Carbon Isotopic Insights into Biological Processing of Marine Organic Matter and Transfer to Sea Spray Aerosol
Abstract
Organic matter in sea spray aerosol (SSA) affects their climate-relevant properties such as hygroscopicity, reflectivity, and ice nucleation ability. The effect of biological activity on SSA organic carbon (OCSSA) composition, and therefore these climate-relevant properties, is still not fully understood. To assess the influence of biological activity on OCSSA composition, two microcosm phytoplankton bloom experiments were conducted in a Marine Aerosol Reference Tank. Stable carbon isotopic compositions (δ13 C) and concentrations were measured in the particulate (POC), dissolved (DOC), and sea surface microlayer (OCSSML) seawater carbon pools as well as in SSA to evaluate changes in OCSSA composition. Both experiments demonstrated a significant biological influence on OCSSA composition. Based on isotopic signatures, the largest proportional contribution to SSA from OC produced during the phytoplankton bloom, hereafter termed "freshly-produced" OC, was delayed from the Chlorophyll-a peak by 2-3 days. This suggests further bacterial processing after primary production may be necessary to breakdown "freshly-produced" OC into a form that is efficiently transferred into SSA. To further explore differences between submicron and supermicron OCSSA composition, δ13 C and OC concentrations were measured on size-segregated SSA filter samples collected during a mesocosm phytoplankton bloom experiment. Additionally, δ13 C and concentrations of size-segregated POC as well as seawater DOC and OCSSML were measured to evaluate the size-dependent transfer of marine organic matter. A significant contribution of "freshly-produced" OC was observed in supermicron SSA, once again delayed from the Chlorophyll-a peak by around 2 days. In contrast, the submicron OCSSA composition remained constant throughout the mesocosm experiment and did not appear to be strongly influenced by biological activity, suggesting the biological influence on SSA is size-dependent. These studies shed light on the timescales and extent of marine organic matter processing and provide insight into the transfer of organic material into supermicron and submicron SSA.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA046...08C
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0312 Air/sea constituent fluxes;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0315 Biosphere/atmosphere interactions;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES