Wave-induced sediment resuspension in the Öre estuary,northern Sweden

Material transported by the Öre River in northern Sweden is all deposited within the estuary which means that resuspension is necessary for the transport of particles out of the estuary. Wave-induced sediment resuspension in the estuary was studied by monitoring the distribution of suspended particles during a resuspension-redeposition cycle. The particle concentration in the water mass was measured with a light scattering probe, calibrated by comparison with the amount of particles collected on a filter.After a long period with calm weather and a low river input less than 100 tonne of suspended particulate matter was present in the estuary. However, during a period with stormy conditions significant resuspension of sediment particles occurred within the estuary. Two days after the storm approximately 1125 tonne of suspended particulate matter was found in the estuary. Most (61%) of the suspended matter was found in the deepest third of the water column, although up to 17% was present in the top third of the water column. The total load of particulate matter in the water column remained constant until day four after the storm, but a significant redistribution of the particulate matter occurred both in the vertical and horizontal directions. Nine days after the storm, a significant amount of particles (c. 350 tonnes) was still in suspension.     

Using deterministic models to assess risk in sediment-impacted estuaries

Terrestrial sediments transported off disturbed watersheds can threaten downstream estuarine and coastal environments. Practitioners in the field of environmental management need to be able to assess how activities that disturb the land are likely to impact on downstream estuarine and coastal receiving waters. Such assessments usually take the form of estimating risk, which has two components: the extent of undesirable consequences and the probability of occurrence of those consequences. The consequence in this case is primarily the ecological damage. In order to estimate risk, a methodology was developed around the use of a deterministic computational model of watershed/estuarine sediment transport. Model simulations are run which cover the physically realistic range of the controlling variables (e.g., wind speed, wind direction, sediment runoff). The model results are related to estuary damage and combined with the probability of occurrence for each scenario, providing a means of quantifying risk. In addition, answers to `long-term average', `most likely' and `worse case' type questions can be made. The procedure has the advantages of being easily implemented, transparent and repeatable. It is also more efficient than a standard Monte-Carlo procedure. The risk associated with changes in landuse can be examined without repeating model simulations. The example used to illustrate the method is that of a developing watershed in which proposed building activities are expected to alter the sediment yield to the downstream estuary during floods, which in turn is expected to smother shellfish beds. By elucidating risk associated with each development scenario, the management debate can be focused on choice of an acceptable risk level.     

Terminal electron transport system (ETS)-activity in the sediment of Lake Balaton,Hungary

Terminal electron transport system (ETS)-activity of the sediment and plankton of Lake Balaton, the largest shallow lake of Central Europe was measured by tetrazolium-reduction biweekly during 1989–1990 and in the spring of 1991. Sediment proved to be enzymatically active to 30-35 cm down in the hypertrophic Keszthely Bay and to 15–20 cm down in the meso-eutrophic Siófok Basin. Sediment ETS-activity exceeded planktonic activity 15 to 24 fold.The total activity m^–2 showed one or two order of magnitude higher respiratory potential in Lake Balaton than needed for complete oxidation of the planktonic primary production; most of this potential was detected in the upper 3–5 cm sediment layer in springs. Incubations of cell-free homogenates of sediment bacteria showed that ETS remains active days after death of organisms at low temperature. Accumulated postmortem ETS-activity derived from the benthic diatoms, bacteria, plankton deposit and dead summer macrophytes seems to be responsible for the high ETS-activity of the sediment in the warming periods in springs. These enzyme fractions may contribute to the rapid oxidation of the alkaline, well-aerated lake.     

Numerical modelling of suspended sediment transport in tidal estuaries: A comparison between the Tagus (Portugal) and the Scheldt (Belgium-the Netherlands)

A numerical model to simulate the transport of suspended sediment in tidal estuaries is presented. The model is applied to the two large European estuaries the Tagus (Portugal) and the Scheldt (Belgium-The Netherlands). Calculated suspended sediment concentrations compare favourably with observations in the Tagus (r=0.84) and in the Scheldt (r=0.73). The parametrization scheme indicates that the bottom content of fine sediment is correlated with depth in the Tagus; but a different relationship is used in the Scheldt. Because of tidal range differences, average suspended sediment concentrations are lower in the Tagus (80 mg l⁻¹) than in the Scheldt (130 mg l⁻¹), but a larger relative variation between spring and neap tide concentrations may occur in the Tagus.     

Effects of food on bacterial community composition associated with the copepod Acartia tonsa Dana

The estuarine copepod Acartia tonsa naturally carried diverse strains of bacteria on its body. The bacterial community composition (BCC) remained very conservative even when the copepod was fed different axenic algal species, indicating that the food per se did not much affect BCC associated with the copepod. In xenic algal treatments, however, copepod-associated BCC differed with each alga fed, even though the same bacterial source was used to inoculate the algae. In addition, starved copepods taken at the same location but at different times significantly differed in their BCC. Algal species composition and copepod life history therefore serve to regulate BCC associated with copepods, and spatial and temporal variations in algal species composition and copepod origin would alter bacteria–copepod interactions.     

闽江河口短叶茳芏群落湿地沉积物反硝化强度对盐度的响应

为了探讨河口区湿地沉积物反硝化强度对盐度的响应,2015年7月选择闽江河口覆盖短叶茳芏的鳝鱼滩和道庆洲湿地沉积物为研究对象,采用密封厌氧培养,计算不同培养时期在不同盐度下的反硝化速率。结果表明,在反硝化培养的初期,鳝鱼滩的反硝化速率从低盐度到高盐度分别为(15.5±1.38)、(4.28±8.46)、(12.94±0.24)mg kg~(-1)d~(-1),道庆洲分别为(31.93±4.89)、(30.66±5.375)、(36.69±3.44)mg kg~(-1)d~(-1),鳝鱼滩的10天反硝化速率在0和10盐度下降幅度分别是5天的36.97%、53.01%,高于道庆洲22.64%、28.84%,后期随着时间的变化整体上呈现减小的趋势并趋于0。另外,鳝鱼滩和道庆洲反硝化活性随着时间呈现逐渐增加的趋势,其鳝鱼滩变化幅度在95.6%—99.8%,道庆洲为90.0%—96.7%,整个培养期间,鳝鱼滩的反硝化活性均高于道庆洲的反硝化活性。以上结果反映出盐度对闽江河口湿地沉积物的反硝化速率起到一定的抑制作用。     

The effects of in situ drying on sediment–phosphate interactions in sediments from an old wetland

We examined the effects of drying on sediment–P interactions for sediments from a shallow wetland ca. 6000 years old. Sediments from this wetland would have been subjected to numerous drying and wetting episodes during the life of the wetland. The factors affecting potential orthophosphate release were compared in surface sediments that had previously been desiccated for 3 months, surface sediments that had remained inundated and wet sediment 25–30 cm below the surface. All sediments released small amounts of orthophosphate once subjected to anaerobic conditions. Sulfate alone stimulated phosphate release from the surface sediment, irrespective of the previous hydrological status, whereas orthophosphate release from deep sediments was co-limited by carbon and sulfate. Decreases in soluble Fe (II) were measured concurrently with sulfate-stimulated P release, which is consistent with formation of iron sulfides. Similar numbers of culturable sulfate-reducing bacteria were obtained from the wet and dry sediments, their tolerance to desiccation explaining why release could occur after extensive drying of the sediment. Phosphate adsorption isotherms of the sediments showed that sediments from all sites had a relatively low affinity for ortho-phosphate. The adsorption data showed reasonable fit to the Freundlich adsorption isotherm. No difference in the maximum amount of ortho-phosphate uptake was observed if the sediment isotherm experiments were done under an inert atmosphere or, following exposure to air, suggesting that even anoxic sediments were not highly reduced. However, significant variations in the value of the Freundlich constants were observed. The results presented in this study are consistent with the hypothesis that repeated wetting/drying cycles select for bacteria that are tolerant to periods of desiccation and/or oxidation. Furthermore, repeated wetting and drying cycles may result in changes to sediment mineralogy.     

Distribution of bacteria in the sediment of an oxbow tropical lake (Lagoa do Infernão,SP, Brazil)

The temporal distribution of bacteria on the surface sediment of the oxbow lake Lagoa do Infernão was studied over a period of one year using different techniques for bacterial counts. Several bacterial groups were differentiated, such a total bacteria and filamentous, heterotrophic, amylolytic, and lipolytic bacteria. The best defined temporal distribution pattern was obtained by total-AO bacterial counts, with a variation of 1.26 × 10¹⁰ to 8.58 × 10¹⁰ bacteria (g dw)^–1 during the dry and rainy seasons, respectively. The electrode potential (Eh) of the surface sediment ranged from – 148 mV during the rainy season to + 371 mV during the dry season. The variations detected on the surface sediment suggest a greater allochthonous contribution of material and bacteria resulting in high decomposing activity during the rainy season.     

Effects of amendments on biodegradation of crude petroleum by sediment bacteria from Bonny River Estuary

The biodegradation of Bonny light crude petroleum by bacteria in batch culture was enhanced by the addition to culture media, of 0.2 mg of urea and soya bean lecithin per 100 ml of crude oil, sediment and water mixture. Biodegradation was found to be purely an aerobic process. There was a direct relationship between hydrocarbon content and proportion (%) of total heterotrophic count that was capable of growing on crude petroleum as sole carbon and energy source.     

五大连池不同火山喷发沉积物的细菌群落多样性研究

【目的】揭示五大连池火山区的细菌多样性。【方法】运用Illumina Miseq高通量测序技术解析五大连池不同火山喷发沉积物中细菌的群落组成和分布规律。【结果】五大连池火山区沉积物中的细菌主要包含厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)、疣微菌门(Verrucomicrobia)、酸杆菌门(Acidobacteria)、绿弯菌门(Chloroflexi)、放线菌门(Actinobacteria)等23个细菌门类,其中,厚壁菌门、变形菌门丰度较高,芽孢杆菌属(Bacillus)为绝对优势菌群。另外,由于火山物质的同源性,导致各沉积物中细菌的代谢通路多与C、N、S、Fe等元素的生化循环相关,群落结构及功能具有一定程度的相似性。但由于各研究区域在沉积组分、环境因素及地质演化进程上的差异,致使芽孢杆菌属、地杆菌属(Geobacter)、酸杆菌属(Acidobacterium)、嘉利翁氏菌属(Gallionella)、Blastocatella等部分种群在不同火山沉积物中呈现差异化分布,具有典型的地域适应特性。【结论】五大连池火山沉积物中含有较为丰富的细菌资源,...     

黄河口潮间带沉积物细菌群落结构特征

选取黄河口潮间带有植被覆盖和无植被覆盖两个区域采集柱状沉积物,利用实时荧光定量PCR技术和高通量测序技术分析有无植被覆盖沉积物中的细菌群落特征和功能差异,探究影响潮间带细菌群落结构的主要环境因子。结果显示,细菌丰度在有植被区域大于无植被区域。沉积物中细菌群落丰富度和多样性在有植被区域随深度的增加而增加,而在无植被区域其最高值出现在沉积物中层（14-16 cm）。两个区域在门分类水平上以变形菌（Proteobacteria）、绿弯菌（Chloroflexi）、放线菌（Actinobacteria）和酸杆菌（Acidobacteria）为主;属分类水平上的优势类群为芽孢杆菌（Bacillus）、苍白杆菌（Ochrobactrum）、拟无枝菌酸菌（Amycolatopsis）和鞘脂单胞菌（Sphingomonas）等。相关性分析发现盐度和亚硝酸盐浓度对细菌群落多样性和丰富度影响显著。功能预测分析表明,有植被区域沉积物细菌在氨基酸代谢、膜运输和碳水化合物代谢方面功能活跃,而无植被区域细菌则在核酸复制和修复、能量代谢过程方面更为活跃。     

Dissolved glucose in a bayou estuary,possible sources and utilization by bacteria

Surface and bottom samples were collected twice a month over a period of one year from three stations in Bayou Texar, Pensacola, Florida. Samples were analyzed for primary productivity, inorganic carbon, bacterioplankton heterotrophic productivity, dissolved glucose, and bacterial numbers. Dissolved glucose concentrations were generally high and displayed a seasonal pattern with variations being accompanied by corresponding changes in rates of glucose uptake by bacteria. A relationship between dissolved glucose and carbon fixation was found to exist at the upper station but diminishes toward the lower stations. It is believed that this is most likely the result of increased mixing by wind action.     

Assessment of possible sediment toxicity of contaminated sediments in Port Jackson, Sydney, Australia

A considerable amount of chemical data is available for surficial sediments in Port Jackson. Some of the highest concentrations of heavy metals, organochlorines and polycyclic aromatic hydrocarbons of any capital port occur in sediments mantling shallow tributaries and embayments close to central Sydney. However, these data have limited ability to predict adverse effects on living resources and in the absence of toxicological data, sediment quality guidelines (SQG) have been used to assess the possible adverse biological effects of sedimentary contaminants in this estuary. Several SQGs are currently available for both fresh and marine environments, but the scheme used in the current study is based on empirical analysis of matching chemical and biological data compiled by the National Oceanographic and Atmospheric Administration (NOAA) in the U.S. The NOAA SQG can be used to assess individual chemicals, or to estimate the probability of acute sediment toxicity by calculating `mean quotients' for a large range of contaminants. Although many individual chemicals in sediment exceed SQG over extensive parts of Port Jackson, `mean quotient' results suggest that only a small proportion (1%) of the harbour may be highly toxic (74% probability of toxicity). However, sediment in a considerably larger proportion of the port (almost 25%) is estimated to have a 49% probability of being toxic using the `mean quotient' approach. These results are indicative at best and contemporaneous chemical/biological/ecotoxicological studies are needed to verify the applicability of SQG developed in the U.S. for use outside North America and site specific studies of this type are still required to determine the toxicity of sediments in Port Jackson.     

Diffusive exchange of linear alkylbenze suifonates (LAS) between overlying water and bottom sediment

Linear alkylbenzenesulfonate (LAS) was detected in a 0–30 cm deep sediment column collected in Lake Teganuma (one of the most polluted lakes in Japan). The range of the LAS concentration in sediments was between 0.1 and 500 µg g^–1 (C₁₁-C₁₄ homologs per dry solid) and its vertical profile showed a seasonal variation. A mathematical model, which includes a diffusion term and a biodegradation term, was used to simulate the temporal variation of LAS in the sediment column and to calculate the diffusive flux rate of LAS across the sediment/water interface. An averaged diffusion coefficient of 2.4 × 10^–5 cm² s^–1 for the sediment interstitial water was obtained from sediment core samples located in Lake Teganuma. The biodegradation rate constant (0.002 d^–1) of LAS in the sediment obtained from the model analysis was considerably less than that reported for LAS in anaerobic waters. These results confirm that a model describing diffusive transport and biodegradation of LAS in the sediments can simulate the temporal variation of LAS in near surface sediments. The diffusive flux rate from overlying water to bottom sediment was calculated to be between –0.20 and 0.52 (C₁₁-C₁₄ LAS) mg m^–2 h^–1 and the annual net flux rate was 0.7 g m^–2 y^–1.     

象山港网箱养殖对近海沉积物细菌群落的影响

微生物在有机物质分解、能量转移等生物地化循环中起着重要作用,研究养殖活动对沉积物中微生物多样性的影响对正确评价近海生态系统结构和功能具有重要意义.结合沉积物的理化分析(T、pH、Eh和SO2-),通过T-RFLP(末端限制性片段长度多态性)分析了象山港网箱养殖对近海不同深度沉积物中细菌群落结构和多样性的影响,构建了对照区0-5 cm沉积物样品的细菌16S rRNA基因克隆文库,并进行了系统发育分析.结果表明,近海网箱养殖活动不但使象山港沉积物Eh、pH值等理化性质有所改变,而且使细菌的群落结构也发生了变化,变形细菌纲细菌的相对丰度降低,细菌群落的多样性和均匀度也显著降低,致使近海沉积物细菌群落由多样性高的稳定结构向多样性降低的不稳定结构转变.     

Dynamics of nutrients and faecal bacteria in a macrotidal estuary,the Bay of Somme (France)

A stratified methodology for water sampling on tidal flats was adopted in 1988 and 1989 in the Bay of Somme. Analyses of nutrients, particulate matter and faecal germs showed the poor mixing of fresh and marine water and the weakness of stratification of the water column. Freshwater is pushed by marine water to the inner reaches of the bay and there are only a few lenses with true estuarine characteristics. In 1990, water was sampled simultaneously on the Somme river, the tidal flats and in the open sea, in order to point out estuarine gradients of several physical and chemical parameters and their evolution during a tidal cycle. The role of continental inputs was confirmed for faecal pollution, nitrate (20–25 mg l⁻¹), nitrite and silicate. The importance of ammonium excreted by the estuarine benthic populations was highlighted. High concentrations of continental chlorophyll (450 mg m⁻³) were also measured and contribute, with nitrates and ammonium, to eutrophication in the Bay of Somme. Pollution of the southern part of the bay by marine waters was regularly observed during the flow, raising doubts about the purifying capacity of sea-water and the conservation of faecal bacteria. A regular survey of fresh-water inputs and sea-water quality, offshore and within the bay, is considered to enable estimation of their respective influences in eutrophication processes in the Bay of Somme.     

洱海沉积物中反硝化细菌的分离与反硝化作用研究

自洱海十个点位的沉积物中富集筛选出101株反硝化细菌并从中筛选出1株较强反硝化能力的细菌,命名为EH314。该细菌接触酶(过氧化氢酶)试验、产硫化氢试验和淀粉水解均为阳性,葡萄糖氧化发酵实验结果为氧化菌,产脂酶(Tween 80)试验结果为阴性;初步鉴定该菌为产碱杆菌属细菌;对细菌反硝化能力进行测定发现,菌株EH314能有效地降解水体中的硝酸盐且反硝化可在有氧条件下进行。     

Influence of bacterial density on the exchange of phosphate between sediment and overlying water

Fluxes of phosphate across the sediment–water interface have been measured using inhibitors of bacterial activity sterilization and chloramphenicol and a control in order to quantify the influence of bacterial abundance on them. Results show that phosphate concentration in the interstitial water decreased when bacteria were present, in relation to treated aquaria. The measured (Jo) and theoretical fluxes (Jd) of phosphate also were higher when bacterial activity was suppressed. Mass balance calculated for Carbon, Nitrogen and Phosphorus in the sediment revealed a loss of theses compounds when bacterial activity was suppressed, and a net accumulation of Carbon and Phosphorus, and loss of Nitrogen under natural conditions.