Dust Nourishment of Global Ocean Ecosystems (Invited Presentation)

While most nutrients sustaining ocean ecosystems originate from upwelling of deep water, evidence is building that the atmosphere makes an important contribution with the deposition of mineral-laden desert dust onto the ocean surface. Numerous previous studies have identified ocean biological responses to intense aerosol events or following very localized seeding of dissolved iron into iron-limited regimes. For the first time, we have used satellite ocean color products to look for an oceanic response to dust deposition events across the entire globe. Ocean color products including chlorophyll concentration, carbon biomass and chlorophyll fluorescence quantum yield were derived from the Aqua MODIS record spanning 2003 – 2016. Dust deposition events were identified using the NASA Goddard Earth Observing System (GEOS) global model. The analysis reveals:

1. There is an ocean response to even modest amounts of deposition in areas outside of the subtropical dust belt.
2. Ocean ecosystems respond to dust deposition events everywhere and not just in iron-limited zones, implying that dust bring macronutrients as well as micronutrients to the ocean.
3. The response to dust deposition events can manifest as an increase in biomass, a change in physiology (health of the phytoplankton), or both.

These results imply that the atmosphere is intrinsically linked to the health of ocean biology. As climate change affects the production and transport of desert dust, ocean phytoplankton will feel those changes and respond.