3. Studies in the Lena River Delta
3.5 Long-term studies on methane fluxes from permafrost ecosystems 19
Dirk Wagner, Jürgen Joseph, Anastasia Germogenova, Maryvone Landolt and Joseph Zeyer
Introduction
The Arctic plays a key role in the Earth’s climate system for two reasons. On one hand, global warming is predicted to be most pronounced at high latitudes, and observational evidence over the past 25 years suggests that this warming is already under way (Serreze et al., 2000; Richter-Menge et al., 2006). On the other hand, one third of the global carbon pool is stored in ecosystems of the northern latitudes (Post et al., 1982; Gorham, 1991). Thus there is considerable socio-economic interest in predicting how the carbon balance of the northern ecosystems will respond to ongoing climate warming.
Global warming will have important implications for the functional diversity of microbial communities in these systems. It is likely that temperature increase in high latitudes may stimulate microbial activity and carbon decomposition in Arc-tic environments and are accelerating climate change through the increase of trace gas (CH4, CO2) release (Melillo et al., 2002; Zimov et al., 2006).
The microorganisms, which are the drivers of methane production and oxidation in Arctic wetlands, have remained obscure. Their function, population structure and reaction to environmental change, which are important parts of the process knowledge on methane fluxes in permafrost ecosystems, are largely unknown (Wagner, 2008). This hampers prediction of the effects of climate warming on arctic methane fluxes, in particular when these predictions are based on models that do not take into account the specific nature of microbial populations in per-mafrost soils and sediments. Understanding these microbial populations is therefore highly important for understanding the global climatic effects of a warming Arctic.
Under the umbrella of the Russian-German Cooperation SYSTEM LAPTEV SEA a multidisciplinary research concept was developed and since 1998 ap-plied on the Arctic methane cycle that connects methane flux measurements with studies on microbial processes and communities (cp. Wagner, 2007). Dur-ing the expedition LENA 2007 methane fluxes were measured, microbial meth-ane oxidation under in situ conditions were studied, and samples from different permafrost ecosystems were taken for further molecular ecological analyses. In particular, the objectives of the field campaign were:
• To measure methane fluxes from polygonal tundra on Samoylov and Ku-rungnakh islands.
• To characterize soil ecological parameters determining microbial proc-esses in permafrost ecosystems.
• To gain more insights into the control functions of methane oxidation as the major sink for methane.
Field Work
Daily measurements of methane emission, thaw depth and soil temperature were determined from July 6 to August 25, 2007 at the long-term study site on Samoylov Island. Additional measurements of methane fluxes from wet polygon tundra were carried out on Kurungnakh Island (N 72°19; E 126°13). The used method and the main investigation sites were described previously (Wagner et al., 2003).
In addition to the close chamber measurements of methane fluxes a new sys-tem for passive soil air sampling called GASSYS (KaiserGEOconsult GmbH, 2005) was installed in the active layer (horizontally) and the perennially frozen ground (vertically) for the determination of in situ methane concentrations in the different horizons of permafrost (Figure 3.5-1). The main feature of this system is a membrane only permeable for gas diffusion, which is mechanically pro-tected by an EVA-tube. When a steady state was reached between the gas phases in the column and the free gases in the soil, samples could be taken by a syringe from the different permafrost depth (chambers depending on column length). The horizontal system consisted of only one chamber containing tube and was implemented 25 cm below the surface. The vertical system was in-stalled in a borehole down to 5.60 meter permafrost depth. After reaching a pla-teau in the chamber pressure curve samples where frequently taken. To learn more about the minimal possible measuring intervals in permafrost soils, pres-sure gradient decrease experiments where executed. First sample meapres-sure- measure-ments in the vertical system showed high methane (> 20%) concentrations.
Figure 3.5-1: Methane gradient analysis in the perennially frozen ground: A: study site on Samoylov Island, Lena Delta; B: tube of the installed GASSYS system for gas sampling and C:
pressure measurements.
To gain more information about the activity of methane producing and methane oxidizing microorganism, vertical methane profiles were measured and dis-solved organic carbon (DOC) were analyzed for the polygonal centre and rim.
Soil methane gradients were measured using brass probes attached to a
Luer-lock three-way stop cock. Every 5 cm a probe was set until the permafrost table was reached. Gas samples were taken by a syringe and directly analyzed by gas chromatography in the field lab. Further details of the gas analyses were described previously (Wagner et al., 2003). DOC was extracted from soil sam-ples of two vertical profiles. Each 5 cm fresh soil material (9 g) was taken to a depth of 30 cm for the polygon centre and to a depth of 40 cm for the polygon border. The samples from each layer were weight into glass flasks (50 ml) and mixed with 45 ml distilled water. The flasks were closed and shaken for 2 h in darkness. Afterwards the suspension was filtered (mesh 0.45 µm, Gelman Sci-ence) and the clear solution was inactivated by the addition of sodium acid.
Samples where taken with a syringe and stored in salt tubes with a defined N2
volume for later analyses in the home lab.
3.6. A high resolution orthorectified picture of Samoylov SPARC group (Julia Boike, Bob Bolton, Maren Grüber, Moritz Langer, Sina Muster, Konstanze Piel, Torsten Sachs, Günter Stoof, Sebastian Westermann) and Marita Scheritz
A high-resolution picture of the island Samoylov was needed for the classifica-tion of vegetaclassifica-tion and surface characteristics and hydrologic modeling. This im-age was created using aerial pictures with a resolution of 0.5 m/pixel and stan-dard photogrammetry software.
The field work for obtaining the aerial pictures from balloons or helicopter flights is described in Chapter 3.1. Furthermore, Scheritz et al. (2008) describe in de-tail the method for creating the digital elevation model, including camera calibra-tion, ground survey and photogrammetric analysis.
Figure 3.6-1: Orthorectified aerial picture of Samoylov Island 2007.
3.7. Hydrobiologycal investigations in the Lena River Delta Irina Vishnyakova and Ekaterina Abramova
Introduction
Low species composition and short food chains are typical for polygonal lakes as well as for most arctic ecosystems. Caused by freezing to the bottom in win-ter the distinguishing feature of polygonal lakes is the absence of fishes as characteristic predators for most other types of water pools. The benthic organ-isms are not abundant, among them the amphibiotic insect larvae, nematodes and ostracods are dominant. Predatory planktonic crustaceans and water birds are terminal links in food chains. The low predator press and good adaptation of zooplankton organisms to the evident variations of abiotic conditions cause ac-tive zooplankton development, which plays a significant role in organic, mineral and energy fluxes in polygonal lakes and in the whole Lena Delta ecosystem.
Given that these polygonal lakes are not exposed to direct anthropogenic pollu-tions, investigations on them could also be used as model objects of natural water ecosystems. This hydrobiological investigations in polygonal lakes are part of a monitoring in the southern part of the Lena Delta River within the ex-pedition “Lena - New Siberian Islands 2007” and are carried out for obtaining detailed data about different aspects of zooplankton existence: species compo-sition, seasonal and inter annual dynamic of quantitative characteristic, ecology and dominant species life circles.
Materials and methods
190 qualitative and quantitative zooplankton samples were gathered from the beginning of July to the end of August in summer 2007. For these monitoring hydrobiologycal investigation we divided all polygons into water of two types:
shallow (0,2-0,6 m depths, partly or completely vegetated by Carex sp. and Arc-tophilla sp.) and deep polygonal lakes (1-1,5 m, without vegetation). The inves-tigations had been carried out in 6 polygonal lakes (3 deep and 3 shallow ones – the same as last year) on Samoylov Island (Figure 3.7-1) and episodically in 11 polygonal lakes on other islands of southern parts of the Delta. The lake wa-ter of both types was transparent, the reaction of wawa-ter was neutral (pH = 6,5-7). Temperature stratification was almost absent, average monthly temperature varied from 12,2 to 12,7°C in July and from 10,4 to 11°C in August.
Zooplankton samples were collected with a periodicity of 5-7 days. Sampling was performed by filtering 50-100 liters of water through an 80-μm mesh size net from the shore of the polygons. A rubber boat was used for sampling from the centre of the lakes. There, a 100-μm mesh size small hand net was ex-tended from the bottom to the surface. Samples were fixed with 70% alcohol or 4% borax-buffered formalin. For statistic calculations, 3 samples from each polygon were collected concurrently. At the same time, the water temperature was measured at the bottom and in surface layers. Also, data on the pH of wa-ter, depth and size of each polygon were obtained.
Zooplankton samples were analyzed in a Bogorov chamber under the binocular microscope MBS-10. Species, sex and moulting stages of each zooplankton organism were determined, abundance of organisms was calculated. For calcu-lation of individual wet weights of organisms the formula W = qlb was used (W = body weight, l = body length in mm, q = weight at 1 mm body length, b = index).
Data were recalculated to 1 m3 of water.
Figure 3.7-1: Polygonal lakes of Samoylov Island are objects of monitoring hydrobiological in-vestigations.
Preliminary results
Same as in our previous investigations qualitative and quantitative characteris-tics of the zooplankton were similar in all studied polygonal lakes. The seasonal dynamic of abundance and biomass recurs from year to year with small varia-tions in period. Usually three to five maximums of abundance and biomass were noticed for polygonal lakes. The development of zooplankton populations be-gins directly after ice melting, which occurred in 2007 in the middle of May.
One well pronounced peak of total abundance and biomass was fixed over the period of investigations (July-August) in polygonal lakes of both types. A corre-lation between quantitative characteristics and water temperature wasn’t no-ticed.
In the following we review in details the structures and dynamics of zooplankton populations of the two polygonal lake types (shallow and deep), where we carry out investigations for more than 5 years.
The zooplankton communities consisted of Cyclopoida and Calanoida popula-tions. The Leptodiaptomus angustilobus dominated during the whole period of investigations. The crustaceans of this species composed about 90 % from the total zooplankton abundance in some samples. The young copepodite stages
(CI-III) of Diaptomus sp. and Cyclopoida families (Cyclops sp., Eucyclops sp.
and Acantocyclops sp.) were abundant at the beginning of studies (early in July). Individuals of Cyclopoida species matured to copepodite stages IV-V by beginning of August (Figure 3.7-2 A).
The populations of Cyclopoida were represented by numerous CIV-V stages by the middle of August and during the rest of observation in all studied lakes. The Copepodits of IV-V stages were dominant in Calanoida populations in the be-ginning of August. Calanoida populations were consisted entirely of adult males and reproducing females with eggs by the middle of august (Figure 3.7-2 B).
A.
0%
20%
40%
60%
80%
100%
06.07. 13.07. 24.07. 31.07. 7.08. 15.08. 22.08. 31.08.
date
abundance, %
СI-III & nauplii CIV-V adult
B.
0%
20%
40%
60%
80%
100%
06.07. 13.07. 24.07. 31.07. 7.08. 15.08. 22.08. 31.08.
date
abundance,%
СI-III & nauplii CIV-V adult
Figure 3.7-2: The population’s age-structure of Leptodiaptomus angustilobus (A.) and Cyclopoida (B.) in the deep polygonal lake I, summer 2007.
The abundance of Daphnia pulex was low during the whole summer period. It should be mentioned that the adult females of Daphnia with efipias were al-ready noted early in July. Efipia is the diapausal stage of Daphnia, which they form before the beginning of unfavorable conditions.
In the deep polygon the maximum of abundance and biomass (38 222 ind./m3 and 2,8 g/m3 respectively) was recorded in the beginning of August at the tem-perature of 9,1°С. L. angustilobus was the most represented species during that period; the main part of this population was composed of CIV-V stages of males and females. The average abundance was the 17825 ind./m3 and biomass -1,4 g/m3 for two months of observations (Figure 3.7-3 A).
In the shallow polygon maximum of quantitative characteristics (abundance - 22111 ind./m3, biomass - 1,8 g/m3) was marked in the end of July at 16,3°С and was concerned with reproduction of different Diaptomus sp. The young copepo-dite stages of L. angustilobus, Arctodiaptomus angustilobus and Mixodiaptomus theeli (CI-III) composed the main mass of zooplankton community. The average zooplankton abundance for shallow polygon was 118999 ind./m3, biomass – 0,9 g/m3 (Figure 3.7-3 B).
06.07. 13.07. 24.07. 31.07. 7.08. 15.08. 22.08. 31.08.
date
6.07. 13.07. 24.07. 31.07. 07.08. 15.08. 22.08. 29.08.
date
Figure 3.7-3: Seasonal dynamic of total zooplankton abundance and biomass in the deep (A) and shallow (B) polygonal lakes I, summer 2007.
Conclusion
The data about zooplankton species composition, structure and quantitative characteristic’ rate of polygonal lakes of the southern part of Lena Delta River obtained in summer 2007 are very similar to our data obtained during previous years (2002-2006). Replacement of periods of dominant species reproduction in time concerned with early ice-melting in lakes and consequently earlier begin-ning of favorable conditions for zooplankton communities is a distinguishing fea-ture of abundance and biomass dynamic course of zooplankton. Therefore we recorded only one maximum of total zooplankton abundance and biomass (dominant species - L. angustilobus) during July-August. Probably 1-2 maxi-mums of qualitative zooplankton characteristics concerned with other dominant species development (Cyclopoida sp., Heterocope borealis, Diaptomus sp., D.
pulex) from the end of May to middle of June – a period that is not included in the investigations.
3.8 Hydrological and geomorphological investigations Dmitry Bolshiyanov, Alexander Makarov and Raisa Terekhova
Hydrometrical measurements in the Lena Delta channels are providing new data of water discharge, sediment load and redistribution of flow between the main branches of the delta (Figure 3.8-1, Table 3.8-1). Investigations of this year concentrated in the central part of the delta. The boat “Kazanka 5M’ with Johnson 30 engine was used for hydrological measurements and for geomor-phological routes. The small ship “Orlan” which is belonging to “Lena Delta Re-serve” was used for hydrometric measurements in main channels (Main Stream, Bykovskaya Channel, Trofimovskaya Channel). The point of water level measurements has been founded on Samoylov Island.
Figure 3.8-1. Investigation area
The additional work has been made in Bulkurskaya Channel. The leveling of water table showed a negative inclination of it in the middle of August. It means that water flow is going from Olenekskaya Channel to Bulkurskaya Channel dur-ing the low water period.
Table 3.8-1: Water discharge and sediment load measured in 2007
Gauge line Date
Measured water discharge, m3/s
Calculated water discharge, m3/s
Measured sediment load kg/s
Mean turbidity, g/l
Water discharge distribution
%
Bykovskaya 23.08.2007 5973,2 92,3 0.015 23,5
Main channel 23.08.2007 26171,5 100
Trofimovskaya 23.08.2007 15543,9 917,2 0.078 56,6
Tumatskaya 02.08.2007 2534,8 79,5 0.034 9,7
Tumatskaya 17.08.2007 1643,5 29,1 0.046 6,5
Olenekskaya-3 08.08.2007 2868,7 42,6 0.08 11,8
Olenekskaya-1 02.08.2007 2488,2 38,2 0.069 9,5
Olenekskaya-1 08.08.2007 3081,6 17,8 0.053 11,0
Olenekskaya-1 19.08.2007 1699,9 14,8 0.082 6,5
The aim of geomorphological and geological investigations was to find key sec-tions of the first terrace and take samples for 14C dating from sediments. One such key cross section is represented on Figure 3.8-2. This cross section illus-trates that fact that almost all islands in the Delta consist of different parts, which have different age of formation in spite of height of terraces. These fea-tures are very important for the understanding of the Delta formation.
Figure 3.8-2: Gusinka outcrop (point 1680. see Figure3.8-1) is situated:
72º19’27?5” N, 126º16’45,9” E
3.9. Studies of coastal dynamics and subsea permafrost Paul Overduin, Waldemar Schneider and Mikhael Grigoriev Introduction and Goals
Following sea level rise during the global Holocene optimum, terrestrial perma-frost on the broad coastal plains of Siberia was inundated. Most of the current shelf area is affected by and underlain by relict permafrost. Ice melting, perma-frost degradation and coastal erosion continue to affect large regions of the Laptev Sea shelf. The low subsurface temperatures and the low diffusivity of the permafrost have the potential to hold and confine gas and gas hydrates beneath and within the permafrost, as has been observed on the Yamal Peninsula and in the MacKenzie Delta.
Drilling and geophysical sounding of the shallow near-shore sediments of the Laptev and East Siberian Seas show great spatial variability in the depth to the upper bound of ice-bound permafrost and in changes in sediment temperature profile with distance from the shore. The influence of near-shore processes (es-pecially the formation of bottom fast ice and brines, wave action and sediment transport, and thermoerosion) on permafrost and permafrost stability beneath the sea bed require study. To determine the net effect of these processes on the boundary conditions at the seabed for subsea permafrost, the field work undertaken in the nearshore zone of the Bykovsky Peninsula includes:
1. repeated annual surveying of the position of the coastal bluff (shoreline) along the eastern coast of the Bykovsky Peninsula and around the north-ern end and along the eastnorth-ern coast of Muostakh Island
2. improving nearshore bathymetry in an area affected by thermokarst processes prior to inundation
3. the deployment of data-loggers to measure temperature, salinity and pressure in the nearshore zone over an annual cycle
Data logger deployment
Data loggers were deployed from the “Puteyski 405”, a vessel operated by the Yakutian River-going Shipping Office, on August 6, 2007. Loggers were bolted to ca. 50 cm x 50 cm square anchoring plates which had been fitted with an-choring rings, to which 50 m lengths of nylon rope were attached (Figure 3.9-1).
Metal anchors were attached to the ends of these ropes. The ship was used to deploy the anchors and logger-plates roughly parallel to the peninsula shoreline west of the data-logger location (roughly NW to SE, Table 3.9-1). To minimize the chances of ice disturbing the data loggers, they were placed in local de-pressions in water depth, ranging between 4.2 and 7.5 m. Figure 3.9-2 shows the location of the data logger deployments, superimposed on a map of bore-hole locations, most from 1983. Previous attempts to deploy data loggers on the sea and river bed in the Lena Delta resulted in the loss of all loggers (From Ap-pendix 4.6, Table A4-1, Rachold, 1999)
Figure 3.9-1: A data logger, attached to a steel plate fitted with attachment rings for the ropes in the background, on board the
“Puteyski 405” in preparation for deployment.
Table 3.9-1: Data logger positions, deployed on August 6, 2007
Device Water depth [m] Latitude Longitude
CTD datalogger 1 4.2 N 71° 47' 19.0" E 129° 25' 46.7"
CTD data logger 2 6.3 N 71° 47' 58.7" E 129° 32' 56.7"
CTD data logger 3 6.2 N 71° 48' 35.0" E 129° 38' 30.2"
CTD data logger 4 7.5 N 71° 49' 33.9" E 129° 46' 26.6"
Water depth logger 10 N 71° 31' 52.3'' E 129° 33' 32.8''
Figure 3.9-2: Red circles in the larger map indicate availability of historical data from boreholes.
Bathymetry was measured within the area marked by the dashed rectangle. The inset map shows the Bykovsky Peninsula. The black square indicates the outline of the larger map and the red symbols show the locations of the data loggers deployed in 2007. Background map created by Guido Grosse.
Figure 3.9-3: Bathymetry measured in the near-shore zone east of the Bykovsky Peninsula during cruising and logger deployment. A total of 10828 depth values are interpolated. As shown here, the bathymetry is not tide or sea-surface height corrected, and was collected on August 6th and 7th, 2007.
3.10 References
Adamsen, A.P.S. and King, G.M. (1993). Methane consumption in temperate and subarctic forest soils: rates. vertical zonation, and responses to water and nitrogen. Appl. Env.
Microbiol. 59: 485-490.
Carini, S.A.; Orcutt, B.N. and Joye, S.B. (2003). Interactions between methane oxidation and nitrification in coastal sediments 20: 355-374.
Fiencke, C., Spieck, E.and Bock, E. (2005). Nitrifying bacteria. In D. Werner, and W. E. Newton (eds.), Nitrogen Fixation in Agriculture, Forestry, Ecology, and the Environment. Sprin-ger, The Netherlands, Dordrecht. 12: 255-276.
Gersper, P.L., Alexander, V.and Barkley, S.A. (1980). The soils and their nutrients. In: Brown, J., P.C. Miller, L.L. Tieszen, F.L. Bunnell (eds.). An Arctic Ecosystem. The coastal Tun-dra at Barrow, Alaska. Stoudsburg: Dowden, Hutchinson & Ross, 219-254.
Gersper, P.L., Alexander, V.and Barkley, S.A. (1980). The soils and their nutrients. In: Brown, J., P.C. Miller, L.L. Tieszen, F.L. Bunnell (eds.). An Arctic Ecosystem. The coastal Tun-dra at Barrow, Alaska. Stoudsburg: Dowden, Hutchinson & Ross, 219-254.