HELGOLA---~DER MEERESUNTERSUCHUNGEN
Helgol~inder Meeresunters. 38, 305-317 (1984)
Temperature tolerance and b i o g e o g r a p h y of s e a w e e d s :
The marine algal flora of H e l g o l a n d (North Sea) as an
example*
K. Lfining
Biologische Anstalt Helgoland (Zentrale); NotkestraBe 31, D-2000 H a m b u r g 52, Federal
Republic of Germany
ABSTRACT: T e m p e r a t u r e tolerance (1 w e e k exposure time) was d e t e r m i n e d at intervals d u r i n g two
successive years in 54 d o m i n a n t m a r i n e b e n t h i c algae growing near H e l g o l a n d (North Sea).
Seawater temperatures n e a r H e l g o l a n d seasonally r a n g e b e t w e e n 3 °C (in some years 0 °) a n d 18 °C.
All algae survived 0 °C, a n d n o n e 33 °C. A m o n g the b r o w n algae, Chorda tomentosa was the most
sensitive species surviving only 18 °C, followed by the Laminaria spp. surviving 20 °, h o w e v e r not
23 °C. Fucus spp. a n d Cladostephus spongiosus were the most heat-tolerant b r o w n algae, surviving
28°C. Among the r e d algae, species of the Delesseriaceae (Phycodrys rubens, Membranoptera
alata) r a n g e d on the lower e n d with a m a x i m u m survival t e m p e r a t u r e of 20°C, w h e r e a s the
representatives of the Phyllophoraceae (Ahnfeltia plicata, Phyllophora truncata, P. pseudoceranoides) exhibited the m a x i m u m h e a t tolerance of the H e l g o l a n d m a r i n e algal flora with
survival at 30 °C. The latter value was also a c h i e v e d by Codium fragile, Bryopsis hypnoides a n d
Enteromorpha prolifera a m o n g the g r e e n algae, w h e r e a s the Acrosiphonia spp. survived only 20 °C,
a n d Monostroma undulatum only 10 °C, not 15 °C. Seasonal shifts of heat tolerance of up to 5 °C were
detected, especially in Laminaria spp. a n d Desmarestia aculeata. The majority of the d o m i n a n t
marine algal species of the H e l g o l a n d flora occurs in the Arctic, a n d it is h y p o t h e s i z e d that also
there the u p p e r lethal limits of these species may hardly h a v e c h a n g e d e v e n today. The data
p r e s e n t e d should provide a b a s e for further analysis of the causes of g e o g r a p h i c a l distribution of the
North Atlantic algal species, b u t h a v e still to b e s u p p l e m e n t e d with similar investigations on other
coasts, a n d s u p p l e m e n t e d with determinations of t e m p e r a t u r e r e q u i r e m e n t s t h r o u g h o u t the life
cycle.
INTRODUCTION
I n v e s t i g a t i o n s o n t h e t e m p e r a t u r e t o l e r a n c e of t h e c o m p o n e n t s of l o c a l a l g a l f l o r a s a t
as m a n y s t a t i o n s a s p o s s i b l e m a y i n c r e a s e o u r k n o w l e d g e of a t l e a s t t h r e e d i f f e r e n t
a s p e c t s of t h e g e o g r a p h i c a l d i s t r i b u t i o n of t h e s e c o m p o n e n t s .
(1) O n t h e b a s i s of s u c h s t u d i e s o n e m a y r e c o g n i z e t h e s p e c i e s w h o s e u p p e r l e t h a l
l i m i t s a r e s o n e a r to t h e l o c a l l y , y e a r l y o c c u r r i n g t e m p e r a t u r e m a x i m a t h a t t h e s e s p e c i e s
at the given locality just survive. On the other hand, one may find those species whose
u p p e r l e t h a l l i m i t s m a y l i e u p to 10 °C a b o v e t h e a c t u a l l y o c c u r r i n g s u m m e r t e m p e r a t u r e s . In t h e l a t t e r c a s e l o w e r t e m p e r a t u r e d e m a n d s for g r o w t h or r e p r o d u c t i o n m a y
* Paper p r e s e n t e d at the S e a w e e d Biogeography Workshop of the International Working Group on
Seaweed Biogeography, held from 3-7 April 1984 at the D e p a r t m e n t of M a r i n e Biology, University
of G r o n i n g e n (The Netherlands). Convenor: C, v a n d e n Hoek
© Biologisehe Anstalt Helgoland, H a m b u r g
306
K. Liining
r e d u c e the d i s t r i b u t i o n a r e a i n c o m p a r i s o n to a n area constructed on the base of
t o l e r a n c e limits. In addition, the case of a species with a very w i d e t e m p e r a t u r e survival
r a n g e m a y also m e a n that this species has not g e n e t i c a l l y a d a p t e d to the local temperature conditions. I n f o r m a t i o n o n t e m p e r a t u r e tolerance a n d on the t e m p e r a t u r e d e m a n d s
of r e p r o d u c t i o n a n d growth m a y b e u s e d for comparisons of the species' actual distribution areas with o c e a n isotherms, as has b e e n d e m o n s t r a t e d by v a n d e n Hoek (1982a,
1982b) a n d i n several p a p e r s of the p r e s e n t v o l u m e ( C a m b r i d g e et al., 1984; McLachlan
& Bird, 1984; Rietema & v a n d e n Hoek, 1984; Yarish et al., 1984).
(2) If tests on t e m p e r a t u r e tolerance are performed t h r o u g h o u t the year, one may
d i s c r i m i n a t e w h e t h e r or not, a n d to what extent, a n algal species can shift its survival
limits d u r i n g the year.
(3) C o m p a r i s o n s of the t e m p e r a t u r e survival r a n g e s of a g i v e n species at different
localities m a y reveal w h e t h e r or not a g i v e n species t h r o u g h o u t its d i s t r i b u t i o n area is
g e n e t i c a l l y flexible e n o u g h to form t e m p e r a t u r e ecotypes a n d by this to e n l a r g e its
d i s t r i b u t i o n area. A first result i n this respect w a s o b t a i n e d b y Bolton (1983} who found
that the u p p e r survival t e m p e r a t u r e s of Ectocarpus siliculosus i n a r a n g e of samples from
the Arctic to w a r m t e m p e r a t e r e g i o n s differed b y as m u c h as 10°C. O n the other h a n d
t e m p e r a t u r e r e q u i r e m e n t s for survival of the g a m e t o p h y t e s of several cold temperate
Laminaria spp. are quite similar i n the n o r t h e r n h e m i s p h e r e (Bolton & Liining, 1983).
(4) Finally, since the fossilization p o t e n t i a l of s e a w e e d s is so small, one may find
that the t e m p e r a t u r e characteristics of species, g e n e r a or e v e n families have b e e n so
stable over m i l l i o n s of years that the t e m p e r a t u r e b e h a v i o u r m a y b e u s e d as a "fossil
trait". For instance, the Arctic coasts are today i n h a b i t e d largely b y algal species which
occur i n the North Atlantic, partly also in the North Pacific. In contrast, the p e c u l i a r a n d
rich s e a w e e d flora of the North Pacific h a r d l y e n t e r e d the Arctic t h r o u g h the Bering
Strait. T h e latter was o p e n for most of the last 4 m i l l i o n s years, a n d only closed at low sea
levels d u r i n g the p l e i s t o c e n e glaciations (Briggs, 1974; Frakes, 1979; v a n d e n Hoek,
1975). This m e a n s that the s e a w e e d s in the North Atlantic, with its wide o p e n connection
to the Arctic Ocean, were exposed for l o n g e r periods to lower t e m p e r a t u r e s t h a n the
s e a w e e d s of the North Pacific, w h e n the process of climate deterioration started by the
e n d of the Tertiary a n d c u l m i n a t e d i n the Ice Age. Will we still be able to detect today a
greater sensitivity in North Pacific a l g a e to t e m p e r a t u r e s n e a r or b e l o w the freezing
p o i n t of s e a w a t e r i n c o m p a r i s o n to North Atlantic a l g a e w h i c h h a d a greater chance to
d e v e l o p cold w a t e r forms a n d possibly, therefore, still today d o m i n a t e the Arctic?
At present, the few i n v e s t i g a t i o n s o n t e m p e r a t u r e tolerance, a n d the still fewer ones
on t e m p e r a t u r e d e m a n d s for growth a n d r e p r o d u c t i o n of the c o m p o n e n t s of local algal
floras are hardly e n l i g h t e n i n g o n the four aspects p r e s e n t e d above. It is h o p e d that the
results p r e s e n t e d i n this p a p e r will stimulate more i n v e s t i g a t i o n s of this k i n d on other
coasts also. The only e x t e n s i v e i n v e s t i g a t i o n s on t e m p e r a t u r e tolerance of different
s e a w e e d species from various g e o g r a p h i c a l locations are those by Biebl (1958, 1962,
1968, 1970; T a b l e 1), w h i c h give a n idea of the different t e m p e r a t u r e r a n g e s tolerated by
s e a w e e d s from G r e e n l a n d , Brittany, the M e d i t e r r a n e a n a n d from Puerto Rico. There are,
however, three major d r a w b a c k s to Biebl's work on t e m p e r a t u r e tolerance. First, he had
to select a l i m i t e d n u m b e r of species from each location, a n d seldom does one find data
for the same species i n v e s t i g a t e d at different locations. Secondly, survival has b e e n
tested after a n e x p o s u r e time of only 12 h to the different temperatures, and, as will be
T e m p e r a t u r e t o l e r a n c e a n d b i o g e o g r a p h y of s e a w e e d s
307
s e e n in t h e p r e s e n t p a p e r , this a p p r o a c h g i v e s u p p e r l e t h a l l i m i t s t h a t a r e too h i g h a n d
m i s l e a d i n g in c o m p a r i s o n to s u c h l i m i t s d e t e r m i n e d o n t h e b a s i s of a n e x p o s u r e t i m e of a
w e e k . T h i r d l y , t h e d e c i s i o n o n t h e s t a t u s " d e a d or a l i v e " r e q u i r e s a s a f e criterion, s u c h as
a m e a s u r a b l e p h o t o s y n t h e t i c rate, w h e r e a s B i e b l h a d to r e l y on q u i c k , b u t s o m e w h a t
u n c e r t a i n m e t h o d s , s u c h as c y t o m o r p h o l o g i c a l criteria.
Table 1. Temperature tolerance of benthic marine algae from different geographical regions (data
from Biebl 1958, 1962, 1968, 1970)
Type of
biogeographical
region
Location
Annual
span
Temperature survival range
after 12 h exposure
Eulittoral species Sublittoral species
(oc)
Arctic
Warm temperature
Warm temperature
Tropical
W-Greenland
Brittany
Naples
Puerto Rico
0
10
14
26
to
to
to
to
6
16
24
28
(oc)
--10
-- 8
-- 7
- 2
to
to
to
to
35
30 (35)
35
35 (40)
(oc)
-
2
to 22
2 (0) to 27
1 (2} to 27
+ 14 (5) to 35
(24)
(30}
(30)
(32)
MATERIAL AND METHODS
A l g a e w e r e c o l l e c t e d at i n t e r v a l s d u r i n g t w o s u c c e s s i v e y e a r s in t h e e u l i t t o r a l z o n e
or b y d i v e r s i n t h e s u b l i t t o r a l z o n e of H e l g o l a n d , N o r t h S e a . E r l e n m e y e r flasks {1 1) w e r e
f i l l e d w i t h s e a w a t e r a n d i m m e r s e d in t h e w a t e r b a t h s of C o l o r a c r y o s t a t s ( C o l o r a
M e s s t e c h n i k , Lorch, FRG}. T h e w a t e r b a t h s w e r e m a i n t a i n e d at 18 o, 20 °, 23 °, 25 °, 28 °,
30 °, 33 °, a n d 35 °C (all __ 0.1 C°). C o n s t a n t t e m p e r a t u r e r o o m s {all +__0.5 °C) w e r e u s e d for
t h e t e m p e r a t u r e s of 0 °, 5 °, 10 °, 15 °C. T h e f l a s k s c o n t a i n e d e a c h a q u a n t i t y of 0 . 5 - 5 g of
fresh w e i g h t of e a c h s p e c i e s , a n d e x p o s u r e t i m e w a s 1 w e e k . T h e m e d i u m w a s r e p l a c e d
e v e r y 2 d a y s b y s e a w a t e r of t h e a p p r o p r i a t e t e m p e r a t u r e . T e m p e r a t u r e of t h e w a t e r b a t h s
w a s m e a s u r e d daily, a n d d e v i a t i o n s w e r e l e s s t h a n +__0.1 °C. C o o l - w h i t e f l u o r e s c e n t l i g h t
( O s r a m - L 65 W / 1 9 , D a y l i g h t 5000 D e - L u x e ) w a s u s e d , a n d t h e p l a n t s r e c e i v e d c o n t i n u o u s l y a p h o t o n f l u x d e n s i t y of 30 ~E m -2 s -1.
S u r v i v a l a f t e r 1 w e e k ' s e x p o s u r e at t h e d i f f e r e n t t e m p e r a t u r e s w a s a s s e s s e d b y
m e a s u r i n g p h o t o s y n t h e s i s b y m e a n s of a n o x y g e n e l e c t r o d e ( Y e l l o w S p r i n g s I n s t r u m e n t
Co., Ohio}. For t h i s p u r p o s e t h e e x p e r i m e n t a l a l g a l m a t e r i a l (0.3-1 g of f r e s h w e i g h t ) w a s
p l a c e d into g l a s s - s t o p p e r e d flasks (100 m l of v o l u m e } c o m p l e t e l y f i l l e d w i t h s e a w a t e r of
k n o w n o x y g e n c o n t e n t , a n d e x p o s e d for 16 h to c o o l - w h i t e f l u o r e s c e n t l i g h t at a p h o t o n
flux d e n s i t y of 50 ~ m -2 s -1, i n a c o n s t a n t t e m p e r a t u r e r o o m at 10°C. T h e o x y g e n
c o n t e n t of a 4 - m l - s u b s a m p l e of t h e s e a w a t e r in e a c h b o t t l e (2 r e p l i c a t e s ) w a s t h e n
d e t e r m i n e d in a m e a s u r i n g t u b e e q u i p p e d w i t h a n o x y g e n e l e c t r o d e a n d m a g n e t i c bar. If
a l g a e w e r e a l i v e , t h e o x y g e n c o n t e n t of t h e s e a w a t e r w o u l d h a v e r i s e n c o n s i d e r a b l y (up
to 200 % of o x y g e n saturation). In t h e c a s e of d e a d a l g a e t h e o x y g e n c o n t e n t d i d n o t
i n c r e a s e , b u t in m o s t c a s e s d e c r e a s e d c o n s i d e r a b l y d u e to b a c t e r i a l a c t i v i t y in t h e w a t e r
containing the dead algae. The boundary between "alive" and "dead" was always
sharp. For e x a m p l e , i n a n e x p e r i m e n t w i t h Ahnfeltia plicata, t h e o x y g e n v a l u e s in t h e
b o t t l e s w h i c h w e r e e x p o s e d to 0 - 2 8 ° C w e r e all in t h e r a n g e of 1 2 0 - 1 6 0 % of t h e
308
K. Lfining
saturation v a l u e . T h e o x y g e n v a l u e s of s a m p l e s w h i c h w e r e e x p o s e d to 30 and 33°C
w e r e in t h e r a n g e of 10-15 % of the saturation value.
RESULTS A N D D I S C U S S I O N
T h e s e a s o n a l course of t h e s e a w a t e r t e m p e r a t u r e in the surface w a t e r s n e a r Helgol a n d w a s a l m o s t i d e n t i c a l d u r i n g t h e two years, in w h i c h the e x p e r i m e n t s w e r e cond u c t e d (Table 2). T h e a n n u a l m i n i m u m in F e b r u a r y was as a m o n t h l y m e a n v a l u e around
3 °C (2.2 °C as a m i n i m u m on a f e w days), a n d t h e a n n u a l m a x i m u m in A u g u s t around
16.5 °C (17.9 °C as a n o c c a s i o n a l m a x i m u m ) . T h e results on t e m p e r a t u r e tolerance, which
are g i v e n in T a b l e s 3-5, w e r e t h e r e f o r e a r r a n g e d in such a w a y that e x p e r i m e n t s
p e r f o r m e d in the s a m e month, but in t h e two different years, a p p e a r one after the other.
This a r r a n g e m e n t shows that i d e n t i c a l results w e r e o b t a i n e d in both years.
Table 2. Seawater temperatures (surface) near Helgoland (from Biologische Anstalt Helgoland,
Jahresbericht 1980, Jahresbericht 1981)
Year
J
F
M
A
M
J
J
A
S
O
N
D
9.4
9.1
6,4
5.0
°C
1980
1981
4.9
3.8
3.4
3.1
3.3
3.8
5.3
6.0
9.0
8.5
1 2 . 3 14.6 1 6 . 7 1 6 . 1 13.4
1 2 . 3 1 5 . 2 1 6 . 6 1 6 . 1 13,1
All i n v e s t i g a t e d a l g a l s p e c i e s s u r v i v e d 1 w e e k ' s e x p o s u r e at 0°C, w h i c h is no
surprise, s i n c e t e m p e r a t u r e s a r o u n d zero occur n e a r H e l g o l a n d at intervals of several
years, a l t h o u g h not d u r i n g the t w o y e a r s of t h e i n v e s t i g a t i o n s . S u r v i v a l at t e m p e r a t u r e s
b e t w e e n 0 °C a n d the f r e e z i n g p o i n t of s e a w a t e r at --2 °C has not b e e n tested, a n d so it
r e m a i n s an o p e n question, w h e t h e r or not characteristic differences m a y still be found for
the v a r i o u s s p e c i e s in this t e m p e r a t u r e range. H e n c e , in the f o l l o w i n g only the speciesspecific d i f f e r e n c e s in h e a t t o l e r a n c e will be treated.
It s h o u l d b e r e a l i z e d that in the course of the p r e s e n t study all survival t e m p e r a t u r e s
w e r e d e t e r m i n e d in the s u b m e r g e d condition, a n d it is w e l l - k n o w n for various droughtt o l e r a n t c r y p t o g a m s i n c l u d i n g s o m e i n t e r t i d a l s e a w e e d s that the u p p e r lethal limit
i n c r e a s e s w i t h d e c r e a s i n g w a t e r c o n t e n t (Kappen, 1981}. A c c o r d i n g to S c h r a m m (1968)
t h e h e a t t o l e r a n c e of I;. vesiculosus w h i c h h a s b e e n d e h y d r a t e d to 30 % of its original
w a t e r content, rises by 5 °C in c o m p a r i s o n to fulty h y d r a t e d thalli. Bangia fuscopurpurea
from N a p l e s s u r v i v e d 42 °C for 12 h, if d e h y d r a t e d , h o w e v e r only 30 °, if s u b m e r g e d
(Biebl, 1939). O n e m i g h t e x p e c t that Blidingia minima, d u e to its surprisingly low heat
t o l e r a n c e in t h e s u b m e r g e d state ( d e a d at 28°C; T a b l e 5), m a y in fact r e q u i r e e m e r s i o n
a n d w a t e r loss for s u r v i v a l n e a r its s o u t h e r n limit.
It is e v i d e n t from t h e p r e s e n t study that in e a r l y s p r i n g the u p p e r survival t e m p e r a ture of n e w - g r o w n tissue of Laminaria saccharina a n d L. digitata was by 2 °C l o w e r than
in s u m m e r , a n d in L, hyperborea, as w e l l as in Desmarestia aculeata this difference
b e t w e e n s p r i n g a n d s u m m e r m a t e r i a l a m o u n t e d to 5 °C (Table 3). In the latter two
s p e c i e s the h e a t t o l e r a n c e of old a n d n e w thallus parts differed e v e n in the s a m e month
by 2°C. T h e s e facts w e r e a l r e a d y i n d i c a t e d by the e a r l y w o r k of L a m p e (1935) and
Temperature
tolerance
and biogeography
of s e a w e e d s
309
T a b l e 3. P h a e o p h y c e a e , T e m p e r a t u r e t o l e r a n c e of d o m i n a n t s p e c i e s n e a r H e l g o l a n d i n t w o s u c c e s sive years. X x x = p l a n t s alive (with m e a s u r a b l e photosynthesis)
Species
T e m p e r a t u r e d u r i n g o n e w e e k (°C)
0
5
10
15
18
20
23
Chorda tomentosa
May80
J u n 81
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XXX
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
XXX
XXX
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
xxx
XXX
XXX
XXX
Xxx
xxx
XXX
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Chorda filum
Jun
Jul
80
81
Laminaria saccharina
Jan
Peb
81
81
M a r 81
A p r 81
May80
Jul
80
Oct 80
O c t 81
N o v 80
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Laminaria digitata
Jan
81
Peb
81
Mar
Old Apt
NewApr
Jun
Jun
Jul
Nov
81
81
81
80
81
81
80
xxx
xxx
xxx
Laminaria hyperborea
Old Jan
O l d Feb
NewFeb
Old Apr
NewApr
Old Jun
New Jun
Jul
81
81
81
81
81
81
81
81
Oct
81
N o v 80
xxx
Desmarestia aculeata
F e b 81
O l d A p r 81
N e w A p r 81
Old May80
New May80
O l d J u n 81
N e w J u n 81
J u l 80
J u l 81
S e p 81
Oct
80
Nov 80
25
28
30
33
K. L i i n i n g
310
T a b l e 3. P h a e o p h y c e a e (continued)
Species
0
5
10
T e m p e r a t u r e during one w e e k (°C)
15
18
20
23
25
28
Desmarestia v~ndi$
Jun
80
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Petalonia fascia
May81
xxx
xxx
Scytosiphon lomentaria
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
XXX
XXX
XXX
xxx
XXX
XXX
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
XXX
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
XXX
xxx
xxx
XXX
xxx
XXX
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
XXX
xxx
xxx
xxx
xxx
XXX
xxx
XXX
xxx
XXX
XXX
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
XXX
xxx
XXX
xxx
xxx
XXX
xxx
XXX
xxx
xxx
XXX
xxx
xxx
xxx
xxx
XXX
xxx
XXX
xxx
xxx
XXX
xxx
xxx
xxx
xxx
XXX
xxx
XXX
xxx
xxx
XXX
XXX
XXX
xxx
xxx
XXX
xxx
xxx
xxx
xxx
XXX
XXX
XXX
xxx
xxx
xxx
XX×
XXX
xxx
xxx
XXX
xxx
xx×
XXX
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
XXX
xxx
XXX
XXX
xxx
xxx
Chordaria flagelliforrnis
Aug81
Jun
80
xxx
xxx
Pylaiella litoralis
Aug81
xxx
Dec 81 X X X
Sphacelar~a radicans
Aug81
D e c 81
XXX
xxx
HaHdrys siliquosa
Jul
80
Pucus sen'atus
Jun
Ju!
81
80
Jul
81
Aug
Oct
80
81
Ascophyllum nodosum
F e b 81
MayS0
Jut
81
Dec
80
xxx
xxx
XXX
xxx
Pucus vesiculosus
F e b 81
May81
AugS0
Oct 8t
Dec 80
Fucus spiralis
Feb
81
May81
Jul
Oct
Dec
81
81
80
Cladostephus spongiosus
P e b 81
May80
Jul 81
Aug81
Sep 80
O c t 81
xxx
xxx
XXX
XXX
xxx
xxx
XXX
xxx
XXX
XXX
xxx
xxx
30
33
T e m p e r a t u r e t o l e r a n c e a n d b i o g e o g r a p h y of s e a w e e d s
311
Table 4. Rhodophyceae. Temperature tolerance dominant species near Helgoland in two successive
years, x x x = plants alive (with measurable photosynthesis)
Species
10
Temperature during one w e e k (°C)
15
18
20
23
25
0
5
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
xXX
xxx
xxx
xxx
xxx
xxx
Xxx
xxx
xxx
xxx
xxx
xxx
XXX
XXX
XXX
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Jul 81
Oct 81
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
Nov 81
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xx×
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Phycodrys rubens
Apr
81
May80
Jul 81
Aug80
Aug81
Sep 80
Membranoptera aIata
lViar 81
Jun 80
J u ] 81
Nov80
xxx
xxx
xxx
xxx
Plocamium cartilagineum
Mar 81 x x x
xxx
Aug81
xxx
xxx
Rhodomela confervoides
Jan 81 x x x
xxx
Apt 80 x x x
xxx
Jul 8 0 X X X
XXX
Rhodomela virgata
Jun 81 x x x
xxx
AugS0 xxx
xxx
Nov 80 X X X
XXX
Delessez~a sanguinea
Mar 81
Apt 80
Apr 81
May80
Jun 81
xxx
xxx
xxx
xxx
xxx
Plumaria elegans
Mar 81
Apr
80
Cystoclonium purpureum
Apr 81
May80
Jul
81
xxx
xxx
xxx
Pouahyra linearis
Jan 81
xxx
Porpyhyra umbilicalis
Jan 81
May81
Nov 81
xxx
xxx
xxx
Bangia fuscopuropurea
Nov81
xxx
Dumontla contorta
Jun 80
Jul 81
xxx
xxx
28
30
33
312
K. L i i n i n g
T a b l e 4. R h o d o p h y c e a e ( c o n t i n u e d )
Species
T e m p e r a t u r e d u r i n g o n e w e e k (°C)
0
5
i0
15
18
20
23
25
xxx
XXX
xxx
XXX
xxx
xxx
xxx
28
30
Rhodochorton floridulum
Oct
81
xxx
C e r a m i u m rubrum
Jan
81
Jun
80
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
Jul
Nov
81
81
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
Ceramium deslongchampsii
Jan
81
Jul
81
xxx
xxx
Polysiphonia urceolata
M a r 81
A p r 81
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
xxx
xxx
XXX
xxx
Jun
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
80
Corallina officinalis
May81
J u n 80
Jul 80
Jul 81
Aug81
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
Bonnemaisonia hamifera ( T r a i l l i e l l a - p h a s e )
Aug81
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Chondrus crispus
Jan
81
F e b 81
A p t 80
May81
Aug80
Aug81
Nov81
D e c 80
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
A h n f e l t i a plicata
Jul
80
xxx
xxx
xxx
xxx
xxx
XXN
XXX
xxx
XXX
Jul
81
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Aug81
Phyllophora truncata
May80
J u n 80
Aug81
xxx
xxx
xxx
Phyllophora p s e u d o c e r a n o i d e s
MayS0
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
Jul
80
XXX
xxx
xxx
XXX
XXX
XXX
XXX
XXX
XXX
XXX
Jul
81
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
xxx
XXX
xxx
xxx
XXX
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
XXX
xxx
XXX
xxx
XXX
Poll/ides rotundus
May80
J u l 80
J u l 81
Sep
80
33
T e m p e r a t u r e t o l e r a n c e a n d b i o g e o g r a p h y of s e a w e e d s
313
Table 5, Chlorophyceae, Temperature tolerance of d o m i n a n t species n e a r Helgoland in two
successive years, x x x = plants alive (with m e a s u r a b l e photosynthesis)
Species
0
5
10
Temperature during one w e e k (°C)
15
18
20
23
25
28
30
Monostroma undulatum
Apr 8 0
May81
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
xxx
XXX
XXX
XXX
XXX
XXX
xxx
XXX
XXX
XXX
xxx
XXX
xxx
XXX
XXX
XXX
XXX
XXX
xxx
XXX
XXX
XXX
XXX
XXX
xxx
XXX
XXX
XXX
xxx
XXX
xxx
XXX
XXX
XXX
xxx
XXX
xxx
XXX
XXX
XXX
xxx
XXX
xxx
Acrosiphonia arcta
Feb
81
Apr 81
xxx
xxx
Acrosiphonia sonderi
Apr 80
xxx
Blidingia minima
May81
Jun 80
Aug81
Oct
81
Dec 81
xxx
xxx
xxx
xxx
xxx
Chaetomorpha melagonium
Jul
Oct
80
81
Nov81
XXX
xxx
xxx
XXX
xxx
xxx
Chaetomorpha tortuosa
Jun 80
Aug81
Oct
81
xxx
xxx
xxx
xxx
xxx
xxx
Rhizoclonium riparium
Aug81
XXX
Cladophora rupestris
May81
Jul 81
Aug81
Sep
Oct
80
81
Nov81
XXX
XXX
XXX
XXX
XXX
xxx
Ulva lactuca
Apr 80
May80
May81
Jul 81
Aug80
Aug81
Nov 81
XXX XXX
xxx
xxx
xxx
XXX
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Ulva curvata
Nov 81
Enteromorpha prolifera
May81
Aug81
xxx
XXX
XXX
xxx
xxx
XXX
xxx
xxx
xxx
XXX
xxx
XXX
XXX
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
XXX
xxx
Codium fragile
Jan 81
Apr
80
Aug81
Oct
81
Bryopsis hypnoides
Jun 81 X X X
Jul
81
xxx
33
group
N-Norway
N-Norway
N-Norway
Atlantic
(b) E u r o p e a n - N o r t h A t l a n t i c
B: Larninaria hyperborea
B: Halidrys siliquosa
R: Delesseria sanguinea
North
Newfdl.,N-Norway
Novaya Zemlya
Newfdl., N-Norway
Newfdl., M - N o r w a y
temperature,
Europe
M - P o r t u g a l (19)
N - P o r t u g a l (18}
N - F r a n c e (17)
N - A f r i c a (22)
N - P o r t u g a l (18)
S - P o r t u g a l (20)
N - F r a n c e (17)
N - F r a n c e (17)
N - F r a n c e (17)
N - P o r t u g a l (18)
N - A f r i c a (20)
I r e l a n d (15}
N - F r a n c e (17)
N - F r a n c e (17}
N - F r a n c e (17)
S - A l a s k a (15)
N - W a s h i n g t o n (15)
S - A l a s k a (15)
O r e g o n (16)
M e x i c o (25)
S - A l a s k a (15)
O r e g o n (16)
M e x i c o (25)
S - A l a s k a (15)
S - A l a s k a (15)
-
N-Asia
-
K o r e a (25}
Kuril Is. (16)
S - J a p a n {25)
S - J a p a n (25)
W l a d i w . (19)
K o r e a (25)
H o k k a i d o (20)
Och. S e a (15)
D e l a w a r e (22)
N - W a s h i n g t o n (15) St. L a w r e n c e G u l f (14) N e w J e r s e y (20)
D e l a w a r e (22)
-
C o n n e c t i c u t (19}
C o n n e c t i c u t (19)
N o r t h C a r o l i n a (24)
N o r t h C a r o l i n a (24)
N e w J e r s e y (20)
N e w H a m p s h i r e (16)
C o n n e c t i c u t (19)
C o n n e c t i c u t (19)
C o n n e c t i c u t (19)
C o n n e c t i c u t (19)
C o n n e c t i c u t {19)
C o n n e c t i c u t (19)
N e w York (19}
C o n n e c t i c u t {19)
C a p e C o d (18)
C o n n e c t i c u t (19)
Pacific
N-America
Southern Boundary
N-America
Atlantic
N - F r a n c e (17)
M - P o r t u g a l (19)
N - F r a n c e (17)
N - P o r t u g a l (18}
N - P o r t u g a l (18)
S - P o r t u g a l (20)
N - F r a n c e (17}
group
{a) A m p h i - a t l a n t i c
B: Fucusspiralis
B: Fucusserratus
R: Chondrus crispus
R: Phyllophorapseudoceranoides
(3) C o l d
N-Arctic
M-Arctic
S-Arctic
S-Arctic
N-Arctic
S-Arctic
N-Arctic
N-Arctic
Atlantic
North
Chorda tomentosa
Laminaria digitata
Ascophyllum nodosum
Fucus vesiculosus
Phyllophora truncata
Membranoptera alata
Phycodrys rubens
Rhodomela confervoides
(2) A r c t i c - c o l d t e m p e r a t e ,
B:
B:
B:
B:
R:
R:
R:
R:
B:
B:
B:
B:
B:
R:
R:
N-Arctic
N-Arctic
N-Arctic
S-Arctic
N-Arctic
S-Arctic
S-Arctic
N-Arctic
amphioceanicgroup
Northern Boundary
Chordaria flagelliformis
Desmarestia aculeata
Desmarestia viridis
Chorda ilium
Laminaria saccharina
Ahnfeltia plicata
Dumontia contorta
G: Chaetomorpha melagonium
(1) A r c t i c - c o l d t e m p e r a t u r e ,
Species
20
25
23
28
25
28
30
18
20
28
28
28
20
20
23
23
23
23
20
20
28
25
25
Upper
survival
temperat u r e (°C)
T a b l e 6. O c c u r r e n c e a n d g e o g r a p h i c a l b o u n d a r i e s (after Liining, 1985) of s e l e c t e d a l g a l s p e c i e s , oI w m c n m e u p p e r mLqal nm~ts I* w e v x
e x p o s u r e ) h a v e b e e n d e t e r m i n e d in t h e p r e s e n t p a p e r for H e l g o l a n d m a t e r i a l . B = b r o w n a l g a ; R = r e d a l g a ; G = g r e e n alga. N = north,
n o r t h e r n ; S = s o u t h , s o u t h e r n ; M = m i d d l e . T e m p e r a t u r e v a l u e s in b r a c k e t s f o l l o w i n g t h e g e o g r a p h i c a l b o u n d a r i e s i n d i c a t e t h e m e a n A u g u s t
i s o t h e r m s {according to A t l a s o k e a n o v , 1974-1977) of t h e s u r f a c e s e a w a t e r at t h e c o r r e s p o n d i n g l o c a t i o n s
t~
¢,0
T e m p e r a t u r e tolerance a n d b i o g e o g r a p h y of s e a w e e d s
315
Montfort et al. (1957) a n d are i n accord with the w e l l - k n o w n h i g h e r heat sensitivity of
actively g r o w i n g p l a n t tissue i n g e n e r a l (Larcher, 1980). T h e occurrence of a s u m m e r
p e a k in heat tolerance is also w i d e s p r e a d a m o n g h i g h e r p l a n t s ("S-type" response; see
Larcher et al., 1973; Kappen, 1981). As m a y be s e e n from the data i n T a b l e s 3 a n d 2, the
seasonal course of t e m p e r a t u r e t o l e r a n c e of D. aculeata follows the s e a s o n a l course of
seawater temperature. It r e m a i n s at its s u m m e r m a x i m u m at least u n t i l N o v e m b e r , w h e n
the seawater t e m p e r a t u r e has d r o p p e d a l r e a d y to 9 °C.
Seasonal shifts of h e a t tolerance b y 2 °C w e r e also o b s e r v e d i n a few red a n d g r e e n
algal species (Tables 4-5), a n d p r o b a b l y more e x a m p l e s m i g h t have b e e n detected, if
e x p e r i m e n t s h a d b e e n c o n d u c t e d more f r e q u e n t l y d u r i n g the year. In g e n e r a l , however,
seasonal differences in heat tolerance of 5 °C are obviously not surpassed, a n d this is
exactly the m a g n i t u d e w h i c h has b e e n f o u n d for s e a s o n a l shifts of h e a t t o l e r a n c e i n
m a n y other plants, w h i c h contrast to the m u c h b i g g e r s e a s o n a l c h a n g e s i n cold tolerance
(Larcher et al., 1973). Fucus vesiculosus, w h i c h did not show a s e a s o n a l shift of h e a t
tolerance i n the p r e s e n t investigation, withstood i n s u m m e r - 3 0 ° C , b u t - 4 5 ° C i n
winter, as d e t e r m i n e d for m a t e r i a l from Long I s l a n d by Parker (1960).
In view of the relatively small s e a s o n a l c h a n g e s of h e a t t o l e r a n c e it is clear that the
species-specific differences in heat tolerance (Tables 3-5) are g e n e t i c a l l y fixed, not only
for species, b u t also for h i g h e r t a x o n o m i c entities. B e g i n n i n g with the P h a e o p h y c e a e
(Table 3), the u p p e r survival limits r a n g e from 18 °C i n case of the spring a n n u a l Chorda
tomentosa or from 20 °C i n case of the other r e p r e s e n t a t i v e s of the L a m i n a r i a l e s to 28 °C
in the representatives of the Fucales, except for Fucus serratus a n d Halidrys siliquosa,
which survive only 25 °C. Here the striking difference i n r e g a r d to the u p p e r survival
t e m p e r a t u r e s b e t w e e n the r e p r e s e n t a t i v e s of the two b r o w n algal orders, e m p h a s i z e d
a l r e a d y by Setchell (1920), b e c o m e s evident. T h e i n v e s t i g a t e d H e l g o l a n d r e p r e s e n t a tives of the Desmarestiales, the Scytosiphonales a n d the S p h a c e l a r i a l e s are characterized by u p p e r survival t e m p e r a t u r e s at 23-25 °C.
A m o n g the Rhodophyceae (Table 4) the most sensitive species are the r e p r e s e n t a tives of the Delesseriaceae w h i c h only survive 20 °C {Phycodrys rubens, Membranoptera
alata} or 23 °C (Delesseria sanguinea}, the latter t e m p e r a t u r e also m a r k i n g the u p p e r
survival limit of the H e l g o l a n d Rhodomela spp., w h e r e a s the Ceramium spp. survive
25 °C. In contrast, the r e p r e s e n t a t i v e s of the G i g a r t i n a l e s (Phyllophora spp., Ahnfeltia
plicata, Chondrus crispus, Polyides rotundus) are all found at the u p p e r e n d of the
t e m p e r a t u r e survival scale, with survival t e m p e r a t u r e s of 2 8 - 3 0 °C. Biebl (1958), w h e n
i n v e s t i g a t i n g the t e m p e r a t u r e tolerance of a l g a e from the coast of Brittany, h a d f o u n d a n
u p p e r survival t e m p e r a t u r e of 27°C for Phycodrys rubens, Membranoptera alata, a n d
Delesseria sanguinea, thus 7 °C or 4 °C (D, sanguinea} h i g h e r t h a n i n the p r e s e n t
investigation. This difference is p r o b a b l y artificial a n d d u e to the short exposure time of
12 h used by Biebl.
The most sensitive species of the C h l o r o p h y c e a e i n the H e l g o l a n d s e a w e e d flora
(Table 5) is the early spring a n n u a l Monostroma undulatum w h i c h survives 10°C, b u t
dies at 15°C. Next on the scale are the Acrosiphonia spp., a g a i n s p r i n g a n n u a l s , with
u p p e r survival limits of 20 °C, the Chaetomorpha spp., w h i c h survive 25 °C, a n d f i n a l l y a
s o m e w h a t bigger, h e a t - t o l e r a n t group with u p p e r survival limits at 28°C (Cladophora
rupestris, Ulva spp.) or finally at 30°C (Enteromorpha prolifera, Codium fragile, a n d
Bryopsis hypnoides).
316
K. Lfining
The m o r p h o l o g i c a l l y larger of the 54 i n v e s t i g a t e d species, i.e. 23 species, are again
listed in T a b l e 6 with r e g a r d to their affiliation to four g e o g r a p h i c a l distribution groups,
according to their occurrence i n the Arctic, i n the North Atlantic, a n d i n the North
Pacific. The fact that the 16 species listed as occurring also i n the Arctic (groups 1 a n d 2}
display similar u p p e r survival limits as the species with cold t e m p e r a t u r e distributions
(groups 3a a n d 3b) i n d i c a t e s that the species which i n v a d e d the Arctic after the last
g l a c i a t i o n can hardly b e characterized b y r e d u c e d u p p e r survival temperatures,
a l t h o u g h data on t e m p e r a t u r e t o l e r a n c e of s e a w e e d s in the Arctic is still largely lacking.
The few data o n t e m p e r a t u r e tolerance of Arctic s e a w e e d s supports the view that time
has b e e n too short i n the Arctic for the formation of real cold water a l g a e which lose their
a b i l i t y to survive at t e m p e r a t u r e s a b o v e 18 or 20 °C. Biebl (1968; T a b l e 1) found as a
result of short (12 h) exposures to v a r y i n g t e m p e r a t u r e s that Agarum cribrosum a n d
Laminaria saccharina from West G r e e n l a n d h a d u p p e r survival t e m p e r a t u r e s of 24 °C.
Bolton & L i i n i n g (1982) detected a n u p p e r survival limit of 23°C for Laminaria saccharina subsp, longicruris g a m e t o p h y t e s from the C a n a d i a n Arctic, or from N e w f o u n d land, e x p o s e d for 4 w e e k s to v a r y i n g temperatures. E v e n the g a m e t o p h y t e s of the arctice n d e m i c L, solidungula survive 18 °C, h o w e v e r not 20 °C, according to the latter authors.
A more p r o n o u n c e d a d a p t i o n to cold c o n d i t i o n s is to b e expected i n the subantarctic a n d
antarctic r e g i o n s with a l o n g e r history as cold w a t e r habitats t h a n the Arctic, a n d the
o n l y result i n this respect, the d e a t h of Durvillaea antarctica at 14 °C (Del~pine & Asensi,
1976) points in this direction. Also the fact that tropical sublittoral algae may have a
lower lethal t e m p e r a t u r e as h i g h as 14 °C, as f o u n d b y Biebl (1962; T a b l e 1}, shows that
s e a w e e d s do c h a n g e their t e m p e r a t u r e characteristics d r a m a t i c a l l y g i v e n a long e n o u g h
geological time period.
Of the species listed i n T a b l e 6, several cases have b e e n a n a l y s e d i n detail by Hoek
(1982a, 1982b) with r e g a r d to their g e o g r a p h i c a l d i s t r i b u t i o n a l o n g seawater isotherms
as c o m p a r e d to the t e m p e r a t u r e tolerances, a n d t e m p e r a t u r e d e m a n d s for growth or
reproduction, of a p a r t i c u l a r species. T h e s e species are Chondrus crispus, Desmarestia
aculeata, D. viridis (van d e n Hoek, 1982a}, Laminaria saccharina, L. digitata, a n d
L. hyperborea (van d e n Hoek, 1982b). I n a s m u c h as a m p h i - a t l a n t i c species are concerned, u s u a l l y composite b o u n d a r i e s s e e m to limit the d i s t r i b u t i o n to the south, i.e.
u p p e r survival limits d e t e r m i n e the s o u t h e r n b o u n d a r y of occurrence on the A m e r i c a n
side, a n d t e m p e r a t u r e r e q u i r e m e n t s for growth a n d / o r r e p r o d u c t i o n on the European
side of the Atlantic. S i m i l a r a n a l y s e s m a y b e also possible i n the future for the rest of the
species listed i n T a b l e s 2-5 w h i c h only provide information on t e m p e r a t u r e tolerance.
However, to a c h i e v e this goal, more data a b o u t the species' t e m p e r a t u r e tolerance from
other coasts is required, as well as a b o u t the t e m p e r a t u r e r e q u i r e m e n t s for growth and
reproduction.
The possibility that Chordaria flagelliformis, Chorda ilium, a n d D. viridis m a y differ
with r e g a r d to their u p p e r survival t e m p e r a t u r e s i n the North Pacific a n d i n the North
A t l a n t i c is i n d i c a t e d b y the f i n d i n g that the u p p e r survival t e m p e r a t u r e of 23 °C, as
d e t e r m i n e d for these species in H e l g o l a n d material, w o u l d not e n a b l e the Pacific
c o u n t e r p a r t s to r e a c h their actual s o u t h e r n limits (Table 6).
T e m p e r a t u r e t o l e r a n c e a n d b i o g e o g r a p h y of s e a w e e d s
317
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