Climatic Change (2013) 119:407–419
DOI 10.1007/s10584-013-0724-5
Warnstorfia exannulata, an aquatic moss in the Arctic:
seasonal growth responses
Cai-Qing Guo & Ryszard Ochyra & Peng-Cheng Wu &
Rodney D. Seppelt & Yi-Feng Yao & Lin-Gen Bian &
Su-Ping Li & Cheng-Sen Li
Received: 12 October 2010 / Accepted: 17 February 2013 / Published online: 8 March 2013
# Springer Science+Business Media Dordrecht 2013
Abstract The moss, Warnstorfia exannulata (Schimp.) Loeske, was first reported forming a
carpet beside a water pool in Ny-Ålesund (78°56′N), Svalbard in 1959. Fifty years later, in
2008, it was found growing as an aquatic in a pool. The moss is sensitive to seasonal
changes and exhibits a pattern of seasonal growth: summer stems with densely arranged
leaves and lateral branches, and winter growth with short-leaved stems and no lateral branch.
The mean daily increase in stem length is 0.68 mm in summer and 0.07 mm in winter. The
longest specimens were up to 8 years old. The growth of the moss reflects closely seasonal
temperature and growth conditions. World distribution is discussed and global distribution
mapped.
1 Introduction
Changes in climatic regime may influence both the habit and habitat of terrestrial and aquatic
plants. The sensitivity of plants to changes may provide evidence of trends in global climatic
C.-Q. Guo : P.-C. Wu : Y.-F. Yao : C.-S. Li (*)
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy
of Sciences, Beijing 100093, China
e-mail: [email protected]
R. Ochyra
Institute of Botany, Polish Academy of Sciences, Kraków 31-512, Poland
R. D. Seppelt
Australian Antarctic Division, Kingston 7050 Tasmania, Australia
L.-G. Bian
Chinese Academy of Meteorological Sciences, Beijing 100081, China
S.-P. Li
Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
408
Climatic Change (2013) 119:407–419
shifts over time. Bryophytes are important components of the flora in terrestrial and aquatic
ecosystems in the Arctic, with over 500 species being recorded. On Svalbard, 373 species,
including 85 hepatics and 288 mosses belonging to 137 genera, have been found (Frisvoll
and Elvebakk 1996).
Warnstorfia exannulata (Schimp.) Loeske was first reported from Svalbard, an archipelago in the Arctic Ocean, in the Ny-Ålesund area in 1959, growing in a moss carpet with
Pseudocalliergon turgescens (T.Jensen) Loeske, Campylium polygamum (Schimp.)
C.E.O.Jensen and Limprichtia revolvens (Sw.) Loeske beside a pool, but there was no
mention of its occurrence in the pool at that time (Arnell and Mårtensson 1959). In 2008,
during an expedition by the Chinese National Arctic Research Expedition to Svalbard,
specimens of W. exannulata were collected from a pool in the northwestern part of NyÅlesund (78°56′30″N, 11°49′6″E) (Fig. 1) by C.-S. Li. The mean air temperature in NyÅlesund in the coldest month (February) is −14 °C, while the warmest month (July) has a
mean temperature of 5 °C. The mean annual precipitation is 370 mm (Kings Bay 2008;
Muraoka et al. 2008).
In this work, we studied the morphological and anatomical features of an aquatic
moss Warnstorfia exannulata in Ny-Ålesund, and found the seasonal growth pattern
of the moss, which also showed the responses of the lateral branch growth to the
daily air temperature changes in the summer of 2007. We also discussed the global
distribution of the moss.
2 Site descriptions
Four small pools were located in the northwestern part of Ny-Ålesund, arranged from
east to west, with a separation of 30–60 m. Many specimens of Warnstorfia exannulata
were collected from the western pool (78°56′30″N, 11°49′6″E) (Figs. 2 and 3a), which
is a closed water body, about 100 m in diameter and less than 6 m in depth. The pool
has water year-round, and is ice and snow free in summer. Rainfall is very low in NyÅlesund in summer and most of the precipitation falls as snow. The snow covers much
of the area from early September to late May or early June (Birks et al. 2004), and
begins to disappear in early June (Gerland et al. 1999; Scannet 2010). Meltwater from
snow and glaciers on the mountains is the main source of the pool water. The plants of
W. exannulata were anchored on the muddy bottom of the pool near the bank and
formed dense mats at a depth of about 30–40 cm. The mosses Limprichtia revolvens,
Paludella squarrosa (Hedw.) Brid. and Calliergon cordifolium (Hedw.) Kindb. were
growing on the bank (Fig. 3b), but no W. exannulata was found there. The pool was
revisited again by C.-S. Li in the summer of 2011, and he found no observable change
in the pool on 8 August 2011.
3 Materials and methods
The Chinese National Arctic Research Expedition (CNARE) spent 3 weeks in NyÅlesund in the summer of 2008, and the moss samples were collected with a longhandled tool from the western pool on 14 July, 2008. All specimens were brought
back to the laboratory in Beijing for further investigation.
We noted that the uppermost parts of stems, produced in the years close to 2008, showed
leaves and lateral branches produced in summer, whereas the lower parts of those stem
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409
Fig. 1 Location of sampling site in Ny-Alesund, Svalbard archipelago
segments have only leaves with no lateral branches. That is, summer stems produce more
lateral branches and are more densely clothed with leaves than those segments grown in
winter, making the annual growth segments distinct (Fig. 5). Using this marker, the lengths
of the summer and winter stem segments and leaves of 20 separate specimens produced in
2006 and 2007 were measured using a ruler under a microscope in the laboratory and we
used an average of them as relative lengths. The growth rate of stems was calculated by
dividing the lengths of the stem in summer and winter by the number of summer (1 June to
31 August) and winter (1 September to 31 May) days respectively.
We measured the length of 119 leaves and 18 lateral branches from a stem produced in
the summer of 2007 (Fig. 5a), and based on these measurements a growth curve for W.
exannulata was drawn and divided into three stages (Fig. 7).
Meteorological data (daily average air temperature at 2 m above the land surface) from 1
May to 30 September 2007 in Ny-Ålesund was obtained from the Chinese Academy of
Fig. 2 A typical pool in Ny-Alesund, Svalbard archipelago, where the aquatic moss Warnstorfia exannulata
(Schimp.) Loeske was collected
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Fig. 3 Mosses growing in the water and on the bank of the pool in Fig. 1. a Warnstorfia exannulata was
collected from the pool; b Limprichtia revolvens (Sw.) Loeske, Paludella squarrosa (Hedw.) Brid. and
Calliergon cordifolium (Hedw.) Kindb. are growing on the bank of the pool
Meteorological Sciences. Based on the Meteorological data, the curve of air temperature in
the summer of 2007 was compiled (Fig. 6) and compared with the growth curve of the
mosses in the same summer (Fig. 7). The two curves show the identical trends and three
stages (Stage I: 1 June to 6 August, Stage II: 7 to 24 August, Stage III: 25 August to 31
September).
The specimens studied are deposited in the Herbarium, Institute of Botany, Chinese
Academy of Sciences, Beijing (PE, identification number: C.-S. Li 200805). Duplicates are in the Herbarium of the Institute of Botany of the Polish Academy of
Sciences, Kraków (KRAM, 182084, 182085). The samples information and data are
issued by the Resource-sharing Platform of Polar, and the extra samples are maintained by Polar Research Institute of China (PRIC) and Chinese National Arctic &
Antarctic Data Center (CN-NADC).
4 Specimen descriptions
The plants were yellowish-when young, and became yellow-brown to brown with age.
Stems (primary branch) were up to 28 cm long, regularly or irregularly pinnately
branched, with lateral (secondary) branches (Fig. 4a). In section, the stems were nearly
round, the cortical cells rounded-hexagonal in shape, thick-walled and arranged in two
layers; medullary cells were hyaline, thin-walled, 54×46 μm in diameter (Fig. 4b, c).
Stem leaves were linear-lanceolate, straight to falcate, 3−4 mm long and 0.4−0.5 mm
wide, gradually tapering to a long, subulate acumen. The leaf base was hardly decurrent
and the margins were finely and remotely serrulate throughout (Fig. 4d, e, g).The costa
was single, fairly strong, 40−55 μm wide at the base, reaching from 2/3 leaf length to
percurrent (Fig. 4d−f). Alar cells were thin-walled, rectangular or quadrate, 20−33 μm
long and 5−10 μm wide, hyaline and pellucid, arranged in 2−3 rows and forming a
large transversely triangular group which was distinctly delimited from the adjacent
laminal cells and reaches the costa (Fig. 4h); median lamina cells were long linear, thinwalled, 70−120 μm long and 4−6 μm wide (Fig. 4i). Branches were falcate-curved.
Branch leaves were similar to the stem leaves, but usually narrower, 0.25−0.35 mm wide
(Fig. 4f).
As is the case with all mosses growing in aquatic or otherwise hydrophytic habitats,
Warnstorfia exannulata exhibits a remarkable phenotypic plasticity resulting in the
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411
formation of innumerable phenovariants which were often recognized as separate taxa and
given varietal and/or form names. The extreme phenovariants of the terrestrial and submerged or freely floating plants are usually unlike each other and sometimes imitate distinct
species in their own rights (Mönkemeyer 1927; Tuomikoski 1949). Yet, they retain a set of
stable and constant characters which warrant the specific distinctness of W. exannulata
which are discussed below. The submerged and freely floating plants often possess longer
and slender leaves arranged at lower densities on stems than the terrestrial ones (Priddle
1979; Rice and Schuepp 1995). In addition, the stems are generally longer, to 30 cm, the
leaves are gradually long- to filiform-acuminate, 3−5 mm long and 0.4−0.6 mm wide and the
mid-leaf cells are elongate-linear, to 195 or, occasionally, 215 μm long and 4.5−6.5 mm
wide. In contrast, the terrestrial plants have shorter stems, to 10 cm, ovate-lanceolate
Fig. 4 Morphology and anatomy of Warnstorfia exannulata. a habitat (scale bar 1 cm); b cross section of
stem (scale bar 0.1 μm); c portion of cross section of stem (scale bar 0.1 μm); d and e stem leaves (scale bar
1 mm); f branch leaves (scale bar 1 mm); g leaf apex (scale bar 12 mm); h basal leaf cells (scale bar 12 mm); i
median leaf cells (scale bar 12 mm) (PE, identification number: C.-S. Li 200805)
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Fig. 5 Morphological differences of Warnstorfia exannulata in consecutive winters and summers. a, b, c
three main stems segments produced in the winter of 2006 to the summer of 2008; the arrows A, C indicate the
beginning of summer growth of 2007 and 2008 respectively; the arrow B indicates the beginning of the winter
growth of 2007
leaves, gradually shorter acuminate, 2−3 mm long and 0.5−1.0 mm wide and mid-leaf
cells short-linear, (25−)35−60(−80) μm long and 6−8 mm wide (Limpricht 1895;
Ochyra 1995; Hedenäs 2003; Hu and Wang 2005). The morphological changes of
the aquatic specimens are related with the adoption of the aquatic habitat. It is likely
they are adaptations to the competition with phytoplankton for light (Spence 1975)
and low CO2 availability in water (Beever 1995; Rice and Schuepp 1995).
The genus Warnstorfia is a segregate of the broadly conceived genus Drepanocladus
(Müll.Hal.) G.Roth, and is characterized by the following combination of characters:
serrulate leaf margins, distinct alar cells which form a triangular to ovate, mostly decurrent
group, leaves that are triangular, ovate to lanceolate with nematogen cells at the apex which
usually produce rhizoids, and the presence of reddish coloration under normal growth
conditions (Loeske 1907; Tuomikoski and Koponen 1979).
Warnstorfia exannulata is easily distinguished by its prominent decurrent auricles which
form a large transversely triangular alar group extending to the costa. The auricles are clearly
delimited from the adjacent laminal cells and they are composed of large hyaline cells
arranged in 2−3 tiers. Additionally, the stem leaf margins are serrulate throughout and
Fig. 6 Graph of temperature change from 1 May to 30 September 2007 in NyÅlesund. Data from Chinese
Academy of Meteorological Sciences
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413
Fig. 7 Lengths of leaves and lateral branches along stem of Warnstorfia exannulata in the summer of 2007.
Dates applied to three growth stages: Stage I: 1 June to 6 August, Stage II: 7 to 24 August, Stage III: 25
August to 31 September; Continuous line represents the growth trends of lateral branches; Black and hollow
bars indicate the length of leaves and lateral branches respectively
the costa is strong, ending in the upper third of the leaf or, in some submerged plants,
extending nearly to the apex. Such forms have been recognized as a separate species,
W. rotae (De Not.) Wheld. or variety, W. exannulata var. nigricans (Brid.) Ochyra
(Ochyra 1995), and the plants collected in Ny- Ålesund clearly represent this phenotype. Warnstorfia exannulata may be distinguished from the closely related species W.
fluitans (Hedw.) Loeske and W. pseudostraminea (Müll.Hal.) Tuom. & T.J.Kop. by its
dioicous sex condition, whereas the other two mentioned species are autoicous.
Moreover, the alar group in W. fluitans is narrowly triangular along the leaf insertion
and usually indistinctly delimited and weakly inflated, the costa is plano-convex and
the plants are mostly green to brownish, hardly ever red, but sometimes brown-red. In
W. pseudostraminea the alar cells of stem leaves form, together with the supra-alar
cells, an ovate or ovate-triangular, distinctly delimited group along the leaf margin
(Luca et al. 2003).
Fig. 8 Global distribution of Warnstorfia exannulata. Shadowed areas indicate genera distribution locations;
★ indicates specific distribution locations
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5 Results and discussion
Based on morphological characteristics, specimens of Warnstorfia exannulata showed
regular or irregular pinnate branching, producing the main stems (primary branch) and
lateral (secondary) branches in a growth season in a similar manner to that of Fontinalis
species (Glime and Raeymaekers 1987).
Warnstorfia exannulata exhibits a typical pattern of seasonal growth. In summer, the
stems produce more lateral branches and are more densely clothed with leaves than those in
winter. The mean daily extension rate of the stems is 0.22−1.36 mm in summer and
0.03−0.14 mm in winter. The longest specimen was 28 cm and estimated to have
been submerged in the lake for up to 8 years. Growth measurements of lateral
branches of W. exannulata show that growth increment is controlled more by temperature than by light intensity for most of the time in summer, since during a large
part of the summer there are 24 h of daylight in the area of Ny-Ålesund. However, as
temperature is closely linked to ice cover and hence light (Smol and Douglas 2007),
the two variables are not completely independent.
Figure 7 shows the varied length of the lateral branches and leaves produced in the
summer of 2007. And then we compared the curve of the branch lengths (Fig. 7) with the
curve of air temperature in the same summer in Ny-Ålesund (Fig. 6). The two curves show
an identical trend.
5.1 Seasonal growth patterns
Pronounced seasonal changes exert a strong influence on the growth of plants in high
latitudes. In summer, day length is long and temperatures comparatively warm, whereas in
winter the nights are long and temperatures are cold. There are two opinions on the seasonal
division of a year in Ny-Ålesund. A year has two seasons, winter and summer (Liengen and
Olsen 1997), or four seasons (Iversen 1989). In this work, we follow the first opinion. In NyÅlesund, the air temperature first falls to be below 0 °C in early September and rises above
0 °C in late May. The winter may be considered to extend from 1 September to 31 May and
summer from 1 June to 31 August. In this case, the effective duration of the winter season is
about 273 days, and summer is about 92 days (Liengen and Olsen 1997).
The seasonal growth patterns of aquatic mosses produce differences in shoot and leaf
dimensions on both stems and branches. The stems have shorter internodes, more densely
arranged leaves and longer lateral branches in summer than in winter (Seppelt 1983; Seppelt
and Selkirk 1984; Li et al. 2009). This may be useful in reconstructing annual growth of
aquatic mosses and also to estimate growth rates (Ilyashuk 2001).
Warnstorfia exannulata in Svalbard shows a distinct seasonal growth pattern. The
summer leaves are about 2.4 mm long and winter leaves 1 mm. On average, there are about
12 leaves per centimeter on stems produced in summer and about seven leaves per centimeter on stems produced in winter. Color of the leaves is slightly lighter in summer than in
winter. Most lateral branches are initiated in summer while almost none appear in winter
(Fig. 5). We measured the length of the main stems of 20 separate specimens produced in
2006 and 2007 with distinct summer and winter growth pattern. Increase in main stem length
is 0.7−3.7 cm (mean 1.87 cm) in winter and 2.0−12.5 cm (mean 6.28 cm) in summer.
Considering the total number of days in winter and summer separately, the mean daily
extension of the main stems is about 0.07 mm in winter and 0.68 mm in summer.
To estimate the age of this aquatic moss by its mean annual growth rate, we divided the
length of a stem by the annual extension rate of 3.6−12.3 cm (the summer length plus winter
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length in a year, mean 7.6 cm). The longest specimens collected were 28 cm in length. Growth
measurements indicate submergence in water of the shortest to longest plants for 2–8 years.
5.2 Responses to temperature changes
The summer growth in 2007 showed three phases of development (Figs. 5 and 7). The stems
start to grow in Stage I, producing dense leaves and many lateral branches. Stage II is
represented by a phase of leaf growth only. This is followed by a third phase of growth
(Stage III) in which leaves and lateral branches are again produced, although the lateral
branches produced are shorter in length than those in stage I and the lateral branches finally
rarely being produced in the winter of 2007.
We consider two primary factors, which might influence the summer growth of Warnstorfia exannulata in the Arctic area: ambient light intensity and temperature. During the
summer (from 1 June to 31 August), especially during the polar day (from 19 April to 23
August) when the sun remains above the horizon, there is an excess of photosynthetically
active radiation (Imura et al. 2003; Leu et al. 2006) and ambient temperatures may exert a
greater influence on assimilation and growth.
The temperature of the lake waters is influenced at least in part by solar radiation and
ambient temperatures, especially in shallow lakes (Douglas and Smol 1994). In summer, the
monthly mean air temperatures correspond well with water temperatures of the uppermost
meters of lakes, and they correspond with each other more closely in June and July than in late
summer (August) (Livingstone and Lotter 1998). The mean water temperature in a lake
of Lützelsee (maximum depth <6.2 m) mirrors the air temperature from spring to autumn
(Livingstone and Schanz 1994). In this work, we have accepted the premise that the air temperature may be a useful alternative to reflect water temperature (Livingstone and Lotter 1998).
Due to logistical limitations we were not able to obtain water temperatures in NyÅlesund; daily average air temperatures at the height 2 m above the land surface from 1
May to 30 September 2007 in Ny-Ålesund were obtained and we used the assumption that
the temperature changes in water and in air follow the same pattern (Hondzo and Stefan
1993; Livingstone and Lotter 1998; Livingstone and Schanz 1994) (Fig. 6). We divided the
temperature changes into five stages. In Stage I−1 from 1 to 19 June, the air temperatures
increased from +1.70 °C to +5.92 °C. At the beginning of summer, the availability of light
intensity in lakes increases following the increased day length and the melting of snow and
ice, and the nutrients in this period also increase in water. All factors benefit the onset of
aquatic moss growth in this period. Temperatures rose gradually from 20 June to 6 August
(Stage I−2) (+3.98 °C to +10.3 °C). Active growth of the moss occurs during this time. In
stage II, from 7 August to 24 August, the temperatures decreased from +9.87 °C to −0.04 °C.
During this stage the moss did not produce lateral branches. In Stage III−1 (from 25 August to
14 September) the temperature increased from −1.62 °C to +3.81 °C. In the last stage III−2,
from 15 September to 30 September, mean daily temperatures were from −3.4 °C to 3.21 °C,
with some daily maxima above 0 °C. In general, it starts to snow in late August (for example, on
10 August 2011) or in early September in Ny-Ålesund. But it was warm in September 2007, and
the daily maximum temperatures were still high (above 0 °C) on about 20 days (Fig. 6). The
moss still produced lateral branches in September.
To further consider the influence of temperature changes on the growth of aquatic
Warnstorfia exannulata, we selected the specimen (a) (Fig. 5) as representative of the
moss collection, as it possessed the same growth pattern in the summer of 2007. In
Fig. 7 there were five stages of growth. In stage I−1, with the resumption of growth
under the influence of an increase of temperature, the leaves were 0.06 cm−0.18 cm,
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and the lateral branches were 0.78 cm−1.09 cm long. In stage I−2, when the moss
grew quickly and produced more lateral branches, the leaves were 0.15 cm−0.39 cm
and the lateral branches were 0.91 cm−1.21 cm long. In stage II, the air temperature
decreased remarkably from 9.87°C to −0.04°C, and the moss produced leaves only, measuring
0.15−0.42 cm in length. In stage III−1, the moss resumed growth quickly and the leaves produced
were 0.15−0.33 cm and the lateral branches were 0.45−1.30 cm long. In the last stage III−2 in the
summer of 2007, the mosses grew very slowly with the decrease of temperature. The new lateral
branches were shorter than in the former stage and ceased to be produced in winter. The leaves and
lateral branches produced were 0.15−0.33 cm and 0.36−0.55 cm long respectively.
Changes in leaf and branch length in these different growth phases are depicted in Fig. 7,
mirroring temperature changes in the same summer (Fig. 6). As an aquatic moss, Warnstorfia exannulata appears to be very sensitive to temperature changes, and may be particularly useful as an indicator of environmental changes.
5.3 Global distribution
Warnstorfia exannulata is a bipolar species with some intermediate altimontane localities in
the tropics of Africa and South America (Fig. 8). It has a continuous range throughout much
of the cold, cool and temperate regions in the Northern Hemisphere, reaching maximum
geographical latitudes on Axel Heiberg Island at ca. 79°25′N (Kuc 1973) and on northern
Ellesmere Island at ca 81°N (Brassard 1971) in the Canadian Arctic Archipelago in North
America and in northwestern Spitsbergen at ca. 78°56′N. It extends southwards to northern
California and Colorado in the western part of the continent to the Great Lakes region and
the northwestern United States in North America, and from eastern North American south to
New York and Pennsylvania. It extends from the southern Iberian Peninsula, to Sicilia, the
Balkan Peninsula and the Caucasus in Europe, and Central Asia, Central Siberia and
northern Mongolia, northeastern China and central Honshu, Japan in Asia. It is also known
from the Sino-Himalayan region and northern India and central China in Asia. In the
Southern Hemisphere it has a bi-centric distribution. It is common and locally abundant in
Tierra del Fuego (Ochyra and Matteri 2001) and western Patagonia, and occasional on the
Falkland Islands and subantarctic South Georgia (Ochyra et al. 2002) in the Western
Hemisphere and in southeastern Australia, Tasmania and on the South Island of New
Zealand, extending to subantarctic Macquarie Island in the Eastern Hemisphere (Ellis et
al. 2011). W. exannulata is quite frequent in the Northern Andes and in Bolivia (Hedenäs
2003) and rare in East Africa (O’Shea 2006).
As far as is known Warnstorfia exannulata only occupied terrestrial habitats in NyÅlesund 50 years ago (Arnell and Mårtensson 1959). Aquatic specimens of W. exannulata
were found for the first time in a pool in this district of Spitsbergen in 2008 and had been
growing there for at least 2 years.
The distribution patterns of aquatic mosses at high latitude regions of the earth are
controlled strongly by climate, light availability and water chemistry. Global warming and
its impact on the climatically sensitive ecosystems of high latitudes, such as in the Arctic,
may also be reflected in the environmental conditions of lakes and pools (Smol 1983, 1988;
Douglas and Smol 1994; Schindler and Smol 2006).
Otherwise terrestrial mosses may be found growing in lakes, having been transported
there as fragments or other propagules (Kanda and Mochida 1992). It is also possible that
some species may have persisted from earlier times only in the lake, having disappeared
from the surrounding land (Li et al. 2009). Riis and Sand-Jensen (1997) indicate that mosses
extend from shallow to deep water in Lake Grane Langso, Mid-Jutland, Denmark, and they
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are exposed to the decline of irradiance with depth and the extended summer stratification
(May-October), which may result in the accumulation of CO2 and depletion of O2 in the
hypolimnion in the deep water (below 8 m). The worldwide dominance of mosses in lakes of
cold regions and at depth within lakes (Frantz and Cordone 1967; Priddle 1980; McIntire et
al. 1994) suggests that many species are well-adapted to growth and survival under low light
and low temperature. Some normally terrestrial mosses are quite capable of growing in lakes
and they may grow at considerable depths.
In this work, we focus on the possible relationship between seasonal growth patterns of
the aquatic moss Warnstorfia exannulata and the daily changes of air temperature in the
summer of 2007 and the potential use of seasonal growth increments as a surrogate measure
of past temperature changes. The changes of light intensity (Riis and Sand-Jensen 1997;
Imura et al. 2003; Kudoh et al. 2003; Leu et al. 2006), day length, nutrient and CO2
availability (Riis and Sand-Jensen 1997) also influence growth and development of both
terrestrial and aquatic mosses. Further detailed field measurements are needed to elucidate
the interplay of these factors on aquatic moss growth in Ny-Ålesund.
Acknowledgments We wish to express our sincere gratitude to the Chinese Arctic and Antarctic Administration, the State Oceanic Administration of China. Many thanks also to the members of the 5th Chinese
Antarctic Scientific Expedition teams for their help during the field work. We would like to thank Halina
Bednarek-Ochyra for providing the drawings of the leaves. This study was supported by the International Cooperation Project of Chinese Arctic and Antarctic Administration (No. IC 201103), the Innovation Key
Program of the Chinese Academy of Sciences (No. KSCX2-EW-J-1) and the National Natural Science
Foundation of China (No. 41271222).
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