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Open sea cultivation of Palmaria palmata (Rhodophyta)
on the northern Spanish coast
Brezo Martínez
a,
⁎, Rosa M. Viejo
a
, Jose M. Rico
a
, Ruth H. Rødde
b
, Vanesa A. Faes
a
,
Jesús Oliveros
a
, Dámaso Álvarez
a
a
Departamento de Biología de Organismos y Sistemas, Universidad de Oviedo, c/ Catedrático Rodrigo Uría s/n, E-33071 Oviedo, Spain
b
Department of Biotechnology, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
Received 6 April 2005; received in revised form 2 October 2005; accepted 7 October 2005
Abstract
The aim of this study was to adapt the techniques of rope culture to the cultivation of the edible seaweed Palmaria palmata on
the northern Spanish coast. Vertical rope rafts were installed in two locations. Fronds were attached to 4-mm polyethylene ropes
that were suspended from a steel frame secured in position using weights and buoys. In the first two trials (April to August 1999)
we investigated the effects of the outplanting season (spring–summer), and length of the cultivation period (number of weeks) on
the growth of P. palmata. Cultivation in autumn and winter was not performed due to the rough sea conditions. The following three
trials (April to August 2000) aimed to test the effects on the growth and quality (i.e. N content) of the fronds of other additional
factors: cultivation technique (fronds inside mesh bags versus directly inserted into ropes), use of marginal proliferations as source
stock (versus field material), different stocking densities, and addition of nutrients versus no enrichment. Maximum observed
growth during the best cultivation season in spring was about 14% of the initial fresh weight per day (about 0.7 g FW). The growth
of cultivated fronds was noticeably greater than the growth of field individuals and four weeks was a suitable period for cultivation.
The bag method was better than inserting the fronds into ropes due to the avoidance of frond loss, and enhancement of the quality.
Appropriate stocking density was very important when using bags since the growth tended to decrease with increasing number of
fronds per bag. The artificial nutrient enrichment also enhanced the quality of the fronds in two locations, and the growth in one site
(with lower seawater nutrient concentration). Nutrient enhanced fronds grew at a rate similar to that observed one month and a half
earlier when nutrient concentration was higher. In Spain the stock of P. palmata is limited. However, the marginal proliferations
grew at a similar rate than field material partially solving this limitation. Results from these trials suggest the potential to
aquaculture P. palmata in northern Spain.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Bag cultivation; Fertilizer; Mariculture; Palmaria palmata; Rope cultivation
1. Introduction
Humans have carried out the culture of seaweeds for
hundreds of years and it is well developed in several
Asian countries (Perez, 1992; Ohno and Critchley,
1993; Lobban and Harrison, 1997; Neori et al., 2004).
Aquaculture 254 (2006) 376–387
www.elsevier.com/locate/aqua-online
⁎Corresponding author. Present address: Área de Biodiversidad y
Conservación, Escuela Superior de Ciencias Experimentales y
Tecnología, Universidad Rey Juan Carlos. c/ Tulipán s/n, Móstoles,
E-28933, Madrid, Spain. Tel.: +34 914888102; fax: +34 916647490.
E-mail address: brezo.martinez@urjc.es (B. Martínez).
0044-8486/$ - see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.aquaculture.2005.10.025
Nowadays, cultured seaweeds represent most of the
seaweed production, which is about 10 million tons
fresh weight (FW) worldwide (Lüning and Pang, 2003).
However, the use of seaweeds as food and its cultivation
in western countries is by far less developed (Browne,
2001). Palmaria palmata (Linnaeus) Kuntze is probably
the most popular seaweed used as food in North
America and Europe, and has been also used for feeding
abalone in hatcheries (Morgan et al., 1980a; Irvine and
Guiry, 1995; Le Gall et al., 2004). This species,
commonly known as “dulse”in the northern Europe,
is a good source of dietary requirements, rich in vitamins
and minerals, proteins, and fibre (Morgan et al., 1980b;
Lahaye et al., 1993). P. palmata is commercially
harvested and sold in dry form by several food selling
companies in Canada, USA, Ireland, and UK (Chopin,
1998; Browne, 2001). The development of the maricul-
ture of this species has been suggested to have high
potential in Canada and in the USA (Chopin, 1998;
Cheney, 1999). Cultivation in small tanks (8 l) received
large attention in the 1980s in Nova Scotia (Morgan et
al., 1980a; Morgan and Simpson, 1981a,b,c). Recently,
cultivation in larger tanks has been developed with
fronds collected from Roscoff (France), and open sea
cultivation has been tested in Northern Ireland (Browne,
2001; Pang and Lüning, 2004).
We summarize in this paper the results from the first
open sea cultivation of P. palmata on the northern
Spanish coast. The cultivation technique was modified
from rafts culture methods developed for Laminaria
japonica Areschoug mass cultivation in China, and from
P. palmata experimental cultivation in Northern Ireland
(FAO, 1989, 2001, 2003; Perez, 1992; Ohno and
Critchley, 1993; Browne, 2001). The aim of our study
was to adapt the known techniques of vertical rope raft
culture to suit the local conditions of the coast of
Asturias (northern Spain). For this purpose, we
investigated the effects of several factors on the growth
and quality (i.e. N content) of the fronds during five
successive cultivation trials.
The two first trials aimed to test the best outplanting
season given that field P. palmata showed their highest
growth rates during spring (Faes and Viejo, 2003). The
optimum length of the cultivation period (number of
weeks) was also tested. High growth during the first
weeks followed by reduced growth has been observed in
cultures of Gigartina atropurpurea J. Agardh and other
red seaweeds (McNeill et al., 2003).
In the next trial the cultivation of fronds inside mesh
bags was compared to the cultivation of fronds directly
inserted into ropes following the more traditional
vertical rope culture techniques (FAO, 1989, 2001,
2003; Perez, 1992; Ohno and Critchley, 1993). The
coast of Asturias is exposed to waves with few
moderately sheltered sites. The use of mesh bags in
such conditions has been shown to prevent the
detachment of algal material (Ask and Azanza, 2002;
Reddy et al., 2003).
The efficiency of an alternative method to the
collection of field material for culturing was tested in
the fourth trial. The ultimate objective was the reduction
of harvest pressure on the natural populations. P.
palmata develops marginal proliferations that were
collected from the material harvested in the third trial
and used as source stock. Pruning methods are common
in algal cultivation procedures to assure the sustainabil-
ity of the cultivation system (Melo et al., 1991; Perez,
1992; Ohno and Critchley, 1993; Lobban and Harrison,
1997; McNeill et al., 2003).
The third and fourth trials also tested the hypothesis
that increasing the density on ropes, or increasing the
number of fronds inside mesh bags, would cause a
decrease in growth due to the reduction of light and
nutrients (Browne, 2001).
Finally, in the fifth trial we tested the effect of an
artificial fertilizer on frond growth and quality. In the
studied area, the growth of P. palmata fronds from the
field populations is limited by very low nutrient
concentrations in late summer (Martínez and Rico,
2002; Faes and Viejo, 2003). Nutrient enrichment
treatments have been shown to prevent growth and
quality decay in cultures from other geographic areas
(FAO, 1989, 2001, 2003; Ask and Azanza, 2002; Tseng,
2004).
These experiments represented a pioneer activity in
Spain since algae are not traditionally consumed nor
cultured in this country (Juanes and Sosa, 1998).
2. Material and methods
2.1. Sites
The P. palmata culture rafts were placed in two
locations along the coast of Asturias (northern Spain):
Ensenada de Arnao (43°33′N, 7°01′W) and Concha de
Artedo (43°34′N, 6°12′W). The Ensenada de Arnao
(Arnao) is a bay at the eastern side of the mouth of an
embayment about 5 km long (Ría de Ribadeo). The
hydrography and dynamics of the Ría de Ribadeo are
dominated by tidal and wave forcing. The site where the
rafts were set is subjected to a significant outflow
current caused by the wave breaking at the west side
(Piedracoba et al., in press). The Concha de Artedo
(Artedo) is a bay dominated by wave forcing due to its
377B. Martínez et al. / Aquaculture 254 (2006) 376–387
reduced size (about 1.5 km long). The seasonal
variations of major environmental factors in Artedo
have been published elsewhere (Martínez and Rico,
2002). Temperature records from the temperature
monitoring program currently undergoing by the
Ecology Department of the University of Oviedo reveal
that the temperature regime in Arnao is similar to the
seasonal variation measured at Artedo and summarized
in Martínez and Rico (2002). These sites were selected
because they are moderately sheltered to the dominant
wave regimes, providing some protection to the culture
units. They have the suitable water depth for accom-
modating the floating rafts, and are easily accessible by
boat. Both represent the best potential sites for the
installation of commercial seaweed farms in the coast of
Asturias.
2.2. Cultivation procedure
A total of 3–5 culture ropes (depending on the
trial) were secured to a steel bar (1 m long). The bar
was suspended 1m below the sea surface from two
buoys and fixed in position on the seabed by two
concrete anchor weights (40 kg each). Four-millimeter
polyethylene ropes were used for growing the fronds;
each one was 3 m in length. A second steel bar at the
bottom kept all ropes in place avoiding rope twisting.
Three independent floating rafts separated 3 m and
sited in parallel were adopted as the cultivation unit
(Fig. 1). One cultivation unit was used per locality in
1999 and two units separated around 50 m were set up
in 2000.
P. palmata fronds collected subtidally at Artedo were
used as source stock material. When inserting the fronds
was not possible the same day of collection, fronds were
kept submersed in the sea inside a wide mesh bag (1 cm
width) less than 24 h. Only fronds free from epiphytes
and dark-red in colour (healthy-looking fronds) were
selected for cultivation. Many fronds were ramified
showing small marginal proliferations at the time of
collection.
2.3. Cultivation experiments in 1999
The effect of the outplanting season (spring–
summer), and length of the cultivation period (number
of weeks) were analysed during 1999 in two locations
(Artedo–Arnao). One trial started in April (spring
culture) and a second trial in June (summer culture).
Trials in autumn and winter were not performed due
to rough sea conditions that are common at these
seasons in the studied area. A culture period of
approximately three months was used. The initial
mean length of the fronds was 14.8 cm (± 0.16 SE,
n=969). Frond length and numbers were monitored
weekly or fortnightly. Single fronds were inserted in
the lay of the ropes by opening the twist and pushing
the fronds through the lay (see Kain (Jones), 1991).
Fifteen vertical ropes were seeded and hung from the
three floating rafts installed at each locality (five ropes
per raft). All ropes in each cultivation unit were
seeded with a mean density of 12–15 fronds/m of
rope in spring and 22–25 in summer.
2.4. Cultivation experiments in 2000
The following three trials were set up in the spring
and summer of 2000. The fronds were only attached to
the bottom meter of each rope between 3 and 4 m depth.
This reduced the amount of material needed for the
experiments, and thus the demand of individuals from
natural populations. The deepest meter was chosen
because individuals from filed populations growing
Weight
Steel bar
MESH BAGS
with P. palmata
ROPES
3 m
1 m
1 m
Weight -40 Kg
Buoy
3 m
Fig. 1. Vertical rope culture rafts adapted for the local conditions and
experiments done. Each unit consisted of three floating rafts.
378 B. Martínez et al. / Aquaculture 254 (2006) 376–387
underneath kelp canopies showed higher nutritional
value and quality (i.e. N and protein content) than those
growing in high light conditions (Martínez and Rico,
unpublished data).
The third cultivation trial was done in Artedo (April–
May) and examined the effects of cultivation procedure
(fronds inserted into ropes at density of 30/m, and
compared to fronds placed inside bags with 10 fronds/
bag and 3 bags/m), and frond density (10, 30 and 60
fronds/m of rope) on the growth rate. The bags were
made of a 25×30 cm polyethylene net 4 mm in width,
which filtered out 10% of the incident light. The effect
of using bags in the quality of the fronds was also tested.
In subsequent experiments only the bag procedure was
used as a consequence of the results of this experiment.
In the fourth trial (Artedo, May–June) the growth
and quality of the marginal proliferations collected from
the material cultivated in the third trial were compared to
that from small fronds collected in the field at a density
of 10/bag. Small marginal proliferations (b7cmin
length) were excised at their base from the edge of
bigger fronds. The effect of the different density of
fronds inside bags (10, 20 and 30 fronds/bag and 3 bags/
m) on the growth was also tested.
The fifth experiment (July–August) tested the
combined effect of Locality (two locations: Artedo
versus Arnao) and Enrichment (control versus nutrient
enhanced units) on the growth and quality of the fronds.
A pair of fishnet stockings, each containing 250 g of a
controlled release fertilizer (Multicote 4 months,
20N: 10P : 20K, Haifa Chemicals Ltd., Haifa Bay,
Israel), was attached to half of the ropes close to each
bag. All the bags contained 10 fronds both in the
nutrient enhanced and control treatments.
To compare frond growth among trials run during
spring and summer, bags with a density of 10 fronds/bag
were included in the three cultivation trials done during
2000.
In all trials, the ropes were randomly located in the
two units available. However, in the last trial (effect of
Locality and Enrichment) all the nutrient enhanced
ropes were set together in a single cultivation unit per
locality to avoid an undesirable enrichment of the water
around the control ropes. Therefore, the effects of the
addition of fertilizer may be confounded with possible
spatial differences in this trial. However, previous study
in Artedo showed no spatial changes in nitrogen (N) and
phosphorus (P) inorganic concentration according to the
very low values of these compounds in summer
(Martínez and Rico, unpublished data).
At the start of the experiments in 2000, the initial
mean fresh weight per frond was 0.73 g (±0.02 SE,
n=47) without significant differences among treat-
ments, locations or periods. The number and weight
(FW) of fronds per meter of rope (or per bag) were
recorded at the beginning and the end of each
experiment. The mean increase in FW (final–initial
FW) per frond per day was calculated in order to make
comparisons among trials, and densities. Additionally,
in the third trial the lengths of the fronds were also
measured. Mean initial length in this trial was 7 cm
(±0.3 SE, n=55). The experiments were run for 23 to
33 days.
2.5. Biochemical analyses
Nutrient contents of fronds from different cultivation
procedures: bags versus fronds inserted into ropes (third
trial), origin of the fronds (newly collected versus
marginal proliferations; fourth trial), and Locality and
Enrichment treatments (fifth trial), were recorded in the
experiments of 2000 to characterize the quality and
nutritional value of the fronds. Two samples per
treatment were analysed in the third and fourth trials,
and 10 samples in the fifth trial. Biochemical analyses
were performed after drying the samples in a circulation
dryer at temperatures below 40 °C, and grinding the
dried sample in a hammer mill with a 2 mm sieve.
Thallus N content was measured using a CNH
Elemental Analyser (Perkin Elmer Analytical Instru-
ments, Shelton). P extraction from thallus was per-
formed by alkaline persulphate digestion (Ameel et al.,
1993), and phosphate was measured as described in
Koroleff (1983).
To further characterize the dietary value and
physiological status of the fronds cultured by the two
different methods (bags and fronds inserted into ropes),
ash and main carbohydrates content (xylan, glucose and
floridoside) were analysed in two samples from the third
trial. Thallus ash content was determined by heating the
samples to 530 °C for 18 h (Larsen, 1978). For
carbohydrate extraction dry algal powder was subjected
to pre-hydrolysis with 80% sulphuric acid (18 h, 4 °C)
prior to hydrolysis by 1 M sulphuric acid (4 h, 100 °C)
according to Haug and Larsen (1962). The quantitative
monosaccharide composition was determined by gas
chromatography (Chaplin, 1982), and new extinction
coefficients were calculated. The concentrations of
xylan, a dietary fibre, and glucose were determined
according to methods in Dubois et al. (1956). Flori-
doside was extracted in boiling water for 4 h and
then determined by the method of Dubois et al.
(1956) after a new extinction factor was calculated by
gas chromatography.
379B. Martínez et al. / Aquaculture 254 (2006) 376–387
2.6. Seawater nutrient concentrations
N and P levels in seawater were monitored during the
fifth trial (2000) near the nutrient enhanced and the
control ropes. A total of two samples per treatment and
locality at 4 different dates were taken. Seawater
concentrations of nitrate, nitrite, and orthophosphate
were measured as described in Koroleff (1983) and
ammonium as outlined in Álvarez (1993) using a
Technicon II Autoanalyzer (Industrial Method no.
158-71 W/A, Ireland). All the inorganic N forms
showed parallel trends during the experiment thus
their concentration values were summed to calculate
total N.
2.7. Statistical analyses
The initial length of fronds varied between
locations in experiments of 1999. Mean frond length
was compared between sites after four weeks of
cultivation using Analysis of Covariance (ANCOVA),
with initial length as covariate. Mean increases in FW
per frond in experiments of 2000 were analysed using
uni- or bifactorial Analysis of Variance (ANOVAs).
Locality was considered a fixed factor. Analyses of
total N and P in seawater and of thallus constituents
were also done using multi- and unifactorial ANO-
VAs. In ANOVAs involving bag cultivation proce-
dures an additional factor, Rope, was nested in the
combination of main treatments. Cochran's test was
used to test for heterogeneity of variances. When
indicated data were transformed to homogenize
variances (see Tables). Student–Newman–Keul
(SNK) tests were used to discriminate among different
treatments after significant F-tests. All tests were done
with SPSS (11.0.1) for Windows.
3. Results
3.1. Cultivation experiments in 1999
Mean length of cultivated fronds increased in 1999
during the first trial (spring), and at the beginning of
the second trial (summer) (Fig. 2). The increase was
especially marked in the first four weeks of culture in
spring. During this time interval, the growth was
similar between locations (ANCOVA for differences
between locations in final mean length of fronds,
F
1, 290
=0.13, p=0.713). Fronds in Arnao grew for a
longer period than in Artedo during the spring
experiment. Plants from both sites were bleached
and covered by epiphytes at the end of the cultivation
period, and there were considerable losses of fronds
attached to ropes from the beginning of the experi-
ments. In Arnao, 76.1% of all fronds in spring and
90.6% in summer were lost. Losses in Artedo were
lower (22.4% in spring and 56.5% in summer).
3.2. Cultivation experiments in 2000
In the third trial, fronds cultured inside bags, and
those directly inserted into ropes at different densities,
showed similar growth rates (Fig. 3,one-way
ANOVA, F
3, 12
=1.80, p=0.201). Mean daily frond
growth was 103.7 mg FW (±7.49 SE, n= 16). This
corresponded to a daily increase of about 14% of the
mean initial weight of the fronds. Fronds cultured
inside bags during this trial showed a final mean
length of 21 cm (±1.5 SE, n=10). The density of
fronds directly inserted into ropes varied during the
8
12
16
20
24
28
152
152
145
142
128
118
180
205
217
246
275
297
308
313
315
ARTEDO
8
12
16
20
24
28
180
169
145
123
98
63
320
318
312
255
187
157
139
60
ARNAO
298
30
78
187
148
154
136
Mean length (cm)
April May June July August
A
p
ril Ma
y
June Jul
y
Au
g
ust
Fig. 2. Temporal changes in frond length of Palmaria palmata
inserted into ropes in 1999 at Artedo and Arnao (first and second
trials). Closed symbols indicated the first trial (spring) and open
symbols indicate the second trial (summer). Error bars represent
standard error, numbers indicate total number of fronds (n) inserted
into 15 vertical ropes.
380 B. Martínez et al. / Aquaculture 254 (2006) 376–387
experiment due to losses. The proportion of frond
losses was similar at all densities used (one-way
ANOVA, F
2, 9
=1.89, p=0.207), with an overall mean
of 28% (±21.5 SE, n=12) of the initial number of
fronds. Moreover, fronds directly inserted into ropes
bleached by the end of the experiment independently
of the cultivation density used. This was associated
with significant differences in the physiological status
of the fronds. Floridoside content was higher in fronds
directly inserted into ropes than in fronds within bags
(Table 1). The opposite trend was detected for N
content. Low glucose content was measured and no
significant differences were found in this component
or in P content, xylan, and ash between cultivation
methods.
In the forth experiment a trend was observed for
frond growth to decrease with increased frond density
inside bags (Fig. 4). Moreover, marginal proliferations
tended to grow more than newly collected fronds at any
density (nested ANOVA, F
3, 8
=3.90, p=0.054). Signif-
icant differences in thallus N and P content were not
observed (one-way ANOVAs, overall mean % DW;
nitrogen: F
3, 4
=0.70, p=0.601, 1.1 ± 0.06 SE; phospho-
rous: F
3, 4
=1.36, p=0.375, 0.1 ± 0.01 SE; n= 8).
In the enrichment experiment (fifth trial during
July–August), N and P in seawater around control and
nutrient enhanced ropes varied among locations and
dates (ANOVAs, significant interaction Enrichmen-
t×Locality ×Date,F
3, 16
=31.37, p=6.19×10
−7
for
total N; F
3, 16
=14.47, p=8.04 × 10
−5
for orthophos-
phate). A significant increase in total N around
nutrient enhanced ropes was detected at Arnao in
the first and last dates and at Artedo in the first and
second dates. Differences in orthophosphate between
Table 1
Analyses of variance for differences in N, P, floridoside, xylan, glucose, and ash content in fronds cultivated inside bags or inserted into ropes in the
third trial (April–May 2000)
df MS
source
MS
residual
FpMean ± SE % DW, n=2
Bags Ropes Overall
N 1,2 0.374 0.015 25.142 0.038 2.25±0.3 1.28±0.1 –
P 1,2 0.003 0.001 2.473 0.256 ––0.183±0.03
Floridoside 1,2 136.890 0.530 258.283 0.004 14.50±0.7 26.20± 0.2 –
Xylan 1,2 2.723 3.262 0.834 0.457 ––27.37±1.0
Glucose 1,2 4.000 0.565 7.080 0.117 –– 4.75±0.8
Ash 1,2 124.769 16.544 7.542 0.111 ––25.74 ±4.2
Variances were homogeneous.
0
20
40
60
Frond growth (mg FW
•
day
-1
)
Marginal
proliferations
Collected
fronds
30•m
-1
60•m
-1
90•m
-1
Fig. 4. Mean daily frond growth of Palmaria palmata cultivated inside
bags during the forth trial (May–June 2000). Fronds were collected
from the field and grown at three densities or marginal proliferations
excised from harvested fronds and grown at one density. Error bars
represent standard error (n=9).
0
25
50
75
100
125
150
Frond growth (mg FW
•
day
-1
)
Ropes
Bags
10•m-1 30•m-1 60•m-1
Fig. 3. Mean daily frond growth of Palmaria palmata cultivated inside
bags and inserted into ropes at three densities in the third trial (April–
May 2000). Error bars represent standard error (n= 4).
381B. Martínez et al. / Aquaculture 254 (2006) 376–387
treatments were detected at Arnao in the last date (Fig.
5). These data support that inorganic nutrients were
released from the fertilizer pellets. When only controls
were compared, total N was higher in Arnao than in
Artedo in 2 out of 4 sampling dates (Table 2, SNK
test). P levels were also higher at Arnao in 2 out of 4
sampling dates, and at Artedo in 1 date. Frond growth
was affected by the combined effect of Locality and
Enrichment treatments (Table 3,Fig. 6A). Fronds on
nutrient enhanced ropes in Artedo had higher growth
rates compared to those on control ropes, whereas no
significant differences were found between treatments
at Arnao. Higher N content was observed in nutrient
enhanced fronds from both sites. In addition, fronds
from Arnao had higher N content than those from
Artedo irrespective of the treatment (Table 4,Fig. 6B).
P content was higher in fronds from Arnao than from
Artedo but no differences were observed in response
to the addition of nutrients within locations (Table 4,
Fig. 6C).
Growth was highest at the beginning of the spring
(April–May 2000), and declined towards July–August
in Artedo (Fig. 7,ANOVA,F
3, 12
= 52.13, p=3.7 ×10
−7
).
Frond growth in nutrient enhanced bags in July–August
18-Jul
20-Jul
3-Aug
10-Aug
17-Aug
0
5
10
15
20
25
Control
0
5
10
15
20
25
Concentration of total N in seawater (μM)
ARNAO
ARTEDO
0
0.2
0.4
0.6
18-Jul
20-Jul
3-Aug
10-Aug
17-Aug
0
0.2
0.4
0.6
Concentration of P in seawater (μΜ )
Nutrient enhanced
Fig. 5. Changes in levels of total N and P through time around culture rafts of Palmaria palmata during the fifth trial (July–August 2000) at
Arnao and Artedo. Closed and open symbols indicate nutrient enhanced or control cultures, respectively. Error bars represent standard error
(n=2).
Table 2
Analyses of variance of differences in (a) total N and (b) orthophosphate in seawater around control ropes in the different locations (Artedo and
Arnao) and sampling dates (experiment of July–August 2000)
Source df (a) N in seawater (b) P in seawater
Mean square FpMean square Fp
Locality 1 0.876 3.330 0.165 1.41×10
−4
0.031 0.871
Date 3 3.001 72.860 0.001 0.83 × 10
−4
0.290 0.831
Locality ×Date 3 0.263 6.374 0.016 44.90×10
−4
15.676 0.001
Residual 8 0.041 2.87×10
−4
SNK tests Dates 2, 3: ArnaoNArtedo Date 1: ArtedoNArnao
Dates 1, 4: Arnao≈Artedo Dates 2, 4: ArnaoNArtedo
Date 3: Arnao≈Artedo
Mean values differing between locations are indicated (from SNK tests). Variances were homogeneous.
≈non-significant differences at pb0.05.
Nsignificantly higher at pb0.05.
382 B. Martínez et al. / Aquaculture 254 (2006) 376–387
was similar to that in control bags in the previous period
(April–May).
4. Discussion
Spring was the optimal season for mariculture of P.
palmata in northern Spain. Spring is frequently the
best cultivation season for seaweeds from diverse
geographic areas (e.g. McNeill et al., 2003). The
individuals cultivated, irrespective of the method used,
reached their annual maximal growth in May 1999
and 2000. Parallel growth trends were observed in
individuals from a close population (Faes and Viejo,
2003). P. palmata is a pseudoperennial seaweed that
shows its maximal growth during spring; growth is
reduced during summer and ceases in August in the
studied area (Faes and Viejo, 2003). A small
proportion of the thallus persisted over autumn and
winter, but showed no evidence of growth and thus
cultivation at these seasons could hardly proceed.
Moreover empty rafts were left and damaged by
winter and autumn storms that are common in the
studied area.
Growth of cultured fronds was noticeably greater
than values from natural populations. The elongation of
fronds at the beginning of spring 2000 (April–May) was
about 14 cm showing a final mean length of about 21
cm. This elongation was noticeably greater than the
increase of about 3.5 cm showed by field individuals
during the same period (Faes and Viejo, 2003). At this
time of the year, the daily weight increase (about 14%
initial FW) was among growth values observed in tank
cultures in previous experiments (Morgan et al., 1980a;
Morgan and Simpson, 1981a,b,c; Pang and Lüning,
2004). However, growth rates were higher in fronds
cultured in open sea in Strangford Lough, Northern
Ireland (Browne, 2001). The vicinity of the Spanish
cultures to the southern distributional limit of P. palmata
may explain this difference. Spanish populations
typically show smaller individuals probably due to
their peripheral nature (Kain, 1986; Irvine and Guiry,
1995). This pattern has also been observed in other
macroalgae (Carter and Prince, 1988; Bengtsson, 1993).
Table 3
Analysis of variance of the effect of Locality and Enrichment on the
daily frond growth (experiment of July–August 2000)
Source Mean square df F p
Locality 0.023 1 2.62× 10
−5
0.996
Enrichment 407.450 1 0.471 0.498
Locality ×Enrichment 864.861 1 12.199 0.002
Pooled Residual 70.897 27
a
The effect of Rope (nested in the interaction Locality ×Enrichment)
was not significant (pN0.25) and it was thus pooled with Residual
(Winer et al., 1991).
a
In order to homogenize variances, one data was replaced by the
mean of the group and 1 df subtracted from Residual.
0
10
20
30
Frond growth (mg FW • day-1)
Arnao Artedo
Nutrient enhanced
Control
a
b
ab
ab
A
0
1
2
3
4
N content (% DW)
Arnao Artedo
B
0
0.05
0.1
0.15
0.2
0.25
P content (% DW)
Arnao Artedo
C
Fig. 6. Differences in daily frond growth (A), N content (B), and P
content (C), in Palmaria palmata cultivated inside bags during the
fifth trial (July–August 2000) at Arnao and Artedo. Solid bars
indicated nutrient enhancement and open bars indicated control fronds.
Error bars represent standard error (n=8 for daily frond growth, n=10
for N or P). In A) lower case letters denote significantly different mean
values (pb0.05; Student–Newman–Keul test after significant F-test).
383B. Martínez et al. / Aquaculture 254 (2006) 376–387
Four weeks was a suitable period for cultivation.
Growth was severely reduced if fronds were cultured
over a longer period particularly at one of the studied
sites (Artedo), and several problems, such as frequent
frond loss, bleaching, and coverage by epiphytes,
increased with the length of rope cultivation in both
locations. A period of 4 weeks also produced the highest
sustained yields in open sea cultivation in Strangford
Lough and in tank culture (Morgan et al., 1980a;
Browne, 2001). Maximal growth rates were also
observed in the thirty days after pruning and transplan-
tation in many seaweeds (e.g. McNeill et al., 2003).
The growth of the fronds cultured inside bags and
inserted into ropes was similar, but the bag method
solved the problem of frond loss. Very often when
fronds were passed through the ropes the tissue
underneath the rope bleached and eventually broke.
Especially in Arnao, where an outflow current is present
(Piedracoba et al., in press), entire fronds were also
detached from the rope. Wave force in both sites, and the
wave and tidal driven currents in Arnao accelerated
frond losses. The bag method is particularly recom-
mended in the exposed conditions that prevail along the
northern Spanish coast. This procedure also provided
more consistent yields as it avoided the problem of frond
detachment and lessened the impact of grazing, both
problems also associated with rope culture of other
species (Ask and Azanza, 2002; Reddy et al., 2003).
Moreover, the use of bags enhanced the dietary value
of the harvested material increasing the N content of
fronds. In P. palmata the protein pool represents up to
93% of total cell N, thus higher N content of fronds was
related to higher protein and food quality (Martínez and
Rico, 2002). Furthermore, fronds cultured inside bags
exhibited lower floridoside content. Higher incident
light in the fronds inserted into ropes may explain these
differences. Storage of carbohydrates (such as florido-
side) was activated to benefit from higher light
conditions (Meng and Srivastava, 1993). This response
is well known in macroalgae (Neish et al., 1977;
McGlathery and Pedersen, 1999; Lüning and Pang,
2003) and particularly in this species (Morgan and
Simpson, 1981a; Martínez and Rico, 2002), and is
commonly associated with a decrease in the N content of
the thallus as shown in this study (Neish et al., 1977;
McGlathery and Pedersen, 1999). In addition to
increased yield and quality, the use of bags reduced
the personnel required particularly during outplanting
due to the easier manipulation.
Appropriate stocking density was very important
when using bags. The growth rate tended to decrease
with increasing number of fronds per bag. Reduced
turbulence, and thus lower nutrient supply, and lower
irradiance due to self-shading of the fronds explained
similar results in Strangford Lough (Browne, 2001).
Lower growth rates with increasing density were also
measured in cultures of Chondrus crispus Stackhouse
inside cylindrical mesh containers (Zertuche-González
et al., 2001).
Table 4
Analysis of variance of the effect of Locality and Enrichment treatment on (a) the N and (b) P content of fronds (experiment of July–August 2000)
Source df (a) Thallus N content
a
(b) Thallus P content
b
Mean square FpMean square Fp
Locality 1 0.009 39.497 0.001 0.042 23.220 0.001
Enrichment 1 0.002 9.052 0.005 0.002 1.102 0.301
Locality ×Enrichment 1 0.0003 1.502 0.228 0.006 3.490 0.070
Residual 36 0.0002 0.002
a
Data were arcsine transformed to homogenize variances.
b
In order to homogenize variances, one data was replaced by the mean of the group and 1 df subtracted from Residual.
0
20
40
60
80
100
Frond growth (mg FW • day-1)
April-May May-June Jul-Aug
(enriched)
Jul-Aug
a
b
b
c
Fig. 7. Mean daily frond growth of Palmaria palmata cultivated inside
bags through time in the trials done during spring and summer 2000 in
Artedo (nutrient enhanced or not nutrient enhanced in July–August).
Error bars represent standard error (n=4). Lower case letters denote
significantly different mean values (pb0.05; Student–Newman–Keul
test after significant F-test).
384 B. Martínez et al. / Aquaculture 254 (2006) 376–387
Nutrient enrichment at the end of summer enhanced
growth at one of the studied sites. In Artedo, nutrient
enhanced fronds in July–August grew at a rate similar
to fronds cultured one month and a half earlier. A
resin-coated fertilizer, of the same type used in this
research, was shown to improve Gelidium cultivation
in the sea (Melo et al., 1991). In situ nutrient
enrichment methods have been extensively used in
cultivation of Laminarial and Euchematoid species,
and have caused the fast development of kelp farming
in oligotrophic Chinese coastal areas (FAO, 1989,
2001, 2003; Ask and Azanza, 2002; Tseng, 2004).
Our results suggested that the addition of nutrients
would allow the cultivation of P. palmata during
summer in locations not receiving high nutrient inputs
such as Artedo in this study. Fronds also showed
higher N in response to the higher seawater nutrient
levels due to the enrichment irrespective of the
location. The fertilizer increased the quality of the
harvested material slowing down the trend of
decreasing N content as the cultivation proceeded
(source material collected in April: mean % DW: 4.3
±0.42 SE, n= 2). Field individuals also showed this
natural trend in response to the nutrient starving
conditions during summer (Martínez and Rico, 2002).
In spite of the increase in quality, the growth of fronds
from Arnao was not enhanced in response to the
addition of nutrients. In Arnao growth was not
nutrient limited probably due to the higher nutrient
concentration associated with the estuary and with the
nutrient load from large oyster and clam farms
operating in this location. Similar growth responses
have been observed in bays with high nutrient loading,
which are traditionally selected for extensive L.
japonica cultivation and do not require fertilizer
additives (FAO, 1989). Cultivation of macroalgae in
such areas may prevent harmful effects from eutro-
phication, balancing the negative effects of animal
cultivation (FAO, 1989; Fei and Tseng, 2003; Fei,
2004). The integration of P. palmata cultivation with
the bivalves' cultivation in Arnao would reduce
potential eutrophication effects. P. palmata has been
mentioned as a good candidate for such integrated
cultivation systems (Chopin et al., 2001; Lüning and
Pang, 2003; Neori et al., 2004; Pang and Lüning,
2004).
As pointed out by Waaland (1978), the major
requirement for sustained marine algal cultivation is
the availability of sufficient source stock. P. palmata is
patchily distributed and populations are isolated along
the Spanish coastline (Faes and Viejo, 2003). The
marginal proliferations were suitable source material
for the following cultivation trial. Similar procedures
are common in macroalgal farming on a commercial
scale. In many species the individuals can be pruned
back to seedling size to allow a second harvest (Melo
et al., 1991; Perez, 1992; Ohno and Critchley, 1993;
Lobban and Harrison, 1997; McNeill et al., 2003).
The use of marginal proliferations would partially
solve the limitation of source material but research is
needed to assure the sustainability of the cultivation
system. Le Gall et al. (2004) suggested the possibility
of seeding the culture ropes with spores of P. palmata
and then transferring seeded ropes to the sea for
cultivation.
Results from these trials suggest the potential to
aquaculture P. palmata in northern Spain. Cultivation
methods should be preferred to harvesting natural
populations since the natural stock is limited. To this
end, preliminary techniques developed from these trials
have been transferred to a new company. This company
has installed vertical rope rafts in one of the locations
used in this research. Fronds are being cultivated during
four weeks inside mesh bags similar to those used in this
study.
Acknowledgements
This study has been carried out with financial support
from the Commission of the European Communities,
Agriculture and Fisheries (FAIR) specific RTD
programme, project CT97-3828, PALMARIA. J. Sos-
tres and E. Cabal were an invaluable help with analytical
procedures. Sincere thanks to the Dirección General de
Pesca del Principado de Asturias, and especially
Manolo and Eva, for their help with fieldwork. We
gratefully acknowledge A. Gatti for correcting the
English style, and several anonymous reviewers for
helpful comments on the manuscript.
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