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大亚湾浮游植物粒级结构对温排水和营养盐输入的响应
No full text大亚湾核电站温排水对其邻近海域的生态效应日益突出。文章结合现场调查和室内模拟实验,研究了夏季和冬季大亚湾海域沿温排水温度梯度的浮游植物粒径结构特征,探讨了营养物质的输入可能对其产生的影响,以期深入了解浮游植物对升温以及富营养化作用的响应机制。结果表明,适温条件对浮游植物的生长起促进作用,在极高温(36.0℃)环境下则产生抑制作用,在排水口邻近高温区夏季和冬季浮游植物叶绿素a含量均呈较低分布。交互模拟实验发现不同季节浮游植物对于温度和营养盐的敏感性存在差异,夏季营养盐对浮游植物生长的促进作用比温度明显,冬季温度的作用则更为显著。现场观测和模拟实验均显示,水温升高和营养盐加富均可造成小粒级浮游植物(<20μm)所占比例的增加;因此,升温和营养盐输入均可能导致浮游植物粒级结构呈小型化趋势,并对食物网能量流动与物质循环、生态系统的结构稳定性以及海洋渔业的产量造成潜在影响
两种造礁石珊瑚对海水酸化和溶解有机碳加富的响应
No full text文章选择鹿回头近岸海域常见的板叶角蜂巢珊瑚(Favites complanata)和十字牡丹珊瑚(Pavona decussata)为研究对象,采用室内连续培养的方法,探究两种不同造礁石珊瑚对酸化和溶解有机碳(DOC)加富的响应。结果表明:酸化(p H7.6)并不会影响两种珊瑚的钙化速率和生长速率;但DOC加富(524.03±78.42μmol?L-1)使两种珊瑚的钙化速率分别降低67%和47%、生长速率降低59%和40%。当二者共同作用时,两种珊瑚的钙化速率降低30%和11%、生长速率降低46%和59%,大多没有DOC单独作用时强烈,表现出一定的拮抗作用。两种珊瑚共生虫黄藻叶绿素荧光指数(Fv/Fm)均升高后降低,板叶角蜂巢珊瑚Fv/Fm最先降低。实验表明,这两种珊瑚虽然对海洋酸化的敏感度不高,但是对有机物加富有不同的响应,板叶角蜂巢珊瑚更为敏感,可能导致这两种珊瑚在未来环境变化中有不同命运
Copper bioaccumulation and biokinetic modeling in marine herbivorous fish Siganus oramin
No full textMarine herbivorous fish directly consume macroalgae, which commonly accumulate high levels of trace metals in polluted areas. We proposed that herbivorous fish could be better candidates for biomonitoring marine metal pollution than carnivorous fish. To date, the trophic transfer of Cu from macroalgae to marine herbivorous fish is unclear. In this study, the kinetics of Cu bioaccumulation in a widespread marine herbivorous fish, Siganus oramin, were investigated, and biokinetic modeling was applied to estimate the Cu levels in the fish sampled from different sites and seasons. The results showed that Cu accumulation in the fish was linearly correlated to the dietary Cu levels in the different prey species, which were proportional to the waterborne Cu concentrations. The Cu found in the subcellular trophically available metal fraction (TAM) in the prey contributed the largest proportion of accumulated Cu in S. oramin. The dietary assimilation efficiencies (AEs) of Cu were 15.56 +/- 1.76%, 13.42 +/- 2.86%, and 21.36 +/- 1.47% for Ulva lactuca, Gracilaria lemaneiformis and Gracilaria gigas, respectively. The calculated waterborne uptake rate constant (k(u)) of Cu was 0.023 +/- 0.011 L g(-1) d(-1), and the efflux rate constant (k(e)) was 0.055 +/- 0.021 (d(-1). Dietary Cu accounted for 60%-75% of the body Cu in S. oramin, suggesting that dietary uptake could be the primary route for Cu bioaccumulation in herbivorous fish. The biokinetic model demonstrated that the Cu concentrations in the water and fish presented a positive linear relationship, which was in line with our field investigation along the coastal areas of South China. Therefore, we suggested that S. oramin could be used as a biomonitoring organism for Cu pollution in the marine environment. However, the heterogeneities between the predicted levels and the measured levels of Cu implied that seasonal changes should be taken into account to improve the accuracy of the model
Increased temperature mitigates the effects of ocean acidification on the calcification of juvenile Pocillopora damicornis, but at a cost
No full textThis study tested the interactive effects of increased seawater temperature and CO2 partial pressure (pCO(2)) on the photochemistry, bleaching, and early growth of the reef coral Pocillopora damicornis. New recruits were maintained at ambient or high temperature (29 or 30.8 A degrees C) and pCO(2) (similar to 500 and similar to 1100 mu atm) in a full-factorial experiment for 3 weeks. Neither a sharp decline in photochemical efficiency (Fv/Fm) nor evident bleaching was observed at high temperature and/or high pCO(2). Furthermore, elevated temperature greatly promoted lateral growth and calcification, while polyp budding exhibited temperature-dependent responses to pCO(2). High pCO(2) depressed calcification by 28% at ambient temperature, but did not impact calcification at 30.8 A degrees C. Interestingly, elevated temperature in concert with high pCO(2) significantly retarded the budding process. These results suggest that increased temperature can mitigate the adverse effects of acidification on the calcification of juvenile P. damicornis, but at a substantial cost to asexual budding
Diisonitrile Natural Product SF2768 Functions As a Chalkophore That Mediates Copper Acquisition in Streptomyces thioluteus
No full textA nonribosomal peptide synthetase (NRPS) gene duster (sfa) was identified in Streptomyces thioluteus to direct the biosynthesis of the diisonitrile antibiotic SF2768. Its biosynthetic pathway was reasonably proposed based on bioinformatics analysis, metabolic profiles of mutants, and the elucidation of the intermediate and shunt product structures. Bioinformatics-based alignment found a putative ATP-binding cassette (ABC) transporter related to iron import within the biosynthetic gene: cluster, which implied that the product might be a siderophore. However, characterization of the metal-binding properties by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), metal-ligand titration, thin-layer chromatography (TLC), and chrome azurol S (CAS) assays revealed that the final product SF2768 and its diisonitrile derivatives specifically bind :topper, rather than iron, to forth. stable complexes. Inductively coupled plasma mass spectrometry (ICP-MS) analysis revealed that the intracellular cupric content of S. thioluteus significantly increased upon incubation with the copper-SF2768 complex, direct evidence for the copper, acquisition function of SF2768. Further in vivo functional characterization of the transport elements for the copper-SF2768 complexes not only confirmed the chalkophore identity of the compound but also gave initial clues into the copper uptake mechanism of this nonmethanotrophic microorganism
Pelagibacterium lentulum sp nov., a marine bacterium from the culture broth of Picochlorum sp 122
No full textA Gram-stain-negative, motile, non-spore-forming, rod-shaped bacterium, designated strain B2(T), was isolated from the culture broth of a marine microalga, Picochlorum sp. 122. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain B2(T) forms a robust cluster with members of the genus Pelagibacterium, and shares the highest sequence similarity of 96.80% with Pelagibacterium halotolerans CGMCC 1.7692(T). Optimal growth of strain B2(T) was observed at 33 degrees C, at pH 8 and in the presence of 1% (w/v) NaCl. The predominant ubiquinone of strain B2(T) was Q-10, and the G+C content of the genomic DNA was 58.6 mol%. The major fatty acid profile comprised C-18 : 1 omega 7c/omega 6c, C-19 : 0 cyclo omega 8c and C-16 : 0. The major polar lipids of strain B2(T) were diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and seven unidentified lipids. Comprehensive analyses based on a polyphasic characterization of strain B2(T) indicated that it represents a novel species of the genus Pelagibacterium, for which the name Pelagibacterium lentulum sp. nov. is proposed. The type strain is B2(T) (= MCCC 1K03218(T) = CGMCC 1.15896(T) = KCTC 52551(T))
Multi-scale variability of the tropical Indian Ocean circulation system revealed by recent observations
No full textThe tropical Indian Ocean circulation system includes the equatorial and near-equatorial circulations, the marginal sea circulation, and eddies. The dynamic processes of these circulation systems show significant multi-scale variability associated with the Indian Monsoon and the Indian Ocean dipole. This paper summarizes the research progress over recent years on the tropical Indian Ocean circulation system based on the large-scale hydrological observations and numerical simulations by the South China Sea Institute of Oceanology (SCSIO), Chinese Academy of Sciences. Results show that: (1) the wind-driven Kelvin and Rossby waves and eastern boundary-reflected Rossby waves regulate the formation and evolution of the Equatorial Undercurrent and the Equatorial Intermediate Current; (2) the equatorial wind-driven dynamics are the main factor controlling the inter-annual variability of the thermocline in the eastern Indian Ocean upwelling; (3) the equatorial waves transport large amounts of energy into the Bay of Bengal in forms of coastal Kelvin and reflected free Rossby waves. Several unresolved issues within the tropical Indian Ocean are discussed: (i) the potential effects of the momentum balance and the basin resonance on the variability of the equatorial circulation system, and (ii) the potential contribution of wind-driven dynamics to the life cycle of the eastern Indian Ocean upwelling. This paper also briefly introduces the international Indian Ocean investigation project of the SCSIO, which will advance the study of the multi-scale variability of the tropical Indian Ocean circulation system, and provide a theoretical and data basis to support marine environmental security for the countries around the Maritime Silk Road
Extreme subsurface warm events in the South China Sea during 1998/99 and 2006/07: observations and mechanisms
No full textConductivity-temperature-depth observations, objectively analyzed data, and model output are used to investigate the variability of subsurface temperature in the South China Sea (SCS) during 1948-2010. Two extreme subsurface warm events are identified during 1998/99 and 2006/07, with no corresponding extreme surface warming except in 1998. Mixed-layer heat budget analysis reveals that the lack of significant heat input from surface net heat flux or from current advection is responsible for the absence of extreme surface warming during 1999, and 2006/07. The surface net heat flux alone cannot explain the first phases of subsurface warming during 1998/99 and 2006/07. Warm advection from the southern SCS in 1998/99 and from the Kuroshio intrusion in 2006/07, induced by anomalous ocean currents, is likely the major contributor to warming of the subsurface water. During the second phase of warming, the surface net heat flux plays a damping role to cool the subsurface water, and the warm advection induced by anomalous SCS western boundary currents from the southern SCS leads to extremely warm subsurface water anomalies. The results show the importance of the Pacific western boundary currents, especially the Kuroshio, in maintaining extreme subsurface warm events in the SCS
东印度洋2017年春季活体浮游有孔虫的组成与分布
No full text通过对2017年3月在东印度洋海区6个站位53个垂直分层拖网浮游有孔虫样品进行了定量分析,探讨了该海区春季现代浮游有孔虫的组成、分布及其影响因素。东印度洋春季0-3000m水层内共鉴定出17个浮游有孔虫属种,主要是Globigerinoides ruber,Globoro taloides hexagona,Globigerinoides sacculifer,Globigerinella aequilateralis,Neogloboquadrina dutertrei,Globorotalia menardii,Globiberinell
南海西北部放射虫群落季节性特征及其环境意义
No full text水体中放射虫通量、群落结构与海洋环境季节与年际变化之间的关系,是合理利用放射虫化石进行古环境解释的基础。利用南海西北部西沙海槽2009-2011年沉积物捕获器样品初步探讨了放射虫季节与年际特征及其对主要环境因素变化的响应特征与规律。结果显示,南海西北部海区放射虫通量的季节性变化较显著,放射虫通量峰值主要出现于冬季风盛行的高初级生产力时期。这可能与冬季风活动期海水垂直混合作用加强有关,风力作用下上层水体混合作用的加强促使表层水体中营养物质及初级生产力增加,进而促进相应季节放射虫生产力升高。此外,放射虫通量在年际尺度上也存在一定差异,总体上,2009-2010年放射虫通量平均值及峰值均小于2010-2011年,这一差异可能与相应时期西太平洋的El Ni?o事件有关。受El Ni?o事件的影响,2009-2010东亚冬季风偏弱,南海上层海水垂直混合深度相对较浅,初级生产力偏低,从而一定程度上限制了放射虫生产力增加。此外,对主要放射虫属种进行了Q型因子分析,识别出具有环境指示意义的二个主因子。因子1主要由热带-亚热带表层暖水种组成,包括Botryocyrtis scutum,Dictyocoryne profunda,Didymocyrtis tetrathalamust.,Euchitonia elegans,Pterocorys hertwigii和Stylochlamydium asteriscus,其总通量在7-9月份显著增加,与表层水体温度变化有较好的对应关系,可作为表层水体温度变化的指示物;其中,该组合中D.tetrathalamus,E.elegans和S.asteriscus是西太平洋的主要属种,三者季节性含量变化较一致,较好地记录了不同季节西太平洋水体对南海北部水团的影响程度。因子2主要的放射虫属种有Actinomma arcadophorum,Larcopyle butschlli,Pterocanium praetextum p.和Spongotrochus glacialis,其中,A.arcadophorum和L.butschlli两者通量的峰值对冬季风盛行期初级生产力的增加有较好的响应,是冬季风活动及初级生产力变化的潜在指标