Comparison of net community and primary production estimates in the Bay of Biscay.

Oceanic-dissolved gas concentrations in the upper ocean are governed by biological and physical processes. Biological activity comprises the oxygen (O2) production by phytoplankton during photosynthesis and consumption through respiration by the marine community. The balance between the two processes is the net community production (NCP). It can be estimated from a time series of oxygen measurements if the physical processes can be evaluated.

Among the physical, the air-sea gas exchange is the main one controlling oxygen concentrations in the ocean mixed layer, and the contribution of bubbles created by breaking waves is a first order event at moderate to high wind speeds (u10 > 7m/s), in young (wind) seas mainly.

In this work, we use different model of the role of bubbles in air‐sea gas exchange (different parameterizations calculated the contribution of bubbles in the air-sea exchange flux) to estimate the NCP in the North Atlantic. Biological contributions are calculated by subtracting the calculated physical changes from the measured dissolved oxygen and compared with primary production estimates based on chlorophyll algorithms.

For this aim, long-term oceanographic time series data from the ocean observatory SATS (Santander-Atlantic-Time-Series) have been employed. These data include measurements from the ocean-meteorological buoy (AGL) at its associated oceanographic station running since 2007 in the southern Bay of Biscay.

We find that the contribution of bubles is minor (5-10 %), thus we can assume that the estimates of NCP are reliable, in good agreement with primary production estimates at the surface. In addition, the wave age has been measured and found to be mostly a mature sea, with very few days of young waves.