Widespread presence of hydrophobic paralytic shellfish toxins in Gymnodinium catenatum

The toxic dinoflagellate Gymnodinium catenatum Graham produces a newly discovered sub-class of paralytic shellfish toxins (PSTs, saxitoxins) that contain a hydroxybenzoate moiety in place of the carbamoyl group (GC toxins: GC1–GC3). GC toxins bind strongly to sodium channels and their lipophilic nature may increase their potential to bioaccumulate in marine organisms. Cultures Australian G. catenatum strains were found to contain 12–63 mol% GC toxins. The GC toxins were also detected in strains from China (38 mol%), Japan (1–2 mol%), Portugal (58 mol%), Spain (36–54 mol%), and Uruguay (10–16 mol%). A cluster analysis of molar proportions of saxitoxin derivatives produced by strains showed clear clustering by country/region of origin, indicating that GC toxins may be very useful markers to identify the source of G. catenatum in the case of new outbreaks. The GC toxins dominate the toxin profiles of many G. catenatum strains, and can contribute significantly to sample toxicity, yet these toxins may easily escape detection using conventional chromatography, resulting in significant underestimates of sample toxicity. This has significant implications for shellfish monitoring and safety.     

Photosynthetic photon flux effects on bean response to nitrogen dioxide

Phaseolus vulgaris L. cv. Kinghorn Wax seedlings, supplied with nutrient solution containing either 0 or 5 mM nitrate as sole N source, were exposed to 0.25 μl/l NO₂ for 6 hr each day for 10 days at continuous photosynthetic photon flux (PPF) of 100, 300, 500 or 700 μmol m⁻² sec⁻¹. There was a significant interaction of PPF and nitrate. Shoot and root dry weights increased with increasing PPFs only when nitrate was supplied. The main effects of NO₂ on plant growth were significant; none of the interactions involving NO₂ were significant. Exposure to NO₂ decreased shoot and root dry weight in both the presence and absence of nutrient N and at all PPF levels. All interactions were significant for in vitro leaf nitrate reductase activity (NRA), which increased markedly at PPFs above 100 μmol m⁻² sec⁻¹ when nitrate was supplied. Treatment with NO₂ strongly inhibited enzyme activity in the presence of nitrate, particularly at the 300 μmol m⁻² sec⁻¹ PPF level. These experiments demonstrated that PPF level does not modify the effect of NO₂ on growth but does have a major effect on NRA and on NO₂ effects on NRA in the presence of nutrient nitrate.     

Uptake and release effects of diethylpropion and its metabolites with biogenic amine transporters

Three metabolites of diethylpropion (1), (±)-2-ethylamino-1-phenyl-propan-1-one (2), (1R,2S)-(−)-N,N-diethylnorephedrine (3a) and (1S,2R)-(−)-N,N-diethylnorephedrine (3b) were synthesized. Their uptake and release effects with biogenic amine transporters were evaluated. A major finding of this study is that the in vivo activity of diethylpropion on biogenic amine transporters is most likely due to metabolite 2 as diethylpropion (1) and the metabolites 3a and 3b showed little or no effect in the assays studied. These studies also revealed that 2 acted as a substrate at the norepinephrine (IC₅₀=99 nM) and serotonin transporters (IC₅₀=2118 nM) and an uptake inhibitor at the dopamine transporter (IC₅₀=1014 nM). The potent action of 2 at the NE transporter supports the hypothesis that amphetamine-type subjective effects may be mediated in part by brain norepinephrine.     

中国近海甲藻环沟藻属2个新记录种:纺锤环沟藻和莫氏环沟藻

甲藻环沟藻属于一类无色素体、表面有脊的裸甲藻, 因可捕食一些重要的赤潮生物而在海洋生态系统中扮演着重要的角色。有关中国近海环沟藻属的物种多样性信息非常有限。本文报道了2个新记录种——纺锤环沟藻(Gyrodinium fusiforme)和莫氏环沟藻(G. moestrupii)。纺锤环沟藻细胞呈纺锤形, 长48.0-58.0 μm, 宽18.0-23.0 μm, 长宽比为2.4-3.0, 和模式种相比体型和长宽比都较小。莫氏环沟藻细胞也呈纺锤形, 长约30 μm, 宽约15 μm。我们测定了纺锤环沟藻和莫氏环沟藻大亚基的部分序列, 并根据大亚基序列利用最大似然法和贝叶斯法建立了系统发育树。结果显示环沟藻属是单源的, 纺锤环沟藻和裂缝环沟藻(G. fissum)聚合在一起, 但是与螺旋环沟藻(G. spirale)分离。纺锤环沟藻和莫氏环沟藻分别可以摄食米氏凯伦藻(Karenia mikimotoi)和具齿原甲藻(Prorocentrum dentatum), 前者在米氏凯伦藻赤潮中的大量出现显示它可以促进赤潮的消退。     

Effects of season on the yield and quality of agar from Gracilaria species (Gracilariaceae, Rhodophyta)

The effect of season on yield and physical properties of agars extracted from Gracia gracilis and G. bursa-pastoris were determined. The agar yield from G. gracilis was maximum during spring (30%) and minimum during autumn (19%). In G. bursa-pastoris, the agar yield was greatest in summer (36%) and lowest in winter (23%). Agar yield from G. bursa-pastoris was positively correlated with temperature (r=0.94; P<0.01) and salinity (r=0.97; P<0.01) and negatively with nitrogen content (r=−0.93; P<0.01). Agar gel strengths fluctuated from 229 to 828 g cm⁻² and 23 to 168 g cm⁻² for G. gracilis and G. bursa-pastoris, respectively. The gelling temperature showed significant seasonal variation for both species. Chemical analysis of agar from the two seaweeds indicated variation in 3,6-anhydrogalactose and sulfate content (P<0.01). Furthermore, there was an inverse correlation between the two chemical variables. In general, agar extracted from G. gracilis possessed better qualities than agar extracted from G. bursa-pastoris and can be considered a candidate for industrial use.     

Leaf gas exchange, chlorophyll fluorescence and growth responses of Genipa americana seedlings to soil flooding

Effects of soil flooding on photosynthesis and growth of Genipa americana L. seedlings, a neotropical fruit-tree species used in gallery forest restoration programs, were studied under glasshouse conditions. Despite the high survival rate and wide distribution in flood-prone habitats of the neotropics, previous studies demonstrated that growth of G. americana is reduced under soil flooding. Using leaf gas exchange and chlorophyll fluorescence measurements, we tested the hypothesis that stomatal limitation of photosynthesis is the main factor that reduces carbon uptake and growth rates of G. americana seedlings. Throughout a 63-day flooding period, the survival rates were 100%. The maximum values of the net photosynthetic rate (A) and stomatal conductance to water vapor (g_s) of control seedlings were 9.86 μmol CO₂ m⁻² s⁻¹ and 0.525 mol H₂O m⁻² s⁻¹, respectively. The earliest effects of flooding were significant decreases in g_s and A, development of hypertrophied lenticels and decrease in the dry weight of roots. A strong effect of the leaf-to-air vapor pressure deficit (LAVPD) on g_s and A were observed that was enhanced under flooded conditions. Between 14 and 63 days after flooding, significant reductions in g_s (31.7% of control) and A (52.9% of control) were observed followed by significant increments in non-photochemical quenching (q_N) (187.5% of control). During the same period, there were no differences among treatments for the ratio between variable to initial fluorescence (F_v/F₀), the maximum quantum efficiency of the photosystem II (F_v/F_m) and photochemical quenching (q_P), indicating that there was no damage to the photosynthetic apparatus. Based on the results, we conclude that decreases in stomatal opening and stomatal limitation of photosynthesis, followed by decrease in individual leaf area are the main causes of reductions in carbon uptake and whole plant biomass of flooded seedlings.     

Seagrass depth limits

Examination of the depth limit of seagrass communities distributed worldwide showed that sea-grasses may extend from mean sea level down to a depth of 90 m, and that differences in seagrass depth limit (Z_c) are largely attributable to differences in light attenuation underwater (K). This relationship is best described by the equation

log Z_c (m) = 0.26 − 1.07 log K (m⁻)

that holds for a large number of marine angiosperm species, although differences in seagrass growth strategy and architecture also appear to contribute to explain differences in their depth limits. The equation relating seagrass depth limit and light attenuation coefficient is qualitatively similar to previous equations developed for freshwater angiosperms, but predicts that seagrasses will colonize greater depths than freshwater angiosperms in clear (transparency greater than 10 m) waters. Further, the reduction in seagrass biomass from the depth of maximum biomass towards the depth limit is also closely related to the light attenuation coefficient. The finding that seagrasses can extend to depths receiving, on average, about 11% of the irradiance at the surface, together with the use of the equation described, may prove useful in the identification of seagrass meadows that have not reached their potential extension.     

Modelling the influence of copepod behaviour on faecal pellet export at high latitudes

The contribution of faecal pellet (FP) production by zooplankton to the downward flux of particulate organic carbon (POC) can vary from <1 % to more than 90 % of total POC. This results from varying degrees of interception and consumption, and hence recycling, of FPs by zooplankton in the upper mixed layers, and the active transport of FP to depth via diel vertical migration (VM) of zooplankton. During mid-summer at high latitudes, synchronised diel VM ceases, but individual zooplankton may continue to make forays into and out of the surface layers. This study considers the relative importance of different VM behaviours on FP export at high latitudes. We focussed on copepods and parameterised an individual-based model using empirical measures of phytoplankton vertical distribution and the rate of FP production, as a function of food availability. FP production was estimated under three different behaviours common to high-latitude environments (1) no VM, (2) foray-type behaviour and (3) synchronised diel VM. Simulations were also made of how each of these behaviours would be observed by an acoustic Doppler current profiler (ADCP). The model found that the type of copepod behaviour made a substantial difference to the level of FP export to depth. In the absence of VM, all FPs were produced above 50 m, where the probability of eventual export to depth was low. In foray-type scenarios, FP production occurred between 0 and 80 m, although the majority occurred between 30 and 70 m depth. Greatest FP production in the deeper layers (>70 m) occurred when diel VM took place. Simulated ADCP vertical velocity fields from the foray-type scenario resembled field observations, particularly with regard to the occurrence of positive anomalies in deeper waters and negative anomalies in shallower waters. The model illustrates that active vertical flux of zooplankton FP can occur at high latitudes even when no synchronised VM is taking place.     

Critical thermal maximum and body water loss in first instar larvae of three Cetoniidae species (Coleoptera)

Critical thermal maximum (CT_max) and body water losses were measured in first instar larvae of Gnorimus nobilis, Osmoderma eremita (Trichiinae) and Cetonischema aeruginosa (Cetoniinae) when air temperature was increased gradually (0.5 °C/min) from 20 °C to the critical thermal maximum (CT_max), in dry air (near 0% R.H.).

The CT_max was significantly lower in O. eremita (45.6±0.7 °C) than in G. nobilis (48.5±0.6) and C. aeruginosa (51.4±0.9 °C).

An increase of 10 °C (30–40 °C) induced a 2-fold increase of the water loss in C. aeruginosa and O. eremita (Q₁₀=2.10±0.12 and 2.13±0.20, respectively). In the range from 40 to 45 °C to CT_max a strong increase of the water loss was observed in O. eremita and C. aeruginosa, respectively. Body water losses were significantly lower in C. aeruginosa than in O. eremita and G. nobilis over the range 20 °C—CT_max; no significant difference occurred between G. nobilis and O. eremita.     

Calcareous dinoflagellate cyst distributions in surface sediments from upwelling areas off NW Africa, and their relationships with environmental parameters of the upper water column

Only very few studies have focussed on the spatial distribution and ecology of calcareous dinoflagellate cysts (dinocysts) in upwelling areas. Here, distributions of individual calcareous dinocyst species in surface sediment samples from the coastal upwelling zone off NW Africa and their relationships with known environmental parameters of the (sub-)surface waters have been analysed in order to enhance our knowledge on their modern distribution patterns and to determine the ecological significance and palaeoenvironmental reconstruction potential of each calcareous dinocyst species within this exemplary high-productivity region. In addition to calculating relative cyst abundances, well-constrained sedimentation rates have allowed the calculation of dinocyst accumulation rates (cysts cm^− 2 ka^− 1) for most of the surface sample positions, thus providing a much more accurate estimation of actual calcareous dinocyst production in the upper water column than could be warranted in similar studies so far. Distinct differences in the geographic distribution patterns of nine species were observed. In general, high accumulation rates of calcareous dinocysts were found around and south of 29°N and offshore the westernmost Canary Island La Palma, with slightly lower accumulation rates in the upwelling-influenced areas off Cape Yubi and in the upwelling filament area off Cape Ghir. Multivariate ordination techniques were applied in order to compare the cyst accumulation rates of individual species with physical parameters (temperature, salinity, density, mixed layer depth) and the trophic state (nitrate, phosphate and chlorophyll concentrations) of the overlying (sub-)surface waters. All species were found to relate significantly to one or more of the environmental parameters, partly confirming previous results on cyst ecology but also providing new information which will be useful for future palaeoenvironmental reconstructions within upwelling areas.     

基于线粒体COI基因分析钩手水母的群体遗传结构

钩手水母(Gonionemus vertens)为大西洋和太平洋广布种, 是我国习见的有毒水母种类之一。本文对采自黄渤海海域4个地理群体的104个钩手水母线粒体COI基因序列进行扩增, 并结合GenBank上其他182个钩手水母同源序列进行序列变异分析。在286个基因序列中共检测出52个多态位点, 定义了14种单倍型。总群体的单倍型多样性和核苷酸多样性分别为0.743 ± 0.012和1.046% ± 0.097%, 与其他几种大型水母相比, 钩手水母总群体的遗传多样性处于较高水平。AMOVA结果显示, 60.17%的分子变异源于群组间, 13.37%的分子变异源于群体内, 26.46%的分子变异源于组内群体间, 群组间、群体内和组内群体间的遗传分化均极显著。F_st值统计检验表明, 中国厦门群体与乐亭、东营、烟台、大连群体间存在显著的遗传分化, 大连与东营、烟台群体间也存在显著的遗传分化。系统分析结果显示, 钩手水母群体间存在2个明显的单倍型谱系分支。不同的钩手水母地理群体间具有复杂的遗传模式, 钩手水母复杂的生活史、扩散能力、地理隔离和海流分布可能是影响钩手水母遗传结构的重要因素。     

The new enneanuclear nickel carbonyl anion [Ni9(CO)16] and its relationships with the [Ni12(CO)21] and [Ni6Rh3(CO)17] clusters

The reaction of [N(PPh₃)₂]₂[Ni₆(CO)₁₂] with Cu(PPh₃)_xCl (x=1, 2), as well as the degradation of [N(PPh₃)₂]₂[H₂Ni₁₂(CO)₂₁] with PPh₃, affords the new and unstable dark orange–brown [N(PPh₃)₂]₂[Ni₉(CO)₁₆].THF salt in low yields. This salt has been characterized by a CCD X-ray diffraction determination, along with IR spectroscopy and elemental analysis. The close-packed two-layer metal core geometry of the [Ni₉(CO)₁₆]²⁻ dianion is directly related to that of the bimetallic [Ni₆Rh₃(CO)₁₇]³⁻ trianion and may be envisioned to be formally derived from the hcp three-layer geometry of [Ni₁₂(CO)₂₁]⁴⁻ by the substitution of one of the two outer [Ni₃(CO)₃(μ−CO)₃]²⁻ layers with a face-bridging carbonyl group.     

Effects of different nitrogen:phosphorus levels on the growth and ecological stoichiometry of Glycyrrhiza uralensis

Aims The increase in atmospheric nitrogen (N) deposition has accelerated N cycling of ecosystems, probably resulting in increases in phosphorus (P) demand of ecosystems. Studies on the effects of artificial N:P treatment on the growth and carbon (C), N, P ecological stoichiometry of desert steppe species could provide not only a new insight into the forecasting of how the interaction between soils and plants responses to long-term atmospheric N deposition increase, but also a scientific guidance for sustainable management of grassland in northern China under global climate change. Methods Based on a pot-cultured experiment conducted for Glycyrrhiza uralensis (an N-fixing species) during 2013 to 2014, we studied the effects of different N:P supply ratios (all pots were treated with the same amount of N but with different amounts of P) on aboveground biomass, root biomass, root/shoot ratio, and C:N:P ecological stoichiometry both in G. uralensis (leaves and roots) and in soils. Additionally, through the correlation analyses between biomass and C:N:P ecological stoichiometry in leaves, roots, and soils, we compared the differences among the C:N:P ecological stoichiometry of the three pools, and discussed the indication of C:N:P ecological stoichiometry in soils for the growth and nutrient uptake of G. uralensis. Important findings The results showed that, reducing N:P decreased C:P and N:P ratios both in G. uralensis (leaves and roots) and in soils but increased aboveground biomass and root biomass of G. uralensis, indicating that low to moderate P addition increased P availability of soils and P uptake of G. uralensis. However, excessive low N:P (high P addition) led to great decreases in soil C:P and N:P ratios, thus hindering N uptake and the growth of G. uralensis. C:N:P ratios in the two pools of G. uralensis (especially in leaves) had close correlations with soil C:N:P ratio, indicating that the change in soil C:N:P ratio would have a direct influence on plants. Our results suggest that, through regulating C:N:P ratio in leaves and soils, appropriate amounts of P addition could balance soil P supply and plant P demand and compensate the opposite influences of long-term atmospheric N deposition increase on the structure of desert steppe.     

Dihydroxamic acid complexes of iron (III): ligand pKa and coordinated water hydrolysis constants

A series of dihydroxamic acid ligands of the formula [RN(OH)C(O)]₂(CH₂)_n, (n = 2, 4, 6, 7, 8; R = CH₃, H) has been studied in 2.0 M aqueous sodium perchlorate at 25.0 °C. These ligands may be considered as synthetic analogs to the siderophore rhodotorulic acid. Acid dissociation constants (pK_a) have been determined for the ligands and for N-methylacetohydroxamic acid (NMHA). The pK_a1 and pK_a2 values are: n = 2, R = CH₃ (8.72, 9.37); N = 4, R = CH₃ (8.79, 9.37); N = 6, R = CH₃; N = 7, R = CH₃ (8.95, 9.47); N = 8, R = CH₃ (8.93, 9.45); N = 8, R = H (9.05, 9.58). Equilibrium constants for the hydrolysis of coordinated water (log K) have been estimated for the 1:1 feeric complexes of the ligands n = 2, 4, 8; R = CH₃. The N = 8 ligand forms a monomeric complex with Fe(III) while the n = 2 and 4 ligands form dimeric complexes. For hydrolysis of the n = 8 monomeric complex, log K₁ = −6.36 and log K₂ = −9.84. Analysis of the spectrophotometric data for the dimeric complexes indicates deprotonation of all four coordinated waters. The successive hydrolysis constants, log K_1–4, for the dimeric complexes are as follows: n = 2 (−6.37, −5.77, −10.73, −11.8); n = 4 (−5.54, −5.07, −11.57, −10.17). The log K₂ values for the dimers are unexpectedly high, higher in fact than log K₁, inconsistent with the formation of simple ternary hydroxo complexes. A scheme is proposed for the hydrolysis of the ferric dihydroxamate dimers, which includes the possible formation of μ-hydroxo and μ-oxo bridges.     

Characteristics of soil nitrogen mineralization in the rhizosphere of trees,shrubs, and herbs in subtropical forest plantations

为了探讨人工林内优势乔木和林下灌草根际土壤氮矿化特征, 明确乔灌草根际土壤氮转化差异, 该研究以江西泰和千烟洲站区典型人工杉木(Cunninghamia lanceolata)、马尾松(Pinus massoniana)和湿地松(Pinus elliottii)林为对象, 在植被生长季初期(4月)和旺盛期(7月)分析3种人工林内乔木、优势灌木(檵木(Loropetalum chinense)、杨桐(Adinandra millettii)、格药柃(Eurya muricata))和草本(狗脊蕨(Woodwardia japonica)、暗鳞鳞毛蕨(Dryopteris atrata))根际土壤的净氮矿化速率、土壤化学性质及土壤微生物特征。结果发现: 1)物种、林型和取样季节显著影响了根际土壤净氮矿化速率(N_min)、净铵化速率(N_amm)和净硝化速率(N_nit)。马尾松和湿地松林内林下灌草根际土壤净氮矿化的季节敏感性高于乔木: 4月乔木根际土壤N_min和N_amm显著高于大多数林下灌草, 而7月林下灌草根际土壤N_min和N_amm显著提高, 与乔木不再具有显著差异, 与主成分综合得分方差分析的结果一致。一般情况下, 杉木林N_min和N_nit显著高于马尾松林和湿地松林。7月净氮矿化显著高于4月。2)土壤铵态氮、硝态氮、全氮及土壤微生物量氮含量是影响根际土壤净氮矿化的主要因素。土壤化学性质对人工林根际土壤净氮矿化变异的贡献率为29.2%, 显著高于土壤微生物的解释率。充分考虑不同季节林下植被根际土壤的净氮矿化及其关键影响因素可为准确评估人工林生态系统养分循环状况提供重要支撑。     

亚热带人工林乔灌草根际土壤氮矿化特征

为了探讨人工林内优势乔木和林下灌草根际土壤氮矿化特征, 明确乔灌草根际土壤氮转化差异, 该研究以江西泰和千烟洲站区典型人工杉木(Cunninghamia lanceolata)、马尾松(Pinus massoniana)和湿地松(Pinus elliottii)林为对象, 在植被生长季初期(4月)和旺盛期(7月)分析3种人工林内乔木、优势灌木(檵木(Loropetalum chinense)、杨桐(Adinandra millettii)、格药柃(Eurya muricata))和草本(狗脊蕨(Woodwardia japonica)、暗鳞鳞毛蕨(Dryopteris atrata))根际土壤的净氮矿化速率、土壤化学性质及土壤微生物特征。结果发现: 1)物种、林型和取样季节显著影响了根际土壤净氮矿化速率(N_min)、净铵化速率(N_amm)和净硝化速率(N_nit)。马尾松和湿地松林内林下灌草根际土壤净氮矿化的季节敏感性高于乔木: 4月乔木根际土壤N_min和N_amm显著高于大多数林下灌草, 而7月林下灌草根际土壤N_min和N_amm显著提高, 与乔木不再具有显著差异, 与主成分综合得分方差分析的结果一致。一般情况下, 杉木林N_min和N_nit显著高于马尾松林和湿地松林。7月净氮矿化显著高于4月。2)土壤铵态氮、硝态氮、全氮及土壤微生物量氮含量是影响根际土壤净氮矿化的主要因素。土壤化学性质对人工林根际土壤净氮矿化变异的贡献率为29.2%, 显著高于土壤微生物的解释率。充分考虑不同季节林下植被根际土壤的净氮矿化及其关键影响因素可为准确评估人工林生态系统养分循环状况提供重要支撑。     

北京西山绿化树种秋季滞纳PM2.5能力及其与叶表面AFM特征的关系

以北京西山6种绿化树种白皮松、油松、柳树、五角枫、银杏、山杨为对象,应用气溶胶再发生器对植物叶片秋季PM_2.5吸附量进行定量研究,同时应用原子力显微镜(AFM)观察叶表面微形态特征,分析了叶表面粗糙度等参数,阐释了各树种叶片吸附PM_2.5的机制.结果表明: 不同树种单位叶面积PM_2.5吸附量排序为白皮松(2.44±0.22 μg·cm^-2)＞油松(2.40±0.23 μg·cm^-2)＞柳树(1.62±0.09 μg·cm^-2)＞五角枫(1.23±0.01 μg·cm^-2)＞银杏(1.00±0.07 μg·cm^-2)＞山杨(0.97±0.03 μg·cm^-2);从秋季不同月份来看,不同树种单位叶面积PM_2.5吸附量表现为11月(2.33±0.43 μg·cm^-2)＞10月(1.62±0.64 μg·cm^-2)＞9月(1.51±0.50 μg·cm^-2).白皮松和油松有大量凹陷和突起,相对高差较大,粗糙度较大,吸滞PM_2.5能力强;柳树和五角枫叶片有褶皱,粗糙度相对较高,分布有大量的突起和凹陷,吸滞PM_2.5能力居中;银杏和山杨因其叶表面平滑、气孔多为长圆形,粗糙度较小,吸滞PM_2.5能力较弱.不同树种正背面粗糙度平均值为白皮松(149.91±16.38 nm)＞油松(124.47±10.52 nm)＞柳树(98.85±5.36 nm)＞五角枫(93.74±21.75 nm)＞银杏(80.84±0.88 nm)＞山杨(67.72±8.66 nm),这与不同树种单位叶面积PM_2.5吸附量排序完全一致,叶片粗糙度与单位叶面积PM_2.5吸附量呈显著正相关(R²=0.9498).为提高城市植被的环境效应,可选择叶表面形态有利于吸滞PM_2.5等颗粒物的树种.     

Chemical composition, nutritive value, fatty acid and amino acid contents of Galega officinalis L. during its growth stage and in regrowth

The aim of this study was to determine the chemical composition, nutritive value, fatty acid profile and amino acid concentrations of Galega officinalis L. during its first growth cycle and in regrowth. Herbage samples were collected three times at progressive morphological stages from the vegetative to the budding stage, and during regrowth. The dry matter (DM), organic matter (OM), neutral detergent fibre (NDFom), acid detergent fibre (ADFom), lignin (sa) and gross energy (GE) increased during maturation, while the crude protein (CP), ether extract (EE), ash and OM digestibility (OMD) decreased with increasing stage. During the whole growth cycle, and in regrowth, the NE_L was unchanged. Analyses of fatty acids did not reveal differences among plant stages, but did instead between the first cut and regrowth cut. The fatty acid profiles in the plant during growth was characterised by three dominant fatty acids, being -linolenic acid (C_{18:3n − 3}), palmitic acid (C_16:0), and linoleic acid (C_{18:2n − 6}). The -linolenic acid content was instead lower than in the whole plant during growth. The n − 6/n − 3 polyunsaturated fatty acid ratio of the plant was steady at 0.13 during the growth cycle and in regrowth, while it was 0.78 in the seed. The individual amino acid contents of G. officinalis declined with increasing stage of maturity, as the CP declined, but with the exception of the serine content, there was no change in the relative proportions of the individual amino acids due to stage of maturity. Data shows that the nutritive value of G. officinalis forage did not diminish during its growth cycle and that it can improve the self sufficiency of dairy farms. Autumn regrowth was judged to be a good quality forage with a high nutritive value and a higher level of -linolenic acid than during the first growth cycle.     

A modelling exploration of vertical migration by phytoplankton

The behaviour of phytoplankton having different abilities to assimilate N in darkness was considered in simulations of vertical migrations. Such behaviour is especially important for the competitive advantage of flagellates, including harmful algal species. Three phases of biomass development were apparent. (1) Cells remained at a subsurface location with migration down to avoid photoinhibitory light at midday; as the attenuation of light increased with biomass growth, the mean depth became shallower. (2) On exhaustion of nutrients in surface waters, cells migrated down through the nutricline in the latter half of the daylight period, with a subsurface maximum in the photic zone as long as light penetration matched requirements. When that condition was no longer met (3), cells migrated between the very surface (forming dense aggregations) and the nutricline. While the ability to perform dark N-assimilation is not critical when N-sources are available at low concentrations, it is important when (as encountered following migration down to a nutricline), nutrients are available at higher concentration in darkness. The most advantageous configuration tested, where nitrate assimilation (as well as that of ammonium) continued at a high rate in darkness as long as C-reserves remained, is not actually used in migratory species but in non-migratory diatoms. The use of the outwardly inferior configurations typical of migratory species, in which dark nitrate-assimilation is notably poorer than assimilation in the light, reflects a deficient metabolism or indicates that N-sources other than nitrate are more important. It is unfortunate then that most attention has been paid to nitrate nutrition in experiments on migrating species. While an ability to continue N-assimilation in darkness as well as during daylight is advantageous, there is no evidence for phytoplankton to be able to grow at high growth rates when decoupling photosynthesis at the surface and N-assimilation at depth.     

长山列岛邻近海域鱼类群落种类组成和多样性时空变化

为了解黄、渤海生态系统交错带长山列岛邻近水域鱼类群落种类组成和多样性,根据2016年10月,2017年1月、5月及8月进行的鱼类资源底拖网调查数据,应用相对重要性指数、物种多样性指数、k优势度曲线等方法,研究了长山列岛邻近海域鱼类群落种类组成、物种多样性时空变化及其与环境因子的关系。结果表明: 该海域共计捕获鱼类77种,以温水性、底层、洄游性鱼类为主,优势种组成季节变化明显,春季、冬季主要优势种为黄鮟鱇,夏季以日本鲭、鳀等中上层鱼类为主。全年共计出现洄游性鱼类46种,季节间物种迁移指数均在100以上,其中秋季物种迁移指数最大。鱼类群落物种丰富度指数在春季最高、Shannon多样性指数和均匀度指数在秋季最高。夏季物种丰富度指数与表层水温呈显著负相关;冬季物种丰富度指数与水深、底层水温呈极显著正相关,Shannon多样性指数与底层水温呈极显著正相关。长山列岛邻近海域作为黄、渤海两大生态系统的交错带,鱼类群落表现出高物种多样性、洄游种多以及明显的时空异质性。