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(1)Carbon Cycling in Baltic Sea Sediments – In situ investigations with benthic landers. Madeleine Nilsson Doctoral Thesis. Department of Marine Sciences Faculty of Science 2018.

(2) Madeleine Nilsson Carbon Cycling in Baltic Sea Sediments – In situ investigations with benthic landers. Cover photo by: Astrid Hylén, edited by Jonas Porsgaard Printed by BrandFactory AB, Gothenburg, Sweden 2018 © Madeleine Nilsson ISBN: 978-91-7833-071-3, (Print) ISBN: 978-91-7833-072-0, (PDF) Available at http://handle.net/ /2077/56260.

(3) Abstract Coastal seas, estuaries and continental shelves are the connection between land ƒ† –Š‡ ‘’‡ ‘ ‡ƒǡ ƒ† †—‡ –‘ Š‹‰Š ’”‘†— –‹˜‹–› ƒ† •–”‘‰ ‹ϐŽ—‡ ‡ ˆ”‘ land a majority of the marine organic carbon (OC) cycling and preservation in sediments occurs in these areas. Sediments are hotspots in the C cycle also since they constitute a link between the biogeochemically active C pool and the C pool that cycles on much longer timescales, and benthic processes will thus have an effect on atmospheric CO2 levels. To accurately predict future atmospheric CO2 levels it is of great importance to understand how C is recycled and preserved in sediments of coastal seas and estuaries. This thesis investigates benthic OC cycling in the Baltic Sea with emphasis on understanding and quantifying the recycling and preservation of OC. The investigations were made in situ using advanced benthic chamber landers that incubate an area of sediment and overlying water. By discrete water sampling or continuous measurements by sensors it is possible to detect the concentration change of a solute over time resulting from early diagenetic processes in the •‡†‹‡–Ǥ ‹••‘Ž˜‡† ‹‘”‰ƒ‹  ƒ”„‘ ȋ

(4) Ȍ ϐŽ—š‡• ™‡”‡ ‡ƒ•—”‡† ‹ –Š‡ ‹ —„ƒ–‹‘ Šƒ„‡”• ƒ† —•‡† ƒ• ƒ ’”‘š› ˆ‘”  ‘š‹†ƒ–‹‘Ǥ ‘”‡‘˜‡”ǡ –Š‡ vertical distribution of OC in the sediment solid phase together with sediment accumulation rates were used to quantify the OC preservation or burial. It was found that OC recycling rates in Baltic Sea sediments are much larger and burial rates lower than previously thought. In total 96 % of the OC that †‡’‘•‹–•‘–Š‡•‡ƒϐŽ‘‘”‹•”‡ › Ž‡†„ƒ –‘–Š‡™ƒ–‡” ‘Ž—Ǥ ‘™‡˜‡”Žƒ”‰‡ variations between the different Baltic Sea sub-basins were observed as well as between different bottom types. The highest OC recycling rates (~ 32 mmol m-2 d-1 on average) were observed in the deep accumulation areas of the Baltic ”‘’‡”ǡ ™Š‡”‡ ƒŽ•‘ –Š‡ Ž‘™‡•– „—”‹ƒŽ ‡ˆϐ‹ ‹‡ › ȋ„—”‹ƒŽ ”ƒ–‡Ȁ†‡’‘•‹–‹‘ ”ƒ–‡Ȍ was found (2.5–3.5 %). OC recycling rates in general tended to increase with ‹ ”‡ƒ•‹‰ ™ƒ–‡” †‡’–Šǡ ƒ† •‘ †‹† –Š‡  ‘š‹†ƒ–‹‘ ‡ˆϐ‹ ‹‡ ›ǡ ‹Ǥ‡Ǥ –Š‡ 

(5)  ϐŽ—š ’‡”ƒ˜ƒ‹Žƒ„Ž‡  ‹ –Š‡ ”‡ƒ –‹˜‡ •‡†‹‡–•—”ˆƒ ‡ Žƒ›‡”Ǥ Š‹•™ƒ• Žƒ”‰‡Ž› ‡š’Žƒ‹‡† „› ˆ‘ —•‹‰ ‘ˆ ˆ”‡•Š Žƒ„‹Ž‡  ƒŽ‘‰ –Š‡ †‡’–Š ‰”ƒ†‹‡– ™‹–Š‹ –Š‡ basin. It was estimated that nearly half of the OC that deposits on shallow bottoms in erosion-transportation areas of the Baltic Proper is resuspended ƒ†”‡†‹•–”‹„—–‡†–‘†‡‡’‡” ƒŽ‡”ƒ ——Žƒ–‹‘’ƒ”–•‘ˆ–Š‡„ƒ•‹Ǥš›‰‡‹ iii.

(6) –Š‡‘˜‡”Ž›‹‰™ƒ–‡”Šƒ†‘•‹‰‹ϐ‹ ƒ–‡ˆˆ‡ –‘–Š‡”‡ › Ž‹‰”ƒ–‡•ƒ•ˆ‘—† ˆ”‘‘„•‡”˜ƒ–‹‘•„‡ˆ‘”‡ƒ†ƒˆ–‡”ƒ•‘Ǧ ƒŽŽ‡†ƒŒ‘”ƒŽ–‹ ‹ϐŽ‘™Ǥ During the thesis work the benthic chamber landers have been updated with regard to control of quality and performance of the sediment-water incubations. Š‡ ‡ƒ•—”‡† „‡–Š‹  ϐŽ—š‡• ƒ ‘™ „‡ †‡–‡”‹‡† ™‹–Š Š‹‰Š‡” ƒ —”ƒ › ƒ†”‡Ž‹ƒ„‹Ž‹–›‘ˆ Šƒ„‡”ˆ— –‹‘‹‰ǡƒ†•–‹ŽŽ‡ƒ„Ž‡ƒ‡ˆϐ‹ ‹‡–ˆ—ŽŽŽƒ†‡” deployment-incubation-recovery cycle in one day. One major step forward was the installation of conductivity sensors to determine chamber volume from the dilution of salinity resulting from a small injection of MQ water. The benthic landers used in this work are considered to be one of the most suitable systems ƒ˜ƒ‹Žƒ„Ž‡ ‹ –Š‡ ϐ‹‡Ž† –‘†ƒ›Ǥ Š‡ ‘—– ‘‡ ‘ˆ –Š‹• ‹ •‹–— •–—†› ‹’”‘˜‡• –Š‡ understanding of the carbon cycle and its dynamics in the Baltic Sea.. iv.

(7) Populärvetenskaplig sammanfattning Kustnära grunda hav är de områden som förbinder land med öppna oceanen.

(8) †‡Š¡”‘”¤†‡ƒ¡”’”‹¡”’”‘†—–‹‘‡ȋ†Ǥ˜Ǥ•Ǥ–‹ŽŽ˜¡š–ƒ˜˜¡š–’Žƒ–‘‡ŽŽ‡” ‹”‘ƒŽ‰‡”Ȍ ‘ Š †¡”ƒ˜ „‹Ž†‹‰‡ ƒ˜ ‘”‰ƒ‹•– ƒ–‡”‹ƒŽ ‡š–”ƒ ŠÚ‰ ’¤ ‰”—† av hög tillförsel av näringsämnen från land. Organiskt material tillförs även —•–‘”¤†‡†‹”‡–˜‹ƒϐŽ‘†‡”Ǥ”‰ƒ‹•–ƒ–‡”‹ƒŽ„‡•–¤”–‹ŽŽ•–Ú”•–ƒ†‡Ž‡ƒ˜‘Ž i organisk form. Detta innebär att kustnära hav är områden med hög omsättning ƒ˜‘”‰ƒ‹•–‘Ž‘ Š†‡¡”†¡”ˆÚ”‡š–”ƒ˜‹–‹‰ƒ‹†‡‰Ž‘„ƒŽƒ‘Ž ›‡ŽǤ Sedimenten i grunda havsområden tillförs stora mängder organiskt kol som antingen kan brytas ner av mikroorganismer och sedimentlevande djur, eller begravas under långa tidsskalor. Sedimenten utgör därför en viktig plats där kol bortföres genom begravning från den oceana biogeokemiska cirkulationen, ˜‹Ž‡– ’¤˜‡”ƒ” ƒ–‘•ˆ¡”‡• ‹‡Š¤ŽŽ ƒ˜ ‘Ž†‹‘š‹† ’¤ Ž¤‰ •‹–Ǥ ‡†‹‡–‡ utgör också en viktig plats för nedbrytning av organiskt kol till löst oorganiskt kol som återcirkulerar till vattenmassan. Den här avhandlingen fokuserar på sedimenten i Östersjöns som är ett grunt, kustnära innanhav starkt påverkat av omkringliggande länder. Det övergripande målet har varit att bestämma hur mycket kol som begravs i Östersjöns sediment och hur mycket som återvänder (eller återcirkulerar) i löst oorganisk form till vattenmassan på grund av nedbrytningen av organiskt material. Det visade sig att så mycket som 96 % av det kol som tillförs sedimenten bryts ner och återcirkuleras till vattenmassan. Nedbrytningen av organiskt material ‹•‡†‹‡–‡–ƒ’¤˜‡”ƒ•ƒ˜ϐŽ‡”ƒˆƒ–‘”‡”‘ Š‹†‡ƒ•–—†‹‡Šƒ”¤Ž‡–‘ •¤ ˜ƒ”‹–ƒ––‹†‡–‹ϐ‹‡”ƒ˜‹Žƒƒ˜†‡••ƒˆƒ–‘”‡”•‘¡”ƒ˜„‡–›†‡Ž•‡ˆÚ”•‡†‹‡–‡ ‹ Y•–‡”•ŒÚǤ –– ‡š‡’‡Ž ¡” ƒ–– ˜‹ —†‡”•Ú– ‡ˆˆ‡–‡”ƒ ƒ˜ ‡–– •–‘”– •›”‡”‹– ˜ƒ––‡‹ϐŽÚ†‡ •‘ †¤ ‘ Š †¤ •‡” –‹ŽŽ Y•–‡”•ŒÚ •‘ ˆÚ”›ƒ” ‡ŽŽ‡” „›–‡” —– åldrat syrefritt vatten ur Östersjöns djupaste delar. Den här studien visade att nedbrytningen av organiskt material i sediment inte verkade påverkas av ett •¤†ƒ–•›”‡”‹–‹ϐŽÚ†‡Ǥ‹ˆƒ‹•–¡ŽŽ‡–ƒ––†‡ŠÚ‰ƒ‡†„”›–‹‰•Šƒ•–‹‰Š‡–‡”ƒ av organiskt kol kunde förklaras av omfördelning av sedimentpartiklar från grunda bottnar till djupa bottnar. Denna omfördelning av partiklar/ material ger upphov till en anrikning av färskt organiskt material som är ‡š–”ƒŽ¡––‡†„”›–„ƒ”–‘ Š•¤Ž‡†‡•ڍƒ”‡†„”›–‹‰•Šƒ•–‹‰Š‡–‡”ƒ‹†‡†Œ—’ƒ bottnarna. v.

(9) I studien har sedimenten undersökts med hjälp av avancerad mätteknik, så kallade bottenlandare, som kan utföra kammarinkubationer av sedimentytan och på så sätt mäta nedbrytningsprocesserna in situ, dvs. under verkliga förhållanden nere på havsbotten. Detta är en viktig aspekt eftersom sediment Ž¡–– ’¤˜‡”ƒ• ‘ †‡ •–—†‡”ƒ• ‡š •‹–—ǡ †˜•Ǥ ‘„‘”† ’¤ ˆƒ”–›‰‡– ‡ŽŽ‡” ‹ ‡–– laboratorium på land. Användandet av bottenlandare är ofta tekniskt krävande ‘ Š‡–‘†‡—–˜‡ Žƒ••–¡†‹‰–Ǥ†‡”†‡Š¡”•–—†‹‡Šƒ”ϐŽ‡”ƒˆÚ”„¡––”ƒ†‡ åtgärder gjorts för att få en högre kvalitet och bättre kontroll över mätningarnas tillförlitlighet. Den här studien har visat att sedimenten i Östersjön begraver (långsiktigt lagrar) betydligt mindre kol än vad man tidigare har trott. Denna kunskap kan leda till att prognoser om kustnära havs betydelse för att långsiktigt ta upp ‘Ž†‹‘š‹†ˆ”¤ƒ–‘•ˆ¡”‡ƒ„‡ŠÚ˜ƒ”‡˜‹†‡”ƒ•Ǥ Utfallet av studien bidrar till en ökad förståelse för Östersjöns kolcykel, och till ƒ––„‡ϐ‹–Ž‹‰ƒ‘†‡ŽŽ‡”ˆÚ”Y•–‡”•ŒÚ•‘Ž‘•¡––‹‰ƒˆÚ”„¡––”ƒ•Ǥ. vi.

(10) Part I Carbon Cycling in Baltic Sea Sediments. 1. Aims. 12. 1. Introduction. 13. 1.1 Carbon in the marine and brackish water environments 1.2 Primary production and benthic pelagic coupling ͳǤ͵ƒ”Ž›†‹ƒ‰‡‡•‹•ƒ†•‡†‹‡–Ǧ™ƒ–‡”ϐŽ—š‡•‘ˆ ƒ”„‘ 1.4 Burial or preservation of OC. 2. The Baltic Sea ʹǤͳƒ–‡”•—’’Ž›ƒ†‡š Šƒ‰‡ ʹǤʹ—–”‘’Š‹ ƒ–‹‘ƒ†Š›’‘š‹ƒ 2.3 Sediments. 3. Methods 3.1 Benthic Landers to study early diagenetic processes in situ 3.2 Sediment cores to study OC burial or preservation. 0DLQ¿QGLQJVDQGGLVFXVVLRQ 4.1 OC recycling and burial in Baltic Sea sediments ͶǤʹ”‡ › Ž‹‰‡ˆϐ‹ ‹‡ ›ƒ†ˆƒ –‘”•‹ϐŽ—‡ ‹‰„‡–Š‹ ”‡ › Ž‹‰ 4.3 Improvement of benthic landers. 13 14 15 17 19 20 22 23 25 25 27 31 31 33 35. 5. Conclusions. 37. 6. Future outlook. 39. 7. Acknowledgements. 43. 8. References. 45. vii.

(11) Part II: Papers Paper I Nilsson, M., Kon‘‡–•ǡ Ǥǡ ‡”‘–Šǡ Ǥǡ ‹–‘”••‘ǡ Ǥǡ ›Ž±ǡ Ǥǡ ‘‡”ǡ Ǥǡ Pfannkuche, O., Almroth-Rosell, E., Atamanchuk, D., Andersson, J. H., Roos, P., Tengberg A. and Hall, P. O. J. Organic carbon recycling in Baltic Sea sediments – An integrated estimate on the system scale based on in situ measurements. Marine Chemistry, submitted. Paper II Nilsson, M.ǡ‡”‘–ŠǡǤǡ‘‘‡–•ǡǤǡ ›Ž±ǡǤǡ‹–‘”••‘ǡǤǡŽ”‘–ŠǦ‘•‡ŽŽǡ E., Roos, P., Tengberg, A. and Hall P. O. J. ƒ”–‹ Ž‡•Š—––Ž‹‰ƒ†‘š‹†ƒ–‹‘‡ˆϐ‹ ‹‡ ›‘ˆ‘”‰ƒ‹  ƒ”„‘Ȃ

(12) •‹–—•‡†‹‡– observations in contrasting brackish marine environments. (Manuscript). Paper III Kononets, M., Nilsson, M.ǡ‡‰„‡”‰ǡǤǡ‡”‘–ŠǡǤǡ ›Ž±ǡǤǡ˜ƒ†‡‡Ž†‡ǡǤǡ Blomqvist, S. and Hall, P. O. J. In situ incubations with a benthic chamber lander system: Performance, quality control and capabilities with recommendations for a best practice (Manuscript). Paper IV Hall, P. O. J., Almroth-Rosell, E., Bonaglia, S., Dale, A. W., Hylén, A., Kononets., M., Nilsson, M.ǡ‘‡”ǡǤǡ˜ƒ†‡‡Ž†‡ǡǤƒ†‹–‘”••‘ǡǤ

(13) ϐŽ—‡ ‡ ‘ˆ ƒ–—”ƒŽ ‘š›‰‡ƒ–‹‘ ‘ˆ ƒŽ–‹  ”‘’‡” †‡‡’ ™ƒ–‡” ‘ „‡–Š‹  recycling and removal of phosphorus, nitrogen, silicon and carbon Frontiers of Marine Sciences (2017) 4:27, doi: 10.3389/fmars.2017.00027. Publication not included in thesis ‹–‘”••‘ǡǤǡ‡”‘–ŠǡǤǡNilsson, M., Kononets, M. Y. and Hall, P. O. J. Phosphorous recycling in sediments of the central Baltic Sea Biogeosciences (2013) 10:6, doi: 10.5194/bg-10-3901-2013. viii.

(14) Author’s contribution Paper I Designed the study together with PH, NE, MK and SS. Contributed to the coordination of sediment sampling and to the lander deployments. Participated ‘ ‡š’‡†‹–‹‘• ƒ† ’”‘ ‡••‹‰ ‘ˆ •ƒ’Ž‡•Ǥ ƒ†‡ ‘•– ‘ˆ –Š‡ ƒŽ —Žƒ–‹‘•ǡ statistical analyses and evaluation of data. Did most of the writing of the manuscript.. Paper II Designed the study together with PH, NE and MK. Contributed to the coordination of sediment sampling and to the lander deployments. Participated ‘ ‡š’‡†‹–‹‘• ƒ† ’”‘ ‡••‹‰ ‘ˆ •ƒ’Ž‡•Ǥ ƒ†‡ ‘•– ‘ˆ –Š‡ ƒŽ —Žƒ–‹‘•ǡ statistical analyses and evaluation of data. Did most of the writing of the manuscript.. Paper III Contributed to the improvement of the benthic landers. Implemented the new technique to determine chamber volume together with AT. Participated on ‡š’‡†‹–‹‘•ǡƒ†‹’”‘ ‡••‹‰‘ˆ•ƒ’Ž‡•ƒ†ϐŽ—š†‡–‡”‹ƒ–‹‘•Ǥƒ†‡ƒ› of the calculations, statistical analyses and evaluation of data. Contributed to the writing of the manuscript.. Paper IV Contributed to the coordination of sediment sampling and to the lander †‡’Ž‘›‡–•Ǥ ƒ”–‹ ‹’ƒ–‡† ‘ ‡š’‡†‹–‹‘ ƒ† ’”‘ ‡••‹‰ ‘ˆ •ƒ’Ž‡•Ǥ Contributed to calculations, and evaluation of data. Contributed to writing of the manuscript.. ‹š.

(15)

(16) Part I Carbon Cycling in Baltic Sea Sediments - In situ investigations with benthic landers.

(17) Aims The main aim with this thesis was to study organic carbon (OC) cycling in sediments of the Baltic Sea and compare the patterns observed between the †‹ˆˆ‡”‡–•—„Ǧ„ƒ•‹•ǡ™Š‹ Š†‹ˆˆ‡”‹–‡”•‘ˆˆ‘”‡šƒ’Ž‡—–”‹‡–Ž‘ƒ†ǡ–”‘’Š‹  •–ƒ–—•ǡ•ƒŽ‹‹–›ƒ†‘š›‰‡”‡‰‹‡ȋ‹Ǥ‡Ǥ†‹ˆˆ‡”‡–‘š›‰‡Ž‡˜‡Ž•‹–Š‡‘˜‡”Ž›‹‰ bottom water). Another aim was to quantify, on a Baltic Sea system scale, –Š‡†‡’‘•‹–‹‘‘ˆ‘–Š‡•‡ƒϐŽ‘‘”ƒ† ‘’ƒ”‡–Š‹•‡•–‹ƒ–‡™‹–Š‘™ sources of OC. The rates of mineralization and preservation of OC and the factors that can ‹ϐŽ—‡ ‡‘” ‘–”‘Ž–Š‡•‡’”‘ ‡••‡•™‡”‡ƒŽ•‘‹˜‡•–‹‰ƒ–‡†ǤŠ‡‹˜‡•–‹‰ƒ–‹‘• were performed with benthic chamber landers, an advanced in situ technique which results in high quality measurements of the sediment biogeochemical processes with minimal disturbance of the sediment-water interface. Paper I of this thesis had the main goal to quantify the carbon recycling and „—”‹ƒŽ‹ƒŽ–‹ ‡ƒ•‡†‹‡–•ƒ†–‘ ‘•–”— –ƒ„ƒ•‹Ǧ•’‡ ‹ϐ‹ ǡ„‡–Š‹  ƒ”„‘ budget on the system-scale Paper II‹˜‡•–‹‰ƒ–‡•™Šƒ–ˆƒ –‘”• ‘–”‘Ž‘”‹ϐŽ—‡ ‡–Š‡•‡†‹‡–”‡ › Ž‹‰ ƒ†„—”‹ƒŽ”ƒ–‡•‘ˆ‹–Š‡ƒŽ–‹ ‡ƒǤ

(18) –Š‹• ‘–‡š–‘š‹†ƒ–‹‘‡ˆϐ‹ ‹‡ ›ǡ ‹Ǥ‡Ǥ ‘š‹†ƒ–‹‘ ”ƒ–‡ ’‡” ƒ˜ƒ‹Žƒ„Ž‡ ǡ ‹• ’”‡•‡–‡† ƒ• ƒ ’ƒ”ƒ‡–‡” –‘ ‡š’Žƒ‹ variability of OC recycling rates within and between basins. During my PhD studies there has also been work on developing and improving the benthic landers and how to optimize this in situ method. This work is discussed in Paper III. ƒ–—”‡ ‰ƒ˜‡ —• –Š‡ ‘’’‘”–—‹–› –‘ •–—†› –Š‡ ‡ˆˆ‡ –• ‘ˆ ƒ ƒ–—”ƒŽ ‘š›‰‡ƒ–‹‘ ‘ˆŽ‘‰Ǧ–‡”ƒ‘š‹ „‘––‘•ǤŠ‹•‘š›‰‡ƒ–‹‘™ƒ•†—‡–‘ƒŽƒ”‰‡‹–”—•‹‘‘ˆ ‘š›‰‡ƒ–‡†•ƒŽ–›™ƒ–‡”‹–‘–Š‡ƒŽ–‹ ”‘’‡”ǡƒ•‘Ǧ ƒŽŽ‡†ƒŒ‘”ƒŽ–‹ ‹ϐŽ‘™ǡ ™Š‹ Š•–ƒ”–‡†ƒ––Š‡‡†‘ˆʹͲͳͶǤŠ‡‡ˆˆ‡ –•‘ˆ–Š‹•ƒ–—”ƒŽ‘š›‰‡ƒ–‹‘‡˜‡– on benthic recycling of OC and other biogenic elements are discussed in Paper IV.. 12.

(19) 1. Introduction 1.1 Carbon in the marine and brackish water environments Carbon (C) is an element that has an important role in regulating the global climate. In the marine environment C is present in both organic form (total organic carbon, TOC) and inorganic form (total inorganic carbon, TIC). The TOC and TIC consist of both a particulate (POC and PIC) and a dissolved (DOC and DIC) fraction. POC and PIC is the C associated with living or dead biomass (e.g. detritus, fecal pellets and shells), whereas DOC and DIC are released during †‡‰”ƒ†ƒ–‹‘ ‘ˆ  ‘” †‹••‘Ž—–‹‘ ‘ˆ 

(20) Ǥ › ‘’‡”ƒ–‹‘ƒŽ †‡ϐ‹‹–‹‘  ‹• separated from DOC as the particle size fraction that does not pass through a ͲǤʹȂͳǤͲɊϐ‹Ž–‡”ȋ‹††‡Ž„—”‰‡–ƒŽǤǡͳͻͻ͵ȌǤ ‘™‡˜‡”–Š‡• ƒŽ‡ˆ”‘†‹••‘Ž˜‡† ‘”‰ƒ‹ •’‡ ‹‡•–‘’ƒ”–‹ Ž‡•‹• ‘–‹—‘—•ƒ†‡š–”‡‡Ž›•ƒŽŽ’ƒ”–‹ Ž‡•ǡ ‘ŽŽ‘‹†• ƒ†ƒ‰‰”‡‰ƒ–‡•ƒ›’ƒ••–Š”‘—‰Š–Š‡ϐ‹Ž–‡”ƒ†ƒ”‡–Š—•‘’‡”ƒ–‹‘ƒŽŽ›†‡ϐ‹‡† as dissolved (Linders et al., 2018 and references therein). Some marine phytoplankton produce hard shells, some of which are made of calcium carbonate (CaCOΝȌǤ Š‡•‡ •–”— –—”‡• †‡ϐ‹‡ –Š‡ 

(21)  ˆ”ƒ –‹‘ ƒ† contribute to DIC and alkalinity production upon dissolution. The DIC species are present in equilibrium with each other and form the marine carbonate system: COΜȋ‰Ȍ֖Μ(aq) (the equilibrium of gaseous and aqueous COΜ) Subsequent hydration and dissociation reactions: COΜ + HΜ֖ ΜCOΝ֖ ΆΪ Ν·֖ʹ ΆΪΝψ– (Eq. 1) The DIC or total carbonate (Cę) is the sum of the dissolved inorganic carbon •’‡ ‹‡•ƒ†‹ Ž—†‡• ƒ”„‘†‹‘š‹†‡ȋΜ), carbonic acid (HΜCOΝ), bicarbonate ion (HCOΝ–) and carbonate ion (COΝψ–) in aqueous form (Eq. 2). Bicarbonate and carbonate are the dominant forms in sea water. The COΜ(aq) and the HΜCOΝ ȋ™Š‹ Š‡š‹•–•‹˜‡”›Ž‘™ ‘ ‡–”ƒ–‹‘•Ȍƒ”‡‘ˆ–‡ ‘„‹‡†ƒ†”‡ˆ‡””‡†–‘ as COΜ* (Eq. 3).. 13.

(22) DIC or Cę = [COΜ(aq)]+ [HΜCOΝ]+ [HCOΝ–] + [COΝψ–] (Eq. 2) –. –. DIC or Cę = [COΜ*] + [HCOΝ ] + [COΝψ ] (Eq. 3) In a typical marine water mass below the photic zone, the dominant form of carbon is DIC. The higher concentration compared to the photic zone is mainly resulting from degradation of organic matter in the water column and sediments.. 1.2 Primary production and benthic pelagic coupling Particulate organic matter is formed during primary production with a stoichiometric composition of carbon and (macro) nutrients according to the ‡†ϐ‹‡Ž†”ƒ–‹‘ȋǣǣ‘ˆͳͲ͸ǣͳ͸ǣͳȌȋ‡†ϐ‹‡Ž†ǡͳͻͷͺȌǣ 106 COΜ + 16 NOΝ– + HPOΞψ– + 122 HΜΪͳͺ Ά -> (CHΜO)ΛΚΠ(NHΝ)ΛΠ(HΝPOΞ) + 138 OΜ (Eq. 4) When light and nutrient conditions are favorable, phytoplankton growth and primary production are stimulated. During primary production, COΜ or HCOΝ– is assimilated through photosynthesis ƒ†–”ƒ•ˆ‘”‡†–‘‹„‹‘ƒ••Ǥ‘‡‘ˆ–Š‡ȋ–Š‡‡š’‘”–’”‘†— –‹‘Ȍ sinks through the water column and is degraded and mineralized in the water column into DIC. The reverse form of the formula for photosynthesis (Eq. 4) represents respiration (i.e. organic matter degradation). The fraction of •‹‹‰–Šƒ–‡• ƒ’‡•’‡Žƒ‰‹ ‹‡”ƒŽ‹œƒ–‹‘†‡’‘•‹–•‘–Š‡•‡ƒϐŽ‘‘”ǤŠ‹• drawdown of C from the ocean surface to the deeper layers and sediments is known as the ‘biological C pump’ (Fig. 1). –Š‡”•‘—” ‡•ƒŽ•‘ ‘–”‹„—–‡–‘–Š‡˜‡”–‹ ƒŽ’ƒ”–‹ Ž‡ϐŽ—šǡ‡•’‡ ‹ƒŽŽ›‹ ‘ƒ•–ƒŽ seas were land derived POC is transported to the sea via rivers (Elmgren, 1984;. —•–ƒˆ••‘‡–ƒŽǤǡʹͲͳͶȌǡƒ†‹‡•–—ƒ”‹‡•™‡”‡‹š‹‰‘ˆˆ”‡•Šƒ†•ƒŽ‹‡™ƒ–‡”• ”‡•—Ž–•‹ƒ‰‰”‡‰ƒ–‹‘‘”ϐŽ‘ —Žƒ–‹‘‘ˆȋ•ƒŽƒ‡–ƒŽǤǡʹͲͳͶƒ†”‡ˆ‡”‡ ‡• therin). 14.

(23) KЇ KЇ ŽŽƉůĂŶŬƚŽŶĂŶĚĂŶŝŵĂůƐ WŚLJƚŽƉůĂŶŬƚŽŶ WK ĂĐƚĞƌŝĂ. /. Figure 1 ‹‘Ž‘‰‹ ƒŽ’—’ƒ†‡šƒ’Ž‡•‘ˆ ‘—’Ž‹‰„‡–™‡‡’‡Žƒ‰‹ ƒ†„‡–Š‹ ’”‘ ‡••‡•. Š‡ ˜‡”–‹ ƒŽ  ϐŽ—š –Š—• ‘•‹•–• ‘ˆ „‘–Š ‘ˆ •‹‹‰ ƒ”‹‡  ȋȌǡ –‡””‡•–”‹ƒŽȋ–Ȍƒ†ƒ‰‰”‡‰ƒ–‡•‘”ϐŽ‘ •‘ˆǤ. (DUO\GLDJHQHVLVDQGVHGLPHQWZDWHUÀX[HVRIFDUERQ • ‘”‰ƒ‹  ƒ––‡” •‡––Ž‡• ‘ –Š‡ •‡ƒ ϐŽ‘‘” ‹– ™‹ŽŽ „‡ †‡‰”ƒ†‡† „› ‹ ”‘„‡• ƒ† ˆƒ—ƒǤ Š‡ •–”— –—”‡ ‘ˆ –Š‡ „‡–Š‹  ‘—‹–› ‹• †‡–‡”‹‡† „› –Š‡ ’Š›•‹ ‘ Š‡‹ ƒŽ ˆƒ –‘”• ƒ– –Š‡ •‡ƒ ϐŽ‘‘” ‡Ǥ‰Ǥ ™ƒ–‡” Š›†”‘†›ƒ‹ • ȋ„‘––‘Ǧ •–”‡••Ȍǡ †‡’‘•‹–‹‘ƒŽ ‘†‹–‹‘•ǡ Ž‹‰Š–ǡ –‡’‡”ƒ–—”‡ ƒ† —–”‹‡– ƒ˜ƒ‹Žƒ„‹Ž‹–› ȋ‡‹‰ ƒ† ƒ”‘••ǡ ͳͻͻ͵Ǣ ڕ–‡” ƒ† ‡›‡”Ǧ‡‹Žǡ ʹͲͲͳȌǤ  Š‡ „‹‘Ž‘‰‹ ƒŽǡ Š‡‹ ƒŽ ƒ† ’Š›•‹ ƒŽ ’”‘ ‡••‡• ƒˆˆ‡ –‹‰ –Š‡ ‘’‘•‹–‹‘ ƒ† “—ƒ–‹–› ‘ˆ ‘”‰ƒ‹ ƒ––‡”™‹–Š‹–Š‡•‡†‹‡–ƒˆ–‡”†‡’‘•‹–‹‘‹• ƒŽŽ‡††‹ƒ‰‡‡•‹•Ǥƒ”Ž› †‹ƒ‰‡‡•‹•”‡ˆ‡”•–‘–Š‡‘•–”‡ ‡–’”‘ ‡••‡•–Šƒ––ƒ‡’Žƒ ‡‹–Š‡—’’‡”Žƒ›‡” ‘ˆ–Š‡•‡†‹‡–ȋ‡”‡”ǡͳͻͺͲǢ ‡”‹ Š•ǡͳͻͻʹȌǤ Š‡ ’‘‘Ž ‘ˆ ‘”‰ƒ‹  ƒ––‡” ‹ –Š‡ •‡†‹‡– ƒ† ’‘”‡ ™ƒ–‡” •›•–‡ ‘•‹•–• ‘ˆƒ‹š–—”‡‘ˆ†‹ˆˆ‡”‡–ˆ”ƒ –‹‘•‘ˆƒ†

(24) ǤŠ‡‰‡‡”ƒŽŽ›Žƒ”‰‡•–’‘‘Ž‹ ‘ƒ•–ƒŽ ƒ† ‘–‹‡–ƒŽ ƒ”‰‹ •‡†‹‡–• ‹•  ƒ† ‘Ž› ƒ ˆ‡™ ’‡” ‡– ‹•  ƒ† „‹‘ƒ•• ƒ”„‘ ȋȌ ȋڕ–‡” ƒ† ‡›‡”Ǧ‡‹Žǡ ʹͲͲͳȌǤ ‘™‡˜‡”ǡ ‹ •‡˜‡”ƒŽ †‡‡’Ǧ•‡ƒ •‡†‹‡–•ǡ •— Š ƒ• ƒŽ ƒ”‡‘—• ‘‘œ‡ •‡†‹‡–•ǡ –Š‡ ƒŒ‘”  ‘’‘‡–‹•

(25) ȋ‡Ǥ‰Ǥ–¤ŠŽ‡–ƒŽǤǡʹͲͲͶ„ȌǤŠ‡†‹ˆˆ‡”‡–•‘—” ‡•ƒ”‡‘ˆ–‡ ͳͷ.

(26) Žƒ••‹ϐ‹‡†ƒ ‘”†‹‰–‘–Š‡‹””‡ƒ –‹˜‹–›™‹–Š”‡•’‡ ––‘‹‡”ƒŽ‹œƒ–‹‘’”‘ ‡••‡•ǡ going from labile (short lived, most reactive) to refractory (long lived, least reactive) (Hansell, 2013). Among the more refractory materials are terrestrial OC, which can be transported long distances from its origin. On the other end of the spectra is the more labile marine OC. Š‡ƒ””‹˜‡•ƒ––Š‡•‡†‹‡–•—”ˆƒ ‡ƒ•‹–—•–ϐ‹”•–„‡–”ƒ•ˆ‘”‡†–‘ DOC before it can be used as an energy source by bacteria. This transformation can occur both through grazing by benthic fauna or by hydrolyzation with ‡š–”ƒ ‡ŽŽ—Žƒ” ‡œ›‡• „› ‹ ”‘„‡•Ǥ  ƒ „‡ ’”‘–‡ –‡† ˆ”‘ ‹ ”‘„‹ƒŽ degradation by adsorbtion to particles (Borch and Kirchman, 1999; Keil et al., ͳͻͻͶȌǤƒ –‡”‹ƒ‰ƒ‹‡‡”‰›ˆ”‘‘š‹†ƒ–‹‘‘ˆ™‹–Š†‹ˆˆ‡”‡–‘š‹†ƒ–•ǡ•— Š ƒ•‘š›‰‡ǡ‹–”ƒ–‡ȋΝ–Ȍǡƒ‰ƒ‡•‡ƒ†‹”‘‘š‹†‡•ȋΜ and Fe(OH)Ν), and sulfate (SOΞψ–). The different diagenetic pathways, their reactions and energy ›‹‡Ž†•ȋȟ φ) are described in Table 1. The most energetic reaction is favored —–‹Ž –Š‡ ‘””‡•’‘†‹‰ ‡Ž‡ –”‘ ƒ ‡’–‘” ‹• ˆ—ŽŽ› †‡’Ž‡–‡†ǡ –Š‡ –Š‡ ‡š– ‘•–‡ˆϐ‹ ‹‡–”‡ƒ –‹‘•–ƒ”–•Ǥ ‘™‡˜‡”ǡ–Š‡‹–‡”ƒ –‹‘•„‡–™‡‡–Š‡†‹ˆˆ‡”‡– ’ƒ–Š™ƒ›•ƒ”‡‘”‡ ‘’Ž‡šƒ•†‹• —••‡†‹‡Ǥ‰Ǥƒϐ‹‡Ž†‡–ƒŽǤȋͳͻͻ͵ȌǤŠ‡‡– effect of early diagenetic processes in terms of carbon is the conversion of POC to DOC, DIC and methane (CHΞ). Table 1 ‹ƒ‰‡‡–‹  ’ƒ–Š™ƒ›• ‘ˆ ‘š‹†ƒ–‹‘ ‘ˆ ‘”‰ƒ‹  ƒ”„‘ ‹ ƒ”‹‡ •‡†‹‡–• ȋƒϐ‹‡Ž†ǡ 1993). Marked in bold are the C species that contribute directly to the DIC formation in sediments according to Eq. 3.. ȟ ͼ. Diagenetic pathway. Reaction. Aerobic respiration. CHΜO + OΜ = COΜ + HΜO. ‡‹–”‹ϐ‹ ƒ–‹‘. CHΜΪϊΤΟΝ = ϊΤΟ Ν + χΤΟΜΪψΤΟΜΪωΤΟ ΜO. Manganese reduction Iron reduction. –. -475 –. +. –. CHΜO + 3COΜ + HΜO + 2MnOΜ = 2Mnψ + 4HCOΝ +. –. CHΜO + 7COΜ + 4Fe(OH)Ν = 4Feψ + 8HCOΝ + 3HΜO –. –. -448 -349 -114. Sulfate reduction. CHΜO + ½SOΞψ = ½HΜS + HCOΝ. -77. Methanogenesis. CHΜO = ½CHΞ + ½COΜ. -58. The mineralization of organic matter has traditionally been, and is still often “—ƒ–‹ϐ‹‡†ƒ•–Š‡Ž‘••‘ˆ‘š›‰‡‘”ƒ•–Š‡‹ ”‡ƒ•‡‘ˆŠ›†”‘‰‡•—Žϐ‹†‡ȋ ΜS). This approach is not representative for total mineralization rates since several ‘–Š‡” ‘š‹†ƒ–• ȋ‘– ‘Ž› ‘š›‰‡ ƒ† •—Žˆƒ–‡Ȍ ƒ”‡ —•‡† –‘ ‘š‹†‹œ‡  †—”‹‰ ‡ƒ”Ž› †‹ƒ‰‡‡•‹• ȋƒ„Ž‡ ͳȌǤ

(27)  ˆƒ – ‘š›‰‡ ‹• •‡Ž†‘ –Š‡ ƒ‹ †‹”‡ – ‘š‹†ƒ– 16.

(28) in sediments with high sediment accumulation rates and high OC contents, ™Š‹ Š‘ˆ–‡‘Ž›Šƒ˜‡ƒˆ‡™†‡’–Š‘ˆ‘š›‰‡’‡‡–”ƒ–‹‘ǡ‘”Žƒ ‘š›‰‡ ‘’Ž‡–‡Ž› ȋ‡‰Ǥ ‘ŠŽ‡ ‡– ƒŽǤǡ ʹͲͳͳǢ ƒϐ‹‡Ž† ‡– ƒŽǤǡ ʹͲͲͷȌǤ

(29)  •‡†‹‡–• –Šƒ– —†‡”Ž‹‡ƒ‘š‹ ™ƒ–‡”•‹–‹•‘ˆ ‘—”•‡‹’‘••‹„Ž‡–‘‡•–‹ƒ–‡‹‡”ƒŽ‹œƒ–‹‘‘ˆ ‘”‰ƒ‹ ƒ––‡”„›‡ƒ•—”‹‰‘š›‰‡ ‘•—’–‹‘Ǥ › ‘–”ƒ•–ǡ‘š‹†ƒ–‹‘‡•–‹ƒ–‡†ˆ”‘–Š‡”‡Ž‡ƒ•‡‘ˆ

(30) ˆ”‘–Š‡•‡†‹‡–• ƒ’–—”‡• –Š‡ ‡– ”‡•—Ž– ˆ”‘ ƒŽŽ ‘š‹†ƒ–‹‘ •–‡’•ǡ ’”‘˜‹†‡† –Šƒ– ƒ”„‘ƒ–‡ dissolution and methanogenesis is negligible. If there is a large contribution from carbonate dissolution it can lead to an overestimate of organic matter mineralization, since the process will yield carbonate ions (Eq. 3). Also, if the sediment has a high rate of methanogenesis, a large amount of methane is produced. A fraction of it can be lost in dissolved form or as gas bubbles to the ‘˜‡”Ž›‹‰ ™ƒ–‡” ™‹–Š –Š‡ ’‘–‡–‹ƒŽ ”‹• ‘ˆ —†‡”‡•–‹ƒ–‹‰ –Š‡  ‘š‹†ƒ–‹‘ ”ƒ–‡Ǥ ‘™‡˜‡”ǡ‘•–‘ˆ–Š‡’”‘†— ‡†‡–Šƒ‡‹•‘š‹†‹œ‡†‹–Š‡—’’‡”•‡†‹‡– layer with nitrate, nitrite (NOΜ–) or sulfate to DIC (e.g. Iversen and Jørgensen, 1985): CHΞ + 4NOΝΫ՜COΜ + 4NOΜΫ + 2HΜO 3CHΞ + 8NOΜΫΪͺ Ά՜3COΜ + 4NΜ + 10HΜO CHΞ + SOΞψΫ՜HCOΝΫ + HSΫ + HΜO Š‡‡ˆˆ‡ –‘‡ƒ•—”‡†

(31) ϐŽ—š‡•‘ˆ’”‘ ‡••‡•‘ˆ ƒŽ ‹— ƒ”„‘ƒ–‡†‹••‘Ž—–‹‘ and methanogenesis can be corrected for by simultaneous measurements of ƒŽƒŽ‹‹–› ‘” ‡–Šƒ‡ ϐŽ—šǤ ‡–‡”‹‹‰ ‘”‰ƒ‹  ƒ––‡” ‹‡”ƒŽ‹œƒ–‹‘ ˆ”‘ 

(32) ϐŽ—š‡ƒ•—”‡‡–•ˆ”‘–Š‡•‡†‹‡–‹•ˆ‘”–Š‡”‡ƒ•‘•‡–‹‘‡†ƒ„‘˜‡ ’”‡ˆ‡”ƒ„Ž‡ ™Š‡ ™‘”‹‰ ‹ ‘”‰ƒ‹  ”‹ Š •‡†‹‡–• ‹ Ž‘™ ‘š›‰‡ ‘” ƒ‘š‹  environments.. 1.4 Burial or preservation of OC The fraction of OC that escapes mineralization, either because of its chemical structure or the environmental conditions, will be buried for long timescales. The burial of marine OC will thus have an effect on the ocean’s capacity to take up atmospheric COΜ on these timescales (Berner, 2004; Burdige, 2007; Hedges and Keil, 1995).. 17.

(33) —”‹ƒŽ‹•‡š’‡ –‡†–‘‹ ”‡ƒ•‡ƒ•–Š‡†‡’‘•‹–‹‘”ƒ–‡‘ˆ‹ ”‡ƒ•‡•ȋ ‡”‹ Š• and Reeburgh, 1987; Müller and Suess, 1979; Stein et al., 1986) since the ƒ˜ƒ‹Žƒ„Ž‡‘š‹†ƒ–•ȋ’”‹ƒ”‹Ž›‘š›‰‡Ȍ‰‡–†‡’Ž‡–‡†ˆƒ•–†—‡–‘–Š‡‹–‡•‹ϐ‹‡†  ‘š‹†ƒ–‹‘ ȋƒϐ‹‡Ž†ǡ ͳͻͻ͵Ȍǡ ƒ† ƒ‘š‹  ‘š‹†ƒ–‹‘ ‘ˆ  ‹• •Ž‘™‡” ƒ† Ž‡•• ‡ˆϐ‹ ‹‡––Šƒƒ‡”‘„‹ ȋ —Ž–Š‡‡–ƒŽǤǡͳͻͻͺȌǤ —”‹ƒŽ‡ˆϐ‹ ‹‡ ›ǡ™Š‹ Š‹•–Š‡”ƒ–‹‘‘ˆ„—”‹ƒŽ”ƒ–‡ƒ†–Š‡ ƒ”„‘†‡’‘•‹–‹‘ rate to the sediment surface, can be used to compare preservation rates between areas of different productivity and sedimentary deposition. Several factors are •—‰‰‡•–‡†–‘‹ϐŽ—‡ ‡–Š‡„—”‹ƒŽ‡ˆϐ‹ ‹‡ ›‘ˆƒ•‡†‹‡–ǢͳȌŠ‡•‡†‹‡– ƒ ——Žƒ–‹‘”ƒ–‡ȋ‡Ǥ‰ǤŽŽ‡”ǡʹͲͳͶǢƒϐ‹‡Ž†ǡͳͻͻͶƒ†”‡ˆ‡”‡ ‡•–Š‡”‡‹ȌǤʹȌ The composition and reactivity of the organic matter. Marine organic matter is preferentially degraded compared to terrestrial organic matter (Burdige, ʹͲͲ͸ȌǤ͵ȌŠ‡†‘‹ƒ–‘š‹†ƒ–ƒ†–‹‡‘ˆ‡š’‘•—”‡–‘‘š›‰‡ȋ ƒ”–‡––‡–ƒŽǤǡ ͳͻͻͺȌǤ ”‡•ŠŽƒ„‹Ž‡‘”‰ƒ‹ ƒ––‡”‹•†‡‰”ƒ†‡†‡“—ƒŽŽ›ˆƒ•–‹‘š‹ ƒ†ƒ‘š‹  sediments, however old and refractory organic matter is degraded slower in ƒ‘š‹ –Šƒ‹‘š‹ •‡†‹‡–•ȋ —Ž–Š‡‡–ƒŽǤǡͳͻͻͺȌǤ

(34) –Šƒ•ƒŽ•‘„‡‡‘„•‡”˜‡† –Šƒ– ”‡’‡ƒ–‡† ‡š’‘•—”‡ ‘ˆ ‘Ž† ƒ† ”‡ˆ”ƒ –‘”› ‘”‰ƒ‹  ƒ––‡” –‘ ‘š›‰‡ ƒ† ƒ‘š‹ƒȋˆƒ ‹Ž‹–ƒ–‡†‡Ǥ‰Ǥ„›„‹‘–—”„ƒ–‹‰ƒ‹ƒŽ•Ȍ•–‹—Žƒ–‡•†‡‰”ƒ†ƒ–‹‘ȋ —Ž–Š‡ et al., 1998; Aller, 2014 and references therein). 4) Degradation protection by adsorption to mineral surfaces (Hedges and Keil, 1995; Mayer, 1994). Marine sediments can have a total organic carbon (TOC) content from less than 0.0025 % C of sediment dry weight (% dwt) in open ocean sediments to about 20 % dwt, in coastal sediments (Burdige, 2007 and references therein). —”‹ƒŽ‡ˆϐ‹ ‹‡ ‹‡•ȋ„—”‹ƒŽ”ƒ–‡Ȁ†‡’‘•‹–‹‘”ƒ–‡Ȍ‘ˆ–‡‡š ‡‡†ͳͲȂʹͲΨ‹ sediments with high sediment accumulation rates in normal marine settings. ‘™‡˜‡”ǡ–Š‡„—”‹ƒŽ‡ˆϐ‹ ‹‡ ‹‡•‘ˆƒ”‹‡–‡†–‘„‡Ž‘™‡”‹—††›†‡Ž–ƒ‹  •‡†‹‡–• ™‹–Š ƒ”‹‡ ‘”‰ƒ‹  ƒ––‡” „‡‹‰ ‘”‡ ‡ˆϐ‹ ‹‡–Ž› ”‡‹‡”ƒŽ‹•‡† than terrestrial organic matter (Burdige, 2006).. 18.

(35) 7KH%DOWLF6HD Š‡ƒŽ–‹ ‡ƒȋ͵ͻʹͻ͹ͺ;ǡ ‹‰ǤʹȌ‹•–Š‡™‘”Ž†ǯ•Žƒ”‰‡•– ‘–‹‡–ƒŽ„”ƒ ‹•ŠǦ ™ƒ–‡”•‡ƒȋ‘‡‹Œ•Ǧ‡‹Œ‘ƒŽ‡–ƒŽǤǡʹͲͳ͸Ȍǡ™‹–Šƒ‡ƒ†‡’–Š‘ˆͷͶƒ†ƒ ˜‘Ž—‡‘ˆʹͳʹͲͷωȋ‡’’¡”ƒ–ƒƒ†›”„‡”‰ǡʹͲͲͻȌǤ Š‡ƒŽ–‹ ‡ƒ‹•†‹˜‹†‡†‹–‘ƒ—„‡”‘ˆ•—„Ǧ„ƒ•‹•ǤŠ‡ƒŽ–‹ ”‘’‡”ƒ† –™‘ƒŒ‘”‰—Žˆ•ǡ–Š‡ —Žˆ‘ˆ‘–Š‹ƒƒ†–Š‡ —Žˆ‘ˆ ‹Žƒ†ƒ”‡ ‘•‹†‡”‡†‹ –Š‹•–Š‡•‹•Ǥ. Figure 2 ƒ’‘ˆ–Š‡ƒŽ–‹ ‡ƒǤ. Š‡ƒ‹„ƒ•‹ȋ͸ͶΨ‘ˆ–‘–ƒŽ™ƒ–‡”˜‘Ž—‡Ȍ‹•–Š‡ƒŽ–‹ ”‘’‡”ǡ™Š‡”‡–Š‡ ‰”‡ƒ–‡•– †‡’–Š ȋ–Š‡ ƒ†•‘”– †‡‡’ǡ Ͷͷͻ Ȍ ‹• ˆ‘—† ȋ‘‡‹Œ•Ǧ‡‹Œ‘ƒŽ ‡– ƒŽǤǡʹͲͳ͸ȌǤ‘–Š‡”†‡‡’•‹–‡‹–Š‡ƒŽ–‹ ”‘’‡”‹•–Š‡ ‘–Žƒ††‡‡’ȋʹͶͻȌ Ž‘ ƒ–‡†‹–Š‡ƒ•–‡” ‘–Žƒ†ƒ•‹™Š‡”‡•‡˜‡”ƒŽ•–ƒ–‹‘•‘ˆ–Š‹••–—†›ƒ”‡ Ž‘ ƒ–‡†ǤŠ‡ƒŽ–‹ ”‘’‡”‹• ‘‡ –‡†–‘–Š‡ —Žˆ‘ˆ‘–Š‹ƒ‹–Š‡‘”–Šƒ† –‘–Š‡ —Žˆ‘ˆ ‹Žƒ†‹–Š‡‡ƒ•–Ǥ Š‡•‹ŽŽ•ȋǮ‘—–Š‡”—ƒ”ǯǡ͹ͲȌƒ†–Š‡•ŠƒŽŽ‘™” Š‹’‡Žƒ‰‘‡ƒ„‡–™‡‡–Š‡ ƒŽ–‹ ”‘’‡”ƒ†–Š‡ —Žˆ‘ˆ‘–Š‹ƒŽ‹‹–•–Š‡™ƒ–‡”‡š Šƒ‰‡„‡–™‡‡–Š‡Ǥ ‘™‡˜‡”ǡ–Š‡”‡‹•‘•‹ŽŽ–Šƒ–†‡ϐ‹‡–Š‡„‘”†‡”„‡–™‡‡–Š‡ƒŽ–‹ ’”‘’‡”ƒ† –Š‡ —Žˆ‘ˆ ‹Žƒ†ȋ‘‡‹Œ•Ǧ‡‹Œ‘ƒŽ‡–ƒŽǤǡʹͲͳ͸Ȍƒ‹‰‹–’‘••‹„Ž‡ˆ‘”ƒ Ž‘•‡”‹–‡”ƒ –‹‘„‡–™‡‡–Š‡•‡–™‘•›•–‡•ǤŠ‡ —Žˆ‘ˆ ‹Žƒ†‹•–Š‡‘•– ͳͻ.

(36) •ŠƒŽŽ‘™•›•–‡™‹–Šƒƒ˜‡”ƒ‰‡™ƒ–‡”†‡’–Š‘ˆ͵͹ǡ™Š‡”‡ƒ•–Š‡ƒš‹— water depth is 123 m (Leppäranta and Myrberg, 2009). The Gulf of Bothnia has a mean depth of 54 m and is further sub-divided into –Š‡‘–Š‹ƒ‡ƒƒ†‘–Š‹ƒƒ›™‹–Šƒš‹—™ƒ–‡”†‡’–Š•‘ˆʹͻ͵ƒ† 146 m, respectively. The sill between them is only 25 m (‘Northern Quark’) (Leppäranta and Myrberg, 2009). The Gulf of Bothnia has a mean depth of 54 m and is further sub-divided into –Š‡‘–Š‹ƒ‡ƒƒ†‘–Š‹ƒƒ›™‹–Šƒš‹—™ƒ–‡”†‡’–Š•‘ˆʹͻ͵ƒ† 146 m, respectively. The sill between them is only 25 m (‘Northern Quark’) (Leppäranta and Myrberg, 2009).. :DWHUVXSSO\DQGH[FKDQJH The Baltic Sea can be seen as a large semi-enclosed brackish water estuary with a mean salinity of 7.4 (Leppäranta and Myrberg, 2009), with a large (on average 500 kmω yr–χȌ”‹˜‡”‹‡‹ϐŽ‘™‘ˆˆ”‡•Š™ƒ–‡”‹–Š‡‘”–Š‡”ƒ†‡ƒ•–‡” part. In the southern part the Baltic Sea is connected to the North Sea via the Danish straits and Öresund through which denser more saline water enters the •›•–‡ƒŽ‘‰–Š‡•‡ƒϐŽ‘‘”Ǥ The ten largest rivers (according to their drainage area) that discharge into the Baltic Sea (summarized in Table 2) account for 55 % of the total freshwater ‹ϐŽ‘™Ǥ Š‡ ‹ϐŽ‘™ ˆ”‘ ”‹˜‡”• ƒ† –Š‡ ‡š Šƒ‰‡ –Š”‘—‰Š –Š‡ •–”ƒ‹–• ƒ”‡ ‹’‘”–ƒ– processes that affect the physical, biogeochemical and ecological state of the •›•–‡ǤŠ‡‘—–ϐŽ‘™‘ˆ„”ƒ ‹•Š™ƒ–‡”‹•„ƒŽƒ ‡†„›ƒ‹ϐŽ‘™‘ˆ†‡•‡”•ƒŽ‹‡ ™ƒ–‡””‡•—Ž–‹‰‹ƒ‡–‘—–ϐŽ‘™–Š”‘—‰Š–Š‡•–”ƒ‹–•‘ˆͷͲͲω yr–χ (Gustafsson, ʹͲͳͲȌǤŠ‡‹ϐŽ‘™‹‰™ƒ–‡”†‘‡•‘–Šƒ˜‡–Š‡•ƒ‡•ƒŽ‹‹–›ƒ•–Š‡‘”–Š‡ƒ ™ƒ–‡”ǡ™Š‹ Š‹†‹ ƒ–‡•–Šƒ––Š‡‹ϐŽ‘™‹‰™ƒ–‡”‹•ƒ‹š–—”‡‘ˆ‘Ž†ƒŽ–‹ ‡ƒ water and North Sea water. —”‹‰ ‡”–ƒ‹™‡ƒ–Š‡” ‘†‹–‹‘•ƒ•‘Ǧ ƒŽŽ‡†ƒŒ‘”ƒŽ–‹ ‹ϐŽ‘™ ƒ‘ —”Ǥ longer period (weeks) of strong easterly winds can push the Baltic Sea water out of the system with a resulting decrease in sea level. If the winds then change direction to the west, the sea level in the Kattegat will rise. The sea 20.

(37) 21. 392 338. 40 100 37 200. SWE/FIN. FIN. Torne. Kymi 7658. 574. 50 100. SWE. Göta. 1 015 400. 562. 51 400. Kemi. Total. 403. 659. 87 900 56 200. 632. 98 200. FIN. ȀȀȀȀ. Daugauva. 573. 118 900. EST/RUS. BY/LIT/RUS. Nemunas. 1065. 2460. Mean annual discharge (mω s–χ). 194 400. 281 000. (kmψ). Drainage area. Narva. POL/GER/CZR. Odra. POL/UKR/BY/SLK. RUS/FIN. Neva. ‹•–—Žƒ. Country. River. 55. 2.4. 2.8. 4.1. 4.0. 2.9. 4.7. 4.5. 4.1. 7.6. 17.6. % of total ”‹˜‡”‹ϐŽ‘™–‘ the Baltic Sea. 8.2. 9.1. 9.8. 11.5. 11.0. 7.2. 7.5. 6.4. 4.8. 5.5. 5073.5. 21.9. 28.9. 63.8. 1.3. 384. 1068. 609. 431. 1168.1. 1295. 2427.5. 46.2. 102.4. 80.5. 2.1. 190.9. 210.7. 123.4. 75.5. 175.6. 1209.5. (Gg yr–χ). (Gg yrǧχ). (L km–ψ s–χ). 8.8. TOC. TIC. Run off. Table 2 The ten largest rivers according to drainage area feeding into the Baltic Sea region (BACC Author Team, 2015; Kulinski and Pempkowiak, 2011). The Göta river is draining into the Kattegat, which is sometimes included into the Baltic Sea region..

(38) level difference between the Kattegat and the Baltic Sea may then result in a Žƒ”‰‡‹ϐŽ‘™‘ˆ†‡•‡•ƒŽ–›•‡ƒ™ƒ–‡”ƒŽ‘‰–Š‡•‡ƒϐŽ‘‘”‹–‘–Š‡ƒŽ–‹ ‡ƒǤ

(39)  the northernmost basin, the Bothnian Bay, the circulation and renewal of deep water take place in winter when surface water is cooling and thus gets heavier ƒ†•‹•–‘™ƒ”†•–Š‡•‡ƒϐŽ‘‘”Ǥ. (XWURSKLFDWLRQDQGK\SR[LD The drainage area of the Baltic Sea is 1.74 million km² and it is inhabited „› ƒ’’”‘š‹ƒ–‡Ž› ͳͷͲ ‹ŽŽ‹‘ ’‡‘’Ž‡ ‘ˆ ™Š‹ Š ͺͲȂͻͲ ‹ŽŽ‹‘ Ž‹˜‡ ‹ ‘ƒ•–ƒŽ areas (BACC Author Team, 2015; Leppäranta and Myrberg, 2009; SnoeijsLeijonmalm et al., 2016). The 10 largest rivers (Table 2.) contribute with nearly 70 % of the total C (10.9 Tg C yr–χ, (Kulinski and Pempkowiak, 2011) load to the Baltic Sea region. The fraction of OC load is around 40 % (4.09 Tg C yr–χ) of this total C load (Kulinski and Pempkowiak, 2011). The northern parts of the basin are characterized by less populated areas and rivers drain the boreal zones resulting in a river load enriched in carbon, but low in nutrients. The low nutrient input to the Gulf of Bothnia makes this ecosystem oligotrophic, especially in the Bothnian Bay (Humborg et al., 2003; Lundberg et al., 2009). The large rivers draining the eastern Baltic states results in a large nitrogen and phosphorous load. The largest load is found in the Gulf of Finland where –Š‡”‹˜‡”‡˜ƒ†‡Ž‹˜‡”•ƒ”‘—†ͳ͹Ψ‘ˆ–Š‡–‘–ƒŽ‹ϐŽ‘™‘ˆ™ƒ–‡”–‘–Š‡ƒŽ–‹  ‡ƒǤ ‹˜‡”• ‘–”‹„—–‡ ™‹–Š ƒ’’”‘š‹ƒ–‡Ž› ͹Ͳ Ψ ‘ˆ –Š‡ ƒ—ƒŽ ’Š‘•’Š‘”‘—• and 50 % of the annual nitrogen input to the Baltic Sea (Wulff et al., 2001). In an enclosed system, like the Baltic Sea, the long renewal time of the water masses (30–40 years) (Snoeijs-Leijonmalm et al., 2016) makes the system especially sensitive to land and human activities. This means that carbon and associated nutrients are recycled several times before they get buried or leave –Š‡•›•–‡–Š”‘—‰Š™ƒ–‡”‡š Šƒ‰‡™‹–Š–Š‡•‡ƒ‘—–•‹†‡Ǥ

(40) ˆ–Š‡„ƒŽƒ ‡„‡–™‡‡ the sources and sinks of a system is disturbed it can have consequences on the ‡ ‘•›•–‡ǡ•— Šƒ•‡—–”‘’Š‹ ƒ–‹‘ƒ†•’”‡ƒ†‹‰‘ˆ‘š›‰‡†‡’Ž‡–‡†ȋŠ›’‘š‹ Ȍ ‘”ƒ‘š‹ ƒ”‡ƒ•Ǥ The use of industrial fertilizers increased during the 1950s and led to increased amounts of bioavailable nutrients (nitrogen and phosphorous) and ‡—–”‘’Š‹ ƒ–‹‘ ‹ –Š‡ ƒŽ–‹  ‡ƒǤ Š‡ –‘–ƒŽ ‡š–‡”ƒŽ •—’’Ž› ‘ˆ ‹–”‘‰‡ ƒ† 22.

(41) phosphorous has increased by a factor of two and three, respectively, during the last century (Savchuk et al., 2008). This has led to an enhanced net production of organic matter (Schneider and Kuss, 2004). If the supply of organic matter is large enough, and especially when water renewal is infrequent, the degradation of organic matter, both in the water ‘Ž—ƒ†ƒ––Š‡•‡ƒϐŽ‘‘”ǡ ƒŽ‡ƒ†–‘†‡’Ž‡–‹‘‘ˆ‘š›‰‡‹–Š‡™ƒ–‡”ƒ••Ǥ ›’‘š‹ƒ‹• ‘‘‹ƒ”‡ƒ•™‹–ŠŽ‹‹–‡†‡™•—’’Ž›‘ˆ‘š›‰‡ƒ–‡†™ƒ–‡”ƒ† ƒ’”‘‘— ‡†•–”ƒ–‹ϐ‹ ƒ–‹‘‘ˆ–Š‡™ƒ–‡” ‘Ž—ǡ™Š‹ Š‹•–Š‡ ƒ•‡‹’ƒ”–•‘ˆ –Š‡ ƒŽ–‹  ‡ƒǤ Š‡ ƒŽ–‹  ‡ƒ Šƒ• ‡š’‡”‹‡ ‡† Š›’‘š‹ƒ ‘ ƒ•‹‘ƒŽŽ› •‹ ‡ ‹–• ˆ‘”ƒ–‹‘ ȋ‹ƒ Š‹ ‡– ƒŽǤǡ ʹͲͲͲǢ ‹ŽŽ± ‡– ƒŽǤǡ ʹͲͲͺȌǤ ‹ ‡ –Š‡ ͳͻͷͲ• Š›’‘š‹ƒ has increased, both in intensity and in spatial coverage (Conley et al., 2009b). Š‡ƒ”‡ƒ™‹–ŠŠ›’‘š‹ ™ƒ–‡”•‹”‡ ‡–›‡ƒ”•‹•ƒ„‘—–ˆ‘—”–‹‡•Žƒ”‰‡”–Šƒ‹ the 1960s (Jonsson et al., 1990), and covered an area averaging 49 000 km² in –Š‡’‡”‹‘†ͳͻ͸ͳȂʹͲͲͲȋ‘Ž‡›‡–ƒŽǤǡʹͲͲͻƒȌǤŠ‡‡ƒƒ”‡ƒŽ‡š–‡–‘ˆŠ›’‘š‹ƒ ƒ† ƒ‘š‹ƒ ™ƒ• ‹ ʹͲͳ͹ ‡•–‹ƒ–‡† ƒ– ƒ”‘—† Ͷ͸ Ψ ‘ˆ –Š‡ ƒŽ–‹  ”‘’‡” ƒ”‡ƒ (Hansson et al., 2017). Š‡ ‹ ”‡ƒ•‡ ‘ˆ Š›’‘š‹  ƒ”‡ƒ• ‹ –Š‡ ƒŽ–‹  ”‘’‡” Šƒ• Ž‡† –‘ ƒ Ž‡•• ‡ˆϐ‹ ‹‡– phosphate retention in the sediments. The phosphate that is released from –Š‡•‡†‹‡–•”‡ƒ Š‡•–Š‡•—”ˆƒ ‡™ƒ–‡”•†—”‹‰™‹–‡”‹š‹‰‘”—’™‡ŽŽ‹‰ during summer and will give a lower nitrogen to phosphorous ratio, which are ‘‡‘ˆ–Š‡ƒ‹†”‹˜‡”•ˆ‘” ›ƒ‘„ƒ –‡”‹ƒ„Ž‘‘•‹–Š‡ƒŽ–‹ ‡ƒȋƒŠ–‡”ƒ‡– ƒŽǤǡ ʹͲͲ͹ȌǤ Š‡•‡ ‘”‰ƒ‹•• Šƒ˜‡ –Š‡ ƒ’ƒ„‹Ž‹–› –‘ ϐ‹š †‹••‘Ž˜‡† ‹–”‘‰‡ ‰ƒ• (NΜ) and they are therefore not limited by nitrogen as other phytoplankton organisms. The magnitude and frequency of these cyanobacteria blooms have increased since the 1960 (Finni et al., 2001).. 2.3 Sediments Sediments in the Baltic Sea are important zones for degradation and recycling of OC. Due to the shallowness of the Baltic Sea, a relatively large proportion of –Š‡’”‹ƒ”›’”‘†— –‹‘‹•‡š’‡ –‡†–‘‡• ƒ’‡†‡‰”ƒ†ƒ–‹‘‹–Š‡™ƒ–‡” ‘Ž— ƒ††‡’‘•‹–ƒ––Š‡•‡†‹‡–•—”ˆƒ ‡™Š‡”‡‘š‹†ƒ–‹‘ƒ†”‡ › Ž‹‰‘ˆ™‹ŽŽ continue. The primary production during spring bloom is dominated by diatoms ƒ††‹‘ϐŽƒ‰‡ŽŽƒ–‡•‹–Š‡ƒŽ–‹ ‡ƒǤ‹ƒ–‘•Šƒ˜‡Š‹‰Š‡”•‹‹‰”ƒ–‡ƒ†ƒ”‡ considered to constitute the major transport pathway of organic material to the 23.

(42) •‡ƒϐŽ‘‘”ȋŽ‘“˜‹•–ƒ† ‡‹•ƒ‡ǡʹͲͲͳƒ†”‡ˆ‡”‡ ‡•–Š‡”‡‹Ǣ ‡‹•ƒ‡ and Kononen, 1994). Despite their high abundance, the cyanobacteria biomass ‹• ‘– „‡Ž‹‡˜‡† –‘ ‘–”‹„—–‡ –‘ ƒ Žƒ”‰‡ ‡š–‡– –‘ –Š‡ †‡’‘•‹–‹‘ ‘ˆ ‘”‰ƒ‹  matter to the sediments (Heiskanen and Kononen, 1994; Olli and Heiskanen, ͳͻͻͻȌǡ„—–‹–•’”‡•‡ ‡‹•‹†‹ ƒ–‡†„› ›ƒ‘„ƒ –‡”‹ƒ•’‡ ‹ϐ‹ ’‹‰‡–•ˆ‘—† in sediment (Poutanen and Nikkilä, 2001). With increasing organic matter production due to eutrophication it is also believed that burial of OC in sediments have doubled during the last century (Emeis et al., 2000). In contradiction to this, sediment accumulation rates appear to not have changed during the past 100 years (Hille, 2006). Organic matter deposition to sediments is not homogenous; sedimentation patterns are instead closely related to basin topography and level of bottomstress. A large part (~75%) of the Baltic Sea is shallow (<70 m), which makes –Š‡ •›•–‡ Žƒ”‰‡Ž› ‹ϐŽ—‡ ‡† „› ”‡•—•’‡•‹‘ ‹†— ‡† „› ™‹† ƒ† „‘––‘ currents (Snoeijs-Leijonmalm et al., 2016). It is not clear if this resuspension have direct effects on the degradation rates of organic matter (Almroth et al., 2009; Ståhlberg et al., 2006). Moreover, the vertical transport of particles to deep less energetic areas (Almroth-Rosell et al., 2011) and its effect on OC ”‡ › Ž‹‰ ”ƒ–‡• ‹• ‘– ‘™Ǥ ’’”‘š‹ƒ–‡Ž› ͵ͲȂͶͲ Ψ ‘ˆ –Š‡ •‡ƒϐŽ‘‘” ‹ –Š‡ Baltic Sea is of accumulation type (Carman and Cederwall, 2001), thus it is important to understand how this vertical transport of particles will affect „—”‹ƒŽƒ†”‡ › Ž‹‰‡ˆϐ‹ ‹‡ ‹‡•Ǥ Š‡ •‡†‹‡– ”‡•’‘•‡ –‘ ‡—–”‘’Š‹ ƒ–‹‘ ƒ† Š›’‘š‹ƒ ‹ –‡”• ‘ˆ ƒ”„‘ burial and recycling thus remains unclear. To resolve the role of sediments, the spatial distribution and burial of carbon in Baltic Sea sediments has received considerable attention (Emeis et al., 2000; Hille, 2006; Leipe et al., 2011; Winogradow and Pempkowiak, 2014). However, benthic recycling of OC is often overlooked and much less studied (Kulinski and Pempkowiak, 2012; Winogradow and Pempkowiak, 2014), signifying the need for investigations, preferably in situ, of Baltic Sea sediments and their role in the C cycle.. 24.

(43) 3. Methods 3.1 Benthic Landers to study early diagenetic processes in situ The Gothenburg benthic landers used in this study are advanced in situ ‹•–”—‡–• –Šƒ– ƒ •‹ –‘ –Š‡ •‡ƒ ϐŽ‘‘” ƒ† ’‡”ˆ‘” „‹‘‰‡‘ Š‡‹ ƒŽ measurements in the bottom water and sediment. Different modules can be mounted on the landers for different purposes (e.g. planar optodes, incubation chambers, micro electrodes). During this study both the big (Fig. 3) and small Gothenburg landers were used equipped with 4 and 2 incubation chambers ”‡•’‡ –‹˜‡Ž›ǤŠ‡„‹‰Žƒ†‡”‹•ˆ—ŽŽ›ƒ—–‘‘‘—•ƒ† ƒ•‹–‘–Š‡•‡ƒϐŽ‘‘”ƒ† perform incubations of the sediment water interface without any connection to the surface. The small lander must have a rope attached for deployment and recovery.. Figure 3 The big Gothenburg benthic lander at recovery (left) and a close up of the chamber module and attached syringes (right).. ˆ–‡”–Š‡‹•–”—‡–Šƒ•Žƒ†‡†‘–Š‡•‡ƒϐŽ‘‘”ƒ†‡“—‹Ž‹„”ƒ–‡†–‘•—””‘—†‹‰ bottom water conditions (i.e. ventilation phase) the chambers are gently inserted into the sediments. Another ventilation phase is made with chambers inserted to assure that no water from above is left inside and then the lids 25.

(44) ƒ”‡ Ž‘•‡†ƒ†–Š‡‹ —„ƒ–‹‘„‡‰‹•Ǥƒ Š Šƒ„‡”‹• ‘‡ –‡†–‘ƒ•‡–‘ˆͳ ‹Œ‡ –‹‘ƒ†ͻ•ƒ’Ž‹‰•›”‹‰‡•–Šƒ––ƒ‡™ƒ–‡”•ƒ’Ž‡•ƒ–’”‡•‡––‹‡•ǤŠ‡ ‹Œ‡ –‹‘•›”‹‰‡‹•—•‡†–‘‹Œ‡ –ƒ–”ƒ ‡”‘”™ƒ–‡”–‘„‡ƒ„Ž‡–‘†‡–‡ ––Š‡ ‹ —„ƒ–‡†™ƒ–‡”˜‘Ž—‡ǡ™Š‹ ŠŠƒ•–‘„‡‘™‹‘”†‡”–‘ ƒŽ —Žƒ–‡•‘Ž—–‡ ϐŽ—š‡•ǤŠ‡˜‘Ž—‡‘ˆ–Š‡‹ —„ƒ–‡†™ƒ–‡”™‹ŽŽ†‹ˆˆ‡”„‡–™‡‡‹ —„ƒ–‹‘••‹ ‡ –Š‡’‡‡–”ƒ–‹‘†‡’–Š˜ƒ”‹‡•Ǥ Š‡ •‘Ž—–‡ ‘ ‡–”ƒ–‹‘ Šƒ‰‡ ‘˜‡” –‹‡ ‹•‹†‡ –Š‡ Šƒ„‡” ‹• ‘‹–‘”‡† ‡‹–Š‡”„›•‡•‘”•‘”„›†‹• ”‡–‡™ƒ–‡”•ƒ’Ž‹‰ƒ†‡„›•›”‹‰‡• ‘‡ –‡†–‘ –Š‡ Šƒ„‡”ǤŠ‡„‡–Š‹ •‘Ž—–‡ϐŽ—š‹•†‡”‹˜‡†ˆ”‘–Š‡ ‘ ‡–”ƒ–‹‘ Šƒ‰‡ ‘ˆ–Š‡•‘Ž—–‡‘˜‡”–‹‡ǡ–Š‡ƒ”‡ƒ‘ˆ–Š‡‹ —„ƒ–‡†•‡†‹‡–ƒ†–Š‡˜‘Ž—‡‘ˆ –Š‡‹ —„ƒ–‡†™ƒ–‡”Ǥ Š‡ ‰”‡ƒ– ƒ†˜ƒ–ƒ‰‡• ‘ˆ –Š‹• ƒ’’”‘ƒ Š ‹• –Šƒ– ƒ ”‡Žƒ–‹˜‡Ž› Žƒ”‰‡ ƒ”‡ƒ ‘ˆ –Š‡ •‡†‹‡– ȋͶͲͲ ψ ˆ‘” –Š‡ Šƒ„‡”• ‘ –Š‡ ‘–Š‡„—”‰ „‡–Š‹  Žƒ†‡”•Ȍ ‹• ‹ —„ƒ–‡†‹•‹–—™‹–Š‹‹ƒŽ†‹•–—”„ƒ ‡”‡•—Ž–‹‰‹ƒ‰‘‘†”‡’”‡•‡–ƒ–‹‘ ‘ˆ–Š‡ƒ–—”ƒŽϐŽ—š„‡–™‡‡–Š‡•‡†‹‡–ƒ†‘˜‡”Ž›‹‰™ƒ–‡”ȋ‡‰„‡”‰‡–ƒŽǤǡ ͳͻͻͷȌǤ. ^LJƌŝŶŐĞƐĨŽƌ ǁĂƚĞƌƐĂŵƉůŝŶŐ. ŵWK. ƚWK. ^ƚŝƌƌŝŶŐͲ ǁŚĞĞů. WK. /. tĂƚĞƌ ^ĞĚŝŵĞŶƚ. KƉƚŽĚĞƐ ΘƐĞŶƐŽƌƐ. WK. /. /ŶĐƵďĂƚŝŽŶ ĐŚĂŵďĞƌ ŝŶƐĞƌƚĞĚŝŶ ƐĞĚŝŵĞŶƚ. ƵƌŝĂů Figure 4 ƒ•‹  ’”‹ ‹’Ž‡• –‘ •–—†› ‡ƒ”Ž› †‹ƒ‰‡‡–‹  ’”‘ ‡••‡• ‹ –Š‡ •‡†‹‡–• ™‹–Š Šƒ„‡” ‹ —„ƒ–‹‘• ’‡”ˆ‘”‡† ™‹–Š „‡–Š‹  Žƒ†‡”•Ǥ Š‡ –‘–ƒŽ †‡’‘•‹–‹‘ ‘ˆ  ‘•‹•– ƒ‹Ž› ‘ˆ ƒ –‡””‡•–”‹ƒŽ’ƒ”–ȋ–Ȍƒ†ƒƒ”‹‡’ƒ”–ȋȌǤŠ‡–”ƒ•ˆ‘”ƒ–‹‘‘ˆ–‘

(45) ƒ”‡†‡• ”‹„‡† ‹•‡ –‹‘ͳǤ͵Ǥ. ʹ͸.

(46) The basic principle of chamber incubations to study the process of OC degradation in sediments during early diagenesis is depicted in Fig. 4. Deposition of POC (marine (mPOC) and terrestrial (tPOC)) to the sediments will „‡’ƒ”–Ž›„—”‹‡†ƒ†’ƒ”–Ž›Š›†”‘Ž›œ‡†ƒ†ˆ—”–Š‡”‘š‹†‹œ‡†–‘

(47) ȋ†‡• ”‹„‡† ‹•‡ –‹‘ͳǤ͵ȌǤŠ‡’”‘†— –‹‘‘ˆ

(48) †—”‹‰‘š‹†ƒ–‹‘‘ˆ”‡•—Ž–•‹ƒϐŽ—š of DIC out of the sediment, which can be determined in chamber incubations. As mentioned in section 1.3, calcium carbonate dissolution can contribute to the production of DIC. However, carbonate dissolution is considered negligible in Baltic Sea sediments (Leipe et al., 2011; Schneider et al., 2002), which is also suggested from results in this study (PIC<1% dwt). Furthermore, C loss in terms of bubble emission of methane are not found to be important in Baltic Sea sediments (Sawicka and Brüchert, 2017). Š—•ǡ™‡‡š’‡ ––Šƒ–‘ƒŽƒ”‰‡ƒŽ–‹ ‡ƒ•›•–‡• ƒŽ‡ǡ–Š‡’”‘ ‡••‡•‘ˆ ƒŽ ‹— carbonate dissolution and methanogenesis will have a negligible net effect on ‘—”‡•–‹ƒ–‡•‘ˆ”‡ › Ž‹‰”ƒ–‡•ǡ‹Ǥ‡Ǥ™‡ ‘•‹†‡”–Š‡

(49) ϐŽ—š„‡‹‰‡“—ƒŽ–‘ –‘–ƒŽ‘š‹†ƒ–‹‘Ǥ ‡†‹‡–• ‘˜‡”Žƒ‹† „› ‘š›‰‡ƒ–‡† „‘––‘ ™ƒ–‡” ƒ”‡ ‹Šƒ„‹–‡† „› „‡–Š‹  fauna that make burrows and re-work the sediment. They have an important ‹ϐŽ—‡ ‡‘†‡‰”ƒ†ƒ–‹‘ƒ† ƒ‡Šƒ ‡–Š‡„‡–Š‹ ϐŽ—š‘ˆ•‘Ž—–‡••‡˜‡”ƒŽǦ ˆ‘Ž†–Š”‘—‰Š„‹‘–—”„ƒ–‹‘ȋ‡Ǥ‰ǤŽŽ‡”ǡʹͲͳͶȌǤŠ‡‹ϐŽ—‡ ‡‘ˆ„‡–Š‹ ƒ‹ƒŽ•‘ –Š‡„‡–Š‹ ϐŽ—š‹•‹ Ž—†‡††—”‹‰ Šƒ„‡”‹ —„ƒ–‹‘•Ǥ

(50) •‡†‹‡–•™‹–Šˆ‡™ „—–Žƒ”‰‡ƒ‹ƒŽ•ǡŠ‘™‡˜‡”ǡ–Š‡‡ƒ•—”‡†ϐŽ—šƒ›‘–„‡”‡’”‡•‡–ƒ–‹˜‡‘ƒ larger spatial scale unless a large number of chamber incubations are made. Typically the macrofauna contribution to the overall respiration has been estimated to be 40–75 % (Glud et al., 1998; 2003). The incubated sediment ƒ„‡•‹‡˜‡†ˆ‘”ƒ‹ƒŽ•ƒˆ–‡”‹ —„ƒ–‹‘–‘‰‡–ƒϐ‹”•–‡•–‹ƒ–‡‘ˆ„‹‘–—”„ƒ–‹‘ effects.. 3.2 Sediment cores to study OC burial or preservation —Ž–‹’Ž‡ ‘”‡”ȋǡϐ‹”•–†‡• ”‹„‡†„›ƒ”‡––‡–ƒŽǤǡȋͳͻͺͶȌ ‹‰ǤͷȌ™ƒ•—•‡† to sample short sediment cores (<50 cm) for obtaining vertical distribution of C in recent sediment. The MUC can retrieve up to eight cores in one deployment. Only sediment cores of high quality were used. Sediments were sliced in 0.5–2 cm depth intervals with highest resolution in the upper part of the core. 27.

(51) Each slice was sampled and analyzed for particulate C species (POC and PIC). šƒ’Ž‡‘ˆƒ•‡†‹‡–’”‘ϐ‹Ž‡‘ˆ‹••‡‡‹ ‹‰Ǥ͸ǤŠ‡ ‘ ‡–”ƒ–‹‘ †‡ ”‡ƒ•‡•™‹–Š•‡†‹‡–†‡’–Šƒ•ƒ”‡•—Ž–‘ˆ–Š‡‘š‹†ƒ–‹‘ǡ™Š‹ Š†‡ ”‡ƒ•‡• the sediment OC content over time.. Figure 5 Multiple corer (left) that can take up to eight sediment cores (right). Tubes are 55 cm in length and 9.9 cm in inner-diameter.. The layer where the steepest decline of OC occur with sediment depth, i.e. ™Š‡”‡–Š‡ƒŒ‘”’ƒ”–‘ˆ‘š‹†ƒ–‹‘‘ —”•ǡ‹•†‡ϐ‹‡†ƒ•–Š‡reactive layer (indicated by the shaded area in Fig. 6) in this thesis. The total amount of OC in this reactive layer is termed the POC inventory. The POC inventory can be seen ƒ•ƒ‡ƒ•—”‡‘ˆ–Š‡–‘–ƒŽƒ˜ƒ‹Žƒ„Ž‡’‘‘Ž–Šƒ– ƒ—†‡”‰‘‘š‹†ƒ–‹‘‘–Š‡ –‹‡Ǧ• ƒŽ‡–Šƒ–‹•”‡ϐŽ‡ –‡†‹–Š‡–‘–ƒŽ

(52) ϐŽ—š‡ƒ•—”‡†„›–Š‡Žƒ†‡”Ǥ At a certain sediment depth the OC concentration reaches a stable low concentration, i.e. only OC of lower quality, which does not easily undergo ˆ—”–Š‡” ‘š‹†ƒ–‹‘ǡ ‹• Ž‡ˆ–Ǥ Š‹• •–ƒ„Ž‡ Ž‘™  ‘ ‡–”ƒ–‹‘ ‹• †‡ϐ‹‡† ƒ• –Š‡ OC burial concentration (indicated by the dashed line in Fig. 6). The rate of OC burial was estimated from the OC burial concentration and the sediment accumulation rate (SAR). The main focus of this thesis work has been to describe differences and quantify process rates for different depositional regimes that are present in the Baltic Sea. For this purpose the Baltic Sea have been divided into accumulation areas 28.

(53) ƒ† ‡”‘•‹‘Ȁ–”ƒ•’‘”–ƒ–‹‘ ƒ”‡ƒ•Ǥ Š‡ Žƒ••‹ϐ‹ ƒ–‹‘ ‹–‘ ƒ ——Žƒ–‹‘ ƒ† ‡”‘•‹‘Ȁ–”ƒ•’‘”–ƒ–‹‘ƒ”‡ƒ•™ƒ•ƒ†‡„ƒ•‡†‘–Š‡•‡†‹‡–™ƒ–‡” ‘–‡– ‹ –Š‡ –‘’ ‡–‹‡–‡” ‘ˆ –Š‡ •‡†‹‡– ƒˆ–‡” ”‡ ‘‡†ƒ–‹‘• ‹ ȋ ¤ƒ•‘ ƒ† ƒ••‘ǡ ͳͻͺ͵ȌǤ

(54)  ‰‡‡”ƒŽǡ •‡†‹‡–• ™‹–Š ™ƒ–‡” ‘–‡–• Š‹‰Š‡” –Šƒ ͹ͷ Ψ ™‡”‡ Žƒ••‹ϐ‹‡† ƒ• ƒ ——Žƒ–‹‘ –›’‡ •‡†‹‡–•Ǥ ‘™‡˜‡”ǡ ƒ††‹–‹‘ƒŽ Šƒ”ƒ –‡”‹•–‹ ••— Šƒ• ‘–‡–ƒ†–Š‡•Šƒ’‡‘ˆ–Š‡•‡†‹‡–’”‘ϐ‹Ž‡‘ˆ ™‡”‡ƒŽ•‘—•‡†–‘ Žƒ••‹ˆ›–Š‡•‡†‹‡–•‹–Š‹•‹˜‡•–‹‰ƒ–‹‘Ǥ. Figure 6 ‡”–‹ ƒŽ †‹•–”‹„—–‹‘ ‘ˆ  ȋΨ  ‘ˆ •‡†‹‡– †”› ™‡‹‰Š–Ȍ ‹ –Š‡ –‘’ ʹͲ  ‘ˆ •‡†‹‡– ‹ –Š‡ ƒŽ–‹  ”‘’‡” ƒ ——Žƒ–‹‘ ƒ”‡ƒǤ Š‡ •Šƒ†‡† ƒ”‡ƒ ‹†‹ ƒ–‡• –Š‡ ƒ –‹˜‡ œ‘‡ ‘ˆ ‡ƒ”Ž› †‹ƒ‰‡‡•‹• ƒ† ‹• ƒŽŽ‡† –Š‡ ”‡ƒ –‹˜‡ Žƒ›‡”Ǥ Š‡†ƒ•Š‡†Ž‹‡‹†‹ ƒ–‡•–Š‡•–ƒ„Ž‡ ‘ ‡–”ƒ–‹‘ ”‡ƒ Š‡† ™‹–Š †‡’–Šǡ ™Š‹ Š ‹• †‡ϐ‹‡† ƒ• –Š‡ „—”‹ƒŽ ‘ ‡–”ƒ–‹‘‹–Š‹•–Š‡•‹•Ǥ. ʹͻ.

(55)

(56) 0DLQ¿QGLQJVDQGGLVFXVVLRQ 2&UHF\FOLQJDQGEXULDOLQ%DOWLF6HDVHGLPHQWV Š‡ƒŽ–‹ ‡ƒ•‡†‹‡–•ƒ”‡•—„Œ‡ ––‘‹–‡•‡†‡’‘•‹–‹‘‘ˆ‘”‰ƒ‹ ƒ––‡” ƒ•ˆ‘—†‹Paper IǤ

(57) –‘–ƒŽǡ™‡ˆ‘—†–Šƒ–‡ƒ”Ž›ʹ͵‰†‡’‘•‹–•ƒ––Š‡•‡ƒ ϐŽ‘‘”‡ƒ Š›‡ƒ”ȋ ‹‰Ǥ͹ȌǤͻ͸Ψȋʹʹ‰Ȍ‘ˆ–Š‹•‹•”‡ › Ž‡†„ƒ –‘–Š‡™ƒ–‡” ‘Ž—‹–Š‡ˆ‘”‘ˆ

(58) †—‡–‘‘š‹†ƒ–‹‘Ǥ. ŵWK. ƚWK. ϭ͘ϯ ϭϲ͘ϴ Ϯϭ͘ϲ. WK hŶĐĞƌƚĂŝŶƚŝĞƐ ĂŶĚŽƚŚĞƌƐŽƵƌĐĞƐ ϮϮ͘ϲ. ZĞĐLJĐůŝŶŐ. ĞƉŽƐŝƚŝŽŶ Ϭ͘ϵϱ ƵƌŝĂů. Figure 7 ‡–Š‹ ƒ••„ƒŽƒ ‡ˆ‘”–Š‡ƒŽ–‹ ‡ƒƒ•†‡˜‡Ž‘’‡†‹ƒ’‡”

(59) ǤŽŽ—„‡”•‹‰›”ȂχǤ. Š‡–‘–ƒŽ„—”‹ƒŽˆ‘”ƒŽ–‹ ‡ƒ•‡†‹‡–•‘ˆͲǤͻͷ‰ˆ‘—†‹–Š‹••–—†›‹•Ž‘™‡” ‘” ‹ –Š‡ •ƒ‡ ”ƒ‰‡ –Šƒ ’”‡˜‹‘—• •–—†‹‡• ȋ”ƒ‰‹‰ ˆ”‘ ͳǤʹȂ͵Ǥͷ ‰  ›”Ȃχǡ ȋ —•–ƒˆ••‘ ‡– ƒŽǤǡ ʹͲͳͶǢ —Ž‹•‹ ƒ† ‡’‘™‹ƒǡ ʹͲͳͳǢ ‡‹’‡ ‡– ƒŽǤǡ ʹͲͳͳǢ ‹‘‰”ƒ†‘™ƒ†‡’‘™‹ƒǡʹͲͳͶȌȌ ‘”‡‘˜‡”ǡ–Š‡„—”‹ƒŽ‡ˆϐ‹ ‹‡ ›‘–Š‡ƒŽ–‹ ‡ƒ•›•–‡• ƒŽ‡‹•‹–Š‡Ž‘™‡” ȋͶ ΨȌ ”ƒ‰‡ ™Š‡ ‘’ƒ”‡† –‘ ‘–Š‡” ƒ”‹‡ •›•–‡• ȋƒ„Ž‡ ͵ǡ ȋ ƒ”–‡–– ‡– ƒŽǤǡ ͳͻͻͺǢ ƒ”–‡• ‡– ƒŽǤǡ ͳͻͻʹǢ –¤ŠŽ ‡– ƒŽǤǡ ʹͲͲͶƒǡ ʹͲͲͶ„ǡ ʹͲͲͶ Ȍǡ „—– Žƒ”‰‡ ˜ƒ”‹ƒ–‹‘•„‡–™‡‡–Š‡ƒŽ–‹ ‡ƒ•—„Ǧ„ƒ•‹•™‡”‡‘„•‡”˜‡†ȋʹǤͷȂͳͳΨȌǤ—”‹ƒŽ ‡ˆϐ‹ ‹‡ ‹‡•‹–Š‡ƒŽ–‹ ‡ƒŠƒ˜‡’”‡˜‹‘—•Ž›„‡‡ˆ‘—†–‘”ƒ‰‡ˆ”‘ͳͺȂͷ͹ Ψ ȋƒϐ‹‡Ž†ǡ ͳͻͻ͵ ƒ† ”‡ˆ‡”‡ ‡• –Š‡”‡‹ȌǤ —” „—”‹ƒŽ ‡ˆϐ‹ ‹‡ ‹‡• ƒ”‡ — Š. ͵ͳ.

(60) Ž‘™‡”ȋ͸Ȃͳ͸Ψˆ‘”ƒ ——Žƒ–‹‘ƒ”‡ƒ•ƒ†ʹǤͷȂͳͳΨ‘ƒ–‘–ƒŽ„ƒ•‹Ǧ• ƒŽ‡ǡ‹Ǥ‡Ǥ ‹ Ž—†‹‰‡”‘•‹‘Ȁ–”ƒ•’‘”–ƒ–‹‘ƒ”‡ƒ•ǡ™Š‹ ŠŠƒ˜‡‘‡–„—”‹ƒŽȌ Table 3 ‡–Š‹   ’”‘ ‡•• ”ƒ–‡• ȋ‘Ž Ȃψ †ȂχȌ ƒ† „—”‹ƒŽ ‡ˆϐ‹ ‹‡ ‹‡• ȋǡ „—”‹ƒŽ ”ƒ–‡Ȁ†‡’‘•‹–‹‘ ”ƒ–‡Ȍ ˆ‘—† ‹ ‘–Š‡” •‡ƒ• ȋ–¤ŠŽ ‡– ƒŽǤǡ χʹͲͲͶƒǡ ψʹͲͲͶ„ǡ ωʹͲͲͶ Ȍǡ ϊȋ ƒ”–‡––‡–ƒŽǤǡͳͻͻͺȌǢϋȋƒ”–‡•‡–ƒŽǤǡͳͻͻʹȌǤ. Deposition. Recycling. Burial. BE (%). Ǥ‡‰‡ƒ‡ƒω. ͵Ǥ͸. ͵Ǥͷ. ͲǤͳ. ͳǤ͹. ‘” —’‹‡„›••ƒŽŽƒ‹;. ͳǤʹ. ͳǤʹ. ͲǤͲ͵. ʹǤͷ. ƒŽ–‹ ”‘’‡”ȋŠ‹••–—†›Ȍ. ͳ͹Ǥʹ. ͳ͸Ǥͺ. ͲǤͶ. ʹǤͷ. —Žˆ‘ˆ‘–Š‹ƒȋŠ‹••–—†›Ȍ. ʹǤͺͳ. ʹǤͷͺ. ͲǤʹͶ. ͺǤͶ. —Žˆ‘ˆ ‹Žƒ†ȋŠ‹••–—†›Ȍ. ʹǤͷ͵. ʹǤʹͷ. ͲǤʹͺ. ͳͳ. ƒ•Š‹‰–‘•Š‡Žˆϊ. ʹͳǤʹ. ͳͺ. ͵Ǥʹ. ͳͷ. ƒ•Š‹‰–‘•Ž‘’‡ϊ. ͳͳǤʹ. ͺǤ͹. ʹǤͷ. ʹ͸. ‡š‹ ƒ•Š‡Žˆϊ. ͸ǤͶ. ͷǤͲ. ͳǤͶ. ʹ͵. ‡š‹ ƒ•Ž‘’‡ϊ. ͶǤʹ. ʹǤͷ. ͳǤ͹. ͵ͺ. ƒ‰‡””ƒχ. ʹͳ. ͻǤʹ. ͳʹ. ͷ͹. ƒ’‡‘‘‘—–‹‰Š–ϋ. Ͷͷʹ. ͳ͵Ͳ. ͵ʹͳ. ͹ͳ.

(61)  Paper IV –Š‡ ‡ˆˆ‡ –• ‘ˆ –Š‡ Žƒ”‰‡ ‹ϐŽ‘™ ‘ˆ ‘š›‰‡ƒ–‡† •ƒŽ–› ™ƒ–‡” –Šƒ– ‘ —””‡† ‹ –Š‡ ƒŽ–‹  ‡ƒ ƒ– –Š‡ ‡† ‘ˆ ʹͲͳͶ ƒ”‡ ‹˜‡•–‹‰ƒ–‡†Ǥ Š‡ ‹ •‹–— ‡ƒ•—”‡†„‡–Š‹ 

(62) ϐŽ—š‡•‹–Š‡ƒ•–‡” ‘–Žƒ†ƒ•‹†—”‹‰ʹͲͲͺȂʹͲͳͲǡ ™Š‡–Š‡™ƒ–‡” ‘Ž—„‡Ž‘™ƒ„‘—–ͳͲͲ†‡’–Š™ƒ•ƒ‘š‹ ǡ™ƒ• ‘’ƒ”‡† –‘‡ƒ•—”‡‡–• ‘†— –‡†‹‡ƒ”Ž› —Ž›ʹͲͳͷǡŽ‡••–Šƒˆ‘—”‘–Š•ƒˆ–‡”–Š‡ ‹ϐŽ‘™”‡ƒ Š‡†–Š‡ƒ•–‡” ‘–Žƒ†ƒ•‹Ǥ. Figure 8 

(63) ϐŽ—š‡•„‡ˆ‘”‡ȋʹͲͲͺƒ†ʹͲͳͲǡ „Ž—‡ƒ†‰”‡‡†‘–•Ȍƒ†ƒˆ–‡”ȋʹͲͳͷǡ”‡† †‘–•Ȍ–Š‡ƒŒ‘”ƒŽ–‹ ‹ϐŽ‘™Ǥ. ͵ʹ.

(64) Š‡ „‡–Š‹  ƒ‘‹—ǡ •‹Ž‹ ƒ–‡ ȋ‘– •Š‘™Ȍ ƒ† 

(65)  ϐŽ—š‡• ȋ ‹‰Ǥ ͺȌ †‹† ‘– Šƒ‰‡ •‹‰‹ϐ‹ ƒ–Ž› †—”‹‰ –Š‡ ‘š›‰‡ƒ–‹‘ ‡˜‡– ‘’ƒ”‡† –‘ –Š‡ ϐŽ—š‡• —†‡” ƒ‘š‹  ‘†‹–‹‘• ‹ ʹͲͲͺǦͳͲǤ ‘™‡˜‡”ǡ –Š‡ ’Š‘•’Šƒ–‡ ϐŽ—š‡• „‡ ƒ‡ Ž‘™‡”‘”–—”‡†‹–‘ƒ‹ϐŽ—š‹ͷͲΨ‘ˆ–Š‡ Šƒ„‡”‹ —„ƒ–‹‘•Ǥ Measurements of OC recycling rates in this study were made over several years (2001–2017) and included different seasons (April, July, August, Fig. 9). We ˆ‘—†‘•‹‰‹ϐ‹ ƒ–•‡ƒ•‘ƒŽ˜ƒ”‹ƒ–‹‘•Ǥ. Figure 9 Seasonality at the two deepest stations (E and F) of the Eastern Gotland Basin.. We hypothesize that the sediment pool of OC is so large that any potential •‡ƒ•‘ƒŽ ˜ƒ”‹ƒ–‹‘ ‹  †‡’‘•‹–‹‘ –‘ –Š‡ •‡†‹‡– †‘ ‘– ‹ϐŽ—‡ ‡ –Š‡ 

(66)  ϐŽ—š‡• •‹‰‹ϐ‹ ƒ–Ž›Ǥ —” ‡•–‹ƒ–‡• ‘ˆ  ”‡ › Ž‹‰ ”ƒ–‡• ƒ –Š‡”‡ˆ‘”‡ „‡ looked upon as resembling the average annual rate at present time. However, — ‡”–ƒ‹–‹‡•‡š‹•–†—‡–‘•’ƒ–‹ƒŽŠ‡–‡”‘‰‡‡‹–›Ǥ. 2&UHF\FOLQJHႈFLHQF\DQGIDFWRUVLQÀXHQFLQJEHQWKLF2& recycling Deep sediments in the Baltic Proper and Gulf of Finland release large amounts ‘ˆ

(67) ƒ•ƒ”‡•—Ž–‘ˆ‹–‡•‹˜‡‘š‹†ƒ–‹‘Ǥ

(68) Paper II, the observed increase 33.

(69) in OC recycling rates with normalized water depth is discussed. The term ‘”ƒŽ‹œ‡†™ƒ–‡”†‡’–Šȋ‹Ǥ‡Ǥƒ –—ƒŽ™ƒ–‡”†‡’–ŠȀƒš‹—™ƒ–‡”†‡’–Š‘ˆ–Š‡ basin) was introduced in order to compare accumulation bottoms between „ƒ•‹•™‹–Š†‹ˆˆ‡”‡–ƒš‹—™ƒ–‡”†‡’–ŠǤ

(70) – ™ƒ• ˆ‘—† –Šƒ– •‡†‹‡–• ‹ †‡‡’ ƒ ——Žƒ–‹‘ ƒ”‡ƒ• ƒ”‡ ‘”‡ ‡ˆϐ‹ ‹‡– in mineralizing OC, as suggested from the increase of the DIC/OC inventory ”ƒ–‹‘ ȋŠ‡”‡ ƒŽŽ‡† –Š‡  ‘š‹†ƒ–‹‘ ‡ˆϐ‹ ‹‡ ›Ȍ ™‹–Š ‘”ƒŽ‹œ‡† ™ƒ–‡” †‡’–ŠǤ ‘™‡˜‡”ƒˆ‡™•–ƒ–‹‘•ȋǡ ǡƒ†ȌŽ‘ ƒ–‡†‹’‡”ƒ‡–Ž›‘š›‰‡ƒ–‡† ƒ”‡ƒ• ‘ˆ –Š‡ ƒŽ–‹  ”‘’‡” •Š‘™‡† –Š‡ Š‹‰Š‡•– ‡ˆϐ‹ ‹‡ ‹‡•Ǥ Š‡  ‘š‹†ƒ–‹‘ ‡ˆϐ‹ ‹‡ ›ƒ––Š‡•‡•‹–‡•ȋͲǤͷȂͳ›”–χ) also indicates that within a time period of less than one year the major part of the OC in the reactive layer of the sediment is recycled to overlying waters. The OC and the chlorophyll-a inventories (Chl-a, an indicator for fresh labile ƒ–‡”‹ƒŽȌƒŽ•‘‹ ”‡ƒ•‡†™‹–Š‘”ƒŽ‹œ‡†™ƒ–‡”†‡’–ŠǤ ‘™‡˜‡”ǡ–Š‡

(71) ϐŽ—š ™ƒ• ‘– ‡š’Žƒ‹‡† „› –Š‡ ‹ ”‡ƒ•‡† ƒ‘—– ‘ˆ ƒ˜ƒ‹Žƒ„Ž‡  ‘” ˆ”‡•Š Žƒ„‹Ž‡ material (i.e. did not correlate with these inventories; p>0.05, R2<0.2, no •‹‰‹ϐ‹ ƒ– ‘””‡Žƒ–‹‘„‡–™‡‡

(72) ϐŽ—šƒ†‹˜‡–‘”›‘”ŠŽǦƒ‹˜‡–‘”› in sediment). Resuspension and redistribution of OC is needed to balance the measured OC recycling and burial rates within the Baltic Proper. The results suggest that about 4.8 Tg of C is redistributed from ET areas and is redeposited at deeper calmer accumulation areas in the Baltic Proper (Table 4). Deposition of OC in deep accumulation areas of the Baltic Proper is 12 Tg C yr–χ according to our estimates. We can estimate that marine primary production delivers ƒ’’”‘š‹ƒ–‡Ž›ŠƒŽˆ‘ˆ–Š‹•ƒ–‡”‹ƒŽȋͷǤ͹‰›”–χ). The rest is likely resulting from redistribution of sediment particulate material from ET areas. This redistribution of 4.8 Tg C yr–χ†‘‡•‘–ˆ—ŽŽ› ‘’‡•ƒ–‡ˆ‘”–Š‡†‡ϐ‹ ‹–ȋȂ͸Ǥ͵ Tg C yr–χ) in deposition observed in A-areas. But when also taking into account riverine input (around 0.2 Tg C, Gustafsson et al., (2014)) and other point sources as well as uncertainties of the estimates, the numbers are considered to match (Table 4).. 34.

(73) Table 4 Local OC budget (Tg C yr–χ) ˆ‘” –Š‡ ƒŽ–‹  ”‘’‡” •—‰‰‡•– –Šƒ– ƒ’’”‘š‹ƒ–‡Ž› 4.8 Tg C yr–χ is redistributed from shallow erosion/transportation areas and is redeposited in deeper, less energetic accumulation areas.. Recycling Burial. ET. +/-. A. +/-. 4.8. 2.4. 11. 4.8. 0.4. 0.2. 0. Deposition. 4.8. 2.4. 12. 4.8. Marine PP. 9.6. 0.003. 5.7. 0.002. Diff (Marine PP-Deposition). 4.8. 2.37. –6.3. 4.8. 4.3 Improvement of benthic landers Š‡•–—†›‹‰•‡†‹‡–ǡ™ƒ–‡”ϐŽ—š‡•‹•‹–—‹˜‡•–‹‰ƒ–‹‘•ƒ”‡’”‡ˆ‡”ƒ„Ž‡•‹ ‡ they are considered to give the highest quality data (e.g. (Glud et al., 1994; Hall ‡–ƒŽǤǡʹͲͳ͹Ǣ—†„›‡–ƒŽǤǡͳͻͺ͸Ǣ‡‰„‡”‰‡–ƒŽǤǡͳͻͻͷȌǤ‡†‹ˆϐ‹ —Ž–›‘ˆ—•‹‰ benthic lander is that they are technically challenging and need continuous •‡”˜‹ ‡ƒ†ƒ‹–‡ƒ ‡–‘‡‡’‘’–‹ƒŽ’‡”ˆ‘”ƒ ‡Ǥ•ˆ‘”ƒŽŽϐ‹‡Ž†•ƒ’Ž‹‰ and measurements technical instruments and methods have to be improved and developed to obtain as high quality data as possible. Paper III describes work that has been made with the Gothenburg benthic landers during the past –™‡Ž˜‡›‡ƒ”•–‘‹’”‘˜‡–Š‹••›•–‡™‹–Š–Š‡ƒ‹–‘•Šƒ”‡‘—”‡š’‡”‹‡ ‡ˆ”‘ the more than 250 deployments made in total. This has not been described for this type of system, since the early lander review that was published more than 20 years ago (Tengberg et al., 1995). Paper III also demonstrates that many ’‘••‹„‹Ž‹–‹‡• ‡š‹•– –‘ ƒ‹’—Žƒ–‡ –Š‡ ƒ–—”ƒŽ •›•–‡ ‹ •‹–— –‘ –ƒ”‰‡– •’‡ ‹ϐ‹  •‡†‹‡–ƒ”› ’”‘ ‡••‡•ǡ ˆ‘” ‡šƒ’Ž‡ ‹Œ‡ –‹‘• ‘ˆ –”ƒ ‡”• ‘” ‹–”‘†— ‹‰ physical stress by increased stirring speed (Almroth-Rosell et al., 2012). One major improvement of our benthic lander system has been in measuring –Š‡‹ —„ƒ–‹‘˜‘Ž—‡–‘†‡–‡”‹‡–Š‡‹ —„ƒ–‡†™ƒ–‡”Š‡‹‰Š–‡‡†‡†ˆ‘”ϐŽ—š calculations. Originally the height was determined from camera observation of a ruler mounted inside the chamber, and later on by injection of a non-reactive tracer (bromide) and subsequent analysis of the dilution in the proceeding water samples. Today conductivity sensors are installed inside the chambers that can determine very small changes in salinity. By injection of milli-Q water the incubation volume can be determined from the observed change in salinity. 35.

(74) The salinity data also let us detect if there is a leakage during the incubation. Š‹•‡™‡–Š‘†‹•˜‡”›–‹‡Ǧ‡ˆϐ‹ ‹‡–ƒ†‰‹˜‡•ƒ‘”‡ƒ —”ƒ–‡†‡–‡”‹ƒ–‹‘ of the volume; the incubated volume can now be measured with an accuracy of 1 ± 4 %. This is an important step forward for in situ chamber incubation measurements since a 10 % error in the volume determination results in a 10 % error in the ƒŽ —Žƒ–‡† ϐŽ—šǤ  —”–Š‡”‘”‡ǡ •‹ ‡ –Š‡ ˜‘Ž—‡ †‡–‡ –‹‘ ‹• ‘™ ƒ†‡ „› sensors rather than by discrete water sampling, no valuable sample volume is lost for this purpose and can be used for analysis of other solutes of interest. The method also has the advantages of providing the results right after recovery and download of the data. In this way we can quickly determine if the incubations were successful and discard chambers that show signs of leakage or any other problems. This saves time and efforts in further analysis of syringe samples.

(75) –‹•‘–‘Ž› ”— ‹ƒŽ–‘ϐ‹†–Š‡‡šƒ –˜‘Ž—‡‘ˆ–Š‡‹ —„ƒ–‡†™ƒ–‡”ǡ‹–‹•ƒŽ•‘ important to identify that syringes are released at the time they are supposed –‘ ‹ ‘”†‡” –‘ ‰‡– Š‹‰Š ƒ —”ƒ › ‹ –Š‡ ϐŽ—š ƒŽ —Žƒ–‹‘•Ǥ ˜‡ ‹ˆ –Š‡ •›”‹‰‡• are pre-programmed they can be delayed or pre-released due to mechanical dislocations in the trigger system or get released upon impact with the water •—”ˆƒ ‡†—”‹‰–Š‡†‡’Ž‘›‡–Ǥ‘„‡ƒ„Ž‡–‘†‡–‡ –‡šƒ –Ž›™Š‡–Š‡•›”‹‰‡ samples are taken a pressure sensor has been installed and tested successfully.. 36.

(76) 5. Conclusions The benthic landers used in this study allow for high quality measurements ‘ˆ •‡†‹‡–Ǧ™ƒ–‡” ϐŽ—š‡• ‘ˆ 

(77)  ƒ† ™‡ ‘™ Šƒ˜‡ ƒ •—„•–ƒ–‹ƒŽ –‘‘ŽǦ„‘š ˆ‘” evaluating and controlling the functionality and reliability of the lander Šƒ„‡”‹ —„ƒ–‹‘•ǤŠ‡‹•‹–—‡ƒ•—”‡‡–•‘ˆ„‡–Š‹ 

(78) ϐŽ—š‡• ‘†— –‡† in the Baltic Sea during this thesis work are unique and have enhanced the understanding of OC cycling in the Baltic Sea.

References

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