Is it stochastic? Chaoborus larvae bioturbation likely affect the timing of daily methane (CH4) ebullitive flux in a tropical reservoir

Abstract

Controlling factors of CH4 ebullitive flux are still poorly understood within daily timescales in aquatic environments. Here, we explored if Chaoborus larvae bioturbation can influence the timing of daily CH4 ebullitive flux and how this emission pathway is affected considering direct observations in a tropical reservoir. For this, we collected CH4 bubbles on two different days and three sampling periods: 1–4 pm, 4–7 pm and 7–10 pm. In the middle of each period, we collected Chaoborus larvae, chemical, and environmental variables and acoustically surveyed the underwater environment. We found similar temporal patterns of CH4 emissions between the periods in both days. The intervals of higher CH4 ebullitive flux (1–4 pm and 4–7 pm) appeared to correspond with the exit period of Chaoborus larvae from sediment (2:30 pm to 5:30 pm). Furthermore, the density of benthic larvae, a proxy of the bioturbation intensity, was the only variable that significantly correlated with the ebullitive flux, presenting a high and positive relation. Our findings suggest that the stochastic nature of the CH4 ebullitive flux may not be absolute truth, and this emission pathway might be enhanced daily by a Chaoborus-driven physical disturbance.