ALBERT

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 Delta will melt at increasing rates. With this melting, high amounts of methane will reach the waters of the Lena and the adjacent Laptev Sea. Methane oxidation by methanotrophic bacteria is the only biological way to reduce methane concentrations within the system. However, the polar estuary of the Lena River is a challenging environment for bacteria, with strong fluctuations in salinity and temperature. We determined the activity (tracer method) and the abundance (qPCR) of aerobic methanotrophic bacteria. We described the methanotrophic population with MISA; as well as the methane distribution (head space) and other abiotic parameters in the Lena Delta in September 2013. In 'riverine water' (S 〈5) we found a median methane concentration of 22 nM, in 'mixed water' (5 〈 S 〈 20) the median methane concentration was 19 nM and in 'polar water' (S 〉 20) a median 28 nM was observed. The Lena River was not the methane source for surface water, and bottom water methane concentrations were mainly influenced by the concentration in surface sediments. However, the methane oxidation rate in riverine and polar water was very similar (0.419 and 0.400 nM/d), but with a higher relative abundance of methanotrophs and a higher 'estimated diversity' with respect to MISA OTUs in the 'rivine water' as compared to 'polar water'. The turnover times of methane ranged from 167 d in 'mixed water', 91 d in 'riverine water' and only 36 d in 'polarwater'. Also the environmental parameters influencing the methane oxidation rate and the methanotrophic population differed between the water masses. Thus we postulate a riverine methanotrophic population limited by sub-optimal temperatures and substrate concentrations and a polar methanotrophic population being well adapted to the cold and methane poor environment, but limited by the nitrogen content. The diffusive methane flux into the atmosphere ranged from 4 -163 µmol m2 d-1 (median 24). For the total methane inventory of the investigated area, the diffusive methane flux was responsible for 8% loss, compared to only 1% of the methane consumed by the methanotrophic bacteria within the system.

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 Delta will melt at increasing rates. With this melting, high amounts of methane will reach the waters of the Lena and the adjacent Laptev Sea. Methane oxidation by methanotrophic bacteria is the only biological way to reduce methane concentrations within the system. However, the polar estuary of the Lena River is a challenging environment for bacteria, with strong fluctuations in salinity and temperature. We determined the activity (tracer method) and the abundance (qPCR) of aerobic methanotrophic bacteria. We described the methanotrophic population with MISA; as well as the methane distribution (head space) and other abiotic parameters in the Lena Delta in September 2013. In riverine water (S 〈 5) we found a median methane concentration of 22 nM, in mixed water (5 〈 S 〈 20) the median methane concentration was 19 nM and in polar water (S 〉 20) a median 28 nM was observed. The Lena River was not the methane source for surface water, and bottom water methane concentrations were mainly influenced by the concentration in surface sediments. However, the methane oxidation rate in riverine and polar water was very similar (0.419 and 0.400 nM/d), but with a higher relative abundance of methanotrophs and a higher estimated diversity with respect to MISA OTUs in the rivine water as compared to polar water. The turnover times of methane ranged from 167 d in mixed water, 91 d in riverine water and only 36 d in polarwater. Also the environmental parameters influencing the methane oxidation rate and the methanotrophic population differed between the water masses. Thus we postulate a riverine methanotrophic population limited by sub-optimal temperatures and substrate concentrations and a polar methanotrophic population being well adapted to the cold and methane poor environment, but limited by the nitrogen content. The diffusive methane flux into the atmosphere ranged from 4–163 µmol m2 d−1 (median 24). For the total methane inventory of the investigated area, the diffusive methane flux was responsible for 8 % loss, compared to only 1 % of the methane consumed by the methanotrophic bacteria within the system.

Description: The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The predicted increases in global temperatures are expected to cause the permafrost areas surrounding the Lena Delta to melt at increasing rates. This melting will result in high amounts of methane reaching the waters of the Lena and the adjacent Laptev Sea. The only biological sink that can lower methane concentrations within this system is methane oxidation by methanotrophic bacteria. However, the polar estuary of the Lena River, due to its strong fluctuations in salinity and temperature, is a challenging environment for bacteria. We determined the activity and abundance of aerobic methanotrophic bacteria by a tracer method and by the quantitative polymerase chain reaction. We described the methanotrophic population with a molecular fingerprinting method (monooxygenase intergenic spacer analysis), as well as the methane distribution (via a headspace method) and other abiotic parameters, in the Lena Delta in September 2013. The median methane concentrations were 22 nmol L−1 for riverine water (salinity (S)  

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: 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: 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 and with the Elbe river high amounts of methane are imported into the water column of the North Sea. The major biological sink is the oxidation of methane by aerobic methanotrophic bacteria. Eight cruises from November 2013 until November 2014 were conducted from Hamburg towards Helgoland. Methane oxidation rate was measured with radiotracers and methanotrophic abundance was assessed by q-PCR. Community fingerprinting was performed with monooxygenase intergenic spacer analysis (MISA). Combining all the data we could identify four environments (marine, coast, outer and inner estuary) with significantly different abundances. The marine environment had lowest abundances and highest abundances were found in the inner estuary. Comparison of the corresponding communities is in progress.

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 the methane distribution and other abiotic parameters. Activity was determined with 3H-CH4 as radioactive tracer and abundance was determined with quantitative PCR. 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.