Fig 2. Example of eddy covariance data treatment for calculating daily seafloor productivity rates from the MM site.

The collected datasets for PAR (15 min, A) and the eddy fluxes (15 min, B) were bin-averaged by the hour of day to produce a single 24 h time series for PAR (C, mean ± SD, n = 3) and eddy flux (D, mean ± SE, n = 3). The eddy flux time series was separated into day-time and night-time fluxes to compute daily rates of seafloor gross primary productivity (GPP), respiration (R), and net ecosystem metabolism (NEM) (E, in mmol O₂ m^-2 d^-1, see Methods).