Red Tide Occurrence Research Articles

Modulatory effects of Enteromorpha prolifera powder and its enzymatic hydrolysate on growth performance, antioxidant capacity, and non-specific immunity of Trachinotus ovatus

The excessive proliferation of the genus Enteromorpha serves as the primary catalyst for the occurrence of red tides. Nonetheless, this genus is abundant in sulfated polysaccharides, phenolic compounds, peptides, and alkaloids, which exhibit remarkable efficacy in antioxidation, anti-inflammation, and immune response modulation. Consequently, Enteromorpha-derived products hold promising application prospects as aquatic feed additives. The primary objective of this study was to evaluate the impact of E. prolifera powder (EPM) and its enzymatic hydrolysate (EPH) on the growth, antioxidant capacity, intestinal morphology, and immunity of juvenile Trachinotus ovatus. Four isonitrogenous and isolipidic diets were formulated with varying levels of Enteromorpha products: 0 % (Control), 0.1 % EPH (EPH0.1), 0.3 % EPH (EPH0.3), and 3 % EPM, and were administered to juvenile T. ovatus for eight weeks. The findings revealed that growth performance in the EPH0.3 and EPM groups surpassed that of the control group, concomitant with increased feed intake and elongated intestinal villi. Notably, Enteromorpha-derived products supplementation significantly bolstered the antioxidant capacity of T. ovatus through activation of the Nrf2-Keap1 signaling pathway, leading to elevations in antioxidant enzymes such as SOD and CAT, as well as T-AOC. Conversely, MDA levels were conspicuously reduced in the Enteromorpha-treated groups. Moreover, Enteromorpha-derived products supplementation exhibited pronounced anti-inflammatory effects, marked by the downregulation of proinflammatory cytokine expression and upregulation of anti-inflammatory cytokines, along with decreased apoptotic gene expression. These observations highlight the potential anti-inflammatory properties of EPM and EPH, which may contribute to the preservation of hepatic tissue health and homeostasis. In summary, the optimal growth performance and antioxidant capacity were achieved with 0.3 % EPH supplementation, indicating the efficacy of this concentration in promoting the overall wellbeing of T. ovatus. Remarkably, the employment of processing methodologies, notably enzymatic hydrolysis, has not only facilitated the manifestation but also potentially augmented the inherent beneficial attributes traditionally ascribed to EPM. Furthermore, this refinement process has enabled a reduction in the inclusion rate of EPM within feed formulations, thereby enhancing cost-effectiveness. Consequently, Enteromorpha-derived products emerge as highly promising candidates for aquatic feed additives, with the potential to mitigate the economic burdens imposed by red tide management strategies. Their utilization represents a strategic approach towards sustainable aquaculture practices.

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.

Zirconium-based metal-organic framework composites for solid phase extraction of brevetoxin-A from seawater

Red tides are a type of natural marine disaster caused by harmful algae characterized by a high toxicity, wide distribution, and long duration. Since the concentration of algal toxins in seawater increases with the occurrence of red tides, algal toxins detected in seawater could be used to predict the occurrence and evolution of red tides. Brevetoxin-A (BTX-A) is a secondary metabolite produced by the harmful algae Karenia brevis, whose detection in seawater could form the basis of an accurate warning system for incoming red tides. However, due to the inherent complexity of the seawater matrix and the extremely low levels of BTX-A in seawater, the use of instruments for its direct detection is difficult. Therefore, there is an urgent need to develop a sample pretreatment method for the efficient enrichment of BTX-A in seawater. In this study, a metal-organic backbone material (UiO-66) and its composite with silica microspheres (SiO2@UiO-66) were successfully synthesized using the solvothermal method. The prepared SiO2@UiO-66 exhibited good hydrophilicity, water stability, and large specific surface area. Furthermore, it also exhibited hydrogen bonding and electrostatic interactions with BTX-A, had a strong affinity for BTX-A, and was able to efficiently adsorb BTX-A in complex matrices. Therefore, SiO2@UiO-66 showed potential as a novel packing material for the extraction of BTX-A from solid phase extraction columns. Combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), a highly sensitive detection method for the determination of BTX-A in marine water was established. The established analytical method had a low detection limit (3.0 pg/mL), a wide linear range (10.0 -200.0 pg/mL), and a good linear relationship (R=0.9992). Combined with the Fujian Province Red Tide Monitoring and Early Warning Information 2021 issued by the Fujian Provincial Oceanic and Fisheries Bureau, the analytical method established herein was successfully applied to analyze and monitor the content of BTX-A in actual seawater samples. This highlights the proposed system's potential for use as an early warning factor in the monitoring of red tides, representing a simple and fast pretreatment methodology for the detection of BTX-A in seawater.

Experimental analysis on the optimal spectral index for the risk assessment of red tide occurrence

Experimental analysis on the optimal spectral index for the risk assessment of red tide occurrence

Mechanistic characterization of dissolved inorganic phosphorus in water during the red tide

The eutrophication of water, such as excessive nitrogen and phosphorus, are closely associated with the outbreak of red tide. However, the response of dissolved inorganic phosphorus (DIP) to red tide remained unclear in water. In this study, three species of diatoms capable of causing red tides were cultured in simulated seawater with different concentrations of DIP. The changes of biomass, chlorophyll a concentration and the carbon stable isotope composition of microalgae, the DIP concentration and pH of the culture medium were compared among the experimental groups. In addition, correlation verification was used to test the correlation between the change of DIP concentration and other indicators. The results showed that in the experimental period, the DIP concentration of each experimental group decreased significantly first, and the concentration dropped to less than 40% of the initial level. After that, the pH of the medium, the biomass, chlorophyll a concentration and carbon stable isotope composition of the microalgae showed varying degrees of increase, and then stabilized or decreased. These also marked the outbreak of red tide. Moreover, the correlation test showed that there was a correlation between them and the change of DIP concentration. Therefore, by exploring the relationship between the change of DIP concentration in water and the occurrence of red tide, this study provides a possible direction for the current prediction of red tide, and provides a basis for further investigation of the occurrence mechanism of red tide.

Marine heatwaves alter competition between the cultured macroalga Gracilariopsis lemaneiformis and the harmful bloom alga Skeletonema costatum

Seaweed cultivation can inhibit the occurrence of red tides. However, how seaweed aquaculture interactions with harmful algal blooms will be affected by the increasing occurrence and intensity of marine heatwaves (MHWs) is unknown. In this study, we run both monoculture and coculture systems to investigate the effects of a simulated heatwave on the competition of the economically important macroalga Gracilariopsis lemaneiformis against the harmful bloom diatom Skeletonema costatum. Coculture with G. lemaneiformis led to a growth decrease in S. costatum. Growth and photosynthetic activity (Fv/Fm) of G. lemaneiformis was greatly reduced by the heatwave treatment, and did not recover even after one week. Growth and photosynthetic activity of S. costatum was also reduced by the heatwave in coculture, but returned to normal during the recovery period. S. costatum also responded to the stressful environment by forming aggregates. Metabolomic analysis suggests that the negative effects on S. costatum were related to an allelochemical release from G. lemaneiformis. These findings show that MHWs may enhance the competitive advantages of S. costatum against G. lemaneiformis, leading to more severe harmful algal blooms in future extreme weather scenarios.

엘니뇨/라니냐와 한국 연안의 적조 발생 관계

엘니뇨/라니냐와 한국 연안의 적조 발생 관계

Observations of water optical properties during red tide outbreaks off southeast Hokkaido by GCOM-C/SGLI: implications for the development of red tide algorithms

ABSTRACT A severe red tide event, caused primarily by dinoflagellate Karenia selliformis, occurred during the autumn of 2021 in the waters off southeast Hokkaido and resulted in damage of $70 million to fishery industries. There is a high demand for early warning methods based on ocean colour observations to respond to future occurrences of red tides. We therefore used a quasi-analytical algorithm to compute the total absorption coefficient (a) from the Second Generation Global Imager (SGLI) remote sensing reflectance and assessed its potential to detect blooms of K. selliformis. We discovered that, within the same range of SGLI-retrieved chlorophyll-a concentrations, the a at a wavelength of 530 nm a(530) tended to be lower during K. selliformis blooms than during diatom blooms. The a(530) observed by the SGLI therefore showed promise as an optical property for detecting K. selliformis blooms. We discuss the reasons for selection of a(530) and the limitations of the current study’s bloom detection method.

Red Tide Detection Method Based on Improved U-Net Model-Taking GOCI Data in East China Sea as an Example.

In the coastal areas of China, the eutrophication of seawater leads to the continuous occurrence of red tide, which has caused great damage to Marine fisheries and aquatic resources. Therefore, the detection and prediction of red tide have important research significance. The rapid development of optical remote sensing technology and deep-learning technology provides technical means for realizing large-scale and high-precision red tide detection. However, the difficulty of the accurate detection of red tide edges with complex boundaries limits the further improvement of red tide detection accuracy. In view of the above problems, this paper takes GOCI data in the East China Sea as an example and proposes an improved U-Net red tide detection method. In the improved U-Net method, NDVI was introduced to enhance the characteristic information of the red tide to improve the separability between the red tide and seawater. At the same time, the ECA channel attention mechanism was introduced to give different weights according to the influence of different bands on red tide detection, and the spectral characteristics of different channels were fully mined to further extract red tide characteristics. A shallow feature extraction module based on Atrous Spatial Pyramid Convolution (ASPC) was designed to improve the U-Net model. The red tide feature information in a multi-scale context was fused under multiple sampling rates to enhance the model's ability to extract features at different scales. The problem of limited accuracy improvement in red tide edge detection with complex boundaries is solved via the fusion of deep and shallow features and multi-scale spatial features. Compared with other methods, the method proposed in this paper achieves better results and can detect red tide edges with complex boundaries, and the accuracy, precision, recall, and F1-score are 95.90%, 97.15%, 91.53%, and 0.94, respectively. In addition, the red tide detection experiments in other regions with relatively concentrated distribution also prove that the method has good applicability.

Assessment of Eutrophication Characteristics and Evaluation of the First-Generation Eutrophication Model in the Nearshore Waters of Shantou City

Based on the water quality monitoring results from 2002 to 2018 in the coastal waters of Shantou City, this study used eight methods, including the single-factor index method, eutrophication index method, nutrient status quality method, comprehensive index method, organic pollution index method, nitrogen–phosphorus ratio method, potential eutrophication evaluation, and dissolved oxygen saturation parameter method, to evaluate the eutrophication and organic pollution status of the area. The applicability of the first-generation eutrophication model was assessed from the perspective of red tide occurrence, and a comparison was made among the various evaluation methods. The results indicate that the coastal waters of the study area were mostly in a phosphorus-limited state, with a few periods of nutrient deficiency and a very small portion of time in a moderately nutritious state with both nitrogen and phosphorus limitations. The overall N/P ratio showed an increasing trend primarily due to the gradual increase in inorganic nitrogen content. In terms of evaluating eutrophication based on red tide symptoms, the comprehensive index method showed better performance in reflecting eutrophication conditions, while the eutrophication index method and dissolved oxygen saturation parameter method highlighted problematic areas but often exaggerated their extent. The nutrient status quality method and organic pollution index method did not provide distinctive indications and could not verify red tide symptoms. The nitrogen–phosphorus ratio method and potential eutrophication evaluation could reflect certain nutrient structures and eutrophication characteristics but also failed to verify red tide symptoms. Furthermore, this study found a certain correlation between the occurrence of red tide and the ratio of nitrate nitrogen to ammonia nitrogen, which consistently ranged from 1.15 to 1.94 during red tide events. Therefore, whether this ratio can serve as a characteristic value for red tide occurrence and be used for early warning and monitoring still requires further validation.

Influence of terrestrial organic matter loading on the occurrence of red tides and hypoxia in Isahaya Bay, Japan

Influence of terrestrial organic matter loading on the occurrence of red tides and hypoxia in Isahaya Bay, Japan

Analysis of hydrodynamic characteristics during the occurrence of red tide in the Qinhuangdao sea area

The Qinhuangdao coastal area in northern China is a significant site for aquaculture and coastal tourism. However, frequent red tides have adversely affected water quality and fishery resources in recent years. This research investigates the hydrodynamic characteristics of the area by conducting continuous seabed observations during the summer of 2019 and analyzing historical data. The goal is to identify potential impacts on bath water quality and red tide disasters. The findings indicate that Qinhuangdao falls under the diurnal tide sea area category with a small tidal range. The northern and southern regions experience regular and irregular diurnal tides, respectively, with tropic and equinoctial tides occurring every half a month. The prevailing tidal current type is an irregular semidiurnal tidal current, with M2 tidal current prevailing along the coast, exhibiting weak power and slightly higher offshore velocity. During the summer, the residual current velocity is relatively small, mainly flowing northeastward along the isobaths, while the surface residual current in the southeast of Beidaihe flows toward the shore. The area has several rivers with high summer runoff, resulting in pollutants from Tanghe, Daihe, and Yanghe river estuaries being easily transported to the beach, adversely affecting water quality and the environment. Pollutant accumulation on the north side of the bath, near the harbor area, is likely due to weak water exchange and offshore residual current inflow, which may trigger red tide outbreaks.

Review on an integrated pre-treatment system to reduce membrane accelerated biofouling during red tide occurrences in Oman

The increasing pressure on available freshwater resources to meet the demand for all human activities raised the importance of finding new water resources. Desalination of seawater and water reuse considered the most reliable sources of fresh water. Seawater desalination is a high-powered consuming process therefore seawater reverse osmosis desalination is currently the most widely implemented technology because of its lower power consumption compared to thermal desalination also it requires less footprint, generates less waste, and has reliable performance. To ensure preserving high performance of Seawater reverse osmosis (SWRO) plants, there is a need for an active pre-treatment system to deliver a continuous good quality feed for the RO membranes. Among various issues faces the use of RO membranes like chemical attack and scaling of membrane, but membrane fouling is the most challenging issue. As per the literature study, there are various pre-treatment systems implemented worldwide in SWRO plants and they are classified as conventional technologies including coagulation, sedimentation, media filtration, and flotation or membrane-based technologies like microfiltration, ultrafiltration, and nanofiltration. Conventional systems are more complex to design & operate, require a high footprint, and are better option when seawater has high contents of oil and organic matters. While membrane-based systems have less space requirements, simple to operate, and more effective for particulate matter removal but they are costly and sensitive for algal bloom. This comprehensive review study focusses on feasibility of utilizing Dissolved Air Flotation (DAF) in an integrated system that combines conventional and membrane pre-treatment systems to provide a decent quality feed water for SWRO. Integrated system is proposed as a pre-treatment system because dissolved air flotation characterized by high organic foulants removal and membrane-based pre-treatment are reliable and have high permeate flux.

Nutrient Flux under the Influence of Melt Water Runoff from Volcanic Territories and Ecosystem Response of Vilyuchinskaya and Avachinskaya Bays in Southeastern Kamchatka

Nutrient fluxes with river runoff can largely determine the state of coastal water ecosystems. The Vilyuchinskaya and Avachinskaya Bays of Kamchatka Peninsula were surveyed on 4–5 July 2022, just after the peak of the spring–summer flood of the Vilyucha and Avacha Rivers associated with the snow melting in volcanic areas. Additionally, water sampling was performed in river water in December 2022, in the period of winter low water. A general undersaturation of CO2 of surface waters was observed in the Vilyuchinskaya and Avachinskaya Bays. Strong supersaturation of CO2 of the near-bottom waters was observed, due to microbial destruction of organic matter, especially in Avachinskaya Bay. This organic matter was formed as a result of photosynthesis in the water column, which subsequently gravitated to the bottom and concentrated in specific bottom depressions in the studied bays. In these depressions, black sediments were found, in which sulfate reduction occurred. The porewater of sediments had a very high concentration of organic carbon, dissolved and organic nitrogen, and phosphates, as well as CO2 partial pressure. The source of nutrients for the studied bays is tephra (volcanic suspended particles), which covers all the watersheds, including the soil and snow, as a result of volcanic activity in the study region. Based on the calculated nutrient fluxes in river runoff for the summer and winter seasons and the DIN/DIP ratios in river, sea, and pore waters, the causes of phytoplankton blooms, including the occurrence of red tides, are discussed. The maximum flux of nutrients and, accordingly, phytoplankton blooms should be expected in the years with the highest volcanic activity and high summer air temperatures, since the melting of nutrient-rich snow and ice will be maximum. This will determine the flux of nutrients in the river runoff of the Kamchatka Peninsula and contribute to phytoplankton blooms.

H3K79 methylation promotes rapid growth of Alexandrium pacificum under high light intensity via increased photosynthesis

Alexandrium pacificum is one of the main species responsible for harmful algal blooms, posing serious threats to coastal ecosystems, economies, and public health. Light intensity is an important abiotic factor affecting the occurrence of red tides. In a certain range, increasing light intensity can promote the rapid growth of A. pacificum. This study aimed to elucidate the molecular mechanisms of H3K79 methylation (H3K79me) in response to high light intensity during the rapid growth of A. pacificum and the formation of toxic red tides. The research found that the abundance of H3K79me increased 2.1-fold under high light (HL, 60 μmol photon m−2 s−l) compared to control light conditions (CT, 30 μmol photon m−2 s−l), which was consistent with the trend of rapid growth under HL, and both can be inhibited by EPZ5676. Then effector genes of H3K79me under HL were identified using ChIP-seq and a virtual genome constructed based on transcriptome data of A. pacificum for the first time. The results showed that the differential modification-associated genes were primarily enriched in the pathways of “energy metabolism”, “carbon metabolism”, and “amino acid metabolism”. These findings were confirmed through ChIP-qPCR. Subsequently, H3K79me-associated genes CP43 and GOGAT were identified by combined analysis of ChIP-seq and differentially expressed genes. Finally, pharmacological experiments using the H3K79me inhibitor EPZ5676 showed that the expression of the photosynthesis-related gene CP43 was significantly reduced by 2.5-fold and the maximum photochemical quantum efficiency of A. pacificum was reduced by 1.2 to 1.8-fold in HL compared with CT, leading to inhibited growth of A. pacificum. These results suggest that H3K79me plays a role in regulating the rapid growth of A. pacificum and photosynthesis is likely an important regulatory pathway, which is the first to provide epigenetic evidence underlying the formation of toxic red tides from the perspective of H3K79me.

Incidence of harmful algal blooms in pristine subtropical ocean: a satellite remote sensing approach (Jeju Island)

Despite the increasing numbers of red tide events in the pristine subtropical ocean, a paucity of previous observations has limited understanding of harmful algae in the seas around the Korean Peninsula. Therefore, using six years (2012–2017) of Geostationary Ocean Color Imager (GOCI) satellite data, we characterized the red tides around Jeju Island, a volcanic island located near the paths of the Jeju Warm Current and Tsushima Warm Current, using the Normalized Red Tide Index (NRTI) method. The seawater around Jeju Island has for a long time been considered to be very clear, with relatively low suspended particulate matter concentrations and few harmful algae. Nonetheless, the satellite-based NRTI detection method used in this study detected and supported the existence of red tides in the coastal region around Jeju Island. Analysis of the red tide distribution showed that red tide first began to appear near the western coast of Jeju Island, then developed in the northern and eastern coastal regions, and finally vanished in the eastern coastal region. The monthly averages of the NRTI demonstrated a bloom event from April to May in every year. Additional fall blooms were detected in August–September, particularly in 2013 and 2016. The NRTI revealed strong interannual variations. The longest blooms occurred in 2015, and the most comprehensive and strongest event occurred in the spring of 2016. The latter three years (2015–2017) had much higher NRTI than the former three years (2012–2014). The probability of red tide occurrence at a given point during the 6-year study period revealed spatial differences. Relatively high probability of 0.3–0.5 was determined along the northern coastal region, whereas low probability of less than 0.2 was found along the southern region. Ground truth data also showed more frequent observations and higher red tide cell densities along the northern coast. Changes in NRTI in spring are positively correlated with changes in ENSO indices in winter. This study is the first to use a satellite-based approach with a vast long-term satellite database to elucidate the existence and probability of red tides near Jeju Island. We anticipate that this study will provide a useful strategy for remote monitoring of harmful algal blooms over wide regions using optical data.

A novel algicidal properties of fermentation products from Pseudomonas sp. Ps3 strain on the toxic red tide dinoflagellate species.

The viability of both China's offshore fishing operations and the global marine fishing industry is threatened by the occurrence of red tides caused by Gymnodinium catenatum and Karenia mikimotoi. Effective control of these dinoflagellate-mediated red tides has become a pressing issue that requires immediate attention. In this study, High-efficiency marine alginolytic bacteria were isolated and underwent molecular biological identification to confirm their algicidal properties. Based on a combination of morphological, physiological, biochemical, and sequencing results, Strain Ps3 was identified as belonging to the species Pseudomonas sp. We examine the effects of algicidal bacteria on the red tide species G. catenatum and K. mikimotoi within an indoor experimental setting. Then gas chromatography- mass spectrometry (GC-MS) was used to analyze the structure of the algolytic active substances. This investigation demonstrated that with exposure to the algae-lysis experiment, the Ps3 strain has the best algae-lysis effect, with G. catenatum and K. mikimotoi reaching 83.0 and 78.3%. Our results from the sterile fermentation broth experiment showed that the inhibitory effect on the two red tide algae was positively correlated with the concentration of the treatment. At a treatment concentration of 2.0% (v/v), the 48 h lysis rates of G. catenatum and K. mikimotoi due to exposure to the Ps3 bacterial fermentation broth were 95.2 and 86.7%, respectively. The results of this study suggest that the algaecide may be a rapid and effective method to control dinoflagellate blooms, as evidenced by the observed changes in cellular morphology in all cases. In the ethyl acetate phase of Ps3 fermentation broth, the cyclic (leucine-leucine) dipeptide was the most abundant. The findings of this study contribute to our understanding of red tide prevention and control and provide a theoretical foundation for further research in this field.

Evaluation of environmental impact of red tide around Pearl River Estuary, Guangdong, China

This paper presents a case study of red tide hazards around the Pearl River Estuary (PRE). Red tide hazards, meteorological data, and seawater monitoring data were collected from 1996 to 2020 at different locations around the PRE to investigate the internal and external factors influencing the occurrence of red tides. The enhancement of the assessment of estuarine trophic status (ASSETS) method enables us to evaluate the effects of meteorological factors and seawater eutrophication status on the red tide risk level. Using ASSETS, we established a framework for red tide risk assessment of the Pearl River Estuary. We analysed the external and internal factors causing the red tide based on meteorological data and seawater monitoring data in the PRE. The results show that the temperature was higher than the annual monthly average temperature of 1.265 °C, and east and north winds at velocities of 3–4 m/s could result in the formation of red tides. However, precipitation inhibits the formation of the red tide in PRE.

PIRT: A Physics-Informed Red Tide Deep Learning Forecast Model Considering Causal-Inferred Predictors Selection

In this paper, a Physics-Informed Red Tide forecast model (PIRT) considering causal-inferred predictors selection is proposed. Specifically, the directed acyclic graph-graph neural network (DAG-GNN) method is first applied to quantify the causality among multiple ocean-atmosphere-biology variables for selecting the most significant predictors of the red tides (or other chlorophyll variations). Then, the encoder-decoder model consisting of an Energy Attention Module (EAM) is built for daily red tide forecasting. The multi-sourced multivariate dataset during 2010-2020 covering the East China Sea serves to train and evaluate PIRT. The experimental results demonstrate that the predictors in the learned causal graph are closely related to the occurrence and decay of red tides, which exhibits high physical interpretability. PIRT has a superior forecasting skill, the predictions of which are with highly consistent spatial patterns especially in extreme events. The 7-lead-day forecast errors for chlorophyll are within 0.9 mg∙m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> , which is much better than the other models. This also indicates that PIRT can be used as a reliable tool to study the ecology of the East China Sea.

Prediction of chlorophyll‐a data based on triple‐stage attention recurrent neural network

AbstractMarine Internet of Things (IOT) is the use of Internet technology to connect various sensing devices at sea, so as to integrate maritime information and realize the monitoring and systematic management of complex data at sea. The marine environment is complex and changeable, and marine disasters occur frequently, such as red tides. Due to the sudden and destructive nature of red tide, it plays a pivotal role to monitor the occurrence of the red tide for the marine IoT, where machine learning has been widely used to predict red tides. However, they were rarely able to catch the sudden change of chlorophyll‐a, which has important practical significance for predicting the occurrence of red tide. In order to deal with the above problems, this paper proposes the triple‐stage attention‐based recurrent neural network, which can enhance the representation ability of input sequences, selectively capture dynamic spatial correlations between input multi‐channel observations in the input sequence, meanwhile adaptively capturing dynamic temporal correlations between different time intervals in the input sequence. The results show that this method outperforms the state‐of‐art baseline methods here.