ion replacement, indicating the voltage-gated currents were mixed. This method can be used as a technical basis for the electrophysiological study of dinoflagellates and provides a new perspective for the study of stress tolerance, red tide succession, and the regulation of physiological function of dinoflagellates.

Initial estuarine response to inorganic nutrient inputs from a legacy mining facility adjacent to Tampa Bay, Florida

Legacy mining facilities pose significant risks to aquatic resources. From March 30th to April 9th, 2021, 814 million liters of phosphate mining wastewater and marine dredge water from the Piney Point facility were released into lower Tampa Bay (Florida, USA). This resulted in an estimated addition of 186 metric tons of total nitrogen, exceeding typical annual external nitrogen load estimates to lower Tampa Bay in a matter of days. An initial phytoplankton bloom (non-harmful diatoms) was first observed in April. Filamentous cyanobacteria blooms (Dapis spp.) peaked in June, followed by a bloom of the red tide organism Karenia brevis. Reported fish kills tracked K. brevis concentrations, prompting cleanup of over 1600 metric tons of dead fish. Seagrasses had minimal changes over the study period. By comparing these results to baseline environmental monitoring data, we demonstrate adverse water quality changes in response to abnormally high and rapidly delivered nitrogen loads.

The Synthesis of an Acrylamide Copolymer and its Synergistic Effects on Clay Flocculation of Red Tide Organisms

The Synthesis of an Acrylamide Copolymer and its Synergistic Effects on Clay Flocculation of Red Tide Organisms

The association between algae organisms and environmental factors in Hai-tan Strait of Fujian, China

27 points were surveyed, and then algae and seawater samples were collected in Hai-tan Strait. The correlation on HAB (harmful algae blooms) species and environmental factors were studied. Water temperature (T) and salinity (S) ranging from 11.9 °C to 27.8 °C and 20.4 to 33.7 in the year, respectively. Dissolved inorganic nitrogen (DIN) in surface water ranged from 0.098 to 0.776 mg·L−1, PO4-P ranged from 0.0016 to 0.0729 mg·L−1. And Eutrophication index (E) ranged from 0.03 to 13.8, varied different. 102 species of algae belonging to 4 classes and 52 genera were identified. The diversity was increasingly from winter to summer, decreasingly from summer to autumn, highest in summer. 49 species of red tide organisms were found in Hai-tan Strait, main two classes were Bacillariophyta and Pyrrophyta. Ceratium tripos and Noctiluca scintillans were dominant species in spring, Skeletonema costatum was common, and was also mainly HABs dominant species in summer, autumn and winter. Pearson correlation and Canonical correspondence analysis (CCA) showed that environment factors had significant correlation with dominance HABs species in different extent, and the ordination result was that S(Salinity) > T(Temperature) > pH > E(Eutrophication index) > DO(dissolved oxygen) > DIN > PO4-P. Prorocentrum donghaiense, Skeletonema costatum, Noctiluca scintillans and Karenia mikimotoi caused many times red tide in 2011 to 2016. However, Prorocentrum donghaiense and Karenia mikimotoi cell density was low in survey year. North of the strait and east coast of the southern strait were sensitive sea area of red tide. The work highlights for the first time ecological characteristic of HAB was studied in Hai-tan Strait. Further, the data and results of this study will help us to improve efficiency for controlling HAB. Even, it is worthwhile to the management and response to the red tide disaster. Ordination result can also be a good indicator of ecological risk.

Prey preference, environmental tolerances and ichthyotoxicity by the red-tide dinoflagellate Noctiluca scintillans cultured from Tasmanian waters

AbstractThe large phagotrophic dinoflagellate Noctiluca has become a prominent red tide organism in southeast Australian waters since the 2000s, raising concerns for beach tourism, grazing impacts as well as ichthyotoxicity for finfish aquaculture. Satisfactory culture growth rates (0.23–0.56 per day) were obtained by feeding with small Thalassiosira diatom and Tetraselmis flagellate diets, while optimal growth rates sustained for up to 8 months (0.69 per day) were achieved by feeding in a plankton wheel with the large chain-forming dinoflagellate Gymnodinium catenatum. Noctiluca was highly tolerant towards salinities from 20 to 35 and growth was stimulated by temperatures increasing from 10 to 23°C, which in combination with the key factor of prey abundance explains the incidence in southeast Australia of predominantly summer and spring but occasionally also winter blooms. Fatty acid biomarkers suggest that Tasmanian field populations indiscriminately feed on available diatom and dinoflagellate mixtures. Noctiluca exhibited very limited ichthyotoxicity, and only at the highest cell concentrations of 2 000 000/L (50% reduction in RTgill W1 cell viability). Only the densest red tide surface slicks contained acutely toxic levels of unionized ammonia of 242 to 510 μg/L while inshore slicks generated oxygen concentrations as low as 0–1.5 ppm. Lipid phycotoxins (eicosapentaenoic acid, docosahexaenoic acid) did not appear to contribute to Noctiluca ichthyotoxicity. The fatty acid 20:0 eicosanoic acid may serve as a potential Noctiluca biomarker in marine food webs and sediments.

Inhibition effect of natural flavonoids on red tide alga Phaeocystis globosa and its quantitative structure-activity relationship

Red tides that occur off coasts have become a worldwide phenomenon over the past decades. In order to mitigate the damage of the red tides on the aquatic ecosystems, it is crucial to develop a method for predicting algicidal activities that requires less labor and time, and most importantly, this method can quickly screen potential algicides to control red tides. In this study, we have investigated the algicidal activity of 19 natural flavonoids against a typical red tide alga, Phaeocystis globosa. Our results indicate that after 5 days of flavonoid exposure, the half inhibition concentrations (IC50) ranged from 0.068 to 3.065 mg L-1, which showed the strong algicidal activities of the flavonoids. Furthermore, quantitative structure activity relationship (QSAR) model has been carried out between negative scale logarithm (pIC50) of the flavonoids and the corresponding molecular descriptors. The developed model was validated, both internally and externally, which displayed statistical robustness (R2 = 0.867, p = 0.0002, Q2LOO = 0.825, RMSEC = 0.182, Q2extF3 = 0.896, RMSEP = 0.161, CCC = 0.935). This indicates that the developed model was obtained successfully with satisfactory predictability and robustness for the future rapid screening of natural flavonoids with high inhibition activity on the red tide alga growth. Moreover, the main descriptors in the QSAR model were the molar refractivity, partition coefficient, lowest unoccupied molecular orbital, and highest occupied molecular orbital, illustrating that the molecular electro-chemical characteristics are significant in the algicidal actions of the flavonoids. Graphical abstract Red tides frequently occur worldwide and have become a global environment problem. Flavonoids showed great potential in allelopathic control of the excessive growth of red tide algae. In this study, the algicidal activity of 19 natural flavonoids was investigated on a typical red tide organism Phaeocystis globosa. Futhermore, we applied the quantitative structure-activity relationship (QSAR) model to the experimental data. The model between molecular descriptors of flavonoids and their antialgal activity displays statistical robustness, and 4 of 45 selected molecular descriptors were obtained by regression of training set. The numbers in the figure represent the half inhibition concentration (IC50) of flavonoids. Our results show that the algicidal activity of flavonoids is closely related to molar refraction, partition coefficient, lowest unoccupied molecular orbital, and highest occupied molecular orbital. The QSAR model can efficaciously predict the algicidal activity and provide insights into the inhibitory mechanisms of flavonoids.

The outbreak of Chochlodinium sp.: the red tide maker in the coastal of Lampung Bay

Red tide is a common phenomenon and almost present every year in Lampung Bay. In 2012, the red tide in Lampung Bay showed a different characteristic compared to the previous ones. The research was conducted to analyze the characteristics of organisms causing the red tide and the factors affecting its occurrence. Assessments were done by identifying the dominant phytoplankton and observing the environmental condition using rapid assessment method. Seawater sampling was conducted in 15 stations in December 2012 to monitor the phytoplankton abundance, nutrient, and physical condition. The results showed that the organism dominating the phytoplankton population is Cochlodinium sp., comprising of 85.89% of the total phytoplankton suggesting it was the red tide organism in the Bay. The average abundance of this species in the stations was 2.0 × 104cells/L. Choclodinium sp. was present agglomerated and distributed along the west coast of the bay. The highest concentration of the organism was found around the tip of the bay. The outbreaks of Choclodinium sp. were induced by the high concentration of nitrogen in the coastal water with N:P ratio of 35.5. Moreover, the physical condition of the coastal water strongly influenced the distribution and abundance of Cochlodinium sp. in the bay.

Studies on the ·OH Inactivation of Non-native Aquatic Organisms and Potential Disinfection Byproduct Formation for Oceanic Environmental Safety

This work was carried out based on the principles of biological effectiveness and environmental acceptability of the International Maritime Organization (IMO). The non-native red tide organisms Prorocentrum donghaiense and Scrippsiella trochoidea were selected to examine ·OH inactivation to meet the IMO standard of ballast water discharge (< 10 cells/mL). The effective quantum yield of photosystem II of algal chlorophyll rapidly decreased to zero within a contact time of only 6 s. Under scanning electron microscope (SEM) observation, the algal cells treated with the ·OH inactivation dose still had an intact shape and did not release cellular material, and thus, there are no risks associated with oceanic environmental safety. The potential disinfection byproducts (DBPs) from discharged ship’s ballast water at high salinity (33.7 PSU) treated at a maximum TRO dose of 2.41 mg/L were analyzed by 5-day storage experiments. The results indicated that the contents of bromate, trihalomethanes (THMs), haloacetic acids (HAAs) and haloacetonitriles (HANs) were below the WHO drinking water standards. Therefore, discharged ship’s ballast water with ·OH inactivation is safe for oceanic environments.

Ichthyotoxic Cochlodinium polykrikoides red tides offshore in the South Sea, Korea in 2014: III. Metazooplankton and their grazing impacts on red-tide organisms and heterotrophic protists

Ichthyotoxic Cochlodinium polykrikoides red tides offshore in the South Sea, Korea in 2014: III. Metazooplankton and their grazing impacts on red-tide organisms and heterotrophic protists

Ichthyotoxic Cochlodinium polykrikoides red tides offshore in the South Sea, Korea in 2014: II. Heterotrophic protists and their grazing impacts on red-tide organisms

Ichthyotoxic Cochlodinium polykrikoides red tides offshore in the South Sea, Korea in 2014: II. Heterotrophic protists and their grazing impacts on red-tide organisms

Ichthyotoxic Cochlodinium polykrikoides red tides offshore in the South Sea, Korea in 2014: I. Temporal variations in three-dimensional distributions of red-tide organisms and environmental factors

Ichthyotoxic Cochlodinium polykrikoides red tides offshore in the South Sea, Korea in 2014: I. Temporal variations in three-dimensional distributions of red-tide organisms and environmental factors

Influences of Zeta Potential, Water Absorption and Surface Roughness of Porous Ceramics on Marine Bio-fouling

The red tide organisms occurring at seashores in Korea damage the marine fish-raising industry every summer. Several methods to prevent the occurrence of red tide organisms, therefore, have been tried; one of them is to filter out red tide organisms using a membrane filled with porous ceramic bodies, allowing only fresh seawater to pass into a fish farm. When this method is used for long period of time, however, the problem of marine bio-fouling can develop on the surfaces of the porous ceramic body, deteriorating the filtering function of the porous bodies. In this paper, the influences of the zeta potential, water absorption and surface roughness of porous ceramics on marine bio-fouling have been inspected. In order to control the above three factors, three kinds of ceramic powders, alumina, titania and zirconia, were coated on the porous bodies. As a result, the water absorption and the surface roughness of the porous ceramics were found to be equally important factors in preventing bio-fouling, while the zeta potential of the specimens did not show a prominent effect. In detail, the water absorption of specimens was an effective factor in the early stages of bio-fouling for about one month; on the other hand, the surface roughness of the specimen was a main factor that could be used to control the amount of bio-fouling after one month. Among the three ceramic powders used as coatings, alumina, by imparting lower water absorption and higher surface roughness to the specimens, proved to be the optimum one to prevent marine bio-fouling.

A hierarchy of conceptual models of red-tide generation: Nutrition, behavior, and biological interactions

Red tides – discolorations of the sea surface due to dense plankton blooms – occur regularly in coastal and offshore waters along much of the world's coastline. Red tides often cause large-scale mortalities of fish and shellfish and significant losses to the aquaculture and tourist industries of many countries. Therefore, understanding and predicting the mechanisms controlling the outbreak, persistence, spread, and decline of red tides are important concerns to scientists, officials, industry, and the public. With increasing knowledge of red-tide species and red-tide events, new mechanisms have been discovered. Based on the nutrition and behaviors of red-tide organisms and biological interactions among them, red-tide outbreaks can be categorized into a hierarchy of four generation mechanisms (GM1–GM4). In the simplest, GM1, all phototrophic red-tide species were treated as exclusively autotrophic organisms without the ability to swim. However, this GM cannot explain red-tide outbreaks in oligotrophic surface waters offshore. Vertical migration (considered in GM2) and mixotrophy (GM3) enable red-tide flagellates to acquire growth factors from nutrient-rich deep waters or co-occurring prey, respectively. In natural environments, all red tides occur by those species outgrowing co-occurring organisms; red-tide species dominate communities by eliminating other species or reducing their abundances. Thus, GM4 contains the direct biological interactions (i.e., inhibition by physical contact or chemical effects) and indirect biological interactions (i.e., acquiring resources faster than others) that can affect the dominance of red-tide species under given conditions. Correctly choosing one of these four GMs for red tides dominated by one causative species is important because the accuracy of predictions may be outweighed by the costs and time required to acquire the relevant information. In this study, mechanisms describing the outbreak, persistence, and decline of red tides were reviewed, the advantages and limitations of each mechanism were evaluated, and insights about the evolution of the mechanisms were developed.