中国林蛙蝌蚪对盐度和pH的耐受性

分别在正常盐度不同 pH值、正常 pH值不同盐度和相同水温 18 3～ 2 0 7℃的条件下 ,进行中国林蛙蝌蚪对盐度和 pH值的耐受性实验。结果表明 ,在pH值为 6 8～ 7 0时 ,盐度在 2 0～ 3 0g·L-1对蝌蚪 96h存活率没有明显影响 ;随着盐度的增加 ,蝌蚪存活率下降 ;盐度对蝌蚪 2 4、4 8、72和 96h的TLm 值分别为 8 79,7 12 ,5 6 4和 3 83g·L-1,安全浓度为 1 73g·L-1。在盐度为 0 18g·L-1时 ,pH值在 4 3～ 9 7范围内对蝌蚪 96h存活率没有明显影响 ;pH值对蝌蚪的 2 4 ,4 8,72和 96h的TLm 值分别为 10 33,10 18,10 0 8和 10 0 2。生产上中国林蛙蝌蚪生存的适宜 pH值为 6 0～ 9 0 ,适宜盐度为 1 0～ 2 0g·L-1。     

紫外线诱变选育聚丁二酸丁二醇酯（PBS）高降解活性菌株

以PBS降解菌HJ03（Alternariasp．）为出发菌株,通过紫外诱变,透明圈初筛及PBS薄膜复筛,获得一株降解能力增强且对温度和pH耐受力均得到提高的突变株HJ10。与出发菌株相比,HJ10在培养初期气生菌丝少,而培养7d时菌落致密且生长速度较快。经过连续继代培养7代后发现,突变株的降解活力保持了良好的遗传稳定性,其降解率较出发菌株提高百分比达14．4％以上;在最适降解温度范围内（25℃～30℃）和不适宜降解的温度条件下突变菌株Ⅻ10的降解率均高于出发菌株;各pH条件下,突变株对PBS的降解能力明显优于出发菌株,尤其在pH5．0时降解率提高了22．80％。     

一种生活在污水中的螺旋藻新品系的分离和培养

从污水中分离到一种螺旋藻新品系,并筛选到适合的培养基。藻体长1750μm,在适宜的条件下,藻体活跃地摆动和转动。其生活环境水质呈弱酸性和中性,盐度低,温度变化范围5～34℃,氮(N)、磷(P)浓度分别为4．53～4．96mg／L和0．39～0．48mg／L,达到超富营养化水平;培养试验表明,这种螺旋藻只适应在弱光下生长,与一般螺旋藻喜高温、高光、耐碱耐盐的特性显著不同。NH4^ 有利于这种螺旋藻的生长,是一种适合于在污水中生长的螺旋藻,有可能在水质净化方面得到应用。     

盐度和pH对平凡舟形藻生长和油脂积累的影响

为研究盐度和pH对淡水硅藻生长和油脂含量的影响,对一株分离自野外采集水样中的平凡舟形藻(Navicula trivialis)进行研究,通过设置不同盐度0、0.03、0.06、0.12、0.18和0.24 mol/L和不同pH 4.5、6.0、7.5、8.5、9.5和10.5进行胁迫,测定各处理对平凡舟形藻的生长、叶绿素a含量、叶绿素荧光参数和油脂含量的影响。结果表明:盐浓度为0.12 mol/L、pH 7.5时,平凡舟形藻细胞密度和叶绿素a含量最高;盐浓度为0.24 mol/L、pH 7.5时,总脂含量最高,分别为34.93%和33.5%。结果表明,平凡舟形藻对不同盐度和pH的适应性不同,这在一定程度上影响其生长和油脂含量。     

几种主要环境因子对布朗葡萄藻(Botryococcus braunii)光合作用的影响

利用测定净光合放氧速率的方法研究了光照强度、温度、 pH值、盐度对布朗葡萄藻Botryococcus braunii UTEX 572和B.braunii UTEX 2441两个品系的光合作用的影响.B.braunii UTEX 572的适宜光照强度范围400～1600 μmol·m-2·s-1,光饱和点在800 μmol·m-2·s-1附近;适宜温度范围25～35℃,最适温度30℃;适宜pH范围5.0～8.0,最适pH7.0;适宜盐度范围0～0.2 mol/L,最适盐度0.1mol/L.B.braunii UTEX 2441的适宜光照强度范围400～1600 μmol·m-2·s-1,光饱和点在400 μmol·m-2·s-1附近;适宜温度范围25～35℃,最适温度30℃;适宜pH范围5.0～8.0,最适pH 7.0;对盐度的适应范围较小,盐度升高,光合放氧速率明显下降.两个布朗葡萄藻净光合放氧速率随光照强度、温度、pH值和盐度变化的规律,表明布朗葡萄藻的基本生理生态学特征:适应于较强的光照强度、较高的温度、中性偏酸的环境和较低的盐度.对布朗葡萄藻基本生理生态学特征的了解,为培养条件的优化提供了依据.2个布朗葡萄藻品系对光强、温度、pH值和盐度变化的反应有所不同:与B.braunii UTEX 2441相比,B.braunii UTEX 572具有更高的光饱和点,适应更高的温度,对pH值变化有更宽的适应范围,适当提高盐度对其光合作用有促进作用,表明B.braunii UTEX 572在快速生长繁殖方面具有更大的潜力,这一研究结果为筛选适合于大量培养的优良藻种提供了依据.     

一株芦荟抗菌内生细菌的分离鉴定及生物学性质研究

从药用植物中华芦荟组织中分离出一株抗菌内生细菌A11#,该菌产生广谱抗菌活性物质,对金黄色葡萄球菌、枯草芽孢杆菌等革兰氏阳性细菌和植物病原真菌均有较强的抑制作用;通过形态学观察及生理生化特征测定,初步鉴定归属于芽孢杆菌属(Bacillus)。该菌在初始pH值为5．0～10．0的PDA培养基上生长旺盛,生长最适pH为5～7,培养液初始pH为6～10时发酵产生大量粘性物质;生长温度范围在10～45℃,最适温度28～37oc;在初始pH5．0和30．5℃条件下发酵,其发酵液抑菌作用最强;该菌所产抗菌物质能耐121℃处理30min而不影响其活性。在阿须贝无氮培养基上生长良好,在不加葡萄糖、蔗糖或淀粉的LB和牛肉膏蛋白胨培养基上不生长;同时还产生对高岭土有絮凝活性的物质。     

紫外辐射和低盐胁迫对浒苔生长的影响

探究了不同紫外曝光量及低盐胁迫对浒苔生长的影响。结果显示,紫外辐射对浒苔生长有抑制作用,甚至使浒苔呈负增长,而且在盐度为24时抑制作用比盐度为12时大,藻体湿重下降明显。2.3×10⁴KJ·m^-2～4.7×10⁴KJ·m^-2的紫外曝光量使藻体变细、变软、变散,在显微镜下观察发现部分藻体受到损伤,死亡后内容物外溢;1.9×10⁴KJ·m^-2紫外曝光量对浒苔生长率影响较小。实验设置了0、6、12、24四个盐度梯度,培养42d,在盐度为0的情况下,前21 d浒苔藻体颜色没有明显变化,但藻体变软,变散,随后,藻体颜色慢慢变黄、变白直至死亡;其它各组生长均正常,显示出浒苔的盐度适应范围广,对低盐具有一定的耐受性,但不能长时间耐受0盐度。     

温度、光照和pH值对锥状斯氏藻和塔玛亚历山大藻光合作用的影响及光暗周期对其生长速率和生物量的影响

用测定净光合放氧速率的方法研究了温度、光照和pH对锥状斯氏藻(Scrippsiella trochoidea)和塔玛亚历山大藻(Alexandrium tamarense)光合作用的影响.在不同光暗周期(L∶D)条件下培养锥状斯氏藻和塔玛亚历山大藻,研究了光暗周期对生长繁殖速率和生物量的影响.2种藻对温度的变化敏感,适宜的温度范围是17～25℃,最适温度20～22℃,低于10℃和高于30℃不能生长;锥状斯氏藻的光饱和点是400 μmol·m-2·s-1,塔玛亚历山大藻的光饱和点是650 μmol·m-2·s-1, 都属于喜高光强的微藻;2种藻对pH值的变化极其敏感,适宜的pH值范围很小,为7.0～9.0, 最适pH值7.5～8.0, 与其生活的海洋环境一致,pH值高于9.5时, 不能进行有效的光合作用,pH值10.0可致全部细胞死亡;在一定范围内,2种藻的生长速率(μ)和生物量随着光照时间的延长呈比例增加.     

盐度及pH对星斑裸颊鲷受精卵孵化和仔鱼耐饥饿能力的影响

比较观察了不同盐度(0、5‰0、10‰、15‰、20‰、25‰、30‰、35‰、40‰和45‰)及不同pH(5.5、6.0、6.5、7.0、7.5、8.0、8.5、9.0和9.5)条件下,星斑裸颊鲷(Lethrinus nebulosus)受精卵的孵化时间、孵出期、孵化率、畸形率及一定时间内(24h和48h)仔鱼成活率,并且在以上盐度和pH条件下对星斑裸颊鲷初孵仔鱼进行耐饥饿试验,测定其不投饵存活指数(survival activity index,SAI).结果表明,只有SAI值大于3的星斑裸颊鲷仔鱼才有可能被进一步培育成苗,低于3的将在数天内死亡;星斑裸颊鲷受精卵孵化的适宜盐度范围是10‰～45‰,最适宜盐度范围15‰～40‰,适宜pH是6.5～9.0,最适宜pH范围7.0～8.5;初孵仔鱼生存的适宜盐度范围是10‰～40‰,最适宜盐度范围20‰～25‰,适宜pH是5.5～9.5,最适宜pH范围7.0～8.5.     

海洋赤潮生物与厦门海域几种细菌的生态关系研究

选择我国沿海易发有毒赤潮藻——塔马亚历山大藻 [Alexandrium tamarense (Lebour) Balech,1 985 ]和从厦门海域筛选的海洋细菌作为实验材料 ,研究在实验生态条件下 A.tamarense的生理生态特征 ,及其与 3株从厦门海域筛选的海洋细菌 S5,S7,S10 与 A.tamarense共同培养表现的生态关系的差异性。结果表明 :在实验室条件下 ,A.tamarense可以较好地生长并保持自然状态下的若干特性 ,其生长曲线与微型生物的生长曲线相似 ;分别在藻细胞生长的延滞期和指数期加入细菌过滤液 ,发现 3种海洋细菌的过滤液对 A.tamarense生长有不同的抑制作用效果。三者的抑藻能力大小依次为 S10 >S5>S7。本文对海洋细菌抑藻作用机理、赤潮的生物防治可能性进行了讨论。     

Effects of salinity on growth and survival in five Artemia franciscana (Anostraca: Artemiidae) populations from Mexico Pacific Coast

Salinity is an important factor influencing growth and survival of aquatic organisms such as Artemia, a valuable aquaculture species. This study evaluated the effects of salinity on A. franciscana populations from different water bodies in Mexico's Pacific Coast. With this purpose, five autochthonous bisexual Artemia populations were tested to assess their survival and growth values against salinities of 40, 60, 80, 100 and 120 g/l, under laboratory conditions (25 +/- 2 degrees C; pH 8-10; constant light and aeration). The organisms were fed with 100 mL of rice bran and 2L of Tetraselmis suecica (500 000 cel/ml). The culture experiments were made in 200L plastic tanks, and survival and growth final values were obtained after 21 culture days. Survival and growth curves were determined by a regression analysis (R2). The significant differences between salinities were determined by ANOVA test (p < 0.05). The best survival and growth rates were found at salinities of 100-120 g/l. When the Mexican Artemia populations were cultivated at 40 g/l of salinity, 100% mortality was observed in the juvenile stage. This study determined that survival and growth values of A. franciscana populations increased with salinity. The five A. franciscana populations presented significant differences in their survival rate under various salinity regimes. The studied populations experienced high mortality at salinities under 60 g/l and over 200 g/l, and especially during the metanauplius stage. The present study confirms that growth rates in Mexican A. franciscana populations from Pacific Coast habitats are not inversely proportional to salinity. These A. franciscana populations should be cultured at 100-120 g/l of salinity to obtain better survival and growth rates. This data is useful to improve culture systems in aquaculture biomass production systems.     

低盐对菊黄东方鲀幼鱼生长、存活、耗氧、鳃Na /K -ATP酶以及肝抗氧化酶的影响

通过探讨低盐(盐度为0、1.7、5、10、15和20)对菊黄东方鲀(Takifugu flavidus)幼鱼生长、存活、耗氧、鳃Na+/K+-ATP酶以及肝抗氧化酶的影响,研究了菊黄东方鲀幼鱼对低盐的适应性。结果显示,菊黄东方鲀幼鱼在盐度0组实验3周后全部死亡;盐度1.7组实验6周幼鱼大量死亡,最后成活率相当低,仅17.33%;盐度5、10、15和20组的幼鱼在整个实验中没有出现死亡现象。全长特定生长率在盐度1.7~20组之间没有显著差异。体重特定生长率,1.7盐度组比其他盐度组显著低(P0.05),5~20盐度组之间没有显著差异(P0.05)。最高的全长特定生长率和最高的体重特定生长率均出现在10盐度组。前6周的饵料系数在盐度1.7~20组之间没有显著差异,但最高(1.27)和最低(1.17)的饵料系数分别出现在1.7和10盐度组,总饵料系数在5~20盐度组之间没有显著差异。幼鱼的耗氧率在5~20盐度组之间没有显著差异,但最低的耗氧率出现在10盐度组。最低的鳃Na+/K+-ATP酶(NKA)活性出现在10盐度组,5~20盐度与NKA活性的关系可以用二次函数来拟合(y=0.083 2 x2﹣2.125 2 x+20.915,r2=0.977 9),由此得到理论上最低NKA活性值出现在盐度12.77。肝超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-PX)活性在盐度1.7~20组之间均无显著差异,而10和15盐度组的过氧化氢酶(CAT)活性比1.7和20盐度组的显著低(P0.05),1.7~20盐度与CAT活性关系可以用二次函数来拟合(y=0.257 7 x2﹣5.807 6 x+87.357,r2=0.877 1),由此得到理论上最低CAT活性值出现在盐度11.27。研究结果表明,盐度1.7是菊黄东方鲀幼鱼的生存极限低盐,盐度5以上已经能适合其存活和生长,盐度10~15是的菊黄东方鲀幼鱼的最适宜盐度范围,适当降低盐度对菊黄东方鲀幼鱼的养殖生产是有利的。建议菊黄东方鲀幼鱼养殖盐度至少在5以上,最好在10~15范围。     

Effects of salinity on growth, photosynthesis and respiration in a freshwater alga Rhizoclonium riparium (Chlorophyceae, Cladophorales)

A freshwater green alga, Rhizoclonium riparium (Roth) Harvey, was found to grow in diluted seawater with salinities (PSU) from 0.1 to 34.0 (0.1–34.0 S). It grew best at 13.6 S and least at 0.1 S which was the least salinity reported in its habitat. Net photosynthetic oxygen production of R. riparium rose with salinity up to 34.0. However, in the medium adjusted at pH 8.1. the net photosynthesis rose at low ranges of salinity and was almost at the same level in all ranges of salinities examined. The net photosynthesis was increased by the addition of bicarbonate in the medium. Respiratory oxygen consumption did not rise with the increase of external salinities from 0.1 to 34.0. The results indicate that R. riparium can grow by increasing net photosynthesis in diluted seawater in which the pH value is suitable for effective bicarbonate supply to photosynthesis.     

The effect of salinity on the growth,toxin production,and morphology of <Emphasis Type="BoldItalic">Nodularia spumigena</Emphasis> isolated from the Gulf of Gdańsk,southern Baltic Sea

Culture experiments on the toxic Nodularia spumigena strain NSGG-1 isolated from the Gulf of Gdańsk showed a significant effect of salinity on growth and nodularin production. Growth of the NSGG-1 strain, was optimal between 7 and 18 psu, lower at 3 and 24 psu and was significantly inhibited at the extreme salinities of 0 and 35 psu. Nodularin (NOD) content of N. spumigena, estimated by the NOD/Chla ratios, correlated positively with salinity and increased from 0 to 35 psu. The NOD/Chla ratio on day 10 of growth was high, and, reached the maximum at day 30. A sudden increase in salinity from 7 to 18 and 35 psu resulted in plasmolysis of Nodularia cells. Salinity was also observed to have other effects on NSGG-1; the filaments were longest at 7 psu, while an increased number of akinetes were formed at 35 psu. The number of heterocytes was markedly reduced at the extreme salinities. This latter finding might explain why Nodularia blooms do not occur outside a certain salinity range in nitrogen-deficient waters.     

There are high levels of functional and genetic diversity in Oxyrrhis marina

Oxyrrhis marina, a widely distributed marine protist, is used to model heterotrophic flagellate responses in microbial food webs. Although clonal variability occurs in protists, assessments of intraspecific diversity are rare; such assessments are critical, particularly where species are used as models in ecological studies. To address the extent of intraspecific variation within O. marina, we assessed diversity among 11 strains using 5.8S rDNA and ITS sequences. The 5.8S rDNA and ITS regions revealed high divergence between strains: 63.1% between the most diverse. To compare O. marina diversity relative to other alveolates, 18S rDNA sequences for five strains were analysed with sequences from representatives of the major alveolate groups. 18S rDNA also revealed high divergence in O. marina. Additionally, consistent with phylogenies based on protein coding genes, maximum likelihood analysis indicated that O. marina was monophyletic and ancestral to the dinoflagellates. To assess ecophysiological differences, growth rates of seven O. marina strains were measured at 10 salinities (10-55 per thousand). Two salinity responses occurred: one group achieved highest growth rates at high salinities; the other grew best at low salinities. There was no clear correlation between molecular, ecophysiological, or geographical differences. However, salinity tolerance was associated with habitat type: intertidal strains grew best at high salinities; open-water strains grew best at low salinities. These data indicate the need to examine many strains of a species in both phylogenetic and ecological studies, especially where key-species are used to model ecological processes.     

A Kinetic and Factorial Approach to Study the Effects of Temperature and Salinity on Growth and Toxin Production by the Dinoflagellate Alexandrium ostenfeldii from the Baltic Sea

Alexandrium ostenfeldii is present in a wide variety of environments in coastal areas worldwide and is the only dinoflagellate known species that produces paralytic shellfish poisoning (PSP) toxins and two types of cyclic imines, spirolides (SPXs) and gymnodimines (GYMs). The increasing frequency of A. ostenfeldii blooms in the Baltic Sea has been attributed to the warming water in this region. To learn more about the optimal environmental conditions favoring the proliferation of A. ostenfeldii and its complex toxicity, the effects of temperature and salinity on the kinetics of both the growth and the net toxin production of this species were examined using a factorial design and a response-surface analysis (RSA). The results showed that the growth of Baltic A. ostenfeldii occurs over a wide range of temperatures and salinities (12.5–25.5°C and 5–21, respectively), with optimal growth conditions achieved at a temperature of 25.5°C and a salinity of 11.2. Together with the finding that a salinity > 21 was the only growth-limiting factor detected for this strain, this study provides important insights into the autecology and population distribution of this species in the Baltic Sea. The presence of PSP toxins, including gonyautoxin (GTX)-3, GTX-2, and saxitoxin (STX), and GYMs (GYM-A and GYM-B/-C analogues) was detected under all temperature and salinity conditions tested and in the majority of the cases was concomitant with both the exponential growth and stationary phases of the dinoflagellate’s growth cycle. Toxin concentrations were maximal at temperatures and salinities of 20.9°C and 17 for the GYM-A analogue and > 19°C and 15 for PSP toxins, respectively. The ecological implications of the optimal conditions for growth and toxin production of A. ostenfeldii in the Baltic Sea are discussed.     

Effects of reduced salinity on survival, growth, reproductive success, and energetics of the euryhaline polychaete Capitella sp. I

Physiological adjustment to water of reduced salinity requires energy expenditure. In this study we sought to determine the fitness costs associated with such adjustment in the euryhaline polychaete Capitella sp. I, and the extent to which such costs could be explained by increased rates of energy expenditure. In a series of experiments conducted at 20 degrees C, salinity was reduced from 30 per thousand to either 25, 20, 15, 12, or 10 per thousand within 72 h after the larvae had been induced to metamorphose. Juveniles were reared on fine, organic-rich sediment. Over the next 15-30 days, we determined survival, growth, fecundity, and rates of respiration and feeding (via fecal pellet production). Larval salinity tolerance was also determined. Juvenile survival at salinities as low as 12-15 per thousand was comparable to that at 30 per thousand. The lower limit of salinity tolerance was 10-12 per thousand at 20 degrees C for both larvae and juveniles. Juveniles grew significantly more slowly at 12-15 per thousand in six of the seven experiments. Fecundity, however, was generally highest at intermediate salinities of 20-25 per thousand, and comparable at 30 and 15 per thousand. No individuals released embryos at 12 per thousand over the approximately 30-day observation periods in any of the three experiments in which the worms were reared at this low salinity. Reduced growth rates were not explained by differences in rates of respiration at different salinities: at reduced salinity, respiration rates were either statistically equivalent to (P>0.10) or significantly below (P<0.05) those recorded for animals maintained at 30 per thousand. Lower growth rates at lower salinities were best explained by reduced feeding rates. Further studies are required to determine whether digestive efficiency, growth hormone concentrations, or reproductive hormone concentrations are also altered by low salinity in this species.     

Effect of salinity on growth and toxin production of <Emphasis Type="Italic">Alexandrium minutum</Emphasis> isolated from a shrimp culture pond in northern Vietnam

A clonal culture of a Vietnamese strain of Alexandrium minutum, AlexSp17, was subjected to different salinity treatments to determine the growth and toxin production of this strain that produces a novel toxin analogue, deoxy GTX4-12ol. The experiment was carried out in batch cultures without pre-acclimatization at seven salinity treatments from 5 to 35 psu, under constant temperature of 25°C, illumination of 140 μmol photon m⁻² s⁻¹, and 12:12 light/dark photoperiod. The strain grew in all salinity treatments, with optimum growth at 10–15 psu. However, the specific growth rate (0.2 day⁻¹) was lower than those reported in Malaysian strains and other strains from different geographical areas. The optimum range of salinity for the growth of this species agreed with field observations of the locality of origin. No significant change in toxin profiles was observed at different salinities. The cellular toxin quota, Qt, was not affected by the salinity-dependent growth rate. The toxin GTX4-12ol is presumed to be a transformation product of GTX4 from specific cellular reductase enzymes. Further investigation at the molecular level of toxin biosynthesis and subcellular enzyme activities is needed to provide insight in the production of this unique toxin analogue.     

Paralytic shellfish toxins or spirolides? The role of environmental and genetic factors in toxin production of the Alexandrium ostenfeldii complex

Dinoflagellates of the Alexandrium ostenfeldii complex (A. ostenfeldii, A. peruvianum) are capable of producing different types of neurotoxins: paralytic shellfish toxins (PSTs), spirolides and gymnodimines, depending on the strain and its geographic origin. While Atlantic and Mediterranean strains have been reported to produce spirolides, strains originating from the brackish Baltic Sea produce PSTs. Some North Sea, USA and New Zealand strains contain both toxins. Causes for such intraspecific variability in toxin production are unknown. We investigated whether salinity affects toxin production and growth rate of 5 A. ostenfeldii/peruvianum strains with brackish water (Baltic Sea) or oceanic (NE Atlantic) origin. The strains were grown until stationary phase at 7 salinities (6–35), and their growth and toxin production was monitored. Presence of saxitoxin (STX) genes (sxtA1 and sxtA4 motifs) in each strain was also analyzed. Salinity significantly affected both growth rate and toxicity of the individual strains but did not change their major toxin profile. The two Baltic Sea strains exhibited growth at salinities 6–25 and consistently produced gonyautoxin (GTX) 2, GTX3 and STX. The two North Sea strains grew at salinities 20–35 and produced mainly 20-methyl spirolide G (20mG), whereas the strain originating from the northern coast of Ireland was able to grow at salinities 15–35, only producing 13-desmethyl spirolide C (13dmC). The effects of salinity on total cellular toxin concentration and distribution of toxin analogs were strain-specific. Both saxitoxin gene motifs were present in the Baltic Sea strains, whereas the 2 North Sea strains lacked sxtA4, and the Irish strain lacked both motifs. Thus sxtA4 only seems to be specific for PST producing strains. The results show that toxin profiles of A. ostenfeldii/peruvianum strains are predetermined and the production of either spirolides or PSTs cannot be induced by salinity changes. However, changes in salinity may lead to changed growth rates, total cellular toxin concentrations as well as relative distribution of the different PST and spirolide analogs, thus affecting the actual toxicity of A. ostenfeldii/peruvianum populations.     

The combined effect of salinity and temperature on the growth and toxin content of four Chilean strains of Alexandrium catenella (Whedon and Kofoid) Balech 1985 (Dinophyceae) isolated from an outbreak occurring in southern Chile in 2009

The toxic dinoflagellate Alexandrium catenella has been detected in the southern Chile since 1972, causing severe negative impacts on public health and aquaculture activities. Several environmental factors have been determined to affect growth and toxin production in Alexandrium strains. The aim of this study was to determine the effect of four combined conditions of two temperatures (10 and 15 °C) and two salinities (15 and 35 psu) on the growth and the Paralytic Shellfish Poisoning (PSP) toxin content and composition in four Chilean strains of A. catenella (PFB41, PFB42, PFB37 and PFB38), isolated during a summer outbreak occurred in southern Chile in 2009. The growth curves showed a higher effect of the salinity in strains PFB41 and PFB42 than in strains PFB37 and PFB38. The values of growth rates and maximum cell densities ranged from 0.25 to 0.73 div day⁻¹ and 1.1 × 10⁴ to 5.2 × 10⁴ cells mL⁻¹, respectively. All of the strains showed the highest values for both growth parameters at 15 °C and 35 psu. In general, growth parameters were higher at 35 psu independently of the temperature. On the other hand, the total PSP toxin content ranged widely from 3.99 to 239 fmol cell⁻¹. The highest values of PSP toxin content were attained at 10 °C and 35 psu for all of the strains, at both stages of growth. All of the strains displayed different toxin compositions, with neoSTX, GTX4-1, GTX3-2 and GTX5 being the main toxins detected. The results showed significant differences in the absolute values of growth and toxin production parameters among the strains grown under the same culture conditions, and for each strain grown under different combined conditions of temperature and salinity. These findings demonstrate that abiotic factors can differentially affect the population dynamics of the A. catenella toxic genotypes, thus making it extremely difficult to predict the ecological behavior of this species in the field in terms of the intensity of a potential outbreak.