碳、氮、磷营养对7种海洋微藻种群增长的影响研究

文章采用批次培养方式研究双胞旋沟藻(Cochlodinium geminatum)、米氏凯伦藻(Karenia mikimotoi)、中肋骨条藻(Skeletonema costatum)、牟氏角毛藻(Chaetoceros muelleri)、球形棕囊藻(Phaeocystis globosa)、亚心形扁藻(Platymonas subcordiformis)和眼点拟微绿球藻(Nannochloropsis oculata)在不同碳(C)、氮(N)、磷(P)条件下的生长特性,以期为养殖尾水的原位处理筛选优良藻种(株)。结果表明,这7种微藻的比生长速率与C、N、P浓度总体呈正相关。相较对照组,C对旋沟藻、骨条藻和拟微绿球藻比生长速率的促进作用分别为35%、19%和19%,P对比生长速率的最大促进作用介于25.01%~446.60%,硝酸盐为16.54%~77.52%,铵盐为15.79%~88.82%,尿素为25.16%~71.43%。7种微藻的最大比生长速率与细胞体积总体呈负相关,棕囊藻的比生长速率最高,拟微绿球藻和扁藻最大比生长速率与其他藻华种相比无显著差别。微藻的氮磷吸收速率随细胞体积增加呈升高趋势,单位氮磷利用效率随细胞体积增加呈降低趋势。培养液中P吸收速率显著高于N,氮磷比均呈升高趋势。眼点拟微绿球藻和亚心形扁藻可用于养殖尾水氮磷的快速去除。     

The growth rate of two species of microalgae used in shellfish hatcheries cultured under two light regimes

Abstract. The production potential of any shellfish hatchery depends on the capacity of its algal system. The hypothesis that microalgal cultures grown under 12:12h light:dark photoperiod may produce the same cell densities as those using constant light is tested.
Two species of marine microalgae used in shellfish hatcheries. Chaetoceros gracilis Schütt and Isochrysis galbana clone T-iso, were grown in cultures at 18°C, under continuous light (1.43 × 10⁷μ^-2day^-1) and 12:12h light:dark cycles (2.87 × 10⁷μE m^-2 day^-1). Both light regimes provided equal amounts of light per day. In the continuous light cultures the mean doublings per day for exponentially growing cells were 1.37 and 1.49 for C. gracilis and I. galbana respectively and for the 12:12h light:dark cycles were 1.47 and 1.56 respectively. After 14 days of growth, the numbers of cells per unit of volume showed no significant differences between the two light regimes. The results are discussed in terms of a review of other authors' findings and in terms of the usefulness of the continuous light method in producing algae to be used in shellfish hatcheries.     

Fatty Acid Composition of Three Cultured Algal Species (Isochvysis galbana, Chaetoceros gracilis and Chaetoceros calcitrans) Used as Food for Bivalve Larvae

Fatty acids of three cultured unicellular algae wldely used in aquaculture ( Isochrysis galbana , clone T-iso, Chaetoceros calcitrans , and Chaetoceros gracilis ) were analyzed in detail by gas-liquid chromatography and mass spectrometry. Fatty acid compositions of the individual species, harvested at monthly intervals during a four month period, showed a very consistent pattern. Shorter chain (C16) fatty acids accounted for more than 70% of total fatty acids in the diatoms but less than 20% in I. galbana . Medium chain (C18) and the long chain 22:6w3 unsaturated fatty acids represented more than 50% of the total fatty acids in I. galbana but less than 10% of the total In the Chaetoceros spp. However, in the latter, 20:5w3 replaced 22:6w3 at an equivalent level. Fatty acid profiles of c. calcitrans and c. gracilis were similar, except that the latter contained lower levels of 16:2w4, 16:3w4 and 16:4w1, and higher levels of 18:2w6 and 18:3w6. In particular C. gracilis contained a higher proportion of the biochemically important fatty acid 20:4w6 (arachldonic acid). One of the salient features of I. galbana lipids was the presence of the fatty acid 18:5w3. This fatty acid is not generally reported in algae or invertebrate lipid analyses, but is a typical component of I. galbana and of other marine photosynthetic flagellates. Its potential for utilization by aquatic organisms is unknown.     

Evaluation of Fatty Acid Enrichment of Live Food for Yellowtail Snapper Ocyurus chrysurus Larvae

Abstract— The purpose of this study was to examine the effect of varying dietary levels of highly unsaturated fatty acids (HUFA) in Live prey on the standard length, specific growth rate, survival, and fatty acid composition of yellowtail snapper Ocyurus chrysurus larvae. Two experiments were conducted utilizing rotifers and Artemiu enriched with live algae ( Isochrysis galbana or Nannochloris oculata ) or commercial preparations (Aquagrow Advantage, Aquagrow Advantage plus Aquagrow arachidonic acid, and Algarnac 2000). Larval growth and fatty acid composition were evaluated during the rotifer, B rachionus plicatilis , and Artemia feeding periods and survival rates were calculated at the termination of each trial (18 or 20 d after hatching). In general, prey enriched with the commercial products contained higher levels of docosahexaenoic acid, eicosapentaenoic acid, n-3 HUFA, and × HUFA than those enriched with live algae. The addition of arachidonic acid to the Aquagrow Advantage enrichment medium significantly increased the amount of this fatty acid in rotifers but not in Artemia . At the end of the growth trials, larval standard length was highest when larvae were fed prey enriched with I. galbanu (6.4 mm) or commercial preparations (6.7–7.1 mm) versus N. oculatu (5.2 mm). Furthermore, larvae fed prey enriched with commercial preparations had significantly ( P < 0.05) higher survival rates (2.2-5.9%) than those fed prey enriched with live algae (1.1-1.4%). These results suggest that yellowtail snapper larvae require dietary levels of HUFA beyond those achieved by enriching prey with live N. oculata or I. galbana     

球等鞭金藻生长抑制物对自身藻细胞的抑制效应

研究了生长抑制物1-羟基,丙二酸二乙酯-十二烯酸异丙酯（HDMA）对自身细胞生长、叶绿素和丙二醛（MDA）含量、胞外可溶性蛋白质和多糖含量、硝酸还原酶（NR）、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性等生理指标的影响,分析HDMA对球等鞭金藻的抑制效应。结果表明,HDMA显著降低了细胞密度、叶绿素含量以及NR、SOD和POD活性,显著增大胞外可溶性蛋白质和多糖的比值,并且还明显提高MDA含量。因此,我们认为HDMA能够影响微藻细胞的某些生理生化过程。其中包括降低叶绿素含量,影响光合作用;改变胞外可溶性蛋白质和多糖的比值,增强细胞的疏水性,促使细胞絮凝;降低微藻硝酸还原酶和抗氧化体系酶的活性,影响细胞内营养平衡,并加速细胞体内活性氧的积累,导致细胞发生过氧化反应,从而影响微藻生长。     

滇池氮磷浓度变化对蓝、绿、硅藻年际变化的影响

为了探究滇池水体中藻类变化规律及营养盐对浮游藻类结构的影响,在滇池草海和外海共设10个采样点,于2013年5月至2015年4月,每月监测藻类变化及氮、磷含量。结果表明,草海在每年9月至来年2月,蓝藻、绿藻呈互为消长的变化趋势,硅藻生物量在8-10月和2-4月含量较高,变化范围5.81~44.80 mg/L;外海以蓝藻、绿藻为主,两种藻类在每年的11月至来年1月呈互为消长,而来年2种藻5-7月逐渐升高、10月开始又逐渐降低。草海和外海水体中的总磷均以在5-9月含量最高,变化范围分别为0.82~3.37 mg/L和0.20~0.51 mg/L;总氮全年变化剧烈,草海总氮为2.85~11.7 mg/L,外海总氮为1.05~4.89 mg/L。总体上看,草海的氮、磷含量高于外海,说明草海富营养化水平高于外海;而水体中绿藻生物量高于蓝藻成为绝对优势藻种,且绿藻生物量远远高于外海,表明高氮、磷水体中绿藻比蓝藻有更强的利用优势,致使在超富营养化水体中蓝藻不占优势。滇池水体中氮磷比较低的月份,水体中蓝藻和绿藻共存;在高氮磷比的时间段,绿藻生长占优势,说明滇池水体中绿藻比蓝藻更适合高氮磷比的环境。     

pH和氮磷比对微小原甲藻和青岛大扁藻生长竞争的影响

为探讨pH和氮磷比对青岛大扁藻(Tetraselmis helgolandica)和微小原甲藻(Prorocentrum minimum)生长竞争的影响,本研究首先根据对虾养殖水体pH值的范围设置了7.5,8.0,8.5和9.0共4个pH梯度,获得了青岛大扁藻抑制微小原甲藻的最佳pH;在该pH条件下,设置了氮磷比分别为3:2(高富磷组),6:1(富磷组),24:1(对照组)和96:1(富氮组)等4个梯度,其中,单种培养体系中只接种青岛大扁藻或者微小原甲藻,混合培养体系中同时按照1:1的比例接种青岛大扁藻和微小原甲藻。结果表明,混合培养体系中,青岛大扁藻在pH 8.5和pH 9.0时,出现拐点时间最晚,均为7 d;而微小原甲藻在pH 8.5和pH 9.0时,出现拐点时间最早,均为3 d。pH 8.5时青岛大扁藻对微小原甲藻的竞争抑制参数最大,青岛大扁藻抑制微小原甲藻的最佳pH为8.5。单种培养体系中,微小原甲藻拐点出现的时间在高富磷组、对照组和富氮组中均晚于青岛大扁藻;混合培养体系中,对照组中微小原甲藻和青岛大扁藻拐点出现时间分别为4 d和3 d,而其他处理组2种微藻拐点出现的时间分别相同。氮磷比影响混合培养中2种微藻的竞争抑制参数,其中,96:1(富氮组)中拐点之后青岛大扁藻对微小原甲藻的竞争抑制参数(α)的平均值为9.2063,微小原甲藻对青岛大扁藻的竞争抑制参数(β)为3.4886。以上研究表明,对虾养殖水体中,青岛大扁藻抑制微小原甲藻的最佳条件是:pH为8.5,氮磷比为96:1。     

Efficacy of Concentrated Algal Paste During Greenwater Phase of Cobia Larviculture

ABSTRACT

The purpose of this study was to determine if concentrated algal paste could effectively replace live algae during the greenwater stage of cobia fingerling production without negative impact upon larval growth or survival. Mean cobia survival per tank from 2 dph through post weaning at 28 dph for the live algae treatment was 24.44 ± 2.43% (mean ± SD) as compared to 24.47 ± 2.48% for the algal paste treatment. Furthermore, the number of fish produced per liter for the live algae treatment was 2.44 ± 0.24 fish/L compared to 2.47 ± 0.25 fish /L recorded from the algal paste treatment. Mean fish weight for cobia weanlings from the live algae treatment was 0.417 ± 0.059 g compared to 0.411 ± 0.026 g for the algal paste treatment. These observations demonstrate that during the greenwater stage of cobia larviculture, live algae can be completely replaced with commercially available, concentrated algal paste without negative impact upon cobia growth, survival, or resultant weanling production per unit volume.     

微藻饵料对紫海胆浮游幼体生长及存活影响的研究

文章采用湛江叉鞭金藻(Dicrateria zhanjiangensis)、纤细角毛藻(Chaetoceros gracilis)、绿色巴夫藻(Pavlova viridis)、扁藻(Platymonas subcordiformis)、小球藻(Chlorella vulgaris)及混合藻(金藻和角毛藻1∶1混合)投喂紫海胆(Anthocidaris crassispina),研究了微藻饵料对紫海胆浮游幼体生长发育的影响。结果表明,不同饵料对紫海胆浮游幼体生长发育的效果有差异,金藻是最佳饵料品种,角毛藻次之,其后分别为巴夫藻、小球藻和混合藻,扁藻不适于作为紫海胆浮游幼体的开口饵料。就饵料种类而言,金藻作为紫海胆浮游幼体饵料的成活率可达(23.12±1.8)%,显著高于其他单胞藻类(P<0.05)。就发育速度而言,以角毛藻和金藻混合喂食的海胆浮游幼体整体发育速度最快,幼体平均体长为(885.25±30.49)μm,显著高于其他5种处理(P<0.05);投喂巴夫藻的浮游幼体前期生长较慢,体长为(337.98±24.56)μm,后期较其他单胞藻类生长快,体长可达(580±32.95)μm,适宜作为紫海胆浮游幼体后期饵料。     

Population Growth and Production of Apocyclops dengizicus (Copepoda: Cyclopoida) Fed on Different Diets

This study was carried out to investigate the effects of various diets: 4 monoalgal diets: Nannochloropsis oculata (N), Isochrysis galbana (I), Chaetoceros calcitrans (C), and Tetraselmis tetrathele (T); 4 mixed algal diets: N+I+C+T(NICT), N+I+C(NIC), C+T(CT), and I+T(IT); and 2 nonalgal diets: baker's yeast (BY) and prepared shrimp feed (SF) on population growth and density of Apocyclops dengizicus . The type and density of diet had significant effects on the growth and density of A. dengizicus ( P  < 0.01). Of tested diets, T and CT were optimum diets due to higher density and growth rate of A. dengizicus compared to other diets. Their high dietary value was related to the higher contents of polyunsaturated fatty acid, particularly docosahexaenoic acid (22:6n-3), eicosapentaenoic acid (20:5n-3), and arachidonic acid (20:4n-6) compared to A. dengizicus cultured on other diets. The results of the present study illustrated that T. tetrathele was the most suitable food for the culture of A. dengizicus .     

Optimum temperature and salinity conditions for growth of green algae <Emphasis Type="Italic">Chlorella ellipsoidea</Emphasis> and <Emphasis Type="Italic">Nannochloris oculata</Emphasis>

ABSTRACT:   The effects of temperature and salinity on growth of green algae Chlorella ellipsoidea and Nannochloris oculata were determined to compare the optimum culture conditions. A four-temperature (15, 20, 25, and 30°C) × three-salinity (10, 20, and 30) factorial design with triplicates was applied. Specific growth rate (SGR), maximum density, and duration to reach maximum density of C. ellipsoidea were significantly affected by both temperature and salinity. The highest SGR was observed in C. ellipsoidea at 25°C and salinity 10, but the maximum density was very low. The highest maximum density was achieved in C. ellipsoidea at 15°C and 10. The slope constant of the linear relationship between semilogarithmic growth of C. ellipsoidea and day of culture was highest at 15°C and 10. The SGR and duration to reach maximum density of N. oculata were significantly affected by both temperature and salinity. However, maximum density of N. oculata was significantly affected by temperature, but not salinity. The highest maximum density was achieved in N. oculata at 25°C and 30, but SGR was significantly lower than that of N. oculata at 25°C and 10. The slope constant of the linear relationship between semilogarithmic growth of N. oculata and day of culture was highest at 25°C and 30. Based on these results, the condition of 15°C and salinity 10 seemed to be optimal for maximum density of C. ellipsoidea , and the condition of 25°C and 10 and 30 for SGR and maximum density for N. oculata , respectively.     

NaHCO3浓度对等鞭藻3011、等鞭藻塔溪堤品系和绿色巴夫藻生长的影响

对等鞭藻3011(Isochrysis galbana3011)、等鞭藻塔溪堤品系(Tahitian Isochrysis galbana)和绿色巴夫藻(Pavlova viridisai)3株微藻种进行培养。NaHCO     

不同浓度的Cd~(2+)、氮及其交互作用对小球藻和微绿球藻生长及叶绿素荧光特性的影响

研究了不同的Cd2+浓度与氮浓度交互作用对小球藻和微绿球藻生长及叶绿素荧光特性的影响。结果表明,Cd2+浓度、氮浓度、胁迫时间及三者的交互作用对小球藻和微绿球藻的生长及光合作用均具有显著影响(P<0.05),其中Cd2+浓度对2株微藻的Fv/Fm(光系统Ⅱ的最大光化学量子产量)和Yield(光系统Ⅱ的实际光能转化效率)影响最显著,氮浓度对2株微藻的NPQ(非光化学淬灭)和微绿球藻的qP(光化学淬灭)影响最显著。相关性分析结果表明,2株微藻的细胞密度、叶绿素相对含量及部分荧光参数(Fv/Fm和Yield)均与Cd2+浓度呈显著的负相关关系。在低氮(55μmol/L)条件下,小球藻和微绿球藻的荧光参数Fv/Fm、Yield和NPQ均有明显下降,细胞密度和叶绿素相对含量也均有不同程度的降低。小球藻的Fv/Fm和Yield在高氮(7040μmol/L)和低浓度Cd2+条件下,下降幅度小,表现为拮抗作用。试验还发现,在低氮和高氮条件下,高浓度Cd2+对小球藻的胁迫作用加强,表现为协同作用。微绿球藻在高氮条件下,其处理组间荧光参数差别不明显,表现为拮抗作用。     

Impact of Copper Sulfate on Plankton in Channel Catfish Nursery Ponds

Many fish culturists are interested in applying copper sulfate pentahydrate (CSP) to channel catfish, Ictalurus punctatus, nursery ponds as a prophylactic treatment for trematode infection and proliferative gill disease by killing snails and Dero sp., respectively, before stocking fry. However, copper is an algaecide and may adversely affect phytoplankton and zooplankton populations. We evaluated the effects of prophylactic use of copper sulfate in catfish nursery ponds on water quality and phytoplankton and zooplankton populations. In 2006, treatments of 0 mg/L CSP, 3 mg/L CSP (0.77 mg/L Cu), and 6 mg/L CSP (1.54 mg/L Cu) were randomly assigned to 0.04‐ha ponds. In 2007, only treatments of 0 and 3 mg/L CSP were randomly assigned to the 16 ponds. Ponds treated with CSP had significantly higher pH and significantly lower total ammonia concentrations. Treatment of both CSP rates increased total algal concentrations but reduced desirable zooplankton groups for catfish culture. CSP has been shown to be effective in reducing snail populations at the rate used in this study. CSP treatment also appears to be beneficial to the algal bloom, shifting the algal population to green algae and increasing total algal biomass within 1 wk after CSP treatment. Although zooplankton populations were adversely affected, populations of important zooplankton to catfish fry began rebounding 6–12 d after CSP treatment. Therefore, if CSP is used to treat catfish fry ponds of similar water composition used in this study, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to begin increasing.     

Growth,settlement and survival of Dicathais orbita (Neogastropoda,Mollusca) larvae in response to temperature,diet and settlement cues

The southern Australian whelk, Dicathais orbita, is a potential candidate for aquaculture, as both seafood and for bioactive compound production. Larval rearing experiments to determine the effects of temperature and diet on the growth and survival of D. orbita larvae under laboratory conditions comprised five different unicellular algal diets of two brown algal species; Isochysis galbana and Chaetoceros muelleri, two green algae; Tetraselmis seucica and Nannochloropsis oculata, and a mixture of all four strains for larvae maintained at 16 and 22°C. Absolute growth, specific growth rate (SGR) and survival were determined regularly. Larvae reared at 22°C on a mixed diet, or brown algae, performed significantly better than those reared on green algal diets alone. Preliminary trials with settlement cues were undertaken on different aged larvae to determine when larvae become competent. An array of natural cues (carrion, Xenostrobus pulex, adult mucus and Ulvella lens), as well as concentrations of KCl was tested. KCl(concentration of 20 mM) induced the greatest settlement, however, no larvae metamorphosed under the conditions provided. This study confirms long‐lived planktotrophic larval development for Dicathais orbita with higher development rates at the higher water temperatures. Further studies will optimize culture conditions and cues for settlement and metamorphosis.     

6种微藻生长及脂肪累积对氮含量变化的响应

研究了绿色巴夫藻、米氏凯伦藻、球等鞭金藻、三角褐指藻、海水小球藻、衣藻的生长及脂肪累积对氮含量变化的响应。试验结果表明,6种微藻生长及总脂对不同氮含量均有一定程度的响应。微藻生长,绿色巴夫藻、米氏凯伦藻、球等鞭金藻3种微藻响应明显,绿色巴夫藻以氮含量100%组生长最快,第10d时,比氮含量40%组快512%,比氮含量20%组及60%组分别快62%、61%;米氏凯伦藻氮含量80%组生长最快,第10d达到最高值,超出其他试验组约60%;球等鞭金藻氮含量80%组最快,第10d生长量超过100%试验组67%;三角褐指藻、海水小球藻、衣藻响应程度小于其他微藻。总脂积累,三角褐指藻氮含量80%组总脂含量最高,达细胞干质量的80.77%,是氮含量100%组2.5倍;绿色巴夫藻氮含量60%组最高,达细胞干质量的73.68%,是氮含量100%组3.4倍;其他4种微藻在降低氮含量后,总脂均超过细胞干质量的30%。三角褐指藻在生物柴油制备方向极具开发前景。     

The enrichment and retention of ascorbic acid in rotifers fed microalgal diets

The enrichment and retention of ascorbic acid (AA) was investigated in rotifers Brachionus plicatilis fed on microalgae ( Nannochloropsis oculata and Isochrysis sp. (T.ISO)) and baker's yeast Saccharomyces cerevisiae . The concentrations of AA of the rotifer diets used in the study differed significantly: 4200 μg g⁻¹ of dry weight in Isochrysis sp. (T.ISO), 2600 μg g⁻¹ in N. oculata and only 77 μg g⁻¹ in S. cerevisiae . Rotifers contained 620 μg AA g⁻¹ prior to the experimental feeding. When subsequently fed for 3 h on microalgae at a ration of 0.13 mg dry microalgae per 10⁶ rotifers rapidly and efficiently increased their content of AA: Isochrysis sp.-fed rotifers contained 1600 μg AA g⁻¹ and N. oculata -fed rotifers contained 1100 μg AA g⁻¹. Concentrations were boosted by a further feeding of a second ration of algae at three times the initial feeding ration; 21 h later, Isochrysis sp.-fed rotifers contained 2500 μg AA g⁻¹ and N. oculata -fed rotifers contained 1700 μg AA g⁻¹. This represented a 180% and 310% increase in the pre-feeding vitamin concentrations in Isochrysis sp. and N. oculata -fed rotifers, respectively. There were no significant changes in AA concentration in rotifers fed a similar ration of yeast throughout the feeding period (520-620 μg AA g⁻¹). Rotifers retained AA during a subsequent 24 h non-feeding period, with no significant changes in the concentrations in any of the rotifer groups. The production of rotifers rich in AA may be particularly valuable for the culture of fish larvae that have a high requirement for the vitamin.     

COMPARATIVE GROWTH OF Isochrysis galbana PARKE AND Isochrysis aff. galbana,CLONE T-ISO AT POUR TEMPERATURES AND THREE LIGHT INTENSITIES

The growth of a temperate and a tropical strain of Isochrysis was studied at four temperatures and three light intensity levels. All algal cultures were grown in an enriched artificial seawater medium under constant illumination and were bubbled with air enriched with 0.1% CO₂. Culture density (cells/ml) was measured periodically during exponential growth. Average growth rates for each combination of temperature and light intensity are presented as doublings/day. Observations of growth under the various culture conditions indicate that T-ISO (tropical strain) grows rapidly over a much broader range of temperatures than does I. galbana. Variations in growth at different light intensity levels suggest that the optimum light level increases as a function of temperature for T-ISO and that the growth of I. galbana is inhibited by high levels of light (1500 μW/cm²). The relative value of both strains as food for larval and juvenile oysters and the advantages and limitations of large scale culture are discussed.     

Effects of foam fractionation and chemical disinfection on the removal of different microalgae cultures

The recent development of recirculation aquaculture systems (RAS) potentially allows more sustainable and controlled rearing conditions. However, control of suspended microparticles and microalgae in RAS is challenging, as uncontrolled blooms of toxic algae or heterotrophic dinoflagellates can have catastrophic impacts on the production of fish. In this study, we tested the potential of protein skimmers to remove microalgae. In 100 L batch tests, protein skimmers were tested separately and in combination with ozone (O₃), ultraviolet (UV) or hydrogen peroxide (H₂O₂). Three different and distinct microalgae cultures were tested with densities from 30,000 to 120,000 algae cells/ml in a triplicated experimental setup. Trial 1 included twelve 24‐hr replicated tests where protein skimmers with air or with two levels of ozone (low and high O₃ exposure) were compared. The protein skimmer with air alone had a limited effect on the removal of microalgae compared to the untreated control algae tanks. When ozone and protein skimmers were combined, a clear additive effect was found, and all added microalgae were removed. Low O₃ dosage and protein skimmers completely removed the algae cultures within 12 hr, while more than 95% of the algae were removed within 7 hr when a higher ozone dose was used. The second trial compared the removal capacity of protein skimmers in combination with UV, H₂O₂ and O₃. These experiments showed no to limited additive effect of UV combined with protein skimming, but significantly increased removal efficiency (270% and 1,300%, respectively) was found when H₂O₂ and ozone were combined with a protein skimmer. The study showed an algae species‐specific response to a protein skimmer with ozonation and provided information on the transition from reactivity and consumption to accumulation of ozone‐produced oxidants.     

Large-scale microalgae production for nursery rearing of marine bivalves

The feasibility of large-scale bloom induction of nutritionally suited natural phytoplankton species, to feed a semi-industrial nursery of edible shellfish, built on the Belgian coast, was tested.The outdoor microalgal production unit consisted of four tanks of 100 m² surface each (two of 1 m depth and two of 0·5 m depth), equipped with different mixing devices.The cultures were run as chemostats in which seawater was enriched with commercial inorganic N, P, and Si fertilizers. Depending on the season, between 5–10 and 80% of the culture volume could be harvested daily, with algal densities ranging from 50 000 to 500 000 cells per ml.By manipulation of operational parameters such as detention time, nutrient levels and nutrient ratios (N:Si:P), unsuited or less suited species of algae (e.g. Chlorella and Phaeodactylum) could be replaced by more desirable species (e.g. Skeletonema, Nitzschia, Chaetoceros).Various biological and technological problems encountered during year round operation, including collapsing of the culture, seawater enrichment, water quality, fouling and water treatment, are commented.