River Warnow Research Articles

Solar UV-assisted sample preparation of river water for ultra-trace determination of uranium by adsorptive stripping voltammetry

The article describes how solar ultraviolet-A radiation can be used to digest samples as needed for voltammetric ultratrace determination of uranium(VI) in river water. We applied adsorptive stripping voltammetry (AdSV) using chloranilic acid as the complexing agent. Samples from the river Warnow in Rostock (Germany) were pretreated with either soft solar UV or wit artificial hard UV from a 30-W source emitting 254-nm light. Samples were irradiated for 12 h, and both methods yielded the same results. We were able to detect around 1 μg·L−1 of uranium(VI) in a sample of river water that also contained dissolved organic carbon at a higher mg·L−1 levels. No AdSV signal was obtained for U(VI) without any UV pre-treatment. Pseudo-polarographic experiments confirmed the dramatic effect of both digestion techniques the the AdSV response. The new method is recommended for use in mobile ultratrace voltammetry of heavy metals for most kinds of natural water samples including tap, spring, ground, sea, and river waters. The direct use of solar radiation for sample pre-treatment represents a sustainable technique for sample preparation that does not consume large quantities of chemicals or energy.

Solar UV Photooxidation as Pretreatment for Stripping Voltammetric Trace Metal Analysis in River Water

The application of solar ultraviolet radiation as sample pretreatment or preparation step in stripping voltammetric analysis of trace metals in presence of low levels of dissolved organic carbon (DOC) natural water samples (river water) was studied. River water samples were collected from downstream of Warnow river (Germany) and acidified to pH of2±0.2(by addition of 1 mL of ultrapure 65% HNO3per liter sample). Furthermore, 100 μL/L of hydrogen peroxide solution (ultrapure, 30% H2O2) was added to the samples as photochemical reaction initiator. The samples were transferred to polyethylene terephthalate (PET) bottles and irradiated with solar radiation of UV-A intensity of 3.6 mW/m2for six hours, and the concentrations of Zn, Cd, Pb, and Cu were determined by differential pulse anodic stripping voltammetry (DPASV). The comparison of the values with the results obtained for the original untreated sample and artificial UV-treated one proved that solar UV radiation can be applied to the digestion of dissolved organic carbon in trace metal analysis in natural waters like river water, lake waters, well waters, and so forth.

Bacterial Activity and Bacterioplankton Diversity in the Eutrophic River Warnow—Direct Measurement of Bacterial Growth Efficiency and Its Effect on Carbon Utilization

The influence of bacterial activity and diversity on bacterial growth efficiency was investigated in a flatland river. Eutrophic River Warnow drains predominantly agricultural land and is heavily loaded with nutrients, dissolved and particulate organic matter (DOM and POM), especially humic substances. Although the water column bacterial community consists of many inactive or damaged cells, bacterioplankton sustained a high bacterial secondary production of 0.2-14.5 μg C L(-1) h(-1) and a high DNA synthesis (thymidine uptake) of 6.1-15.5 μg C L(-1) h(-1). The direct and short-term measurement of bacterial respiration (by optodes) revealed high respiration rates especially in summer leading to directly estimated bacterial growth efficiencies (BGE) of 2-28%. These values are compared to calculations based only on bacterial production, which considerably overestimated BGEs. From all these data, River Warnow can be characterized as a strongly remineralizing system. River Warnow was dominated among others by Cytophaga/Flavobacteria and Actinobacteria which are typical for organic rich waters because of their ability to degrade high molecular weight compounds. However, community composition did not significantly affect BGE.

Substrate Utilization Profiles of Bacterial Strains in Plankton from the River Warnow, a Humic and Eutrophic River in North Germany

Bacteria are very important degraders of organic substances in aquatic environments. Despite their influential role in the carbon (and many other element) cycle(s), the specific genetic identity of active bacteria is mostly unknown, although contributing phylogenetic groups had been investigated. Moreover, the degree to which phenotypic potential (i. e., utilization of environmentally relevant carbon substrates) is related to the genomic identity of bacteria or bacterial groups is unclear. The present study compared the genomic fingerprints of 27 bacterial isolates from the humic River Warnow with their ability to utilize 14 environmentally relevant substrates. Acetate was the only substrate utilized by all bacterial strains. Only 60% of the strains respired glucose, but this substrate always stimulated the highest bacterial activity (respiration and growth). Two isolates, both closely related to the same Pseudomonas sp., also had very similar substrate utilization patterns. However, similar substrate utilization profiles commonly belonged to genetically different strains (e.g., the substrate profile of Janthinobacterium lividum OW6/RT-3 and Flavobacterium sp. OW3/15-5 differed by only three substrates). Substrate consumption was sometimes totally different for genetically related isolates. Thus, the genomic profiles of bacterial strains were not congruent with their different substrate utilization profiles. Additionally, changes in pre-incubation conditions strongly influenced substrate utilization. Therefore, it is problematic to infer substrate utilization and especially microbial dissolved organic matter transformation in aquatic systems from bacterial molecular taxonomy.

Dissolved inorganic nutrients and organic substrates in the River Warnow (North-Eastern Germany) – Utilisation by bacterioplankton

After 1990, external loads of Central European rivers with inorganic nutrients (nitrogen and phosphorus) and organic material were reduced because of changed environmental laws. However, in the eutrophic lowland River Warnow, North-Eastern Germany, nitrate concentrations remained high with 35–185 μmol l −1 without a significant decrease since 1992. In contrast, phosphate concentrations, varying between 0.3 and 5.2 μmol l −1 during the growth season 2002, decreased significantly over the years. However, its concentrations still exceeded 1 μmol l −1 regularly in the growth seasons. This load led to a substantial accumulation of organic matter additional to high terrestrial inputs. Despite the high organic load, the remineralising bacteria were mainly inactive in River Warnow. Therefore, the composition of the dissolved organic material, especially its bioavailability, were investigated during the growth season 2002 and discussed with other potential controlling factors. River Warnow carried a high load of dissolved organic carbon (14 mg l −1), especially of humic substances (5.5 mg C l −1). Bacterial abundance (12×10 6 ml −1) as well as production (1.7 μg C l −1 h −1) depended on temperature. During late spring and summer at constantly higher temperatures, bacterial production correlated positively to readily utilisable substrates and to humic compounds. Thus, the bacterial community in River Warnow may be well adapted or contain enough species using the available amino acids and carbohydrates as well as humic matter compounds. However, calculated from protozoan biomass, grazing may control bacterial biomass and perhaps community composition profoundly, what lead to the low percentages of active bacteria.

Bacterial Abundance, Activity, and Viability in the Eutrophic River Warnow, Northeast Germany

The River Warnow is the drinking water source for the city of Rostock. Its eutrophic status is accompanied by high amounts of bacteria, which may reach up to 24 x 10(6) cells mL(-1) as recorded during a seasonal study in 2002. Because the river is eutrophic and also heavily loaded with organic matter, this burden is a problem for drinking water purification, as it must be removed completely to not trigger new bacterial growth in the pipeline network. Therefore, restoration measures in the river have to be planned, and bacteria have to be favored as decomposers. That includes the investigation of the physiological state of bacteria in situ. Viable and active cells in the lower reaches of River Warnow were estimated using a broad set of methods. Intact bacteria were investigated by the LIVE/DEAD BacLight bacterial viability kit, containing a mixture of permeant and impermeant nucleic acid stains. Cells with ribosomes were visualized by fluorescence in situ hybridization with the EUB338 oligonucleotide probe. Intact cells and ribosome-containing bacteria represented 24% of total numbers stained by 4'6,-diamidino-2-phenylindole (DAPI) or 66 and 62%, respectively, in relation to all bacteria visualized by the LIVE/DEAD kit. Both fractions were considered as viable, although the fraction of RIB + bacteria is most likely underestimated by the protocol applied. 5-Cyano-2,3-ditolyltetrazolium chloride (CTC) was applied to mark respiring bacteria. The esterase substrate CellTracker Green 5-chloromethylfluorescein diacetate showed cells with intracellular hydrolytic activity. Whereas 1.5% of DAPI-stained bacteria were observed as respiring, 3.8% exhibited intracellular hydrolytic activity on average. If these active fractions were calculated as the percentages of intact cells, much higher fractions of 5.4% were respiring and 16% hydrolytic. Temperature was a main factor influencing total and viable cell numbers simultaneously. The results confirm that there are different states of viable and active cells in natural bacterioplankton communities. However, it remains unclear why fractions of viable and active cells were rather low in this eutrophic river in comparison to similar waters. We recommend to carefully address cells as viable in contrast to nonviable, i.e., dead. As viable cells may be active or inactive with respect to many different activities, e.g., substrate uptake, respiration, hydrolysis, and cell deviation, it is necessary to choose the method to visualize active cells according to the question to be answered.

Dynamic features along the German Baltic Sea coast: contribution to coastal monitoring

Based on satellite imagery in combination with ground data measurements and numerical modelling, the distribution patterns of water masses along the German Baltic Sea coast of the state of Mecklenburg–Vorpommern (M–V) were investigated. The dynamic processes forming these patterns are driven by the local wind. Distinct wind directions induce typical features in several regions of the M–V coast. The processes considered are the distribution of Oder river water in the Pomeranian Bight, the upwelling off Hiddensee and off the coast of the Mecklenburg Bight including the Warnow river outflow, and the special dynamic regime in Lübeck Bay. In the Pomeranian Bight, a strong relation was found between the wind and transport direction of river water which was also applied to interpret the distribution of inorganic and organic pollutants. During easterly winds, different upwelling cells arise with the highest intensity in the Hiddensee area. The cells merge by increasing wind velocity. Lübeck Bay is mainly excluded from water exchange during the dominant wind directions. The first results of this systematic remote sensing study along the entire coast of M–V are summarized and will be continued to support the coastal monitoring programme of regional authorities.

Longitudinal patterns of phosphorus and phosphorus binding in sediment of a lowland lake–river system

In the Warnow River and its tributaries in North Germany, measurements were made to characterise the longitudinal patterns of nutrients in the riverbed and lake sediments. The sediment composition was analysed based on dry weight, organic matter, mean grain size and concentration of carbon, nitrogen, phosphorus, iron, aluminium and sulfur. Sediment phosphate was investigated in more detail by means of a sequential chemical extration. The phosphate was differently bound to the sediment particles in the upstream region than in the impounded section of the Warnow River and ist tributaries. Accumulation of fine sediment with high P-concentrations was recorded in the lake sediments and in the impounded section of the river. These impounded sections were the most important P-pool in the whole catchment area and played an important role in P-retention in the river system. Organic matter concentration, P-accumulation and P-binding in the sediment of the impounded section is corresponding with those of lake sediments. During the summer, anoxic P-release from the sediment in the impounded section was measured and calculated. The reductant-soluble fraction of the P-fractionation underestimated the release under anoxic condition. Adsorbed phosphorus and organic phosphate play an important role in P-release in the impounded part of the river.

Chlorinated Hydrocarbons in River Sediments of Mecklenburg-West Pomerania - Patterns, Levels, and Regional Distribution

As a first contribution to the assessment of organic microcontaminants in rivers of Mecklenburg-West Pomerania, the patterns, levels, and regional distribution of chlorinated hydrocarbons (PCB, HCH, DDT, and HCB) in river sediments were investigated. The sediment sampling was carried out at selected stations in rivers of Mecklenburg-West Pomerania (Peene, Uecker, Randow, Zarow, Ziese, Warnow, Elde, and Elbe) in August/September 1996. The chlorinated hydrocarbons were determined by GC/ECD following ultrasonic extraction. Generally, the contents of chlorinated hydrocarbons in the river Warnow and rivers of West Pomerania were at a low level, up to 15 ng/g (given for TOC). In Elde sediments, three to ten times higher contents of CHC were found, due to a higher degree of industrialization in the catchment area. Much higher CHC contents up to a factor of 100 higher than in the river Warnow occurred in Elbe sediments between the towns Dömitz and Boizenburg. A comparison of the CHC contents in river sediments of Mecklenburg-West Pomerania with those in Elbe sediments reflects the difference between rivers with a large and highly industrialized catchment area and much smaller rivers, only affected by agriculture and municipal sewages. The contribution from rivers of Mecklenburg-West Pomerania to the riverine input of organic microcontaminants into the innercoastal waters (boddens, hafts, and sounds) and the adjacent Baltic Sea seems to be low. Chlorierte Kohlenwasserstoffe in Flußsedimenten Mecklenburg-Vorpommerns – Verteilungsmuster, Konzentrationsniveaus und regionale Verteilung Als ein erster Beitrag zur Belastungseinschätzung der Flüsse Mecklenburg-Vorpommerns mit organischen Spurenstoffen wurden die Muster, Konzentrationsniveaus und die regionale Verteilung von chlorierten Kohlenwasserstoffen (PCB, HCH, DDT und HCB) in den Sedimenten der Flüsse untersucht. Die Probenahme erfolgte an ausgewählten Stationen in den Flüssen Mecklenburg-Vorpommerns (Peene, Uecker, Randow, Zarow, Ziese, Warnow, Elde und Elbe) im August/September 1996. Die chlorierten Kohlenwasserstoffe (CKW) wurden nach Ultraschallextraktion mit Hilfe der GC/ECD-Technik quantitativ bestimmt. Die CKW-Gehalte in der Warnow und den Flüssen in Vorpommern lagen auf einem geringen Niveau bis maximal 15 ng/g (auf TOC-Basis). In den Sedimenten der Elde wurden 3- bis 10fach höhere CKW-Gehalte gemessen, welche auf den höheren Grad der Industrialisierung im Einzugsgebiet zurückzuführen sein sollten. In den Sedimenten der Elbe zwischen den Städten Dömitz und Boizenburg traten an einigen Stationen teilweise 100fach höhere CKW-Gehalte im Vergleich zu den Warnowsedimenten auf. Ein Vergleich der CKW-Gehalte in den Flußsedimenten Mecklenburg-Vorpommerns mit den Gehalten im Sediment der Elbe weist auf den Unterschied hin zwischen Flüssen mit großen und hochindustrialisierten Einzugsgebieten und Flüssen mit weitaus kleineren Einzugsgebieten, die vorrangig durch Landwirtschaft und städtische Abwässer beeinflußt werden.

Downstream changes in phytoplankton composition and biomass in a lowland river–lake system (Warnow River, Germany)

To determine longitudinal changes in phytoplankton composition and biomass in the Warnow River (Germany), single water parcels were followed during their downstream transport in August and October 1996 and April 1997. In summer, the phytoplankton assemblage was dominated by centric diatom and cyanobacteria species. Stephanodiscus hantzschii, Pseudanabaena limnetica, Planktothrix agardhii and Aulacoseira granulata var. angustissima were the most frequent species. In autumn, small centric diatoms dominated the whole river course. Irrespective of the season, in the fluvial lakes of the upper river, a substantial increase of phytoplankton biomass was observed. Shallow upstream river stretches were associated with large biomass losses. In the deep, slow flowing lower regions, total biomass remained constant. Longitudinal changes in biomass reflected downstream variations in flow velocity and river morphology. Cyanobacteria, cryptophytes and diatom species were subjected to large biomass losses along fast flowing, shallow river sections, whereas chlorophytes were favoured. Diatoms and cryptophytes benefited from low flow velocity and increased water depth in the downstream river. Changes in water depth and flow velocity have been found as key factors that cause the longitudinal differences in phytoplankton composition and biomass in small rivers.

Hazards for the Rostock water supply from a tar-contaminated sediment in the river Warnow

By the gas plant at Schwaan (a small city near Rostock), tar and other by-products were released into the river Warnow which supplies Rostock with drinking water 20 km downstream. The tar-contaminated river sediment contained phenols and polycyclic aromatic hydrocarbons (PAH), indicating a mutagenic potential. Investigations in the catchment area and on tributaries showed PAH contents up to about 10 ng/l in the water. The river sediment was found to be the sole PAH source. Although the PAH level is very low, sediment disturbances may produce an increase in concentrations. The consequences of such a worst case are difficult to estimate, even though the content of seston and humic substances in the river seems to reduce the PAH concentrations. Although this lowers the probability that increased PAH concentrations reach the Rostock water supply, the removal of the tar-contaminated sediment from the river is strongly recommended.

Inventories of point and diffuse sources and estimated nutrient loads - a comparison for different river basins in Central Europe

A comparison of the estimated emissions (input) with the measured loads at monitoring stations (output) is presented for the large Rivers Rhine, Elbe and its main tributaries and for the River Warnow, a smaller river in the north-east part of Germany. The comparison shows that the discrepancies between the estimated emissions and the measured load is small for the Rhine and its main tributaries, Mosel, Neckar and Main. Large discrepancies were found for the Elbe and its main tributaries. For all investigated river systems a strong relationship exists between the quotient of measured nutrient load versus the estimated sum of point and diffuse emissions of nutrients and the areal specific runoff. A function is derived for the dependency of the sum of retention and/or losses in a river system on the specific runoff and the nutrient concentration in the river. The high accuracy of the estimated retention and/or losses within the different river basins offer the possibility to use these equations for a prediction of the emitted nutrients from measured nutrient load in similar rivers.

Inventories of point and diffuse sources and estimated nutrient loads - a comparison for different river basins in central europe

A comparison of the estimated emissions (input) with the measured loads at monitoring stations (output) is presented for the large Rivers Rhine, Elbe and its main tributaries and for the River Warnow, a smaller river in the north-east part of Germany. The comparison shows that the discrepancies between the estimated emissions and the measured load is small for the Rhine and its main tributaries, Mosel, Neckar and Main. Large discrepancies were found for the Elbe and its main tributaries.For all investigated river systems a strong relationship exists between the quotient of measured nutrient load versus the estimated sum of point and diffuse emissions of nutrients and the area) specific runoff. A function is derived for the dependency of the sum of retention and/or losses in a river system on the specific runoff and the nutrient concentration in the river. The high accuracy of the estimated retention and/or losses within the different river basins offer the possibility to use these equations for a prediction of the emitted nutrients from measured nutrient load in similar rivers.

In situ phosphorus release experiments in the Warnow River (Mecklenburg, northern Germany)

In situ phosphorus release experiments in the Warnow River (Mecklenburg, northern Germany)

Structural Compositions of Pelagic Communities in the River Warnow and their Changes

The phytoplankton and heterotrophic microbial communities from the Oberwarnow and Unterwarnow were analyzed from November 1987 to May 1988. The production potential of the microorganisms was quantified in laboratory experiments. On the average, phytoplankton accounted for 73 % of the total biomass in the Oberwarnow and 59 % in the Unterwarnow. The corresponding figures for bacterial biomass were 24 % and 33 %, respectively. If the nutrient supply is unlimited and phytoplankton biomass predominates, the development of primary producers in eutrophic to polytrophic waters is not regulated by metazooplankton. Top-down regulation is possible only if prevailing conditions limit the growth of the dominant phytoplankton species.

Mikroskopische und elektronische Zählung von Sestonpartikeln im Wasser der Warnow — ein Vergleich

In 37 samples from the river Warnow in the course of one annual variation the seston particles were counted in the inverted microscope in three size classes: A <8 μm, B 8 … 25 μm C>25μm. Parallel to that, counting was performed with the electronic particle counting device Picoscale 4, which is used for the counting of blood cells, in the setting WBC for leucocytes with a nozzle 200 μm in diameter, so that the setting approximately corresponded to the size range B of the microscopic count. The microscopic particle numbers per ml were 800,000 … 5,200,000 for A, 10,000 … 96,000 for B and 2,000 … 21,000 for C. In principle, there is a correlation between microscopic and electronic results for the particles B and C. The regression analysis, however, produces a considerable residual scattering because of the morphological variety of the particles and its changes in the course of the seasonal change of mass. Therefore, the conclusion of the particle density from results of electronic counting is connected with considerable indistinctness, so that the electronic counting can be used only as a supplementary method for the estimation of the density of suspended matter.