Methane as a Source of Carbon and Energy for Lake Pelagic Food Webs

Abstract

Water‐column methane oxidation can represent a substantial carbon transformation pathway in lakes, and circumstantial evidence indicates that methane may be a potentially important source of carbon for pelagic food webs. We estimated methanotrophic bacterial production (MBP), methanotrophic bacterial growth efficiency (MBGE), heterotrophic bacterial production (HBP), primary production (PP), and the relative contribution of methanotrophic bacteria to overall bacterial biomass in three very different lakes during summer and winter. In addition, we measured stable carbon isotope ratios in particulate organic matter (POM), surface sediments, zooplankton, and methane. MBP corresponded to 0.3–7% of the organic C production by primary producers, and 0.5–17% of HBP during summer. During winter, MBP was 3–120% of HBP. MBP generally dominated the heterotrophic bacterial production at greater depths. Methanotrophic biomass was 3–11% of total bacterial biomass on a depth‐integrated basis. Zooplankton were generally more depleted in 13C than POM. If phytoplankton δ13C signatures were −35 to −30‰, such as the POM signals, observed zooplankton signatures could be explained by a fraction of 5–15% methanotrophic bacteria in their diet. The results indicate that methanotrophic bacteria can provide a significant food source for zooplankton, and that methane oxidation represents a potentially important benthic–pelagic carbon and energy link in many lakes, particularly during winter. Corresponding Editor: J. B. Yavitt.

Methane as a carbon source for the food web in raised bog pools

“…Elucidation of the various pathways by which MOB-derived C is assimilated by zooplankton and the relative importance of MOB in bog pools requires further investigation, but the available data indicate that MOB are a significant direct food source for pelagic zooplankton in bog pools (Fig. 3), a finding also reported in lake pelagic food webs (Bastviken et al 2003, Taipale et al 2007, Sanseverino et al 2012). …”

“…In bogs, CH 4 is produced during the decomposition of peat (Raghoebarsing et al 2005). CH 4 -derived C could contribute to the food web via methanotrophic bacteria, which are ingested by zooplankton (Bastviken et al 2003, Taipale et al 2007), chironomid larvae (Jones et al 2008), and caddisfly larvae grazing their own cases (Trimmer et al 2009). So in total, 3 potential basal C sources exist in bog pools: primary producers, bacteria feeding on humic substances, and CH 4 -derived C.…”

Seasonality of stable carbon and nitrogen isotopes within the pelagic food web of Taihu Lake

“…Potentially they can cast new light on food web structure and on sources of materials and their fluxes through ecosystems (Grey et al 2001, Bastviken et al 2003. Many studies rely on rather limited temporal sampling, with an inherent assumption that seasonal variation in the isotope values of the sampled organisms is small relative to the variation between food web components.…”

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“…Notably, our results reflect exclusively the incorporation of dissolved inorganic carbon as CO 2 , and not chemosynthesis based on other C1 compounds, an important pathway in particular considering methanotrophic bacteria (Bastviken et al 2003a;Ravinet et al 2010;Sanseverino et al 2012). This indicates that the results obtained with the method provided in this study are a conservative estimation of DCF.…”