ALBERT

Description: Rivers represent a transition zone between terrestrial and aquatic environments, as well as a transition zone between methane rich and methane poor environments. Methane concentrations are generally higher in freshwater systems than in marine systems. The Elbe River is one of the crucial drainages into the North Sea and by this high amounts of methane are imported into the marine water column. Oxidation of methane by aerobic methanotrophic bacteria is the major biological sink. Six cruises from November 2013 until June 2014 were conducted along the salinity gradient from Hamburg towards Helgoland. Methane oxidation rate was measured with radiotracers and the abundance of methanotrophic bacteria was assessed via real-time PCR. A newly designed primer targeting the genomic sequence encoding the α-subunit of the functional pMMO enzyme in water column organisms was amplified and tested against the conventional primer set. At the marine stations the cell number was relatively stable with 3 x 104 cells per L, while in the Elbe cell numbers ranged between 103 – 106 cells per L. Environmental parameters (temperature, salinity, SPM) seemed to have no influence on the abundance. However the interaction between activity and abundance seemed to be more complex.

Description: Methods for measuring aerobic methane oxidation (MOx) rates in aquatic environments are often based on the incubation of water samples, during which the consumption of methane (CH4) is monitored. Typically, incubation vessels are sealed with butyl rubber because these elastomers are essentially impermeable for gases. We report on the potential toxicity of five different commercially available, lab-grade butyl stoppers on MOx activity in samples from marine and lacustrine environments. MOx rates in incubations sealed with non-halogenated butyl were 〉 50% lower compared to parallel incubations with halogenated butyl rubber stoppers, suggesting toxic effects associated with the use of the non-halogenated butyl type. Aqueous extracts of non-halogenated butyl rubber were contaminated with high amounts of various organic compounds including potential bactericides such as benzyltoluenes and phenylalkanes. Comparably small amounts of organic contaminants were liberated from the halogenated butyl rubber stoppers but only two halogenated stopper types were found that did not seem to leach any organics into the incubation medium. Furthermore, the non-halogenated and two types of the halogenated butyl elastomers additionally leached comparably high amounts of zinc. While the source of the apparent toxicity with the use of the non-halogenated rubber stoppers remains elusive, our results indicate that leaching of contaminants from some butyl rubber stoppers can severely interfere with the activity of MOx communities, highlighting the importance of testing rubber stoppers for their respective contamination potential. The impact of leachates from butyl rubber on the assessment of biogeochemical reaction rates other than MOx seems likely but needs to be verified.

Description: River estuaries are responsible for high rates of methane emissions to the atmosphere. The complexity and diversity of estuaries require detailed investigation of methane sources and sinks, as well as of their spatial and seasonal variations. The Elbe river estuary and the adjacent North Sea were chosen as the study site for this survey, which was conducted from October 2010 to June 2012. Using gas chromatography and radiotracer techniques, we measured methane concentrations and methane oxidation (MOX) rates along a 60 km long transect from Cuxhaven to Helgoland. Methane distribution was influenced by input from the methane-rich mouth of the Elbe and gradual dilution by methane-depleted sea water. Methane concentrations near the coast were on average 30 ± 13 nmol L−1, while in the open sea, they were 14 ± 6 nmol L−1. Interestingly, the highest methane concentrations were repeatedly detected near Cuxhaven, not in the Elbe River freshwater end-member as previously reported. Though, we did not find clear seasonality we observed temporal methane variations, which depended on temperature and presumably on water discharge from the Elbe River. The highest MOX rates generally coincided with the highest methane concentrations, and varied from 2.6 ± 2.7 near the coast to 0.417 ± 0.529 nmol L−1 d−1 in the open sea. Turnover times varied from 3 to 〉1000 days. MOX rates were strongly affected by methane concentration, temperature and salinity. We ruled out the supposition that MOX is not an important methane sink in most of the Elbe estuary and adjacent German Bight.

Description: Microbial methane oxidation rates in ocean and freshwater systems reveal how much of emitted methane from the sediments is oxidized to CO2 and how much can reach the atmosphere directly. The tracer-method using 3H-CH4 provides a way to measure MOX-rates even in water with low methane concentrations without needing any specific instrumentation. We assessed this method by implementing several experiments, collecting data from various environments, and including recent literature concerning the method to identify any uncertainties that should be considered. Our assessment reveals some difficulties of the method but also reassures previous assumptions to be correct. Some of the difficulties are hardly to be avoided, such as incubating all samples at the right in-situ temperature or limiting the variability of MOX-rate measurements in water of low methanotrophic activity. Other details, e.g. quickly measuring the total radioactivity after stopping the incubation, are easy to adapt in each laboratory. And yet other details as shaking during incubation and bottle size seem to be irrelevant. With our study we hope to improve and to encourage future measurements of MOX-rates in different environments and to provide a standard procedure of MOX measurements to make data of MOX better comparable.

Description: Rivers represent a transition zone between terrestric and aquatic environments, as well as a transition zone between methane rich and methane poor environments. Methane concentrations in freshwater systems are in general higher than in marine systems. The Elbe River is one of the important rivers draining into the North Sea, as is the Lena River draining into the Laptev Sea. High methane concentrations have been observed within both rivers, and additional hot spots in the Lena Delta. However due to different stratification patterns in the mixing zones, the further fate of methane in the North Sea and the Laptev Sea is different. Methane consuming bacteria are known from both environments. However, in the transition zone between marine and limnic systems the shift in salinity imposes an osmotic stress for most organisms. In this study we want to compare the environmental data obtained in both estuaries with the methane oxidation to elucidate the efficiency of the respective methane oxidizing bacteria.

Description: Rivers are suspected to be a main source of greenhouse gases (methane and carbon dioxide) for coastal seas, while the role of the interjacent tidal flats is still ambiguous. In this study we investigated the role of the river Elbe and the Elbe estuary as source of methane to the North Sea. With high spatial resolution by an underway degassing system and subsequent analysis by cavity ring down spectroscopy a high resolution picture of the methane distribution in surface waters and hydrographic parameters was obtained in autumn to spring 2018/19. For most areas, riverine methane was simply diluted by seawater, overlain by a strong tidal influence. However at several occasions unexpected high methane concentrations were observed. By further detailed analysis we will elucidate the role of riverine versus tidal impact on the methane flux from the coastal North Sea

Description: The Lena River is one of the biggest Russian rivers draining into the Laptev Sea. Due to predicted increasing temperatures the permafrost areas surrounding the Lena will melt at increasing rates. With this melting high amounts of carbon, either organic or as methane will reach the waters of the Lena and the adjacent Laptev Sea. As methane is an important green house gas its further fate in the Lena Delta is of uttermost importance. Methane oxidation by methanotrophic bacteria is the only biological way to reduce methane concentrations. However, the polar estuary of the Lena River is a challenging environment, with strong fluctuations in salinity and temperature. We determined the activity and abundance of aerobic methanotrophic bacteria (MOB), as well as their population structure. Activity was determined with 3H-CH4 as radioactive tracer, abundance was determined with quantitative PCR and the population structure was characterized by a fingerprinting method (MISA). Methane concentrations were rather low (41 ± 44 nM), as well as methane oxidation rates (1.1 ± 1.6 nM/d). In polar water (cold and saline) highest activities were found, whereas the highest abundance of MOB was in surface waters. The relation between methane turnover and abiotic factors will be used to characterize the eco-physiology of these polar and estuarine methanotrophs

Description: Permafrost thaw affects global climate, the land surface and coastal structures. Under subaquatic conditions, permafrost thaw is often more rapid than on land. The thaw depth below water bodies (taliks) and changes in biogeochemical gradients are difficult to predict. The influence of taliks and biogeochemical gradients on the production and release of the greenhouse gases methane and carbon dioxide is not clear yet. Although our research in this region has produced multi-decadal data sets, most of our knowledge on the methane cycle pertains only to the summer. We focus on water bodies in the Lena Delta region, including thermokarst ponds, lakes, lagoons and the marine shoreface. For most of the year, however, ice covers these water bodies, creating a barrier between the water column and the atmosphere, and changing benthic conditions. It is therefore important to assess methane-related processes during the ice-covered season. In spring 2017 we investigated the Lena Delta and Tiksi Bay at the end of winter, while still ice-covered. Thirty ice cores of different water bodies were obtained by Kovacs ice corer. The in situ temperature of the ice cores was measured immediately afterwards. Methane oxidation rates were determined with radio tracer method in melted ice core samples. Analyses of methane concentration and further hydrochemical analyses are on their way. Initial results indicate rather low activities of methane oxidation in the ice cores, but active biological processes in the water below.

Description: In intertidal areas, large amounts of organic matter in the form of kelp are regularly deposited on the beach. Mineralization of this organic matter leads to the release of many intermediates and end products into? the sediments. A wide variety of aerobic and anaerobic microorganisms control the mineralization process. The high input of reduced matter into the local ecosystem is apparent from elevated levels of sulfide and the abundance of white filamentous bacteria in the nearby surfaces? Or sediments?. The input of nutrients into this normally oligotrophic environment may subsequently also stimulate primary production of the microphytobenthos. We investigated the influence of kelp deposits on in situ concentrations of CO, H2, Fe(II), sulfide, CH4 and various nutrients on a beach on Helgoland. Our preliminary results show an enrichment of CO and H2 below kelp deposits. Exposure to O2 seemed essential for CO and H2 release during the process of kelp degradation, as was observed during incubation experiments. The most pronounced influence of kelp deposits was observed for Fe(II), with higher Fe(II) concentrations below kelp deposits, although large heterogeneity exists. Sulfide and CH4 were found in significant concentrations within sediments between kelp deposits and the adjacent sea. Remarkably, their levels were lower directly? below the kelp, whereas Fe(II) showed the opposite trend. We aim to define the processes responsible for the high sulfide and CH4 concentrations within the sediments, with a focus on the role of the high CO and H2 levels for sulfate reduction and methanogenesis. Through in situ measurements we will study the effects of variable oxygenation on the release of these compounds. We also aim to study and model the hydrology of the beach to assess the transport modes of the intermediates and nutrients through the permeable sands. We will furthermore determine the consequences of the nutrient input for the local microphytobenthos.