Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 20 cm below, and ∼ e and Murrell, 2009) of ff Peru and implications 10579 10580 ff Peru. Samples were collected from the SML and from ff This discussion paper is/has beenPlease under refer review to for the the corresponding journal final Biogeosciences paper (BG). in BG if available. GEOMAR – Helmholtz Centre for Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Abstract The surface microlayerdrosphere (SML) with is the at atmosphere, theclimate-related and very processes. central The surface to presence of and a theSML enrichment range have ocean, of been of organic linking suggested global compounds to the in influence biogeochemicalemission hy- air–sea the and of gas exchange primary processes as organicplankton well aerosols. origin, as Among the are these dissolved exopolymers, organicand specifically compounds, gel polysaccharides primarily particles, and of proteins, Stainable such Particles as (CSP). Transparent These Exopolymer organicocean when Particles substances plankton often productivity (TEP) is accumulate high. and in2012 Here, we Coomassie the during report surface the results SOPRAN obtained in Meteorregime December 91 o cruise to the highly productive, coastal were analyzed for polysaccharidicand and dissolved proteinaceous organic carbon, compounds, bacterial gelvides and particles, insight phytoplankton to total abundance. the Our study physicalSML, and pro- and biological discusses control of thechange organic processes. potential matter role enrichment in of the organic matter in the1 SML for air–sea Introduction ex- The sea-surface microlayerthe (SML) interface is between the thematter, uppermost distinct ocean physical layer and and of chemical the(neuston) properties the distinguish atmosphere. and water-column a the The specific and SML accumulationhas organismal as community been of a suggested organic unique that the biogeochemicalvarying SML thickness and has with ecological a dissolved system. polymeric gel-likewell It nature carbohydrates as and (Cunli gel amino particles, acidsridic such present as as composition, Transparent and Exopolymer Particles Coomassie (TEP) Stainable of Particles polysaccha- (CSP) of proteinaceous com- Germany Received: 29 May 2015 – Accepted: 03Correspondence June to: 2015 A. – Engel Published: ([email protected]) 09 July 2015 Published by Copernicus Publications on behalf of the European Geosciences Union. for air–sea exchange processes A. Engel and L. Galgani The organic sea surface microlayerupwelling in region the o Biogeosciences Discuss., 12, 10579–10619, 2015 www.biogeosciences-discuss.net/12/10579/2015/ doi:10.5194/bgd-12-10579-2015 © Author(s) 2015. CC Attribution 3.0 License. 5 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | usive ff S. In this ◦ ecting gas exchange in ff 10581 10582 Peru extends between 4 and about 40 ff usion of gases (Frew et al., 1990; Liss and Duce, 2005) ff ects gas exchange rates particularly at lower wind speed (Jähne and ff Peru are characterized by high biological productivity supported by deep- ff erent stations, providing the most extensive data-set the SML in EBUS so far. ff The upwelling coastal region o During the SOPRAN cruise Meteor91 (M91), we drove our attention to organic matter Accumulation of organic matter in the SML may be tightly coupled to phytoplankton area, upwelling processes areinter-annual sustained ecosystem variability by induced winds by the allcycle El along (Tarazona Niño–Southern and Oscillation the Arntz, (ENSO) year 2001).the but system Eastern feature o Boundary high Upwelling Systems (EBUS) like and advective, mechanisms, whereasmatter, biological provide processes, sinks (Lachkar i.e. and respiration Gruber,for 2011). of major OMZs organic are significant relevant sourceand regions gases nitrous such oxide as (Paulmier et carbon al., dioxide, 2008, methane, 2011). hydrogen Processes sulfide a upwelling of nutrients and(OMZs). often The supply associated of with oxygen to subsurface the Oxygen OMZ is Minimum largely Zones controlled by physical, i.e. di biogenic material as polysaccharidesing and and amino alters acids, the leads molecular to di capillary wave damp- and therewith a Haußecker, 1998). In this respect,of the biological understanding components of in sources, composition thevance and surface for fate layer environments of where theregimes. biological ocean productivity becomes is of high, particular like rele- in coastal upwelling components at the surface sincetainty properties for gas, of heat the and SMLconcentration aerosol may and fluxes represent composition in a of this majoron region. the uncer- 39 During di SML our and cruise, the organic underlying matter was studied Galgani et al., 2014).may Thus, also organic matter reflect accumulation thevironmental and sensitivity composition changes, of in marine which the waset SML in al., shown 2013; the during Riebesell surface et previous oceanmatter al., mesocosms 2009; to accumulation Schulz en- studies and et al., (Engel compositionalmain 2013). changes Processes processes in determining that organic the occuroceanic SML at may feedback be the on relevant air–sea atmosphericcomposition for interface and dynamics: two air–sea and sea-spray gas are aerosol exchangeods, processes. important (SSA) a During high to emission biologically amount productive understand and of peri- ocean’s SSA with surface a (O’Dowd predominant et organiccharidic al., composition is 2004). gel-like emitted These from composition, compounds the polysaccharides suggesting primarily and reveal that a marine the polysac- gelstion abundance of in SSA and the (Orellana et size seapresence al., surface 2011; of of Russell surface may dissolved et active influence al., substances 2010). the () It in organic has the also frac- sea-surface been shown microlayer, like that the these regions need tofrom be the understood ocean in to order the atmosphere to and accurately consequences estimate on trace climate. gas fluxes dynamics in the water-column (Bigg et al., 2004; Gao et al., 2012; Matrai et al., 2008; position. These compoundsreleased originate form from phytoplankton high andet molecular bacterial al., cells weight 1998; by polymers Engel exudation etas that and al., cell are transparent 2004; break Verdugo exopolymer et up al., particlesexudation (Chin 2004). (Passow, (TEP), Polysaccharide-rich 2002), gels, were known whilecoomassie attributed stainable the mainly particles production (CSP) to hasas of phytoplankton been well protein-containing related as to gels, cell toAzam, such lysis the and 1996). as absorption decomposition, Gels of arePassow, 2004; proteins transported Zhou onto et to al., non-proteinaceous 1998) thethe particles or air–sea SML are (Long interface produced by and during from risingpromote dissolved surface precursors wave bubbles microbial directly action (Azetsu-Scott at biofilm (Wurl and et formationganic matter al., (Bar-Zeev transport, 2011). et either Gel to al.,2011) particles the or 2012) can atmosphere to and (Leck the and deep mediate Bigg, ocean vertical 2005; (Passow, 2002). Orellana or- et al., 5 5 10 15 20 25 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 C ◦ . The 1 − W from 3 to ◦ 20 cms 5mm (thickness) ∼ × C). Samples were acid- , prepared from a potas- S and 77.5 ◦ 1 ◦ Peru (Bange, 2013). Sam- − is the sampling area of the ff A 250mm (width) × the Peruvian coast (Fig. 1), a total of ff W, and 15.4 ◦ S o ◦ Peru in order to assess the importance of ective sampling surface area of 2000 cm ff ff 20 cm depth by holding an acid cleaned (HCl 10583 10584 ∼ S and 82.0 ◦ is the number of dips. n ) was estimated as follows: erence between TOC and DOC. ) and m ff 2 , d 2000 cm = ) (1) A erent stations between 5 and 16 n ff is the SML volume collected, i.e. 60–140 mL, × V A ( V/ At the same stations, after sampling the SML about 500 mL samples from the under- The SML thickness ( On 37 di = ified with 80 µL of 85 % phosphoric acid, heat sealed immediately, and stored at 4 lying seawater (ULW) were collected at Samples for TOC andDOC DOC after (20 mL) filtration were through collected combusted in GF/F to filters combusted (8 h, glass 500 ampoules, (considering both sides). For eachperpendicular sample, to the glass the plate surfacesample, was retained and inserted on into withdrawn the the at glassof water a because a Teflon of wiper. controlled Samples surface were rate tension, collectedwith was against of the wind removed rubber direction with boat to the and avoidtwenty contamination help for times. each The sample exact the numberSamples glass of plate were dips was collected and dipped the into andtles, total acid wiped and volume cleaned about the collected (HCl, first were milliliters 10 recorded. sampling, %) were both and discarded glass Milli-Q and used washedrinsed plate to glass with and rinse Milli-Q bot- wiper the water. bottles. Atwith were Prior the seawater washed in sampling to order site, with each to both HCl minimizehandling instruments any or (10 were possible transporting %) contamination copiously the with and rinsed devices. alien intensively material while 10 %) and Milli-Qa rinsed rubber glass boat bottle. could be For made safety only reasons during2.2 daylight sampling hours. for the Chemical SML and from biological analyses 2.2.1 Total organic carbon (TOC) and dissolved organic carbon (DOC) d Where sium hydrogen phthalate standard (Merck(MilliQ) 109017). Every water measurement was day, ultrapure usedment for of setting deep-sea water the with instrument knownUniversity DOC/TOC baseline, concentration of (Dennis followed Hansell, by Miami) RSMAS, thewithin to measure- the verify range results.a of Additionally, potassium two those hydrogen internal in phthalatedetermined standards samples (Merck in with were 109017). each DOC prepared DOC samplewas and each determined from TOC as measurement 5 the concentration to day di was 8 using injections. Particulate organic carbon (POC) glass plate ( in the dark until analysis.temperature DOC catalytic and oxidation TOC samples method wereSuzuki (TOC analyzed -VCSH, (1988). by Shimadzu) applying The the afterdard high- instrument Sugimura solutions was and of 0, calibrated 500, every 1000, 1500, 8–10 days 2500 and by 5000 measuring µgCL stan- 23 December in 2012.chemical The study overall on goal the of upwelling M91 region was o to conduct an integrated biogeo- 39 SML samples was collecteding from to a the rubber original boat approach usingsampled described a by twice glass Harvey plate in and sampler Burzell a accord- (1972).glass time Two plate stations frame with were of the dimensions 24 h ofwas 500mm (stations made (length) 12_1 of and silicate 12_3, glass 16_2 and and 16_3). had Our an e 2 Material and methods 2.1 Field information and sampling The R/V Meteor cruise M91 studied the upwelling region o oxygen minimum zones (OMZs)trace for gases the and sea–air tropospheric chemistry. exchange of various climate-relevant ples were collected between 4.59 5 5 15 20 25 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C to ◦ (2) p d 20 − 4.6 mm) × slides and © erent amino ff ) of gel particles p d C, hydrolyzed for 20 h ◦ (Merck 105065). Particulate C) and kept frozen at ◦ C until analysis. Samples for ® ◦ 1 kDa (THCHO and DHCHO), > 20 is a constant that depends on the − k C. Samples were washed with water 0) describes the spectral slope of the ◦ erence between THCHO and DHCHO. ff δ < ( δ erence between TN and TDN. 10586 10585 ff syringe filters and then stored in the same way as ® C) and stored at column (Phenomenex Kinetex, 2.6 µm, 150 ◦ er (PH 7.0), Solvent B was acetonitrile. A gradient was ff 18 is related to the slope of the cumulative size distribution δ , which chemiluminesces when mixed with ozone and can be x C with hydrochloric acid (suprapur, Merck) and neutralized by acid ◦ C until microscopy analysis. ◦ C) Two replicate samples were analyzed. Particulate hydrolysable carbo- , prepared with potassium nitrate Suprapur ◦ 1 δ is the number of particles per unit water volume in the size range 20 p syringe filters. The analysis was conducted according to Engel and Hän- − )) (Mari and Kiørboe, 1996). The factor − p ® N kd C with 0.8 M HCl final concentration, and neutralized through acid evaporation d ◦ = d( ) p + , 5 h, 50 N 2 The size-frequency distribution of polysaccharidic and proteinaceous gels was de- Analysis was performed on a 1260 HPLC system (Agilent). Thirteen di d p d d d( size distribution. The value where d ( total number of particles per volume, and 2.2.4 Total and dissolved combined carbohydrates For total and dissolved hydrolysable carbohydrates 20 mL were filled into pre-combusteduntil glass analysis. vials Samples (8 h, for 500 DHCHO wereAcrodisc additionally filtered through 0.45del µm Millipore (2011) applying HPAEC-PADby on membrane a dialysis Dionex (1 kDa ICSat MWCO, 100 3000. Spectra Por) Samples for were(N 5 h desalinated at 1 2.2.5 Gel particles Total area, particle numbers and equivalent spherical diameter ( stored at scribed by: hydrates (PHCHO) were determined as the di nitrogen (PN) was determined as the di were determined by microscopytered after onto Engel 0.4 µm (2009).Blue Nuclepore Therefore, solution 20 membranes for polysaccharidic to (Whatmann) gels,1 30 i.e. and mL mL transparent stained Coomassie exopolymer were particles Brilliant with fil- (TEP), Blue 1 and Coomassie mL G Stainable Particles Alcian (CBBG) (CSP). working Filters solution were mounted for onto proteinaceous Cytoclear gels, i.e. 2.2.2 Total nitrogen (TN) and totalTN dissolved and nitrogen TDN (TDN) were determinedthe simultaneously TNM-1 with detector TOC on and theand DOC, Shimadzu converted respectively, analyzer. using to Nitrogen in NO detected the using samples a is photomultiplier combusted was (Dickson done et every al., 8–10 days800 2007). µgNL by Calibration measuring of standard the solutions instrument of 0, 100, 250, 500 and 2.2.3 Total, dissolved and free aminoFor acids total hydrolysablecombusted amino glass vials acids (8dissolved h, (THAA), hydrolysable 500 (DHAA) 5 mL andthrough free of 0.45 amino µm sample Millipore acids Acrodisc (FAA) were were filled additionally filtered into pre- after in-line derivatization with o-phtaldialdehyde5 % and mercaptoethanol. Solvent acetonitrile Aphospate was (LiChrosolv, (Merck, suprapur) Merck, bu HPLC gradient grade) in sodiumdihydrogen- samples for THAA. Analysis wasand performed Dittmar according et al. to (2009) Lindrothfor with and 20 some Mopper h modifications. (1979) Duplicate atevaporation samples 100 under were vacuum hydrolyzed in ato microwave remove at remaining 60 acid. acids were separated with a C run from 100 % solvent Asamples to 78 without % prior solvent A hydrolysis in inacids 50 min. separate (PHAA) FAA were analyses. were determined determined Particulate from by hydrolysable DHAA subtracting amino DHAA from THAA. 5 5 25 10 20 15 10 20 15 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − (4) (3) ce Ex- popula- ffi ). To determine p 1. d < Synechococcus )) vs. log( p ) with the addition of 1 µm- d 1 of the semi-empirical relation- test) were accepted as signifi- − d( δ t N/ 1, depletion by EF > , the greater is the fraction of larger gels. δ 39–41 µLmin C until enumeration. Phytoplankton counts ◦ C until enumeration. Samples were stained ∼ erent components can be readily compared. ◦ 10588 10587 ff 80 20 − − 1 standard deviation. ± 1. The less negative is + β ULW ) C) were recorded indicating the colder, upwelling deep water (Table 1, ◦ = A were derived from regressions of log(d ( ) 0.05. Average values for total concentrations are given by their arithmetic δ / k 19 δ ) is the concentration of a given parameter in the SML or ULW, respectively < − by SML p < A ) 26.2 β and p A (64 erences in data as revealed by statistical tests ( ( δ ad ff = = = Di The fractal dimension (D1) was calculated based on , data for CSP and TEP were fitted over the size range 1.05–14.14 µm ESD. Where ( (GESAMP, 1995). Because the concentrationues of in a component the isEnrichment underlying normalized of to water, a its EF component val- is for indicated di by EF 2.2.8 Data analysis The relative concentration of a substancewater A (ULW) in by the the SML was enrichment compared factor to (EF), the defined underlying by: EF cant for mean, averages for ratiosillustration by of their the geometric data mean. were performed Calculations, with statistical the tests software packages and Microsoft O cel 2010, Sigma Plotvalues 12.0 are reported (Systat) with and Ocean Data View (Schlitzer, 2013). Average 3.1 The physical environment Coastal upwelling of deep waterperature resulted and in salinity strong along gradientsthe of shelf the surface during Peruvian seawater M91. shelf tem- Salinitykeel measured as varied at well about between 1 32 as m and depthat with 35 corresponding stations psu increasing to 10_1 with the distance to the ship’s 10_4, to lowestaverage 14_1 values ( and occurring 14_2 close and to 15_1Fig. the to 2). coast 15_3. Wind Here, speed temperatureswith encountered below during the the lower cruise wind ranged between speeds 0.6 also and observed 9.0 ms closer to the coast, i.e. between 12 and 3 Results Both ship (Burd and Jackson, unpublishedas applied data, for as TEP referred also to by in Harlay Mari et al., and 2009): Burd,D1 1998 and δ N were performed with a FACSCaliburan flow-cytometer air-cooled (Becton laser Dickinson) equipped providingcells with 15 mW were at analyzed 488 nm at and high with flow a standard rate filter ( set-up. The 2.2.7 Phytoplankton For autotrophic cell numbers, 4 mLfinal samples were concentration), fixed with and 20 µL glutaraldehyde stored (25 % at 2.2.6 Heterotrophic For bacterial cell numbers, 4final mL samples concentration) were and fixed withwith stored 200 SYBR µL Green at glutaraldehyde I (25 (Molecular % a Probes). Heterotrophic flow bacteria cytometer were (Becton enumerated using 488 & nm Dickinson and FACScalibur) detected equipped byrescence with (FL1). their a Yellow-green latex signature laser beads in (Polysciences, emitting 0.5standard. a µm) at were plot used of as side internal scatter (SSC) vs. green fluo- tions) fluorescence. Cell counts were analyzed using BD CellQuest Pro-Software. fluorescent beads (Trucount, BD). Autotrophicof groups were their discriminated forward on or theand right basis phycoerythrin angle (characteristic light for scatter cyanobacterial, (FALS, RALS) mainly as well as from chlorophyll 5 5 10 20 15 20 15 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 1 − − for 39, 39). = 1 mL = − 5 0.001). n n 10 ered spa- mL ff p < 5 × 0.44, 10 − , and between 30, 2 × 8.9 µm ( = − = r ± n and 3.0 3 with highest numbers 1 10 − and 1.9 0.81, × , and was clearly higher 1 = − mL 3 0.001) (Table 3). DOC con- r 6 10 10 p < × × 0.48, (Table 2) and, in contrast to POC, was − 1 ) was observed at station 15_2, slightly − and 8.5 = 1 4 − r ) and between 5.4 0.001; PHAA: 0.001), linking their accumulation in the SML 10 10590 10589 × p < were observed at stations 9 and 9_2 (Fig. 5), but p < 1 39, − 30, 550 nmolL = erence between TOC and DOC and ranged between ff = n ± e et al., 2011, 2013). n ff ) (Table 2). In general high DHCHO concentration was more 1 0.70, − 0.47, = Synechococcus spp. − r = r (data from shipboard measurements on R/V Meteor were retrieved . Highest POC concentration was observed at the upwelling stations (mean: 1111 erences were less pronounced than for DHCHO. Both components of 1 2 ff 0.001) and to wind speed ( 1 − − -shore stations having higher surface water temperatures, leading to − ff 359 nmolL p < ± 0.67, − 0.001; DHAA: S and at the northern stations (Fig. 2). Thus, higher wind speed was observed ◦ = Concentrations of combined carbohydrates and amino acids in particles and in gels DHHA concentration was on average lower than DHCHO concentration (Table 2) In general, concentration of organic components in the SML showed spatial distri- Unless stated otherwise, all observations described inPhytoneuston this paragraph abundances relate to ranged the between 3.7 TOC concentration ranged between 82 and 199 µmolL r south of the(mean: station 770 14_1 exhibiting highest DHAA concentrations of 2017 nmolL excluding these stations fromwind analysis speed did either. DOC nottory is reveal compounds a a that bulk correlation are measure to independentlinked and from to temperature is recent productivity or biological quantitatively and productivity. dominatedruvian More likely by coast closely stimulated are refrac- by labile the andhydrates semi-labile upwelling and compounds of amino such nutrients acids. as Indeed, dissolved alongtrations combined both at the carbo- DHCHO the Pe- upwelling and stations DHAAof (Fig. reached 2668 5). highest nmolL Thereby, maximum concen- concentration of DHCHO not significantly related toconcentrations temperature of or about 100 wind µmolL speed (Table 3). Relatively high DOC (TEP, CSP) in particular were highestcarbohydrates at and the amino coastal upwelling acids stations (PHCHO,centrations also. PHAA) (PHCHO Particulate were highly correlated to POC con- to productivity in the cold upwelling waters. In contrast to the dissolved components, particles contained on average higher con- p < (Fig. 5). In general, POC( concentration was highly inversely correlated to temperature tration was calculated as2.3 the to di 96 µmolL and horizontal di semi-labile DOC were inversely correlated to temperature (DHCHO focused to the upwelling, andsouthern exhibited stations. strong horizontal gradients to the northern and This value is inpled good with accordance a with glass previous plate (Cunli observations for the SML when sam- centration ranged between 71 and 122 µmolL bution patterns resembling those ofhighest temperature values and for wind nearly speed all (compareto components Figs. 10_4, were 3–5); 14_1 observed and at the 14_2 upwelling and stations 15_1 10_1 to 15_3SML. (Fig. 1). 0.8 and 71 Wm at the more o significant co-variation between surfaceGlobal water radiation temperature and and UV wind radiation speed varied (Fig. betweenfrom 10 3). DSHIP and software) with 1103 Wm no significant impact of SML3.2 organic matter accumulation. Organic matter in the SML The thickness ofranged the between SML 45 calculated and from 60 µm, glass with plate an overall sampling mean during value this of cruise 49 14 cyanobacteria (mainly for other pico- and nanoautotrophs. Generallytotrophs highest in abundance of the nano- SML andOn picoau- was all other determined stations, on celltially, abundance and with of close higher cyanobacteria to and abundance phytoplankton thenumbers of di of upwelling cyanobacteria phytoeukaryotes at stations at the (Fig. northern thedetermined 4). stations in southern (Fig. abundances between 4). stations 3.0 Heterotrophic and bacteria were higher than DOC concentration on all stations. Particulate Organic Carbon (POC) concen- observed at the upwelling stations and southeast of the upwelling (Fig. 4). 5 5 25 15 20 10 15 10 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | at 1 − L 2 erent com- ect on most ff ff erent from those ff . The EF of CSP total area 1 − was observed at station 11_1 shore station 18_2 at a higher 1 ff − L 2 at station 15_1, about 100 nautical 1 − L 2 erent gel particle types determined in this ff ected by changes in wind speed more than ff 10592 10591 at station 14_1. 1 erences in the accumulation dynamics. − ff L 2 . For TEP as well as for CSP median EF varied around 1 − erences were observed between EF values of di ff . In proximity of this station, the lowest EF of TEP was determined (station 1 ).The largest variability of EF was observed for abundance and total area − 1 − ered from that of CSP (Fig. 5). While higher TEP abundance was observed at the erences were observed for the two di Enrichment factors indicated a general accumulation of organic matter in the SML In general, CSP were more abundant than TEP (Table 2), but variability of gel par- ff ff with respect to thetions. underlying Thereby, seawater clear (ULW) di (Fig. 6), which happened at most sta- mostly related to theirticulate abundance components in in ULW. the However,concentration with SML of dissolved the were compounds exception a (Table 3). of CSP, par- 15_3) indicating a clear depletion at wind speed of 7 ms most all stations (Fig. 6),were with 1.7 EF and of 0.8–4.6 1.4 (DHAA)carbohydrates for and (THCHO, DHAA 0.4–3.4 DHCHO) and (THAA). concentrations THAA, Median inULW, respectively. EFs with the Total EF SML and values were dissolved ranging often hydrolysable between(THCHO), similar 0.6 respectively. to and In the 1.4 contrast (DHCHO) towere and all found between other to 0.3 organic be and 1.7 EF depleted chemical in compounds, of the bacteria 0.8. SML Variabilityparticulates, at of suggesting almost again EF all di was stations (Fig. generally 6), smaller having for a dissolved median components than for a value of one,and in suggesting our that cruise marine marinedissolved gels gel hydrolysable did not accumulation amino generally is acids become enriched (THAA, spatially in DHAA) highly the were variable, SML. Total enriched and in the SML at al- ponents. The highest enrichmentenriched was more observed than 10-fold for at some freein stations. amino Moreover, the FAA were SML, acids consistently except (FAA) enriched for that one(49 nmolL station were where the lowest FAAof concentration was gel determined particles. Forest TEP EF observed total at area, the valueswas coastal 0.6 upwelling of ms station EF 14_1, ranged where the between wind 0.2–12, speed with recorded high- ranged between 0.4 and 4.8.and Thus in highest contrast EF to ofwind TEP CSP speed it was rate was clearly observed of lower at than 9.2 ms for the TEP, more o ticles abundance was high, yielding lowest values of total TEP area of 6.9 mm centrations of aminorapid acids loss compared of DHAA to after carbohydrates release from (Table particles. 2), indicating a more station 13_1 and highest values of 408 mm miles apart. Although highestto abundance of the both coastal TEP upwelling,di and apart CSP were from observed this close area distribution of TEP in the SML clearly northern stations, CSPMoreover, abundance stations of was highest and more lower pronounced concentration of at CSP were the di southern stations. of TEP. Lowest value of CSP total area of 137 mm and highest value of 3051 mm 3.3 Accumulation patterns in the SML For almost all componentswas significantly investigated related to during the thiscorrelations respective between concentration study, in SML concentration the and ULW in ULWticularly (Table 3). were the for Thereby, strongest SML DHCHO. for combined Closemeasurements, carbohydrates, i.e. correlations par- TOC, DOC, were and also derivedcompounds, therefrom observed i.e. POC. TDN, For for FAA dissolved and bulk nitrogenous DHAAtrations organic no were relationship carbon observed, between SML suggesting andwere that faster ULW than loss concen- exchange or processes with gain the of ULW. Temperature had these an compounds e in the SML organic compounds in the SML,ature with (Table 3). generally Concentrations higher of concentrationsand at particulate particulate lower components nitrogen temper- POC, (PN) TEP, wereCHO PHCHO, also PHAA and inversely DHAA related to weredi wind inversely speed, related whereas to DH- study. temperature In but contrast not to towind speed, TEP, wind neither nor speed. to abundance Clear seawater nor temperature. Instead total abundance area of CSP of in CSP the were SML was related to 5 5 25 20 10 15 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | δ and 0.95, 1.12, δ − = 2 = r 1 − , of the size 0.20). How- δ = 1.51, p , suggesting that − 1 − = 39, 1 − mL = 5 n CSP at 0.6 ms 10 0.008 the fractal dimension 7). δ × 0.001). A loss of larger CSP ± = 0.19, n − p < = r 37, erences in the accumulation behav- TEP at 0.6 ms and 2.33 0.97, ff 7) (Fig. 8a). In particular, at the high = δ 4 = = n 2 10 n r × 0.61, Peru with generally higher organic matter con- 10594 10593 0.95, 0.010. This value is close to 2.55 proposed by − 1.45, 1.38, revealing an average fractal scaling expo- ff 7 µm was observed in the SML compared to the ± − = = − > 2 r = r 1 − 2.51 = 2.31, TEP vs. wind speed: 2.01. With a D1 value of 2.50 2.63 and − δ 7 µm were rather increased in the SML at low wind speed − − = > 1 − TEP at 9.0 ms 1.12 and δ − , while for CSP, variability of abundance in the 1.25–1.77 µm size class 1 7; CSP vs. wind speed: − δ = mL n 4 erent organic matter components were determined during this study and are TEP at 9.0 ms ff δ 10 0.92, × 7; = No overall relationship was established between the slope of the size distribution The number of TEP in the smallest size class (1.25–1.77 µm) ranged from 96 to For CSP a significant inverse relationship was observed between the slope = 2 4 Discussion It has been suggested thatries the presence of of processes organiccomponents. matter relevant EBUS in to are the characterized SML air–sea by influences highshelf exchange a biological gradients se- productivity of of and organic gases, strong matter across tems dissolved concentration. to and Therefore study EBUS particulate the areto linkages ideal characteristics of model of biological sys- organic productivityenrichment matter and in composition SML the and properties, SML. factors with controlling respect organic matter 4.1 Organic matter characteristics of theStrong SML horizontal gradients in organicfor matter the coastal concentration and of shelf-break the regioncentrations SML o in were observed the SMLter. towards Hence, the increasing area ecosystem of productivity upwellingconcentrations is of one of likely colder, organic factor nutrient-rich responsible components deepmatter for in concentrations wa- higher in the the SML. SML Significant andbasically ULW reflects correlations were the determined of underlying and organic showed seawatercrolayer that organic system. the properties The SML and close biological connectivity developmentmesocosm was between study, also mi- indicating shown that during ecosystem a recent composition changes and impact concentration microlayer (Galgani organic et matter al.,a 2014). more Despite general this characteristic finding that ofior relates the to of SML, di clear di in good accordance with previouswas observations. observed A for generally higher aminoamino SML acids accumulation acids compared in to theocean carbohydrates. SML Significant sites, has and enrichment been higher of observed determined accumulation previously of during for FAA this compared coastalWilliams, to study, as 1985; DHAA appears well and Carlucci to as THAA, et open be as al., a also 1992; consistent Kuznetsova SML and feature Lee, 2001, (Henrichs 2002; and Kuznetsova of TEP and wind velocity ( of CSP was almost identical to that of TEP. was much smaller and ranged betweenproteinaceous 1.46 particles represent theTEP, largest size distribution fraction of of CSP smallvalues followed gel between the particles. power Similar law to relationship of Eq. (2), yielding 1.38 3.4 Size distribution of gel particlesAbundance within of the SML polysaccharidic gelaccording particles, to the i.e. power TEP, decreased law function with given increasing in size Eq. (1) (Fig. 7). TheMari and slope, Burd (1998) for seawater TEP. ever, TEP size distributioncompared was to much the steeper one at with the lowest wind station velocity with ( highest wind speed spectrum varied between n nent of TEP in the SML of D1 wind speed a loss of larger TEP, i.e. ULW and relative to the low wind speed station. compared to the ULW and to the high wind speed stations ( was also observed by(Fig. direct 8b). comparison But between here, CSP low and highr wind speed stations wind speed ( 5 5 10 15 20 25 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 > ciencies ffi erences in erent pools ff ff erent for open ff erent, e.g. TEP ff erences were observed for ff 7 µm) from the SML relative to the ULW and 10596 10595 > and above. It has been suggested that TEP aggre- 1 − 5 ms ∼ erent locations (Wallace and Duce, 1978; Zhou et al., 1998). Bubble scaveng- ff erent coastal Baltic Sea sites, Stolle et al. (2010) determined a lowered bacterial ff In contrast to TEP,no impact of wind speed was determined for CSP accumulation, or In addition to ULW properties, wind speed was determined as a factor controlling gation rates in theby shear SML or are bubble higher bursting. TEP than have in been shown the to ULW, control due coagulation to e enhance collision rates for CSP enrichment in thethe SML. distribution Moreover, of clear TEP spatial andticles di CSP that in form the SML. fromspatial Although dissolved both and organic TEP temporal and precursors occurrence CSP released are in by gel marine microorganisms, par- systems their can be quite di for TEP in theTEP SML at also wind at speed higher of wind speed, we found the SMLof to solid be particles, depleted such2000; of as Chow et diatoms al., andwith 2015). coccolithophores solid At particles, (Logan higher eventually et containing windof al., mineral speed, aggregates ballast, 1995; that increased may Engel, become aggregation thusplain negatively favor rates the buoyant the of and formation observed TEP sink loss outto of of the larger SML the TEP at SML. ( low Thisinverse wind relationship may speed. between Enhanced ex- POC aggregation rates and could wind then speed, also observed explain during the this study. accumulate towards the end ofmaximum phytoplankton phytoplankton abundance blooms (Cisternas- Novoa while et CSPMoreover, al., the 2015; rather Engel depth co-occur et distribution with al., 2015). ocean of sites TEP (Cisternas-Novoa and et CSPthe al., was occurrence 2015). of shown These TEP to and spatial be CSP and in di temporal the water di column may explain the spatial separation ing of DOM in theof upper TEP water at column the may SML, thus becauseet be al., more responsible 2011; TEP for Gao precursors high et are concentrations al., liftedcapillary 2012). up waves In the may addition, increase water-column compression (Wurl the and rateaggregation dilatation of of (Carlson, the polymer 1993). SML collision, due subsequently During to related facilitating M91, gel to TEP wind enrichment speed, inet supporting al., the 2009, SML earlier 2011). was observations However, in inversely of contrast to Wurl earlier and observations colleagues showing EF (Wurl values from di et al., 2004; Reinthalerhave et, not al. been 2008). identified Asthe as for past physical this (Kuznetsova factors et study, responsible wind al.,and for 2004). velocity taken-up amino FAA and by acid and temperature heterotrophic enrichment DHAAtimes microorganisms in are of (Keil labile these and to components semilabileto Kirchman, days in substrates 1992). (Fuhrman the Turn-over and water Ferguson,FAA 1986; column and Benner, DHAA are 2002). in usually The theFor observed in di SML accumulation the may of therefore range be of related minutes to a reduced activity of bacteria. gation of precursors or duecharides to when coalescence entrained of pre-cursor air molecules,sorption bubbles primarily of burst DOM polysac- at onto bubble the surfacesdetermined sear and TEP during surface formation (Wurl experimental by bubble flotation et bursting and al., have been bubbling 2011). studies Ad- using surface seawater accumulation of particulate material, inparticles particular that TEP, in have the SML. beenhigh TEP hypothesized water are to content marine (Engel be gel andwere neutrally Schartau, moreover or suggested 1999; to positively Azetsu-Scott form buoyant and within thanks Passow, the 2004). to SML, TEP either by wind-shear induced aggre- biomass production in the SML,the despite bacterial ULW. During cell M91 numbers bacteria being weresupporting similar mostly to the those depleted in idea in the ofstudies SML showed the compared that to SML some the being bacteria ULW as may an be in “extreme adapted the to environment” ULW UVby for (Carlucci radiation bacteria. bacterioneuston in et the Earlier under al., SML UV-B asmay 1985; stress well give Agogue may an et be explanation al.,during for reduced 2005). M91. the (Santos However, Amino higher no et acid concentrations significantradiation al., consumption correlation of or 2012), between FAA between bacterial which and UV abundance radiation DHAAwere and and observed in amino UV during the acid this SML concentrations study,radiation in suggesting may the that be di history responsible for rather controlling thanthe bacteria instantaneous SML. and UV organic matter components in 5 5 10 20 15 25 25 10 15 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 0.3 % 0.4 % ) does 2 ± ± ected by ff erent behaviors: ff , suggesting that an 1 − usion rates at the interface 5 ms ff > , encompassing the full range 1 0.3 % (tyrosine) and 1.9 0.2 % (tyrosine) and 2.9 − ± 30 % of the atmospheric concen- ± ∼ O in oceanic regions like OMZs a 2 10598 10597 O, it has recently been shown that it can interact usivity across the SML has been proposed being 2 ff di 4 e et al., 2013). About ff O), one of the strongest greenhouse gases and responsible 2 ) shows a discontinuous concentration while carbon dioxide (CO 4 O production, oxygen minimum zones (OMZs) contribute about 25–75 % erences in relation to wind speed suggest that additional factors control the 2 ff ecting the exchange of gases and heat at the air–sea interface (Davies, 1966; ff ect of these “insoluble” components on gas exchange is, if any, operating only at low Across the water–air interface, gases of climatic relevance exhibit di More independent of wind speed was the accumulation of dissolved organic compo- ff methane (CH mediated by SML bacteria, asthis possible greenhouse sink gas (Upstill-Goddard (Cunli et al., 2003) or source of not (Upstill-Goddard, 2006). CH a changing climate. In the case of N of wind speed determinedtant during as M91. observed Thus, during this accumulationas study of well. may natural have had organic an surfac- influence on gas exchanges rates tration of nitrous oxide (N for ozone depletion, isoceanic supported N by oceanic sources (Solomon et al., 2007). Of total with biological processes specificallyamino by acids binding like to tyrosine aromatic andin groups phenilanine the present SML (Cao in of et our certain al., studywith 2014). represented averages a Tyrosine in and small the molar phenilanine dissolved percentage fraction of total (DHAA) amino of acids 1.5 pool, (Bange et al., 2001). Inineralization EBUS, high associated primary with production(Gutknecht and large-scale induced et circulation high al., aerobic maintain rem- 2013;have the been Paulmier presence expanding and and of intensifying Ruiz-Pino,tilation due OMZs 2009), to (Keeling enhanced which, et stratification in and al.,derstand reduced the how ven- 2010; organic last Stramma matter decades, accumulation etof in al., trace- the 2008). and SML might Our greenhouse mediate study gases the transfer was like rate intended N to un- (phenilanine), and in the total(phenilanine), fraction but (THAA) were of present. 2.2 Ascumulation we during found our evidence cruise, of for overall those amino amino acids acids SML in ac- particular the median EF both in tificial surfactants can suppress gas transferof velocity k666 by (i.e. up kw to normalized 55 topending % a at on Schmidt sea. wind number Suppression speed, of 666) but during was their detected field up study to was 11 de- ms of both types ofserved marine di gels in the SML observed during this study. However, the ob- 4.2.1 Air–sea gas exchange Although the SML andlieved a surface active substances (surfactants) within are widely be- enrichment of TEP andto CSP aggregation in than the TEP SML.be It (Prieto less has et involved been al., in shown 2002;speed. aggregation that Engel Yet, CSP formation an et are and inverse al., less sinkingthe relationship 2015). prone SML out between Similarly, and CSP of the wind may the slopeat speed of SML low was the at wind observed CSP higher during speed.formation size wind M91, This that distribution showing becomes suggests in disrupted larger that when CSP CSP wind in speed as the increases. well SML 4.2 as TEP may Implications be of organic involved matter in accumulation slick in EBUS sea-surface alter the gas transferof the velocity SML in with water respect (kw). to Our TEP data and showed POC at a wind depletion speeds 1988; Frew eta al., dampening 1990). of The small, reduction capillary of waves. Salter kw et is al. thereby (2011) believed recently to showed be that ar- related to Frew, 1997; Salter et al.,have 2011), little particularly quantitative knowledge at on lower how wind natural organic speeds components (Liss, at 1983), the we immediate still nents in the SMLand during amino M91. acids, Dissolved have organicvelocity demonstrated matter, in like water dissolved properties carbohydrates (kw) and at reduced low gas transfer wind speed in laboratory experiments (Goldman et al., between air and sea. e wind speed. Due to theirvolume ratio fractal and scaling, may gel act particles as have a a cover, reducing relatively molecular large di surface to 5 5 10 25 15 20 10 15 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Peru. ff while the SML 1 − ects of climate change during cruise leg M91 for ff 1, suggesting a possible in- > Meteor are not directly related to the organic a 1.7 (DHAA). Amino acids enrichment in O in the coastal upwelling region o = 2 e et al., 2013; Henrichs and Williams, 1985), 10600 10599 ff Peru the wind-driven export of polysaccharidic compo- ff 1.3 (THAA) and EF = We thank the captain and crew of R/V of the size distribution spectra for both TEP and CSP, the less negative δ ects the processes at the air–water interface relevant for climate. ff , the larger is the fraction of marine gels comprising bigger particles, revealing that Peru. erently a δ In the upwelling region o This characteristic might be valid for many oceanic regions. EBUS and OMZs are Overall, our results showed that accumulation of organic substances occurs in EBUS ff ff concentration of particulate proteinaceousby compounds the (CSP) slope did not. As determined is CSP were generally larger thanlation TEP. In patterns the may suggest light a of compositionaldi these organic observations, matter these partitioning accumu- in the SML that nents to the atmosphere mightfrom represent the a SML loss-pathway that ofInstead, would these amino-acids organic then and compounds contribute proteinaceous tosurface compounds a exerting are their larger influence probably extent on more to air–sea stable the gas at organic exchange by the SSA capillaryspecial mass. wave systems damping. with high levelficult of productivity to and attribute degradation specific rates, organicchange so and sources it SSA might to production. be the However, dif- theand processes accumulation controlling the of air–sea distinct organic gas matter behavioran ex- in of important the certain issue SML, for compounds allthat exchange at processes in the between the water–air the scenario ocean interface of and anthropogenic is the climate certainly atmosphere changeAcknowledgements. needs to be deeplylogistic investigated. support during sampling,as especially H. help Bange related asJ. to chief Roa the for scientist rubber helping and boatrespectively. with operation, all Further SML as the technical sampling well scientific help onfor crew. board amino was A and acids provided great for and by acknowledgement TOC/TN microscopy R. goes and analysis, Flerus, carbohydrates to as analysis, S. well as Manandhar T. and Klüver N. for flow-cytometry Bijma counts. This proteinaceous material quite independently ofdrates the wind that speed, had as similar opposedinstead, to concentrations carbohy- like in TEP the and SMLother CSP, and processes did determining ULW. not Particulates their preferentially production compounds a and accumulate close aggregation inverse in relationship dynamics. to the TEP wind showed SML, speed, being inferring depleted to above 5 ms the total (THAA) and in the dissolved (DHAA) fraction was teraction of SML organic components with N carbon content of SSAoceanic (Quinn surface et layer al., and 2014), therefore still are organic also SSA subject largely to derive the from e the The structure of sea-spraysurface is aerosols a (SSA) function originating ofmay biological, comprise by chemical a bubble and vast bursting array physicalexopolymer of at properties organic gels of the surface-active (Leck the compounds, sea SML, and microorganisms,dences and which Bigg, showing 2005; that Quinn high levels and of Bates, chlorophyll 2011). Despite recent evi- In details, median EF forwe tyrosine found was a 1.5 median (both EF the THAA and SML DHAA) has and been for previously2004; phenilanine reported van (Kuznetsova Pinxteren and et Lee, 2002; al., Kuznetsova 2012; et Cunli al., and is related toticularly the important increased role productivity. Hence, forhigh the exchange organic organic of matter SML climate production mayo and relevant play resulting gases a anoxia that par- in are upwelling associated systems to like the4.2.2 one Organic aerosol production on marine systems (Andreaeridic nanogels and (Russell Crutzen, et 1997). al.,acids Polysaccharides 2010; and Orellana and proteinaceous et compounds polysaccha- al.,SSA (Kuznetsova 2011) et particles. as al., During well our 2005) as cruise arelate particulate we present compounds, amino found in the a organic first distinct beingEF behavior of rather for dissolved enriched DOC) and in but particu- the mainly SML composed (as of also amino shown acids by contributing median to an accumulation of and might beteristics due of to the high molecules,speeds, surface-active probably thus creating properties representing a an because important rather of barrier stable for layer zwitterionic air–sea even gas charac- at exchange. higher wind 5 5 10 15 20 25 20 15 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 ff southern california, J. 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C., Almeida, A., Cor- 5 5 10 15 20 10 25 30 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 2 − : number n UV Radiation (Wm n ) 2 − Peru in 2012 (M91). ff Global Radiation (Wm ) 1 − Wind speed (ms 1176 7741955 205745 208 30 3956 53 29 8538 36 5.4 300 35 770 359 423 2017 30 151 104 49 531 37 1084 130016 4112.5 4.93.3 5156 4.0 34 118 8.7 3.7 7.71024 72 28 25 728 bd 19 39 137 16 39 3051 311 39 39 39 1111 550 507 2668 39 94127 1333 3319 71 25100 82 15 122 106 199 2.3 39 1.8 96 6.9 39 63 408 39 39 39 1 1 − − 1 1 10610 10609 1 1 1 1 1 1 1 1 1 1 1 1 1 C) − − − − − − − − − − − − − − − ◦ mL mL L L temperature ( L L 3 3 6 6 2 2 10 10 10 10 × × × × Unit Avg. SD min max Salinity Air C) ◦ Temperature ( bacteria phytoplankton PHAA nmolL DHAA nmolL TNTDNPNCSP number CSP areaFAA µmolL µmolL µmolL mm nmolL PCCHO nmolL DOC µmolL TOCPOCTEP number TEP areaDCCHO µmolL µmolL mm nmolL Hydrographic conditions encountered during SML sampling o Concentration of various organic components in the SML during M91, given as average averageSD 19.25MinMax 1.70 34.87 15.91 21.90 19.67 0.50 32.02 35.32 17.30 0.89 5.66 21.50 570 0.60 2.14 9.00 37 935 10 366 1103 71.10 0.812 23 384 of observations. Table 2. (avg.) and standard deviation (SD), as well as minimum (min) and maximum (max); Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C), and wind ◦ , T

3

1

ap ap m m 0.01 are marked bold. 0.37 0.53 0.35 0.48 0.69 0.69 0.29 0.38 0.05 0.43 0.31 − − − − − − − − − − − p < 0.47 0.64 0.040.53 0.06 0.67 0.58 0.65 0.44 0.59 0.18 0.55 0.040.36 0.15 0.34 0.19 TU − − − − − − − − − − − − − − 10612 10611 0.56 0.75 0.79 0.68 0.51 0.58 0.94 0.77 0.59 0.53 0.68

2

ap m PHAA SMLDOC TOC xULW CSP area DHAA 0.30 POC TEP number TEP area DCCHO PCCHO TDNPN CSP number FAA 0.24 0.34 cients between concentrations of various organic components in the ffi ). Correlations yielding significance level of Peru in 2012. 1 ff − Maps of stations where sampling for sea surface microlayer (SML) and underlying , ms Correlation coe U Figure 1. seawater (ULW) was conductedwelling during area the o SOPRAN Meteor 91 cruise along the coastal up- speed ( Table 3. SML and their concentration in the underlying seawater (xULW), temperature ( Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (b) ) 1 − and wind speed (ms (a) C) ◦ 10614 10613 39. Data in dotted rectangles were selected for analysis = n 0.58, = r 0.001, Surface water (1 m depth) temperature ( ects at similar temperatures, see Fig. 7. ff p < Direct relationship between surface water temperature and wind speed during M91 Figure 3. SML sampling, of wind speed e Figure 2. (a, b) during M91. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 1 − Peru during ff ) in the SML o 1 − ). 1 − ), dissolved hydrolysable amino acids 1 − ), dissolved organic carbon (DOC, µmolL 1 − ) and CSP (L 1 − 10616 10615 ) and abundance of TEP (L 1 − Phyto- and bacterioneuston abundance (number mL Surface distribution patterns of organic matter concentrations in the SML during M91 (DHAA, nmolL dissolved hydrolysable carbohydrates (DHCHO, nmolL Figure 5. showing particulate organic carbon (POC, µmolL Figure 4. M91: NCPPL: “Non-cyanobacterial-type” picophytoplankton, CPPL:phytoplankton, “cyanobacterial-type” HPL: pico- heterotrophic picoplankton. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Filled (b) ) on the total area concentration of TEP 1 − 10618 10617 and relationship between TEP enrichment factors (EF) and wind (a) Influence of wind speed (ms 1

10 0,1 ) for stations of similar as indicate in Fig. 3.

100 1 EF − Box and whisker plot of enrichment factors (EF) calculated for various particulate and ) in the SML 1 − L 2 dots indicated data from stations of similar sea surface temperature. speed (ms (mm Figure 7. (a, b) Figure 6. dissolved components during M91. Eachof box the encloses variable 50 displayed % as oflimit a the line. of data The data. bottom with The of thepercentiles lines the median within box extending value the marks from data the the set 25 and %, top and the and the filled bottom top circles of the indicate 75 each the % data box outside mark of the this 10 range. and 90 % Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − observed during the M91 (b) ) was fitted to the particles in the size p and CSP d (a) (circles) and highest wind speed of 9.0 ms 1 − )) vs. log( 10619 p d d( N/ Size frequency distribution of TEP range of 1.05–14.14 µm ESD. cruise for samples collected fromthe the stations SML with (open lowest symbols) wind and speed in of the 0.6 ms ULW (filled symbols) at Figure 8. (a, b) (triangles). Linear regression of log(d