Part D | 23
592 Part D Marine Algal Biotechnology
state. Soon afterwards, on December 6 and 20 of the
same year, Gay-Lussac presented his results about the
compounds that this novel element forms with others [23.6, 7].
Amazingly, despite the war in which most of Europe was embroiled in at that time, scientific exchange
between opposing powers was little affected. Sir Davy,
the leading British chemist of the time, corresponded
with his French colleagues (mail was transported between the warring countries by smugglers and cartels).
Napoleon himself, enthusiastic about science, gave him
free passage to France and onwards to Italy. Ampère
gave Davy a sample of iodine, inducing him to conduct
his own research on the new substance (Davy was traveling with a portable chest for chemical experiments).
After initially believing that it was merely a compound
of chlorine, Davy ultimately came to conclude that it
was an element in its own right [23.8], and competed
for a while with Gay-Lussac over priority rights (even
though both Davy and Gay-Lussac always acknowledged Courtois as the discoverer of iodine). Despite
the scientific fame of the discovery and rising commercial interest in iodine, e.g., for the treatment of
wounds, Courtois failed to capitalize on his discoveries and, sadly, died in poverty on September 27, 1838,
aged only 62 [23.3]. Iodine production from seaweeds
became a major economic activity in coastal regions of
Europe – in particular, in parts of Brittany, Normandy,
Ireland, and Scotland, and it features in many historic
and travel accounts of these places (e.g., [23.9]).
While the chemical knowledge of the novel element progressed, iodine-accumulating seaweeds did
not receive much research attention until the end of
the nineteenth century. Exemplary for this period are
the studies of Eschle [23.10], who investigated the
iodine content of Fucus vesiculosus and Laminaria
digitata. As early as 1894 Golenkin reported on the
release of free iodine by the red alga Bonnemaisonia
asparagoides – detected by a blue stain of starch in
paper [23.11]. Several decades passed until this was
more widely accepted by the community, in particular
by the studies of Sauvageau [23.12] on red algae and
of Kylin [23.13] and Dangeard [23.14] in the 1920s.
The latter, obviously working in competition, were the
first to report the emission of molecular iodine (I 2 ) from
kelp (L. digitata) surfaces, termed iodovolatilization.
Remarkably, their discovery was forgotten or ignored
until the re-discovery of molecular iodine emissions in
recent years [23.15, 16].
The rise of nuclear physics and the availability
of radioisotopes enabled studies of the uptake mechanism of iodine in brown algae, notably those of Tong
and Chaikoff on the Pacific kelp Nereocystis luetkeana [23.17], of Bailey and Kelly on Ascophyllum nodosum [23.18], and of Shaw on Laminaria [23.19, 20].
In about the same era, the requirement of macroalgae
for iodine as a micronutrient was recognized [23.21].
The implications of iodine emissions for atmospheric and marine chemistry were not recognized until
the findings of strongly increased methyl iodide concentrations around kelp beds by Lovelock [23.22]. The
vast majority of these studies focused on organic iodine
compounds, curiously ignoring the findings of inorganic, molecular iodine emissions made more than half
a century earlier [23.23]. More evidence for the impact
of kelp forests on the coastal atmosphere came from research by Alicke et al. [23.24], detecting iodine oxide,
and O’Dowd et al. [23.25], highlighting the role of iodine oxides in aerosol formation in the marine boundary
layer (however, postulating diiodomethane as the precursor). Not until the work of McFiggans et al. [23.15]
and Palmer et al. [23.16], however, did the importance
of inorganic iodine emissions for coastal, ultrafine particle formation become clear.
Our research on iodine metabolism in Laminaria
started with a study on its uptake mechanism, based
at the Station Biologique de Roscoff in the 1990s.
Initially, this work confirmed that iodide (and not iodate, present at roughly equal levels in surface sea
water, with a total iodine concentration of around
0:5 M [23.31, 32]) is the species taken up. Total iodine concentrations of up to over 5% dry weight were
observed in young Laminaria thalli – effectively constituting the strongest iodine accumulators observed so
far among all living systems. It also revealed that an
intact cell wall is required for sustained iodine uptake – protoplasts (i. e., algal cells, from which the
cell wall has been enzymatically removed) do no take
up iodine [23.26]. However, iodine uptake in protoplasts can be restored to levels corresponding to those
observed in Laminaria tissues under physiological conditions when either exogenous H 2 O 2 or a constitutively
H 2 O 2 -producing, enzymatic system are added. These
results highlighted the importance of hydrogen peroxide in iodide uptake. Subsequently, experiments were
conducted with Laminaria tissues, investigating the
effect of exogenously added H 2 O 2 . Remarkably, exogenous H 2 O 2 did enhance iodide uptake – but only
up to H 2 O 2 levels of around 25 M. Higher hydrogen
peroxide levels resulted in a pronounced efflux of previously accumulated iodine – providing first clues of
the biological significance of iodine accumulation in
592 Part D Marine Algal Biotechnology
state. Soon afterwards, on December 6 and 20 of the
same year, Gay-Lussac presented his results about the
compounds that this novel element forms with others [23.6, 7].
Amazingly, despite the war in which most of Europe was embroiled in at that time, scientific exchange
between opposing powers was little affected. Sir Davy,
the leading British chemist of the time, corresponded
with his French colleagues (mail was transported between the warring countries by smugglers and cartels).
Napoleon himself, enthusiastic about science, gave him
free passage to France and onwards to Italy. Ampère
gave Davy a sample of iodine, inducing him to conduct
his own research on the new substance (Davy was traveling with a portable chest for chemical experiments).
After initially believing that it was merely a compound
of chlorine, Davy ultimately came to conclude that it
was an element in its own right [23.8], and competed
for a while with Gay-Lussac over priority rights (even
though both Davy and Gay-Lussac always acknowledged Courtois as the discoverer of iodine). Despite
the scientific fame of the discovery and rising commercial interest in iodine, e.g., for the treatment of
wounds, Courtois failed to capitalize on his discoveries and, sadly, died in poverty on September 27, 1838,
aged only 62 [23.3]. Iodine production from seaweeds
became a major economic activity in coastal regions of
Europe – in particular, in parts of Brittany, Normandy,
Ireland, and Scotland, and it features in many historic
and travel accounts of these places (e.g., [23.9]).
While the chemical knowledge of the novel element progressed, iodine-accumulating seaweeds did
not receive much research attention until the end of
the nineteenth century. Exemplary for this period are
the studies of Eschle [23.10], who investigated the
iodine content of Fucus vesiculosus and Laminaria
digitata. As early as 1894 Golenkin reported on the
release of free iodine by the red alga Bonnemaisonia
asparagoides – detected by a blue stain of starch in
paper [23.11]. Several decades passed until this was
more widely accepted by the community, in particular
by the studies of Sauvageau [23.12] on red algae and
of Kylin [23.13] and Dangeard [23.14] in the 1920s.
The latter, obviously working in competition, were the
first to report the emission of molecular iodine (I 2 ) from
kelp (L. digitata) surfaces, termed iodovolatilization.
Remarkably, their discovery was forgotten or ignored
until the re-discovery of molecular iodine emissions in
recent years [23.15, 16].
The rise of nuclear physics and the availability
of radioisotopes enabled studies of the uptake mechanism of iodine in brown algae, notably those of Tong
and Chaikoff on the Pacific kelp Nereocystis luetkeana [23.17], of Bailey and Kelly on Ascophyllum nodosum [23.18], and of Shaw on Laminaria [23.19, 20].
In about the same era, the requirement of macroalgae
for iodine as a micronutrient was recognized [23.21].
The implications of iodine emissions for atmospheric and marine chemistry were not recognized until
the findings of strongly increased methyl iodide concentrations around kelp beds by Lovelock [23.22]. The
vast majority of these studies focused on organic iodine
compounds, curiously ignoring the findings of inorganic, molecular iodine emissions made more than half
a century earlier [23.23]. More evidence for the impact
of kelp forests on the coastal atmosphere came from research by Alicke et al. [23.24], detecting iodine oxide,
and O’Dowd et al. [23.25], highlighting the role of iodine oxides in aerosol formation in the marine boundary
layer (however, postulating diiodomethane as the precursor). Not until the work of McFiggans et al. [23.15]
and Palmer et al. [23.16], however, did the importance
of inorganic iodine emissions for coastal, ultrafine particle formation become clear.
Our research on iodine metabolism in Laminaria
started with a study on its uptake mechanism, based
at the Station Biologique de Roscoff in the 1990s.
Initially, this work confirmed that iodide (and not iodate, present at roughly equal levels in surface sea
water, with a total iodine concentration of around
0:5 M [23.31, 32]) is the species taken up. Total iodine concentrations of up to over 5% dry weight were
observed in young Laminaria thalli – effectively constituting the strongest iodine accumulators observed so
far among all living systems. It also revealed that an
intact cell wall is required for sustained iodine uptake – protoplasts (i. e., algal cells, from which the
cell wall has been enzymatically removed) do no take
up iodine [23.26]. However, iodine uptake in protoplasts can be restored to levels corresponding to those
observed in Laminaria tissues under physiological conditions when either exogenous H 2 O 2 or a constitutively
H 2 O 2 -producing, enzymatic system are added. These
results highlighted the importance of hydrogen peroxide in iodide uptake. Subsequently, experiments were
conducted with Laminaria tissues, investigating the
effect of exogenously added H 2 O 2 . Remarkably, exogenous H 2 O 2 did enhance iodide uptake – but only
up to H 2 O 2 levels of around 25 M. Higher hydrogen
peroxide levels resulted in a pronounced efflux of previously accumulated iodine – providing first clues of
the biological significance of iodine accumulation in