Diversity of active aerobic methanotrophs along depth profiles of arctic and subarctic lake water column and sediments

Abstract

Methane (CH(4)) emitted from high-latitude lakes accounts for 2-6% of the global atmospheric CH(4) budget. Methanotrophs in lake sediments and water columns mitigate the amount of CH(4) that enters the atmosphere, yet their identity and activity in arctic and subarctic lakes are poorly understood. We used stable isotope probing (SIP), quantitative PCR (Q-PCR), pyrosequencing and enrichment cultures to determine the identity and diversity of active aerobic methanotrophs in the water columns and sediments (0-25 cm) from an arctic tundra lake (Lake Qalluuraq) on the north slope of Alaska and a subarctic taiga lake (Lake Killarney) in Alaska's interior. The water column CH(4) oxidation potential for these shallow (∼2 m deep) lakes was greatest in hypoxic bottom water from the subarctic lake. The type II methanotroph, Methylocystis, was prevalent in enrichment cultures of planktonic methanotrophs from the water columns. In the sediments, type I methanotrophs (Methylobacter, Methylosoma and Methylomonas) at the sediment-water interface (0-1 cm) were most active in assimilating CH(4), whereas the type I methanotroph Methylobacter and/or type II methanotroph Methylocystis contributed substantially to carbon acquisition in the deeper (15-20 cm) sediments. In addition to methanotrophs, an unexpectedly high abundance of methylotrophs also actively utilized CH(4)-derived carbon. This study provides new insight into the identity and activity of methanotrophs in the sediments and water from high-latitude lakes.

Shifts in Identity and Activity of Methanotrophs in Arctic Lake Sediments in Response to Temperature Changes

“…At the continuous CH 4 ebullition site in the lake reported here, dissolved CH 4 concentrations were less than 15 mol liter Ϫ1 from a sediment depth of 0 to 10 cm and increased to 1,334 mol liter Ϫ1 at a 25-cm sediment depth. In other parts of this lake, as well as in other lakes in Alaska in our study, dissolved CH 4 concentrations at a sediment depth of 1.5 cm were 109 to 505 mol liter Ϫ1 , and the maximum measured dissolved CH 4 concentration was 2,062 mol liter Ϫ1 at a 25.5-cm sediment depth (28). The saturated CH 4 concentration, calculated by Henry's law and the van't Hoff equation, in the pore water in SIP microcosms was 151 mol liter Ϫ1 at the initial CH 4 concentration of 10% (vol/vol).…”

Methanotrophic bacteria in oilsands tailings ponds of northern Alberta

“…This is within the range of rates seen in natural lake and ocean waters (for example, Bastviken et al, 2002;Carini et al, 2005;Krü ger et al, 2005;He et al, 2012), although soils and sediments in similar climates can show much higher rates, ranging from 0.17-80 mmol CH 4 g À 1 d…”

“…À 1 (Kravchenko, 2002;Wagner et al, 2005;Kip et al, 2010;Graef et al, 2011;Lee et al, 2011;Barbier et al, 2012;He et al, 2012). The aeration depth of the ponds was estimated as 60 cm for Pond B and 1.5 m for Pond A (Supplementary Table S1).…”

Geographic and seasonal variation of dissolved methane and aerobic methane oxidation in Alaskan lakes

“…These affinity constants are highly variable, because their determination is challenging and subject to relatively high determination error (Segers et al, 1998) and because the methanotrophic community is sensitive to numerous factors and changes over time and space (Carini et al, 2005;He et al, 2012). For instance, Lofton et al (2014) reported a variation of 150 % in K S−CH 4 within the hypolim-K. Martinez-Cruz et al: Geographic and seasonal variation of dissolved methane 4603 netic water column of two lakes with similar characteristics.…”