Forecast of Red Tide in the South China Sea by Using the Variation Trend of Hydrological and Meteorological Factors

Many studies point out that weather conditions involving temperature, wind power, monsoon transform, air pressure, sea condition, tide, ocean current, salinity, eutrophic environment and so on are key factors causing Red Tide. In the red tide high frequency areas of the South China Sea, the eutrophic environment of sea water has already existed, so the key elements such as meteorological and hydrological conditions play an importance role in the occurrence of red tide. The atmospheric circulation maintenance and variation decide whether meteorological phenomena, and hydrological key elements stabilize or change. Moreover, the red tide organisms＇ breeding from the initial stage to the blooming reproduction stage, until reaching the biological density of the red tide, generally takes 4 - 5 days. In the paper, the red tide examples are analyzed in the past 10 years, and the weather circulation situation and hydro-meteorological key elements of it are counted to find the previous circulation mode and bring out important factors inducing the blooming of red tide. The predicted result in 2003 according to this method was satisfactory.

Time series analysis of red tide's disaster characteristics in China seas

The annual frequency of red tides from 1977 to 2012 and the monthly frequency of red tides from 2001 to 2012 in China seas were used to establish the time series of red tide annual frequency and monthly frequency, respectively. The annual frequency fit well with time segments revealed by piecewise linear regression analysis. The seasonal maximum of monthly frequency was in May （-18.22）, and the stochastic volatility tended to increase gradually with time series, with peak values occurring from May to July. Holt exponential smoothing and Holt-winter exponential smoothing were used to predict red tide annual and monthly frequencies, which revealed that the annual frequency of red tides would rise slowly by one time from 2013 to 2020, and that red tides would mainly occur from May to July in 2013-2016 with a peak value of about 25 times in May.

FIVE RED TIDE SPECIES IN GENUS PROROCENTRUM INCLUDING THE DESCRIPTION OF PROROCENTRUM DONGHAIENSE LU SP. NOV.FROM THE EAST CHINA SEA

A new planktonic dinoflagellate, Prorocentrum donghaiense Lu sp. nov., is described in the present paper. The water sample was collected from the Changjiang Estuary, the East China Sea. The species identification is based on shape, size, surface micro morphology, ornamentation of thecal plates and the architecture of the periflagellar area and the intercalary bands as seen by light and scanning electron microscope. Prorocentrum donghaiense Lu sp. nov. is compared with other prorocentrum species with respect to morphological characteristics and bloom behavior. It is not known whether Prorocentrum donghaiense Lu sp. nov produces phycotoxins like some other Prorocentrum species. Four other red tide species in the family Prorocentraceae (Dinophyceae), namely P. balticum , P. minimum, P. micans, P. triestinum , were examined and identified by light and scanning electron microscope. They have been recorded as bloom forming species. Some aggregates of Prorocentrum are observed at the end of blooms. An event of strong discoloration caused by P. donghaiense could be detected by satellite sensor in the East China Sea in the late spring of 1995.

APPLICATION OF CLAYS TO REMOVAL OF RED TIDE ORGANISMS II. COAGULATION OF DIFFERENT SPECIES OF RED TIDE ORGANISMS WITH MONTMORILLONITE AND EFFECT OF CLAY PRETREATMENT

Study on the coagulation of four species of red tide organisms (Nitzschia pungens, Skeletonema costatum, Prorocentrum minimum and Noctiluca scintillans) with montmorillonite, and the effect of montmorillonite pretreatment on the coagulation shows that the capability for montmorillonite to coagulate with them is in the order: N. pungens > S. costatum > P. minimum > N. scintillans. The coagulation is discussed from the aspects of the structure, shape, size, movement, habit, etc. of different species and the results are explained theoretically. The experimental results also indicate that the treatment of montmorillonite with acid can enhance its coagulating capability. This is due to the fact that A1(OH2)6+3, exchanged from the clay lattice by hydrogen ion H+, forms hydroxy-aluminum polymers on the surface of the montmorillonite. The hydroxy-aluminum polymers positively charge and increase the positive characteristic of the clay surface, and also serves as a bridge between adjacent surfaces of particles. These two functions enhance the montmorillonite's capability for coagulating with the organism cells.

APPLICATION OF CLAYS TO REMOVAL OF RED TIDE ORGANISMS I. COAGULATION OF RED TIDE ORGANISMS WITH CLAYS

Coagulation of red tide organism cells with clays is discussed in theory and the effects of some factors on it are studied. A quantitative model is presented which describes how the coagulation varies with pH in solution. According to the model, within the pH-range between pHzpcb, and pHzpcb, VR is negative and the coagulation is strong and strongest at pH = (pHzpca + pHzpcb)/2. It is also demonstrated that when the diameter of clay particles is close to that of cells, the collision probability is low, resulting in weaker coagulation. The model results have been corroborated by experiments and so are scientific and theoretical bases for application.

APPLICATION OF CLAYS TO REMOVAL OF RED TIDE ORGANISMS III. THE COAGULATION OF KAOLIN ON RED TIDE ORGANISMS*

This article reports studies on the coagulation of kaolin(from Wuxian, Jiangsu, China) on various red tide organisms, and the observation for the first time that the coagulation of kaolin is much greater than that of montmorillonite so that kaolin is a more effective clay for removing red tide organisms. The authors' theoretical explanation and analysis by a mathematical-physical model prove that compared to montmorillonite. kaolin has greater attraction for organism cells and therefore greater coagulation capabil-ity. This project's studies on the effects of pH and acid-treatment show that the acid-treatment does not have much influence on the kaolin system; whereas the effect of pH on the kaolin system is the same as that on the montmorillonite system.

A relationship between red tide outbreaks and urban development along the coasts of Guangdong Province

Red tides are one of the main coastal catastrophic events in Guangdong Province of southern China. The comparison between the number of red tide events and the development indexes of cities along the coasts of the province shows that the regional differences in red tide outbreaks has close relations with the coastal urban developments. The cause for an initiation of red tide blooms may be natural factors, while wastewater caused by the fast development of population, industry and aquiculture of the coastal cities enhanced the blooms. It may explain why the two periods of frequent outbreaks of the red tides over the last two decades matched the urban developments in the coastal areas of Guangdong not only spatially but also temporally. The red tides in the first period were restricted only to the coasts of middle Guangdong, where urbanization process was at a higher speed than the other coastal areas of the province. In the second period, fast development of the coastal cities in eastern Guangdong led to an increase in the occurrence of red tides in local sea areas of the same coasts.

Notes Effects of four nitrogen substrates on growth of several red tide species

Eight common red tide species including the Dinoflagellates Alejcandrium tamarense,Prorocentrum minimum , Prorocentrum mican , Diatoms Skeletonema costatum , Cerataulina pelag-ica, Leptocylindrus minimus, a Raphidophyte Heterosigma akashiwo and a Chrysophyte Isochrysis galbana were chosen to study the effect of four nitrogen substrates (NOs ?N, NHi - N, Urea ?N, Mixed ?N) on the growth of these algae. After two transfers, the results showed that at N concentration of 550 fano\, NO; - N was the best nitrogen source among these four nitrogen substrates; Urea - N and Mixed ~ N were also good for the growth of most algae, but not as good as NQj ?N for some species; NH??N inhibited the growth of all these species except H. akashrwo. At concentrations of 280 and 50 fimol experiments on the growth of /. galbana , P. minimum and L. minimus in Nri( - N and NO; - N substrates were also performed. The results showed that the growth rates of /. galbana were not significantly different from each other in NO; - N and NH?- N substrates both concentrations of 280 and 50 fonol. In concentration of 280 (anol NHt - N substrate, the growth rates of P. minimum and L. minimus were slower than in same concentration of NO? ~~ N; At concentration of 50 (unol , the growth rate of P. minimum in NH?- N was not significantly different from that in NOj ?N, while the growth rate of L. minimus was only about 30% of that in NQ3 ~ N substrate. The results indicated that each alga had its own preference in N-substrate and concentration, therefore, different nitrogen substrates may play a role in red tide formation.

Secondary pollution from sediment and red tide occurrence

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Study on Red Tide Remote Sensing Monitoring in the Bohai Sea in 2014

Since 2000, red tides have been reported in the Bohai Sea every year, whichoften made coastal waters of the Bohai Sea suffering from red tides. Satellite remotesensing technology and the ocean color observation satellite images have beensuccessfully used to identify and observe the initiation, evolution, and dissipation of redtide. However, due to different water bodies, remote sensing data and modelingmethods, a specific model of red tide inversion should be established for the watercharacteristics of the Bohai Sea. In this paper, the correlation analysis between MODISspectral reflectivity data and measured concentration of chlorophyll a in the Bohai Seawas carried out. The expression （B10-B8） / （B13-B8） was chosen as the indicator of redtide inversion in the Bohai Sea, the correlation coefficient reached 0.7815, showingsignificant correlation results. It was found that the spatial and temporal distribution ofred tide in the Bohai Sea in 2014 was obvious. The main causes of the large-scale outbreak of red tide in the Bohai Sea are due to the poor water exchange caused by thesemi-enclosed geomorphology and the large amount of terrestrial matter input fromcoastal runoff. The river input is the main source of land-based pollution into the sea.Then, a red tide inversion model based on a modified red tide index was established byusing GOCI remote sensing data with less cloud coverage, and proven effective indelineating the red tide in turbid waters. The hourly RI images on 15, 26 and 28 May2014 showed consistent evolution, and the area of red tide in the Bohai Sea changedsignificantly during one day. Vertical migration of the dominant species of red tide algaemay be the main reason for the short-term changes in the surface expression.

A new algorithm based on the background field for red tide monitoring in the East China Sea

Remote sensing has been proven to be an effective means of monitoring red tides. The spectral information is an important basis for establishing a model to monitor red tides. The spectral curves of red tide events are analyzed and compared with multiyear monthly averaged spectral curves based on MODIS data from July 2002 to June 2012, as well as spectral differences at the same location during red tide presence and absence. A red tide monitoring algorithm is developed based on the background field to extract the red tide information of the East China Sea （ECS）. With the application of the algorithm in the ECS, the results reveal that the developed model can effectively determine the location of red tides, with good correspondence to the results from an official bulletin. This demonstrates that the algorithm can effectively extract the red tide information.

Research on Prediction of Red Tide Based on Fuzzy Neural Network

In this paper, a four-layer fuzzy neural network using the Back Propagation （BP） Algorithm and the fuzzy logic was built to study the nonlinear relationships between different physical -chemical factors and the denseness of red tide algae, and to anticipate the denseness of the red tide algae. For the first time, the fuzzy neural network technology was applied to research the prediction of red tide. Compared with BP network and RBF network, the outcome of this method is better.

Influence of the concentration ratio of nitrogen to phosphorus on the growth and interspecies competition of two red tide algae

The growth and interspecies competition of two red tide algal species Thalassiosira pseudonana Hasle et Heimdal and Gymnodinium sp. were studied under different concentration ratios of nitrogen to phosphorus, and the algal hatch culture experiments were conducted. The physiological and biochemical indexes were measured periodically, including the maximum comparing growth rate, relative growth rate, average double time and chlorophyll a concentration. The results showed that when the concentration ratio of nitrogen to phosphorus was 16： 1, the maximum comparing growth rate, relative growth rate and chlorophyll a concentration of Thalassiosira pseudonana all reached the highest,and average double time was the shortest. This implied that the optimal concentration ratio of nitrogen to phosphorus of Thalassiosira pseudonana is 16： 1. When the concentration ratio of nitrogen to phosphorus was 6：1, the maximum comparing growth rate, relative growth rate and the chlorophyll a concentration of Gymnodinium sp. reached the highest, and average double time was the shortest, so the optimal concentration ratio of nitrogen to phosphorus of Gymnodinium sp. is 6： 1. From the growth curves as indicated both in the cell density and the chlorophyll a concentration, it is suggested that the influence of concentration ratio of nitrogen to phosphorus on the chlorophyll a concentration and the cell density are almost the same. Different concentration ratios of nitrogen to phosphorus had weak influence on community succession and the competition between the two algae. Gymnodinium sp. may use the phosphorus in vivo for growth, so it is important to pay attention to the concealment of phosphorus, in order to avoid the outbreak of red tide. On the basis of the importance of nitrogen and phosphorus and the ratio of their concentration, the possible outbreak mechanism of red tide of the two algae was also discussed.

Analysis of the inter-annual variability and southward expansion of red tides in the Zhejiang coastal waters from 1981 to 2018

A time series dataset spanning 39 years(1981-2018) on red tide events in Zhejiang coastal waters was used to study the characteristics of inter-annual spatial and temporal variations. A distinct inter-annual pattern characterized by low frequency, explosive growth and fluctuating decline stages was found over the studied time scale. Most red tide events occurred in parallel to the bathymetric contour, and 95.4% were located to the west of the 50 m isobath. Additionally, the high-incidence area of red tides is expanding southward. In this paper, local sea surface temperature(SST), mariculture area and secondary industry growth rate are introduced and identified as the main factors influencing the nutrient and hydrometeorological conditions. A multivariate nonlinear regression equation based on these factors was constructed, and the goodness of fit coefficient was 0.907. The causes of the annual variation and high-frequency area in the southward expansion were quantitatively analyzed based on the proposed regression model. Finally, the results indicated that 68.7% of the annual occurrence variation of red tide was due to the SST and mariculture area, which are the main impact factors;however,secondary industry growth could compensate for the nutrient deficiency caused by the sharp mariculture area reduction and decreased SST. The background nutrient level, which is elevated by coastal economic development, especially secondary industry, is the main determinant of the southward expansion. Although the trend of the southward expansion of high-frequency areas has not changed, the red tide frequency in coastal cities has decreased by half and remained at a stable level after 2010 due to substantial economic restructuring and environmental protection.

STUDY OF RED TIDE PREDICTION MODEL FOR THE CHANGJIANG ESTUARY

This paper based on field data (on red tide water quality monitoring at the Chaggjiang River mouth and Hutoudu mariculture area in Zhejiang Province from May to August in 1995, and May to September in 1996) presents an effective model for short term prediction of red tide in the Changjiang Estuary. The measured parameters include: depth, temperature, color diaphaneity, density, DO, COD and nutrients (PO4?P, NO2?N, NO3?N, NH4?N). The model was checked by field-test data, and compared with other related models. The model: Z=SAL?3.95 DO?2.974 PH?5.421 PO4?P is suitable for application to the Shengsi aquiculture area near the Changjiang Estuary. Key words Changjiang Estuary - red tide - prediction model Project 493007 supported by the Natural Science Foundation of Zhejiang Province, and also supported by the Science and Technology Committee of Zhejiang Province (Key Project No. 618).

Studies on Biquaternary Ammonium Salt Algaecide for Removing Red Tide Algae

The paper deals with the removal and control of red tide algae,Phaeoecystis globosa and Alexandrium tamarense by biquaternary ammonium salt algaecide.The results show that the efficient concentration of biquaternary ammonium salt to control the two algaes in 96 h is 0.8 mg·L^(-1)and 0.4 mg·L^(-1),respectively.It is found that biquaternary ammonium salt has high efficiency and longer duration of action in the removal and control of algae.Biquaternary ammonium salt might be an excellent algaecide to control HAB.

Microbial Communities in Water during Red Tides along the Coast of China-A Case Study of Prorocentrum Donghaiense Red Tide in the East China Sea

Red tides are a major public hazard in the global oceans.The coast of the East China Sea is the sea area where red tide disasters are the most frequent and serious in China.In order to accurately grasp the occurrence of red tides in the coastal waters of the East China Sea,and to understand the microbial communities in the waters during the occurrence of red tides in the East China Sea,a special survey of red tides in the coastal waters of Zhejiang,China was carried out in June 2018.The results showed that nutrient concentrations of N and P were generally high in this area,DIN concentrations in most areas exceeded the permitted limit of Chinese seawater quality grade I.There were significant differences in dissolved oxygen,pH,COD,chlorophyll and phytoplankton abundance of red tides.During the investigation,red tides were found in the waters near the Yushan Islands.The content of chlorophyll a was 42.12mg/m3,the cell abundance of phytoplankton was 8.16×108/L,and the abundance of Prorocentrum edulis accounted for 98.5%.The Illumina MiSeq sequencing platform was used for 16s high-throughput sequencing of water microorganisms,and a total of 16 bacteria were identified.Proteobacteria is the first dominant phylum,followed by Cyanobacteria and Bacteroides.Some differences in bacterial community compositions between HAB and the nearby seawater were observed.The predominant bacteria in the red tide occurrence area were Proteobacteria,comprising 46.1%of the relative abundance;while the predominant bacteria in the nearby sea area,comprising 42.0%of the relative abundance.

3-D observations of a red tide event in the offshore water along the western Guangdong coast

From November 24 to 26, 2014, a red tide event occurred in the offshore water off the Hailing Island located at the western Guangdong coast. The red tide appeared as pink strips distributed within 3 km in the offshore water and extended for about 10 km along the shoreline. During the flood tide, the pink seawater rushed to the beach with breaking waves, forming foam strips on the beach. Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction Technologies, Guangdong Ocean University, emergently responded to the event and organized three-dimensional observations from the air, onboard and on beach. The preliminary analyses of the cruise data and water samples indicate that the event was induced by non- toxic Noctiluca scintillans, of which the concentration reaches as high as 4 200 cells/L near the surface and 2600 cells/L at the bottom.

The recognition of ocean red tide with hyper-spectral-image based on EMD

A new technique is introduced in this paper regarding red tide recognition with remotely sensed hyper-spectral images based on empirical mode decomposition （EMD）, from an artificial red tide experiment in the East China Sea in 2002. A set of characteristic parameters that describe absorbing crest and reflecting crest of the red tide and its recognition methods are put forward based on general pictre data, with which the spectral information of certain non-dominant alga species of a red tide occurrence is analyzed for establishing the foundation to estimate the species. Comparative experiments have proved that the method is effective. Meanwhile, the transitional area between red-tide zone and non-red-tide zone can be detected with the information of thickness of algae influence, with which a red tide can be forecast.

The Monitoring of Red Tides Based on Modular Neural Networks Using Airborne Hyperspectral Remote Sensing

This paper proposes a red tide monitoring method based on clustering and modular neural networks. To obtain the features of red tide from a mass of aerial remote sensing hyperspectral data, first the Log Residual Correction （LRC） is used to normalize the data, and then clustering analysis is adopted to select and form the training samples for the neural networks. For rapid monitoring, the discriminator is composed of modular neural networks, whose structure and learning parameters are determined by an Adaptive Genetic Algorithm （AGA）. The experiments showed that this method can monitor red tide rapidly and effectively.