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Nitratreduzierende mikrobielle Gemeinschaften aus porösem Gestein und Klüften im verkarsteten und geklüfteten Grundwasserleiter des Einzugsgebiets der Bronnbachquelle (Südwestdeutschland)

Verkarstete, zerklüftete unterirdische Aquifere sind wichtige Trinkwasserquellen. Der Einsatz von Düngemitteln in der Landwirtschaft hat jedoch zu einer Nitratinfiltration geführt. Der Konsum von nitrathaltigem Trinkwasser könnte zu gesundheitlichen Problemen führen, und die Europäische Union hat festgelegt, dass die Stickstoffkonzentration im Trinkwasser weniger als 50 mg/L betragen muss, um trinkbar zu sein. In landwirtschaftlich genutzten Regionen liegen die Nitratkonzentrationen jedoch häufig über diesem Grenzwert. So wurden beispielsweise im Einzugsgebiet der Ammer (Deutschland) Nitratkonzentrationen von bis zu 60 mg/l gemessen, während die Abflussgebiete nur 1 mg/l Nitrat enthielten. Diese Konzentrationsunterschiede lassen auf eine intensive Denitrifikation schließen. In unterirdischen oligotrophen Umgebungen können Mikroorganismen die Nitratreduktion mit der Eisen-/Schwefeloxidation koppeln. Die Bestimmung räumlicher Hot Spots, in denen Mikroben eine wichtige Rolle bei der Denitrifikation im Untergrund spielen, ist eine Herausforderung, und es ist daher nicht bekannt, ob die Denitrifikation nur in Klüften oder auch in der porösen Gesteinsmatrix stattfindet. Wir haben Gesteinskerne aus 70 m Tiefe entnommen - der gesättigten Zone der Bronnbachquelle (Deutschland). Das einzigartige Bohrloch ohne Verrohrung diente der Errichtung einer Grundwassermessstelle. Das erste Ziel dieses Projekts besteht darin, die Taxonomie und die funktionellen Fähigkeiten der denitrifizierenden Mikroorganismen zu bestimmen, die das Karbonatgestein bewohnen. Das zweite Ziel ist die Charakterisierung der mikrobiellen Besiedlung Pyrit-haltiger künstlicher und natürlicher poröser Gesteinsmatrixen und der Pyritoxidationsrate durch Laborexperimente. Für diese In-vitro-Studie werden Mikroorganismen verwendet, die zuvor aus Karbonatgestein angereichert wurden und die die Nitratreduktion mit (Eisen/Schwefel)-Oxidation verbinden. Das dritte Ziel besteht darin, die In-situ-Pyrit-Oxidationsrate in den künstlichen und natürlichen porösen Gesteinsmatrixen zu bestimmen. Dies wird durch die langfristige Inkubation von Pyrit-haltigen mikrobiellen Fallen (MTDs; mit Gesteinsmatrixen) im neu installierten Grundwasserbrunnen und durch die Überwachung der Veränderungen in der Zusammensetzung und der Funktionen der mikrobiellen Gemeinschaften, die die MTDs besiedeln, erreicht. Mittels der kombinierten Ergebnisse der Feld- und Laborarbeiten werden wir Folgendes ermitteln: i) die ökologischen Nischen der nitratreduzierenden Mikroorganismen im Grundwasserleiter des Einzugsgebiets der Bronnbachquelle, ii) die wichtigsten Mikroorganismen, die für den Nitratumsatz verantwortlich sind, iii) die Stoffwechseleigenschaften und Funktionen der nitratreduzierenden Mikroorganismen, iv) das Potenzial der Denitrifikanten, die poröse Gesteinsmatrix zu besiedeln, v) die Faktoren, die die Effizienz der Denitrifikation beeinflussen, und v) die Pyritoxidationsrate innerhalb der porösen Gesteinsmatrix.

Nanofiltration zur Grundwasseraufbereitung und Sulfatabscheidung bei der Trinkwasseraufbereitung am Beispiel von kippenbelastetem Grundwasser in einem Braunkohlentagebaurevier

Erhöhte Konzentrationen an Sulfat im Trinkwasser können negative Auswirkungen auf die Gesundheit der Konsumenten haben und führen zu einem erhöhten Risiko für Korrosionen im Leitungsnetz. Aufgrund dessen schreibt die Trinkwasserverordnung einen Grenzwert von 240 mg/l vor. Erhöhte Konzentrationen an Sulfat im Grundwasser, die eine spezielle Aufbereitungstechnik erfordern, kommen vor allem durch den Einfluss von Tagebauaktivitäten zustande. Im ausgehobenen Kippenmaterial kommt es zur Oxidation des Pyrits, was nach der Verfüllung der Gruben zu einem Anstieg der Sulfat-, Calcium- und Schwermetallkonzentration im Grundwasser führt. In betroffenen Grundwasservorkommen in Deutschland wurden Konzentrationen von bis zu 2500 mg/l Sulfat gemessen. Die Nanofiltration ist eine mögliche Aufbereitungstechnologie, die die Grundwassernutzung in derart beeinträchtigten Standorten auch nach der Verfüllung der Gruben erlaubt. Es wird erwartet, dass die Nanofiltration im Vergleich zu den anderen in Frage kommenden Technologien Ionenaustauscher, Destillation, Elektrodialyse und Umkehrosmose vor allem bei höheren Sulfatkonzentration in der Größenordnung >1000 mg/l das wirtschaftlichste Verfahren darstellt. In dem Projekt Nanofiltration zur Sulfatabscheidung bei der Trinkwasseraufbereitung wird die Aufbereitung mittels Nanofiltration experimentell im Labor- und Pilotmaßstab untersucht. Es wird dabei schwerpunktmäßig ein Standort betrachtet, der im Einflussgebiet des Braunkohletagebaureviers Inden I liegt und derzeit Sulfatkonzentrationen von 1000-1500 mg/l in einem Trinkwasserbrunnen aufweist. Neben der Untersuchung der Nanofiltration an sich wird eine Konzentrataufbereitung mittels CaSO4-Kristallisation auf ihre Effektivität geprüft.

Seawater carbonate chemistry and maximum growth rates of Skeletonema marinoi and Alexandrium ostenfeldii, toxin composition of Alexandrium ostenfeldii in a laboratory experiment

Phytoplankton populations can display high levels of genetic diversity that, when reflected by phenotypic variability, may stabilize a species response to environmental changes. We studied the effects of increased temperature and CO2 availability as predicted consequences of global change, on 16 genetically different isolates of the diatom Skeletonema marinoi from the Adriatic Sea and the Skagerrak (North Sea), and on eight strains of the PST (paralytic shellfish toxin)-producing dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Maximum growth rates were estimated in batch cultures of acclimated isolates grown for five to 10 generations in a factorial design at 20 and 24 °C, and present day and next century applied atmospheric pCO2, respectively. In both species, individual strains were affected in different ways by increased temperature and pCO2. The strongest response variability, buffering overall effects, was detected among Adriatic S. marinoi strains. Skagerrak strains showed a more uniform response, particularly to increased temperature, with an overall positive effect on growth. Increased temperature also caused a general growth stimulation in A. ostenfeldii, despite notable variability in strain-specific response patterns. Our data revealed a significant relationship between strain-specific growth rates and the impact of pCO2 on growth-slow growing cultures were generally positively affected, while fast growing cultures showed no or negative responses to increased pCO2. Toxin composition of A. ostenfeldii was consistently altered by elevated temperature and increased CO2 supply in the tested strains, resulting in overall promotion of saxitoxin production by both treatments. Our findings suggest that phenotypic variability within populations plays an important role in the adaptation of phytoplankton to changing environments, potentially attenuating short-term effects and forming the basis for selection. In particular, A. ostenfeldii blooms may expand and increase in toxicity under increased water temperature and atmospheric pCO2 conditions, with potentially severe consequences for the coastal ecosystem.

Integrierte Schädlingsbekämpfung in Lychee (Litchi chinensis) in Bergregionen Nordthailands

Die ökologische Nachhaltigkeit der Anbausysteme in Bergregionen Thailands wird durch Erosion, Abnahme der Bodenfruchtbarkeit, sowie hohen Druck durch Unkräuter und Schädlinge in Frage gestellt. Die Lychee-Produktion im Untersuchungsgebiet ist gekennzeichnet von suboptimaler Bestandesführung und starkem Befallsdruck durch die Schädlinge Aceria litchi, Conopomorpha sinensis, Indarbela dea und Tessaratoma papillosa, der zu schweren Ertragsverlusten führt. In dieser Untersuchung soll die Wirksamkeit von Azadirachtin, Bacillus thuringiensis, Beauveria bassiana, Steinernema carpocapsae und synthetischen Akariziden (u.a. Spiromesifen) auf die Schadorganismen in Laborversuchen ermittelt werden. Auf Grundlage dieser Ergebnisse sowie der Erfahrungen örtlicher Landwirte sollen dann verschiedene Kontrollmethoden integriert und unter Feldbedingungen erprobt werden.

Seawater carbonate chemistry and growth, reproduction of calcifying and non-calcifying epibionts of a brown macroalga in a laboratory experiment

Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida) and Electra pilosa (Bryozoa) and the non-calcifier Alcyonidium hirsutum (Bryozoa) were maintained for 30 days under three pCO2 conditions: natural 460±59 µatm, present-day upwelling1193±166 µatm and future upwelling 3150±446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm) but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic. Only extreme future upwelling conditions impacted the tubeworm S. spirorbis, but not the bryozoans.

Seawater carbonate chemistry and benthic foraminifera Ammonia sp. mass, size, and growth rate during experiments, 2013

About 30% of the anthropogenically released CO2 is taken up by the oceans; such uptake causes surface ocean pH to decrease and is commonly referred to as ocean acidification (OA). Foraminifera are one of the most abundant groups of marine calcifiers, estimated to precipitate ca. 50 % of biogenic calcium carbonate in the open oceans. We have compiled the state of the art literature on OA effects on foraminifera, because the majority of OA research on this group was published within the last three years. Disparate responses of this important group of marine calcifiers to OA were reported, highlighting the importance of a process-based understanding of OA effects on foraminifera. We cultured the benthic foraminifer Ammonia sp. under a range of carbonate chemistry manipulation treatments to identify the parameter of the carbonate system causing the observed effects. This parameter identification is the first step towards a process-based understanding. We argue that CO3 is the parameter affecting foraminiferal size-normalized weights (SNWs) and growth rates. Based on the presented data, we can confirm the strong potential of Ammonia sp. foraminiferal SNW as a CO3 proxy.

Seawater carbonate chemistry and growth of calcifying tubeworm shells (Spirorbis spirorbis)

The calcareous tubeworm Spirorbis spirorbis is a widespread serpulid species in the Baltic Sea, where it commonly grows as an epibiont on brown macroalgae (genus Fucus). It lives within a Mg-calcite shell and could be affected by ocean acidification and temperature rise induced by the predicted future atmospheric CO2 increase. However, Spirorbis tubes grow in a chemically modified boundary layer around the algae, which may mitigate acidification. In order to investigate how increasing temperature and rising pCO2 may influence S. spirorbisshell growth we carried out four seasonal experiments in the Kiel Outdoor Benthocosms at elevated pCO2 and temperature conditions. Compared to laboratory batch culture experiments the benthocosm approach provides a better representation of natural conditions for physical and biological ecosystem parameters, including seasonal variations. We find that growth rates of S. spirorbis are significantly controlled by ontogenetic and seasonal effects. The length of the newly grown tube is inversely related to the initial diameter of the shell. Our study showed no significant difference of the growth rates between ambient atmospheric and elevated (1100 ppm) pCO2 conditions. No influence of daily average CaCO3 saturation state on the growth rates of S. spirorbis was observed. We found, however, net growth of the shells even in temporarily undersaturated bulk solutions, under conditions that concurrently favoured selective shell surface dissolution. The results suggest an overall resistance of S. spirorbis growth to acidification levels predicted for the year 2100 in the Baltic Sea. In contrast, S. spirorbis did not survive at mean seasonal temperatures exceeding 24 °C during the summer experiments. In the autumn experiments at ambient pCO2, the growth rates of juvenile S. spirorbis were higher under elevated temperature conditions. The results reveal that S. spirorbis may prefer moderately warmer conditions during their early life stages but will suffer from an excessive temperature increase and from increasing shell corrosion as a consequence of progressing ocean acidification.

Seawater carbonate chemistry and benthic foraminifera Ammonia sp. uranium incorporation during experiments, 2013

The chemical and isotopic composition of foraminiferal shells (so-called proxies) reflects the physico-chemical properties of the seawater. In current day paleoclimate research, the reconstruction of past seawater carbonate system to infer atmospheric CO2 concentrations is one of the most pressing challenges and a variety of proxies have been investigated, such as foraminiferal U/Ca. Since in natural seawater and traditional CO2 perturbation experiments, the carbonate system parameters co-vary, it is not possible to determine the parameter of the carbonate system causing e.g. changes in U/Ca, complicating the use of the latter as a carbonate system proxy. We overcome this problem, by culturing the benthic foraminifer Ammonia sp. at a range of carbonate chemistry manipulation treatments. Shell U/Ca values were determined to test sensitivity of U incorporation to various parameters of the carbonate system. We argue that CO3 is the parameter affecting the U/Ca ratio and consequently, the partitioning coefficient for U in Ammonia sp DU. We can confirm the strong potential of foraminiferal U/Ca as a CO3 proxy.

Seawater carbonate chemistry and in situ and laboratory measurements of calcification

Ocean acidification (OA) is generally assumed to negatively impact calcification rates of marine organisms. At a local scale however, biological activity of macrophytes may generate pH fluctuations with rates of change that are orders of magnitude larger than the long-term trend predicted for the open ocean. These fluctuations may in turn impact benthic calcifiers in the vicinity. Combining laboratory, mesocosm and field studies, such interactions between OA, the brown alga Fucus vesiculosus, the sea grass Zostera marina and the blue mussel Mytilus edulis were investigated at spatial scales from decimetres to 100s of meters in the western Baltic. Macrophytes increased the overall mean pH of the habitat by up to 0.3 units relative to macrophyte- free, but otherwise similar, habitats and imposed diurnal pH fluctuations with amplitudes ranging from 0.3 to more than 1 pH unit. These amplitudes and their impact on mussel calcification tended to increase with increasing macrophyte biomass to bulk water ratio. At the laboratory and mesocosm scales, biogenic pH fluc- tuations allowed mussels to maintain calcification even under acidified conditions by shifting most of their calcification activity into the daytime when biogenic fluctuations caused by macrophyte activity offered temporal refuge from OA stress. In natural habitats with a low biomass to water body ratio, the impact of biogenic pH fluctuations on mean calcification rates of M. edulis was less pronounced. Thus, in dense algae or seagrass habitats, macrophytes may mitigate OA impact on mussel calcification by raising mean pH and providing temporal refuge from acidification stress.

Seawater carbonate chemistry and biological processes during experiments with four strains of Emiliania huxleyi

Four strains of the coccolithophore E. huxleyi (RCC1212, RCC1216, RCC1238, RCC1256) were grown in dilute batch culture at four CO2 levels ranging from ~200 µatm to ~1200 µatm. Growth rate, particulate organic carbon content, and particulate inorganic carbon content were measured, and organic and inorganic carbon production calculated. The four strains did not show a uniform response to carbonate chemistry changes in any of the analysed parameters and none of the four strains displayed a response pattern previously described for this species. We conclude that the sensitivity of different strains of E. huxleyi to acidification differs substantially and that this likely has a genetic basis. We propose that this can explain apparently contradictory results reported in the literature.

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