Seasonal and altitudinal variations in snow algal communities on an Alaskan glacier (Gulkana glacier in the Alaska range)
Seasonal and altitudinal variations in snow algal communities on an Alaskan glacier (Gulkana...
Snow and ice algae are cold tolerant algae growing on the surface of snow and ice, and they play an important role in the carbon cycles for glaciers and snowﬁelds in the world. Seasonal and altitudinal variations in seven major taxa of algae (green algae and cyanobacteria) were investigated on the Gulkana glacier in Alaska at six different elevations from May to September in 2001. The snow algal communities and their biomasses changed over time and elevation. Snow algae were rarely observed on the glacier in May although air temperature had been above 0 C since the middle of the month and surface snow had melted. In June, algae appeared in the lower areas of the glacier, where the ablation ice surface was exposed. In August, the distribution of algae was extended to the upper parts of the glacier as the snow line was elevated. In September, the glacier surface was ﬁnally covered with new winter snow, which terminated algal growth in the season. Mean algal biomass of the study sites 2 2 continuously increased and reached 6:3 10 l m in cell volume or 13 mg carbon m in September. The algal community was dominated by Chlamydomonas nivalis on the snow surface, and by Ancylonema nordenskioldii ¨ and Mesotaenium berggrenii on the ice surface throughout the melting season. Other algae were less abundant and appeared in only a limited area of the glacier. Results in this study suggest that algae on both snow and ice surfaces signiﬁcantly contribute to the net production of organic carbon on the glacier and substantially affect surface albedo of the snow and ice during the melting season. Keywords: snow algae, glacier, Alaska, community structure S Online supplementary data available from stacks.iop.org/ERL/8/035002/mmedia 1. Introduction They grow in cryoconite holes and on thawing snow or ice surfaces and produce a substantial amount of organic carbon. For example, in situ measurements revealed that the primary Snow and ice algae are autotrophic microbes and are commonly observed on glaciers and snowﬁelds worldwide. productivity in cryoconite holes has the potential to produce as much as 98 Gg of carbon per year on a global basis (Anesio Content from this work may be used under the terms of et al 2009) although considerable uncertainty surrounds the the Creative Commons Attribution 3.0 licence. Any further validity of the global upscaling. Moreover, models of carbon distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. ﬂuxes on the Greenland ice sheet predicted that algae on 1748-9326/13/035002C10$33.00 1 2013 IOP Publishing Ltd Printed in the UK Environ. Res. Lett. 8 (2013) 035002 N Takeuchi glacial ice surfaces considerably ﬁx more carbon than those and ice areas Yoshimura et al 1997), and opportunist algae, in cryoconite holes, suggesting that the glacier surfaces are which could grow in special conditions, appear in certain potentially of global importance in carbon cycling (Cook et al areas of glaciers (e.g. Cylindrocystis brebissonii ´ in Alaska, 2012). In Alaska, an estimate with a satellite image showed which appeared in only the area near the glacier terminus, that 1:2 kg km of carbon can be produced by snow algae Takeuchi 2001). Total algal biomass also signiﬁcantly changes during the summer on the Harding Iceﬁeld (Takeuchi et al with elevation; it is greater in the lower part in Himalayan 2006a). The algal products sustain heterotrophic organisms glaciers (e.g. Yoshimura et al 1997, Takeuchi et al 1998) or including cold tolerant animal and bacterial communities in the middle part in an Alaskan glacier (e.g. Takeuchi 2001). which live there. For example, there are midges and copepods However, these observations were based on a single snap-shot on Himalayan glaciers, and ice worms and collembolas on during the melting season and biomass and community North American glaciers (see e.g. Goodman 1971, Kohshima structure can possibly change intra-seasonally. 1984, Kikuchi 1994, Hoham and Duval 2001, Aitchison Ice core studies revealed that algal biomass and species 2001). These organisms can store or transform organic carbon composition preserved in the past layers of the glacier showed on glaciers, and release it into a proglacial stream thus signiﬁcant inter-annual variation (e.g. Yoshimura et al 2000, affecting carbon cycling in glacier-fed rivers (e.g. Singer et al Takeuchi et al 2009). This is probably due to variations in 2012). Therefore, snow algae play an important role as a physical conditions, such as air temperature, precipitation, and primary producer in such simple food webs and carbon cycles solar radiation during the melting season and/or in chemical on snowﬁelds and glaciers (e.g. Kohshima 1987, Hoham and conditions of snow, which could affect algal growth. As Duval 2001, Hodson et al 2008, 2010). physical and chemical conditions on the glacier surface also Bloom of snow algae can visibly change the color of the change through the melting season, the snow algal community snow or ice and can alter its surface albedo. Red colored snow would seasonally change in biomass or species composition. is a typical algal bloom (usually by Chlamydomonas nivalis) However, little is known about the intra-seasonal change of observed on snow surfaces worldwide (e.g. Hoham and Duval the algal community on glaciers. The seasonal changes could 2001). Organic matter derived from such snow algae including be valuable in understanding the ecology of glacial algae and algal cells, dead body of algae, and some other materials, can in evaluating the net production of organic carbon on glaciers reduce the surface albedo, enhance the absorbance of solar and their effect on the surface albedo of snow and ice. radiation, and then accelerate the melt rate of the snow or In this study, the author aims to describe a seasonal ice surface (e.g. Thomas and Duval 1995, Takeuchi 2009). change of snow algal communities on an Alaskan glacier Studies on the Greenland ice sheet have recently shown that (Gulkana glacier in central Alaska). The altitudinal distri- strongly pigmented ice algae have a potential impact on ice bution of the algal community was investigated four times surface albedo (Yallop et al 2012) and that cyanobacteria from May to September in 2001. The seasonal variation of also play a role in forming dark regions, such as the the community is discussed in terms of the physical and low-albedo ice surfaces that have appeared in the west margin chemical conditions of the glacier surface. The effect of the of the Greenland ice sheet (Wientjes and Oerlemans 2010, algal community on surface albedo is also discussed with the Wientjes et al 2011). On Asian glaciers, abundant ﬁlamentous spectral reﬂectivities that were simultaneously measured and cyanobacteria form granular algal mats (cryoconite granules) has been published elsewhere (Takeuchi 2009). and cover the entire glacier surface (Takeuchi et al 2001, Takeuchi and Li 2008). They signiﬁcantly reduce the surface 2. Study site and methods albedo of glaciers and could affect their mass balance. Thus, it is important to determine the factors affecting algal biomass The investigations were carried out in 2001 on the Gulkana and community structure for evaluation of the melt rate of glacier, located in the Alaska Range, in Alaska, United States snow and ice. of America (ﬁgure 1, photographs of the glacier are available Snow algal communities on glaciers usually consist of as supplementary information available at stacks.iop.org/ several taxa including green algae and cyanobacteria and ERL/8/035002/mmedia). The glacier ﬂows west to south from vary signiﬁcantly among different altitudes of the glacier Icefall Peak (about 2440 m above sea level (a.s.l.)) down to the surface. Spatial variation in snow algal communities has been terminus at an elevation of about 1220 m a.s.l. This glacier is described on glaciers in the Himalayas, Altai, Patagonia, easily accessible from the Richardson Highway and has been Alaska, and Greenland (e.g. Yoshimura et al 1997, Takeuchi monitored for several decades by the University of Alaska and 2001, Takeuchi and Kohshima 2004, Takeuchi et al 2006b, the United States Geological Survey (USGS, e.g. Josberger Uetake et al 2010). According to these studies, the algal et al 2007). The glacier has been generally receding over the community in the upper snow area of glaciers is usually last 50 years and has lost 11 5 m in ice equivalent thickness dominated by snow environment specialists, which preferably grow on a snow surface, whereas that in the lower ice averaged over the whole glacier between 1954 and 1993 area is dominated by ice environment specialists, which (Dowdeswell et al 1997). The length and area of the glacier preferably grow on an ice surface. Furthermore, generalist are approximately 4 km and 21:8 km , respectively. The algae, which could grow on both snow and ice surfaces, equilibrium line of the glacial mass balance in the year (2001) can be distributed in all areas of glaciers (e.g. Mesotaenium was approximately 1790 m a.s.l. by USGS measurement berggrenii in the Himalayas, which appeared in both snow (http://ak.water.usgs.gov/glaciology/gulkana/index.html). 2 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi Figure 1. A map of the Gulkana glacier in the Alaska range, showing sampling sites and locations of the snow line in each study month on the glacier surface. The snow line in May was located about 3 km downstream from the glacier terminus at an elevation of 1055 m. Prior to this research, sampling was conducted on the glacier in August 2000. The investigation revealed that the snow algal community on the glacier consisted of seven taxa and the biomass and community structure varied with altitude (Takeuchi 2001). The abundance of organic matter and mineral particles on the glacier surface ranged from 0.09 Figure 2. Air temperature (a) and glacier discharge (b) recorded at 2 2 the Gulkana glacier during the study period by USGS, and the to 7:9 g m , and from 0.67 to 97:8 g m , respectively, 30 year average of monthly solar radiation (1961–1990) and varied with the elevation (Takeuchi 2002). Recently, (c) measured at the metrological station (Gulkana Station). Dashed community structure and phenotypes of bacteria and yeasts lines indicate the dates of sample collection. on the glacier have been described by DNA analysis and culturing (Segawa et al 2010, Uetake et al 2012). While these studies were based on a single sampling in the summer ice/snow were carried out at six sites, from 1270 m to 1770 m melting season, this paper aims to describe seasonal variations a.s.l. (S1–S6, ﬁgure 1). The six sites were the same locations in the community based on four sampling occasions in 2001. as the sites of the former study in 2000 (Takeuchi 2001) and Daily means of air temperature and discharge of the were determined by GPS. All sites were at least 500 m away glacier, measured from May to September in 2001 at the from the side margin of the glacier. The number of sites was automatic station of the Gulkana glacier by USGS (http://ak. decided by considering possible logistics of the sampling and water.usgs.gov/glaciology/gulkana/index.html), are shown in sufﬁcient numbers to describe seasonal changes of the algal ﬁgure 2. The discharge is roughly indicative of melt activity community. The slope of the sampling surface varied from on the glacier surface, although the discharge lagged from 7 to 12 between site S2 and S6, and was slightly steeper meltwater production by a few days due to water storage in at site S1 (12 –15 ). The samples in May and September in the drainage system of the glacier (Kido et al 2007). Since 2001 were collected only at sites 2 and 4, and at sites 1–5, solar radiation was not measured at the station, a 30 year respectively. average of monthly solar radiation, 1961–1990, measured Surface ice/snow was collected with a stainless-steel at the meteorological station (Gulkana Station, located at scoop (1–2 cm in depth). Five samples were collected from approximately 123 km south from the glacier, the data can the randomly selected surfaces at each site. The collected be downloaded from the National Solar Radiation Data Base, area on the surface was measured to calculate the amount of www.nrel.gov/rredc/solar data.html) is shown in ﬁgure 2. algal volume biomass per unit area. The collected samples The sampling was carried out four times from spring to were melted and preserved as a 3% formalin solution in clean late summer of 2001. The four periods of the sampling were 125 ml polyethylene bottles. All samples were transported to in May (from 28 May to 1 June), in June (from 25 to 29 June), the International Arctic Research Center, University of Alaska in August (from 6 to 10 August), and in September (from Fairbanks (about 4 h). Electrical conductivity (EC) and pH 3 to 7 September). In each sampling, collections of surface for glacial meltwater and snow were measured in situ and in 3 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi the laboratory, respectively, with a portable pH–conductivity meter (Cyberscan PC300, Eutech Instruments Pte Ltd, USA). The algal biomass of each site was represented by algal cell volume (biovolume) per unit area. Cell counts and estimations of cell volume were conducted with an optical microscope (Nikon E600). The samples were stained with 0.5% erythrosine (0.1 ml was added to 3 ml of the sample) and ultrasonicated for 5 min to loosen sedimented particles. 50–1000 l of the sample water was ﬁltered through a hydrophilized PTFE membrane ﬁlter (pore size 0:5 m, Millipore FHLC01300), which became transparent with water, and the number of algae on the ﬁlter was counted (1–3 lines on the ﬁlter). The counting was conducted 3–6 times on each sample. From the mean results and ﬁltered sample water, the cell concentration (cells ml ) of the sample was obtained. Mean cell volume was estimated by measuring the size of 50–100 cells for each species, which was identiﬁed as described in Takeuchi (2001). The total algal biomass was estimated by summing values obtained by multiplying algal concentrations by the mean cell volume. This calculation was done for each species at each site. To obtain the spatial biomass at each site, the total biomass was represented as Figure 3. Seasonal change in the altitudinal distribution pattern of a cell volume per unit area of glacier surface (l m ). the total algal cell volume biomass on Gulkana glacier from May to September 2001. The dashed lines indicate the location of the snow Community structure was represented by the mean proportion line. Error bar D standard deviation. of each species in ﬁve samples to the total algal volume at each sampling point. In order to facilitate comparison with other studies, algal biomass was also expressed in carbon equivalent were no algae on the glacier, visible red snow was observed (mg C), using a conversion factor of 0.02 mg carbon per 1 l approximately 3 km downstream from the terminus of the cell volume (Fogg 1967). glacier. The winter snow was still on the ground down to about the elevation of 1055 m. The red snow was apparent just 3. Results above the snow line. Microscopy revealed that the red snow contained abundant spherical red algal cells of Cd. nivalis. 3.1. Snow algae on the glacier Thus, although snow alga had not appeared yet on the glacier surface in this month, snow algae bloomed on the seasonal Seven taxa of snow algae were observed on the glacier snow cover further downstream of the glacier. surface. The algal taxa observed in this study season In June, snow algae were observed at the lower three sites. were the same as those observed in the previous year The mean algal biomass among the sites ranged from 213 to 2 2 in 2000 (Takeuchi 2001). The algae included ﬁve green 262 l m or from 4.3 to 5:2 mg C m . There was no algae (Chlorophyta) and two cyanobacteria. The green signiﬁcant difference in the biomass among the sites (one-way algae are Chlamydomonas (Cd.) nivalis, Mesotaenium (M.) ANOVA, F D 3:885; P D 0:946 > 0:05). berggrenii, Ancylonema (A.) nordenskioldii ¨ , Cylindrocystis In August, snow algae were observed at all of the study (Cyl.) brebissonii ´ , Raphidonema sp. Both of the cyanobacteria sites (ﬁgure 3). The mean algal biomass ranged from 166 to 2 2 are ﬁlamentous Oscillatoriaceae cyanobacteria. 521 l m or from 3.3 to 10:4 mg C m . There was no signiﬁcant difference in the biomass among the sites (one-way ANOVA, F D 2:621; P D 0:130 > 0:05). 3.2. Seasonal and spatial variations in the total biomass of In September, the algae were observed at the lower ﬁve snow algae sites on the glacier (ﬁgure 3). The sample at the highest site Microscopy of the snow and ice samples revealed that (site S6) could not be collected in this month due to heavy snow algae were not present on the glacier in May, but snow fall during the sampling. The snow line was located they appeared from late spring (June) until late summer above site S5, thus all of the lower ﬁve sites are in the ice area. (September, ﬁgure 3). In May, neither snow sample collected The mean algal biomass ranged from 190 to 1178 l m or at two sites on the glacier (sites S2 and S4) contained any from 3.8 to 23:6 mg C m . The biomass gradually increased 2 2 algal cells. The glacier surface at this time was still completely from the lowest site (S1, 190 l m or 3:8 mg C m ) 2 2 covered with winter snow. The snow depths were 39 cm to the middle site (S4, 1178 l m or 23:6 mg C m ), at site S2 and 54 cm at site S4 when the samples were and decreased at the higher site (S5, 619 l m or collected. The surface snow was thawing in daytime in all 12:4 mg C m ). There was a signiﬁcant difference in the the study sites. The snow temperatures were constantly 0 C biomass among the sites (one-way ANOVA, F D 2:866; P D from the surface to the bottom in both sites. Although there 0:002 < 0:01). The algal biomass in August and September 4 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi Figure 4. Seasonal change in the altitudinal distribution pattern of seven algal taxa (cell volume biomass) on the Gulkana glacier from May to September 2001. The dashed lines indicate the location of the snow line. was comparable to those in August of the previous year, 2000, generally distributed from the ice area to the upper snow which ranged from 84 to 882 l m (Takeuchi 2001). The area. Its distribution expanded gradually upward of the glacier altitudinal trend of the biomass observed in September was from June to September. The maximum biomass was always also similar to that in 2000. located at the snow surface near the snow line. The location The biomass at all of the sites on the glacier generally moved upward as the snow line rose; it was at site S3 in increased from May to September (ﬁgure 3) although the June and at site S5 in August and September. The maximum appearance of algae on the surface was delayed at higher site was visibly recognized as red snow in the ﬁeld since sites. The mean algal biomass of the study sites continuously this alga has a red pigment. Red snow was always observed 2 2 increased from 0:0 l m in May to 628 l m or at just above the snow line throughout the study period. M. 13 mg C m in September. Although the appearance of algae berggrenii and A. nordenskioldii ¨ distributed in the entire ice was late at site S4, its biomass showed signiﬁcantly higher surface and their distribution expanded to the upper part as 2 1 2 1 increasing rate (25:1 l m day or 0:50 mg C m day ) the ice surface was exposed from June to September. The 2 1 compared with other sites (0:21–11:6 l m day or maximum biomasses of both algae were observed at the 2 1 0:004–0:23 mg C m day ). A statistical test shows that middle part (sites S3 or S4) of the glacier. Their biomass the seasonal variations in the biomass were signiﬁcant at sites gradually increased until September. Cyl. brebissonii ´ and S2–S6, (one-way ANOVA, S2: F D 5:82; P D 0:006I S3 V Oscillatoriacean cyanobacterium 2 appeared at the lowest F D 4:35; P D 0:037; S4: F D 26:1; P D 0:000; S5: F D site of the ice surface throughout the seasons. Raphidonema 10:7; P D 0:002; S6: F D 60:1; P D 0:000), while they were sp. appeared near the snow line in the ice area. Its location not signiﬁcant at site S1 (F D 1:21; P D 0:33 > 0:05). moved with the rising snow line. The altitudinal distribution EC and pH were did not signiﬁcantly vary among the of community structure in August agreed well with that in study sites and seasons. All of the ECs measured on the glacier August of the previous year, 2000 (Takeuchi 2001). were less than 4:0 S cm . The EC for snow in May was Seasonal change in the algal community structure at slightly higher, but there was no signiﬁcant difference among each study site showed that the structure generally changed the study sites and seasons. pH ranged from 4.80 to 5.69, and from the dominance of Cd. nivalis to the dominance of A. showed no clear trend among the study sites, seasons, snow, nordenskioldii ¨ and M. berggrenii (ﬁgure 5). In the snow area, or ice. the biomass of Cd. nivalis accounted for more than 99% to the total algal biomass (e.g. site S3 in June, S5 in August). After 3.3. Seasonal change in the algal community the snow disappeared and the bare ice surface was exposed, A. nordenskioldii ¨ and M. berggrenii appeared. In the bare Each algal taxon showed a distinctive pattern of spatial ice area, the two algae accounted for 44–96% to the total and seasonal changes of its biomass (ﬁgure 4). Cd. nivalis biomass. The proportion of A. nordenskioldii ¨ was slightly 5 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi growth are those for Cd. nivalis on the snow surface. The appearance of Cd. nivalis started in the snow surface further brébissonii downstream from the glacier terminus in May, then gradually berggrenii moved up to the glacier: site S3 in June and site S5 in August. These areas were the snow surfaces just above the snow line, suggesting that the snow depth on the ice surface nordenskiöldii is one of the important conditions. As described in other studies on snowﬁelds (e.g. Hoham 1980), snow algal blooms are initiated when air temperatures remain above freezing for several consecutive days, a meltwater develops in the berggrenii snow, nutrients and dissolved gases are available to algae, and light penetrates through the snow. With a combination of the above factors, the resting zygospores germinate at the nordenskiöldii snow–previous ice surface interface releasing zoospores that swim in the liquid meltwater towards the surface of the snow, causing visible blooms only a few days after germination. When algae were rarely observed on the glacier in May, the berggrenii air temperature had been above freezing since the middle of May (ﬁgure 2) and the surface snow melted in all of the study areas, indicating that snow melting is not the only condition nordenskiöldii for the initiation of algal growth on the glacier. Chemical conditions such as EC and pH seem not to associate with the algal initiation since there was no signiﬁcant difference among the study sites and seasons. However, no other chemical berggrenii analyses were carried out in this study and thus the inﬂuence of other chemical variables (e.g. nitrogen and phosphorus) on nordenskiöldii the growth of algae during the melt season is still unknown. The snow depths on the glacier in May were 39 cm and 54 cm at sites S2 and S4, respectively, which were almost the same as or deeper than the limit of the snow depth for algal growth (40 cm, Muller ¨ et al 2001). The snow depth that is shallow enough (less than 40 cm) for light penetration and migration for algae under the snow, which occurred in June, is probably an important condition on this glacier. The area in which algae were observed was also characterized by high liquid water content. Melt water of the snow surface usually percolates down in the layers and ﬂows to the lower area along the ice surface below, and thus the water content of snow is very high at the transition zone of snow and ice. Snow Figure 5. Seasonal change in algal community structure at study algae grows in the liquid water ﬁlm surrounding snow grains sites S1–S5 on the Gulkana glacier from June to September 2001. (e.g. Fukushima 1963), thus water contents could also play a role in the initiation of algal growth. Once the algae appeared on the surface, the algal biomass larger than that of M. berggrenii (mean: 40% versus 28%). generally kept increasing until the end of the melt season Cyl. brebissonii, which appeared only at the lowest site (S1), (September) in most of the sites (sites S2 to S6), but it did accounted for 6–27% of the total biomass at the site. The other not signiﬁcantly change in the lowest site S1. The increase algae observed on the glacier were rather minor in terms of the of biomass throughout the melt season suggests that the algal cell volume biomass, accounting for less than 8% of the total growth rate was always larger than the rate of death and biomass. removal of algae. Although solar radiation, air temperature, and melt activity decreased from August (ﬁgure 2), the 4. Discussion biomass kept increasing. The continuous increase suggests a lack of any physical or chemical limitation for algal growth 4.1. Appearance and seasonal change of snow algae on the during the melt season in this area. On the contrary, the glacier biomass without signiﬁcant change at the site S1 suggests that The difference in timing of the algal appearance among the the algal growth rate was roughly equivalent to the rate of study sites is likely attributed to the condition of the snow. death or removal of algae. As described in previous papers The taxon that appeared ﬁrst was Cd. nivalis in all of the (Takeuchi 2002, 2009), amounts of surface dust at the site study sites, thus the conditions of the beginning of algal S1 are signiﬁcantly greater than those at the upper sites. 6 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi This is likely due to the larger supply of windblown mineral surface. Since the mineral dust has lower reﬂectance than ice, particles from the surrounding ground, and of subglacial ﬁne it could absorb solar radiation and slightly increase meltwater temperature on the ice surface. These conditions may be sediment (till) from basal ice. The large amounts of mineral preferable to the algae. dust covering the ice surface may limit photosynthesis of Raphidonema sp. appeared on the glacier from June to the algae. Furthermore, since the slope is a major factor determining the accumulation of organic matter (Stibal et al September and were observed at only the area just below the 2012), the steeper slope and greater running meltwater on the snow line. Stibal and Elster (2005) reported that Raphidonema surface in this lowest area possibly wash the algal cells out of nivale observed on a glacier in Svalbard is a soil species, which is well adapted to soil environment and is only the glacier. occasionally brought on snow by wind. Since Raphidonema sp. observed on the Gulkana glacier is morphologically very 4.2. Seasonal changes and type of snow algal taxa similar to Raphidonema nivale, it may also be a soil alga. The proportion of Raphidonema sp. to the total algal biomass According to the previous study of snow algae on the glacier was very small (less than 0.01% to the total cell volume), (Takeuchi 2001), the snow algae can be classiﬁed into three suggesting that they are not specialized on snow or ice. The types based on their spatial distribution. Cd. nivalis was clas- alga was observed on the area just below the snow line, siﬁed as a snow environment specialist. A. nordenskioldii ¨ and probably because the amount of running meltwater in this area M. berggrenii were classiﬁed as ice environment specialists. is less than in the lower area. The four other algae, Cyl. brebissonii ´ , Raphidonema sp., The two Oscillatoriacean cyanobacteria observed on the and two Oscillatoriaceae cyanobacteria, were classiﬁed as ice surface are also probably originally from soil. It has been opportunists. The seasonal changes in distribution patterns of reported that most of the cyanobacteria observed on glaciers each taxon were also distinct among the types. The results were also be found in soil around the glacier (e.g. Stibal et al supported the spatial distribution of each algal taxon being 2006). Their appearance is, therefore, similar to the other soil determined by their preferable conditions on the glacier algae on the glacier. surface throughout the melting seasons. The seasonal change These differences of each alga are important to evaluate of the distribution of each taxon is likely due to changes of the the net production of organic carbon on the glacier. In physical conditions associated with the retreat of the seasonal particular, Cd. nivalis in the snow area and A. nordenskioldii ¨ snow line. and M. berggrenii in the ice area, are likely to be the major The snow environmental specialist, Cd. nivalis, was algae to produce organic carbon on this glacier. The results dominant on the snow area throughout the seasons. However, indicate that algae grew on all of the exposed ice area, but its distribution did not extend to all of the snow area, but to on the limited part on the snow area throughout the melting the limited areas, which were the snow surfaces just above the season. The proportion of algal biomass between snow and ice snow line. As mentioned above, the distribution may be due to areas did not change greatly from June to August, which were high liquid water content in the snow and/or a snow depth that 37.3% and 62.7% in June and 36.3% and 63.7% in August. is shallow enough for the migration of algae from the bottom The result suggests that algae on the ice areas account for of the snow. the large part of the net production of organic carbon on the The ice environment specialists, A. nordenskioldii ¨ and glacier, but algae on the snow area also signiﬁcantly contribute M. berggrenii, appeared on the ice surface immediately after to it during the melting season. In order to evaluate exactly the winter snow disappeared. They distributed widely on the the relative importance between snow and ice algae for the bare ice area and remained dominant until the end of the net production of organic carbon, more information on algae melting season, suggesting that these two algae are the most and other organic matter is necessary, such as life span and the adaptable taxa to the ice environment. This is consistent with biomass–carbon ratio of each alga, and altitudinal distribution the studies on ecophysiology and ultrastructure of the two of the glacier area. taxa, which showed that they have a freezing tolerance, and are adapted to temperatures close to the freezing point and 4.3. Effect of algal community on the spectral albedo of the to high light conditions (Remias et al 2009, 2012). Their glacier surface biomass kept increasing from June to September in the middle area of the glacier, suggesting that there was no limitation, According to a study on spectral reﬂectance on the glacier such as nutrients, for their growth in this area. surface (Takeuchi 2009), it varied spatially and seasonally, The opportunist algae, Cyl. brebissonii ´ and Oscillatori- and was altered substantially by impurities, such as mineral acean cyanobacterium 2, were distributed only in the lowest particles, organic matter, and algal cells on snow and ice of site (S1), and did not expand their distribution to the upper this glacier. Since each algal taxon has different secondary part throughout the seasons. They are likely to associate with pigments, change in algal biomass and community structure special conditions of the lowest area of the glacier. It has may affect the spectral reﬂectance on the glacier surface. In been reported that Cyl. brebissonii ´ is a soil alga and has a order to evaluate the effect of algal community on the surface higher optimum growth temperature (C10 C, Hoham 1975). albedo, the spectral reﬂectances reported in Takeuchi (2009) As mentioned above, large amounts of mineral dust covered were reexamined with the results of this study. the bare ice surface in this area. The abundant mineral dust The snow surfaces showing the distinctive spectrum may alter surface ice structure and chemical conditions on the with two absorptions at wavelength ranges of 400–600 and 7 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi effect of other impurities, such as dead bodies of algae, humic substance, and mineral particles, which may be more abundant and have a larger effect on the spectrum compared with the algae. In contrast to the spectrum at site S4, that of the bare ice surface at site S1 was slightly different. The spectrum did not show absorption at wavelength ranges of 670–680 nm, but a ﬂat peak at 540 nm (ﬁgure 6). The algal community at the site was predominantly A. nordenskioldii ¨ and M. berggrenii and the total algal biomass was comparable to that at the other sites, but amounts of mineral particles on the surface was three- to four-fold greater than those of the ice surface of the upper sites (Takeuchi 2009). Thus, the effect of mineral particles is likely much stronger than that of algae, causing the spectrum that did not show any algal absorption features. The results showed that the algal community does affect spectral albedo on the glacier surface, but the effect may not be apparent if other impurities, such as mineral and other organic particles, are more optically effective. To parameterize surface albedo on the glacier, it is essential to quantify the supply and optical effect of mineral particles and to understand the formation process of humic substances and other organic particles, as well as to study quantitatively the seasonal variation of snow algae on the glacier surface. 5. Conclusions Investigations on the Gulkana glacier in Alaska in a melting season from May to September 2001 revealed that the algal Figure 6. Spectral reﬂectance curves on the snow and ice surfaces community and biomass on the glacier surface varied spatially at sites S1, S4, and S5, taken in August 2001 on the Gulkana and seasonally although there is still a potential to miss glacier, sourced from Takeuchi (2009). The curves show absorption other transient events due to the limited temporal resolution features of algal pigments (a), enlargement of the spectra in the reﬂectance between 0.1 and 0.3 (b). The arrows indicate the peaks of sampling in this study. Algae appeared on the snow of curves. The dashed line indicates 680 nm, where chlorophyll surface when the snow line was close to the area. Algal absorption is maximal. biomass continuously increased until the end of the melting season (September), except at the lowest area of the glacier, 670–680 nm (ﬁgure 6) corresponded to the surfaces where where the algal biomass did not signiﬁcantly change. The Cd. nivalis were abundant. The spectrum agreed with the algal community started with a predominance of Cd. nivalis absorptions of primary and secondary pigments of Cd. nivalis; (snow environment specialist), then changed to dominance the range of 400–600 nm was mainly due to carotenoids, of A. nordenskioldii ¨ and M. berggrenii (ice environment while the range of 670–680 nm was due to chlorophylls specialists). In some locations, other opportunist algae, which (e.g. Bidigare et al 1993). This type of spectrum was observed are originally from soil surrounding the glacier, appeared, but at S3 in June and at S5 and S6 in August, where Cd. nivalis they accounted for only a small part to the total algal biomass. was dominant and its biomass was more than 150 l m . This seasonal change is basically caused by the change of The spectrum of the bare ice surface at site S4 in surface conditions, i.e. from snow to ice. The change in August, where A. nordenskioldii ¨ and M. berggrenii were algal community at lower sites proceeded to that of upper dominant, was generally low and ﬂat in the visible range, parts of the glacier as the snow line rose on the glacier. but there was a small absorption at wavelength ranges of Although this study is limited to a single melting season, 670–680 nm, corresponding to chlorophylls, and a gradual the altitudinal distribution of algal biomass and community decrease as wavelength decreased at ranges of 350–590 nm structure in the summer season repeated in 2000 and 2001, (ﬁgure 6). The absorption of 350–590 nm is probably due thus the distribution probably appears in every year. However, to the brownish secondary pigment of A. nordenskioldii ¨ and recent retreat and shrinkage of the glacier may affect the M. berggrenii (Yallop et al 2012, Remias et al 2009, 2012). spatial and/or seasonal variations in algal communities on the The spectral absorption of the pigment gradually increases as surface. wavelength decreases in the range of 350–590 nm (Remias Results in this study also showed that Cd. nivalis in et al 2012), which agrees with the spectrum of the glacial the snow area and A. nordenskioldii ¨ and M. berggrenii surface. However, the feature of these algal pigments was in the ice area, were the major algae to produce organic very small on the spectrum. This is probably due to the carbon and to affect surface albedo on the glacier. The 8 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi three algae were common taxa observed on other glaciers Dowdeswell J A et al 1997 The mass balance of circum-Arctic glaciers and recent climate change Quat. Res. 48 1–14 in Alaska and worldwide. The snow environment specialist, Fogg G E 1967 Observations on the snow algae of the South Orkney Cd. nivalis, is reported all over the world as a cause of Islands Phil. Trans. R. Soc. B 252 279–87 the red snow phenomenon (e.g. Hoham and Duval 2001). Fukushima H 1963 Studies on cryophytes in Japan J. Yokohama Two ice environment specialist algae, A. nordenskioldii ¨ City Univ. C 43 1–146 and M. berggrenii are commonly observed on the bare Goodman D 1971 Ecological investigations of ice worms on ice surface of Alaska, Greenland, Svalbard, Altai, and the Casement glacier, Southeastern Alaska Institute of Polar Studies Report 39 (Columbus, OH: The Ohio State University Himalayas (e.g. Kol 1942, Yallop et al 2012, Takeuchi et al Research Foundation) 2003, 2006b, Remias et al 2009, 2012). A similar seasonal Hodson A, AnesioA M, Tranter M, Fountain A, Osborn M, Priscu J, change in algal community may occur on such glaciers, Laybourn-Parry J and Sattler B 2008 Glacial ecosystems Ecol. however, community structure and total algal biomass vary Monogr. 78 41–67 geographically (e.g. Takeuchi et al 2006b). Since the algal Hodson A, Cameron K, Bøggild C, Irvine-Fynn T, Langford H, community could affect the net carbon ﬂux and surface albedo Pearce D and Banwart S 2010 The structure, biological activity on the glacier, it is important to know what is responsible and biogeochemistry of cryoconite aggregates upon an Arctic valley glacier: Longyearbreen, Svalbard J. Glaciol. 56 349–62 for the geographical variations not only to understand glacier Hoham R W 1975 Optimum temperatures and temperature ranges ecosystems but also to evaluate glacial melting. Seasonal for growth of snow algae Arct. Alp. Res. 7 13–24 variation in algal community on the glacier could be useful to Hoham R W 1980 Unicellular chlorophytes–snow algae understand the conditions that determine the algal community Phytoﬂagellates ed R E Cox (New York: Elsevier in each geographical location. Although water content and North-Holland) pp 61–84 surface conditions seem to be important on the studied glacier, Hoham R W and Duval B 2001 Microbial ecology of snow and effects of windblown dust and nutrient availabilities, and freshwater ice Snow Ecology (Cambridge: Cambridge University Press) pp 168–228 climate conditions such as precipitation and solar radiation, Josberger E G, Bidlake W R, March R S and Kennedy B W 2007 may also be important on other glaciers. Furthermore, we Glacier mass-balance ﬂuctuations in the Paciﬁc Northwest and need to understand the life cycles of each alga on the glacier. Alaska, USA Ann. Glaciol. 46 291–6 Although further studies are necessary, understanding of snow Kido D, Chikita K A and Hirayama K 2007 Subglacial drainage and ice algal communities on glaciers is important to predict system changes of the Gulkana Glacier, Alaska: discharge and future changes of glacier ecosystems as a result of global sediment load observations and modelling Hydrol. Process. climate change. 21 399–410 Kikuchi Y 1994 Glaciella, a new genus of freshwater Canthocampyidae (Copepoda Harpacticoida) from a glacier in Acknowledgments Nepal, Himalayas Hydrobiologia 192/193 59–66 Kohshima S 1984 A novel cold-tolerant insect found in a Himalayan I wish to thank Drs Syunichi Akasofu, Motoyoshi Ikeda, and glacier Nature 310 225–7 Kohshima S 1987 Glacial biology and biotic communities Evolution Noriyuki Tanaka of the International Arctic Research Center, and Coadaptation in Biotic Communities (Tokyo: Tokyo University of Alaska Fairbanks for their generous support University Press) pp 77–92 and encouragement of this project, and Leonard Hansen, Les Kol E 1942 The snow and ice algae of Alaska Smithsonian Leslie, Naoaki Uzuka, Shiro Kohshima, Takahiro Segawa, and Miscellaneous Collection 101 1–36 Jun Uetake for expert ﬁeld assistance. I am also indebted Muller ¨ T, Leya T and Fur G 2001 Persistent snow algal ﬁelds in to two anonymous reviewers for valuable suggestions, Spitsbergen: ﬁeld observations and a hypothesis about the which greatly improved this letter. The ﬁeld work and annual cell circulation Arct. Antarct. Alp. Res. 33 42–51 Remias D, Holzinger A, Aigner S and Lutz ¨ C 2012 Ecophysiology laboratory analyses were funded by a project of the Frontier and ultrastructure of Ancylonema nordenskioldii ¨ Observational Research for Global Change (funded by (Zygnematales, Streptophyta), causing brown ice on glaciers in the Japan Marine Science and Technology Center) and Svalbard (high arctic) Polar Biol. 35 899–908 JSPS KAKENHI Grant Numbers 21681003, 23221004, and Remias D, Holzinger A and Lutz ¨ C 2009 Physiology, ultrastructure and habitat of the ice alga Mesotaenium berggrenii (Zygnemaphyceae, Chlorophyta) from glaciers in the European Alps Phycologia 48 302–12 References Segawa T, Takeuchi N, Ushida K, Kanda H and Kohshima S 2010 Altitudinal changes in a bacterial community on Gulkana Aitchison C W 2001 The effect of snow cover on small animals Glacier in Alaska Microbes Environ. 25 171–82 Snow Ecology (Cambridge: Cambridge University Press) Singer G A, Fasching C, Wilhelm L, Niggemann J, Steier P, pp 229–65 Dittmar T and Battin T J 2012 Biogeochemically diverse Anesio A M, Hodson A, Fritz A, Psenner R and Sattler B 2009 High organic matter in Alpine glaciers and its downstream fate microbial activity on glacier: importance to the global carbon Nature Geosci. 5 710–4 cycle Glob. Change Biol. 15 955–60 Stibal M and Elster J 2005 Growth and morphology variation as a Bidigare R R, Ondrusek M E, Kennicutt M C II, Iturriaga R, response to changing environmental factors in two Arctic Harvey H R, Hoham R and Wand Macko S A 1993 Evidence species of Raphidonema (Trebouxiophyceae) from snow and for a photoprotective function for secondary carotenoids of soil Polar Biol. 28 558–67 snow algae J. Phycol. 29 427–34 Cook J M, Hodson A J, Anesio A M, Hanna E, Yallop M, Stibal M Stibal M, Sabacka ´ M and Kasto ˇ vska ´ K 2006 Microbial communities and Huybrechts P 2012 An improved estimate of microbially on glacier surfaces in Svalbard: impact of physical and mediated carbon ﬂuxes from the Greenland ice sheet chemical properties on abundance and structure of J. Glaciol. 58 1098 cyanobacteria and algae Microb. Ecol. 52 644–54 9 Environ. Res. Lett. 8 (2013) 035002 N Takeuchi Stibal M, Telling J, Cook J, Mak K M, Hodson A and Anesio A M Takeuchi N and Li Z 2008 Characteristics of surface dust on 2012 Environmental controls on microbial abundance and Urumqi ¨ glacier No. 1 in the Tien Shan mountains, China Arct. activity on the greenland ice sheet: a multivariate analysis Antarct. Alp. Res. 40 744–50 approach Microb. Ecol. 63 74–84 Takeuchi N, Uetake J, Fujita K, Aizen V and Nikitin S 2006b A Takeuchi N 2001 The altitudinal distribution of snow algae on an snow algal community on Akkem glacier in the Russian Altai Alaska glacier (Gulkana Glacier in the Alaska Range) Hydrol. mountains Ann. Glaciol. 43 378–84 Process. 15 3447–59 Thomas W H and Duval B 1995 Sierra Nevada, California, USA, Takeuchi N 2002 Surface albedo and characteristics of cryoconite snow algae: snow albedo changes, algal-bacterial (biogenic surface dust) on an Alaska glacier, Gulkana Glacier interrelationships, and ultraviolet radiation effects Arct. Alp. in the Alaska Range Bull. Glaciol. Res. 19 63–70 Res. 27 389–99 Takeuchi N 2009 Temporal and spatial variations in spectral Uetake J, Naganuma T, Hebsgaard M B and Kanda H 2010 reﬂectance and characteristics of surface dust on Gulkana Communities of algae and cyanobacteria on glaciers in west Glacier, Alaska Range J. Glaciol. 55 701–9 Greenland Polar Sci. 4 71–80 Takeuchi N, Dial R, Kohshima S, Segawa T and Uetake J 2006a Uetake J, Yoshimura Y, Nagatsuka N and Kanda H 2012 Isolation Spatial distribution and abundance of red snow algae on the of oligotrophic yeasts from supra-glacial environments of Harding Iceﬁeld, Alaska derived from a satellite image different altitude on the Gulkana Glacier (Alaska) FEMS Geophys. Res. Lett. 33 L21502 Microbiol. Ecol. 82 279–86 Takeuchi N, Fujita K, Nakazawa F, Matoba S, Nakawo M and Wientjes I G M and Oerlemans J 2010 An explanation for the dark Rana B 2009 A snow algal community on the surface and in an region in the western melt zone of the Greenland ice sheet ice core of Rikha-Samba Glacier in Western Nepali Himalayas Cryosphere 4 261–8 Bull. Glaciol. Res. 27 25–35 Wientjes I G M, Van de Wal R S W, Reichart G J, Sluijs A and Takeuchi N and Kohshima S 2004 A snow algal community on a Oerlemans J 2011 Dust from the dark region in the western Patagonian glacier, Tyndall glacier in the Southern Patagonia ablation zone of the Greenland ice sheet Cryosphere 5 589–601 Iceﬁeld Arct. Antarct. Alp. Res. 36 91–8 Yallop M L, Anesio A M, Perkins R G, Cook J, Telling J, Fagan D, Takeuchi N, Kohshima S and Fujita K 1998 Snow algae community MacFarlane J, Stibal M, Barker G and Bellas C 2012 on a Himalayan glacier, Glacier AX010 East Nepal: Photophysiology and albedo-changing potentialof the ice algal Relationship with glacier summer mass balance Bull. Glacier community on the surface of the Greenland ice sheet ISME J. Res. 16 43–50 6 2302–13 Takeuchi N, Kohshima S and Segawa T 2003 Effect of cryoconite Yoshimura Y, Kohshima S and Ohtani S 1997 A community of and snow algal communities on surface albedo on maritime snow algae on a Himalayan glacier: change of algal biomass glaciers in south Alaska Bull. Glaciol. Res. 20 21–7 and community structure with altitude Arct. Alp. Res. Takeuchi N, Kohshima S and Seko K 2001 Structure, formation, 29 126–37 darkening process of albedo reducing material (cryoconite) on Yoshimura Y, Kohshima S, Takeuchi N, Seko K and Fujita K 2000 a Himalayan glacier: a granular algal mat growing on the Himalayan ice-core dating with snow algae J. Glaciol. glacier Arct. Antarct. Alp. Res. 33 115–22 46 335–40
http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.pngEnvironmental Research LettersIOP Publishinghttp://www.deepdyve.com/lp/iop-publishing/seasonal-and-altitudinal-variations-in-snow-algal-communities-on-an-7NjxJFAEeL
Seasonal and altitudinal variations in snow algal communities on an Alaskan glacier (Gulkana glacier in the Alaska range)