Abstract
Atmospheric dust/aerosol deposition is an important source of external nutrients for the surface of the ocean. This study shows high-resolution observational data gathered in situ over a period of four years on bacterial and phytoplankton abundance and activity during typical background atmospheric conditions and during intense dust storm events in the low-nutrient, low-chlorophyll (LNLC) coastal waters of the southeastern Mediterranean Sea (SEMS). Chlorophyll a (an estimate for phytoplankton biomass) and bacterial abundance show moderate changes in response to dust deposition/events (−10% and +20%, respectively), while primary production, bacterial production, and N2 fixation rates were all significantly and positively affected by deposition (+25 to +40%; p < 0.05). The rapid changes in bacterial and/or phytoplankton rate parameters suggest that the released micro-/macronutrients from atmospheric deposition are tunneled directly in metabolic processes and, to a lesser extent, for biomass accumulation. The predicted expansion of LNLC areas in oceans in the future, and the projected increase in dust emission due to desertification, may affect the production of marine microbial communities in the surface of the ocean, yet only moderately affect their biomass or standing stock. Such alterations may impact carbon sequestration to the deep ocean.
Highlights
Desert dust is a source of micro- and macronutrients [1,2,3,4] and airborne microbes [5,6,7,8,9] for ocean surfaces worldwide
Primary and bacterial production (PP and BP, respectively) as well as N2 fixation rates are usually low in the southeastern Mediterranean Sea (SEMS) [22,27]
Previous studies show that phytoplankton at the SEMS coast are mainly N-limited [23] and heterotrophic bacteria and diazotrophs (N2 fixers) are
Summary
Desert dust is a source of micro- and macronutrients [1,2,3,4] and airborne microbes [5,6,7,8,9] for ocean surfaces worldwide. Numerous studies show that dust deposition in seawater can alter bacterial and phytoplankton biomass and activity [12,13,14,15,16,17,18]. Dust is recognized as an important factor that affects the ecology of many aquatic settings, especially low-nutrient, low-chlorophyll (LNLC). The coastal southeastern Mediterranean Sea (SEMS) is an LNLC oligotrophic environment [20,21,22,23]. Primary and bacterial production (PP and BP, respectively) as well as N2 fixation rates are usually low in the SEMS [22,27]
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