Environmental factors as forces structuring the fish community of the Elbe Estuary

Smelt, flounder, eel, three-spined stickleback, twaite shad, ruffe and herring were the major species among 62 forming the fish community of the Elbe estuary. Species richness, species diversity, evenness and total fish biomass decreased in the upstream direction. Total abundance was greatest during summer. Salinity was the most significant physico-chemical factor affecting species richness and total fish biomass, whereas water temperature was the best predictor of total abundance. Marine fish species decreased with decreasing salinity, while the freshwater species roach and ide were absent at salinities > 15‰. Bream, blue bream, white bream, perch and pikeperch occurred more frequently in shallow marginal regions with lower current velocities, while herring and other marine species occurred closer to the deep central regions with high current velocities. Annual and seasonal variations of the community structure mainly reflected in population dynamics of smelt, flounder, twaite shad, three-spined stickleback and eel, especially those of 0-age smelt. Populations of smelt and ruffe and their importance in the fish community increased between 1989 and 1992, while those of twaite shad and eel decreased. At oxygen concentrations <3 mg I¹, smelt and flounder were rare, but eels were at their maximum at 3.5 mg I⁻¹. Changes of species composition and fish abundance were closely related to daytime and tidal cycle.     

The Antenna Size of QB-reducing Photosystem 2 Complexes in Different Fractions of Subchloroplast Particles

The antenna sizes of QB-reducing photosystem 2 (PS2) complexes in two different fractions of the subchloroplast particles were compared by measuring time corresponding to the second maximum of the first derivative from induction curve of chlorophyll fluorescence as a function of actinic irradiance. The QB-reducing PS2 complexes in the fraction of particles that originated from inner parts of grana thylakoids had smaller antennae than those in the fraction from non-appressed regions of thylakoid membranes.     

ATP Synthesis Coupled to Nitrate Photoreduction in the Alga Hydrodictyon africanum

The presence of exogenous stimulates O₂evolution in illuminated H. africanum cells at the CO₂ compensationpoint, and it is likely that reduction in the light uses reductant produced in non-cyclic electron flow.When sources of ATP other than fermentation are absent, thepresence of , light, and a functional non-cyclic electron transport pathway stimulates active, ATP-dependentH₂ influx. This is consistent with non-cyclic electron flow associated with reduction being coupled to ATP synthesis. This -dependent ATP synthesis may be quantitatively important as a source ofATP during photolithotrophic growth with as N source in H. africanum and other algal unicells.     

Degradation of Phenol Compounds by Microbial Communities of the Amur Estuary

The microbiological transformation of various phenol compounds and their origin in the mixing zone of the Amur Estuary is considered. The results of the model experiments on the decomposition and transformation of phenol compounds by microbial communities and bacteria are reported. Self-depuration of the Amur Estuary depends on the mechanisms of the transformation of aromatic compounds in the presence of cosubstrates, the enzymatic activity of microbial communities, and the temperature. In winter, the ecological risk of pollution by aromatic compounds increases.     

Observations of the Suspended Matter Distribution Dynamics in the Elbe Estuary from Time Series Aerial Photographs

Series of aerial photographs taken with an interval of 6 Minutes were used to study the dynamics of the suspended matter distribution in a 1 km section of the Elbe Estuary. The observations show heterogeneous distribution patterns which are different at each phase of the tidal cycle. The comparison with the bathymetry indicates that the distribution is mainly a function of the river bed topography, which modifies the local current structure. The surface distribution in the fairway region is especially determined by the ship traffic.     

Soil Ingestion Estimates for Children in Anaconda Using Trace Element Concentrations in Different Particle Size Fractions

This investigation assessed the effect of soil particle size on soil ingestion estimates of children residing at a superfund site. Earlier research indicated that wide intertracer variability in soil ingestion estimates are based on soil concentrations with a soil particle size of 0 to 2?µm was markedly reduced when the estimates were based on soil tracer concentrations for a soil particle size of 0-250?µm. The reduced intertracer variation was principally attributed to changes in soil concentrations of only three of the soil tracers (i.e., Ce, La, Nd) which became concentrated in the finer particle size by approximately 2.5 to 4.0-fold. It was hypothesized that the intertracer agreement in soil ingestion estimates may continue to improve if the estimates are based on concentrations of tracers at finer particle sizes assuming that children ingest finer particles and that the above three tracers would continue to be further concentrated in the finer sized soil particles. The principal findings indicate: 1. The soil concentrations of Al, Si, and Ti do not increase at the two finer particle size ranges measured. 2. The soil concentrations of Ce, La, and Nd increased by a factor 2.5 to 4.0 in the 100 to 250?µm particle size range when compared with the 0 to 2?µm particle size range. No further substantial increase in concentration was observed in the 53 to 100 |jm particle size range. 3. The soil ingestion estimates are consistently and markedly changed only between the estimates based in 0 to 2?µm and 100 to 250?µm for Ce, La, and Nd. These changes reduced the intertracer variability in estimating soil ingestion, suggesting that the children eat finer soil particle sizes. 4. Because the particle sizes for all tracers (except Zr) were only modestly affected at the 53 to 100?µm range, it was not possible to confidently resolve the particle size of soil ingested by the children. 5. Residual intertracer variability in soil ingestion estimates based on Ce, La, Nd are likely to be significantly affected by non-food, non-soil sources of these tracers (i.e., source error). 6. Soil ingestion estimates of this study will be more reliable when derived from the finer-sized particles.     

Contribution of Priority PAHs and POPs to Ah Receptor-Mediated Activities in Sediment Samples from the River Elbe Estuary,Germany

The estuary of the River Elbe between Hamburg and the North Sea (Germany) is a sink for contaminated sediment and suspended particulate matter (SPM). One major concern is the effect of human activities on the hydrodynamics, particularly the intensive dredging activities in this area that may result in remobilization of sediment-bound pollutants. The aim of this study was to identify pollutants contributing to the toxicological risk associated with re-suspension of sediments in the Elbe Estuary by use of an effect-directed analysis that combines chemical and biological analyses in with specific fractionation techniques.Sediments were collected from sites along the Elbe Estuary and a site from a small harbor basin of the Elbe Estuary that is known to be polluted. The sixteen priority EPA-PAHs were quantified in organic extracts of sediments. In addition, dioxin equivalents of sediments were investigated by use of the 7-ethoxyresorufin O-deethylase assay with RTL-W1 cells and the Ah receptor-mediated luciferase transactivation assay with H4IIE-luc cells.Quantification of the 16 priority PAHs revealed that sediments were moderately contaminated at all of the sites in the Elbe River Estuary (<0.02–0.906 µg/g dw). Sediments contained relatively small concentrations of dioxin equivalents (Bio-TEQ) with concentrations ranging from 15.5 to 322 pg/g dw, which were significantly correlated with dioxin equivalents calculated based on toxicity reference values and concentrations of PAH. The concentration of Bio-TEQ at the reference site exceeded 200,000 pg/g dw. In a potency balance the 16 PAHs explained between 47 and 118% of the Bio-TEQ in the luciferase assay, which can be explained by the constant input of PAHs bound to SPM from the upper course of the Elbe River into its estuary. Successful identification of a significant portion of dioxin-like activity to priority PAHs in complex environmental samples such as sediments has rarely been reported.     

Melano-macrophage centres in liver and spleen of ruffe(Gymnocephalus cernua) from the Elbe Estuary

Macrophages with yellow or black deposits of melanin occur singly or in groups in the melano-macrophage centres are functionally the primitive analogues of lymph nodes in birds and mammals. From 1980 to 1982, tumours and pretumorous tissue changes in ruffe from the Elbe Estuary were studied. Pathological alterations occur mainly in the liver and spleen. In connection with both, neoplastic abnormalities in liver and spleen, and fatty degenerative processes in the liver, an obvious increase in number and size of the melano-macrophage centres was observed. The colour, structure and some histochemical properties of melano-macrophage centres in the liver differ somewhat from those in the spleen. The majority of splenic centres were filled with large amounts of haemosiderin, whereas many hepatic macrophages contained fatty inclusions. Possible differences in the functions of splenic and hepatic melano-macrophage centres are discussed.     

Trophic diversity within the planktonic food web of the Elbe Estuary determined on isolated individual species by 13C analysis

The uptake of organic substrates by heterotrophic planktonicorganisms was studied along the freshwater Elbe Estuary in May,July and October 2000 using ¹³C analysis of individually isolateddominant species of copepoda, cladocera, rotifera and ciliata.Non-sedimenting suspended particulate matter (SPM_ns) was separatedfrom sedimenting matter and further analysed for the chemicalcomposition of its different size fractions in order to estimatesubstrate availability. Particles <5 µm accounted for15% of total SPM_ns [40 mg dry weight (DW) L^–1] and containedC:N ratios indicating a predominance of living matter (i.e.mass C:N of phytoplankton). All species under study exhibiteda high capacity for selective feeding with little variationin the diet along the whole freshwater profile. Picoplanktonof 0.2–1.2 µm formed mainly by bacteria had a ¹³Cvalue of –26 in May and July and –29 in October,similar to the ¹³C of the dissolved organic carbon (DOC). Bacteriadid not fractionate isotopically and did not preferentiallyconsume specific subunits of their substrate, i.e. they exhibitedno trophic shift. It appears that phytoplankton exudates werea minor component to total DOC in this estuary. Phytoplanktonwas the exclusive food for all phagotrophic organisms understudy in July, thus only one trophic level was exhibited. DuringMay and October the grazers under study used different substrates,resulting in a planktonic food web of three trophic levels formedby different species of the taxonomic groups under study. Theresults indicate a conditioned behaviour with regard to substrateselection allowing the grazers to produce high abundances evenwhen particles were abundant and competition for phytoplanktonwas high.     

Pigment characterisation of suspended matter in association with particulate heavy metal loadings in the German Bight and Elbe Estuary

The pigment fingerprints, determined by HPLC, of suspended matter from different areas of the German Bight and from the Elbe Estuary are presented. These include areas with suspended matter concentrations varying between 10 mg l^–1 in the deeper waters in the middle of the Bight and 150 mg l^–1 in the Elbe mouth. Pigment data allows the identification of three groups of suspended matter (marine, turbidity zone and Elbe) for the numerous different locations. The changes in pigment concentrations in the suspended matter over tidal cycles are considered. The presence of pigments and pigment breakdown productsi.e. lutein and chlorophyllides is used to assess the possible condition of the phytoplankton present in the suspended matter. These pigment characteristics are compared with the loading of the heavy metals cadmium, copper, manganese, iron, zinc and lead in the particulate matter. It has been demonstrated that the pigments of the planktonic material can be used very effectively to identify different types of suspended matter and that the heavy metal loadings of the suspended matter were significantly correlated with chlorophyll-a.     

Degradation of Fibre and Non-fibre Fractions During Anaerobic Digestion in Silages of Maize,Sunflower and Sorghum-Sudangrass of Different Maturities

This study investigated the temporal dynamics of the degradation of organic matter (OM), fibre, protein and remaining organic constituents during anaerobic digestion of silages from maize, sunflower and sorghum-sudangrass that were harvested at different maturity stages. The tests were conducted using an in sacco method in 20 l digesters. The degradation kinetics of fibres showed some similarity for maize and sorghum-sudangrass with a continuous progress, whereas in sunflower it developed with a strong degradation right after incubation to reach a quasi-constant level for the rest of the 35 days lasting fermentation time. The degradation process for crude protein was usually intense from the very beginning and levelled off after only 5 days. Methane yield after 35 days amounted to 358, 278, and 320 l_N CH₄/kg OM for maize, sunflower and sorghum-sudangrass respectively but could not be predicted with high accuracy by regression models based on organic constituents.     

Avoidance of oxygen-poor zones by fish in the Elbe River

For three selected weeks in July, August, and October 1985, catches from anchor net vessels at ten stations along the tidal Elbe River (northern Germany) were analyzed and related to oxygen conditions in the river. The oxygen concentrations decreased from an average of 6.6 ml/L in the estuary to an average of 1.4 mg/L upstream. Fish were found to be concentrated downstream from the low-oxygen zone and at the entrance to a shallow side arm of the main stream. Highest catches of eel were made where oxygen levels were in the range of 1.2–3 mg/L, highest catches of flounder at 3–4 mg/L, and highest catches of juvenile and adult smelt in areas with more than 5 mgO₂/L. Such a situation enables fishermen to make extraordinarily high catches. It is concluded that despite high levels of toxicants, the tidal Elbe still offers living conditions adequate for the mass of fish species as long as there is a sufficient supply of oxygen.     

牙周再生膜体外降解的实验研究

目的研究牙周再生膜在体外动态和静态降解体系中的降解性能。方法用聚乳酸乙醇酸制作的牙周再生膜在动态(降解介质流速为250μl/min)和静态两种降解体系中进行降解,分别在材料降解前的第0周和降解后的第1、2、4、6周测定牙周再生膜在体外动态和静态降解体系中的残存质量、平均分子量、弹性模量、孔隙率和渗透性的变化并对两种降解体系中的降解性能进行比较。结果降解过程中,牙周再生膜实验材料的质量随着降解的进行而不断损耗,残存的质量越来越少。实验材料的分子量随着降解的进行而不断减少。牙周再生膜的质量和分子量在静态降解体系中损失速度显著高于在动态降解体系(P<0.01);在两种实验条件下,牙周再生膜实验材料的弹性模量都是在第2周时开始上升,随后下降。材料的弹性模量在动态降解体系中较之静态降解体系能维持较长时间;无论在动态降解条件下,还是在静态降解条件下,实验材料的孔隙率都是从第2周时开始下降,而后逐渐增加。降解系统的状态对材料孔隙率变化的影响无显著差异(P>0.05);材料在静态降解体系中的渗透性显著高于动态降解体系(P<0.01)。材料在两种降解介质中的降解性能相似,但是在所测定的降解指标中,材料在人工唾液中的变化速度显著高于在PBS中的(0.01相似文献   

铵离子对不同基因型水稻吸收硝酸根离子的影响1

NH+4可在很短时间内影响两种不同水稻亚种吸收NO-3,即可以影响NO-3的最初跨膜运输.籼型稻在NH+4存在时对NO-3吸收有促进,而粳型稻NO-3吸收则明显减少.     

Production of N2 through Anaerobic Ammonium Oxidation Coupled to Nitrate Reduction in Marine Sediments

In the global nitrogen cycle, bacterial denitrification is recognized as the only quantitatively important process that converts fixed nitrogen to atmospheric nitrogen gas, N₂, thereby influencing many aspects of ecosystem function and global biogeochemistry. However, we have found that a process novel to the marine nitrogen cycle, anaerobic oxidation of ammonium coupled to nitrate reduction, contributes substantially to N₂ production in marine sediments. Incubations with ¹⁵N-labeled nitrate or ammonium demonstrated that during this process, N₂ is formed through one-to-one pairing of nitrogen from nitrate and ammonium, which clearly separates the process from denitrification. Nitrite, which accumulated transiently, was likely the oxidant for ammonium, and the process is thus similar to the anammox process known from wastewater bioreactors. Anaerobic ammonium oxidation accounted for 24 and 67% of the total N₂ production at two typical continental shelf sites, whereas it was detectable but insignificant relative to denitrification in a eutrophic coastal bay. However, rates of anaerobic ammonium oxidation were higher in the coastal sediment than at the deepest site and the variability in the relative contribution to N₂ production between sites was related to large differences in rates of denitrification. Thus, the relative importance of anaerobic ammonium oxidation and denitrification in N₂ production appears to be regulated by the availability of their reduced substrates. By shunting nitrogen directly from ammonium to N₂, anaerobic ammonium oxidation promotes the removal of fixed nitrogen in the oceans. The process can explain ammonium deficiencies in anoxic waters and sediments, and it may contribute significantly to oceanic nitrogen budgets.     

Variations in the Natural Abundance of 15N in Nitrogenous Fractions of Komatsuna Plants Supplied with Nitrate

Komatsuna (Brassica campestris L. var. rapa) plants were grownhydroponically under various conditions with respect to thesupply of nitrate, and the variations in levels of natural ¹⁵Nabundance (¹⁵N) in nitrogenous fractions of leaf blades, petiolesplus midribs, and roots in these plants were analyzed. The fractionation of nitrogen isotopes during uptake of nitratewas null irrespective of the concentrations of nitrate in theculture medium. The roots had lower ¹⁵N values than that inthe nitrate applied to plants. The nitrate in the three tissuesexamined had higher ¹⁵N values than that in the nitrate applied:the values were highest in the leaf blades which were presumedto have highest activities in terms of reduction of nitrate.In contrast, the amino acids and residual fractions had lower¹⁵N values than those in the nitrate applied. These resultssuggest that reduction of nitrate is a critical step in thefractionation of nitrogen isotopes in plant tissues in vivo. ¹Permanent address: Fukuoka Agricultural Experiment Station,Yoshiki 587, Chikushino, 818 Japan. (Received March 10, 1989; Accepted July 10, 1989)     

Norfloxacin Sorption to Different Fractions in Sediments from Typical Water Systems in China

Sorption isotherms of Norfloxacin (NOF) to different fractions from six typical sediments in China were determined to compare the NOF sorption behavior and contribution of different fractions to total sorption. All sorption isotherms were nonlinear and fitted well with the Freundlich model. Sorption coefficients (K _f) by original sediments changed in larger magnitude, from 114 (mg/g)/(mg/L)ⁿ to 5271 (mg/g)/(mg/L)ⁿ, and black carbon with more aromatic carbon has more sorption capacity and nonlinearity. The sorption capacity K _f values were found to significantly correlate with SSA (specific surface area), OC (organic carbon), BC (black carbon), and TON (total organic nitrogen) (p < 0.05), but had no obvious relation with pH, CEC (cation exchange capacity), TOC/TON, and BC/TOC. The DOC removed, NaOH extracted, and 375°C heated fractions showed more nonlinear sorption than the original sediments, suggesting more heterogeneous sorption sites in these fractions. Among different sediment fractions, the 375°C heating fractions were responsible for >50% of the total NOF sorption over the whole concentration range. The contribution of DOC removed fractions to the total sorption was the highest at higher NOF concentration.     

Chemical Speciation of Lead and Cadmium in Different Size Fractions of Dust Samples from Two Busy Roads in Irbid City,Jordan

Concentrations of Pb and Cd in different size fractions in road dust samples taken from areas of high traffic flows in two streets in Irbid City, Jordan, have been measured using graphite furnace atomic absorption spectrometry (GFAAS). A series of road dust particles in the following size ranges, < 90, 90–106, 106–125, 125–250, 250–1000 and 1000-2000 μ m, were investigated to evaluate the ratio between metal content in each fraction of particle size and total metal content. Results show most of the highest levels were found in the small particle sizes. Sequential extraction procedure was used for chemical speciation in road dust samples of < 90 μ m. Two standard reference materials, CRM142R and SRM 2709, were analyzed to assess the accuracy and the reliability of the proposed method, and the precision of the results was expressed by relative standard deviation (rsd < 6%).