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Title

Effect of Saharan dust on dynamics of nutrients and marine microbial plankton

AuthorsMarín, Isabel ; Nunes, Sdena ; Estrada, Marta ; Peters, Francesc
Issue Date27-Nov-2013
CitationIntegrating New Advances in Mediterranean Oceanography and Marine Biology. Meeting program: 61 (2013)
AbstractThe Mediterranean Sea is a low-nutrient low-chlorophyll region, especially affected by aerosol deposition. The Sahara desert is considered the most important source of crustdominated aerosols in the world and to the Mediterranean basin, with the potential of providing essential nutrients for plankton growth. Previous amendment experiments with Saharan dust in seawater are not conclusive about the effects on the dynamics and composition of marine microorganisms. We performed an amendment experiment with aerosols of Saharan origin at realistic deposition rates, separating effects on bacteria from phytoplankton. Four containers were filled with 7.5 L of seawater (Barcelona, NW Mediterranean coastal water from 10 m depth) pre-meshed through 150 μm. Two of the containers were further filtered through 0.8 μm. The containers were incubated at 14 ºC with a 13:11 h light:dark cycle. At day 10, two of the containers were amended with 1.3 mg L-1 of Saharan dust (150D and 08D), while the two other served as controls (150K and 08K). Subsamples were taken daily for inorganic nutrients, chlorophyll a and flow cytometry determination. Results showed that 1 mg L-1 of dust produced an increase of 1.95 μmol L-1 of DIN, 4.49 μmol L-1 of SiO2 and 0.19 μmol L-1 of PO43- in container 150D, and 2.20 μmol L-1 of DIN, 4.61 μmol L-1 of SiO2 and 0.20 μmol L-1 of PO43- in 08D. Chlorophyll a concentration started to increase in 150D after the dust was added, reaching a concentration six times higher three days later. Autotrophic nanoeukaryotes and picoeukaryotes were mostly responsible for this increase, although Synechococcus cell abundance also increased in this container. Contrary, Synechococcus cell abundance showed a light decrease in 08D after the dust addition. In both containers, the total abundance of bacteria increased three days after the dust was added. However, the increase in 08D was larger than in the control. We conclude that Saharan dust affects phytoplankton abundance directly and has the potential to also affect bacteria directly. Effects on bacterial abundance may be delayed due to phytoplankton competition for nutrients or result from secondary stimulation owing to nutrient recycling. Further studies are needed to clarify the response under different initial conditions
DescriptionSymposium on Integrating New Advances in Mediterranean Oceanography and Marine Biology, 26-29 November 2013, Institut de Ciències del Mar (CSIC), Barcelona, Catalunya, Spain
Publisher version (URL)http://www.icm.csic.es/bio/medocean/information.htm#schedule
URIhttp://hdl.handle.net/10261/96687
Appears in Collections:(ICM) Comunicaciones congresos
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