Gunnar Nützmann

Exposure to human pharmaceuticals Carbamazepine, Ibuprofen and Bezafibrate causes molecular effects in Dreissena polymorpha

Carbamazepine (CBZ), Ibuprofen (IBU) and Bezafibrate (BEZ) were tested for their potential to bioaccumulate and provoke molecular changes in the non-target organism Dreissena polymorpha. mRNA changes of enzymes and other proteins involved in the prevention from protein damage (heat shock protein 70, hsp70) and oxidative stress (superoxide dismutase, SOD; catalase, CAT; metallothionein, MT), biotransformation (pi-class glutathione S-transferase, piGST; aryl hydrocarbon receptor, AH-R), elimination (P-glycoprotein, P-gp) and reversible protein posttranslational modification (protein phosphatase 2A, PP2A) served as molecular biomarkers. Mussels were exposed in a flow-through system to increasing concentrations of the three substances (1, 10, 100 and 1000 nM). The two lower concentrations correspond to environmentally relevant concentrations detected in surface and effluent waters, respectively. Measuring tissue concentration after one, four and seven days the uptake of CBZ and IBU by the mussels could be evidenced, whereas no accumulation data could be achieved for BEZ. The bioconcentration factor was highest for mussels exposed to the lowest CBZ and IBU concentrations, with 90 and 460-fold higher tissue concentration, respectively, after seven days. CBZ was the only substance tested which caused a significant increase in gill mRNA level of hsp70 after only one day exposure, evidencing the potential of CBZ to immediately provoke a stress condition and assumingly protein damage in gills. After longer exposure, mussels displayed down-regulated mRNA levels of hsp70 and SOD in gills, as well as of MT and P-gp in the digestive gland, hinting on an inhibitory character of CBZ. In IBU exposed mussels increased oxidant stress conditions were evidenced by induced mRNA levels in the digestive gland of CAT and MT, as well as SOD after one and four days, respectively. A concentration as found at sewage treatment plant effluents provoked an increase in transcript levels of piGST, suggesting enhanced need for biotransformation of IBU or by-products derived from oxidative stress. Also exposure to an environmentally relevant BEZ concentration provoked an immediate increase in piGST transcript level in the digestive gland followed by up-regulated hsp70 after four and seven days evidencing a chronic stress condition for the mussels.

Tube‐dwelling invertebrates: tiny ecosystem engineers have large effects in lake ecosystems

There is ample evidence that tube-dwelling invertebrates such as chironomids significantly alter multiple important ecosystem functions, particularly in shallow lakes. Chironomids pump large water volumes, and associated suspended and dissolved substances, through the sediment and thereby compete with pelagic filter feeders for particulate organic matter. This can exert a high grazing pressure on phytoplankton, microorganisms, and perhaps small zooplankton and thus strengthen benthic-pelagic coupling. Furthermore, intermittent pumping by tube-dwelling invertebrates oxygenates sediments and creates a dynamic, three-dimensional mosaic of redox conditions. This shapes microbial community composition and spatial distribution, and alters microbe-mediated biogeochemical functions, which often depend on redox potential. As a result, extended hotspots of element cycling occur at the oxic-anoxic interfaces, controlling the fate of organic matter and nutrients as well as fluxes of nutrients between sediments and water. Surprisingly, the mechanisms and magnitude of interactions mediated by these organisms are still poorly understood. To provide a synthesis of the importance of tube-dwelling invertebrates, we review existing research and integrate previously disregarded functional traits into an ecosystem model. Based on existing research and our models, we conclude that tube-dwelling invertebrates play a central role in controlling water column nutrient pools, and hence water quality and trophic state. Furthermore, these tiny ecosystem engineers can influence the thresholds that determine shifts between alternate clear and turbid states of shallow lakes. The large effects stand in contrast to the conventional limnological paradigm emphasizing predominantly pelagic food webs. Given the vast number of shallow lakes worldwide, benthic invertebrates are likely to be relevant drivers of biogeochemical processes at regional and global scales, thereby mediating feedback mechanisms linked to climate change.

The β-receptor blocker metoprolol alters detoxification processes in the non-target organism Dreissena polymorpha.

Due to increasing amounts of pharmaceutically active compounds (PhACs) in the aquatic environment, their largely unknown effects to non-target organisms need to be assessed. This study examined physiological changes in the freshwater mussel Dreissena polymorpha exposed to increasing concentrations (0.534, 5.34, 53.4 and 534 microg L(-1)) of the beta-blocker metoprolol in a flow-through system for seven days. The two lower concentrations represent the environmentally relevant range. Surprisingly, metallothionein mRNA was immediately up-regulated in all treatments. For the two higher concentrations mRNA up-regulation in gills was found for P-glycoprotein after one day, and after four days for pi class glutathione S-transferase, demonstrating elimination and biotransformation processes, respectively. Additionally, catalase and superoxide dismutase were up-regulated in the digestive gland indicating oxidative stress. In all treated mussels a significant up-regulation of heat shock protein mRNA was observed in gills after four days, which suggests protein damage and the requirement for repair processes. Metoprolol was 20-fold bioaccumulated for environmentally relevant concentrations.

Software, Data and Modelling News: FLake-Global: Online lake model with worldwide coverage

An online lake-modeling tool FLake-Global allows virtually instantaneous estimation of the seasonal cycle of temperature and mixing conditions in any shallow freshwater lake around the world. The tool is built on the basis of the lake model FLake (www.lakemodel.net) and a year- long near-surface meteorological data from the NCEP/NCAR Reanalysis Project (http://www.esrl.noaa.gov/psd/data/reanalysis). FLake-Global gives estimates of the surface and bottom water temperatures, mean temperature of the water column, surface mixed layer depth, and ice cover duration and thickness, using geographical coordinates, mean depth to the bottom and water transparency of the lake in question, and the NCEP atmospheric forcing as input. The tool is suitable for a wide spectrum of applications, including general limnology, lake management and restoration, fisheries, and recreation.

The Synthetic Gestagen Levonorgestrel Impairs Metamorphosis in Xenopus laevis by Disruption of the Thyroid System

Synthetic gestagens, including levonorgestrel (LNG), are active compounds in contraceptives, and several studies report their occurrence in surface waters. However, information about endocrine-disrupting effects in nontarget organisms is scarce. The present study investigated effects of LNG exposure on thyroid hormone-dependent metamorphosis of Xenopus laevis. Premetamorphic X. laevis tadpoles at Nieuwkoop and Faber (NF) stage 48 were exposed in a flow-through culture system to four LNG concentrations (10(-11), 10(-10), 10(-9), and 10(-8)M) over the period of metamorphosis. At NF 58 and 66, tadpoles were examined sex specifically. Developmental time and organismal responses were recorded and correlated with molecular and histopathological endpoints. Exposure to 10(-8)M LNG caused an inhibition of metamorphosis resulting in developmental arrest at early climax stages as giant tadpoles or tailed frogs. In brain-pituitary tissue of NF 58 tadpoles, gene expression of thyroid-stimulating hormone (β-subunit; TSHβ), TH receptor β (TRβ), and deiodinase type 3 (D3) was not changed. Instead, prolactin (PRL) messenger RNA (mRNA) was significantly increased by 10(-9)M LNG in females and by 10(-8)M LNG in both sexes. In NF 66 tadpoles, mRNA levels of TSHβ mRNA were significantly increased in the 10(-9) and 10(-8)M LNG treatment groups indicating a hypothyroid state. No changes of TRβ, D3, and PRL gene expression were detected. Histopathological evaluation of thyroid gland sections revealed no typical sign of hypothyroidism but rather an inactivated appearance of the thyroid. In conclusion, our data demonstrate for the first time a completely new aspect of thyroid system disruption caused by synthetic gestagens in developing amphibians.

The Synthetic Gestagen Levonorgestrel Disrupts Sexual Development in Xenopus laevis by Affecting Gene Expression of Pituitary Gonadotropins and Gonadal Steroidogenic Enzymes

In the present study, Xenopus laevis tadpoles were chronically exposed to four concentrations of the synthetic gestagen Levonorgestrel (LNG; 10(-11), 10(-10), 10(-9), and 10(-8)M) starting at Nieuwkoop and Faber (NF) stage 48 until completion of metamorphosis. At NF 58 and 66, brain-pituitary and gonad samples were taken for gene expression analyses of gonadotropins and gonadal steroidogenic enzymes. Exposure to 10(-9) and 10(-8)M LNG until NF 58 repressed messenger RNA (mRNA) expression of luteinizing hormone (LH) β in both genders. This decrease was persistent after further treatment until NF 66 in the 10(-8)M LNG treatment. Expression of follicle-stimulating hormone (FSH) β was affected sex-specifically. No effect was present in NF 58 females, whereas LNG at 10(-9) and 10(-8)M significantly increased FSHβ mRNA levels in males. In NF 66 females, 10(-9)M LNG treatment increased FSHβ gene expression, whereas a decrease was observed in NF 66 males exposed to 10(-8)M LNG. In gonads, expression of steroid-5-alpha-reductase was affected sex-specifically with increased mRNA levels in females but repressed levels in males. Gene expression of further gonadal steroidogenic factors was decreased by 10(-8)M LNG in both genders at NF 66. Assessment of gonad gross morphology and histology revealed poorly developed testes in the 10(-8)M LNG treatment. Our results reveal considerable effects of chronic LNG exposure on sexual development of amphibians. The persistent inhibition of LHβ expression concomitant with decreased mRNA levels of gonadal steroidogenic enzymes is suggested to result in the disruption of reproduction in adult amphibians.

Seeking a compromise between pharmaceutical pollution and phosphorus load: Management strategies for Lake Tegel, Berlin.

Lake Tegel (Berlin, Germany) is controlled by two main inflows: inflow #1 (River Havel) is heavily phosphorus-laden, whereas inflow #2 is an artificial confluence that includes discharge from a municipal wastewater treatment plant distinguished by high levels of phosphorus and pharmaceuticals. To reduce the phosphorus load on the lake, a phosphorus elimination plant (PEP) is situated at inflow #2. Moreover, the two inflows are short-circuited by a pipeline that transfers part of the inflow #1 water to the PEP and finally releases it into inflow #2. The pipeline and the PEP have contributed to a continuous reduction in the total phosphorus concentration of Lake Tegel in the past 25 years. We investigate the question of whether the existing lake pipeline can also be used to reduce the amount of pharmaceuticals in Lake Tegel originating from inflow #2 by dilution with water from River Havel, by diverting part of inflow #2 around the lake, or by a combination of both strategies. The circulation pattern of Lake Tegel is complicated by complex bathymetry and numerous islands and is therefore highly sensitive to winds. We tested seven different management scenarios by hydrodynamic modeling for a period of 16 years with the two-dimensional version of the Princeton Ocean Model (POM). None of the scenarios provided a strategy optimal for both pharmaceuticals and phosphorus. Nonetheless, compound regimes, such as alternating the pipe flow direction or adding another pipeline, allowed the most abundant pharmaceutical (carbamazepine) to be reduced while maintaining the current phosphorus level. This study demonstrates the ability of immediate lake regulation measures to maintain water quality. In the case of Lake Tegel, the pipeline can be fully effective with regard to pharmaceuticals only in combination with additional efforts such as advanced pharmaceutical treatment of wastewater and/or phosphorus reduction in the River Havel catchment.

Model based verification and prognosis of acidification and sulphate releasing processes downstream of a former sewage field in Berlin (Germany)

An ammonium contamination plume originating from sewage field management practices over several decades is affecting the water quality at the well fields of the Friedrichshagen waterworks in Berlin, Germany. Because hydraulic measures were unsuccessful due to the fixation of ammonium on the aquifer matrix by cation exchange, an in situ nitrification measure by injection of oxygen gas was chosen to protect the extraction wells. In order to assess the hydro chemical processes accompanying this in situ measure, reactive transport modelling was performed. The relevant processes are the dissolution of oxygen gas and the nitrification of ammonium which initiate secondary geochemical processes like sulphate release, acidification and hardening. The reactive transport modelling began with the deduction of a reaction network, followed by the mathematical formulation and incorporation of reactive terms into a reactive transport solver. Two model versions were set up: (1) a simplified large scale model to evaluate the long-term reaction zoning to be expected due to permanent oxygen gas injection, and (2) a verification of the monitored hydrochemistry during a first field test performed near the contamination source. The results of reactive transport modelling demonstrate that in situ injection of oxygen gas will be effective in reducing the ammonium load from the well fields, and that acidification processes near the production wells can be minimized. Finally, a line of gas injection wells extending over the whole width of the ammonium contamination plume will be constructed to protect the well fields from further ammonium load.

Measurement techniques for quantification of pumping activity of invertebrates in small burrows

The quantification of exchange processes across sediment-water interfaces needs precise measurements of burrow ventilation of tube-dwelling invertebrates, including small species which can occur in high densities. Since most studies have focused on relatively large organisms, established techniques are usually suitable for burrow diameters clearly > 2 mm. Our aim was to test video analyses, colour tracers, O 2 and flow velocity microelectrodes, thermal flow sensors, particle image velocimetry, and conductive exchange experiments, for quantifying pumping activity in burrows ≤ 2 mm in diameter in muddy sediment. To assure comparability, all measurements were performed with the same species (Chironomus plumosus, 4 th instar larvae). On average we determined a flow velocity of 14.9 mm s -1 , an individual pumping time of 33 min h -1 , an individual pumping rate of 61 ml h -1 (1.7 mm burrow diameter), and a population pumping rate of 1.09 m 3 m -2 d -1 (745 larvae m -2 , 20-23 °C). Our values are higher than mostly reported for other small invertebrates. The differences might be caused by the artificial set-ups used in previous studies, and by the fact that C. plumosus conducts pumping not only to meet its oxygen demand such as other species but also to filter-feed. All seven techniques tested in this study are applicable for burrow diameters of 1.7-2 mm in muddy sediments. We recommend colour tracers and particle image velocimetry to measure flow velocity, and flow velocity microelectrodes and thermal flow sensors to determine the individual pumping time. Conductivity exchange experiments are suitable to directly measure individual pumping rates.

Investigating groundwater-lake interactions by hydraulic heads and a water balance.

Discharge of groundwater into lakes (lacustrine groundwater discharge, LGD) can play a major role in water balances of lakes. Unfortunately, studies often neglect this input path because of methodological difficulties in its determination. Direct measurements of LGD are labor-consuming and prone to error. The present study uses both spatially variable hydraulic-head data and meteorological data to estimate groundwater input by LGD and lake water output through infiltration. The study sites are two shallow, groundwater-fed lakes without any surface inflows or outflows. Horizontally interpolated groundwater heads were combined with lake water levels to obtain vertical hydraulic gradients between the aquifer and the lake, which are separated by a thick layer of lake bed sediment which has a much lower hydraulic conductivity than the underlying aquifer. By fitting the hydraulic gradient to the results of a simple mass balance and considering the process of clogging, we were able to estimate the hydraulic conductivity of the lake bed sediments. We calculated groundwater inputs by LGD and lake water outputs by infiltration on an annual basis. Although our method requires several assumptions, the results are reasonable and provide useful information about the exchange between the aquifer and the lake, which can, for example, be used for the calculation of nutrient mass balances.