Modelling dimethylsulfide diffusion in the algal external boundary layer: implications for mutualistic and signalling...

Area of Science:

• Marine microbial ecology
• Biogeochemical cycles
• Chemical oceanography

Background:

• Dimethylsulfide (DMS) is a key sulfur compound in marine environments.
• DMS is produced by phytoplankton and influences microbial interactions.
• The concentration of DMS near algal cells is critical for its proposed signaling functions.

Purpose of the Study:

• To model dimethylsulfide (DMS) enrichment at the surface of marine algal cells.
• To investigate the influence of DMS production rate, cell size, and turbulence on surface DMS concentrations.
• To assess the ecological significance of DMS microscale enrichments for marine microbial communities.

Main Methods:

• Development of a mathematical model for DMS surface enrichment.
• Simulation of DMS concentrations under varying algal physiological states (unstressed vs. stressed).
• Analysis of the impact of algal cell radius and turbulence on DMS diffusion and accumulation.

Main Results:

• DMS surface enrichment was <1 nM for unstressed algae with low production rates.
• Mechanically stressed algae with high DMSP-lyase activity showed DMS enrichments up to ~10 nM.
• Potential for μM level DMS enrichments in large algal cells was indicated, significantly exceeding ambient ocean concentrations.

Conclusions:

• Microscale DMS enrichments at algal surfaces can be substantial, particularly under stress.
• These enrichments likely attract bacteria to the phycosphere, supporting mutualistic interactions.
• DMS plays a crucial role in mediating beneficial relationships between algae and bacteria in the ocean.