Older populations participating in many kinds of social activities exhibited preserved cognitive function even after adjusting for area-level social participation variables. Copyright © 2016 John Wiley & Sons, Ltd.

We proposed an empirical equation of sea surface dimethylsulfide (DMS, nM) using sea surface temperature (SST, K), sea surface nitrate (SSN, µM) and latitude (L,

Dimethyl sulfide (DMS) derived from marine biological activity affects radiative forcing of the climate. The general analytical technique for DMS in seawater (purge and trap analytical method, P&T) is complex onboard ship. Thus it is difficult to obtain sufficient data for a comprehensive understanding of the spatiotemporal variability of DMS in the sea surface layer. On the other hand, a new analytical method for DMS using SPME (solid-phase microextraction) has recently been developed as an alternative method to P&T. This method is simpler than P&T because no special or complex apparatus is needed. If it is possible to preserve DMS for an extended period in excess of the duration of the cruise, the SPME method is a promising method for measuring DMS in seawater. We assessed an analytical method which can allow us to preserve DMS on the long-term scale using SPME. In liquid nitrogen (-196 degrees C), as preserved environment, for a period of 20 days after sampling, we found the preservation rate of DMS to be 94.7 +/- 4.4% (n = 6) in this study. Furthermore, estimating the distribution coefficient with respect to the effect of salinity on SPME, we found that DMS changed by 0.1 nM/% sal, suggesting that salinity has only a minor influence on oceanic DMS measurements in the open ocean because the minimal change of the open ocean salinity is within 2 %. Applying the SPME method to open ocean samples, we found that there were no significant differences in DMS between the unpreserved and preserved samples (r = 0.99, n = 26, SE = 0.01, p < 0.0001), showing the SPME method has potential for use for open ocean surveys.