Using satellite data for the surface ocean, aerosol optical depth (AOD), and cloud microphysical parameters, we show that statistically significant positive correlations exist between ocean ecosystem productivity, the abundance of submicron aerosols, and cloud microphysical properties over different parts of the remote oceans. The correlation coefficient for remotely sensed surface chlorophyll a concentration ([Chl-a]) and liquid cloud effective radii over productive areas of the oceans varies between and . Special attention is given to identifying (and addressing) problems from correlation analysis used in the previous studies that can lead to erroneous conclusions. A new approach (using the difference between retrieved AOD and predicted sea salt aerosol optical depth, ) is developed to explore causal links between ocean physical and biological systems and the abundance of cloud condensation nuclei (CCN) in the remote marine atmosphere. We have found that over multiple time periods, 550？nm (sensitive to accumulation mode aerosol, which is the prime contributor to CCN) correlates well with [Chl-a] over the productive waters of the Southern Ocean. Since [Chl-a] can be used as a proxy of ocean biological productivity, our analysis demonstrates the role of ocean ecology in contributing CCN, thus shaping the microphysical properties of low-level marine clouds. 1. Introduction Aerosols influence the planetary radiation balance directly by scattering and absorbing sunlight, and indirectly by modifying cloud microphysical properties [1–4]. Marine aerosols are particularly important, as they contribute considerably to the global aerosol load, are emitted from a large surface area, and have an ability to strongly influence reflective properties and lifetime of marine stratiform clouds [5]. Marine aerosols could be especially important for understanding the cloud-mediated effects of aerosols on climate, because cloud properties are most sensitive to the addition of particles when the background concentration is low [6]. Factors that regulate the concentration of marine aerosols, and thus the reflectivity of low-level marine clouds, can strongly affect the whole climate system [7, 8]. Cloud droplet number concentration (CDNC) over the remote oceans ranges from a few tens per cm3 in biologically inactive regions (seasons) to a few hundred per cm3 under biologically active conditions [9]. Despite recognizing their crucial role, the source strength and chemical composition of marine aerosols remain poorly quantified [10, 11]. Aerosols over the remote oceans consist
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