Advances in Polar Science

Contents Vol.23 No.3 September 2012

Articles

Characteristics and variations of the picophytoplanktoncommunity in the Arctic Ocean ...... 133 MA Yuxin, HE Jianfeng, ZHANG Fang, LIN Ling, YANG Haizhen & CAI Minghong

Factors influencing small-scale distribution of 10 macrolichens in King George Island, West Antarctica ...... 141 LIU Huajie, WU Qingfeng & FANG Shibo

Comparison of the defluoridation efficiency of calcium phosphate and chitin in the exoskeleton of Antarctic krill ...... 149 WANG Zhangmin & YIN Xuebin

Eco-environmental spatial characteristics of Fildes Peninsula based on TuPu models ...... 155 PANG Xiaoping & LI Yanhong

Vertical structure of low-level atmosphere over the southeast Indian Ocean fronts ...... 163 FENG Lin, LIU Lin, GAO Libao & YU Weidong

Cognitive effects of long-term residence in the Antarctic environment ...... 170 YAN Gonggu, WU Songdi, WANG Tianle, ZHANG Xuemin & SAKLOFSKE Donald H

Letters

Russian researchers reach subglacial Lake Vostok in Antarctica ...... 176 Pavel Talalay

Trend

Development of the geodetic coordinate system in Antarctica ...... 181 ZHANG Shengkai & E Dongchen · Article · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00133 September 2012 Vol. 23 No. 3: 133-140

Characteristics and variations of the picophytoplankton community in the Arctic Ocean

1,2 1,2* 1 1 2 1 MA Yuxin , HE Jianfeng , ZHANG Fang , LIN Ling , YANG Haizhen & CAI Minghong

1 SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai 200136, China; 2 College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China

Received 2 March 2012; accepted 14 June 2012

Abstract Picophytoplankton are responsible for much of the carbon fixation process in the Arctic Ocean, and they play an im- portant role in active microbial food webs. The climate of the Arctic Ocean has changed in recent years, and picophytoplankton, as the most vulnerable part of the high-latitude pelagic ecosystem, have been the focus of an increasing number of scientific studies. This paper reviews and summarizes research on the characteristics of picophytoplankton in the Arctic Ocean, including their abun- dance, biomass, spatial distribution, seasonal variation, community structure, and factors influencing their growth. The impact of climate change on the Arctic Ocean picophytoplankton community is discussed, and future research directions are considered.

Keywords Arctic Ocean, picophytoplankton, climate change, review

Citation: Ma Y X, He J F, Zhang F, et al. Characteristics and variations of the picophytoplankton community in the Arctic Ocean. Adv Polar Sci, 2012, 23: 133-140, doi: 10.3724/SP.J.1085.2012.00133

both total phytoplankton biomass and production in marine 0 Introduction* ecosystems, especially in oligotrophic waters where they can account for up to 90% of the total photosynthetic bio- The Arctic Ocean has been a semi-enclosed basin for [8-9] [1-2] mass and carbon production . Recent studies show that 60–100 million years , and throughout this period it has the Arctic Ocean has active microbial food webs that are slowly exchanged surface waters with other oceanic re- [10-11] [3] often dominated by cells with a diameter <3 µm , and gions . The special characteristics of physical isolation, that cells <5 µm in diameter are responsible for much of the perennially low water temperatures, and extreme cycles of carbon fixation over wide regions in the Arctic Basin[12-13]. polar day and night, mean that the Arctic Ocean provides a Picophytoplankton have a large surface-area-to-volume unique marine habitat for organisms, and is very sensitive [4] ratio, which facilitates effective acquisition of nutrient sol- to climate change . utes and photons, and provides hydrodynamic resistance to Climate change is already evident in the Arctic Ocean. sinking[14]. As climate changes, these cells could be ex- The temperature of the Arctic system has been increasing [5] pected to increase in number in a regime of lower nitrate over the past 100 years , and as a result the extent of sea supply and greater hydrodynamic stability[15]. Therefore, as ice coverage has declined[6]. Some models predict that the [7] one of the most sensitive components of high-latitude pe- Arctic Ocean will be ice-free in summer by 2040 . lagic ecosystems, picophytoplankton could be viewed as Picophytoplankton are photosynthetic plankton with a both sentinels and amplifiers of global climate change[16]. diameter <2 µm, including three cell types, cyanobacteria The aim of this paper is to summarize research on the (Synechococcus), Prochlorococcus, and picoeukaryotes, characteristics and variation of picophytoplankton in the although Prochlorococcus have not been reported in the Arctic Ocean, including studies on picophytoplankton Arctic Ocean. Picophytoplankton contribute substantially to abundance, biomass, spatial distribution, seasonal variation, community structure and influencing factors, and the im- pact of climate change on picophytoplankton growth. We * Corresponding author (email: [email protected]) also discuss the prospects for future study in this field. It

journal.polar.gov.cn 134 MA Yuxin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 should be noted that picophytoplankton are defined as and ocean forcing (e.g., through flow, upwelling, wind, and phytoplankton with a diameter <2 µm, however, some of tidal mixing)[23]. the reviewed studies focused on cells with a diameter <5 Cottrell and Kirchman[24] studied the coastal waters of µm, referred to as ultraphytoplankton. Therefore, for this the Chukchi and Beaufort Seas and found the abundance of paper, we reviewed studies on both picophytoplankton and Chl a-containing picoeukaryotes in summer was about ultraphytoplankton. 5.4×103 cells·mL-1. Not et al.[25] discovered that the picoeu- karyotic community at the boundary between the Norwe- 1 Abundance and biomass gian, Greenland, and Barents Seas, was primarily composed of photoautotrophs in late summer (75% of the cells on 1.1 Central Arctic Ocean average), and on average 44% of the Chl a biomass in this region could be attributed to picophytoplankton (including Recent studies have revealed a more dynamic carbon cycle Synechococcus and picoeukaryotes). Schloss et al.[26] found in the surface waters of the Arctic Ocean[12,17] than previ- [18] that picophytoplankton represented an average of 71% of ously estimated . Research has also shown that picophy- total cells (<20 µm) in the southeastern Beaufort Sea toplankton dominate the phytoplankton biomass and pro- [12,19] [19] (Mackenzie Shelf and Amundsen Gulf regions). The highest duction in central Arctic waters . Booth and Horner concentration of picophytoplankton cells was 13 810 cells·mL-1 discovered that picophytoplankton in the Canada and in the area influenced by the Mackenzie River, while the Makarov Basins contributed 93% to autotroph cell numbers -1 -1 lowest concentration was <1 500 cells·mL in the vicinity (1 300–10 020 cells·mL ) and 36% to autotroph biomass [26] [27] -1 [11] of the Amundsen Gulf . Wang et al. found that auto- (1.0–7.1 µg·cL ). Sherr et al. showed that autotrophic trophic picoflagellate abundance in Kongsfjorden, Svalbard, protists were numerically dominated by cells sized <5 µm, ranged from 46–35 200 cells·mL-1, while autotrophic nan- which made up 44%–99% (average 95%) of cells in the oflagellate abundance ranged from 40–4 600 cells·mL-1. phytoplankton assemblage during the growing season in the The above studies demonstrate that picophytoplankton upper water column of the central Arctic Ocean. Lee and [13] are dominant organisms in the oligotrophic, strongly strati- Whitledge found that small phytoplankton (0.7–5 µm) fied waters of the Arctic Basin, and also in the coastal re- represented about 70% of the total phytoplankton biomass gions, and areas strongly influenced by inflows of fresh in the upper mixed layer over all open-water stations during water. summer in the Canada Basin. However, the mean propor- tion decreased to 44.4% of the total biomass in the chloro- 2 Seasonal variation phyll-maximum layer, in spite of high variability[13]. There- fore, picophytoplankton are dominant organisms in the In the Arctic, all groups of pelagic microbes respond oligotrophic, strongly stratified central Arctic Ocean, espe- strongly to the large annual variation in the amplitude of cially in the upper layers. solar radiation, generally with lower biomass in spring, In the Arctic, polynyas are open water regions sur- higher biomass during the short summer growing season [20] rounded by sea ice . Polynyas have been referred to as the (June—September), and decreasing biomass during autumn oases of the Arctic because of their high productivity. and winter. Among them, phytoplankton show the largest Working on the Northeast Water Polynya, located in the variation in seasonal abundance and biomass, and there is a permanent Arctic ice pack on the North East Greenland rapid increase in phytoplankton stocks in June, after winter [21] Shelf, Pesant et al. found that small phytoplankton cells snow cover melts from the ice surface[11]. Recent studies (<5 µm) dominated both the biomass and primary produc- have shown that picophytoplankton play an increasingly tion in heavy ice-covered waters, while in open water, and important role in pelagic microbe systems, and that their in waters with mixed-ice conditions, the biomass was abundance changes significantly with the seasons[28-31]. dominated by large (>5 µm) phytoplankton, and primary In spring, the initial bloom takes place, and different production was shared between small and large cells. stages of the spring bloom are dominated by phytoplankton Size-fractionation experiments conducted by Legendre et of different sizes. The traditional view was that the pre- and [22] al. in the marginal ice zone in the Greenland Sea also post-bloom periods were dominated by small cells like pi- revealed that the phytoplankton biomass was dominated by cophytoplankton[28-29], while the bloom period itself was small cells (<5 µm), and the primary production was shared dominated by larger cells. However, in a recent study, Ho- between small and large cells depending on the hydro- dal and Kristiansen[30] investigated the phytoplankton in graphical conditions. spring blooms at the marginal ice zone in the northern Bar- ents Sea, and demonstrated that small cells dominated both 1.2 Arctic shelves and adjacent seas biomass and primary production at the early- and a The distribution of picophytoplankton in the waters of the late-bloom stages (71% and 63% of total Chl concentra- Arctic shelves and adjacent seas has been studied exten- tions, respectively), while within an ongoing bloom, large cells only dominated during the narrow period at the peak sively. The abundance and biomass on Arctic shelves varied [31] greatly in response to differences in ice (e.g., concentration, of the bloom. Hancke also found that the peak bloom thickness, duration), riverine input (e.g., nutrients, particles), group was dominated by diatoms while the early- and Characteristics and variations of the picophytoplankton community in the Arctic Ocean 135 late-bloom groups were more diverse and dominated by Arctic Ocean (Table 1), with one or two blooms occurring small cells like prymnesiophytes. Therefore, these recent regularly in summer. However, Sherr et al.[11] studied the studies have shown that, in some regions of the Arctic autotrophic microbes in the upper water column of the cen- Ocean, picophytoplankton are dominant over more of the tral Arctic Ocean and observed three distinct blooms over bloom period than previously reported. the summer. The initial bloom consisted of diatoms and Many studies have focused on picophytoplankton, and phytoflagellates, mainly 2 µm-sized Micromonas sp., while have found these organisms to be relatively abundant dur- the two subsequent blooms were dominated by the flagel- ing summer and early autumn in different regions of the lated non-colonial Phaeocystis sp. (4–6 µm in diameter)[11].

Table 1 Picophytoplankton and nanophytoplankton abundance in the Arctic Ocean Abundance/ Regions Groups Method Season Reference (103 cells·mL-1) Central Arctic Ocean (Canada and Makarov Basins) Pico- 1.3–10.02 EFM; LM Late summer [18] Greenland Norwegian and Barents Sea (GNB) Pico- 3–15 EFM; FCM Late summer [24] Southeastern Beaufort Sea (Mackenzie Shelf and Amund- Pico- 1.5–13.81 FCM Autumn [25] sen Gulf) Nano- 0.003–2.90 Coastal waters of the Chukchi Sea and the Beaufort Sea Pico- 5.37±1.83* FCM Summer [23] Pico- 0.046–35.2 Kongfjorden, Svalbard EFM Late summer [26] Nano- 0.036–4.6

Note: “*”: on average; FCM: flow cytometry; EFM: epifluorescence microscopy; LM: inverted light microscopy.

In autumn, especially in the transition period from late using 18S rRNA gene clone libraries. The ribotypes were summer to early autumn, some differences in picophyto- diverse and picophytoplankton mainly included phototro- plankton abundance have been observed. As shown in Table phic stramenopiles, with sequences related to dictyocho- 1, in some regions, particularly the southeastern Beaufort phytes, diatoms and bolidophytes. Alveolates were also Sea, picophytoplankton were as abundant (1.5×103– identified, with similarity to dinoflagellates, and sequences 13.81×103 cells·mL-1) in autumn as in summer in other re- for other algae were recovered, including cryptophytes gions. A lot of nutrients are consumed by algal blooms dur- from the Beaufort Sea, a haptophyte from the GNB, and ing summer, and nutrient concentrations are relatively low prasinophytes, including Bathycoccus, Micromonas, and in autumn. Because of their large surface-area-to-volume Mantoniella[32]. The diversity of picoprasinophytes was ratio picophytoplankton take up nutrients efficiently even at further discussed by Lovejoy et al.[33] in 2007. Not et al.[34] low concentrations, which might explain their abundance at identified a novel group, picobiliphytes, within the photo- the surface layer in autumn[26]. synthetic stramenopiles, and proposed that it was an inde- There has been little research on phytoplankton in pendent lineage, possibly with a weak sister relationship to winter because logistical support is challenging and limited. the cryptophyte/katablepharid clade. Sherr et al.[11] found persistent stocks of heterotrophic and The Arctic has proved to be a rich source of microbes autotrophic microbes during winter months, but the cell with novel genetic sequences. In the study conducted by abundance was low. The winter stocks consisted of pico- Lovejoy et al.[32], 42% of sequences recovered had less than and nanoflagellates, mainly Micromonas sp., and unidenti- 98% similarity to any sequences in GenBank. Furthermore, fied haptophytes, with an abundance of hundreds of 15% of these sequences had less than 95% similarity to any cells·mL-1, and diatoms and pigmented dinoflagellates previously recovered sequences. These results indicate the >20 µm in diameter, with an abundance of about existence of endemic or under-sampled taxa in the Arctic 1 cell·mL-1[11]. Cottrell and Kirchman[24] found Chl Ocean environment[32]. a-containing picoeukaryotes decreased 200-fold, from 5.4×103 cells·mL-1 in summer to 0.02×103 cells·mL-1 in 3.2 Cyanobacteria winter, probably reflecting the cessation of primary produc- Synechococcus and Prochlorococcus are two main repre- tion during winter darkness. sentative groups of marine cyanobacteria. The almost com- plete absence of Prochlorococcus in the Arctic Ocean might 3 Community structure be a result of the ecological differentiation caused by the 3.1 Diversity low temperature of the Arctic waters. It is likely that geo- graphical isolation and natural selection also contribute to [24,35] Lovejoy et al.[32] analyzed microbial eukaryote diversity the lack of Prochlorococcus in the Arctic Ocean . during the summer of 2002, focusing on picoeukaryotes Synechococcus abundance was lower in the Arctic (<3 µm-diameter cells) in the Beaufort Sea, the Greenland, Ocean than in temperate and tropical waters, and this group [36] Norwegian, and Barents Seas (GNB), and the Arctic Ocean, was also absent in the central region of the Arctic Ocean . 136 MA Yuxin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

Their poor performance in the Arctic might be caused by Not et al.[25] first reported their existence in the GNB, and their temperature-depressed growth rates, and a resulting Lovejoy et al.[33] found they were widely distributed in inability to keep up with grazing by nanoflagellates, ciliates northern waters. Furthermore, the genetic variability of and other fine-particle collectors[35,37]. Studies have shown a Bathycoccus was much less than for Micromonas[33,42]. higher abundance of Synechococcus in the Beaufort Sea coastal waters (3.503–6.713×103 cells·mL-1) than other Arc- 3.4 Other dominant picoeukaryotes tic waters, including the Chukchi Sea (4–80 cells·mL-1), the 3 -1 After prasinophytes, prymnesiophytes (haptophyta) are the Greenland Sea (0–1.079×10 cells·mL ), and the Canada 2 -1 [24,33,36,38] second most dominant picoeukaryotes in the Arctic Ocean. Basin (0–6.0×10 cells·mL ) . The discharge of the During the 1994 AOS expedition across the polar cover, warmer, fresher, nutrient rich waters from the Mackenzie [19] Booth and Horner found maximum abundances for flag- River might explain the higher abundance in the Beaufort ellated Phaeocystis pouchetii and 2 µm phytoflagellates Sea coastal waters. (tentatively identified as Micromonas pusilla) of 470 and Research into the diversity of the Arctic Synechococ- -1 10 000 cells·mL respectively. The importance of hapto- cus is still very limited. One study using 16S ribosomal phyta pigment signatures in the pico-size fraction has been gene sequencing of Synechococcus showed that a Synecho- [43] demonstrated in many oceanic regions . Among the three coccus rich in phycocyanin, sampled from the Canada Ba- [11] blooms observed by Sherr et al. in the upper water col- sin, was most similar (98%–99%) to Microcystic elabens, a [35] umn of the central Arctic Ocean, the last two were domi- common species of freshwater phytoplankton , while [38] nated by flagellated non-colonial Phaeocystis sp. (4–6 µm Waleron et al. found that Synechococcus from the coastal -1 in size) with a peak abundance of 18 000 cells·mL . Hap- waters of the western Canadian Arctic Ocean were closely [25, 32] tophyta have also been found in the GNB . related to freshwater and brackish Synechococcus. No typi- cally marine Synechococcus sequences were recovered[38]. These findings support the hypothesis of an allochthonous 4 Influencing factors origin of cyanobacteria in the coastal regions of the Arctic Ocean, from the Mackenzie River and other nearby inflows, 4.1 Nutrients and light and are also consistent with the survival but little net In the oligotrophic waters of high-latitude Arctic seas, low growth of cyanobacteria under present conditions in north- [38] levels of nutrients have been considered to be the limiting ern high-latitude seas . factor for phytoplankton blooms[44-45]. However, according to the resource competition theory, small cells, with large 3.3 Picoprasinophytes surface-area-to-volume ratios, are more effective in the ac- [46] Slapeta et al.[39] studied the Micromonas ecotype and its quisition of nutrient solutes and photons . Therefore, they global dispersal, and Lovejoy et al.[33] examined and sum- are likely to be predominant in oligotrophic waters, and marized the biogeography, diversity, and growth character- their dominant biomass and cell abundance in the central istics of picoprasinophytes, especially the Micromonas Arctic Ocean supports this viewpoint. In both the Northeast Micromonas ecotype, in the Arctic. In combination with records from Water Polynya and the North Water (NW), earlier research on Arctic Ocean phytoplankton, these stud- was found in ice-free areas when nitrate was at a low con- centration (0.83 µM in the Northeast Water Polynya, and ies provided broad evidence that picoprasinophytes are spa- [47] tially and temporally prevalent throughout the Arctic re- 0.1–0.7 µM in the NW) . gion[11,19,25,40]. Phytoplankton blooms in summer consume a large A widely accepted oceanographic paradigm is that amount of nutrients, and therefore picophytoplankton might photosynthetic picoplanktonic cyanobacteria are continu- predominate at the surface layer in autumn or late summer. NO − ously abundant in the ocean, while larger-celled eukaryotes When 3 was almost depleted in the upper mixed layer including diatoms, prymnesiophytes, and dinoflagellates of open-water stations in the Canada Basin, small phyto- plankton (0.7–5 µm) represented 69.3% (SD = ±10.6%) of rise above this phototrophic background and produce sea- [13] [41] the total phytoplankton biomass at the surface . Schloss et sonal blooms under specific hydrographic conditions . An [26] unusual feature of Arctic marine ecosystems is that the al. found that picophytoplankton were the most abundant background population of cyanobacteria is conspicuously phytoplankton during the autumn season, probably reflect- absent or sparse. Therefore, in the Arctic Ocean picoprasi- ing low nitrate concentrations (surface waters average= 0.65 µM). In all the transects sampled by Not et al.[25], nophytes have replaced cyanobacteria in the baseline com- -1 munity and persist throughout all seasons. Lovejoy et al.[33] abundance of picoeukaryotes greater than 4 000 cells·mL determined that the Arctic Ocean Micromonas ecotype was was always restricted to the uppermost 30 m of the water a unique pan-Arctic form that differed genetically, and in column. terms of growth characteristics, from Micromonas pusilla There have been some studies on light intensity and ultraviolet radiation, and their influence on the phytoplank- clades collected elsewhere in the world. [48-49] Bathycoccus also form part of the baseline picophyto- ton community and growth in the Arctic Ocean , but plankton community in the Arctic, replacing cyanobacteria. few have focused on picophytoplankton. Characteristics and variations of the picophytoplankton community in the Arctic Ocean 137

4.2 Temperature and salinity flows northward along the western coast of Greenland in autumn, bringing warmer, more saline water to the eastern Phytoplankton community composition is influenced by the part of the NOW, while surface Arctic water (colder, less stable cold temperature of high-latitude waters, which se- saline) coming from the Kane Basin flows southward along lects for specific species in polar seas. Picophytoplankton in the western part of the NOW. These two distinct water Arctic waters are mainly composed of psychrotrophics and masses, with their different physical and chemical charac- psychrophilics, and as typical representatives of picophyto- teristics, govern picophytoplankton and nanophytoplankton plankton, cyanobacteria were found to be psychrotrophic [53] [37] distributions in the NOW during the autumn . The find- rather than psychrophilic . They were tolerant to cold ings of Schloss et al.[26], on abundance in ice melt waters as water conditions, with low growth rates under cold ambient discussed above, also supports the influence of small scale temperatures, while their optimum temperature for growth [37] water masses on picophytoplankton community structure was higher than 15℃ . In contrast, Micromonas, the and distribution[26]. dominant species in the high-latitude waters, preferred The inflow of fresh water from several rivers also con- lower temperatures (optimal growth at 6–8℃), showed im- tributes significantly to production over the Arctic shelves. paired growth rates at 12.5℃, and failed to grow at 15℃ in [33] The Mackenzie River, the largest input to the Beaufort laboratory tests . Sea-Mackenzie Shelf region, introduces a great deal of Within the temperature range of Arctic waters, the dis- fresh water, dissolved organic matter (DOM), particulate tribution of picophytoplankton indicated a preference for organic matter (POM), and planktonic cells to the Beaufort warmer and less saline waters, typically surface layers and [32-33,38,54-56] [26] [26] Sea . Schloss et al. also found maximum pico- areas of fresh water discharge. Schloss et al. reported that and nanophytoplankton cell concentrations in the area in- the environmental variable salinity was well correlated with fluenced by the Mackenzie River. phytoplankton abundance, especially with the most abun- dant phytoplankton group, the picophytoplankton. They 4.4 Biotic factors found picophytoplankton abundance was significantly In addition to abiotic factors, biotic factors also have an higher in low-salinity and high-temperature surface waters [26] important influence on picophytoplankton in the Arctic (above 10 m) than in deeper waters . Significantly higher Ocean. As primary producers in the microbial loop, pico- picophytoplankton abundances were also found in water phytoplankton play an important role in the conversion of masses with relatively higher temperatures and lower salin- POM and DOM, but they are also influenced by the pres- ity, such as the Mackenzie River (MR) plume and ice melt [26] ence and activities of other microbes, including grazing by waters, as compared to all other water masses . Waleron [38] herbivorous protozoa, interactions with bacteria, and lysis et al. studied the input of cyanobacteria and picoeu- by viruses. karyotes to coastal waters of the Arctic Ocean from the To date, few studies have focused on the influence of Mackenzie River, and found them to be allochthonous, and bacteria and viruses on picophytoplankton, but there has typically land-derived, and consequently cyanobacteria and been some research on the grazing of picophytoplankton by picoeukaryotes were more abundant in surface waters. herbivorous protozoa in the Arctic Ocean. In the central 4.3 Water masses Barents Sea, phytoplankton growth and microzooplankton grazing rates were closely coupled during early summer[57]. The Arctic Ocean is a semi-enclosed basin, and various Dilution experiments showed that grazing losses ranged water masses with different chemical and physical charac- from 64%–97% of daily Chl a production, and were greater teristics flow into it. As a result, the picophytoplankton for smaller size fractions[57]. Sherr et al.[58] conducted the community structure and distribution may be influenced by first study of microzooplankton grazing impact on phyto- the factors discussed above. [32] plankton in the western Arctic Ocean during spring and Lovejoy et al. found that pico-size phototrophic summer, in an area encompassing parts of the Chukchi Sea, stramenopiles from the Arctic Ocean were mostly araphid the Beaufort Sea, and the Canada Basin. Their dilution ex- diatoms, while centric diatoms and bolidophytes were re- periments revealed that, on average, microzooplankton covered from the GNB. They proposed that the difference grazing consumed only 22±26% of phytoplankton daily was likely a consequence of the histories of the water [58] [58] [32] growth . The lower grazing rates found by Sherr et al. masses . The GNB cuts across southward-flowing Arctic might be explained by the low temperature limitation to the water and northward-flowing Atlantic water, which is rela- [25] growth of herbivorous heterotrophic protists, because the tively low in silicic acid required for diatom growth . In abundance variation of phytoplankton and heterotrophic contrast, Pacific water, which is the source of the upper bacteria is always coupled. In the central Arctic Ocean, mixed layer of the western Arctic Ocean, is high in silicic [50-51] when algal blooms were dominated by small-sized cells, the acid . stocks of bacteria and heterotrophic protists also increased, Even on small scales, water masses can have an influ- with no time delay[11]. ence on picophytoplankton community structure and dis- tribution[52]. Mostajir et al.[53] reported that a surface current 138 MA Yuxin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

5 Community and climate change summer, and these waters contain bottom sediments and benthic microbial mats. The main biomass constituents of [62] 5.1 Ecological winners in the central Arctic Ocean the mats are oscillatorian cyanobacteria . As discussed above, cyanobacteria have already been identified in estu- Climate change is already evident in the Arctic Ocean, with aries and continental shelf regions of the Arctic Ocean. As the retraction of sea ice, higher water temperatures, in- the Arctic Ocean warms it becomes more susceptible to creased input of riverine waters, and other physical charac- invasive species from the south. Cyanobacteria may even- [5-7] teristics . These changes have been accompanied by tually replace picoprasinophytes, and the arrival of harmful variations in phytoplankton communities. algal bloom species may result in the modification of As global climate changes, conditions will favor some dinoflagellate assemblages. Cyanobacteria are still absent organisms more than others, and there will be ecological or sparsely distributed in Arctic waters, but their abundance winners and losers. Melting sea ice, combined with in- is likely to increase with increasing water temperatures. creasing input from large river runoff, is affecting the physical characteristics of the Arctic Ocean. Li et al.[14] car- 5.3 Lack of biodiversity ried out environmental monitoring of the Canada Basin The uniquely polar phylotypes are a vulnerable component during 2004—2008, and observed warming, freshening, [32] of global genetic diversity. Lovejoy et al. found a sur- decreasing density, and decreasing nutrient levels in the prising lack of picoeukaryote diversity in the Arctic Ocean upper water layer. In contrast, the density and nutrient lev- compared with other waters. The Arctic has historically els in the deep water layer were maintained, resulting in been covered with thick multiyear ice, but in 2002 warm stronger stratification and greater hydrodynamic stability of [14] conditions caused a retraction of the ice cover over the the water column . These changes were accompanied by a western Arctic, exposing the underlying waters to high sur- shift in phytoplankton size structure towards small micro- [50] [14] face irradiance for the first time . The depauporate micro- bial eukaryotes, and cold-adapted picoprasinophytes . The bial assemblages, rare colonizers of marine species, may fossil record suggests that, over the past 34 million years, [32] reflect the limitation of nutrient supply in this region . the average size of diatoms has decreased by almost a fac- [59] This phenomenon is similar to primary succession on land tor of triple . Isotopic analyses of benthic and planktonic following glacial retreat. With the continued decline in an- foraminifera have indicated that this decline in size was nual sea ice, and the ongoing effects of climate change, correlated with an increase in thermal stratification or sta- such conditions may be increasingly common in this region, bility, similar to the changes currently taking place in the and the variations and adaptations of these colonizers in central Arctic Ocean. response to the new environment warrant further study. Small cells are much less efficiently transferred within marine food webs relative to larger phytoplankton, and they 6 Conclusions and prospects for future re- are also less subject to sinking losses in stratified, nutrient poor conditions. Consequently, it is possible that less bio- search genic carbon will be exported either for extraction (e.g., As discussed above, picophytoplankton are widely distrib- harvest), or for sequestration (e.g., burial), and the organic uted in the Arctic Ocean, and display obvious seasonal carbon export to fish communities and benthic ecosystems variation, with relatively high abundance in hydrodynami- will be altered. Such effects could be enhanced by warmer cally stable waters and areas of fresh water discharge. Gen- temperatures that speed up respiration and microbial loop [14,16] erally, they prefer oligotrophic waters with relatively higher processes . However, the exact extent of these proposed temperature and lower salinity. An unusual feature of the shifts is unknown and further monitoring is required. Arctic marine ecosystems is that Arctic Ocean picoprasi- Moreover, in eukaryotic phytoplankton, cell size is posi- nophytes replace cyanobacteria, and form the basis of the tively correlated with genome size and genome-size evolu- picophytoplankton community throughout all seasons. tion. Consequently, climate-driven changes potentially alter Compared with other regions, the biodiversity of picoeu- the genomic structure and the evolution tempo of marine [60] karyotes in the Arctic Ocean is quite low. However, the eukaryotic microorganisms . Arctic Ocean has proved to be a rich source of novel se- 5.2 Competition between cyanobacteria and Mi- quences. With changing climate, the natural selectivity of cromonas picophytoplankton as ecological winners has already taken place in the central Arctic Ocean, further confirming that The unique pan-Arctic ecotype, Micromonas, displays a this pelagic ecosystem is very sensitive to change, and in- narrow thermal niche in keeping with the stable dicating that picophytoplankton can serve as both sentinels cold-temperature regime of high-latitude seas[33,61]. How- and amplifiers of global climate change. ever, polar cyanobacteria tend to be cold tolerant rather than Current studies on picophytoplankton community psychrophilic, with slow growth rates under cold ambient structure in the Arctic Ocean have focused on the North temperatures and a preference for warmer temperatures[37]. Atlantic sector, with little research on the Pacific sector. 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· Article · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00141 September 2012 Vol. 23 No. 3: 141-148

Factors influencing small-scale distribution of 10 macro- lichens in King George Island, West Antarctica 1* 1 2 LIU Huajie , WU Qingfeng & FANG Shibo

1 Key Laboratory of Microbial Diversity Research and Application of Hebei Province, College of Life Sciences, Hebei Uni- versity, Baoding 071002, China; 2 Institute of Eco-environment and Agro-meteorology, Chinese Academy of Meteorological Sciences, Beijing 100081, China

Received 5 June 2012; accepted 7 July 2012

Abstract Lichens are among the main primary colonists in most terrestrial ecosystems of Antarctica, where the effects of envi- ronmental factors on spatial distribution of lichens are essential to understanding the functioning of Antarctic terrestrial ecosys- tems. We measured abundance of 10 frequently observed macrolichens and 15 environmental factors at a small scale (20 cm× 20 cm), in the ice-free areas of Fildes Peninsula and Ardley Island, King George Island, West Antarctica, and assessed the effects of environmental factors on the local distribution of these lichens. Canonical correspondence analyses (CCA) show that 8 out of 15 environmental factors, belonging to 4 sets of variables, are important in spatial distribution of the 10 lichens. Variation partitioning analyses show that most of the variation in distribution of the 10 lichens is described by the spatial heterogeneity of substrate, bird influence and microclimate and topography, whereas human impact has no significant effects. Keywords bird disturbance, canonical correspondence analysis, lichen ecology, maritime Antarctica, soil accumu- lation

Citation: Liu H J, Wu Q F, Fang S B. Factors influencing small-scale distribution of 10 macrolichens in King George Island, West Antarctica. Adv Polar Sci, 2012, 23: 141-148, doi: 10.3724/SP.J.1085.2012.00141

near the Polish Arctowski Station[17]. They occupy a wide 0 Introduction* range of diverse habitats due to their different responses to environmental factors[18]. Although the general ecology and Lichens are widespread in diverse environments all over the distribution of these lichens have been described[3,16,19], world, due to their high ability to survive environmental factors influencing the distribution of these species need extremes. They are among the primary colonists of Antarc- further study to better understand the mechanisms that gov- tic terrestrial ecosystems[1-2], and make up significant com- [3] ern the structure, function and dynamics of Antarctic ter- ponents of Antarctic vegetation . They play important restrial ecosystems. This is especially important under in- roles in biotic weathering of rocks and soil formation[4-8] [2] creasing human activity, which has been reported in King and nutrient cycling processes , and provide suitable habi- George Island to potentially impact diversity of local spe- tats for other organisms, such as mite and tardigrade spe- [20] [3,9] cies, such as penguins . cies . They also serve as reliable bio-monitors for evalu- The aims of this study are to quantify and test the rela- ating global atmospheric transport and deposition of at- [10-15] tive effects of environmental factors and human impact on mospheric contaminants . the cover of the 10 macrolichens in Fildes Peninsula and In King George Island, 62 species were reported near [16] Ardley Island. These lichens were chosen because they are the Korean Antarctic Scientific Station , and 104 taxa common in the investigated microhabitats, are easily identi- fied in the field, and thus can be useful in elucidating the major factors influencing spatial distribution of lichens. The * Corresponding author (email: [email protected]) 10 macrolichens are Caloplaca regalis, Cladonia borealis,

journal.polar.gov.cn 142 LIU Huajie, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

Himantormia lugubris, Placopsis contortuplicata, Rama- more than 200 m above sea level. The hills are largely free lina terebrata, Sphaerophorus globosus, Stereocaulon of snow and ice during the austral summer, and the vegeta- alpinum, Umbilicaria antarctica, Usnea antarctica and Us. tion is mainly dominated by lichens, mosses, algae, and aurantiacoatra. cyanobacteria. Two species of phanerogams, Colobanthus quitensis (Caryophyllaceae) and Deschampsia antarctica 1 Materials and methods (Poaceae), are sporadic in distribution and confined to patches with soil. 1.1 Study area 1.2 Field investigation The investigation was carried out in two localities of Ant- arctic Specially Protected Areas (ASPA): Fildes Peninsula Field work was conducted in the 2009/2010 austral summer. (ASPA no. 125) and Ardley Island (ASPA no. 150). Both A total of 360 plots each measuring 20 cm×20 cm, over an localities are situated in the southwestern part of King altitude gradient varying from sea level up to 200 m, were George Island (63°23′S, 57°00′W), South Shetland Islands, selected in various habitats to include as many of the poten- West Antarctica. Fildes Peninsula (62°12′S, 58°58′W) is tial microhabitats as possible. All plots contained at least 10 km long and 5 km wide. Ardley Island (62°13′S, one of the selected target species. These lichens were not found in the rivulets and marshy areas dominated by 58°56′W), 2.0 km long and 1.5 km wide, is situated about [21] 500 m east of the coast of Fildes Peninsula. They are in the mosses , and so these habitats were not included in the maritime Antarctic region and are characterized by an oce- investigation. anic climate with an average annual temperature of -2.5°C Percentage of lichen cover was estimated in each plot using the Braun-Blanquet method[22], adapted to Antarctic and the annual precipitation of 500 mm rainfall equivalent, [23-24] falling as both rain and snow. High air humidity is main- conditions . Fifteen variables in 4 sets were recorded tained throughout the year, amounting on average to about simultaneously in each plot (Table 1). 80%[17]. The topography is hilly with the highest peak no

Table 1 Measured variables and the results of Monte Carlo permutation tests Monte Carlo Sets Variables permutation results Name Abbr. Name Abbr. Units Data type F p! * Distance from ground DG cm Continuous 10.56 0.000 5 * Distance from coast DC Factor (1–3) 8.53 0.000 5 Microclimate Water availability WA Factor (1–3) 2.53 0.017 0 {C} and topography Light availability LA Factor (1–3) 1.79 0.080 5 Altitude Alt m Continuous 1.13 0.325 3 Slope Slo Continuous 0.79 0.979 0 * Soil cover SC % Continuous 41.22 0.000 5 * Moss cover MC % Continuous 8.52 0.000 5 * Substrate {S} Soil depth SD cm Continuous 3.23 0.004 5 Rock size RS cm Continuous 2.12 0.038 0 Substrate roughness SR Factor (1–2) 1.35 0.200 4 Distance from bird excrement DBE Factor (1–3) 36.10 0.000 5* Bird influence {B} Distance from bird nest DBN Factor (1–3) 4.47 0.000 5* Distance from the closest road DCR m Continuous 3.05 0.006 0* Human impact {H} Distance from the nearest station DNS m Continuous 0.99 0.423 3 Notes: “!” denotes the significant levels are Bonferroni-corrected (0.05/number of variables) and therefore different between sets of variables. “*” denotes that a specific variable is statistically significant at a Bonferroni-corrected significance level. The Monte Carlo permutation test was separately applied to each set of variables.

The microclimate and topography set {C} included 6 ornithocoprophilous lichens), 2=31–100 m (dominated by variables: (1) distance from ground (DG) representing the rocks with soil among rocks, and high bird influence but height of the substrate surface occupied by lichens; (2) dis- relatively lower coverage of ornithocoprophilous lichens), tance from the coast (DC: 1=0–30 m (mostly dominated by 3≥100 m (environmentally diverse, with lowest bird in- rocks, with highest bird influence and high coverage of fluence and lowest coverage of ornithocoprophilous li- Factors influencing small-scale distribution of 10 macrolichens in King George Island, West Antarctica 143 chens)); (3) water availability (WA: 1=exposed with little separately applied to each variable set, under full model capability to sustain water, 2=high capability to remain with the number of permutation=2 000, to test the signifi- moist, 3=keeps moist over days); (4) light availability (LA: cance of variables to be included in the model. The signifi- 1=exposed, 2=in cleft with most of the day in shadow, cance levels were corrected by a Bonferroni correction, 3=completely sheltered); (5) altitude (Alt) measured using which is a quotient of the desired overall significance level an altimeter; and (6) slope (Slo) angle. (α=0.05) divided by the number of variables. The signifi- The substrate set {S} had 5 variables: (1) soil cover cant explanatory variables were first subjected to a CCA (SC); (2) moss cover (MC); (3) soil depth (SD); (4) rock analysis, then a Partial CCA with variation partitioning was size (RS); (5) substrate roughness (SR) on an ordinal scale conducted to estimate the proportions of variation in the from 1 to 2 (1=smooth, 2=rough). species data explained by single sets of variables, and The bird influence set {B} consisted of distance from shared variation between the variable sets. bird excrement (DBE: 1=0–2.0 m, 2=2.1– 5.0 m, 3≥5.0 m; The selected variables were further subjected to an the thresholds were determined according to the distribution unrestricted Monte Carlo permutation test to determine of lichens) and distance from bird nest (DBN: 1=0–5 m, which variables could potentially explain a significant 2=5.1–20 m, 3≥ 20 m; the thresholds were determined amount of species/plot distribution along each CCA axis. according to the degree of bird trampling and distribution of The impact size of variables was estimated by comparing lichens). The human impact set {H} consisted of distance to their correlations with axes[26]. Those variables with larger the closest road (DCR) and distance to the nearest station correlation coefficient have greater impact on the CCA axis. (DNS). The t-value is regarded as an approximate guide and the critical value of significance at p=0.05 was set to 2.0[27]. 1.3 Statistic analyses Those variables with larger t-values than the critical value The computer program CANOCO 4.5 was used for all or- were regarded as significant in explaining the species/plot dinations[25]. Detrended correspondence analysis (DCA) dispersion along the CCA axis under discussion. was used to estimate the amount of compositional turnover in standard deviations. Because the gradient length of the 2 Results first DCA axis was 4.667 SD, canonical correspondence analysis (CCA) is therefore the appropriate method for The Monte Carlo permutation tests applied separately to these data[25-26]. each set of variables show that the following 8 variables in Ten species, 360 plots and 4 variable sets consisting of the 4 sets can be included in the CCA analyses: DG and DC 15 variables were subjected to a CCA analysis. The abun- in {C}; SC, MC and SD in {S}; DBE and DBN in {B}; and dance data for each species, and continuous data were DCR in {H} (Table 1). The other 7 variables were excluded log-transformed, and rare species were downweighted. because they were not significant in explaining the dataset Diagrams were drawn in CanoDraw[25]. Biplot scaling with (Table 1). The first four CCA axes are statistically signifi- a focus on inter-species distance was used, and default set- cant ( p = 0.000 5) and reflect 20.4% of species variation tings were accepted in the rest of the analysis. (Table 2). A set of sequential Monte Carlo permutation tests were

Table 2 Summary of CCA analysis CCA axes 1 2 3 4 Eigen values 0.321 0.101 0.027 0.014 Species-environment correlations 0.767 0.482 0.353 0.242 Cumulative percentage variance of species data 14.1 18.5 19.7 20.4 Cumulative percentage variance of species-environment relation 67.7 89.1 94.8 97.8 Sum of all eigen values 2.275 Sum of all canonical eigen values 0.474 (F = 11.541, p = 0.000 5)

Notes: Eight explanatory variables were included in the analysis (Table 1). 2.1 Variation explained by the sets of explanatory variation [B|(C∪S∪H)] (that is the amount of variation explained by the bird influence set {B} along, but not variables shared with any other variable sets) is statistically signifi- 2.1.1 Pure variation cant. This is also true for the pure microclimate and topog- raphy variation [C|(S∪B∪H)], and the pure substrate Variation partitioning shows that the pure bird influence variation [S|(C∪B∪H)]. The pure human impact variation 144 LIU Huajie, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

[H|(C∪S∪B)] is not statistically significant ( p = 0.222; 1). The largest shared variation is pooled between {S} and Table 3). {B} (FTVE=21.1%), followed by variations shared by {C} The largest faction of total variation explained (FTVE) and {B} (FTVE=13.9%), and {C} and {S} (FTVE= 12.9%, by a single variable set when effects of other variable sets Figure 1). are excluded, is the pure substrate variation (FTVE=38.0%, When considering pure variation plus shared variation Table 3, Figure 1), followed by the pure bird influence (that is the amount of variation explained by a single set of variation (FTVE=23.2%, Table 3, Figure 1) and microcli- explanatory variables, with effects of other variable sets mate and topography variation (FTVE=7.2%, Table 3, Fig- being included) {S} explained 63.3% of TVE, followed by ure 1). Only 1.5% of total variation explained (TVE) is at- {B} (49.4%) and {C} (24.7%). {S} and {B} together tributable to the human impact variable set (Table 3, Figure 1). explained 91.6% of TVE. However, {H} explained 4.0% of TVE, and the variation was not statistically significant 2.1.2 Shared variation (Table 3, Figure 2). The 4 sets of explanatory variables share variation (Figure

Table 3 Partitioning of variation in distribution of the 10 lichens on 4 sets of variables Variation explained Remarks VE F p FTVE /% C 0.117 9.654 0.000 5* 124.7 Variation explained by {C}, shared with other sets of variables S 0.300 18.050 0.002 0* 63.3 Variation explained by {S} B 0.234 20.456 0.002 0* 49.4 Variation explained by {B} H 0.019 3.048 0.004 0 4.0 Variation explained by {H} C|(S∪B∪H) 0.034 3.342 0.002 0* 7.2 Variation purely explained by {C}, not shared with other vari- able sets S|(C∪B∪H) 0.180 11.660 0.002 0* 38.0 Purely by {S} B|(C∪S∪H) 0.110 10.733 0.002 0* 23.2 Purely by {B} H|(C∪S∪B) 0.007 1.379 0.222 0 1.5 Purely by {H} C∪S 0.356 13.117 0.002 0* 75.1 Explained by {C} and {S}, shared with other sets of variables C∪B 0.285 12.711 0.002 0* 60.1 Explained by {C} and {B} C∪H 0.127 7.010 0.002 0* 26.8 Explained by {C} and {H} S∪B 0.434 16.676 0.002 0* 91.6 Explained by {S} and {B} S∪H 0.318 14.398 0.002 0* 67.1 Explained by {S} and {H} B∪H 0.242 14.097 0.002 0* 51.1 Explained by {B} and {H} (C∪S)|(B∪H) 0.232 9.052 0.002 0* 48.9 Purely by {C} and {S}, not shared with other sets of variables (C∪B)|(S∪H) 0.156 7.612 0.002 0* 32.9 Purely by {C} and {B} (C∪H)|(B∪S) 0.040 2.606 0.002 0* 8.4 Purely by {C} and {H} (B∪S)|(C∪H) 0.347 13.521 0.002 0* 73.2 Purely by {B} and {S} (H∪S)|(B∪C) 0.189 9.197 0.002 0* 39.9 Purely by {H} and {S} (B∪H)|(C∪S) 0.118 7.678 0.002 0* 24.9 Purely by {B} and {H} (C∪S∪B)|H 0.455 12.656 0.002 0* 96.0 Purely by {C}, {S} and {B}, not shared with {H} (C∪S∪H)|B 0.240 7.792 0.002 0* 50.7 Purely by {C}, {S} and {H} (C∪B∪H)|S 0.173 6.760 0.002 0* 36.5 Purely by {C}, {B} and {H} (S∪B∪H)|C 0.357 11.597 0.002 0* 75.3 Purely by {S}, {B} and {H}

Notes: Abbreviations for the sets of variables are given in Table 1; VE, variation explained; FTVE, fraction of total variation explained. The symbol “∪” stands for unions, while “|” indicates “without”. “*” denotes that a specific variation is significantly explained at a Bonferroni-corrected significance level p=0.002 1 (0.05/24). VE is given in inertia units (IU). The total inertia is 2.275 IU, and the total variation explained is 0.474 IU (Table 2). Factors influencing small-scale distribution of 10 macrolichens in King George Island, West Antarctica 145

explain the potential spread of species and plots along axis 1 (t > 3.0, Table 4). The next most influential variable is DBE (r = -0.56), followed by MC (r = -0.49, Table 4); their explanatory power of species distribution along axis 1 are also significant due to their high t-values (Table 4). DBN and DG are significant in explaining species disper- sion along axis 1 (t = -3.46 and t = 2.21, respectively), but their impact size is smaller (r = -0.38 and r = 0.31, respec- tively, Table 4). The other variables have minimal explana- tory power of dispersion of species and plots along axis 1 (all t < 1.10, Table 4). CCA axis 1 mainly reflects a substrate and bird influ- ence gradient, where the left end of the axis represents habitats with deep soil and mosses (such as fellfield or ex- panses of surface soil), and lower bird excrement and bird Figure 1 Path diagram of fractions of total variation explained population, while the right end reflects boulder and scree purely by 4 variable sets, and shared variation between them. An with little soil cover and higher bird influence (Figure 3). arrow pointing from a variable set to distribution of the 10 mac- rolichens shows the fraction of total variation explained (FTVE) are purely attributable to this variable set, when effects of all other variable sets were removed. An arrow between variable sets indi- cates the FTVE shared by the two variable sets (effects of other variables were not removed). The solid lines and “*” indicate a specific FTVE is significant at p=0.002.

Figure 3 Lichen species and environmental variables on the biplot of canonical correspondence analysis (CCA) of the first and second axes. Abbreviations for species are: Cr, Caloplaca regalis; Figure 2 Path diagram of fractions of total variation explained Cb, Cladonia borealis; Hl, Himantormia lugubris; Pc, Placopsis by 4 variable sets and their combinations. An arrow pointing from contortuplicata; Rt, Ramalina terebrata; Sa, Stereocaulon alpinum; one or two variable sets to distribution of the 10 macrolichens Sg, Sphaerophorus globosus; Uman, Umbilicaria antarctica; Usan, shows that the fraction of total variation explained (FTVE) are Usnea antarctica; Usau, Us. aurantiacoatra. Abbreviations for attributable to this variable set or the combination of the two vari- variables are given in Table 1. able sets (effects of other variable sets were not removed). The solid lines and values with “*” indicate a specific FTVE is sig- 2.2.2 CCA axis 2—Bird influence gradient nificant at p=0.002. The second axis reflects 4.4% of species variation (Table 2). 2.2 CCA axes The most influential environmental variable along axis 2 is DBE (r = -0.29), which has significant explanatory power 2.2.1 CCA axis 1—Substrate and bird influence of the species spread along axis 2 (t = -6.88, Table 4). The gradient next most influential variables are MC (r = 0.20) and DC (r = -0.19), which can both explain dispersion of species The first axis reflects 14.1% of species variation (Table 2). and plots along axis 2 (all t > 2.1; Table 4). The most influential variables along axis 1 are SC and SD, Axis 2 mainly reflects the gradient of bird influence. as indicated by their highest correlation coefficients with The positive end of the axis represents the coast with bird axis 1 (r = -0.64 and -0.62, respectively, Table 4) and their colonies, penguin rookeries and an abundance of bird ex- long vectors (Figure 3). Both variables can significantly crement, while the negative end represents the inland with 146 LIU Huajie, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 little bird influence (Figure 3).

Table 4 Inter-set correlations and t-values (in parenthesis) of explanatory variables with CCA-axes CCA axes Variables Axis 1 Axis 2 Axis 3 Axis 4 DG 0.31(2.21)* -0.03(0.62) 0.21(5.03)* 0.08(1.43) SC -0.64(-3.96)* 0.14(3.01)* 0.06(-0.06) -0.03(-0.58) DC -0.24(0.64) -0.19(-2.51)* 0.01(1.82) 0.05(0.87) SD -0.62(-3.13)* 0.13(0.82) 0.12(3.01)* -0.03(-0.87) MC -0.49(-5.09)* 0.20(3.71)* -0.08(-2.45)* 0.11(3.06)* DBN -0.38(-3.46)* -0.15(-1.34) -0.02(-0.15) -0.12(-2.94)* DBE -0.56(-6.64)* -0.29(-6.88)* 0.03(-0.23) 0.04(1.87) DCR 0.12(1.08) 0.12(-0.18) 0.13(2.94)* -0.02(0.31) Notes: Abbreviations for the variables are given in Table 1. “*” indicates that a specific variable has significant explanatory power of the species spread along the axis.

The third axis reflects only 1.2% of species variation Usnea antarctica (Usan), Us. aurantiacoatra (Usau) (Table 2), its importance in interpreting the distribution of and Himantormia lugubris (Hl) occur in diverse habitats, the 10 lichens is negligible. from bare rocks to fellfield with deep soil. Caloplaca re- galis and Ramalina terebrata prefer coastal rocks with di- 3 Discussion rect input of bird excrement, as indicated by their high spe- cies scores on both axis 1 and 2 (Figure 3). This demon- Substrate variation and bird influence are two major factors strates their ability to use soluble nutrients leached from determining distribution of the 10 macrolichens, and jointly, excrement or ornithogenic soils and their tolerance of high they explain 91.6% of the TVE in the cover of the 10 li- levels of atmospheric ammonium derived from bird excre- chens in King George Island (Figure 2). Variation in micro- ment[36]. The terricolous lichens, Cladonia borealis (Cb), climate and topography is also an important factor, whereas Sphaerophorus globosus (Sg) and Stereocaulon alpinum (Sa) human impact cannot be considered a key factor influenc- are often dominant lichens on soils and co-occur with ing the distribution of the 10 lichens. mosses to form large stands of tundra vegetation[24], as in- dicated by the low species scores along axis 1 (Figure 3). 3.1 Substrate variation They can be found on both mineral and ornithogenic soils, Substrate variation is the principle factor determining dis- indicating that they can use the increased nutrients derived tribution of the 10 lichens. It explains 38.0% of the TVE from birds. (Table 3, Figure 1), and shares 21.1% of TVE with the set 3.2 Bird influence of bird influence variables (Figure 1). Environmental gra- dient reflected by CCA axis 1 also suggests that effects of The second major factor determining lichen distribution is substrate variation are often associated with bird influence variation in bird influence, which purely explains 23.2% of (Figure 3). the TVE (Table 3, Figure 1). It shares 13.9% of the TVE In the set of substrate variables, three variables are sig- with the set of microclimate and topography variables (Fig- nificant in explaining the variation in species data: soil ure 1). In this variable set, distance from bird excrement cover, soil depth and moss cover (Table 1). All three vari- and distance from nest are significant in explaining the spe- ables reflect soil accumulation in microhabitats. cies data (Table 1). Soils in the investigated area can be classified into Although positive effects of bird excrement on soil non-ornithogenic and ornithogenic soil. The nutrient availability and vegetation development have been non-ornithogenic soils are generally poor in organic materi- [29,32-35] [8] demonstrated in many ecosystems in Antarctica , the als and available nutrients . The ornithogenic soils are negative influence of birds on lichen distribution can be often dominant near bird colonies or penguin rookeries, readily seen from the dispersion of species (Figure 3) along where the bird droppings can significantly elevate the con- CCA axis 2. Two ornithocoprophilous lichens, C. regalis tent of nutrients in both soil[8,28-31] and associated lichen [32-34] and R. terebrata, are abundant in sites with high bird influ- thalli . Accumulation of soil is necessary for the estab- ence near the coast, while the other eight lichens are sparse lishment of terricolous lichens, and the increased availabil- in such microhabitats. Greater input of ornithogeni- ity in ornithogenic soils can be beneficial for vegetation cally-derived nutrients does not necessarily support a development, and the survival and growth of lichens that [37] [32-35] greater species-rich lichen community , but favors a can tolerate or require these higher nutrient levels . community dominated by ornithocoprophilous lichens[2]. Factors influencing small-scale distribution of 10 macrolichens in King George Island, West Antarctica 147

Bird droppings can increase environmental salinity[1-2], availability is one of the major factors influencing lichen which can greatly affect survival, growth and distribution of distribution in Antarctica. For example, in the Soya and lichens[34]. Caloplaca regalis, R. terebrata and Umbilicaria Prince Olav Coastal regions of East Antarctica with annual antarctica can tolerate high levels of salinity[3], and they precipitation <150 mm, lichens are abundant in sites where prefer coastal habitats with bird excrement (Figure 3). The an adequate summer seasonal moisture availability is other species, however, appear to be less salt tolerant. Al- maintained, but are generally absent or poorly developed in though they can be found on ornithogenic soils, they prefer the dry or exposed sites[41]. A possible explanation is that microhabitats far away from bird colonies and coast. Spe- water deficiency is not a limiting factor in King George cies such as Us. antarctica, Us. aurantiacoatra and H. lu- Islands, due to the high precipitation (500 mm·a-1), high air gubris, when growing near bird colonies, are sparse and humidity (about 80%)[17], and the capability of lichens to restricted to cliffs or shelter microhabitats. use water vapor from clouds[9,41]. Animal trampling can also affect lichen distribution in maritime Antarctica by the effects of damage to the lichens 3.4 Human impact [34,38-39] thallus and disruption of soil stability . On Ardley As noted by Øvstedal and Smith[3], human impact in Ant- Island, a geological time scale study (about 2 400 years) arctica is on such a small and limited scale that no lichens showed that lichen abundance decreased whenever penguin [40] are considered to be threatened by humans on the continent. populations increased, and vice versa . A study conducted This study also found that human impact cannot be consid- near the Polish Research Station on King George Island ered as an important factor influencing distribution of the clearly showed a distinct zonation of vegetation related to 10 macrolichens in King Gorge Island. Because the inves- penguin rookeries, where lichen richness decreased with [37] tigated sites were designated as ASPA, all activities that decreasing distance from penguin rookeries . may be potentially harmful to native plants are strictly pro- The adaptation of lichens to bird trampling is related to hibited. growth form, thallus size and substrate preference. The re- duced soil stability due to bird trampling makes the micro- 4 Conclusion habitats unfavorable to terricolous lichens[3]. Crustose and dwarf lichens can survive greater penguin disturbance than The CCA analyses show that the small-scale spatial distri- [37] the foliose, tall fruticose lichens . The dwarf thallus of C. bution of the 10 macrolichen in King George Island, West regalis (thallus commonly < 3 cm in height), and pendulous Antarctica is mainly influenced by spatial heterogeneity of [3] and soft thallus of R. terebrata on cliffs , may be helpful substrate, bird influence, and microclimate and topography, for both species in alleviating the damage of bird tram- whereas humans have little impact. [17] pling . The other lichens, either with a fruticose and stiff thallus up to 5 cm in height, or with a foliose thallus, are Acknowledgements We thank the Chinese Arctic and Antarctic Administra- attached to the substrate by a single holdfast that can be [3] tion, SOA for its logistical support. This study was funded by the the Polar easily damaged by birds . Holdfast remnants or broken Science Strategic Research Foundation of China (Grant no. 20080205), Na- thalli of Usnea spp. were frequently observed on rocks near tional Natural Science Foundation of China (Grant nos. 30700107, 31000239) bird colonies. and Natural Science Foundation of Hebei Province (Grant no. C2010000268). The climate data are from those issued by the Data-sharing Platform of Polar 3.3 Effects of microclimate and topography Science（http://www.chinare.org.cn）maintained by Polar Research Institute of China(PRIC) and Chinese National Arctic & Antarctic Data Center The third most important factor is variation in microclimate (CN-NADC). and topography, which purely explains 7.2% of TVE (Table 3, Figure 1), and shares 13.9% of TVE with the set of bird influence variables and 12.9% with the set of substrate References variables (Figure 1). Distance from coast and distance from ground are significant in explaining the distribution of the 1 Lindsay D C. The role of lichens in Antarctic ecosystems. The Bryologist, 10 lichens (Table 1). 1978, 81(2): 268-276. Distance from coast is highly related to bird influence. 2 Barrett J E, Virginia R A, Hopkins D W, et al. Terrestrial ecosystem proc- In King George Island, bird colonies and penguin rookeries esses of Victoria Land, Antarctica. Soil Biol Biochem, 2006, 38(10): are often distributed along or near the coast, and bird con- 3019-3034. centrations generally declines with increasing distance from 3 Øvstedal D O, Smith R I L. Lichens of Antarctica and South Georgia: A [37] Guide to Their Identification and Ecology. Cambridge: Cambridge Uni- the coast . Distance from ground is related to the degree versity Press, 2001. of soil accumulation: Soil is commonly accumulated in flat 4 Chen J, Blume H P. Biotic weathering of rocks by lichens in Antarctica. and low-lying microhabitats, whereas soil cover and depth Chinese Journal of Polar Science, 1999, 10(1): 25-32. is low on the top of rocks. 5 Ascaso C, Wierzchos J, Castello R. Study of the biogenic weathering of Water availability is not statistically significant in ex- calcareous litharenite stones caused by lichen and endolithic microorgan- plaining the distribution of the 10 lichens (Table 1). This is isms. Int Biodeterior Biodeg, 1998, 42(1): 29-38. inconsistent with other studies documenting that water 6 Chen J, Blume H P, Beyer L. Weathering of rocks induced by lichen colo- 148 LIU Huajie, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

nization-a review. Catena, 2000, 39(2): 121-146. 24 Victoria F C, Albuquerque M P, Pereira A B. Lichen-moss associations in 7 Adamo P, Vingiani S, Violante P. Lichen-rock interactions and bioforma- plant communities of the southwest Admiralty Bay, King George Island, tion of minerals. Dev Soil Sci, 2002, 28: 377-391. Antarctica. Neotr Biol Conserv, 2006, 1(2): 84-89. 8 Bölter M. Soil development and soil biology on King George Island, 25 terBraak C F G, Šmilauer P. CANOCO Reference Manual and CanoDraw Maritime Antarctic. Polish Polar Research, 2011, 32(2): 105-116. for Windows User's Guide: Software for Canonical Community Ordina- 9 Green T G A, Schroeter B, Sancho L G. Plant life in Antarctica//Pugnaire tion (version 4. 5). Ithaca: Microcomputer Power, 2002. F I, Valladares F. Handbook of Functional Plant Ecology. New York: 26 Lepš J, Šmilauer P. Multivariate Analysis of Ecological Data Using Marcel Dekker Inc, 1999: 496-543. CANOCOTM. 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· Article · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00149 September 2012 Vol. 23 No. 3: 149-154

Comparison of the defluoridation efficiency of calcium phosphate and chitin in the exoskeleton of Antarctic krill

1,2 1,2* WANG Zhangmin & YIN Xuebin

1 School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China; 2 Advanced Lab for Eco-safety and Human health, Suzhou Institute of USTC, Suzhou 215123, China

Received 25 June 2012; accepted 16 August 2012

Abstract Calcium (Ca), phosphorus (P), and chitin are the main components of the exoskeleton of krill. Defluoridation of a solu- tion of sodium fluoride (NaF) using calcium phosphate (Ca3(PO4)2) and chitin as defluoridation agents was studied. Orthogonal experiments were designed to find the optimum reaction conditions for defluoridation, to obtain the maximum defluoridation effi- ciency and fluoride removal capacity of calcium phosphate and chitin. At the same time, a comparison of the capacity of the two defluoridation agents was made. The results suggest that calcium phosphate has a far greater capability than chitin for the removal of fluoride (F) from water under similar reaction conditions. It is also suggested that Antarctic krill is likely to adsorb fluoride via compounds such as calcium phosphate, hydroxyapatite, and other compounds of Ca and P with the general form (Ca, X)x(PO4, HPO4, Y)y(OH, Z)z, in addition to chitin.

Keywords calcium phosphate, chitin, defluoridation, krill, orthogonal design

Citation: Wang Z M, Yin X B. Comparison of the defluoridation efficiency of calcium phosphate and chitin in the exoskeleton of Antarctic krill. Adv Polar Sci, 2012, 23: 149-154, doi: 10.3724/SP.J.1085.2012.00149

comparatively low F content of chitin compared with the 0 Introduction* overall F content of the krill exoskeleton suggests that chi- tin may not be the main reason that krill adsorb F from sea Fluorine (F) is an essential trace element for human beings. water. However, the Ca and P content have been reported to As F is a dual-threshold element, a deficiency or an exces- be proportional to the F content in different parts of the sive can have adverse effects on human health. Fluorine is krill’s body[4]. Thus, it is possible that Ca and P also con- normally present in bones and teeth, although excessive tribute to the high F content in the krill’s exoskeleton. To amounts can be toxic and lead to debilitating fluorosis in determine how krill adsorb F, by either chitin or calcium humans and animals[1-3]. Antarctic krill (Euphausia superba) -1[4] phosphate, we designed various orthogonal experiments. In is rich in F and they contain greater than 1 000 mg·kg , -1[5] this study, we optimized the reaction conditions, analyzed with the exoskeleton containing as much as 5 477 mg·kg . how much F was removed from a sodium fluoride (NaF) Calcium (Ca), phosphorus (P), and chitin are the main solution by calcium phosphate and chitin, and compared the components of the exoskeleton of krill. It has been reported capabilities of the two defluoridation agents. Finally, we that the chitin structures in the exoskeleton play an impor- [6-7] present a tentative explanation for the high F content of tant role in F concentration . Chitin accounts for 20%— krill. 30% of the dry weight of the shrimp’s exoskeleton, while Ca, P and other inorganic mineral elements make up 30%— 1 Materials and methods 40%[8]. According to some reports, the F content of chitin in -1[4] - -1 the krill exoskeleton is only about 200 mg·kg . The NaF standard solution (F , 100 mg·L ) was used to draw the standard curve for the F ion-selective electrode (ISE)[9]. Chitin, calcium phosphate, and NaF (AR) were purchased *Corresponding author (email: [email protected]) from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). 100 mL PTFE beakers and deionized water

journal.polar.gov.cn 150 WANG Zhangmin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

(18 MΩ·cm water obtained from a Milli-Q water purifica- dation agents. Initial experiments were conducted to deter- tion system) were used to minimize loss or gain of F, which mine the three main factors, which were determined to be could cause experimental error. A 10-channel analog mag- the defluoridation time (t), pH, and mass of defluoridation netic stirrer with several PTFE magnetons was used for agents (m). Each factor had three levels, which were listed 3 mixing the F solutions. The pHs of the solutions were in Table 1. The parameters of the L9(3 ) orthogonal tests are measured using a DELTA-320 pH meter (Mettler-Toledo shown in Tables 2—4. CO., Ltd, Shanghai, China). A PXSJ-226 ion-activity meter (Shanghai Precision & Scientific Instrument Co., Ltd, Table 1 The factors and levels for the orthogonal tests Shanghai, China) was used with the ISE. Level t/min pH m/g To optimize the defluoridation efficiency of chitin and calcium phosphate, orthogonal tests were designed with 3 1 80 4 0.2 factors at 3 different levels and the analysis of the F con- 2 120 5 0.4 centration was conducted using the ISE. Many factors were 3 160 6 0.6 taken into consideration, such as particle size, defluorida- tion time, pH, reaction temperature, and mass of defluori-

Table 2 F removal rate and the adsorption capacity for *5.553 mg·L-1 NaF solution with chitin as the defluoridation agent Factors Tested results Computed results Orthogonal test *CF/ F adsorption capacity design items t/min pH m/g F removal rate/% (mg·L-1) /(mg·kg-1) T1 80 4 0.2 4.011 27.77 385.5 T2 80 5 0.4 4.724 14.93 103.6 T3 80 6 0.6 5.432 2.18 10.1 T4 120 4 0.4 3.933 29.27 202.5 Levels T5 120 5 0.6 4.743 14.59 67.5 T6 120 6 0.2 5.251 5.44 75.5 T7 160 4 0.6 3.904 29.70 137.4 T8 160 5 0.2 4.655 16.17 224.5 T9 160 6 0.4 5.193 6.48 45.0 K1 (%) 14.96 28.88 16.46 Range trend K2 (%) 16.40 15.23 16.86 analysis of K3 (%) 17.45 4.70 15.49 F removal rate R 2.49 24.18 1.37 K-1 (mg·kg-1) 166.4 241.8 228.5 Range trend K-2 (mg·kg-1) 115.2 131.9 176.9 analysis of K-3 (mg·kg-1) 135.6 43.5 71.7 adsorption capacity R 51.2 198.3 156.8

*Already deducted value of blank F concentration (CF)

A total ionic strength adjustment buffer (TISAB) pH. The 250 mg·L-1 F- solution was prepared by dissolving buffer was prepared by dissolving 14.2 g of C6H12N4 (AR), 0.055 3 g NaF powder in 100 mL of deionized water in a 8.5 g of KNO3 (AR), and 1 g of C6H4Na2O8S2·H2O (AR) in 100 mL PTFE volumetric flask, and then the mixture was 500 mL of deionized water. The pH of the TISAB buffer shaken well. A 49 mL portion of the blank TISAB buffer solutions were then adjusted to the required pH values (pH was transferred to a 100 mL PTFE beaker, and 1 mL of -1 -1 -1 - = 4, 5 or 6) using HCl (aq, 0.01 mol·L and 0.001 mol·L ). 250 mg·L F was added. The original F concentration of The TISAB buffer was prepared for later use and to avoid the solution was then determined using the ISE. interference of the F analysis by Fe and Al compounds. A A 49 mL portion of the TISAB buffer with the required blank TISAB buffer was also prepared without adjusting pH (pH = 4, 5 or 6) was then transferred to another 100 mL Comparison of the defluoridation efficiency of calcium phosphate and chitin in the exoskeleton of Antarctic krill 151

PTFE beaker and 1 mL of 250 mg·L-1 F- was added. The required time (t = 80, 120 or 160 min). The final F concen- required amount (m = 0.2 g, 0.4 g or 0.6 g) of the defluori- tration was determined using the ISE. Duplicates were pre- dation agent (chitin or calcium phosphate) was added. Then, pared for each treatment. The orthogonal test design is a PTFE magneton was placed in the beaker and the solution shown in Tables 2—4. was mixed in a 10-channel analog magnetic stirrer for the

Table 3 F removal rate and the adsorption capacity for *5.881 mg·L-1 NaF solution with calcium phosphate as the defluoridation agent Factors Tested results Computed result Orthogonal experimental *CF F adsorption capacity design items t/min pH m/g F removal rate/% /(mg·L-1) /(mg·kg-1) T1 80 4 0.2 0.002 99.966 1 469.8 T2 80 5 0.4 0.005 99.915 734.5 T3 80 6 0.6 T4 120 4 0.4 0.000 100.000 735.1 Levels T5 120 5 0.6 0.001 99.983 490.0 T6 120 6 0.2 0.509 91.345 1 343.0 T7 160 4 0.6 0.000 100.000 490.1 T8 160 5 0.2 0.000 100.000 1 470.3 T9 160 6 0.4 0.907 84.577 621.8

*Already deducted value of blank CF

Table 4 Comparison of the efficiency of the two defluoridation agents chitin and calcium phosphate -1 Orthogonal experimental Factors F removal rate/% F adsorption capacity/(mg·kg ) design items t/min pH m/g Chitin Calcium Phosphate Chitin Calcium phosphate T1 80 4 0.2 27.77 99.966 385.5 1 469.8 T2 80 5 0.4 14.93 99.915 103.6 734.5 T3 80 6 0.6 2.18 10.1 T4 120 4 0.4 29.27 100.000 202.5 735.1 Levels T5 120 5 0.6 14.59 99.983 67.5 490.0 T6 120 6 0.2 5.44 91.345 75.5 1 343.0 T7 160 4 0.6 29.70 100.000 137.4 490.1 T8 160 5 0.2 16.17 100.000 224.5 1 470.3 T9 160 6 0.4 6.48 84.577 45.0 621.8 Maximum 29.791 100.000 385.5 1 470.3

1 The maximum F removal rate for chitin was obtained using the optimum reaction conditions determined from the orthogonal experiments (defluoridation time: 160 min, pH = 4, and amount of chitin: 0.4 g).

experiments. All the F removal rates are less than 30%. The 2 Results and discussion highest F removal rate (29.70%) was observed with T7 treatment (defluoride time: 160 min, pH: 4, and chitin: 2.1 Defluoridation rate of chitin 0.6 g). The range trend analysis of F removal rate for the dif- The F removal rate with chitin as the defluoridation agents ferent levels and factors was calculated and the results are was calculated from the final F concentration (Table 2). As listed in Table 2. The values of K1, K2, and K3 represent shown in Table 2, the F removal rate of chitin in T7, T4, the individual F removal rate for each selected level and and T1 are the highest, and are much higher than the other factor. For example, the K1 value of column pH means that 152 WANG Zhangmin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 the F removal rate of level 1 (pH = 4) is 28.88%, which is level 1 for pH (pH = 4), and level 1 for mass of chitin (0.2 g), the average value of the data of level 1 (27.77%, 29.27%, so the optimal reaction conditions for the orthogonal ex- and 29.70%), and the K3 value of column t means that the periment are t1-pH1-m1. In conclusion, we get a maximum F removal rate of level 3 (t = 160 min) is 17.45%, which is F adsorption capacity of 385.5 mg·kg-1 using chitin as the the average value of the data of level 3 (29.70%, 16.17%, fluoride removal agent. and 6.48%). The value of R represents the range of K1, K2, and K3 in the same column: RpH (24.18) > Rt (2.49) > Rm (1.37), indicating that these three factors affect the F re- moval rate in the order: pH value of the solution > de- fluoridation time > amount of chitin. The range trend of F removal rate for the different levels and factors is shown in Figure 1. The optimal levels of the three factors are level 3 for defluoridation time (160 min), level 1 for pH (pH = 4), and level 2 for amount of chitin (0.4 g). Therefore, the optimal reaction conditions for the orthogonal experiment are t3-pH1-m2, which was not in- cluded in the orthogonal test design. In a supplementary Figure 2 The range trend of the F adsorption capacity for dif- experiment under the optimal reaction conditions, the F ferent levels and factors. removal rate was 29.79% (Table 4), which is slightly higher than the value of T7 (29.70%). 2.3 Defluoridation capability of calcium phosphate The F removal rate and F adsorption capacity of calcium phosphate are given in Table 3. The orthogonal experimen- tal design using calcium phosphate as the defluoridation agent was the same as for chitin. The same reaction condi- tions are used to enable direct comparison of the efficiency of chitin and calcium phosphate. After determining the final fluoride concentration, the F removal rate and F adsorption capacity of calcium phosphate were calculated. The fluoride concentration for T3 treatment could not be obtained be- cause of an error in the ISE. Hence, the range trend analysis Figure 1 The range trend of the F removal rate for different for calcium phosphate could not be carried out. levels and factors. It was observed that the final fluoride contents are all very low, with most of them close to zero (Table 3). Thus, 2.2 Fluoride adsorption capacity of chitin the F removal rates are all close to 100%. In contrast, the F adsorption capacities are different. The maximum F adsorp- The adsorption capacities with chitin as the defluoridation tion capacity is 1 470.3 mg·kg-1 with T8 conditions. The F agent are listed in Table 2. The adsorption capacity was adsorption capacities with T1 and T6 conditions are close to calculated using the formula: that of the T8 treatment, and significantly higher than the -1 Adsorption capacity (mg·kg ) = (Co - Cf ) × V / m, (1) others. The values of the fluoride content close to zero in- -1 where Co and Cf denote the F concentration (mg·L ) of the dicate that there is an excess of calcium phosphate for the original and final solution, V and m denote the volume (mL) remove of F. In other words, the actually maximum adsorp- of the F solution and the mass (g) of chitin added as the tion capacity of F using calcium phosphate as the defluori- defluoridation agent. The F adsorption capacities of chitin dation agent will be greater than 1 470.3 mg·kg-1. show significant differences (Table 2), with the maximum adsorption capacity (385.5 mg·kg-1) observed for T1 treat- 2.4 Comparison of the efficiency of the two de- ment (defluoride time: 80 min, pH: 4, and chitin: 0.2 g). fluoridation agents A range trend analysis of F adsorption capacity rate for the different levels and factors was conducted and the cal- The efficiency of the two defluoridation agents (chitin and culated results are listed in Table 2. The F removal rate is in calcium phosphate) was compared using the same reaction the order RpH (198.3) > Rm (156.8) > Rt (51.2), indicating conditions and the results are shown in Table 4. Compared that the three factors affect the F adsorption capacity of with chitin, both the F removal rate and the F adsorption chitin in the order: pH value of the solution > amount of capacity of calcium phosphate are higher. The maximum F chitin > defluoridation time. removal rate of chitin is 29.79%, while that of calcium The plots of the adsorption capacity for the different phosphate is 100%. Similarly, the maximum F adsorption levels and factors (Figure 2) shows the optimal levels of the capacity of chitin is 385.5 mg·kg-1, while it is at least three factors are level 1 for defluoridation time (80 min), 1 470.3 mg·kg-1 for calcium phosphate. These results indi- Comparison of the defluoridation efficiency of calcium phosphate and chitin in the exoskeleton of Antarctic krill 153 cate that calcium phosphate is more effective than chitin for richment of Antarctic krill. During the growth process of removing F from water, and thus calcium phosphate is a Antarctic krill, Ca and P would be transported to the clear- more effective defluoridation agent. ance of chitin in the krill exoskeleton by the krill body, generating stable compounds in the form of various calcium 2.5 Possible reasons for high F content of krill phosphates. These compounds would fill in the clearance of In general, Antarctic creatures have high F content, and a chitin structure and tightly integrate with chitin. The con- strong ability for fluorine accumulation and a high F toler- centration of F is high in sea water, and it will slowly seep ance[10]. Krill is an important species in Southern Ocean into the krill exoskeleton via the chitin structure, and then ecosystems, because it is an important food source for seals react with the stable compounds made of Ca and P, forming and other Antarctic animals. To investigate whether Ca and a stiff crust that can protect the soft body from physical P, or their compounds, can increase the F content in the damage. Deposition of F in the Antarctic krill exoskeleton exoskeleton of krill, we made a rough calculation of the F can also prevent excess F from entering the krill body. content of krill exoskeleton. 1 kg of krill exoskeleton con- Fluoride uptake by various calcium phosphates, such tains 4 028 mg F[4], and the chitin component is about 250 g, as hydroxyapatite[Ca10(PO4)3(OH)2, HAP], octacalcium [8] · because it contains 20%—30% chitin . It has been re- phosphate[Ca8H2(PO4)6 5H2O, OCP], and dicalcium phos- phate dihydrate[CaHPO4·2H2O, DCPD]) has been studied ported that the F content in chitin is not high, only about [16] 200 mg·kg-1[4]. In our orthogonal experiments, the maxi- by Yang et al. . They found that the calcium phosphates mum F adsorption capacity of chitin was estimated to be absorb fluoride through fluorapatite formation via dissolu- · -1 tion and recrystallization. Chen et al. has also studied the 385.5 mg kg . Therefore, the F content of chitin in the krill [17] exoskeleton constitutes only 2.4% of the total exoskeleton F, reaction of DCPD, HAP with F . The reaction products indicating that chitin isn’t the main reason for the high F were anhydrous dicalcium phosphate[CaHPO4, DCPA], content of krill. The Ca and P content in krill exoskeleton fluor-hydroxyapatite[Ca10(PO4)3Fx(OH)2-x, FHAP], fluora- are reported to be 3.55% and 5.59%[4]. Assuming that the patite[Ca10(PO4)6F2, FAP], and calcium fluoride [CaF2], Ca and P in the krill exoskeleton only exist in the form of depending on the F ion concentration. These results com- calcium phosphate, it can adsorb 1 470.3 mg·kg-1 F based bined with our experiment data suggest that F may deposit our orthogonal experiments, although this is an under- with calcium phosphates in the chitin structure, forming estimation of the actual maximum F adsorption capacity. substances like Cax(PO4, HPO4)y(OH, F)z. Moreover, cations like Mg2+, Sr2+, Ba2+, and Zn2+ have similar properties to The estimated F content contributed by calcium phosphate 2+ 2- - 2- - - Ca , and anions like CO3 , HCO3 , SO4 , Cl , and NO3 in the krill exoskeleton is about 3.4% of the total exoskele- 2- - ton F using the percentage of Ca, and 10.2% using the per- have similar properties to PO4 and HPO4 , and they are all centage of P. Although it also only contributes a small por- abundant in the ocean. Thus, we suggest that they may also tion of the total F in the krill exoskeleton, it is higher than play a role in the enrichment of F in krill, by forming com- that of chitin. Moreover, the actual F adsorption capability pounds like (Ca, Mg)x(PO4, HPO4, CO3)y(OH, Cl, F)z, and of calcium phosphate is expected to be considerably greater (Ca, Sr)x (PO4, HPO4, SO4)y(OH, NO3,F)z. than that estimated in the present study. Thus, calcium 3 Conclusions phosphate adsorbs more F from solution than chitin, and this partly explains the high F content of krill. In the next In this study, the defluoridation of solutions of sodium fluo- section we will attempt to explain the source of the re- ride (NaF) using calcium phosphate and chitin as defluori- mainder of F in krill. dation agents was studied. We designed orthogonal experi- 2.6 What is the main source of fluorine in krill? ments to determine the optimum reaction conditions for defluoridation. The maximum defluoridation efficiency and Ca and P are the principal components of the bones of ani- fluoride removal capacity of calcium phosphate and chitin mals, with Ca and P making up 39.9% and 18.5% of the were determined. Calcium phosphate was found to have a weight of bone. The ratio of Ca to P is 2.16, and the major greater F removal capacity than chitin under similar reac- form of inorganic calcium is Ca10(PO4)6-x(CO3)x(OH)2+x, [11] tion conditions. Based on the results of our experiments, the which is deposited in the collagen molecule clearance . mechanism of the F enrichment in Antarctic krill can Similarly, in the exoskeleton of krill, P often exists in Ca mainly be explained by the existence of substances such as compounds[12], and Ca usually exists as calcium carbonate [13] calcium phosphate, hydroxyapatite, and other compounds and calcium phosphate . It has been reported that Ca and of Ca and P with the general form (Ca, X)x(PO4, HPO4, [4, 14-15] 2+ 2+ 2+ 2+ P are very rich in Antarctic krill . We suggest that F Y)y(OH, Z)z, where X = Mg , Sr , Ba or Zn , and Y = 2- - 2- - - would be physically or chemically adsorbed by chitin in the CO3 , HCO3 , SO4 , Cl , or NO3 . Further research into the krill exoskeleton during the Antarctic krill growth process, mechanism of Antarctic krill F enrichment is required. since we found that chitin has a F adsorption capacity of -1 about 385.5 mg·kg . This may be caused by the structure Acknowledgements Financial support from the National Natural Science and strong ion exchange ability of chitin. We propose that Foundation of China (Grant nos. 40601088, 40476001 and 40231002) and the Ca, P, and chitin may have a synergistic effect in the F en- Open Research Fund from the Key Laboratory of Polar Science, State Oceanic 154 WANG Zhangmin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

Administration, P. R. China (Grant no. KP201106) is greatly appreciated. We ronmental media in Antarctica. Environ Geochem Health, 2003, 25(4): would like to thank Miss Zhang Ling and Dr. Yuan Linxi for help with the 483-490. aspects of paper discussion and modification. 10 Xiang J H. Antarctic krill and fluorine. Marine Science, 1985, 9(3): 57-59 (in Chinese). 11 Xu S Q, Wang J, Cheng B B, et al. Concentrations of Ca, P and Sr and References characteristics of Ca/P and Ca/Sr in the bones of typical seabirds in the Antarctic. Journal of University of Science and Technology of China, 1 Boulton I C, Cooke J A, Johnson M S. Fluoride accumulation and toxicity 2007, 37(8): 995-1002 (in Chinese). in wild small mammals. Environ Pollut, 1994, 85(2): 161-167. 12 Brannon A C, Rao K R. Barium, strontium and calcium levels in the exo- 2 Choubisa S L. Endemic fluorosis in Southern Rajasthan, India. Fluoride, skeleton, hepatopancreas and abdominal muscle of the grass shrimp, Pa- 2001, 34(1): 61-70. laemonetes pugio: relation to molting and exposure to barite. Comparative 3 Li Y M, Liang C K, Slemenda C W, et al. Effect of long-term exposure to Biochemistry and Physiology, 1979, 63(2): 261-274. fluoride in drinking water on risks of bone fractures. J Bone Mineral Res, 13 Deshimaru O, Yone Y. Requirement of prawn for dietary minerals. Bulle- 2001, 16(5): 932-939. tin of the Japanese Society of Science Fisheries, 1978, 44(8): 907-910. 4 Zhang H S, Xia W P, Cheng X H, et al. A study of fluoride anomaly in 14 Sun S, Yan X J. Active substances in the Antarctic krill. Chinese Journal Antarctic krill. Antarctic Research, 1991, 3(4): 24-30 (in Chinese). of Polar Research, 2001, 13(3): 213-216 (in Chinese). 5 Sands M, Nicol S, McMinn A. Fluoride in Antarctic marine crustaceans. 15 Zhu Y Y, Yin X B, Zhou S B. A preliminary study of selenium and mineral Mar Biol, 1998, 132(4): 591-598. elements in Antarctic krill. Chinese Journal of Polar Research, 2010, 22(2): 6 Yin X B, Chen L A, Sun L G, et al. Why do penguins not develop skeletal 135-140 (in Chinese). fluorosis? Fluoride, 2010, 43(2): 108-118. 16 Yang T, Kim C, Jho J, et al. Regulating fluoride uptake by calcium phos- 7 Zhu B Y, Wang X Y, Hu Q X. A study of fluoride in Antarctic krill. Ant- phate minerals with polymeric additives. Colloids and Surfaces A: Phys- arctic Research, 1988, 1(1): 51-55 (in Chinese). icochemical and Engineering Aspects, 2012, 401: 126-136. 8 Zhang X G, Zhou A M, Lin X X, et al. Comparative study of chemical 17 Chen F, Feng Z D, Lin C J. Effect of sodium fluoride solution on the hy- compositions of white shrimp head and shell. Modern Food Science and drolysis of CaHPO4·2H2O and the solubility of its hydrolysate. Journal of Technology, 2009, 25(3): 224-227 (in Chinese). Xiamen University (Natural Science), 2001, 40(1): 52-58 (in Chinese). 9 Xie Z Q, Sun L G. Fluoride content in bones of Adelie penguins and envi-

· Article · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00155 September 2012 Vol. 23 No. 3: 155-162

Eco-environmental spatial characteristics of Fildes Pen- insula based on TuPu models

1,2 1* PANG Xiaoping & LI Yanhong

1 School of Resources and Environment Science, Wuhan University, Wuhan 430079, China; 2 Chinese Antarctic Center of Surveying and Mapping, Wuhan University, Wuhan 430079, China

Received 27 July 2012; accepted 17 September 2012

Abstract This study applies a TuPu analysis to investigate ecological and environmental aspects of an Antarctic ice-free area, using Fildes Peninsula as an example. The TuPu unit was determined using a vector-grid mixed data model. Information from the eco-environment elements was effectively extracted, and was generalized into different classes by means of data mining technol- ogy. A series of single-factor thematic information TuPu models, such as topography, soil, animal and vegetation, and human ac- tivities for Fildes Peninsula were built in this study. The topography TuPu model contained information on elevation and slope. The soil TuPu model involved soil development stages and soil thickness information. The animal and vegetation TuPu model contained the distribution of animals, plant types, lichen cover and lichen height. The human activities TuPu model included popu- lation density and human disturbance index information. The landscape comprehensive information TuPu model of Fildes Penin- sula also was established, and contains twenty-nine landscape units and twelve types of combined environments. The study quan- titatively revealed the spatial morphology and correlation of the regional eco-environment based on the analysis of these TuPu models. From these models, we can draw the conclusion that there is a regular differentiation of eco-environment from the coastal bands to the central hills in Fildes Peninsula, and that the eco-environment condition of the eastern coasts is different from that of the western coasts. The eco-environmental spatial variation also differs greatly from north to south. Based on analysis of spatial correlation, the vegetation in Fildes Peninsula has the greatest correlation with human activity, and has a certain correlation with topography and soil. This research may provide a new technical approach and scientific basis for the in-depth study of Antarctic eco-environments.

Keywords eco-environment, Fildes Peninsula, information TuPu model, analysis of TuPu model

Citation: Pang X P, Li Y H. Eco-environmental spatial characteristics of Fildes Peninsula based on TuPu models. Adv Polar Sci, 2012, 23: 155-162, doi: 10.3724/SP.J.1085.2012.00155

vestigation and dynamic monitoring, and also can show 0 Introduction* spatial structural characteristics and temporal variations of ecological environments with graphical analysis of topo- Geo-information TuPu is based on the theory of spatial graphic maps, thematic maps and remote sensing images[2]. cognition, and it is supported by remote sensing, geo- Research on regional ecological environment information graphic information systems, as well as computer graphics Tupu has achieved phased results in China. The classifica- technology. The system expresses the spatial structural fea- tion and database building of eco-environmental compre- tures and temporal variation of objective things and phe- hensive information TuPu in Fujian Province has already nomena, with production of an intuitive information series been achieved by Chen et al.[3-5]. Wang studied land use of graphics, images and schemata by means of data mining [1] change evaluations by eco-environment information at- and special processing . Eco-environment information las-spatial analysis techniques in the Songnen Plain[6], and TuPu can be produced on the basis of eco-environment in- Tian studied the geo-informatic TuPu model of ecological [7] environment in the city of Qinhuangdao . Antarctic ice-free areas are mainly distributed in *Corresponding author (email: [email protected])

journal.polar.gov.cn 156 PANG Xiaoping, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 coastal zones and inland bare rock areas of Antarctica. The TuPu can be divided into single-factor thematic information characteristics and evolution of the geology, geomorphol- TuPu or multi-factor comprehensive information TuPu. The ogy, biology, soil and climate contain a wealth of environ- Antarctic ice-free area forms unique ecological characteris- mental history information, and are key areas of scientific tics with its internal and external forces. For the case of research. In recent years, a series of Antarctic Fildes Peninsula, a multi-level and wide-angle information eco-environmental studies have been carried out, including TuPu system should be established under certain refining environmental background value surveys, biodiversity sur- models using a variety of principles and techniques, such as veys, environmental impact assessments, and ecological geographic mechanism exploration, data mining, spa- baseline spatial differentiation analyses. We took Fildes tial-temporal analysis and information visualization[14-15]. Peninsula as an example, and we clarified its eco-environ- Figure 1 shows the process of eco-environment TuPu mental spatial characteristics by constructing construction, which includes the following important parts: eco-environment information TuPu models. These models (1) Collection of regional eco-environment informa- deepened the excavation of eco-environment internal laws tion, including observational data, map data, image data and and their multi-dimensional expression. fieldwork data. Then, the elements phenomena and prob- lems of the eco-environment are analyzed to grasp macro 1 Overview of study region patterns and laws. (2) Defining TuPu units, which are the basic space- Fildes Peninsula is located in the southwestern area of King time complex units for organizing geographic information George Island, which is near the tip of the Antarctic Penin- and establishing the computational model or mathematical sula. The latitude of Fildes Peninsula ranges roughly from simulation models. We used a hybrid model, which com- 62°08'48"S to 62°14'02"S, and the longitude ranges from bines planar vector units and regular grid units to determine about 58°40'59"W to 59°01'50"W. The length of the region TuPu units. A 20 m×20 m regular grid was used as the basic from north to south is about 8 km, and the width from east unit for environmental factor analysis, and it was further to west is 2.5—4.5 km. The total area of the peninsula is 2 overlaid on the landform type zoning, soil type zoning and approximately 38 km . Fildes Peninsula is a hilly region vegetation type zoning to product vector planar units of with an altitude below 170 m. It has characteristic landform comprehensive nature zoning, which were used as the TuPu types of mainly denuded hills, eroded tablelands and coastal units for overlaying analysis and regional analysis. terraces. The soils of the peninsula show strong physical processes at the surface, and the soil types mainly are cam- bisols and entisols. Areas with dense vegetation and pen- guin habitats usually have histosols, and the beach terraces have sandy soils[8]. The peninsula belongs to the sub- Antarctic oceanic climate, with tundra habitat characteris- tics of low temperature, high winds and precipitation. Snow is mainly seasonal and linked to the distribution of precipi- tation[9]. The region has unique species, and the plant com- munity is mainly made up of cryptogamic plants, such as lichens, mosses and algae[10]. More than 15 species of sea- birds are distributed on the island, and the community structure is mainly made up of penguin-skua-tern. The re- gional eco-environment has low capacity of self-purifica- tion and resistance to external stress. Thus, the eco-envi- ronment is very primitive and vulnerable[11]. There are sci- entific research stations from China, Russia, Chile, Uruguay, Argentina and other countries on Fildes Peninsula. Owing to its special location and particular environment, Fildes Peninsula has several Antarctic Specially Protected Areas (ASPA). At the eighth Antarctic Treaty Consultative Figure 1 Construction of processes for eco-environment infor- Meeting (ATCM), these were identified as having high sci- mation TuPu development. entific research importance[12-13]. (3) Generalizing the eco-environment information to 2 Construction of eco-environment informa- extract the basic eco-environment elements or factors and tion TuPu classifying the eco-environment information by means of data mining and knowledge innovation. In addition, this The eco-environment system is complex, and contains a part includes the establishment of standard types and scop- variety of environmental elements and factors. According to ing the distribution of the various characteristic elements information properties, the eco-environment information through classification and merging of data. The specific Eco-environmental spatial characteristics of Fildes Peninsula based on TuPu models 157 approach of the generalization of environmental factor in- twenty-one typical observation points of Fildes Peninsula, formation is shown in the part of TuPu model generation. and the planar distribution data of soil thickness was ob- (4) Producing and expressing the TuPu models. We tained when the point data were inserted in the ArcGIS. established the database and mathematical models to obtain Based on the relationship between soil development extent a series of diagrams in the form of analysis maps, and de- and topography, soil thickness was divided into six grades, scribed the series of graphics with mathematical parameters and the respective eigenvalues determined. to quantify and formalize the formation of the regional (3) Animal and vegetation elements: We studied the eco-environment TuPu. In this study, we designed the spa- distribution of penguins, skuas and other seabirds to reflect tial visualization of TuPu to obtain the function of computer the animal character of the peninsula. The data came from recognition and virtual reality. The TuPu included both the long-term surveys by Wang[16]. The plant types of the pen- single-factor thematic information TuPu and the compre- insula also were studied. Lichens are widely distributed in hensive information TuPu[14]. the study region, and are environmentally sensitive. We selected lichen coverage rates and lichen heights as indica- 2.1 Generation of thematic information TuPu models tors to reflect the vegetation status of the peninsula. On the In this study, climatic and hydrological factors were not basis of existing vegetation research, we interpolated the involved because the climatic element spatial variation is lichen field measurement data of Great Wall Station in the not very clear and surface runoff is usually scarce in Fildes twenty-third Chinese National Antarctic Research Expedi- Peninsula. The eco-environment information of the research tion (23rd CHINARE). According to distribution character- includes topography, soil, animals and vegetation, and hu- istics of the interpolation results, we extracted the informa- man activities. The extraction and summarization of the tion on lichen coverage rate and lichen height. The distribu- eco-environment information is as follows: tion of field vegetation survey points and routes are shown (1) Topographic elements: Elevation and slope are in Figure 2. important factors reflecting the different landform types and morphology of Fildes Peninsula. As the feature contours of 150 m, 50 m, 20 m, and 3 m express basic characteristics of the topographic contours of the region, the classification assignment of elevation was determined according to these feature contours and landform types. The extraction of landform slope indices was based on contour lines and ele- vation points of terrain data. The regional surface model was established by means of ArcGIS 3D_Analyst module, and the slope was divided into six grades in the comprehen- sive consideration of the slope shape, soil erosion, perigla- cial mudslides process, gravity process and other factors. The six grades were ≤4°, 4°—8°, 8°—15°, 15°—25°, 25° —35°, >35°. The value of 4° was included in the grade ≤4°, and the values of 8°, 15°, 25°, 35° were respectively included in the grade of 4°—8°, 8°—15°, 15°—25°, 25°— 35°. The slope of each grid cell (1 m × 1 m) was calculated, and the thematic raster data layer of the slope indicator was fully established. (2) Soil elements: Soil elements included soil devel- opmental stage and soil thickness. The soil classification map was used as the data source to complete data collection, data testing and topology building of vector data. As the soil spatial heterogeneity of the peninsula is very strong, the complex domain can be shown in a small area, and the dif- ferent soil types have different developmental stages. The eigenvalue of soil developmental stages in the complex region was the average of the eigenvalues of corresponding stages of the two main types in the study area. According to Figure 2 Distribution of field vegetation survey points and sur- the correspondence between soil classification and soil de- vey routes. velopment stage, soil developmental stage of Fildes Penin- sula was divided into six stages, and the eigenvalues of soil (4) Elements of human activity: The elements of hu- developmental stages were derived. The discrete point data man activity included annual average population density of of soil thickness was obtained from the monitoring data of research stations and human disturbance indices. The an- 158 PANG Xiaoping, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 nual average population density of research stations was buffer zone which had the building as its center and used determined by person numbers in summer in a buffer zone, 50 m as its radius. Road area was the area of the annular the center of which was in the middle of five research sta- buffer zone which used the road centerline as its center and tions (Great Wall Station, Frei Station, Marsh Base, Bel- 30 m as its radius. Expedition route area was the area of the lingshausen Station, Artigas Station), and the buffer radius annular buffer zone which used the expedition route center- was 50 m. The population density index in the TuPu unit line as its center and 50 m as its radius. was generated in accordance with the statistical unit. Hu- According to the extraction and summary of eco- man disturbance index meant that the human impact extent environment information of Fildes Peninsula, we built a on the eco-environment was reflected by floor-area ratio, series of thematic eco-environment information TuPu mod- and it was defined as follows: els of the region, including a topography TuPu model (Fig- Human disturbance index = (building area × 1+ road ure 3), a soil TuPu model (Figure 4), an animal and vegeta- area × 0.5 + expedition route area × 0.25)/ TuPu unit area tion TuPu model (Figure 5), and a population TuPu model Building area was defined as the area of the circular (Figure 6).

Figure 3 Topography TuPu model of Fildes Peninsula. a,The elevation of Fildes Peninsula. b,The slope of Fildes Peninsula.

Figure 4 Soil TuPu models of Fildes Peninsula. a, Soil developmental stages of Fildes Peninsula. b, Soil thickness of Fildes Peninsula. Eco-environmental spatial characteristics of Fildes Peninsula based on TuPu models 159

Figure 5 Animal and vegetation TuPu models of Fildes Peninsula. a, The animal distribution of Fildes Peninsula. b, The plant types of Fildes Peninsula. c, The lichen cover rate of Fildes Peninsula. d, The lichen height of Fildes Peninsula.

ducted a systematic study of eco-environmental types of 2.2 Generation of landscape comprehensive infor- Fildes Peninsula, and he divided the regional environment mation TuPu model into four types. The four environmental types are coastal environment, periglacial environment, ice water environ- Landscape is the complex product of many ecosystems, ment and artificial environment. The four types were di- which are impacted by topography, soil and other outside vided into 29 environmental landscape units according to factors. It is the basis of the modeling and prediction of the soil classifications, soil macro-character composition and geographical things trend. The classification of landscape biome characteristics. The numbers of specific environ- TuPu should be under the principle of combining the com- mental types and landscape units were identified system- prehensive factor and dominant factor, and it should reflect atically in Zhao’s study. The coexistence of two landscape both effect of the natural environment background and im- units can be seen in the same local area, which is called a pact of human activities. On the basis of emphasizing composite environment. The composite environment was natural differentiation, such as the basic geological struc- not numbered individually in this study, and it was repre- ture and landform types of the region, we focused on the sented by the sum of the numbers of the corresponding role of human activities and associated regional differences landscape units. Based on Zhao’s research, we conducted [17] and changes of the spatial landscape pattern. Zhao con- the visualization of the landscape comprehensive informa- 160 PANG Xiaoping, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 tion TuPu of Fildes Peninsula by drawing different colors landscape types and their spatial distributions at Fildes or textures to indicate different types. The environmental Peninsula are shown in Figure 7.

Figure 6 Population TuPu model of Fildes Peninsula. a, The population density of Fildes Peninsula. b, The human disturbance index of Fildes Peninsula.

Figure 7 Landscape TuPu model of Fildes Peninsula. Eco-environmental spatial characteristics of Fildes Peninsula based on TuPu models 161

Peninsula is significantly different. The east coast, with 3 Analysis of eco-environment information higher plant cover, is mostly a debris sedimentary coast, TuPu model and sediment soils or tundra soils usually can be seen under the vegetation. The west coast, with a small amount of 3.1 Analysis of spatial variation vegetation, is mainly bedrock erosion coastal, and biologi- cal effects on soil development processes are relatively When we overlay and contrast the series of thematic infor- weak from lack of vegetation, and the lithosol landscape mation TuPu models with the landscape comprehensive usually can be seen here. TuPu model, it can be seen that the characteristics of the (3) The eco-environmental spatial variation of Fildes natural environment of Fildes Peninsula is based on its Peninsula differs greatly from north to south because of the eco-environment spatial variation. However, this variation different impacts of lithology and regional ice sheet retreat [18] also is affected by the disturbance of human activity . The processes. The eco-environment of the northern peninsula is environmental landscape around the stations and the airport different from that of the southern peninsula. Flat terraces have significant heterogeneity with unique artificial envi- are the main geomorphologic type in the northern peninsula ronment characteristics. Specific ecological environmental and vegetation can grow over large areas. The environ- spatial variation characteristics are summarized as follows: mental landscape types here are few but are continuously (1) The eco-environment from coastal bands to central distributed. The terrain is very uneven and the surface is hills shows generally a regular differentiation. This differ- more broken toward the south of the peninsula. The growth entiation can be expressed as follows: The landscapes be- of lichens and mosses is greatly limited by the strong dis- low altitude 20 m are mostly debris coast-lichen and turbance of freeze-thawing and erosion of ice and water. moss-tundra soil (or sediment soil). The landscapes be- There are many environmental landscape types in the tween altitude 20 m and 60 m are mainly terraces, slopes southern peninsula, and the distribution of landscapes is and beach-lichen, moss and algae-tundra soil, skeletal soil, relatively heterogeneous. lithosol, disturbed soil and a small amount of histosols. The landscapes above altitude 60 m are mostly hilly steep slopes 3.2 Analysis of spatial correlation and tableland-lichen-skeletal soil, redox soil, carbonate soil [17] Eco-environmental factors could be mutually linked, and and lithosol . the spatial correlation between factors can be a good indi- The reason for this regular differentiation can be gen- cator of their relationship. A series of single-element the- eralized as follows. In altitudes lower than 20 m, lichens matic eco-environment information TuPu of Fildes Penin- and mosses are relatively dense, and more marine animals sula were used as the foundation, and the Spearman’s map can inhabit these locations in summer. With bio-organic rank correlation model was used as the tool to study the matter entering into the terrestrial ecosystem, surface bio- interdependence and mutual influence between the ele- logical processes are apparent, and results in more soil hu- ments. The Spearman’s map rank correlation model does mus layers. The marine salt enters the surface ecosystem not need to derive the exact value of the phenomenon, but with summer storms, which have an important impact on uses the “rank” (grade serial number) of the same partition regional soil material and the growth of terrestrial plants. units instead of specific values to calculate the correlation For altitudes between 20 and 60 m, regional surface proc- coefficient[11]. Thus, this approach reflects the correlation esses are mainly frost weathering, frost sorting, peristalsis between elements. The correlation analysis was conducted movement and snow thawing. Biological processes are sig- between topography, soils, human activities and the sensi- nificantly weakened and show permafrost landscapes. In tive vegetation factor of Fildes Peninsula in this specific altitudes higher than 60 m, regional surface processes are study. The rank correlation coefficients between terrain mostly frost weathering and strong erosion processes. Be- elevation, slope, soil thickness, soil development stage, cause there is only minor accumulation of surface debris, building area, population density factor and lichen height the landscapes of this region are trough and exposed bed- [17] and lichen coverage were calculated, respectively. The cor- rock on steep slopes . relation coefficient calculation used formula (1). The corre- (2) The eco-environmental states of the eastern coasts lation coefficient of the same factor is 1, and the correlation differ significantly from those of western coasts because of coefficients between indicators and lichen cover and lichen rock types, wind and peripheral currents. Thus, the state of height are shown in Table 1. the environment on the eastern and western coasts of Fildes

Table 1 Correlation coefficient of environmental factors in Fildes Peninsula Lichen Lichen Soil Soil development Building Population Elevation Slope coverage height thickness stage area density

Lichen coverage 1 0.434 0.183 0.038 0.265 0.025 0.299 0.477 Lichen height 0.434 1 0.124 0.051 0.063 0.110 0.281 0.517 162 PANG Xiaoping, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

n 2 Liao K, Qin J X, Zhang N. On Geo-informatic TuPu and digital Earth. 2 6∑ ()ppai− bi Geographical Research, 2001, 20(1): 56-61. r =−1 i=1 , (1) 3 Chen J. On the comprehensive information TuPu of eco-environment—A s 3 nn− case study on Fujian Province. Dissertation, Fujian Normal University, where pai is the grading number of element a, and pbi is 2006. the grading number of element b, and n is the number of 4 Yu M, Liao K, Li C H. The study of database system building and reali- statistical areas. zation on the environmental complex information TuPu in Fujian prov- It can be seen from Table 1 that lichen coverage and ince. Geo-Information Science, 2005, 7(4): 117-121. lichen height have the highest correlation with population 5 Chen J, Liao K. Classification of the comprehensive informatic TuPu for density, and the correlation coefficients are 0.477 and 0.517, the region’s eco-environment: a case study on Fujian province. Geo-Information Science, 2007, 9(2): 85-90. respectively. At the same time, lichen coverage and lichen 6 Wang C Y. Research on land use changes evaluation and optimization height also have a strong correlation with building area, supported by eco-environment information atlas-spatial analysis tech- and the correlation coefficients are 0.299 and 0.281, re- nique in Songnen plain. Dissertation, Jilin University, 2009. spectively. This reflects the very sizable impact of human 7 Tian J Y. Study on geo-informatic TuPu model of ecological environment activities on vegetation growth on the peninsula. In addi- and ecological security in Qinhuangdao city. Dissertation, Jilin University, tion, the vegetation has a certain correlation with topogra- 2007. phy and soil. Specifically, the correlation coefficient be- 8 Zhao Y, Li T J. The pedogenic groups and diagnostic characteristics on tween lichen cover and soil thickness is 0.265, which indi- fildes peninsula of King Georg island, Antarctica. Journal of Beijing cates that the distribution of vegetation on the peninsula is Normal University (Natural Science), 1994, 30(4): 529-535. largely impacted by soil thickness. The correlation coeffi- 9 Shen J, Xu R M, Zhou G F, et al. Research on the structure and relation- cient between lichen height and elevation is 0.124, which ship of terrestrial, freshwater, intertidal and shallow sea ecosystems in Fildes Peninsula, Antarctica. Chinese Journal of Polar Research, 1999, indicates that the growing condition of vegetation on the 11(2): 100-111, 211. peninsula is impacted by elevation to a certain extent. 10 Inoue M. Floristic notes on lichens in the Fildes Peninsula of King George Island and Harmony Cove of Nelson Island, the Antarctic. Polar 4 Conclusions Biol, 1993, 6: 106-120. 11 Pang X P. GIS-based assessment of eco-environmental vulnerability of In this study, the geographical information TuPu model ice-free areas in Antarctica. Dissertation, Wuhan University, 2007. was introduced into eco-environment research of the Ant- 12 Zhao Y. Late Holocene sea-level changes in Fildes Peninsula, Antarctica. arctic ice-free area. In this approach, we extracted and Earth Science Frontiers, 2002, 9(1): 137-142. generalized the information of topography, soil, animals, 13 Smith R I L. Signy Island as a paradigm of biological and environmental vegetation and human activity on Fildes Peninsula, and change in Antarctic terrestrial ecosystems. Antarctic Ecosystems. Berlin: built a series of single-factor thematic information TuPu Spring-Verlag, 1990. models and landscape comprehensive information TuPu 14 Chen J, Liao K. Classification of the comprehensive informatic TuPu for models. Based on the analysis of TuPu models, we quanti- the region’s eco-environment: a case study on Fujian province. Geo-Information Science, 2007, 9(2): 85-90. tatively revealed spatial morphology and spatial correlation 15 Liao K, Chen W H. Design and implementation of ecological environ- of the regional eco-environment. From the spatial variation mental dynamic monitoring and management information system. Sci- analysis of TuPu models, we can see that there is a regular ence of Surveying and Mapping, 2004, 29(6): 11-14. differentiation of eco-environment from the coastal bands 16 Wang Z P. Species and distribution of the birds on Fildes Peninsula, King to the central hills in Fildes Peninsula, and the George Island, Antarctica. Chinese Journal of Polar Research, 2004, eco-environment condition of eastern coasts is different 16(4): 271-280. from that of western coasts. Also, the eco-environmental 17 Zhao Y. The soil and environment in the Fildes Peninsula of King George spatial variation differs greatly from north to south. Based Island, Antarctica. Beijing: Ocean Press, 1999. on analysis of spatial correlation, the vegetation on Fildes 18 Pang X P, E D C, Wang Z P, et al. GIS-based assessment of Peninsula has the greatest correlation with human activity, eco-environmental vulnerability of ice-free areas in Antarctica. Geomat- and has a certain correlation with topography and soil. ics and Information Science of Wuhan University, 2008, 33(11): 1174-1177.

References

1 Chen S P. Exploration and research on Geo-information Tupu. Beijing: the Commercial Press, 2001.

· Article · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00163 September 2012 Vol. 23 No. 3: 163-169

Vertical structure of low-level atmosphere over the south- east Indian Ocean fronts

* FENG Lin, LIU Lin , GAO Libao & YU Weidong

Center for Ocean and Climate Research, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China

Received 10 July 2012；accepted 30 August 2012

Abstract During the 25th Chinese National Antarctic Research Expedition, GPS radiosondes were launched to detect the atmos- pheric vertical structure over the southeast Indian Ocean frontal region. Some low-level characteristics along the cruise are studied based on in-situ observation. The observations reveal that vertical distributions of the low-level wind field and air temperature field on both sides of the Subantarctic Front are very different. A stronger (weaker) vertical gradient is on the cold (warm) side, which demonstrates that the mid-latitude ocean-atmosphere interaction is active in the southeast Indian Ocean frontal region. A low-level -1 jet is observed over the Subantarctic Front, with speed up to 14 m·s . For the Antarctic polar front, low-level wind speed near the sea surface is greater than that aloft, in contrast with the situation of the Subantarctic Front. Comparing satellite remote sensing data and widely-used reanalysis datasets with our in-situ observations, differences of varying magnitudes are found. Air tempera- ture from Atmospheric Infrared Sounder (AIRS) data has a limited difference. The European Center for Medium Range Weather Forecasts Interim Re-Analysis (ERA Interim) dataset is much more consistent with the observations than the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1 in the southeast Indian Ocean frontal region. Keywords Subantarctic Front, Antarctic polar front, wind speed, air temperature

Citation: Feng L, Liu L, Gao L B, et al. Vertical structure of low-level atmosphere over the southeast Indian Ocean fronts. Adv Polar Sci, 2012, 23: 163-169, doi: 10.3724/SP.J.1085.2012.00163

phere on ocean, through changing ocean-atmospheric heat 0 Introduction* fluxes and the Ekman effect. However, SST has a signifi- cant positive correlation with sea surface wind in a strong Front is a common phenomenon in the global ocean. It is a frontal region, through vertical mixing induced by changes narrow region where oceanic physical property such as of static stability in the atmospheric boundary layer[1,6], temperature or salinity changes so sharply that the gradient high wind speed is likely to appear over warm SST region, across it is maximum. On both sides of a thermal front, sea whereas low wind speed is predominant over cold SST re- surface temperature (SST) can modulate latent heat flux gion[6-8]. Previous studies also indicate that on both sides of and sensible heat flux at the air-sea interface, and impact the front, changes of surface wind strength induced by SST local atmospheric circulations above the front. The mid- always result in a linear relationship between surface wind latitude ocean-atmosphere interaction near the front is very [9-15] [1] vorticity or divergence fields and SST gradient . different from that in the large-scale tropical region . Ob- Vertical shear associated with low-level wind speed servations show a significant negative correlation between [2-5] near the front is considered to be the dominant cause of the SST and sea surface wind speed in the tropical ocean . positive correlation between SST and sea surface wind The warmer the SST, the weaker the sea surface wind and field[16-17]. Studies on the vertical structure of the low-level vice versa. This highlights the one-way effect of atmos- atmosphere over the front have clearly revealed the interac- [18-19] tion between SST and sea surface wind . There are various fronts broadly distributed in the * Corresponding author (email: [email protected])

journal.polar.gov.cn 164 FENG Lin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 southern Indian Ocean[20-22]. Since these fronts are mainly southern Indian Ocean fronts lasted 8 days. During the in prevailing westerlies regions far from the continent, voyage, we released 6 radiosondes across the Subantarctic sparse in situ observations have been conducted[23-28], which Front and Antarctic polar front. The launched locations are hinders description and understanding of detailed vertical shown in Figure 1, overlaid on the SST and sea surface structures of the low-level atmosphere in the Southern wind field. The daily SST data are from the TRMM Ocean. Actually, there is no systemic observation of fronts (Tropical Rainfall Measuring Mission) Microwave Imager in the southeast part of the Indian Ocean by radiosonde as (TMI), the first well-calibrated microwave radiometer ca- the conditions are so unfavorable. As a result, there are very pable of accurate through-cloud SST retrieval[29]. Its hori- few studies on fronts in this region, especially regarding zontal resolution is a quarter degree (~25 km). The sea sur- vertical atmosphere structures above the front. With in situ face winds are daily Quick Scatterometer (QuikSCAT) data from radiosondes, launched during the 25th Chinese data[30]. We selected the background on 9 November to rep- National Antarctic Research Expedition, we analyze the resent the entire voyage. The Subantarctic Front and the vertical structure of low-level wind and temperature fields Antarctic polar front are determined according to certain over the southeast Indian Ocean fronts between Fremantle, criterias[25]. The boundary of the Subantarctic Front is Australia and the Chinese Antarctic Zhongshan Station. where the maximum gradient of SST is between 5℃ and 9℃. For the other front, the criterion is that the northern 1 Data and methods terminus of the subsurface minimum temperature layer is bounded by the 2℃ isotherm in the 100—300 m layer. The 1.1 In situ data result is that the two fronts are located at 45°S and 56°S, respectively. The R/V XUE LONG icebreaker left Fremantle for Zhong- shan Station on 8 November 2008. The cruise crossing the

Figure 1 SST (shading, unit is °C) and sea surface wind (vectors, unit is m·s-1) in the southeast Indian Ocean on 9 November 2008. Small red boxes represent locations of radiosonde launches.

The radiosonde used in this expedition was the GPS ters for Environmental Prediction/National Center for At- low-level system produced by Lingheng Science and Tech- mospheric Research (NCEP/NCAR) Reanalysis 1[32] and nology Development Company (Beijing, China)[31]. Its re- European Centre for Medium Range Weather Forecasts ceiver frequency is 407 MHz. GPS orientation technology (ECMWF) Interim Re-Analysis (ERA Interim)[33], respec- replaced radar telemetry for measuring wind speed and di- tively. All three datasets are interpolated onto the same grid rection, and a fast-response thermometer measured tem- as our observations for comparison. perature. The vertical resolution was around 4 m per second for the experiment. Data were effectively transferred by 2 Results and discussion data-transmission radio instead of an analog station. The equipment was tested in previous Antarctic and Arctic ex- 2.1 Vertical characteristics of the atmosphere over peditions, proving its good stability for signal reception. the southeast Indian Ocean fronts 1.2 Reanalysis and satellite data The SST decreased from 20°C to −2°C along the cruise, and westerlies prevailed during the entire period (Figure 1). We select some widely-used datasets, including those from The vertical distribution of horizontal wind speed below satellite remote sensing and reanalysis for cross calibrations. 1 500 m is shown in Figure 2a. Obviously, there is a Daily air temperature data are the Atmospheric Infrared low-level strong flow over the Subantarctic Front, which is Sounder (AIRS) global 1.0°×1.0° product (http://disc.sci. at about 250—350 m, with maximum speed reaching -1 gsfc.nasa.gov/giovanni/overview/index.html). The 4-times 18 m·s . This strong wind speed area, with speeds exceed- -1 daily wind and air temperature data are from National Cen- ing 16 m·s , stretches from 45°S to 48°S and occupies 80 m Vertical structure of low-level atmosphere over the southeast Indian Ocean fronts 165

(270—350 m) vertically. On either side of the front, the Zhongshan Station. This is consistent with prior observa- near-sea surface wind speed is much smaller than aloft. The tions in the southeast Indian Ocean by Pezzi et al.[24]. The wind speed increases with height, with a maximum larger largest vertical gradient is at 150 m. This indicates that the -1 than 20 m·s at 1 300 m. This distribution is also found in mechanism that SST controlling low-level wind via modu- middle levels (Figure 3a). However, vertical structures of lation of atmospheric static stability is also applicable to wind speed on either side of the Subantarctic Front are not mid-latitude weak fronts, where horizontal SST gradients identical, especially at low levels. Below 400 m, the gradi- are not so intensive. ent on the cold side (48°—50°S) is stronger than that on the Westerlies prevailed at the low levels, from Fremantle warm side (40°—42°S). The largest gradient is at a height to the Zhongshan Station (Figure 2b). Vertical structure of of 150 m. zonal wind velocity is very similar to the horizontal wind Around the Antarctic polar front (53°—59°S), the speed pattern. For instance, it is roughly symmetrical about near-surface horizontal wind speed is stronger than that the Subantarctic Front. Even so, the details are different. from 150 m to 1 000 m. Moreover, the vertical structure The most significant feature is a jet stream emerging on the shows that wind speed increases northward throughout cold side of that front, whose center has speeds reaching most of the low levels, which is very different from the 14 m·s-1 at 300 m. The jet extends over 500 km meridion- symmetrical structure over the Subantarctic Front. ally and 300 m vertically. At the same location on the warm The vertical distribution of wind field over the side, there is a minimum area where the velocity is only Subantarctic Front is closely related to ocean-atmosphere 10 m·s-1. And the symmetric feature of the low-level verti- interaction of the mid-latitudes. On the cold side of the cal structure is broken off. Subantarctic Front, lower SSTs enhance the static stability The meridional wind has a different vertical structure of the overlying atmosphere, forming strong stratification compared to either horizontal wind speed or zonal wind velocity near the sea surface and preventing downward energy (Figure 2c). The meridional wind below 200 m around the transport from upper to lower levels. This results in weak Subantarctic Front (40°—50°S) is controlled by northerlies. wind speeds near the surface. Above 150 m, atmospheric Above 200 m, the wind direction is opposite with maxi- stratification is not so strong and wind speed increases with mum speed at 300 m, which generates the largest vertical the height. Based on our analysis, SST can affect vertical gradient at 250 m. This region of strong southerlies is about stratification of the low-level atmosphere (below 150 m) 100 m in vertical direction and covers 200 km meridionally. around the Subantarctic Front between Freemantle and

Figure 2 Latitude-height cross sections of horizontal wind speed (a), zonal wind velocity (b), meridional wind velocity (c), and air tem- perature (d) over the southeast Indian Ocean below 1500 m. Units of wind speed and temperature are m·s-1 and °C, respectively. 166 FENG Lin, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

It is also the strongest meridional wind speed (>8 m·s-1) side of the Subantarctic Front. In particular, the gradient is region at low levels around the Subantarctic Front. Never- less than 0.01°C·m-1 and the isotherms are close to vertical theless, vertical structure above this front can still be con- at 40°S nearby. Over the cold side of the front, the vertical sidered symmetrical between 40° and 50°S, without regard temperature gradient is greater. Correspondingly, the me- to that above 1 000 m. Over the Antarctic polar front, ridional gradient on the warm side is stronger than that on southerlies are everywhere to form a barotropic distribution the cold side. Further, there is a cold gap 800 m above the vertically. Wind speed near the sea surface is stronger than front, which is more clearly depicted in Figure 3d. For that in the upper levels, but its variation along height is higher mid levels, vertical structures of horizontal wind modest. As the height enlarges, the south wind becomes speed, zonal wind velocity, meridional wind velocity and strong. Overall, zonal wind is stronger than meridional air temperature are shown in Figure 3. Wind speed in- wind over the southeast Indian Ocean fronts, making the creases with height on both sides of the Subantarctic Front, low-level structure of wind speed primarily controlled by and it is stronger on the cold side (Figure 3a and 3b). For the distributions of zonal wind. meridional wind, the direction changes from about 2 700 m Figure 2d is the vertical distribution of air temperature. to higher levels at 37°S nearby (Figure 3c). The air tem- It shows that the vertical gradient is smaller on the warm perature decreases at mid levels (Figure 3d).

Figure 3 Latitude-height cross sections of horizontal wind speed (a), zonal wind velocity (b), meridional wind velocity (c), and air tem- perature (d) over the southeast Indian Ocean. Units of wind speed and temperature are m·s-1 and °C, respectively. And the vertical extent is up to 4 000 m.

errors compared to in situ observations. We do a simple 2.2 Comparison to satellite and reanalysis datasets analysis on the satellite remote sensing data and the popular Satellite remote sensing and reanalysis datasets are the reanalysis datasets to investigate their differences between dominant resources for research on the Southern Ocean due the observations preliminarily. to a lack of in situ data. Naturally, a question should be Compared to observations, AIRS temperature (Figure answered. In the southern Indian Ocean, it remains a ques- 4a) is able to capture the dominant features of the vertical tion as to which dataset is more reliable or gives smaller structure presented by our radiosonde observation, though

Figure 4 Latitude-height cross sections of air temperature from AIRS observation (a), and difference between radiosonde and AIRS observations (the former minus the latter) (b) over southeast Indian Ocean. Unit of temperature is °C. Vertical structure of low-level atmosphere over the southeast Indian Ocean fronts 167 not so detailed. Difference between AIRS and observation and horizontal wind speed is somewhat symmetrical with is shown in Figure 4b. The difference is smaller below the Subantarctic Front. Although the ERA Interim data 1 500 m. Observed data are colder than AIRS data on the cannot reproduce the mid-level jet stream between the two cold side of the Subantarctic Front, and warmer over the fronts either, its quality is much better according to the dif- Antarctic Front. The major difference is over the Antarctic ference in Figure 6. This dataset captures the main features Front. of the vertical structure, except in the near sea surface areas. The observations are also compared with NCEP/ For instance, the near-sea surface wind speed above the NCAR Reanalysis 1 and ERA Interim data. The difference Antarctic polar front is smaller than aloft, and there are no with NCEP/NCAR Reanalysis 1 is remarkable, not only for northerlies over the Subantarctic Front. Among the four values but also the spatial patterns (Figure 5). The situation variables, air temperature has the smallest difference, and seems not so poor at low levels, as the distribution of zonal horizontal wind fields needs more improvements.

Figure 5 Latitude-height cross sections of differences in horizontal wind speed (a), zonal wind velocity (b), meridional wind velocity (c), and air temperature (d) between radiosonde observations and NCEP/NCAR Reanalysis 1, over southeast Indian Ocean. Units of wind speed and temperature are m·s-1 and °C, respectively.

Figure 6 Latitude-height cross sections of differences in horizontal wind speed (a), zonal wind velocity (b), meridional wind velocity (c), and air temperature (d) between radiosonde observations and NCEP/NCAR Reanalysis 1, over southeast Indian Ocean. Units of wind speed and temperature are m·s-1 and °C, respectively.

of the Subantarctic front are not completely symmetrical, 3 Summary and conclusions especially regarding the vertical gradient near the sea sur- face. There is a strong gradient on the cold side, and its Based on in situ observations from radiosondes launched maximum is around 150 m high. This proves that mid- over the southeast Indian Ocean, vertical structure of the latitude ocean-atmosphere interaction is still active in the low-level atmosphere over oceanic fronts is described. The southeast Indian Ocean frontal region. Wind direction has structures above the Subantarctic Front and the Antarctic an obvious change at about 200 m, with northerlies near the polar front are different. At 250 m to 350 m above the for- sea surface and southerlies above. Wind speed increases mer one, there is a region of strong wind with speed up to -1 with height. Over the Antarctic polar front, wind speed near 14 m·s , and westerlies make the major contribution. 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· Article · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00170 September 2012 Vol. 23 No. 3: 170-175

Cognitive effects of long-term residence in the Antarctic environment

1,2* 3 1 1,2 YAN Gonggu , WU Songdi , WANG Tianle , ZHANG Xuemin & 4 SAKLOFSKE Donald H

1 School of Psychology, Beijing Normal University, Beijing 100875, China; 2 Key Laboratory of Applied Experimental Psychology of Beijing, Beijing 100875, China; 3 Department of Neurology, Xi’an No.1 Hospital, Xi’an 710002, China; 4 Department of Psychology, University of Western Ontario, Ontario N6A 3K7, Canada

Received 1 June 2012; accepted 17 July 2012

Abstract This study examined whether prolonged residence in the Antarctica had a significant impact on cognitive performance. Participants were members of the 24th and 25th Chinese National Antarctic Research Expeditions. Cognitive performance was measured with tests designed to evaluate short-term recognition, memory search and spatial cognition, measured four times: Janu- ary, March, April, and June 2010. Age was controlled as a covariate, and data were analyzed using repeated-measures ANOVA. The results revealed that subjects’ short-term memory and recognition ability remained stable, while 82% of team members exhib- ited improved scores on a spatial cognitive ability test. These findings have important implications for furthering our understanding of cognitive functioning in extreme environments.

Keywords Antarctica, prolonged residence, cognitive performance, memory, spatial cognition

Citation: Yan G G, Wu S D, Wang T L, et al. Cognitive effects of long-term residence in the Antarctic environment. Adv Polar Sci, 2012, 23: 170-175, doi: 10.3724/SP.J.1085.2012.00170

conditions such as frigid cold and prolonged isolation may 0 Introduction* negatively impact vigilance, concentration, memory, and reasoning ability[4]. White and colleagues argued that, com- The Antarctic environment is characterized by a number of pared to a control group, the winter-over team performed unique features: geographical remoteness, strong wind, worse on cognitive tests[5]. However, some researchers have heavy snow, and polar nights. Scientific research teams suggested that with increased time in the Antarctic, people endure extreme temperatures and extended periods of con- actually exhibited improvements in certain areas aspects of finement in a monotonous location. Solitude and the re- cognitive performance[6-7]. For example, Defayolleet et al.[8] moval of familiar perceptual and cognitive environments reported that Antarctic expeditioners’ cognitive performance present several potential cognitive challenges to team improved on measures of transient memory, visual dis- members, including response accuracy and processing crimination and reaction time. More recently John et al.[9] speed, which are associated with short-term memory and reported that during long-term Antarctic residence, explor- spatial cognitive skills. ers exhibited improved short-term recognition, delayed Several previous studies have suggested that pro- recognition, and digit symbol substitution scores, while longed exposure to extreme conditions, such as those found their concentration level remained stable. These findings in the Antarctic, may cause impairments in cognitive suggest that long periods of relative deprivation in the Ant- [1-3] functioning . It has been reported that certain extreme arctic may not negatively impact cognitive functioning, and might even lead to improvement in some aspects of cogni-

tion[10-11]. * Corresponding author (email: [email protected])

journal.polar.gov.cn Cognitive effects of long-term residence in the Antarctic environment 171

A small number of Chinese psychological studies have involves not only spatial perception, but also concentration, focused on changes in cognition in the polar environment, search, mental rotation, and other advanced cognitive proc- producing variable results. For example, Xue et al. [12] esses. We used a mental rotation task to assess changes in argued that personnel staying over winter at Great Wall spatial cognition. Spatial cognition has not been examined Station of China demonstrated stable reaction times in dis- in previous studies, adding another dimension to the impact criminative and choice reaction tasks, delayed simple task of the Antarctic environment on cognitive functioning. reaction time, and improved memory scores. However, Yan et al. [13] surveyed 38 winter-over staff who had served at 1 Method Great Wall and Zhongshan stations at least once between 1984 and 2002, finding that 42% of test subjects reported 1.1 Participants memory impairment during the mission, and 68% reported memory problems after they returned to China. A total of 26 participants (23 males and 3 females, includ- The conflicting results described above may be ex- ing scientific, technical and construction personnel) of the plained by the use of different tests to measure different 25th CHINARE from Great Wall Station of China aspects of cognitive ability, with some studies using simple (62°12'59''S, 58°57'52''E) volunteered to participate in this tasks and others using complex tasks. Suedfeld[14] evaluated study. The mean age of participants was 35 a (Standard De- the complexity of different cognitive tests, suggesting that viation (SD) = 9.67 a). The Great Wall Station experiences prolonged residence in the Antarctic was positively corre- a typical Antarctic marine climate. In January, the warmest ℃ lated with improvements in basic cognitive skills such as month, the average temperature was 1.5 and the highest ℃ memory, vigilance, and simple learning in contrast to a temperature was 13 . In August, the coldest month, the - ℃ negative correlation with more complex cognitive skills. average temperature was 7.8 and the lowest tempera- - ℃ Zhang and colleagues observed and evaluated the team ture was 28.5 . members of the 6th Chinese National Antarctic Research Five of 26 participants had served in the 24th CHI- Expedition (CHINARE) at Great Wall Station and the team NARE winter-over team for 12 months, and agreed to work members of the 8th CHINARE at the Zhongshan Station. with the 25th CHINARE in Antarctica for 3 additional They concluded that after 2 months in Antarctica, simple months, referred to as the ‘overwintered members’ in this memory-related cognitive abilities remained stable, while study. 21 newly arriving participants belonging to the 25th complex memory decoding abilities declined; after 3-6 CHINARE were also assessed within one month of arriving months in Antarctica, more complex abstract character at the Antarctic station referred as newly arrived in the coding abilities declined significantly; nevertheless, the study. However, two of these participants did not undergo easiest 3-digit addition skills remained stable[15-16]. How- the recognition and memory search tasks, and three did not ever, Palinkas and colleagues reported that performance undergo the spatial cognition task. Eleven members of the improved in three complex tasks but deteriorated in two 25th wintering-over team stayed in the Antarctic for an en- — simple tasks[10]. tire summer winter period, from December 2008 to De- As discussed above, several theories have been pro- cember 2009. They participated in the longitudinal study. posed to explain the change of cognitive performance in After being informed of the objectives and data collec- extreme environments, including sensory deprivation and tion procedure of this study, all 26 participants agreed to task complexity. However, only a few studies have exam- take part in the research. The first author of this study ined the relationship between the length of residence and worked as a psychologist in the expedition team and con- the change in cognitive skills, and the findings are equivo- ducted an assessment in the first session. It should be noted cal. Therefore, the present study tested the length of resi- that there was an internet connection at Great Wall Station, dence as an independent variable and changes in cognitive so all participants were able to freely communicate with the performance as a dependent variable, seeking to further outside world. This changes the view of isolation in the explore the relationship between the length of residence and context of extreme environmental conditions, and adds an- cognitive performance. other unique dimension to the study. We employed computer-based tests to examine the 1.2 Experimental design and procedure cognitive performance of winter-over expeditioners in the 25th CHINARE at Great Wall Station. Memory is an im- Two short-term memory tests and one computer-based spa- portant cognitive function, and forms the foundation of tial cognition test were administered to participants as fol- more complex cognitive activities. In this study, a lows. 16 participants were assessed only once during the short-term recognition task and a typical memory search summer, in Januray 2009. The other 11 participants were task were used to examine memory. Recognition tasks are assessed three times (January, April and June) to examine relatively simple, reflecting basic memory functionality. memory-related cognition and four times (January, March, Memory search tasks, however, are more complex, requir- April and June) to measure spatial ability. The accuracy rate ing both recognition and search. Moreover, spatial cogni- (ACC) and reaction time (RT) for correct responses were tion, a more complex cognitive skill, is also important for measured as dependent variables. All three tests were con- people working in extreme environments. Spatial cognition ducted using E-prime software, and administered by the 172 YAN Gonggu, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 first author of this study and the physician on Great Wall presentation of 2 min, subjects were then presented with 40 Station. A repeated-measures within-subjects design was characters and asked to identify the 20 characters that were employed in the three assessments. previously displayed. The obtained accuracy score (ACC) is the number of correct responses to the 20 stimulus items. 1.3 Materials 1.3.2 Memory search task As described above, the present study contained three tests, which were easy to administer and could be broadly viewed The memory search task was used to assess short-term as measures of working memory and spatial cognitive abil- working memory and to gauge concentration level. In this ity. Character recognition and memory search were em- test, a single character (number or capital letter) was first ployed to measure memory-related cognition, and the men- presented as a target for 2 s. A stimulus set consisting of 2 tal rotation task was used to measure spatial cognition abil- to 8 characters was then presented. The subject was asked ity. To avoid the effects of practice, two parallel test materi- to judge whether the stimulus set contained the target or not, als were used alternately. by pressing key Y for “yes” or N for “no” on the keyboard. Each subject repeated this test 64 times. As shown in Table 1.3.1 Recognition task 1, the test was designed to balance two factors: the length In the recognition test, 20 two-character Chinese words of stimulus set and the location of the target stimulus. This were first presented one by one; each word was displayed measure comprises both ACC and RT measures, with the in the middle of the screen for 1 s, then a black screen was latter measure reflecting the time to respond following the presented for 0.5 s. The subjects were instructed to memo- presentation of the stimulus set. rize as many items as possible. Following an interference

Table 1 The design of memory search experiment Length of stimuli (No. of characters)

2 4 6 8

Position of target stimulus 1 21234 345 6 2 4 6 8 Times of responses on each kind of stimulus 4 2

1.3.3 Mental rotation task longer than those of the more recently arrived personnel in both memory search and mental rotation. We conducted an A mental rotation task was used to assess spatial cognitive ANOVA while controlling for age as a covariate. The re- ability. Test materials included 80 custom-made image sults revealed that ACC in the mental rotation task was sig- stimuli, displaying a vertical or horizontal line of five let- nificantly higher in the overwintered group than in the ters; 40 pictures contained the letter E and another 40 of newly arrived group (FACC_rotation (1,20) = 4.98, pACC_rotation = them contained the letter H. The design was balanced 0.04 < 0.05), whereas no significant difference was found among three factors: color (green or red), position of target between the two group in the RTs in the mental rotation - letter (1 5), and direction (vertical or horizontal). Subjects task, or in other tasks (F(1,21)ACC_recognition=1.12, were asked to identify whether the picture contained E or H pACC_recognition=0.30; F(1,21)RT_recognition=0.86, pRT_recognition by pressing the E or H keys on the keyboard. Each picture =0.36; F(1,21)ACC_search=0.32, pACC_search=0.57; was displayed randomly three times. In total, 240 responses F(1,21)RT_search=1.32, pRT_search=0.26; F(1,20)RT_rotation=0.30, were collected. The ACC and RT of each response were pRT_rotation =0.59). recorded. 2.2 Longitudinal study of cognitive performance 2 Results from summer to mid-winter All 11 members of the wintering-over group participated in 2.1 Comparison of overwintered and newly arrived the longitudinal study. The mean scores and SDs of re- explorers sponses on tasks measured at three different phases of win- tering are presented in Table 3. As shown in Table 2, in the first test session in January we The AAC of the recognition tasks exhibited a gener- compared the mean score and SD of responses between the ally declining trend, while RTs fluctuated from summer to overwintered and the newly arrived subjects. mid-winter. ACC gradually declined over the four times, In the recognition task, ACC of overwintered explorers during which the memory search task was administered, was lower than those of the newly arrived members, while while the RTs in the mental rotation task became shorter. RT was longer. The RTs of overwintered participants were However, when age was controlled as a covariate, the re- Cognitive effects of long-term residence in the Antarctic environment 173

peated-measures ANOVA indicated that none of the 0.68; F(3,18)ACC_search=2.62, pACC_search=0.08; F(3,18)RT_search changes were significant (F(2,12)ACC_recognition=0.01, = 0.60, pRT_search=0.62; F(3,18)ACC_rotation=0.26, pACC_rotation = pACC_recognition=0.99; F(2,12)RT_recognition=0.40, pRT_recognition= 0.85; F(3,18)ACC_rotation=0.38, pACC_rotation=0.77).

Table 2 Comparison of the overwintered and newly arrived personnel ACC RT Task Groups N Mean (SD) Mean (SD) Newly arrived 19 0.812 (0.060) 787.079 (101.571) Recognition Overwintered 5 0.775 (0.064) 885.900 (267.779) Newly arrived 19 0.947 (0.031) 775.079 (171.03) Memory search Overwintered 5 0.963 (0.034) 924.500 (153.20) Newly- arrived 18 0.970 (0.023) 772.583 (101.918) Spatial cognition Overwintered 5 0.994 (0.007) 817.900 (66.089)

Importantly, among 11 wintering-over explorers, 60% RTs of 82% of the subjects became shorter. showed a decline in ACC in the three recognition tasks, The data presented above indicate that after prolonged while 60% exhibited shorter RTs in the same tests. Across residency in the Antarctic, Chinese polar explorers’ per- the four memory search task sessions, ACC of 54% of the formance in short-term recognition and memory search wintering-over explorers declined, while the RTs of 91% of tasks remained stable, while spatial cognition significantly subjects became shorter. Across the four mental rotation improved. tasks, the ACC of 72% of the subjects increased, and the

Table 3 Accuracy and reaction time of responses in three experiments during a wintering-over expedition in Antarctica Jan Mar Apr Jun ACC(SD) 0.838(0.076) — 0.866(0.086) 0.831(0.087) Recognition RT(SD) 807.750(100.189) — 733.188(73.278) 815.375(216.457) ACC(SD) 0.961(0.031) 0.959(0.012) 0.953(0.022) 0.951(0.033) Memory search RT(SD) 813.375(209.631) 764.438(181.346) 699.438(142.143) 730.00(156.420) ACC(SD) 0.972(0.016) 0.975(0.018) 0.972(0.020) 0.974(0.025) Spatial cognition RT(SD) 779.563(127.555) 755.938(86.074) 734.813(79.900) 751.250(138.384)

3 Discussion lated Antarctic environment. These findings are consistent with those, for example, of John et al.[9], and Xue et al.[12]. The purpose of this research was to further examine the Previous studies of memory employed different types of [8] effects of extreme environments on specific cognitive func- cognitive measurement, including transient memory tasks , [11] tions. In particular, we examined memory, attention and short-term recognition tasks , and short-term memory [15] information processing among CHINARE who spent part tasks . Taken together with previous findings, the current of the year (summer only) or who stayed for a full year, results support the notion that the Antarctic winter experi- including the winter period, in the Antarctic. When control- ence does not negatively impact on basic cognitive func- ling for age as a covariate, the results suggested that the tioning and performance. In contrast, some cognitive scores summer only and the wintered-over staff exhibited no sta- appeared to improve slightly, although this improvement tistically significant differences in either of the memory may be due to artifacts of small sample size or measure- measures. Our longitudinal study of the wintering-over ment error. team members also showed that, from summer to Importantly, the memory test score findings reported mid-winter, short-term recognition memory and memory here conflict with self-reports from Antarctic team members search ability exhibited a small and statistically obtained after they completed their expeditions. In a previ- [13] non-significant decline. These results indicated that basic ous study by Yan and Tang , Chinese Antarctic explorers memory functioning was not significantly affected by a reported that they believed they had experienced memory prolonged period spent in the climatically extreme and iso- deterioration, including difficulty memorizing task details 174 YAN Gonggu, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 and recognizing familiar objects. Zhang et al.[16] reported and equipment for outside work have improved so that ex- that memory coding abilities showed some decline after 3 treme climatic conditions are less critical than they were in to 6 months in Antarctica. There are two possible interpre- the past. Regarding social isolation, internet access, includ- tations for these inconsistent findings. First, stimulus dep- ing Skype, has become available during the research period. rivation may have influenced the results. People working in Chinese Antarctic explorers are now able to communicate Antarctica before 2005 faced a much more isolated and with their families, friends and the “outside world”, acquir- confined environment than the participants in the current ing instant and current information. Thus, the availability of study. Information from outside the station was rare and the Internet has changed the cognitive and social environ- extremely limited before 2005, especially during the long ment previously experienced in remote and harsh environ- winter. For example, the most precious source of outside ments, and now provides explorers with access to aspects of information for previous stationers was calling home, their external lives that are relevant and important. These which they were able to do for less than 5 min per month. changes may be key in preventing the deterioration of cog- This proposed explanation should be tested by further in- nitive abilities and other psychological factors. Second, this vestigation. Second, the inconsistent result could be attrib- research is limited in several ways (e.g., the specific tests uted to the specific tasks used in the study, which call for a used, the limited range of cognitive variables, etc.), par- different level of information processing. The transient and ticularly the length of this study, which only lasted six short-term memory tasks employed in present study can be months from summer to mid-winter. The findings and ten- classified in the easy-mid level of difficulty. In contrast, the tative conclusions presented in this study require further subjective reports from explorers mainly concerned confirmation, as do the other research studies cited in this long-term memory, which is more difficult, and the memory paper, since their data on cognitive changes in the polar coding tasks employed in Zhang’s study also required more environment also spanned less than one year. complex cognitive skills. Suedfeld[14] had earlier offered an As explorations of extreme environments such as deep explanation that might shed light on this varying memory sea, outer space, and Antarctica continue, it is obvious that data obtained from the Antarctic scientific teams. These explorers will be required to reside or work in those envi- findings suggest that performance on easy-to mid-level ronments for much longer periods of time, in some cases memory tasks remains stable or may even improve over years and even decades. Thus, future research should in- time, whereas more complex and challenging memory tasks clude prolonged longitudinal studies. Finally, it should be may show some decline with time. noted that the changes we observed, including the deterio- The spatial ability test revealed that the accuracy rates ration and improvement of basic cognitive abilities, arise of overwintered explorers were significantly higher than from certain physiological bases. In test results from 101 those of the summer-over residents. The results showed that Chinese Antarctic explorers’ between 1986 and 1996, Xue 72% of the overwintered explorers exhibited improvements et al.[17] found that the secretion of the adrenal cortex, three in spatial cognitive performance and 82% of the overwin- hormones from the medulla region, and male hormone in- tered explorers exhibited shorter RTs. Thus mental rotation creased. This increase lasted for approximately one year, scores reflecting spatial ability were not impaired by time and was sometimes found even after the explorers returned spent in the Antarctic environment and in fact showed a home. Incidentally, the four measured hormones are known small improvement. This is important to note, because spa- to facilitate concentration and thus promote cognitive func- tial cognition is important for survival in extreme environ- tioning. Thus, future research on human responses to ex- ments, so it is encouraging that the present findings suggest treme environments should also consider the interface be- that this ability does not decline within the time frame of tween physical and psychological factors. the study. However, as Suedfeld suggested, because of the complexity of the tasks, researchers should be cautious 4 Conclusion when examining spatial cognitive abilities in extreme envi- ronments without first examining simple, medium and more The present study assessed the cognitive performance of difficult and complex variants of spatial reasoning ability. team members of the 25th CHINARE (2009) at Great Wall More comprehensive and ecologically relevant research Station, and found that, from summer to mid-winter: should be conducted before firm conclusions are drawn. (1) Short-term recognition and memory search ability Taking the results of the memory and spatial cognition scores were stable. tasks together, the current findings support the view that, at (2) 82% of winter-over explorers exhibited some im- least within a year of time spent in Antarctica, basic cogni- provement in mental rotation performance. tive skills such as short-term memory recognition, memory (3) Shorter periods of time (less than a year with or search, and spatial cognition are not negatively or adversely without wintering over) spent in the Antarctic scientific impacted. Rather, spatial cognition even tended to show research station did not have a negative impact on the cog- some improvement with time. However, several confound- nitive functions assessed in this study. ing factors may have influenced these results, and the ex- treme conditions attributed to Antarctic expeditions appear Acknowledgements This research was supported by the Fundamental Re- to have substantially changed over time. Accommodation search Funds for the Central Universities by Ministry of Education, and by the Cognitive effects of long-term residence in the Antarctic environment 175

Chinese Arctic and Antarctic Administration, SOA. The authors would like to during long-term residence in a polar environment. J Environ Psychol, thank all the volunteers of the 25th CHINARE at Great Wall Station who coop- 2010, 30(1): 129-132. erated and participated in the data collection, and Mr. Taiyi Yan for editing the 10 Palinkas L A, Mäkinen T M, Pääkkönen T, et al. Influence of seasonally English edition. adjusted exposure to cold and darkness on cognitive performance in cir- cumpolar residents. Scand J Psychol, 2005, 46(3): 239-246. 11 Mäkinen T M, Palinkas L A, Reeves D L, et al. Effect of repeated expo- References sures to cold on cognitive performance in humans. Physiol Behav, 2006, 87(1): 166-176. 1 Mullin C S Jr. Some psychological aspects of isolated Antarctic living. 12 Xue Z H, Zhang Y, Yao Z. A Study on the personality and psychological Am J Psychiatry, 1960, 117: 323-325. characteristics of winter-over members in the Antarctic Great Wall Station. 2 Angus R G, Pearce D G, Buguet A G, et al. Vigilance performance of men Chinese Journal of Polar Research, 1997, 9(3): 207-213 (in Chinese). sleeping under arctic conditions. Aviat Space Environ Med, 1979, 50(7): 13 Yan G G, Tang X Y. The Psychological Adaption of Antarctic Winter-over 692-696. Expeditioners. Office of Chinese Arctic and Antarctic Administration. 3 Palinkas L A. Going to extremes: The cultural context of stress, illness 2003, (in Chinese). and coping in Antarctica. Soc Sci Med, 1992, 35(3): 651-664. 14 Suedfeld P. Changes in intellectual performance and in susceptibility to 4 Palinkas L A. Mental and cognitive performances in the cold. Int J Cir- influence//Zubek J P. Sensory Deprivation: Fifteen Years of Research. cumpolar Health, 2001, 60(3): 430-439. New York: Appleton-Century-Crofts, 1969: 126-166. 5 White K G, Taylor A J W, McCormick I A. A note on the chronometric 15 Yu Y Z, Zhang W C, Deng X X. Antarctica and human brain func- analysis of cognitive ability: Antarctic effects. NZ J Psychol, 1983, 12: tion-memory performance and EEG examination among 17 subjects of the 36-44. Chinese 6th Antarctic explorers. Chinese Mental Health Journal, 1991, 6 Le Scanff C, Larue J, Rosnet E. How to measure human adaptation in ex- 5(1): 15-17 (in Chinese). treme environments: The case of Antarctic wintering-over. Aviat Space 16 Zhang W C, Tian Y, Wu W, et al. Analysis of EEG and physio-sychologi- Environ Med, 1997, 68(12): 1144-1149. cal state among expeditioners at the Antarctic. Chinese Journal of Indus- 7 Marrao C, Tikuisis P, Keefe A A, et al. Physical and cognitive perform- trial Hygiene and Occupational Diseases, 1997, 15(5): 291-294 (in Chi- ance during long-term cold weather operations. Aviat Space Environ Med, nese). 2005, 76(8): 744-752. 17 Xue Q F, Xue Z H, Deng X X, et al. Effect of residence in Antarctic on 8 Defayolle M, Boutelier C, Bachelard C, et al. The stability of psychomet- physical and psychological health and the prevention. Bulletin of Medical ric performance during the International Biomedical Expedition to the Research, 2001, 30(3): 24-25 (in Chinese). Antarctic (IBEA). J Human Stress, 1985, 11(4): 157-160. 9 John P F U, Manas K M, Ramachandran K, et al. Cognitive performance

· Letter · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00176 September 2012 Vol. 23 No. 3: 176-180

Russian researchers reach subglacial Lake Vostok in Ant- arctica TALALAY Pavel

Polar Research Center, Jilin University, Changchun 130026, China

Received 3 May 2012; accepted 17 July 2012

Abstract Opening a new scientific frontier lying under the Antarctic ice, Russian researchers have drilled down and finally reached the surface of the gigantic freshwater lake, Lake Vostok. The mission chief likened the achievement to placing a man on the moon. Drilling in the area of the lake began 22 years ago in 1990, but progressed slowly as a result of funding shortages, equipment breakdowns, difficulties of drilling in the “warm” ice, and environmental concerns. In 1996, six years after drilling was started, a group of Russian and British scientists discovered the lake believed to be one of the largest fresh water reservoirs on the planet. This lake is among the last unexplored places on Earth. Sealed from the Earth’s atmosphere for millions of years, it may provide vital information about microbial evolution, the past climate of the Earth, and the formation of the Antarctic ice sheet. Russian experts waited several years for international approval of their drilling technology before proceeding. As anticipated, lake water under pressure rushed up the borehole, pushing the drilling fluid up and away, then froze, forming a protective plug that prevented contamination of the lake. In December of the next Antarctic season, 2012—2013, researchers plan to re-drill the frozen sample of subglacial water for analysis.

Keywords Lake Vostok, Antarctic subglacial environment, ice drilling

Citation: Talalay P. Russian researchers reach subglacial Lake Vostok in Antarctica. Adv Polar Sci, 2012, 23: 176-180, doi: 10.3724/SP.J. 1085.2012.00176

#4G-2 to 2 546.4 m in 1989[2]. Drilling of a new deep hole, 0 Introduction* Hole #5G, started in February 1990[3–4], six years before the large subglacial lake under Vostok Station was officially The Soviet Antarctic research station, Vostok, was estab- recognized[5]. Twenty-two years later, on February 5, 2012, lished at the center of the East Antarctic Ice Sheet (78°28'S, Russian researchers made contact with Lake Vostok water, 106°48'E, 3 488 m a.s.l.) in 1957 (Figure 1). The first drill- at a depth 3 769.3 m. ing was carried out in 1958 when four boreholes were drilled with a hot point thermal drill to a maximum depth of 1 Lake Vostok 52 m[1]. Deep ice core drilling at Vostok Station began in 1970, and during the 1970s a set of open uncased holes Lake Vostok, with dimensions of 280 km × 50 km, is the were drilled using a thermal drill system suspended on ca- largest among more than 400 subglacial lakes identified by bles. The deepest dry hole in the ice reached 952.4 m (Hole radar and seismic surveys in Antarctica. The area of Lake #1, May 1972). For drilling at greater depths it was neces- Vostok is about 15 790 km2, and the thickness of the ice sary to prevent hole closure by filling the borehole with a sheet in the region of Lake Vostok varies from 1 950 m to low-temperature fluid. Therefore, from 1980 new thermal 4 350 m[6]. Absolute heights of the water table range from and electromechanical drill systems working in fluid were −600 m at the northern part of the lake to −150 m at the used. Two boreholes reached depths of more than 2 000 m. south. Lake Vostok is at least 1 000 m deep at the southern Hole #3G-2 was extended to 2 201.7 m in 1985, and Hole end (Figure 2), and relatively shallow to the north and ex- treme southwest. The volume of water in the lake is about 6 100 km3, and the average depth is about 400 m. There * Corresponding author (email: [email protected]) may be several hundred meters of glacial sediment depos-

journal.polar.gov.cn Russian researchers reach subglacial Lake Vostok in Antarctica 177 ited over its floor. 2 Drilling

Drilling of the deep Hole #5G started in February 1990, using a TELGA-14M thermal drill for dry coring to a depth of 120 m[8], and a TBZS-152M thermal drill for fluid-filled holes down to 2 502.7 m. However, this drill became stuck during tripping out, at a depth of 2 259 m, as a result of hole closure caused by insufficient fluid pressurization. Recovery attempts failed, and the cable was pulled out of the top of the drill. About 35 m of artificial core was then dropped on top of the stuck drill, creating a base for a new offset hole. A TBZS-132 thermal drill was used to sidetrack and drill Hole #5G-1 (Figure 3). In 1993, Hole #5G-1 reached 2 755.3 m in depth, a new record for thermal drill- ing in ice.

Figure 1 Vostok Station and other deep ice coring sites in Ant- arctica.

Figure 3 Schematic drawing of deep Hole #5G (showing #5G-1 and #5G-2).

In November 1994, drilling operations in Hole #5G-1 [6] Figure 2 Bedrock topography in the region near Lake Vostok . resumed with a KEMS-135 electromechanical drill, reach- ing 3 350 m by January 1996. From 1996—1997 the drill- The origin, evolution, and the present-day state of the ing operations were limited by the short Antarctic summers Lake Vostok system are closely related to the tectonic evo- but drilling of Hole #5G-1 continued until January 1998, lution, the climatic history, and the development of the reaching a depth of 3 623 m. Antarctic ice sheet. The lake represents an old (Late Juras- After an eight-year hiatus, Hole #5G-1 was reopened — sic Early Cretaceous) rift structure bounded by deep faults in the summer of 2005—2006, and was deepened to and, as an ancient and deep tectonic lake isolated from the 3 658 m in January 2007, but at this depth the drill became surface biota for millions of years, it has great potential for stuck at the bottom of the hole. A drill team that remained at harboring prehistoric life. Vostok Station over winter filled the lower hole with 80 L Samples of water from Lake Vostok are required for of an antifreeze agent. The drill was captured with an over- the investigation of physical and chemical processes, and shot gripper and was lifted to surface on the first attempt, for the identification of life within the lake. Researchers and then the water-glycol solution was removed from the elected to use the existing deep hole, Hole #5G, to gain ac- [7] hole. cess to the lake to collect samples of subglacial water . In May 2007 drilling continued to a depth of 3 668 m. Unfortunately, during enlargement of the hole in October 178 TALALAY Pavel. Adv Polar Sci September(2012) Vol. 23 No. 3

2007, the core barrel suddenly dropped to the bottom. All ice thickness at Vostok Station should range from 3 751– attempts to recover it failed, and operations did not resume 3 757 m with the temperature at the ice-water boundary until December 2008. Starting at a depth of 3 580 m, a new ranging from –2.9℃ to –2.75℃. The small variation is deviated hole was drilled using a KEMS-135 electrome- caused by different estimations of the Clapeyron tempera- chanical drill with a special drill head and cutters. In the ture-pressure slope. The hydrostatic pressure of the drilling summers of 2009—2010 and 2010—2011 drilling at Vostok fluid column at a depth of 3 700 m was measured as 328.96 continued, and Hole #5G-2 was deepened to 3 720.5 m bar, 2.64 bar less than the overburden pressure of ice at this (Figure 4). According to radar and seismic observations, the depth. ice-water interface at Lake Vostok was at a depth of 3 755 ± Drilling of Hole #5G-2 resumed on January 2, 2012. 15 m[9], and the remaining ice thickness was estimated to be The drilling was conducted on a three-shift, twenty- about 35 m. four-hour cycle, with an average progress rate of 1.75 m per day. The first water entry occurred at a depth of 3 766.3 m on February 4, and about 30–40 L of the water was pumped into the inner part of the drill by a down-hole pump. No cracks or capillaries in the ice core were observed at this time. The drilling continued, recovering the core with a length of 0.3–0.9 m per run, and the next day, February 5, the subglacial water finally entered into the hole at a depth of 3 769.3 m. The drilling fluid consisted of a mixture of kerosene and Freon 141b, which is less dense than lake water, and it began to rise rapidly up the borehole. As a result, about 3 Figure 4 Drilling complex at Vostok Station, January 2011 1.5 m of this fluid poured out through the mouth of the (Photograph: G. P. Talalay). borehole into special trays, installed in the drilling building. The pulling of the drill started after 4 s, when the sensors 3 Reaching Lake Vostok came into action, and 2.5 h later the drill was recovered to the surface (Figure 5). Russian scientists reached the lake In December 2011 the drilling complex at Vostok Station just before they had to leave the station at the end of the was reopened, and all surface and bottom drilling equip- Antarctic summer, when plunging temperatures put a halt to ment was rechecked and maintained. Logging of the bore- all travel to the region (Figure 6). On February 6, several hole showed that the inclination of the hole at depths deeper hours after the historical event, the summer’s last flight of than 3 590 m varied from 4.6° to 5.7°, and the liquid level the DC-3 BT 67 “Turbo Basler” departed, and the drilling in the hole was stable at 54 m. Temperature measurements team left Vostok Station. in the hole (Table 1) enabled the prediction of temperature conditions at the bed of the ice sheet, taking into account that the basal ice temperature above the subglacial lake is equal to the pressure melting value.

Table 1 Temperature and pressure measurements in Hole #5G (5G-1, 5G-2), December 6, 2011 Depth/m Temperature/℃ Hydrostatic pressure/bar 1 000 - 49.26 — 1 600 - 42.05 — Figure 5 The refrozen Lake Vostok water recovered from the 2 200 - 32.93 189.78 last run, February 5, 2012 (Photograph: N. I. Vasiliev). 2 600 - 25.74 230.92 3 000 - 18.10 266.33 3 510 -7.66 311.95 3 550 -6.84 315.54 3 610 -5.61 320.89 3 650 -4.79 324.49 3 700 -3.76 328.96 Figure 6 Russian researchers at Vostok Station pose for a picture after reaching subglacial Lake Vostok, February 5, 2012 Based on extrapolation of the temperature profile, the (http://www.aari.nw.ru). Russian researchers reach subglacial Lake Vostok in Antarctica 179

It is symbolic that, on February 4, Vostok Station was subglacial refrozen water was completely gone from the visited by Yuri Trutnev, Minister of Natural Resources and core after the first 14 m of re-drilling. Ecology of the Russian Federation. Yuri Trutnev took the Unfortunately, the technology used for the Lake first water sample from subglacial Lake Vostok and deliv- Vostok access did not comply with the draft Comprehensive ered it to Moscow. On February 10, he presented Vladimir Environmental Evaluation “Water Sampling of the Subgla- Putin, Prime Minister of the Russian Federation, with a cial Lake Vostok” submitted to the Committee for Envi- small glass canister containing the first sample of the pre- ronmental Protection (CEP), and considered by the XXV historic water, a yellowish liquid with the inscription “Lake Antarctic Treaty Consultative Meeting (ATCM), in Warsaw, Vostok, aged more than 1 million years” (Figure 7). Poland, from 10–20 September, 2002[11]. According to the proposal submitted for evaluation, a liquid such as silicon oil would be delivered to the bottom of the borehole using a special device[7]. It was anticipated that, being heavier than the drilling fluid and lighter than the water, this hydropho- bic liquid would create a 100 m-thick “buffer-layer” of ecologically friendly fluid at the bottom of the hole. In fact, Lake Vostok was accessed without this “buffer-layer”, using a mixture of kerosene and Freon 141b. Kerosene is a mate- rial that poses a significant risk to the environment[12], and the concentration of aromatics in kerosene-like turbine fuel is 20%–25%. Aromatics are the most hazardous hydrocar- bons, and in aquatic environments concentrations of aro- -3 matics greater than 1 mg·m can be toxic to microorgan-

isms. Figure 7 Russia’s Natural Resources Minister, Yuri Trutnev, When the subglacial water first entered the borehole, it presented Prime Minister Putin with a canister containing the first contacted and mixed with the toxic drilling fluid. The sub- sample of water from Lake Vostok (http://www.1tv.ru/news/so- glacial water was almost certainly contaminated by the cial/198799). drilling fluid, and it is likely that it will be of no use for the investigation and identification of new forms of life within 4 Discussion and plans for the future it. This concern is supported by microbiological studies of frozen subglacial water recovered from the NGRIP bore- Researchers predicted that the water would rise in the hole in Greenland in July 2004[13], and from the EPICA near-bottom part of the borehole, up to 30–40 m from the borehole at Base Kohnen, in January 2007[14]. The subgla- water table. In fact, because of the volume of fluid that cial water samples that had contacted drilling fluid similar filled the empty space inside the casing and effused to the Vostok drilling fluid were totally contaminated. through the mouth of the borehole, the water rose from the There is good reason to believe that the real interface lake to a height of about 600 m. The pressure difference between the ice sheet and the subglacial water lies a few between the hydrostatic pressure of the drilling fluid and meters below the bottom of the hole, and that lake water the lake pressure had been calculated incorrectly, and the rose into the hole through intergranular cracks formed sec- pressure in Lake Vostok was much higher than expected. ondary to the large pressure difference between the lake and This will need to be taken into consideration for future ex- the fluid in the borehole. This phenomenon is widely ploration. known in geology and mining as fracturing, and it occurred The next stage of Lake Vostok sampling is planned for in Greenland in 2004, when subglacial water rose into the — the 2012 2013 Antarctic summer season, and will be hole although the ice sheet bed was about 6 m beyond the conducted after confirmation that freezing in the hole has bottom of the borehole[10]. During the Antarctic summer finished. Coring of the frozen lake ice will be carried out season of 2006—2007, in a deep borehole at the Dome Fuji with a KEMS-135 electromechanical drill. It is likely that it Station, subglacial water began to leak into the borehole a will only be possible to re-drill the upper 10–15 m of the few meters above the ice sheet bed[15]. frozen water because the main hole is inclined from the Despite the difficulties and challenges, reaching the vertical by several degrees, and the re-drilled hole will de- surface of Lake Vostok, the crown jewel of Antarctic lakes, viate rapidly from the previous direction. This occurred in came after more than two decades of drilling, and was a the North Greenland Ice Core Project (NGRIP) borehole in major achievement avidly anticipated by scientists around 2003–2004. Subglacial water was reached at a depth of the world. Although the samples collected were likely con- 3 085 m, and the water replaced the drilling fluid and rose [10] taminated by the drilling fluid, contamination of the lake was to a height of 43 m . The NGRIP borehole had a slight avoided as the subglacial water entered into the borehole and inclination from the vertical, and during re-drilling the drill froze. For the future exploration of Lake Vostok it is essential moved away from the axis of the main hole, and the pro- that researchers focus on developing new methods and pro- portion of pure ice core increased steadily with depth. The tocols to minimize the risk of contamination. 180 TALALAY Pavel. Adv Polar Sci September(2012) Vol. 23 No. 3

References 8 Vasiliev N I, Talalay P G. Twenty years of drilling the deepest hole in ice. Scientific Drilling, 2011, 11: 41-45.

1 Ueda H T, Talalay P G. Fifty years of Soviet and Russian drilling activity 9 Lukin V V, Masolov V N, Mironov A V, et al. Rezultaty geophizicheskikh in Polar and Non-Polar ice. A chronological history. ERDC/CRREL issledovanyi podlednikovogo ozera Vostok (Antarktida) v 1995-1999 gg. TR-07-20, 2007: 1-130. (Results of geophysical investigations of subglacial Lake Vostok (Antarc- 2 Kudryashov B B, Vasiliev N I, Talalay P G. KEMS-112 Electromechanical tica) in 1995–1999). Problemy Arktiki i Antarktiki (Problems of Arctic ice core drill. Mem Natl Inst Polar Res, 1994, 49(Special Issue): 138-152. and Antarctica), 2000, 72: 237-248 (Text in Russian).

3 Kudryashov B B, Vasiliev N I, Vostretsov R N, et al. Deep ice coring at 10 Talalay P G. Pervie itogi bureniya samoi glubokoi skvazhiny vo l’dakh Vostok Station (East Antarctica) by an electromechanical drill. Mem Natl Grenlandii (The first results of drilling of the deepest hole in Greenland Inst Polar Res, 2002, 56(Special Issue): 91-102. ice sheet). Priroda (Nature). 2005, 11: 32-39 (Text in Russian).

4 Vasiliev N I, Talalay P G, Bobin N E, et al. Deep drilling at Vostok Station, 11 Water sampling of the subglacial Lake Vostok. Draft Comprehensive En- Antarctica: history and recent events. Annal Glaciol, 2007, 47(1): 10-23. vironmental Evaluation. XXV ATCM, Working Paper WP-019, Agenda 5 Kapitsa A P, Ridley J K, de Robin Q G, et al. A large deep freshwater lake Item: CEP 4c: 1-45.

beneath the ice of central East Antarctica. Nature, 1996, 381(5684): 12 Talalay P G, Gundestrup N S. Нole fluids for deep ice core drilling. Mem 684-686. Natl Inst Polar Res, 2002, 56(Specical Issue): 148-170.

6 Popov S V, Masolov V N, Lukin V V. OzeroVostok, Vostochnaya Antarc- 13 Bulat S, Alekhina I, Petit J R, et al. Bacteria and archaea under Greenland tida: moschnost’ lednika, glubina ozera, podlyednyi i korennoi relyef ice sheet: NGRIP ‘red’ ice issue. Geophysical Research Abstracts, 2005, (Lake Vostok, East Antarctica: thickness of ice, depth of the lake, subgla- 7.

cial and bedrock topography). Sneg i Lyed (Snow and Ice), 2011, 1 (113): 14 Wilhelms F. Sub-glacial penetration from an ice driller’s and a biologist’s 25-35 (Text in Russian). perspective. Geophysical Research Abstracts, 2007, 9, 09619.

7 Verkulich S R, Kudryashov B B, Barkov N I, et al. Proposal for penetra- 15 Motoyama H. The second deep ice coring project at Dome Fuji, Antarc- tion and exploration of sub-glacial Lake Vostok, Antarctica. Mem Natl tica. Scientific Drilling, 2007, 5: 41-43. Inst Polar Res, 2002, 56(Special Issue): 245-252.

· Trend · Advances in Polar Science doi: 10.3724/SP.J.1085.2012.00181 September 2012 Vol. 23 No. 3: 181-186

Development of the geodetic coordinate system in Antarc- tica 1,2* 1,2 ZHANG Shengkai & E Dongchen

1 Chinese Antarctic Center of Surveying and Mapping, Wuhan University, Wuhan 430079, China; 2 Key Laboratory of Polar Surveying and Mapping, SBSM, Wuhan 430079, China

Received 20 July 2012；accepted 30 August 2012

Abstract Defining a universal geodetic coordinate system is one of the fundamental challenges of geodesy. We present a review of the basic general coordinate systems — the space rectangular coordinate system, the geodetic coordinate system, the topocentric coordinate system, and the plane coordinate system. We then look at the World Geodetic System WGS72 and WGS84 and the In- ternational Terrestrial Reference Frames ITRF2000 and ITRF2005, which were introduced when space technology became avail- able. The history of international geodetic coordinate systems in the Antarctic region is briefly reviewed and the development of the geodetic coordinate systems in the Chinese Great Wall Station and Zhongshan Station in Antarctica is outlined. Finally, the issue of coordinate system transformation is discussed. Keywords Antarctic, coordinate system, ITRF, GPS

Citation: Zhang S K, E D C. Development of the geodetic coordinate system in Antarctica. Adv Polar Sci, 2012, 23:181-186, doi: 10.3724/SP.J.1085.2012.00181

ference system, but the relationship between the datum and 0 Introduction* the coordinate reference system is very close and in many cases there is no clear distinction between the two. The ex- To accurately describe a location in space, a suitable coor- tent and connotation of the coordinate reference system is dinate reference system and coordinate system have to be wider than that of the datum. Although the definition of the defined. A coordinate system is a system that uses one or coordinate reference system is very clear and strict, it is more numbers, or coordinates, to uniquely determine the [1] abstract and difficult to use. The coordinate reference sys- position of a point or a geometric element . The main task tem needs to be applied through a concrete form before it of geodesy is to measure and map the surface of the earth. can be widely used. In practice, the coordinate reference To denote, describe, and analyze the results of the mea- system is constructed through a reference frame, which is a surements, a geodetic coordinate system has to be defined. group of points under a corresponding coordinate reference There are two types of geodetic coordinate systems: The system. The International Terrestrial Reference System earth-centered coordinate system and the local coordinate [2] (ITRS) is the most accurate and stable earth-centered coor- system . dinate system and is constructed through the International In practice, a coordinate system alone cannot deter- Terrestrial Reference Frame (ITRF). mine the location of a point: The coordinate system has to At present, the earth-centered coordinate system is be used in conjunction with a predetermined datum to form widely used all over the world. The geodetic coordinate a coordinate reference system. The location of the point can system in China developed from the ellipse-centered coor- then be defined by this reference system. A geodetic datum dinate system to the earth-centered coordinate system. The is a reference from which measurements are made. Strictly first Chinese geodetic coordinate system in the 1950s was speaking, the datum is not equivalent to the coordinate re- the Beijing Geodetic Coordinate System 1954 (BJS54), which was an extension of the Pulkovo Coordinate System 1942 of the former Soviet Union. In the 1980s, the BJS54 * Corresponding author (email: [email protected])

journal.polar.gov.cn 182 ZHANG Shengkai, et al. Adv Polar Sci September(2012) Vol. 23 No. 3 was replaced by the Xi’an Geodetic Coordinate System along the normal of the reference ellipsoid that passes 1980 and the new BJS54. On 1 July, 2008, the China Geo- through point P and points to the zenith. The N axis is per- detic Coordinate System 2000 (CGCS2000) was adopted as pendicular to the U axis and points to the semi-minor axis. the new national geodetic coordinate system to replace the The E axis is perpendicular to the U and N axes, and com- old systems, and it is still in use today. CGCS2000 is geo- pletes the left-handed coordinate system. centric, the center of mass being defined for the whole earth including the oceans and atmosphere[3-4]. The Antarctic geodetic coordinate system was devel- oped through a similar course. In the second half of the 20th century, some countries established their own coordi- nate systems in different regions of Antarctica. With the development of geodetic techniques, the Antarctic Coordi- nate System, a geocentric system that refers to the Interna- tional Terrestrial Reference Frame (ITRF), was established. 1 General coordinate systems 1.1 The Cartesian coordinate system

The Cartesian coordinate system, also named the space Figure 1 Definition of the geodetic system. rectangular coordinate system, is a system in which the location of a point is given by coordinates that represent its 1.4 The plane coordinate system distances from perpendicular lines that intersect at a point called the origin. A Cartesian coordinate system in a The plane coordinate system is established by the projec- three-dimensional (3D) space has three perpendicular axes, tion of the geodetic coordinate system; it is also called the the X axis, Y axis, and Z axis. If the origin, orientations of grid coordinate system. The projection is a mapping func- the three axes, and scale are determined, the space rectan- tion between the spherical coordinates and the plane coor- gular coordinate system in the 3D space is defined. In ap- dinates and can be described as follows: plications of surveying and mapping, the origin is usually ⎧ x= f1 () B, L located at the center of the earth, the Z axis is identical to ⎨ the reference pole and parallel to the earth’s rotation axis, ⎩y =f2 () BL, the X axis lies on the reference meridian, and the Y axis Where x and y are the coordinates of the plane coordinate completes the right-handed coordinate system. system, B is the geodetic latitude, L is the geodetic longi- 1.2 The geodetic system tude, and f1 and f2 are the mapping functions. The Trans- verse Mercator Projection and Gauss Projection are widely The geodetic system is established based on the geodetic used in surveying and mapping because they retain shape datum, also called the ellipsoidal coordinate system. The similarity after the projection. geodetic datum is a set of parameters that are used to define the reference ellipsoid of the Earth. The parameters include 2 The international terrestrial reference sys- the size and shape of the ellipsoid, the orientation of the tems and reference frames in Antarctica minor semi-axis of the ellipsoid, and the locations of the center of the ellipsoid and the prime meridian. The geodetic 2.1 The World Geodetic System 1972 (WGS72) coordinates are described as the geodetic longitude (L), geodetic latitude (B), and geodetic height or ellipsoidal With the development of space technology the World Geo- height (H). The geodetic longitude is the angle between the detic System was established by the United States Depart- prime meridian and the meridian that passes through the ment of Defense as a geocentric coordinate system that point. The geodetic latitude is determined by the angle be- answered the needs of global mapping. It has a series of tween the normal of the spheroid and the plane of the versions including WGS60, WGS72, and WGS84. The ori- equator. The geodetic height is the distance from the point gin of the WGS72 is located at the center of the earth, the Z to the reference ellipsoid along the normal (Figure 1). axis is identical to the Conventional Terrestrial Pole (CTP), the X axis passes through the prime meridian, and the Y 1.3 The topocentric coordinate system axis completes the right-handed coordinate system. The origin of the topocentric coordinate system is located at The geodetic parameters of the WGS72 are: the observation site. It has two forms: the topocentric rec- Semimajor axis of the ellipsoid: a = 6 378 135 m tangular coordinate system and the topocentric polar coor- Flattening of the ellipsoid: f = 1/298.26 dinate system. It is usually described as point P (N, E, U). Earth’s gravitational constant: × 14 3· -2 The origin is located at the observation site P; the U axis is GM = 3.986 008 10 m s Development of the geodetic coordinate system in Antarctica 183

Angular velocity of the earth: The ellipsoidal parameters of WGS84 are as follows: ω＝7.292 l15 147×10-5 rad·s-1 Semimajor axis of the ellipsoid: a = 6 378 137 m Flattening of the ellipsoid: f = 1/298.257 223 563 2.2 The World Geodetic System 1984 (WGS84) Earth’s gravitational constant: × 14 3· -2 The World Geodetic System 1984 (WGS84) is a reference GM = 3.986 004 418 10 m s system composed of a global geocentric reference frame, a Angular velocity of the earth: ω＝ × -5 · -1 series of models, and a relevant geoid. WGS84 was devel- 7.292 l15 10 rad s oped by the National Imagery and Mapping Agency in the 2.3 ITRF2000 and ITRF2005 middle of the 1980s, and replaced WGS72 in 1987. WGS84 is a conventional terrestrial reference system and right- The International Terrestrial Reference Frame (ITRF), a handed coordinate frame; it is defined as follows (Figure 2): realization of the International Terrestrial Reference System (1) The origin is located in the center of mass of the (ITRS) includes the positions and velocities for a set of Earth. global tracking sites. The coordinates and velocities of (2) The Z axis is identical to the reference pole defined these sites are derived from space geodetic techniques such by the International Earth Rotation Service (IERS) and is as Very Long Baseline Interferometry (VLBI), Lunar Laser associated with the conventional pole of the Bureau Inter- Ranging (LLR), Satellite Laser Ranging (SLR), the Doppler national de I’Heure (BIH) in the 1 984.0 epoch. Orbitography and Radio positioning Integrated by Satellite (3) The X axis lies in the IERS reference meridian (DORIS), and GPS. ITRF is established and maintained by (IRM). the IERS. Since 1988, IERS has published ITRF88, ITRF89, (4) The Y axis completes the right-handed Earth-centered ITRF90, ITRF91, ITRF92, ITRF93, ITRF94, ITRF96, and Earth-fixed orthogonal coordinate system. ITRF97, ITRF2000 and ITRF2005. ITRF2000 and ITRF2005 have been widely used over the last ten years. ITRF2000 is defined as follows[5]. (1) Origin: The ITRF2000 origin is defined by the earth’s center of mass sensed by Satellite Laser Ranging (SLR). (2) Scale: The ITRF2000 scale and scale rate are de- fined by a combination of Very Long Baseline Interferome- try (VLBI) and Satellite Laser Ranging (SLR) estimates. (3) Orientation: The ITRF orientation and its drift are defined by alignment with historical earth orientation measurements and the condition of no net drift with respect to the plate motion model NNR-NUVEL1A. ITRF2005 is the updated version of ITRF2000; the

stations used for the TRF computation are shown in Figure 3. Figure 2 Definition of WGS84. ITRF2005 is defined as follows[6-7].

Figure 3 The global geodetic stations map of ITRF2005. 184 ZHANG Shengkai, et al. Adv Polar Sci September(2012) Vol. 23 No. 3

(1) Origin: The ITRF2005 origin is defined in such a 1984/1985 austral summer and set up Great Wall Station in way that there are null translation parameters at epoch the Fildes Peninsula, King George Island, West Antarctica. 2 000.0 and null translation rates between the ITRF2005 Surveying was carried out primarily to support the and the ILRS SLR time series. establishment of Great Wall Station[13]. The Doppler satel- (2) Scale: The ITRF2005 scale is defined in such a lite positioning technique was used to establish a geo- way that there is a null scale factor at epoch 2 000.0 and a detic coordinate system at Great Wall Station and provide null scale rate between the ITRF2005 and the IVS VLBI the geocentric coordinates in WGS72. The coordinates of time series. Great Wall Station were established as: X＝1 536 848.80 ±

(3) Orientation: The ITRF2005 orientation is defined 1.63 m, Y＝−2 554 169.62 ± 0.86 m, Z＝−5 619 835.53 ± in such a way that there are null rotation parameters at ep- 0.53 m. The mean square position error of this station was och 2 000.0 and null rotation rates between the ITRF2005 within ±1.9 m. and ITRF2000. A local height system was established at Great Wall Station. The datum was the mean sea level determined by 3 The geodetic coordinate system in Antarctica direct reading of a tide staff during a period of a little over one month. Several bench marks were laid; these bench 3.1 International geodetic coordinate systems in marks were connected by geometric leveling and served as Antarctica height control points for various construction surveys and topographic leveling. Gravity connection observations were The coordinate systems in Antarctica were established by made along the route of the Ushuaia–Great Wall Sta- different countries and were locally based rather than hav- tion–Punta Arenas by using relative gravimeters ZF-I and ing one coordinate system for the whole continent. Because ZF-II on the voyage from Tierra del Fuego in South Amer- several countries carried out expeditions in the same area, ica to King George Island and back. The gravity value of one region could have different coordinate systems. These Great Wall Station was 982 208.83 mgal. An azimuth de- coordinate systems were based on arbitrary reference ellip- termination from the astronomic station to an azimuth sta- [8-9] soids according to the needs of each expedition . There- tion was made by two methods: gyro-bearing and astro- fore, in the gazetteer and map database of the Scientific nomic observation. The gyro systems JT15 and WILD GK1 Committee on Antarctic Research (SCAR), some features were used for gyro-hearing. The plane coordinates for the are defined by different coordinates. Antarctic geoscience topographic mapping were obtained by converting the geo- scientists needed to establish a united geodetic coordinate centric coordinates of the Doppler station by using the system for the whole continent. Gauss Kruger projection. The distance and azimuth of the In the 1970s, the Antarctic coordinate systems were geodetic route of the communication between Beijing and mainly established by using satellite Doppler techniques. In Great Wall Station was calculated. After two years of con- 1976, SCAR tried to unify the Antarctic coordinate systems, tinuous measurement, the geodetic reference system was but due to logistic limitations, the plan was not successful. established at Great Wall Station, including a geodetic co- In the late 1980s, with the development of GPS, the Antarc- ordinate system, a height system and a gravity system[14-15]. tic coordinate systems were unified into the global refer- In 1995, Great Wall Station was involved in the ence frame and the WGS84 was adopted universally. In SCAR Epoch GPS Campaigns and the WGS84 coordinate 1990, the GPS technique was first applied in Antarctica system was applied to the surveying and mapping at Great during the SCAR90 Program. In 1991, the SCAR91 Pro- Wall Station. In 2009, the GPS site at Great Wall Station gram continued the GPS Campaign. In 1994, the Geo- was updated to a continuous GPS site. science Standing Scientific Group (GSSG) of SCAR initi- ated the SCAR Epoch GPS Campaigns. Due to the particu- 3.3 The coordinate system in Zhongshan Station lar circumstances of Antarctica and because of logistical During the 1988/1989 austral summer, China carried out the needs, the observation period of the GPS Campaigns had to first expedition in eastern Antarctica and established be scheduled for the Austral summer season. It was decided Zhongshan Station in the Larsemann Hills. The coordinate to define a core observation period of three weeks between system of Zhongshan Station was determined by satellite January 20 and February 10 every year. The GPS Cam- Doppler technique and WGS72 was adopted. The coordi- paign has been ongoing since 1994 with more than 30 sta- nates of the geodetic origin of Zhongshan Station were tions participating in the campaign. So far, 11 Antarctic measured as follows: (1) the location of the geodetic origin GPS stations have been established as IGS permanent sta- was determined by satellite Doppler technique; (2) the co- tions and have made contributions to the ITRF series: ordinates of the geodetic origin were calculated using a PALM, OHI2, OHI3, ROTH, VESL, SYOG, MAW1, DAV1, [10-12] traverse survey. The coordinates of the geodetic origin of CAS1, DUM1 and MCM4 . Zhongshan Station are as follows: B＝69°22'28.345'', L＝ 3.2 The coordinate system in Great Wall Station 76°22'22.434''. The plane coordinates for the topographic mapping were obtained by the Gauss Kruger projection. China carried out its first Antarctic expedition during the The height system was established from tide gauge meas- Development of the geodetic coordinate system in Antarctica 185 urements and the heights of the control points were ob- two sites within the ITRF frame were obtained. The geo- tained by leveling surveying[16]. After four years of con- detic control networks of the two stations were measured tinuous measurements beginning in 1988, the geodetic con- again using GPS, which resulted in an improvement in the trol network in the Larsemann Hills was completed. In accuracies of the control points to cm level; the multi-scale 1997, Zhongshan Station took part in the SCAR Epoch GPS maps were updated accordingly. Campaigns and WGS84 was applied in the surveying and mapping[17]. 5 Conclusions and discussions 4 The coordinate transformation With the development of space geodesy, GPS stations, ab- solute gravity stations, and tide gauges were established in Various transformations between the different coordinate both Great Wall and Zhongshan stations. The Chinese Ant- systems are useful in geodesy and other fields. The Carte- arctic geodetic system changed from a 2D coordinate sys- sian coordinate system (X, Y, Z) can be transformed into the tem to a 3D coordinate system and from a topocentric coor- geodetic system (B, L, H) or into the topocentric coordinate dinate system to a geocentric coordinate system. In 2009, system (N, E, U); the geodetic system (B, L) can be trans- the third Chinese Antarctic station Kunlun Station was set formed into the plane coordinate system (x, y), and vice up at Dome A, the summit of the Antarctic ice sheet and a versa[1,18-19]. GPS site was established there. Kunlun Station is the first The different reference systems can be transformed Chinese Antarctic inland ice sheet station, thus extending using the Seven Parameters method. There are two common the scope of Chinese Antarctic expeditions from coastal models, the Bursa model and the Molodensky model. The 7 areas to the inland ice sheet. Chinese geodesists are plan- parameters include 3 rotation parameters, 3 translation pa- ning to unify the geodetic coordinate systems of Great Wall, rameters and 1 scale parameter. Theoretically, the transfor- Zhongshan, and Kunlun stations, and establish a geodetic mation results of the Bursa and Molodensky models are the link between the Chinese Antarctic coordinate systems and same. In fact, there is a small difference in the transforma- the ITRF. The main tasks of the Chinese Antarctic geode- tion results between the two models. The Bursa model is sists is to maintain the stability and continuity of the Chi- usually used in global datum transformations or in trans- nese Antarctic geodetic coordinate system while contribut- formations of large areas. ing to scientific advancement in the field including the new The different ITRF frames can also be transformed. version of ITRF that IERS will be publishing in the near The IERS published the transformation parameters between future. ITRF2005 and ITRF2000, between ITRF2000 and former ITRF versions, and between ITRF and WGS84. After the 7 Acknowledgments This study was supported by the National Natural Science parameter transformation, the difference between WGS84 Foundation of China (Grant nos. 41176173, 41176172), the Chinese Arctic and (G730) and ITRF92 is within 10 cm, WGS84 (1150) is Antarctic Administration, SOA (Grant no. CHINARE2012-02-02), and the identical to ITRF2000 within 1 cm. If the measurement National Administration of Surveying, Mapping and Geoinformation of China adopts broadcast ephemeris, the results belong to WGS84, (Grant no. 1469990324229), and the Data-sharing Platform of Polar Science （ http://www.chinare.org.cn ） maintained by Polar Research Institute of if the measurement adopts precise ephemeris, the results China(PRIC) and Chinese National Arctic & Antarctic Data Center belong to ITRF. 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