Integrated tank cultivation of salmonids and Gracilaria chilensis (Gracilariales,Rhodophyta)

In order to study the N and P balances in the Driss I reservoir, we measured concentrations in the water of these elements, their sedimentation rates, and their input by the river Inaouen and output through the dam. Supply and loss of N and P were calculated from samples collected every 48 hours and were for N 15 and 27. 5 mg m⁻² d⁻¹ and for P 33.6 and 1.1 mg m⁻² d⁻¹ respectively. The sedimentation rates, determined using sediment traps, were high, about 75 mg m⁻² d⁻¹ for N and 34 mg m⁻² d⁻¹ for P. Phosphate input came from point sources and was mainly in particulate form. A large fraction of the phosphate sedimented in the form of calcium bound phosphate, with some iron bound phosphate. Bioavailability was, however, low, as the particulate phosphate disappeared rapidly from the epilimnion because of the high sedimentation rate. The ratio Tot-N/Tot-P of the sedimented particulate matter varied between 0.05 and 7.74 and depended on primary production and watergate management.     

A study on biological activity measurements and heterotrophic bacteria in a small freshwater lake

A 6-m-deep lake has been sampled to measure the temporal and depth-wise distribution of heterotrophic bacteria and biological activity in the water. Surface, mid-depth and bottom waters were analysed at monthly intervals for a period of one year. The coefficient of heterotrophic activity, alkaline phosphatase activity and biological oxygen demand are used as an index of biological activity. The bacterial community was at maximum during spring, coinciding with high values of biological activity. Highest biological activity was observed in the bottom waters. Dissolved organic carbon showed a significant positive correlation with most of the biological activity parameters. This suggests that biological activity, as measured by the coefficient of heterotrophic activity, was more closely related to the concentration of substrates than to population density of heterotrophic bacteria.     

Mass cultivation of seaweeds: current aspects and approaches

A word-wide overview is presented of the current state of mass cultivation of seaweeds. In comparison with a total annual commercial production of fish, crustaceans and molluscs of about 120 × 10⁶t, of which one-third is produced by aquaculture, the production of seaweeds is about 10 × 10⁶t wet weight; the majoirty of this comes from culture-based systems. The Top Ten Species List is headed by the kelp Laminaria japonica with 4.2 × 10⁶t fresh weight cultivated mainly in China. The productivity of a well-developed, multi-layered, perennial seaweed vegetation is as high as dense terrestrial vegetation, and even higher annual values for productivity have been reported for tank cultures of macroalgae. Epiphytes provide a major problem for the seaweed cultivator, but can be controlled by growing plants at high densities in rope cultures in the sea, or, more easily, in seaweed tank cultures on land. The main environmental problem of animal (fed) aquaculture is the discharge of nutrient loads into coastal waters, e.g., 35 kg N and 7 kg P t^–1 aquacultured fish. Integration of fish and seaweed farming may help to solve this problem, since seaweeds can remove up to 90% of the nutrient discharge from an intensive fish farm. Mass culture of commercially valuable seaweed species is likely to play an increasingly important role as a nutrient-removal system to alleviate eutrophication problems due to fed aquaculture.     

Studies of enzyme reactions in open systems

An experimental arrangement is described which allows studies of the temporal performance of enzyme reactions (also reactions of complexes of enzyme chains) under conditions of open systems. The various steady-state properties of such open systems can be recognized by measuring their input and output [1,2]. The various levels of flowing equilibria are perturbed by applying molecular modulators to the system, and the data obtained are compared to those found in closed systems. In order to prove the accuracy of the experimental configuration, the determination of K_m in a one-substrate reaction is carried out in the open system, using only one concentration of substrate at various flow rates.     

硝尔库勒湖可培养放线菌多样性及其功能酶和抗细菌活性

【目的】认识和了解硝尔库勒湖可培养放线菌的多样性、功能酶和抗细菌活性特点,为今后的开发和利用奠定基础。【方法】应用可培养技术和基于16S r RNA基因序列的系统发育分析硝尔库勒盐湖沉积物中放线菌的多样性。常规方法检测样品成分因子,并筛选了嗜盐放线菌的蛋白酶、淀粉酶和酯酶活性;抑菌圈法检测放线菌新种的抗细菌活性。【结果】分离获得了51个OTUs,分属于24个不同的属,其中15个OTUs代表了放线菌新种;链霉菌属是优势菌属,占全部分离菌株数量的16.25%。硝尔库勒湖放线菌类群数量一定程度上受样品成分因子的协同影响。代表新种的菌株展示了良好的功能酶活性和抗细菌活性,其中代表链霉菌新种的菌株XHU5011不仅具有多种酶活性,而且具有强大的抗金黄葡萄球菌、耻垢分枝杆菌和荧光假单胞菌的能力,具有很好的开发潜能。【结论】硝尔库勒盐湖中存在丰富的可培养放线菌多样性,潜藏着大量的放线菌新资源,并且具有很好的功能酶和天然产物挖掘潜力。     

广西三种真红树植物可培养细菌多样性及其生物活性初筛

为了挖掘真红树植物潜在细菌新物种和生物活性物质,丰富红树林微生物多样性,为新型活性产物开发提供菌株资源。该文从秋茄、木榄和红海榄三种广西来源的真红树植物及其生境中,按根、茎、叶、花、果实和泥土分成22份样品,选用8种不同培养基分离可培养细菌,通过16S rRNA基因序列鉴定,分析其多样性,采用纸片法筛选细菌发酵粗提物的抑菌活性,点植法测试其酶活性。结果表明：(1)共分离获得可培养细菌35株,隶属于23个科28个属,芽孢杆菌属占细菌总数的14.3%,为优势菌属,同时发现11株潜在的新细菌资源。(2)活性筛选获得4株细菌具有抑菌活性,16株细菌具有酶活性,芽孢杆菌属是酶活性优势菌属。综上所述,广西真红树植物可培养细菌多样性丰富,部分细菌具有抑菌活性和酶活性,在新型抗生素和酶应用方面具有一定的开发潜力。     

白灵侧耳栽培过程中胞外酶和呼吸酶活及离子流速的研究

研究了白灵侧耳Pleurotus nebrodensis栽培过程中生长发育各阶段的漆酶、羧甲基纤维素酶（CMC酶）、半纤维素酶和淀粉酶等4种胞外酶及苹果酸脱氢酶、葡萄糖-6-脱氢酶和6-磷酸葡萄糖酸脱氢酶等3种呼吸酶的活性变化,同时测定了菌丝表面H+、K+、Ca2+离子流速。结果表明,整个生育期的胞外酶活性变化具有明显的阶段性。漆酶酶活在菌丝生长阶段第28天时达到最大值,纤维素酶和半纤维素酶酶活在子实体生长阶段第107天时达到最大值,子实体收获后活性下降,而淀粉酶活性在各时期均比较低,说明白灵侧耳对木质素类物质利用最早。苹果酸脱氢酶、葡萄糖-6-脱氢酶和6-磷酸葡萄糖酸脱氢酶酶活在后熟期、温差刺激及子实体生长期出现3个峰值。整个栽培周期的菌丝表面H+、K+、Ca2+离子流速各个阶段有不同的变化规律,Ca2+在菌丝生长阶段内流,从后熟期开始外排,K+和H+在整个周期外排;C/N和温度对离子的流速有一定的影响。     

生物炭对杉木人工林土壤养分、酶活性及细菌性质的影响

为了探究添加生物炭对南方红壤杉木人工林土壤养分含量、酶活性及细菌丰度和群落结构及多样性的影响,分析三者之间的作用机制,基于高通量测序技术,通过添加不同生物炭对人工杉木林土壤环境中细菌群落进行培养和测定,同时挑选与土壤C、N循环相关的4种酶,分析4种酶与土壤养分含量及土壤细菌相对丰度的关系。结果表明:添加生物炭总体使得土壤pH值,全磷、有效磷、速效钾等含量有所提高,同时促进土壤-α-葡萄糖苷酶、土壤-β-葡萄糖苷酶及脲酶的活性,对过氧化氢酶的影响不显著;由于生物炭制备原料不同,其自身性质和物质含量也存在差异,因此杉叶炭对土壤养分的提高量大于木屑炭,而木屑炭处理的土壤全碳含量高于杉叶炭;低添加量生物炭对参与碳循环的土壤葡萄糖苷酶活性提高程度大于高添加量生物炭,而与氮循环有关的土壤脲酶活性随着生物炭添加量的增加而提高,尤其3%BL600处理对土壤脲酶影响十分显著;向土壤添加杉叶炭能够提高土壤细菌丰度,而木屑炭降低了土壤细菌丰度,低温炭大于高温炭;添加生物炭对土壤pH值,全碳、全磷、有效磷、速效钾含量等具有直接影响,土壤组分和性质对不同细菌种群生活习性与功能产生不同的影响,土壤酶活性与土壤细菌存在密切的联系,细菌丰度的变化又会引起土壤酶活性的改变,因此土壤酶活性和细菌群落相对丰度对添加生物炭的响应存在一定的相关关系。     

Abundance and distribution of picoplankton in tropical, oligotrophic Lake Kivu, eastern Africa

1. We used flow cytometry to characterize freshwater photosynthetic picoplankton (PPP) and heterotrophic bacteria (HB) in Lake Kivu, one of the East‐African great lakes. Throughout three cruises run in different seasons, covering the four major basins, phycoerythrin‐rich cells dominated the PPP. Heterotrophic bacteria and PPP cell numbers were always high and spatial variations were modest. This represents an important difference from temperate and high latitude lakes that show high fluctuations in cell abundance over an annual cycle. 2. Three populations of picocyanobacteria were identified: one corresponded to single‐cells (identified as Synechococcus by epifluorescence microscopy, molecular methods and pigment content), and the two other that most probably correspond to two and four celled colonies of the same taxon. The proportion of these two subpopulations was greater under stratified conditions, with stronger nutrient limitation. 3. High PPP concentrations (c. 10⁵ cell mL^?1) relative to HB (c. 10⁶ cell mL^?1) were always found. Lake Kivu supports relatively less bacteria than phytoplankton biomass than temperate systems, probably as a consequence of factors such as temperature, oligotrophy, nutrient limitation and trophic structure. 4. A review of PPP concentration across aquatic systems suggests that the abundance of Synechococcus‐like cyanobacteria in large, oligotrophic, tropical lakes is very high. 5. Photosynthetic picoplankton cell abundances in the oligotrophic tropical lakes Kivu and Tanganyika are comparable to those of eutrophic temperate lakes. This apparently contradicts the view that PPP abundance increases with increasing eutrophy. More data on PPP in tropical lakes are needed to explore further this particular pattern.     

Seasonal changes in alkaline phosphatase activity of bacteria and microalgae in Lake Pavin (Massif Central,France)

Seasonal changes in alkalinephosphatase activity of bacteria and microalgae werestudied in the dimictic Lake Pavin (Massif Central,France), to test whetherthis activity is primarily algal or bacterial andwhether the APA presents seasonal variations coupledwith abiotic and biotic variables. Samples werecollected at different depths from May 1992 to May1993. The specific phosphatase activities wereanalysed spectrophotometrically with p-NitrophenylPhosphate (p-NPP) as substrate and were related to theprotein concentrations. No correlation was foundbetween alkaline phosphatase activity and solublereactive phosphorus (SRP) concentrations across anannual cycle. The specific activities of the smallclass (0.2–1.2 m) were the highest and thecontribution of this picoplanktonic size class(0.2–1.2 m) increased with depth. In addition, thelinear correlations between alkaline phosphataseactivity and protein concentration seemed to indicatethat most of these enzymes are constitutive. However,it cannot be excluded that the high phosphorusconcentrations repress APA.Finally, the measure of APA does not seem to be avalid quantitative test of the deficiency ofphosphorus for aquatic microorganisms.     

Acclimation of brown seaweeds in an outdoor cultivation system and their cytokinin-like activity

Four of the most abundant intertidal eastern Mediterranean brown seaweeds were repeatedly inoculated in an outdoor cultivation system for acclimatization. Diciyopteris membranacea was best acclimated and survived for nine months in the system. D. membranacea growth rate showed a positive relationship with irradiance and temperature during nine months of cultivation. Cystoseira sp., Sargassum vulgare and Padina pavonia were not acclimated and survived for shorter times, presumably because of inadequate conditions. All four species showed a cytokinin-like activity assayed with the barley leaf senescence, and promoted radish seed germination. The cytokinin-like activity in Diciyopteris membranacea was relatively stable throughout the cultivation time, as shown by the barley leaf senescence assay, and it acted as a growth promoter of bean and lettuce seedlings. Partial fractionation of the crude seaweed extract showed an ash active component and a natural cytokinin one, which was presumably composed of minor polar and major nonpolar fractions.     

Annual patterns of phytoplankton density and primary production in a large, shallow lake: the central role of light

1. We studied the seasonal dynamics of suspended particulate matter in a turbid, large shallow lake during an annual period (2005–06). We relate the patterns of seston concentration (total suspended solids), phytoplankton biomass and water transparency to the seasonal pattern of incident solar radiation (I₀). We also report the seasonal trends of phytoplankton primary production (PP) and photosynthesis photoinhibition due to photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) (I_β and UV₅₀). 2. We first collected empirical evidence that indicated the conditions of light limitation persisted during the study period. We found that the depth‐averaged irradiance estimated for the time of the day of maximum irradiance (I_mean–noon) was always lower than the measured onset of light saturation of photosynthesis (I_k). 3. We then contrasted the observations with theoretical expectations based on a light limitation scenario. The observed temporal patterns of seston concentration, both on a volume and area basis, were significantly explained by I₀ (R² = 0.39 and R² = 0.37 respectively). The vertical diffuse attenuation coefficient (kd_PAR) (R² = 0.55) and the depth‐averaged irradiance (I_mean) (R² = 0.66), significantly increased with the I₀; while the irradiance reaching the lake bottom (I_out) significantly decreased with the incident irradiance (R² = 0.49). However, phytoplankton biovolume maxima were not coincident with the time of the year of maximum irradiance. 4. A significant positive relationship was observed between PP estimated on an area basis and I₀ (R² = 0.51, P < 0.001). In addition, the parameters describing the photosynthetic responses to high irradiances displayed marked seasonal trends. The photosynthesis photoinhibition due to PAR as well as to UV were significantly related to incident solar radiation (PAR: R² = 0.73; UV: R² = 0.74). These results suggest adaptation of the phytoplankton community in response to changes in incident solar radiation.     

A comparison of screening methods for antioxidant activity in seaweeds

The inhibition of lipid peroxidation and radical scavenging effects were studied to evaluate the antioxidant activity for extracts of 17 species of seaweed. The antioxidant effect was evaluated by determination of lipoxygenase activity and by α, α-diphenyl-β-picrylhydrazyl (DPPH) decolorization. Lipoxygenase activity was depressed in the presence of aqueous and ethanol extracts of 4 algal species; Sargassum species had the highest antioxidant activity of all the species examined. The ethanol extracts of one Sargassum species showed competitive inhibition with the substrate. The same species also showed radical scavenging activity in the DPPH decolorization test. Comparison of these results shows no relationship between enzyme inhibition and radical scavenging activity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Biocontrol of Meloidogyne incognita inciting disease in tomato by using a mixed compost inoculated with Paenibacillus ehimensis RS820

Meloidogyne spp. causes root-knot disease in tomato plants. Biological control of the disease may present economically feasible, agronomically durable and environmentally safe alternative of nematicides. A chitinolytic bacterial strain, Paenibacillus ehimensis RS820, previously isolated from the soil in Korea, produced lytic enzymes in higher amounts and inhibited the growth of phytopathogenic root-knot nematodes. Moreover, the juveniles and eggs of root-knot nematodes induced secretion of lytic enzymes by RS820 including chitinases, gelatinases and collagenases. Furthermore, mixed compost containing increased amounts of chitin and inoculated with RS820 was prepared in the present study. Use of the mixed compost not only reduced the disease caused by root-knot nematodes but also improved the plant growth. The extent of inoculation of the mixed compost with RS820 significantly influenced its ability to control the root-knot disease in tomato. The mixed compost also significantly altered the activity and density of the rhizosphere bacteria. Chitinase and gelatinase producing soil bacteria, as well as their enzyme activities, were significantly influenced by the mixed compost. The mixed compost proposed in the present study may represent a viable alternative to nematicides against the root-knot nematodes in tomato.     

中度嗜盐菌产木聚糖酶发酵条件的研究

中度嗜盐菌在盐碱环境下生长繁殖,其产生的木聚糖酶也同样具有在盐碱环境下发挥作用的特性。本文对一株中度嗜盐菌的产木聚糖酶活性进行了初步研究。研究包括氮源、液体种子接种量、培养温度、pH值、培养时间等因素对该菌株产木聚糖酶能力的影响。结果表明,最佳培养氮源为蛋白胨;最佳产生木聚糖酶的发酵条件是液体种子接种量为6%,温度为35℃,pH值7,培养时间为4 d。     

Effect of UV radiation on photoinhibition of marine macrophytes in culture systems

The present study examined the effect of UV andphotosynthetically active radiation (PAR) onphotoinhibition and recovery in the Phaeophyte Macrocystis pyrifera, the Rhodophyte Chondruscrispus and the Chlorophyte Ulva lactuca underoutdoor culture conditions. There was an increase inphotoinhibition as a consequence of high exposure toUV-B radiation in M. pyrifera, however, highlevels of PAR accounted for most of thephotoinhibition in C. crispus and U.lactuca. Photodamage by UV-A, UV-B and PAR wascompletely repaired within 5 h and effective quantumyield reached pretreatment values in the three speciesstudied. Species were less susceptible tophotoinhibition after being incubated for 5 d underhigh exposures of natural irradiance suggesting aphotoadaptive process. The recovery of the effectivequantum yield was impaired by long exposure to highlevels of UV-B in C. crispus and UV-A, UV-B andPAR in M. pyrifera. This suggests a differentkind of damage by UV-A and PAR radiation, one to thephotosynthetic apparatus and another which affects therepair mechanism of some species. There was anincrease in UV-absorption ( 330 nm) in M. pyrifera and C. crispus within four days ofthe initiation of the experiment suggesting that thesespecies photoprotect their photosynthetic system whenexposed to elevated UV and PAR levels.     

分离自茯砖茶的真菌菌株MJAU EC021的鉴定及培养过程中生理特性

【目的】从茯砖茶样中分离纯化得到生长优势菌株,研究其液体培养时的生理生化特性,为茯砖茶实际生产提供依据。【方法】用PDA平板稀释涂布法从茯砖茶中分离纯化菌株。采用常规真菌发酵培养方法,单因素筛选其培养条件,再利用响应面法优化最优培养条件,测定冠突散囊菌发酵液中还原糖、多酚、胞外酶酶活及抗氧化的能力。【结果】利用形态学与ITS序列分析鉴定优势菌株MJAU EC021为冠突散囊菌Eurotium cristatum;最优的培养条件:转速187 r/min,培养时间10 d,培养温度28°C,冠突散囊菌生物量为21.52 g/L。冠突散囊菌发酵培养过程中4种胞外酶活性均在第10天时达到最大值,第9天时胞外多酚含量达到峰值为0.588 g GAE(没食子酸)/m L;发酵液对1,1-二苯基-2-苦基肼(DPPH)、羟基自由基的清除率达到最大值分别是90%、94%。【结论】真菌菌株MJAU EC021是株冠突散囊菌E.cristatum,发酵液具有较好的抗氧化能力,是潜在的抗氧化添加剂。     

Vertical diffusion and nutrient transport in a tropical lake (Lake McIlwaine,Rhodesia)

Measurements of the vertical temperature in tropical Lake McIlwaine were used to calculate the time-averaged ( 6 months) vertical diffusivity coefficient (K_z) in the metalimnion and hypolimnion. The mean value of K_z (0.21 cm² s^–1) was correlated with the lake surface area. The mass transport rates of PO₄-P and NH₄-N, upward from the hypolimnion to the metalimnion, were calculated using K_z and measured values of the nutrient concentration gradients. During a period of 4.5 months when the water was stably stratified, PO₄-P was transported upward at a mean rate of 42 kg day^–1 and NH₄-N at a mean rate of 162 kg day^–1 over the entire lake.     

洞庭湖区退田还湖后不同恢复模式下土壤酶活性的变化

以洞庭湖区退田还湖后不同恢复模式下(恢复自然水域、种植芦苇、种植杨树)的典型堤垸（青山垸、官垸和小集成）为研究对象,通过与相邻堤垸农田生态系统（水田、旱田）土壤中蔗糖酶、脲酶、磷酸酶和过氧化氢酶活性的比较,揭示不同退田还湖模式下土壤酶活性的变化及其与土壤化学特性的相关关系.结果表明：与水田、旱田相比,在表层土壤中,以种植杨树为恢复方式的小集成样地的过氧化氢酶活性显著增加,其他酶活性无显著变化;以种植芦苇为恢复方式的官垸样地的蔗糖酶和磷酸酶活性有所下降,其他酶活性无显著变化;恢复自然水域的青山垸样地中,除磷酸酶活性下降外,其他酶活性没有表现出明显的差异性.相关分析表明,土壤有机质含量与4种酶活性均表现出显著的正相关关系（P<0.01）,说明退田还湖后系统恢复模式导致的土壤有机质含量的变化是土壤酶活性变化的主要原因.     

Photoinhibition of Photosynthesis in Plants Growing in Natural Tropical Forest Gaps. A Chlorophyll Fluorescence Study

Photoinhibition of photosynthesis was monitored by means of chlorophyll a fluorescence in leaves of plants growing in 60–80 m² light gaps in a moist tropical lowland forest located on Barro Colorado Island in central Panama. In these forest gaps, photon flux density was low (less than 100 μmol photons m^?2 s^?1) during most of the day, but increased on clear days to 1.7-1.8 mmol photons m^?2 s^?1 for 1–2 h during midday. Nine species representing different taxa and life-forms were examined. Leaves of all species exhibited substantial photoinhibition in situ during high light exposure, as manifested by a decrease in the ratio of variable to maximum fluorescence emission, F_V/F_M. Recovery (reversion of fluorescence quenching) took place in the shade following high light exposure. The major part of recovery occurred in a fast phase within about 1 h after the high light period. A slow phase of recovery proceeded for another 4–5 h until sunset. After 30–60 min of recovery in the shade, calculated rates of PSII electron transport remained significantly (5–15%) reduced in comparison to rates obtained prior to high light exposure; after about 2 h of recovery, inhibition was negligible. All species responded to the high light periods and following shade periods in a very similar manner. It is concluded that photoinhibition and recovery exhibited by these gap leaves reflect a dynamic regulatory mechanism of thermal energy dissipation that allows plants of different life-forms to cope with periods of high light in tropical forest gaps.