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Vegetative aquaculture of Fucus in the Baltic Sea—obtaining low-fertility biomass from attached or unattached populations?

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  • Coastal Research and Management GbR Kiel Germany
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Vegetative aquaculture of Fucus in the Baltic Sea—obtaining low-fertility biomass from attached or unattached populations?

Abstract and Figures

An experimental farm has been installed in the Kiel Fjord, western Baltic Sea, aiming at the development of a sustainable production process for Fucus species ( Fucus vesiculosus , Fucus serratus ). The envisaged cultivation method includes the unattached rearing of thalli in baskets deployed in the sea and their vegetative reproduction. Fertility (i.e., receptacle formation) is expected to be problematic for this approach, because receptacles are terminated in growth and degrade after gamete release. In culture experiments, natural fertility led to only minimal overall growth in F. vesiculosus and even weight loss in F. serratus . Therefore, we tested if long-term unattached cultivation of formerly attached thalli leads to a lowering of fertility by an acclimatization process. However, fertility after 1 and 2 years of unattached cultivation was statistically equal and still comparable to the high fertility of attached populations. Furthermore, we tested if the only known naturally unattached population in the western Baltic Sea near Glücksburg, which remains largely infertile in the wild, keeps its low fertility if put under culture conditions. During an experimental 1-year cultivation, thalli from this population remained almost entirely vegetative (2.0 ± 3.1% fertile apices). Hence, the Glücksburg population is a promising source of aquacultural seedling biomass. Yet, further tests are necessary to check, if the fertility remains low over several years of cultivation. If unattached populations are used as source for commercial cultures, the collection of seedling material should always be accompanied by strong measures to ensure the continued integrity of these valuable habitats.
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Vegetative aquaculture of Fucus in the Baltic Seaobtaining
low-fertility biomass from attached or unattached populations?
Rafael Meichssner
1,2
&Peter Krost
2
&Rüdiger Schulz
1
Received: 20 August 2020 / Revised and accepted: 3 January 2021
#The Author(s) 2021
Abstract
An experimental farm has been installed in the Kiel Fjord, western Baltic Sea, aiming at the development of a sustainable
production process for Fucus species (Fucus vesiculosus,Fucus serratus). The envisaged cultivation method includes the
unattached rearing of thalli in baskets deployed in the sea and their vegetative reproduction. Fertility (i.e., receptacle formation)
is expected to be problematic for this approach, because receptacles are terminated in growth and degrade after gamete release. In
culture experiments, natural fertility led to only minimal overall growth in F. vesiculosus andevenweightlossinF. serratus.
Therefore, we tested if long-term unattached cultivation of formerly attached thalli leads to a lowering of fertility by an accli-
matization process. However, fertility after 1 and 2 years of unattached cultivation was statistically equal and still comparable to
the high fertility of attached populations. Furthermore, we tested if the only known naturally unattached population in the western
Baltic Sea near Glücksburg, which remains largely infertile in the wild, keeps its low fertility if put under culture conditions.
During an experimental 1-year cultivation, thalli from this population remained almost entirely vegetative (2.0 ± 3.1% fertile
apices). Hence, the Glücksburg population is a promising source ofaquacultural seedlingbiomass. Yet, further tests are necessary
to check, if the fertility remains low over several years of cultivation. If unattached populations are used as source for commercial
cultures, the collection of seedling material should always be accompanied by strong measures to ensure the continued integrity
of these valuable habitats.
Keywords Fucus vesiculosus .Fucus serratus .Phaeophyceae .Aquaculture .Ecad .Vegetative reproduction .Fertility
Introduction
The brown algal genus Fucus is known for its high content in
bioactive ingredients like phlorotannins and fucoxanthin
(Catarino et al. 2018). Fucus biomass is therefore used for a
variety of products like cosmetic extracts and food supple-
ments (Ferreira et al. 2019; Torres et al. 2020). Currently,
the entire market demand is satisfied by biomass harvested
from wild populations, e.g., in France and Ireland (netalgae.
eu). In Germany, harvesting from wild populations is
prohibited and Fucus stands listed as protected habitat
(Bundesamt für Naturschutz 2013; HELCOM 2013). Yet,
German companies desire regional biomass, because
regionalityis a valuable claim in the targeted markets (L.
Piker, pers. comm.). The only means to obtain regional bio-
mass from the German Baltic Sea coast is therefore aquacul-
ture. Fucus aquaculture could potentially become necessary in
other countries, too, if the market pull increases (Cherry et al.
2019), or environmental change puts wild populations at risk
(Nicastro et al. 2013). Consequently, an experimental Fucus
farm has been established in the Kiel fjord at the German
Baltic Sea coast aiming at the development of a method for
the production of local Fucus species (Fucus vesiculosus,
Fucus serratus) in aquaculture.
A key step in the development of a commercial cultivation
process is the establishment of a successful reproduction
method.Commercially cultivated seaweeds can be placed in
two categories with respect to reproduction: The first is pro-
duced in a process involving sexual reproduction (e.g.,
Saccharina latissima,Undaria pinnatifida,Pyropia spp.), in-
cluding the rearing of different life stages (gametophyte,
(tetra-)sporophyte, in red algae also carposporophyte), the
production of seeded ropes in land-based hatcheries, and their
later deployment in the sea for the outgrowth of the germlings
*Rafael Meichssner
rafael.meichssner@crm-online.de; rmeichssner@bot.uni-kiel.de
1
Physiology and Biotechnology of the Plant Cells,
Christian-Albrechts-University, Kiel, Germany
2
CRM (Coastal Research & Management), Kiel, Germany
https://doi.org/10.1007/s10811-021-02419-x
/ Published online: 15 March 2021
Journal of Applied Phycology (2021) 33:1709–1720
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
to harvest size (Yarish and Pereira 2008;Grahametal.2009;
Hurd et al. 2014; Azevedo et al. 2019). The second category is
produced in a process involving vegetative reproduction
(Eucheuma spp./Kappaphycus spp., Gracilaria spp.), where
thalli are reared either tethered to ropes, pegged to the sedi-
ment, or freely floating in tanks or baskets. Fragments for the
next growing season (seedlings) are obtained by cutting
small pieces from the cultivated thalli. No hatchery is needed
for vegetative reproduction and only one stage of the life cycle
is cultivated (Yarish and Pereira 2008;Grahametal.2009;
Hurd et al. 2014). Due to the ease of the process, vegetative
reproduction was envisaged for Fucus aquaculture. The over-
all cultivation method comprises the cutting of fronds from
wild specimens, which grow unattached in floating baskets
until harvest size (Fig. 1). From the harvest, small pieces con-
taining apical meristems are generated, e.g., by automated
shredding, which are used as seedlings for the next growing
season, and so forth.
Typical wild Fucus populations produce high numbers of
sexual structures (receptacles) at their thallus apices. During
receptacle formation, the activity of the apical meristem is
terminated and, after shedding of the gametes, the receptacle
including the former meristem and the tissue below the recep-
tacle degrades down to the next branch that bears a vegetative
apex (Knight and Parke 1950;Moss1967). During a typical
reproductive season, 70100% of the apices turn into recep-
tacles and degrade later (Knight and Parke 1950;Bäcketal.
1991; Graiff et al. 2017), which causes attached Fucus popu-
lations to lose significant amounts of biomass (F. vesiculosus:
ca. 25% (Berger et al. 2001), F. serratus:3050% (Arrontes
1993; Brenchley 1996)). This process is expected to lead to
severe growth reductions in unattached cultures which consist
only of fronds. However, these fertility-related growth reduc-
tions have not been precisely determined yet, and it is unclear
how detrimental they are for successful cultivation. In general,
culture biomass with constantly low fertility is expected to be
advantageous for effective biomass production with the de-
scribed cultivation method.
Interestingly, there are some Fucus populations occurring
in certain habitats like estuaries, salt marshes, or blue mussel
banks, which naturally produce no or only few receptacles and
would thus be very suitable for vegetative cultivation (Norton
and Mathieson 1983; Mathieson and Dawes 2001). These
populations are not found attached to hard substrata but live
entangled in salt marsh angiosperms, embedded in mud, or are
held by the byssus filaments of blue mussels (Baker and
Bohling 1916; Nienburg 1925; Nienhuis 1970; Norton and
Mathieson 1983). It is usually assumed that they initially
Fig. 1 aPackage of cultivation
baskets for experiment 1 (bottom,
quadratic) and cultivation baskets
for experiment 3 (top, round). b
White boxes with side windows
installed in the Jetfloat system. c
Packages of cultivation baskets
for experiment 2 which were
inserted in the white boxes shown
in b
1710 J Appl Phycol (2021) 33:1709–1720
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
had a holdfast, but were pulled off from their substrate and
drifted to their current location, where angiosperms, mud, or
blue mussel byssus filaments prevented them from being
washed ashore (Norton and Mathieson 1983). Being trapped
this way, they are supposed to have reproduced by vegetative
fragmentation, thus forming larger populations (Mathieson
et al. 2006). They share some typical features like absence
of holdfast, low fertility, i.e., almost no receptacles, often
small size, and atypical, curling growth. Due to these features,
they are termed ecadsto indicate that their morphology is a
result of the environmental conditions (e.g., Baker and
Bohling 1916). However, there is some confusion if the un-
usual morphological features, especially the low fertility,
arose from acclimatization to the specific conditions of their
current growth locations, or if it required adaptation, i.e., only
certain genotypes, which show low fertility or are able to
quickly shift towards low fertility, have successfully colo-
nized these locations after arrival (Wallace et al. 2004;
Mathieson et al. 2006).
Some unattached populations have been shown to be
hybrids of F. vesiculosus and F. spiralis (Wallace et al.
2004; Coyer et al. 2006; Mathieson et al. 2006; Sjøtun et al.
2017), or result from backcrosses between these hybrids and
F. vesiculosus (i.e., introgression, Wallace et al. 2004), or they
are polyploids of F. vesiculosus (Coyer et al. 2006; Sjøtun
et al. 2017). As hybridization and polyploidy are known to
often cause sterility in land plants, it can be speculated that
these genetic changes are causal for the low fertilities of these
populations, which in turn can be regarded as a result of
adaptation and not acclimatization. However, in the study of
Mathieson et al. (2006), thalli of the unattached F. spiralis
ecad lutarius, found in the Gulf of Maine, were genetically
equal to neighboring attached F. vesiculosus or F. spiralis,
which indicates an acclimatization origin of these thalli, but
it was questioned how long they might persist as ecads.
From the western Baltic Sea, only one unattached popula-
tion is known from Glücksburg in the Flensburg fjord
(Maczassek 2014), where thalli morphologically similar to
F. vesiculosus are found embedded in mud, showing a strik-
ingly low number of receptacles. So far, the genetic affinities
of this population are unresolved. Maczassek (2014) first de-
scribed it as F. vesiculosus f. mytili, although the genetic rela-
tionship between the unattached population from Glücksburg
and F. vesiculosus f. mytili, an unattached population
described from the Wadden Sea (Nienburg 1931), is unclear.
Therefore, we use the term Glücksburg populationin the
following. Maczassek (2014) hypothesized that it arose
through acclimatization of local attached F. vesiculosus thalli
and that the acclimatization process was induced by detach-
ment from the substrate. Following this reasoning, the long-
term cultivation of local attached F. vesiculosus thalli with the
envisaged cultivation protocol, which includes the detachment
of thalli from the substrate and their unattached rearing, could
potentially induce an acclimatization towards the morphology
of the Glücksburg population, including the low fertility.
If the Glücksburg population itself is put under culture
conditions, it will retain its low fertility if this feature is genet-
ically fixed. If the low fertility is the result of an acclimatiza-
tion process, it could also be retained depending on the culture
conditions. In any of the two scenarios, the Glücksburg pop-
ulation itself could potentially be a useful seedling source for
aquaculture. For successful vegetative cultivation, it is crucial
to know, if biomass which continuously remains at a state of
low fertility, can be obtained via acclimatization from attached
populations and/or if the unattached Glücksburg population
can be used, because it retains its low fertility in culture.
From a quantitative perspective, the acclimatization of former
attached thalli would be advantageous, because most of the
402 km of the western Baltic Sea coastline of Germany
(Schleswig-Holstein) are colonized by attached
F. vesiculosus and F. serratus populations (Fürhäupter et al.
2008), while the Glücksburg population only covers an area of
about 50 m
2
in the Flensburg fjord and thus represents only a
limited source for seedling material.
Based on these considerations, three questions were ad-
dressed in this study:
(1) How strong is the fertility-related reduction of growth in
unattached culture, and is it detrimental for commercial
cultivation (Experiment 1)?
(2) Do Fucus thalli from attached populations (F. vesiculosus,
F. serratus) survive long-term unattached cultivation, and
does this long-term unattached cultivation reduce the fer-
tility? Specifically, are less receptacles formed in the sec-
ond year of unattached culture than in the first year of
unattached culture (Experiment 2)? F. serratus was includ-
ed in this experiment, although the acclimatization hypoth-
esis of Maczassek (2014, see above) only concerned
F. vesiculosus.
(3) Do thalli from the Glücksburg population grow in cul-
ture and does their fertility change under culture condi-
tions (Experiment 3)?
Materials and methods
All experiments were conducted at the premises of Kieler
Meeresfarm (GmbH & Co. KG), located in the northwestern
part of the Kiel fjord (54.381975 N; 10.162034 E). For exper-
iments 1 and 2, individuals from local attached populations
were collected, Fucus vesiculosus from Kiel/Holtenau
(54.368966 N; 10.154112 E) and Fucus serratus from Bülk
(54.455146 N; 10.198858 E). For experiment 3, individuals
from the Glücksburg population were collected from its only
known growth location in the Flensburg fjord (54.837671 N;
1711J Appl Phycol (2021) 33:1709–1720
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9.521850 E, Fig. 2). For all experiments, whole plants were
transported in seawater to the cultivation site and stored in
buckets overnight. The following day, thallus pieces of 3
10 cm in length (F. vesiculosus and Glücksburg population)
and 515 cm in length (F. serratus) were cut from the plants
and used to start the experimental cultures. The sizes represent
typical fronds of the species, when cut above the stipe. The
size difference was accepted, because no inter-species com-
parisons were intended. Measured response variables during
the experiments were wet weight, total number of apices, and
fertility. Wet weight was regularly assessed by weighing the
cultured biomass with a lab scale (Kern EMB 1200) under
wind protection after 15 s of drying with a salad spinner.
The total number of apices was assessed by counting all apices
in the experimental cultures. Apices were counted as 1,if
the gap between two dividing apices was smaller than 1 mm,
and as 2,if it was larger than 1 mm. Fertility was calculated
as the percentage of fertile apices (receptacles) of the total
number of apices. An apex was considered as fertile as soon
as receptacle formation was initiated, discernable by a com-
mencing swelling of the apex and the formation of high num-
bers of conceptacles (visible when thalli were hold up against
the light).
Experiment 1effect of fertility on growth in culture
In order to test the impact of fertility on the growth of culti-
vated Fucus thalli, culture biomasses with different initial fer-
tilities were created by assembling thalli with ripe fertile and
vegetative apices. The following groups were prepared:
F. vesiculosus: 100% receptacles, 80% receptacles, 0% recep-
tacles; F. serratus: 100% receptacles, 70% receptacles, 0%
receptacles.
For F. vesiculosus, 80% receptacles represents the estimat-
ed fertility during the spring reproductive season (Graiff et al.
2017, own pre-experiments). The experiment for this species
was started during this season (14 May 2019) and lasted until
04 September 2019. Measurements of response variables were
performed ca. weekly due to the high growth rates during
summer. For F. serratus, 70% receptacles represents the esti-
mated fertility during its reproductive period in late autumn/
winter (own pre-experiments). The experiment for this species
was therefore started on 20 December 2019 and lasted until 1
April 2020 with measurements every 24 weeks due to the
low growth rates during winter. The difference in season was
accepted, because a direct comparison of the two species was
not intended.
The same experimental setup was used for both species:
nine black plastic baskets (BAUHAUS; Oase Pflanzkorb;
edge length: 28 cm; volume: 14 L) served as cultivation de-
vices, allowing for permanent inflow of seawater by holes of
ca. 0.3 × 0.3 cm at all sides. The baskets were arranged in three
packages of three and covered with transparent plastic nettings
to avoid loss of culture material (Fig. 1). Each of the three
groups (100%; 80%/70%; 0%) was represented with one rep-
licate in each of the three packages, at a different position in
each package. Thus, position effects could be excluded. The
packages were deployed in the sea with polyethylene foam
pipe insulation as floating bodies (Fig. 1). The packages were
protected from wave activity by a pipe frame (2 × 4 m).
Cultures were started with 20 g biomass of the respective
fertility per basket. The total number of apices at the beginning
of the experiments was not equal among the groups, because
receptacles are heavier than vegetative thallus apices.
Therefore, the percentual change of the total number of apices
was calculated as an additional response variable using the
following formula:
Percentual change of total number of apices
¼TNAtend=TNAt0
ðÞ=TNAt0
ðÞ¼100
Fig. 2 aGlücksburg population growing embedded in mud (see arrow) in
the understory of larger F. vesiculosus thalli with receptacles. bThalli
from Glücksburg population after collection, showing no receptacles and
a dark coloration of the thallus parts that were embedded in anoxic mud
1712 J Appl Phycol (2021) 33:1709–1720
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where TNA is the total number of apices, t
0
is the beginning of
the experiment, and t
end
is the end of the experiment.
The weight data were of main interest and are presented
here; the total number of apices, the fertility over the course of
the experiment, and the percentual change of the total number
of apices are shown in the supplementary material (Fig. 3,Fig.
S1,Tab.S1).
Experiment 2fertility of attached populations un-
der long-term unattached culture
In order to investigate the growth and fertility of former-
ly attached thalli during long-term unattached culture,
F. vesiculosus and F. serratus thalli were cultivated un-
attached for 24 months (24 May 201829 May 2020) in
the same type of plastic baskets used in experiment 1.
The baskets were not submerged directly into the sea as
in experiment 1, but inserted into white boxes (glass
fiber reinforced plastic, shape: turned truncated pyramid,
upper opening: 80 × 80 cm, basal area: 64 × 64 cm,
height: ca. 40 cm, Fig. 1). The white boxes had a win-
dow (35 × 37 cm) at each of the four side faces to allow
water inflow. They were hung in the gaps of a swimming
platform of black Jetfloat elements (Jetfloat International,
double elements: 100 × 50 × 40 cm, single elements: 50 ×
50 × 40 cm, Fig. 1). Thus, the baskets were deployed in
the sea, but with less water flow-through than under di-
rect deployment, resulting in significantly less epizoans
colonizing the thalli (e.g., barnacles, blue mussels, bryo-
zoans), than if baskets were directly deployed in the sea
(own pre-experiments). Using this setup it was possible
to conduct a long-term cultivation experiment without
the necessity of frequent cleaning of the thalli from
epibionts, which might have caused considerable damage
to the thalli (own pre-experiments). Six white boxes were
available, containing a package of eight black baskets
each, resulting in a total of 48 experimental units. The
white boxes were only used for installation and hence
not considered as entities; thus, the 48 baskets were con-
sidered as independent experimental units. The position
of the baskets within the white boxes was changed reg-
ularly to avoid position effects. Of the 48 baskets, 36
were used for other experiments and 12 were used for
this experiment, yielding 4 groups of 3 replicates each:
F. vesiculosus: unattached cultivation starting on 24
May 2018
F. vesiculosus: unattached cultivation starting on 24
May 2019
F. serratus: unattached cultivation starting on 24
May 2018
F. serratus: unattached cultivation starting on 24
May 2019
The experimental cultivation was started with 20 g of
vegetative thalli per basket and lasted until 29 May 2020.
Thus, for each Fucus species, one group was cultivated
unattached for 2 years and the second group was cultivat-
ed unattached for 1 year, parallel to the second year of the
first group (Figs. 4and 5). Weight was recorded during
the entire experiment. The total number of apices (data
not shown) and fertility was recorded three times during
the first year and every 24 weeks during the second year.
Thus, it was possible to compare the fertility of the group
cultivated for 2 years between year 1 and year 2.
Furthermore, it was possible to compare the fertility of
the group cultivated for 2 years with the fertility of the
group cultivated for 1 year at the same time points and
under the same environmental conditions during year 2. A
higher measurement frequency was chosen during year 2
to ensure the detection of even small fertility differences
between the two groups cultivated in parallel.
During year 1, a harvest was performed in September 2018
to avoid limitation of growth by too high densities. Density
limitation occurs above ca. 100 g basket
1
(i.e., ca 2.5 kg m
2
)
(own pre-experiments). During this harvest, all sexual thalli
were removed and the cultures were continued with 20 g of
vegetative thalli. After 1 year of cultivation (24 May 2019),
the biomass was again harvested and cultivation was contin-
ued with the vegetative biomass present in the cultures at this
point (F. vesiculosus:6g;F. serratus: 11 g), with the parallel
groups of year 2 being added to the experiment
(F. vesiculosus:6g;F. serratus:11g).
Fucus vesiculosus shows two reproductive periods in
the western Baltic Sea, the first from November to May
(spring reproductive season (SRS)) and the second from
July to November (autumn reproductive season (ARS)).
Two genotypes occur in the Kiel Bay, from where the
thalli were collected; the first genotype is fertile only
during the SRS (only spring bloomers) and the second
genotype shares this reproductive period but is fertile
also during the ARS (autumn and spring bloomers)
(Berger et al. 2001, F. Weinberger, pers. comm.).
Vegetative thalli of these two genotypes cannot be dis-
tinguished in the field. Therefore, thalli were randomly
picked and initially both genotypes were present in the
culture biomass in the ratio of the natural field popula-
tions. The ratio of the two genotypes changed uninten-
tionally during year 1, due to the intermediate harvests
(see Results).
Fucus serratus has only one long reproductive period
from July to March (winter reproductive season (WRS)) in
the western Baltic Sea and no genotypic variants with re-
spect to reproductive behavior have been observed in the
sampling area (pers. observation, see also Malm et al.
(2001) for similar observations at the Swedish Baltic Sea
coast).
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Experiment 3fertility of unattached Glücksburg
population in culture
In order to investigate if biomass from the unattached
Glücksburg population retains its low fertility under culture
conditions, thalli were cultivated for 1 year. Four larger black
plastic baskets (BAUHAUS; Oase Pflanzkorb; round; diame-
ter: 40 cm; volume: 35 L) were used as cultivation devices and
tethered individually to the 2 × 4-m pipe frame using the same
floating bodies as in experiment 1 (Fig. 1). The experiment
was started on 29 June 2019 with 5562 g of thalli, which was
cultivated until 29 June 2020. Weight, total number of apices,
and fertility were recorded regularly. No intermediate harvests
were necessary, because the limiting density was not reached
in this experiment. Epibionts had to be carefully removed in
November 2019, since the thalli were heavily colonized. This
was not necessary in experiments 1 and 2.
Statistics
Statistical analysis was performed using the R software pack-
age (R Core Team 2013). For experiment 1, weight and fer-
tility of experimental groups at t
end
as well as percentual
change of the total number of apices over the experimental
time were compared by one-way ANOVA and TukeysHSD
post hoc test. For experiment 2, the fertility of the experimen-
tal groups was compared by Welchs two-sample ttest at
defined time points of the experimental cultivation period.
Experiment 3 did not require statistical analysis. Normality
of residuals was tested by Shapiro-Wilks test and homogene-
ityofvarianceswastestedbyFligners test. pvalues below
0.05 were considered statistically significant. The detailed re-
sults of the statistical analysis are depicted in the supplemen-
tary material (Tab. S2S5).
Results
Effect of fertility on growth in culture (experiment 1)
Both species showed strong growth when the initial culture
biomass consisted only of vegetative thalli, but showed only
marginal growth or even weight loss, when the biomass
consisted of thalli with the typical fertility found in
attached wild populations (F. vesiculosus: 80%,
F. serratus: 70%), or when the biomass consisted of thalli
with 100% fertility (Fig. 3). Detailed results are given in the
following:
For F. vesiculosus, thalli of the purely vegetative treatment
(0% fertility) increased in weight from 20 g to 126 ± 16 g
during the experimental time, while thalli in the other two
treatments, after an initial weight increase ending at mid of
July, showed only slight growth or even weight decreases
ending at 30 ± 2 g for the 80% treatment and at 19 ± 6 g for
the 100% treatment (one-way ANOVA of weight at t
end
:p=
2.3 × 10
5
, significant differences in post hoc TukeysHSD
between 100 and 0%; 80 and 0%, Fig. 3).
For F. serratus, the thalli of the 0% treatment showed a
weight increase from 20 to 42 ± 9 g during the time frame of
the experiment (Fig. 3). At the same time, the thalli of the 70%
treatment decreased in weight from 20 to 18 ± 3 g and the
thalli of the 100% treatment from 20 to 13 ± 1 g by slow
degradation of the receptacles and the thallus tissue below
the receptacles (one-way ANOVA of weight at t
end
:p=
0.0021, significant differences in post hoc Tukeys HSD be-
tween 100 and 0%; 80 and 0%). The weight results of both
species were paralleled by the total number of apices
(Supplementary material, Fig S1). The fertility during the ex-
periment matched the expectations with an increasing share of
vegetative thalli over time in the groups that contained vege-
tative apices and no change in the 100% group
(Supplementary material, Fig. S1).
Fig. 3 Effect of fertility status at the beginning of experimental
cultivation (termed initial fertility,measured as percentage of
receptacles of total number of apices) on wet weight of F. vesiculosus
(a)andF. serratus (b). Data displayed as mean ± SD, N= 3 baskets. The
total number of thallus apices and the fertility during the subsequent
cultivation period are shown in the supplementary material (Fig. S1)
1714 J Appl Phycol (2021) 33:1709–1720
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Fertility of attached populations under long-term
unattached culture (experiment 2)
It was possible to cultivate both Fucus species for 2 years as
unattached thalli. They remained viable and produced new
biomass from the vegetative apices present in the cultures
(Figs. 4and 5). The fertility of both species was not reduced
during the 2 years of cultivation. It was statistically equal
between year 1 and year 2 of the same culture and between
cultures of different ages (first vs. second year in culture)
during the same year (Figs. 4and 5). As it remained at the
high levels typical for wild attached populations, no acclima-
tization towards low fertility, which is typical for wild unat-
tached populations, could be observed. However, for both
species, unattached cultivation over time led to disoriented,
twisted growth (Fig. 6), resulting in a morphology similar to
that of unattached populations in the wild (Norton and
Mathieson 1983). In addition, F. vesiculosus thalli showed a
reduction in width, which has also been observed in wild
unattached populations (Mathieson and Dawes
2001; Mathieson et al. 2006). Species-specific results will be
given in the following:
Fucus vesiculosus showed fast growth during the first
months of cultivation reaching 57 ± 5 g after 2.5 months;
therefore, a harvest to 20 g was performed on 9 August
2018 to avoid reduction of growth by density limitation
(Fig. 4). During this harvest, which fell in the ARS (au-
tumn reproductive season), all fertile thalli (which were
the vast majority but not counted at that point) were re-
moved and the 20 g, which were used for the continuation
of the culture, consisted only of vegetative thalli. Thus,
the ratio of spring and autumn bloomersto only spring
bloomersin the cultivated biomass was probably shifted
from its natural value in the field strongly towards only
spring bloomers.This was reflected in the fertility during
the continuing ARS 2018 as well as during the ARS
2019, when only few sexual organs were formed (6
November 2018: 16.2 ± 1.4%; 30 October 2019: 30.8 ±
Fig. 4 Unattached cultivation of formerly attached F. vesiculosus thalli
over 2 years (24 May 201829 May 2020). Comparison between first and
second year of cultivation of the same thalli (first vs. second year of the
light green group) and thalli cultivated unattached for 1 and 2 years at the
same time period (black vs. light green group during year 2). aWet
weight. bFertility. During year 1, two intermediate harvests have been
performed (09 August 2018, 24 May 2019, indicated by arrows). Data
displayed as mean ± SD, N= 3 baskets. ARS, autumn reproductive
season (July to November); SRS, spring reproductive season
(November to May)
1715J Appl Phycol (2021) 33:1709–1720
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
5.4% fertility). The parallel group, which was added in
year 2, consisted of the natural mixture between the two
genotypes and produced up to 67.2 ± 8.5% receptacles
during ARS 2019. Thus, the difference in fertility during
ARS 2019 has to be considered as artifact caused by the
shift of the genotype ratio. This artificial difference led to
different growth patterns between the two groups: the
thalli in the first cultivation year showed a marked weight
decrease after the ARS 2019 due to many degrading re-
ceptacles. The thalli in the second cultivation year pro-
duced less receptacles during the ARS 2019 and did con-
sequently not show this marked weight decrease (Fig. 4).
A valid comparison of fertility was possible during the
SRS 2020, when both genotypes were expected to pro-
duce receptacles. During this reproductive season, the fer-
tility of thalli which were in the first year of cultivation (7
January 2020: 84.8 ± 2.6%) was statistically equal to the
fertility of thalli which were in the second year of culti-
vation (7 January 2020: 88.6 ± 3.4%; Welchstwo-sample
ttest: p= 0.203). The group cultivated for 2 years showed
statistically equal fertilities during the SRS of both years
(8 January 2019: 89.3 ± 5.4%, 7 January 2020: 88.6 ±
3.4%; Welchstwo-samplettest: p= 0.445).
The frequent measurements during year 2 revealed
very rapid increases in fertility for both groups. The actual
fertility increase might have been slightly more gradual,
but small differences in the timing of the receptacle initi-
ation of individual apices were not detectable by the mea-
surement method.
For F. serratus, no difference in fertility was observed be-
tween year 1 and year 2 (6 November 2018 vs. 30 October
2019: Welchstwo-samplettest: p= 0.138), as well as be-
tween thalli cultured for 1 and 2 years during year 2 (30
October 2019: Welchs two-sample ttest: p=0.234,Fig.5).
The typical reproductive season in winter was clearly observ-
able. Although the same harvests as for F. vesiculosus were
performed during year 1, no artificial change in reproductive
behavior could be observed, because F. serratus only occurs
with one known genotype with respect to the reproductive
season. The weight loss due to the degradation of receptacles
Fig. 5 Unattached cultivation of formerly attached F. serratus thalli over
2 years (24 May 201829 May 2020). Comparison between first and
second year of cultivation of the same thalli (first vs. second year of the
light green group) and thalli cultivated unattached for 1 and 2 years at the
same time period (black vs. light green group during year 2). aWet
weight. bFertility. During year 1, two intermediate harvests have been
performed (09 August 2018, 24 May 2019, indicated by arrows). Data
displayed as mean ± SD, N= 3 baskets; WRS, winter reproductive season
(JulytoMarch)
1716 J Appl Phycol (2021) 33:1709–1720
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
was partly compensated by new biomass from vegetative api-
ces, which was well visible at the end of year 1 and year 2.
Fertility of unattached Glücksburg population in
culture (experiment 3)
Thalli of the Glücksburg population remained almost en-
tirely infertile during 1 year of cultivation; only very few
receptacles were formed during spring 2020 leading to a
maximum fertility of 2.0 ± 3.1% at 29 June 2020 (t
end
).
Within the first month of cultivation, the weight increased
from 58 ± 3 to 144 ± 15 g (Fig. 7a). However, growth did
not continue in the following, probably due to decreasing
light and temperature in autumn and commencing grazing.
Beginning in autumn 2019 and especially during spring
2020, the number of apices was strongly reduced by in-
tense grazing by amphipods (Gammarus sp.) and isopods
(Idotea baltica), which accumulated in the baskets during
the experiment (Fig. 7b). As the grazers in most cases
consumed only the fresh apical parts including the meri-
stems, this process did not lead to drastic losses of weight
but rather limited further growth. The cultures also
suffered from coverage by filamentous diatoms during
spring 2020, which might have led to an additional reduc-
tion of growth during this time of the experiment. Intact
apices continued to produce fresh tissue during the entire
experiment, visible by the light green color of newly
formed apical tissue. Therefore, a suppressing effect of
the general culture conditions (basket, location) on the
growth of the thalli can be excluded.
Discussion
In this study, we confirmed the expectation that the typical
fertility of attached Fucus populations (F. vesiculosus:~
80% receptacles, F. serratus:~70%receptacles)isdetrimen-
tal for unattached vegetative cultivation. As expected from
wild populations, degrading receptacles caused significant
biomass losses in experimental cultures with natural fertility,
leading to only little overall biomass gain (F. vesiculosus)or
even biomass loss (F. serratus, Fig. 3.). The observed growth
reduction during reproductive phases was more severe than
reported for wild Fucus plants (e.g., Arrontes 1993; Berger
Fig. 6 a,bF. vesiculosus and F. serratus thalli from the attached origin
after collection from the field with typical flat and well-oriented shape. c,
dF. vesiculosus and F. serratus thalli showing disoriented, twisted shape
after ca. 14 months of unattached culture
1717J Appl Phycol (2021) 33:1709–1720
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
et al. 2001). This was probably due to the fact that fronds were
used in the experimental cultures, which sometimes degraded
completely, while entire Fucus plants are able to retain the
stipe from which growth can continue (Knight and Parke
1950). Our experiment underlined the necessity of low-
fertility biomass for successful vegetative unattached Fucus
aquaculture.
In experiment 2, we tested if low-fertility biomass can be
obtained from attached thalli through long-term acclimatiza-
tion in unattached culture. Within a 2-year period, no acclima-
tization of formerly attached thalli towards reduced fertility
was observed (Figs. 4and 5). Therefore, we conclude that it
is impossible to acclimate attached Fucus populations to low
fertility by unattached culture, which is in contradiction to the
hypothesis of Maczassek (2014). Maczassek had assumed that
the unattached Glücksburg population resulted from the
detachment-induced acclimatization of F. vesiculosus thalli
towards low fertility. Whether other factors present at the
growth location of the population (e.g., reduced salinity,
low/ high nutrients, low oxygen levels, or others) and not
detachment alone are causal for a potential acclimatization is
unclear. If so, acclimatization in aquaculture would be com-
plicated, because usually the conditions of the used water
body can hardly be changed in the large-scale culture. If the
acclimatization process just requires more than 2 years, seed-
ling production would be very ineffective. However, this is
unlikely, because no signs for the initiation of an acclimatiza-
tion process were visible. Other features typical for unattached
populations (unoriented growth, reduced size) were induced
by unattached culture (Fig. 6). This suggests that these fea-
tures can be acquired via acclimatization and probably result
from the absence of a fixation to the substrate and the con-
comitant constant orientation in space (Norton and Mathieson
1983).
In experiment 3, we tested if biomass collected from the
unattached Glücksburg population retains its low fertility un-
der culture conditions. During 1 year of cultivation, it
remained almost entirely receptacle-free (Fig. 7) showing only
the minor fertility which is typical for the wild population
(pers. observation, Maczassek 2014). Consequently, biomass
losses due to receptacle degradation are expected to be very
low and generated seedlings have a high probability to contain
and retain viable meristems and produce new biomass. Thus,
the Glücksburg population seems to be a good candidate for
vegetative culture and reproduction of Fucus. Based on the
morphology of the Glücksburg population, the produced bio-
mass could be considered as vesiculosus-type biomass.
However, based on our data, it cannot be guaranteed that
the fertility of biomass from the Glücksburg population re-
mains low for several years, since a slow back-
acclimatization towards higher fertilities cannot be excluded.
Maczassek (2014) found a maximum of 30% fertility for the
Glücksburg population in mesocosm experiments, which sug-
gests that higher fertilities are possible. So far, all observed
fertilities were not high enough to be detrimental for aquacul-
tural success. A genetic determination of the low fertility of
the Glücksburg population would be desirable for the plan-
ning of future aquaculture efforts. However, it is impossible to
prove a genetic fixation at the current state of knowledge,
because the genes responsible for receptacle formation are
not known and no Fucus genome has been published yet.
Even if hybridization or polyploidy would be shown for the
Glücksburg population, as have been for other unattached
populations by analysis of microsatellites, mtDNA RFLP,
and nuclear DNA content (Coyer et al. 2006; Mathieson
et al. 2006;Sjøtunetal.2017), no permanence of low fertility
could be guaranteed, because no causal connection between
polyploidy/hybridization and low fertility has been shown for
Fucus species so far. Therefore, further cultivation trials over
longer time spans are necessary to ensure the long-term us-
ability of the Glücksburg population. Based on the results
presented here, we assume that biomass from the
Glücksburg population retains a low fertility also for longer
cultivation periods.
Fig. 7 Cultivation of thalli from unattached Glücksburg population over
the course of 1 year. aWet weight. bTotal number of apices. Data
displayed as mean ± SD, N= 4 baskets. Heavy grazing is visible by a
reduction of the total number of apices in spring 2020
1718 J Appl Phycol (2021) 33:1709–1720
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
As the focus of this study was on fertility, no optimization
of growth was aimed at in the experimental culture of biomass
from the Glücksburg population. Grazing by Gammarus sp.
and I. balthica was therefore not sufficiently dealt with, which
led to only little growth in the second half of the experimental
culture year. If this factor had been controlled, continuous
growth could have been expected. Grazing on the thalli from
the Glücksburg population seemed to be more intense than
grazing on thalli from the attached origin. One explanation
is that grazers prefer vegetative material and avoid slimy re-
ceptacles (Hemmi et al. 2005). Another explanation is that the
Glücksburg population has a comparatively poor grazing de-
fense, which is not known so far, but could be tested in grazer
preference experiments (Goecker and Kåll 2003). A reduction
of grazing might be possible by regular air exposure or fresh
water treatment of the cultivated biomass. Air exposure can in
addition be used to reduce the number of fouling organisms
(Meichssner et al. 2020). For commercial-scale culture, we
suggest baskets of about 1 m
2
area, similar to baskets for
Eucheuma cultivation shown in Hurtado et al. (2008). This
size would allow for easy handling and air exposures could
potentially be performed. Plastic or other solid material should
be used for the base of the baskets to create a plane area where
the biomass can be well spread. If too flexible material is used,
the biomass tends to aggregate at the lowest point, which
limits growth (own observation). An alternative option would
be cultivation in land-based tanks similar to Gracilaria tank
cultures (Friedlander and Levy 1995). In this case, grazing
could be excluded by pre-filtering the used seawater.
The principle of using unattached Fucus populations for
vegetative aquaculture can of course be applied at other loca-
tions, too. Unattached populations with low fertility are
known from other parts of the Baltic Sea as well as from many
coasts of the North Atlantic and the North Pacific (Luther
1981; Norton and Mathieson 1983; Neiva et al. 2012). Some
populations are genetically affiliated to F. serratus,
F. gardneri,F. ceranoides, and F. spiralis; thus, biomass oth-
er than the vesiculosus type can potentially be produced
(Norton and Mathieson 1983; Neiva et al. 2012). However,
the principle might also be used for the culture of other genera
of the Fucales, as unattached populations with low fertility are
also known from Ascophyllum,Hormosira,andSargassum
(Norton and Mathieson 1983).
Amainconcernwiththecommercial utilization of un-
attached populations is that they are not very large in most
cases and therefore prone to extinction, not only by envi-
ronmental change but also by random events. Unattached
populations from the Baltic Sea, like the one from
Glücksburg, are therefore listed by HELCOM as endan-
gered habitats (HELCOM 2013). The continued existence
of these populations should therefore always be priori-
tized before commercial utilization. In our opinion, a use
of unattached populations as seedling source could be
approved by governmental authorities, if the following
conditions are fulfilled: (1) a maximum of 510% of the
standing stock is collected and (2) the collection of mate-
rial is accompanied by regular monitoring of the popula-
tion, which guarantees the maintenance of the population
size. We suggest that only little amounts are collected as
stock, from which larger amounts are produced to start
commercial culture. Optimally, seedling biomass has to
be taken only once and can be generated from culture in
subsequent growing seasons.
Conclusion and outlook
Low fertility has proven to be crucial for unattached vegeta-
tive aquaculture of Fucus species. Based on our results, bio-
mass with this feature can only be obtained from unattached
populations, like the Glücksburg population in the western
Baltic Sea. For successful implementation, the fertility has to
remain low over consecutive years in culture, and grazing has
to be controlled. Both require further studies. The relatively
easy cultivation protocol presented here offers not only a pos-
sible solution for the production of Fucus biomass but could
also be applied for the cultivation of other species of Fucales
for scientific and commercial purposes.
Supplementary Information The online version contains supplementary
material available at https://doi.org/10.1007/s10811-021-02419-x.
Acknowledgments Open Access funding enabled and organized by
Projekt DEAL. We want to thank Kieler Meeresfarm GmbH & Co. KG
for providing the space for the experiments and a lot of help with con-
struction and maintenance. Special thanks go to Florian Weinberger for
the helpful advice on the study concept.
Author contributions Rafael Meichssner designed and conducted the
experiments, performed the statistical analysis, and wrote the manuscript.
Peter Krost assisted in data analysis and Rüdiger Schulz in the study
conceptualization. Peter Krost and Rüdiger Schulz reviewed and edited
the manuscript.
Funding The study was funded by Studienstiftung des Deutschen
Volkes, Fazit-Stiftung, and the InterReg-Deutschland-Denmark project
FucoSan.
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
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... Alongside the reproductive mode, polyploidization (wholegenome multiplication) is an important variable affecting population divergence and gene flow (Brown & Young, 2000), and the interaction between asexual reproduction and polyploidization may affect genetic diversity and spatial genetic structure. Polyploidization often causes sterility as has been observed in angiosperms (Meichssner et al., 2021) and in some cases algae (Lewis & Neushul, 1995;Zhang & van der Meer, 1988). However, polyploids are often more vigorous compared to diploid conspecifics (Renny-Byfield & Wendel, 2014) although polyploidization has been seen to pose little to no advantage in some algae (Patwary & van der Meer, 1984;van der Meer & Patwary, 1983;Zhang & van der Meer, 1988). ...
... Although clonality within the attached Baltic Sea F. vesiculosus form is more commonly documented, unattached forms are also observed to display clonal growth. An embedded form of F. vesiculosus in the western Baltic Sea near Glücksburg (Germany) reproduces entirely by clonal growth (Meichssner et al., 2021). However, the mode of reproduction is poorly understood in free-living F. vesiculosus. ...
... ). Unique MLGs found in free-living populations could be contributed by sexual reproduction of free-living thalli, but there is no direct evidence of sexual reproduction in free-living populations. The closest available comparison comes from an embedded Fucus population in the western Baltic Sea near Glücksburg, which is largely infertile in the wild and maintains low fertility under laboratory conditions(Meichssner et al., 2021). Thus, free-living populations most likely emerge from detached pieces of thalli aggregating in sheltered locations, but further tests are required to confirm zygote viability and successful development of unattached zygotes into mature free-living individuals on suboptimal substrates.There are indications that unattached algal populations can partially maintain themselves once a small input of source material has aggregated(Lobban and Harrison, 1997). ...
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Genetic characteristics of populations can have substantial impacts on the adaptive potential of a species. Species are heterogeneous, often defined by variability at a range of scales including at the genetic, individual and population level. Using microsatellite genotyping, we characterize patterns underlying the genetic heterogeneity in marine macroalga Fucus vesiculosus, with a particular focus on two forms: attached and free-living. Here we demonstrate that sympatric populations representing the two forms display marked differences in characteristics of reproduction and genetic diversity. Asexual reproduction was ubiquitous in the free-living form despite being almost entirely absent in the attached form, while signals of polyploidy were common in both forms despite the distinct reproductive modes. Gene flow within and between the forms differed, with barriers to gene flow occurring between forms at various spatial scales due to the reproductive modes employed by individuals of each form. The divergent genetic characteristics of F. vesiculosus demonstrate that intraspecific differences can influence the properties of populations with consequential effects on the whole ecosystem. The differing genetic patterns and habitat requirements of the two forms define separate but closely associated ecological entities that will likely display divergent responses to future changes in environmental conditions.
... Hitherto, no commercial Fucus farm exists worldwide and only little related literature is published (Haglund & Pedersen 1988;Ryzhik et al. 2014;Meichssner et al. 2020Meichssner et al. , 2021. Therefore, an experimental Fucus aquaculture was established in 2015 in the Kiel Fjord, western Baltic Sea, aiming at the development of a sustainable and regional production method for F. vesiculosus and F. serratus. ...
... Thus, the intended method is similar to Kappaphycus/Eucheuma basket culture in Indonesia (Hurtado et al. 2014). Meichssner et al. (2021) could show that the method only works if the culture biomass retains low fertility, because fertile apices (receptacles) degrade after gamete shedding, which causes severe biomass losses. The necessary low-fertility biomass can be achieved by using unattached Fucus populations with naturally low fertility as initial source of seedlings (Meichssner et al. 2021). ...
... Meichssner et al. (2021) could show that the method only works if the culture biomass retains low fertility, because fertile apices (receptacles) degrade after gamete shedding, which causes severe biomass losses. The necessary low-fertility biomass can be achieved by using unattached Fucus populations with naturally low fertility as initial source of seedlings (Meichssner et al. 2021). Furthermore, a successful method for the reduction of fouling on the culture biomass has been developed (Meichssner et al. 2020). ...
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In the Kiel Fjord, western Baltic Sea, an experimental culture of Fucus vesiculosus and Fucus serratus has been established in order to develop a sustainable method for biomass production of these species. The cultivation method includes the unattached rearing of fronds in drifting baskets and their vegetative reproduction by cutting of small vegetative apices. In this study, we performed culture experiments to measure growth rates with this method at different initial stocking densities (1–5 kg m ⁻² ) and during different seasons of the year. Using the results, we modelled growth over 1 year for different cultivation scenarios (different initial stocking densities (1–4.75 kg m ⁻² ) and harvest densities (1.25–5 kg m ⁻² )) in order to identify optimal scenarios and estimate annual yields and the number of necessary harvests in these scenarios. Fucus vesiculosus showed a parabolic yield–density relationship with decreasing yields at high initial stocking densities (> 2.5 kg m ⁻² ). In contrast, F. serratus showed an asymptotic yield–density relationship with rather constant yields at high initial stocking densities. Both species showed a typical seasonal growth pattern with low growth rates during winter and high growth rates during summer; however, F. serratus seemed to be growth limited during summer which was not observed for F. vesiculosus . The modelling results reflected the results of the Density experiment: for F. vesiculosus , optimal cultivation scenarios were found for intermediate cultivation densities (initial stocking densities, 1.75–2.25 kg m ⁻² ; harvest densities, 3–4 kg m ⁻² ); for F. serratus , optimal cultivation scenarios included higher densities (initial stocking densities, 2.5–4 kg m ⁻² ; harvest density, 5 kg m ⁻² ). The model scenarios predicted maximal annual yields of 6.65–6.76 kg m ⁻² for F. vesiculosus and 6.88–6.99 kg m ⁻² for F. serratus . For both species, the number of harvests necessary to achieve these yields varied depending on the cultivation scenario from 2 to 6. Scenarios with only 1 harvest per year yielded slightly lower annual yields. We conclude that the modelling results offer a valid and helpful orientation for future efforts to produce Fucus species in commercial culture.
... In conclusion, we have identified temporal variations in the thermal sensitivity and warming vulnerabilities of recruits of a key temperate canopy-forming species, with relevant implications for the conservation, restoration, management and even the macroalgal industry of this and similar species (Meichssner et al., 2021). We demonstrated that early development of F. guiryi embryos would not be hampered by or may even benefit from warmer winters, but heat stress at the beginning of the summer may impose a critical limitation for their recruitment. ...
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Macroscopic marine algae, or seaweeds, form an important living resource of the oceans as primary producers. People have collected seaweeds for food, both for humans and animals. They also have been a source of nutrient-rich fertilizers, as well as a source of gelling agents known as phycocolloids. More recently, macroalgae play significant roles in medicine and biotechnology. Today, seaweed cultivation techniques are standardized, routine, and economical. Several factors, including understanding the environmental regulation of life histories and asexual propagation of thalli, are responsible for the success of large-scale seaweed cultivation. Different taxa require different farming methodologies. During the last 50 years, approximately 100 seaweed taxa have been tested in field farms, but only a dozen are commercially cultivated today. Of these, only five genera (Laminaria, Undaria, Porphyra, Eucheuma/Kappaphycus, and Gracilaria ) represent around 98% of the world’s seaweed production.
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Macroalgae have a high potential to advance sustainability through a broad range of applications, from greener chemicals and solvents to novel pharmaceuticals and sustainable biofuels, biofeedstocks, and bioplastics. Nevertheless, a key question is whether the cultivation and processing of seaweed can be performed in an ecofriendly and sustainable way. Sustainable Seaweed Technologies collates key background information on efficient cultivation and biorefinery of seaweeds, combining underlying chemistry and methodology with industry experience to address this issue. Beginning with a review of the opportunities for seaweed biorefinery and the varied components and properties of macroalgae, the book goes on to review all of the key steps needed to develop macroalgae for use in industrial applications, from its cultivation, collection, and processing, to extraction techniques, concentration, and purification. A range of important applications are then discussed, including the production of energy and novel materials from seaweed, before a set of illustrative case studies showcase how these various stages work in practice. Drawing on the expert knowledge of a global team of editors and authors, Sustainable Seaweed Technologies is a practical resource supporting both researchers and businesses who currently work with macroalgae, and those who are considering doing so in a drive for more sustainable processes and products. Key Features • Highlights the specific challenges and benefits of developing seaweed for sustainable products • Presents useful case studies showing varied approaches and methodologies in practice • Covers the complete seaweed chain from cultivation to waste management
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Genetic affiliation, nuclear DNA content, and gamete functioning were examined in small salt marsh Fucus from three localities in western Ireland. Individuals with small and dioecious receptacles were found at all localities, but production of germlings was only evident at Locality 1. Here, the Fucus vegetation formed a morphological cline from F. vesiculosus with bladders in the mid-intertidal to small Fucus individuals lacking bladders in the salt marsh of the upper intertidal. Measurements of nuclear DNA content ranged from 1–1.8 pg at this locality, with F. vesiculosus individuals in the lower range. At the two other localities, the small salt marsh Fucus consisted of distinct morphological entities. Microsatellite analyses revealed that individuals at Locality 2 were derived mainly from F. vesiculosus, whereas those from Locality 3 were hybrids between F. vesiculosus and F. spiralis with greatest affiliation to F. spiralis. While the small salt marsh Fucus forms from Locality 2 had high nuclear DNA content (c. 4 pg) and were probably octoploids, the small salt marsh Fucus from Locality 3 formed two groups: one with high (3.9–4.6 pg) and one with low (1.5–1.9 pg) nuclear DNA content. Nuclear DNA content measured in individuals from Locality 3 varied between 1.1–2.8 pg in F. vesiculosus and 2–3.5 pg in F. spiralis, and showed a more or less stepwise increase in both species, consistent with polyploidy. We hypothesize that the small salt marsh Fucus forms originate from genome size changes in the parental taxa.