Vibrio spp. respond to the addition of particulate Sahara dust compared to leached dust in Florida Keys microcosm study following Saharan nutrient pulse

Transport and deposition of desert dust aerosols is a major contributor to micro and macronutrients across downstream habitats. In marine systems, dust deposition events can affect biogeochemistry of surface waters, in addition to autotrophic and heterotrophic responses. The tropical and subtropical Atlantic Ocean receives a large portion of dust aerosols, arriving from the Sahara and Sahel, which can drive microbial processes. Of particular interest is the early biological response to dust arrival, which can have a dramatic effect on processing and bioavailability of nutrients and trace metals, especially dissolved or bioavailable forms of iron. Much of our understanding of biological responses to dust have come from studies on the soluble fraction leached from dust particles; however, recent work on in situ responses to dust events suggest that leached materials may drive different responses than deposition of whole dust. Here we show that dust delivery method has a significant effect on microbial community composition, especially among early responders (24 h or less). We found that with the addition whole dust aerosols, natural seawater bacterial community composition shifted significantly by 16 h post-incubation. Furthermore, the primary taxa driving the change in composition were in the order Vibrionales, which increased significantly in whole dust treatments compared to both leachate and controls (p=0.02). This was further supported by direct measurements of Vibrio in these microcosms, which also showed a significant proportional growth in whole-dust treatments (P = 0.03). Aside from the change in Vibrio, the relative abundances a total of 9 taxonomic families changed significantly between the control and leachate treated samples. These findings confirmed prior studies on microbial response to dust in situ and suggests that factors associated with delivery of particulates as well as dissolved fractions of dust are critical in how the microbial community responds to dust.