Effects of the toxic dinoflagellate Alexandrium tamarense on the greenshell mussel Perna canaliculus

Abstract

Oxygen consumption, grazing rate, and byssus production of the greenshell mussel Perna canaliculus were measured following exposure to bloom concentrations (10⁶ cells l^?1 ) of a toxic clone of the dinoflagellate AIexandrium tamarense (GT429), using anon‐toxic clone of the same species (PLY173) as control. Following feeding for 1 h on GT429, mussels (dry weight 54–127 mg) showed significantly increased oxygen uptake at 15°C (0.08 μl O₂ (mg dry tissue weight)^?1 ) compared with control mussels. However, following 24 h recovery, oxygen uptake was similar to initial values in all experimental conditions. The grazing rate of P. canaliculus fed upon toxic clone GT429 was 4.58 ± 0.76 cells mg^?1 h^?1 compared with 1.99 ± 0.47 cells mg^?1 h^?1 for PLY173. On exposure to A. tamarense, mussels maintained normal opening behaviour and there was no change in the byssus production over 24 h. It was concluded that P. canaliculus showed no dramatic physiological effects following short‐term feeding on the toxic strain of A. tamarense. During 2 weeks’ exposure to twice daily bloom concentrations of GT429, there was no mussel mortality. Toxicity in the tissues was 1295 μg STX equivalent per 100 g tissue, levels at which these mussels would be unsuitable for human or animal consumption.     

Effects of toxic dinoflagellate Alexandrium tamarense on the energy budgets and growth of two marine bivalves

Harmful algal blooms (HAB) may impose a serious threat to aquatic lives and human health. We determined the effects of a toxic dinoflagellate Alexandrium tamarense (clone ATCIO1, isolated from Hong Kong coastal waters) on the energy budget, quantified as scope for growth (SFG), and the growth rate of the manila clam Ruditapes philippinarum and the green-lipped mussel Perna viridis. To quantify the SFG, clams and mussels were dosed with different amounts of toxic A. tamarense for 6 days, resulting in different toxin burdens in the tissues. Clearance rate, absorption efficiency, and respiration rate were subsequently measured in these toxin containing bivalves. Clearance rate significantly declined at the highest toxin burden in the clams only, while there was no significant difference in the clearance rate among different treatments for the mussels. The respiration rate of either bivalve was not significantly affected by toxin accumulation in the tissues. In contrast, the absorption efficiency of both clams and mussels decreased, in a concentration-dependent manner for mussels but not for clams, when the tissue accumulated the toxins. With an increase in paralytic shellfish poisoning (PSP) toxin burden, SFG in both clams and mussels was significantly reduced, primarily because of the decrease of absorption efficiency. The growth rate of juvenile clam R. philippinarum, measured as an increment in tissue dry weight over a 15 d exposure period, was significantly lower during their feeding on toxic dinoflagellate than the growth rate of clams feeding on the diatom Thalassiosira pseudonana. The juvenile mussel P. viridis, however, exhibited similar growth rates after feeding on the toxic dinoflagellates and the nontoxic diatom. This study showed that SFG can provide a sensitive and integrated measure of the effect of HAB on the physiology of bivalves. Clam R. philippinarum may be more sensitive, in terms of their energy budget, to PSP toxin accumulation than the mussel P. viridis.     

厦门湾沉积物中有害有毒甲藻休眠孢囊及塔玛亚历山大藻的潜在危害

本工作通过分析厦门湾表层沉积物中的甲藻休眠孢囊，发现了1种有毒塔玛亚历山大藻(Alexandrium tamarense)休眠孢囊，及两种有害甲藻休眠孢囊：锥状斯氏藻(Scrippsiella trochoidea)、具刺膝沟藻(Gonyaulax spinifera)．对塔玛亚历山大藻进行了培养。并初步研究了该藻的毒性及贝类对其毒素的积累．研究结果表明，厦门海域沉积物中的塔玛亚历山犬藻是有毒的．它的较适宜生长环境条件是：水温20～25℃．盐度为25～30，光照度为3000～50001x．塔玛亚历山大藻在每年的4月26日至6月10日、10月11日至11月20日可能会形成有害藻华，危害厦门海域的海洋生物并可能威胁到人类的健康和生命安全．     

Seasonal variations of water temperature and salinity in Osaka Bay

The characteristics of seasonal variations of water temperature, salinity and density in the upper, middle and lower layers in Osaka Bay are described. Osaka Bay is considered to be an estuary, because the weak mixed state appears in spring and summer and the moderate mixed state in autumn and winter. Osaka Bay is divided into three areas, the eastern shallow area that has a large amplitude of seasonal variation of water temperature and low average salinity, the southwestern deep area which has small amplitude of seasonal variation of water temperature and high average salinity, and the northwestern deep area, which has small amplitude of seasonal variation of water temperature and low average salinity.     

Mechanisms of high-frequency dinoflagellate blooms of Scrippsiella trochoidea in Daya Bay,South China Sea

Harmful algal blooms (HABs), such as dinoflagellate blooms, have adverse effects on coastal water environments, causing seafood contamination and aquaculture ec...     

有毒甲藻—塔玛亚历山大藻在厦门地区虾塘引起赤潮

材料于１９９４年７月采自厦门及邻近地区对虾养殖池。塔玛亚历山大藻藻体细胞形态准圆形，长略大于宽。细胞和１６－３１μｍ，宽１３－３０μｍ。甲板排列公式为Ａｐ，４＇，６″，６ｃ，８ｓ，其孢囊长椭圆形，长径２２－２６μｍ，短径１８－２２μｍ，表面光滑。采样期间虾池表层水温２８－３１℃，盐度１５－３１。     

Heavy metals and accumulation rates of sediments in Osaka Bay,the Seto Inland Sea,Japan

The metal load into sediments and the change in the sedimentary environment of Osaka Bay in the Seto Inland Sea have been studied through geochemical analysis of core sediments, using both Pb-210 dating and a selective chemical leaching technique. Analytical results from a 6-m core of sediment show that copper and zinc pollution started in the late 1800's and the present enrichment ratios of copper and zinc, relative to background levels (20 mg kg^–1 for Cu and 94 mg kg^–1 for Zn), are 2.8 and 4.1, respectively. The present anthropogenic copper and zinc loads into Osaka Bay sediments, are 47 and 368 ton yr^–1, while natural copper and zinc loads are 40 and 186 ton yr^–1, respectively. Osaka Bay sediment at the present day is considered to be seriously polluted by zinc, now. The vertical profiles of copper and zinc in four successively separated fractions (10% acetic acid soluble fraction: F-HAC, 0.1M hydrochloric acid-soluble fraction: F-HCl, hydrogen peroxide-soluble fraction: F-H₂O₂ and hydrofluoric acid-soluble fraction: F-HF) from the core sediments indicate that enrichments of copper and zinc in the upper layer of the sediment are dependent on increases in the metal contents of the F-HAC, F-HCl and F-H₂O₂ fractions. Copper in F-HAC, and zinc in F-HAC and F-HCl, seem to be of anthropogenic origin.Results of sequential studies of the whole Seto Inland Sea can be summarized as follows: At the present time, the sedimentary loads of copper and zinc over the whole Seto Inland Sea area are 630 and 3,500 ton yr^–1, respectively, while the natural and anthropogenic loads are 320 and 310 ton yr^–1 for copper and 1,800 and 1,700 ton yr^–1 for zinc, respectively.     

Assessment of the consecutive harmful dinoflagellate blooms during 2015 in the Izmit Bay (the Marmara Sea)

A series of red tides were observed during 2015 in the Izmit Bay(the Marmara Sea) which is located in the most industrialized and populated region of Turkey. Six samplings were carried out in this area following the red tides.Nitrite-N, nitrate-N, ammonia, silica and orthophosphate concentrations were analyzed spectrophotometrically.Physicochemical conditions were measured by CTD probe. Plankton quantification was performed using counting chambers under microscopes. Prorocentrum micans was the most abundant species, except on May 14,2015, when Noctiluca scintillans was dominant. The abundance of P. micans reached average 18×10~6 ind./L on May 3, 2015 in the Karamürsel station, simultaneously with elevated levels of NH_3 and o-PO_4~(3–). The sample was also abundant in dead amphipods((72±12) ind./L) that had been covered by mucilage aggregates produced by P.micans. The highest biomass(calculated by carbon) was recorded as(268±26.0) mg/L on May 14 in the Hereke station. Beside the anthropogenic wastewater discharges, unknown sources and resuspensions caused increases in nutrient levels. After long term northeaster gusts(35 km/h for 5 d) an upwelling occurred on November 6, 2015 after wind-induced sediment resuspension. Although nutrient discharges remarkably decreased over 30 years through established wastewater treatment plants, harmful phytoplankton blooms still occur. Comparing the present results with other studies in nearby Mediterranean seas reveals that the most intense harmful dinoflagellate bloom in recent years occurred in the Izmit Bay. Therefore, additional protection measures necessary for a cleaner Izmit Bay. These incidents also demonstrate that contaminants, accumulated in sediment,may have long-lasting effects on enclosed marine ecosystems.     

温、盐度及营养盐对不同藻株塔玛亚历山大藻生长的影响

利用2001年11月至2003年2月从长江口、闽江口和北部湾水域表层沉积物中分离的休眠孢囊,萌发获得三株塔玛亚历山大藻,并研究了温度、盐度、营养盐对它们生长的影响。实验结果表明,来源于三个不同海区的藻株在水温32℃的条件下均无法存活,温度对长江口藻株(ATDH01)及广西北部湾藻株(ATGX02)的生长有极显著影响(P<0.01),而对闽江口藻株(ATMJ02)的生长无显著影响(P>0.05)。不同海区的藻株,其生长特性有明显差异,ATDH01藻株最适生长温度为24℃,最适生长盐度为30,且在盐度15和35仍有较高的生长率;而ATMJ02藻株及ATGX02藻株最适生长温度分别为24℃和20℃,最适生长盐度范围为20～30,盐度超出此范围生长率明显降低。ATDH01藻株的生长繁殖能力最强。营养盐对三个不同海区藻株生长的影响基本一致,在低P(1.2μmol/L)组中,三株藻的指数生长期较短,细胞密度明显的低于f/2组;而在低N(44μmol/L)组中,虽然在培养初期,三株藻的细胞生长明显快于f/2组,但在生长后期由于氮的限制,最终细胞密度仍低于f/2组。     

Differences in abundance and distribution of Alexandrium cysts in Sendai Bay,northern Japan,before and after the tsunami caused by the Great East Japan Earthquake

The tsunami caused by the Great East Japan Earthquake on 11 March 2011 greatly influenced the coastal benthic environment on the northern Pacific coast of Japan. We used the direct count method to investigate changes in the abundance and distribution of Alexandrium (Alexandrium tamarense and Alexandrium catenella) cysts before and after the tsunami in Sendai Bay. Densities of Alexandrium cysts in sediments collected in summer 2011 ranged from 0 to 8,190 cysts cm^?3. In the western part of the bay, the density increased greatly after the tsunami, the highest density being approximately 10 times the density recorded in 2005. Molecular identification of single cysts with multiplex polymerase chain reaction (PCR) showed that Alexandrium tamarense dominated the cyst population in the southwestern part of the bay in 2011. Furthermore, accumulation of cysts on the surface sediment after disturbance of the sediment was confirmed by a laboratory experiment. The main factor causing the drastic changes in abundance and distribution of Alexandrium cysts after the earthquake was considered to be vertical and horizontal redistribution of the cysts in sediments after the tsunami.     

The blooms of a cyanobacterium, Microcystis cf. aeruginosa in a severely polluted estuary, the Golden Horn, Turkey

The distribution of toxic cyanobacterium Microcystis cf. aeruginosa in the severely polluted Golden Horn Estuary was studied from 1998 to 2000. Microcystis persisted at the upper estuary where the water circulation was poor and values ranged between 2.9 × 10⁴ and 2.7 × 10⁶ cells ml⁻¹ throughout the study. Simultaneously measured physical (salinity, temperature, rainfall and secchi disc) and chemical parameters (nutrients and dissolved oxygen) were evaluated together with Microcystis data. Although the Microcystis blooms generally occur in summer due to the increase in temperature, the blooms were recorded in winter in the present study. The abundance of Microcystis depended on the variations in salinity and both blooms were recorded below S = 2. A moderate partial correlation between Microcystis abundance and salinity was detected in the presence of temperature, dissolved oxygen and precipitation data (r = −0.561, p = 0.002). The M. cf. aeruginosa abundance was low in the summer when the salinity was higher than winter. A remarkable increase in the eukaryotic phytoplankton abundance following the improvements in the water quality of the estuary occurred, whilst the Microcystis abundance remained below bloom level.     

海洋生态重要性区域的内涵与识别方法研究——以黄河口为例

海洋生态环境目前正在承受来自人类活动和气候变化的巨大压力;急需必要的管理工具或决策支持系统来应对这些压力所带来的生态环境问题。对海洋生境的分类识别是开展生物多样性保护的基础和前提;海洋生态重要区识别作为一种客观、科学和灵活的生境分类评估和选划方法;已被科学界和管理者广泛接受和认可。本文首先介绍了海洋生态重要区的概念内涵以及识别方法的研究进展;给出了海洋生态重要区的定义;之后以黄河口为例;初步建立了针对该区域的生态重要区识别标准和评价方法;对黄河口及邻近海区进行了生态重要性等级划分。本文是对生态重要区识别方法在我国近海的首次应用尝试;研究结果可为我国基于生态系统的海洋管理提供科学方法和工具;也可为其他区域的研究提供借鉴。     

A three-dimensional numerical study of river plume mixing processes in Otsuchi Bay,Japan

The three-dimensional numerical model SUNTANS is applied to investigate river plume mixing in Otsuchi Bay, an estuary located along the Sanriku Coast of Iwate, Japan. Results from numerical simulations with different idealized forcing scenarios (barotropic tide, baroclinic tide, and diurnal wind) are compared with field observations to diagnose dominant mixing mechanisms. Under the influence of combined barotropic, baroclinic and wind forcing, the model reproduces observed salinity profiles well and achieves a skill score of 0.94. In addition, the model forced by baroclinic internal tides reproduces observed cold-water intrusions in the bay, and barotropic tidal forcing reproduces observed salt wedge dynamics near the river mouths. Near these river mouths, vertically sheared flows are generated due to the interaction of river discharge and tidal elevations. River plume mixing is quantified using vertical salt flux and reveals that mixing near the vicinity of the river mouth, is primarily generated by the barotropic tidal forcing. A 10 ms^?1 strong diurnal breeze compared to a 5 ms^?1 weak breeze generates higher mixing in the bay. In contrast to the barotropic forcing, internal tidal (baroclinic) effects are the dominant mixing mechanisms away from the river mouths, particularly in the middle of the bay, where a narrow channel strengthens the flow speed. The mixing structure is horizontally asymmetric, with the middle and northern parts exhibiting stronger mixing than the southern part of the bay. This study identifies several mixing hot-spots within the bay and is of great importance for the coastal aquaculture system.     

Reproductive success of Calanus pacificus during diatom blooms in Dabob Bay, Washington

While numerous laboratory studies in the last decade have shown that diatoms can induce reproductive failure in copepods, field evidence for a negative diatom effect is equivocal. To unambiguously elucidate the effects diatoms have on copepod reproduction in situ, we undertook a study of the abundance, distribution, grazing rates, and reproductive success of Calanus pacificus in Dabob Bay, Washington, USA, during two spring bloom periods. We simultaneously measured the phytoplankton composition, abundance, and distribution. Here we present results for the reproductive success of C. pacificus using four measurements: egg production rate, clutch size, egg hatching success, and naupliar survival (to the first feeding stage). Egg production rate was positively correlated with chlorophyll a concentration, and egg hatching success and naupliar survival were usually greater than 80%. However, in February 2002 and 2003 – during blooms of diatoms of the genus Thalassiosira – either egg hatching success, naupliar survival, or both were significantly depressed compared to other times in spring and summer. These effects, combined with evidence that C. pacificus was grazing aldehyde-producing Thalassiosira at the time of their blooms, indicate that diatoms can negatively affect copepod reproduction in the field, albeit only under specific circumstances and for brief periods.     

Cyclic behaviour and liquefaction resistance of Izumio sands in Osaka,Japan

Abstract

This article presents a study of liquefaction resistance behaviour of sand using a cyclic triaxial test. The site investigation was performed, and frozen undisturbed specimens were taken from the Izumio site in Osaka, Japan. According to the evidence in 1995 Kobe Earthquake, the first two sand layers are vulnerable to undergo liquefaction. The effect of deviatoric stress on liquefaction resistance was focused on in this study. The excess pore pressure ratio, hysteresis loop, and effective stress path from the cyclic triaxial tests were reported. A multispring element model was employed to simulate the soil behaviour under cyclic loading. The results showed that applied deviatoric stress could influence the liquefaction resistance of sandy soil samples. The plots of the cyclic stress ratio versus the number of cycles to generate liquefaction known as a liquefaction resistance curve can be then constructed and compared with other sands.     

环境因子对塔玛亚历山大藻生长的综合影响

利用多因子实验设计,研究了主要环境因子温度、盐度和光照强度对麻痹性贝毒产毒藻——塔玛亚历山大藻(Alexandrium tamarense)生长的影响.经三维ANOVA统计分析(Tukey test)结果表明,在实验条件范围内(温度12,19,25,32℃;盐度10,18,25,30,35和光照强度0.02×1016,0.08×1016,0.3×1016,1.6×1016s-1/cm2),温度、光照强度和盐度对藻生长率有显著的影响(P<0.001).光照强度和温度、盐度和温度、光照强度和盐度以及这3个因子之间存在显著的相互作用(P<0.001),在本实验中该藻生长的最适条件是19℃,1.6×1016s-1/cm2,盐度30.根据塔玛亚历山大藻的生长特性,我们探讨了这些环境因子在塔玛亚历山大藻赤潮形成机制中的作用.     

Adsorption—desorption control of phosphate in anoxic sediment of a coastal sea,Funka Bay,Japan

Sediment core samples were taken once a month from July 1980 to September 1981 at a station in Funka Bay (92-m depth) for the determination of phosphate, silicate and alkalinity in interstitial water. A remarkable seasonal variation was found for interstitial phosphate, that is, distinct maxima appeared in spring (March—April), just after a phytoplankton bloom which brought a large amount of settling particles to the bottom, and in summer (July—August) when the water was stratified and the dissolved oxygen content of the bottom water decreased due to the decomposition of organic matter. The high interstitial phosphate concentration was always accompanied by a sharp increase in alkalinity, indicating sulfate reduction. This large seasonal variation in interstitial phosphate cannot be explained by in situ decomposition of organic matter and/or the diffusive loss of interstitial phosphate. A more likely explanation is adsorption and desorption of interstitial phosphate coincident with the depth of the active sulfate reduction layer.     

Environmental control of short-term variation in the plankton community of inner Tokyo Bay, Japan

Water temperature, salinity, nutrient concentrations and the composition of the plankton community were recorded at three stations in inner Tokyo Bay over a period of 328 days (from June 8, 1995 to April 30, 1996) with a nominal sampling frequency of once per day. Inspection of the results revealed that the data could be divided into two blocs as an aid to analysis: the period from June to October was characterized by the development of stratification of temperature and salinity (stratification period), and November to March was characterized by uniform temperature and salinity in the water column due to vertical mixing (mixing period). Oxygen-depleted water forms in the bottom layer during the stratification period, but vertical mixing of the water column, due to changing wind and rainfall conditions caused by passing weather fronts, results in the breakdown of the oxygen-depleted water mass. Nutrient loads are high in the surface water due to the freshwater supply, but occasional pulses of primary production cause a depletion of phosphate in the surface water, suggesting that the phosphorus becomes a limiting nutrient for phytoplankton growth in this period. Several short-term peaks of plankton abundance (blooms) occurred as responses to temporal changes in water quality from June to November, with consequent species succession. Significant fluctuations in the densities of the diatom Skeletonema costatum and several species of ciliates corresponded to the daily changes in the physical and chemical characteristics of the coastal environment. During the mixing period, when water temperature and solar radiation decreased, there were no short-term variations in water quality and although nutrient concentrations gradually increased from November to February, primary production remained low. This study shows that the short-term dynamics of the phytoplankton community are closely coupled to fluctuations in environmental forcing, and that the degree of coupling is stronger during periods when solar radiation is greater. The results provide a novel typological understanding of seasonal plankton dynamics in a shallow, eutrophicated marine embayment, and suggest how such systems may be treated in simulation modeling.     

Deposition Rates of Terrestrial and Marine Organic Carbon in the Osaka Bay, Seto Inland Sea, Japan, Determined Using Carbon and Nitrogen Stable Isotope Ratios in the Sediment

Carbon and nitrogen stable isotope ratios (¹³C and ¹⁵N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The ¹³C and ¹⁵N of surface sediments in the estuary of the Yodo River were less than –23 and 5 respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving ¹³C of about –20 and ¹⁵N about 6). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.