Effect of wind speed on the size distribution of gel particles in the sea surface microlayer: insights from a wind–wave channel experiment

• Main Authors: C.-C. Sun, M. Sperling, A. Engel
• Format: Article
• Language: English
• Published: Copernicus Publications 2018-06-01
• Series: Biogeosciences
• Online Access: https://www.biogeosciences.net/15/3577/2018/bg-15-3577-2018.pdf

Gel particles, such as transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP), are important organic components in the sea surface microlayer (SML). Here, we present results on the effect of different wind speeds on the accumulation and size distribution of TEP and CSP during a wind wave channel experiment in the Aeolotron. Total areas of TEP (TEP_SML) and CSP (CSP_SML) in the surface microlayer were exponentially related to wind speed. At wind speeds  &lt;  6 m s⁻¹, accumulation of TEP_SML and CSP_SML occurred, decreasing at wind speeds of  &gt;  8 m s⁻¹. Wind speeds  &gt;  8 m s⁻¹ also significantly altered the size distribution of TEP_SML in the 2–16 µm size range towards smaller sizes. The response of the CSP_SML size distribution to wind speed varied through time depending on the biogenic source of gels. Wind speeds  &gt;  8 m s⁻¹ decreased the slope of CSP_SML size distribution significantly in the absence of autotrophic growth. For the slopes of TEP and CSP size distribution in the bulk water, no significant difference was observed between high and low wind speeds. Changes in spectral slopes between high and low wind speed were higher for TEP_SML than for CSP_SML, indicating that the impact of wind speed on size distribution of gel particles in the SML may be more pronounced for TEP than for CSP, and that CSP_SML are less prone to aggregation during the low wind speeds. Addition of an <i>E. huxleyi</i> culture resulted in a higher contribution of submicron gels (0.4–1 µm) in the SML at higher wind speed ( &gt;  6 m s⁻¹), indicating that phytoplankton growth may potentially support the emission of submicron gels with sea spray aerosol.