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Doctoral Dissertations Student Scholarship
Spring 1991
Environmental and biological factors affecting tissue composition of marine macrophytes
Zhanyang Guo University of New Hampshire, Durham
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Environmental and biological factors affecting tissue composition of marine macrophytes
Guo, Zhanyang, Ph.D.
University of New Hampshire, 1991
UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106
ENVIRONMENTAL AND BIOLOGICAL FACTORS AFFECTING TISSUE COMPOSITION OF MARINE MACROPHYTES
EY
ZHANYANG GUO B.S. Shandong College of Oceanography, 1982 M.S. University of New Hampshire, 1986
DISSERTATION
Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of
Doctor of Philosophy
in
Botany and Plant Pathology
May, 1991 This dissertation has been examined and approved.
Dissertation Director, Dr. Arthur C. Mathieson Professor of Plant Biology
Dr. Alan L. Bake'r, Professor of Plant Biology
A r - j l fi\fr,K)w3 Dr. Larry Harris, Professor of Zoology
Dr. Leland S./dahpt(e, Professor of Plant Biology
Dr. Galen E. Jones, Professor of Microbiology
A ' " 7
Dr. Thomas D. Lee, Professor of Plant Biology
Dr. Frederick T. Short, Professor of Natural Resources
March 6, 1991 TABLE OF CONTENTS
ACKNOWLEDGEMENTS...... v
USTOFTABLES...... v i i
LIST OF FIGURES...... ix
ABSTRACT...... xiv
PART 1: EFFECTS OF AMBIENT ENVIRONMENTAL AND BIOLOGICAL FACTORS UPON MARINE MACROPHYTE TISSUE COMPOSITION ...... 1
1.1 INTRODUCTION ...... 2
1 .2 MATERIALS AND METHODS...... 4
1.3 RESULTS ...... 7
Gradlaria Light Experiment...... 7
Effects of Different Fucoid Estuarine Distribution Patterns ...... 8
Effects of Vertical Transplantation upon Fucoid Algae...... 9
Effects of Different "Ages" in Ascophyllum ...... 1 0
Effects of Different Plant Parts in Fucoid Algae and Two Halophytic Plants...... 1 0
Effects of Varying Functional Forms in 49 Seaweed Taxa ...... 11
Effects of Different Seasons in 49 Seaweed Taxa ...... 1 2
Effects of Ice-rafting in Several Seaweeds ...... 13
Long-term Correlation between Tissue and Ambient Nutrients...... 13
iii 1 .4 DISCUSSION ...... 1 3
PART 2: EFFECTS OF DIFFERENT N: P RATIOS IN CULTURE MEDIA UPON SEVERAL BIOCHEMICAL AND PHYSIOLOGICAL FEATURES OF SEAWEEDS ...... 5 6
2.1 INTRODUCTION ...... 5 7
2.2 MATERIALS AND METHODS...... 5 8
2.3 RESULTS ...... 6 0
GrowlhRates...... 6 0
Net Photosynthesis ...... 6 0
Tissue CNP and Ash Contents ...... 61
Pigments ...... 6 2
2.4 DISCUSSION ...... 6 2
LIST OF REFERENCES...... 8 5
iv ACKNOWLEDGEMENTS
The seven years I have spent at the University of New Hampshire completing my M. S. and Ph. D. dissertations represent a very memorable period of my total education.
The friendship, encouragement, and assistance of advisors and colleagues are deeply
appreciated. In addition, the hospitality of the New England people will be carried with me for the rest of my life.
Dr. Arthur C. Mathieson provided me with constant guidance and support. His
knowledge and interest in marine/estuarine sciences are substantial and have been very
helpful. His family also made us feel at home and welcome.
I would also like to thank the other members of my committee: Drs. Alan L. Baker,
Larry G. Harris, Leland S. Jahnke, Galen E. Jones, Thomas D. Lee, and Frederick T.
Short for their assistance with many aspects of this research and their critical review of this
manuscript. To Dr. Short, who allowed me to use some of his supplies, I am very grateful.
Dr. Larry Harris helped me collect specimens of several subtidal crusts that I had difficulties finding intenidally. Dr. Lee's patience and understanding of my broken english,
particularly when I first arrived from China, and his many other assistances are greatly
appreciated. I am also deeply grateful to Dr. Jones who helped me understand the Redfield
theory during his marine microbiology course, plus providing me a picture of Dr. Redfield
for my seminar. Both Drs. Jahnke and Baker are acknowledged for their valuable
assistance with biochemical and computer techniques, respectively. Dr. Theodore Loder,
although not a member of my committee, provided a variety of historical nutrient data from
the Great Bay Estuarine System, some of which is evaluated in my dissertation.
It would be impossible to list all of the other advisors and friends who have
contributed ideas and assistance during my graduate career. In particular, I am deeply
v grateful to Drs. Bo-lin Cheng, C. K. Tseng, C. Y. Wu, T.-C. Fang and J.-Y Li in China for their encouragement and guidance. 1 would also like to express my gratitude to all of the staff and fellow students both in the Department of Plant Biology and at the Jackson
Estuarine Laboratory for their assistance and friendship. Among them, Dr. Clayton
Penniman is acknowledged for his many ideas and suggestions that have contributed to this research.
I am also grateful to the Department of Botany and Plant Pathology (now, Plant
Biology) for offering me a research assistantship during September, 1987 to May, 1991.
The present research was also supported in part by a UNH CURF grant (account number
3012 UFR CURF).
My wife, Hong, has been a continuous source of support. Her continuous encouragement and understanding have made this dissertation possible. I would also like to thank my parents, in-laws and other relatives for their interest in my career and their support of my education.
vi LIST OF TABLES
Table 1-1: Student-Newman-Keul multiple comparisons of mean growth (% biomass increase/month) ofGracilaria tikvahiae under different light intensities, plus variations in mean tissue composition versus growth rates. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for growth and tissue composition are listed in order of increasing magnitude of corresponding mean values. Values underlined indicate that mean values for these conditions are not significantly different (p > 0.05)......
Table 1-2: Student-Newman-Keul multiple comparisons of mean tissue composition withinAscophyllum nodosum and Fucus vesiculosus v. spiralis at eight different sites within the Great Bay Estuarine System. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for the different sites are listed in order of increasing magnitude of corresponding mean values. Sites underlined are not significantly different (p> 0.05) ......
Table 1-3: Analysis of variance (ANOVA) table assessing tissue C, N, P and ash contents withinAscophyllum nodosum and Fucus vesiculosus v. spiralis versus time (July to November, 1987) and elevation (four tidal levels) ......
Table I-4: Student-Newman-Keul multiple comparisons of mean tissue composition withinAscophyllum nodosum of different ages. Tissue C, N and P contents are expressed as mmol/g ash- free dry wt and ash as % dry wt. The values for the different years are listed in order of increasing magnitude of corresponding mean values. Years underlined are not significantly different (p > 0.05)......
Table I-5: F values of ANOVA on tissue C, N, P and ash contents within vegetative and reproductive parts of seven fucoid taxa. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as %drywt......
Table I- 6 : Student-Newman-Keul multiple comparisons of mean tissue composition within the roots/rhizome, stems/sheath and leaves of Spartina alterniflora and Zostera marina. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for the different parts are listed in order of increasing magnitude of corresponding mean values. Parts underlined are not significantly different (p > 0.05)...... 32
Table 1-7: Date, location, tissue composition and elemental ratios of marine algal taxa collected for different functional form study...... 33
Table 1-8: Student-Newman-Keul multiple comparisons of mean tissue composition within seaweeds of seven functional form groups. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for the different groups are listed in order of increasing magnitude of corresponding mean values. Groups underlined are not significantly different (p>0.05)...... 34
Table 1-9: Summary of mean tissue C: N, C: P and N: P ratios within seven functional form groups, as well as within three seaweed divisions...... 35
Table 1-10: Student-Newman-Keul multiple comparisons of mean tissue C: N, C: P and N: P ratios within seven functional form groups, as well as within three seaweed divisions. The values for different groups or divisions are listed in order of increasing magnitude of corresponding mean values. Groups or divisions underlined are not significantly different (p > 0.05)...... 36
Table 1-11: Date and location of marine algal taxa regrouped into different seasons ...... 37
Table 1-12: Summary of N: P atomic ratios in marine macrophytes collected during June, 1987 to February, 1990 from the Great Bay Estuarine System and the adjacent open coast of New Hampshire...... 38
Table 1-13: Summary of N: P atomic ratios within ambient waters of multiple sites within the Great Bay Estuarine System ...... 39
Table 11-1: Correlations and F values on selected physiological and biochemical characteristics of Ascophyllum nodosum and Gracilaria tikvahiae grown under different supplements of NO3 -N orP04-P...... 67
viii LIST OF FIGURES
Figure 1 -1 : Map of the Great Bay Estuarine System of New Hampshire- Maine, showing nine study sites. 1 - Isles of Shoals; 2 - Fort Stark; 3 - Fort Constitution; 4 - I-95 Bridge; 5 - Dover Point; 6 - Cedar Point; 7 - Adams Point; 8 - Woodman Point; 9 - Weeks Point...... 40
Figure 1-2: Growth (% biomass increase/month) ofGracilaria tikvahiae under different light intensities plus variations in the plant's tissue composition (C, ash, N & P) versus monthly growth. Tissue C, N and P contents are expressed as mmol/g ash-free dry wtandashas%drywt...... 41
Figure 1-3: Tissue C, N, P & ash contents (± s.d.) withinAscophyllum nodosum and Fucus vesiculosus v. spiralis from eight sites within the Great Bay Estuarine System. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 42
Figure 1-4: Concentrations (iiM) of surface water inorganic nitrogen (NO 3 , NO2 & NH4 - N) and orthophosphate at eight sites within the Great Bay Estuarine System ...... 43
Figure 1-5: Temporal and spatial variations of tissue C , N , P & ash contents within Ascophyllum nodosum populations transplanted to five elevations (-0.46 to +1.60 m) at Adams Point, Little Bay, New Hampshire. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. Each bar represents the mean of three replicates ...... 4 4
Figure 1-6: Temporal and spatial variations of tissue C , N , P & ash contents within Fucus vesiculosus v. spiralis populations transplanted to five elevations (-0.46 to -1-1.60 m) at Adams Point, Little Bay, New Hampshire. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. Each bar represents the mean of three replicates ...... 45
Figure 1-7: Concentrations (^M) of surface water inorganic nitrogen (NO3, NO2 & NH4- N) and orthophosphate during fucoid transplant
ix studies at Adams Point, Little Bay, New Hampshire (June - November, 1987) ...... 4 6
Figure 1-8: Tissue C, ash, N & P contents (± s.d.) withinAscophyllum nodosum tissues of different ages. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 4 7
Figure 1- 9: Tissue C, N, P & ash contents (± s.d.) within vegetative and reproductive parts of seven fucoid taxa. See Table I-5 for names of the taxa. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as %dry wt...... 4 8
Figure 1-10: Tissue C, ash, N & P contents (± s.d.) within the roots, stems and leaves of Spartina alterniflora. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 4 9
Figure 1-11: Tissue C, ash, N & P contents (± s.d.) within the roots/ rhizome, sheath and leaves of Zostera marina. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % d ry w t ...... 5 0
Figure 1-12: Tissue C, ash, N and P contents (± s.d.) within individual seaweed taxa from seven functional form groups. See Table I-7 for names of the taxa, dates and sites of collections. Tissue C, N and P contents are expressed as mmol/g ash-free drywtandashas%drywt...... 51
Figure 1-13: Mean values of tissue C, ash, N & P contents (± s.d.) for seaweeds within seven different functional form groups. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash a s% d ryw t...... 5 2
Figure 1-14: Tissue C, ash, N & P contents (± s.d.) within seaweeds collected at different seasons. See Table 1-11 for names of the taxa, dates and sites of collections. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 5 3
Figure 1-15: Mean values of tissue C, ash, N & P contents (± s.d.) within all seaweeds collected at different seasons. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 5 4
Figure 1-16: Tissue C, ash, N & P contents of eight ice rafted estuarine
x macrophytes collected at Adams Point, Little Bay, New Hampshire. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt...... Codes for species names are: A n -Ascophyllum nodosum; Ans -A. nodosum ecad scorpioided; Fvs -Fucusvesiculosus v. spiralis; Gt -Gracilaria tikvahiae; Pp -Palmaria palmata; Sa -Spartina alterniflora; Ul -Utva lactuca; Zm -Zostera marina;
Figure 2-1: Growth (biomass increase/month, ± s.d.) of Ascophyllum nodosum under different supplements of NO3 -N. Neither NO 3 -N nor PO4 -P were added to the control, while 5 pM PO 4 -P was provided for each treatments ......
Figure 2-2: Growth (biomass increase/month, ±. s.d.) ofGracilaria tikvahiae under different supplements of NO3 -N. Neither NO 3 -N nor PO4-P were added to the control, while 5 pM PO4-P was provided for each treatments ......
Figure 2-3: Growth (biomass increase/month, ± s.d.) ofAscophyllum nodosum under different supplements of PO4 -P. Neither NO 3 -N nor PO4 -P were added to the control, while 200 pM NO 3 -N was provided for each treatments ......
Figure 2-4: Growth (biomass increase/month, ± s.d.) ofGracilaria tikvahiae under different supplements of PO4-P- Neither NO 3 -N nor PO4-P were added to the control, while 2 0 0 pM NO3 -N was provided for each treatments ......
Figure 2-5: Net photosynthesis ofAscophyllum nodosum grown under different supplements of NO3-N. Neither NO3-N nor PO4-P were added to the control, while 5 pM PO4-P was provided for each treatments. The rates of net photosynthesis are expressed as both p i0 2 /g damp-dried wt/minute (± s.d.) and pi 0 2 /mg chi a/minute (± s.d.)......
Figure 2-6: Net photosynthesis of Gracilaria tikvahiae grown under different supplements of N0 3 -N- Neither NO 3 -N nor PO4 -P were added to the control, while 5 pM PO 4 -P was provided for each treatments. The rates of net photosynthesis are expressed as both pi0 2 /g damp-dried wt/minute (± s.d.) and pi 0 2 /mg chi a/minute (± s.d.). 73
Figure 2-7: Net photosynthesis of Ascophyllum nodosum grown under different supplements of PO4 -P. Neither NO 3 -N nor PO4 -P were added to the control, while 200 NO 3 -N was provided for each treatments. The rates of net photosynthesis are expressed as both 11I 0 2 /g damp-dried wt/minute (± s.d.) and nl 0 2 /mg chi a/minute (± s.d.)...... 7 4
Figure 2-8: Net photosynthesis of Gracilaria tikvahiae grown under different supplements of PO4 -P. Neither NO 3 -N nor PO4 -P were added to the control, while 200 11M NO3 -N was provided for each treatments. The rates of net photosynthesis are expressed as both )il 0 2 /g damp-dried wt/minute (±. s.d.) and (il 0 2 /mg chi a/minute (± s.d.)...... 7 5
Figure 2-9: Tissue C, ash, N & P contents (± s.d.) withinAscophyllum nodosum fragments grown under different supplements of NO3 -N. Neither NO 3 -N nor PO4-P were added to the control, while 5 |iM PO4 -P was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 7 6
Figure 2-10: Tissue C, ash, N & P contents (± s.d.) within Gracilaria tikvahiae fragments grown under different supplements of NO3 -N. Neither NO 3 -N nor PO4 -P were added to the control, while 5 11M PO4-P was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 7 7
Figure 2-11: Tissue C, ash, N & P contents ( 1 s.d.) within Ascophyllum nodosum fragments grown under different supplements of PO4 -P. Neither NO 3 -N nor PO4 -P were added to the control, while 200 11M NO3 -N was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 7 8
Figure 2-12: Tissue C, ash, N & P contents (± s.d.) within Gracilaria tikvahiae fragments grown under different supplements of PO4 -P. Neither NO 3 -N nor PO4 -P were added to the control, while 200 11M NO3 -N was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt ...... 7 9
Figure 2-13: A plot of tissue N: P ratios within fragments of
xii Ascophyllum nodosum and Gracilaria tikvahiae versus the N: P ratios of their growth media......
Figure 2-14: Chlorophyll a and c contents (mg/g damp-dried wt, ± s.d.) within fragments of Ascophyllum nodosum grown under different supplements of NO3 -N. Neither NO 3 -N nor PO4 -P were added to the control, while 5 pM PO4 -P was provided for each treatments ......
Figure 2-15: Chlorophyll a, phycocaynin, allophycocaynin and phycoerythrin contents (mg/g damp-dried wt, ± s.d.) within fragments of Gracilaria tikvahiae grown under different supplements of NO3 -N. Neither NO 3 -N nor PO4 -P were added to the control, while 5 pM PO4 -P was provided for each treatments ......
Figure 2-16: Chlorophyll a and c contents (mg/g damp-dried wt, ± s.d.) within fragments of Ascophyllum nodosum grown under different supplements of PO4 -P. Neither NO 3 -N nor PO4 -P were added to the control, while 200 pM NO3 -N was provided for each treatments ......
Figure 2-17: Chlorophyll a, phycocaynin, allophycocaynin and phycoerythrin contents (mg/g damp-dried wt, ± s.d.) within fragments of Gracilariatikvahiae grown under different supplements of PO4-P. Neither NO 3 -N nor PO4-P were added to the control, while 200 pM NO3 -N was provided for each treatments ...... I
ABSTRACT
ENVIRONMENTAL AND BIOLOGICAL FACTORS AFFECTING TISSUE COMPOSITION OF MARINE MACROPHYTES
by
Zhanyang Guo University of New Hampshire, May, 1991
The tissue nitrogen and phosphorus composition of 59 marine macrophytes from
the Great Bay Estuarine System, NH-Maine and adjacent coast is affected by a variety of
environmental and biological factors; by contrast, tissue carbon is more consistent. The
overall mean CNP ratio of these plants was 612: 29: 1, which deviated significantly from
that previously recorded for phytoplankton.
The C: N: P ratios within seaweeds were more closely related to functional forms
than phylogenetic relationships. Brown algae had higher C: N ratios than green and red
algae. This pattern primarily resulted from the very high C: N ratios within thick bladed and
coarsely branched species, which dominanted the Phaeophycean taxa evaluated. Overall,
the tissue nutrient status within an alga depends upon ambient nutrient availability, as well
as a plant's uptake efficiency, storage capacity, and consumption rate(s).
The present study suggests that neither N nor P limitations should be solely
delineated by ratios of tissue composition. An assessment of tissue C: N ratios of marine
macrophytes (mean = 21: 1) and long-term ambient nitrogen and phosphorus
concentrations suggests that nitrogen is the primary limiting nutrient within the Great Bay
Estuarine System. On the other hand, tissue N: P ratios (mean = 29: 1) suggest that
phosphorus is most limiting. Based upon C: N and N: P ratios, some algae would appear
to be limited by both N and P. Such a response seems questionable.
xiv Under laboratory conditions tissue N: P ratios within both Ascophyllum nodosum and Gracilaria tikvahiae were physiologically determined, although they were somewhat affected by ambient N: P ratios. Both algae absorbed N more efficiently when ambient N: P ratios were low, while P uptake efficiency was elevated with increased ambient N: P ratios.
Tissue nitrogen and phosphorus, but not carbon, were strongly affected by N or P supplements. In culture studies Chlorophyll g concentrations were mainly affected by N rather than P concentrations. The biliprotein pigments in Gracilaria were closely related to
N: P ratio within the media.
XV PARTI
EFFECTS OF AMBIENT ENVIRONMENTAL AND BIOLOGICAL FACTORS
UPON MARINE MACROPHYTE TISSUE COMPOSITION 1.1 INTRODUCTION
Since the introduction of the Redfield Ratio (Redfield, 1958; Redfield et al.,
1963) many scientists have assessed the tissue composition of marine organisms, finding
an average carbon : nitrogen : phosphorus atomic ratio of 106 : 16 : 1 for living organisms
and a similar nitrogen : phosphorus ratio for detrital materials within the deep sea (15 : 1).
The uptake of nitrogen and phosphorus by phytoplankton also occurs in a 16 : 1 ratio, with
these plants transferring nutrients to zooplankton, the next stage in the food chain, in the
same ratio. Upon death and decomposition, phytoplankton and zooplankton release N and
P back into the water column in the same ratio. Nitrogen fixation by some marine blue-
green algae (cyanobacteria) plays a critical role in balancing the N : P ratio within the photic
zone of the world's ocean.
The concepts described by Redfield (1958) are now even used to infer nutrient
limitation for marine plants, especially phytoplankton (Birchet al., 1981; Bjomsater and
Wheeler, 1990; Goldman et al., 1979; Lapointe and Ryther, 1979; Ryther and Dunstan,
1971; Smith, 1984). Thus, when the N : P ratio is > 30 : 1 phosphorus is suggested as being the limiting element, while nitrogen is limiting when it is < 10 ; 1. Furthermore, most culture media used for both phytoplankton and seaweeds have nitrogen : phosphorus ratios of approximately 16: 1 (McLachlan, 1973).
Several different patterns of chemical composition occur within benthic marine plants.
Foremost many marine plants show significant deviations from Redfield's (1958) generalized model (Atkinson and Smith, 1983; Birch, 1975; Faganeli etal., 1986;
Hardwick-Witman and Mathieson, 1986; Johnston, 1971; Lapointe, 1987, 1989; Mann,
1972; Niell, 1976; Short et al., 1985; Wallentinus, 1981). For example, Atkinson and
Smith (1983) surveyed 92 macrophyte taxa throughout the world and found a mean C: N:
2 P ratio of 700: 35:1. Spatial differences of tissue composition within individual species may also occur, depending upon trophic levels, with plants from oligotrophic environments usually having significantly higher C: N and C: P ratios than those from eutrophic habitats
(Atkinson and Smith, 1983; Lapointe, 1989). Among others, Hardwick-Witman &
Mathieson (1986) and Wheeler & Srivastava (1984) have recorded seasonal variations of tissue chemistry for temperate seaweeds. Typically, tissue nutrient levels show winter maxima and summer minima, paralleling ambient nutrient concentrations. However, a time lag between tissue and ambient nutrients exists. Some differences in tissue chemistry have also been recorded between vegetative and reproductive portions of plants, as well as between different developmental stages (Niell, 1976).
Recently, the role of ontogenetic development and morphological features in determining algal tissue chemistry has received enhanced interest. For example, Niell
(1976) and Lapointe (1989) recorded higher C: N ratios in phaeophycean (brown algae) than chlorophycean (green algae) or rhodophycean (red algae) taxa, while Komfeldt (1982) found lower N: P ratios in brown than red taxa. On the other hand, tissue composition may be more closely related to functional forms of seaweeds (cf. Littler and Littler, 1980;
Steneck and Watting, 1982) than to phylogenetic relationships, as brown algae are usually much larger than green and red algae. The idea of using tissue C: N and N: P ratios as indicators of nutrient status or limiting elements has also become popular (Bjomsater and
Wheeler, 1990; DeBoer, 1981; Hanisak, 1979; Hansen, 1977; Lapointe and Ryther, 1979;
Ryther and Dunstan, 1971; Smith, 1984).
In the present study, I evaluated the tissue CNP composition within 59 conspicuous marine macrophytes from the Great Bay Estuarine System. Such a study is essential to understand nutrient dynamics within estuarine and coastal ecosystems, as well as to quantify a variety of correlations between plant tissue and ambient nutrients. The four primary objectives of the present study were as follows: 1. To evaluate the effects of selected environmental and biological factors upon
3 the tissue CNP contents of a variety of marine macrophytes within the Great Bay Estuarine System of NH and Maine.
2. To examine the relationship between the tissue CNP composition of these seaweeds and their "functional form" characteristics.
3. To assess any possible long-term correlations between tissue and ambient N: P ratios within the Great Bay Estuarine System.
4. To provide basic information regarding any possible nutrient limitations to primary productivity within the Great Bay Estuarine System.
1.2 METHODS AND MATERIALS
In assessing the tissue composition of 59 marine macrophytes, 428 measurements
of carbon, nitrogen and phosphorus (CNP) contents were performed. With the exception
of the light experiment with Gracilaria tikvahiae and the ice rafted plant materials (see
bellow), at least three samples of each seaweed for each treatment were collected at various
open coastal and estuarine locations within the Great Bay Estuarine System, New
Hampshire-Maine during 1987 -1990 (cf. Fig. 1-1). Upon return to the Jackson Estuarine
Laboratory, the plants were cleaned of epiphytes and debris and then oven dried at 80 °C
for 24 hours prior to analysis. Measurements of carbon and nitrogen contents within dried, ground tissue were made with a Carlo Erba Elemental Analyzer (Model Nitrogen Analyzer
1500). Tissue phosphorus concentrations were determined according to the method of
Murphy and Riley (1962), following persulfate oxidation (Menzel and Corwin, 1965). The ash contents of dried algal samples were measured after burning in a muffle furnace (Model
Thermolyne Fumatrol II) for 24 hours at 500 °C. Hence, all of the tissue carbon, nitrogen and phosphorus values are expressed as millimoles per gram ash-free dry matter. Water samples collected simultaneously with the plant specimens were assayed for ambient nutrient levels, utilizing the procedures outlined by Strickland and Parsons (1972).
4 The effects of several environmental and biological factors upon tissue CNP composition were experimentally evaluated. That is, experiments were conducted to assess the effects of different seasons, habitats (coastal and estuarine, upper versus lower shores, etc.), light regimes, growth rates, "ages", vegetative versus reproductive state, and functional forms (cf. Littler and Littler, 1980; Steneck and Watling, 1982). A comparison of several ice-rafted versus in situ macrophytes was also made at Adams Point during the early spring of 1988. As both the acquisition and processing of the ice-rafted materials were very time consuming and difficult, no replicates were taken.
The tissue composition of cultured populations of the red algaGracilaria tikvahiae was assessed during the summer of 1988, utilizing a series of outdoor tanks (mesocosms) and adjusting ambient light levels with a series of screens (cf. Howard and Short, 1986;
Short, 1987). Two large plants (~ 20 g fresh weight each) per tank were grown for 30 days in this mesocosm system, which was located at the Jackson Estuarine Laboratory (i.e.
Adams Point). Ultimately, the tissue CNP contents and growth rates (% biomass increase/month) were quantified versus light intensity.
Collections of two dominant fucoid algal species,Ascophyllum nodosum and
Fucus vesiculosus v. spiralis, were made during December 1988 at eight stations from the mouth to the head of the Great Bay Estuarine System (Fig. 1-1), in order to assess spatial differences of tissue composition. The sites included Fort Stark, Fort Constitution, the 1-95 Bridge, Dover Point, Cedar Point, Adams Point, Woodman Point and Weeks
Point, which ranged from 0-15 miles inland (Fig. 1-1). During these collections, simultaneous surface water samples were taken for enumeration of ambient nutrients. The effects of varying elevations upon the same two dominant fucoid algae were assessed by a series of vertical transplants conducted at Adams Point during June to November, 1987.
Specimens of both fucoid taxa were collected from the mid-intertidal zone (~ +0.23 m) at
Adams Point and then transplanted to five different levels (-0.46, -0.19, +0.23, +0.94, and
5 + 1.60 m). Each month, tissue samples were taken from these transplanted specimens for
analysis, while water samples were collected simultaneously for enumeration of ambient
nutrients. A two-way analysis of variance was performed on the transplant specimens. A
Student-Newman-Keul’s (SNK) multiple range test was also employed to assess potential differences of tissue CNP contents between experimental replicates. Correlations
(Pearson's r) between tissue and ambient nutrients were also calculated (Ary and Jacobs,
1976; Sokal and Rohlf, 1969).
The effects of "aging" in Ascophyllum nodosum were assessed, as the position between subsequent air bladders is analogous to the "annual rings" of trees, being produced annually during the initiation of growth (Baaidseth, 1970; Moss, 1969). That is, a minimum tissue age (Cousens, 1985) was recorded for each frond segment by counting the numbers of vesicles in a basipetal direction. Materials formed yearly during 1983 to
1988 were delineated and analyzed for tissue C, N, and P contents. A comparison of the tissue composition of vegetative and reproductive tissues of seven fucoid taxa (i.e., species or subspecies) was also made. An analogous comparison of the tissue CNP contents within the different tissues of two halophytic plants,Spartina altemiflora and Zostera marina was performed. That is, tissue composition of their roots/rhizome, stems (ofSpartina) or sheath (of Zostera), and leaves was analyzed.
The tissue composition of 49 seaweed taxa was compared in order to evaluate potential differences between functional forms. Seven groups were delineated based upon the studies of Littler & Littler (1980) and Steneck & Watling (1982), except for a few modifications in order to emphasize thallus morphology, nutrient uptake efficiency and storage capacity. The crustose group consisted of both calcified (e.g.Phymatolithon) and non-calcified forms (e.g. Ralfsia), while the thin sheets included both monostromic and distromatic thalli (Porphyra and Utva). Many blades exhibited a similar sheet-like stature
(e.g. blades of Laminaria and Palmaria), except for their thicker thallus construction. I
Species designated as hollow tubes were at least partially hollow when sampled (e.g.
Enteromorpha and Dumontia). Uniseriate, filamentous taxa were either branched or
unbranched, while complex filaments were multicellular, filamentous plants. The coarsely
branched taxa contained large tough thalli like Ascophyllum and Fucus. Specimens
utilized in the functional form tissue characterizations were collected during several seasons
between November, 1987 and February, 1990.
In order to evaluate possible long-term relationships between tissue and ambient
nutrients all of the tissue nitrogen and phosphorus data described above were correlated
(Broecker and Peng, 1982; Goldman et al., 1979; Redfield, 1958; Redfield et al., 1963)
with a detailed historical synopsis of ambient nutrients from the Great Bay Estuarine
System (Emerich-Penniman et al, 1985; Jackson Estuarine Laboratory, unpublished data;
Loder et at, 1983; Loder et al, unpublished data). That is, tissue N & P or N: P ratios
were correlated with this data set Tissue nitrogen and phosphorus contents are illustrated
utilizing an atomic ratio of 30: 1, which approaches the overall mean ratio (29: 1) recorded
from these macrophytes (Tab. 1-10).
1.3 RESULTS
Gracilaria Light Experiment
Figure 1-2 illustrates the growth of Gracilaria tikvahiae under different light
intensities. Maximum growth occurred at 61% of ambient sunlight, while negative growth
was recorded at 11% sunlight As shown in Table 1-1, the plant's growth was significantly
different (p < 0.05) under various light regimes. As Gracilaria's tissue carbon, nitrogen,
phosphorus and ash contents showed a greater negative correlation with growth (Pearson's
r = -0.74, -0.94, -0.98 and -0.75, respectively) than with light intensities (-0.57, -0.57, -
0.64 and -0.04, respectively), its tissue components were plotted against growth (Fig. 1-2
B & C). In spite of highly negative coefficients, only the differences in tissue phosphorus
7 contents were significantly different. That is, the concentrations of phosphorus were markedly higher at 11, 20, and 50% sunlight, which corresponded to reduced growth rates. See Table 1-1 for a multiple comparison of mean tissue phosphorus contents. The lowest tissue C: N: P ratio (512 : 40 : 1) was recorded in the slowest growing plants (11% full sunlight), while the highest ratio (953 : 59 : 1) occurred in the fastest growing plant
(61% sunlight). The mean C: N: P ratio for G. tikvahiae plants grown under different light intensities was 683 : 47 : 1.
Effects of Different Fucoid Estuarine Distribution Patterns
The CNP and ash contents of Ascophyllum nodosum and Fucus vesiculosus v. spiralis at eight sites within the Great Bay Estuarine System are shown in Figure 1-3. The locations of these sites and their ambient nutrient levels are summarized in Figures 1-1 and
1-4, respectively. The carbon contents in A. nodosum showed little variations, while F. vesiculosus v. spiralis exhibited significant differences (p < 0.05). That is, the carbon contents within F. vesiculosus v. spiralis was higher at outer and mid estuarine sites (0.0,
1 and 5 miles inland) than at inner estuarine habitats. The highest tissue nitrogen and phosphorus concentrations in both fucoid species were recorded at the 1-95 Bridge site (5 miles inland), plus one or two other sites, depending upon the nutrient considered. All of these variations, except for nitrogen levels in F. vesiculosus v. spiralis, were significantly different (p < 0.05).
A multiple comparison of the mean tissue CNP and ash in both fucoid algae is given in Table 1-2. The highest ambient nitrogen concentration was recorded at the 1-95
Bridge (5 miles inland), which is consistent with the tissue composition. On the other hand, the highest level of ambient phosphorus was found at Fort Constitution (1 mile inland). Thus, the correlation coefficients between plant and ambient nitrogen contents were relatively strong (Pearson's r = 0.68 for A. nodosum and 0.43 for F.vesiculosus v. spiralis), whereas they were very poor for phosphorus (-0.33 and 0.16, respectively).
8 Overall, the tissue nitrogen and phosphorus contents withinA. nodosum were lower than
those in F. vesiculosus v. spiralis, while little differences were evident for tissue carbon.
The mean C: N: P ratio for A. nodosum was higher (759: 25 :1) than for F. vesiculosus
v. spiralis (526 : 22 : 1).
Effects of Vertical Transplantation upon Fucoid Algae
Figures 1-5 and 1-6 summarize the tissue CNP and ash contents within transplanted
Ascophyllum nodosum and Fucus vesiculosus v. spiralis, while Figure 1-7 shows ambient nitrogen and phosphorus during the experiment. The CNP values for both fucoid
algae were irregular at +1.60 m versus the other four elevations. That is, the plants at
+1.60 m died after 1 to 2 months, while those at the other four elevations survived at least five months. All of the data, except for the plants growing at +1.60 m, were processed by two-way analysis of variance. The total variance consisted of three components: elevation
(spatial), time (temporal), and their interaction. Table 1-3 summarizes a multiple regression analysis of variance for these components. The tissue carbon contents in A. nodosum were only slighdy affected, with the values being relatively constant both temporally and spatially (i.e. different elevations). By contrast, the tissue carbon in F. vesiculosus v. spiralis was strongly influenced by temporal changes, as well as the interaction of temporal and elevational factors (p < 0.001); elevation did not seem to have a major effect alone. Thus, the highest levels of tissue carbon in F. vesiculosus v. spiralis occurred during July and August (Fig. 1-5A). The patterns of nitrogen concentrations in both fucoid algae seemed to be primarily influenced by temporal changes of ambient nitrogen (cf. Fig.
1-7) and the interaction between temporal and elevational two factors. Again elevation did not seem to have a major effect alone. The tissue phosphorus and ash values in both species were strongly affected by all three factors, except for the effects of temporal factors on ash content in A. nodosum . The highest values of tissue nitrogen and phosphorus occurred within both fucoid algae during July and/or November, while lower concentrations were evident between August and October (Figs. 1-5B, 1-5C, 1-6B and 1- 6C). The correlation between tissue and ambient nitrogen for A. nodosum was moderate
(r = 0.61), while little correlation existed for F. vesiculosus v. spiralis (r = -0.1). The correlations between plant tissue and ambient water for phosphorus were poor for both fucoid algae (-0.37 and 0.14, respectively). Generally, both species tended to have their highest phosphorus concentrations in the lowest zone (-0.46 m), with the opposite pattern occurring in the highest zone (+0.94 m). Dense epiphyte cover was also observed on plants transplanted below mean low water.
Effects of Different "Ages" in Ascophvllum
Figure 1-8 shows the CNP and ash contents of Ascophyllum nodosum tissue formed between 1983 and 1988. No significant differences in tissue carbon were evident (p
> 0.05). However, significantly higher tissue nitrogen, phosphorus and ash contents occurred within the younger (1988) than older tissues. Table 1-4 summarizes a multiple comparison of mean tissue N & P components, these values were fairly consistent between
1983 to 1987.
Effects of Different Plant Parts in Fucoid Aleae and Two Halophvtic Plants
Figure 1-9 illustrates the tissue CNP and ash contents of vegetative and reproductive portions of seven fucoid taxa. The carbon contents within the vegetative and reproductive portions of each taxa were almost the same. By contrast, pronounced differences for tissue nitrogen and phosphorus were evident. That is, vegetative tissues of all seven fucoid algae showed lower nitrogen and phosphorus contents than their receptacles. Even so, only two of the seven fucoid taxa (Ascophyllum nodosum and
Fucus distichus subsp. distichus) showed significant (p < 0.05) differences of tissue nitrogen within vegetative and receptacular tissues, while tissue phosphorus was significantly different for all plants (p < 0.05), except forF. spiralis. Table 1-5 summarizes a series of F-tests on the variance of tissue compositions within vegetative and reproductive portions of the same seven fucoid algae. The C: N: P ratios were higher in
10 vegetative than reproductive portions. For example, the mean C: N: P ratio for vegetative parts was 1164: 43: 1, while the mean ratio for receptacles was 697: 32: 1. The highest C:
N: P ratio for vegetative tissue was recorded in F. distichus subsp. edentatus (2173: 95:
1), while F. distichus subsp. distichus had the lowest ratio (492: 25: 1). By contrast, the
C: N: P ratios for reproductive materials of the same two species were 1285: 60: 1 and 301:
2 2 : 1, respectively.
Figures 1-10 and 1-11 show the tissue CNP and ash values for the roots/rhizome, stems or sheath, and leaves of two halophytic species,Spartina alterniflora and Zostera marina. The carbon contents within the different parts of cord grass and eelgrass showed little differences (p > 0.05). On the other hand, the tissue nitrogen and phosphorus, plus ash, contents for the root/rhizomes of both plants were significantly lower than their corresponding stems (or sheath) and leaves (Table 1-6).
Effects of Varying Functional Forms in 49 Seaweed Taxa
Figure 1-12 summarizes the tissue carbon, nitrogen, phosphorus and ash contents within 49 different seaweed taxa, including seven different functional form groups. The mean tissue composition for each group is shown in Figure 1-13, while specific details regarding types of taxa, dates and sites of collections, tissue elemental composition and ratios, etc. are summarized in Table 1-7. The two calcareous crusts (Clathromorphum circumscriptum and Phymatolithon lenormandii) had very high carbon values, no doubt because of their tissue calcification. That is, CO 2 molecules resulted from dissolved calcium carbonate at the high temperature (1200 °C) within Carlo Erba Elemental Analyzer and registered by the recorder. Hence, the carbon data from these two taxa were excluded from calculations of mean values and other statistical evaluations. Overall the tissue carbon contents of the remaining 47 taxa were rather uniform, ranging from 32.43 to 46.17 millimoles per gram of ash-free dry weight (Fig. 1-12A) and the mean carbon contents within the seven groups were not significantly different (Fig. 1-13A). By contrast, tissue
11 nitrogen and phosphorus showed large variations between and within groups. Even so, only the mean values of tissue nitrogen were significantly different (p < 0.05). Table 1-8
summarizes multiple comparisons of these mean values. Overall, the highest nitrogen
values were recorded for crustose taxa (e.g. Phymatolithon lenormandii, Ralfsia bornetii
and Hildenbrandia rubra) and complex filamentous species (e.g.Chondria baileyana and
Lomentaria baileyana), while thick blades and coarsely branched plants showed the lowest contents (cf. Fig. 1-12B and Fig. 1-13B). Three taxa, including Phymatolithon
lenormandii (crust), Pilayella littoralis (uniseriate filament), and Desmarestia aculeata
(coarsely branched, Fig. 1 -12B) showed extremely high phosphorus contents. By contrast,
the mean value of tissue phosphorus for the other coarsely branched species was rather low
as compared to the other functional groups (Fig. 1-13B). Even so, these variations were
not significantly different (p > 0.05). The mean tissue C: N, C: P and N: P elemental ratios within seven functional form groups and within three seaweed divisions are summarized in Table 1-9, while the results of multiple comparisons of these ratios are given in Table I-10. Species within the thick bladed and coarsely branched groups had significantly (p < 0.05) higher C: N ratios than other functional form groups. Algae of complex filaments and crusts showed the highest mean C: P and N: P ratios, while thick blades had the lowest N: P ratio; even so these differences were not significant (p > 0.05, Table I-10). Phaeophycean species showed significantly higher C: N ratio than either Chlorophycean or Rhodophycean taxa. On the other hand, tissue N: P ratios within brown algae were lower than green and red algae, but these variations were not statistically significant. The mean ratios of tissue C: P within the three seaweed divisions were relatively uniform.
Effects of Different Seasons in 49 Seaweed Taxa Figure 1-14 and Table 1-11 illustrates the tissue carbon, nitrogen, phosphorus and ash contents of the 49 seaweed taxa according to their seasonal occurrence and collections. The mean values of these tissue components within each seasonal group are shown in Figure 1-15. Relatively large variations of tissue nitrogen and phosphorus were found both
12 between and within groups. By contrast, tissue carbon was relatively uniform, except for the two calcified species that were excluded for statistical purposes. The mean values of all three tissue components (i.e, CNP) showed the same pattern, being higher in winter and spring than during summer and fall. However, these differences were not statistically significant, as large within group variations occurred. Effects of Ice-Rafting in Several Seaweeds
The tissue carbon, nitrogen, phosphorus and ash contents of eight ice-rafted taxa
are shown in Figure 1-16. As with in situ samples, tissue carbon was rather constant,
ranging from 35.1 to 39.4 millimoles per gram or 42.1 to 47.3% based upon ash-free dry
weight. By contrast, pronounced differences in tissue nitrogen and phosphorus were
recorded. Overall, Palmariapalmata had the highest tissue nitrogen and phosphorus contents, resulting in the lowest C: N: P ratio (150: 20: 1). As Spartina alterniflora had
the lowest phosphorus concentration its C: P value was the highest (1491: 1). The N: P ratio in Ulva lactuca was the highest (90: 1), as it contained very high nitrogen and relatively low phosphorus. The mean C: N: P ratio for the eight ice-rafted plants was 792:
41: 1.
Long-term Correlation between Tissue and Ambient Nutrients Table 1-12 summarizes the tissue N: P ratios in 59 taxa based upon 428 samples collected at a variety of estuarine and open coast sites (see 1.2). Table 1-13 illustrates similar ratios for ambient nutrients based upon several long-term hydrographic studies described above (see 1.2). The mean ratio for the 59 taxa was about 29: 1, with a range of 5.6: 1 to 141.8: 1. By comparison, the mean N: P ratio for 560 water samples was 11:1, although it ranged from approximately 3: 1 to 90: 1. Thus, the differences between tissue and ambient N: P ratios were significant.
1.4 DISCUSSION
The mean tissue C: N: P ratio resulting from 420 samples of 59 in situ marine
13 macrophytes was 609: 29: 1 versus 792: 41: 1 for the 8 ice-rafted samples. Such results are similar to those of Atkinson and Smith (1983), who recorded a mean ratio of 700: 35: 1 for 92 marine macrophytes. Faganeli et al. (1986) also recorded comparable results for
Fucus virsoides (804: 58: 1) and Ulva rigida (579: 75: 1). By contrast, Lapointe (1987,
1989), while working with Florida populations of Gracilaria tikvahiae, recorded C: N: P ratios of 892-2694: 73-157: 1 during the winter versus 1098-2816: 93-250: 1 in summer.
My results confirm that C: N: P ratios in marine macrophytes differ significantly from marine phytoplankton (106: 16: 1 - see Redfieldet al., 1963). The higher C: N: P ratios in seaweeds than phytoplankton are probably due to their greater quantities of structural and stored carbon (Lewin, 1962; Lobban et al., 1985; Stewart, 1974). The average percentages of carbohydrate and protein in seaweeds are about 80 and 15% of ash free dry weight, respectively (Atkinson and Smith, 1983), whereas the generalized contents for phytoplankton are 35 and 50%, respectively (Lobban et al., 1985; Parsons et al., 1977)
Light intensity is a well known factor affecting the growth and tissue composition of seaweeds (Christeller and Laing, 1989; Lapointe et al., 1984). In the present study,
Gracilaria tikvahiae exhibited maximum growth at 61% full sunlight, while 11% sunlight was inadequate. The anomalous growth at 50% was probably caused by high numbers of the herbivorous amphipod, Hyale nilsonii (McBane and Croker, 1983). Interestingly, very strong negative correlations existed between the tissue components and growth rates of G. tikvahiae. However, only tissue phosphorus values were significantly different (p
< 0.05) under varying growth rates (Fig. 1-2 and Table 1-1). Thus, the ratios of tissue C:
N, C: P, and N: P in G. tikvahiae decreased with increasing growth rates. For example, the N: P ratio shifted from 40: 1 in the slowest growing plants to about 60: 1 in the fastest ones, suggesting that phosphorus was a critical factor limiting growth during the summer of 1988. Such results suggest that G. tikvahiae can store nutrients (nitrogen and phosphorus, particularly the latter) or endure less nutrient deficiency when growing slowly
14 under dim light. Similar trends have been reported by several investigators (Fricdlander et
al., 1987; Lapointe, 1981; Lapointe et al., 1984; Mann, 1972; Niell, 1976; Penniman and
Mathieson, 1987).
The tissue carbon contents within estuarine populations ofAscophyllum nodosum
and Fucus vesiculosus v. spiralis were quite uniform (Fig. 1-3), in spite of the values of
the latter taxa being significantly different (p < 0.05) between the eight sites. In addition,
significantly higher nitrogen and phosphorus values were recorded for both fucoid algae at
the 1-95 Bridge (5 miles inland), as well as at one or two other stations. A water quality
survey conducted near the 1-95 Bridge during the fall-winter of 1989 found substantial
inputs of inorganic nitrogen (mainly NO3) near North Mill Pond (Balsam, 1990). Other
historical data (Emerich-Penniman et al., 1985; Loder et al., 1983, Loder unpublished data, Norall and Mathieson, 1976; Norall et al., 1982) similarly documented maximum
nitrogen concentrations between the 1-95 and Dover Point Bridges (5 to 9 miles inland),
while soluble inorganic phosphorus varied from station to station with no generalized pattern. The correlation coefficients between ambient and tissue nitrogen in both fucoid
algae were moderate (i. e., 0.68 for A. nodosum and 0.43 for F. vesiculosus v. spiralis), while they were very poor (i.e. -0.33 and 0.16, respectively) for phosphorus.
The results described above suggest that the concentrations of ambient nutrients are not the only factor affecting macrophyte tissue composition, especially for phosphorus.
Water motion and the temporal lag between ambient and tissue nutrient levels are probably the most important factors influencing seaweed tissue composition. Water movement increases the availability of nutrients to marine macrophytes (Neushul, 1972; Norton et al., 1981; Wheeler and Neushul, 1981) just as wind enhances carbon dioxide availability
(Nobel, 1981). That is, tidal currents and wave action are the primary vectors transporting nutrients to algal surfaces. Assuming similar nutrient concentrations, currents will enhance nutrient availability to plants versus calm conditions. Fast water motion also reduces the boundary layer thickness over an alga, reducing resistance to nutrient uptake. Currents also
15 keep the surfaces of algae free of debris and epiphytic organisms. Even so, certain trade
offs are involved for seaweeds growing in rapid current environment, including reduced
surface/volume ratios (Koehl, 1986). Thus, maximum nutrient uptake and photosynthesis
for an alga can only be achieved under suitable water motion environments. The fact that
the currents near the 1-95 Bridge are much stronger than at the other seven study sites (cf.
Brown and Arrellano, 1979; Mathieson etal., 1977, 1983; Schmidt, 1980; Swenson et
al., 1977) may have contributed to significantly higher tissue nutrients at this site.
As outlined by Chapman and Craigie (1977) a lag between tissue and ambient
nutrient levels is to be expected, masking a close correspondence when plants and water
samples obtained at the same time. In other words, when an alga is transferred into a new
nutrient medium it takes a certain period to reach an equilibrium. The equilibrium period
may vary from minutes in unicellular phytoplankton (Blum, 1966) to days in seaweeds
(Lapointe and Ryther, 1979). As noted by Hardwick-Witman and Mathieson (1986) the
tissue nitrogen content of Ascophyllum nodosum coincided somewhat with ambient inorganic nitrogen, although a one month lag existed. It is well documented that dramatic temporal changes in nutrient concentrations may occur within the Great Bay Estuarine
System (Emerich-Penniman et al., 1985; Loder et al., 1983; Mathieson and Hehre,
1986; Norall and Mathieson, 1976; Norall etal., 1982), because of runoff from wastewater plants, overflows from combined sanitary and storm sewers, and various non point sources (Normandeau, 1973). In turn, the distribution of nutrients within the estuary is subjected to the mixing of fresh and salt water, with the process depending upon many factors, including tidal currents, waves and topography.
As outlined in Table 1-3, most of the variation of tissue composition within transplanted Ascophyllum nodosum and Fucus vesiculosus v. spiralis was caused by temporal and spatial changes or their interaction. However, each of these components played a different role in affecting tissue composition. Elevation (the spatial factor) had a
16 small (0.05 < P < 0.01) or non-significant effect except upon the phosphorus contents in both fucoid algae, plus the ash content in F. vesiculosus v. spiralis (P < 0.001, Tab. I-
3). Tissue carbon in A. nodosum showed limited variability, with the values being almost the same temporally and spadally (Fig 1-5). By contrast, very high levels of carbon were recorded for F. vesiculosus v. spiralis during July and August (Fig. 1-6). Both fucoid algae exhibited elevated nitrogen levels during early summer / late fall. Phosphorus levels were highest in plants grown near low tide levels. Overall, ambient N & P nutrients increased form June to November except for an ammonia peak recorded in July (Fig. 1-7).
Thus, the correlation coefficients for ambient and tissue N were only moderate in A. nodosum (0.61) and poor for P (-0.37 for A. nodosum and 0.14 for F. vesiculosus v. spiralis).
As noted earlier, rapid temporal changes and patchy distributional patterns of nutrients within the estuary may be partially responsible for the above described patterns.
Furthermore, other physical and biological factors may cause variations in ambient nutrients. For example, the fucoid plants transplanted to +1.60 m died after one or two months, as this elevation was beyond both of their tolerances to desiccation and high temperatures (Schonbeck and Norton, 1978, 1980). On the other hand, both fucoid algae became heavily epiphytized when transplanted to the subtidal zones (-0.19 and -0.46 m), particularlyF. vesiculosus v. spiralis. Epiphytes have both direct and indirect effects on fucoid tissue composition. One direct effect is a reduction of available nutrients
(Wallentinus, 1991), while an enhanced thickness of the boundary layer may also lower nutrient uptake efficiency of an alga. An indirect effect of epiphytes is shading, which greatly diminishes photosynthetic activity of the host plant It should be recalled that photosynthesis provides ATP and other energy-rich compounds for nutrient uptake and translocadon. In summary, the results from the fucoid transplant experiments support the hypothesis that the upper limits of seaweeds are governed by physiological stresses
17 associated with emersion, while lower boundaries are determined by biological competition and/or predation (Brown, 1987; Norton, 1986; Schonbeck and Norton, 1980; Zaneveld,
1969).
As noted previously, Ascophyllum nodosum exhibited significantly higher N & P contents in younger than older tissues, while its carbon levels were relatively constant
(Figs. 1-8; Tab. 1-4). Komfeldt (1982) recorded similar patterns for Fucus serratus, with higher nitrogen and phosphorus contents in apical than basal portions. However, Moss
(1948) found that total organic nitrogen was lower in distal (tips) than in proximal (basal) frond segments, probably because of different patterns of organic and total nitrogen content
(cf. Asare and Harlin,1983). A comparison of the tissue C, N & P constituents in seven fucoid taxa showed a pattern of uniform C and variable N & P contents. That is, the tissue nitrogen and phosphorus within vegetative portions were lower than in reproductive parts
(Fig. 1-9). Even so, not all of these variations were significantly different (Tab. 1-5).
Hence, C: N: P ratios in these fucoid algae were much higher within vegetative than reproductive portions. Fucoid algae concentrate nutrients in their receptacles as intensive cell divisions occur there, requiring large quantities of DNA, RNA, plus various enzymes.
Thus, fucoid receptacles are "sinks", as in some terrestrial grain-bearing plants (Latshaw and Miller, 1924; Stiles, 1969). Moss (1950) recorded a contrasting pattern of organic nitrogen in Fucus vesiculosus. That is, utilizing a fresh weight enumeration, she found higher percentages of protein in vegetative than fertile tips. However, if her data are converted to an ash-free dry calculation the opposite pattern is true, as receptacles have much higher amounts of water and ash than their vegetative tips.
The elevated nutrient levels within new and receptaclar tissues of fucoid algae suggests that nutrients may be actively translocated to these tissues. Several investigations have provided evidence for nutrient translocation within Lanunaria and other phaeophycean species (Floc’h and Penot, 1974; Lobban, 1978; Schmitz, 1981). For
18 example, up to 70% ofLaminaria' s nitrogen demand for meristematic growth is provided
by active transport from mature blades (Lobban et al., 1985). Velocities of nutrient
translocation in kelp can be as fast as 80 cm h ' 1 (Parker, 1965; Schmitz and Srivastava,
1979). By contrast, the process is much slower in fucoid algae (Floc'h and Penot, 1974).
A transfer of nutrients to actively growing tissues also occurs in higher plants. As higher
plant tissues (e.g. leaves) age they become a source, providing phosphorus and other
mobile elements to young active growing parts or "sinks" (Biddulph et al., 1958;
Weatherley, 1969). As fucoid algae may actively transfer nutrients from vegetative to
receptacular tissues, they may possess a more efficient uptake mechanism on their
reproductive than vegetative surfaces in order to meet the high demands for nutrients within
receptacles. Although there is evidence of nutrient movement between one part and another
in seaweeds (Schmitz, 1981) further experiments should evaluate the efficiency of nutrient
uptake within different parts.
High levels of nitrogen and phosphorus were recorded during mid-June within the
green, rapidly-growing photosynthedc tissues ofSpartina alterniflora and Zostera
marina, comparing the low levels of nutrients within their root/rhizome systems. Similar
patterns occur in terrestrial vascular plants, like com (Latshaw and Miller, 1924; Stiles,
1969). With respect to nutrient acquisition in the two halophytes studied, all (cordgrass) or
part (eelgrass) of the inorganic nutrients they utilize are taken up by their roots/rhizome and
subsequently transported to their shoots where diverse pigments and enzymes are located.
Aside from the two calcareous crustose species (Clathromorphum circumscriptum
and Phymatolithon lenormandii), the carbon contents within the other 47 species were relatively uniform - even though they represented seven different functional form groups.
Thus, most of seaweeds contained ~ 38 milimoles per gram (32.43 to 46.17) or about
45% ash-free dry weight. Such results contrast with those of Lapointe (1989) and Niell
(1976), who recorded dry weights o f-13 to -40%. The differences are probably due to varying ash contents. All of the CNP data in the present study are expressed as ash-free dry
19 weight values, while Lapointe and Niell used % dry weight. As shown in Figures 1-12, 1-
14 and Table 1-7, the ash content of different seaweed matter varies tremendously. For
example, the ash contents of Desmarestia viridis and Hildenbrandia rubra are only 5-
7%, while in a spongy plant likeCodium fragile subsp. tomentosoides it is more than
45% (Fig. 1-12).
As the C: N and C: P ratios in seaweeds reflect changes in tissue nitrogen or
phosphorus contents, then compositional data should be based upon ash-free dry weight
calculations. Using such a designation, the values of tissue nitrogen within the seven
functional groups showed significant differences (Figs. 1-12 & 1-13, Tab. 1-8). The
crustose group had the highest mean value, presumably because of the slow growth rates
for most species in this group. Thick bladed and coarsely branched taxa had the lowest
tissue nitrogen values as they possess the smallest surface area/volume (SA/V) ratios.
Some complex filamentous and opportunistic annuals (e.g.Chondria baileyana and
Lomentaria baileyana) showed very high nitrogen levels, even though they were collected during the summer. Overall, intermediate levels of nitrogen were found in most opportunistic forms, i.e, thin sheets, hollow tubes, and uniseriate filamentous forms. The values of tissue phosphorus for the seven functional form groups showed pronounced variations - both between and within groups (Figs. 1-12 and 1-13). Extremely high concentrations were recorded within Phymatolithon lenormandii, Pilayella littoralisand
Desmarestia aculeata. The coarsely branched group had a low mean value of phosphorus, while the other 6 groups showed no marked differences.
From the above information it is obvious that the nutrient status of an alga's tissues depends upon a variety of factors, including availability of ambient nutrients, as well as the plant's uptake efficiency, its storage potential, and utilization for growth. The temporal effects of nutrient availability are clearly shown in Figures 1-14 & 1-15, with a trend of higher nutrient levels during winter/spring months than the rest of a year. Similarly,
20 elevation (i.e. duration of submergence) may also influence nutrient availability in seaweeds. For example, Raifsia verrucosa was the only crustose species that showed low
levels of tissue nutrients. It often grows in tidepools, where limited water movement may reduce nutrient availability. The nutrient uptake efficiency of seaweeds is generally determined by their surface area/volume (SA/V) ratios (Rosenberg and Ramus, 1984;
Rosenberg et al., 1984). For example, the upper tide pool endemicFucus distichus subsp. distichus had the greatest SA/V ratio and the highest tissue N & P contents of the seven fucoid algae evaluated. Hence, F. distichus subsp. distichus also had the lowest
C: N: P ratios, being 492: 25: 1 for vegetative and 301: 22: 1 for reproductive (Fig. 1-9).
By contrast, F. distichus subsp. edentatus, which was one of the largest fucoid algae growing in the low intertidal - shallow subtidal zone, had a reduced SA/V ratio and the lowest tissue N & P levels. As a result its C: N: P ratios were much high, being 2173: 95:
1 for vegetative and 1285:60: 1 for reproductive portions, respectively. Another example is from the fucoid study of diverse estuarine populations. The tissue nitrogen and phosphorus contents within Ascophyllum nodosum were lower than those of Fucus vesiculosus v. spiralis at any given station, also because of the reduced SA/V ratios in the former than the latter species (Fig. 1-3). The critical role of surface area/volume ratios can also be seen in different functional form groups. Despite their collection during the late spring and summer, Palmaria palmata and Petalonia fascia had the highest SA/V ratios of the thick- bladed forms; therefore, they had elevated tissue N & P contents. By contrast, the thick- bladed shot-gun kelp (Agarum cribrosum), which was sampled during the winter, had much lower nutrient levels than other plants collected simultaneously. The same situation was evident for coarsely branched taxa like Ascophyllum nodosum as well as its detached ecad scoipioides, which were collected during the winter. That is, the tissue N & P contents in attached and detached Ascophyllum populations were among the lowest recorded; again they had very low SA/V ratios. Among the coarsely branched group the
21 most delicate alga evaluated was Ceramium rubrum; it had relatively high N & P
concentrations even though it was collected during the fall. The typical opportunistic
species (i.e. thin sheets, hollow tubes and uniseriate filaments) possessed large surface
area/volume ratios and were capable of efficient nutrient uptake, even under undetectable
ambient nutrient levels (Rosenberg and Ramus, 1984; Rosenberg et al., 1984). However,
their potential for nutrient storage is limited (Fujita, 1985). Another primary characteristics
of opportunistic algae is rapid growth, which requires high nutrient supplies (Littler, 1981;
Littler and Littler, 1980). Thus, such intermediate levels of tissue nutrients may result from rapid uptake and fast utilization, along with minimal storage. As compared to long-term
perennials, opportunistic annuals exhibited fast growth rates and short life histories, which make excessive nutrient storage less critical. From a ecological point of view, these species are probably best adapted to short-term nutrient pulses (Rosenberg et al., 1984), such as those found within the Great Bay Estuarine System (Daly and Mathieson, 1979; Daly et al., 1979).
Phymatolithon lenormandii, Pilayella littoralisand Desmarestia aculeata showed a conspicuous accumulation of phosphorus. Other investigators have recorded similar patterns forAsterionella (Mackereth, 1953), Chlorella (Scott, 1945), Euglena
(Blum, 1966) and some blue-green species (Stewart and Alexander, 1971), even under phosphate deficiency. Kuhl (1968) reported that the phosphorus content in P-deflcient
Chlorella increased - sixty times four hours after the addition of phosphate. The ability to accumulate a specific element is not related to a plant's functional form, nor any phylogenetic pattern. For example, with the two calcareous crustose species, the tissue P content in Clathromorphum circumscriptum was only one third of that in Phymatolithon lenormandii. Pilayella littoralis had 67 to 342% more P than other uniseriate filaments.
Similarly Desmarestia aculeata and D. viridis, although members of the same genus, had very different tissue N & P composition.
Niell (1976) and Lapointe (1989) reported higher C: N ratios in Phaeophycean than
22 Chlorophycean and Rhodophycean, which is supported by the results from this study
(Tables 1-9 and MO). Even so, functional form designations may be more useful for interpreting these ratios. That is, species within the thick bladed and coarsely branched groups, which primarily consisted of the majority of the Phaeophycean taxa, tended to have the highest tissue C: N ratios. Tissue C: N ratios within brown algae having different morphologies were generally low. For example,Elachista fucicola (complex filament),
Pilayella littoralis (uniseriate filament) and Ralfsia bornetii (crust) are opportunistic species (Mathieson and Hehre, 1982,1986; Shannon etal., 1988) with relatively high tissue nitrogen. Their correspondingly C: N ratios (7.8 - 8.9: 1) were among the lowest ones for all the seaweeds studied. By contrast, the C: N ratios within the perennial green and red algae, like Codium fragile subsp. tomentosoides and Devaleraea ramentaceum, were very high (17.5 - 20.4: 1), presumably because of their low surface area/volume ratios. Thus, we might predict relatively low C: N ratios in other delicate brown algae (e.g.
Ectocarpus), with higher ratios in heavily textured red and green algae (e.g. the red alga,
Ahnfeltia).
One complication of comparing species within different functional form groups is the extended sampling period involved - i. e. from November, 1987 to February, 1990.
Even so, each of the functional form groups is represented by plants collected at different seasons. Overall, the seasonal patterns of tissue nitrogen and phosphorus contents were, as expected, lowest in summer and highest during the winter / spring (Figs. 1-14 & 1-15), which is consistent with ambient nutrient levels (Emerich-Penniman et al., 1985; Loder et al., 1983). Similar results have been reported elsewhere (Asare and Harlin, 1983;
Chapman and Craigic, 1977; Chaumont, 1978; Penniman and Mathieson, 1987; Topinka and Robbins, 1976).
The mean C: N: P ratio for the eight ice-rafted samples was 792: 41:1, which is somewhat higher than for the 420 in situ samples (i.e., 609: 29: 1). The elevated C: N: P
23 ratio in the ice-rafted plants was chiefly due to low tissue nitrogen and phosphorus contents, especially the latter element in the cordgrass and eelgrass samples. By contrast to
the high levels of tissue nitrogen and phosphorus in actively growing leaves and
stems/sheath of Spartina alterniflora and Zostera marina, the same nutrients within the
ice-rafted materials decreased 30 & 81% within leaves and stems of S. alterniflora, respectively, versus 31% and 6 6 % decline within similar structures in Z. marina. By contrast, tissue carbon in both plants showed no marked changes. Thus, the C: N: P ratios
within the leaves and the stems or sheath of both halophytic taxa were quite low during the growing season but very high during the winter. For example, the mean ratio for leaves and stems of S. alterniflora during mid-June was 308: 14: 1 versus 1491: 47: 1 for the
ice-rafted samples. The roots/rhizomes of cordgrass and eelgrass function as storage organs, just as seeds, bulbs, corms, tubers and other kinds of reproductive bodies do in various flowering plants. As winter approaches mobile nutrients within assimilatory tissues are translocated into their roots for storage. Thus, both halophytic plants conserve considerable nutrients within subterranean rhizomes in order to re-initiate growth next spring (Stiles, 1969). By contrast, the patterns of seaweed tissue composition within ice- rafted and summer/fall samples were quite different, presumably because of variations in functional form groupings and growth strategies. For example, two of the three coarsely branched taxa {Ascophyllum nodosum and Fucus vesiculosus v. spiralis) showed little or no differences in tissue CNP and ash contents, while tissue N and P contents in the thick-bladed red alga, Palmaria palmata, were twice of its summer concentrations, while carbon was almost the same. By contrast, the tissue CNP and ash concentrations in ice- rafted specimens ofGracilaria tikvahiae (complex filament) showed a notable decrease versus summer materials utilized in the light experiment. Lastly, the tissue composition in the sheet-like green alga, Ulva lactuca, was approximately the same, except for a little decrease in phosphorus contents. Unfortunately, the above described patterns could not be
24 statistically confirmed, as no replicates were taken.
As outlined previously, the overall mean N: P ratio for the 59 taxa studied was about 29: 1 (Tab. 1-12), while long-term hydrographic data from the Great Bay Estuarine System showed a mean N: P ratio of about 11:1 (Tab. 1-13). Thus, the ambient N: P ratio is very close to Redfield's ratio (15: 1), while that of the macrophytes was nearly twice this value. In other words, the mean N: P ratio within macrophytes was almost three times as much as the surrounding water. Thus, the correlation between tissue and ambient N: P ratios was rather poor, except for a few dates (i.e. ambient N: P ratio = 31: 1 in December, 1988, Fig. 1-4). Based upon the above-described data, it would seem that the efficiency of phosphorus utilization by seaweeds is much higher than by phytoplankton. That is,
seaweeds integrate about 600 atoms of carbon and 30 atoms of nitrogen into their tissues for a single unit of phosphorus, while the pattern in phytoplankton is ~ 106 carbon and 16 nitrogen per phosphorus atom (Broeckerand Peng, 1982; Goldman etal., 1979; Redfield, 1958; Redfield etal., 1963). The above-described results suggest that nitrogen may be the most limiting element for estuarine macrophyte growth - i.e. by comparing the demand with supply. Similar conclusion can be reached from tissue C: N ratios of the macrophytes studied (Tabs. 1-7 &
1-9) as many marine biologists (DeBoer, 1981 ; Fredriksen and Rueness,1989; Lapointe,
1989; Niell, 1976) suggest that critical C: N ratios for seaweeds occur between 10: 1 and 15: 1. Higher C: N values indicate nitrogen deficiency and lower ones nitrogen storage. The mean C: N ratio from this study was -21:1, but it ranged from 7: 1 to 46: 1. Ryther & Dunstan (1971) and Smith (1984) suggest tissue N: P ratios may be another indicator for inferring nitrogen or phosphorus limitation. That is, when N: P ratios < 10: 1 nitrogen is limiting, while phosphorus is limiting when ratios are > 30: 1. The mean ratio of nitrogen to phosphorus from the 420in situ samples in this study was 29: 1, but the individual ratios ranged from 6 : 1 to 142: 1 (Tab. I-10). Such patterns suggest that phosphorus, rather than nitrogen, may be limiting the productivity of most species within the Great Bay
Estuarine System. Thus, contrary conclusions can be reached from different points of
25 view. More interestingly, several species (such as Agarum cribroswn, Ascophyllum nodosum ecad scorpioides, Enteromorpha intestinalis, and Ralfsia verrucosa, sea Table 1-9) appeared to be simultaneously limited by both N and P as their C: N > 15 and their N:
P > 30. Such a phenomenon must be rare if it exists at all (Lobban et al., 1985). Therefore, whether N or P limiting plant growth cannot be discriminated simply by tissue elemental ratio(s) without well-controlled experiments, as C: N and N: P ratios vary between species and within individual plants temporally. Furthermore, seaweeds are physiologically different from phytoplankton. The efficiency of nitrogen uptake in marine macrophytes may be higher than phosphate, and high tissue N contents may be maintained in spite of relatively low ambient concentration. Most importantly, the elemental composition of
marine macrophytes is affected by a variety of environmental and biological factors, including ambient nutrients. The most dependable method of determining elemental nutrient limitation involves controlled growth assays (i.e. culture studies) after enrichment with a specific element (Lapointe, 1989). Another method is to determine a plant's "critical internal nutrient concentration", which occurs when tissue nutrients fall just below those giving optimum growth. A 5 or 10% reduction in growth rate is generally chosen (see DeBoer, 1981). Employing such an approach, Hanisak (1979) found that ~2% nitrogen (in
dry matter) is a better indicator than C: N data when assessing N-limitation for Codium fragile. Similarly DeBoer (1981) states the critical nitrogen concentrations in Gracilaria foliifera (probably = G. tikvahiae) and Agardhiella subulata were between 1 .8 to 2.0%. The most direct method is probably to monitor changes in tissue N: P ratios when algae are cultivated under varying N: P ratios. In contrast to phytoplankton, no comparable experiments have been done for seaweeds, except the most recent work of Bjomsater and
Wheeler (1990). One of the major goals of Part II was to bridge this gap.
26 Table M : Student-Newman-Keul multiple comparisons of mean growth (% biomass increase/month) of Gracilaria tikvahiae under different light intensities, plus variations in mean tissue composition versus growth rates. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for growth and tissue composition are listed in order of increasing magnitude of corresponding mean values. Values underlined indicate that mean values for these conditions are not significantly different (p > 0.05).
A. Growth rale under different light intensities:
% Sunlight: J J 50 20 94 41 61
B . Tissue CNP and ash contents under different grovth rates:
Carbon - not significantly different (p >0.05) Nitrogen- not significantly different (p >0.05)
Phosphorus -
Growth Rates: 102.9 71.3 59.95 12.65 34.55 -13.5
Ash - not significantly different (p > 0.05)
27 I
Table 1-2: Student-Newman-Keul multiple comparisons of mean tissue composition withinAscophyllum nodosum and Fucus vesiculosus v. spiralis at eight different sites within the Great Bay Estuarine System. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for the different sites are listed in order of increasing magnitude of corresponding mean values. Sites underlined are not significantly different (p > 0.05).
A.. Tissue c,HP uvd ash contents vithin Ascophyllum nodosum at eight sites: Carbon - not significantly different (p >0.05) Nitrogen - Cedar Woodman Fort Fort Weeks Dover Adams 1-95 Point Point Constitution Stark Point Point Point Bridge
Phosphorus -
Woodman Cedar Fort Stark &. Dover Weeks Adams 1-95 Point Point Fort Constitution Point Point Point Bridge
Ash - Woodman Adams Cedar 1-95 Dover Weeks Fort Fort Point Point Point Bridge Point Point Constitution Stark
B. Tissue CM P and ash contents vithin Fucus vesiculosus v. spiroll's at eight sites .
Carbon - Woodman Adams Weeks Cedar Dover Fort Fort 1-95 Point Point Point Point Point Constitution Stark Bridge
Nitrogen - not significantly different (p > 0.05) Phosphorus - Dover Cedar Woodman Weeks Fort Adams Fort 1-95 Point Point Point Point Constitution Point Stark Bridge
Ash- Weeks Cedar Fort Woodman Adams Fort Dover 1-95 Point Point Stark Point Point Constitution Point Bridge
28 Table 1-3: Analysis of variance (ANOVA) table assessing tissue C, N, P and ash contents within Ascophyllum nodosum and Fucus vesiculosus v. spiralis versus time (July to November, 1987) and elevation (four tidal levels). A. Ascophyllum nodosum SyElement C arbon N itro g en
S o u rc e ^ ^ . d.f. M. S. F P d. f. M. S. F P elevation 3 7.02 3.27 * 3 0.0793 3.33 * temperate 4 7.83 3.64 * 4 0.8063 33.88 **# interaction 12 2.70 1.26 ns 12 0.1070 4.48 *# residual 40 2.15 40 0.0238 sNFlement P h o sp h o ru s Ash
Source d.f. M. S. F P d. f. M. S. FP elevation 3 0.0009 30.51 **« 3 2.749 2.63 ns temperate 4 0.00057 19.49 ••• 4 135.0 143.5 interaction 12 0.00023 7.63 *** 12 14.45 15.35 *** residual 40 0.00003 40 0.941 B. Fucus vesiculosus v. s p ir o /is *'vElement C arbon N itro g en
Source . d.f. M. S. F P d. f. M. S. FP elevation 3 3.24 0.87 ns 3 0.1313 2.46 ns temperate 4 39.28 10.52 4 4.0825 76.38 #*» interaction 12 15.59 4.18 tt# 12 0.3860 7.22 ### residual 40 3.73 40 0.0535 “VElement Phosphorus Ash
Source^n^ d.f. M. S. F P d. f. M. S. FP elevation 3 0.00193 29.74 *** 3 40.5 22.90 #*# temperate 4 0.00089 13.65 4 123.5 69.83 *«# interaction 12 0.00517 7.95 «## 12 60.95 34.46 #*# residual 40 0.00007 40 1.769 *** p< 0.001; ** o.ooi
0.05 d.f., degree of freedom; MS, mean squares, F,F-ratio
29 Table 1-4: Student-Newman-Keul multiple comparisons of mean tissue composition withinAscophyllum nodosum of different ages. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for the different years are listed in order of increasing magnitude of corresponding mean values. Years underlined are not significantly different (p > 0.05). A.. Carbon - wot significantly different (p > 0.05) B. Nityroten- Yearof tissue occurrence: 1984 1985 1986 1987 1983 1988
C. Phosphorus - Year of tissue occurrence: 1986 1987 1985 1984 1983 1988
D. Ash - Year of tissue occurrence: 1985 1983 1984 1986 1987 1988
30 Table 1-5: F values of ANOVA on tissue C, N, P and ash contents within vegetative and reproductive parts ot seven fucoid taxa. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt.
CARBON NITROGEN TAXA F P F P Ascophyllum nodosum 0.05 ns 62.94 *» Fucus distichus subsp. anceps 0.45 ns 7.1 1 ns F. distichus subsp. distichus 3.49 ns 167.3 *** F. distichus subsp. edentatus 0.16 ns 0.09 ns F. distichus subsp. evanescens 1.53 ns 2.12 ns F. spiralis 4.34 ns 0.03 ns F. vesiculosus v. spiralis 0.45 ns 6.39 ns
PHOSPHORUS ASH TAXA F P F P Ascophyllum nodosum 161.1 *** 90.72 **• Fucus distichus subsp. anceps 45.8 •* 7.37 ns F. distichus subsp. distichus 253.5 *»* 109.7 »** F. distichus subsp. edentatus 56.28 ** 0.13 ns F. distichus subsp. evanescens 23.22 *» 19.74 F. spiralis 2.90 ns 32.34 ** F. vesiculosus v. spiralis 26.81 *• 693.9 ft** *»* p< 0.001; ** 0.001
31 Table 1-6: Student-Newman-Keul multiple comparisons of mean tissue composition within the roots/rhizome, stems/sheath and leaves ofSpartina alterniflora and Zostera marina. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for the different parts are listed in order of increasing magnitude of corresponding mean values. Parts underlined are not significantly different (p > 0.05).
A. Tissue CNP and ash contents vithin Sportino olternfftoro
Carbon - not significantly different (p > 0.05) Nitrogen -
Part of plant: Roots Stems Leaves
Phosphorus - Part of plant: Roots Stems Leaves
Ash - not significantly different (p > 0.05)
B . Tissue CNP and ash contents vithin Zosterom ori/70 Carbon - not significantly different (p > 0.05)
Nitrogen -
Part of plant: Roots/Rhizome Leaves Sheath
Phosphorus - Part of plant: Roots /Rhizome Leaves Sheath
Ash - Part of plant: Roots/Rhizome Leaves Sheath
32 Table i-7: Date, location, tissue composition and elemental ratios of marine algal taxa collected for different functional form study.
functional Form Group Nama ol Taxa Data of Location of Ash _ c N P EiamanttJ Atomic Ratios and Taxa Coda Coliaaion Col* act ton 1%) (mmol/a ash traa dry wt) C/N CV fiP Group 1. t Clathromorphurt circumscriptum 2/10/90 Fort Stark 81.33 75.34 2 96 0.1428 25.5 527 6 20.7 C'uata 2 Hildanbrandia rubra 1 /9/90 Fori Stark 5 87 43.27 5 79 0 1080 7.5 400 6 53 6 3 Patrocalls cruanta 5 /2 9 /8 9 Fort Stark 22.51 37.25 4.31 0.1112 8.6 335 0 38 8 4 Phymatollthon lanormandll 2 /1 0 /8 9 Fort Stark 80.59 74.67 6.97 0.4046 '.0 7 184 6 17 2 5 Rallsia bornalll 12/18/89 tsias of Shoais 20.83 46.17 5 91 0 .0857 7.8 536 7 69.0 6 Ralfsla varrucosa 6/1 /89 Fort Constitution 16.63 40.51 2.09 0.0646 19.4 627.1 32 4 Group 2: 1 Agarum crtbrasum 1 2 /1 8 /8 7 Fort Stark 19.46 37.78 2.52 0 0831 15.0 598.7 39.9 Thick Bladts 2 Alana aacutanta 9/23/88 Islas of Shoais 20 14 35.76 1.67 0.1660 21.4 215.4 10.1 3 Laminaria digTaia HM9/87 Fort Stark 22.43 36 03 1.97 0 .1 26C 18.3 286.0 15.6 4 Laminaria iorglcrurik 9/23/88 Islas ot Shoals '8.06 3 7 43 1 11 0.1290 33.7 290 2 8 6 5 Laminaria saccharina 1 1 /1 9 /8 7 Fort Stark 28 47 35 39 1.68 0.17* 6 18.8 206.0 10.9 6 Paima'la paimata 9/23/88 Islas of SHon1* 16.22 38 98 2 29 0 .1247 1 7 0 312.6 18 4 7 Pataionia fascia 6 /1 /8 9 Fort C o rat union 17.04 39.66 2 67 0.1070 14 9 370 7 25.0 Group 3 1 Monostroma pjtchrum 4/26/86 Fort Stark '0.72 39.34 3.59 0.1155 11.0 34C.6 31.1 Thin Shaats 2 Porphyra minlaia 5/3W89 Fort Stark 24 37 40.22 3 62 0.1752 11 1 229 6 20 7 3 P. umbil'calis 11 /' 9/8 7 Fort Stark 10 03 36 99 3.68 0.1165 13.1 31 7.5 31,5 4 P. umbi!«calls f. aplphytica 5 /2 9 /6 9 Fort S'ark 11.91 40 91 4.98 0.1729 8.2 236.6 28.6 5 P'asioia stipitata 6/1/89 Fon Const lution 9.15 42.C< 3.32 0.1445 12.7 290.9 23. C 6 Diva iactuca 11 '1 9 /8 7 Fort Stark 12 92 3 7 66 4.22 0 1120 9 0 3 38.C 37.7 0 3 7 Ulvarla obscura 11/19/87 Fort Stork 12.43 38 26 4.15 0.1008 9 2 379 6 41.2 0 3 8 Ulvarla oxvsoarma 1 1 /2 5 /8 7 O vstar Rivsr 14 14 37.17 3 20 0.1514 11.8 245 5 21.1 G rojp 4 : 1 Oumontla contorta 4/15/66 Fort Stark 24 98 37 02 4.41 0.1626 6 4 227 7 27 1 Hollow Tubat 2 Entaronorpha Iniastinaiis 5/29/89 Fori Stark 98.98 40 95 2 36 0.0740 1 7.4 553.4 31 9 3 Enlaromorpha Ilnza 11/25/87 Oystar RKsr 18 53 39 47 4 54 0 1805 0.7 218.7 25 2 4 Enta'omorpha proltfora 12/17/87 Adams Point 19.49 36 53 4 47 0 2329 8 6 165.4 19 2 5 Scvtosiphon lomaniaria 7/12/88 Islas of Shoais 18.79 40.16 2.12 0.0771 18 9 520.9 27.5 Group 5: 1 Chaatomorpha Mnum 1 1 /1 9 /8 7 Fort S tark 21 29 37 87 3.42 0.0753 11.1 502.9 45 4 Unisariata Fllamanta 2 Chaatonorpha picquotlna 5/29/89 Fori Stark 14.56 37 48 3 40 0.0809 11.0 463 3 42 0 3 Ctadophora sarlcaa 4/26/89 Fort Stark 27.39 39.75 4.05 0.1026 9.8 387 4 39 5 4 Pllayalla llttoralls 5/26/89 Fcrt Stark 28.81 42 89 5 21 0.3326 8 2 129.0 15.7 5 Rhlzoclonlum tortuosum 7 (6 /8 8 Fori Stark 20.75 36 34 4.14 0 .1096 9.3 349 8 37 8 8 Spongomorpha spinascans 5/31/89 Fori Stark 38.14 42.26 4.53 0.1992 9 3 212 1 22.7 7 Urospora panicllliformis S /1 /8 9 Fort Constitution 16.69 36 95 2.94 0 .1318 12.6 260.3 22 3 jGroup 6: Bonnamafsonia hamllara 7 /8 /8 6 Fon Stark 2C.4 38.45 4.30 0.0303 8.9 1269 0 141.9 jcomplai Filamantt 2 Chondrla ballayana 7 '29/88 Adams Pcint 32.97 41.26 5.70 0.0913 7.2 451 9 62 4 3 Cystoclontum purpuraum 11/19/87 Fon Stark 27 01 32.43 4.13 0 .1723 7.9 188.2 24.0 4 Eiachista fuclcoia 5/26/69 Fon Siark 25.61 43.72 4.91 0 .2442 8 9 179.0 20.1 5 Lomaniaria banayana 7 /2 9 /9 8 Adams Point 70 62 38.03 5 39 0.1339 7 1 284 0 40.3 6 Polyslphonia lanosa 11/19/67 Fon Stark 18.1 36.51 3.91 0.0732 9.3 498.8 53.4 7 Polvsiphonia niarsscans 1 2 /8 /8 9 Adams Point 22 65 41.47 4.14 0.0772 10.0 537.2 53.6 Group 7: Ascophyllum nodosum 1 2 /1 6 /8 7 Cadar Point 17.05 16.69 0.99 0 0430 37.1 853.3 23.0 CoArsaty Bran chad 2 A nodosum scad 1 2 /1 8 67 Cadar Point 21.64 36 36 1.67 0.0511 21.8 7 '1 .9 32.7 3 Caramlum rubrum 1 1 /1 9 /8 7 Fon Stark 33.31 37.37 4.97 0 1434 7 5 260 6 34.7 4 Chondrus crispus 11/19/87 Fon Stark 19 19 33.11 3 34 0.1041 9 9 318.1 32.1 5 Codium fragila ssp tomantosoidas 9/28/88 Islas of Shoals 45 32 41.33 3.35 0.0796 12 3 519.2 42.1 6 Oasmarastia acuiaata 11/19/87 Fon Stark 17 8 37.13 1.79 0.3188 20.7 116 5 5.6 7 0. viridiS 5 /2 9 /8 9 Fon Stark 5 35 38 95 3 50 0 .1173 11. 332.1 29 8 6 Oevalaraaa ramantacaum 7 /1 2 /8 8 Islas of Shoais 20 53 37.33 1 83 0 .1033 20 4 361.4 17 7 i 9 Mastocarpus sialiaijs 11/19/8 7 Fon Stark 37.11 40 00 3.30 0.1210 12.1 330 6 27 3 I
Table 1-8: Student-Newman-Keul multiple comparisons of mean tissue composition within seaweeds of seven functional form groups. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. The values for the different groups are listed in order of increasing magnitude of corresponding mean values. Groups underlined are not significantly different (p > 0.05).
A. Carbon - not significantly diffemt (p > 0.05)
B. Nitrogen -
Thick Coarsely Hollov Thin Uniseriate Complex crusts Blades Branched Tubes Sheets Filaments Filaments
C. Phosphorus - not significantly diffemt (p >0.05) D. Ash - not significantly diffemt (p >0.05)
34 Table 1-9: Summary of mean tissue C: N, C: P and N: P ratios within seven functional form groups, as well as within three seaweed divisions.
A. Ratios within the seven functional form groups: G rouo f# of Taxa) C: N C: P N: P Crusts (6) mean ± s.d. 10.8±5.7* 474±130* 48.4±16.3 range: 7.5 - 19.4* 184 - 623* 17 - 69 Thick Blades (7) mean ± s.d 19.9±6.5 326±133 18.4±11.1 range: 15 - 43 206 - 500 8.6 - 40 Thin Sheets (8) mean ± s.d 10.4±1.5 297±55.5 29.4±7.5 range: 8.2 - 13 230 - 379 21 - 38 Hollow Tubes (5) mean ± s.d 12.4±5.3 337±185 26.2±4.6 range: 8.4 - 18.9 165 - 553 19 - 32 Uniseriate Filaments (7) mean ± s.d 10.2±1.5 332±134 32.2±11. range: 8.2 - 12.6 129 - 505 15 - 39 Complex Filaments (7) mean ± s.d 8.5±1.1 489±379 56.8±41. range: 7.2 - 10 179 - 1282 20 - 143 Coarsely Branched (9) mean ± s.d 17.0±9.2 423±232 27.2±10.7 range: 7.5 - 37.1 116 - 853 5.6 - 42 * with the exclusion of the 2 calcified crusts.
B. Ratios within the three algal divisions: Division (# of taxa) C: N C: P N: P Chlorophyta (15) mean ± s.d 10.9±2.3 350±119 32.1 ±9.1 range: 8.6 - 17.4 165 - 553 19 - 46 Rhodophyta (19) mean ± s.d 10.1±3.6* 384±243* 39.3±28.7 range: 7.1 - 20.4* 184 - 1282* 17 - 142 Phaeophyta (15) mean ± s.d 18.4±8.4 398±228 24.4±15.9 range: 7.8 - 37.1 116 - 853 5.6 - 69 * with the exclusion of the 2 calcified crusts.
35 Table 1-10: Student-Newman-Keul multiple comparisons of mean tissue C: N, C: P and N: P ratios within seven functional form groups,as well as within three seaweed divisions. The values for different groups or divisions are listed in order of increasing magnitude of corresponding mean values. Groups or divisions underlined are not significantly different (p > 0.05).
A. Ratios within seven functional form groups:
C: N Ratios: complex uniseriate thin crust hollow coarsely thick filament filament sheet tubes branched bladed
C: P Ratios: Not significantly different (p > 0.05).
N: P Ratios: Not significantly different (p > 0.05).
B. Ratios within three seaweed divisions:
C: N Ratios: Rhodophyta Chlorophyta Phaeophyta
C: P Ratios: Not significantly different (p > 0.05).
N: P Ratios: Not significantly different (p > 0.05).
36 Table 1*11: Date and location of marine algae regrouped into different seasons.
Season/Taxa Code Species Date Location SPRING 1 Chaetomorpha picquotina 5 /2 9 /8 9 Fort Stark (Apr.15-Jun.1) 2 Cladophora sericea 4/26/89 Fort Stark 3 Desmarestia viridis 5 /2 9 /8 9 Fort Stark 4 Dumontia contorla 4/1 5 /89 Fort Stark 5 Elachista fucicola 5 /2 6 /8 9 Fort Stark 6 Enteromorpha intestinalis 5 /2 9 /8 9 Fort Stark 7 Monostroma pulchrum 4 /2 6 /8 9 Fort Stark 8 Petalonia fascia 6/1/89 Fort Constitution 9 Petrocelis cruenta 5/29/89 Fort Stark 1 0 Pilayella littoralis 5 /2 6 /8 9 Fort Stark 1 1 Porphyra miniata 5 /3 1 /8 9 Fort Stark 1 2 P. umbilicalis f. epiphytica 5 /2 9 /8 9 Fort Stark 1 3 Prasiola stipitata 6 /1 /8 9 Fort Constitution 1 4 Ralfsia verrucosa 6 /1 /8 9 Fort Constitution 1 5 Spongomorpha spinescens 5/31/89 Fort Stark 1 6 Urospora penicilliformis 6 /1 /8 9 Fort Constitution SUfvtvtR 1 Alaria esculenta 9 /2 3 /8 8 Isles of Shoals (Jul.8-Sep.28) 2 Bonnemaisonia hamifera 7/8/88 Fort Stark 3 Chondria baileyana 7 /2 9 /8 8 Adams Point 4 Codium fragile ssp. tomentosoides 9 /2 8 /8 8 Isles of Shoals 5 Devaleraea ramentaceum 7/1 2/88 Isles of Shoals 6 Laminaria longicruris 9 /2 3 /8 8 Isles of Shoals 7 Lomentaria baileyana 7 /2 9 /8 8 Adams Point 8 Palmaria palmata 9 /2 3 /8 8 Isles of Shoals 9 Rhizoclonium tortuosum 7 /8 /8 8 Fort Stark 1 0 Scytosiphon lomentaria 7/1 2/88 Isles of Shoals FALL 1 Ceramium rubrum 1 1/1 9/87 Fort Stark (Nov.19-25) 2 Chaetomorpha linum 1 1/1 9/87 Fort Stark 3 Chondrus crispus 11/1 9/87 Fort Stark 4 Cystoclonium purpureum 1 1/1 9/87 Fort Stark 5 Desmarestia aculeata 1 1/1 9/87 Fort Stark 6 Enteromorpha linza 1 1/25/87 Oyster River 7 Laminaria digitata 1 1/1 9/87 Fort Stark 8 Laminaria saccharina 1 1/1 9/87 Fort Stark 9 Mastocarpus stellalus 1 1/1 9/87 Fort Stark 1 0 Polysiphonia lanosa 1 1/1 9/87 Fort Stark 1 1 Porphyra umbilicalis 1 1/1 9/87 Fort Stark 1 2 Ulva lactuca 1 1/1 9/87 Fort Stark 1 3 Ulvaria obscura 1 1/19 /87 Fort Stark 1 4 Ulvaria oxysperma 1 1/2 5/8 7 Oyster River WINTER 1 Agarum cribrasum 1 2 /1 8 /8 7 Fort Stark (Dec.18-Feb.10) 2 Ascophyllum nodosum 12 /1 8 /8 7 Cedar Point 3 A. nodosum ec a d 1 2 /18 /8 7 Cedar Point 4 Clathromorphum circumscriptum 2/1 0 /9 0 Fort Stark 5 Enteromorpha prolifora 1 2 /1 7 /8 7 Adams Point 6 Hildenbrandia rubra 1 /9 /9 0 Fort Stark 7 Phymatolithon lenormandii 2/1 0/89 Fort Stark 8 Polysiphonia nigrescens 1 2 /8 /8 9 Adams Point 9 Ralfsia bornetii 1 2 /1 8 /8 9 Isles of Shoals
37 Table 1-12: Summary of N: P atomic ratios in marine macrophytes collected during June, 1987 to February, 1990 from the Great Bay Estuarine System and the adjacent open coast of New Hampshire.
Taxa code Location Date/Duration • Samples N/P Range of N/P Reference Ot Adams Point Aug.-Sep., 1988 12 46.9 39.4-59.5 Fig.1-2 An different sites Dec. 17+18, 1988 24 25.1 21.6-28.6 Fig.1-3 Fvs different sites Dec. 17+18, 1988 24 22.4 19.4-24.9 Fig.1-3 An Adams Point June-Nov., 1987 69 24.0 14.2-37.7 Fig. 1-5 Fvs Adams Point June-Nov., 1987 66 24.6 14.7-45.3 Fig. 1-6 An Adams Point July 21,1988 18 34.4 28.2-42.6 Fig. 1-8 7 fucoids different sites Jul.,,88-Apr.,'89 42 37.5 20.0-95.0 Fig. 1-9 Sa Adams Point June 16+17,1987 9 13.9 13.3-14.2 Fig. 1-10 Zm Adams Point June 16+17,1987 9 17.9 17.3-19.5 Fig.1-11 49 algae different sites Nov.,‘87-Feb.,'90 147 32.5 5.6-141.8 Fig. 1-12 8 ice rafted Adams Point Mar. 12-16,1988 8 41.1 19.6-90.4 Fig. 1-16 Tot/Mean 428 29.3 5.6-141.8
The taxa codes are as follow: Gt - Gracilaria tikvahiae An - Ascophyllum nodosum Fvs - Fucus vesiculosus v. spiralis Sa - Spartina alterniflora Zm - Zostera marina
38 Table 1-13: Summary of N: P atomic ratios within ambient waters of multiple sites within the Great Bay Estuarine System.
Location Date/Duration t Samples N:P Ranee of N/P Data Source 7 different sites Jan. 1976-June ,1978 481 10.7 3.1-89.9 Loderetal, 1980 7 different sites Sep. 28, 1987 14 9.7 8.5-11.0 Loder et al, unpub 8 different sites Dec. 17&.18,1988 8 31.2 23.0-37.4 Fie 1-4 Adams Point Jun-Nov., 1988 6 10.9 8.3-16.9 Fie. 1-7 Adams Point July, 'S a -F e b .^ 65 10.7 4.8-26.0 J.E.L. unpub. TOTAL/MEAN 560 11.0 3.1-89.9
39 MAINE
GREAT BAY
PORTSMOUTH
NEW HAMPSHIRE ,Q
ATLANTIC OCEAN
42°5 5 -
70 55 70 45
Figure 1-1: Map of the Great Bay Estuarine System of New Hampshire- Maine, showing nine study sites. 1 - Isles of Shoals; 2 - Fort Stark; 3 - Fort Constitution; 4 - I-95 Bridge; 5 - Dover Point;6 - Cedar Point; 7 - Adams Point; 8 - Woodman Point; 9 - Weeks Point.
40 130 -I
100 - I It
1
-20 0 20 40 60 80 100 % of full Sunlight B. 65 □ carbon ♦ ash
5 5 -
* « -
| 3 5 - S
25 - i ------1------1---- 1------|------1------1 -20 20 40 60 80 100 120 Growth Rate (%/Month)
5 -| □ nitrogen ♦ phosphorus 1-0.15 4 -
3 - -0.10 ^ E 2 - E -0 .0 5 1
0 - r- —r~ —r~ — | — — i— — i— 0.00 -20 0 20 40 60 80 100 120 Growth Rate (X/Month)
Figure 1-2 : Growth (% biomass increase/month) ofGracilaria tikvahiae under different light intensities plus variations in the plant's tissue composition (C, ash, N & P) versus monthly growth. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt.
41 B. feooptyuum Fuous
2 .0-1
1 57 -
35 0.8 0 4 8 12 16 0 4 8 12 16 Miles from Coast Miles from Coast c. i ^ i — D. flfOBfnjIIM I . Funs 0.10 22 - |
0 .08 - 20 ■:
m 0 .0 6 - u a lit R 0 .0 4 - 42 i — ■— 1— 1— r 4 8 12 o 4 8 12 16 Miles from Coast Miles from Coast
Figure 1-3: Tissue C, H, P & ash content (+s.d.) vithin AscophyJh/m nodosum and Fucus vesiculosus v. s p fr o J is t from eight sites vithin the Great Bay Estuaiine System. Tissue C, H and P are expressed as mmol/g ash-free dry v t and ash as % dry vt. A. 18.0-1
■ N03 □ N02 ■ NH4
Ft Stk Ft Cons 1-95 Br Dovor Cedar Adams Woodm Weeks
B. 0 .6 -
0 .5 -
0 .4 - c
* 0 .3 - £ 0 .2 -
0.1 -
0 .0 - Ft Stk Ft Cons 1 -9 5 Br Dover Cedar Adams Woodm Weeks
S ta tio n
Figure 1*4 : Concentrations (^M) of surface water inorganic nitrogen (NO3 , NO2 & NH4 - N) and orthophosphate at eight sites within the Great Bay Estuarine System.
43 I—
r 3.0
'4 0
-20
"-o.o Jun 1 .60 Jun Jul 0.94 Aug 0.23 0.23 l/a . spP Oct t y / f Oct 0 1 9 > ' ° Nov -0.46 Noy -0.46 u r4 5
-0.05 -15 *
■-o.o Jun 1.60 Jun 1 .60
^ 0.94 Aug Aug 23 ^ Sep Oct XTP M U ) / Nov -0.46 Nov -0.46
Figure 1-5: Temporal and spatial variations of tissue C , N , P & ash contents withinAscophyllum nodosum populations transplanted to five elevations (-0.46 to +1.60 m) at Adams Point, Little Bay, New Hampshire. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. Each bar represents the mean of three replicates. r4.5
P3.0
-20 £
L-0.0 Jun 1.60 1.60 Jul 0.94 Aug 0.23 0.23 "V ' p 7 Oct Nov -0.46 Nov
CJ1 r0.15 D
1-0.10 ~ r i -0.05
0.0 ^0.0 Jun 1.60 1 .60 Jul y r 0.94 0.94 Aug Aug 0.23 0.23 ^
Oct Oct -0.46 ^ Nov
Figure 1-6: Temporal and spatial variations ol tissue C , N , P & ash contents withinFocus vesiculosus v. spiralis populations transplanted to live elevations (-0.46 to +1.60 m) at Adams Point, Little Bay, New Hampshire. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. Each bar represents the mean ol three replicates. A. 10.0 -I □ N02
B.
1 .0 - P 0 .
0 . 8 - r 4 0.6 -
£ 0 .4 -
0 .2 -
Ju l Aug S*p
Month
Figure 1-7: Concentrations (jiM) of surface water inorganic nitrogen (NO3, NO2 & NH4 - N) and orthophosphate during fucoid transplant studies at Adams Point, Little Bay, New Hampshire (June - November, 1987).
46 ■ carbon 0 ash
1983 1984 1985 1986 1987 1988 Tissue Age (Years)
H nitrogen E3 phosphorus (mmol/g) P P
1983 1984 1985 1986 1987 1988 Tissue Age (Years) Figure 1-8: Tissue C, ash, N & P contents (± s.d.) within Ascophyllum nodosum tissues of different ages. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt.
47 50 - Y*9#t«t 40 30 20 1B 10 O 0 - 3 - Fys 0.15 -i C 0 .0 5 - Fvs Plant Parts Figure 1-9: Tissue C, N, P & ash contents (± s.d.) within vegetative and reproductive parts of seven fucoid taxa. See Table I-5 for names of the taxa. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 48 H carbon root stom loaf Plant Parts B. H nitrogon 0 phosphorus P (mmol/g) P root stom loaf Plant Parts Figure 1-10: Tissue C, ash, N & P contents (± s.d.) within the roots, stems and leaves of Spartina alterniflora. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 49 carbon 0 ash root/rhizome sheath leaf Plant Parts B nitrogen 0 phosphorus u0.15 -0.10 0.05 (mmol/g) P P 0.0 0.00 xoot/rhizome sheath leaf Plant Parts Figure 1-11: Tissue C, ash, N & P contents (± s.d.) within the roots/rhizome, sheath and leaves of Zostera marina. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 50 carbon B ash 12 3 4 5 67 12345678 12345 1234567 thick blades thin sheets hollov tubes uxusenate complex filaments filaments coarsely branched 0.5 nitrogen □ phosphorus P P (mmol/g) til 12 3 4 5 6 ' 1 2 3 4 5 6 7 ' 1 2 3 4 5 6 7 8 ’ 1 2 3 4 5 1 2 3 4 5 67 12 3 4 5 6 7 12345678 9 crusts duck blades dun sheets hollov tubes uniseiiate complex filaments filaments coarsely branched Functional Form Groups Figure 1-12. Tissue C, ash, N& p contents (±s.d.) vithin individual seaveedtaxa from seven functional form groups. See Table 1-7 for names of the taxa, dates and sites of collections. Tissue C,N and P are expressed as mmol/g ash-free dry v t and ash as % dry vt. A. Carbon 0 ash crusts thick. thin hollov uniseriatr complex coarsely blades sheets tubes filaments filaments branched B. Nitrogen 0 Phosphorus 0.2 - 0.1 P P (mmol/9) 0.00 crusts thick thin hollov uniseriate complex coarsely blades sheets tubes filaments filaments branched Functional Form Groups Figure 1-13: Mean values of tissue C, ash, N & P contents (± s.d.) for seaweeds within seven different functional form groups. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 52 carbon B ash Sprint Summer Fall Winter nitrogen B phosphorus 1 2 3 4 5 e 7 M 10 11 U o H 6 K 1 2 3 4 5073$ 10 1 234 5 t7 8 $ 1 0 1112t3i4 1 2 3 4 5 * 7 8 $ Sprint Summer FaU Winter Seasons of Collection Fiture 1-14: Tissue C, ash, N & p contents (± s.d.) vithin seaveeds collected at different seasons. See Table 1-11 for names of the taxa, dates and sites of collections. Tissue C/N and P contents are expressed as mmol/g ash-free dry v t and ash as % dry vt. carbon 0 ash Spring Summer Fall V inter B. 8.0 n nitrogen phosphorus —i— - 0.20 - 0.15 0.10 P P (mmol/g) 0.00 Spring Summer Fall W inter Season of Collection Figure M 5: Mean values of tissue C, ash, N & P contents (± s.d.) within all seaweeds collected at different seasons. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 54 A. C m m ol/g A sh « 42 4 i e An Ans Fvs Gt Pp Sa U1 Zm B rO.3 e.o- mtrogon E3 phosphorus 6 .0 - IS>0 1 4 .0 - E X 2 .0 - 0 .0 - Taxa Figure 1-16: Tissue C, ash, N & P contents of eight ice rafted estuarine macrophytes collected at Adams Point, Little Bay, New Hampshire. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. Codes for species names are: An - Ascophyllum nodosum; Ans - A. nodosum ecad scorpioided; Fvs - Fucus vesiculosus v. spiralis; Gt - Gracilaria tikvahiae; Pp - Palmaria palmata; Sa - Spartina alterniflora; Ul - Ulva lactuca; Zm - Zostera marina; 55 PART II EFFECTS OF DIFFERENT N: P RATIOS IN CULTURE MEDIA UPON SEVERAL BIOCHEMICAL AND PHYSIOLOGICAL FEATURES OF SEAWEEDS 2.1 INTRODUCTION The effects of different N: P ratios in culture media upon various biochemical and physiological features of freshwater and marine phytoplankton have been extensively studied (Caperon, 1968; Droop, 1973, 1974; Goldman et al., 1979; Rhee, 1973, 1974 , 1978). By contrast, relatively few comparable studies have been conducted with seaweeds. Of the few studies conducted with marine macrophytes some positive correlations have been reported between nitrogen supply and growth, photosynthesis, chlorophyll and tissue nitrogen (Chapman etal., 1978; Lapointe, 1981; Lapointe and Ryther, 1979; Lapointe and Tenore, 1981; Penniman and Mathicson, 1987). Recently, the phycobiliprotein pigments in red algae have been suggested as being storage sites for nitrogen, besides their traditional role as accessory pigments (Birdet al., 1982; Hanisak, 1983; Lapointe, 1981; Ryther et al., 1981). That is, the concentrations of phycobiliproteins usually increase with increasing tissue nitrogen or with decreasing tissue C: N ratios. To date, virtually no data exist concerning the effects of different atomic N: P ratios in culture media upon these physiological features. Furthermore, and as outlined in the Part I, the correlation coefficients between algal tissue contents and ambient nutrients can range from moderate (0.68) to very poor (-0.37) as these tissues are subjected to various environmental and biological effects. Ultimately, an assessment of such interactions can only be delineated with experimental cultures utilizing well-controlled conditions. As the fucoid brown alga Ascophyllum nodosum and the agarophyte red alga Gracilaria tikvahiae are the two most abundant and economically important seaweeds within the Great Bay Estuary System, they were chosen for a series of culture experiments, with the following objectives; (1) To evaluate the effects of different N: P ratios in culture upon seaweed CNP tissue composition, plus selected physiologic?, features; 57 (2) To investigate the possible role(s) of phycobiliproteins in red algae as nitrogen "sinks" under varying N: P combinations. 2.2 MATERIALS AND METHODS Ascophyllum nodosum and Gracilaria tikvahiae represent different types of functional forms, with the former being a coarsely branched brown alga and the latter a complex filamentous red alga (Taylor, 1957). The maximum biomass of A. nodosum occurs within the mid-intertidal (Chock and Mathieson, 1983), while G. tikvahiae is most abundant within the shallow subddal (Penniman, 1983). At selected shallow subtidal sites within the Great Bay they may grow together. Samples for culture studies were collected at sites where they grew together. Samples were collected on October 10,1989, when the water temperature and salinity were 16 °C and~21%o, respectively. Specimens were immediately returned to Jackson Estuarine Laboratory where they were sorted into healthy specimens, cleaned of epiphytes, and transferred into cultures. Apical sections of Ascophyllum nodosum (5 to 8 cm) with one terminal bladder were utilized, while whole plants ofGracilaria tikvahiae were employed, except for their holdfasts. Filtered and autoclaved sea water was employed as a culture medium, being enriched with an ESS stock solutions (Penniman et al., 1986) having variable nitrate and phosphate concentrations. The sea water was collected near the Isles of Shoals on August 18,1989. It had a salinity of ~29 %o and low total nitrogen and phosphorus levels of 1.41 pM and 0.117 pM, respectively. Glycerophosphate in the ESS formula was replaced by sodium phosphate (monobasic). The following concentrations of nitrogen and phosphorus were employed in these culture experiments: controls with no N or P added but a supplement of vitamins and trace metals; an N-enrichment series with 5 pM P04 added plus supplements of 0,25, 50, 100 or 200 pM NO3 . The resulting N: P atomic ratios were 58 -0.3, 5, 10, 20 and 40. In the P-enrichment series, 200 pM NO3 was added plus supplements of 0, 5, 10, 20 or 40 pM PO4 , respectively. The resulting N: P ratios were -1700, 40, 20, 10, and 5, respectively. Pyrcx (100x80) jars were used for culture containers. That is, 200 ml of specific N and P supplements were transferred into each jar, along with 2.0 g ofAscophyllum nodosum or Gracilaria tikvahiae. A "starvation" period of 4 days in nutrient poor (summer) seawater was provided, prior to the onset of the experiment The plants were grown at 15 °C with a 14: 10 light - dark cycle, and a photon flux density of -60 pE s-'m- 2 provided by G-E cool white fluorescent lamps. The flasks were hand shaken once a day during the 120 day experiment while new media were provided every 5-10 days. At the end of the experiment the fresh weight of each plant sample was determined in order to calculate its growth (% biomass increase/month). Aside from growth, the net photosynthesis of algal materials utilized in each treatment was measured with a Gilson Differential Respirometer (Model GRP-14). Measurements were made at 60 pE n r2 s 1 and 15 °C. A diethanolamine solution was used to produce a 2% carbon dioxide atmosphere (Mathieson, 1965). A pretreatment of 30 minutes was provided for each sample, utilizing the same conditions described above. See Guo (1986) and Mathieson (1965) for further details regarding manometric procedures. All of the manometrie studies were conducted between 8 A.M. to 4 P.M. in order to avoid diel variations (Guo, 1986). Photosynthetic rates are expressed as pi 0 2 /mg chlorophyll a/min and piO^/g fresh wt/min. Tissue CNP contents were quantified as in Part I. The concentrations of chlorophyll a and £ inAscophyllum nodosum, plus the chlorophyll a and phycobiliprotein (phycocaynin, allophycocaynin and phycoerythrin) contents Gracilariain tikvahiae, were measured according to the procedures outlined by Jeffery & Humphrey (1975) and Siegelman & Kycia (1978). A Student-Newman-Keul's (SNK) multiple range test was used to evaluate statistical differences between the biochemical and physiological parameters evaluated. 59 Correlations (Pearson’s r) between these parameters and concentrations of nitrate or phosphate in the culture media were also calculated (Ary and Jacobs, 1976; Sokal and Rohlf, 1969). 2.3 RESULTS Growth Rates The growth of Ascophyllum nodosum and Gracilaria tikvahiae under various supplements of NO3 -N and PO4 -P is illustrated in Figures 2-1 to 2-4. In the N-enrichment experiment, both plants showed slow growth in control and zero 11M-NO3 (with 5 pM PO4 addition), while their growth rates were relatively constant in 25 to 200 pM NO3 (Figs. 2- 1,2-2). In the P-enrichment experiment, the growth of both plants was relatively uniform in all treatments, except for the reduced growth of the controls (Figs. 2-3, 2-4). Even so, none of the above described variations were significantly different (Tab. II-1, p = 0.05 level). Overall, the growth of both A. nodosum and G. tikvahiae was slow, being only 6-9%/month for the former and 4-6%/month for the latter. Net Photosynthesis Figures 2-5 to 2-8 summarize the net photosynthesis of Ascophyllum nodosum and Gracilaria tikvahiae under various enrichments of NO3 -N and PO4 -P, with the rates being expressed as both damp-dried weight and chlorophyll a content Ascophyllum exhibited a slight increase in net photosynthesis between 0-200 pM NO3 -N based upon damp-dried weight calculations; on the other hand, maximum and minimum photosynthesis were recorded at 50 and 100 pM NO3 , respectively, based upon chlorophylla determinations (Fig. 2-5). When enriched with PO4 -P the photosynthetic responses ofA. nodosum (damp-dried weight) were relatively uniform, except for the low rate of the control. On the other hand, the control samples exhibited maximum net photosynthesis (chlorophyll a), while minimal photosynthesis occurred at 40 pM PO4 -P ( Figs. 2-7). 60 None of Ascophyllum's photosynthetic rates were significantly different in the various nutrient supplements (Tab. II-1, p > 0.05). By contrast,Gracilaria exhibited enhanced photosynthesis with increasing NO3 -N levels (damp-dried weight and chlorophyll a), with the rates at 100 and 200 pM NO3 -N being much higher than the other treatments ( Fig. 2- 6 ). In the PO4 -P enrichment experiments Gracilaria's highest photosynthetic rates (damp- dried and chlorophyll a) were recorded at 5 and 40 pM, with controls being the lowest (Fig. 2-8). In contrast to A. nodosum, Gracilaria’s photosynthetic responses were significantly different (Tab. II-1, p < 0.05). Tissue CNP and Ash Contents The tissue CNP and ash contents within Ascophyllum nodosum and Gracilaria tikvahiae fragments grown under different NO3 -N and PO4 -P supplements were relatively constant (Figs. 2-9 to 2-12). Figure 2-13 illustrates the variations of tissue N: P ratios within these seaweeds grown in different N: P ratios. Ascophyllum's tissue carbon ranged from 38.9 to 40.9 mmol/g ash-free dry weight, with its ash content being 21.6 to 25.8% dry matter. By contrast, the same tissue components withinGracilaria varied from 34.7 to 40.0 mmol/g ash-free dry weight and from 26.4 to 30.3% dry matter, respectively. As shown in Table II-1 the tissue carbon and ash contents within both algae were not significantly different between the various N and P supplements, except for Ascophyllum's carbon content in various PO 4 -P enrichments. Ascophyllum's tissue nitrogen showed little variation between 0.0 and 50 pM NO3 (i.e. 0.3- 10 in N: P ratio); by contrast, substantial differences were evident between 100 and 200 pM (i.e. 20 and 40 in N; P ratio. Fig. 2-9). Gracilaria showed a similar pattern (Fig. 2-10), although its tissue nitrogen enhancement started at 50 pM (i.e. an N: P ratio of 10). With increasing PO4 -P supplements, the tissue phosphorus contents in both plants increased linearly ( Fig. 2-11 and 2-12). As shown in Figure 2-13, N uptake of these algae was most efficient when grown under low N: P ratios (limited N is available); conversely the uptake of P was most 61 I efficient when the plants were grown under high N: P ratios. It was calculated from the regression equations that both seaweeds would have the same N: P ratios with their culture media only when ambient N and P ratios were 15 or 16: 1 (Fig. 2-13). Despite such deviations, a relatively strong correlation existed between the N: P ratios within both plants and their culture media (i.e. Pearson’s r ranged from 0.79 to 0.94, Table II-1). Pigments The chlorophyll a and £ contents inAscophyllum nodosum fragments grown under various NO3 -N and PO4 -P levels are shown in Figures 2-14 and 2-16; similarly the chlorophyll a and phycobiliprotein levels inGracilaria tikvahiae under similar conditions are shown in Figures 2-15 and 2-17. Both plants exhibited increased chlorophyll a contents with increasing NO3 -N supplements. A similar pattern was evident for chlorophyll £ within A. nodosum, while under PO4 -P enrichment chlorophyll a in both plants and chlorophyll £ in A. nodosum were quite uniform, being higher than the controls (Figs. 2-16 and 2- 17). However, only the chlorophyll a contents in A. nodosum under different N- and P- enrichments were significant. The phycobiliprotein contents within G. tikvahiae showed a linear increase with enhanced NO3 -N (Fig. 2-15); the correlation coefficients were 0.85, 0.88 and 0.86 for phycocaynin, allophycocaynin and phycoerythrin, respectively (Tab. II- 1). By contrast, the same three phycobiliproteins dramatically decreased with increasing supplements of PO4 (Fig. 2-17). The same correlations between phycobiliprotein contents and PO4 levels were almost negatively perfect (Tab. II-1). 2.4 DISCUSSION As noted previously, the growth in culture of both Ascophyllum nodosum (6 - 9%/month) and Gracilaria tikvahiae (2-4%/month) was very slow as compared to "optimal" in situ growth during the spring or summer (cf. Mathiesonet al., 1976; Penniman et al., 1986). The slow growth in culture is not too surprising as these studies were conducted during the winter period of minimal growth, presumably caused by internal 62 seasonal rhythms and low ambient temperatures (Baardseth, 1970; Friedlander et al., 1987; Mathieson etal., 1976). For example, Normandeau Associates (1980) recorded minimal winter elongation rates (1-3 mm/month) for branch tips of A. nodosum growing near the Schiller Power Plant on the Piscataqua River versus much faster growth (i.e. 15- 25 mm/month) during the summer. Friedlander and co-workers (1987) also documented negligible winter growth for G. tikvahiae populations in Israel. It should be recalled that a relatively high temperature (15 °C) was employed for the culture studies, being near the optimal temperature forin situ growth during the spring (Mathiesonet al., 1976; Penniman and Mathieson, 1985). By contrast, in situ temperatures were as low as -2 °C during the period of the culture experiments. Such dramatic changes in temperature and intrinsic physiological and biochemical features may have minimized plant growth in culture. Depending upon the basis of calculation, the net photosynthesis ofAscophyllum nodosum (Fig. 2-5, 2-7, 2-13 and 2-15) cither increased slightly with enhanced nutrients (wet weight basis) or exhibited the opposite pattern (chlorophylla). Even so, these variations were not significantly different (p > 0.05). Gracilaria tikvahiae exhibited significantly higher photosynthetic rates between 100 and 200 jiM of NO3 -N (Fig. 2-6, Table II-1), whether based upon wet weight or chlorophyll a- On the other hand, Gracilaria exhibited an irregular photosynthetic pattern under different PO4 -P enrichments (Fig. 2-8). The winter photosynthetic rates for A. nodosum recorded here were higher than those recorded by Chock and Mathieson (1979); such differences may be associated with the 2% CO2 supplement provided in the present study (see section 2.2), but not by Chock and Mathieson (1979). By contrast, the winter photosynthetic rates for G. tikvahiae were comparable to those reported by Penniman and Mathieson (1985), who also employed a2% CO2 supplement. The growth in culture of Gracilaria tikvahiae did not parallel its net photosynthetic 63 responses under varying N or P concentrations, particularly with different N enrichments. That is, the plant's growth was not significantly different in various nitrogen levels, while its net photosynthesis increased dramatically with increasing NO3 -N concentrations (p < 0.001 and n= 0.99, Table II-1, Fig. 2-2 and 2-6). It should be recalled that growth is the summation of many metabolic processes and cannot be solely equated with short-term photosynthesis/respiration data (Lapointe, 1981; Merrill and Waaland, 1979). Furthermore, high concentrations of nitrogen may elevate the photosynthetic capacity in some seaweeds (Chapman et al., 1978; Lapointe and Tenore, 1981). The tissue carbon and ash contents within Ascophyllum fragments grown under different N- and P-enrichments were relatively constant, with the values being comparable to those recorded earlier during transplants experiments (see Part I). By contrast, the levels of tissue carbon within Gracilaria were conspicuously lower than those observed during the outdoor mesocosm experiments (see Part I). Such differences may be due to the varying nutrient status of the plants, with those in the mesocosms being under nutrient stress because of their very fast growth and low ambient nutrients. Several investigators (DeBoer, 1979, 1981; Healey, 1973; Neish and Shacklock, 1971; Neish eta l. , 1977) have described the accumulation of carbon compounds in seaweeds under nutrient limitations, particularly with nitrogen deficiency. The relatively constant tissue carbon contents for both species during cultivation is consistent with the data described earlier (see Figs. 1-2, 1-3, 1-5, 1-6, 1-8, 1-9 & 1-12). Marked changes in the tissue nitrogen contents of Ascophyllum and Gracilaria were observed in culture after a "critical level" of 50-100 p.M NO 3 -N with the former and 25-50 |i.M NO3 -N in the latter. Below these concentrations the tissue nitrogen values showed little changes, while dramatic increases occurred at higher levels ( Fig. 2-9 and 2- 10). The varying "critical levels" for the two species are probably due to their different surface area/volume (i.e. SA/V) ratios (cf. Littler and Littler, 1980; Rosenberg, 1984). It should be recalled that Ascophyllum is a coarsely branched plant with a smaller SA/V ratio 64 than that of Gracilaria - a complex filamentous alga. By contrast to tissue nitrogen, the phosphorus contents within both plants increased with increasing PO4 -P supplements (Fig. 2-11 and 2-12). Despite the relatively strong correlations between tissue N: P ratios and nutrient supplements (Pearson's r values ranging from 0.79 to 0.94), the tissue N: P ratios were primarily determined by their physiological features and were only slightly affected by the N: P ratios in the culture media. Based upon regression equations the theoretical N: P ratios for both Ascophyllum and Gracilaria appear to be about 15 - 16: 1. When N: P ratios in a culture medium are below these values seaweeds tend to absorb N efficiently, while the uptake efficiency for P is enhanced if they are higher than such values. Thus, the N & P uptake behavior of seaweeds is similar to phytoplankton (cf. Droop, 1974; Goldman et al., 1979; Redfield, 1958; Redfield etal., 1963). The values of chlorophyll a in both Ascophyllum and Gracilaria, plus the chlorophyll £ contents in the former species, increased somewhat with increasing nitrogen levels (Figs. 2-14 and 2-15). Chapman et al. (1978) and DeBoer (1981) have reported similar positive correlations between chlorophyll and nitrogen supplement. By contrast, the chlorophyll contents in both plants studied here were relatively uniform under various phosphorus supplements (Fig. 2-16 and 2-17). The phycobiliprotein contents in Gracilaria showed an analogous pattern to chlorophyll a inAscophyllum, increasing proportionally with NO3 -N supplements. As the PO4 -P concentration in the nitrogen enrichment series was identical (i.e. 5 pM), the enhancement of NO3 -N levels caused a corresponding increased in the N: P ratios. Phycobiliproteins play a dual role, providing nitrogen storage and being accessory photon receptors (Bird et al., 1982; Lapointe, 1981; Penniman and Mathieson, 1987; Ryther et al., 1981). Several investigators have recorded similar "dual" roles for phycobiliprotein in various red algae (cf. Calabrese and Felicili, 1970; DeBoer and Ryther, 1977; Healey, 1973; Lapointe and Tenore, 1981). In contrast to the N-cnrichment experiment, the phycobiliprotein pigments showed a dramatic decrease with PO4 -P enhancements; in fact these correlations were almost negatively perfect ( Fig. 2-17 and Table II-1). Supplements 65 of PO4-P also caused reduced N: P ratios, as 200 pM NO3-N was provided in all treatments. The present study suggests that phycobiliproteins are positively related to N: P ratios in their surrounding solution, rather than to nitrogen levels alone. In other words, elevated phycobiliprotein levels indicate high N: P ratios in ambient media, as well as possible P-limitations. After P supplementation some phycobilin pigments are converted into other molecules, resulting in reduced pigment contents. For example, the phycobiliprotein contents decreased nearly 20% when P increased from 20 to 40 pM (i.e. the N: P ratios changed from 10 to 5). 66 Table 11-1: Correlations and F values on selected physiological and biochemical characteristics of Ascophyllum nodosum and Gracilaria tikvahiae grown under different supplements of NOa-N or PO4-P. Physiological / B iochemical Nutrient A. nodosum G. tikvnfo iae Features Measured Enriched F P RF PR Orovth N03 0.84 ns 0.48 1.77 ns 0.82 Grovth P04 0.70 ns 0.51 2.39 ns 0.55 NetP.S. (txl02/e vetvt/min) N03 2.59 ns 19.9 *** 0.99 Net P. S. (vl02lg vetvt/min) P04 1.30 ns 0.21 8.06 ** 0.52 Net P. S. (pi 02/me chi a/min) N03 0.40 ns -0.43 12.4 *** 0.99 Net P. S. (pi 02/me chi a/min) P04 1.64 ns -0.81 7.74 ** 0.49 Tissue Carbon N03 1.84 ns 0.75 1.29 ns 0.57 Tissue Carbon P04 10.7 *+* 0.33 2.08 ns 0.21 Tissue Nitroeen N03 13.6 *** 0.96 10.7 *+* 0.99 Tissue Nitxoeen P04 3.80 * 0.50 14.6 +++ 0.54 Tissue Phosphorus N03 6.98 ** 0.16 2.80 ns 0.43 Tissue Phosphorus P04 132.2 +*+ 1.00 73.1 ++* 0.93 Ash Content N03 1.45 ns 0.50 0.34 ns 0.47 Ash Content P04 1.82 ns 0.76 0.65 ns 0.75 Chlorophyll a N03 10.3 +** 0.77 1.92 ns 0.92 Chlorophyll a P04 4.69 * 0.65 1.31 ns 0.32 Chlorophyll c N03 2.14 ns 0.56 n/a n/a n/a Chlorophylla P04 2.60 ns 0.75 n/a n/a. n/a Phycocaynin N03 n/a n/a n/a 19.1 ++* 0.85 Phycocaynin P04 n/a n/a n/a 14.1 *** -1.00 AUophycocaynin N03 n/a n/a n/a 16.1 +++ 0.88 Allophycocaynin P04 n/a n/a n/a 23.8 *** -0.97 Phycoerythrin N03 n/a n/a n/a 16.4 *++ 0.86 Phycoerythrin P04 n/a n/a n/a 15.7 *** -0.95 N/P Ratios N03 44.0 +*+ 0.79 13.7 *++ 0.94 *+* N/P Ratios P04 61.5 *** 0.85 39.1 0.87 F, F-ratio; *** p < 0.001; ♦+ 0.001 < p < 0.01; * 0.05 < P < 0.01; ns, p > 0.05 n/a, not applicable 67 N 0 3 (IIM) Added Figure 2-1: Growth (biomass increase/month, ± s.d.) ofAscophyllum nodosum under different supplements of NO3 -N. Neither NO 3 -N nor PO4 -P were added to the control, while 5 jiM PO4 -P was provided for each treatments. C 0 25 50 100 200 N 0 3 (iiM) Added Figure 2-2: Growth (biomass increase/month, ± s.d.) of Gracilaria tikvahiae under different supplements of NO3 -N. Neither NO 3 -N nor PO4-P were added tc the control, while 5 pM PO4 -P was provided for each treatments. 69 C 0 5 10 20 40 P04 friM) Added Figure 2-3: Growth (biomass increase/month,± s.d.) of Ascophyllum nodosum under different supplements of PO4 -P. Neither NO 3 -N nor PO4 -P were added to the control, while 200 jaM NO3 -N was provided for each treatments. 70 I C 0 5 10 20 40 P04 (nM) Added Figure 2-4: Growth (biomass increase/month, ± s.d.) ofGracilaria tikvahiae under different supplements of PO4-P- Neither NO 3 -N nor PO4-P were added to the control, while 200 nM NO3 -N was provided for each treatments. 71 A. 20 n e i 5 1 ,0 N o * o C 0 25 50 100 200 B. 24 C 0 25 50 100 200 NO3 (|tM) Added Figure 2-5: Net photosynthesis ofAscophyllum nodosum grown under different supplements of NO3 -N- Neither NO 3 -N nor PO4 -P were added to the control, while 5 pM PO4 -P was provided for each treatments. The rates of net photosynthesis are expressed as both p i (ty g damp-dried wt/minute (± s.d.) and pi 0 2 /mg chi a/minute (± s.d.). 72 e I I C 0 25 50 100 200 C 0 25 50 100 200 NOs (Jin) Added Figure 2-6: Net photosynthesis ofGracilaria tikvahiae grown under different supplements of NO3-N. Neither NO3-N nor PO4-P were added to the control, while 5 11M PO4-P was provided for each treatments. The rates of net photosynthesis are expressed as both ^1 02/g damp-dried wt/minute (± s.d.) and jj.1 02/mg chi a/minute (± s.d.). 73 I A. 18 -i C 0 5 10 20 40 24- i C 0 5 10 20 40 P04 (Jin) Added Figure 2-7: Net photosynthesis ofAscophyllum nodosum grown under different supplements of PO4-P. Neither NO3-N nor PO4-P were added to the control, while 200 pM NO3-N was provided for each treatments. The rates of net photosynthesis are expressed as both jil 02/g damp-dried wt/minute (± s.d.) and ^1 02/mg chi a/minute (± s.d.). 74 I e 6.0 I v . 5 ^ 4.0 ? N e 13 2.0 0.0 C 0 5 10 20 40 B. 30 -i C 0 5 10 20 40 P04(jin) Added Figure 2-8 : Net photosynthesis ofGracilaria tikvahiae grown under different supplements of PO4-P. Neither NO3-N nor PO4-P were added to the control, while 200 |iM NO3-N was provided for each treatments. The rates of net photosynthesis are expressed as both ^1 02/g damp-dried wt/minute (± s.d.) and p.1 02/mg chi a/minute (± s.d.). 75 I ■ Carbon B 3.0 Nitrogan 0 Phosphorus rO.IO 0.075 O 2 .0 0.05 1 . 0 - P (m m ol/g) -0.025 0.0 **-4-0.00 0 25 50 100 200 N03 (|1M) Added Figure 2-9 : Tissue C, ash, N & P contents (± s.d.) withinAscophyllum nodosum fragments grown under different supplements of NO3-N. Neither NO3-N nor PO4-P were added to the control, while 5 nM PO4-P was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 76 H Carbon B. N (mmol/g) E2 Phosphorus 4.5-1 rO.15 o 3.0 - - 0.10 I C 1.5- -0.05 P (m m ol/g) 0.0 0.00 25 50 100 200 NOs (uM) Added Figure 2-10: Tissue C, ash, N & P contents (± s.d.) withinGracilaria tikvahiae fragments grown under different supplements of NO3-N. Neither NO3-N nor PO4-P were added to the control, while 5 PO4-P was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 77 I Carbon E2 ash u 10 - 100 200 B. 12.0 i r0.4 Nitro^on 0 Phosphorus 9.0 6.0 3 .0 ■ ■ 0.0 C 0 3 10 P 0 4 OiM) Added Figure 2-11: Tissue C, ash, N & P contents (± s.d.) withinAscophyllum nodosum fragments grown under different supplements of PO4-P. Neither NO3-N nor PO4-P were added to the control, while 200 jiM NO3-N was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 78 A. 50 1 ■ Carbon 0 45h C 0 S 10 20 40 B. B Nitrogon 0 Phosphorus (mmol/g) P P POs (|iM) Added Figure 2-12: Tissue C, ash, N & P contents (± s.d.) withinGracilaria tikvahiae fragments grown under different supplements of P0 4 -P. Neither NO3-N nor PO4-P were added to the control, while 200 pM NO3-N was provided for each treatments. Tissue C, N and P contents are expressed as mmol/g ash-free dry wt and ash as % dry wt. 79 Figure Figure A TISSUE N:P RATIO TISSUE N:P RATIO nodosum Ascophyllum Gracilaria tikvahiae Gracilaria rwh media. growth nodosum 2 - 20 - 30 0 - 30 40 - 40 -I 50 10 10 13 - - : A plot of tissue N: P ratios within fragments of of fragments within ratios P N: tissue of plot A : -3 0 0 and rclra tikvahiae Gracilaria 10 10 =9. +0. ‘ =0. 2 2 .8 0 = R‘2 x 2 0 9 6 .3 0 + 2 6 1 .3 9 = y 3 8 5 0 - R*2 5x 1 4 6 .4 0 + 6 2 1 .4 8 - y MEDIUM RATIO N:P MEDIUM RATIO N:P 20 20 80 versus the N: P ratios of their their of ratios P N: the versus 30 30 40 40 Ascophyllum 1700 1700 Figure Figure Chi a (mj/g vet v t ) a poie fr ah treatments. each for provided was of fragments NO3-N. Neither NO3-N nor nor NO3-N Neither NO3-N. 0.0 0.2 4 - .4 0 0 0 1 0 -i1 0 . . 6 8 2 - - - 14 : Chlorophyll a and c contents (mg/g damp-dried wt, ± s.d.) within within s.d.) ± wt, damp-dried (mg/g contents c and a Chlorophyll : sohlu nodosum Ascophyllum 2 50 100 0 5 25 0 PO4-P NOs (|iM) Added (|iM) NOs h a Chi 81 were added to the control, while while control, the to added were grown under different supplements of of supplements different under grown ic h C 0 200 5 jaM 0. 4 .0 -0 - . 8 0.0 0.00 0.12 0.20 0.16 PO4-P Chl c (mg/g vet v t ) Figure Figure CM • and Biliproteins (mg/9 wet v t) contents (mg/g damp-dried wt, ± s.d.) within fragments of of fragments within s.d.) ± wt, damp-dried (mg/g contents raments. treatm PO tikvahiae 0.00 24- 4 .2 0 0.36-1 4 2 -P - 15 were added to the control, while while control, the to added were : Chlorophyll a, phycocaynin, allophycocaynin and phycoerythrin phycoerythrin and allophycocaynin phycocaynin, a, Chlorophyll : rw udr ifrn splmns f O-. ete N3N nor NO3-N Neither NO3-N. of supplements different under grown 0 0 200 2 100 0 5 5 2 0 C h APC ■ a Chi ■ N03 N03 82 PC ( jin ) ) jin ( 5 i O- ws rvdd o each for provided was PO4-P jiM Added Gracilaria Figure Figure Chi i (mg/g vet v t ) fragments of of fragments O- ws rvdd o ec treatments. each for provided was NO3-N PO4-P. Neither NO3-N nor PO4-P were added to the control, while while control, the to added were PO4-P nor NO3-N Neither PO4-P. 0.00 - 5 .2 0 0.50 - 0.75 1.00 -i 1.25 2 - - 16 : Chlorophyll a and c contents (mg/g damp-dried wt, ± s.d.) within within s.d.) ± wt, damp-dried (mg/g contents c and a Chlorophyll : sohlu nodosum Ascophyllum 5 10 5 0 P 0 4 (jiM) added (jiM) 4 0 P 83 rw udr ifrn splmns of supplements different under grown hic ch 0 200 i jiM .25 0 r -0.05 - -0.15 - 0.20 0.00 0.10 Chi c (mg/g vet v t ) ■ Chli 1 PC ■ APC 0 PE C 0 5 10 20 40 P04 (jiM) Added Figure 2-17: Chlorophyll a, phycocaynin, allophycocaynin and phycoerythrin contents (mg/g damp-dried wt, ± s.d.) within fragments of Gracilaria likvahiae grown under different supplements of PO4-P. Neither NO3-N nor PO4-P were added to the control, while 200 |iM NO3-N was provided for each treatments. 84 LIST OF REFERENCES Ary, D. and L. C. Jacobs. 1976. Introduction to statistics - purposes and procedures. Holt, Rinehart and Winston. 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