Bange, Hermann W.

Peeken, Ilka

Zindler, Cathleen

English

OceanRep

Dimethylsulfide (DMS) and Dimethylsulfoniopropionate (DMSP) in the Mauritanian Upwelling (NW Africa) Introduction•Measurements of dissolved DMS and DMSP in surface seawater during the SOPRAN cruise ATA-03 in the eastern tropical North Atlantic Ocean in February 2008 are presented•During ATA-03, nutrient rich upwelled water triggered a phytoplankton bloom dominated by diatoms along the Mauritanian coastCathleen Zindler (czindler@ifm-geomar.de), Ilka Peeken* and Hermann W. BangeIFM-GEOMAR, Leibniz Institute of Marine Science (at Kiel University), Germany; *Alfred-Wegener-Institut of Polar and Marine Science, Bremerhaven, Germany0123456781 2 3 4 6 7 8 10 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40station no.phytoplankton group and total Chl a [mg L-1 ]phosphat [µmol L-1 ]05101520temperature [°C]cyanobacteriadino flagellateshaptophytesdiatomstemperaturephosphatto tal Chl aSurface distribution of DMS(P) 0246810121 2 3 4 6 7 8 10 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40station no.DMS and DMSP dissolved[nmol L-1 ]01002003004005006007008009001000DMSP p [nmol L-1 ]DMSDMSP dDMSP p01234567829 30 32 33 34 35 36 37 38 39station nophytoplankton groups and total Chl a [mg L-1 ] phosphat [µmol L-1 ]0510152025temperature [°C]cyanobacteriahaptophytesdiatomsdinoflagellatestemperaturephosphattotal Chl a00.050.10.150.20.250.30.3529 30 32 33 34 35 36 37 38station nophytin and phorbid [mg L-1]024681012DMS and DMSP dissolved [nmol L-1]haptophytesdinof lagellatesDMSDMSP dConclusion•The patchy distribution of DMSP producing algae was roughly consistent with the distribution pattern of DMSP and DMS•The DMS distribution was also partly dependent on the grazer abundance and senescence of phytoplankton•Along the 18° N transect the phytoplankton abundance and DMS(P) concentration decrease with distance to the coastThe sampling site of the ATA-03cruise on the R/V Atalante,3rd to 20th February 20080.000.050.100.150.200.250.300.35station no.phytoplankton groups [mg L-1]024681012DMS/DMSP dissovled [nmol L-1]haptophytesdinoflagellatesDMSP dDMS0.00.10.20.30.40.50.60.70.81 2 3 4 6 7 8 10 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40station no.Phorbid a or Phytin a [mg L-1]024681012DMS and DMSP dissolved [nmol L-1 ]total phytin atotal phorbid aDMSP dDMSSouthward shifting of the upwelling area during the ATA-03 cruise 2-9 Feb. 08 10-17 Feb. 08MODIS (NASA)onshoreonshoreoffshoreonshoreoffshore offshoreThe Mauritanian Upwelling region The phytoplankton and DMS(P) distribution of the sampling siteDistribution of DMSP producing algaeDistribution of grazer and senescence indicators•The upwelling area along the Mauritanian coast is a dynamic system due to its southward expansion during the ATA-03 cruise•The induced phytoplankton bloom was mainly dominated by diatoms whereas dinoflagellates and haptophytes were more abundant in areas of upwelled water mixed with oligotrophic open ocean water; cyanobacteria were dominant in oligotrophic offshore regions a succession of phytoplankton composition dependent on the nutrient concentration (Fig. 1)•Elevated dissolved DMS(P) concentrations was mainly dependent on dinoflagellates abundant (Fig. 3)•DMS concentrations were also elevated in areas with high grazer pressure and high abundance of aged algae -this is probably due to enhanced release of algae DMSP which is used as a nutrient by bacteria, a process at which DMS can be produced DMS and DMSP peaks coincidence with high dinoflagellates and haptophytes abundance as well as with high grazer pressure and with aging of the phytoplanktonThe 18° N transect The Phytoplankton distribution from the coast to the open oceanDistribution of the DMSP producing algae and of the dissolved DMS(P)•Along the 18° north transect diatoms dominated the coastal area of the upwelling region whilst haptophytes and dinoflagellates were more abundant further offshore where also DMS(P) was highest concentrated•In the open ocean phytoplankton abundance and DMS(P) concentrations were lowFig. 1Fig. 2Fig. 3Fig. 4Cape VerdeMauritaniaFig. 5Fig. 6

Diemethlsulfide (DMS) and Dimethylsulfoniopropionate (DMSP) in the Mauritanian Upwelling (NW Africa)

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