Relevance and challenges in monitoring marine biotoxins in non-bivalve vectors

Seafood poisoning outbreaks can be caused by marine biotoxins which are naturally produced by harmful algal blooms. To minimize the risk of acute intoxications due to consumption of contaminated seafood a proper monitoring program must be in place. In recent decades several directives have been laid down by the European Commission to regulate known toxins, reassess their regulatory limits and update their reference detection methods. However, a revision of the seafood organisms that can act as toxin vectors has not been carried out. The control system has been designed based on physiological specificities of live bivalve mollusks. Although the prescribed controls in EC regulation 854/2004 apply to echinoderms, tunicates and marine gastropods, several difficulties are posed to a cost-effective monitoring program for these quite diverse and non-analogous groups of seafood organisms. Echinoderms, tunicates and marine gastropods are frequently secondary target species for toxins surveillance. In this study, the potential of non-bivalve organisms as toxin vectors and their threat for public health is evaluated based on their feeding behavior (i.e. filter-feeders, herbivores, predators), growth and metabolic rates, motile capacity and dynamics of toxin accumulation/elimination. A summary of previous reports on toxin accumulation and human incidents is presented to highlight the seafood species of higher risk to consumers, including crustaceans that are not listed in the EU directives for toxins monitoring and should be strongly considered as potent vectors of biotoxins to humans. Finally, the challenges in terms of sampling efforts and analytical determination for the regular surveillance of biotoxins in non-bivalve vectors are discussed.     

How Brittany and Florida coasts cope with green tides

Although the direct involvement of nitrogen and phosphorus has been shown, eutrophication remains poorly managed to this day. The excessive growth of some opportunist seaweeds is the consequence in coastal ecosystems close to agricultural or strongly urbanized and industrialized zones. In Brittany, a leading tourist region of France, green tides set down on the beaches big quantities of Ulva, of which some 100,000 m³ are harvested annually, with significant ecological and economic consequences. In Florida, although the macroalgae (notably Codium) drift about with the currents, they are of sufficient mass and spread over such areal extent to inhibit penetration of sunlight through the water column to the coral reef surface. They strand also on the beaches. Stabilization of algae by composting and methanization of hydrolyzed and pressed algae juice are two methods which have been studied in Brittany and can be used to enhance the value of the harvested seaweed, depending on local conditions and on evolution of needs in energy, basic materials or organic products. But the parallel made here between two very different ecosystems, both disturbed, leads above all to the question of what course to follow now to avoid a worldwide disaster.

Bien que le rôle de l’azote et du phosphore dans les processus d’eutrophication ait été montré, celle‐ci reste mal contrôlée à ce jour. La croissance excessive d’algues opportunistes en est la conséquence dans des écosystèmes côtiers proches de zones agricoles ou fortement urbanisées et industrialisées. En Bretagne, région touristique de France, des marées vertes déversent sur les plages de grandes quantités d’ulves, dont environ 100,000 m³ sont récoltés annuellement, avec d’importantes conséquences écologiques et économiques. En Floride, bien que les macroalgues (notamment Codium) dérivent avec les courants, elles sont en masse suffisante et suffisamment réparties pour empêcher la pénétration de la lumière dans la colonne d’eau jusqu’au récif de corail. Elles s’échouent également sur les plages. La stabilisation par compostage et la méthanisation de jus d’algues hydrolysées et pressées sont deux méthodes qui ont été étudiées en Bretagne afin de valoriser l’algue récoltée, en fonction des conditions locales et de l’évolution des besoins en énergie, matières premières ou produits organiques. Mais le parallèle fait ici entre deux écosystèmes très différents, tous deux perturbés, mène surtout à se demander quelle voie suivre maintenant pour éviter un désastre mondial.     

Intraparticle diffusivity of Cd ions in a new biosorbent material

Cadmium equilibrium sorption isotherms were determined for formaldehyde crosslinked Sargassum fluitans, establishing that an effective regeneration of the new biosorbent material is possible by an acid wash. Batch desorption kinetics were investigated at pH values of 1·0 and 2·0. By incorporating the linear and non-linear Langmuir equilibrium isotherm relationships into the rate equations, a mathematical model was proposed for modeling the metal desorption process. The model was solved numerically and a MATLAB computer program was used to curve-fit the experimental data. The model successfully predicted the Cd²⁺ elution concentration profile in a batch reactor. The average values of the intraparticle diffusivity of Cd²⁺ in the algal biosorbent calculated from the model were 3·40 × 10⁻⁶ and 1·65 × 10⁻⁶ cm² s⁻¹, 0·473 and 0·229 times the molecular diffusivity of Cd²⁺ in water, at pH values of 1·0 and 2·0, respectively. These values agreed well with theoretical predictions.     

Calmodulin and Its Interactive Proteins Participate in Regulating the Explosive Growth of Alexandrium pacificum (Dinoflagellate)

Alexandrium pacificum is a typical dinoflagellate that can cause harmful algal blooms, resulting in negative impacts on ecology and human health. The calcium (Ca²⁺) signal transduction pathway plays an important role in cell proliferation. Calmodulin (CaM) and CaM-related proteins are the main cellular Ca²⁺ sensors, and can act as an intermediate in the Ca²⁺ signal transduction pathway. In this study, the proteins that interacted with CaM of A. pacificum were screened by two-dimensional electrophoresis analysis and far western blots under different growth conditions including lag phase and high phosphorus and manganese induced log phase (HPM). The interactive proteins were then identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Four proteins were identified, including Ca²⁺/CaM-dependent protein kinase, serine/threonine kinase, annexin, and inositol-3-phosphate synthase, which all showed high expression levels under HPM. The gene expression levels encoding these four proteins were also up-regulated under HPM, as revealed by quantitative polymerase chain reaction, suggesting that the identified proteins participate in the Ca²⁺ transport channel and cell cycle regulation to promote cell division. A network of proteins interacting with CaM and their target proteins involved in the regulation of cell proliferation was raised, which provided new insights into the mechanisms behind the explosive growth of A. pacificum.     

基于胃肠动态消化系统分析两种不同藻油剂型的消化特性和生物可及性

利用体外动态模拟消化系统评价了两种不同二十二碳六烯酸(Docosahexaenoic acid,DHA)藻油剂型的消化速率及其生物可及性,以期找到消化特性更佳的DHA藻油产品。对凝胶糖果和软胶囊两种不同剂型的DHA藻油样品进行体外胃肠动态消化,并从粒径及表面电势、微观结构和DHA含量等方面对消化特性进行分析,多角度探究两种剂型藻油产品对其消化行为的影响。结果表明添加胰酶组在肠消化60 min后,凝胶糖果消化产物粒径极显著低于软胶囊消化产物(p0.01);未添加胰酶组软胶囊肠消化30 min至90 min后,产物粒径显著大于凝胶糖果(p0.05)。添加胰酶组中凝胶糖果肠消化产物ζ电位绝对值随时间增加而增大,且均高于30 mV。随着肠消化时间延长,凝胶糖果游离脂肪酸(Non esterified fatty acid,NEFA)释放量逐步增加,达到缓释效果,软胶囊NEFA量与消化时间无明显关系。凝胶糖果消化产物在荧光图像中呈现分散均一的小液滴,软胶囊消化产物形态大小各异,均一性差。综上所述,凝胶糖果的消化特性及油脂的释放与分散性能更好,且其DHA释放量为软胶囊的6.75倍,具有较好的生物可及性。     

三峡水库支流库湾水流输移水华藻团能力研究

为研究水流对水华藻团的输移能力,将水华藻团概化为水体中的物质粒子,忽略其生物抗力,应用流体力学相关理论推导了水流对水华藻团的粘性阻力,并借鉴粒子在水流中的跟随性分析了不同优势种的水华藻团随水流被输移的效果。研究表明,不同的藻种由于颗粒大小不同而略有差异,但总体上跟随性很好,水流均能对其产生显著的推流输移作用。结合三峡水库香溪河库湾秋季水华过程及对应的水动力特性,以2007、2010年为例,证明汛末蓄水期间干流中层倒灌异重流引起库湾表层持续流向河口的水流趋势是秋季水华消退的直接原因之一。     

Effect of oxidants on microalgal flocculation

The effects of chlorine, ozone and chlorine dioxide on Scenedesmus sp. cultures were studied. Algal cell viability and chlorophyll concentration decreased, and the concentration of dissolved organic substances increased with increasing applied oxidant concentration. Pretreatment with chlorine dioxide (1, 3 or 5 mg l⁻¹) or ozone (2.6, 4.6 or 8.1 mg l⁻¹) on algal cultures enhanced algal flocculation with alum, while prechlorination with 10 or 20 mg l⁻¹ increased the required dosage of alum by 15%. Scanning electron micrographs of oxidized cells revealed drastically adverse effects upon the cell surface architecture: in addition to the oxidation of noncellular organic materials, the oxidants damaged both cell surface structures and intracellular components. A model explaining the effects of the different oxidants on microalgal flocculation is suggested.     

高藻期超滤膜制水中试研究

针对太湖水高藻期水质特征,以超滤膜为终端处理技术,前端有混凝沉淀技术、预氧化技术或吸附技术,形成组合工艺进行中试研究.研究结果表明:混凝-沉淀-超滤膜、高锰酸钾-混凝-沉淀-超滤膜和高锰酸钾-混凝-沉淀-粉末活性碳-超滤膜3组组合工艺出水水质良好,出水浑浊度均低于0.1 NTU,藻类数量控制在2.5×104个/L左右,其它检测指标达到生活饮用水卫生标准(GB5749 2006).高藻水中有机物以疏水性有机物为主,疏水性有机物是造成膜污染的主要因素,有效的超滤膜前段处理技术降低进入膜组件的疏水性有机物,缓解高藻期超滤膜污染.     

A systematic study on spatial and seasonal patterns of eight taste and odor compounds with relation to various biotic and abiotic parameters in Gonghu Bay of Lake Taihu, China

A systematic study was conducted on seasonal and spatial patterns of taste and odor (T&O) compounds with relation to biotic and abiotic parameters at fifteen sites in Gonghu Bay of Lake Taihu in 2008. We developed a sensitive and automated method to simultaneously analyze eight T&O compounds (boiling points ranging from 38 °C to 239 °C) by using Purge-and-Trap (P&T) coupled with GC/MS. Maximum particulate dimethyl trisulfide (DMTS, 69.6 ng/L) exceeded its odor threshold concentrations (OTC, 10 ng/L) and maximum dissolved DMTS was 6.1 ng/L, but still far below concentration in the drinking water pollution incident of Wuxi City in 2007 when DMTS reached 1768-11,399 ng/L. Geosmin (GEO), 2-methylisoborneol (MIB), β-cyclocitral, β-ionone and 2-isobutyl-3-methoxypyrazine (IBMP) occasionally or frequently exceeded their OTCs, whereas 2-isopropyl-3-methoxypyrazine (IPMP) and dimethyl sulfide (DMS) did not. We found for the first time significant correlations between particulate β-cyclocitral and β-ionon concentrations and intracellular and extracellular microcystin concentrations. Spatially, Nanquan Waterworks faced more risk by T&O contamination than Xidong Waterworks. High concentrations of NO₃-N, TDN and TN could be risky signs of taste and odor events by DMS, DMTS, IPMP, IBMP and GEO.     

Controlling harmful cyanobacterial blooms in a world experiencing anthropogenic and climatic-induced change

Harmful (toxic, food web altering, hypoxia generating) cyanobacterial algal blooms (CyanoHABs) are proliferating world-wide due to anthropogenic nutrient enrichment, and they represent a serious threat to the use and sustainability of our freshwater resources. Traditionally, phosphorus (P) input reductions have been prescribed to control CyanoHABs, because P limitation is widespread and some CyanoHABs can fix atmospheric nitrogen (N₂) to satisfy their nitrogen (N) requirements. However, eutrophying systems are increasingly plagued with non N₂ fixing CyanoHABs that are N and P co-limited or even N limited. In many of these systems N loads are increasing faster than P loads. Therefore N and P input constraints are likely needed for long-term CyanoHAB control in such systems. Climatic changes, specifically warming, increased vertical stratification, salinization, and intensification of storms and droughts play additional, interactive roles in modulating CyanoHAB frequency, intensity, geographic distribution and duration. In addition to having to consider reductions in N and P inputs, water quality managers are in dire need of effective tools to break the synergy between nutrient loading and hydrologic regimes made more favorable for CyanoHABs by climate change. The more promising of these tools make affected waters less hospitable for CyanoHABs by 1) altering the hydrology to enhance vertical mixing and/or flushing and 2) decreasing nutrient fluxes from organic rich sediments by physically removing the sediments or capping sediments with clay. Effective future CyanoHAB management approaches must incorporate both N and P loading dynamics within the context of altered thermal and hydrologic regimes associated with climate change.