Effects of waterborne nitrite onphase I–II biotransformation in channel catfish(Ictalurus punctatus)     

J. F. Gonzlez  P. L. Del Valle  S. Thohan  A. S. Kane 《Marine environmental research》2000,50(1-5)

The effects of waterborne nitrite (3 mg/l NO₂) on channel catfish were studied to evaluate changes in hematological parameters and phase I–II biotransformation in liver slices. Nitrite-exposed fish had significantly higher methemoglobin, blood and liver nitrite, and significantly lower pO₂ than control fish. Total phase I-mediated metabolism of 7-ethoxycoumarin (EC) was not altered in nitrite-exposed fish compared with control fish (291±43 and 312±20 pmol/mg/h, respectively). However, phase II glucuronosyltransferase-mediated metabolism of 7-hydroxycoumarin (HC), both as a phase I metabolite of EC and as a parent substrate, was elevated in nitrite-exposed fish (204±17 and 1007±103 pmol/mg/h, respectively) as compared to control fish (149±14 and 735±87 pmol/mg/h) (P<0.05). Sulfotransferase-mediated metabolism of HC (as a metabolite of EC and as a parent substrate) was not notably altered in nitrite-exposed fish (95±16 and 617±33 pmol/mg protein/h, respectively) as compared with control fish (118±24 and 575±55 pmol/mg/h, respectively). These studies indicate that in vivo nitrite exposure and associated changes in hematological parameters do not appear to affect hepatic phase I EC biotransformation in channel catfish. However, subtle but significant changes in phase II glucuronidation, but not sulfation activity, were observed. The mechanism of these alterations is unclear. However, the data suggest that environmentally realistic concentrations of nitrite may affect the dynamics of conjugative metabolism in exposed fish.  相似文献   

Detecting nutrient deficiency in spruce forests using multispectral satellite imagery     

《International Journal of Applied Earth Observation and Geoinformation》2020

Nutrient deficiency in forest stands has a negative impact on timber production. Although there are numerous studies investigating nutrient deficiency in forests using remote sensing, research has usually focused on extracting nutrient/pigment concentrations using hyperspectral imagery. Results of studies using this method of assessment are uncertain at the canopy level. This study proposes using freely available multispectral imagery to identify nutrient deficiency in commercially managed forest plantations. A classification map of nutrient deficient, healthy, and a third class, other, for State spruce forests in the Republic of Ireland was constructed using multispectral Sentinel 2 images from Spring and a Random Forest model. The forest area of interest (AOI) was Sitka spruce or Norway spruce plantations greater than 12 years old. Results showed that the overall accuracy was 89% and the associated Kappa Index of agreement was 79%. An unbiased area estimator was vital for an accurate estimate of the scale of nutrient deficiency, which concluded that 23% of the AOI was nutrient deficient. Early detection of nutrient deficiency is crucial to mitigate negative impacts on productivity so a time series analysis of the spectral response of healthy and nutrient deficient classes using Google Earth Engine's Landsat 5, 7, and 8 archive was carried out. A control of known nutrient deficient sites, as identified through foliar analysis, was used for comparison with the nutrient deficient and healthy training data. The spectral response showed a decrease through time for all of the foliar analysis and training data using the green (520–600 nm), red (630–690 nm), and SWIR spectra (1550–1700 nm) during Spring. This decreasing trend is due to the growth of foliage, with the difference in spectral response between nutrient deficient and healthy stands being attributed to the presence of chlorosis in stands suffering from nutrient deficiency. Spectral thresholds using digital numbers for nutrient deficient stands were identified for an operational optimum age cohort of between 10–12 years old which will be used for early detection.  相似文献   

温度和盐度对两种海洋桡足类动物摄食和代谢的影响   总被引：3，自引：0，他引：3  

薛泽  朱丽岩  王博渊  刘正宇 《海洋与湖沼》2020,51(1):95-102

本研究在实验室模拟生态条件下,以两种常见的海洋桡足类动物为受试生物,着重研究了温度和盐度变化对火腿许水蚤(Schmackeria poplesia)和拟长腹剑水蚤(Oithona similis)的滤水率、摄食率、耗氧率和排氨率的影响,统筹分析了两种海洋桡足类响应温度和盐度变化的摄食与代谢策略,以期为两种海洋桡足类的室内培养提供理论支持和技术指导。结果发现:(1)在5—30°C的温度范围内两种桡足类动物的摄食与代谢均呈现随温度升高而先升高后降低的变化趋势,其中火腿许水蚤的摄食率、滤水率、耗氧率和排氨率的最大值均出现在15°C,而拟长腹剑水蚤则在25°C到达峰值,说明拟长腹剑水蚤对温度具有较高的耐受性。(2)当暴露于不同盐度(15—35)时,火腿许水蚤可在低盐度(25)条件下保持较高的摄食能力,且当盐度为25时其摄食率、滤水率达到峰值,之后便显著下降;拟长腹剑水蚤则在盐度为30时开始下降。前者的代谢能力在盐度为25时开始下降,后者在高盐度(35)时代谢能力依然有回升的趋势,说明拟长腹剑水蚤对盐度的耐受性更强。而火腿许水蚤及拟长腹剑水蚤对低盐度(20—25)有一定的偏好,二者通过强化自身代谢以抵消低盐度引起的渗透压变化对自身的影响。(3)基于氧氮比(O/N)变化的代谢作用分析显示:在整个温度梯度(10—25°C)中火腿许水蚤的氧氮比波动较大,而拟长腹剑水蚤除在高温(35°C)条件下,其氧氮比均低于24。盐度则会抑制火腿许水蚤的摄食能力从而迫使其分解体内储能物质(O/N24),而对盐度耐受性较好的拟长腹剑水蚤则可始终维持较高的摄食和代谢能力(O/N24)。因此拟长腹剑水蚤能在较大的温、盐度范围内保持稳定的氨氮代谢水平,具有更高的环境耐受性。  相似文献   

饲料蛋白质水平对大黄鱼体内蛋白质的沉积和代谢反应的影响     

林淑琴  成琳  张文兵  徐玮  麦康森  申屠基康 《中国海洋大学学报(自然科学版)》2014,44(5):32-39

进行9周的养殖实验,比较分析饲料蛋白质水平对3个不同生长阶段大黄鱼体内蛋白质沉积和代谢反应相关指标的影响。实验用大黄鱼分为3种规格,分别是小规格鱼(SF,初始体重:(12.80±0.08)g)、中规格鱼(MF,初始体重:(137.90±0.81)g)和大规格鱼(LF,初始体重:(194.10±2.37)g)。饲料中的7个蛋白质梯度设置为30.4%,34.2%,38.5%,42.2%,46.0%,50.3%和54.3%。结果表明,随着饲料蛋白质水平的上升,SF的蛋白质含量和氮保留率显著升高(P0.05),而MF和LF的全鱼蛋白质含量(BP)和氮保留率(NR)未见显著变化(P0.05)。从不同生长阶段来看,氮保留率MF显著低于SF和LF(P0.05)。3个生长阶段,大黄鱼肝脏中的谷草转氨酶(AST)和谷丙转氨酶(ALT)活性,以及血清中的血氨、尿素氮和总氨基酸含量均随着饲料蛋白质水平的上升而显著升高(P0.05)。从不同生长阶段来看,血氨含量MF显著高于SF和LF(P0.05)。研究表明,大黄鱼体内蛋白质沉积和氨基酸代谢随饲料蛋白质水平的上升而增强,大黄鱼的氮保留能力MF阶段低于SF和LF阶段。  相似文献   

不同类型糖源对大菱鲆脂肪代谢酶活性和脂肪酸组成的影响     

苗惠君  聂琴  苗淑彦  陈尘悦  李静  张文兵  麦康森 《中国海洋大学学报(自然科学版)》2014,44(4)

以初始体质量(8.77±0.16)g的大菱鲆(Scophthalmus maximus)幼鱼为研究对象,在室内流水系统中进行9周的养殖实验,比较分析饲料中3种不同类型的糖源(葡萄糖、蔗糖和糊精)对大菱鲆脂肪代谢相关酶活性和肌肉脂肪酸组成的影响。结果表明,不同类型的糖源显著影响肝脏中与脂肪合成相关的葡萄糖-6-磷酸脱氢酶(G6PD)和苹果酸酶(ME)的活性(P0.05)。饲料糖源为葡萄糖时,大菱鲆肝脏中G6PD和ME的活性显著高于其他处理组,而蔗糖和糊精处理组之间没有显著差异。对与脂肪分解代谢相关酶的活性分析表明,肠道脂肪酶的活性受饲料中不同糖源的影响显著(P0.05);肝脏脂蛋白脂酶的活性在糖源为葡萄糖时显著低于其他处理组(P0.05);不同糖源对肝脂酶的活性无显著影响(P0.05);糊精组的总脂酶活性显著高于葡萄糖组(P0.05)。葡萄糖组大菱鲆肌肉中的C16∶0和C18∶0的含量显著高于糊精组,而C16∶1和C18∶1n-9的含量显著低于糊精组(P0.05)。研究表明,饲料中不同类型的糖源对大菱鲆肌肉脂肪酸的影响集中在饱和脂肪酸和单不饱和脂肪酸上,而对多不饱和脂肪酸的影响有限。  相似文献   

Diapycnal nutrient fluxes on the northern boundary of Cape Ghir upwelling region     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

In this study we estimate diffusive nutrient fluxes in the northern region of Cape Ghir upwelling system (Northwest Africa) during autumn 2010. The contribution of two co-existing vertical mixing processes (turbulence and salt fingers) is estimated through micro- and fine-structure scale observations. The boundary between coastal upwelling and open ocean waters becomes apparent when nitrate is used as a tracer. Below the mixed layer (56.15±15.56 m), the water column is favorable to the occurrence of a salt finger regime. Vertical eddy diffusivity for salt (K_s) at the reference layer (57.86±8.51 m, CI 95%) was 3×10⁻⁵ (±1.89×10⁻⁹, CI 95%) m² s⁻¹. Average diapycnal fluxes indicate that there was a deficit in phosphate supply to the surface layer (6.61×10⁻⁴ mmol m⁻² d⁻¹), while these fluxes were 0.09 and 0.03 mmol m⁻² d⁻¹ for nitrate and silicate, respectively. There is a need to conduct more studies to obtain accurate estimations of vertical eddy diffusivity and nutrient supply in complex transitional zones, like Cape Ghir. This will provide us with information about salt and nutrients exchange in onshore–offshore zones.  相似文献   

Effects of anthropogenic disturbance on the abundance and size of epibenthic jellyfish Cassiopea spp     

Stoner EW  Layman CA  Yeager LA  Hassett HM 《Marine pollution bulletin》2011,62(5):1109-1114

Jellyfish blooms in pelagic systems appear to be increasing on a global scale because of anthropogenic impacts, but much less is known about the link between human activities and epibenthic jellyfish abundance. The aim of this study was to investigate whether the epibenthic jellyfish, Cassiopea spp., were found in greater abundance, and attained larger sizes, in coastal habitats adjacent to high human population densities compared to sites adjacent to uninhabited areas on Abaco Island, Bahamas. Cassiopea spp. were found to be significantly more dense and larger in areas with high human population densities. Ambient nutrient levels and nutrient content of seagrass were elevated in high human population density sites, and may be one mechanism driving higher abundance and size of Cassiopea spp. Cassiopea spp. may have important effects on community structure and ecosystem function in critical coastal ecosystems (e.g., seagrass beds), and their impacts warrant further study.  相似文献   

Modeling and Validating Long‐Term Dynamics of Diel Dissolved Oxygen with Particular Reference to pH in a Temperate Shallow Lake (Turkey)     

Nusret Karakaya  Fatih Evrendilek  Kerem Güngör 《洁净——土壤、空气、水》2011,39(11):966-971

Long‐term monitoring of changes in dissolved oxygen (DO) and pH is of great importance to quantifying aquatic ecosystem metabolism, particularly for lakes under the changing global environment. During 173 days, diel DO cycles were measured in situ along with the main driving variables of pH, wind speed (WS), and net solar radiation (Rn) in a temperate shallow lake. Best‐fit multiple non‐linear regression (MNLR) models of diel DO time series were built and validated on a monthly basis, with R² values ranging from 42.4% in September to 95.4% in November for validation. The strong relationship between diel DO and pH (r = 0.6) appeared to be related to the patterns of ecosystem productivity and respiration, and sensitivity of decomposing bacteria to changes in pH. pH‐driven lake metabolism appears to have significant implications for diel and seasonal lake metabolism in a changing global environment.  相似文献   

Mussel farming as a nutrient reduction measure in the Baltic Sea: consideration of nutrient biogeochemical cycles   总被引：1，自引：0，他引：1  

Stadmark J  Conley DJ 《Marine pollution bulletin》2011,62(7):1385-1388

Nutrient loads from the land to the sea must be reduced to combat coastal eutrophication. It has been suggested that further mitigation efforts are needed in the brackish Baltic Sea to decrease nutrients, especially in eutrophic coastal areas. Mussel farming is a potential measure to remove nutrients directly from the sea. Mussels consume phytoplankton containing nitrogen (N) and phosphorus (P); when the mussels are harvested these nutrients are removed from the aquatic system. However, sedimentation of organic material in faeces and pseudo-faeces below a mussel farm consumes oxygen and can lead to hypoxic or even anoxic sediments causing an increased sediment release of ammonium and phosphate. Moreover, N losses from denitrification can be reduced due to low oxygen and reduced numbers of bioturbating organisms. To reveal if mussel farming is a cost-effective mitigation measure in the Baltic Sea the potential for enhanced sediment nutrient release must be assessed.  相似文献   

Ecology and functional roles of biological soil crusts in semi-arid ecosystems of Spain   总被引：1，自引：0，他引：1  

F.T. Maestre  M.A. Bowker  Y. Cantón  A.P. Castillo-Monroy  J. Cortina  C. Escolar  A. Escudero  R. Lázaro  I. Martínez 《Journal of Arid Environments》2011,75(12):1282-1291

Biological soil crusts (BSCs), composed of lichens, cyanobacteria, mosses, liverworts and microorganisms, are key biotic components of arid and semi-arid ecosystems worldwide. Despite they are widespread in Spain, these organisms have been historically understudied in this country. This trend is beginning to change as a recent wave of research has been identifying BSCs as a model ecological system. Many studies and research projects carried out in Spain have explored the role of BSCs on water, carbon and nitrogen fluxes, the interactions between BSCs and vascular plants, their dynamics after disturbances, and their response to global change, among other topics. In this article we review the growing body of research on BSCs available from semi-arid areas of Spain, highlighting its importance for increasing our knowledge on this group of organisms. We also discuss how it is breaking new ground in emerging research areas on the ecology of BSCs, and how it can be use to guide management and restoration efforts. Finally, we provide directions for future research on the ecology of BSCs in Spain and abroad.  相似文献