Biogeochemical transformations in the Baltic Sea : observations through carbon dioxide glasses

119 Pages·2018·4.832 MB·English

by  Müller, Jens Daniel, Schneider, Bernd

Springer Oceanography
Bernd Schneider
Jens Daniel Müller
Biogeochemical
Transformations
in the Baltic Sea
Observations Through Carbon Dioxide
Glasses
Springer Oceanography
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ü
Bernd Schneider Jens Daniel M ller
(cid:129)
Biogeochemical
Transformations in the Baltic
Sea
Observations Through Carbon Dioxide
Glasses
123
BerndSchneider Jens DanielMüller
Department ofMarine Chemistry Department ofMarine Chemistry
LeibnizInstitute for Baltic SeaResearch LeibnizInstitute for Baltic SeaResearch
Warnemünde Warnemünde
Germany Germany
ISSN 2365-7677 ISSN 2365-7685 (electronic)
SpringerOceanography
ISBN978-3-319-61698-8 ISBN978-3-319-61699-5 (eBook)
DOI 10.1007/978-3-319-61699-5
LibraryofCongressControlNumber:2017945697
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Preface
This book is the product of our joint efforts to present the biogeochemistry of the
Baltic Sea from a unique perspective, “through carbon dioxide glasses.” We are
convinced that this view advances our understanding of the organic matter pro-
duction and mineralization processes that constitute the basic biogeochemical
transformations in the sea and that trigger many secondary processes. The term
“understanding”heremeanstobeabletodescribetransformationsasafunctionof
time, to identify the controlling variables and finally to deduce the kinetics of the
considered process. This allows us to explain the current biogeochemical status
oftheBalticSeabut,moreimportant,isarequisitefortheuseofnumericalmodels
torealisticallypredictthedevelopmentoftheecologicalstatusoftheBalticSeaina
changing environment. Current biogeochemical models using state-of-the-art pro-
cess parameterizations haveincreased ourcomprehensionofthefunctioningofthe
BalticSeaecosystemandofthecomplexrelationshipbetweenbiogeochemistryand
hydrography. Nonetheless, model simulations of the carbon cycle and thus of the
marineCO systemeitherhavefailedtosimulatetheseasonalandregionalpatterns
2
of the CO system or were able to reproduce them only by invoking biogeo-
2
chemical assumptions yet to be verified by observations. Therefore, investigations
of the marine CO system, which is intimately connected to all biogeochemical
2
processes, have two functions: Identification of gaps in our process understanding
and filling the gaps by improving the process parameterizations.
A recognition of the importance of studying the CO system in the Baltic Sea
2
developed during the past 25 years of related research carried out at the Leibniz
InstituteforBalticSeaResearch.Theaccumulationofahugeamountofdataduring
14yearsofautomatedCO measurementsmadefromacargoshiphasprovidedthe
2
basis for several publications. This refers also to studies of the deepwater CO
2
accumulation in connection with the Institute’s long-term observation programme.
Herewepresentasynopticviewofthecollecteddataandthegaininknowledgeby
connectingtheresultsofpreviouslypublishedprocessstudiestoanoverallpicture.
We consider our book as a contribution to the biogeochemical discussions within
the Baltic Earth Network which is a scientific network for regional Earth system
sciencefortheBalticSearegion(www.baltic.earth).Wealsohopethatitwillguide
v
vi Preface
theinclusionofthecarboncycleintobiogeochemicalmodelsandtheintegrationof
CO measurements into Baltic Sea monitoring programs, such as proposed by the
2
BONUS project INTEGRAL.
The cooperation between the authors in writing this book is also worthy of
mention. Whereas BS was able to draw extensively on his own decades-long
research in different fields of chemical oceanography, JDM is a Ph.D. student and
thus at the beginning of his scientific career. His skills in dealing with large
amounts of data and in the creative visualization of the inherent information were
essential to the success of the investigations and the presentation of their results.
Thebridgebetweenourgenerationsenabledmanyfruitfulandinspiringdiscussions
from which both the book and we profited.
Regarding the automated surface CO measurements on a cargo ship, we are
2
muchobligedtotheFinnishEnvironmentalInstitute(SYKE),whichhasbeenusing
thecargoshipsince1993forautomatedfluorescence(chlorophylla)measurements
and for taking samples for the analysis of nutrient concentrations within the
AlgalineProject.Duetotheinstitute’sgenerouscooperation,wewereabletomake
useofthesameinfrastructureforthedeploymentofourownmeasurementsystem.
Furthermore, our Finnish partners made nutrient data available for CO data
2
analyses and for use in this book. During 2012–2016, the operation of our CO
2
measurement system was generously funded by the German Federal Ministry of
EducationandResearch(BMBF)intheframeoftheGermancontributiontoICOS
(Integrated Carbon Observation System) (Grant Numbers 01LK1101F and
01LK1224D).
WealsothanktheSwedish AgencyforMarineandWaterManagement andthe
SMHI (Swedish Meteorological and Hydrographical Institute) for ready access to
their monitoring database.
Finally, we sincerely appreciate the willingness of the following experts and
colleagues to check the content of the book for scientific correctness and clarity:
Profs. L.Anderson andD.Turner(UniversityofGothenburg),Prof. A.Körtzinger
(HelmholtzCentreforOceanReserachKiel,GEOMAR),andDr.N.Wasmundand
Dr. T. Seifert (Leibniz Institute for Baltic Sea Research, Warnemünde). Their
thorough review resulted in a number of comments and recommendations that led
to considerable improvements in the text and its presentation.
At the IOW, we are indebted to many of our colleagues, especially
B.Sadkowiak,whoconstructedtheautomatedmeasurementsystem’shardwareand
ensuredproperoperationofthesystem.WearealsogratefultotheMonitoringteam
for their regular collection of samples for total CO investigations, and to the staff
2
of the IOW’s CO lab for performing the respective analyses.
2
Warnemünde, Germany Bernd Schneider
Jens Daniel Müller
Contents
1 Introduction.... .... .... ..... .... .... .... .... .... ..... .... 1
1.1 History of CO System Research in the Baltic Sea.... ..... .... 1
2
1.2 Objectives of This Book.... .... .... .... .... .... ..... .... 3
References.. .... .... .... ..... .... .... .... .... .... ..... .... 5
2 The Marine CO System and Its Peculiarities in the Baltic Sea ........ 7
2
2.1 Atmospheric CO Over the Baltic Sea . .... .... .... ..... .... 7
2
2.2 Aqueous Equilibrium Chemistry of CO ... .... .... ..... .... 8
2
2.3 Measurable Variables of the Marine CO System. .... ..... .... 15
2
2.3.1 CO Equilibrium Fugacity and Partial Pressure. ..... .... 15
2
2.3.2 Total CO and pH... .... .... .... .... .... ..... .... 15
2
2.3.3 Alkalinity .... ..... .... .... .... .... .... ..... .... 18
2.3.4 Physico-Chemical Properties of the Master Variables. .... 21
2.4 CO Air-Sea Gas Exchange . .... .... .... .... .... ..... .... 27
2
References.. .... .... .... ..... .... .... .... .... .... ..... .... 33
3 The Main Hydrographic Characteristics of the Baltic Sea..... .... 35
3.1 Water Budget and Estuarine Circulation.... .... .... ..... .... 35
3.2 Seasonality of the Stratification .. .... .... .... .... ..... .... 36
3.3 Stagnation and Inflow Events.... .... .... .... .... ..... .... 39
References.. .... .... .... ..... .... .... .... .... .... ..... .... 41
4 The Database... .... .... ..... .... .... .... .... .... ..... .... 43
4.1 Studies of the Surface Water CO System .. .... .... ..... .... 43
2
4.2 Investigations of the Deep Water CO Accumulation.. ..... .... 47
2
References.. .... .... .... ..... .... .... .... .... .... ..... .... 48
vii
viii Contents
5 Surface Water Biogeochemistry as Derived from pCO
2
Observations ... .... .... ..... .... .... .... .... .... ..... .... 49
5.1 Seasonal and Regional Patterns of pCO and C . .... ..... .... 49
2 T
5.1.1 Characteristics of the pCO Time Series.. .... ..... .... 49
2
5.1.2 Long-Term Changes in pCO .. .... .... .... ..... .... 53
2
5.1.3 The Seasonal Fine Structure of the pCO . .... ..... .... 54
2
5.1.4 From pCO Measurements to Total CO Data . ..... .... 56
2 2
5.2 A Walk Through the Seasons.... .... .... .... .... ..... .... 58
5.2.1 Timing of the Spring Bloom and the Role of Solar
Radiation. .... ..... .... .... .... .... .... ..... .... 58
5.2.2 Quantification of Spring Bloom Productivity .. ..... .... 63
5.2.3 Nitrogen Supply for the Spring Bloom... .... ..... .... 71
5.2.4 Net Community Production and Nutrient Consumption ... 74
5.2.5 The “Blue Water” Period . .... .... .... .... ..... .... 75
5.2.6 Control of Mid-Summer Net Community Production
and N-fixation. ..... .... .... .... .... .... ..... .... 76
5.2.7 Estimation of Depth-Integrated N-fixation. .... ..... .... 82
5.2.8 Autumn Mixing and Upwelling: The Occurrence
of a Last Bloom Event ... .... .... .... .... ..... .... 84
5.2.9 Annual C * Cycling Presented as C * Versus SST
T T
Diagrams. .... ..... .... .... .... .... .... ..... .... 87
References.. .... .... .... ..... .... .... .... .... .... ..... .... 90
6 Organic Matter Mineralization as Reflected in Deep-Water C
T
Accumulation... .... .... ..... .... .... .... .... .... ..... .... 93
6.1 Total CO Dynamics During Periods of Stagnation
2
and Water Renewal .. ..... .... .... .... .... .... ..... .... 93
6.2 Organic Matter Mineralization Rates Derived from C
T
Mass-Balance Calculations.. .... .... .... .... .... ..... .... 96
6.3 Release and Transformations of Nutrients During OM
Mineralization... .... ..... .... .... .... .... .... ..... .... 101
References.. .... .... .... ..... .... .... .... .... .... ..... .... 104
7 Progress Made by Investigations of the CO System
2
and Open Questions . .... ..... .... .... .... .... .... ..... .... 105
Index .... .... .... .... .... ..... .... .... .... .... .... ..... .... 109
About the Authors
Bernd Schneider studied Chemistry at the Christian-
Albrechts-Universität in Kiel, Germany. His scientific
career as a marine chemist started in 1975 as a Ph.D.
student at the Institute of Marine Research in Kiel. In
the years that followed he acted as a researcher at dif-
ferent research institutes in Germany and temporarily
also at research facilities in the US and Sweden. For
more than a decade he was working on the deposition
of atmospheric trace substances before starting studies
on the marine CO system and the relationship to bio-
2
geochemical processes. Currently he is a senior scien-
tist at the Leibniz Institute for Baltic Sea Research in
Warnemünde,Germany. Photo:©KristinBeck,IOW.
Jens Daniel Müller finished his Bachelors studies in
Chemistryin2009,whereafterhecompletedaMasters
program in Biological Oceanography at Geomar in
Kiel.Since2014hehasbeenaPh.D.studentinGregor
Rehder’s working group “Biogeochemistry of envi-
ronmentally relevant gases”. Within the framework
oftheBONUSprojectPINBAL(GrantNo.03F0689A)
hisfocusisonspectrophotometricpHmeasurementin
brackish waters. Besides his fascination for biogeo-
chemicalandCO systemresearch,heisanenthusiastic
2
scientificdiverandsailor. Photo:©KristinBeck,IOW.
ix