The effects of the winter of 1962/63 on the british marine fauna
British m a r i n e fauna
DENNIS J. CRisP 0
0 Marine Science Laboratories , Menai Bridge, Anglesey , U. K
KURZFASSUNG: Die Wirkungen des Winters 1962/63 auf die Britische Meeresfauna. W~ihrend des ungewShnlich kalten Winters 1962/63 herrschten die niedrigsten Temperaturen an der Stidostkilste Groi~britanniens. Die grSflten negativen Anomalien dagegen wurden an den Kiisten yon Hampshire und Dorset, im Bristol-Kanal und in Teilen yon Nor&Wales festgestellt. Die nSrdlichen Formen wurden im allgemeinen nicht ernstlich beeintrilchtigt, aber einige keltische und siidliche Formen erlitten sehr hohe Verluste im Bereich der Gezeitenzone, insbesondere in mehr oder minder abgeschlossenen Buchten im Gebiet der oben erwiihnten Lokalifiiten. Bei den siidlichen Formen der exponierten Kiisten der westlichen Vorgebirge war die Sterblichkeit relativ gering; marine Algen wurden ebenfalls nur wenig gesch~idigt. Der Tod trat nicht nur als direkte Folge der K~ilteeinwirkung auf die Gewebe ein, sondern wurde auch durch die zu welt gehende Herabsetzung der Aktivit~it (etwa unzureichende Zilienaktivit~it zur Entfernung sedimentierender Schlammpartikel, mangelnde Anhaftungsf~ihigkeit an die Felsoberfl~iche oder ungentigendes EingrabungsvermSgen) verursacht. Selbst in Situationen, in denen hohe Sterblichkeitsraten auftraten, iiberlebten im allgemeinen einige wenige (vielteicht resistentere) Individuen in giinstigen Habitaten, so dag die Verbreitungsgrenzen nur geringfiigig beeinfluflt wurden. Bei vMen Litoralformen spielte zudem ein adaptives Verhalten eine wichtige Rolle Rir das erfolgreiche 13berstehen der Kiilteperiode.
C O N D I T I O N S I N B R I T A I N D U R I N G J A N U A R Y A N D F E B R U A R Y 1963
part of southern England averaged between 5 and 60 C below the seasonal average.
pressure to the north and low pressure to the south of the British Isles brought an
easterly air stream across the southern half of the country. Oi~en, as on the occasion
illustrated, the easterly wind was of gale force in m a n y coastal areas and these gales,
coupled with the intense cold, were a major factor in dama
ge to marine life (GIBSON
). A t other times high pressure centred over the British Isles produced calm clear
weather with extremely severe frost at night. The isotherms shown in Figure 1 do not
refer to any one particular occasion but are intended to show the areas most generally
affected by severe cold. They are based on the average of the 6 a. m. temperature
readings following four of the coldest nights (Jan. 12, 22; Feb. 4 and 25). I t can be
seen from the hatched area indicating an average of below - 7 ? C on these four nights
that, although the south and south east were the most severely affected areas as in most
winters, severe weather extended unusually far westward reaching the coasts of Dorset
and Hampshire, the Bristol Channel and N o r t h Wales. Figure 2 gives the negative
anomalies of the mean minimum temperatures averaged over J a n u a r y and February
for a number o? coastal and inland stations. From this map it can be seen that the
greatest anomalies, exceeding 5 C over the whole period, occurred in a wide band
19 J A N , 1964 0 6 . 0 0
WI N DS > 2OK NOTS
- s o C
< - 7 o C .
\ \ \ \
d-~ , - T - - - ~ - - - ~ T ~ ' - ~
Fig. 1: Weather map illustrating typical conditions in the British Isles during the winter of
1962/63. The isotherms are based on the average 6.0 a.m. temperatures aRer the four cold
nights of Jan. 12, 22, Febr. 4, and 25, and indicate the generally coldest areas throughout the
period. Data from daily weather maps, Meteorological Office, London
running from north-west to south-east and affecting the coasts of North Wales, much
of the Bristol Channel and the south coast from Devon to Hampshire. Further west,
along the peninsulas of south-west England, South Wales, North Wales, throughout
northern Scotland, the Hebrides, Shetlands and the whole of Ireland, the extremes of
cold, both absolute and relative, diminished considerably. Much of the south~west of
Ireland and extreme west of Ireland and Scotland were little affected by freezing
conditions. Both temperatures and anomalies were less severe than might have been
expected on the north east coast of England and Scotland, perhaps on account of the
moderating effect of air flowing almost continuously off the North Sea.
The winter of 1962/63 therefore provided a large scale natural experiment, the
results of which may allow marine organisms to be classified according to their
tolerance to cold, and the part played by severe winters in determining their distribution
to be assessed. To this end a number of independent observers in Britain jointly
reported in detail the effects they had observed on marine organisms at various parts
of the coast (CRIsv et al. 1964). The account that follows is a summary of these
observations and I wish to acknowledge the co-operation of all those who took part.
T H E D I S T R I B U T I O N OF T H E M A R I N E F A U N A I N B R I T A I N
The effects of the winter are best considered in relation to the distribution of three
rnain elements comprising the British fauna. The northern forms, whose distribution
extends northwards well into the Arctic circle, do not spread far, if at all, to the south
of the British Isles. Many extend all round the British coast, but some are more
abundant in the north and east. The Celtic forms, whose centre of distribution is
located approximately at the latitude of the British Isles, range both to the north and
to the south and occur on all parts of the British coast. The southern forms, whose
centre of distribution is usually in Mediterranean latitudes, reach their northern limits
in Britain and are found only on the west and south west coasts. Some of these forms,
such as Chtharnalus stellatus and Gibbula umbilical#, extend eastward as far as the
Isle of Wight and reach the north of Scotland (Fig. 3); others, such as Paracentrotus
lividus, are confined to the extreme south west and west of Ireland. Southern forms
with intermediate limits are shown in Figures 4, 5 and 6.
The distribution of the fauna as a whole, and of such southern forms as
Chtharnalus stelIatus in particular
(MooRr & KITCHING 1939, K~CHING 1950)
pattern of winter temperature. The milder Atlantic air over the west and south west
normally alleviates the colder continental conditions that frequently affect the eastern
half of the country. Whether these lower winter temperatures exert a critical influence
on the north eastward extension of these forms, or whether some other factor associated
with proximity to the Atlantic controls their distribution, has been the subject of
debate. Other possible influences are proximity to deep water and wave exposure
(FIscHE~-PIEvTr 1936), the nature of submarine deposits (SMITH1953), and differences
in the biological or chemical constituents of Atlantic water
(REID 1935, MooR~ &
KITCrtING 1939, POXVrLL1954, M o x s r 1963)
. The results of a long period of negative
temperature anomaly should help to discriminate between these alternatives.
M O R T A L I T Y OF I N T E R T I D A L FORMS
In the south and south east where temperatures were minimal, the fauna consists
only of northern and Celtic forms. Estimates of mortalities in the intertidal zone made
by several observers in this area are summarized in Table 1.
Fig. 3" Mortality observed in the topshell Gibbula umbilicalis. Size of circles represent previous
abundance; large circles: abundant, medium circles: common or frequent, small circles: rare
or local. The fraction of the circle blacked out represents reported mortality. Clear circles:
reports that mortality was insignificant. Question marks: absence of relevant data. Broken
lines indicate previously established limits of distribution
Intertidal mortalities reported from south and south east England. (100 % mortality implies
that dead individuals only were found in the intertidal zone after the frosts. Individuals below
low water mark may have survived)
Lanice conchilega (PALLAS)
Gibbula cineraria (L.)
Anomia ephippium L.
Scrobicularia plana (hA COSTA) 100 ?/o
Ensis siliqua (L.)
Ensis ensis (L.)
Pholas dactytus L. 95 ?/o
Ostrea edulis L. 1
Venerupis pullastra (MoNTAGO)j 50-100 ?/o
Cardium edule L. 50- 60 ?/o
Mytilus edulis L. 0- 30 ?/o
BaIanus balanoides (L.) 10- 20 ?/o
PoIydora ciliata (JoHNsToN) "1
Hyas araneus (L.) ~ Negligible
Asterias rubens L. J
Crassostrea angulata LAMARCIi;
Ostrea edulis L.; Brittany race
Elrninius rnodestus DAI~WIN;
50- 80 %
Crepidula fornicata (L.);
E. United States
Venus mercenaria L.;
E. United States
UrosaIpinx cinerea SAY;
E. United States
Clearly many Celtic forms suffered heavy mortality but northern forms, as a
whole, escaped. Immigrants from the eastern coast of the United States, where
extremes of temperature are regularly encountered, were also little affected. Conditions very
similar to those of the south east were experienced on the shallow sandy coasts of
the eastern Irish Sea and the Solway Firth where the resident fauna is similarly
depleted of southern forms.
Land influenced western and south western coasts
Under this heading I include those parts of the west and south west coast that lie
nearest to the centre of the main land mass of the British Isles over which the coldest
air was located (Fig. 1). They comprise the coast from Hampshire to east Devon, the
coasts of the Bristol Channel and parts of the coast of N o r t h Wales. These areas are
of particular interest not only because they mark the limits of distribution of certain
(CRIsv & KNIC~T~JoN~s 1954, CRISV & SOUTHWAI~D1958)
because they experienced the largest negative temperature anomalies during the cold
spell (Fig. 2). I t is not surprising therefore that some southern forms suffered complete
or nearly complete mortality in these areas. These animals are listed in Table 2.
Farther west, where conditions were milder, an increasing proportion of the
population of these same animals survived. Hence extreme temperature in winter appears
to be one factor, and probably the main one, limiting their distribution. However,
other forms with similar limits of distribution, such as the barnacle, Chthamalus
stellatus, and the algae, Cystoseira granulata and C. ericoides, were unaffected by the
cold. Furthermore, many of the Celtic forms which suffered high mortality in the
south east were killed in these land influenced western areas also.. High mortalities
between the tide marks were recorded for Actinia equina, Cereus peduneulatus,
SabeIIa pavonina and Portunus puber, in addition to those animals listed in Table 1.
D. J. CRisv
Anemonia sulcata (PENNANT) Branchiomma vesiculosum (MoNTAOU) Audouinia tentaculata (MoNTaGU) Sabellaria alveolata (L.)
Patella intermedia J~FFr~Ys
Monodonta lineata (DA COSTA)
Gibbula umbilicalis (DA COSTA)
Pharus legumen (L.)
Balanus perforatus BRUGUIkRE
Regions where heavy mortalities were observed
Hampshire-Dorset, Bristol Channel
North Wales, Cardigan Bay
Dorset, Bristol Channel and
East Devon, Bristol Channel, North Wales
Hampshire-Dorset, Bristol Channel,
Bristol Channel, North Wales
Hampshire-East Devon, Bristol Channel
(absent from North Wales)
Atlantic influenced western coasts
Under this heading are included the peninsulas of south west England and Wales
and the west coasts of Ireland and Scotland. The negative anomaly was not as great as
elsewhere because these areas are at all times under the influence of the open sea, but
the winter was nevertheless exceptional, except perhaps in west Scotland and in the
Hebrides. Surprisingly, none of the forms investigated that were typically restricted to
these western shores showed any evidence of exceptional mortality. These included
Bifurcaria rotunda, Cystoseira sp., Paracentrotus lividus and Xantho incisus. Table 3
lists all the southern forms which did not appear to have been influenced b y the cold
and whose distribution limits, therefore, probably should not be attributed to winter
extremes of climate.
Southern forms which did not experience exceptional mortality
Bifurcaria rotunda (H~Ds.) PAVENF. Cystoseira ericoides (L.) AG. Cystoseira granulata Ao. Cystoseira fibrosa (HuDs.) AG.
Chthamalus stellatus (POLl) Xantho incisus L~ACH Clibanarius misanthropus Rlsso Paracentrotus lividus (LAMA~CK)
It is interesting to note that, except for Patella intermedia, most of the cold
sensitive forms shown in Table 2 occur more abundantly in sheltered or embayed areas,
where greater extremes of local heating and cooling occur, than on the more equable
exposed coasts of the western promontories. These promontories thus function as
refuges where survival is possible during and a~er extreme winters as can be seen
from the changed distributions shown in Figures 3 to 6. The apparently cold tolerant
forms (except Cystoseira granulata) are by contrast more common on or near these
exposed promontories, so that their most favoured habitats are seldom visited by
severe frosts. However, there can be little doubt that Chthamatus stelIatus, at least,
is a genuinely cold tolerant form, since it can survive transplantation to the east coast
of Britain (C~isv 1950) and artificial exposure for over 12 hours to temperatures of
- 1 0 ? C (SouvrtWARI) 1958). Apart from the high proportion of southern forms that
were unaffected the mortalities experienced by each of the three faunal groups (Table 4)
followed the expected pattern.
M O R T A L I T I E S BELOW T H E T I D E MARKS
Deaths of fish and of sub-littoral invertebrates, thoiigh most obvious in relatively
shallow parts of the sea near the coast, were also evident over large areas of the North
Sea. Most obviously affected, both among vertebrates and invertebrates, were southern
forms such as the fish, Conger conger, Solea vulgaris, Gobius paganellus, Labrus
bergylta, and L. ossifagus; the crustacea Maia squinado, Palinurus vulgaris, Porcellana
longicornis, Corystes cassivelaunus and species of Portunus; and the cephalopods
Octopus vulgaris and Sepia officinalis. Bivalves suffered particularly heavy mortality
and included such forms as Nucula nucleus, Ostrea edulis, Pecten maximus, Cardium
echinaturn, Spisula solida, Mactra corallina, Lutraria lutraria, all British species of
Ensis and Pharus legumen. Considerable numbers of Echinocardiurn cordatum and
Psammechinus miliaris were reported killed in the more severely affected areas.
CAUSES OF D E A T H
Mortality may result either from the direct effect of low temperature on the
tissues or from the indirect results of lowered metabolism and consequent disorganization
of vital processes. Direct tissue damage may result from the intrusion of ice crystals,
the formation of air bubbles, or from the raised osmotic pressure of the unfrozen tissue
(Sc~oLANDI~r,et al. 1953)
. Some cold hardy forms can tolerate the freezing of
60 to 70 % of their water, provided that the ice crystals form in the intercetlular
). Hence intertidal forms such as Chthamalus stellatus,
Elminius modestus and Balanus balanoides, which are subject to desiccation by evaporation
in summer, may be pre-adapted to withstand the effects of dehydration of the tissue
fluids by freezing in winter.
Although temperatures within the intertidal zone fell to values at which ice
crystals might be expected to form in the tissues of many organisms, and although deaths
immediatly following the hard frosts were observed on some occasions, there was much
evidence to indicate that the indirect effects of the cold weather were also a frequent
cause of death. The evidence is summarized below.
a) Algae, even those such as Pelvetia canaliculata growing at the highest tidal
levels, were not seriously affected. The mortality observed was ahnost entirely confined
to animals. Animals exhibit a greater degree of physiological complexity and therefore
would be more likely to become disorganized by prolonged cold (see
b) Severe mortality in many animals did not coincide with the coldest period but
was delayed until later in, or even at%r, the cold spell.
c) Many fish and sub-littoral invertebrates were killed at temperatures above
zero and appeared externally to be in perfect condition.
d) In some instances the younger and more active individuals were less affected
than the older ones.
e) Fatal results of cold torpor and debilitation were obvious in flat fish (dermal
sores), bivalves (failure to clear debris and mud from the mantle space), topshells
(buried in gravel), razor shells (inability to burrow), and limpets and anemones (loss
f) Many organisms were stranded and lefL open to attack by predatory birds
because their normal activities were slowed down.
FACTORS I N SURVIVAL
Despite heavy mortalities to certain organisms, particularly in the intertidal zone,
the complete destruction of a species over a significant length of shore, even at the
extreme limits of its range, was unusual. Gibbula umbilicalis, Monodonta lineata,
Balanus per~oratus and SabelIaria alveolota, southern forms with a limited vertical range
on the shore, afford some of the few examples of extensive and complete mortality
(Figs. 3-6). Even in these species, however, the distribution limits were not necessarily
modified because isolated populations survived on the milder promontories (see above).
In most species studied however some individuals escaped in almost every locality by
one of the following means.
Individual variations in tolerance
Not only were young forms of certain species found alive more commonly than
adults (e. g. Carcinus maenas, Anomia ephippium, Pholas dactylus) but the existence
of racial differences in tolerance can also be inferred. Ostrea edulis of the Britanny
race died more readily than native oysters. Actinia equina, although it extends as far
north as the White Sea, suffered heavy mortality in South Wales (93 0/0 in an area
carefully observed by MoxsE & N~LsoN-SMIvtt) and elsewhere (CRIsv et al. 1964). Similarly
) found that 50 % of the population of British specimens of Balanus
balanoides could not survive for more than a day below - 1 0 ? C whereas PrvrRsrN
(1962) reports survival of the same species in Greenland after having remained in the
ice foot over the winter at temperatures falling to - 350 C. It therefore seems likely that
more tolerant races must exist in Arctic waters. If such racial variations in tolerance
have evolved in different areas, individual differences must presumably exist in any
Variations within the habitat in the degree of exposure to cold
At the shore level where the lowest ebb tides coincide with severe frosts, an abrupt
change must occur in the temperature minimum experienced by the habitat. Beyond
this point the habitat is continuously immersed and the temperature cannot therefore
fall below -1.9 ? C, the freezing point of sea water of normal salinity, except in the
very unlikely event of super-cooling. Not surprisingly, therefore, many populations
that were completely eliminated within the intertidal zone survived below low water
mark (e. g. Lanice conchilega, Sabella pavonina and Pharus legumen).
The higher the shore level the longer is the rock exposed to radiation cooling
during frost. Clearly marked increases in mortality at higher shore levels could be
observed in such forms as Patella vulgata growing on exposed rock, Tanais chevreuxi
living in crevices, and Sabellaria alveolata living in its own sand tubes. On parts of
the coast where the shore line was steep and deep water not far distant, the mortalities
of intertidal forms were considerably lower than those on flat sandy shores nearby
where the water was shallower and therefore colder. Animals that had been able to
retreat into crevices, below the surface of deep pools or beneath thick beds of algae,
survived better than those remaining on bare rock surfaces. There was some evidence
that lowered salinity and the associated silt in estuarine waters tended to increase
Many free-living intertidal forms, particularly shore fish, crustacea and
gastropods, move down the shore during winter, sometimes entering deep pools and
sometimes penetrating into deep water beyond the tide marks
(YoNcE 1949, JANNS~N1960,
. Species that were observed to have disappeared after the frosts but
which returned during the following spring and summer were Blennius pholis, Gobius
paganellus, Ligia oceanica and Diogenes pugilator. One member at least of the fauna
inhabiting rock crevices, Tanais chevreuxi, was observed to have moved deeper down
the crevice and away from the region of ice crystal formation at its entrance. In
contrast many individuals of Audouinia tentaculata, for reasons not understood, emerged
from their burrows and were in consequence completely exposed to the cold. It is
thus clear the behaviour of the animal may play an important part in its survival
during exceptionally cold winters.
1. During the exceptionally cold winter of 962/63
the south east coasts of Great
Britain suffered the coldest conditions, but the coasts of Hampshire and Dorset, the
Bristol Channel and parts of N o r t h Wales the greatest negative anomalies.
2. Northern forms were not generally seriously affected, but some Celtic and southern
forms suffered very high mortality in the intertidal zone, particularly in embayed
situations in the areas mentioned above.
3. Southern forms limited to exposed western promontories did not suffer much
damage; marine algae were also little affected.
4. Death was caused, not only as a direct result of exposure of the tissues to extreme
cold, but also from the general lowering of the animals' activity; for example,
failure to remove silt by ciliary action, to cling to rock surface, and to burrow, led
to m a n y deaths.
5. Even where high mortality was experienced, a few, perhaps more resistant,
individuals of the species generally survived in favourable habitats, so that distribution
limits were little affected. Adaptive behaviour played an important part in the
survival of m a n y littoral forms.
L I T E R A T U R E C I T E D
Discussion following the paper by CRIsv
BOOI~.HOUT: Was there any evidence that northern animals moved southward as a result of
the severe winter of 1963? At Beaufort, North Carolina (USA), Mytilus edulis moved in and
covered the pilings. This has not been the case at Beaufort before.
CRIsp: No., I don't think there was any evidence of northern forms becoming more common.
The only effect observed of this nature was that some of the northern forms, such as Balanus
balanoides and Mytilus edulis, had a particularly heavy spat fail in the following spring.
W~LLS: When the rising tide arrives, a littoral animal may experience a sudden change of
temperature. H a v e you data on the difference between air and water temperature in various
places, which would show whether such shocks, as distinct from the actual temperature levels,
have had significant effects?
CRIsv: What we could give are the differences in mean temperature of air and sea but not the
absolute or relative values at the time the tide was rising. The intertidal temperatures on the
shore itself were not measured. It would be very interesting to know just what these are and
to what extent they act as a limiting factor and whether any part is played by temperature
shocks. Many animals live almost buried in the sand, and these would not suffer such a sudden
change as the animals living on the rocks.
BOOLOOTIAN:H o w did you ascertain your figures for mortality rates?
C~Isv: I have presented the results of the cooperation of many people, including Dr. Alan
J. SOUTHWARD,Mr. MoYs~, Mr. Nelson SMITH and Dr. Duncan WAUCH. Various methods
have been used. One hundred per cent mortality is easy to measure: one didn't find any
animals alive. The lower mortalities were more difficult. In some cases we compared counts
made at different times, previous to the cold winter, with counts made subsequently. In other
cases counts were made of the number of living and dead organisms during and just after the
Wirs~t~: Did the small animals survive better than the large ones because they could hide
better (in crevices, for example) or because they were more resistant?
CR~sv: I can only guess as to the answer to that. I suspect that the young ones may survive
because the hungry gulls would not notice them, if they could conceal themselves. This would
not, however, apply to animals, like the piddocks, that remain concealed in any case.
CRISV , D. J. , t950 . Breeding and distribution of Chthamalus stellatus . Nature , Lond. 166 , 31I .
- - & SOUTHWm~D, A . J., 1953 . Isolation of intertidal animals by sea barriers . Nature , Lond. 172 , 208 .
-- & KI~ IGt-IT-JoNEs , E. W. , 1954 . Discontinuities in the distribution of shore animals in North Wales . Rep. Bardsey Observatory 2 , 29 - 34 .
-- & SOUTrtWARD , A. J. , 1958 . The distribution of intertidal animals along the coasts of the English Channel . J. Mar. biol. Ass . U. K. 87 , 157 - 208 .
--, MorsE, J., NELSoN-SM~T~ , A. & others , 1964 . The effects of the severe winter of 1962-63 on marine life in Britain . J. Anita. Ecol . 3 : 3 , 165 - 210 .
FISCHER-PIETTE , E. , 1936 . Etudes sur la biog~ograpbie intercotidai des deux rives de laManche . J. Linn. Soc. (ZooI.) 40 , 181 - 272 .
G ~soN, F. A. , 9 63 . Mortalities in marine animals during storms , January 1963 . Irish Nat . J . 14 , 118 - 119 .
JhNNSEN , C. R. , 1960 . The influence of temperature on geotaxis and phototaxis in Littorina obtusata (L) . Archs n~erl . Zool . 113 , 500 .-- 10 .
KANWIS~ZR , J. W. , 1955 . Freezing in intertidal animals . Biol. Bull. mar biol . Lab ., Woods Hole 109 , 56 - 63 .
- - 1957 . Freezing and drying in intertidal algae . Biol. Bull. mar. biol. Lab ., Woods Hole 1113 , 275 - 285 .
KITCHING , J. A. , 1950 . The distribution of the littorat barnacle Chthamalus stetlatus round the British Isles . Nature, Lond. 165 , 820 .
MOORE , M. B. & KITCHING , J. A. , 1939 . The biology of Chthamalus stelIatus (Poll) . J. Mar. biol. Ass . U. K. 23 , 521 - 541 .
MOYSE , J. , 1963 . A comparison of the value of various flagellates and diatoms as food for barnacle larvae . J. Cons . 28 , 175 - 87 .
NAYLOR , E. , 1963 . Seasonal changes in a population of Carcinus maenas (L) in the littoral zone . J. Anirn. Ecol . 31 , 601 - 9 .
PETERSEN , G. H. , 1962 . The distribution of Balanus balanoides (L) and Littorina saxatilis (OIivi) var. groenlandica Mencke in northern west Greenland . Medd. Gronland 159, No 9 , 1 - 47 .
POW ~LL, H. T., 1954 . Occurrence of Chthamalus stellatus (Poll) in Fair Isle and Shetland . Nature, Lond. 173 , 688 .
RrID , D. M. , 1935 . The range of the sea urchin Echinus eseulentus . J. Anita. Ecol. 4 , 7 - 16 .
SC~OLANDER , P. F. , FLAOG , W. , HOCK , R. J. & IRWNC , L. , 1953 . Studies on the physiology of frozen plants and animals in the Arctic . J. celt. comp. Physiol. 42 (Suppl. 1) , 1 - 56 .
SMITH , J. E. , 1953 . Maintenance and spread of sea shore fauna . Advrnt Sci., Lond. (Set. 10) No 38 , 145 - 156 .
SOUTHWARD , A. J. , 1958 . Note on the temperature tolerances of some intertidal animals in relation to environmental temperatures and geographical distribution . J. Mar. biol. Ass . U. K. 87 , 49 - 66 .
YONCE , C. M. , 1949 . The sea shore . Collins, London, 278 pp.