Responses of production and concentrations of marine biogenic sulfur to atmospheric dust deposition in the Northwest Pacific

Biogenic dimethylated sulfur compounds such as dimethylsulfide (DMS), methanethiol (MeSH), and dimethylsulfoniopropionate (DMSP) are ubiquitous in marine environments, playing pivotal roles in the global sulfur cycle and climate regulation. Atmospheric dust deposition exerts a significant impact on the Northwest Pacific ecosystem. However, its impact on these compounds in the upper ocean remains inadequately understood. This research examines the effects of atmospheric dust deposition, along with the subsequent influx of nutrients and Fe ions on the phytoplankton community and biogenic sulfur cycle in the Northwest Pacific, utilizing a ship-based incubation experiment. Our findings reveal that nutrient influx, stemming from both dust deposition and nutrient addition, has spurred phytoplankton growth, in which dust deposition also altered the structure of the algae community. These changes have consequently increased DMSP production per phytoplankton cell, leading to higher DMSP concentrations. The abundant nutrient has further amplified the DMSP cleavage pathway, a source of DMS, resulting in elevated DMS levels. Interestingly, the increase in DMSP has offset the reduced DMSP demethylation pathway, a source of MeSH, thus raising MeSH concentrations. While Fe ion addition did not directly boost phytoplankton biomass, it induced environmental oxidative stress, which in turn promoted cellular DMSP synthesis, enhancing both DMSP and subsequently DMS and MeSH production. Nevertheless, the swift oxidation of MeSH by active Fe ions led to a reduction in its concentration. This study elucidates the responses of phytoplankton and biogenic dimethylated sulfur compounds to atmospheric dust deposition, along with the subsequent influx of nutrients and Fe ions. These insights are crucial for accurately modeling the implications of such environmental changes on future climate dynamics.