A muscoides-like Fucus from a Maine salt marsh: Its origin, ecology, and taxonomic implications

30 Pages·2001·13.5 MB·English

by  A C Mathieson

RHODORA,
Vol. 103, No. 914, 72-201. 2001
pp.
1
FROM
A MUSCOIDES-LIKE FUCUS A MAINE SALT
AND
MARSH: ECOLOGY,
ORIGIN,
ITS
TAXONOMIC
IMPLICATIONS
Arthur and Clinton Dawes
C. Mathii;son' 2
J.
Department of Planl Biology and Jackson Kstuarine Laboratory,
New NH
University Hampshire. Durham, 03824
oi'
'e-mail: arthurO^ hopper.unh.edu; 2e-mail:cdawes@chumal .cas.usr.edu
abstract. The morphology and habitat dwarf moss-like or nuiscoi-
o\' a
des-like fucoid brown alua were studied in the Brave Boat Harbor sail marsh
of York-Kittery, Maine, U.S.A. using transect studies and transplant experi-
ments. The plant, which lacks a holdfast, forms a dense embedded turf
amongst
sparse Spartina patois populations the high marsh, particularly
in
on well-drained sandy sediments near the Harbor's mouth. The plant's di-
chotomously branched were
fronds smaller than those previously reported
for
mm mm
=
muscoides-like populations from Europe (mean 13.2 long,
1.1
wide, and 0.1 g damp-dried weight), while they had a similar dominance oi
marginal hair pits or cryptostomata. Transplantation in situ Fucus spiralis
o\'
from the lower to the upper marsh resulted in enhanced fragmentation, stunt-
ing, proliferation, and reduced reproduction. Reciprocal transplantation of the
muscoides-like Fucus from upper lower elevations caused enhanced frond
to
length and proliferation. Based upon detailed transplant and morphological
we
studies, conclude that the muscoides-like Fucus plants from Brave Boat
Harbor represent a phenotypic variant of F. spiralis, caused by detachment,
extensive proliferation, and subsequent degeneration detached fragments.
oi'
The plant's dwarf morphology primarily linked to a series unique en-
is o\'
vironmental conditions (desiccation and low nutrients), plus the type
o\' at-
tached parental material available. Thus, the dwarf muscoides-like Fucus
in
some may
luii'ope and Northwest Atlantic sites be derived from F. vesieu-
An
while Brave Boat Harbor
losus, in the parental material F. spiralis.
is
analogous pattern also evident between Ascophyllum nodosum and de-
is its
tached ecad scorpioides, with the presence of dwarf specimens and the oc-
currence of conspicuous morphological continuum between two
a the plants.
Key Words: Brave Boat Harbor Maine, ecad ecologv. fucoid
alizae. salt
marsh seaweed development, taxonomy
algae,
common
Seaweeds
that lack holdfasts (free-living) are through-
embay men
out the world, particularly within protected
salt
ts,
marshes, and estuaries (Norton and Mathieson 1983). The tem-
perate North Atlantic fucoid genera Ascophyllum and Fucus con-
tain several free-living marsh plants (Baker and Bohling
salt
which
1916; Fritsch 1945; Niell 1980), can contribute major
et al.
quantities of biomass and primary productivity (Brinkhuis 1976;
172
—
Dawes
Mathieson and Muscoides-like Fucus 173
2001]
Chock Ma-
Brinkhuis and Jones 1976; Brinkhuis 1976; and
et al.
thieson 1976). Several positive interactions occur between salt
marsh flowering plants and unattached fucoids, including reduced
desiccation and enhanced survival of A. nodosum (L.) Le Jolis
(Hornemann)
ecad scorpioides Reinke, plus increased cordgrass
biomass due enhanced sediment
(Spartina alterniflora Loisel.) to
(Chapman Chapman The
nutrients and 1999; Gerard 1999). tax-
onomy
of unattached fucoids poorly understood (Fritsch 1945;
is
Norton and Mathieson 1983; Sears 1998), with plants being var-
megaecads, and (Bak-
iously classified as ecads, species, varieties
Wynne
Mag-
and Bohling 1916; Sears 1998; Taylor 1957; and
er
The morphology
ne 1991). "altered" of free-living fucoids,
which includes dwarfing, spiral twisting, profuse branching, veg-
etative propagation, and the lack of a holdfast (Baker and Bohling
Norton and Mathieson
1916; Fritsch 1945; Niell 1980;
et
al.
The
1983) has contributed these taxonomic problems. varied
to
morphologies of free-living fucoids have been attributed to re-
duced nutrients and/or sluggish currents, and enhanced
salinities,
Chapman
desiccation (Boney 1966; 1964). In discussing the or-
emphasizes
igin of free-living fucoids Fritsch (1945) that they
"are derived by vegetative propagation from saxicolous
all
types/'
One embedded
of the most unique marsh fucoids the dwarf,
is
moss-like Fucus frequently found within upper marsh-
that salt
is
5-6
es of Europe and the British Isles. It is described as being
mm
cm
having compressed branches (1-3
cylindrical to
tall,
wide), and bearing marginal hair or cryptostomata Fritsch
pits (cf.
Lynn Newton and Cooke
1945; Jorde 1966; 1935; 1931; Valera
Although anchored
1979). lacking a holdfast, the plant
is (i.e.,
partially embedded) in firm sand or peat-like sediments within
Magne
high marshes (Cotton 1912; Feldmann and 1964;
tidal
Lynn Norton and Mathieson Muscoides-like Fucus
1935; 1983).
plants have been variously designated as varieties (Cotton 1912;
Lynn 1935), ecads (Baker and Bohling 1916; Niell et 1980),
al.
Magne
(Feldmann and Parke and
or as distinct species 1964;
Wynne Magne
Dixon 1976; and 1991). In Cottoirs (1912) initial
characterization of muscoides-like Fucus, he treated taxo-
this
it
nomically as F. vesiculosus L. muscoides and described as
var.
it
forming moss-like carpets swards) within the high intertidal
(i.e.,
zone Clare Subsequently Baker and Bohling
Island, Ireland.
at
(1916) designated the plant as F. vesiculosus ecad muscoides,
Rhodora
174
|Voi. 103
emphasizing that was part of a morphological cline within the
it
megaecad limicola Baker Bohling (Clements 1905); the ecads
et
caespitosus Baker Bohling, Agardh, nanus
et filiformis
J. J.
Agardh, subecostatus Agardh. and (Hudson) Turner
volubilis
J.
were megaecad
also included within the limicola of F. vesiculo-
Feklmann Magne
and
sus. (1964) elevated F. vesiculosus var.
On
muscoides
to a distinct species, F. muscoides. the other hand,
during recent survey of Spanish vesiculosus populations,
a F.
Niell (1980) agreed with Baker and Bohling's (1916)
et al. inter-
pretation, designating various ecads within vesiculosus megae-
F.
cad limicola and showing gradation of morphology ranging
a
from
F. vesiculosus axillaris to F. vesiculosus ecads volubilis,
f.
caespitosus, and muscoides.
Wynne Magne
and (1991) also agreed with Feklmann and
Magne
(1964), stating that this plant should be recognized the
at
name
However, employed
species level. they pointed out that the
Magne
by Feklmann namely Fucus muscoides
(1964), (Cotton)
et
Feldman and Magne, homonym now
created a later of a red alga
known
Acanthophora muscoides Bory
as (L.) de Saint- Vincent
new
(1828). Accordingly they proposed a name, F. cottonii M.
Wynne
Magne, honor of A. D. Cotton, suggesting
et in that
J.
the dwarf morphology and unique ecological niche within high
marshes
tidal clearly delineated the taxon.
The was
present study undertaken
after a investigation
floristic
of seaweeds within Brave Boat Harbor, York-Kittery, Maine,
U.S.A. (Figure revealed the occurrence of a muscoides-
1) first
Fucus North America (Mathieson
like plant in et 2001). In the
al.
we
summarize
present account detailed morphological, ecologi-
and
cal, transplant data regarding these unique populations,
in
order taxonomy, and
to clarify the plant's origin, biology.
MATERIALS AND MITMODS
Mathieson et al. (2001) have given a detailed characterization
of the Brave Boat Harbor marsh (43°06.0'N, 70°39.33'W;
salt
BBH),
hereafter including geography, hydrographic conditions
its
(temperature and composi-
salinity), habitat variability, species
tion, and site locations within the main tidal channel and four
The
contiguous biomass mus-
tidal tributaries. patterns for the
Fucus and marsh were
coides-like other plants recorded
salt at
seven transect sites along the main tidal channel (Fimire with
1),
—
Dawes
Mathieson and Muscoides-like Fucus 175
2001
MAINE
BRAVE BOAT
HARBOR
43°05'
OCEAN
ATLANTIC
70°44' 70°43'40"
Figure Brave Boat Harbor. York-Kiltery. Maine showing the location
I.
of seven transect sites within the main tidal channel. See Figure in
I
Maine
Mathieson (2001) for details of the southern coast.
et al.
mean
Table Distribution and biomass of dominant seaweeds and flowering plants on seven transects within Brave Boat
1.
%
Harbor. Maine. Symbols: = percent occurrence, X = present, and mean biomass = g dry wt./m 2 ± SD (± SE).
1
1
# Mean
Site 2 4 6 Biomass
3 5 7
1
Distance inland from mouth (km) 0.29 0.31 0.38 0.40 0.79 0.86 1.12 present)
(sites
9c
f
SEAWEEDS
Ascophyllam nodosum Le X
(L.) Jolis 28.6 20.5 14.8 (10.6)
Ascophyllum nodosum Le
(L.) Jolis
ecad scorpioides (Hornemann) Reinke X X X X X X
85.7 868.2 1255.0 (500)
70
Fucus "muscoides-like" x X X X X X X
sp. 100 266.3 122.3 (46.2)
o
Fucus X X X X X X
spiralis L. 85.7 327.8 395.0 (161.4)
o
Fucus
spiralis L.
X
ecad Sauvageau
lutarius (Kiitzing) 14.3 130.0 94.8 (94.8)
Fucus
vesiculosus
L.
ecad (Hudson) Turner X X
volubilis 28.6 647.8 590.8
(341.5)
Melanosiphon X X X X
intestinalis (D. A. Saunders) 57.1 378.6 124.0 (62.0)
Wynne
M. X X X X X X X
J. 100 12.6 108.8 (41.1)
1
Rhizoclonium riparium (Roth) Harvey X X X X X X X 100 112.6 108.8 (41.1)
Vaucheria
spp.
TOTAL
SEAWEEDS/SITE
6 7 6 6 6 6
5
<
c
oj
to
o
Table Continued,
1.
Ef
Site # ? 3 4 5 6 7 Mean Biomass
1
o
Distance inland from mouth (km) 0.29 0.31 0.38 0.40 0.79 0.86 1.12 (sites present)
9?
'O
%
[Mean # taxa 6.0 0.57; Mean 66.9 35.1%; Mean Biomass present) = 313.8 ± 281.0 dry wt./m 2
(sites (93.7) g
]
FLOWERING PLANTS
X ±
Festuca rubra L. 28.6 5095.7 4159.2 (2949.8)
c
Limonium x X X X ±
Small
nashii 85.7 226.0 229.6
(93.7)
C/3
X
europaea
Salicornia L. 14.3 28.0 38.9
(38.9)
X X X X X
Spartina alteruiflora Loisel. 85.7 298.6 367.0 (149.8)
Spartina patens (Aiton) Muhl. X X X X 100 915.9 968.9
(365.6)
O
Suae da Dumort. X
maritime* (L.) 14.3 253.0 238.3 (238.3)
o
x
Triglochin maritima L. 14.3 63.0 89.1 (89.1)
CD
TOTAL FLOWERING
PLANTS/SITE
2 3 4 3 5 5 2
i
%
[Mean # taxa = 3.4 ± 1.3; Mean 49.0 39.4%; Mean Biomass (sites present) = 982.8 ± 1836.9 (693.2) g dry wt./m 2
]
Rhodora
178
Vol. 103
I
km km
these sites varying from 0.29 to 1.12 inland from the
mouth. Elevation records were determined using a line level and
(Dawes
a surveying rod 1998; Mathieson 1998). with ver-
et al.
MLW)
mean
heights above or below low water being
tical (i.e.,
from (Harbor Master Program.
calculated predicted tidal levels
The
Version Zihua Software, Marlboro. CT). delay
3, in tidal rise
inner transect was calculated by subdividing the main
for sites
channel into four 15-minute increments that matched the one-
hour delay noted the innermost part the marsh.
at o\^
May
were conducted between and
Transect studies (Figure
1)
September, 1998 seven Metered of variable lengths
at sites. lines
(5-7 m), depending upon shore topographies, were established
al
right angles to the shoreline, extending from the tidal channel to
the high marsh community dominated by SparUna patens (Ailon)
A minimum
Muhl. two biomass cores per meter were taken
oi^
cm
along each transect with a polyvinylchloride tube (95 2 par-
),
when
ticularly conspicuous vegetational changes occurred or
where the muscoides-like Fucus was evident. Each core was
la-
beled and returned to the laboratory within one hour where was
it
stored 10°C being processed. Ultimately the macroalgae
until
at
and marsh plants within each core were separated and their
salt
damp-dried biomass values converted dry wl./m 2 using wet
to g a
A
com-
dry weight conversion determined each
to for species.
mean
parison species composition and biomass for the seven
o\'
transects summarized (Table Morphological assessments o(
is
).
1
live the six fucoid taxa found were made, including Fucus
oi'
nodosum
spiralis L., Ascophyllum (L.) Le Jolis ecad scorpioides
(Hornemann)
Reinke, spiralis ecad lularius (Kutzing) Sauva-
F.
geau, F. vesiculosus L. ecad volubilis (Hudson) Turner, and the
Fucus
muscoides-like (Figures 2 and
3).
cm
Fucus
Reciprocal transplants of cores (92 2 containing spir-
)
and muscoides-like Fucus were during June
alis plants initiated
km
1998 at a site located 0.38 inland from the mouth along the
BBH. made
main channel were from
tidal Vertical transfers
oi'
MLW
m
+
2.0 to +3.4 above and vice versa, with four different
types oi populations being assessed: high populations
situ
(1) in
muscoides-like Fucus mixture fragmented
or a spiralis
F.
oi' oi'
ecad and muscoides-like low
lutarius plants; (2) in situ F. spir-
low were from
transplants or plants transferred the
alis: that
(3)
higher to the lower fucoid /one; and (4) high transplants or plants
that were transferred from the lower to the higher fucoid zone.
—
Dawes
Mathieson and Muscoides-like Fucus 179
200
i
|
cm
2
D
V
E
V
A.
J
<
v
(
m
^
u
v
1)
v-
vh
>
f
^
5
•
1
G
H
F
Figure Silhouettes of morphological variability three fucoid popu-
2. in
lations from Brave Boat Harbor. Attached Fucus spiralis ranging from germl-
ings (A. group ol' 8). to a pair of reproductively mature adults (B), to residual
and proliferous specimens (C, group o( Detached specimens of F. spiralis
5).
more
ecad lutarius grading from large, fragmented fronds (D, group of to
5),
proliferous, smaller plants (E, group Turf-like populations of muscoi-
o\' 8).
des-like Fucus ranging from tufted, elongated specimens (F, group o\' 12). to
short, individual fronds (G, group of 18), to minute plants (H, group of 22).
Rhodora
180
Vol. 103
|
A
B
C
>£7
y
r
D
cm
H
2
Figure Silhouettes of morphological variability two fucoid taxa from
3. in
Brave Boat Harbor, Maine. Detached Ascophyllum nodosum grading from two
more
large fragments (A), to a pair of proliferous fragments (B). to progres-
sively smaller fronds (C, group of and finally to minute plants of the ecad
6),
scorpioides (D, group of Attached (E) and detached fronds of Fucus
II).
vesiculosus (F) grading into F. vesiculosus ecad volubilis (G, group of
3),
and then more proliferous and smaller residual specimens (H, group of
to
3).
—
Dawes
Mathieson and Muscoides-like Fucus
2001] 181
Tabic Sediment characteristics of core samples (top 5 cm) from each
2.
of seven transect sites within Brave Boat Harbor's main tidal channel. The
SD
± means
data represent percentages of total values based on the of
1
duplicate cores.
%
SD
Mean ±
12 composition
total
1
Site # 3 4 5 6 7
Distance inland (km) 0.29 0.31 0.38 0.40 0.79 0.86 1.12
Water content (%) 26.0 30.0 37.0 36.0 51.0 54.0 55.0
±0.9 ±2.4 ±1.2 ±1.5 ±2.3 ±0.5 ±0.7
Medium
70.0 55.0 58.0 58.0 30.0 32.0 33.0
size particles
mm)
(> 0.125 ±8.1 ±6.6 ±8.8 ±14.0 ±7.4 ±7.4 ±3.1
Fine sand, parti- 3.0 3.0 4.0 5.0 10.0 11.0 11.0
silt
mm)
(< 0.063 ±1.0 ±1.3 ±1.3 ±1.3 ±1.7 ±2.5 ±3.4
cles
Thus, the terms low and high transplants refer to the resulting
rather than the materials. Duplicate cores of each situ
initial in
were biomass and
population taken order evaluate
in to initial
morphometric patterns (see below). The transplant samples were
harvested approximately one year June 1999) and sev-
after
(i.e.,
morphometric were compared with previous
eral features in situ
materials (see above).
Replicate core samples individual transect were pooled
at sites
and the frond morphology of 25 plants assessed, including their
(mm)
length (cm), width (mm), weight burial depth or the
(g),
numbers
blackened zone due anoxic conditions, of branches
to
and and numbers of marginal and cryptos-
fertile tips, surficial
Only
tomata or hair pits (cf. Niell el al. 1980). flattened fronds
of Fucus plants were assessed for cryptostomatal patterns, as the
small cylindrical branches of the muscoides-like Fucus had few
compared
cryptostomata and could not be directly with other
flat-
tened taxa. Cryptostomatal ratios were assessed using a represen-
mean and
ocular (100 X). Ultimately, values standard
tative field
deviations for each of the above described morphometric param-
were
eters calculated.
Sediment and water content were determined
particle size
at
each of the seven transect sites (Table using a stainless steel
2),
cm cm
were
tube (11.3 2 Duplicate cores (10 long) extracted at
).
each within dense populations of muscoides-like Fucus and
site
placed in individually labeled plastic bags that were returned to
the laboratory. Samples were either processed immediately or re-
The above-ground ma-
10°C
frigerated for later analysis. plant
at