Monitoring cyanobacteria-dominant algal blooms in eutrophicated Taihu Lake in China with synthetic aperture radar images

Monitoring algal blooms by optical remote sensing is limited by cloud cover.In this study,synthetic aperture radar(SAR) was deployed with the aim of monitoring cyanobacteria-dominant algal blooms in Taihu Lake in cloudy weather.The study shows that dark regions in the SAR images caused by cyanobacterial blooms damped the microwave backscatter of the lake surface and were consistent with the regions of algal blooms in quasi-synchronous optical images,confirming the applicability of SAR for detection of surface blooms.Low backscatter may also be associated with other factors such as low wind speeds,resulting in interference when monitoring algal blooms using SAR data alone.After feature extraction and selection,the dark regions were classified by the support vector machine method with an overall accuracy of 67.74%.SAR can provide a reference point for monitoring cyanobacterial blooms in the lake,particularly when weather is not suitable for optical remote sensing.Multi-polarization and multi-band SAR can be considered for use in the future to obtain more accurate information regarding algal blooms from SAR data.     

A niche model to predict Microcystis bloom decline in Chaohu Lake, China

Cyanobacterial blooms occur frequently in lakes due to eutrophication. Although a number of models have been proposed to forecast algal blooms, a good and applicable method is still lacking. This study explored a simple and effective mathematical-ecological model to evaluate the growth status and predict the population dynamics of Microcystis blooms. In this study, phytoplankton were collected and identified from 8 sampling sites in Chaohu Lake every month from July to October, 2010. The niche breadth and niche overlap of common species were calculated using standard equations, and the potential relative growth rates of Microcystis were calculated as a weighted-value of niche overlap. In July, the potential relative growth rate was 2.79 (a.u., arbitrary units) but then rapidly declined in the following months to -3.99 a.u. in September. A significant correlation (R=0.998, P<0.01) was found in the model between the net-increase in biomass of Microcystis in the field and the predicted values calculated by the niche model, we concluded that the niche model is suitable for forecasting the dynamics of Microcystis blooms. Redundancy analysis indicated that decreases in water temperature, dissolved oxygen and total dissolved phosphorus might be major factors underlying bloom decline. Based on the theory of community succession being caused by resource competition, the growth and decline of blooms can be predicted from a community structure. This may provide a basis for early warning and control of algal blooms.     

The decline process and major pathways of Microcystis bloom in Taihu Lake, China

Eutrophication has become a serious concern in many lakes, resulting in cyanobacterial blooms. However, the mechanism and pathways of cyanobacteria decline are less understood. To identify and define the growth and decline of Microcystis blooms in Taihu Lake of China, and to illuminate the destination of surface floating blooms, we investigated the biomass distribution and variations in colony size, morphology, and floating velocity from October 2008 to September 2009. The results showed that the Microcystis bloom declined in response to biomass decrease, colony disaggregation, buoyancy reduction, and increased phytoplankton biodiversity, and these indicative parameters could be applied for recognition of the development phases of the bloom. Three major decline pathways were proposed to describe the bloom decline process, colony disaggregation (Pathway Ⅰ), colony settlement (Pathway Ⅱ), and cell lysis in colonies (Pathway Ⅲ). We proposed a strategy to define the occurrence and decline of Microcystis blooms, to evaluate the survival state under different stress conditions, and to indicate the efficiency of controlling countermeasures against algal blooms.     

Macroalgae blooms and their effects on seagrass ecosystems

Seagrass decline caused by the macroalgae blooms is becoming a common phenomenon throughout temperate and tropical regions. We summarized the incidence of macroalgae blooms throughout the world and their impact on seagrass beds by direct and indirect ways. The competition for living space and using resources is the most direct effect on seagrass beds when macroalgae are blooming in an aquatic ecosystem. The consequence of macroalgae blooms (e.g., light reduction, hypoxia, and decomposition) can produce significant indirect effects on seagrass beds. Light reduction by the macroalgae can decrease the growth and recruitment of seagrasses, and decomposition of macroalgae mats can increase the anoxic and eutrophic conditions, which can further constrict the seagrass growth. Meanwhile, the presence of seagrass shoots can provide substrate for the macroalgae blooms. Controlling nutrient sources from the land to coastal waters is a general efficient way for coastal management. Researching into the synergistical effect of climate change and anthropognic nutrient loads on the interaction between searsasses and macroalgae can provide valuable information to decrease the negative effects of macroalgae blooms on seagrasses in eutrophic areas.     

太湖蓝藻水华遥感动态监测预警信息系统

太湖蓝藻水华暴发对其周边地区的生态、经济和社会造成了严重影响,对蓝藻水华进行监测预警对于改善太湖水环境具有重要意义。本文在分析蓝藻水华遥感监测预警研究动态基础上,从信息系统构建角度,结合太湖蓝藻水华监测情况,对太湖蓝藻水华遥感监测预警流程进行系统性分析,提出建立太湖蓝藻水华遥感监测预警系统的总体框架,利用C#语言和IDL语言实现了该框架的软件架构,并且论述了实现该系统框架所采用的系统集成技术和软件模式技术。     

Quantitative proteomics provides insight into the response of the marine dinoflagellate Prorocentrum donghaiense to changes in ambient phosphorus

Journal of Oceanology and Limnology - Dinoflagellates are the major causative agents of harmful algal blooms in the global ocean and they usually form blooms under conditions of very low dissolved...     

Increased diversity and environmental threat of harmful algal blooms in the Southern Yellow Sea,China

Journal of Oceanology and Limnology - Harmful algal blooms (HABs) in the Southern Yellow Sea (SYS) have shown a trend of increasing diversity and detrimental effects. While the Bohai Sea, East...     

Dynamics of Phaeocystis globosa bloom and implications for its seed sources in the Beibu Gulf,China

Journal of Oceanology and Limnology - Algal blooms of haptophyte Phaeocystis globosa have been recorded in the Beibu Gulf, South China Sea (SCS) since 2011. Recent evidence suggests that Type I and...     

太湖蓝藻水华遥感动态监测预警模型的建立

湖泊富营养化和蓝藻水华暴发是当前我国湖泊面临的最重要的环境问题之一。本文分析了内陆湖泊太湖蓝藻监测的主要问题。并详细阐述了蓝藻水华遥感动态监测预警模型的建立,即,采用生物光学模型与气象环境预警模型相结合的方式,辅以图形图像学的模块匹配验证,对蓝藻水华暴发前进行临界状态的灾害等级警示,理论上较单纯监测微囊藻叶绿素a浓度值来实现水华暴发预警更为准确。这样,提前采取相应的技术措施,减少蓝藻水华暴发带来的影响和损失。     

Assessment of different mcy genes for detecting the toxic to non-toxic Microcystis ratio in the field by multiplex qPCR

Harmful cyanobacterial blooms, especially Microcystis blooms, occur worldwide and draw widespread attention. The dynamics of microcystin-producing Microcystis and competition between microcystin-producing Microcystis and non-microcystin-producing Microcystis are key to predicting and treating Microcystis blooms. Multiplex qPCR is a useful tool to assess such issues. In this study, we developed multiplex qPCR methods with newly-designed probes and primers for the microcystin-synthesis related genes mcyA and mcyE. We used seven toxic Microcystis strains and four non-toxic Microcystis strains to compare the differences in the ratios of toxic and non-toxic Microcystis in mixed cultures, which were calculated using abundances of the genes mcyA, mcyB, mcyD, mcy E and phycocyanin( PC). We also compared traditional cell counting and multiplex qPCR. Hierarchical clustering and principal component analysis indicated that mcyD was the most suitable mcy gene for quantification in laboratory experiments. mcyB abundances were always higher; we suggest that the amount of toxic Microcystis measured using mcyB might overestimate the actual percentages.     

Identification of paralytic shellfish toxin-producing microalgae using machine learning and deep learning methods

Journal of Oceanology and Limnology - Paralytic shellfish poisoning (PSP) microalgae, as one of the harmful algal blooms, causes great damage to the offshore fishery, marine culture, and marine...     

Phytoplankton community dynamics during Alexandrium blooms in 2019 off the Qinhuangdao coast,Bohai Sea,China

Journal of Oceanology and Limnology - Alexandrium blooms in the northwest area of the Bohai Sea (Qinhuangdao coastal area), China, produce large amounts of toxins that could be enriched in...     

Variability of Prorocentrum donghaiense response to allelopathic action from Alexandrium pacificum in laboratory culture

The dinoflagellates Alexandrium pacificum and Prorocentrum donghaiense are two wellknown harmful algal blooms(HABs)-forming species,both were usually found in the same sea areas in form of HABs in China.To date,there is no mechanistic model that can fully explain the occurrence of P.donghaiense blooms with A.pacificum.We found that different strains of P.donghaiense had different intrinsic growth rates of 0.107-0.215/d,and these strains exhibited different responses to the allelopathic action from A.pacificum.Some strains of P.donghaiense could grow well despite some degrees of inhibition in a short period,suggesting the two algal species P.donghaiense and A.pacificum could coexist,even if A.pacificum was allelopathic.Our findings may advance the understanding of phenotypes in P.donghaiense and provide a potential mechanism involved in the coexistence of P.donghaiense and A.pacificum in the same area.     

基于MODIS数据的太湖浮游植物物候变化及其对水表温度的响应

浮游植物物候能够反映浮游植物的生长变化与湖泊生态系统的变化,水温、营养盐浓度等因素对物候有重要影响。太湖富营养化程度较高,水温的影响作用日趋显著,物候与水温关系的研究对理解、控制和改善太湖生态系统具有重要意义。本研究利用2003—2018年MODIS遥感数据计算浮游植物物候指标和湖泊水表温度（Temperature of Water Surface,LSWT）,通过分析太湖浮游植物物候时空变化特点探究了不同区域的物候特征,并结合LSWT揭示了浮游植物物候对LSWT变化的响应关系。结果表明：① 不同浮游植物物候指标具有不同空间分布特点,水华发生次数、峰值叶绿素a（Chla）浓度和水华总持续时间呈现由西部沿岸向湖心区递减的趋势;浮游植物生长开始时间和峰值Chla发生时间分布复杂但在沿岸区域相对较早;② 太湖可被划分为4种具有不同物候特征的区域,Ⅰ类区域主要位于贡湖湾、东部沿岸以及太湖中部开阔水域,该区Chla浓度范围为50~60 μg/L,且波动平缓,水华发生次数最少、开始最晚、持续时间最短;Ⅱ类区域主要分布于太湖西部沿岸,Chla浓度范围为50~90 μg/L且变化剧烈,该区水华发生次数最多、开始最早、持续时间最长;Ⅲ和Ⅳ类属于过渡区域,前者主要分布于梅梁湾、竺山湾及入湾口,后者主要位于南部沿岸以及太湖中部;③ 浮游植物物候对LSWT变化的响应受营养水平影响,当营养水平较高时,浮游植物的生长受LSWT的促进作用显著,LSWT年际变化的升高趋势对浮游植生长物候提前、生物量增加的影响明显,反之,则LSWT变化对浮游植物生长的影响减弱。     

Dynamic Diurnal Changes in Green Algae Biomass in the Southern Yellow Sea Based on GOCI Images

Macroalgae blooms of Ulva prolifera have occurred every summer in the southern Yellow Sea since 2007, inducing severe ecological problems and huge economic losses. Genesis and secular movement of green algae blooms have been well monitored by using remote sensing and other methods. In this study, green algae were detected and traced by using Geostationary Ocean Color Imager(GOCI), and a novel biomass estimation model was developed from the relationship between biomass measurements and previously published satellite-derived biomass indexes. The results show that the green algae biomass can be determined most accurately with the biomass index of green algae for GOCI(BIGAG), which is calculated from the Rsurf data that had been atmospherically corrected by ENVI/QUAC method. For the first time, dynamic changes in green algae biomass were studied over an hourly scale. Short-term biomass changes were highly influenced by Photosynthetically Available Radiation(PAR) and tidal phases, but less by sea surface temperature variations on a daily timescale. A new parameter of biomass changes(PBC), calculated by the ratio of the biomass growth rate to movement velocity, could provide an effective way to assess and forecast green tide in the southern Yellow Sea and similar areas.     

Distribution of Dissolved Inorganic Arsenic and Its Seasonal Variations in the Coastal Area of the East China Sea

Water samples were collected in the coastal area of the Changjiang Estuary on four cruises from August 2002 to May 2003. The seasonal variations of dissolved inorganic arsenic （DIAs） distributions were analyzed. The results showed that the distributions of DIAs were mainly influenced by Water （KSSW）. The concentration of the total dissolved the terrestrial input and the intrusion of the Kuroshio Subsurface inorganic arsenic （TDIAs） decreased consecutively from winter to summer, while it increased in autumn. The distributions of TDIAs showed some relationships with salinity and suspended particulate matter （SPM）. The relationships between DIAs speciation （including arsenite [ As（ Ⅲ ） ] and arsenate [ As（ Ⅴ ） ]）, biological activity and the availabilities of the phosphate were investigated in the study area for the cruise August 2002. The ratio of As （Ⅲ）/TDIAs increased with the decrease of phosphate concentrations. In the bottom water, the As（ Ⅲ ）/TDIAs ratio decreased with the increasing of N/P. The concentration of TDIAs decreased 28.7% approximately after the occurrence of harmful algal blooms （HAB） because of the uptake of arsenate by algae. Further study is needed about the arsenic source/sink relationships in their vertical or horizontal profiles and the uptake mechanism during the occurrence of harmful algal blooms.     

Free polyamine content during algal bloom succession in the East China Sea in spring 2010

We measured the concentrations and distribution of major polyamines(spermine, putrescine and spermidine) in seawater during successive spring algal blooms in an area of frequent harmful blooms in the East China Sea. Spermine, putrescine, and spermidine concentrations were analyzed by high performance liquid chromatography and ranged from 1–64, 7–81, and 0–19 nmol/L. Spermine was present at the highest concentrations, followed by putrescine and spermidine. In late April, when a diatom bloom dominated by Skeletonema costatum dispersed, polyamine concentrations increased, presumably as a result of diatom decomposition. In early May, when a dinoflagellate bloom dominated by Prorocentrum donghaiense occurred, the polyamine concentration decreased from the level seen in late April. The abundant polyamines that decomposed and were released during the diatom bloom in late April may have promoted the growth of P. donghaiense, resulting in its dominance.     

Harmful algal blooms and eutrophication: ��strategies�� for nutrient uptake and growth outside the Redfield comfort zone

While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.     

Biodiversity and distribution of benthic dinoflagellates in tropical Zhongsha Islands,South China Sea

Journal of Oceanology and Limnology - Benthic dinoflagellates have attracted increasing attention in recent years because of their toxicity and ability to form extensive harmful algal blooms....