Carbon flow across the sediment-water interface in Lake Vechten,The Netherlands

The turnover and exchange rates, as well as the diffusion processes, concerning the input and output of carbon compounds at the mud-water interface, were studied. The carbon input rates were derived from the annual sedimentation rates of particulate organic matter (about 1 100 kg C · yr⁻¹). The nature of the sedimented POC, and its breakdown pathways and turnover rates towards important metabolic intermediates in methanogenesis, were examined. The breakdown kinetics ofChlorella cell walls, a dominant green alga in Lake Vechten, was studied using U-¹⁴C-labelled cell walls. The breakdown of the cell walls appears to the rate-limiting step in anaerobic mineralization. Using first order kinetic equations, and HPLC and GLC and radio-chemical methods, turnover rate constants (k-values) of between 0.18 and 0.32 day⁻¹ and pool sizes of algal cell walls of 37 to 80 μg · g⁻¹ wet mud were found, giving turnover rates of 7.7 to 25.6 μg · g⁻¹ · day⁻¹ of cell wall material. The turnover rates (k-values between 0.07 and 0.31 h⁻¹) of acetate, the most important breakdown product, and its concentration gradients (between 5 and 30 μmol) and diffusion coefficient (D_s = 2.2 × 10⁻⁶ cm² · s⁻¹) just in and above mud-water interface, was quantified. The diffusion of acetate, within the sediments, could not account for the turnover rates observed. Finally, from acetate flux data and from those on the rates of formation of carbon dioxide and methane, the output of carbon and its cycling in Lake Vechten are discussed.     

全氟辛酸在沉积物-水界面污染及吸附迁移行为研究进展

全氟辛酸(PFOA)是一种重要的全氟化表面活性剂,具有环境持久性、高毒性和生物累积性等特征,成为当前备受关注的新污染物。沉积物是PFOA的重要环境储蓄库,被污染后的沉积物可作为长期污染源造成上覆地表水及周边地下水污染。本文结合近年来国内外研究,对地表水和沉积物中PFOA的来源、污染现状和界面吸附迁移行为进行了综述。结果表明: 地表水体和沉积物中PFOA最主要的污染来源为工业废水排放。全球范围地表水体和沉积物中PFOA污染水平普遍为ng·g^-1和ng·L^-1数量级,且国内部分地区污染形势更为严峻。沉积物组分、水化学条件、有机质及表面活性剂等因素均影响沉积物中PFOA的吸附行为,但目前在吸附主控机制方面仍然存在争议。沉积物中PFOA迁移行为的研究正处于起步阶段,相关报导还较为缺乏,对于迁移机理的认识还很不足,今后需在该方面加大研究力度。     

Incidence of mussel culture on biogeochemical fluxes at the sediment-water interface

Upward nutrient fluxes at the sediment-water interface were studied in a mussel farming zone (Carteau, Gulf of Fos, France) in order to estimate the impact of organic matter input from biodeposition. Nitrate, nitrite, ammonia, silicate, phosphate and oxygen were measured. Fluxes were estimated by means of polyacrylate benthic chambers placed at sites located under (UM) and outside (OM) the rope hanging structures. Transformation of biodeposited organic matter increases phosphate, silicate and ammonia fluxes. No variation in nitrite fluxes could be detected and only minor differences were observed in nitrate and the oxygen production/consumption equilibrium at the two stations. Phosphate and silicate fluxes, which were always higher at the UM than at the OM site, decreased from spring to winter. Ammonia fluxes were very high under mussel cultures in May and September and lower in November. The fact that ammonia flux was always higher at the UM than at the OM sites might be explained by degradation of mussel biodeposit, as well as by benthic macrafauna excretion. Discrepancies between fluxes of the nutrients studied at the UM and OM sites increased as organic particulate matter in the water column decreased. Variations of oxygen flux followed a different pattern, since they were correlated with presence and abundance of photosynthetic microphytes on the bottom and in the water. Bottom respiration exceeded production of oxygen only in May 1988 at the UM station.As it now stands, biodeposit input into the sediment under mussel ropes does not affect the ecosystem, although the flow of nutrients towards the water column is higher than in other areas.     

亚热带河口陆基养虾塘水体溶解性碳浓度及沉积物-水界面碳通量时空动态特征

以福建闽江和九龙江河口陆基养虾塘为研究对象,通过野外原位观测和室内模拟培养实验,开展了河口陆基养虾塘养殖期间水体溶解性有机碳(DOC)和溶解性无机碳(DIC)及养虾塘沉积物-水界面碳交换通量变化特征的研究。结果表明:时间变化上,养虾塘水体溶解性碳浓度及沉积物-水界面碳通量在闽江河口呈现8月中旬10月中旬6月中旬的特征,在九龙江河口表现为随养殖阶段推移而增加的趋势;空间变化上,闽江河口养虾塘水体溶解性碳浓度及沉积物-水界面碳通量显著高于九龙江河口;沉积物释放溶解性碳速率与水体溶解性碳浓度呈现显著正相关关系,沉积物碳释放过程是引起养虾塘水体溶解性碳浓度时空变化的重要因素。表明河口区水产养虾塘碳循环研究时需考虑不同形态碳生物地球化学循环的时空差异性。     

Influence of oyster culture on biogeochemistry and bacterial community structure at the sediment-water interface

Bacterial community structure and some biogeochemical parameters were studied in the sediment of two Pacific oyster farming sites, Aber Beno?t (AB) and Rivière d'Auray (RA) in Brittany (France), to examine the ecological impact of oysters and to evaluate the emission of sulfide and ammonia from sediment. At AB, the organic matter accumulated in the sediment beneath the oyster tables was rapidly mineralized, with strong fluxes of ammonia and sulfide that reached 1014 and 215?μmol?m(-2) h(-1) , respectively, in June 2007. At RA, the fluxes were about half as strong on average and better distributed through the year. The ammonia and sulfide concentrations in the overlying water never reached levels that would be toxic to oysters in either site, nor did hypoxia occur. Total culturable bacteria (TCB) varied greatly according to the temperature: from 1.6?×?10(4) to 9.4?×?10(7) cell?g(-1) sediment. Inversely, the bacterial community structure remained surprising stable through the seasons, marginally influenced by the presence of oysters and by temperature. Bacterial communities appeared to be characteristic of the sites, with only one common phylotype, Vibrio aestuarianus, a potential oyster pathogen. These data refine the hypothesis of seawater toxicity to oysters because of ammonia and sulfide fluxes and show that the measured environmental factors had only a weak influence on bacterial community structure.     

鄱阳湖秋季水-气界面CH4排放通量的区域差异及影响因素

有限的观测点以及空间的异质性已经成为准确估算湖泊水-气界面CH4通量的挑战。鄱阳湖是我国最大的淡水湖,为了解秋季湖区水-气界面的CH4排放通量,2010年10月利用密闭静态箱-气象色谱法对星子、都昌、南矶山和吴城4个湖区水-气界面CH4排放通量及气象、底泥、水体等因素进行了测定。研究表明,都昌湖区CH4排放通量平均值为0.26mg·m-2·h-1,显著高于星子(0.15mg·m-2·h-1)、吴城(0.13mg·m-2·h-1)和南矶山(0.10mg·m-2·h-1)湖区。鄱阳湖水-气界面秋季CH4排放通量平均为0.17mg·m-2·h-1,变异系数为58.6%。相关分析表明,风速显著影响CH4排放通量(P<0.01)。在排除风速>5m·s-1的数据后,底泥有机碳以及水体铵态氮含量与CH4排放通量显著相关,而水体DOC含量与CH4排放通量呈显著负相关(P<0.05)。对鄱阳湖CH4排放量的精确估算,依赖于较广区域和较长时间的观测。     

Sewage pollution and the infaunal benthos of Victoria Harbour,Hong Kong

Victoria Harbour, Hong Kong, receives 800 million litres · day^?1 of untreated sewage from 3.6 million people, but is flushed by tidal currents at velocities up to 1.1 m · s^?1. Two replicate Smith-McIntyre grab samples were collected at 66 stations in August 1979, yielding a total of 5797 animals belonging to 68 species. Agglomerative hierarchical classification was used to delineate five station groups; a sixth group contained four stations where no fauna were found. All but one of the groups inhabited fine sediments (> 70% silt-clay) and could be placed along a gradient conforming to the typical pattern of organic pollution effects found in boreal and temperate waters. Abiotic areas, found in enclosed typhoon shelters, were successively replaced by a very poor fauna, a peak of opportunists, an ecotone point and a transition to normal fauna. The peak of opportunists was dominated by the oligochaete Thalassodrilidesgurwitschi (Hrabe); the polychaetes Capitella capitata (Fabricius) and Minuspio cirrifera (Wiren) were also numerous. Overall abundance was low (784 individuals · m^?2) compared with opportunists in boreal and temperate waters. The remaining station group was found in coarser sediments (<40% silt-clay) and an inflexion was observed in the log-normal distribution of individuals per species. Dominant species included the bivalve Tapes philippinarum (Adams & Reeve) and the polychaete Minuspio cirrifera; overall abundance was high (1103 individuals · m^?2). In general, pollution was assessed by the pattern of changes in number of species, abundance, biomass, diversity and evenness, by log-normal distributions of individuals per species, and by the indicator species M. cirrifera. When compared with earlier (1976) data, community conditions were generally similar but the abundance of individual species varied greatly and M. cirrifera was absent. The severely polluted area was ≈ 15 km²; this is similar in extent to offshore discharge sites and indicates the importance of tidal flushing in this inshore channel.     

Assessing the impact of sewage effluent on the ecosystem health of the Toronto Waterfront (Ashbridges Bay), Lake Ontario

The ecosystem health of the Toronto Waterfront (Ashbridges Bay), Lake Ontario which receives treated sewage effluent was investigated during 1987 and 1988 by means of a functional and structural battery of tests. The functional tests included in situ size-fractionated primary productivity, Algal Fractionation Bioassays (AFBs), unfiltered and filtered bioassays, and sediment assays with Daphnia magna and Hyalella azteca. The structural evaluation involved the biomonitoring of the components of the microbial loop, such as bacteria, autotrophic picoplankton, heterotrophic nanoflagellates, and protozoa. The experimental results reveal a diversity of physiological responses to the complex nutrient and contaminant regimes by the indigenous phytoplankton. There was no evidence of the impact of chlorination on the primary productivity of the Bay. The overall productivity was higher during the post-chlorination period than the pre-chlorination phase. The high rates of microplankton + netplankton productivity near the outfall have been attributed to the bioavailability of nutrients which, quite possibly, exert ameliorating effects on metal toxicity. In contrast, the low ultraplankton rates have been interpreted to be due to their well-known sensitivity to contaminants. The Effluent Receiving Water Bioassays (ERWB) with filtered and unfiltered experiments provided interesting insight and appear to be a potentially useful assessment tool. Generally, the unfiltered water compared to the filtered was toxic to the offshore test phytoplankton. This demonstrates a unique ecological adaptation to the prevailing in situ conditions by the Bay community which might be important from the restoration point of view. However, the offshore population was found to be sensitive to the particulate-bound toxicity as indicated by the unfiltered bioassays. Consequently, it is essential to probe the complexity of nutrient-contaminant interactions which ultimately appear to determine the toxicity and the resulting health of the biota. Furthermore, our experiments have shown that the particulate-matter is an important carrier of both nutrients and contaminants in Ashbridges Bay. The sediment bioassays for Station 419 indicated that sediments were toxic during both the pre- and post-chlorination phases. Both solid and liquid phase testing indicated toxicity of sediment to the acute Daphnia test. The Hyalella chronic assay showed good survival during the 4-wk period of the experiment, in contrast to the toxicity observed for phytoplankton and Daphnia. This may be due to large mounts of organic matter available in the Bay. The invertebrate bioassays confirmed the lack of impact of chlorination. Finally, the microbial loop seems to be a sensitive, rapid, and an early warning bioindicator of anthropogenic stress. The multi-trophic battery of structural and functional strategy adopted in our laboratory appear to be holistic and effective. The strategy has a considerable potential for developing eco-technology for a badly needed assessment and restoration of ecosystem health of the Great Lakes as well as other perturbed environments in the world.     

太湖梅梁湾冬季水-气界面二氧化碳通量日变化观测研究

应用静态箱式法对太湖梅梁湖区冬季(2003年12月23日8:00~26日6:00)的水气界面CO2通量进行了昼夜连续观测,共测得60组数据,分析了梅梁湾湖区CO2通量的冬季日变化规律。结果表明,在光照条件较好,风速较小情况下,白天梅梁湾湖区为CO2的汇,极大值出现在14:00时,其平均CO2通量为-3.01 mg.m-2.h-1;夜间梅梁湾湖区CO2通量值为-0.897~1.006 mg.m-2.h-1,其平均通量为-0.02 mg.m-2.h-1;在阴天、风速较大时,湖区CO2通量日变化与前面有较大差异,表现为CO2的强源,最大CO2通量达到76.53 mg.m-2.h-1。     

Application of SWITCH,a model for sediment-water exchange of nutrients,to Lake Veluwe in The Netherlands

The formulations of SWITCH, a model for prediction of nutrient fluxes across the sediment-water interface, are presented. Results of the application to data on the sediment of Lake Veluwe are presented and discussed.SWITCH calculates the thicknesses of the aerobic and denitrifying layers on the basis of a step-wise steady state approach. The concentrations of detritus, ammonium, nitrate and phosphate in the sediments and the pore water are simulated dynamically using mass balance equations.Analysis of the data for Lake Veluwe show large spatial heterogeneity. This presents a major drawback for the calibration of SWITCH, which focused on the silty part of the lake. The results show that the model simulates realistically and consistently layer thicknesses, concentrations and mass fluxes connected with the transport and conversion processes. The model appears to have potential for describing both seasonal patterns and developments on the long term.SWITCH calculates strongly increased phosphate return fluxes, following total reduction of the top sediments. An important hypothesis in the model is that phosphate precipitated in reduced sediment layers is transferred to the oxidized layer and dissolves instantaneously. This results in a decrease of the phosphorus content of the sediment, but also maintains high release rates of phosphorus after the reduction of the external phosphorus loading of Lake Veluwe. Model results and mass balance studies for the overlying water indicate that the removal of phosphorus to deeper sediment layers is underestimated or that dilution of the sediments occurs as the result of sedimentation.     

miRNAs at the interface of cellular stress and disease

microRNAs (miRNAs) are a family of small, non‐coding RNAs, which provides broad silencing activity of mRNA targets in a sequence‐dependent fashion. This review explores the hypothesis that the miRNA machinery is intimately linked with the cellular stress pathway and apparatus. Stress signaling potentially alters the function of the miRNA‐bioprocessing core components and decompensates regulation. In addition, dysregulation of miRNA activity renders the cell more prone to stress and emerges as a new pathway for age‐related insults and diseases, such as neurodegeneration.     

Evaluation and use of a diffusion-controlled sampler for determining chemical and dissolved oxygen gradients at the sediment-water interface

Field and laboratory evaluations were made of a simple, inexpensive diffusion-controlled sampler with ports on two sides at each interval which incorporates 0.2-m polycarbonate membrane to filter samples in situ. Monovalent and divalent ions reached 90% of equilibrium between sampler contents and the external solution within 3 and 6 hours, respectively. Sediment interstitial water chemical gradients to depths of tens of centimeters were obtained within several days after placement. Gradients were consistent with those determined from interstitial water obtained by centrifugation of adjacent sediment. Ten milliliter sample volumes were collected at 1-cm intervals to determine chemical gradients and dissolved oxygen profiles at depth and at the interface between the sediment and water column. The flux of dissolved species, including oxygen, across the sediment-water interface can be assessed more accurately using this sampler than by using data collected from benthic cores.     

Chemical characteristics,with particular reference to phosphorus,of the rivers draining into Lake Naivasha,Kenya

The loss of phosphorus from the catchment of Lake Naivasha, Kenya, was 0.2 kg ha^–1 ann^–1, 76% of it particulate in a `normal' year of wet and dry periods. It rose to a mean of 1.8 kg ha^–1 ann^–1, 90% of which was particulate, in the months following the extreme rainfall which followed the 1997–1998 El Niño event in the Southern Atlantic. Total and particulate phosphorus were positively correlated with suspended solids and with discharge, and conductivity was negatively correlated with discharge. The magnitude of losses pose both threats to the water quality of Lake Naivasha and to the sustainable soils resources of the catchment.     

Physiological responses to stress with reference to the domestic fowl.

Environmental stress may effect the outcome of routine investigations as well as experimental procedures. This is illustrated by investigations in the domestic fowl.     

Morphology and ultrastructure of teratological forms of the diatoms Stephanodiscus niagarae and S. parvus (Bacillariophyceae) from Hamilton Harbour (Lake Ontario,Canada)

Teratological forms of Stephanodiscus niagarae Ehrenb. and S. parvus Stoermer & Håkansson were observed during a study of diatoms preserved in a radiometrically dated core from Hamilton Harbour (Lake Ontario, Canada). Morphological features and ultrastructures of both species were studied under the light and scanning electron microscope. The valve structure of abnormal forms of S. niagarae appears to be weakly silicified, especially in the central area. The shape of satellite pores are very irregular in comparison with the round shape of the normal specimen. The central fultoportulae are characterized as small tubes extending out of the external valve. Two types of abnormal frustules are present in the population of S. parvus studied. In one type valves are underdeveloped and only the siliceous layer and ribs are present, and in the other type the valves are strongly silicified and the areolae are almost completely occluded.The teratological forms of both species appeared in the core sediments after 1911, and both became the dominant components of diatom assemblages after 1970. Their occurrence and increased abundance coincides with records of heavy metal pollution in the harbour.     

Conflicting interests in Toronto: anatomy of a controversy at the interface of academia and industry

In December 2000, the University of Toronto breached a contract it held with me, initiating a sequence of events that has led to a public letter to the University from a large number of senior figures in the psychopharmacology community, protesting against the infringement of academic freedom involved, and a first-ever legal action seeking redress for violation of academic freedom. This case has been intertwined from the start with a longer running debate about the possibility that the SSRI group of antidepressants may have the potential to trigger suicidality or other serious effects in a subgroup of takers. And this specific issue connects to concerns about conflict of interest in the domain of therapeutics, as well as in science in general, the ghostwriting of scientific articles, and a series of other hot-spots on the interface between academia and industry.     

Biological consequences of marine pollution with special reference to the North Sea fisheries

Summary 1. A case of copper pollution on the Dutch coast is used to demonstrate that waste disposal in inshore waters can easily lead to damage to the living resources of the sea, since dilution is under such conditions a much slower process than is usually assumed.2. Pollution by domestic sewage, its direct hazards for human health, and its contaminating effect on shellfish, is discussed. Next to these direct and indirect health hazards, discharge of domestic waste may lead to eutrophication, which in its turn can contribute to the development of plankton blooms producing truly poisonous metabolites. Some examples of eutrophication of the marine environment are given.3. Of the industrial waste, examples are given which clearly demonstrate how dangerous discharge of heavy metals and pesticides can be, also in the marine environment. Possible effects of petrochemical waste products and of synthetic detergents and soaps are discussed.4. Radio-active waste disposal in sea is more carefully studied and monitored than disposal of other types of waste.5. The increasing quantity and variety of industrial waste is a reason for serious concern. Careful discrimination between the many products is advocated and discharge far offshore is advised for certain categories of pollutants. Pesticides and other very dangerous products should never be admitted in the shallow sea areas, so important as nursery grounds for the fishery resources.

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Biologische Konsequenzen der Meerwasserverschmutzung unter besonderer Berücksichtigung der Nordseefischerei

Kurzfassung Obwohl das Gesamtvolumen der Ozeane erheblich größer ist als der Süßwasservorrat der Welt, so kann doch das hemmungslose Einbringen von Haus- und Industrieabwässern in das Meer zu schädlichen Folgen für den Bestand der Meeresflora und -fauna führen. Besonders anfällig sind die Küstengewässer, da diese oft die Ernährungsgrundlage für viele Nutzfische bieten und zudem dort Austern und Miesmuscheln gezüchtet werden. Aus wirtschaftlichen Gründen erfolgt andererseits das Verklappen von Abfall und Unrat vorzugsweise dicht unter der Küste. Schädliche Wirkungen können erfolgen durch Bakterien- und Virusinfektionen, durch biologische Akkumulation von Schwermetallen und von Schädlingsbekämpfungsmitteln (unter ihnen besonders chlorhaltige Kohlenwasserstoffe), durch petrochemische Produkte, wodurch übler Geschmack bei Fischen und Muscheln hervorgerufen wird, und durch eine allgemeine Eutrophierung, die zu einer Vermehrung von unerwünschtem Plankton führen kann.

     

Biogenic silica record in the sediments of Little Round Lake,Ontario

The biogenic silica (BSi) record has been determined in the sediments of Little Round Lake, Ontario in order to review its postglacial development and study the relationship between BSi and diatoms. BSi concentrations in the sediment stratigraphy were found to correspond for the most part to the trophic history of Little Round Lake. Calculation of accumulation rates for BSi improved the correspondence of the BSi profile to the trophic history. Thus, BSi is a valuable paleoindicator when concentration and flux profiles are considered concurrently. Regression analysis of BSi and diatoms revealed that the concentration of BSi in the sediments was not a simple function of diatom numbers or biovolume, but that factors such as a correction for the rate of dissolution and abundance of chrysophycean scales and cysts were also important.     

Ecology of the bacteria of the sulphur cycle with special reference to anoxic-oxic interface environments

H2S is produced as a main end-product of anaerobic mineralization in anoxic, sulphate-rich environments by a diverse population of sulphate-reducing bacteria. The sulphate reducers can carry out an almost complete oxidation of detrital organic matter to CO2. The H2S consequently becomes an important electron carrier from the anoxic to the oxic world. Thiobacilli and other colourless sulphur bacteria have the potential to oxidize the H2S at the oxic-anoxic interface in sediments or stratified waters, but their role is still poorly understood. A comparison of sulphide oxidation processes in the chemoclines of the Black Sea, the Solar Lake and in A beggiatoa mat indicated that depth scales and retention times of coexisting O2 and H2S regulate the bacterial involvement in the sulphide oxidation. The H2S specialists, Beggiatoa and Thiovulum, are optimally adapted to compete with the autocatalytic oxidation of H2S by O2. Microelectrode measurements show retention times of O2-H2S in the bacterial mats or veils of less than 1 s. In photic chemoclines of stratified waters or sulfureta, the phototrophic sulphur bacteria or cyanobacteria interact with the sulphide oxidation at the O2-H2S interface. Short cycles between H2S and intermediate oxidation products, So or S2O2 3-, are created. The bacteria of the sulfuretum are highly adapted to the diurnal rhythm of light, O2 and H2S.