FLUCTUATION OF SIZE-FRACTIONATED ALKALINE PHOSPHATASE AFTER BLOOM DISAPPEARANCE IN TWO SHALLOW PONDS

The temporal and vertical fluctuations of size fractionated alkaline phosphatase activity (APA) and kinetics parameters as well as orthophosphate (o-P) and chlorophyll concentrations were investigated after bloom disappearance in two shallow ponds A and B from 27 October 2001 to 15 April 2002. Pond A (Microcystis) bloomed seriously but pond B did not. The data of o-P and chlorophyll suggested that phosphorus was the principal limiting nutrimental element and its vertical flux should be regarded as an important driving factor for algal growth. In pond A, the accumulation of algae-derived detritus after bloom disappearance in overlying water stimulated excretion of algal fraction APA, mainly produced by attached bacteria responsible for detritus decomposition, whereas bacterial fraction APA preferred to function in surface water. Interestingly, completely contrary phenomena were observed in pond B. In season, even though no obvious difference for size-fractionated APA in both ponds, the total APA in pond A peaked earlier showing higher activity and efficiency (low K-m and high V-max values) as a result of algal-derived detritus input. In summary, it is suggested that the excretion of alkaline phosphatase with strongly catalyzing efficiency and high activity should be taken as important contributor to algal-derived detritus decomposition, further fueling nutrient recycle and accelerating algal development next year. Furthermore, some inhibitors and surfactants were testified to be good tools to identify the origin of dissolved alkaline phosphatase.

Morphology and infraciliature of three species of Metaurostylopsis (Ciliophora, Stichotrichia): M. songi n. sp., M. salina n. sp., and M. marina (Kahl 1932) from sediments, saline ponds, and coastal waters.

Two new urostylid ciliates, Metaurostylopsis songi n. sp. and Metaurostylopsis salina n. sp. and Metaurostylopsis marina (Kahl 1932) are investigated using live observation and protargol impregnation. These species were isolated in Korea from intertidal sediments, saline ponds, and coastal waters. Metaurostylopsis songi is in vivo about 120 pm x 25 mu m, has a slenderly ellipsoidal body, colorless cortical granules in rows on ventral and dorsal body sides, about 54 macronuclear nodules, 28-47 adoral membranelles, five frontal, two or three frontoterminal and six or seven transverse cirri, and 9-12 midventral cirral pairs followed posteriorly by 1-3 single cirri. In vivo M. salina is about 60 pin x 25 mu m, has a pyriform body, colorless cortical granules irregularly arranged, about 45 macronuclear nodules, 18-23 adoral membranelles, three frontal, three to five frontoterminal and two to five transverse cirri, and four or five midventral cirral pairs followed posteriorly by five to seven single cirri. Both species have three marginal cirral rows on each body side and 3 long dorsal kineties. The Korean specimens of M. marina match the Chinese population in all main features. Metaurostylopsis songi differs from M. marina by the more slender body, the number of frontal cirri (invariably five vs. four), and the arrangement of cortical granules (in rows on dorsal and ventral cortex vs. only along dorsal kinetics and anterior body margin). Metaurostylopsis salina differs from its congeners by the distinctly smaller size, the pyriform body shape, the scattered cortical granules (vs. in rows), and number of frontal cirri. It differs from M. marina also by the number of midventral cirral pairs (four or five vs. seven to 11).

淹水对三峡库区几种植物的生理生态影响

自然界木本植物在某些情况下可能面对淹水带来的胁迫伤害，木本植物对淹水的生理生态响应及适应机制的研究，不仅可以从机理上解释河岸带和消落区树种分布的规律，对于大型水库消落区的治理也能起到理论依据的作用，因此，木本植物对淹水的生理生态响应及适应机制历来是植物生理生态研究领域的热点问题之一。 三峡水库蓄水造成库区部分陆地岛屿化，这将对岛屿优势植物带来深远影响。短柄枹栎(Quercus glandulifera)、栓皮栎(Quercus variabilis)、马尾松(Pinus massoniana)是这些岛屿上的三种优势树种。在岛屿形成初期，应用生理生态学手段，在7月和9月分别对其水势和叶绿素荧光进行了野外测定，从而为岛屿化对植物生理生态影响的研究和监测提供重要的本底数据。研究结果表明马尾松较其它两种植物更耐旱。水势和Fv/Fm在清晨高中午低，经过一个晚上可以基本恢复，因此就目前状况看岛上的三种优势植物均生长健康。但是库区蓄水后，在淹水胁迫下植物的生理生态过程将如何变化，还需要后期的连续观测。 枫杨（Pterocarya stenoptera）、池杉（Taxodium ascendens）和栓皮栎（Quercus variabilis）是三峡库区河岸带和库塘消落区常见的植物，对于河岸带和库塘消落区的水土保持和水源涵养具有十分重要的作用。通过设计模拟淹水实验，研究了这三种植物对淹水的生理生态响应及适应机制。淹水对枫杨和栓皮栎生理生态过程的早期影响是快速降低了二者的最大净光合速率、气孔导度、最大光化学量子效率（Fv/Fm）。但经过最初的下降后，枫杨的最大净光合速率、气孔导度和最大光化学量子效率逐渐恢复，而栓皮栎的则持续下降。在试验过程中，枫杨和池杉均产生了有利于吸收氧气的不定根和肥大的皮孔，而栓皮栎没有产生不定根。随淹水时间的增加枫杨的叶绿素含量与对照没有显著差异;而栓皮栎的叶绿素含量在第33天后大幅降低，Chla/Chlb的比值下降。淹水后第10天和70天测定的清晨水势，受淹栓皮栎比对照高，而受淹枫杨比对照低。淹水导致池杉和栓皮栎的根/茎/叶膜质过氧化状态均呈现动态变化。淹水处理的栓皮栎根的MDA含量低于对照而池杉的高于对照，比如：淹水24天后，栓皮栎根的丙二醛含量是对照的73％;而池杉是对照的111.5％。淹水处理第10天和第24天两个种的叶和茎MDA含量均高于对照但第50天则略低于对照。淹水导致池杉和栓皮栎两个种的根/茎/叶可溶性糖含量呈现动态变化。持续淹水导致栓皮栎叶片可溶性糖含量相比于对照先略下降后上升，茎可溶性糖含量显著上升而根可溶性含量先下降后上升。而池杉根/茎/叶可溶性糖含量对照和处理之间差异不显著。淹水导致栓皮栎的比叶重（Leaf dry mass per area）持续升高，池杉的与对照没有显著差异。淹水导致栓皮栎的根系活力持续下降，池杉则开始时下降后又升高，这可能与池杉在淹水过程中产生了有利于吸收氧气的不定根，而栓皮栎没有产生不定根有关。 以上生理生态的实验结果说明相对枫杨和池杉，栓皮栎应属于对淹水较敏感的树种。并得到以下一些结论：1）间接支持了“长期淹水导致不耐淹种（如栓皮栎）库量减小，进而导致光合速率下降的负反馈效应”假说;2）淹水对不耐淹种光合速率下降的影响至少包括气孔开度降低、光化学量子效率降低和库尺寸下降导致的光合速率下调的负反馈效应（长期）三个生理生态原因;3）淹水对水势的影响与树种相关;4）淹水并未导致不耐淹种（如栓皮栎）根膜质过氧化状态上升，而是导致其下降。导致其下降的主要原因是根系缺氧造成的;5）淹水胁迫初期耐淹种（如枫杨和池杉）和不耐淹种（栓皮栎）均出现部分生理生态过程的下调，持续时间大概在1－10天内。随后耐淹种生理过程逐渐恢复而不耐淹种在略为恢复1－2天后逐渐下降到较低水平。耐淹种恢复的关键原因可能是不定根和肥大的皮孔的出现。 令人意外的是70天的淹水过程并没有导致栓皮栎的死亡，这说明该树种对淹水具有一定的忍耐能力。因此，栓皮栎分布于河岸带和消落区较高海拔处并很少受到季节性淹水影响的生理生态原因可能还包括其他方面。淹水后可能要面对土壤透气性恢复带来的生理干旱胁迫可能对栓皮栎的生理过程造成影响。因此进一步研究淹水后恢复过程中三个种的生理生态过程对于深刻理解河岸带和消落区树种分布的生理生态原因无疑具有十分重要的理论意义。

In situ nutrient removal from aquaculture wastewater by aquatic vegetable Ipomoea aquatica on floating beds

Nutrient-rich effluents caused rising concern due to eutrophication of aquatic environment by utilization of a large amount of formula feed. Nutrient removal and water quality were investigated by planting aquatic vegetable on artificial beds in 36-m(2) concrete fishponds. After treatment of 120 days, 30.6% of total nitrogen (TN) and 18.2% of total phosphorus (TP) were removed from the total input nutrients by 6-m(2) aquatic vegetable Ipomoea aquatica. The concentrations of TN, TP, chemical oxygen demand (COD) and chlorophyll a in planted ponds were significantly lower than those in non-planted ponds (P<0.05). Transparency of water in planted ponds was much higher than that of control ponds. No significant differences in the concentration of total ammonia nitrogen (TAN), nitrate nitrogen (NO3-N) and nitrite nitrogen (NO2--N) were found between planted and non-planted ponds. These results suggested that planting aquatic vegetable with one-sixth covered area of the fishponds could efficiently remove nutrient and improve water quality.

Effects of arsenate on the growth and microcystin production of Microcystis aeruginosa isolated from Taiwan as influenced by extracellular phosphate

Arsenic pollution and eutrophication are both prominent issues in the aquaculture ponds of Taiwan. It is important to study the effects of arsenic on algal growth and toxin production in order to assess the ecological risk of arsenic pollution, or at least to understand naturally occurring ponds. The sensitivity of algae to arsenate has often been linked to the structural similarities between arsenate and phosphate. Thus, in this study we examined the effects of arsenate (10(-8) to 10(-4) M) on Microcystis aeruginosa TY-1 isolated from Taiwan, under two phosphate regimes. The present study showed that M. aeruginosa TY-1 was arsenate tolerant up to 10(-4) M, and that this tolerance was not affected by extracellular phosphate. However, it seems that extracellular phosphate contributed to microcystin production and leakage by M. aeruginosa in response to arsenate. Under normal phosphate conditions, total toxin yields after arsenate treatment followed a typical inverted U-shape hormesis, with a peak value of 2.25 +/- 0.06 mg L-1 in the presence of 10(-7) M arsenate, whereas 10(-8) to 10(-6) M arsenate increased leakage of similar to 75% microcystin. Under phosphate starvation, total toxin yields were not affected by arsenate, while 10(-6) and 10(-5) M arsenate stimulated microcystin leakage. It is suggested that arsenate may play a role in the process of microcystin biosynthesis and excretion. Given the arsenic concentrations in aquaculture ponds in Taiwan, arsenate favors survival of toxic M. aeruginosa in such ponds, and arsenate-stimulated microcystin production and leakage may have an impact on the food chain.

Growth kinetics of 1-2 mm and 3-4 mm colonies of Nostoc sphaeroides (Cyanophyta) in outdoor culture

Nostoc sphaeroides Kutzing was cultivated in paddlewheel-driven raceway ponds and the growth kinetics of 1-2 mm and 3-4 mm colonies of N. sphaeroides was studied. The biomass productivities in 2.5 m(2) raceway ponds inoculated with 1-2 mm and 3-4 mm colonies were 5.2 and 0.25 g dry wt m(-2) stop d(-1), respectively. Furthermore, differently sized colonies showed different relative water content, total soluble carbohydrates, chlorophyll a content and density of filaments. This is the first report on mass culture of N. sphaeroides under outdoor conditions.

In situ study on effect of food competition on diet shifts and growth of silver and bighead carps in large biomanipulation fish pens in Meiliang Bay, Lake Taihu

Silver and bighead carps were cultured in large fish pens to reduce the risks of cyanobacterial bloom outbreaks in Meiliang Bay, Lake Tauhu in 2004 and 2005. Diet compositions and growth rates of the carps were studied from April to November each year. Both carp species fed mainly on zooplankton (> 50% in diet) in 2004 when competition was low, but selected more phytoplankton in 2005 when competition was high. Silver carp had a broader diet breadth than did bighead carp. Higher densities and fewer food resources increased diet breadths but decreased the diet overlap in both types of carps. It can be predicted that silver and bighead carps would be released from diet competition and shift to feed mainly on zooplankton at low densities, decreasing the efficiency of controlling cyanobacterial blooms. Conclusively, when silver and bighead carps are used to control cyanobacterial blooms, a sufficiently high stocking density is very important for a successful practice.

Photosynthesis and growth of Arthrospira (Spirulina) platensis (Cyanophyta) in response to solar UV radiation, with special reference to its minor variant

The minor variant of the economically important cyanobacterium, Arthrospira platensis, usually appears in commercial production ponds under solar radiation. However, how sensitive the minor variant to solar UVR and whether its occurrence relates to the solar exposures are not known. We investigated the photochemical efficiency of PSII and growth rate of D-0083 strain and its minor variant in semi-continuous cultures under PAR (400-700 nm) alone, PAR + UV-A (320-400 nm) and PAR + UV-A + UV-B (280-700 nm) of solar radiation. The effective quantum yield of D-0083 at 14:00 p.m. decreased by about 86% under PAR, 87% under PAR + UV-A and 92% under PAR + UV-A + UV-B (280-315 nm), respectively. That of the minor variant was reduced by 93% under PAR and to undetectable values in the presence of UV-A or UV-A + UV-B. Diurnal change of the yield showed constant pattern during long-term (10 days) exposures, high in the early morning and late afternoon but the lowest at noontime in both strains, with the UVR-related inhibition being always higher in the variant than D-0083. During the long-term exposures, cells of D-0083 acclimated faster to solar UV radiation and showed paralleled growth rates among the treatments with or without UVR at the end of the experiment; however, growth of the minor variant was significantly reduced by UV-A and UV-B throughout the period. Comparing to the major strain D-0083, the minor variant was more sensitive to UVR in terms of its growth, quantum yield and acclimation to solar radiation. (c) 2007 Elsevier B.V. All rights reserved.

Clonal diversity and genealogical relationships of gibel carp in four hatcheries

To conserve and utilize the genetic pool of gynogenetic gibel carp (Carassius auratus gibelio), the Fangzheng and Qihe stock hatcheries have been established in China. However, little information is available on the amount of genetic variation within and between these populations. In this study, clonal diversity in 101 fish from these two stock hatcheries and 35 fish from two other hatcheries in Wuhan and Pengze respectively was analysed for variation in serum transferrin. Thirteen clones were found in Fangzheng and Qihe, of which 12 were novel. Six clones were specific to Fangzheng and three specific to Qihe, whereas four were shared among the Fangzheng and Qihe fish. To obtain more knowledge on genetic diversity and genealogical relationships within gibel carp, the complete mitochondrial DNA (mtDNA) control region (similar to 920 bp) was sequenced in 64 individuals representing all 14 clones identified in the four hatcheries. Differences in the mtDNA sequences varied remarkably among hatcheries, with the Fangzheng and Qihe lines demonstrating high diversity and Wuhan and Pengze showing no variation. The Fangzheng and Qihe lines might represent two distinct matrilineal sources. One of the Qihe samples carried the haplotype shared by a most widely cultivated Fangzheng clone, indicating that a Fangzheng clone escaped from cultivated ponds and moved into the Qihe hatchery. Four Fangzheng samples clustered within the lineage formed mainly by Qihe samples, most likely reflecting historical gene flow from Qihe to Fangzheng. It is suggested that clones in Wuhan originated from Fangzheng, consistent with their introduction history, supporting the hypothesis that gibel carp in Pengze were domesticated from individuals in the Fangzheng hatchery.

Relationship between organic carbon concentration and potential pond bottom soil respiration

There was a positive correlation between the concentration of organic carbon and potential respiration as measured by carbon dioxide evolution (R-2 = 0.923) and oxygen consumption (R-2 = 0.986) in soil samples collected from the bottoms of drained ponds. This finding supports the frequent use of organic carbon analysis as an indicator of sediment respiration rate under optimal conditions in commercial aquaculture facilities. (c) 2005 Elsevier B.V. All rights reserved.

Effects of dissolved organic matter on the growth and pigments synthesis of Spirulina platensis (Arthrospira)

Excessive accumulation of dissolved organic matter (DOM) in the culture ponds of Spirulina platensis is usually considered to be one of the potential factors affecting the production of S. platensis, however, we are not quite aware of effects of DOM on the growth and pigments synthesis of S. platensis. In the present study, S. platensis was grown in batch or semi-continuous cultures using the filtrate in the culture ponds that had not been renewed for years. It was found that disssolved organic carbon up to 60 mg/L did not bring about an inhibitory effect on the growth of S. platensis, but increased the contents of chlorophyll a and phycocyanin instead. However, further accumulation of dissolved organic matter could decrease the content of chlorophyll a.

Measurement of 5-day biochemical oxygen demand without sample dilution or bacterial and nutrient enhancement

A direct method for measuring the 5-day biochemical oxygen demand (BODS) of aquaculture samples that does not require sample dilution or bacterial and nutrient enrichment was evaluated. The regression coefficient (R-2) between the direct method and the standard method for the analyses of 32 samples from catfish ponds was 0.996. The slope of the regression line did not differ from 1.0 or the Y-intercept from 0.0 at P = 0.05. Thus, there was almost perfect agreement between the two methods. The control limits (three standard deviations of the mean) for a standard solution containing 15 mg/L each of glutamic acid and glucose were 17.4 and 20.4 mg/L. The precision of the two methods, based on eight replicate analyses of four pond water samples did not differ at P = 0.05. (c) 2005 Elsevier B.V All rights reserved.

The impact of silver carp (Hypophthalmichthys molitrix) on the rotifer community in a eutrophic subtropical Chinese lake

From 20 April to 25 June in 1999, an enclosure experiment was conducted in Lake Donghu to assess the impact of planktivorous silver carp on the planktonic rotifer community. We set up four treatments with silver carp biomass at 0, 116, 176, and 316 g m(-2). Total rotifer density was significantly higher in the no-fish enclosure than in fish-present enclosures. Fish predation on the rotifers alleviated zooplankton competition and resulted in dominance of small zooplankton species (Anureaopsis fissa, Trichocerca pusilla and Moina micrura) in fish-present enclosures. However, some relatively larger species (Polyarthra vulgaris, Brachionus angularis, Brachionus calyciflorus, and Asplanchna spp.) showed higher densities in the no-fish enclosure than in fish-present enclosures.

Mobility and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans in sediment of Ya-Er Lake, China

The sediment of Ya-Er Lake had been heavily polluted by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the former chloralkali industry. The total amounts of PCDD/Fs and I-TEQ decreased along the water flow direction and also decreased from top to bottom layers of sediment cores. Sediment of Pond 1 was dominated by PCDF, especially TCDF. In contrast, in the other four ponds, PCDD dominated in all layers and octachlorinated dibenzo-p-dioxin (OCDD) predominated in all of the homologues. When homologue profiles from sediments and water samples were compared using principal component analysis (PCA), the first two principal components represented 95.2% of the variance in the data. The first component explained 75.9% of the variance and the second one 19.3%. Two clusters were most distinct, presenting a shift in PCDD/Fs composition from PCDF to heptachlorinated dibenzo-p-dioxin (HpCDD) and OCDD in sediments and water from Pond I to Ponds 2-5. The pattern variation between Pond 1 and Ponds 2-5 in Ya-Er Lake was most likely due to the change of process in the chemical plant after the dams between the ponds were built. The results of the present study also showed that log K-oc of PCDD/Fs calculated from data of sediment and water in the field were comparable with theoretical log K-oc. The results also implied that the concentrations of PCDD/Fs in water and sediments could be predicted from each other by log K-oc. (C) 2001 Elsevier Science Ltd. All rights reserved.