I*! · 2004. 9. 1. · I would like to th& Dr. Thierry Chopin for his guidance and encouragement...

National Library I*! of Canada Bibliothèque nationale du Canada

Acquisitions and Acquisitions et Bibliographie Services services bibliographiques

395 Wellington Street 395, ~e Wellington Ottawa ON K1A ON4 OttawaON K1AON4 Canada Canada

The author has granted a non- exclusive licence ailowing the National Library of Canada to reproduce, loan, distniute or sel1 copies of this thesis in microform, paper or electronic formats.

The author retains owaership of the copyright in this thesis. Neither the thesis nor substantial extracts fiom it may be printed or othexwise reproduced without the author's permission.

L'auteur a accordé une licence non exclusive permettant à la Bibliothèque nationale du Canada de reproduire, prêter, distriiuer ou vendre des copies de cette thèse sous la forme de microfiche/film, de reproduction sur papier ou sur format électronique.

L'auteur conserve la propriété du droit d'auteur qui protège cette thèse. Ni la thése ni des extraits substantiels de celle-ci ne doivent être imprimés ou autrement reproduits sans son autorisation.

The impact of harvesting on the nitrogen (N), phosphorus (P), and carbon (C)

contents ofAscophyZZum nodosum was studied for 13 rnonths after an experimental

harvest at Letite, in the Bay of Fundy, New Brunswick, Canada. Nutrient contents (N, P,

C) were measured in apical tips, mid-sections and basal shoots of intact plants in control

plots and were compared to nutrient contents of the segment of the thallus irnmediately

below truncation due to harvesting and basal shoots in harvested plots. From these

measurements, nutrient ratios (NP, C:N, C:P) were calculated for each part sampled. For

al1 parameters considered, the tissue below the point of harvesting showed nutrient

physiology more similar to that of mid-sections in intact plants than to apical tips. This

was consistent with the observation that d l regrowth on stumps was due to growth of

lateral shoots below the point of truncation and never fkom a new apical meristem. There

was no signincuit difference in the nutrient contents and ratios between basal shoots

below intact and harvested canopies.

I would like to th& Dr. Thierry Chopin for his guidance and encouragement

throughout this project. 1 thank Dr. Kate Frego for much help with experimental design,

statistical analyses and the writing of this thesis. Dr. John Johnson provided many useful

suggestions during the planning of this project and thesis preparation.

1 sincerely thank EUen Belyea for teaching me the laboratory techniques used in

this study and much help with all aspects of the research. Thanks to Tania Morais and

Teri McLean for help with field work. I thank Dr. Matthew Litvak for help with statistical

analyses, and WiIfied Moms and Rabindra Singh for help with cornputer programs.

Finally, I would like to thank my f d y for their confidence and encouragement.

TABLE OF CONTENTS

............................................. TABLE OF CONTENTS iv

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LISTOFTABLES vi

.................................................. LIST OF FIGURES vii

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . m O D U C I l O N 1

................................. Ascoplynum nodosum (L.) Le Jolis 1

Distribution ................................................... 1

............................. Morphology. growth and reproduction 4

Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 i.Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

ii.Phospho nu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

.................................... Uses of Ascophynum nodbsurn 11

Harvestingofrockweed ......................................... 14

Purposeofthestudy ........................................... 16

........................................... Pre-hawest sampling 17

................................................... Harvesting 20

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Post-harvest tagging 20

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Post-harvest sampling 20

Nutrientanalyses .............................................. 21

.................................... i.Nitrogenandcarbon 21

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LPhosphorus 22

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i i i Seawater autrients 22

S tathtical analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Tissue total aitrogen content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Tissue total phosphoms content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Tissue total carbon content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Nitrogen:Phosphorus ratio (N:P) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Carbon:Nitrogen ratio (C:N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Carbon:Phosphorus ratio (C:P) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Seawater nutrîents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Phosphoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Nutrientlimitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

........................................... hnpactofha~esting 56

................................................... Condusion 59

Futurestudies ................................................ 59

LIST OF TABLES

ms . . . . . . . . . W e s t related tenninology for AscophyIIum nodomm morphology.. 5

One way analysis of variance of nutrient contents and ratios in AscophyfIum nodoszim according to plot. (a) Nitrogen; @) Phosphonis; (c) Carbon; (d) NP ratio; (e) C:N ratio; (f) C P ratio. * Significant at p<0.05,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ns not signiticant at p>O.O5. 24

Analysis of variance of nitrogen content in Ascop&IIum nodcsum according to month, part, and plot (nested within treatments) (n = 30). . . . . . . 26

Range of tissue total phosphorus, nitrogen and carbon contents in apical and cut tipq mid-sections, and basal shoots fiom control and harvested plots of AscophyZZum nodosum. Values represent means (n = 30) * SE. . . . . . . 28

Analysis of variance of phosphorus content in AscophyIZum n o d o m accordiig to month, part, and plot (nested within treatments) (n = 30). . . . . . . 3 1

Analysis of variance of carbon content in Ascophyllm nodomm accordig to month, part, and plot (nested withh treatments) (n = 30). . . . . . . . . . . . . . . 35

Analysis of variance of the N:P ratio in Ascophylum nodosurn according to month, part, and plot (nested within treatments) (n = 30). . . . . . . . . . . . . . . . . 38

Range ofNP, C:N, and C 9 ratios in apical and cut tips, mid-sections, and basal shoots fkom control and hwested plots of AscophyZZum nodosum. Values represent means (n=30) SE. ............................... 39

Analysis of variance of the C:N ratio in Ascophyllum nOd;Osum according to month, part, and plot (nested within treatments) (n = 30). .............. 4 1

Anaiysis of variance of the CrP ratio in AscophyZm nodoszim accordig to month, part, and plot (nested within treatments) (n = 30). ................ 45

Critical nitrogen contents for several seaweeds. ........................ 54

LIST OF FIGURES

Ascophyllm nodosum. A- Apical tip; V-Vesicle; R-Receptacle; P-Primary Eaoe

shoot; S-Stump; C-Cut tip; B-Basal shoots ............................ 2

Distribution ofAscophyI2um nodosum (bold line) dong the Atlantic coasts ..... 3

Two components of algirîic acid: (a) polyrnannuronic acid, @) polyguluronnic acid (after Lobban and Harrison 1994). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Area map of Letite, NB, and study site (arrow). ........................ 18

Layout of the 10 x 10 m plots at the study site. C = Control plots, H = Harvested plots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Seasonal variations of the tissue total nitrogen content (mg N g DW') of AscophyZZum nodosum collected at Letite, NB. Values represent means

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (n= 30) * SE. 27

Seasonai variations of tissue total phosphorus content (mg P g DW') of Ascophyhm nodosum coliected at Letite, NB. Values represent means (n=3O)*SE.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Seasonal variations of tissue total carbon content (mg C g DWL) of AscophyfIum nodosum coiiected at Letite, NB. Values represent means (n= 30) * SE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Seasonal variations of the N:P atomic ratio of Ascophyh nodosurn collected at Letite, NB. Values represent means (n = 30) * SE.. . . . . . . . . . . . . 37 Seasonal variations of the C:N atomic ratio of Ascophyllum nodomm coilected at Letite, NB. Values represent means (n = 30) * SE.. ............ 42

Seasonal variations of the C:P atomic ratio of Ascophyllum nodosunt colieaed at Letite, NB. Values represent means (n = 30) * SE.. ............ 44

Seasonal variations of dissolved inorganic N ( Dm; as the sum of NEZ' + NO< + NO;) and dissolved inorganic P (DIP; as PO,$) concentrations in seawater collected at Letite, NB. .................................. 47

(A) Stump showing eut tips (Cl, C2, C3) and lateral shoots (LI, L2, L3) one month aAer harvesting (September 1996). @) The same stump 11 months after hamesting (July 1997), showing no change in cut tips (Cl, C2, C3) and growth of laterai shoots (Ll, L2, L3) below cut tips. .......... 57

-vii-

INTRODUCTION

Ascophy&m nodosum (L.) Le Jolis

AscophyZZum nodowm is a common interiidai brown seaweed of the Order

Fucaleq Family Fucaceae (Fig. 1). It was originally descnied as Funrs nodoszinz L. in

1753 and was transfened to the genus AscophyIJum by Stackhouse as A. laevig-

(Papenfiiss 1950). In 1863, Le Jolis described it as A. nodosum (Baardseth 1970).

Common names used for A. nodosum in Canada are rockweed, bottle kelp and goPrnon &

roche.

Distribution

AscophyZIum nOC(Osum is cornmon throughout the North Atlantic and the adjoining

parts of the Arctic Ocean (Fig. 2). In the notthwest Atlantic, it is found on rocky

substrates from Baf'iin Island to New Jersey, and fiom the Russian Arctic (White Sea) to

northem Portugal in the northeast Atlantic. Within the intertidal zone, it is found Born the

upper intertidal to the mean low tide level (Baardseth 1970). AscophyZZum nodosum

seems to thrive on intermittent exposure to air and is especially abundant in areas of high

tidal amplitude, such as the Bay of Fundy. In areas with no tide, it is nibtidal in shdow

water (Baardseui 1970).

Wave exposure is an important factor determinhg the dimiution ofA. nodom.

Vadas and Wright (1986) observed the oldest plants, highest coverage, growth, and

relative abundance at sheltered sites, although biomass was highest at intermediate

Figure 1 : AscophyIZm nodosum. A-Apical tip; V-Vesicle; R-Receptacle; P-PMnary shoot; S-Stump; C-Cut tip; BBasal shoots (modified fiom Sharp 1987). For description of temis, see Table 1, p. 5.

Figure 2 : Distn ion of AscophyZZltm, nOdDsum @old iine) dong the Atlantic CO-.

exposure. Moderate exposure is believed to provide a refbge fiom ice-scouring

experienced in sheltered sites, and rnay increase the level of numents available to the

plants through water motion (Vadas and Wright 1986). In the Bay of Fundy, however, A.

nodomm is dominant throughout its range, regardless of wave exposure (Thomas et al.

1983).

AscophyZIum nodoswt is considered an euryhaline species. It thrives in salinities

around 32 %O but is tolerant of periodic salinity changes, to as low as 0.0 %O (Baardseth

1970). AscophyZIum nodosum is found at the mouth of the Saint John and Kennebecasis

nvers where salinity may drop to 10 %O (S. Brillant, pers. comm.).

Morpbology, growth and reproduction

Plants ofA. norjosum consist of an irregular discoid holdfast f?om which arises a

compressed linear shoot with no midni. The shoot elongates by apical growth and

branches dichotomously once each year in most individuals (David 1943, Moss 1970). In

spring of each year, new air bladders are produced below the apical tip by swelling of the

shoot. This results in regularly spaced vesicles dong the shoot, each corresponding to one

year of growth (Cousens 1984). Since it is not possible to detennine the number of years

before a basal shoot produces its fim vesicle, the segment fkom the holdfiist to the oldest

vesicle is conservatively assumed to represent at lest one year's growth (Cousens 1984).

Therefore the minimum age of an intact fiond can be determined by counting vesides

dong the primary, unbroken shoot and adding 1 year. Lateral branches mise from pits on

the p r i m q shoot and may be vegetative or reproductive, the latter bearing receptacles.

The teminology used to describe A. nodomm morphology varies among authors.

This study will use the terminology of Cousens (1 98 l), modified by Sharp (1987), to

descn%e harvest related morphology (Table 1, Fig. 1).

Table 1 : Harvest related terminology for AscophyJJum nodomm morphology.

Part Description

Shoot

Primary shoot

Basal shoot

Lateral shoot

Intact shoot

Apical tip

Cut tip

Stump

Frond

Plant

Stand

Vesicle

axis which results âom growth of an apical meristem

shoot originating fiom a single meristematic protnision fiom the hof dfast

unbranched juvenile shoot with no vesicles

shoot uising fiom a lateral pit on another shoot

shoot with at least one apical meristem, no evidence of harvesting

portion of shoot distai to the youngest vesicle, including apical meris t em

the 1.5 cm of tissue below the tnuicated end of a harvested tip

shoot lacking an apical meristem (no apical tip)

the system of shoots derived fkom a single meristematic protmsion from the h o l d h

assemblage of âonds arising âom a common holdfiist

a group of plants within a defined geographical area

vegetative dation at intervals dong the shoot, related to rate of annuai shoot elongation

re~roductive structure found on fertile lateral shoots

AscophyIZuum nodo- is a dioecious species with a garnetic life history. Fertile

receptacles arise one year before maturation, as lateral branches âom nodes of previous

6

seasons' growth (hdoss 1970). In sunken chambers Li the receptacles, calied conceptacles,

antheridia and oogonia produce haploid gametes (Moss 1970). These are released into the

water column where syngamy occun. Full maturation and dehiscence of receptacles

usuaily takes place within one month, after which receptacles decay. The timing of

dehiscence varies yearly (Mathieson et al. 1 W6), with tidal height (David 1943), among

sites (Keser and Larson 1984) and with latitude (David 1943). For example, maximal

dehiscence takes place in March-April in New Hampshire (Mathieson et al. 1976) but not

until May-June in Nova Scotia (MaFarlane 1932) and New BmflSWick (pers. observ.).

Despite a large reproductive effort (Aberg 1 W6), A. nodosum is very slow to

recolonize disturbed patches within its range (Keser et al. 198 1) and is rare in wave-

exposed sites. Although the timing of gamete release is cued by favourable conditions

(Bacon and Vadas 1991), few zygotes establish as successful recmits. Vadas et al. (1990)

found that often one low energy wave rernoved 85.99% of recently settled ygotes fkom

artincial substrates. In addition, growth of established germhgs is very slow compared to

germlings of other fùcoid algae (Sundene 1973). Vegetative propagation by growth of

established basal shoots is considered to contribute more to the alga's dominance than

sexual reproduction (Baardseth 1970).

Production

Seasonal changes in A. nodom biomass Vary among sites and notably with

latitude (David 1943). Generaily, there is a growth spurt in spring, attributed primarüy

to rishg water temperatures and increasing irradîance (Mathieson et al. 1976). Growth

decreases through m e r and fail, with little or no growth through winter (Baardseth

1970, Chock and Mathieson 1983).

Two measures of growth are cornmonly used : elongation and biomass increase.

Elongation for A. nodanm in New England ranges fi0111 1.9 to 2.5 cm mon&'

(Mathieson et al. 1976), to 6 to 10 cm year-' (Vadas and Wright 1986), and 25 and 2 cm

year*' for intertidal and subtidal plants, respectively (Peckol et al. 1988). Sharp (198 1)

estimated an average growth rate of 9 cm yeaf' at a site near Halifax, Nova Scotia

Estimates of total annuai production vary dependiig on the site and method used.

In harvesting experiments, Keser et al. (198 1) estimated total annual production in Maine

to be 1.86 kg DW m-* yeaf'. Westlake (in Cousens 1984) obtained an estimate of 2.0-

2.82 kg DW m-' yeaf' in southwest Nova Scotia, assuming a standing crop of 8 kg DW

ma'. Chock and Mathieson (1983) used the net biomass differences between periods of

minimal and maximal standing crop to calculate a daily production estimate of 8 g DW

m-2 day? Using two methods, with varying assumptions, Cousens' (1984) estimates

ranged Born 0.6 1 to 2.82 kg DW ma* year*!

Confounding factors are the loss of biomass to storms and by ice scouring in

winter (Mathieson et al. 1982, McCook and Chapman 1993). the maturation and release

of receptacles in spring and early summer (Baardseth 1970, Josselyn and Mathieson

1978), and nahird mortality (David 1943).

Nutrients

Although seaweeds take up nutrients over their entire surface area, nutrient

contents are not uniform in al1 parts of morphologically complex species, such as

A. nodosum. There could be differential rates of uptake, incorporation and storage, and

translocation of nutrients fiom parts with low demand to parts with high demand. These

differences among parts genedy lead to high nutrient content miabiliry in growllig

tissues (meristems) and relatively stable contents in older, less active tissues, such as

holdfâsts and stipes (Lobban and Harrison 1994).

i. Nitrogen

Nitrogen (N) is an essentiai elernent for plant growth and development because it

is a structural constituent of amino acids and nucleotides. In temperate coastal systems, N

is the most commonly limiting nutrient, as has been demonstrated by Nt siru seaweed

growth experiments with F m s qiralis L. (Topinka and Robbins 1976). Lamima

l o n g i c ~ s De la Pylaie (Chapman and Craigie 1977) and Lamilullla riigtatu (Huds.)

Lamour. (Davison et al. 1984). Since seaweeds cannot fix inorganic gaseous nitrogen

(Nd, N is taken up primarily as nitrate (NO;) and ammonium (MI;), with some uptake

of nitrite (NO;) and organic forms such as urea and amino acids (Lobban and Harrison

1994).

Tot al N content of seaweeds varies t emporaiiy, geographically, between age

classes (Wheeler and North 1980, Thomas et al. 1985) and within an individual plant

(Ciillanders and Brown 1994). Temporal variations generally parailel changes in extemal

seawater N concentnitb, being highest in winter and lowest in summer in temperate

waters ofthe northem hernisphere (Chapman and Craigie 1977, Hanisak 1983, Wheeler

9

and Srivastava 1984). Asare and Hariin (1983) observed depletion of tissue N before the

end of the spring growth spurt for A. nudosum. This suggested that inorganic N was

taken up fiom extremely low levels in the ambient seawater and incorporated into new

tissue, rather than accumulating as reserves. Intemal NO,' reserves in Inminaria

Iongicruns in Nova Scotia were depleted after seawater NO,' levels dropped in eady

summer (Chapman and Craigie 1977). Growth peaked while NOi reserves were being

depleted and decreased when reserves were exhausted. However, a high growth rate was

maintained at one site by fertiliring the kelp bed with NaNO,. MacPherson and Young

(1952) found no signiticant seasonal variation in the organic N content ofA. ~ O C ~ O S U ~ ,

suggesting that most variation in total N is due to the accumulation and depletion of

inorganic reserves.

When interpreting seasonal variations, attention must be given to which tissue

segment is analysed in rnorphologicdy complex seaweeds. In the fucoid alga Xiphophora

gladuta Rice, N content was highest in spring in the middle part of the plant (Gillanders

and Brown 1994), and dïerences among parts of plant were significant only in

individuals greater than 3 0 cm in total length. It was suggested that the relatively low

physiological activity in the middle section accounted for its high level of N. In A.

nodosan, however, N content was higher in apical tips than in mid-sections (Chopin et al.

1996). These studies dernonstrate that the commonly observed seasonal variations in N

(Asare and Harlin 1983, Hanisak 1983) are not uniform throughaut tissues of

morphologically complex seaweeds.

iL P h o s p h o ~ s

Phosphoms (P) is a constituent of nucleic acids, proteins, phospholipids and many

high energy compounds such as adenosine tri-phosphate (ATP). Algae take up P

primarily as orthophosphates (PO,%) . Other potential sources are inorganic

polyphosphates and organic phosphorus compounds which some seaweeds can use by

producing extracellular aikaline phosphatase (Lobban and Hamison 1994). Phosphoms

may be stored in the vacuole, in polyphosphate vesicles, as phosphorylated metabolites

(Chopin et al. 1990) or polyphosphate granules in the cytoplasm (Chopin et al, 1997).

In some tropical marine environrnents, P cornmonly limits dgal growth (Lobban

and Hamson 1994). In the Florida Keys, Lapointe (1 987) observed higher growth of

Gracilma tikvahiae McLachlan through enrichment with P than with N. The results of

the growth experiment, and elevated C:P and N:P ratios in surnrner, suggested P

limitation.

In temperate waters, P is not usually a limiting nutrient for algd growth.

However, under certain conditions and at certain tirnes of the year, it has been interpreted

as limiting seaweed growth. Wheeler and BjBnisater (1992) considered a N:P ratio

greater than 17 * 6 as evidence of P limitation in Pelvetiopsis limitata Setcheli,

Enteromorpha infestinaZis (Linnaeus) Link., and Ulvo fenestratu Postels et Ruprecht,

whereas a NI ratio less than 12 * 4 was considered indicative of N limitation. Based on

these parameters, they concluded that growth of 5 species of rnacroalgae in the northeast

PaQnc was more often limited by P than by N. Application of these NP thresholds to A.

ncuhstmt and its associated species in the Bay of Fundy would suggest strong P limitation

duMg most of the year (Chopin et al. 1996). However, N limitation has been

demonstrated for C h o h s crispus Stackhouse and phytoplankton in the Bay of Fundy

(Wddish et al. 1993, Chopin et al. 1999, and P limitation was deemed UnlikeIy. The NP

ratio, like certain critical N and P Ievels, may only be refleaive of N and P requirements

and may Vary among species (Chopin et al. 1996).

Uses of AscophyIJum nodosum

Ascophyllum nodomm is harvested for 3 principal uses : animal feeds, fertilizers

and a range of industrial chemicals. It has been used as fodder for livestock in Europe for

centuries (Baudseth 1970). Although low in caloric value and high in mineral content,

rockweed is nch in trace elements and vitamins which makes it a good dietary supplement.

Its use in commercial seaweed meal is estimated to be worth 5 million US$ year*'

(Lobban and Hanison 1994).

AscophyIIum nodosum has a long history of use as a fertiljzer in the British Isles,

Iceland and France (Baardseth 1970). Rockweed may be simply used as âesh or

decomposed material, or as extracted products and fo lk sprays (Waaiand 1981). As a

nutrient additive, it is rich in N, potassium and trace elements but weak in P (South and

Wttick 1987). A benefit of seaweed fertiliren is the absence of weeds and terrestrial

fiingi which may be present in terrestriai manures. It is believed that growth factors such

as auxins, giiberih, cytokinins or abscissic acid may promote seed germination, plant

productivity, and disease and fkost hardimess (Waaland 198 1). Certain fractions of a

commercial A. nociosum preparation were found to stimulate the activity of endogenous

12

vascular plant glycanases, which are involved in the synthesis of pathogenesis-related

proteins (Patier et al. 1993).

By far the most common industrial extract ofA. noalosum is alginic acid. This cell-

wali polysaccharide is cornposed of either pure mannuronic or guluronic acids, or of

blocks of altemating residues (Fig. 3). Alginates are extracted by acid leaching, alkaline

digestion, washing, bleaching, drying and chopping to produce cnide extract of alginate

salts. The salts differ in their properties and uses. Sodium and potassium salts are viscous

alginate liquids, and are used as polishes and coatings for textile and paper production,

and as emulsifiers in paint, food, cosmetics and pharmaceutical sectors to mspend water

immiscible substances. Calcium-alginate salts are used as stabilizers in gels, gums and

molds (South and Whittick 1987).

Beyond its present primary use as an alginate mat* for other drugs (Waaland

198 l), several potential pharmacological uses of extraas from A. nodosum bear fùrther

study. Sterols extracted from A. nodom have shown anti-cholesterol activity in

mammals (Blunden et al. 1975). Alginates fiom A. nodosurm bind cholesterol and lead to

elevated fecal excretion of cholesterol, although there was no consistent change in s e m

total cholesterol levels in rats wshide et a2. 1993). Fucans extracted fiom A. nudbstnn

have demonstrated antiturnor and antiproliferative activity against a human

bronchopuhonary carcinoma (Riou et al. 1996). Although these studies are only

preliminary, they clearly establish biological activity, and potentiai chical use, of

polysaccharides fiom A. ndsrrm.

i @ COOH <' ...-Bq q (HO o.-,. : HO 1 I

COOH I I !

Figure 3 : Two components of a l e c acid: (a) polymaf]nuronic a d , @) polyguiuronnic acid (der Lobban and Harrison 1994).

Harvesting of rockweed

There has been a long history of rockweed harvesting in Europe and Eastern

Canada. Since 1959 there has been commercial-scde harvest ofA. nodomm in Nova

Scotia (NS) for extraction of alginates. ûfthe esthated standing crop of 180 000 to 240

000 wet tonnes (WT) within the harvesting area in southwest NS, 6 000 WT were

harvested a ~ u a l i y in the early 1980s (Sharp 198 1) and between 20 000 and 30 000 WT

in the late 198091 early 1990s (Chopin 1998). A pilot harvest of A. n&mm began in NB

in 1995 based on a harvestable resource exceeding 140 000 WT, with an annual pilot

harvest of 10 000 WT. Evidence fiom Europe and North America has show that

excessive, unregulated seaweed harvesting can be detrimental to the harvested population

and to its community Wght and Parke 1950, Boney 1965, Baardseth 1970, Keser et al.

198 1). Seaweed beds are important habitats because they moderate local

environmental conditions by serving as a breakwater at high tide and a moist protective

blanket at low tide (Lobban and Harrison 1994). Seaweeds are also important for nutrient

cycling and primary productivity in coastal marine systems. AscophylZum n&- is the

dominant organism within much of its range, providing food for grazers (Lubchenco

1978) and substratum for epibiota (Sharp et al. 1997, Cardinal and Lesage 1992, Lining

and Garbary 1992). For these reasons there has been public conceni over the potentially

detrimental impact ofrockweed hamesting in New Brunswick

For the deveiopment of a sustainable management of the rockweed resource, and

consistency of the products exîracted fiom it, it is essentid to assess the impact of

harvesting. Recovery of A. nodosrmi beds after hamesting is dependent upon site

15

productivity, size distriiution of the standing crop, presence or absence of grazers, and

degree and method of harvesting (Keser et al. 198 1, Sharp 1987). In southwest NS, when

sites were left with ca. 40 % residual biomasq harvestable biomass recovered after 1 year

(Sharp 1987). Most regrowth was attniuted to elongation of basal shoots and the

initiation of new lateral branches on stumps. Lazo and Chapman (1996) found that

growth rates were higher in harvested plots than in controls, regardless of intensity or

season of harvest, and that the srnailest shoots contniuted the most to population

regrowth. Successive annual harvesting in Maine Ied to declining yields over a 3 year

experiment (Keser et al. 198 1). However, Keser et ai. (198 1) concluded that with

d c i e n t residual biornass and less muen t harvesting, complete recovery was possible.

Sharp (198 1) suggested that cutting may enhance production, because "primary growing

points will not be reduced in proportion to shoot truncation since the majority of primary

shoots are below 15 cmy7. The capacity of the srnailest shoots to restore biomass

foilowhg harvest supports a harvesting strategy (a) aimed at the largest plants in a stand,

@) which does Mnimal damage to holdfasts.

Under the Federal Fisheries Act of 1977, it was stipulated that "no person shall

harvest rockweed unless he uses an instrument that severs with a cutting action and leaves

a length of at least 5 inches (12.5 cm) above the holdfâst." Of the two harvesting methods

being used in NS, hand-&g and mechanical harvester, the former was found to remove

more holdfksts fiom the substratum (1 6.1 8.4 % by weight) than the latter (1 -9 * 1.1

%) (Sharp 1981). For sociosconomic reasons, however, hawesting in NB is done with

hand-des, modined to prevent cutting below 25 cm. A harvesting agreement developed

16

by the Canadian and New Brunswick governments stipulates that physicd disruption of

the substrate and holdfàst removal must be minimal. Mean cutting height must be at least

25 cm, and the maximum allowable h e s t in any one area is 50 % by weight.

Purpose of the study

The purpose of the present shidy was to assess the impact of harvesting of A.

nodosam by measuring the physiological response of shoots truncated by harvesting. To

help explain how truncated shoots regrow, and how basal shoots respond to the thinring

of the adult canopy, nutnent (N, P, C) contents were measured as a relatively stable, rnid

to long-term (1 year) indicator of physiological activity. Nîtrogen, P and C contents of

intact apical tipq cut tips, Md-sections, and basal shoots were meamred for 14 months

following harvesting. Differences in the total nutrient contents, nutrient ratios (C:N, N:P,

C:P), and their pattern of seasonal variations were used to investigate the impact of

hawesting.

MATERIALS AND METHODS

Study Site

The study site was a stretch of rocky shoreline dong Letite Nanows in southwest

New Brunswick, Canada pig.4). The area is moderately exposed and the substratum is

mostly soiid rock with some boulder fields. AscophyIZm nodosunt is the dominant

seaweed in this site, ranghg âom the high intertidal zone to low water mark. with an

average biomass of 9.4 kg mo2 (R. Ugarte, pers. cornrn.). By agreement between the

Province of New Brunswick, Acadian Seaplants Ltd. and hamsters, no commercial

hawesting takes place within this designated study site.

Experimental plots

Six permanent 10 x 10 m quadrats were established in July 1996 : 3 treatment (to

be harvested), and 3 controls (Fig. 5). Quadrats were simiiar in elevation, lying in the rnid

intertidal zone. The substratum of two of the treatment and one control plots was typified

by boulders, whereas the other three plots lay mostly on solid rock.

Pre-hiwest srmphg

On July 5, 1996, 10 randomly selected entire plants h m each plot were

destmaively sampled dong with several (4-5) basal shoots from the holdf'ast of each

plant. Basai shoots were Iess than 10 cm in length and lacked vesicles. Although they

were associated with the addt holdfast, it was not determined ifbasal shoots were

geneticdy related to the ad& plant sampled.

Figure 4 : Area map of Letite, NB, and study site (arrow).

Figure 5 : Layout of the 10 x 10 m plots at the study site. C = Control plots, H = Harvested plots.

Ha mes ting

On July 20, 1996, commercial harvesters were instmcted to harvest within the

treatment plots of the study site. This was done with rakes at Md-tide and approxhately

17 % of the biomass was rernoved âom each plot accordmg to usual harvesting practices

(G. Sharp, pers. corn.).

Post-harvcst tagging

In order to ensure that harvested plants (stumps) would be identifiable and

distinguishable Born natudy truncated plants for the duration of the study (1 year), rake

truncated (hawested) plants were tagged within one week of harvesting. Harvested plants

were easily identifiable by a clean, &sh cut across the main axis and laterds. Stumps

were tagged with Trilene" fishing line and neoprene tags, which have been shown to

cause minimal damage (Sharp and Tremblay 1985).

In each harvested plot, 10 uclumps" of stumps were tagged. The stump showing

evidence of harvesting, closest to a random CO-ordinate, was first tagged. The 15 next

closest harvested sturnps were tagged with the same identification, up to a 1 m radius of

the first tagged stump. This constituted a "clump" fiom which tagged stumps could be

destnictively sampled monthly for a year, dong with the associated basai shoots.

Post-harvest sampling

Each month, beginning in August 1996, 10 ta@ stumps, and associated basal

shoots, were destmcîively sampled fiom each harvested plot. In each control plot,

random coordinates were used to sample 10 plants and associated basal shoots.

Seaweeds were fiozen (-20°C) within 5 hours of sampiing. Tissue fiom the apical

and Md-sections of each control plant were analyzed for nutrient content. The apical

portion was initiaily defined as the entirety of the growing tips, distal to the newest vesicle

formed. This was, however, an impractical definition since during the formation of new

vesicles in the spring there was not enough tissue above the newest tip to analyze reliably.

Therefore, it was decided to use the top 1.5 cm of each tip, regardless of vesicles, as the

apical tip. The Md-section was defined as the portion of the primary shoot 25-30 cm

from the holdfast. This corresponds to the minimal height at which plants should be

twcated by harvesting rakes, due to the 25 cm protective cages on the rakes. Ifthe

control plant was less than 25-30 cm in height, a section of tissue was taken at the mid-

height of the shoot. For stumps, the top 1.5 cm below the tnincation were analyzed. This

was referred to as a cut tip. For basal shoots from control and harvested plots* 4-5 entire

shoots were dried and analysed for each plant sampled.

Nutrien t anaiyses

i. Carbon and nitrogen

The tissue portions to be analysed were dried for 48 hours at 60' C before

approximately haif of the sample was ground to a fine, homogeneous powder using a

Retsch mixer miii. The powder was again dried for a minimum of 48 hours before being

d y s e d using a Perkin Elmer 2400 Series II CHNS/O elemental analyzer.

22

ii. Phosphoms

Tissue total P content was measured by the method of Murphy and Riley (1962)

after acid mineralization K S O , and HNO3 in Büchi 430 and 435 digester units.

iii. Seawater nutrients

At each sampling date, 3 d a c e water samples were collectecl in s m d (125 ml)

high density polyethylene boales and immediately k e n upon returning to the laborato~y

(within 1 hour). Dissolved inorganic P @Il?; as PO,*) and N @IN; as the sum of N'Hl +

NO; + NO,? concentrations in seawater were measured by the rnethods of Murphy and

Riley (1962) and Grasshoff et al. (1983), respectively, using a Technicon Autoanalyser II

segmented flow analyser.

S tatistical analyses

Prior to ANOVq aU data were tested for depamires corn norrnality using the

Shapiro-Wilk statistic generated by the SAS procedure UNIVARlATE (SAS 1990, Cody

and Smith 1991), and no transformation was necessary. Data were also tested for

homogeneity of variance using an F,, test (Sokal and Rohlf 1995), and no transformation

was necessary.

Initial analyses of nutrient (N. P, C) contents and ratios (C:N, C2, N:P) for pre-

harvest samples (July 1996) were performed using a one-way ANOVA to determine if

there were significant daerences among plots prior to harvesting. There were indeed

signiIicst~lt clifferences among plots for P content and NT ratio @ c0.05, Table 2).

23

Therefore, to account for the potential confounding of plot and hamesting effects, data

fiom each plot were nested within the treatments in a nested ANOVA design. For the

sake of consistency, this was done for the analyses of al dependent variables (N content, P

content, C content, and C:N, C:P, NP ratios).

Table 2 : One way analysis of variance of pre-harvest nutrient contents and ratios in Ascophyllum nodanrm according to plot. (a) Nitrogen; (b) Phosphorus; (c) Carbon; (d) NP ratio; (e) C:N ratio; (f) C:P ratio. *SiZpiificant at p<0.05, ns not siBnificmt at pW.05.

Source DF Sums of Squares Mean Square F Vaiues

(a) Nitrogea Content

Plot

Corrected Totd 174 1629.81

@) Phosphorus Content

Plot 5 4.2 1 O. 84

Error 171 58.28 0.34

Corrected Totd 176 62.49

(c) Carbon Content

Plot 5 1 374.44 274.89

Error 169 24 948.50 147.62 -- -

Corrected Total 174 26322.94

(d) N:P Ratio

Plot 5 271.3 1 54.26

Error 167 3 212.76 19.24 - --

Corrected Total 172 3 484.07

(e) C:N Ratio

Plot 5 325.45 65.09

Error 169 6474.03 38.3 1


( f ) C:P Ratio

Plot 5 165 496.52 33 099.30

Error 167 3776345.81 22 612.85

Corrected Total 172 3941842.33

RESULTS

Tisue total nitrogen content

Ali main &ects and interactions were signincant sources of variation in the N

content of A. nodoam (Table 3). There was a significant variation in N content by month

('p0.0001) and by part @<0.0001), with a sipifkant interaction between these 2 &-S.

Tukey post hoc tests were mn for each month to interpret the month by part interaction,

and to aid in the discussion of the plotted data (Fig. 6). There were significant Merences

arnong plots, nested within treatments, @<0.00 1) and significant interactions between

month and part effects. The differences among plots, nested within treatments, were

determineci using a Tukey test for grand means and for the interaction e e c t with month.

Although significant, no consistent patterns emerged in the merences among plots and no

attempt was made to explain this variation.

Nitrogen was not distributed unifody throughout the plant, and apical parts had

seasonal variations (Fig. 6, Table 3). For five months foliowing harvesting, N content in

apical tips was not signincantly different fiom that of basal shoots. Starting in December

1996, there was a strong winter-early spring peak, reaching a maximum of 26.67 0.48

mg N g DWL in Apd 1997 (Table 4). Throughout the sumer, tissue N content in

apical tips rehimed to levels similar to those of basal shoots, reacbg a minimum of 16.96

0.44 mg N g DW' in August 1997.

Table 3: Andysis of variance of nitrogen content in Ascophyllm nodosum according to month, part, and plot (nested within treatments) (n = 30).

Source DF Sum of Mean F Vdues Pr >F Squares Square

Month 12 5 033.92 419.49 92.61 0.000 1

Pm 3 13743.96 4581.32 1011.43 0.0001

Part *Plot(Treat) 6 154.10 25.68 5.67 0.000 1

Month*Part*Plot(Treat) 70 436.47 6.24 1.38 0.0228

Corrected Total 1 917 32 717.51

APICAL TlPS

MID-SECTIONS

BASAL SHOOTS (CONTROL

CUT TlPS

BASAL SHOOTS (HARVESTE

PLOTS)

D PLOTS)

I 1 I I I I I I I I I 1 I

J A S O N D J F M A M J J A

Month

Figure 6 : Seasonal variations of the tissue total nitrogen content (mg N g DW3 of Ascop@IIum nOLtD~~lltt collected at Letite, NB. Values represent means (n = 30) * SE.

Table 4: Ranges of tissue total phosphoms, Ntrogen and carbon contents in apical and ait tips, Md-sections, and basal shoots ftom control and harvested plots of Ascophyhm nodosum. Values represent means (n = 30) * SE.

segment Tissue total P content Total tissue N content Total tissue C content (mg P g DW1) (mg N g DW-' ) (mg C * g DW')

Apical tips

highest content 2.68 * 0.07 (March 1997)

1.72 * 0.06 (August 1997)

26.67 * 0.48 (Aprii 1997)

16.96 * 0.44 (August 1997)

379.0 2.2 (August 1997)

lowest content 353.2 * 1.4 (July 1996)

Cut tips

highest content 2.01 * 0.08 (July 1996)

18.12 * 0.68 (July 1997)

382.2 * 5.1 (August 1997)

353.7 2.3 (July 1996)

lowest content 11 S6 * 0.26 (October 1996)

Mid-sections

highest content 1.83 * 0.09 (July 1997)

15.97 0.26 (September 1996)

377.5 k 1.8 (August 1997)

lowest content 1.42 0.05 (October 1996)

Basal shoots (control)

highest content 2.93 i 0.07 (February 1997)

2 1.34 * 0.4 1 (April 1997)

17.05 * 0.39 (July 1996)

367.2 i 1.7 (August 1997)

345.0 =i 1.6 (July 1996)

lowest content 2.32 * O. 1 1 (October 1996)

highest content 3.09 * 0.09 (March 1997)

2.24 * 0.08 (August 1997)

22.26 0.53 (July 1997)

16.66 * 0.35 (July 1996)

366.9 * 1.2 (August 1997)

345.4 * 1.7 (July 1996)

lowest content

29

Cut tips were clearly more similas to mid-sections than to apical tips with respect

to N content and seasonai variations. While cut tips and Md-sections differed significantly

in tissue N contents for the two months following harvesting in July 1996 (Eg. 6), tiiey

had similar N content with the same pattern of variations fiom October 1996 to June

1997. In July and August 1997, they again dEered signincantly in N content. The

minimai tissue N content in rnid-sections was 12.50 * 0.3 1 mg N g DW' in July 1996

and the maximal level was 15.97 * 0.26 mg N g DW' in July 1997. In cut t ips the

minimal content was 1 1.56 * 0.26 mg N g DW1 in October 1996 and the maximai

content was 18.12 * 0.68 mg N g DW' in July 1997.

The N contents of basal shoots from control and harvested plots were not

significantly dEerent for any month except August 1997. In al1 basal shoots there was a

steady increase in N content fiom December 1996 to April 1997; N content then dropped

to the Iate-surnmer levels of 1996, after a peak in Jdy 1997. The lowest N content

measured was 16.66 * 0.3 5 mg N g DWœi for a harvested plot basal shoot in July 1996

and the highest N content measured was 22.26 0.53 mg N g DW' for July 1997 for

basal shoots fiom a harvested plot (Table 4).

Tissue total phosphonis content

Phosphorus was not distributed unifody throughout the plant and varied

signiticantly with season and among plots (Fig. 7, Table 5). In addition, the interactions

among all main effects were significant sources of variations in the P content of

+ APICAL TlPS

+ MID-SECTIONS

.,..o~... BASAL SHOOTS (CONTROL PLOTS)

+ CUT TlPS

- - -0- - - BASAL SHOOTS (HARVESTED PLOTS)


Month

Figure 7 : Seasonal variations of tissue total phosphorus content (mg P g DW1) of AscophyZZum n&strm coUected at Letite, NB. Vdues represent means (n = 30) SE.

Table 5: Analysis of variance of phosphorus content in Ascop~ZIum noabmm according to month, part, and plot (nested within treatrnents) (n = 30).

Source DF Sum of Mean F Vdues Pr > F Squares Square

Month 12 47.04 3 -92 17.92 0.000 1

Part 3 365.09 121.70 556.22 0.0001

Part *Plot(Treat) 6 3 .O5 0.5 1 2.32 0.0309


32

A. nodomm (Table 5). Phosphorus content had significant variation by month @<0.0001)

and especiaiiy by part @<0.0001, F value = 556.22), with a signifiant interaction between

these 2 effects. Tukeypost hoc tests were mn for each month to interpret the month-by-

part interaction., and aid in the discussion of the plotted data

Fig* n* Tissue total P content was dways highest in basal shoots (control or harvested

plots) and lowest in the rnid-sections and cut tips. Mean P content ranged fiom 1.42 * 0.05 mg P g DWL for mid-sections in October 1996 to 3 .O9 * 0.09 mg P g DW1 for

harvested plot basal shoots in March 1997 (Table 4). Marked seasonal variations were

observed ody in the apical tips where P accumulated in winter to a maximum of 2.68 * 0.07 mg P g DW1 in March 1997 and dropped in late spring and summer to a minimum

of 1.72 * 0.06 mg P g DWL in August 1997.

DifEerences in the P content of mid-sections and cut tips were not significant for

any month. These two parts followed similar patterns of relatively low P content, with no

seasonal variation. As with N contents, P contents of cut tips were clearly more shiiar to

nid-sections of intact plants than to apical tips. Minllnal P content of mid-sections was

recorded in October 1996 (1.42 * 0.05 mg P g DW4) and the rnaxllnal P content in Jdy

1997 (1.83 * 0.09 mg P g Dw-'). Minimal P content in cut tips was observed in January

1997 (1.50 * 0.05 mg P g DW-') and the maximal P content before harvesting in July

1996 (2.01 * 0.08 mg P g DWL).

AU basal shoots had the same pattern ofrelatively hi& P levels and seasonal

variations, ody Mering significantly in July 1996 (Fig. 7). In control basal shoots, P

33

content was lowest in October 1996 (2.32 * 0.11 mg P g DW') and bighest in February

1997 (2.93 * 0.07 mg P g DW1). In basal shoots fiom harvested plots, P content was

lowest in August 1997 (2.24 h 0.08 mg P g DW1) and highest in March 1997 (3 .O9

0.09 mg P g DWL).

Tissue total carbon content

Carbon was not dimiuted uniformiy throughout the plant (Fig. 8, Table 6).

Although the month of sampling was a highly sipüicant source of variation (Table 6), no

consistent pattern of seasonal variations was evident in any of the tissues sampled (Fig. 8).

The other main effect (plot) was a significant source of variation, as were the two-way

interactions among di main effects (Table 6). Tissue C content ranged fiom 345.0 * 1.6

mg C g DWwL for control basal shoots before harvesting (July 1 W6), to 3 82.2 h 5.1 mg C

g DW1 for cut tips in August 1997 (Table 4).

In apical tips, C content varied little with season other than an increase from a

minimum in July 1996 (353.2 1.4 mg C g DW3 to a maximum in August 1997 (379.0

* 2.2 mg C g DW1; Table 4).

Cut tips had the highest mean tissue C content in each month, except Jdy 1996

and March 1997. Carbon content of cut tips was significantly higher than that of nid-

sections except in September 1996, January, March, April, July and August 1997 when it

was not significantly diierent fiom mid-sections (Fig. 8). In mid-sections, C content was

not signincantiy dEerent âom that of apical tips ia al months except July, September,

--tl- APICAL TIPS

+ MID-SECTIONS

----o.... BASAL SHOOTS (CONTROL PLOTS)

--i-- CUT TlPS

BASAL SHOOTS (HARVESTED PLOTS)

I 1 L 1 1 1 1 1 1 1 1 1


Figure 8 : Seasonal variations of tissue total carbon content (mg C g DW3 of Ascophylum nodostmt coIIected at Letite, NB. Values represent means (n = 30) * SE.

Table 6: Analysis of variance of carbon content in AscophyIIum norilostan according to month, part, and plot (nested within treatments) (n = 30).

Source DF Sumof Mean F P r > F Squares Square Values

Month

Par&

Month*Part

Plo t(Treat)

Month*Plot(Treat)

PartZPlot(Treat)

Month*Part*Plot(Treat)

Error

Conected Total 1 917 340 390.99

36

October 1996, and May 1997. It reached a minimum in December 1996 (364.0 * 1.7 mg

C g DW1 ) and a maximum in August 1997 (377.5 * 1.8 mg C g DW'; Table 4).

Basal shoots fiom control and harvested plots dEered significantly from each

other in C content only in December 1996 (Fig. 8). They had significantiy lower C

contents than all other tissues, except in September and December 1996 when basal shoots

from harvested plots were not significantfy dXerent h m apical tips, and Li April 1997

when control plot basal shoots were not significantly different fiom apical tips. There was

no obvious trend to the merences between the basal shoots of each plot type. Tissue C

content in basal shoots of control and harvested plots had no seasonal variation other than

a steady increase. In both control and hawested plot basal shoots, C content was lowest

in July 1996 (345.0 * 1.6 and 345.4 1.7 mg C g DWi, respectively) and highest in

August 1997 (367.2 * 1.7 and 366.9 * 1.2 mg C g DW1, respectively; Table 4).

Nitrogen:Phosphorus ratio (Nd?)

The N:P ratio had some marked spatial and rnonth-to-month variation, but the

overali seasonal variation was relatively low (Fig. 9). AU main effects were sources of

highly significant variation (Table 7). There were significant interactions between month

and plot, and between plot and part (Table 7). The N9 ratio ranged fiom 14.0 * 0.8 for

harvested basai shoots in M y 1996 to 24.9 * 1.2 for cut tips in July 1997 (Tabfe 8).

Apical tips had significantly higher N P ratios than any other tissues for most

months of the study penod. It ranged fiom 18.2 * 0.7 in Decernber 1996 to 23.0 * 0.8 in

May 1997 (Table 8). Seasonal variations were difncdt to interpret, but the NP ratio was

+ APICAL TIPS

,,+,,. MID-SECTIONS

-...O*.- BASAL SHOOTS (CONTROL PLOTS)

-+- CUT TIPS

--+,, BASAL SHOOTS (HARVESTED PLOTS)


Month

Figure 9 : Seasonal variatiom of the N2 atomic ratio of AscophyZIum n&szim collected at Letite, NB. Values represent means (n = 30) SE.

Table 7: Analysis of variance of the N:P ratio in AscophyIIum nnodchMn according to rnonth, part, and plot (nested within treatments) (n = 3 0).

Source DF Sum of Mean F Values Pr >F Squares Square

Month 12 2 270.33 189.19 1 1.77 0.0001

Part 3 6 675.78 2 225.26 138.40 0.0001


Table 8: Ranges ofNP, C:N and C3? ratios in apical and cut tips, Md-sections, and basal shoots fkom control and harvested plots of AscophyIZum nodosum. Values represent means (n = 30) * SE.

Apicai tips

highestcontent 26.6 i 0.7 (August 1997)

16.3 0.3 (April 1997)

lowest content 362.6 * 10.0 (March 1997)

Cut tips

highest CO-t 38.6 * 0.9 (October 1996)

681.1 * 50.4 (September 1996)

lowest content 15.8 * 0.5 (October 1996)

Mid-sections

highest content 21.3 0.8 (April 1997)

682.0 39.4 (October 1996)

iowest content 27.5 0.5 (September 1996)

555.2 k 25.9 (July 1997)

Basai shoots (control)

higllest content 16.9 * 0.6 (August 1997)

420.1 1 15.8 (August 1997)

10- content

Basal shoots -1

highest content 19.0 * 0.7 WY 1997)

14.0 * 0.8 (July 1996)

24.9 ~t 0.7 (August 1997)

18.9 * 0.5 ( M y 1997)

436.7 14.7 (August 1997)

lowest content 304.6 9.5 (March 1997)

lower in winter and higher in swnmer (Fig. 9).

Afthough there were significant dEerences in many months in N:P ratio between

mid-sections and cut tips, neither was consistently higher than the other (Fig. 9).

Both types of basal shoot had little variation âom July 1996 to February 1997, but

then increased in the N:P ratio for the rest of the study penod. There were signifiant

differences in the N:P ratio observed in many months, but without any particular trend.

CarbomNitrogen ratio (C:N)

The C:N ratio varied si@cantly by month, part, and plot, with sigdcant two-

way interactions among ali main effects (Table 9, Fig. 10). It ranged fiom 16.3 * 0.3 for

apical tips in April 1997, to 38.6 0.9 for cut tips in October 1996 (Table 8). For ail

tissue types except apical tips, C:N ratio decreased steadily throughout the study penod,

with a marked increase in August 1997.

The C:N ratio of the apical tips was not signincantly dEerent fiom that of basal

shoots, except from December 1996 to June 1997. Apical tip C:N ratio was lowest in

Apd 1997 (16.3 * 0.3) and reached a high of 26.6 * 0.7 in August 1997 (Table 8).

The C:N ratio was similar in rnid-sections and cut tips for most of the year, despite

some si@cant Merences directly before and after harvesting and for Tanuary and

August 1997 10). The C:N ratio in these two tissue types was always higher than

Table 9: Analysis of variance of the C:N ratio in AscophyIZum nodostrm according to month, part, and plot (nested within treatments) (n = 30).

Source DF Sum of Mean FValues Pr>F Squares Square

Month 12 925 5 -26 77 1.27 66.51 0.000 1

Part 3 39 936.8 1 13 3 12.27 1 147.93 0,0001

-


+ APICAL TlPS

..-+... MID-SECTIONS

----O---- BASAL SHOOTS (CONTROL PLOTS)

-*- CUT TlPS

- - -e- - - BASAL SHOOTS (HARVESTED PLOTS) r

Figure 10 : Seasonal Vanations of the C:N atomic ratio of A s c o p ~ h m nOdDsum coiiected at Letite, NB. Values represent means (n = 30) * SE.

43

in either basal shoots or apical tips. Mid-sections and cut tips showed their Iowest C:N

ratios in September 1996 (27.5 0.5) and July 1996 (24.9 * 0.9), and their highest C:N

ratio in December 1996 (34.5 * 0.8) and October 1996 (38.6 * 0.9), respectively

(Table 8).

Basal shoots fiom both control and harvested plots difred ody slightly fiom each

other in the levels and pattern of seasonai changes in C:N ratio (Fig. 10). It ranged from

20.1 * 0.4 (April 1997) to 24.2 * 0.6 (November 1996) for basal shoots fiom control

plots and flom 18.9 * 0.5 (May 1997) to 24.9 * 0.7 (August 1997) for basal shoots fkom

harvested plots (Table 8). The C:N ratio varied seasonaiiy, decreasing slightly f?om

December 1996 to May 1997, and then increasing in surnmer, except in July 1997.

Carbon:Phosphorus ratio (C:P)

The C:P ratio varied spatiaily within the plant and seasonally throughout the study

period (Fig. 1 1) fiom a minimum of 304.6 9.5 for basal shoots fiom harvested plots in

March 1997 to a maximum of 682.0 39.4 for mid-sections in October 1996 (Table 8).

AU the main efFkcts, and two-way interactions among them. were highiy signincant (Table

10). The C 9 ratio was always the highest in either mid-sections or cut tips; basal shoots

consistently showed the lowest CP ratio. In apical tips, the C:P ratio was intemediate

with marked seasonal variations, being lowest in winter (362.6 10.0 in March 1997) and

highest in late mer-fall(504.4 * 34.0 in October 1996, 594.9 * 19.1 in August 1997;

Table 8).

-+ APICAL TlPS

-+- MID-SECTIONS

O-.. o..-- BASAL SHOOTS (CONTROL PLOTS)

---+- CUT TlPS

-,-+,, BASAL SHOOTS (HARVESTED PLOTS)

Month

Figure 11 : Seasonal variations of the CT atomic ratio of AscophyZIum nodoszim coiieaed at Laite, NB. Values represent means (n = 30) * SE.

Table 10: Anaiysis of variance of the C:P ratio in AscophyZm n o & m according to month, part, and plot (nested within treatments) (n = 30).

Source DF Sum of Mean F Values Pr > F Squares Square

Month

Part

Month*Part

PIot(Treat)

Month4Plot(Treat)

PutWot(Treat)

Monthspart *Plot(Treat)

Error

Corrected Total

46

In mid-sections and cut tips, the C:P ratio was generally the sarne, as was the

pattern of seasonal variation, although there were significant dEerences between them for

certain months (Fig. 1 1). The lowest C:P ratios were observed in July 1997 for mid-

sections (555.2 k 25.9) and in March 1997 for cut tips (533.3 * 22.6). The highest C P

ratio for mid-sections was recorded in October 1996 (682.0 * 39.4) and for cut tips in

September 1996 (681.1 * 50.4). In both tissue types, the C:P ratio had a slight increase

in surnmer and decrease in winter, although these variations were not as pronounced as in

apical tips.

Aithough there were significant dserences in C:P ratio of control and harvest

basal shoots at certain times (Table 10). the seasonal pattern and range observed were

similu. The C:P ratio of harvested plot basal shoots varied slightly throughout the study

penod, fiom a low of 304.6 9.5 in March 1997, to a high of 436.7 * 14.7 in August

1997.

Seawater nutrients

Dissolved inorganic N concentrations ranged âom 2.5 &l (Jdy 1996) to 10

(September 1996). They v&ed seasondy, being high in winter and dropping in spring,

with late surnmer peaks in both years (Fig. 12). Dissolved inorganic P concentrations

were much lower, and ranged fiom 0.54 to 1.73 @M. There were late surnmer peaks, as

observed for Dm.


Figure 12 : Seasonal variations of dissolved inorganic N ( Dm, as the sum of NE,+ + NO; + NO,') and dissolved inorganic P (DIP; as PO,*) concentrations in seawater coiIected at Letite, NB.

DISCUSSION

Nitmgen

The pronounced seasonal variations of tissue total N contents in apical tips are

typical for seaweeds in temperate marine systems (Baarâseth 1970, Moss 1970, Mathieson

et al. 1976, Komfeldt 1982, Hanisak 1983, Asare and Harlin 1983, Vadas and Wright

1986, Sharp 1987). Although tissue N content generally parallels seawater N

concentration, the peaks in seawater in late summer are not reflected in the algal tissue.

This may be because this is a period of active growth when di N taken up would be used

in growth and not accumulate (Chopin et al. 1990).

The range of N contents observed in this study for al1 parts (1 1.6 to 26.7 mg N g

DWi) is similar to other reported ranges for A. nodanm: 10 to 18 mg N g DW' in

Nova Scotia, 16 to 28 mg N g DWi in New Brunswick (Macfherson and Young 1952),

and 10 to 28 mg N g DW' in Rhode Island (Asare and Harlin 1983). Lower values (6.5

to 12 mg N g DWi) were reported by Jensen for A. nodomm in Norway (1960, in Moen

et al. 1997).

MiwimaI values for apical tips (26.7 mg 1q - g DWi) and rnid-section (16.0 mg N

g DW1) N contents in the present study are similar to the mairimai values reported by

Chopin et al. (1 996) for A. nodanm fkom a nearby site at Maces Bay (26.7 mg N g

DW1 for apical tips, 12.4 mg N g DW' for mid-sections), while minimai values (17 mg

N g DW' for apical tips, 12.5 mg N g DW' for mid-sections) are higher (7.4 mg N g

DW' for apical parts, 7.6 mg N g DW-' for mid-sections). This cannot be explained by

49

seawater DIN experienced by the plants, the maximal levels of which were the same (10

&l) and the minimal level was oniy slightly higher at Letite (2.5 than at Maces Bay

(2

Mid-sections and cut tips had the lowest N contents and no seasonai variation.

Similady, Chopin et a& (1996) found the greatest seasonal variation in tissue total N

content in the youngest parts of A. nodosim, and consistentiy less variation in successively

older parts. Both of these studies suggest less physiological activity in older tissues, as

has been observeci in the rates of several physiological processes. In Fucus qiralis, N

uptake was lower in stipes than in growing tips (Topinka 1978), and nitrate reductase

acîivity in Fucus gardhen' was lowest in the stipe (Hurd et al. 1995). Young tissues of F.

gmherr' (as &chus) take up both MI,' and N O , but older fionds and stipes can only

take up Nb+ (Thomas er al. 1985). Kailov (1976) demonstrated higher photosynthetic

fixation of CO, in the younger tissues of A. nodosum relative to mature tissues.

The high N content of basal shoots rnay be due to theû high surface a r a : volume

(SAY) ratio relative to adult plants. In general, fhely branched and monostromatic

species tend to have higher nutrient uptake rates than coarse, thicker plants (Lobban and

Hamson 1994). This should also hold tme for morphologicdy dinerent Me stages of one

species. Alternatively, the low irradiance experienced by basal shoots under the addt

canopy may enhance nitrate uptake. In U1La ficiara, nitrate uptake was, in part,

invedy proportional to irradiance, leading to higher chlorophyll a and N content in low

light, outdoor cultures (Lapointe and Tenore 198 1). Similady, low light induced higher N

content in PuImariapZmata than in samples under high Iight with the sarne nitrate supply

(Morgan and Simpson 198 1 ).

Phosphorus

Phosphorus content of apical tips were high in winter and decreased in spring, as

has been observed in A. nodosum (Chopin et al. 1996) and other seaweeds (Kornfieldt

1982, Chopin et al. 1990, Delgado et al. 1994). As was seen for N, the late summer

peaks in seawater DIP were not reflected in tissue total P content. This may be because at

this t h e of year, dl P uptake is used for growth and does not accumulate.

The ranges of P content of apical tips (1.72 to 2.68 mg P g DW1) and mid-

sections (1.42 to 1.83 mg P g DW3 were comparable to those found for A. nodostlm in

a previous study (1.4 to 3.2 and 0.90 to 1.36 mg P g DWL , respectively; Chopin et ai.

1996) and for whole plants (1 to 1.5 mg P g DWL; Jensen (1960) in Moen et al. 1997).

Other authors have determined similar P contents for Fucus Mrsoides (1.8 to 2.7 mg P g

DW1; Zavodnik 1973), Macrocystispynfera ((1.5 to 3.3 mg P g DW'; Manley and

North 1984), and Cladphura sp. (0.8 to 3.0 mg P g DW1 ; Gordon et al. 198 1).

Phosphorus content ofA. nodosum was always higher in apical portions than in

mid-sections and more seasonally variable, as has been demonstrated for Fucus sematus L.

(Komfeldt 1982) and Chondns cripus (Chopin et QI. 1990). By contrast, in Cystoseira

meditmanea, tissue P contents in stipes (0.07 to 0.28 % ash-fiee DW) and holdfasts

(0.08 to 0.34 % ash-fiee DW) were the same as in growing parts (0.04 to 0.29 % ash-fiee

DW ; Delgado et al. 1994). This is likely due to the redistniution of P âom the perennial

lower shoots of C. mecli'femanea to the annual blades.

Phosphorus content of mid-sections and eut tips showed negligible seasonal

variations, as did the P content of base sections of F. serratus (Komfieldt 1982),

C h o h s m * p s (Chopin et al. 1990), and stipes of Cystoseira meditewanea, for which

seasonal variations were two-fold greater for P than for N (Delgado et al. 1994). As was

concluded for N, it seems that limited seasonal variations refied low physiological activity

and growth. Uptake of P (as phosphate) in Macrocy~nspyn~era was highest in youngest

blades and inversely proportional to tissue P content (Manley unpubl.). In addition,

translocation of P f?om mature, non-growing parts to Young, growing parts has been

observed dong the thallus in Laminariales and via the midrib in Fucales (Floc'h 1982),

although the mechanism, and form of P (inorganic or organic) translocated remain to be

fûUy elucidated (Lobban and Harrison 1994). These two phenornena (higher uptake in

tips and translocation fiom older parts) may contribute to the relatively high P contents

found in growing tips in this study.

As was suggested for N, the high tissue P contents in basal shoots (2.24 to 3.09

mg P g DUT? may be simply due to their high S A Y ratio which would enhance P uptake

relative to the rest of the plant (Hurd and Dring 1990, Lobban and Harrison 1994). For

seaweeds with higher SA:V ratios, reported tissue P contents are higher than for adult

shoots of A. nodosurm in this study: 2.1 to 5.1 mg P g DW-' for Uhafenestrafa and 3 .O

to 5.6 mg P g D w L for Enteromorph intestrna2is (Bjomsiiter and Wheeler 1990).

Carbon

Carbon content for aii parts of A. ndosum showed typicdy low seasonal variation

(Hardwick-W~tman and Mathieson 1986, Delgado et al. 1994, Giilanders and Brown

1994). Aîthough C content accounts for much of the structural tissue which would not be

expected to Vary much seasondy, there are several other organic compounds in A.

n d m m (alginate, mannitol, taminaran and fbcoidan) which vaq seasondy (Baardseth

1970). In Xphophorr ggladata, a large fùcoid, seasonal variation of mannitol is

signincant and most pronounced in the youngest tissues, with mannitol content being

highest in surnmer (Gillanders and Brown 1994). Mannitol and laminaran accumulate in

N-limited h i n a r u longicruriis in summer when photosynthetic rate is high, and are

consumed for growth in winter (Gagné et al. 1982). One would expect to observe sunilas

trends and correspondhg variations in C content in A. nodanm. Despite some small scale

variations, no broad seasonai trend was apparent for any part ofA. n4dusum in this study.

The steady increase in C content in apical tips throughout the study period may reflect a

longer term trend or inter-annual variation.

Nutrien t h i tation

From the results of this experiment, it is not possible to determine ifany of the

tissue parts sarnpled expenenced either N or P limitation during the sampling period.

Authon have used several methods for attempting to determine the occurrence, timing

and severity of nument limitation Increased growth rates due to N enrichment in field

populations (Chapman and Craigie 1 977, Lapointe 1 987) and in l aboratory studies

53

(Topinka and Robbim 1976, Lapointe and Ryther 1979, Hanisak 1979, Gordon et aL

1981, Fujita et al. 1989) have been cited as evidence of nutrient limitation. A deaease in

tissue total N content and growth afker seawater N concentrations drop in spring has aiso

been interpreted as evidence of N limitation (Chapman and Craigie 1977, Wheeler and

BjBmsater 1992). In the present study, there was a drop in seawater P and N levels in

spring, and a subsequent drop in tissue N and P in apical tips. Although this is consistent

with the estabfished pattern of the onset of nutrient limitation in summer, growth was not

measured, hence no conclusion can be made about the impact of the decrease in tissue N

and P contents.

A more direct method used to study nutrient limitation is the detennination of a

species' critical nutrient content, dehed by Hanisak (1983) as the internai n u k t content

that just limits its maximal growth. The cnticai N content has been determined for several

species (Table 11). There is, however, no reported critical nutrient content for A.

nodomm. In apical tips of A. nodumnz, N content ranged from 16.96 to 26.67 mg N g

W . The cntical N content of Pelvetiopns limitata, another fucoid aiga fiom the Pacific

Ocean, was 12 to 15 mg N g DW1, inferred fiom NP ratios (Fujita et al. 1989, Wheeler

and Bjomsater 1992). If these two algae are simüar, this suggests that apical tips of A.

nodosum were never N lunited during the sampling period of the present study. However,

critical N content varies among species and depends on the form of N used for growth

@#ta et al. 1989). RFcophyllum nodosum and P. limitata m e r greatiy in size, ecology,

and distribution, within the intertidd zone and geographically. In addition, critical

nutrient contents are reported for entire plants, but these could be expected to vary

Table 11: Critical nitrogen contents for several seaweeds.

Nutrient Critical content Authors (mg N. g DW1)

-

Chordcuiu jrogell~ormis NH,* ISmgN*gDW1 Probyn and Chapman 1983 (O. F. MûiIer) C. Agardh

NO; 9mgN*gDW1

Cfadophora aibida (Nets) Kntvng

Codium m i l e spp. tornentosoides (van Goor) P.C. Silva

Laminaria saccharina L. Lamour.

Pelvetiopsis limitata (Setcheu) Gardner

Uha rigida C. Agardh

N

NO;

NOi

NOi

NH,'

NO,'

w

Gordon et al. 1981

Hanisak 1983

Chpman et al. 1978

Fujita et al. 1989

Fujita et al. 1989

spatidy in morphologicaiiy complex seaweeds, as do tissue nutrients (Gillanders and

Brown 1994, Chopin et al. 1996, present study) and physiological aaivity (Topinka and

Robbins 1976, Hurd et ai. 1995). Although the nutient status of the whole plants is

relevant ecologidy, it is worth considering that criticai nutrient contents are probabiy

most reflective of the demand of growing tissues.

55

From batch culture experiments with two Pacific green algae, Enteromorph

intesfisfimZis and ndva fenestruta, BjBrnsater and Wheeier (1990) determined that the NP

ratio was a useful indicator of the nutritionai status of macroaigae. In a firrther study of

tissue N and P of five intertidal seaweeds, measured in silu, Wheeler and Bj6rnsater

(1992) proposed N P thresholds to delineate N and P limitations. A N P ratio greater than

17 * 6 was considered indicative of P limitation, whereas a N:P ratio less than 12 * 4 was

considered indicative of N limitation. Based on these thresholds, N:P ratios indicate that

none of the tissue parts of A. naiosum analysed experienced N limitation at any t h e

during this study, al1 tissues expenenced P limitation at some tirne, and apical tips were

always P limited. This is contrary to the studies of Chopin et al. (1995) and Wddish et al.

(1993) which demonstrated that N limitation occurred in C. crispus and phytoplankton in

the Bay of Fundy, but P limitation was unlikely.

This apparent discrepancy may be attributable to geographic diEerences. Nitrogen

limitation may be more likely in the Bay of Fundy than in the northeast Pacific due to

relatively lower N concentrations in the former compared to the latter where the study of

Wheeler and BjBmsater (1992) was conducted. At the site of the present study, DIN and

DIP concentrations ranged fiom 2.5 to 10.0 &l and fhrn 0.54 to 1-73 respectively.

Seaweeds used by WheeIer and Bjomsiiter (1992) were collected in November fiom

seawater with DTN and DIP concentrations of 10 to 15 pM and 0.8 PM, respectively.

Alt ematively, the apparent contradiction may be due to interspecific Werences,

regardless of arnbient nutrients. Without knowing the criticd nutrient contents ofA.

nodch~n and studying the relationship between nutrient supply and NT ratio in culture,

specuiation about nutrient limitation based solely on N:P ratios is risky.

For the purpose of this study, C:N ratios are no more informative than the N data

considered alone. The C:N ratios of A. nodomm mainly refiected the variability of N

contents in relation to the relatively constant C contents. For whole plants of A. nOLtOsum

fiom a New England estuary, C:N ratios showed a similar range (1 3.8 to 26.1) and also

refiected seasonal variation in N contents, against relatively constant C contents

(Hardwick-Witman and Mathieson 1 986). The C:N ratio for Cystoseira medtemanea

(Delgado et al. 1994) showed limited seasonal variations, in a range sirnilar to that ofA.

nodomm in the above study. The C:N ratios fiom ai i of these studies are within the range

determined by Atkinson and Smith (1983) for a wide range of macrophytes (6.6 to 60)

which is signincantly higher than the typical RecEeld C:N ratio of phytoplankton (7). This

reflects the high content of structural C in seaweeds and suggests that seaweeds have

lower nutrient requirements to support growth relative to phytoplankton (Atkinson and

Smith 1983).

Impact of harvesting

The nutrient physiology of cut tips is very different ffom that of apical tips because

afler tnincation of a shoot, growth is by Iateral branches (Moss 1970, Lazo and Chapman

1996). Among the tagged shunps in this study, some had new laterals arigng near the cut,

but there was never any regrowth diedy fiom the primary shoot. One year after

harveszing, stumps were still easily identifiable as having been cut by a rake (Fig. 13).

Regrowth, ifany, was observed always &om fateral branches near the cut tip.

Figure 13 : (A) Stump showing cut tips (Cl, CZ, C3) and lateral shoots (LI, L2, L3) one month d e r tnincation due to harvesting (September 1996). (B) The same shunp 11 months after harvesting (Juiy 1997), showing no change in cut tips (Cl, C2, C3) and powth of lateral shoots (LI, L2, L3) below cut tips.

Vigorous regrowth of basal shoots after harvesting has been observed by several authors

(Keser and Larson 1984, Cousens 1985, Sharp 1987, Lazo and Chapman 1 996), and is

believed to be due to increased irradiance after canopy removal (Cousens 1985). In the

present study, it would be expected that basal shoots of harvested plots, once relieved of

light Iimitation, would grow rapidly and show significant dEerences in nutrient contents

fiom those of basal shoots under intact canopies (control plots). However, there was

essentiaily no dserence in nutrient contents between basal shoots ftom control and

hawested plots, except for a few months.

There are three possible explanations for this similarity. First, the hawesting at

the study site may not have been intense enough to significantly alter the canopy, and

therefore the irradiance experienced by basal shoots. Harvesting intensity in this study

(17 %) was lower than in those of Sharp (1987; 60 %), Ang et al. (1993; 80 %) and Lazo

and Chapman (1996; c a 18 %, 60 %, and 70 %). In the harvesting study of Keser et al.

(198 l), all plants within 25 x 25 cm quadrats were cut at the holdfast or heights of 15 cm

or 25 cm, therefore removing a greater percentage of the biomass than was removed in the

present study. Secondly, measurements of nutrient content may not be sufncientiy

sensitive to detect Merences in the physiology of basal shoots. The high nutrient content

of basal shoots, relative to other parts, suggests that they were not nutrient timited. Other

variables, such as light, could be the lllniting primary factor. Peckol et a% (1988)

concluded that the rarity of subtidal populations of A. nodosum was due primarily to light

limitation. niirdly, some of the basal shoots rnay have been growing so rapidiy that they

59

were excluded âom sampling because they were too long. Ody basal shoots which were

less than 10 cm and had no vesicle throughout the study period were sampled, and growth

was not measured. Fast growing shoots, which account for the regrowth observed in

Lazo and Chaprnan (1996), would not have been sampled once they no longer fit our

definition of a basal shoot,

Conclusion

From d of the parameters considered, it is clear that &er truncation, remaining

parts of the stumps show nutnent physiology more simiiar to that of mid-sections of intact

shoots than to apical tips. This is consistent with the observation that regrowth on stumps

was dways fiom laterd shoots below nit tips, and never from a new apical meristem at

the point of truncation. There is no apparent difference in the nutrient contents and ratios

between basal shoots sampled fkom under intact and harvested canopies.

Future studies

This study has focussed oniy on nutrient contents, and the ratios derived nom

them, but has not attempted to determine why the distribution of nutrients is not unifom

across the plant. It would be interesting to study the rates of nutrient uptake and

incorporation, storage and translocation in the parts ofA. nOLii3sunt studied in this project.

In addition, the regrowth of lateral shoots should be measured after hawesting, as this has

important implications for the morphology of harvested plants, and perhaps for character

of entire stands of harvested A. nodosum.

60

LITERATURE CITED

&erg, P. 1996. Pattern of reproductive S o r t in the brown aiga Ascop~IZum nodosum.

Mar. EcoL Prog. Ser. 138: 199-207.

Ang, P.O., Sharp, G.J. and Semple, RE. 1993. Changes in the population structure of

AscophyIIum noddnm (L.) Le Jolis due to mechanicd harvesting. Hyciobiol.

260/261: 32 1-326.

Asare, S.O. and Harlin, M. M. 1983. Seasonal fluctuations in tissue nitrogen for five

species of perennial macroalgae in Rhode Island Sound. J. Phycol. 19: 254-257.

Atkinson, M. J. and Smith, S. V. 1983. C:N:P ratios o f benthic marine plants. LimnoZ'

Oceanogr. 28: 568-74.

Baardseth, E. 1970. Synopsis of biological data on knobbed wrack AscophyIIum nodom

(Linnaeus) Le Jolis. FA0 Fish Synop. 38 Rev. 1 : 41 pp.

Bacon, L. C. and Vadas, R L. 1991. A mode1 for gamete release in Ascophyllum

nodosurn (Phaeophyîa). J. Phycol. 27: 166- 173.

Bjomsiiter, B. R and Wheeler, P. A 1990. Effect of nitrogen and phosphorus supply on

growth and tissue composition of lllva fenestrafa and Enteromopha intestinaZis

(Uvales, Chlorophyta). J. PhycoL 26: 603-6 1 1.

Blunden, G., Rogers, D.J. and Famham, WP. 1975. Survey of British seaweeds for

hemaggiutinins. LIoydia 38: 16% 168.

Boney, AD. 1965. Aspects of the biology of the seaweeds of economic importance. A h .

MW. &OZ. 3: 105-253,

Cardinal, A and Lesage, V. 1992. Répartition des épiphytes Pil&lla littorallis (L.)

61

Kjeh. et Pofysiphonia lmosa (L.) Tandy sur Ascophyllum nodohnmr (L.) Le Jolis

en baie de Fundy (NB Canada). Cah. Biol. Mm. 33: 125-135.

Chapman, ARO. and Craigie, J.S. 1977. Seasonal growth in Laminana longicniris:

relations with dissolved inorganic nutrients and interna1 reserves of nitrogen. Mm.

B i d 40: 197- 205.

Chapman, A R O., Maricham, J. W. and Lüning, K. 1978. Effects of nitrate

concentration on the growth and physiology of hinmia sacchmm

(Phaeophyta) in culture. J. Phycol. 14: 195-98.

Chock, J.S. and Mathieson, A.C. 1983. Variations of New England seaweed biomass.

Bot. MW. 26: 87-97.

Chopin, T. 1998. The Seaweed Resources of Eastern Canada. In: Critchley, A T. and

Ohno, M. (eds.), Seaweed Resources of the World. Japanese International Co-

operation Agency, Yokosuka: 273-3 02.

Chopin, T., Gdant, T. and Davison, 1. 1995. Phosphonis and nitrogen nutrition in

Chonhs crispus (Rhodophyta): effects on total phosphorus and nitrogen content,

carrageenan production, and photosynthetic pigments and metabolism. J. Phycol.

31: 283-93.

Chopin, T., Le- H. and Haicrow, K. 1997. Polyphosphates in the red rnacroalga

Chonabus mispus (Rhodophyceae). New Phytol. 135: 587-594.

Chopin, T., Marcpis, P.A. and Belyea, E9. 1996. Seasonal dynamics of phosphorus and

nitrogen content in the brown alga AscophylZm nodomm (L.) Le Jolis, and its

associated species PoZysiphonia lanosa @.) Tandy and PiZuyeZIa Zittoralis (L.)

62

Kjehan, âom the Bay of Fundy, Canada. Bot. Mar. 39 : 543-552.

Chopin, T., Houmant, A, Flocph, J.-Y. and Penot, M. 1990. Seasonal variation of growth

in the red alga Chondrus crispus on the Atlantic French coasts. 11. Relations with

phosphorus concentrations in seawater and intemal phosphorylated hctions. Cm

J. Bot. 68: 5 12-5 17,

Cody, R. P. and Smith, J. K. 1991. Applied Statistics und the SAP Programming

k g p a g e . Third Edilon. Prentice-Hall, Englewood Cliffs, 403 pp.

Cousens, R. 198 1. Population ecology of Ascophyllm n o d o m (L.) Le JOBS. PhD.

thesis, Daihousie University, Halifax, NS. 273 pp.

Cousens, R 1984. Estimation of annual production by the intertidd brown alga

AscophyIZum nodosum (L.) Le Jolis. Bot Mar. 27: 217-227.

Cousens, R 1985. Frond size distributions and the effects of the algal canopy on the

behaviour of AscophyZIum noùosum (L.) Le Jolis. J; Exp. Mar. Biol. Ecof. 92:

23 1-49.

David, H. M. 1943. Studies in the autecology of Ascophyhm n0Ci;osirm Le Jol. J EcoL

31 : 178-198.

Davison, 1. R, Andrews, M. and Stewart, WD.P. 1984. Regdations o f growth in

Lumima digiata : use of in-vivo nitrate reductase activities as an indicator of

nitrogen limitation in field populations of h i m a spp. Mm. BioL 84: 207-217.

Delgado, O. E., Bdestros, E. and Vidal, M. 1994. Seasonal variation in tissue nitrogen

and phosphoms of Cystoseim medterranea Sauvageau (Fucales, Phaeophyceae)

in the northwest Mediterranean Sea. Bot. Mm. 37: 1-9.

63

Floc'h, J.-Y. 1982. Uptake of Uiorganic ions and their long distance transport in Fucales

and Laminanales. In: L. M. Srivastava (ed.), Synhetic andDegradrrtr've Processes

in Mmhe Mucroplzytes. Walter de Gruyter, Berlin: 13 9-65.

Fujita, R M., Wheeler, P. A and Edwards, R. L. 1989. Assessrnent of macroalgal

nitrogen limitation in a seasonal upwehg region. Mm. EcoL Prog. Ser. 53: 293-

303.

Gagnd, J. A., Mann, K. H. and Chapman, A. R 0. 1982. Seasonal patterns of growth

and st orage in Laminma longicruris in relation to differing patterns of availability

ofnitrogen in the water. Mm Biol. 69: 91-101.

Giilanders, B.M. and Brown, M.T. 1994. The chernical composition of Xiphophora

gldiata (Phaeophyceae: Fucales): seasonal and within plant variation. Bot. Mm.

37: 483490.

Gordon, D. M., Birch, P. B. and McComb, A. J. 1 98 1. Effects o f inorganic phosphorus

and nitrogen on the growth of an estuarine CIOCii3phora in culture. Bot. Mar. 24:

93-106.

Grasshoff, K., Ehrhardt, M. and Kremlin& K. 1983. Methodr of Semater Ana&sis.

Verlag Chernie, Weinheim. 419 pp.

Hanisaiq M. D. 1979. Growth pattems of Codium fragile ssp. tomentosoicies in response

to temperature, irradiance, salinity, and nitrogen source. M m Biol. JO: 3 19-332.

Hanisak, M. D. 1983. The nitrogen relationships of marine macroalgae. In: E. J.

Carpenter and D. G. Capone (eds.), Nitrogen in the Marine Environment.

Academic Press, New York: 699-730.

64

Hardwick-Wttman, M. N. and Mathieson, A C. 1986. Tissue nitrogen and carbon

variations in New England estuarine Ascophylhm nodosum (L.) Le Jolis

populations (Fucales, Phaeophyta). &tudes 9: 43 -48.

Hurd, C. L. and Dring, M. J. 1990. Phosphate uptake by intertidal algae in relation to

zonation and season. Mm. Biol. 107: 28 1-289.

Hurd, C. L., Berges, J. A, Osborne, J. and Hanison, P. J. 1995. An in vitro nitrate

reductase assay for marine macroalgae: opthkation and characterization of the

enzyme for Fucus g d e r i (Phaeophyta). J. Phycol. 31: 83 5-843.

Josselyn, M. N. and Mathieson, A C. 1978. Contribution of the receptacles fiom the

fùcoid Ascophylum nodosum to the detrital pool of a north temperate estuary.

EstumCIIIes 1: 258-261.

Kailov, K. M. 1976. Physiological heterogeneity of thallus elements in Ascophyllm

nodomm, Fucus vesimZosus and Fucus infatus ftom the Barents Sea. Soviet Plant

P hysiol. (English transl. Fin01 Rast .) 23: 703 -707.

Keser, M. and Larson, B. R 1984. Colonization and growth of Ascop~IZum nodosum

(Phaeophyta) in Maine. J. Phycol. 200: 83-87.

Keser, M., Vadas, R L. and Larson, B. R 1981. Regrowth ofAscophyIIum no&= and

Fucus vesimZusus under various harvesting regimes in Maine, U.S.A. Bot. Mm.

24: 29-38.

KNght, M and Parke, M. 1950. A biological study of Fucus vesiçuIosus L. and F.

serrdus L. J, Mm- Biol. Assoc. UK. 29: 43 9-5 14.

Konifed?, R-A 1982. Relations between nitrogen and phosphorus content of macroalgae

and the waters of Northem Oresund. Bot Mar. 255: 197-20 1.

Lapointe, B. E. 1 987. Phosphorus- and nitrogen-limited phot osynthesis and growth of

Gracilmù tikvahiae (Rhodophyceae) in the Flonda Keys: sn experimental field

study. Mar. Biol. 93: 561-568.

Lapointe, B. E. and Ryther, J. H. 1979. The effects of nitrogen and seawater flow rate on

the growth and biochemicai composition of GracilanP foliifeta v. anwm*ma in

mass outdoor cultures. Bot. Mm. 22: 529-537.

Lapointe, B. E, and Tenore, K. R 1981. Experhental outdoor studies with Uva faciata

Delile. 1. Interaction of iight and nitrogen on nutrient uptake, growth and

biochemicai composition. J Eip. Mm. B a . Ecol. 53: 135-1 52.

Lazo, L. and Chapman, A.R.O. 1996. Effects of harvesting on AscophyZlum nodosum

(L.) Le Jolis (Fucales, Phaeophyta) : a demographic approach. A Appl. PhycoL 8:

87-103.

Lining, T. and Garbary, D. J. 1992. The Ascophyllum/Po&siphonia/lMyco~herella

symbiosis. III. Experimental studies on the interaction between P. Zànosa and

A. nodom. Bot. MW. 35: 341-349.

Lobban, C. S. and Hamison, P. J. 1994. Seaweed Ecoiogy a d Physiology. Cambridge

University Press Cambridge. 366 pp.

Lubchenco, J. 1978. Plant species diversity in a marine intertidal community: importance

of herbivore food preference and algd cornpetitive abilities. Amer. Nd. 112: 23-

39.

MacFarlane, C. 1932. Observations on the annuai growth of AscophylIm ndsrrm.

Proc. ïhm. Nova scotim Itrst. Sci. : 27-32.

MacPherson, MG. and Y o u a E.G. 1952. Sessonal variation in the chernical

composition of the Fzicaceae in the Maritime Provinces. C m J. Bot. 30: 67-77.

Manley, S. L. and North, W. J. 1984. Phosphoms and the growth of juvenile Mawocystrs

pyrijiera (Phaeophyta) sporophytes. J. Phycol. 20: 3 89-393.

Mathieson, A C., Pennirnan, C.A., Pauia, K.B. and Tveter-Gallagher, E. 1982. Effixts of

ice on AscophyJZum nodomm within the Great Bay estuary system of New

Hampshire-Maine. L Phycol. 18: 33 1-336.

Mathieson, k C., Shipman, J. W., O' Shea, J. R. and Hasevlat, R. C. 1976. Seasonal

growth and reproduction of estuarine fucoid dgae in New England. J. Exp. Mm.

Biol. Ecol. 25: 273-284.

McCook, L. J. and Chapman, ARO. 1993. Community succession folowing massive ice-

scour on a rocky intertidal shore: recmitment, cornpetition and predation during

early, primary succession. Mar. B i d 115: 565-575.

Moen, E., Hom, S. and astgaard, K. 1997. Biological degradation of Ascophyhm

nodosum. J. Appl. Phycol. 9: 347-3 57.

Morgan, K. C. and Simpson, F. J. 198 1. Cultivation of Pairnuria (Rhodpennia) pimuta :

effea of high concentration of nitrate and ammonium on growth and nitrogen

uptake. A p a Bot 11: 167-171.

Moss, B. 1970. Meristems and growth control in Ascophyllm n&mm (L.) Le Jol. New

Phytol. 69: 253-260.

67

Murphy, J. and Riley, J. P. 1962. A modified single solution approach for the

determination of phosphate in naturd water. A d Chim. Acta 27: 3 1-36.

Nishide, E., Anzai, H. and Uchida, N. 1993. Effects of alginates on the ingestion and

excretion of cholesterol in the rat. J. Appl. Ph&'. 5: 207-2 1 1.

Papenfiiss, G. F. 1950. Review of the genera of algae descnbed by Stackhouse.

Hyriiobiol. 2: 18 1-207.

Patier, P., Yvin, J.C. , Kloareg, B., Lienart, Y. and Rochas, C.1993. Seaweed liquid

fertilizer fiom Ascophyllm nodosum contains elicitors of plant D-giycanases. J.

Appl. PPhyc* 5: 343-349.

Peckol, P., Harlin, M. M. and Knimscheid, P. 1988. Physiological and population ecology

of intertidal and subtidai AscophyiZuum nodomm (Phaeophyta). J. Phycol. 24: 192-

198.

Probyn, T. A. and Chapman, A R 0. 1983. Surnmer growth rate of Chordmia

flagelllifmis (O. F. Muen.) C. Ag. : physiological strategies in a nutrient stressed

environment. J. Exp. Mm. Biol. Ecol. 73: 243-271.

Riou, D., Coliiec-Jouault, S., Pinczon Du Sel, D., Bôsch, S., Siavoshian, S., Le Bert, V.,

Tomasonî, C., Sinquin, C., Dutanci, P. and Roussakis, C. 1996. Antitumor and

antiproliEerative effects of a fiican extracteci fiom Ascop~lZum nodanm against a

non-smd-ce1 bronchopuimonary carcinoma line. Anticamer Resecach 16: 12 13-

1218.

SAS Institute hc. 1990. SAS Uistitute, Inc. Cary, NC.

Sharp, G. J. 198 1. An assessrnent of AscophyIIum nodosurn harvesting methods in

southwestern Nova Scotia. Cm* Tech. Rep. Fish. Apat Sci. 1012: 28 pp.

Sharp, G.I. 1987. AscophyJJuum n d s u m and its harvesting in eastem Canada. In: Doty,

M.S., Caddy, J. F. and Santelices, B. (eds.), Case study of seven commercial

seaweed resources. FA0 Tech. Pq. 281: 3-48.

Sharp, G. J. and Trernblay, D. M. 1985. A tagging technique for s m d macrophytes. Bot.

MW. 28: 549-55 1,

Sharp, G. J., Semple, R and Barkhouse, 1. 1997. Macro invertebrates associated with

AscophyIZm nodosum &.) Le Jolis canopy in the Guifof Maine and the impact of

harvesting on the canopy. In: G. T. Wallace and E. F. Braasch (eds.). P . . of

the Gulfof Maine Ecosystem Dynumics Scientific S'posium and Wurkshop.

RARGOM Report, 97- 1. Hanover, NH, Regional Association for Research on the

Gulf of Maine, 352 pp.

Sokal, R R and Rom, F. J. 1 905. Biornefry : the Principes and Pructice of Slaristis in

Biologicd Resemch. 3rd ed. W . H. Freeman and Company, New York, 887 pp.

South, G. R and Whittick, A 1987. Introduction to PhycoIogy. BlackweIi SQentific

Publications, Odord, 341 pp.

Sundene, 0. 1973. Growth and reproduction in AscophyIZum nodosun (Phaeophyceae).

NOM. J Bot. 20: 249-255.

Thomas, M. L. H., Arnold, D. C. and Taylor, A R A 1983. Rocky intertidal

cornrnunities. In: Thomas, M. L. K (ed.), M m e and coastd systems of the

@d& Region, N~ou Brunswick Cm. Spec. PPubl. Fish. Aput. Sci. 64: 35-73.

Thomas, TE., Harrison, P. J. and Taylor, E. B. 1985. Nitrogen uptake and growth of the

gennlings and mature thalli of Fu= disfichus. Mar. Bid. 84: 267-274.

Topinka, J. A 1978. Effects of nitrate and ammonium enhancement on growth and

nitrogen physiology in Fucus virafis (Phaeophyceae). J. Phycol. 12: 241-247.

Topinka, J. A and Robbins, J. V. 1976. Effects of nitrate and ammonium enhancernent on

growth and nitrogen physiology in Fucus spiraIis. Lhnol. Oceanogr. 21: 659-

664.

Vadas, R L. and Wright, W. A. 1986. Recruitment, growth and management of

Ascophyllum nodomm. In: R.H. Westermeier (ed.). Actm ll. Congr. A@ Mm.

Chilenar. Universidad Austral de Chile, Valdivia: 10 1 - 1 13.

Vadas, RL., Wright, W.A. and Miller S.L. 1990. Recmitment ofAscophylh nodosunt:

wave action as a source of mortaiity. Mm. Ecol. Pro8 Ser. 61: 263-272.

Waaland, J. R 198 1. Commercial utilîzation. In: C. S. Lobban and M. J. Wynne (eds.),

Ihe BioIogy of Seaweerls. Blackweil Scientific, Oxford, 786 pp.

Wheeler, P A and Bjomsater, B.R 1992. Seasonal fluctutations in tissue nitrogen,

phosphoms, and NP for five macroaigal species comrnon to the Pacific northwest

coast. J PhycoI. 28: 1-6.

Wheeler, P. A and North, W. J. 1980. Effect of nitrogen supply on the nitrogen content

and growth rate of juveniles ofMucroysfispyRfera (Phaeophyta) sporophytes. J.

PhycoI. 16: 577-582.

Wheeler, W. N. and Snvastava, L. M. 1984. Seasonal nitrate physiology ofMucrocysfts

integrifol Boy. J. Erp- MW. Biol. Ecol. 76: 35-50.

70

Wddish, D. J., Keizer, P. D., Wilson, A J. and Martin, J. L. 1993. Seasonal changes of

dissolved oxygen and plant nutrients in seawater near sahonid net pens in the

macrotidai Bay of Fundy. Cm* J . Fish. Aquat. Sci. 50: 303-3 1 1.

Zavodnik, N. 1973. Seasonal variations in rate of photosynthetic activity and chernical

composition of the littoral seaweeds common to North Adriatic. 1. Fucus

virsoides (Don.) J. Ag. Bot. Mm. 26: 1 55- 165.

Date post:	23-Apr-2021
Category:	Documents
Upload:	others
View:	0 times
Download:	0 times

I*! · 2004. 9. 1. · I would like to th& Dr. Thierry Chopin for his guidance and encouragement...

Documents