Effect of dietary supplementation of vitamins A, D-3, E, and C on yearling rice field eel, Monopterus albus: Serum indices, gonad development, and metabolism of calcium and phosphorus

The objective of this study was to determine the effect of dietary vitamins A, D-3, E, and C on the gonad development, lipid peroxidation, and immune response of yearling rice field eel, Monopterus albus. A 6-wk feeding trial was designed according to an L-16(4(5)) orthogonal design, in which four vitamins, each at four supplementation levels, were arranged. Sixteen diets were mixed with the different vitamin levels and randomly assigned to 16 groups of fish. Increasing dietary vitamin E supplementation level significantly (P <= 0.05) increased the gonadosomatic index and lowered the serum content of malondialdehyde of rice field eel. Increasing dietary vitamin A and C levels also showed similar effect, but the differences were not statistically significant. Serum immunoglobulin M content increased significantly (P <= 0.01) as dietary vitamin C supplementation levels increased. The concentrations of calcium in bones showed significant (P <= 0.05) trend with vitamin D-3 and A supplementation levels, but the bone phosphorus content was not affected by the dietary vitamin levels.

Variations and possible source of potentially available phosphorus in a Chinese shallow eutrophic lake

Surface, overlying, and interstitial waters were collected at monthly intervals at three experimental stations in a shallow Chinese eutrophic lake (Lake Donghu) to assess the occurrence, distribution, and status of UV-sensitive phosphorus compounds (UVSP) and phosphatase hydrolyzable phosphorus (PHP), coupled with kinetics of alkaline phosphatase activity (APA). Orthophosphate (o-P) concentrations were generally the highest at Station 1, where chlorophyll a (chl a) was a function of o-P at temporal scale. The V-max/K-m of APA obtained by Michaelis-Menten approach paralleled the chlorophyll data at two stations. These facts imply that the development of phytoplankton may be attributed to APA induced by PHP. The potentially available UVSP and PHP peaked in interstitial, overlying, and surface water simultaneously sometimes in 1995 to 1996 and 1997 to 1999. It is postulated that they may arise from the bottom. UVSP peaked in interstitial water at the 12-16 cm layers in sediment cores. Moreover, in interstitial water, UV irradiation resulted in an elevated o-P concentration and decreased APA in a timeseries analysis. Therefore, the mechanism that APA involved in the process of photorelease of o-P was not demonstrated. UVSP is most likely a functional group of labile phosphorus distinct from the enzymatic substrate in this shallow eutrophic lake.

Dietary phosphorus requirement of juvenile black seabream, Sparus macrocephalus

A growth trial was conducted to estimate the optimum requirement of dietary available phosphorus (P) for black seabream (Sparus macrocephalus) in indoor net cages (1.5x1.0x1.0 m). Triplicate groups of black seabream (11.45 +/- 0.02 g) were fed diets containing graded levels (0.18, 0.36, 0.54, 0.72, 0.89 and 1.07%) of available P to satiation for 8 weeks. The basal diet (diet 1), containing 0.18% available P, was supplemented with graded levels of monosodium phosphate (NaH2PO4 2H(2)O) to formulate five experimental diets. The fish were fed twice daily (08:00 h and 16:00 h) and reared in seawater (salinity, 26-29 g l(-1)) at a temperature of 28 +/- 1 degrees C. Dissolved oxygen during the experiment was above 5 mg l(-1). The specific growth rate (SGR), weight gain (WG), feed efficiency (FE) and protein efficiency ratio (PER) were all significantly improved by dietary phosphorus up to 0.54% (P<0.05) and then leveled off beyond this level. Hepatosomatic index (HSI) was inversely correlated with dietary phosphorus levels (P< 0.05). Efficiency of P utilization stabled in fish fed diets containing 0.18%-0.54% available P and then decreased dramatically with further supplementation of dietary phosphorus. Body composition analysis showed that the whole-body lipid, ash, calcium and phosphorus contents were all significantly affected by dietary available P concentration (P<0.05), however, no significance were found in whole-body calcium/phosphorus (Ca/P) ratios among all the treatments (P>0.05). Dietary phosphorus levels also affected the mineralization of vertebrae, skin and scale (P<0.05). Ca/P ratios in vertebrae and scale were not influenced by dietary P supplementation, while skin Ca/P ratio increased statistically with dietary available P levels (quadratic effect, P<0.001). The blood chemistry analysis showed that dietary available P had distinct effects on enzyme activities of alkaline phosphatase (ALP) and plasma lysozyme (LSZ), as well as contents of triacyglycerol (TG) and total cholesterol (T-CHO) (P<0.05). Broken-line analysis showed maximum weight gain (WG) was obtained at dietary available P concentrations of 0.55%. Quadratic analysis based on P contents in whole fish, vertebrae or scale indicated that the requirements were 0.81, 0.87 and 0.88%, respectively. Signs of phosphorus deficiency were characterized by poor growth, slightly reduced mineralization and an increase in body lipid content. (C) 2008 Published by Elsevier B.V.

TN : TP ratio and planktivorous fish do not affect nutrient-chlorophyll relationships in shallow lakes

1. In previous work, phytoplankton regulation in freshwater lakes has been associated with many factors. Among these, the ratio of total nitrogen to total phosphorus (TN : TP) has been widely proposed as an index to identify whether phytoplankton are N- or P-limited. From another point of view, it has been suggested that planktivorous fish can be used to control phytoplankton. 2. Large-scale investigations of phytoplankton biomass [measured as chlorophyll a, (chl-a)] were carried out in 45 mid-lower Yangtze shallow lakes to test hypotheses concerning nutrient limitation (assessed with TN : TP ratios) and phytoplankton control by planktivorous fish. 3. Regression analyses indicated that TP was the primary regulating factor and TN the second regulating factor for both annual and summer phytoplankton chl-a. In separate nutrient-chl-a regression analyses for lakes of different TN : TP ratios, TP was also superior to TN in predicting chl-a at all particular TN : TP ranges and over the entire TN : TP spectrum. Further analyses found that chl-a : TP was not influenced by TN : TP, while chl-a : TN was positively and highly correlated to TP : TN. 4. Based on these results, and others in the literature, we argue that the TN : TP ratio is inappropriate as an index to identify limiting nutrients. It is almost impossible to specify a 'cut-off' TN : TP ratio to identify a limiting nutrient for a multi-species community because optimal N : P ratios vary greatly among phytoplankton species. 5. Lakes with yields of planktivorous fish (silver and bighead carp, the species native to China) > 100 kg ha(-1) had significantly higher chl-a and lower Secchi depth than those with yields < 100 kg ha(-1). TP-chl-a and TP-Secchi depth relationships are not significantly different between lakes with yields > 100 kg ha(-1) or < 100 kg ha(-1). These results indicate that the fish failed to decrease chl-a yield or enhance Z(SD). Therefore, silver carp and bighead carp are not recommended as a biotic agent for phytoplankton control in lake management if the goal is to control the entire phytoplankton and to enhance water quality.

Phosphorus in interstitial water induced by redox potential in sediment of Dianchi Lake, China

The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads, such as soluble reactive phosphorus (SRP) and total phosphorus (TP), as well as the main elements of sediment extracts in Dianchi Lake. Several strongly reducing substances in sediments, which mainly originated from anaerobic decomposition of primary producer residues, were responsible for the lower redox potential. In a range of -400 to 200 mV raising the redox potential of sediments decreased TP and SRP in interstitial water. Redox potentials exceeding 320 mV caused increases in TP, whereas SRP maintained a relatively constant minimum level. The concentrations of Al, Fe, Ca2+, Mg2+, K+, Na+ and S in interstitial water were also related to the redox potential of sediments, suggesting that the mechanism for redox potential to regulate the concentration of phosphorus in interstitial water was complex.

The research of phosphorus of Xiangxi River nearby the Three Gorges, China

The Xiangxi River is the first middling tributary of the Changjiang River near the Three Gorges Dam. The River is subject to phosphorus pollution mainly from industrial wastewater. As the water quality of the Xiangxi River could directly influence the water quality of the Three Gorges Reservoir, the research on phosphorus levels and its change in the sediment profile of the Xiangxi River could provide useful information in the dynamic changes in the system, thereby offering options for mitigative measures. Water and sediment samples from lower reaches of Xiangxi River were collected and the different forms of phosphorus in sediments of the Xiangxi River were studied. The concentrations of total phosphorus in sediment ranged from 757.67 to 1438.54 mg/kg. Inorganic phosphorus concentrations ranged from 684.63 to 1055.58 mg/kg. Phosphorus contamination was serious in some parts of the Xiangxi River. With an average concentration of 635.17 mg/kg, calcium-bound phosphorus is the main form among different inorganic phosphorus forms. Labile phosphorus and iron/aluminum-bound phosphorus measured 3.40, 0.05and 35.28 mg/kg, respectively. The mobilization potential of phosphorus of sediments was studied through adsorption and release experiments. The equilibrium concentration of phosphorus adsorption and release was around 0.1 mg/L. The initial concentrations of phosphorus in the overlying water and the sediments have obvious effect on phosphorus mobilization potential. In addition, the release rate of phosphorus in sediment increased with water depth.

The picophytoplankton in three Chinese lakes of different trophic status and its relationship to fish populations

A year-round comparison was made of the picophytoplankton populations in three lakes of different trophic status (oligotrophic, mesotrophic, and hypereutrophic), as well as in experimental enclosures stocked with various densities of fish. Picophytoplankton abundance was significantly different between the hypereutrophic lake and the oligotrophic lake (P<0.018) and between the hypereutrophic lake and the mesotrophic lake (P<0.021), whereas the difference between the mesotrophic and oligotrophic lakes was not significant (P<0.745). The effect of total nitrogen:total phosphorus ratio on the abundance of picophytoplankton was demonstrated in the oligotrophic lake, but such effect did not manifest itself in the other lakes or in the experimental enclosures. The average annual picophytoplankton population sizes in the three lakes in 1995-1998 were correlated with estimated fish abundance (r=0.824, n=9, P=0.006). The results of enclosure experiments demonstrated that the abundance of picophytoplankton increased with the stocking density of fish (r=0.619, n=8, P=0.100).

花椒的化感作用对凋落物分解的影响及机理研究

花椒（Zanthoxylum bungeanum）是川西干旱河谷地区重要的经济作物，化感作用是花椒连作障碍的重要原因之一。花椒凋落物分解是影响花椒林地土壤肥力及花椒产量的重要因素，因此系统研究花椒化感作用是否对花椒凋落物的分解产生影响可以为解决花椒连作障碍导致的产量下降等问题提供科学的理论依据。本文通过室内模拟实验研究了花椒凋落物的四个分解动态以及分解后凋落物浸提液对花椒林地土壤性质的影响；通过野外盆栽实验研究了花椒凋落物浸提液对花椒幼苗的生长、花椒凋落物的质量及土壤性质的影响。最终从生理生化角度揭示了花椒的化感作用对凋落物分解的影响机理，为深入解决花椒连作障碍问题、对花椒凋落物采取有效的人工措施提供了科学的理论依据。主要的研究结果如下： 1. 室内分解实验证明，花椒凋落物在分解的60 d 内分解速率呈现由大到小的变化趋势，并且凋落物分解呈现明显的毒性动态。凋落物在分解的10 d、30 d 时，分解速率较大，30 d 以后分解速率显著降低。凋落物分解的10 d 左右酚酸释放量最大，此时凋落物的毒性最大，凋落物分解到10 d 以后，酚酸释放量逐渐减少，凋落物的毒性也逐渐减小。 2. 四个分解动态的花椒凋落物浸提液对土壤化学性质产生了显著的影响。花椒凋落物在分解的60 d 内，其浸提液使土壤pH值均显著的增加。分解0 d 的凋落物浸提液显著的降低了土壤铵态氮的含量，抑制了纤维素分解菌的生长；分解60 d 的凋落物浸提液显著的降低了土壤酚酸含量，增加了土壤有效磷的含量；分解30 d 和60 d 的凋落物浸提液均显著的促进了好气性纤维素分解菌的生长。这说明花椒凋落物在分解过程中呈现出明显的毒性动态：凋落物分解的初期毒性作用较大，随着分解的继续进行特别是在分解的30 d 以后，其毒性作用慢慢降低。 3. 花椒凋落物浸提液对花椒幼苗表现出明显的化感作用。不同浓度的浸提液对花椒幼苗地上及地下生物量、叶面积均产生了显著的抑制作用，并且随着浸提液浓度的升高抑制作用加强。凋落物浸提液对叶片厚度的影响较小，只有Y1对叶片厚度的生长抑制作用显著。 4. 花椒的化感作用改变了凋落物的质量，并对凋落物分解产生了显著的影响。对花椒幼苗用不同浓度的凋落物浸提液进行处理，Y1使凋落物有机碳含量、木质素含量、C/N、木质素/氮显著降低，纤维素含量显著升高；Y3使凋落物有机碳含量、木质素含量、C/N、木质素/氮显著升高。花椒凋落物质量的改变显著的影响了凋落物的分解，凋落物的分解速率大小依次为：Y1（10.15 a-1）> Y2（8.71 a-1）> CK（6.41 a-1）> Y3（5.08 a-1）。 5. 花椒的化感作用改变了土壤性质，并对凋落物分解产生了显著的影响。对花椒幼苗用不同浓度的凋落物浸提液处理的同时，也改变了土壤性质。不同浓度的凋落物浸提液显著的升高了土壤pH值、有机碳含量。各种浓度的凋落物浸提液对土壤多酚氧化酶的活性均起到了显著的促进作用。凋落物浸提液Y1对土壤纤维素分解酶的活性、细菌和真菌的生长也具有显著的促进作用。土壤性质的改变显著的影响了凋落物的分解，凋落物的分解速率大小依次为：Y1（10.30 a-1）>Y2（9.60 a-1）>CK（6.41 a-1）>Y3（6.29 a-1）。 6. 不论是凋落物质量发生改变还是土壤性质发生改变，在凋落物分解的整个过程中，C元素始终处于单调净释放的状态，并且C释放量与分解速率成显著的正相关，即凋落物分解越快，凋落物C释放量越大。凋落物分解过程中，均出现了酚酸大量释放的情况，并与凋落物分解速率成显著正相关。凋落物分解后的木质素含量、木质素/氮均增加，并且随着浸提液浓度的升高，凋落物木质素含量、木质素/氮升高。 Zanthoxylum bungeanum is an important economic crop in dry valley of the Minjiang river (Sichuan, Southwest China), but allelopathy is one of the important reasons for its continuous cropping. Zanthoxylum bungeanum litter decomposition affects Zanthoxylum bungeanum soil fertility and its output. So systemically investigate if allelopathy affects litter decomposition could provide the scientific methods to solve the problem of output fall caused by the continuous cropping. In this paper, the releasing dynamics of phenolic acid during Zanthoxylum bungeanum litter decomposition (0, 10, 30 and 60 days) and the effects of its aqueous extract on soil chemical properties were investigated via the laboratory study. Effects of Zanthoxylum bungeanum litter aqueous extract on the growth of young Zanthoxylum bungeanum seedlings, litter qualities and the soil qualities were investigated via the field study. Finally, we open out the action manner of Zanthoxylum bungeanum allelopathic effect on the litter decomposition, and provide the theoretical basis to solve the Zanthoxylum bungeanum continuous cropping. The main results showed that: 1. The laboratory litter decomposition experiment showed a trend of decomposition rate from large to small and an occurrence of phytotoxicity with clear dynamic patterns during Zanthoxylum bungeanum litter decomposition. The litter decomposition rate was larger at the tenth and 30th day during 60-day litter decomposition and gradually decreased after 30 days of litter decompostion. The releasing quantity of the litter phenolic acid was the highest at the tenth day, and here, the litter toxicity was the biggest. The releasing quantity of the litter phenolic acid gradually decreased after 10 days of litter decomposition, so the phytotoxicity of litter was gradually decreased with the litter decomposition. 2. The Zanthoxylum bungeanum litter aqueous extract after four decomposition stages had significantly effect on the soil chemical qualities. The pH value in soil was significantly increased in litter aqueous extract of four decomposition stages. The NH+4-N concentration was significantly decreased in soil amended with litter aqueous extract of 10-day decomposition which inhibited the growth of Aerobic cellulose-decomposer. The growth of soil Aerobic cellulose-decomposer was promoted by the litter aqueous extract of 30-day decomposition. Available phosphorus concentration was significantly increased and phenolic acid content was significantly decreased in soil amended with litter aqueous extract of 60-day decomposition which promoted the growth of Aerobic cellulose-decomposer. The study results showed an occurrence of phytotoxicity with clear dynamic patterns during Zanthoxylum bungeanum litter decomposition. The phytotoxicity of litter was the largest at the initial stage, but the phytotoxicity gradually decreased with the litter decomposition, especially after 30 days of decomposition. 3. The field study indicated that the Zanthoxylum bungeanum litter aqueous extract had significant allelopathic effects on the growth of young seedlings.Different concentration aqueous extract had signinficant inhibiting effects on biomass and leaf area of young seedlings. The inhibiting effect on the biomass strengthened with the litter aqueous extract concentration augment. Litter aqueous extracts had less effect on the leaf thickness, and only Y1 had significant inhibiting effect on the leaf thickness. 4. The Zanthoxylum bungeanum allelopathy had significant effect on the litter qualities and the litter decomposition. Treating the young Zanthoxylum bungeanum seedlings with different concentration of litter aqueous extracts, the leaf litter organic C, lignin, C/N and lignin/N all decreased and the cellulose content increased under Y1 treatment. The leaf litter organic C, lignin, C/N and lignin/N all increased under Y3 treatment. So the litter decomposition was significant affectded by the litter qualities, and the litter decomposition rate was Y1(10.15 a-1)> Y2(8.71 a-1) > CK(6.41 a-1) > Y3(5.08 a-1). 5. The Zanthoxylum bungeanum allelopathy had significant effect on the soil qualities and the litter decomposition. Treating the young Zanthoxylum bungeanum seedlings with different concentration of litter aqueous extracts, also changed the soil qualities. Different concentration of litter aqueous extracts had significant effects on the soil pH and organic C content. Every concentration of litter aqueous extracts accelerated the soil Polyphenol Oxidase activity and Y1 accelerated the soil Cellulase activity, the number of soil bacteria and fungi. So the litter decomposition was significant affected by the soil qualities, and the litter decomposition rate was Y1(10.30 a-1) > Y2 (9.60 a-1) >CK(6.41 a-1)>Y3(6.29 a-1)。 6. Whether the litter or soil qualities changed, the litter C element at the state of release at all times during the litter decomposition, and the release quantity increased with the decomposition rate augment. Litter released plentiful total penolics content during decomposition, and the release quantity had the positive correlation with the litter decomposition rate. The litter lignin content and the lignin/N all increased with the litter aqueous extracts concentration augment after litter decomposition.

黄土丘陵沟壑区退耕地人工柠条林土壤养分特征及其空间变异

应用时空互代方法,以柠条林为例,对黄土丘陵沟壑区不同利用年限人工林土壤养分特征、空间变异及其演变进行了系统的研究。结果表明,该区人工林土壤肥力处于较低水平;人工林表层土壤养分中速效磷和速效钾的空间变异性较大;各环境因子对土壤养分有一定的影响,海拔、坡度和坡向等环境因子与人工林地土壤养分间呈负相关关系,坡位和地形与人工林地土壤养分间呈正相关关系。随着利用年限的增加,人工林土壤养分各指标含量均增加,与利用年限有显著的相关性。有机质、全氮、有效氮和速效磷的增加量不明显,全磷含量保持相对稳定的水平,速效钾经过多年积累有明显的增加。从土壤养分指数模型可以算出该区的人工林土壤有机质、全氮、有效氮约需35a能达到中上等养分水平,速效钾则约需27a才能达到中上等养分水平。

侵蚀条件下坡地土壤水分与有效磷的空间分布特征

坡地的水土流失及磷素在泥沙中的富集不仅导致土地生产力下降、环境恶化 ,也对下游水体的环境造成严重危害。以不同施磷时间的黄绵土为试验材料 ,通过人工模拟降雨试验观察了坡地侵蚀土壤水分含量 (SM)与有效磷含量 (APC)的空间变化特征。结果表明 :自坡顶向下侵蚀土壤表层 0～ 5 cm与 5～ 10 cm的土壤水分 (SM)呈现出完全一致的波浪状递增趋势。有效磷含量 (APC)的空间变化虽然也为波浪状 ,但其节奏要较水分变化快一倍 ,而且 0～ 5 cm与 5～ 10 cm两层间并不同步 ,下层略有滞后。磷向 2 0 cm以下土层的迁移量极少 ,不同坡位间差别不大。施磷 2 4d以前从坡顶向下有效磷含量 (APC)呈降低趋势 ,而施磷 2 4d以后在坡下则略有富集 ;施磷 6 d以前坡地 0～ 5 cm土层有效磷含量 (APC)较 6 d以后低 8%左右

ROLE OF PHOSPHORUS CYCLING IN ALGAL METABOLISM AND ALGAL SUCCESSION IN LAKE DONGHU, CHINA

The role of phosphorus cycling in algal metabolism was studied in a shallow lake, Donghu, in Wuhan using the methods of measuring cell quota C, N and P, and calculating nutrients uptake rate by algal photosynthesis. The mean daily phosphorus uptake rate of phytoplankton varied between 0.04-0.11 and 0.027-0.053 g/m2/d in station I and station II respectively. The turnover time of phosphorus in phytoplankton metabolism ranged from 0.75-5.0 days during 1979-1986. The available P was 0.176 (+/- 0.156) g/m3 (mean +/- SD) in 1982 and 0.591 (+/- 0.24) g/m3 in 1986. The relationship between P/B ratio (Y) and TP (X: mg/l) was described by the following regression equation Y = 1.163 + 0.512logX (r = 0.731, P < 0.001). The dynamics of algal biomass and algal species succession were monitored as the indicators of environmental enrichment. The small-sized algae have replaced the blue-green algae as the dominant species during 1979-1986. The small-sized algae include Merismopedia glauca, Cryptomonas ovata, Cryptomonas erosa, several species Cyclotella. There has been drastic decrease in algal biomass and an obvious increase in P/B ratio. A nutrient competition hypothesis is proposed to explain the reason of the disappearance of blue-green algae bloom. The drastic change in algal size and the results in high P/B ratio (reaching a maximum mean daily ratio of 1.09 in 1986) may suggest a transition of algal species from K-selection to r-selection in Lake Donghu.

Transfer and transport of phosphorus and silica in the turbidity maximum zone of the Changjiang estuary

The concentration of suspended particulate matter (SPM), sedimentation flux, and various forms of phosphorus and silica in turbidity maximum zone (TMZ) in the Changjiang (Yangtze) estuary was studied. Based on the budget of P and Si, their mass balances in the TMZ were calculated. Results show that the variation in concentration of dissolved inorganic silicon (DISi) was mainly controlled by seawater dilution, while that of dissolved inorganic phosphor-us (DIP) was considerably affected by the buffering of suspended matter and sediment. Our experiments showed that the sedimentation fluxes of SPM and particulate inorganic phosphorus (PIP), total particulate phosphorus (TPP), particulate inorganic silicon (PISi), and biological silicon (BSi) in the TMZ were 238.4 g m(-2) d(-1) and 28.3, 43.1, 79.0, 63.0 mg m(-2) d(-1), respectively. In addition, a simple method to estimate the ratio of resuspension of sediment in the TMZ was established, with which the rate in surface and bottom waters of the TMZ accounted for 55.7 and 66.1% of the total SPM, respectively, indicating that the sediment resuspension in the TMZ influenced significantly the mass balances of P and Si. Particulate adsorbed P (60.8%) and 35.5% of total particulate P discharged from the river were filtered and then deposited in the TMZ. The input flux of PIP from the river mouth was 55.9% of that of DIP, being important as biologically available P, while that of PISi was only 3.5% of DISi, showing that particulate adsorbed Si was much less important than particulate adsorbed P. (c) 2008 Elsevier Ltd. All rights reserved.