Lignins in the ocean

Quelle: Kummer/Stumm
Ein wichtiges Konzept der
Umweltchemie ist es, globale
und regionale Materieflüsse
und Stoffkreisläufe in den
Vordergrund zu stellen
Insbesondere die
Stoffkreisläufe der Elemente
gut erforscht sind der globale
Schwefelkreislauf u.a.
Rolle natürlicher organischer
Komplexbildner für Eisen
The higher dissolution of Fe hydroxide in
seawater has been attributed to the presence of
organic ligands. (Liu and Millero, 2002; Hiemstra
und Riemsdijk, 2006)
Our research will contribute to deeper understanding
of peatlands and their ecosystem services, thereby
providing scientific basis for “ecosystem infrastructure”
(a) Net global peatland C
sequestration rates per
millennium (gigatons C per
(b) True instantaneous C
accumulation rates from
northern peatlands as derived
from net carbon balance (NCB)
in Figure 2a and peatland
areas over time.
Red circle represents
the average of NCB from three
peatland sites
(c) C isotope composition from
atmospheric carbon dioxide
(d) Atmospheric CO2
Note that high C sequestration
peatlands at 7000–10,000
years ago (Figures 2a and 2b)
is likely responsible for the
simultaneous CO2 decrease
(Figure 2d) and d13CO2
increase (Figure 2c);
(Yu et al., Eos, Vol. 92, No. 12, 22
March 2011)
The hypothesis that iron (Fe) can act as
a limiting micro-nutrient in highnutrient low-chlorophyll (HNLC )
regions (first published 1990) has led
to numerous studies that all
demonstrate that the addition of Fe to
HNLC waters causes an increase in
phytoplankton productivity.
The broader implication is that in
HNLC waters, the addition of soluble
Fe(III) can increase the efficiency of the
biological pump and promote drawdown
of atmospheric carbon dioxide.
(H. Planquette et al. / Deep-Sea Research II (2007))
A large diatom bloom peaked in the fourth
week after artificial iron fertilization.
This was followed by mass mortality of
several diatom species that formed rapidly
sinking, mucilaginous aggregates of
entangled cells and chains.
Taken together, multiple lines of evidence
lead us to conclude that at least half the
bloom biomass sank far below a depth of
1,000 m and that a substantial portion is
likely to have reached the sea floor.
Thus, iron-fertilized diatom blooms may
sequester carbon for timescales of
centuries in ocean bottom water and for
longer in the sediments.
In situ iron enrichment experiments in the
open ocean stimulated toxic diatom
production (Trick et al., 2010)
Domoic acid
Recently, several in situ Fe-enrichment
experiments e.g. in the Southern Ocean have
highlighted the importance of Fe availability for
phytoplankton communities in HNLC regions
However, such artificial enrichments could lead
to adverse side effects such as the occurrence of
algal toxins, and reduced oxygen concentration
at depth
natural iron fertilization off the Crozet
Islands in the southern Indian Ocean has
been studied
whereas natural iron fertilization
increased ecosystem biomass, there was no
evidence of damage due to reduced
oxygen concentration at depth, assuaging
the concern that ocean iron fertilization
might cause the seafloor to become a
biodiversity desert due to lack of oxygen
algal toxins were not detectable
In the Southern Ocean, sites of natural and
continuous fertilization of Fe do exist where there
is permanent interaction between water masses
and margins of landmasses
This phenomenon is called ‘‘the island effect’’.
Several studies have inferred Fe-fertilized
phytoplankton blooms around island systems in
the Southern Ocean
Natural sources of Fe, originating either from the
islands directly or from the relatively shallow
surrounding sediments, relieve Fe stress and
therefore promote phytoplankton growth,
particularly by the larger cells typically
responsible for the export of particulate carbon.
Foto: Polar Conservation
H. Planquette et al., Deep-Sea Research II (2007)
H. Planquette et al., Deep-Sea Research II (2007)
A generally depauperate flora and tundra-like vegetation devoid of trees is typical.
Bryophytes are a major component of sub-Antarctic plant communities.
The climatic conditions are very suitable for peat formation,
and an extensive peat cover has developed on these islands at low altitudes. (van der
Putten et al., Palaeogeography, Palaeoclimatology, Palaeoecology 270 , 2008)
Natural iron fertilisation
around the Crozet
Islands southern Indian
Polar Conservation
Fig. 2. NE–SW cross-section of the Morne Rouge crater (Ile de la
Possession, Iles Crozet) with the location of the Morne Rouge sequence
and the two lake cores. Radiocarbon dates of the base of the three cores
are indicated. (van der Putten et al., Palaeogeography, Palaeoclimatology, Palaeoecology
270 , 2008)
Fe nmol L-
Ireland: Peatlands cover 13 470 km² or 16.2%
of the land surface.
Laglera and van den Berg, 2009
Laglera and van den Berg, 2009
Mixing experiments
using a 59Fe
radiotracer method
(filtered Creek water
and filtered coastal
seawater). The
diagram shows the
virtual iron
concentration in the
river water as a
function of salinity.
Data from Krachler et al.,
2005, 2010.
asymmetric Flow Field Flow Fractionation
- differential refractive index
- UV-DAD (=Diodenarray-Detektor)
- Fluorescence (3D)
- Light Scattering (static & dynamic)
Burning of peatland (
Bild: Friends of the Irish Environment
Shatura Power Station (Russia) has the largest peat
power capacity in the world (Bild: Wikipedia)
The Toppila Power Station, a peat-fired facility in Oulu, Finland (Bild:
Autochthonous ligands for
Fe(III) in the ocean
A.E. Witter et al., 2000
Phytic acid (inositol
hexakisphosphate) is
the principal storage form
of phosphorus in many
plant tissues e.g. in
edible legumes, cereals,
and seed
Primary producers in the open ocean are
photosynthetic cyanobacteria and eucaryotic
microorganisms which are unicellular, freeliving, relying on diffusive fluxes of nutrients
Neither group appears to produce siderophores
This is an adaption to the dilute pelagic marine
environment which promotes large diffusive
losses (Hopkinson and Morel, 2009)
Heterotrophic marine bacteria synthesize
siderophores, however when attached to particles
such as marine snow where losses by diffusion
can be reduced
Inevitably some of the siderophores produced
by bacteria are released forming a portion of the
natural iron binding ligands in the ocean
Rapid production of Fe binding compounds of
unknown chemical identity has been detected in
response to experimental Fe addition to ironlimited regions of the open ocean (Buck and
Bruland, 2007)
This response is opposite to that expected of
siderophore production, which is upregulated
under iron stress and turned off when iron is
One compound secreted by a phytoplanktonic
marine eucaryote (Pseudonitzschia), the diatom
toxin domoic acid, has been implicated in metal
uptake (binds Cu).
Domoic acid could play an indirect role in
alleviating iron limitation as Cu is involved in
diatom iron uptake systems
Laglera and van den Berg, 2009:
Evidence for geochemical control of
iron by humic substances in seawater.
A new method, based on the detection of iron-humic
substance (Fe-HS) by cathodic stripping
voltammetry , was used to determine the iron binding
capacity and complex stability of Fe-HS in the
“HS have to be considered as a major ligand for iron,
addition to other ligands that have been
proposed for iron”
“The covariation of iron and HS in the coastal waters
indicates that iron and HS travel together from land
to the open sea.” (Irish Sea)
Discharge a large volume of freshwater
(3300 km3 yr-1)
and terrigenous DOM
(25 Tg C yr-1)
to the shelf and polar surface waters
Lignins, which have no
autochthonous source in the
ocean, have been
nevertheless found in low
concentrations throughout
the entire Arctic, Atlantic,
and Pacific oceans
Opsahl and Benner, 1997; Benner et al.,
2005; Hernes and Benner, 2002; Hernes
and Benner, 2006; Louchouarn et al.,
Concentrations of total dissolved lignin
phenols in polar surface waters: up to 1489
The large contribution of terrigenous DOM
from Arctic rivers is responsible for the
elevated concentrations of lignin phenols in
polar surface waters
Physical transport of terrigenous DOM to
the North Atlantic is a major mechanism
for its removal from the Arctic
This exports compose 25-33% of the
terrigenous DOM discharged annually to
the Arctic via rivers.
The inverse linear
relationship between
dissolved iron and
salinity demonstrates
the important role of
Arctic rivers in the
delivery of dissolved
iron to the Arctic
chemically variable and functionally
heterogeneous polymers (colloids)
derived from plant decomposition
ubiquitous in aquatic ecosystems
accounting for up to 95% of dissolved
organic carbon (DOC) in freshwater
Marine pollution
Threat of hypoxia
Harmful algal blooms
From: World
Census –
A Global
Survey of
Marine Life
2000 – 2010
Through drainage of peatlands in
river catchments, dissolved
humic substances have been
eliminated from river waters
Much of the European peat
resource has vanished as
technology and development
have advanced (web site of the Irish
Peatland Conservation Council)
HS are carbon sources for bacterial
HS as food: HS are directly available to
filter feeding zooplankton
HS shield aquatic organisms from
harmful UV radiation
HS serve as transport vehicles for
bioactive metals
HS exert a mild chemical stress upon
An array of oxidative stress symptoms
have been reported in several organisms
exposed to HS
The interaction between metals and naturally
occurring humic substances and the thereby
induced issues of bioavailability and
hydrogeochemical turnover of metal ions in
natural waters have been the subject of
intense study for decades
However metal complexation by humic
substances in seawater has become a focus of
scientific interest only recently
Effect of different iron species
on oogonium formation of
Laminaria religiosa. Fulvic–
iron complex promoted the
best oogonium formation rate
(79%) of L. religiosa at 35
days compared to amorphous
Fe (41%) and control (3%)
Effect of humic
substances on the
tetraspores growth
of crustose
coralline algae
spp.). FA, fulvic
acid ;HA, humic
Fe limits phytoplankton growth in
extended regions of the ocean
Other metals (Zn, Co, Mn) can also
occasionally limit phytoplankton growth
in the ocean
but may play a more important role in
regulating the composition of
phytoplankton because of large differences
in trace metal requirements among species
Likewise, low Fe availability can have a
critical influence on the composition and
structure of algal communities, because of
differences in requirements among species
It serves essential metabolic
functions in:
photosynthetic electron transport
respiratory electron transport
nitrate and nitrite reduction
sulfate reduction
N2 fixation
detoxification of reactive oxygen
Fe requirements are influenced by a
number of factors such as light
intensity, nitrogen source (NH4+, N2,
NO3-, urea) , CO2 availability etc.
Fe limits phytoplankton growth in high-nitrate
low-chlorophyll waters (25% of the word‘s
Fe limits nitrogen fixation by diazotrophs in
nitrate-poor low-latitude waters
Together, low Fe concentrations limit
productivity in about 50% of the world ocean
Iron deficiency limits the drawdown of CO2
from the atmosphere by phytoplankton
Fe is therefore a critical component of the
Earth‘s climate system
atmospheric dust deposition from arid regions
volcanic ash deposition, extraterrestrial dust
ice melting
hydrothermal vents (not a significant iron
source for microbes in the euphotic zone)
offshore eddy transport of iron-rich coastal
The majority of dissolved Fe in river
water exists as small colloid particles
(Fox,1988; Dai and Martin, 1995; Wen et al.,
Flocculation of these colloids, due to the
change in ionic strength upon mixing of
river water with seawater, causes a
massive removal of the Fe (Sholkovitz,
1978; Sholkovitz et al., 1978).
short residence time of iron, external sources and sinks
We propose that with peat-bog
derived HS as an important carrier
mechanism for riverine Fe, the
influence of this Fe source reaches
further out to sea than previously
Oligomeric lignin
phenols as important
land-derived iron
chelators in the ocean?
The concentrations of
lignin phenols in the
open ocean are small,
but may be sufficient to
keep Fe soluble
Cinnamic Acid
Sinapic Acid
Ferulic Acid
P-Coumaric Acid
Syringic Acid
(Opsahl and Benner, 2000)
Neben Cellulose die häufigsten organischen
Verbindungen auf unserem Planeten.
Etwa 20 % bis 30 % der Trockenmasse verholzter
Pflanzen besteht aus Ligninen. Die Gesamtproduktion
der Lignine wird auf 20 Milliarden Tonnen pro Jahr
Lignine sind wesentlich für die Druck-Festigkeit von
pflanzlichen Geweben. Ihre „Erfindung“ ermöglichte
die Evolution der landlebenden Pflanzen.
Werden nur langsam und nur aerob von bestimmtem
Pilzen und Bakterien abgebaut.
Cumarylalkohol (1),
Coniferylalkohol (2)
Sinapylalkohol (3)
Inorganic iron (the sum of free
hydrated and hydrolyzed ferric
iron species) is directly available
for phytoplankton uptake,
whereas humic-iron complexes
have been thought in the past to
be not bioavailable (Hudson and
Morel, 1993)
The Amur River plume which is transported
by the east Sakhalin current is a major source
of bioavailable iron to the Okhotsk Sea
(Yoshimura et al., 2010)
Amur River
This study concluded that hydrophobic DOM, as chelating agent, is a
biologically important component in natural waters
Jiho Lee et al., Ecotoxicology and Environmental Safety 72 (2009) 335–343
Riverine Fe-HS enhance ocean
productivity and remove carbon
dioxide from the atmosphere
thereby mitigating climate change and
ocean acidification

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