Influence of different diets on the growth,survival, fecundity and proximate composition of brine shrimp Artemia franciscana (Kellog, 1906)

Artemia franciscana was studied under in vitro conditions, and fed with five different microalgae species, two organic diets and one mixed diet to evaluate the nutritional profile and growth performance. The A. franciscana instar‐I nauplii were stocked at a density of 100 per litre of ground borewell water with a salinity of 70 ppt in a plastic container and the culture continued for 12 days. The A. franciscana was fed with five microalgal species, such as Tetraselmis sp., Chaetoceros sp., Isochrysis sp., Thalassiosira sp. and Nannochloropsis sp., and organic diets of rice bran, soybean meal, and a mixture of Tetraselmis sp. and Chaetoceros sp. with rice bran, giving a total of eight experiments. The growth of A. franciscana was measured by length, and was observed to be the greatest (10,850 μm) in the group that was fed the mixed algae combination, and the lowest (7,290 μm) in the group that was fed Nannochloropsis sp. Among the different treatments, the highest survival value of 76% was seen in the group that was fed Chaetoceros sp. The fecundity was higher in A. franciscana that were fed with algae Chaetoceros sp., while the lower rate was observed with the group that was fed Nannochloropsis sp. Analysis of proximate composition showed increased levels in the animals fed with Chaetoceros sp. (lipid, 19.40%; eicosapentaenoic acid, 6.70 mg; docosahexaenoic acid, 10.20 mg; amino acids: proline, 2.06 μg; histidine, 0.77 μg, arginine, 0.65 μg, glycine, 0.80 μg, glutamic acid, 1.75 μg; threonine, 1.42 μg) and the mixed diet (protein, 58.59%; carbohydrate, 21.30%; amino acids: asparagine, 0.90 μg; serine, 1.65 μg; tryptophan, 1.66 μg; leucine, 1.50 μg; phenylalanine, 1.14 μg; valine, 0.66 μg). All components showed the lowest level in the diet fed with Tetraselmis species. These A. franciscana populations showed better survival, higher fecundity and biochemical profiles when cultured with microalgae Chaetoceros sp. These data are useful to improve A. franciscana culture in aquaculture to produce quality cysts and biomass, especially in feeding larvae of marine species.     

Coelastrella terrestris for Adonixanthin Production: Physiological Characterization and Evaluation of Secondary Carotenoid Productivity

A novel strain of Coelastrella terrestris (Chlorophyta) was collected from red mucilage in a glacier foreland in Iceland. Its morphology showed characteristic single, ellipsoidal cells with apical wart-like wall thickenings. Physiological characterization revealed the presence of the rare keto-carotenoid adonixanthin, as well as high levels of unsaturated fatty acids of up to 85%. Initial screening experiments with different carbon sources for accelerated mixotrophic biomass growth were done. Consequently, a scale up to 1.25 L stirred photobioreactor cultivations yielded a maximum of 1.96 mg·L⁻¹ adonixanthin in free and esterified forms. It could be shown that supplementing acetate to the medium increased the volumetric productivity after entering the nitrogen limitation phase compared to autotrophic control cultures. This study describes a promising way of biotechnological adonixanthin production using Coelastrella terrestris.     

Microbial environments in marine larviculture:Impacts of algal growth rates on the bacterial load in six microalgae

The impacts of varying algal growth rates on the bacterial load in the cultures were studied for six marine microalgae: Skeletonema costatum ,Chaetoceros mülleri (Bacillariophyceae), Nannochloropsis oculata (Eustigmatophyceae), Isochrysis galbana, Pavlova lutheri (Haptophyceae), and Tetraselmis sp. (Prasinophyceae). Samples were taken in batch cultures during early exponential phase and in stationary phase when the growth rate was below 5% of maximum growth rate (µ_max). Except for C. mülleri and N. oculata, the microalgae were thereafter grown semi-continuously at dilution rates of 20% and 60% of µ_max and samples taken during a period of 10 days.Higher bacterial levels were associated with slow-growing microalgae on a per volume basis. Per algal cell, variations in the bacterial load were more related to species. Relatively high bacterial densities (5.7–16.4 CFU algal cell^–1) with large proportions of opportunistic and haemolytic species were associated with the Bacillariophyceae. For the other species, the bacterial density was 0.2–4.3 CFU algal cell^–1. Bacterial levels were in general lower and not affected to the same extent by algal growth conditions in Tetraselmis sp. and P. lutheri. No or very low levels of presumptive Vibrio spp. were observed, except in semi-continuous cultures of P. lutheri. Cultures of Tetraselmis sp. had low levels of opportunistic bacteria at all growth conditions.     

条斑紫菜提取物对4种赤潮微藻生长的抑制作用

研究条斑紫菜水溶性抽提液对前沟藻、中肋骨条藻、米氏凯伦藻和塔玛亚历山大藻等4种赤潮微藻生长的影响,在此基础上,利用甲醇、丙酮、乙酸乙酯、氯仿和石油醚等有机溶剂浸泡条斑紫菜干粉,经抑藻圈方法检测条斑紫菜水溶性抽提液的抑藻活性。通过测定藻细胞密度和细胞体积,观察藻细胞形态,分析藻细胞内叶绿素、蛋白质和多糖等生理生化指标的变化,对抑藻活性最大的提取物对前沟藻、米氏凯伦藻、中肋骨条藻和塔玛亚历山大藻赤潮微藻生长的抑制作用进行分析,并依次以石油醚、乙酸乙酯和正丁醇为提取溶剂,采用液液分离法对此提取物做了进一步分离。结果表明,当条斑紫菜水溶性抽提液浓度超过16g/L时能显著抑制4种赤潮微藻的生长,尤其是对前沟藻和米氏凯伦藻具有很强的抑制作用。在5种有机溶剂提取物中,甲醇提取物的抑制作用最为明显。进一步研究发现此提取物对4种赤潮微藻的生长抑制显著且具有浓度效应,在16g/L时,此提取物对前沟藻、米氏凯伦藻、中肋骨条藻和塔玛亚历山大藻的生长抑制率分别为70.5%、79.9%、67.1%和65.1%。同时,致使米氏凯伦藻、中肋骨条藻和塔玛亚历山大藻等3种赤潮微藻体积变小,运动能力下降,藻细胞出现空洞、细胞破碎和色素减褪等现象;...     

珠母贝浮游幼虫饵料的研究

研究了湛江等鞭金藻、等鞭金藻OA-3011、亚心形扁藻、小球藻、绿色巴夫藻、面包酵母、光合细菌单独及多种混合投喂对珠母贝浮游幼虫生长、存活和变态的影响.结果表明:单独投喂时湛江等鞭金藻、等鞭金藻OA-3011效果最好,幼虫壳长93 μm时可投喂亚心形扁藻,小球藻、绿色巴夫藻、面包酵母、光合细菌不宜单独投喂;直线铰合期、壳顶幼虫的最适日投饵量扁藻为2 400cell/mL和5 000 cell/mL,湛江等鞭金藻为3 000 cell/mL和5 500 cell/mL,光合细菌为10 000 cell/mL和15 000cell/mL湛江等鞭金藻、亚心形扁藻、光合细菌和绿色巴夫藻混合投喂对浮游幼虫生长、存活和变态有显著提高,出现壳初、眼点、附着和变态时间显著缩短.     

低盐度养殖池塘常见浮游微藻的种类组成、数量及优势种群变动

于2007年9月至2008年1月在广东珠海地区对低盐度养殖虾池水体的浮游微藻进行全程周期性调查分析.结果共检出常见浮游微藻5门31属49种,其中绿藻13属22种,蓝藻9属16种,硅藻6属8种,裸藻2属2种,隐藻1属1种.优势种有13种,主要是蓝藻,有铜绿微囊藻( Microcystis aeruginosa )、圆胞束球藻( Coelosphaerium naegelianum )、卷曲螺旋藻( Spirulina spirulinoides )、假鱼腥藻( Pseudoanabaena sp . )、绿色颤藻( Oscillatoria chlorine )、拟短形颤藻( Oscillatoria subbrevis )、粘连色球藻( Chroococcus cohaerens )、点状平裂藻( Merismopedia punctata )和针状蓝纤维藻( Dactylococcopsis aciculari ).其次是绿藻和硅藻,有蛋白核小球藻( Chlorella pyrenoidosa )、多粒衣藻( Chlamydomonas.multgranulis )、角毛藻( Chaetoceros sp . )和新月菱形藻( Nitzschia closterium ).低盐度虾池养殖周期浮游微藻细胞数量为0.1×10 7～209.2×10 7 ind·L -1,多样性指数平均为2.5～3.2.浮游藻类的种类数、数量及多样性指数总体表现为养殖前期低后期高的特征.     

河北沿海大型水母生物量调查

河北沿海自2008年起水母数量逐年增加,严重影响渔业生产、破坏近岸旅游业。2012年对河北沿海大型水母进行调查,设置了34个站位,对大型水母生物量和种类、海洋理化因子、浮游动物数量变动及分布进行调查。调查发现大型水母种类4种,其中沙海蛰生物量最大,其次是海月水母,海蛰、霞水母生物量最低。沙海蜇数量均较去年增多,秦皇岛沿海、渤海湾沧州沿海,滦河口数量最高,达到了15~75t/km2;其次是渤海湾,为7.6~15t/km2;最低的为0.5~1.5t/km2。近岸海区营养盐含量较远海高,营养盐含量高的地区水母数量居多,说明水体富营养化在一定程度上导致水母数量增长。浮游植物数量、浮游动物数量与水母分布图分析发现,水母数量较多浮游动植物数量均较少,说明水母和浮游生物量在空间分布上可能具有一定的负相关关系。     

龙须菜苯丙烷类抑藻活性物质的分离纯化及其对6种赤潮微藻的抑藻活性

采用溶剂浸提、液液萃取、硅胶柱层析和硅胶薄层层析等分离方法以及红外光谱、质谱和核磁共振谱等光谱技术,初次从龙须菜中纯化得到4种苯丙烷类化合物:邻苯二丙酸、gossonorol、7,10-epoxy-ar-bisabol-11-ol和对羟基苯乙醇,并进一步分析了此4种苯丙烷类化合物对强壮前沟藻、赤潮异弯藻、米氏凯伦藻、球形棕囊藻、东海原甲藻和中肋骨条藻生长的影响。结果表明,它们对以上6种赤潮微藻的生长表现出明显的选择性抑制作用。其中,邻苯二丙酸、gossonorol和对羟基苯乙醇表现出更为广泛的抑藻活性。比较此4种苯丙烷类化合物和重铬酸钾对赤潮微藻生长的半抑制效应浓度EC50-96 h,发现邻苯二丙酸对强壮前沟藻、赤潮异弯藻和球形棕囊藻,gossonorol和羟基苯乙醇对赤潮异弯藻和球形棕囊藻,7,10-epoxy-ar-bisabol-11-ol对赤潮异弯藻和米氏凯伦藻在生长抑制方面比重铬酸钾更具有优势。     

Optimizing stocking density and microalgae ration improves the growth potential of tropical black‐lip oyster,Saccostrea echinata,larvae

The combined effects of stocking density and microalgae ration on survival and size of Saccostrea echinata larvae were studied in two‐factor experiments for the major developmental stages: D‐veliger (1‐day posthatch [dph], Experiment 1), umbonate (12 dph, Experiment 2), and eyed (19 dph, Experiment 3) larvae. Larvae were stocked into replicate sets of four 10‐L aquaria with ambient 1‐μm filtered sea water (28 ± 1.5°C and 36 ppt) and cultured for four days at densities of 0.5, 2, 5, 7, or 10 larvae/mL and provided with microalgae rations at each of five densities (cells larvae^?1 day^?1); 0, 1, 3, 5, or 8 × 10³ (D‐veliger larvae, Experiment 1); 0, 5, 12, 18, or 25 × 10³ (umbonate larvae, Experiment 2); and 0, 15, 30, 40, or 60 × 10³ (eyed larvae, Experiment 3). Microalgae rations for each larval life stage were selected on the basis of increasing food requirement with larval size and comprised a 2:1:1 mixture of Chaetoceros calcitrans, Tisochrysis lutea, and Pavlova spp., calculated on an equal dry‐weight basis. Contour plots were generated from larval survival and larval size (dorso‐ventral measurement [DVM]) data to determine optimal culture conditions. Larvae showed high survival (54–100%) over a wide range of both treatment parameters across all life stages, confirming broad tolerance limits for this species. The interaction effects of larval stocking density and microalgae ration on larval size were significant (p < 0.001) across all life stages. Results indicate that maximum larval size (DVM) is achieved when S. echinata are cultured at: 6–8 larvae/mL and fed 5–6 × 10³ cells larvae^?1 day^?1 for D‐veligers (mean DVM >80 μm), at 2–8 larvae/mL and fed 11–25 × 10³ cells larvae^?1 day^?1 for umbonate larvae (mean DVM > 190 μm), and at 1–4 larvae/mL and fed 15–40 × 10³ cells larvae^?1 day^?1 for eyed larvae (mean DVM >230 μm). Results will help refine current hatchery methods for S. echinata supporting further development toward commercial aquaculture production of this species.