Beschreibung:
<jats:p>Shallow lentic freshwater aquatic systems are globally important emitters of methane (CH<jats:sub>4</jats:sub>), a highly potent greenhouse gas. Previous laboratory studies indicated that bioturbation by chironomids can reduce CH<jats:sub>4</jats:sub> production and increase CH<jats:sub>4</jats:sub> oxidation by enhancing oxygen transport into sediment. Thus, reduction in chironomid density by application of biocides for mosquito control, such as <jats:italic>Bacillus thuringinesis</jats:italic> var. <jats:italic>israelensis</jats:italic> (Bti), have the potential to affect CH<jats:sub>4</jats:sub> emissions. We evaluated the effect of a 41% reduction in chironomid larvae abundance due to Bti applications on CH<jats:sub>4</jats:sub> dynamics in the aquatic and aquatic-terrestrial transition zones of 12 floodplain pond mesocosms (FPMs) (half treated, half control). We evaluated short-term (2 months) and seasonal effects by measuring CH<jats:sub>4</jats:sub> emissions, dissolved concentrations, and oxidation rates in spring, summer, autumn, and winter. On average, CH<jats:sub>4</jats:sub> emissions from the aquatic-terrestrial transition zone of the treated FPMs were 137 % higher than those of the control FPMs. The lack of differences in mean oxidation rates between the treated and control mesocosms suggests that a reduction in bioturbation and the associated decreased oxygen transport into the sediment promoted CH<jats:sub>4</jats:sub> production in the treated FPMs. Our findings point to potential effects of Bti on CH<jats:sub>4</jats:sub> biogeochemistry through alterations of the chironomid abundance, and highlight the underestimated role of invertebrates in biogeochemical cycling in these ecosystems.</jats:p>