Saharan dust deposition initiates successional patterns among marine microbes in the Western Atlantic

Abstract

Deposition of aerosolized desert dust can affect marine microbial community structure and function through pulsed addition of limiting micro‐ and macronutrients. However, few studies have captured responses to dust deposition in situ following trans‐oceanic transport. We conducted a 26‐d time series evaluating biogeochemical and microbial community response to Saharan dust deposition in surface waters in the subtropical western Atlantic (Florida Keys National Marine Sanctuary, U.S.A.). Following periods of elevated atmospheric dust concentrations, particulate and dissolved iron concentrations increased in surface waters. Autotrophic picoeukaryote abundance increased rapidly, followed by increases in the abundance of heterotrophic bacteria and Synechococcus. Concomitant to cell count changes, we observed successional shifts in bacterial community composition. The relative abundances of Prochlorococcus and Pelagibacter declined with dust arrival, while relative abundance of heterotrophic bacteria increased, beginning with Vibrionales and followed sequentially by Chrysophyceae, Rhodobacteriaceae, and Flavobacteriaceae. Finally, a peak in Synechococcus cyanobacteria was observed. These results provide new insight into microbial community succession in response to Saharan dust deposition, their association with temporal dynamics in surface water dissolved and particulate iron concentrations, and a potential role for bioprocessing of dust particles in shaping marine microbial responses to deposition events.

Bio-Aerosols Negatively Affect Prochlorococcus in Oligotrophic Aerosol-Rich Marine Regions

“…We postulate that airborne component/s within the aerosol used, presumably viruses, small-sized bacteria and/or membrane vesicles, accounted for up to 90% of the change recorded in 'live aerosol' additions ( Figure 5C, calculated as the net difference between the 'live' and 'killed' aerosols divided by the overall change recorded post 'live' aerosol addition). These results are in agreement with field observations in the same area [14], as well as in other oceanic systems [13,[15][16][17].…”

“…Declines in abundances following aerosol additions were previously reported for Prochlorococcus in the tropical northeast Atlantic [15], the Western Atlantic Ocean [16], the northwest Pacific Ocean, [13], the northern Red Sea [17] and the offshore waters of the southeastern Mediterranean Sea [14]. These previous reports attributed the decline in Prochlorococcus abundance solely to toxic quantities of trace metals (such as Cu) leached from the aerosols [18,49], ignoring potential interactions with airborne microbes and/or other biological agents.…”

“…(E) The relationship between Prochlorococcus and aerosol dry deposition. Prochlorococcus data was compiled from [13][14][15][16][17]28,44] and this study. (F) The corresponding % change in Prochlorococcus abundance to aerosol addition (Herut et al, 2005; Chung et al, 2011 and this study).…”

“…Several experimental and modelling studies demonstrated that the supply of nutrients and trace metals via atmospheric deposition may increase the biomass and carbon fixation rates of marine primary producers, including cyanobacteria, thus playing a significant role in the nutrition and ecology of LNLC regions [11,12]. Other studies, however, reported specific reduction in Prochlorococcus activity/biomass following aerosol amendment in the tropical Northeast Atlantic Ocean, the Western Atlantic, the Pacific Ocean, the Red Sea and the Southeast Mediterranean Sea [13][14][15][16][17]. These trends were attributed to the potential release of toxic levels of trace metals from the aerosols [18].…”

The trace metal economy of the coral holobiont: supplies, demands and exchanges

“…The metal seascapes of coral reefs can be influenced by terrestrial forces at different geographical scales. Wind‐delivered (aeolian) dust is a significant source of soluble metals for Caribbean, Red Sea, and Pacific reefs (Jickells, 1999; Borchardt et al ., 2020; Blanckaert et al ., 2022). Metal contributions from dust input are frequently evaluated via Fe and aluminium (Al) inputs but aeolian dust is suspected to transport other trace elements (Measures & Vink, 2000).…”