Ebullitive release of lacunar gases from floral spikes of Potamogeton angustifolius and Potamogeton amplifolius: effects on plant aeration and sediment CH 4 flux

Abstract

Field and laboratory studies examined two Potamogeton species ( P. angustifolius Berchtold Presl. and P. amplifolius Tuckerm.) for effects of ebullition from submersed floral inflorescences, or spikes, upon plant aeration and sediment CH 4 release. Results indicated that daytime release of lacunar gas via ebullition from submersed floral spikes of mature clones was light-dependent and comparable to post-emergence flux. Analysis of tracer movement through plants and measurements of lacunar pressure revealed that daytime convection was driven by a sustained pressure difference (3–6 kPa at midday) between non-ebullient and ebullient clones, and enhanced exchange of lacunar gas between clones connected via rhizome. In comparison to non-ebullient clones, stem lacunae of ebullient clones showed higher concentrations of CH 4 and CO 2 and lower concentrations of O 2. In situ measurements of diffusive and ebullitive CH 4 flux from plants and sediment showed that ebullitive release from submersed floral spikes of P. angustifolius represented 19–29% of total areal CH 4 flux. This indicates that, in addition to effects on plant aeration, ebullitive release of lacunar gases from submersed rhizomatous angiosperms may represent a heretofore-unquantified source of CH 4 emission from aquatic systems.