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1 (This is smple cover imge for this issue. The ctul cover is not yet vilble t this time.) This rticle ppered in journl published by Elsevier. The ttched copy is furnished to the uthor for internl non-commercil reserch nd eduction use, including for instruction t the uthors institution nd shring with collegues. Other uses, including reproduction nd distribution, or selling or licensing copies, or posting to personl, institutionl or third prty websites re prohibited. In most cses uthors re permitted to post their version of the rticle (e.g. in Word or Tex form) to their personl website or institutionl repository. Authors requiring further informtion regrding Elsevier s rchiving nd mnuscript policies re encourged to visit:

2 Journl of Se Reserch 72 (212) Contents lists vilble t SciVerse ScienceDirect Journl of Se Reserch journl homepge: Effects of simulted nturl nd mssive resuspension on benthic oxygen, nutrient nd dissolved inorgnic crbon fluxes in Loch Crern, Scotlnd Elin Almroth-Rosell, Anders Tengberg, Sr Andersson 1, Ann Apler 2, Per O.J. Hll Deprtment of Chemistry nd Moleculr Biology, Mrine Chemistry, University of Gothenburg, SE Gothenburg, Sweden rticle info bstrct Article history: Received 12 October 211 Received in revised form 28 Mrch 212 Accepted 11 April 212 Avilble online 18 My 212 Keywords: Resuspension Oxygen Nutrients Dissolved Inorgnic Crbon Loch Crern Scotlnd The effect of repeted nturl resuspension on benthic oxygen consumption nd the effect of nturl nd mssive resuspension on oxygen consumption nd fluxes of phosphte, silicte, mmonium nd dissolved inorgnic crbon (DIC) were studied t two sttions (S1 nd S2) in Scottish se loch. Sttion S11 hd orgniclly enriched sediment nd sttion S1 hd lower orgnic content in the sediment. The fluxes were mesured in situ using the Göteborg benthic lnder. Nturl resuspension, simulting resuspension events due to strong wind, wves or currents, nd mssive resuspension, simulting resuspension due to e.g. trwling or dredging, were creted inside the incubtion chmbers by regulting the stirring of the incubted overlying wter or by retrcting nd shking the incubted sediment. Nturl resuspension showed cler effects on the oxygen consumption t sttion S11, where it incresed with n verge of 12.8 (stndrd error (s.e.).17) nd 7.7 (s.e..12) mmol m 2 d 1 during the first nd second incubtions, respectively. At sttion S1 there ws no cler effect of nturl resuspension on the oxygen consumption. Mssive resuspension incresed the oxygen consumption on S1 with n verge of 68 (stndrd devition (sd) 366) mmol m 2 d 1 nd on S11 with n verge of 2396 (sd 2265) mmol m 2 d 1. The fluxes of mmonium, phosphte nd silicte were ffected by the mssive resuspension in 5, 14 nd 33% of the chmbers, respectively, on sttion S11. However, in the mjority of the cses there were no effects on the nutrient nd DIC fluxes of mssive resuspension. The bsolute concentrtions of DIC, mmonium nd silicte did however instntly increse with n verge of 419 (sd 297), 48 (sd 27) nd 6.9 (sd 3.7) μm, respectively, t S11 upon mssive resuspension. The concentrtions of phosphte decresed instntly with n verge of.2 (sd.1) μm. On sttion S1 there were effects only on the mmonium nd silicte concentrtions, which incresed with.8 (sd.3) nd 1.13 (sd.36) μm, respectively. The lrge increse in oxygen consumption due to mssive resuspension indictes tht ctivities like e.g. trwling nd dredging tht tke plce in res where wter exchnge occurs infrequently my led to oxygen depletion in bottom wter, which in turn might ffect the ecologicl blnce. Silicte, mmonium nd DIC cn be relesed due to mssive resuspension nd contribute to incresed lgl blooms in surfce wters. 212 Elsevier B.V. All rights reserved. 1. Introduction The world's ocens ct s nturl depository for dissolved nd prticulte substnces trnsported from the continents (Schultz nd Zbel, 2). A mjority of the mteril is deposited in costl res, where it is exposed to different physicl, chemicl nd biologicl processes. By combintion of degrdtion, re-cycling nd removl the sediment cts s regultor of the concentrtions of mny compounds in sewter, Corresponding uthor. Tel.: ; fx: E-mil ddresses: ellm@chem.gu.se (E. Almroth-Rosell), nderste@chem.gu.se (A. Tengberg), sr.ndersson@polr.se (S. Andersson), nn.pler@sgu.se (A. Apler), perhll@chem.gu.se (P.OJ. Hll). 1 Present ddress: Swedish Polr Reserch Secretrit, Box 53, SE-14 5 Stockholm, Sweden. 2 Present ddress: Mrine Geology, Geologicl Survey of Sweden Box 67, SE Uppsl, Sweden. nd hs n importnt influence on the chemicl composition of the ocen (Kennett, 1982). When the criticl sher stress on the se floor is exceeded sediment prticles re lifted up into the overlying wter nd resuspension is induced. Resuspension is common physicl process tht occurs everywhere in the mrine environment, in costl res s well s in the deep se (Gross et l., 1988; Thomsen et l., 1994; Vngriesheim nd Khripounoff, 199). The sher stress cn be result of bottom currents induced from wind wves or from tides, from brotropic (differences in se levels), nd broclinic (differences in density) forcing mechnisms. Resuspension cn lso be induced by biologicl ctivity (Grf nd Rosenberg, 1997) or by nthropogenic perturbtions such s trwling nd dredging. Theimpctofresuspensiononthedegrdtionrteoforgnic mteril in the sediment nd on the fluxes of different solutes between sediment nd overlying wter hs been studied by number /$ see front mtter 212 Elsevier B.V. All rights reserved. doi:1.116/j.seres

3 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) of reserch tems (Almroth, 28; Almroth et l., 29; Blckburn, 1997; Spgnoli nd Bergmini, 1997; Ståhlberg et l., 26; Tengberg et l., 23; Winright, 1987, 199; Winright nd Hopkinson, 1997). Some results indicted tht the degrdtion rte of orgnic mteril ws ffected by resuspension while others found no effects. Also the conclusions regrding the impct of resuspension on the fluxes of solutes vried between the different studies. Most of these studies were performed in lbortories or with models. Only Almroth et l. (29) nd Tengberg et l. (23) performed their studies in-situ, using the sme type of utonomous benthic incubtion lnder. They found no significnt effects of the creted nturl resuspension on benthic nutrient fluxes or on the degrdtion rte of orgnic mteril. The oxygen consumption ws, however, significntly incresed s the sediment ws resuspended (Almroth, 28; Almroth et l., 29). The im of this study ws to further understnd the effects of different strengths of resuspension on benthic fluxes of nutrients, oxygen nd dissolved inorgnic crbon (DIC). Nturl resuspension, induced by e.g. benthic fun nd tidl circultion, nd mssive resuspension, mimicking e.g. dredging, trwling nd lrge nturl events such s turbidity currents nd lndslides on costl sediments, were creted during in situ chmber incubtions using benthic lnder. This study ws performed t two sites in tidlly influenced se loch system locted on the west cost of Scotlnd. One sttion ws orgniclly enriched by former fish frm nd one sttion ws situted further wy from influence of humn ctivities serving s reference sttion. 2. Mteril nd methods 2.1. Study site A two-week field study ws crried out in Loch Crern, se loch (fjord) on the Scottish west cost, north of Obn (Fig. 1) in My 26. Loch Crern is 12.8 km long nd is chrcterized by four sills tht divide the loch into four bsins. The first bsin hs 7 m deep nd 32 m wide sill in the west nd hs mximum depth of 27 m. It is exposed to strong tidl currents; hence the sediment in this bsin is corse (Blck et l., 2). The second bsin hs mximum depth of 49 m. This bsin is chrcterized by corse sediments from the second sill to the deepest prt of the bsin nd therefter by soft, muddy sediments. The sill between the second nd third bsins is 15 m deep. Bsin 3 is reltively shllow, 27 m t the deepest prt, nd the sediment consists of soft mud. Bsins 2 nd 3 form the min body of the loch nd re referred to s the min bsin. The sill tht delimits bsin 3 from bsin 4 is only 3 m deep, nd 1 m wide t low wter. Bsin 4 hs mximum depth of 37 m. The fresh wter supply to the loch is bout m 3 yr 1. There re no severe wve ctions in the sheltered loch, but winds nd high tidl current contribute to high mixing of the fresh nd sline wter. The flushing time for the loch is pproximtely 3 dys, when round 6% of the wter volume is exchnged with costl wters. The short flushing time nd the high mixing prevent the bottom wter from oxygen depletion, s well s serious ccumultion or retention of dissolved contminnts (Blck et l., 2). 5 24'W 5 21'W 5 18'W 5 15'W 56 33'N Bsin 1 Bsin 'N 56 32'N Bsin 'N 56 31'N Bsin 2 S1 S 'N 56 54'N Loch Eli 56 48'N Loch Shiel 56 42'N 56 36'N Loch Sunrt Loch Linnhe Loch Crern 56 3'N Loch Etive Obn 56 24'N 5 45'W 5 3'W 5 15'W 5 'W Fig. 1. A mp of the study site Loch Crern on the west cost of Scotlnd. Sttions S1 nd S11 were studied with chmber incubtions using n utonomous benthic lnder. Between the two sttions recording doppler current meter (RDCP) ws deployed through the whole field work, in order to mesure bckground dt of oxygen, turbidity, currents nd temperture.

4 4 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) The effect of resuspension on benthic solute fluxes ws studied t two sttions, S1 nd S11 locted in the third bsin (Fig. 1). Sttion S11 ws locted t pproximtely 26 m depth. Due to fish frm tht ws ctive t this position between pproximtely 197 nd the end of the 199s (Blck et l., 2), the sediment ws considered orgniclly enriched with n orgnic crbon concentrtion of bout 7% of sediment dry weight (Lois Clder, pers. com.). Sttion S1, locted t pproximtely 29 m depth, served s control sttion nd ws considered to be less ffected by humn ctivities in generl nd by orgnic mtter from fish frming ctivities in prticulr. At sttion S1, the orgnic crbon ws bout 1.5% of the dry weight. These concentrtions of orgnic crbon were mesured in Mrch nd October In-situ chmber incubtions with the Göteborg benthic lnder The Göteborg lnder is normlly utonomous for opertions down to 6 m nd consists of n outer nd n inner frme composed of non-corrosive titnium (Ståhl et l., 24). Autonomous recovery ws not needed during this study nd therefore only the inner frme ws used, in the sme wy s ws described by Tengberg et l. (23). The inner frme ws equipped with four incubtion chmber modules, which ech crried ten syringes for wter injection nd smpling t pre-determined time intervls. Stirring of the overlying wter ws mde by horizontl Mississippi type pddle wheel plced centrlly in the chmbers (Tengberg et l., 24), which cn be run t different speeds to crete different sher stresses nd different levels of resuspension. The lnder frme ws equipped with flots to regulte its weight nd mnully lowered to the bottom where the four chmbers were gently inserted into the sediment. The incubtion strted when the chmber lids were closed nd ended when the chmber lids utomticlly were opened nd the wter in the chmbers ws exchnged. A known volume (bout 6 ml) of 3 mm bromide solution ws injected into ech chmber t the strt of the incubtions. After 3 min the first smple ws drwn with the first syringe. Clculting the dilution fctor of the bromide gve n estimtion of the chmber volume which ws used in the flux clcultions (Ro nd Jhnke, 24). During the incubtions the sediment ws exposed to different levels or strengths of resuspension, which ws creted by ltering the stirring speed of the pddle wheel inside the chmber or by collecting the sediment. The resuspension generted by the chnge in stirring speed eroded the sediment from the top nd ws intended to mimic nturl resuspension events due to high bottom currents nd/or wves. A mssive resuspension event, to mimic e.g. trwling or dredging, ws creted by bruptly cpturing the sediment by retrcting the chmbers nd closing the bottom scoops. All deployments, recoveries nd sediment smplings were performed using the reserch vessels R/V Seol Mr nd R/V Clnus. Deployments were crried out during 24 or 48 h. Two deployments took plce on sttion S1 nd three deployments on sttion S11 (Fig. 1, Tble 1). During the first prt of the incubtions the stirring speed ws low nd no resuspension ws creted. During ll deployments chmbers 1 nd 2 were used s reference chmbers (without resuspension) while nturl resuspension ws creted in chmbers 3 nd 4. During deployments 1 nd 3 the stirring speed ws incresed from low to high level in chmbers 3 nd 4 in the second hlf of the incubtion, to crete nturl resuspension. During deployments 2, 4 nd 5 nturl resuspension ws creted in chmbers 3 nd 4 in two steps. After bout 1/3 of the incubtion time the stirring speed ws incresed from low to medium level, nd fter the subsequent bout 1/3 of the incubtion time the stirring speed ws incresed further to high level. After the whole incubtion the stirring speed ws set to low level gin nd the chmber lids were utomticlly opened for bout 2 h to ventilte the chmbers, letting the chmber wter return to mbient conditions. Then the lids were closed gin nd second incubtion, in the sme wy nd on exctly the sme spot s the first, ws performed. During deployment 2 third incubtion ws performed in the sme wy s incubtions 1 nd 2, with the exception tht t the end of the incubtion the sediment in the chmbers ws cptured, nd mssive resuspension ws creted. During deployments 4 nd 5 the third incubtion strted with low stirring speed in ll four chmbers nd then the sediment ws collected, i.e. mssive resuspension ws creted (Tble 1). Oxygen concentrtions nd turbidity were mesured in ech chmber t 1 minute intervls during the entire durtion of the deployments using oxygen optodes (Tengberg et l., 26) nd turbidity sensors (Almroth et l., 29), respectively. Smples for DIC nd nutrients were collected with syringes t pre-progrmmed discrete times from one incubtion of ech deployment. During deployments 1 nd 3, five nd four smples were collected before nd fter, respectively the stirring speed ws incresed. During deployment 2 three smples were collected during the sme time before nd fter mssive resuspension ws creted. During deployments 4 nd 5, five Tble 1 Field summry. Nme, period nd totl length of deployment, wter depths nd positions of the sttions cn be found in the three first columns. In totl five deployments were performed (deployment number) nd t the most were three incubtions (incubtion number) performed fter ech other during one deployment. Successfully mesured fluxes of oxygen (O 2 ), dissolved inorgnic crbon (DIC) nd nutrients (Nu) were performed in different chmbers (Chmber number) during the different incubtions. Sttion nme Deploy. period Position depth Deployment number Incubtion number Control chmber number Chmber number with nturl resuspension Chmber number with mssive resuspension O 2 DIC, Nu O 2 DIC, Nu O 2 DIC, Nu S1 My 2 3, N 1 1 3, 4 3, 4 24 h W Depth 28.7 m S1 My 4 6, N 2 1 1, 2 3, 4 48 h W 2 1, 2 3, 4 Depth 29.2 m 3 1, 2 3, 4 1, 2, 3 1,2,3 S11 My 7 8, N 3 1 1, 2 1, h W Depth 26.7 m S11 My 9 11, N 4 1 1, 2 3, 4 48 h W 2 1, 2 3, 4 Depth 25.4 m 3 1, 2, 3 1, 2, 3 S11 My 11 13, N 5 1 1, 2 3, 4 42 h W 2 1, 2 3, 4 Depth 25.9 m 3 1, 2, 3, 4 1, 2, 3, 4 Totl numbers of Only concentrtions were mesured before nd fter mssive resuspension, no flux mesurements.

5 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) nd four smples were collected before nd fter, respectively, the mjor resuspension ws creted. After lnder recovery, wter smples were filtered through prerinsed.45 μm pore size cellulose cette filters into different vils. Smples for dissolved inorgnic crbon (DIC) were kept in top filled, gs impermeble glss vils, preserved with zinc chloride nd then brought bck to Gothenburg for nlysis. Incubted sediments were not nlyzed, but investigted for lrger nimls, which were trpped in the chmbers nd possibly could hve influenced the incubtions Study site bckground informtion A profiling current meter (RDCP 6) from Ander Dt Instruments ( ws mounted on seprte frme, which ws deployed during the whole field study on loction between the two sttions S1 nd S11 (Fig. 1). The instrument hd sensors to record turbidity nd optodes to mesure oxygen concentrtions in the bottom wter. It lso mesured pressure which gve both wter level nd wve informtion, slinity, nd temperture. The recordings from this instrument were used s bckground informtion of the bottom wter conditions, i.e. the occurrence of nturl resuspension nd oxygen concentrtions Determintion of the effects of resuspension on solute fluxes To determine if resuspension ws successfully creted in the different chmbers the following criteri were used: 1) the mesured turbidity hd to increse by t lest 1% fter the increse in stirring; nd 2) the verge turbidity hd to be t lest 5 (±5%) norml turbidity units (NTU). If these criteri were fulfilled the chmber ws considered to be successful resuspension chmber nd the results were retined. The fluxes (mmol m 2 d 1 ) were clculted using formul (1), F ¼ k V=A where k is the slope of the liner regression line (chnge in concentrtion over time), V is the chmber volume nd A is the chmber re. The volume in this study vried in the rnge of l. In the control chmbers nd in the chmbers in which nturl resuspension ws creted ll dt points, before nd fter the increse in stirring speed, respectively, were used to clculte the slope. When mssive resuspension ws creted ll the dt points for nutrients nd DIC were used, but for oxygen the dt points were used s long s the slope ws liner. The uncertinty of ech flux, lso clled the stndrd error (s.e.) ws clculted using formul (2), s:e: ¼ F s:e: k =k where k is the slope of the liner regression nd s.e. k is the stndrd error of the slope. If the uncertinty of the flux ws lrger thn the flux, it ws rejected. However, to prevent low fluxes (often with greter uncertinty thn high fluxes) to be rejected to lrger extent thn high fluxes, nd in this wy introduce bis, the low fluxes with n uncertinty greter thn or equl to the flux were tested by specil method. First the lowest ccepted flux (Fcc) from the whole dt set ws identified. Then the low flux hd to be lower thn the Fcc nd the uncertinty of the low flux hd to be lower thn five times the flux. If this ws the cse, then the low flux ws set to zero, otherwise it ws rejected (Almroth et l., 29). The slopes of the regression lines before nd fter the time for the incresed stirring speed (ISS) were tested (using t-test) nd the flux fter ISS ws retined s n ffected flux if the slopes were significntly different (p.5). The fluxes in the resuspension chmbers, where significnt chnge ws found, were compred to the fluxes in the control chmbers where no resuspension ws induced. If ð1þ ð2þ chnges of the fluxes in the resuspension chmbers behved differently compred to chnges of the fluxes in the control chmbers, we considered effects of resuspension to hve occurred (Almroth et l., 29). The clculted initil fluxes were set to be the sme s the flux before the time of ISS in both control chmbers nd resuspension chmbers. The quntifiction of the effect of resuspension on the fluxes ws obtined by clculting the verge chnge of the fluxes in the resuspension chmbers t ech deployment. Any chnge of the fluxes cused by other fctors thn resuspension in the control chmbers during the sme deployment ws clculted in the sme wy nd t the sme time s in the resuspension chmbers. The totl effect of resuspension ws then compensted for these non-resuspension effects. Resuspension might lso ffect the concentrtions in the chmbers with strong response, but with short durtion of less thn the time between smples, thus giving the impression of n instnt effect. To investigte this possibility, confidence intervls for the liner regressions before nd fter the time of resuspension were clculted. If the confidence intervls overlpped, no instnt chnges in concentrtions were considered to hve occurred (Almroth et l., 29). During deployment 2 in this study two smples for nutrients nd DIC were withdrwn before s well s fter mssive resuspension ws creted in the chmbers. The dt set before the resuspension ws then compred with the dt set fter resuspension using t-test to find out if the concentrtions were ffected by the mssive resuspension event Anlyticl methods Concentrtions of DIC (lso clled totl crbonte) were determined with n utomted system bsed on non-dispersive infrred detection of CO 2 using Li Cor 6262 detector (Goyet nd Snover, 1993; O'Sullivn nd Millero, 1998). Prior to detection, ll of the dissolved species of the totl crbonte system in the smple ws converted to CO 2 gs by cidifiction with phosphoric cid in stripping tower. The CO 2 ws then stripped from the smple with N 2 -gs nd crried to the detector. Certified reference mteril (CRM, Dickson Lbortories, Scripps Inst. of Ocenogrphy) ws used for clibrtion nd correction for system drift fter pproximtely every fifteen smples. The nlyticl precision ws.2% RSD (reltive stndrd devition; n=15) or better. The nutrients were nlyzed t the Scottish Assocition of Mrine Science using Lcht Quickchem 8 Flow Inject Autonlyser. The reltive stndrd devition for ll nutrients with concentrtions bove 1 μm ws 1%. Below 1 μm nd bove.2 μm it rises to round 1% for NH4 + nd round 5% for NO3 /NO2, PO4 3, nd SiOH 4. Below.2 μm it cn be up to 5% for NH4 + nd 1% for NO3 /NO2,PO4 3, nd SiOH 4. Oxygen concentrtion nd turbidity inside the chmbers were mesured using four oxygen optodes, model 383, nd four turbidity sensors, model 3612A, respectively, from Ander Dt Instruments ( The sme types of sensors were lso mounted on the RDCP-6 mesuring in the bottom wter t 15 minute intervl during the entire period of the field-work. Oxygen optodes were checked ginst replicte wter smples tht were collected t eight occsions nd nlyzed by Winkler titrtion in the lbortory. The five optodes were found to be without drift nd with n bsolute ccurcy of better thn ±4%. Also previous studies hve demonstrted the ccurcy, precision nd long-term stbility of these sensors (Hydes et l., 29; Körtzinger et l., 24; Tengberg et l., 26). The used turbidity sensors were fctory clibrted (ccurcy±2%) in multiple points with stndrd procedures to output mount of prticles in norml turbidity units (NTU). During this field-work no wter smples were collected to convert from NTU to site-specific bsolute concentrtions of prticles in mg/l. We do therefore not hve detiled informtion bout bsolute concentrtions of prticles

6 42 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) in the wter. Erlier studies (Almroth et l., 29; Tengberg et l., 23) using the sme type of sensors did however give n pproximte conversion eqution of: Suspended prticles (mg/l) =1.2 sensor vlue (NTU).3. In this study we used the bckground vlue mesured by the externl turbidity sensor (mounted on the RDCP) to confirm tht the bckground vlue of prticles inside the chmbers before resuspension ws similr to nturl levels outside incubtion chmbers. 3. Results nd discussion 3.1. Hydrogrphicl vritions During the entire field-work no mjor wve motion ws detected t the bottom with the RDCP (deployed t 23 m) in spite of intermittently windy conditions. The loch's sheltered loction nd nrrow strit nturlly protects it from externl forces such s big wves nd strong winds. The tidl wter level vritions reched mximum mplitude of 3 m nd showed tht the mjor wter circultion mechnism ffecting the bottom t which the instruments were deployed in the loch ws tidl. Approximtely 3.5 m bove the bottom the verge horizontl current ws 7.8 (stndrd devition (sd) 4.1) cm/s with mximum vlue of 26.6 cm/s. This ws not enough to crete ny mjor resuspension of bottom sediments, but smller sediment resuspensions were common nd occurred in every tidl cycle. The verge turbidity ws bout 1.4 (sd.4) norml turbidity units (NTU), with mximum vlue of bout 4 NTU. The bottom wter temperture in the loch incresed during the field cmpign from 8.4 C to 9.2 C with n verge of 8.6 (sd.2) C most likely due to the unusully wrm wether. Slinity, s well s temperture, vried with the tide nd rnged between 32.4 nd The oxygen concentrtions in the bottom wter ws lso ffected by the tidl circultion nd vried with between 23 nd 341 μmol l 1,verge 315 (sd 15) μmol l 1. The vritions were most likely cused by wter circultion, which occsionlly brings in bottom wter with lower oxygen concentrtions. Most of the time the bottom wter ws supersturted (verge 17%) in oxygen indicting tht benthic primry production my occur t these depths Nturl nd mssive resuspension The lnder ws deployed five times, providing in totl 4 chmber mesurements of benthic fluxes of oxygen, nutrients nd DIC with or without creted resuspension (Tble 1). During three deployments (2, 4 nd 5) repeted nturl resuspension experiments were performed by ventilting (opening) the chmbers between multiple incubtions. Thus, the effect of resuspension could be mesured severl times on exctly the sme site. In 14 chmbers, during 7 incubtions, the stirring speed ws incresed in two steps, in order to crete resuspension of different strengths. Nturl resuspension, ccording to our criteri, ws creted in 7 of the chmbers t the first step of incresed stirring speed nd in totl in 11 chmbers fter the second step. The stirring speed ws kept t low level throughout the incubtions in 14 chmbers, which were used s control chmbers. During deployments 1 nd 3 there ws no repeted resuspension experiment nd the stirring speeds incresed from low to high in one step in two nd one of the chmbers, respectively. There ws no control chmber during deployment 1, nd during deployment 3 there were two control chmbers. The turbidity in the resuspension chmbers where nturl resuspension ws successfully creted ws on verge 6.5 NTU (sd 3.9) nd 8.9 NTU (sd 4. NTU) fter the first nd second increses in stirring speed, respectively. These turbidity vlues in the chmbers during resuspension events were well bove the nturl turbidity mesured (verge 1.4 NTU nd mximum 4 NTU) outside the chmbers during the whole field study. The verge bckground level of suspended prticles ws 1 2 NTU both inside the control chmbers nd before incresing the stirring speed in the other chmbers. Using the conversion formuls presented in Almroth et l. (29), see Section 2.5, the depth of the sediment tht ws resuspended (D rsed ) in the chmbers rnged from.26 to 2.6 μm (formul3) D rsed ¼ Turb H=ρ sed where Turb is the verge turbidity in NTU reclculted to turbidity in mg/l, H is the height (dm) of the incubted wter in the chmbers nd ρ sed is the wet sediment density of 1.2 kg l 1 (Almroth et l., 29) Mssive resuspension events were creted during three incubtions, in which fluxes were successfully mesured in ten of the chmbers (Tble 1). The turbidity during these resuspension events reched the mximum vlue of the sensors nd were thus well bove 12 mg/l. These resuspension events were creted s the sediments in ech chmber were utomticlly cptured by springctivted mechnism without ny dmpening, nd thus well shken, simulting dredging or trwling The effect of resuspension on benthic solute fluxes Oxygen consumption Nturl resuspension. The initil oxygen consumption t the fish frm sttion (S11) nd the reference sttion (S1) rnged from 22.9 to 68.9 mmol m 2 d 1 nd from 24.8 to 4.9 mmol m 2 d 1, respectively (Fig. 2). Both the highest nd lowest verge oxygen consumptions were found t the fish frm site S11 indicting tht the sptil vribility between repeted deployments within one sttion ppered to be s lrge s in-between the two sites. The vribility of oxygen uptke rtes most likely reflected combintion of ptchiness of orgnic mtter nd fun distributions in the sediment t the two sttions, especilly t sttion S11. The oxygen consumption in generl seemed to decrese with time during the incubtions giving the concentrtion versus time plots n exponentil (or bnn like ) shpe (Fig. 8). This bnn shpe my be result of decresed oxygen concentrtions in the wter of the chmbers nd thus incresed trnsport resistnce through the diffusive boundry lyer (DBL) (Hll et l., 1989). This phenomenon ws seen during ll deployments nd incubtions. Thus, to be ble to investigte the effect of resuspension on benthic solute fluxes, especilly oxygen, it is very importnt to compre the behvior of fluxes in resuspension chmbers with fluxes in reference chmbers. Oxygen consumption (mmol m 2 d 1 ) Deployment Fig. 2. The verge initil oxygen consumption in the chmbers from the two sttions S1 (deployments 1 nd 2) nd S11 (deployments 3 5). The error br shows the stndrd devition from the repeted incubtions during ech deployment. No error brs men tht there were no repeted incubtions, hence there is only one dt for ech chmber. ð3þ

7 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) At sttion S11, deployments 4 nd 5, there were cler effects on the oxygen consumption s the stirring speed ws incresed the first time (1st ISS), from low to medium level (Fig. 3). As the stirring speed incresed, resuspension of different levels ws creted in the chmbers, nd the oxygen consumption incresed compred to the reference chmbers. The effect on the oxygen consumption ws seen during ll the repeted incubtions in the 4th nd 5th deployments (Fig. 3). However, the effect of resuspension ws lrger during the first incubtion when the oxygen consumption incresed with mmol m 2 d 1, compred to the second incubtion when it incresed with mmol m 2 d 1. This corresponds to n increse in oxygen consumption with 12 36%, which is in ccordnce with the results from study in the Gulf of Finlnd where the oxygen consumption incresed with on verge 59% due to resuspension (Almroth et l., 29). As the stirring speed ws further incresed (2nd ISS), from medium to high level, no further increse in the oxygen consumption ws observed even though the resuspension (s mesured by turbidity) incresed in ll resuspension chmbers. In fct, during the first incubtions the chnge in oxygen consumption decresed during the 2nd ISS, compred to the initil fluxes (Fig. 3b). During the second incubtion there ws no cler pttern (Fig. 3b) of the chnge in oxygen consumption. The increse in consumption t deployments 4 nd 5 t the 1st ISS nd the lck of further incresed consumption during the 2nd ISS seemed to occur regrdless of the strength of the creted resuspension. A plot(fig. 4) of the oxygen consumption versus the turbidity in the chmbers showed tht there ws no reltion between the two vribles. The criteri for successfully hving creted resuspension in chmber (described in Section 2.4) might thus not be necessry to use, t lest not for clculting oxygen fluxes. This is in ccordnce with previous Effect of resuspension (mmolm -2 d -1 ) b Effect of resuspension (mmolm -2 d -1 ) st ISS 3,3 4,3 4,4 5,3 5,4 Deployment, chmber 2nd ISS 3,3 4,3 4,4 5,3 5,4 Deployment, chmber inc 1 inc 2 inc1 inc2 Fig. 3. The effect of resuspension on the oxygen consumption s the stirring speed ws incresed from low to medium level (left) nd from medium to high level (right) t sttion S11. The drk gry brs represent the effect of resuspension during the first incubtion nd the light gry brs represent the effects during the second incubtion (repeted incubtion). Significnt resuspension ws creted in the chmbers mrked with strs. Oxygen consumption (mmol m -2 d -1 ) Fig. 4. The oxygen consumption (mmol m 2 d 1 ) versus turbidity (NTU) in chmbers t sttions S1 nd S11. There is no cler reltion between the two vribles. studies by Jørgensen nd Des Mris (199) who showed n inverse reltion between DBL thickness nd oxygen consumption rtes in sediments with high oxygen consumption. The oxygen influx incresed with incresing wter flow velocity, which compressed the DBL nd in turn incresed the diffusive flux of oxygen into the sediment. The decrese in oxygen consumption, fter the second increse in stirring speed, during the first incubtion, might be becuse the DBL thickness ws lredy compressed nd the mximum oxygen trnsport to the sediment ws thus chieved lredy in the first step. A lrge prt of the reduced substnces ws oxygented lredy during the first increse in stirring speed, i.e. the oxygen demnd ws lower in the resuspension chmber s the stirring speed ws incresed the second time. The lrger increse in oxygen consumption during the first incubtion, t both stirring speeds, compred to the second incubtion, might be due to t lest two resons. First, there were more reduced solutes vilble to oxidize during the first incubtion nd the 1st ISS, thus the oxygen demnd ws lrger then. Second, no new orgnic mtter, or reduced solutes, ws probbly trnsported into the chmbers during ventiltion between incubtions. Insted some of the resuspended prticles (inorgnic s well s orgnic) were probbly ventilted out from the chmbers t the end of the first incubtion. Observtions of the turbidity showed tht the level of resuspension slightly decresed between incubtions, probbly due to the outventiltion of smller prticles s well s re-rrngement of the sediment prticles on the sediment surfce. The lowest oxygen consumption ws found t sttion S11, during deployment 3 (Fig. 2). During this deployment oxygen consumption Tble 2 The verge effects of nturl resuspension on oxygen consumption in mmol m 2 d 1 nd in %, nd the stndrd error (s.e.) of the effects s result of the first step of incresed stirring speed (ISS) re shown for the different incubtions during deployments 3, 4 nd 5. The verge strt vlues of the oxygen concentrtions (μm) in the chmbers re given s the bottom wter (BW) concentrtions. Deployment Incubtion BW [O 2 ] μm Effect of resuspension (mmol m 2 d 1 ) (%) In deployment 3 there ws only one resuspension chmber. s.e. (mmol m 2 d 1 )

8 44 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) O2 (µm) b S1 ws only successfully mesured in one of the two resuspension chmbers, which showed n increse in oxygen consumption s nturl resuspension ws creted (Fig. 3 nd Tble 2). No repeted incubtions were mde t this deployment. Three repeted incubtions were successfully performed t sttion S1 during deployment 2 (Fig. 5). Resuspension bove 5 NTU ws creted in three of six resuspension chmbers nd in the remining three resuspension chmbers the verge turbidity ws bove 3.3 NTU. The effects of resuspension on the oxygen consumption were much lower t S1 compred to sttion S11 nd the pttern ws somewht irregulr. The consumption seemed to lterntively increse or decrese (Fig. 6). The highest observed effect (2.7 mmol m 2 d 1 ) corresponded to 6.6% of the initil consumption. The chnges in oxygen consumption during the second increse in stirring speed were in the sme rnge s during the first increse in stirring speed, nd the lrgest chnge in consumption (3.5 mmol m 2 d 1 ) corresponded to 9.8% of the initil oxygen consumption. The uncler pttern nd the low rnge of chnge during the first increse in stirring speed indicted tht there were no significnt effects of resuspension on the oxygen consumption t sttion S1. During the second increse in stirring speed the oxygen consumption decresed more in the resuspension chmbers compred to the control chmbers, which is the sme behvior s during the first incubtions t sttion S * * * * * Time (h) Fig. 5. Exmple of repeted incubtions t sttion S1, during deployment 2. Repeted incubtions were lso performed during deployments 4 nd 5 t sttion S11. Oxygen concentrtion (strts t letter ) ws mesured with optodes, nd turbidity (strts t letter b) with sensors every minute, inside chmber 1 4 (legend). Smples for nutrients nd DIC were collected during the lst incubtion before nd fter mssive resuspension ws creted. After ech incubtion the chmber lids were opened to ventilte the chmbers, nd oxygen s well s turbidity went bck to initil concentrtions, before the lids were closed nd the next incubtion strted. Δ Oxygen consumption (mmol m -2 d -1 ) dep 2 dep 4 dep 5 Chmber 1 Chmber 2 Chmber 3 Chmber 4 Fig. 7. The chnge in oxygen consumption (mmol m 2 d 1 ) due to mssive resuspension is shown for ech chmber. nd reduced substnces were exposed to the oxygented bottom wter (nd vice vers), resulting in n enormous increse in oxygen consumption, i.e. rpid decrese in oxygen concentrtion in the incubtion chmbers s result (Fig. 8). The lowest increse in consumption ws 252 (s.e. 37.8) mmol m 2 d 1 corresponding to n increse of 113% t sttion S1. The highest increse in consumption ws 525 (se 62) mmol m 2 d 1 corresponding to n increse of 16,948% t sttion S11. This indictes tht mjor resuspension, cused by e.g. dredging or trwling, of orgniclly rich sediments like the ones studied here, will immeditely led to very high consumption of oxygen, which cn hve importnt, t lest temporrily, chemicl nd biologicl effects on the locl environment Dissolved inorgnic crbon nd nutrients Smples for nutrients nd dissolved inorgnic crbon (DIC) were withdrwn in the lst incubtion during ll deployments. Both initil fluxes (Fig. 9), i.e. fluxes before the time when the stirring speed ws incresed, nd fluxes fter resuspension were clculted in both control nd resuspension chmbers. The stirring speed ws incresed in order to crete nturl resuspension in the resuspension chmbers during deployments 1 nd 3. During deployment 1, t sttion S1, the creted resuspension ws low, the turbidity only incresed on verge from 1.36 (sd.) NTU to 3.6 (sd.7) NTU. No dt were S11 Deployment 5, incubtion 3, Mssive resuspension. The effect on oxygen consumption due to mssive resuspension ws drmtic (Fig. 7) in ll cses. When sediment ws collected strong mixing of sediment nd wter occurred Effect of resuspension (mmol m -2 d -1 ) Deployment 2 1,3 1,4 2,3 2,4 3,3 3,4 Incubtion, chmber 1st ISS 2nd ISS O2 (µm) b ** ** * ** *** * ** **** * * * * * ** * ** * * * * ** ** *** *** * ** * * **** * * * *** * ** * ** * *** * ** * *** * *** * ** * ** * **** * ** ** * * * *** * *** * Time (h) Fig. 6. The effects of resuspension during deployment 2 t the non-fish frm-ffected sttion (S1). Resuspension (turbidity >5 NTU) ws creted in the chmbers with the strs. Fig. 8. The oxygen concentrtions (strt t letter ) decresed drmticlly s mssive resuspension ws creted, showed by the incresed turbidity (strts t letter b), in the chmbers (legend).

9 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) mmol m -2 d DIC b mmol m -2 d Ammonium S1 S11 S11 S11 S1 S11 S11 S11 c mmol m -2 d Phosphte d mmol m -2 d Silicte S1 S1 1 S1 1 S11 S1 S1 1 S1 1 S11 Fig. 9. The verge initil fluxes (mmol m 2 d 1 ) of DIC (), mmonium (b), phosphte (c) nd silicte (d) during the different deployments (1,3,4,5) t the two sttions S1 nd S11. The error brs show the stndrd error of the verge fluxes. received from the control chmbers. Also t sttion S11, deployment 3, the creted resuspension ws on the lower limit; the turbidity incresed from 1.3 to 4.8 NTU in only one chmber. Even though the creted resuspension ws low, there ws n incresed stirring speed in three of the in totl five chmbers, which should decrese the DBL thickness (Jørgensen nd Des Mris, 199). However, no sttisticlly significnt chnges in the fluxes or concentrtions of DIC or nutrients were observed due to nturl resuspension or incresed stirring speed in this study. Thus, more field studies need to be performed to be ble to mke conclusions in sttisticlly significnt wy bout the effects of nturl resuspension on benthic fluxes of nutrients nd DIC in se lochs. During deployments 4 nd 5 t sttion S11, mssive resuspension ws successfully creted in seven of the eight chmbers, cusing rpid mixing of oxygented overlying wter, sediment nd pore wter. Due to technicl resons no control chmbers could be used when mssive resuspension ws creted, which mkes the study of its effect somewht uncertin. However, the observed chnges during deployments where mssive resuspension ws creted were not observed during deployments where there were control chmbers or nturl resuspension. Therefore, it cn be suggested tht the observed chnges re due to mssive resuspension. The mgnitude might not be exctly mesurble due to lck of control chmbers, but the errors should be of minor mgnitude. The verge initil DIC fluxes t sttions S1 nd S11 ws 2 (s.e. 3.1) nd 3 (s.e. 14) mmol m 2 d 1, respectively (Fig. 9), which were not ffected by the mssive resuspension in ny of the chmbers (Tble 5). However, the initil concentrtions of DIC (Tble 3) incresed instntly (Fig. 1 left nd Tble 3 Initil verge bottom wter concentrtion (μm) of dissolved inorgnic crbon, mmonium, phosphte nd silicte in the incubtion chmbers t sttions S1 nd S11. The stndrd devitions of the concentrtions re given s ± vlues. Sttion [DIC] [NH + 4 ] 3 [PO 4 ] [Si(OH) 4 ] S ±4. 1.5±.1.27 ± ±.11 S ± ± ± ±.4 Fig. 11) in ll chmbers (Tble 6) with n verge of 419 μm (sd 297), which corresponded to 2.4%. The instnt increse in concentrtion of DIC observed t sttion S11 ws not observed during deployment 2 t sttion S1, where no effects of resuspension on concentrtions were observed. At sttion S1 the verge initil flux of mmonium ws low,.9 (s.e..3) mmol m 2 d 1, s well s t sttion S11 during deployment 3, where it ws 1.2 (s.e..3) mmol m 2 d 1 (Fig. 9b). At S11 during deployments 4 nd 5 the initil flux ws higher due to the orgniclly enriched sediment (Fig. 9b) nd n effect on the mmonium fluxes (Tble 4) ws observed in two out of four chmbers (Tble 5) with significnt fluxes due to creted mssive resuspension. The low initil mmonium flux mesured during deployment 3 is in ccordnce with the lower oxygen consumption during this deployment, which indictes tht there ws ptchiness of the orgnic mteril t sttion S11. During deployments 2, 4 nd 5 the mmonium concentrtions (Tble 3) instntly incresed (Fig. 11b) in ll chmbers (Tble 6). During deployment 2 the concentrtions incresed with n verge of.8 (sd.3) μm corresponding to n increse s lrge s 18% (sd 1%). At sttion S11 the mssive resuspension cused drmtic increse of the mmonium concentrtions (Fig. 11b) rnging from 9.9 to 81 (on verge 48 (sd 27)) μm corresponding to n increse of % (on verge 482%). The increse of mmonium concentrtion due to mssive resuspension events ws probbly cused by mixing of sediment nd pore wter contining lrger concentrtion of mmonium. The lrger increse t S11 ws most likely due to higher pore wter concentrtions of mmonium in the top 25 mm of the sediment; on verge (from two sediment profiles) 157 (sd 47) μm compred to the verge concentrtion t S1 which ws 82 (sd 6.7) μm. Ammonium shows lso n dsorption desorption behvior to prticle surfces (e.g. Lndén nd Hll, 1998). As sediment prticles with high concentrtions of mmonium in the surrounding pore wter were resuspended into the overlying wter the concentrtion in the surrounding wter becme lower nd mmonium might be desorbed from the prticles. Thus, this mechnism could hve contributed to the incresed mmonium concentrtions upon resuspension.

10 46 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) S11 Deployment 5 S11 Deployment 4 DIC (µm) Time (h) 4 1 Phosphte (µm) Time (h) DIC (µm) Phosphte (µm) Time (h) Time (h) Fig. 1. Exmple of the DIC (left) nd phosphte (right) concentrtions with time (filled circles) during the third incubtion in deployments five nd four, respectively. A mssive resuspension ws creted fter bout hlf the incubtion time nd the turbidity (smll dots) quickly incresed. The concentrtions of DIC incresed nd the concentrtions of phosphte decresed instntneously, but the fluxes (clculted by liner regression) remined t the sme level. The dotted lines show the confidence intervl for ech flux. At sttion S11 the initil phosphte concentrtions (Tble 3) instntly decresed in ll chmbers (Tble 6) with n verge of.2 (sd.11) μm s mssive resuspension ws creted (Fig. 11c), which corresponded to decrese of 62%. At sttion S1 no sttisticlly significnt chnge (t-test) in concentrtions ws found due to the mssive resuspension. The verge initil fluxes (Fig. 9c) t sttions S1 nd S11were bout zero mmol m 2 d 1 (.7 (s.e..1) nd b.1 (s.e..1 mmol m 2 d 1 ), respectively). Due to very low fluxes the uncertinties of the fluxes were in mny cses low, but still s lrge or lrger s the flux itself. A chnge in flux (Fig. 1 right) ws only observed in one of the seven chmbers (Tble 5). In this chmber reltively high efflux becme negtive, but with lrger uncertinty of the flux s the resuspension occurred (Tble 4). The lrge chnge in flux ws so cler tht this single result hd reltively high importnce when counting the number of ffected fluxes (Tbles 5, 6). The instnt decrese in phosphte concentrtions cn most likely be explined by phosphte being dsorbed to newly formed iron oxides. As pore wter nd sediment were mixed with overlying wter, oxygen drmticlly decresed when re-oxidizing reduced substnces, e.g. when reduced iron ws oxidized to iron oxides. This my lso 12 DIC b 1 Ammonium Δ concentrtion (µm) Δ concentrtion (µm) : 1 2: 2 2: 4 4: 1 4: 2 4: 3 5: 1 5: 2 5: 3 5:4 2: 1 2: 2 2: 4 4: 1 4: 2 4: 3 5: 1 5: 2 5: 3 5:4 Deployment:Chmber Deployment:Chmber c Δ concentrtion (µm) Phosphte d Δ concentrtion (µm) Silicte : 1 2: 2 2: 4 4: 1 4: 2 4: 3 5: 1 5: 2 5: 3 5:4 2: 1 2: 2 2: 4 4: 1 4: 2 4: 3 5: 1 5: 2 5: 3 5:4 Deployment:Chmber Deployment:Chmber Fig. 11. The chnge in concentrtion (μm) of DIC (), mmonium (b), phosphte (c) nd silicte (d) due to the creted mssive resuspension in the chmbers. The error brs for deployment 2 shows the stndrd devition of the chnge in concentrtions. For deployments 4 nd 5 the error brs show the sum of the confidence intervls.

11 E. Almroth-Rosell et l. / Journl of Se Reserch 72 (212) Tble 4 Nutrient fluxes (mmol m 2 d 1 ) before (BR) nd fter resuspension (AR) in chmbers which were ffected by mssive resuspension. The uncertinty of the fluxes is described by the stndrd error (s.e.). Substnce Sttion Deployment Chmber Flux BR + NH 4 + NH 4 3 PO 4 explin why n efflux of phosphte cn chnge direction nd become n influx. On longer time scle the phosphte might hve been relesed gin if ll the oxygen nd other oxidnts, like the iron oxides, hve been consumed becuse of stimulted oxygen consumption due to resuspension. The initil silicte concentrtions (Tble 3) incresed instntly s mssive resuspension ws creted t both sttions (Fig. 11d) in ll resuspension chmbers (Tble 6). At S1 the concentrtions incresed with n verge of 1.13 (sd.36) μm, which corresponds to n increse of 32.8%, due to mssive resuspension. At sttion S11 the increse in concentrtion ws even lrger (Fig. 11d), by n verge of 6.9 (sd 3.7) μm, which corresponds to 2% increse. The initil silicte fluxes (Fig. 9d) vried between.35 (s.e..1) nd 2.32 (s.e..41) mmol m 2 d 1 with both the highest nd lowest fluxes t sttion S11. The verge flux ws 1.3 (s.e..17) mmol m 2 d 1. The fluxes remined unffected of the resuspension events in four chmbers (Tble 5), but in two chmbers (one in ech of deployments 4 nd 5) the fluxes decresed nd went from being effluxes to become influxes (Tble 4). The uncertinty of the flux fter resuspension during deployment 5 ws too high, but s there ws no doubt tht there ws sttisticlly significnt decrese of the flux it ws included s result. A decrese of silicte fluxes due to resuspension hs lso been observed in n erlier study in the Gulf of Finlnd, Bltic Se (Almroth et l., 29), but we hve no obvious explntion for this behvior. Willims et l. (1985) discussed different wys for which silicte concentrtions cn decrese in se wter, e.g. complextion with mngnese nd sulfte or dsorption of silicte on cly minerls. On the other hnd, Siever nd Woodford (1973) suggested tht dissolved silicte hs to be present in concentrtions higher thn 1 ppm less thn crossover point of 12 ppm (125 μm) to be dsorbed to cly minerls like e.g. kolinite. Thus, this explntion is not likely vlid since the silicte concentrtions re below this crossover point. 4. Concluding remrks Nturl resuspension clerly led to higher benthic oxygen consumption t sttion S11, which hd orgniclly enriched sediment due to orgnic mtter deposition from former fish frm. The effects on the oxygen consumption were higher during the first (of series of multiple incubtions) incubtion in ll resuspension chmbers, where it incresed with n verge of 12.8 (s.e..17) mmol m 2 d 1, compred to the second incubtion, where it incresed with n verge of 7.7 (s.e..12) mmol m 2 d 1. Also resuspension seemed to be more esily creted during the first incubtion compred to the second. At s.e. BR Flux AR S S S Si(OH) 4 S Si(OH) 4 S Tble 5 The frequency of the effect of mssive resuspension on benthic fluxes of nutrients nd DIC t sttion S11 re shown by the reltion (C) between the number of chmbers, with pproved fluxes, in which mssive resuspension ws creted (A) nd the number of chmbers in which there ws n effect on the fluxes due to resuspension (B). DIC + NH 4 PO 4 Si A Nr of chmbers B Effect on fluxes C Frequency (%) s.e. AR Tble 6 The frequency of the effect of mssive resuspension on the concentrtions of nutrients nd DIC t sttion S11() nd t S1(b) is shown by the reltion (F) between the number of chmbers where the concentrtions re compred (D) nd the number of chmbers in which n instnt chnge in concentrtion ws observed (E). DIC + NH 4 PO 4 Si b DIC + NH 4 PO 4 Si D Nr of chmbers E Effect on conc F Frequency (%) the sttion S1, which ws not ffected by the fish frm nd hd lower sedimentry orgnic content thn S11, the effects on the oxygen consumption were not cler. There were not enough dt to be ble to significntly evlute the effect of nturl resuspension on the fluxes of DIC nd nutrients. The oxygen consumption incresed in 1% of the cses due to the creted mssive resuspension. The fluxes incresed on S1 with on verge 68 (sd 366) mmol m 2 d 1 nd on S11 with on verge 2396 (sd 2265) mmol m 2 d 1, corresponding to 238% nd 7366%, respectively. The fluxes of mmonium, phosphte nd silicte were ffected by the mssive resuspension in 5, 14 nd 33% of the chmbers, respectively, on sttion S11. All the ffected fluxes were effluxes tht decresed nd some of them becme influxes. The decresed effluxes of mmonium could be due to tht some of the mmoniums were oxidized to nitrte by stimulted nitrifiction. Unfortuntely there were no nitrte dt in this study. The decrese in phosphte efflux in one of the chmbers might be result of dsorption to iron oxides in this chmber. However, in the mjority of the cses there were no effects of mssive resuspension on the nutrient nd DIC fluxes. On the other hnd, the concentrtions of DIC, mmonium nd silicte instntly incresed with n verge of 419 (sd 297), 48 (sd 27) nd 6.9 (sd 3.7) μm, respectively t S11 upon mssive resuspension, which corresponded to percentge increses of 2.4, 482 nd 2%, respectively. The concentrtions of phosphte decresed instntly with n verge of.2 (sd.1) μm, corresponding to 62%, probbly due to dsorption onto newly formed iron oxides. On sttion S1 there were effects of mssive resuspension only on the mmonium nd silicte concentrtions, which incresed with.8 (sd.3) nd 1.13 (sd.36) μm, respectively. The increse occurred when the sediment nd the pore wter, with high concentrtions of these substnces, were mixed with the overlying wter. Ammonium ws probbly lso desorbed from resuspended sediment prticles, onto which mmonium ws dsorbed in the sediment. Unfortuntely it ws not possible to use ny control chmbers when creting mssive resuspension, i.e. mssive resuspensions were creted in ll four chmbers during the deployments. In spite of this, the bove described chnges in concentrtions nd fluxes re relible in the sense tht they occur, but minor errors in mgnitude, which would hve been corrected if there were control chmbers, might exist. The results from this study suggest tht bottom res with lownorml orgnic crbon content, which regulrly re exposed to nturl resuspension, do not show ny cler trend in oxygen consumption due to resuspension events. However, t bottom res which re orgniclly enriched, e.g. due to fish frming, the oxygen consumption is significntly incresed lso t low resuspension levels. This response to resuspension t orgniclly enriched bottoms cn led to oxygen depletion in res where resuspension frequently occurs nd the wter exchnge is limited. Mssive resuspension led to drmtic increse of oxygen consumption t both the reference sttion nd the orgniclly enriched sttion. This indictes tht ctivities such s trwling nd dredging tht tke plce in res where wter exchnge occurs infrequently my led to oxygen depletion in bottom wter. Silicte, mmonium nd DIC cn be relesed due to mssive resuspension nd contribute to incresed lgl blooms in surfce wters. On shorter time-scles, s in this study, the phosphte concentrtion is decresed s it cn