Sweerts, Jean-Pierre Rudolf Albert

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   University of GroningenOxygen comsumption, mineralization and nitrogen cycling at the sediment-water interface ofnorth temperate lakesSweerts, Jean-Pierre Rudolf AlbertIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1990Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Sweerts, J-P. R. A. (1990). Oxygen comsumption, mineralization and nitrogen cycling at the sediment-water interface of north temperate lakes. s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 08-06-2022.ents. Butterworths,rr velocity on the.), Sediment oxygenSUMMARYAt the sediment-water interface of lakes, deposited organic material is mineralizedand subsequently released as nutrients to the water column or buried. Chemicalgradients in the sediment are often enhanced or createdbythe activities of the dominantorganisaxs, rytrich results in stratiÍication of organisms as well as their mineralization andproduction processes. Therefore, the study of the chemical gradients at thesediment-water interface gives information on the biogeochemical processes in thesediment and the interactions between the sediment and the water col 'mn. In this study,oxygen consuming processes, mineralization and nitrogen cycling at the sediment-waterinterface of temperate lakes differing in trophic state and depth were investigated.The introduction (Chapter 1) gives an overview of physical, biological and chemicalprocesses which are located at the sediment-water interface.In the Materials and Methods section (Chapter 2) the studied lakes and sedimenttypes are described. Sediment pore water analysis and flux calculations across thesediment-water interface are the basis of this study. Microelectrodes for orygen andammonium and a newly developed nitrate microelectrode were used. The nitrateselective microelectrodes (1pm tip diameter) had a liquid membrane ion exchanger anda linear response from L0'1 to L0-5 pM nitrate. Selectivity coefficients were of the sameorder as specified for macroelectrodes. The development of the nitrate microelectrodeallowed the study ofnitrate proÍiles at the required spatial resolution and concentrationrange in lake sediments.To simulate in situ transport rates of solutes across the sediment-water interface, theoverlying water of intact sediment cores was constantly stirred with 3rr impeller at a ratesufficient to mix the water column and maintain the diffusive boundary layer at adetermined thickness. The system allowed standardization of the water circulation inlaboratory sediment core experiments. Oxygen microprofiles measured in situ, and insediment cores with adequately stirred overlying water were similar (Chapter 3).Sediment oxygen consumption was calculated from: (1) measured orygen profiles in thediffusive boundary layer and the molecular diffusion coefficient for orygen in water; (2)the measured orygen decrease in the top of the sediments and the estimated diffusioncoefficient in the sediment; and (3) by oxygen differences in the overlying water afterincubation of sediment cores.Whole sediment molecular diffusion coefficients (Ds) for tritiated water in sedimentof a variety of lakes were determined experimentally. 3HzO was added to the overlyingwater of asphpiated (without bioirrigation) cores, and the resulting pore water profileswere measured after a period of time (Chapter 4). These measured coefficients weret23compared to known diffusion coefficients in pure watcr (D6) to obtain estimatcs ofDo/D.. Do/Dr values were 1.8-r0.1 for low porosity organic-poor sediments and 1.5-r0.2for high porosity organic-rich sediments and Do/Ds declined only slightly as porosityincre ased. Thus, Do/Ds values for high porosity sediments were considerably higher thanpredicted from marine studies.In a survey of 17 North American and European lakes, the average contribution offaunal activity to the effective diffusion coefficient (Ds) was much smaller than reportedfor most coastal marine sediments and some eutrophic lake sediments. Consequently,with the exception of sites with high faunal populations, a small range of effectivediffusion coefficients, at one temperaturc, was observed for sediments of different lakeswith a wide range of porosities. In most sediments, fluxes calculated from measureddiffusion coefficients and concentration profiles were similar to measured consumptionor production in the water column of incubated sediment cores.Distribution of oxygen in the sediments of a variety of temperate lakes was measuredwith microelectrodes. The lakes varied in maximum depth from 2-50 m, in surface areafuom 5-34'700 ha, and in annual primary production from 20-500 gC.--2.y-1. Oxygenconsumption and the depth of orTgen penetration in epilimnetic sediments were onlyslightly related to these three lake characteristics. Orygen penetration depths in summerwere within the upper 1.2-6.5 mm in all gyttja, and flocculant and most sandy sediments:only in shallow sandy shore sediments did the oxygen penetrate up to 15 mm. Inphotosynthetically active sediments of oligotrophic lakes oxygen penetration depthfluctuated between 0 and 3 mm during the day. The upper 20 mm in the littoral sedimentof an oligotrophic lake were oxic due to transport of orygen into the sedimcnt by theroots of plants (Caret spp.). Oxygen penetration depth and consumption varicdseasonally in oligo-mesotrophic and eutrophic lakes (1.6 < Qro. < 4.9). Whereas oxygenpenetration depth (0.1-12.2 mm) of profundal sediments was positively related to thedepth of the lake, the oxygen consumption raLe (5.7-44.6 mmol.m-'.d-') was inverselyrelated to depth. Oxygen penetration depth at 10 m depth varied from 0.1 mm in ameso-eutrophic lake to 4.8 mm in an oligotrophic lake having similar morphometry(Chapter 5).Oxygen consumption processes in the profundal gyttja and littoral sandy sediment ofLake Vechten were determined using sediment pore water analyses and sediment coreincubations (Chapter 6). Sediment oxygen consumption rate was higher in Begg;iatoa spp.mats (44 mmol.m-2.d-l at 7oC) than in profundal g;'ttja sedimenrs (29 mmol.m-2.d-l atfC) in the circulation period. The littoral sandy sediments had much lower rates in bothwinter (8.7 mmol.m-2.d-l at fC) an<t summer (18.6 mmol.m-2.d-l at 22oC). Methane(47-52Vo), ammonium ('7-\2%), iror (2-6%) and sulfide (%) oxidation accounted forroughly 60Va of the oxygen consumed in the profundal sediment. The orygen uptake oforganic matter sedimenoxJgen consumption bydid not give informationThe oxidation of the ri m p o r t a n c e ( <  1 5 í i ) i nOxygen and methanishallow, eutrophic LaVechten. Almost the corlayer, and methane rcleflux out of the anoxic la1rc lcase into the over ly i ranoxic conditions (7.9 mlayer  under ox ic  condi t i rinto the oxic surface la,profundal g1'ttja sedimesediment wcre 1.5 mmrLorvest valuss of 0.1 mnin thc l ittoral sandy secioxJgen consumption vorganic-rich sediment arTo study the nitrogerammonium, nitrate anrcirculation period in the(i) l i ttoral sandy sedimedepth of penetration ofg;'ttja sediment to 5 mmzonc of denitrif icationdcmonstratcd h igh dcniconcentrations in thc oveavailability (Chapter 8)low-porosity sandy l ittorand the Bcg5;iatoa mats.porc water and overl 'denitrification was the ntypes. The fi lamentousabundantly at the organThe Begiatoc mats mayand sulfide, thereby harr124) obtain estimates of:diments and 1.5-r0.2ly slightly as porosityrsiderably higher thanerage contribution ofsmaller than reportedments. Consequently,all range of effectiveents ofdifferent lakeslated from measuredeasured consumption.e lakes was measured-50 m, in surface area)0 gC.m-2.y'1. Oxygen:sediments were onlyion depths in summernost sandy sediments:[e up to L5 mm. In'n penetration depthr the littoral sedimentthe sediment by theconsumption varied1.9). Whereas oxygenitively related to ther'2.d'1) was inverselyd from 0.1 mm in aimilar morphometryal sandysediment ofs and sediment coreherrnBegiatoaspp.(29 mmol.m-z.d-r ath lower rates in bothat 22oC). Methanertion accounted forle oxygen uptake oforganic matter sedimented to the bottom accounted for approximately 40Vo of the totalo{ygen consumption by the sediment. Poisoning the sediment cores with formaldehydedid not give information about the bacterial or chemical nature of the oxidation process.The oxidation of the reduced end-products of anaerobic respiration was of minorimportance (< L5%) in the littoral sandy sediments.Orygen and methane concentration profiles were measured in the sediments of theshallow, eutrophic Lake Loosdrecht and the monomictic, meso-eutrophic LakeVechten. Almost the complete diffusive flux of methane was oxidized in the oxic surfacelayer, and methane release into the overlying water of sediment cores was < 5Vo of theflux out of the anoxic layer into the oxic surface layer for all studied sediments. Methanerelease into the overlying water from the profundal sediment of Lake Vechten underanoxic conditions (7.9 mmol.m-2.d-1) was close to the calculated flux into the oxic surfacelayer under oxic conditions (9.4 mmol.--2.d-1). More than 95 Vo oïthe methane diffusinginto the oxic surface layer was oxidized. Methane oxidation rates were highest in theprofundal gyttja sediment (7.9 to 9.4 mmol.--2.d- t) atfC. Rates in the littoral gyttjasediment were 1.5 mmol.m' z.d'L at 5oC and 6.5 mmol.m-z.d-l at 22oC, respectively.Lowest values of 0.1 mmol..o'2.d'1 atToCand 0.4 mmol.m-2.d-l atzzocwere measuredin the littoral sandy sediment. The contribution of methane oxidation to the sedimentoxygen consumption was 50Vo in the profundal sediments, 27Vo in the littoralorganic-rich sedirnent and3Vo in the littoral sandy sediment (Chapter 7).To study the nitrogen cycle at the oxic-anoxic interface, concentration profiles ofammonium, nitrate and orygen were measured with microelectrodes during thecirculation period in the three dominant sediments of the meso-eutrophic LakeVechten;(i) littoral sandy sediment, (ii) profundal gyttja sediment, and (ili) Beggiatoa mats. Thedepth of penetration of nitrate varied from only 1.3 mm in the organic-rich profundalgyttja sediment to 5 mm in organic-poor littoral sandy sediment. The thickness of thezone of denitrification in the organic-rich sediment was < 500 ,rrm. The resultsdemonstrated high denitrification rates (0.29 to 1.3L mmol.m-t.O-11 at in situ nitrateconcentrations in the overlying water (30 pM) and limitation of denitrification by nitrateavailability (Chapter 8). Orygen and nitrate consumption were much lower in thelow-porosity sandy littoral sediment han in the high porosity gyttja profundal sedimentand the Begiatoa mats. Stable 15N-isotope analysis of the biomass, ammonium in thepore water and overlying water, and the gaseous nitrogen demonstrated thatdenitrification was the major nitrate consuming process (> 80%)in all three sedimenttypes. The filamentous white sulfide-oxidizing bacteria Begiatoa spp. often grewabundantly at the organic rich profundal sediments forming conspicuous white mats.The Begiatoa mats may be responsible for the whole benthic consumption of oxygenand sulfide, thereby harvesting most of the energy input to the sediment. The results ofr25this studyshowthat also thebenthic denitrification activitymaybe attributed toBeggiatoaspp.,thusdemonstratingakeyroleoftheBeggíatoamatsinthebenthiccyclingoforygen,.,rifu,. uod nitrogen. Microprofiles of nitrate n a Begiatoa mat on a lake sedimentdemonstrated that all nitrate taken up from the water phase was consumed within theupper 150 trtm ofthe mat. In semi-purified tufts of Beggiatoa rpp. 1sNO.- was almostcompletely denitrified to 15N2. Denitrification rates in Beggiatoa spp. were among thehighest reported for aquatic sediments'The combination of microelectrodes and 15N .tub1"-irotope analyses allowed thequalification and quantification of the major nitrogen products and their conversionrates at specific locations in the sediments. In gyttja sediment, the NlI4 t influx from thedeeper sediments into the oxic surface layer was 6.L mmol.m-".d-',the efflux out of thesediment was 4.3 mmol.m-2.d'1, therefore l-.8 mmol.m-2.d-1 *u* consumed in the oxicsurface layer, probably by nitrification. Ammonium production in gyttja sediment wasan order of magnitude higher then in sandy sediment. Consequently, the littoral sandysediment was of minor importance for the nitrogen cycle in the lake' A mass balance fornitrogen revealed that permanent burial of sedimented organic material (52-65Vo) andN2-release into the water column and subsequently into the atmosphere bydenitrificatio n (35-a8Vo) were the major nitrogen-removing processes from LakeVechten. The amounts of nitrate diffusing from the water into the sediment, and of nitrateproduced by nitrification in the oxic surface layer, were of similar importance assubstrates for denitrification.SAMENVATTINGZuurstofeonsumplsediment/water grrOp de bodem van nwaardoor een habitiGesedimenteerd orgasediment levende micrhet gesedimenteerdebovenstaande water',fytoplankton en de wihoge matebepaaldwosediment. Tevens kan ten het grondwater.In het sedimentvin<gezóneerd. De dikttproductie-processenelectronendonoren,electronenacceptoren,zijn. In meren met eenplaatsvinden in laagjtbestuderen. De vertikthet resultaat van traÍprofielen kunnen daasediment/water grenrkwantificeren. Fluxende biologische, chemideze studie is het belaorganische stof en deDeze processen op hfluxen van verbindingmicroelectroden om dnitraat en ammoniumtechnieken (bv. stabiemaakte het mogelijk coplossend vermogenL26

Oxygen comsumption, mineralization and nitrogen cycling at the sediment-water interface of north temperate lakes

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Oxygen comsumption, mineralization and nitrogen cycling at the sediment-water interface of north temperate lakes

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