Relationship between aerosol methanesulfonate and remotely sensed phytoplankton activity in central Mediterranean Sea S. Becagli a, L. Lazzara b, F. Fani b, C. Marchese b, R. Traversi a, M. Severi a, A. di Sarra c, D. Sferlazzo d, S. Piacentino e, C. Bommarito e, R. Udisti a a Department of Chemistry, University of Florence, Sesto F.no, Florence, I-50019, Italy b Dep. of Biology, University of Florence, I Sesto Fiorentino, Florence, Italy c ENEA, Laboratory for Earth Observations and Analyses, I Roma, Italy d ENEA, Laboratory for Earth Observations and Analyses, I Lampedusa, Italy e ENEA, Laboratory for Earth Observations and Analyses, I Palermo, Italy Earth observation for ocean-atmosphere interaction science | ESA-ESRIN |28-30 October 2014

From : Stefesl et al., Biogeochemistry (2007) 83:245–275

MSA Biogenic productivity Influence of global change on biogenic productivity. Feedback processes (CLAW hypothesis) Charlson, R. J., Lovelock J.E., Andreae, M. O. and Warren, S. G. (1987). Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate. Nature, 326,

NASA/MODIS 35.5°N, 12.6°E

N Power plant Airport Town

Since Jun 2004 PM10 sampling on Teflon filter…..sampling in progress Aerosol sampling Campaigns

Ion Chromatography Na +, NH 4 +, K +, Mg 2+, Ca 2+, Cl -, NO 3 -, SO 4 2-, MS -, Ac, For, Gly, Ox Al, Cd, Ba, Pb, Si, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Mo ICP AES HNO 3 pH1.5 PIXE: elements total content Dept. of Chemistry, Univ. of Florence Dept. of Physics and INFN Cuting in clean conditions

maximum value of specific absorption in the chlorophyll spectrum (about at 435 nm) maximum quantum yield of phototrophic growth length of day depth of euphotic layer fraction of PAR potentially absorbed by all algal species. PAR (W/m2) was derived from measurements of global downward irradiance. concentration of chlorophyll-a f (x) is a function reproducing the photosynthesis-irradiance relationship (P-E curve) x is the ratio between PUR and Ek (photo-adaptation irradiance) CALCULATION 1/2 Primary Production – PP g C m -2 d -1 Biooptical and physiologically based model of the WRDM (Wavelength-Depth- Resolved-Model) developed by Morel (1991).

chlorophyll-a map calculated by CHL MedOC3 algorithm for the year 2007.

Map of Primary Productivity in the year 2006 calculated for the surroundig area of Lampedusa Island

CALCULATION 2/2 P B : chlorophyll specific production index or assimilation number i.e. the rate of photosynthetic carbon assimilation per weight of chlorophyll-a P B = PP/Chl (integrated values for the euphotic layer) [gC gChl -1 d -1 ] Daily solar radiation dose (SRD) in the upper mixed layer: SRD = f (PAR, MLD, PAR att coeff) daily irradiance measured at Lampedusa Mixed Layer Depth climatology of the Naval Research Laboratory PAR attenuation coefficients from ocean color satellite-derived climatologies (SeaWiFS, ex.html).

The “summer Paradox” seasonal changes in the phytoplankton composition Phytoplankton stress due to high irradiance (UV and visible) and low nutrient availability associated with a shallow mixed layer depth during summer. Chl SRD PP PBPB MS -

DMS in sea water MS - in atmospheric aerosol

Over Western Mediterranean: Positive anomaly of GPH at all atmospheric levels Positive anomaly of GPH at all atmospheric levels Strong subsidence cloud free conditions weak winds leading to short- fetch backward trajectories

E. huxleyi abundances in the Sicily Channel in spring 1996 (Bohm et al., 1998) High MSA in spring 2005 in the Sicily Channel (this work) These steady conditions could have allowed an earlier initiation of the spring bloom favoring the growth of small flagellates and prymnesiophytes (high DMS producer) instead of diatoms

biological causes……the weak winds over the Mediterranean Sea prevent a strong vertical mixing of the water column, thus reducing the upper mixed layer depth and producing effects similar to an increase of SRD Atmospheric causes….the stable atmospheric conditions determine the accumulation of the newly formed MS - in the marine boundary layer.

Conclusions Statistically significant linear relationship between MS - – P B (r 2 = 0.84, p < 0.001), MS - – SRD (r 2 = 0.87, p < 0.001) MS - in the Mediterranean Sea is mainly related to the phytoplankton physiology (growth rate, photo adaptation), which in turn depends on stress factors (i.e., excess radiation and water column stratification during summer in the Mediterranean). Experimental derivation P B from atmospheric parameters validation of biogeochemical model results Improvement in their ability to predict phytoplankton growth rates under light and nutrient limitation modeling of the ocean carbon cycle at the global scale.

Future work MSA-P B Long term correlation Effect of Saharan dust episodes on PP and P B Study of chemical composition of deposition (see poster Santinelli), dust deposition velocity and effect of dust deposition in different oligotrophic condition.

Thank you for your attention!!