Figure 4. Power spectra of deep water oxygen concentrations for
different cases of imposed cyclic variation of the vertical exchange
rate (amplitude in m y-1 as deviation from 11 m
y-1, the MCAHI default value),
representing variability of climatic forcing. Each row represents a
given period (T) and the columns different amplitude of the oscillation.
The dashed line graphs show the power spectra of the inherent
oscillation with constant vertical exchange rate (cf. Fig 3c).
Although enhanced nutrient loading to the Baltic during the MCA has been
suggested (Zillén & Conley, 2010), little evidence for eutrophication
has been found in coastal paleoenvironmental data from this period (Ning
et al., 2016; Jokinen et al., 2018; Norbäck Ivarsson et al., 2019).
Therefore we imposed an external loading of 8000 tonnes P/year for both
the MCAHI and HTMHI simulations, as
derived from estimates of the pre-industrial loading to the Baltic Sea
(Gustafsson et al., 2012). Because this value is at the lower limit of
the range yielding oscillations in most parameterizations (Fig. 3c,d),
we adjusted the vertical exchange parameter D in
MCAHI and HTMHI simulations to
approximately 20% lower than the modern value (Table S1). Lower values
of D favor stagnation and the development of deep water hypoxia,
and tip the system into an oscillatory state at external loading of
<8000 tonnes P/year (Supporting Information Figs. S8 and S9).
Our simulations therefore suggest that climatic factors controlling
vertical mixing may be capable of triggering hypoxia under
pre-anthropogenic P loading, despite a recent study indicating otherwise
(Meier et al., 2019).
3.7 Implications for future management of the Baltic Sea
Under the BSAP (HELCOM, 2007; 2013), riparian countries agreed to limit
external P loading to the Baltic in order to reduce the occurrence of
hypoxia and cyanobacterial blooms in the future. As part of the plan,
maximum allowable inputs of P to the whole Baltic Sea were set at 21716
tonnes P/year (about 18500 tonnes P/year in the region covered by the
model). Our findings suggest that such targets, if met, will improve
water quality but are unlikely to force the system to a fully oxic state
(Fig. 3e). Rather, deep water oxygen concentrations are likely to remain
close to the hypoxia threshold of 63 µmol/L. This finding is consistent
with existing simulations from more complex coupled
physical-biogeochemical models for the Baltic Sea (e.g. Meier et al.,
2018). To achieve a transition beyond hypoxia to quasi-permanent oxic
conditions would require a further load reduction and our model shows
that this will likely proceed via an interval during which the system is
vulnerable to multidecadal oscillations in hypoxia, creating a challenge
for assessments of the success of management efforts. These results
highlight the need to include more details of Fe-P interactions in
models used for management decisions in the Baltic Sea (e.g. BALTSEM;
Savchuk et al., 2012). We suggest that the extent to which oscillations
may impact upon the actual recovery trajectory in the coming centuries
will depend on the speed with which loading reduction targets are
achieved. More rapid reductions are more likely to starve the system of
P and therefore to promote a more linear recovery trajectory.
4 Conclusions
Our study shows that feedbacks in the coupled cycling of Fe and P drove
multidecadal oscillations in the intensity of oxygen depletion during
past hypoxic intervals in the 8000 year history of the Baltic Sea.
In-phase oscillatory profiles of Mo/Al, Br/P and Fe/Al in sediments
suggest large-scale synchronicity in deep water hypoxia, P regeneration
and Fe shuttling, respectively. A simple box model of coupled Fe and P
cycling suggests that internal multidecadal instability in hypoxia
intensity is controlled by non-linear recharging and discharging of the
sedimentary Fe-P reservoir in deeper areas. Crucially, our model
simulations show that oscillatory behavior is sensitive to external P
loading. While low external loads favor stable oxic conditions, and high
loads sustain stable hypoxia, intermediate loads lead to unstable
oscillatory behavior on multidecadal timescales. This observation has
implications for predicting the trajectory of recovery from modern
hypoxia in the Baltic Sea, since external P loading is expected to
decline in accordance with the BSAP. Variable external climate forcing
may influence the frequency and amplitude of oscillations through its
impact on vertical water mass exchange.
Acknowledgments, Samples, and Data
This work was supported by European Research Council (ERC) Starting
Grant (Consolidator Level) 278364 and Netherlands Organisation for
Scientific Research (NWO) Vici grant 865.13.005 to Caroline Slomp,
Academy of Finland Research Fellowship 317684 to Tom Jilbert, the EU
BONUS-HYPER project, Baltic Bridge collaboration between University of
Helsinki and Stockholm University and the program of the Netherlands
Earth System Science Center (NESSC), financially supported by the
Ministry of Education, Culture and Science (OCW).
The raw LA-ICP-MS data and time series analysis outputs are available
free of charge (CC-BY 4.0) on Zenodo at DOI: 10.5281/zenodo.5222925. The
box model (v1.0.2) used for investigating the mechanisms of oscillations
is available (MIT Licence: Copyright Bo Gustafsson) at DOI:
10.5281/zenodo.5235401. The model code was developed using Xcode IDE
(https://developer.apple.com/xcode/) in Swift language.
References
Börgel, F., Frauen, C., Neumann, T., & Meier, H. M. (2020). The
Atlantic Multidecadal Oscillation controls the impact of the North
Atlantic Oscillation on North European climate. Environmental
Research Letters , 15 (10), 104025.
https://doi.org/10.1088/1748-9326/aba925
Carstensen, J., Andersen, J. H., Gustafsson, B. G., & Conley, D. J.
(2014). Deoxygenation of the Baltic Sea during the last century.Proceedings of the National Academy of Sciences , 111 (15),
5628-5633. https://doi.org/10.1073/pnas.1323156111
Conley, D. J., Björck, S., Bonsdorff, E., Carstensen, J., Destouni, G.,
Gustafsson, B. G., Hietanen, S., Kortekaas, M., Kuosa, H., & Markus
Meier, H. (2009). Hypoxia-related processes in the Baltic Sea.Environmental Science & Technology , 43 (10), 3412-3420.
https://doi.org/10.1021/es802762a
Eckert, S., Brumsack, H.-J., Severmann, S., Schnetger, B., März, C., &
Fröllje, H. (2013). Establishment of euxinic conditions in the Holocene
Black Sea. Geology , 41 (4), 431-434.
https://doi.org/10.1130/G33826.1
Gustafsson, B. G., Schenk, F., Blenckner, T., Eilola, K., Meier, H. M.,
Müller-Karulis, B., Neumann, T., Ruoho-Airola, T., Savchuk, O. P., &
Zorita, E. (2012). Reconstructing the development of Baltic Sea
eutrophication 1850–2006. Ambio , 41 (6), 534-548.
https://doi.org/10.1007/s13280-012-0318-x
HELCOM. (2013). Summary report on the development of revised Maximum
Allowable Inputs (MAI) and updated Country Allocated Reduction Targets
(CART) of the Baltic Sea Action Plan. Supporting document for the 2013
HELCOM Ministerial Meeting.
HELCOM, B. (2007). HELCOM Baltic Sea action plan. Adopted in Krakow,
Poland, 15 November 2007.
Hennekam, R., Jilbert, T., Mason, P. R., de Lange, G. J., & Reichart,
G.-J. (2015). High-resolution line-scan analysis of resin-embedded
sediments using laser ablation-inductively coupled plasma-mass
spectrometry (LA-ICP-MS). Chemical Geology , 403 , 42-51.
https://doi.org/10.1016/j.chemgeo.2015.03.004
Ingall, E. D., Bustin, R., & Van Cappellen, P. (1993). Influence of
water column anoxia on the burial and preservation of carbon and
phosphorus in marine shales. Geochimica et Cosmochimica Acta ,57 (2), 303-316.
https://doi.org/10.1016/0016-7037(93)90433-W
Jilbert, T., Conley, D. J., Gustafsson, B. G., Funkey, C. P., & Slomp,
C. P. (2015). Glacio-isostatic control on hypoxia in a high-latitude
shelf basin. Geology , 43 (5), 427-430.
https://doi.org/10.1130/G36454.1
Jilbert, T., de Lange, G., & Reichart, G. J. (2008). Fluid displacive
resin embedding of laminated sediments: preserving trace metals for
high‐resolution paleoclimate investigations. Limnology and
Oceanography: Methods , 6 (1), 16-22.
https://doi.org/10.4319/lom.2008.6.16
Jilbert, T., Slomp, C., Gustafsson, B. G., & Boer, W. (2011). Beyond
the Fe-P-redox connection: preferential regeneration of phosphorus from
organic matter as a key control on Baltic Sea nutrient cycles.Biogeosciences , 8 (6), 1699-1720.
https://doi.org/10.5194/bg-8-1699-2011
Jilbert, T., & Slomp, C. P. (2013). Rapid high-amplitude variability in
Baltic Sea hypoxia during the Holocene. Geology , 41 (11),
1183-1186. https://doi.org/10.1130/G34804.1
Jokinen, S. A., Virtasalo, J. J., Jilbert, T., Kaiser, J., Dellwig, O.,
Arz, H. W., Hänninen, J., Arppe, L., Collander, M., & Saarinen, T.
(2018). A 1500-year multiproxy record of coastal hypoxia from the
northern Baltic Sea indicates unprecedented deoxygenation over the 20th
century. Biogeosciences , 15 (13), 3975-4001.
https://doi.org/10.5194/bg-15-3975-2018
Knudsen, M. F., Seidenkrantz, M.-S., Jacobsen, B. H., & Kuijpers, A.
(2011). Tracking the Atlantic Multidecadal Oscillation through the last
8,000 years. Nature Communications , 2 (1), 1-8.
https://doi.org/10.1038/ncomms1186
Lefort, S., Gratton, Y., Mucci, A., Dadou, I., & Gilbert, D. (2012).
Hypoxia in the Lower St. Lawrence Estuary: How physics controls spatial
patterns. Journal of Geophysical Research: Oceans ,117 (C7). https://doi.org/10.1029/2011JC007751
Lenz, C., Jilbert, T., Conley, D. J., & Slomp, C. P. (2015).
Hypoxia‐driven variations in iron and manganese shuttling in the Baltic
Sea over the past 8 kyr. Geochemistry, Geophysics, Geosystems ,16 (10), 3754-3766. https://doi.org/10.1002/2015GC005960
Lougheed, B. C., Snowball, I., Moros, M., Kabel, K., Muscheler, R.,
Virtasalo, J. J., & Wacker, L. (2012). Using an independent
geochronology based on palaeomagnetic secular variation (PSV) and
atmospheric Pb deposition to date Baltic Sea sediments and infer 14C
reservoir age. Quaternary Science Reviews , 42 , 43-58.
https://doi.org/10.1016/j.quascirev.2012.03.013
Lyons, T. W., & Severmann, S. (2006). A critical look at iron
paleoredox proxies: New insights from modern euxinic marine basins.Geochimica et Cosmochimica Acta , 70 (23), 5698-5722.
https://doi.org/10.1016/j.gca.2006.08.021
Meier, H., Edman, M. K., Eilola, K. J., Placke, M., Neumann, T.,
Andersson, H. C., Brunnabend, S.-E., Dieterich, C., Frauen, C., &
Friedland, R. (2018). Assessment of eutrophication abatement scenarios
for the Baltic Sea by multi-model ensemble simulations. Frontiers
in Marine Science , 5 , 440.
https://doi.org/10.3389/fmars.2018.00440
Meier, H., Eilola, K., Almroth-Rosell, E., Schimanke, S., Kniebusch, M.,
Höglund, A., Pemberton, P., Liu, Y., Väli, G., & Saraiva, S. (2019).
Disentangling the impact of nutrient load and climate changes on Baltic
Sea hypoxia and eutrophication since 1850. Climate Dynamics ,53 (1), 1145-1166. https://doi.org/10.1007/s00382-018-4296-y
Mortimer, C. H. (1941). The exchange of dissolved substances between mud
and water in lakes. Journal of Ecology , 29 (2), 280-329.
https://doi.org/10.2307/2256395
Ning, W., Ghosh, A., Jilbert, T., Slomp, C. P., Khan, M., Nyberg, J.,
Conley, D. J., & Filipsson, H. L. (2016). Evolving coastal character of
a Baltic Sea inlet during the Holocene shoreline regression: impact on
coastal zone hypoxia. Journal of Paleolimnology , 55 (4),
319-338. https://doi.org/10.1007/s10933-016-9882-6
Norbäck Ivarsson, L., Andrén, T., Moros, M., Andersen, T. J., Lönn, M.,
& Andrén, E. (2019). Baltic sea coastal eutrophication in a thousand
year perspective. Frontiers in Environmental Science , 7 ,
88. https://doi.org/10.3389/fenvs.2019.00088
Paillard, D., Labeyrie, L., & Yiou, P. (1996). Macintosh program
performs time‐series analysis. Eos, Transactions American
Geophysical Union , 77 (39), 379-379.
https://doi.org/10.1029/96EO00259
Rabalais, N., Diaz, R. J., Levin, L., Turner, R., Gilbert, D., & Zhang,
J. (2010). Dynamics and distribution of natural and human-caused
hypoxia. Biogeosciences , 7 (2), 585-619.
https://doi.org/10.5194/bg-7-585-2010
Reed, D. C., Slomp, C. P., & Gustafsson, B. G. (2011). Sedimentary
phosphorus dynamics and the evolution of bottom‐water hypoxia: A coupled
benthic–pelagic model of a coastal system. Limnology and
Oceanography , 56 (3), 1075-1092.
https://doi.org/10.4319/lo.2011.56.3.1075
Savchuk, O. P., Gustafsson, B. G., & Müller-Karulis, B. (2012).
BALTSEM: A marine model for decision support within the Baltic Sea
Region. Baltic Nest Institute Technical Report , 7 , 55.
Vahtera, E., Conley, D. J., Gustafsson, B. G., Kuosa, H., Pitkänen, H.,
Savchuk, O. P., Tamminen, T., Viitasalo, M., Voss, M., & Wasmund, N.
(2007). Internal ecosystem feedbacks enhance nitrogen-fixing
cyanobacteria blooms and complicate management in the Baltic Sea.Ambio , 186-194.
Van Cappellen, P., & Ingall, E. D. (1994). Benthic phosphorus
regeneration, net primary production, and ocean anoxia: A model of the
coupled marine biogeochemical cycles of carbon and phosphorus.Paleoceanography , 9 (5), 677-692.
https://doi.org/10.1029/94PA01455
Warden, L., Moros, M., Neumann, T., Shennan, S., Timpson, A., Manning,
K., Sollai, M., Wacker, L., Perner, K., & Häusler, K. (2017). Climate
induced human demographic and cultural change in northern Europe during
the mid-Holocene. Scientific Reports , 7 (1), 1-11.
https://doi.org/10.1038/s41598-017-14353-5
Ziegler, M., Jilbert, T., de Lange, G. J., Lourens, L. J., & Reichart,
G. J. (2008). Bromine counts from XRF scanning as an estimate of the
marine organic carbon content of sediment cores. Geochemistry,
Geophysics, Geosystems , 9 (5).
https://doi.org/10.1029/2007GC001932
Zillén, L., & Conley, D. J. (2010). Hypoxia and cyanobacteria
blooms-are they really natural features of the late Holocene history of
the Baltic Sea? Biogeosciences , 7 (8), 2567-2580.
https://doi.org/10.5194/bg-7-2567-2010
Zillén, L., Conley, D. J., Andrén, T., Andrén, E., & Björck, S. (2008).
Past occurrences of hypoxia in the Baltic Sea and the role of climate
variability, environmental change and human impact. Earth-Science
Reviews , 91 (1-4), 77-92.
https://doi.org/10.1016/j.earscirev.2008.10.001
References cited in Supporting Information
Al-Hamdani, Z., Reker, J., Alanen, U., Andersen, J. H., Bendtsen, J.,
Bergström, U., Dahl, K., Dinesen, G. E., Erichsen, A., & Elhammer, A.
(2007). Towards benthic marine landscapes in the Baltic Sea.BALANCE Interim Report , 10 .
Almroth-Rosell, E., Eilola, K., Hordoir, R., Meier, H. M., & Hall, P.
O. (2011). Transport of fresh and resuspended particulate organic
material in the Baltic Sea—a model study. Journal of Marine
Systems , 87 (1), 1-12.
https://doi.org/10.1016/j.jmarsys.2011.02.005
Almroth-Rosell, E., Eilola, K., Kuznetsov, I., Hall, P. O., & Meier, H.
M. (2015). A new approach to model oxygen dependent benthic phosphate
fluxes in the Baltic Sea. Journal of Marine Systems , 144 ,
127-141. https://doi.org/10.1016/j.jmarsys.2014.11.007
Andersson, L. (1996). Trends in nutrients and oxygen concentrations in
the Skagerrak-Kattegat. Journal of Sea Research , 35 (1-3),
63-71. https://doi.org/10.1016/S1385-1101(96)90735-2
Boudreau, B. P. (1997). Diagenetic models and their
implementation (Vol. 410). Springer, Berlin.
Carstensen, J., Andersen, J. H., Gustafsson, B. G., & Conley, D. J.
(2014). Deoxygenation of the Baltic Sea during the last century.Proceedings of the National Academy of Sciences , 111 (15),
5628-5633. https://doi.org/10.1073/pnas.1323156111
Conley, D. J., Humborg, C., Rahm, L., Savchuk, O. P., & Wulff, F.
(2002). Hypoxia in the Baltic Sea and basin-scale changes in phosphorus
biogeochemistry. Environmental Science & Technology ,36 (24), 5315-5320. https://doi.org/10.1021/es025763w
Eilola, K., Meier, H. M., & Almroth, E. (2009). On the dynamics of
oxygen, phosphorus and cyanobacteria in the Baltic Sea; A model study.Journal of Marine Systems , 75 (1-2), 163-184.
https://doi.org/10.1016/j.jmarsys.2008.08.009
Gustafsson, B. (2001). Quantification of water, salt, oxygen and
nutrient exchange of the Baltic Sea from observations in the Arkona
Basin. Continental Shelf Research , 21 (13-14), 1485-1500.
https://doi.org/10.1016/S0278-4343(01)00014-0
Gustafsson, B. G., Schenk, F., Blenckner, T., Eilola, K., Meier, H. M.,
Müller-Karulis, B., Neumann, T., Ruoho-Airola, T., Savchuk, O. P., &
Zorita, E. (2012). Reconstructing the development of Baltic Sea
eutrophication 1850–2006. Ambio , 41 (6), 534-548.
https://doi.org/10.1007/s13280-012-0318-x
Gustafsson, B. G., & Stigebrandt, A. (2007). Dynamics of nutrients and
oxygen/hydrogen sulfide in the Baltic Sea deep water. Journal of
Geophysical Research: Biogeosciences , 112 (G2).
https://doi.org/10.1029/2006JG000304
Gustafsson, B. G., & Westman, P. (2002). On the causes for salinity
variations in the Baltic Sea during the last 8500 years.Paleoceanography , 17 (3), 12-11-12-14.
https://doi.org/10.1029/2000PA000572
Gustafsson, E., Savchuk, O. P., Gustafsson, B. G., & Müller-Karulis, B.
(2017). Key processes in the coupled carbon, nitrogen, and phosphorus
cycling of the Baltic Sea. Biogeochemistry , 134 (3),
301-317. https://doi.org/10.1007/s10533-017-0361-6
Gustafsson, Ö., Gelting, J., Andersson, P., Larsson, U., & Roos, P.
(2013). An assessment of upper ocean carbon and nitrogen export fluxes
on the boreal continental shelf: A 3‐year study in the open Baltic Sea
comparing sediment traps, 234Th proxy, nutrient, and oxygen budgets.Limnology and Oceanography: Methods , 11 (9), 495-510.
https://doi.org/10.4319/lom.2013.11.495
Hennekam, R., Jilbert, T., Mason, P. R., de Lange, G. J., & Reichart,
G.-J. (2015). High-resolution line-scan analysis of resin-embedded
sediments using laser ablation-inductively coupled plasma-mass
spectrometry (LA-ICP-MS). Chemical Geology , 403 , 42-51.
https://doi.org/10.1016/j.chemgeo.2015.03.004
Hermans, M., Lenstra, W. K., van Helmond, N. A., Behrends, T., Egger,
M., Séguret, M. J., Gustafsson, E., Gustafsson, B. G., & Slomp, C. P.
(2019). Impact of natural re-oxygenation on the sediment dynamics of
manganese, iron and phosphorus in a euxinic Baltic Sea basin.Geochimica et Cosmochimica Acta , 246 , 174-196.
https://doi.org/10.1016/j.gca.2018.11.033
Jilbert, T., Conley, D. J., Gustafsson, B. G., Funkey, C. P., & Slomp,
C. P. (2015). Glacio-isostatic control on hypoxia in a high-latitude
shelf basin. Geology , 43 (5), 427-430.
https://doi.org/10.1130/G36454.1
Jilbert, T., Slomp, C., Gustafsson, B. G., & Boer, W. (2011). Beyond
the Fe-P-redox connection: preferential regeneration of phosphorus from
organic matter as a key control on Baltic Sea nutrient cycles.Biogeosciences , 8 (6), 1699-1720.
https://doi.org/10.5194/bg-8-1699-2011
Jilbert, T., & Slomp, C. P. (2013). Rapid high-amplitude variability in
Baltic Sea hypoxia during the Holocene. Geology , 41 (11),
1183-1186. https://doi.org/10.1130/G34804.1
Jönsson, A., Danielsson, Å., & Rahm, L. (2005). Bottom type
distribution based on wave friction velocity in the Baltic Sea.Continental Shelf Research , 25 (3), 419-435.
https://doi.org/10.1016/j.csr.2004.09.011
Meier, H. M. (2005). Modeling the age of Baltic Seawater masses:
quantification and steady state sensitivity experiments. Journal
of Geophysical Research: Oceans , 110 (C2).
https://doi.org/10.1029/2004JC002607
Mort, H. P., Slomp, C. P., Gustafsson, B. G., & Andersen, T. J. (2010).
Phosphorus recycling and burial in Baltic Sea sediments with contrasting
redox conditions. Geochimica et Cosmochimica Acta , 74 (4),
1350-1362. https://doi.org/10.1016/j.gca.2009.11.016
Pers, C., & Rahm, L. (2000). Changes in apparent oxygen removal in the
Baltic proper deep water. Journal of Marine Systems ,25 (3-4), 421-429.
https://doi.org/10.1016/S0924-7963(00)00031-2
Press, W. H., Teukolsky, S. A., Flannery, B. P., & Vetterling, W. T.
(1992). Numerical recipes in Fortran 77 (Second Edition) .
Cambridge University Press.
Reed, D. C., Gustafsson, B. G., & Slomp, C. P. (2016). Shelf-to-basin
iron shuttling enhances vivianite formation in deep Baltic Sea
sediments. Earth and Planetary Science Letters , 434 ,
241-251. https://doi.org/10.1016/j.epsl.2015.11.033
Reed, D. C., Slomp, C. P., & Gustafsson, B. G. (2011). Sedimentary
phosphorus dynamics and the evolution of bottom‐water hypoxia: A coupled
benthic–pelagic model of a coastal system. Limnology and
Oceanography , 56 (3), 1075-1092.
https://doi.org/10.4319/lo.2011.56.3.1075
Savchuk, O. P. (2002). Nutrient biogeochemical cycles in the Gulf of
Riga: scaling up field studies with a mathematical model. Journal
of Marine Systems , 32 (4), 253-280.
https://doi.org/10.1016/S0924-7963(02)00039-8
Savchuk, O. P., Gustafsson, B. G., & Müller-Karulis, B. (2012).
BALTSEM: A marine model for decision support within the Baltic Sea
Region. Baltic Nest Institute Technical Report , 7 , 55.
Savchuk, O. P., & Wulff, F. (2009). Long-term modeling of large-scale
nutrient cycles in the entire Baltic Sea. In Eutrophication in
Coastal Ecosystems (pp. 209-224). Springer.
https://doi.org/10.1007/978-90-481-3385-7_18
Savchuk, O. P., Wulff, F., Hille, S., Humborg, C., & Pollehne, F.
(2008). The Baltic Sea a century ago—a reconstruction from model
simulations, verified by observations. Journal of Marine Systems ,74 (1-2), 485-494.
https://doi.org/10.1016/j.jmarsys.2008.03.008
Seifert, T., Tauber, F., & Kayser, B. (2001). A high resolution
spherical grid topography of the Baltic Sea–revised edition. Baltic Sea
Science Congress. 25-29.
Stigebrandt, A. (1991). Computations of oxygen fluxes through the sea
surface and the net production of organic matter with application to the
Baltic and adjacent seas. Limnology and Oceanography ,36 (3), 444-454. https://doi.org/10.4319/lo.1991.36.3.0444
Stigebrandt, A., & Gustafsson, B. G. (2003). Response of the Baltic Sea
to climate change—theory and observations. Journal of Sea
Research , 49 (4), 243-256.
https://doi.org/10.1016/S1385-1101(03)00021-2
Tamelander, T., Spilling, K., & Winder, M. (2017). Organic matter
export to the seafloor in the Baltic Sea: Drivers of change and future
projections. Ambio , 46 (8), 842-851.
https://doi.org/10.1007/s13280-017-0930-x
Vollenweider, R. A. (1969). Possibilities and limits of elementary
models concerning budget of substances in lakes. Archive for
Hydrobiology , 66 (1), 1-36.
Ziegler, M., Jilbert, T., de Lange, G. J., Lourens, L. J., & Reichart,
G. J. (2008). Bromine counts from XRF scanning as an estimate of the
marine organic carbon content of sediment cores. Geochemistry,
Geophysics, Geosystems , 9 (5).
https://doi.org/10.1029/2007GC001932