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 fac-tors on it are studied.A quantitative model is presented which describes how the coagulation varies withpH in solution.According to the model,within the pH-range between pHzpcaand pHzpcb,VR is negativeand the coagulation is strong and strongest at pH=(pHzpca+pHzpcb)/2.It is also demonstrated that whenthe diameter of clay particles is close to that of cells,the collision probability is low,resulting in weakercoagulation.The model results have been corroborated by experiments and so are scientific and theoreticalbases for application.

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 ofmontmorillonite pretreatment on the coagulation shows that the capability for montmorillonite to coagu-late with them is in the order:N.pungens】S.costatum】P.minimum】N.scintillans.Thecoagulation is discussed from the aspects of the structure,shape,size,movement,habit,etc.of differ-ent species and the results are explained theoretically.The experimental results also indicate that the treat-ment of montmorillonite with acid can enhance its coagulating capability.This is due to the fact that Al（OH2）6+3,exchanged from the clay lattice by hydrogen ion H+,forms hydroxy-aluminum polymers on thesurface of the montmorillonite.The hydroxy-aluminum polymers positively charge and increase the positivecharacteristic of the clay surface,and also serves as a bridge between adjacent surfaces of particles.Thesetwo functions

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 greaterthan 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 comparedto 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 asthat on the montmonrillonite 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.

Nutrient and chlorophyll a anomaly in red-tide periods of 2003-2008 in Sishili Bay, China

Sishili Bay is the most important aquiculture and tourism area for the city of Yantai, China; however, red tides occurred frequently and have caused huge economic losses in this bay in recent years. To gain a better understanding of the local ecological environments in the bay, we conducted this research between 2003 and 2008 to analyze variations in nutrients and chlorophyll (chl-a) during high frequency red tide period (May to September). The results show that the chl-a concentration increased from 2.70 in 2003 to 7.26 mg/m3 in 2008, while the concentration of total inorganic nitrogen (TIN) and silicate (SiO3-Si) increased lineally from 5.18 and 1.45 μmol/L in 2003 to 18.57 and 9.52 μmol/L in 2008, respectively, and the annual phosphate (PO4-P) varied between 0.15 and 0.46 μmol/L. Special attention was given to a red tide in August 2007 occurred when water temperature was high and nutrient concentrations increased sharply because of a heavy rainfall. Overall, the results show the P limitation in Sishili Bay, and reveal that red tides were caused by eutrophication from terrestrial inputs and local warm weather, particularly during rainy periods. Therefore, to control red tide, greater efforts should be made to reduce sewage discharges into Sishili Bay, particularly during rainfall seasons.

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

ＳｅｃｏｎｄａｒｙｐｏｌｌｕｔｉｏｎｆｒｏｍｓｅｄｉｍｅｎｔａｎｄｒｅｄｔｉｄｅｏｃｃｕｒｒｅｎｃｅＣｈｅｎＣｉｍｅｉ；ＬｉＹｕｅｌｉｎｇ；ＷｕＹｕｄｕａｎＤｅｐａｒｔｍｅｎｔｏｆＯｃａｅａｎｏｇｒａｐｈｙ，ＸｉａｍｅｎＵｎｉｖｅｒｓｉｔｙ，ｘｉａｍ...

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.

EFFECT OF NITROGEN AND PHOSPHORUS ON THE GROWTH OF A RED TIDE DINOFLAGELLATE SCRIPPSIELLA TROCHOIDEA (STEIN) LOEBLICH III

Scrippsiella trochoidea (Stein) Loeblich III was grown in a nitrogen or phosphorus limited batch culture system in laboratory. Growth rates and cellular Chl a were measured as functions of nitrate and phosphate concentrations. Growth rates were hyperbolic with both nitrate and phosphate concentration and fit the Monod equation. The minimum cell quota of nitrogen and phosphorus and then the optimum N:P ratio of S. trochoidea were estimated in this study. Measurement of phosphate concentration in Jiaozhou Bay suggest that phosphorus is the limiting factor of S. trochoidea growth.

RESEARCH ON RED TIDE OCCURRENCES USING ENCLOSED EXPERIMENTAL ECOSYSTEM IN WEST XIAMEN HARBOR, CHINA RELATIONSHIP BETWEEN NUTRIENTS AND RED TIDE OCCURRENCE

This study on the distribution of phosphate and its relation to phytoplankton biomass in Western Xiamen Harbor using marine ecosystem enclosures to isolate the culture water from the tidal currents and salinity changes outside indicated that the phytoplankton biomass variation closely related to dissolved inorganic phosphorus (DIP) in the seawater as described by the equation: [Chl a]=A×e -B[PO4] . The biomass changes lagged by about two days the corresponding DIP. The research also dealt with the minimal DIP concentration for stopping diatom bloom and the possible maximal diatom biomass was estimated from the DIP external concentration in the seawater. The threshold of DIP initiating Skeletonema costatum red tide was calculated for use as an index to forecast its red tides. In addition, the relationships between a dinoflagellate red tide and nutrients are discussed. The results showed that the multiplication of dinoflagellate was not entirely dependent on the nutrients in the seawater.

RESEARCH ON RED TIDE OCCURRENCES USING ENCLOSED EXPERIMANTAL ECOSYSTEMS IN WEST XIAMEN HARBOR, CHINA——RELATIONSHIP BETWEEN VARIOUS FACTORS AND RED TIDE OCCURRENCES

A series of enclosed ecosystem experiments were conducted in a land based tank near the seaside of West Xiamen Harbor.The results of experiments conducted in different seasons and years showed a repeatble phytoplankton succession. In this relatively stable ecosystem with added nutrients and trace metals,diatoms dominated initially,dinoflagellates dominated in the later stage,and dinoflagellate red tides eventually occurred.Vitamin B 12 enrichment may speed up this succession process. Stirring the water column could stop this process. Soluble Mn at a level of 3-4 μg/L in seawater,which also is the existing concentration of solu ble Mn in Xiamen Harbor seawater,is sufficient for the multiplication of algae and occurrence of red tide.The present study showed that excessive soluble Mn in Xiamen Harbor cannot cause red tide,and that Fe was one of the important factors causing diatom red tide in this present study..

EFFECTS OF Fe AND Mn ON THE GROWTH OF A RED TIDE DINOFLAGELLATE SCRIPPSIELLA TROCHOIDEA (STEIN) LOEBLCH Ⅲ

Batch culture experiments were conducted with a red tide dinoflagellate Scrippsiella trochoidea(Stein) Loeblch Ⅲ colleted from Jiaozhou Bay, Shandong, China. Growth rates and Cellular Chl-a were meas ured in media with iron and manganese ion concentrations controlled at different levels using EdTA-trace metal buffer systems. Cell density increased 3.2 times to 6.5 times over the range of lowest (0 mol/L) to highest(10-5 mol/L) iron and manganese ion concentrations. The range of Cell density response was much lower than the range of total available iron and manganese, which was >100-fold that of Fe. This nonlinear relationship indicates that the cells adapt to make more efficient use of iron and manganese un der limiting conditions. The cellular Chl-a content maximized after 3 days incubation and then decreased gradually under either iron or manganese limitation conditions. It indicated that the algae gained higher photosynthesis ability when transferred to a new environment. Growth responses to iron and manganese limitation can be both modeled according to the equation of Monod. The half-saturation constant for growth, k, is 4.6×10-8 mol/L for Fe and 5.1×10-8 mol/L for Mn. Our results showed that the iron availability in Jiaozhou Bay does not limit the growth of S. trochoidea.

Analysis of the development and causes of formation of Eucampia zoodiacus red tide in Xiamen Harbor

The red tide event of 11￣28, May in 1987 was caused by Eucampia zoodiacus, a coastal eurythermic phytoplanktou. Results from the field monitoring indicated that during the red tide occurrence the optimal temperature and salinity for the multiplication of the red tide organism were 20￣25℃ and 26￣28. During the red tide event cell densities in two peak values both reached 3 000×103ind. /din3. Organism number in horizonal distribution increased from the harbour mouth to the inner harbour. Average number of the organism at the monitoring stations in the inner harbour was 2 930×103 md. /dm3 which was 3. 7 and 61 times higher than that at the two control monitoring stations. The organism number in vertical distribution apparently showed stepwise, day and night changes. Daily change of the phytoplankton number with spring and ebb tides exhibited a negative relativity.Major reasons for this red tide event included species competition of red tide organisms, sudden increment in water temperature in short time, sharp decrement in salinity by rainfall, water eutrophication, high contents of stimulating materials such as Fe and Mn, poor water exchange condition and stable synoptic condition, etc.High content of dissolved oxygen and high pH value was resulted from the photosythesis of a great quantity of the red tide organisms.

Inhibitory activity of an extract from a marine bacterium Halomonas sp.HSB07 against the red-tide microalga Gymnodinium sp.(Pyrrophyta)

In recent years,red tides occurred frequently in coastal areas worldwide.Various methods based on the use of clay,copper sulfate,and bacteria have been successful in controlling red tides to some extent.As a new defensive agent,marine microorganisms are important sources of compounds with potent inhibitory bioactivities against red-tide microalgae,such as Gymnodinium sp.(Pyrrophyta).In this study,we isolated a marine bacterium,HSB07,from seawater collected from Hongsha Bay,Sanya,South China Sea.Based on its 16S rRNA gene sequence and biochemical characteristics,the isolated strain HSB07 was identified as a member of the genus Halomonas.A crude ethyl acetate extract of strain HSB07 showed moderate inhibition activity against Gymnodinium sp.in a bioactive prescreening experiment.The extract was further separated into fractions A,B,and C by silica gel column chromatography.Fractions B and C showed strong inhibition activities against Gymnodinium.This is the first report of inhibitory activity of secondary metabolites of a Halomonas bacterium against a red-tide-causing microalga.

Maltivariate Analysis of the Occurring Process of Skeletonema costatum Red Tide in the Changjiang Estuary

Using the SAS software, the data of environmental factors vs. red tide biomass were analysed during the process of Skeletonema costatum red tide which broke out in the Changjiang Estuary on June 9～15, 1990. The results of the multivariate statistical analysis show that the environmental factors are similar in their developing and maintenance periods and that the values of environmental factors begin to be restored to normal levels during the disappearing period.The results obtained from using the methods of correlation, variable cluster and main component analyses are basically identical. The important factors contributing to the occurrence of this red tide are atmospherical pressure, water temperature, salinity, pH, No3-, -N, Po43--P and Fe, among which,salinity, Fe and PO43--P are the leading factors which have triggered the occurrence of the red tide as determined by the step-by-step regression analysis. Meanwhile, the linear discrimination functions have been established for the red tide. The environmental factor data of another occurring process of Skeletonema costatum red tide in the Changjiang Estuary have been chosen for red tide discrimination with satisfactory results.

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 Changjiang 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 (PO 4 P, NO 2 N, NO 3 N, NH 4 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 PO 4 P is suitable for application to the Shengsi aquiculture area near the Changjiang Estuary.

High-frequency acoustic backscattering characteristics for acoustic detection of the red tide species Akashiwo sanguinea and Alexandrium affine

Harmful algal blooms (HABs), caused by the overgrowth of certain phytoplankton species, have negative effects on marine environments and coastal fisheries. In addition to cell-counting methods using phytoplankton nets, a hydroacoustic technique based on acoustic backscattering has been proposed for the detection of phytoplankton blooms. However, little is known of the acoustic properties of HAB species. In this study, as essential data to support this technique, we measured the acoustic properties of two HAB species, Akashiwo sanguinea and Alexandrium affine, which occur in the South Sea off the coast of Korea. Due to the small size of the target, we used ultrasound for the measurements. Experiments were conducted under laboratory and field conditions. In the laboratory experiment, the acoustic signal received from each species was directly proportional to the cell abundance. We derived a relationship between the cell abundance and acoustic signal received for each species. The measured signals were compared to predictions of a fluid sphere scattering model. When A. sanguinea blooms appeared at an abundance greater than 3 500 cells/mL, the acoustic signals varied with cell abundance, showing a good correlation. These results confirm that acoustic measurements can be used to detect HAB species.