TITLE: NOAA R/V Ron Brown Discrete DMS, DMSP and chlorophyll AUTHOR(S): Andrew J. Hind ajhind@googlmail.com Patricia A. Matrai pmatrai@bigelow.org Bigelow Laboratory for Ocean Sciences 180 McKown Point W. Boothbay Harbor, ME 04575 USA Phone 207 633 9600; Fax 207 633 9641 1.0 DATA SET OVERVIEW: Discrete measurements of seawater dimethyl sulphide (DMS) as well as dissolved dimethyl sulfoniopropionate (DMSP) both within particles (DMSPp) and (DMSPd) and chlorophyll. Data was collected during Legs 1 and 2 of the VOCALS cruise Time period covered by the data: Leg 1 data is from 21-Oct-2008 to 2-Nov-2008 and leg 2 is from 10-Nov-2008 until 01-Dec-2008. Platform: Ronald H. Brown Location: mobile 2.0 INSTRUMENT DESCRIPTION: DMS in seawater was discretely sampled in either duplicate or triplicate and determined according to the methods of Matrai and Keller (1993). They were either taken from Niskin bottles on the CTD rosette or from the ship's non-toxic supply (UW) fed from an inlet at approximately 5 metres below the sea surface. Sampling stations of the two types were sequentially numbered (UW1, UW2, UW3; CTD1, CTD2 CTD3 etc.). The system is based on a “purge and trap” GC-FPD design. The instrument was calibrated using liquid DMS or DMSP standards. The DMS and DMSP samples were measured in duplicate or triplicate in nearly all cases and the values in this data set are the means of these. DMSP samples were collected in the same manner as for DMS and analysed using the methods of Matrai and Vernet (1997). The particulate and dissolved fractions were separated by gravity filtration through a 25mm GF/F filter (Whatman Ltd., Kent, UK). Each filter, containing the particulate matter, was sealed into a gastight serum vial containing 10N NaOH. The sample was stored at room temperature at least overnight in the dark and homogenised using low intensity sonicatation. A subsample was introduced into the purge and trap system as for DMS. The filtrate containing the DMSPd was either analysed immediately or frozen at -20°C for later analysis. A subsample was introduced into the purge and trap system with of 10 N NaOH. The NaOH is used to cleave the non volatile DMSP into DMS (and acrylate and a proton) which can then be analysed with the GC. Chlorophyll samples were taken in triplicate from either Niskin bottles on the CTD rosette or from the ship's non-toxic supply as for DMS. The samples were filtered onto 25mm filters (GF/F, Whatman Ltd., Kent, UK) and immediately frozen at ?20°C for subsequent analysis according to Holm-Hansen et al. (1965). These were measured with a 10AU fluorometer fitted with a discrete sample cell and calibrated using pure chlorophyll a (Sigma Biochemicals). Each measurement was made in triplicate. 3.0 DATA COLLECTION AND PROCESSING: The mean chlorophyll concentration was 0.44 with a SE of ± 0.15 and with a range from 0 to 17 microgram/liter. The mean DMS concentration was 2.46 ± 0.09 nM and the range was 0-23 nM. The mean DMSPp was 22.80 ± 2.72 nM and the range was 1-157 nM. The DMSPd mean was 7.72 ± 1.26 nM. and the range was 0 to 39 nM. The errors quoted are the mean standard error of replicate measurements over the whole cruise. 4.0 DATA FORMAT: Column delimited ASCII Headers YYYYMMDDHHmmss.ss Cruise leg Latitude Longitude Station Depth Chl discrete DMS DMSPp DMSPd UTC   Degrees N, digital Degrees E, digital meters Microgram/liter nanomolar nanomolar nanomolar Date of data version: 14-Feb-2011 5.0 DATA REMARKS: REMARKS = These data can be considered final REMARKS = Data point Date/Time provided in UTC REMARKS = Missing data = NaN 6.0 REFERENCES: Holm-Hansen, O., Lorenzen, C., Holmes, R. and Strickland, J., 1965. Fluorometric determination of chlorophyll. ICES J. Mar. Sci., 30: 3-15. Matrai, P.A. and Keller, M.D., 1993. Dimethylsulfide in a large-scale coccolithophore bloom in the Gulf of Maine. Continental Shelf Research, 13(8/9): 831-843. Matrai, P.A. and Vernet, M., 1997. Dynamics of the vernal bloom in the marginal ice zone of the Barents Sea: dimethyl sulfide and dimethylsulfoniopropionate budgets. Journal of Geophysical Research, C: Oceans, 102(C10): 22,965–22,979.