一座南亚热带小型水库水体营养状态与浮游植物的季节变化

小型水库是华南沿海地区重要的城市供水水源。为了解小型水库的富营养化状况与浮游植物群落结构和季节动态之间的关系,于2006年4月、8月、12月采样测定了木头冲水库的环境因子(温度、pH、透明度、氮、磷营养盐浓度)和浮游植物群落结构。结果表明水体中总氮浓度的变化范围在0.34～0.7mg·L^-1之间,总磷浓度的变化范围在0.011～0.019mg·L^-1之间,透明度的变化范围在0.6～1.5m之间,叶绿素a浓度的变化范围在9.18～21.1mg·m^-3之间,依据上述4个指标计算得出的TSI_M指数在30～50之间变化,说明木头冲水库属中营养水体。浮游植物以适宜在中营养水体中生长的种类为主,3次采样共检出浮游植物52种(属),主要由在绿藻门和硅藻门的种类组成。浮游植物生物量的变化范围在4.17～5.38mg·L^-1之间,春夏两季的生物量高于冬季。硅藻门的颗粒直链藻(Aulacoseira granulata)和绿藻门的单针藻(Monoraphidium sp.)是水体中春季的优势种类,夏季浮游植物的优势种为绿藻门的鼓藻(Cosmarium spp.)和硅藻门的颗粒直链藻,随着氮浓度的下降,拟柱胞藻(Cylindrospermopsis rackiborskii)成为水库冬季的优势种类。营养盐是木头冲水库浮游植物变化的主要影响因子。     

一座南亚热带小型贫营养水库浮游植物群落结构及季节变化

库容大小是影响水体水动力学过程的一个重要变量,它能在很大程度决定生态系统的结构,特别是浮游植物的群落结构.为了解小型贫营养水库浮游植物的群落特点,于2006年4、8、12月对位珠海市的贫营养小型水库-吉大水库的浮游植物群落结构进行采样和计数分析.3次采样共检出浮游植物32种,浮游植物细胞丰度的变化范围在69～342 cells·mL^-1,生物量的变化范围在1.34～3.69 mg·L^-1,夏季浮游植物的丰度和生物量明显高于冬季.甲藻是最主要的优势种类,且相对优势度较为稳定.夏季,隐藻门的隐藻(Cryptomonas sp.)和绿藻门的鼓藻(Cosmarium spp.)大量出现,甲藻的相对优势度有所降低.冬季,隐藻数量急剧下降,但硅藻门的颗粒直链藻(Aulacoseira granulata)大量出现,与甲藻共同成为水体中的优势种.由降雨引起的营养盐浓度增加是浮游植物变化的主要影响因子,而透明度全年维持较高的水平为浮游植物的生长形成了有利条件,此外,较为稳定的水体和甲藻利用营养盐的能力使得甲藻成为浮游植物中的最主要的优势种.     

浙南大罗山天河水库浮游植物群落结构的季节变化及对水质的指示作用

为了探究浙南地区山区水库浮游植物群落结构的季节变化及水质状况,于2019年2月—2020年1月对位于温州大罗山天河水库的浮游植物群落结构和水体理化因子进行了调查分析。结果表明: 天河水库浮游植物隶属于7门60属89种,全年浮游植物平均丰度为2.02×10⁵ cells·L^-1,年均生物量为0.26 mg·L^-1。硅藻门在全年均占优势,绿藻门在春、秋季占优势,而蓝藻门仅在夏季占优势,裸藻门和甲藻门在全年均有出现,隐藻门在秋、冬季均有出现,但不占优势。全年主要优势种有颗粒直链藻、尖针杆藻、隐头舟形藻、美丽星杆藻、假鱼腥藻、小新月藻、二角盘星藻、二角多甲藻、圆筒锥囊藻、卵形隐藻。冗余分析(RDA)显示,水库的水温、总氮、化学需氧量(COD_Mn)和 pH值是浮游植物群落结构的主要影响因子。分别运用Shannon指数、Pielou均匀度指数和Margalef丰富度指数,并结合浮游植物的丰度、优势种及综合营养状态指数分析了水体污染情况和富营养程度, 结果显示,天河水库水体介于寡污染到清洁水体带之间,为贫-中营养型水体。     

横岗水库浮游植物种类组成与时空分布

于2005年5月和11月调查了横岗水库的水质和浮游植物,对浮游植物群落结构进行了分析.两次采样期间,浮游植物群落数量组成与种类结构发生明显变化.5月份浮游植物平均细胞数量高达275.41×10⁶cells·L^-1,平均生物量为31.07mg·L^-1;其中优美平裂藻(Oscillatoria.elegans)和银灰平列藻(Oscillatoria.glauca)为绝对优势种,占总细胞数的90%;平裂藻的大量出现导致浮游植物生物量由球体等效半径在10～20μm的种类占主导,但0～5μm区间的小型藻类仍维持较高的生物量.11月份,浮游植物平均细胞数量降低到12.69×10⁶cells·L^-1,平均生物量为20.78mg·L^-1.蓝藻门有16种,优美平裂藻、银灰平列藻的优势度明显下降;绿藻种类数量增加到48种,在新出现的25个种类中,鼓藻科(Desmidiaceae)、盘星藻属(Pediastrum)和栅藻属(Scenedesmus)有较高的细胞数;优势种类没有变化;大细胞种类的生物量明显增加,特别是等效半径大于20μm的种类.整体上看,浮游植物数量和生物量从河流入水口到大坝处有递减趋势,这种趋势在11月份更为明显,这与采样时期水库水动力过程的梯度相一致.     

3座热带亚热带水库枯水期浮游植物的脂肪酸组成特征

测定和分析了热带亚热带地区的3座大型水库———流溪河、飞来峡和公平水库枯水期浮游植物的脂肪酸组成,探讨了热带亚热带地区浮游植物的群落特征与脂肪酸组成之间的关系以及脂肪酸组成特征与水体营养状态之间的关系。3座水库的浮游植物数量很低,没有形成明显的优势种类,但以硅藻的相对丰度较高。公平水库各门类浮游植物的数量均高于流溪河和飞来峡水库,尤其是硅藻的数量。10月份3座水库的营养状态相差较大,流溪河水库接近贫营养状态,公平水库处于中营养状态,而飞来峡水库则处于贫-中营养状态。12月份3座水库均处于中营养状态。3座水库的脂肪酸浓度较低,处于1.783—9.808μg/L之间。两次采样相比,10月份流溪河水库和飞来峡水库的浮游植物脂肪酸种类较多,各种脂肪酸的浓度也相对较高,检测到EPA和DHA,公平水库仅检测到饱和脂肪酸;12月份,3座水库的脂肪酸组成简单,除飞来峡水库检测到2种单不饱和脂肪酸(C16:1和C18:1)外,3座水库只检测到饱和脂肪酸。因此水库的脂肪酸组成特征反映了这3座水库的富营养化程度的差别。另外公平水库两次调查的浮游植物脂肪酸只有饱和脂肪酸,浮游动物难以有效利用,这有可能是该水库浮游植物生物量高的一个重要原因。从本研究结果来看,应用脂肪酸组成对浮游植物群落结构和富营养化水平的指示是灵敏而可行的。     

南亚热带大型贫营养水库浮游植物群落结构与季节变化——以新丰江水库为例

新丰江水库是我国第四大的水库,也是广东省最大的水库和重要的水源地。于2004～2005年2月一次调查了新丰江水库水文、水质和浮游植物分布,分析了浮游植物群落季节动态特征。新丰江水库浮游植物生物量比较低,在0．037—1．497mg·L^-1之间变化。浮游植物种类较多,11次采样共检到158种。在丰度上,水库浮游植物主要以小环藻、蓝纤维藻、小球藻和纤维藻等优势种为主,而在生物量上则以微小多甲藻为优势。浮游植物组成随季节变化而不同,春季以硅藻、甲藻和绿藻为优势类群;夏季以蓝藻、绿藻和硅藻为优势类群;秋季蓝、绿藻减少而硅藻和甲藻增加。2004年的浮游植物季节性变化更为明显,有从硅藻-绿藻优势（2月和4月份）,到蓝藻-绿藻优势（6月和8月份）,到混合优势（10月份）和金藻优势（12月份）这样一个变化过程。2005年硅藻的相对丰度比2004年高出很多。两年浮游植物组成的差异与两年的降水量有关。水动力学对丰水期（6～8月份）浮游植物组成结构有较大影响,导致硅藻和绿藻相对丰度的增加。与温带贫营养型水库相比,新丰江水库的浮游植物群落具有春季和秋季种类多、夏季的蓝藻种类丰富的特点。从细胞大小分布上看,小于20μm浮游植物是生物量的主要贡献者,其次是大于45μm的浮游植物。在粒径小于20μm的浮游植物中,微小多甲藻是最主要的贡献者。浮游植物群落的大小分布受水动力学条件和营养盐浓度动态的影响。     

富营养水体生物修复中浮游植物的群落特征

通过对生物修复中富营养小水体浮游植物群落的分析,探讨了生物修复对浮游植物的影响以及浮游植物对环境因子改变的响应。生物修复实施后的浮游植物种类数比实施前多;浮游植物细胞数和生物量却有明显的下降;而对于Shannon Weaver多样性指数,实施后较实施前有明显的上升;生物修复过程中美丽胶网藻水华得到控制,优势种的指示性由中污变为寡污,优势度也由极度的高优势变为中低度优势,水体治理的前期阶段浮游植物群落的种类组成和结构有明显的改变;浮游植物种类数分别与正磷酸盐和氮磷比呈显著负、正相关,正磷酸盐的浓度与氮磷比的大小对水体浮游植物的种群结构变化具有重要影响。       

营养盐加富和鱼类添加对浮游植物群落演替和多样性的影响

浮游植物是水体生态系统敞水区最重要的初级生产者,其组成与多样性反映了群落的结构类型和存在状态。通过围隔实验,模拟水库春季发生的营养盐加富和鱼类放养的干扰,分析在这两种干扰下的浮游植物群落演替过程中优势种和稀有种的变化,并通过以丰度与生物量为变量的香农和辛普森多样性指数的计算,分析浮游植物群落演替过程中的多样性变化特征。结果表明,营养盐加富干扰下的浮游植物群落的优势种变化和演替更为明显,营养盐加富与鱼类添加对浮游植物群落多样性变化的影响符合中度干扰理论。在优势种优势度变化较大的浮游植物群落演替过程中,多样性指数与浮游植物生物量有较高的负相关性。在浮游植物群落演替过程中,香农和辛普森多样性指数的变化趋势基本一致,采用丰度与生物量为变量的两种多样性指数的计算结果对实验系统中浮游植物群落多样性的分析结果没有明显的影响。     

贵州高原猫跳河流域浮游植物功能群组成特征及其与环境因子之间的关系

猫跳河是典型喀斯特河流,其下游水库为贵阳市重要饮用水源。为探究猫跳河流域浮游植物功能群组成的动态变化特征及其与环境因子的相关性,基于冗余分析、相关性分析方法,于2020年6月、8月和11月对浮游植物与理化指标进行采样分析。结果表明：猫跳河流域调查期间共检出浮游植物7门67种(属),其中绿藻门种类最多;浮游植物群落结构呈时空异构,各采样断面浮游植物细胞丰度变化范围为0.11×10⁶～17.71×10⁶ cells·L^-1,生物量变化范围为29.85～1256.16μg·L^-1;猫跳河流域浮游植物可划分为24个功能群,其中B、MP、S1、Y和D为猫跳河流域主要优势功能群,功能群D的生物量在8月达到峰值1256.85μg·L^-1,主要优势功能群适应生境均为浑浊的中富营养水体;浮游植物功能群呈现显著时间演替特征。冗余分析结果显示：水温、pH和电导率是影响猫跳河流域浮游植物功能类群动态分布的主要环境因素。     

罗非鱼对附着藻类和浮游植物的影响

鱼类通过牧食和营养盐排泄可以对水体生态系统产生影响,杂食性鱼类由于可摄食不同生境中的食物,可使生境之间的耦合作用发生变化。罗非鱼是我国南方很多水体的优势种,食物包括敞水生境的浮游植物和基质表层生境的附着藻类等。为了解罗非鱼对浮游植物和附着藻类的影响,实验在室外模拟条件下,分别设置罗非鱼组和无鱼对照组的两组处理,分析了罗非鱼对附着藻类及浮游植物生物量(叶绿素a)等的影响。结果表明:(1)罗非鱼显著地降低了附着藻类生物量,罗非鱼组中的附着藻类叶绿素a的平均值为0.15 mg·cm^-2,显著低于对照组中的1.26mg·cm^-2;(2)罗非鱼显著地增加了浮游植物的生物量,罗非鱼组中的浮游植物叶绿素a平均值为31.99μg·L^-1,显著高于对照组中的14.99μg·L^-1。研究结果显示,杂食性的罗非鱼可以促进系统的附着藻类向浮游植物转化。从控制浮游植物生物量的角度看,湖泊等水体的管理应该对罗非鱼密度加以有效控制。     

Ca-Cd interaction in the prymnesiophyte Cricosphaera elongata

Abstract. ⁴⁵Ca and ¹⁰⁹Cd uptake were followed in Criscosphaera elongata Prymnesiophyceae. In both cases, after a rapid increase for the first 5 min, the incorporation rate slowed during the hour of observation. Verapamil, a blocker of voltage-dependent slow calcium channels, inhibited ⁴⁵Ca uptake except during the first rapid phase when adsorption should predominate. Cadmium also decreased ⁴⁵Ca labelling, suggesting that the two metals are antagonistic. However, verapamil was shown to augment ¹⁰⁹Cd incorporation, contrary to what occurs in animals cells; this effect is detectable in continuous labelling as well as in pulse experiments. The data support the presence of calcium channels in the alga and suggest several processes in Cd accumulation: adsorption on peripheral envelopes and diffusion of uncharged Cd.     

Defects in mitochondrial DNA replication and oxidative damage in muscle of mtDNA mutator mice

A causal role for mitochondrial dysfunction in mammalian aging is supported by recent studies of the mtDNA mutator mouse (“PolG” mouse), which harbors a defect in the proofreading-exonuclease activity of mitochondrial DNA polymerase gamma. These mice exhibit accelerated aging phenotypes characteristic of human aging, including systemic mitochondrial dysfunction, exercise intolerance, alopecia and graying of hair, curvature of the spine, and premature mortality. While mitochondrial dysfunction has been shown to cause increased oxidative stress in many systems, several groups have suggested that PolG mutator mice show no markers of oxidative damage. These mice have been presented as proof that mitochondrial dysfunction is sufficient to accelerate aging without oxidative stress. In this study, by normalizing to mitochondrial content in enriched fractions we detected increased oxidative modification of protein and DNA in PolG skeletal muscle mitochondria. We separately developed novel methods that allow simultaneous direct measurement of mtDNA replication defects and oxidative damage. Using this approach, we find evidence that suggests PolG muscle mtDNA is indeed oxidatively damaged. We also observed a significant decrease in antioxidants and expression of mitochondrial biogenesis pathway components and DNA repair enzymes in these mice, indicating an association of maladaptive gene expression with the phenotypes observed in PolG mice. Together, these findings demonstrate the presence of oxidative damage associated with the premature aging-like phenotypes induced by mitochondrial dysfunction.     

Mass-spectrometric investigations on hydration of nucleic acid components in vacuum. II. N-methylated adenines

Association reactions between water and N-methylated adenines (M), occurring under field-ionization conditions in a mass spectrometer at the tungsten point emitter surface, were studied at a number of temperatures. The origin of the peaks observed in the mass spectra at m/e ratios corresponding to MH+ was assigned to M X H2O monohydrates , of those corresponding to (MH X H2O)+ and (MH2)2+ to double hydrates M(H2O)3. Measurements of the relative peak intensities allowed calculation of apparent equilibrium constants, Kass, for successive hydration steps, and hence the respective van't Hoff enthalpies of hydration. Both the equilibrium and the energy parameters obtained support the available quantum-mechanical single-layer hydration schemes of adenine and of its N-methylated derivatives.     

Shifts in thermoregulatory strategy during ontogeny in harp seals (Pagophilus groenlandicus)

Heat balance can be difficult for young and/or small animals in polar regions because environmental conditions in combination with small body size or physiological immaturity can increase heat loss. We investigated how thermoregulatory patterns change with ontogeny in 5 age classes of harp seal (Pagophilus groenlandicus) from birth to post-molt to further understand the timing of thermoregulatory development in relation to their potential vulnerability to ongoing fluctuations in the extent and stability of Arctic pack ice. We measured changes in the amount, conductivity, and resistance of the seal pups׳ insulative layers (blubber and fur), the potential for endogenous heat-generation by shivering (muscle enzyme activity), and nonshivering thermogenesis (NST; brown adipose tissue (BAT) uncoupling protein 1 (UCP1) expression and mitochondrial density). There was no significant difference in blubber conductivity among age classes, though the amount of blubber insulation significantly increased from birth to weaning. Pelage conductivity was low (0.12±0.01 W m⁻¹ °C⁻¹) except in 9-day old pups (0.40±0.08 W m⁻¹ °C⁻¹); the significantly higher conductivity may signal the beginning of the molt, and this age group may be the most vulnerable to early water entry. Citrate synthase activity significantly increased (49.68±3.26 to 75.08±3.52 μmol min⁻¹ g wet weight⁻¹) in the muscle; however it is unlikely that increasing a single enzyme greatly impacts heat generation. BAT of younger pups contained UCP1, though expression and mitochondrial density quickly declined, and the ability of pups to produce heat via NST was lost by weaning. While total thermal resistance did not differ, neonatal and early nursing animals gained the majority of their thermal resistance from lanugo (82.5±0.03%); however, lanugo is not insulative when wet, and NST may be important to maintain euthermia and dry the coat if early immersion in water occurs. By late nursing, blubber seems sufficient as insulation (75.87±0.01% of resistance after 4 weeks), but high conductivity of fur may be responsible for retention of UCP1 expression. Weaned animals rely on blubber insulation, and no longer need NST, as wetted fur is no longer a threat to euthermia.     

Role of antigen presentation in the production of pro-inflammatory cytokines in obese adipose tissue

Type II diabetes regroups different physiological anomalies that ultimately lead to low-grade chronic inflammation, insulin resistance and loss of pancreatic β-cells. Obesity is one of the best examples of such a condition that can develop into Metabolic Syndrome, causing serious health problems of great socio-economic consequences. The pathological outcome of obesity has a genetic basis and depends on the delicate balance between pro- and anti-inflammatory effectors of the immune system. The causal link between obesity and inflammation is well established. While innate immunity plays a key role in the development of a pro-inflammatory state in obese adipose tissues, it has now become clear that adaptive immune cells are also involved and participate in the cascade of events that lead to metabolic perturbations. The efficacy of some immunotherapeutic protocols in reducing the symptoms of obesity-driven metabolic syndrome in mice implicated all arms of the immune response. Recently, the production of pathogenic immunoglobulins and pro-inflammatory cytokines by B and T lymphocytes suggested an auto-immune basis for the establishment of a non-healthy obese state. Understanding the cellular landscape of obese adipose tissues and how immune cells sustain chronic inflammation holds the key to the development of targeted therapies. In this review, we emphasize the role of antigen-presenting cells and MHC molecules in obese adipose tissue and the general contribution of the adaptive arm of the immune system in inflammation-induced insulin resistance.     

Differential changes in galactolipid and phospholipid species in soybean leaves and roots under nitrogen deficiency and after nodulation

The availability of nitrogen (N) to plants has a profound impact on carbohydrate and protein metabolism, but little is known about its effect on membrane lipid species. This study examines the changes in galactolipid and phospholipid species in soybean as affected by the availability of N, either supplied to soil or obtained through Bradyrhizobium japonicum nodulation. When N was limited in soil, the content of galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacyglycerol (DGDG), decreased drastically in leaves, while a smaller decrease of DGDG was observed in roots. In both leaves and roots, the overall content of different phospholipid classes was largely unchanged by N limitation, although some individual phospholipid molecular species did display significant changes. Nodulation with Bradyrhizobium of soybean grown in N-deficient soil resulted in a large increase in levels of plastidic lipid classes, MGDG, DGDG, and phosphatidylglycerol, along with smaller increases in non-plastidic phospholipids in leaves. Nodulation also led to higher levels of phospholipids in roots without changes in root levels of MGDG and DGDG. Overall, N availability alters lipid content more in leaves than roots and more in galactolipids than phospholipids. Increased N availability leads to increased galactolipid accumulation in leaves, regardless of whether N is supplied from the soil or symbiotic fixation.     

Oxoeicosanoid signaling mediates early antimicrobial defense in zebrafish

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Mode of action of allatostatins in the regulation of juvenile hormone biosynthesis in the cockroach,Diploptera punctata

The FGLamide allatostatins (FGL/ASTs) are a family of neuropeptides with pleiotropic functions, including the inhibition of juvenile hormone (JH) biosynthesis, vitellogenesis and muscle contraction. In the cockroach, Diploptera punctata, thirteen FGLa/ASTs and one allatostatin receptor (AstR) have been identified. However, the mode of action of ASTs in regulation of JH biosynthesis remains unclear. Here, we determined the tissue distribution of Dippu-AstR. And we expressed Dippu-AstR in vertebrate cell lines, and activated the receptor with the Dippu-ASTs. Our results show that all thirteen ASTs activated Dippu-AstR in a dose dependent manner, albeit with different potencies. Functional analysis of AstR in multiple cell lines demonstrated that activation of the AstR receptor resulted in elevated levels of Ca²⁺ and cAMP, which suggests that Dippu-AstR can act through the Gα_q and Gα_s protein pathways. The study on the target of AST action reveals that FGL/AST affects JH biosynthesis prior to the entry of acetyl-CoA into the JH biosynthetic pathway.