Phytoplankton life cycle transformations lead to species-specific effects on sediment processes in the Baltic Sea     

Kristian Spilling  Magnus Lindstrm 《Continental Shelf Research》2008,28(17):2488-2495

In order to study the sediment response to different addition of organic matter, we added cultures of the dinoflagellates Scrippsiella hangoei and Woloszynskia halophila and the diatom Pauliella taeniata to aquaria containing natural sediment. The biomass added was 1550–3260 mg C m⁻², and in the control, no biomass was added (n=3). Oxygen profiles at the sediment–water interface and inorganic nutrients in the near bottom water were determined once a week. In the additions of P. taeniata and W. halophila the sediment quickly became anoxic, and subsequently there was a flux of >1 mmol PO₄³⁻ m⁻² d⁻¹ out of the sediment in these treatments. The majority of the released P came from P stored in the sediment and not from the organic phosphorus added. The result was very different for the S. hangoei addition. This species underwent a life cycle change to form temporary cysts. During this process there was a net uptake of nutrients. After the formation of cysts the concentration of inorganic nutrient was similar to that of the control. Cysts generally survive for long periods in the sediment (months to years) before germinating, but can also be permanently buried in the sediment. The novel idea presented here is that the phytoplankton composition may directly affect sediment processes such as oxygen consumption and phosphorus release, through species-specific life cycle changes and yields of resting stages produced prior to sedimentation. This can be an important aspect of nutrient cycling in eutrophic waters, like the Baltic Sea, where there is large year-to-year difference in the amount of resting stages settling at the sea floor, mainly due to differences in abundance of diatoms and dinoflagellates during the spring bloom. If yields of resting stages change, e.g. due to changes in the phytoplankton community, it may lead to alterations in the biogeochemical cycling of nutrients.  相似文献   

Estimating uncertainty associated with water stages from a single SAR image     

Guy Schumann  Florian Pappenberger  Patrick Matgen 《Advances in water resources》2008

It is the goal of remote sensing to infer information about objects or a natural process from a remote location. This invokes that uncertainty in measurement should be viewed as central to remote sensing. In this study, the uncertainty associated with water stages derived from a single SAR image for the Alzette (G.D. of Luxembourg) 2003 flood is assessed using a stepped GLUE procedure. Main uncertain input factors to the SAR processing chain for estimating water stages include geolocation accuracy, spatial filter window size, image thresholding value, DEM vertical precision and the number of river cross sections at which water stages are estimated. Initial results show that even with plausible parameter values uncertainty in water stages over the entire river reach is 2.8 m on average. Adding spatially distributed field water stages to the GLUE analysis following a one-at-a-time approach helps to considerably reduce SAR water stage uncertainty (0.6 m on average) thereby identifying appropriate value ranges for each uncertain SAR water stage processing factor. For the GLUE analysis a Nash-like efficiency criterion adapted to spatial data is proposed whereby acceptable SAR model simulations are required to outperform a simpler regression model based on the field-surveyed average river bed gradient. Weighted CDFs for all factors based on the proposed efficiency criterion allow the generation of reliable uncertainty quantile ranges and 2D maps that show the uncertainty associated with SAR-derived water stages. The stepped GLUE procedure demonstrated that not all field data collected are necessary to achieve maximum constraining. A possible efficient way to decide on relevant locations at which to sample in the field is proposed. It is also suggested that the resulting uncertainty ranges and flood extent or depth maps may be used to evaluate 1D or 2D flood inundation models in terms of water stages, depths or extents. For this, the extended GLUE approach, which copes with the presence of uncertainty in the observed data, may be adopted.  相似文献   

Postshield stage transitional volcanism on Mahukona Volcano, Hawaii     

David A. Clague  Andrew T. Calvert 《Bulletin of Volcanology》2009,71(5):533-539

Age spectra from ⁴⁰Ar/³⁹Ar incremental heating experiments yield ages of 298 ± 25 ka and 310 ± 31 ka for transitional composition lavas from two cones on submarine Mahukona Volcano, Hawaii. These ages are younger than the inferred end of the tholeiitic shield stage and indicate that the volcano had entered the postshield alkalic stage before going extinct. Previously reported elevated helium isotopic ratios of lavas from one of these cones were incorrectly interpreted to indicate eruption during a preshield alkalic stage. Consequently, high helium isotopic ratios are a poor indicator of eruptive stage, as they occur in preshield, shield, and postshield stage lavas. Loihi Seamount and Kilauea are the only known Hawaiian volcanoes where the volume of preshield alkalic stage lavas can be estimated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

生物结皮恢复过程中土壤生态因子分异特征   总被引：19，自引：14，他引：5  

吴楠  张元明  张静  王红玲  聂华丽  陈荣毅 《中国沙漠》2007,27(3):397-404

对新疆古尔班通古特沙漠生物结皮恢复过程中土壤因子的动态变化进行关联性测度、方差分析、相关性分析相结合的定量研究,着重分析结皮恢复年限对土壤微生物数量、养分、盐分、土壤酶的影响,有机质与土壤盐分、pH值、土壤酶的线性关系及土壤生态因子间的相关性。结果表明：相对于土层深度,有机养分、土壤酶等生态因子与生物结皮恢复年限的联系更加紧密。结皮恢复年限对全P、全K、有机质、脲酶、真菌的影响极显著（P<0.01）;对速效P、速效K、全N、总盐、中性碱性磷酸酶、蛋白酶的影响显著(P<0.05)。随结皮恢复年限的增加,结皮层和结皮以下土层中有机养分、土壤酶均有不同程度的增加,逐步具备较高的生物学活性,沙土性状变化较快,渐渐形成抗风蚀、抗干扰能力较强的地衣苔藓结皮。结皮恢复过程中pH值与有机质呈显著线性负相关（R2＝0.701,P<0.05）,土壤盐分与有机质存在线性正相关（R2＝0.653）,但显著性不强（P>0.05）。电导率、脲酶、碱性磷酸酶、中性磷酸酶、蛋白酶与有机质存在极为显著的线性正相关（R2分别为0.888、0.993、0.958、0.948、0.911,P<0.01）,土壤生态因子的协调发展和紧密配合促进了生物结皮的恢复。  相似文献   

Two stages of isotopic exchanges experienced by the Ertaibei granite pluton, northern Xinjiang, China   总被引：1，自引：0，他引：1  

LIU Wei 《中国科学D辑(英文版)》2000,43(6):605-616

¹⁸O/¹⁶O and D/H of coexisting feldspar, quartz, and biotite separates of twenty samples collected from the Ertaibei granite pluton, northern Xinjiang, China are determined. It is shown that the Ertaibei pluton experienced two stages of isotopic exchanges. The second stage of¹⁸O/¹⁶O and D/H exchanges with meteoric water brought about a marked decrease in the δ¹⁸O values of feldspar and biotite from the second group of samples. The D/H of biotite exhibits a higher sensitivity to the meteoric water alteration than its¹⁸O/¹⁶O. However, the first stage of¹⁸O/¹⁶O exchange with the¹⁸O-rich aqueous fluid derived from the dehydration within the deep crust caused the Δ¹⁸O_{Quartz-Feldspar} reversal. It is inferred that the dehydration-melting may have been an important mechanism for anatexis. It is shown that the deep fluid encircled the Ertaibei pluton like an envelope which serves as an effective screen to the surface waters.  相似文献   

Resting Stages of Plankton in Recent North Adriatic Sediments   总被引：6，自引：0，他引：6  

Fernando Rubino  Genuario Belmonte  Anna M. Miglietta  Sebastiano Geraci  & Ferdinando Boero 《Marine Ecology》2000,21(3-4):263-284

Abstract. Plankton-derived resting stages were found in 26 sediment cores collected in the North Adriatic Sea; 46 morphotypes were identified, 38 were attributed to taxa according to their morphology and, in some hatching cases, also according to the morphology of the derived active forms. Six species of Dinophyta were recorded for the first time from the North Adriatic Sea. Each morphotype was described in detail. Twenty-nine resting stages were Dinophyta; one was a Chrysophyta; two were Tintinnina; and six were metazoans. At every site Dinophyta cysts were more abundant than Metazoa cysts. Cyst bank densities were variable, with empty forms generally more abundant than full ones; cyst concentrations were highest at the mouth of the Po River delta.  相似文献   

中国地震紧急救援理论研究   总被引：1，自引：0，他引：1  

高建国 《华南地震》2006,26(1):118-125

如何满足国家和社会对地震应急的需求,进一步发展我国的地震应急工作,是地震界面临的课题。根据目前地震应急的现状,提出了以下2个有关地震应急理论的创新点:地震速报的基本模式,新闻媒体传播地震消息模式,地震应急预案启动模式,地震考察地区性差异,地震灾害死伤的基础数据模式,地震应急期分期模式,地震应急期救援真空模式,地震应急期黑箱、灰箱、白箱模式,地震救援队伍的后勤模式,国外地震救援队到中国参加救援法规模式,地震受灾体分类模式,新建和加固农村公共建筑提高一度模式。并且给予了论述。  相似文献   

Distribution and germination of viable diatom resting stage cells in sediments of the East China Sea     

ZHANG Yuyu  LU Songhui  ZHANG Chuansong  GAO Yahui 《海洋学报(英文版)》2010,29(5):121-128

The abundance and temporal patterns of viable diatom resting stage cells in sediments of the East China Sea in 2006 have been investigated. The abundance of viable resting stages was enumerated with the most probable number (MPN) technique. Overall, 25 diatom species (including varieties) belonging to 16 genera were detected. Viable resting stage cells were common, on the order of 10³ to 10⁶ cells/g dry mass. The abundant taxa included Skeletonema marina, S. dohrnii, Chaetoceros curvisetus and Thalassiosira spp., with Skeletonema accounting for 83.3% of the cell. The effects of temperature (10, 15, 20, 25℃), salinity (20, 25, 30, 35 psu) and light intensity (0, 300, 4 000, 8 000 lux) on the germination of resting stages in sediment samples were also determined. The results showed that light intensity had a significant positive effect on the germination of diatom resting stage cells (p <0.01) and that diatoms could not germinate in darkness. Temperature and salinity had no noticeable effects on the germination. The present study suggests that there are abundant diatom resting cells in sediments of the East China Sea, which could serve as a "seed bank" in the phytoplankton population succession and contribute to the initiation of algal blooms.  相似文献   

东海三疣梭子蟹雌体不同生理阶段肝胰腺的生化组成与其组织学结构的关系   总被引：8，自引：0，他引：8  

姚桂桂  吴旭干  成永旭  杨筱珍  王春琳 《海洋学报》2008,30(6):122-131

通过生化分析和组织切片技术,系统研究了东海三疣梭子蟹第一次卵巢发育过程中肝胰腺指数(HSI)、主要生化成分和组织学结构的变化。结果表明:(1)三疣梭子蟹第一次卵巢发育过程中HSI呈先上升后下降趋势,最大值在Ⅳ期[(7.46±1.23)%],最低值在Ⅵ期[(4.62±0.63)%];(2)三疣梭子蟹第一次卵巢发育过程中,肝胰腺中的生化组成存在显著变化,Ⅰ期肝胰腺中水分含量高达67.91%,其他各期间无显著差异(P>0.05),肝胰腺中脂肪/湿重含量呈先上升后下降趋势,Ⅰ期最低(13.48%),Ⅳ期最高(24.24%);肝胰腺中蛋白/湿重并无显著变化(P>0.05),而总糖/湿重呈显著下降趋势(P<0.05);(3)不同生理阶段雌体肝胰腺组织学存在两个较明显的变化—生殖蜕壳及产卵前后,Ⅰ期肝小管中B细胞占优势(约50%左右),R细胞较细长,肝小管内腔中存在大量食物残渣和脱落的B细胞顶泡等,生殖蜕壳后(Ⅱ期后)的雌体肝胰腺中R细胞数量较多,随着时间的推移R细胞逐渐饱满。产卵后雌体肝胰腺中的细胞间界限变得模糊,部分肝小管的管腔开始自溶,但是此时B,F细胞数量开始增多,这说明随着春季东海海区水温的升高,雌体开始恢复摄食,以保证第二次卵巢发育的顺利进行。  相似文献   

Composition,abundance, distribution and seasonality of larval fishes in the shallow nearshore of the proposed Greater Addo Marine Reserve,Algoa Bay,South Africa     

Paula Pattrick  Nadine A. Strydom 《Estuarine, Coastal and Shelf Science》2008

The larval fish assemblage was investigated in the shallow, nearshore region of a proposed marine protected area in eastern Algoa Bay, temperate South Africa, prior to proclamation. Sampling was conducted at six sites along two different depth contours at ∼5 m and ∼15 m to assess shore association. Larvae were collected by means of stepped oblique bongo net tows deployed off a ski-boat, twice per season for 2 years between 2005 and 2007. In total, 6045 larval fishes were collected representing 32 families and 78 species. The Gobiidae, Cynoglossidae, Clupeidae, Engraulidae and Sparidae were the dominant fish families. Catches varied significantly among seasons peaking in spring with a mean of ∼200 larvae/100 m³. Mean overall larval density was higher along the deeper contour, at ∼15 m (40 larvae/100 m³). The preflexion stage of development dominated catches at the ∼5 m (80%) and ∼15 m (73%) depth contours. Body lengths of Argyrosomus thorpei, Caffrogobius gilchristi, Diplodus capensis, Heteromycteris capensis and Solea turbynei, all estuary associated species, were larger at the shallow sites nearer to shore. Larvae of coastal species that produce benthic eggs dominated catches (75%) in the shallow sites (∼5 m) but were less abundant (32%) farther from shore at the deeper (∼15 m) sites. All developmental stages of D. capensis, Engraulis capensis, H. capensis, Sardinops sagax and two Pomadasys species were found in the study area. It appears that some species use the shallow nearshore as a nursery area.  相似文献