A high-resolution time-depth view of dimethylsulphide cycling in the surface sea.

S.-J Royer,A S Mahajan,G L Pérez,E S Saltzman,M Galí,O N Ross,R Simó

doi:10.1038/srep32325

Abstract

Emission of the trace gas dimethylsulphide (DMS) from the ocean influences the chemical and optical properties of the atmosphere, and the olfactory landscape for foraging marine birds, turtles and mammals. DMS concentration has been seen to vary across seasons and latitudes with plankton taxonomy and activity, and following the seascape of ocean’s physics. However, whether and how does it vary at the time scales of meteorology and day-night cycles is largely unknown. Here we used high-resolution measurements over time and depth within coherent water patches in the open sea to show that DMS concentration responded rapidly but resiliently to mesoscale meteorological perturbation. Further, it varied over diel cycles in conjunction with rhythmic photobiological indicators in phytoplankton. Combining data and modelling, we show that sunlight switches and tunes the balance between net biological production and abiotic losses. This is an outstanding example of how biological diel rhythms affect biogeochemical processes.

Highlights

We report results from two Lagrangian studies conducted in open oligotrophic waters of the western Mediterranean Sea illustrating the complex response of DMS cycling to changes in meteorology, solar radiation, and phytoplankton photophysiology
On 14 September winds increased to 7–8 m s−1 for almost 12 hours and on 18–19 September elevated winds associated with a storm exceeded 14 m s−1 and obliged to stop the cruise for 30 hours
The results of this study reveal the strong effects of mesoscale meteorological forcing on DMS production and concentration in the surface sea

Summary

Introduction

One of the impediments to such studies is the difficulty in making trace gas measurements at frequencies sufficient to resolve variability due to changes in meteorological, hydrological and biogeochemical conditions. Vertical profilers have been used to make high frequency measurements of seawater temperature, density or chlorophyll a (chla) fluorescence but traditional analytical methods for DMS take several minutes for a single measurement. This study takes advantage of high frequency mass spectrometric and optical measurements, coupled to continuous vertical sampling with a recently developed profiler to allow a view of upper ocean DMS cycling at unprecedented resolution. We report results from two Lagrangian studies conducted in open oligotrophic waters of the western Mediterranean Sea illustrating the complex response of DMS cycling to changes in meteorology, solar radiation, and phytoplankton photophysiology

Methods

Results

Conclusion