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.

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.

Secondary pollution from sediment and red tide occurrence

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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.

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.

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.

Ecological Characteristics of Phytoplankton in Qinhuangdao Waters during Red Tide Period

The spatio-temporal distribution of phytoplankton is influenced by physical and chemical factors such as water temperature, salinity, dissolved oxygen, Ph and nutrients. Nitrogen （N） and phosphorus （P） are essential for the growth of phytoplankton, which play a key role in determining the abundance of phyto- plankton. The species composition, community similarity and diversity of phytoplankton affect the structure and function of ocean ecosystems. Marine phytoplankton can be used as a rapid and sensitive indicator reflecting environmental changes. The offshore area of Qinhuangdao is a spawning and feeding ground for fish, shrimp and crabs. However, this region has experienced an increase in frequency of red tides as a result of pollution and marine development. In 2010, red tides began in late May and ended in August. We evaluated the species composition, spatio-temporal distribution, community structure of phytoplankton and the relationship be- tween phytoplankton abundance and environmental factors based on data collected from May to September in 2010. The phytuplankton , belonging to 96 species, 46 genera, were identified. The phytoplankton community was primarily composed of Bacillariophyta and Pyrrophyta. The majority were neritic species or eurythermal and euryhaline cosmopolitan species, while the remainders were oceanic warm species or polagic species. The dominant species included Noctiluca scintiUans, Rhizosolenia stolterfothii, Ghaetoceros spp. , Goscinodiscus spp. , and Bacteriastrum spp.. A total of 48 red tide causative species were observed, accounting for 50% of total phytoplankton species. The average phytoplankton abundance ranged from 6.20 × 10^4 cells/m^3 to 4 129.53 × 10^4 cells/ms. Abundance peaked in September 2010 and reached the lowest value in July 2010. The diversity index values were all greater than 1.0, suggested that biodiversity and community structure was healthy. The highest indices of community structure and biodiversity were observed in September, and biediversity was the lowest in June. The community similarity of phytuplankton was relatively high and the similarity range was 40% -70% from May to September. The community similarity of phytoplankton successively were September 〉 July 〉 August 〉 May 〉 June. The average abundance of phytoplankton had significant negative correlation with salinity（ r = - 0. 734, P 〈 0. 01, N = 37 ） and significant positive correlation with inorganic nitrogen nutrients （ r = 0. 753, P 〈 0. 01, N = 37 ）. We concluded that inorganic nitrogen was the primary factor explaining the increase in phytoplankton abundance during the survey period. A canonical correspondence analysis of the relationship between phytoplankton species and environmental factors indicated that N/P, salinity, nitrate, silicate, nitrite and water temperature were the main environmental factors influencing community structure of phytoplankton in Qinhuangdac waters.

Observation of a red tide event in the Western Harbour, Xiamen

Measurements of red tide organism cell counting, chlorophyll a, water temperat-ure, salinity, pH, DO, COD, NH~+, NO, NO, active phosphate, dissolvable siliconwere made in a follow-up observation of a red tide event which occurred in the western harbourof Xiamen from 18th June to 3rd July in 1986.

Red Tide Information Extraction Based on Multi-source Remote Sensing Data in Haizhou Bay

[Objective] The aim was to extract red tide information in Haizhou Bay on the basis of multi-source remote sensing data.[Method] Red tide in Haizhou Bay was studied based on multi-source remote sensing data,such as IRS-P6 data on October 8,2005,Landsat 5-TM data on May 20,2006,MODIS 1B data on October 6,2006 and HY-1B second-grade data on April 22,2009,which were firstly preprocessed through geometric correction,atmospheric correction,image resizing and so on.At the same time,the synchronous environment monitoring data of red tide water were acquired.Then,band ratio method,chlorophyll-a concentration method and secondary filtering method were adopted to extract red tide information.[Result] On October 8,2005,the area of red tide was about 20.0 km2 in Haizhou Bay.There was no red tide in Haizhou bay on May 20,2006.On October 6,2006,large areas of red tide occurred in Haizhou bay,with area of 436.5 km2.On April 22,2009,red tide scattered in Haizhou bay,and its area was about 10.8 km2.[Conclusion] The research would provide technical ideas for the environmental monitoring department of Lianyungang to implement red tide forecast and warning effectively.

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.

Automatic Red Tide Algae Recognition

This paper presents a real-time alga classifier designed for flow-cytometry-based marine alga monitoring systems.The difficulties of such classification include:1)the shape of the same algae category is deformable,and largely variant due to the individual differences and mature stage;2)the image of algae may vary due to different 3D positions to the imaging plane and partial occlusion;3)the images also contain unknown algae and contaminations.In the proposed method,several shape features were developed,a naive Bayes classifier(NBC)was trained to reject the contaminative objects and unknown algae,and a support vector machine(SVM)was used to classify the algae to taxonomic categories.Our approach achieved greater 90%accuracy on a collection of algal images.The test on contaminated algal image set(containing unknown algae and non-algae objects such as sands)also demonstrated promising results.

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 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.

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.

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..