Antarctica

Antarctica

Sea Slush

Description of Niche

Location

Sea slush is located on the southernmost continent on the globe, Antarctica, which covers the South Pole and in the surrounding hydro-areas like the Ross Sea. Each type of ice reflects the age and different forms as well as thickness of ice at different stages of development. Sea slush refers to recently formed ice and characterized by snow, which is saturated and mixed with water on land or ice surfaces that grow to no more than 10cm thick. (1)

Physical Conditions

In general, Antarctica is the coldest, driest, and windiest continent on the planet and has the highest average elevation of all the continents as well. More specifically, Antarctica is the coldest place on earth with an average temperature of -80 to -90 degrees Celsius in the winter and 5 to 15 degrees Celsius in the summer. There is also little precipitation making Antarctica technically the largest desert in the world. On average, the interior of the continent only receives 50mm (2in) and near the coast only about 200mm (8in). However unlike normal deserts, the precipitation does not evaporate. Instead it builds up as snow or ice over hundreds and thousands of years forming the thick ice sheets seen today. (2)

Affect of Adjacent Communities

Although Antarctica may seem like a harsh environment, many flora and fauna live on the hostile continent mostly around the costal areas. Antarctica is home many different types of flora, which include two species of flowering plants, three hundred and fifty species of mosses and hundreds of species of algae. Also, several species of fauna live here, mostly inhabiting the neighboring marine environment such as emperor penguins and krill. (3)

Changing Conditions

Due to the increasing climate change due to human effects such as global warming, Antarctica is sometimes used as a “global warming barometer.” Because of the increasing temperatures, several types of mosses and lichens are able to grow further and further south as increasing periods of thaw occur. (3)

Inhabitants

Microbes

Colwellia polaris, discovered by the LExEn (Life in Extreme Environment) group are gram negative, psychrotolerant, aerobic curved rods, 0.6-0.9 x 0.9-4 m. Cell growth occurs from 4-26C and pH of 5.0-10.00 while optimum growth occurs around 20C. (4). These microorganisms are able to survive and grow at these extreme temperatures because they have thermally adapted to their environment by adopting a variety of strategies such as cold shock proteins as well as structural modifications that allow membrane fluidity to continue in such cold temperatures. In other words, Colwellia polaris are able to deal with the exponential decrease in chemical reaction rates and the increase in membrane rigidity because of their proteins and metabolic enzymes are able to function in such cold environments. See interaction with environment and metabolism.

Other Organisms

Antarctic organisms do not live directly in sea slush however many are present in the surrounding area/continent – see adjacent communities.

Environmental Interaction

Colwellia polaris must be able to stop ice from forming around itself which would render it unable to function in its icy slush environment. In order to combat ice buildup, these organisms produce an extracellular substance called an ice binding protein (IBP) which has a high affinity for ice thus inhibiting it from collecting on the organism itself. Ice inoculated with Colwellia polaris show irregular ice growth and pitting on the edges of the ice while uninoculated ice shows no signs of these irregularities. Another related defense instrument is their ice recrystalization inhibition (RI) activity which prevents the formation of larger ice crystals. Ice culture mediums of Colwellia polaris and bovine serum albumin (BSA) were flash frozen and allowed to recrystalize. Due to the RI activity the medium exposed to Colwellia polaris showed smaller, less dense ice crystals. These two extracellular mechanisms allow Colwellia polaris to maintain a fluid environment thus prevent freezing injury to the cell membrane. (5)

Metabolic Adaptation

One specific example is the thermal adaptation of the 71-kDa protein M1 aminopeptidase which is renamed cold-active aminopeptidase (ColAP) for the cold adapted enzyme. This protein has an optimum pH level of 6-8.5 and temperature of 19C. ColAP’s main function is to assist in proteolytic cleavage, which is important in bacterial metabolism. Proteolytic activity aids these organisms in acquiring dissolved organic nutrients such as nitrogen-rich organic compounds. (6) In general, ColAP is able to maintain “normal” function at cold temperatures due to fewer proline residues, fewer ion pairs and a lower hydrophobic residue content, which contribute to its flexibility, which as mentioned before is essential for survival in cold icy environments. The low number of proline residues affect the backbone structure of the protein, which lead to an increase in local motility of the chain. The fewer number of ion pairs increase flexibility by decreasing the number of stabilizing bonds in the protein and lastly, the lower hydrophobic residues indicate an increase in charged residues which increase the hydrosolubilty of the organism and allow a greater accessibility at the surface of the protein. Furthermore, due to these adaptive abnormalities, ColAP is very sensitive to heat thus exhibiting a decreasing half-life with increasing temperature. For example, at 0C, the enzyme half-life was measured to be between 18 and 45 hours while at 50C the half-life was measured to be only 5 minutes. (7)

Lake Vostok

Used with kind permission from Michael Studinger

Description of Niche

Lake Vostok lies beneath the Russian Research Station Vostok for which it is named. This subglacial lake has been studied since the late 1960’s yet no one has actually sampled the water within it directly. It is the Largest of the approximately 150+ subglacial lakes (Inman) comparable in size to Lake Ontario with approximately 5000 km3 of water (Studinger; Célin, et al.). It is thought that Lake Vostok has been continuously isolated from the earth’s atmosphere for the past 15-30 million years, also rendering it cut off from new carbon sources as well as light (Célin, et al) making it a very unique environment. The ice sheath moves across the lake at a speed of ~3m per year in an easterly direction.(Studinger)

Location

Lake Vostok is located in East Antarctica under approximately 4km of ice. The ice sheath varies in thickness from the northern to the southern region. (Studinger)

Physical Conditions

Lake Vostok, like many other subglacial lakes holds many extreme physical conditions, ranging from high pressure ~350 atm, low temperatures (between -3 and 8°), and permanent darkness. (Steigert) The high pressure exuded from the ice above Lake Vostok keeps it liquid, since water freezes at a lower temperature when under high pressure.(Karl, et al. 1999)

Affect of Adjacent Communities

Lake Vostok was thought to have been not only isolated from the 20th century atmosphere but also from any other surrounding environments. This thinking has now changed as recent imaging studies have shown that these subglacial lakes are potentially connected through a network of rivers. This makes sterile drilling all the more important since if one lake gets contaminated the chances of other subglacial lakes becoming contaminated increases, especially those downstream from the test site. (Studinger) Also, the actual lake itself is in constant balance with the accretion ice above it. The ice melts in the northern part of Lake Vostok possibly delivering nutrients and other microorganisms into the lake. (Studinger) As the ice in the northern region of Lake Vostok melts it sinks to the lake floor, where it is warmed via geothermal activity and/or pressure. As the waters temperature increases it also becomes less dense causing it to rise to the surface in the south. Once the water has resurfaced in the south it freezes and becomes part of the accreted ice. This water movement is important in considering the ice core samples. As the water rises to the surface it can bring some of the sediment and the organisms which reside on the lake floor or event throughout the varying depths with it causing it to become trapped in the ice. The coring at Lake Vostok has penetrated into the accretion zone in the southern portion of the lake. (The accretion zone is the lowest 210m, and the core sample was taken from 150m above the lake)(Steigert) As the ice moves across the sediment a small amount of the sediment becomes entrapped. According to Christner et al., this provides a mechanism by which organism can get transferred into Lake Vostok.

Changing Conditions

Dependent on the depth of the water the physical conditions of Lake Vostok can differ. Lake Vostok has been previously thought to be an area without any seismic activity – this has now changed. A low amount of seismic activity has been noted and this leads to the potential of thermal energy as well as a possible nutrient supply. Furthermore, microseismic activity has been recorded nearby which might drive convection in the Lake. (Studinger)

Inhabitants

Currently there is no definite knowledge on the type of organisms which reside in Lake Vostok. There are many stipulations on the type of organisms, if any, that might be found within. They are most likely extremophiles, tolerant of extremely low temperatures (<0°C). Furthermore they would probably have an adaptation to high pressure. In recent years continued coring has indeed brought evidence of such microbes. According to Karl, et al. the organisms found within one of the core samples were found to be oligotrophic. Oligotrophic organisms live with minimal nutrients, low biomass, and also a low energy flux.(Karl) In one experiment core ice from section 3593 was melted and samples of the melt ice were spread on agar plates, enriched with various nutrients and incubated at 25°C. Four colonies were grew and 16s rDNA comparison was performed. This analysis showed that the microbes, which were produced, have similar 16s sequences. Their nearest phylogenetic neighbors are Brachybacterium conglomeratum (found in cheese), ''Sphingomonas'' sp. (found in Guliya ice core), Paenibacillus amylolyticus (found in soil), Methylobacterium sp. (found as biofilm on cooling fan), and on unidentified organism.(Christner) Another study found fourteen different isolates which had been grown on agar. Cruptococcus sp. And Rhodoturula sp.(both in the yeast family) and the remaining twelve bacteria included Subtercola sp., sphingomaonas sp. leaving nine remaining to be identified.(Raymond)

Microbes

Lake Vostok* Evidence suggests the presence of thermophilic chemoautotrophic microorganisms in Lake Vostok. (Célin, et al.) Hydrogenophilus thermoluteolus (Célin, et al.)

• All organisms mentioned for Lake Vostok are ones found in the accretion ice above Lake Vostok.

Environmental Interaction

. It has been thought that some of the organisms which reside in such extreme cold have an ability which allows them to change the physical structure of the ice around them. Also, these conditions warrant a slow metabolism as well as an alternate energy source. Ice binding proteins, which inhibit ice-recrystalization have been isolated out of core samples at Lake Vostok(Raymond, et al.)

Ross Dependency

Ross Sea Iceberg

Description of Niche

Location

The Ross Dependency is located in the South-western part of Antarctica. It is a large area that encompasses most of the Ross Ice Shelf as well as much of the Ross Sea.

Physical Conditions

The average temperature of ice in the Ross Ice Shelf is -2.13’ to -2.16’ C, slightly colder than -2’C, the temperature at which seawater freezes. The Ross Ice Shelf receives 202.5mm of rainfall per year on average. The average temperature of the Ross Sea is -1.9’C, and it is a salt water sea (Diversity).

Changing Conditions

The Ross Dependency region receives the most rain between February and June, an average of 22.5mm/month. Between July and January the amount of rainfall severely decreases to about 12.7mm/month. The average temperature, between -2’C and -10’C, is highest between November and February. From March to October, the average temperature is between -18’C and -26’C (Ward). The Ross Dependency and all of Antarctica experiences 6 months of continuous sunlight and 6 months of continuous darkness each year.

Inhabitants

Microbes

Many types of phytoplankton live in the Ross Dependency area. These include several species of diatoms, haptophytes, dinoflagellates, and cryptophytes (Smith). Some of the diatoms that live there are Corethron coriophyllum, Pseudonitschia, Fragilariopsis, Rhizosolenia, and Thalassiosira. Diatoms like Fragilariopsis and Pseudoitschia are found in extensive blooms near ice edges in the summer months (Smith). Cryptophytes can also be found in large blooms in the Ross Sea. One of the most studied haptophyte that lives in the Ross Dependency is Phaeocystis antarctica. P. antarctica generally live in hollow colonies though solitary cells have been found, as well. Living in colonies helps this bacterium evade predators as single cells are more likely to be ingested. This microorganism, as well as many other bacteria that live in the Ross Dependency, is most prevalent in spring and populations decline drastically in the summer months (Dennett). The tidal zone of the Ross Ice Shelf has a biofilm made of diatoms and cyanobacteria.

Other Organisms

There are no land based vertebrate animals naturally present in the Ross Dependency, or even in Antarctica. Small invertebrate animals inhabit the island. No trees or bushes can survive there, however around 350 species of mosses, lichens and algae live around Antarctica. In addition to the microbes, many types of marine life including larger plankton, krill, fish, seal, penguins, and whales live in the Ross Sea. Phytoplankton are a direct energy source for some of these organisms. Bacteria is the primary food source for microzooplankton. Ice Krill and plankton eat diatoms, and Antarctic toothfish often consume P. Antarctica (Diversity).

Metabolic Adaptations

Scientists have found that Antarctic ice, including the Ross Ice Shelf, contains extensive criss-crossing acidic "veins" that can have pH as low as 0. Microbes who live in these veins are thought to extract their energy from the acid surrounding them (Price). These acidophiles must also protect themselves from too much acid. In order to keep their intracellular pH ideal, some microbes maintain a positive surface membrane charge, have a membrane that is impermeable to protons, or synthesize proteins that remove protons from the cell. Some microbes may also form spores if they can't regulate intracellular acidity well enough (Price). Unlike an activly metabolizing organism, spores do not need to regulate intracellular pH very tightly.

The extremely low temperatures of the South Pole make it very challenging for microbial life to thrive there. Because of these harsh conditions, microbes that live there often have very low metabolic and division rates; some even shut down all unnecessary energy consumption when the temperatures drop. A microbe may have other responses to the cold, including: an increase in production of chaperones and other stress proteins, express starvation genes, or synthesis of "antifreeze proteins" to protect their cytoplasm from freezing (Price). Addtionally, microbes living in the Ross Dependency necessarily have a greater percentage of unsaturated fatty acids in their membranes than do warmer-dwelling microbes in order to retain membrane fluidity (Price).

Environmental Interactions

P. antarctica produces a lot of dimethylsulfide. This is a volatile substance that is necessary for cloud formation. As dimethylsulfide rises into the atmosphere it transforms into aerosols that attract molecules of water, creating clouds (Norris). Phytoplankton in the Ross Dependency produce chlorophyll. The concentration of chlorophyll in a region can be used to estimate the phytoplankton population at the time. Diatoms and haptophytes also synthesize carbon biomass. This organic matter sinks to a depth of 500 meters by the natural sinking of phytoplankton.

Soil

The Calkin Glacier located in one of the McMurdo Dry Valleys

Description of Niche

Antarctica is a continent found almost entirely south of the Antarctic Circle. The climate is harsh: it is the coldest, driest place on earth, with the highest winds, and highest average elevation. Most Antarctic soil is covered with ice from meters to miles thick; only 2% of soil is exposed. (1) Inland deserts constitute most of these bare regions, such as the McMurdo Dry Valleys, which receive little to no precipitation. In the Dry Valleys, the equivalent of only 50mm of rainfall accumulates every year. Temperatures up to a few degrees above freezing, and as low as -89.2° C have been recorded at the South Pole. All of Antarctica receives very little direct sunlight because of the tilt of the earth; in the summer months Antarctica has almost continuous daylight, and in the winter almost continuous darkness.(2)

Location

Exposed soil is mostly found in the interior of Antarctica in the Mcmurdo Dry Valleys. The coordinates of this region are: 77"00'S, 162O52'E (3) Soil is also found in Cryoconites. Cryoconites are water and sediment filled hollows on the surfaces or edges of glaciers. (4)

Physical Conditions

The soil in Antarctica is freezing, arid, low in clay content and organic matter, and high in salinity. There is very little bio-available water. Due to the lack of precipitation, water does not leach cations from the earth, leaving it with an alkaline pH. Since the average elevation is high, the atmospheric pressure is relatively low. (5)

Cryoconites contain sediment and water that periodically freezes and melts. The dark sediment absorbs more light than the white ice and snow, causing it to heat up and melt the surrounding ice. This forms pockets of subsurface liquid water. In the summer, when the top ice melts, the depressions are open to the atmosphere and receive minerals and microorganisms blown by the wind. The sediment in cryoconites is submerged in water, but is chemically unique from glacial runoff and water found in lakes and rivers. (4)

Although not as common as other soil conditions in Antarctica, geothermal activity brings dirt temperature up to 42-60° C, and pH down to 4.5-7.5. Steam vents that produce the heat also add moisture to the earth. They can be found on northwest slope of Mount Melbourne. (6)

Affect of Adjacent Communities

The Mcmurdo Dry Valleys also hold rivers and lakes and are bounded by glaciers and snow pack. Microbes in these areas can interact with those in the dirt. (3) In addition, the dust from the bare land in the McMurdo Valleys is picked up and blown by the wind to rivers, lakes, and glaciers with cryoconites. The soil carries microbes and minerals with it. The microbes caught in cryoconites can be flushed into streams and lakes by glacial melt, as well. These changes in environment promote genetic mixing. (4) One research group suggested that cyanobacteria originate in bodies of water and adapt as they move from water, to mud, to dry, desert soil. They reason that Beacon Valley has a very low cyanobacteria population because it has no lakes or ponds, while in Miers Valley cyanobacteria florish because bodies of water are present there. (7)

Changing Conditions

The Antarctic soil environment changes seasonally. In the McMurdo Dry Valleys during winter, Antarctica is almost continuously dark, the wind can reach speeds of 110 km/h, and the air temperature drops to -60° C. In the summer there is nearly constant daylight, and the temperature oscillates between -35° C and 3° C, depending on cloud cover and wind chill. Most precipitation falls in the summer. When in prolonged direct sunlight, soil and rocks can heat up to 10° C above ambient temperature. (8) Lots of sunlight also brings increased solar radiation, which can damage DNA. The problem is exascerbated by the large hole in the ozone layer over Antarctica, which admits even more UV rays. (9) The environment also varies from place to place. In one study looking at the correlation between the living soil communities and abiotic soil composition, soil chemistry and elevation data were collected. The information showed that the amount of nitrogen found in soil samples decreased as elevation increased. This implied that fewer organisms live at higher altitudes, which are colder and tend to have higher salinity. (8)

Inhabitants

Microbes

Colonies of bacteria have been found growing in the pores of sandstone rock to avoid exposure to the rapidly changing environment. Organisms that live inside rocks this way are called cryptoendoliths. Endolithic communities are thought to comprise the main forms of life in the polar deserts.

In one study, researchers isolated primarily cyanobacteria and microbial lichen, both primary producing, endolithic organisms, in the soil and rocks of the McMurdo Dry Valleys. To catagorize each individual microbe, they examined their small-subunit (SSU) rRNA genes and matched them with the genes of known microorganisms. They discovered three specific cyanobacteria that were most abundant in their samples. The first, comprising 30% of the sample, is most closely related to Plectonema genus, (97% rRNA sequence identity). The second, 31% of the sample, is most closely linked to Blastomonas ursincola, (94% rRNA sequence identity). It is representative of α-Proteobacteria, a phylum of aerobic, anoxygenic, phototrophs. The third, making up 26% of the sample, is a microbe with no very close relatives, but with a distant relative from the Deinococcus genus, (90% nucleotide sequence identity). It can be categorized in its own clade called Thermus-Deinococcus. They found the remaining percentage to be representatives of green nonsulfur bacteria, Cytophagales, Acidobacteria, and Actinobacteria (6% of clones). Acidobacteria are a phylum of acidophilic bacteria. (10) Actinobacteria are gram-postitive bacteria that can decompose strong molecules such as chitin and cellulose. Most are aerobic, but a few are anaerobic. Some Antiobacteria can produce exospores. (11) Cyanobacteria, another phylum also known as blue-green algae, obtain energy through photosynthesis. They are gram-negative, lack flagella, and usually have thick cell walls. (12)

In the same study, the dry soil was also found to contain organisms that have DNA representative of green algae, fungi, and chloroplasts. The isolated fungus is closely related to ascomycete fungus Texosporium sancti-jacobi, while the algae is very similar to Trebouxia jamesii. Each of these species has been identified as a kind of fungi and algae that participates in lichen symbiosis. Because these specific species made up over 70% of the clones produced through PCR for this experiment, they are thought to make up the dominant lichen in the community. Those performing this study mentioned that while they did not uncover all the species in Antarctic soils, they do believe that that have found the main contributors to the energy cycle. (10)

In the McMurdo Dry Valleys, Cryoconites support cyanobacteria, photosynthetic algae, heterotrophic bacteria, tardigrades, rotifers, and other microorganisms. (4)

A few novel species have been isolated and identified around steam vents in Antarctica. The first of these is Brevibacillus levickii. Another is most closely related to Alicyclobacillus pomorum (91% similarity). The genius Alicyclobacillus is a group of Gram-positive, heterotrophic, bacteria that form endospores. Both species are thermophilic, and, thus, capable of living at very high temperatures. (6) Populations of Archaea are extremely small and belong to the Group II low-temperature Crenarchaeotes. (13)

Early research suggested that diversity was extremely low in the desert inland due to severe environmental conditions, but new experimental methods have shown that the microbial biomass in Antarctic soil is between three to four magnitudes higher than previous estimates, and may have considerably higher diversity, though less diversity than what is found in milder climates. (13)

Other Organisms

As noted above, microbial lichen has been discovered in Antarctica. Lichens are a mutually beneficial arrangement of fungi and single-celled algae called a symbiosis. Together they form a larger, multicellular structure. Fungi cling to rocks to form a foundation on which to live, and compete with other fungi for space. The fungi also give protection and supply water and minerals, while the algae provide nutrients made by photosynthesis. (14)

Certain species of nematodes, springtails, and mites also make the soil and rocks of the Antarctic their home. Those mosses and arthropods may only be able to survive inland in the summer if soil moisture is high enough. (13) Nematodes feed on bacteria, but also provide nutrients for bacteria when they die. (15)

Microbial Interaction

Population density is not high in the desert communities, but since nutrients are so scarce, some competition does occur between different bacterial species. Yet, abiotic factors, such a temperature and soil moisture, are more likely to determine community structure than interaction (competition, herbivory, predation) between organisms. (13)

The heterotrophic bacteria eat other microbes, including cyanobacteria. (16)

Metabolic Adaptations

A few microorganisms, including bacteria, protozoa, lichens and algae, have stress-resistant, or dormant phases to help them endure subzero temperatures and an intermittent water supply, but these strategies can slow, or halt, metabolism and reproduction. In dormant phase, bacteria can alter their DNA to make it more resistant to UV damage. This is especially important because the hole in the ozone layer over Antarctica admits large amounts of solar radiation. (13)

Scientists have analyzed enzymes from psychrophilic bacteria and compared them to functionally equivalent enzymes from microbes that live in warmer locations. A few modified proteins include: alcohol dehydrogenase, xylanase, α-amylase, β-lactamase, aspartate, citrate synthase, transcarbamylase, subtilisin, Ca2+–Zn2+ protease, malate dehydrogenase and triose phosphate isomerase. These enzymes have higher activity in the cold (0-30°C) than their mesophilic counterparts, but at warmer temperatures the cold enzymes denature. Cold-adapted enzymes have a more flexible structure than those from thermophiles, or mesophiles. This flexibility is probably due to weaker bonds within subunits, fewer ion interactions, weaker intramolecular bonds, stronger solvent interactions, higher amounts of glycyl residues, and lower numbers of prolyl and arginyl residues. The extreme cold makes normal enzyme activity impossible because with normal-strength bonds the structures become too rigid to function as catalysts. The weaker bonds allow the microbe to overcome this problem. (17)

In periods of frigid cold, most psychrophilic bacteria are in stationary phase (survival phase), rather than growth phase. Photosynthetic activity in Antarctic lichens has been observed at temperatures as low as -17° C (18)

Environmental Interaction

Some cyanobacteria fix nitrogen, though, it is not yet known whether the species found in Antarctica do this. (12)

Little is known about endolithic microbial communities because not much research has been performed. They are thought to take part in the weathering of rocks and the cycling of elements and nutrients. (10)

Lichen attach to the surfaces of rocks and extract minerals from them. (14)

Sea Ice

Underwater Ice Wall McMurdo Sound

Description of Niche

Location

Antarctic sea ice surrounds the southernmost continent year around. Due to the 3.5% salinity of the ocean water, sea ice forms at a lower temperature than freshwater: -1.8 °C (28.8 °F) compared to 0 °C (32 °F) [1]. The amount of sea ice is consantly changing the size of Antarctica throughout the various seasons. The total land mass of Antarctica without ice is 280,000 km² (108,108.6 sq mi). However, at the peak of winter, Antarctica, when combined with sea ice, reaches a total area of 13,720,000 km² (5,297,321.6 sq mi), which is nearly 1.5 times the size of the United States [2]. Sea ice is often confused with icebergs; the other major form of ice surrounding Antarctica. Icebergs are made from either broken-off portions of glaciers or ice shelves. In comparison, icebergs are produced from precipitation and are therefore freshwater, while sea ice is produced from freezing seawater.

Physical Conditions

Temperature

The temperature of the Southern Ocean fluctuates throughout the seasons. In the northerly regions of Antarctica, Signy Island for example, the ocean temperature ranges between -1.8°C in the winter and +1.0°C in the summer [3]. However, in more southerly areas, such as McMurdo Sound, the ocean temperature ranges between -2.0°C and -1.7°C annually [3]. In comparing the total ocean temperature throughout the Antarctic region, the water temperature rarely fluctuates more than 3°C “making this one of the most thermally stable environments on earth” [3]. According to the studies of Lloyd S Peck [3], the ocean temperature in the Antarctic region has been low and stable for at least 10 million years.

Light

The amount of light that reaches sea ice varies depending on the time of year. Due to the high latitude, seasonal light “varies between no direct sunlight... to 24 h of direct sunlight” [3]. Varying amounts of light causes an enormous shift in sea ice formation. During winter, the light source is limited and decreases the air temperature. This contributes to an overall radiative loss, which causes sea ice to form at a rapid rate. The radiative loss is countered in the summer when the radiative value equals or surpasses that of tropical regions. These opposing radiative values contribute to the annual growth and decline of 10-15 million km¬¬2 of sea ice [3]. During the summer, phototropic microorganisms that are able to survive atop of the sea ice are exposed to harsh temperatures, high amounts of light, and an increasing amount of UV radiation. Phototropic microorganisms under the sea ice have a more stable environment, yet only have access to less than 1% of light. In contrast, when the Antarctic is between solar light cycles during the winter months, phototropic microorganisms must utilize their evolutionary traits to survive nearly 5 months without light [4].

Weather

Antarctica is the coldest and windiest place on Earth. The climate that surrounds Antarctica’s sea ice is some of the most unforgiving on Earth, which is only rivaled by Antarctica’s mountainous terrain. In the winter, the lowest recorded temperature is -89.2°C (-128.6°F) and the highest recorded temperature during summer is +15°C (+59°F). On average the summer temperature is -27.5°C (-17.5°F), contrary to -60°C (-76°F) during the winter. Wind also affects the extreme temperatures of Antarctica. The average inland wind speed is 12 mph. However, on the coast where sea ice is formed, the average wind speed is 198 mph. These high winds in combination with low temperatures make Antarctica the driest desert in the world. These desert conditions arise due to the average humidity revolving around 0.03%, which causes the average precipitation to be less than 1” annually [5].

Changing Conditions

Observations of Antarctic conditions have only been recorded for the last 150 years. However, due to limited resources and technology, constant climate monitoring was not possible until the 1950’s [5]. Currently, many bases are located on the continent and are equipped with advanced weather recording devices to observe conditions year-round. In addition, satellite technology has been utilized to survey the environment and weather patterns. Above the Antarctic sea ice conditions are constantly changing. Frequent changes in weather alter the landscape of the sea ice consistently. Throughout the year, with the combination of unpredictable temperature changes and hurricane force winds, temporary sea ice fluctuates by 10-15 million km¬¬2 [3]. However, as previously stated, the ocean’s temperature rarely alters more then 3°C and has done so for more than 10 million years [3].

Inhabitants

Microbes

The Southern Ocean has a very low temperature and a high concentration of salt, yet microbial life is able to thrive in these extreme conditions. Microbes that are able to live within the freezing temperatures are known as psychrophilies. Some microbes that live within the sea ice are also halophilic because they are able to live in extremely salty conditions.

According to Nichols [1]: “The sea ice produces highly variable microenvironments in terms of temperature, salinity, nutrient concentration, and light intensities within the columns, which may be as thick as 2 m. Salinity in sea ice brine can range from near that of freshwater to >15% at the ice-seawater interface. Temperatures can range from 0°C to -35°C. Sea ice is thus one of the coldest habitats on earth for marine life.”

Some psychrophilic bacteria have evolved to contain gas vacuoles; this allows them buoyancy to float at a certain level in order to regulate their position in vertically stratified water columns and adapt to their environment [6]. These gas vacuole-containing bacteria fall into four main classes: alpha, beta, and gamma Proteobacteria and the Flavobacteria-Cytophaga group. The gas vacuoles give sea ice bacteria an energy-maximizing advantage due to the generally higher enrichment in sea ice compared to other bacteria in open and underlying seawater, which allows bacterial cell biovolumes to grow 5 to 10 times larger [7].

Other Organisms

Phytoplankton living in the Southern Ocean are responsible for it being one of the most productive oceans in the world [8]. Phytoplanktons are photosynthetic organisms. During the transition from winter to spring, the recession of Antarctic sea ice promotes massive phytoplankton blooms. Due to their sudden growth, the normal chlorophyll level rises from less than 5 μg chlorophyll a/liter, to an amazing 1,000 μg chlorophyll a/liter, which not only helps produce half of the worlds oxygen supply but also perpetuates one of the largest links in the Southern Ocean’s food chain [4].

Microbe Interaction

Phytoplanktons produce much of the atmosphere’s oxygen by consuming CO2. Two of the essential nutrients of phytoplankton are nitrate and phosphate. During occasionally large phytoplankton blooms, or in areas of large phytoplankton accumulation, surface nitrate and phosphate may be nearly depleted [9]. When the resources are depleted the phytoplankton die off, creating an accumulation of slow-to-degrade dissolved organic matter (DOM), which fuels bacteria production through the winter [10]. Utilization of DOM by bacteria creates the byproducts nitrogen and phosphate, which contributes to the renutrification of the ocean.

Metabolic Adaptation

Both bacteria and phytoplankton are psychrophilic microbes. Due to the low temperature, these organisms have adapted and evolved. In order to grow and function, they did as follows: “reduced enzyme activity; decreased membrane fluidity; altered transport of nutrients and waste products; decreased rates of transcription, translation and cell division; protein cold-denaturation; inappropriate protein folding; and intracellular ice formation” [11].

Freshwater Ice

Where located?

The Antarctic is one of Earth's extreme places. Many different species of microbes and flora are unique to Antarctica, suggesting many years of evolutionary isolation. Due to the extreme conditions faced by the multitude of microorganisms inhabiting the continent, many have evolved remarkable biochemical, physiological and behavioral adaptations, the study of which is leading to the discovery of useful chemicals and genes. These organisms live in an environment that is rapidly changing due to the effects of global warming. Antarctica is a unique natural laboratory for investigating the effects of environmental changes on the structure and function of biological communities and their genetic makeup.

Physical Conditions?

Approximately 61 percent of all fresh water on the Earth is held in the Antarctic ice sheet, an amount equivalent to 70 m of water in the world's oceans. In East Antarctica, the ice sheet rests on a major landmass, but in West Antarctica the bed can extend to more than 2,500 m below sea level. The land would be seabed if the ice sheet were not there.

Temperatures in the Antarctic can be intense and fluctuate from about -85°C in austral winter, while in summer the temperature can warm to about -13°C (mean monthly air temperature in December is -26°C). Microbes, in particular bacteria, have been cultured from samples taken from Antarctic ice cores, and deep cores from the accreted ice above subglacial Lake Vostok and have revealed a high diversity of species that were reported to be metabolically active when warmed to 3°C [1].

Who lives there?

Do the microbes carry out any metabolism that affects their environment?

Edited by [Srdjan Sonjara], students of Rachel Larsen

Current Research

Ongoing research is constantly being done in order to ascertain how psychophillic bacteria are able to function and survive in the cold harsh Antarctic climate. One such adaptation is the presence of antifreeze proteins (AFPs) which allow microbes to live in subzero temperatures. Furthermore, each bacterium may contain different types of AFPs as this group of proteins is very diverse. Only a handful of bacteria are known to have AFPs which include Pseudomonas putida (Sun et al., 1995; Xu et al., 1998; Kawahara et al., 2001), Micrococcus cryophilus, Rhodococcus erythropolis (Duman & Olsen, 1993), Marinomonas protea (Mills, 1999) and a Moraxella species (Yamashita et al., 2002). Scientists hypothesize that the difference between each AFPs are due to the environments the bacterium resides in which in turn shape the evolution of these proteins. As a result, measuring AFP activity of different organisms using the available techniques may not be sufficient. One study takes a look at the differences in AFPs in different Antarctic environments such as freshwater and seawater which range from average freshwater salinity to 240% salinity and then attempts to develop new assays in order to measure AFP activity in each unique organism. One assay developed, called the HTAP assay measures light refraction in the sample. Samples with no AFP activity will appear to be transparent while samples with AFP activity will appear opaque due to the small dense crystals AFP proteins help create. Another assay, the splat assay which uses crossed polarized microscopy, was used to verify positive AFP activity results from the HTAP assay. This was necessary because color pigmentation from other sources, other than the ice itself, may skew the results of the light based HTAP assay. (8)

Célin, et al – genetic comparisons of 16_ RNA of bacterial DNA extracted from Lake Vostok ice cores. Samples were compared from two different depths in two separate laboratories to minimize contamination. This research is being carried out in part to answer the question of potential life on other planets where there are no carbon sources available or other extreme environments. …

Biotech and pharmaceutical companies are becoming increasingly interested in compounds extracted from Antarctic life forms These organisms live in harsh frozen conditions and have developed complex mechanisms to deal with the low temperature, lack of nutrients, and other difficulties of living in such an extreme environment. Companies that develop industrial processes that keep food or medicines fresh while at a low temperature are currently conducting research on unique enzymes found in Antarctic organisms that can aid the process of chilling without killing. As of 2004, 154 patents have been obtained for compounds naturally found in the Antarctic, including one for a glycoprotein found in a bacterium that has been shown to heal wounds and skin and benefit hair and nails (Williams). The problem with this research is that it is difficult to know how much is purely for scientific purposes and how much is for financial gain. Companies looking for novel compounds to turn into drugs for profit may cause environmental damage or exploit the resources found on the greatly undisturbed continent. Fortunately, many Antarctic researchers have expressed this concern and are trying to put regulations in place to prevent abuse of resources (Williams).

Mars with Polar Ice Cap

Researchers continue to discover microbes deeper and deeper within the soil of the Antarctic Dry Valleys. Since Antarctic conditions are so close to the subzero, anaerobic, icy environment of Mars, many believe that these findings give hope of uncovering microbial life on our neighboring planet. (19)

P. Buford Price from the Physics Department, University of California, Berkeley, CA and Todd Sowers from the Department of Geosciences, Pennsylvania State University, University Park, PA. performed studies on the metabolic rates in microbes at very low temperatures. Price and Sowers compared many different substances to determine different metabolic rates of microbial communities. Their findings demonstrated that there is no minimum temperature for metabolism [12]. In fact, Price and Sowers show that microbes in ice have similar metabolic rates to other substances at the same temperature. Therefore, the data confirms that liquid water inside ice is available for metabolism [12].

Antarctica in current Popular science

Here are some links to Articles about Antarctica which have been published in popular science magazines. http://news.nationalgeographic.com/news/2007/12/071227-antarctica-wetland.html - “Antarctica may contain “Oasis of Life”” http://news.nationalgeographic.com/news/2007/05/070516-deep-sea.html - “Bizarre New Deep-Sea Creatures Found Off Antarctica”

http://www.caml.aq/microbes/index.html - This is a Census of Marine Aquatic life.

References

Sea Slush

1) World Meteroplogical Organization Information Site: http://www.dbcp.noaa.gov/seashelp/HtmlIceGlossary.htm#slush 2. National Geographic Data Center - National Satellite, Data, and Information Service. http://www.ngdc.noaa.gov/mgg/image/2minrelief.html (2006) 3) International Polar Foundation Information Site: http://www.sciencepoles.org/index.php?/home/ 4) Zhang D, Yong Y, Xin Y, Hong L, Zhou P, and Zhou Y. Colwellia polaris sp. Nov., a psychrotolerant bacterium isolated from Arctic sea ice. International Journal of Systematic and Evolutionary Microbiology (2008) Vol. 58 p. 1931-1934 6) Huston A, Haeggstrom J, Feller G. Cold Adaptation of Enzymes: Structural, Kinetic, and Microcalorimetic characterizations of an aminopeptidase from the Arctic psychrophile Colwellia and of Human Leuikotriene A4 Hydrolase. Biochemica et Biophysica Acta (2008) June 13. 7) Huston A, Methe B, Deming J. Purification, Characterization, and Sequencing of an Extracellular Cold-Active Aminopetidase Produced by Marine Psychrophile Colwellia Starin 34H. American Society for Microbiology (2004) Vol. 70(2) p. 3321-3328 5) Raymond J, Fritsen C, Shen K. An Ice-binding Protein from an Antarctic Sea Ice Bacterium. FEMS Microbiology Ecology (2007) Vol. 61(2) p. 214-221 8) Gilbert J, Hill P, Dodd C, Laybourn J. Demonstration of Antifreeze Protein Activity in Antarctica Bacteria. Microbiology (2004) Vol. 150 p. 171-180

Lake Voltok

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by [Sabrina Koperski], students of Rachel Larsen

Ross Dependency

Dennett, Mark R., Mathot, Slyvie, Caron, David A., Smith, Walker O. Jr. and Lonsdale, Darcy J. “Abundance and distribution of phototrophic and heterotrophic nano- and microplankton in the southern Ross Sea”. Elsevier Science Ltd. 2001. [1] “Diversity of Ross Sea Fish”. Science Learning Hub. 25 February 2008. [2]

Norris, Katina Bucher. “Dimethylsulfide Emission: Climate Control by Marine Algae?”. ProQuest. November 2003. [3] Price, P. Buford. “Life in Solid Ice”. Cornell University Library. 2 July 2005. p. 1-11. [4]

Smith, Walker O Jr, Ainley, David G., and Cattaneo-Vietti, Riccardo. “Trophic interactions within the Ross Sea continental shelf ecosystem”. Philosophical Transactions of the Royal Society B: Biological Sciences. 6 December 2006. p. 95-106. [5]

Ward, Paul. “Antarctica Climate Data and Climate Graphs McMurdo, Amundsen-Scott (South Pole) and Vostok Stations”. Cool Antarctica. 17 August 2008. [6]

Williams, Nigel. “Chill Wind Over Antarctic Biodiversity”. Current Biology. 9 March 2004. Volume 14, Issue 5. p.R169-R170. [7]

Soil

(1) "Antarctica - The World Factbook". United States Central Intelligence Agency (2007-03-08). Retrieved on 2007-03-14.

(2) "Weather in the Antarctic". British Antarctic Survey. Retrieved on 2006-02-09.

(3) Lyons, W.B et al. 1998. A Late Holocene desiccation of Lake Hoare and Lake Fryxell, McMurdo Dry Valleys, Antarctica. Antarctic Science. Vol 10 (3): pgs 247-256.

(4) Foreman, C., B. Sattler, J. Mikucki, D. Porazinska and J.C. Priscu. 2007. Metabolic
 Activity and Diversity of Cryoconites in the Taylor Valley, Antarctica. Journal of
 Geophysical Research - Biogeosciences. Pgs 1-43.

(5) Powers, Laura E., Diana W. Freckman, Mengchi Ho and Ross A. Virginia. (1995). McMurdo LTER: Soil properties associated with nematode distribution along an elevational transect in Taylor Valley, Antarctica, Antarctic Journal of the United States, 30 (5): 282-283.

(6) Imperio T, Viti C, Marri L. (2008). Alicyclobacillus pohliae sp. nov., a thermophilic, endospore-forming bacterium isolated from geothermal soil of the north-west slope of Mount Melbourne (Antarctica). Int J Syst Evol Microbiol. 58 (Pt 1):221-5.

(7) Wood, S. et al. (2008). Sources of edaphic cyanobacterial diversity in the Dry Valleys of Eastern Antarctica. The ISME Journal. Vol 2, pgs 308–320.

(8) Ho, Mengchi, Ross A. Virginia, Laura E. Powers, and Diana W. Freckman. (1995). Soil chemistry along a glacial chronosequence on Andrews Ridge, Taylor Valley. Antarctic Journal of the United States. Vol 30 (5): 310-311.

(9) I.D., Craig Cary S., Convey P., Newsham K.K., O'Donnell A.G., Adams B.J., Aislabie J., (...), Wall D.H. (2006). Biotic interactions in Antarctic terrestrial ecosystems: Are they a factor? Soil Biology and Biochemistry, 38 (10), pp. 3035-3040.

(10) de la Torre, J. R., B. M. Goebel, E. I. Friedmann, and N. R. Pace. (2003). Microbial diversity of cryptoendolithic communities from the McMurdo dry valleys, Antarctica. Appl. Environ. Microbiol. 69:3858-3867. [PubMed].

(11) Stackebrandt E, Rainey FA, and Ward-Rainey NL (1997). Proposal for a new hierarchic classification system, Actinobacteria classis nov. Int J Syst Bacteriol 47:479-491.

(12) Mitsui, A. et al. (1986) Strategy by which nitrogen-fixing unicellular cyanobacteria grow photoautotrophically. Nature 323, 720–722.

(13) Hogg I.D., Craig Cary S., Convey P., Newsham K.K., O'Donnell A.G., Adams B.J., Aislabie J., (...), Wall D.H. (2006). Biotic interactions in Antarctic terrestrial ecosystems: Are they a factor? Soil Biology and Biochemistry, 38 (10), pp. 3035-3040.

(14) Rosmarie Honegger. (1991). FUNCTIONAL ASPECTS OF THE LICHEN SYMBIOSIS. Annu. Rev. Plant Physiol. Plant Mol. Biol. Vol 42. pgs 553-7.

(15) Hunt, H. W. (1987). The detrital food web in shortgrass prairie. Biology and Fertility of Soils. Vol 3, pgs 1-2

(16) BOOKRAGS STAFF. "Heterotrophic Bacteria". (2005). August 23 2008. <http://www.bookrags.com/research/heterotrophic-bacteria-wmi/>.

(17) Gerday C., Aittaleb M., Bentahir M., Chessa J.-P., Claverie P., Collins T., D'Amico S., (...). (2000). Feller G. Cold-adapted enzymes: From fundamentals to biotechnology. Trends in Biotechnology, 18 (3), pp. 103-107.

(18) Rivkina, E. I. Friedmann, C. P. McKay, and D. A. Gilichinsky, E. M. Metabolic Activity of Permafrost Bacteria below the Freezing Point. Appl Environ Microbiol. (2000) August; 66(8): 3230–3233.

(19) Wynn-Williams D.D., Edwards H.G.M. Proximal Analysis of Regolith Habitats and Protective Biomolecules in Situ by Laser Raman Spectroscopy: Overview of Terrestrial Antarctic Habitats and Mars Analogs (2000) Icarus, 144 (2), pp. 486-503.

Sea Ice

[1]: Nichols, Carol Mancuso, John P. Bowman, and Jean Guezennec. “Effects of Incubation Temperature on Growth and Production of Exopolysaccharides by an Antarctic Sea Ice Bacterium Grown in Batch Culture.” Applied Environmental Microbiology. 2005 July; 71(7): 3519–3523.

[2]: United States. Central Intelligence Agency. The World Factbook. https://www.cia.gov/library/publications/the-world-factbook/print/ay.html

[3]: Peck, Lloyd S. “Prospects for surviving climate change in Antarctic aquatic species.” Front Zool. (2005); 2:9.

[4]: Morgan-Kiss, Rachael M., et al. “Adaptation and Acclimation of Photosynthetic Microorganisms to Permanently Cold Environments.” MICROBIOLOGY AND MOLECULAR BIOLOGY REVIEWS, Mar. 2006, p. 222–252.

[5]: “Antarctic Weather.” www.antarcticconnection.com

[6]: Gosink, J. J., Staley J. T. “Biodiversity of gas vacuolate bacteria from Antarctic sea ice and water.” Applied and Environmental Microbiology. 1995 September; 61(9): 3486–3489.

[7]: BOWMAN, JOHN P., et al. “Diversity and Association of Psychrophilic Bacteria in Antarctic Sea Ice.” Applied and Environmental Microbiology. Aug. 1997, p. 3068–3078 Vol. 63, No. 8.

[8]: Biuw, M., et al. “Variations in behavior and condition of a Southern Ocean top predator in relation to in situ oceanographic conditions.” Proceedings of the National Academy of Sciences. 2007 August 21; 104(34): 13705–13710.

[9]. Ducklow, Hugh W, et al. “Marine pelagic ecosystems: the West Antarctic Peninsula.” Philosophical Transactions of the Royal Society Biological Sciences. 2007 January 29; 362(1477): 67–94.

[10]. Duck, Hugh, Craig Carlson, “Walker smith Bacterial growth in experimental plankton assemblages and seawater cultures from the Phaeocystis antarctica bloom in the Ross Sea, Antarctica.” MICROBIAL ECOLOGY. (1999) Vol. 19: 215-227.

[11]: D’Amico, Salvino, et al. “Psychrophilic microorganisms: challenges for life.” European Molecular Biology Organization reports. (2006) VOL 7 | NO 4, 385–389.

[12]: Price, Buford P., Todd Sowers. “Temperature dependence of metabolic rates for microbial growth, maintenance, and survival.” Proceedings of the National Academy of Sciences. January 22, 20

Freshwater Ice

[1]: Carpenter, E. J., S. Lin, and D. G. Capone. 2000. Bacterial activity in South Pole snow. Appl. Environ. Microbiol. 66:4514-4517.

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