Physiological adaptations of biota in antarctic oasis lakes
Table 2. incorporation of 14CO2 into lipids incubated in situ at Linnaeus Terrace, Asgard Range, and biomass in respective rock samples expressed in lipid phosphate (Incubation period 7, 14, or 16 days, from 25 November 1981)
Incorporation (disintegration per minute per micromole lipid phosphate) Biomass (micromole lipid phosphate per square centimeter)
7 days (dry rock)
14 days (wet" rock)
16 days (dry rock)
N.D.0
647 ± 117d
395 ± 126
0.110 ± 001d 0.060 ± 0.004
0.068 ± 0.02
16 days (dark , b dry rock)
653 ± 163
0.050 ± 0.006
awet = soaked with CO 2 4ree water prior to incubation. b Oark = glass jars were covered with aluminum toil. C N . D . = none detected (i.e., counts were not above 2 times background). dMean ± SD (n = 3).
References Bligh, E. G., and Dyer, W. J . 1959. A rapid method of total lipid extraction
and purification. Canadian Journal of Biochemistry and Physiology, 37, 911-917. Friedmann, E. I. 1978. Melting snow in the dry valleys is a source of water for endolithic microorganisms. Antarctic Journal of the U.S., 13(4), 162-163.
Physiological adaptations of biota in antarctic oasis lakes B. C. PARKER, G. M. SIMMONS, JR., M. KASPAR, and A. MIKELL Biology Department and
F. C. LOVE Geology Department Virginia Polytechnic Institute and State University Blacksburg, Virginia 2406
K. C. SEABURG Department of Biology Xavier College New Orleans, Louisiana 70035
R. A. WHARTON, JR. Ames Research Center Moffett Field, California 04035
1982 REVIEW
Friedmann, E. I. 1982. Endolithic microorganisms in the antarctic cold desert. Science, 215, 1045-1053. White, D. C., Bobbie, R. J . , Morrison, S. J . , Oosterhof, D. K., Taylor, C. W., and Meeter, D. A. 1977. Determination of microbial activity of estuarine detritus by relative rates of lipid biosynthesis. Limnology and Oceanography, 22, 1089-1099.
White, D. C., Davis, W. M., Nickels, J . S., King, J . D., and Bobbie, R. J. 1979. Determination of the sedimentary microbial biomass by extractable lipid phosphate. Oceologia (Berlin), 40, 51-62.
Our research seeks to identify and characterize the extent to which southern Victoria Land lake communities, species, or strains are physiologically adapted for survival and growth under certain environmental extremes. Field studies during the 1980-81 and 1981-82 austral summers at Lakes Bonney, Fryxell, Hoare (Taylor Valley), and Vanda (Wright Valley) have addressed adaptions to (1) low light, (2) low temperature, (3) hypersalinity, (4) supersaturated oxygen, (5) nutrient limitations (e.g., nitrogen, phosphorus), (6) lack of turbulence, and (7) desiccation or freeze-thaw cycles. We list here only new information on adaptations to variables 1-4 above and discuss briefly the unique stromatolites and endemic algal species. For additional information, see Allnutt and others (1981), Cathey and others (1981, in press), Kaspar and others (in press), Love, Simmons, Wharton, and Parker (in press), Love, Simmons, Wharton, and Parker (in press), Parker and others (1980, 1982, in press, Parker and Simmons (1981), Seaburg, Parker, and Simmons (1981), Simmons and others (1981), Wharton (1982), and Wharton and others (1982). Adaptations to low light. The perennial 3-6-meter-thick, rockand soil-strewn ice covers of the four lakes vary in their average surface light transmittance (as percent) and average extinction coefficients (E PAR) for photosynthetically available radiation (PAR) of 400-700-nanometer wavelength range for their underlying waters: Bonney, percent, 0.157 EPA R; Hoare, 1.7 percent,
191
0. 183 EPAR; Fryxell, 1.5 percent, 0.733 EPAR; and Vanda, 18.6 percent, 0.055 EPAR. Unialgal clonal cultures of Phormidium frigidum Fritsch, the dominant bluegreen alga in all benthic mats, grows in the laboratory with about 0.2 microeinstein per square meter per second of continuous cool white fluorescent light, corresponding closely with PAR values near the maximum depth of algal mats in the lakes (Parker et al. 1980). This supports earlier suggestions that this alga can quantitatively adjust its photosynthetic pigments or chromatically adapt to low light levels (Simmons et al. 1981; Wharton 1982). A clonal isolate of a moss recently discovered in deep-water benthic algal mats of Lake Vanda grows with approximately 2.0 microeinstein per square meter per second of continuous cool white fluorescent light. These findings suggest greater adaptation to low light or lower compensation point intensities than many photosynthetic aquatic organisms. The lowest compensation point levels determined for a Signy Island lake Phormidium sp. was 4.1 microeinstein per square meter per second, and for the aquatic moss Drapanocladus, 5.0 microeinstein per square meter per second (Priddle 1980a, 1980b). Adaptations to low temperature. Seaburg and others (1981) have provided the only definitive treatment on the temperaturegrowth physiological ecology of algae from antarctic lakes. Of 35 algal taxa (128 clonal cultures) from southern Victoria Land, a large proportion were facultatively, and a smaller number obligately, cold adapted. The latter group, the true psychrophiles which grew at less than 20°C, usually with optima of 10°-12°C, came primarily from stable low-temperature lake environments rather than from soils, ephemeral meltstreams, and moat-water habitats. No antarctic algal isolate grew at above 30°C. A parallel study of algal isolates from Virginia habitats revealed no obligately cold-adapted strains, regardless of whether isolates came from winter or summer algal comriunities. However, more cold-tolerant isolates came from winter communities, and a number of isolates grew at 34°C (K. G. Seaburg and B. C. Parker unpublished data, Virginia Polytechnic Institute and State University 1982). Thus, the degree of cold-temperature adaptation for antarctic algae, especially lake algae, is significantly greater than for temperature strains. These findings are further supported by experiments involving incubation of algal communities from the oasis lakes at 2°, 12°, and 25°C. Carbon-14 ('4C)—bicarbonate primary productivity and hydrogen-3 ( 3H)—organic uptake rates were highest at 12° and strongly inhibited at 25°C. Bacterial isolates also appear cold-temperature adapted. Adaptations to hypersalinity. Whereas Lake Hoare is entirely fresh, Lakes Fryxell, Bonney, and Vanda have highly saline waters at greater depths. Planktonic green flagellates and several diatoms now have been isolated into unialgal and/or axenic culture from Lake Bonney and are salt-tolerant (e.g., Navicula shackeltoni, a new Nitzchia species) or salt-requiring (e.g., Pinnularia cymatopleura, figure; a new Navicula species). Of special interest is the fact that our salt-tolerant and salt-requiring diatom isolates are also obligate cold-temperature strains (i.e., psychrophiles), with growth optima at about 10°-12°C. These are the first axenic diatom isolates with both physiological adaptations, and their importance as experimental tools should be obvious. Adaptations to supersaturated oxygen. A rare environmental extreme is perennial oxygen (02) supersaturation, which occurs in
192
Scanning electron micrography of Pinnularla Cf. cymatopleura an axenic haiophllic and psychrophilic diatom isolate from the cold, saline benthos of Lake Bonney. Bar = 1 micrometer.
the shallower waters beneath the perennial ice covers of thee oasis lakes. Two important adaptions to this supersaturated 02 concern (1) the effect on photosynthesis vs. photorespiration and (2) oxygen toxicity to bacteria. We have suggested that the high percentages of extracellular organic products detected in antarctic lake plankton 14C primary productivity studies result from stimulated photorespiratory activity (inhibited photosynthesis) with excretion of organic products by the algae (Parker and Simmons 1981). Presumably, the enzyme Ribulose-bisphosphate carboxylase-oxygenase, which can use both carbon dioxide (CO2) ( carboxylase) and 0 2 (oxygenase) as substrates, under conditions of high 0 2 and low CO2. functions primarily as an oxygenase in photorespiration. Thus, extracellular products such as glycollate, glyoxylate, or certain amino acids are produced in large quantities relative to cellular organic carbon. Supporting this suggestion are field studies showing that the greater percentages of extracellular organic products in primary productivity experiments occur in the shallower, more highly oxygenated depths of Lakes Fryxell, Hoare, and Vanda. Nonphotosynthetic bacteria are the most abundant heterotrophs in the plankton and benthic algal mats, whether detected by viable spread-plate counts or by direct fluorochrome staining. We have found that while bacteria in the mats may be inhibited by supersatured 0 2 conditions, many in the plankton are resistant to or stimulated by supersatured 0 2 . Three 0 2 stimulated bacterioplankton isolates produce about three times the superoxide dismutase (SOD) activity after short-term incubation, indicating that these isolates have an inducible enzyme (E. M. Gregory unpublished data, Virginia Polytechnic Institute and State University 1982). ANTARCTIC JOURNAL
Modern stromatolites—Adaptations to nonturbulence and metazoan absence. Most of the benthic mats of the oasis lakes are being
preserved as ". . . organosedimentary structures produced by sediment trapping, binding, and/or precipitation resulting from metabolic activity and growth of organisms, primarily bluegreen algae" (Awramik, Margulis, and Barghoorn 1976, p. 149), and hence are stromatolites. Diatoms and bacteria also occur in most mat types presently known from Lakes Bonney, Chad, Fryxell, Hoare, and Vanda. These stromatolites represent the highest latitude (>77°S) and only known Recent, cold stromatolites on Earth and, as such, may represent reasonable analogs of the more abundant Precambrian stromatolites. Consequently, they can serve as models for interpreting the development, diagenesis, and paleoecology of ancient stromatolites (Love, Simmons, Parker, and Wharton in press; Parker et al. 1981; Wharton 1982; Wharton et al. 1982). Metabolic activity of the antarctic stromatolite mats results in calcite precipitation, especially under higher alkalinity conditions (Wharton et al. 1982), and probably other minerals biogenically form (Parker et al. 1982). Metabolism and growth of these organisms are influenced by light, temperature, salinity, 02/CO2, nutrient levels, turbulence, or mixing, all of which are under investigation. Organic matter is also well preserved and includes keragen (i.e., organic matter insoluble in organic solvents) and geolipid (i.e., organic matter soluble in organic solvents, e.g., chloroform), the amounts and components of which are currently under investigation. We are grateful for the support of this research by the National Science Foundation under grant DPP 79-20805. References Allnutt, F C. T., Parker, B. C., Seaburg, K. C., and Simmons, G. M., Jr. 1981. In situ nitrogen (C2H2)-fixation in lakes of southern Victoria Land, Antarctica. Hydrobiological Bulletin, 15, 99-109. Awramik, S. M., Margulis, L., and Barghoorn, E. S. 1976. Evolutionary processes in the formation of stromatolites. In M. R. Walter (Ed.), Stromatolites. Amsterdam: Elsevier. Cathey, D. D., Parker, B. C., Simmons, G. M., Jr., VanBrunt, M. R., and Yongue, W. H. In press. Protozoan colonization of artificial substrates in two antarctic lakes. Transactions of the American Microscopical Society.
Physiological adaptations of antarctic terrestrial arthropods RICHARD
E. LEE, JR.* and JOHN G.
BAUST
Department of Biology University of Houston Houston, Texas 77004
*presen t address: Department of Zoology, Miami University-Hamilton, Hamilton, Ohio 45001. 1982 REVIEW
Cathey, D., Yongue, W., Simmons, G. M., Jr., and Parker, B. C. 1981. The microfauna of algal mats and artificial substrates in southern Victoria Land lakes of Antarctica. Hydrobiologia, 85, 3-15. Kaspar, M., Simmons, G. M., Jr., Parker, B. C., Seaburg, K. C., Wharton, R. A., Jr., and Lewis-Smith, R. I. In press. The farthest south deep water moss. The Bryologist. Love, F G., Simmons, C. M., Jr., Parker, B. C., Wharton, R. A., Jr., and Seaburg, K. G. In press. Modern Conophyton-like microbial mats discovered in Lake Vanda, Antarctica. Geomicrobiological Journal. Love, F G., Simmons, G. M., Jr., Wharton, R. A., Jr., and Parker, B. C. In press. Methods for melting dive holes in thick ice and vibraconng beneath ice. Journal of Sedimentary Petrology.
Parker, B. C., and Simmons, C. M., Jr. 1981. Biogeochemical cycles in antarctic oasis lakes. Trends in Biochemistry, 6, 3-4. Parker, B. C., Simmons, G. M., Jr., Seaburg, K. C., Cathey, D. D., and Allnutt, F C. T. In press. Comparative ecology of plankton communities in seven antarctic oasis lakes. Journal of Plankton Research. Parker, B. C., Simmons, G. M., Jr., Seaburg, K. G., and Wharton, R. A., Jr. 1980. Ecosystem comparisons of oasis lakes and soils. Antarctic Journal of the U.S., 15(5), 167-170. Parker, B. C., Simmons, G. M., Jr., Wharton, R. A., Jr., Seaburg, K. G., and Love, F G. 1982. Removal of salts and nutrients from antarctic lakes by aerial escape of bluegreen algal mats. Journal of Phycology, 18, 72-78. Priddle, J. 1980. The production ecology of benthic plants in some antarctic lakes. I. In situ production studies. Journal of Ecology, 68, 141-153. (a) Priddle, J . 1980. The production ecology of benthic plants in some antarctic lakes. II. Laboratory physiological studies. Journal of Ecology, 68, 155-166(b) Seaburg, K. C., Parker, B. C., and Simmons, G. M., Jr. 1981. Temperature-growth responses of algal isolates from antarctic oases. Journal of Phycology, 17, 353-360. Simmons, C. M., Jr., Parker, B. C., Wharton, R. A., Jr., Love, F G., and Seaburg, K. C. 1981. Physiological adaptations of biota in antarctic oasis lakes. Antarctic Journal of the U.S., 16(5), 173-174. Wharton, R. A., Jr. 1982. Ecology of algal mats and their role in the formation of stromatolites in antarctic dry valley lakes. Unpublished doctoral dissertation, Virginia Polytechnic Institute and State University. Wharton, R. A., Jr., Parker, B. C., Simmons, G. M., Jr., Seaburg, K. C., and Love, F G. 1982. Biogenic calcite structures forming in Lake Fryxell, Antarctica. Nature, 295, 403-405. Wharton, R. A., Jr., Vinyard, W. C., Parker, B. C., Simmons, G. M., Jr., and Seaburg, K.G. 1981. Cryoconite holes in antarctic piedmont glaciers. Phycologia, 20, 208-211.
In 1981, investigations of the adaptation of terrestrial arthropods to low temperatures in the maritime Antarctic were expanded to include seasonal monitoring throughout the year at Palmer Station (64°46'S 64°03'W). During the austral summer these species use one of two survival mechanisms, freeze tolerance or freeze avoidance (Lee and Baust 1981). The supercooling point (sCP) refers to the temperature at which spontaneous freezing of body water occurs. For species susceptible to freezing, it represents the lower survival limit. Freeze-tolerant larvae of the chironomid Belgica antarctica maintained their SCP's at relatively high levels throughout the year (table). Winter-acclimatized larvae were freeze-tolerant to - 15°C. This level of tolerance is similar to that of larvae collected 193
Incorporation (disintegration per minute per micromole lipid phosphate) Biomass (micromole lipid phosphate per square centimeter)
7 days (dry rock)
14 days (wet" rock)
16 days (dry rock)
N.D.0
647 ± 117d
395 ± 126
0.110 ± 001d 0.060 ± 0.004
0.068 ± 0.02
16 days (dark , b dry rock)
653 ± 163
0.050 ± 0.006
awet = soaked with CO 2 4ree water prior to incubation. b Oark = glass jars were covered with aluminum toil. C N . D . = none detected (i.e., counts were not above 2 times background). dMean ± SD (n = 3).
References Bligh, E. G., and Dyer, W. J . 1959. A rapid method of total lipid extraction
and purification. Canadian Journal of Biochemistry and Physiology, 37, 911-917. Friedmann, E. I. 1978. Melting snow in the dry valleys is a source of water for endolithic microorganisms. Antarctic Journal of the U.S., 13(4), 162-163.
Physiological adaptations of biota in antarctic oasis lakes B. C. PARKER, G. M. SIMMONS, JR., M. KASPAR, and A. MIKELL Biology Department and
F. C. LOVE Geology Department Virginia Polytechnic Institute and State University Blacksburg, Virginia 2406
K. C. SEABURG Department of Biology Xavier College New Orleans, Louisiana 70035
R. A. WHARTON, JR. Ames Research Center Moffett Field, California 04035
1982 REVIEW
Friedmann, E. I. 1982. Endolithic microorganisms in the antarctic cold desert. Science, 215, 1045-1053. White, D. C., Bobbie, R. J . , Morrison, S. J . , Oosterhof, D. K., Taylor, C. W., and Meeter, D. A. 1977. Determination of microbial activity of estuarine detritus by relative rates of lipid biosynthesis. Limnology and Oceanography, 22, 1089-1099.
White, D. C., Davis, W. M., Nickels, J . S., King, J . D., and Bobbie, R. J. 1979. Determination of the sedimentary microbial biomass by extractable lipid phosphate. Oceologia (Berlin), 40, 51-62.
Our research seeks to identify and characterize the extent to which southern Victoria Land lake communities, species, or strains are physiologically adapted for survival and growth under certain environmental extremes. Field studies during the 1980-81 and 1981-82 austral summers at Lakes Bonney, Fryxell, Hoare (Taylor Valley), and Vanda (Wright Valley) have addressed adaptions to (1) low light, (2) low temperature, (3) hypersalinity, (4) supersaturated oxygen, (5) nutrient limitations (e.g., nitrogen, phosphorus), (6) lack of turbulence, and (7) desiccation or freeze-thaw cycles. We list here only new information on adaptations to variables 1-4 above and discuss briefly the unique stromatolites and endemic algal species. For additional information, see Allnutt and others (1981), Cathey and others (1981, in press), Kaspar and others (in press), Love, Simmons, Wharton, and Parker (in press), Love, Simmons, Wharton, and Parker (in press), Parker and others (1980, 1982, in press, Parker and Simmons (1981), Seaburg, Parker, and Simmons (1981), Simmons and others (1981), Wharton (1982), and Wharton and others (1982). Adaptations to low light. The perennial 3-6-meter-thick, rockand soil-strewn ice covers of the four lakes vary in their average surface light transmittance (as percent) and average extinction coefficients (E PAR) for photosynthetically available radiation (PAR) of 400-700-nanometer wavelength range for their underlying waters: Bonney, percent, 0.157 EPA R; Hoare, 1.7 percent,
191
0. 183 EPAR; Fryxell, 1.5 percent, 0.733 EPAR; and Vanda, 18.6 percent, 0.055 EPAR. Unialgal clonal cultures of Phormidium frigidum Fritsch, the dominant bluegreen alga in all benthic mats, grows in the laboratory with about 0.2 microeinstein per square meter per second of continuous cool white fluorescent light, corresponding closely with PAR values near the maximum depth of algal mats in the lakes (Parker et al. 1980). This supports earlier suggestions that this alga can quantitatively adjust its photosynthetic pigments or chromatically adapt to low light levels (Simmons et al. 1981; Wharton 1982). A clonal isolate of a moss recently discovered in deep-water benthic algal mats of Lake Vanda grows with approximately 2.0 microeinstein per square meter per second of continuous cool white fluorescent light. These findings suggest greater adaptation to low light or lower compensation point intensities than many photosynthetic aquatic organisms. The lowest compensation point levels determined for a Signy Island lake Phormidium sp. was 4.1 microeinstein per square meter per second, and for the aquatic moss Drapanocladus, 5.0 microeinstein per square meter per second (Priddle 1980a, 1980b). Adaptations to low temperature. Seaburg and others (1981) have provided the only definitive treatment on the temperaturegrowth physiological ecology of algae from antarctic lakes. Of 35 algal taxa (128 clonal cultures) from southern Victoria Land, a large proportion were facultatively, and a smaller number obligately, cold adapted. The latter group, the true psychrophiles which grew at less than 20°C, usually with optima of 10°-12°C, came primarily from stable low-temperature lake environments rather than from soils, ephemeral meltstreams, and moat-water habitats. No antarctic algal isolate grew at above 30°C. A parallel study of algal isolates from Virginia habitats revealed no obligately cold-adapted strains, regardless of whether isolates came from winter or summer algal comriunities. However, more cold-tolerant isolates came from winter communities, and a number of isolates grew at 34°C (K. G. Seaburg and B. C. Parker unpublished data, Virginia Polytechnic Institute and State University 1982). Thus, the degree of cold-temperature adaptation for antarctic algae, especially lake algae, is significantly greater than for temperature strains. These findings are further supported by experiments involving incubation of algal communities from the oasis lakes at 2°, 12°, and 25°C. Carbon-14 ('4C)—bicarbonate primary productivity and hydrogen-3 ( 3H)—organic uptake rates were highest at 12° and strongly inhibited at 25°C. Bacterial isolates also appear cold-temperature adapted. Adaptations to hypersalinity. Whereas Lake Hoare is entirely fresh, Lakes Fryxell, Bonney, and Vanda have highly saline waters at greater depths. Planktonic green flagellates and several diatoms now have been isolated into unialgal and/or axenic culture from Lake Bonney and are salt-tolerant (e.g., Navicula shackeltoni, a new Nitzchia species) or salt-requiring (e.g., Pinnularia cymatopleura, figure; a new Navicula species). Of special interest is the fact that our salt-tolerant and salt-requiring diatom isolates are also obligate cold-temperature strains (i.e., psychrophiles), with growth optima at about 10°-12°C. These are the first axenic diatom isolates with both physiological adaptations, and their importance as experimental tools should be obvious. Adaptations to supersaturated oxygen. A rare environmental extreme is perennial oxygen (02) supersaturation, which occurs in
192
Scanning electron micrography of Pinnularla Cf. cymatopleura an axenic haiophllic and psychrophilic diatom isolate from the cold, saline benthos of Lake Bonney. Bar = 1 micrometer.
the shallower waters beneath the perennial ice covers of thee oasis lakes. Two important adaptions to this supersaturated 02 concern (1) the effect on photosynthesis vs. photorespiration and (2) oxygen toxicity to bacteria. We have suggested that the high percentages of extracellular organic products detected in antarctic lake plankton 14C primary productivity studies result from stimulated photorespiratory activity (inhibited photosynthesis) with excretion of organic products by the algae (Parker and Simmons 1981). Presumably, the enzyme Ribulose-bisphosphate carboxylase-oxygenase, which can use both carbon dioxide (CO2) ( carboxylase) and 0 2 (oxygenase) as substrates, under conditions of high 0 2 and low CO2. functions primarily as an oxygenase in photorespiration. Thus, extracellular products such as glycollate, glyoxylate, or certain amino acids are produced in large quantities relative to cellular organic carbon. Supporting this suggestion are field studies showing that the greater percentages of extracellular organic products in primary productivity experiments occur in the shallower, more highly oxygenated depths of Lakes Fryxell, Hoare, and Vanda. Nonphotosynthetic bacteria are the most abundant heterotrophs in the plankton and benthic algal mats, whether detected by viable spread-plate counts or by direct fluorochrome staining. We have found that while bacteria in the mats may be inhibited by supersatured 0 2 conditions, many in the plankton are resistant to or stimulated by supersatured 0 2 . Three 0 2 stimulated bacterioplankton isolates produce about three times the superoxide dismutase (SOD) activity after short-term incubation, indicating that these isolates have an inducible enzyme (E. M. Gregory unpublished data, Virginia Polytechnic Institute and State University 1982). ANTARCTIC JOURNAL
Modern stromatolites—Adaptations to nonturbulence and metazoan absence. Most of the benthic mats of the oasis lakes are being
preserved as ". . . organosedimentary structures produced by sediment trapping, binding, and/or precipitation resulting from metabolic activity and growth of organisms, primarily bluegreen algae" (Awramik, Margulis, and Barghoorn 1976, p. 149), and hence are stromatolites. Diatoms and bacteria also occur in most mat types presently known from Lakes Bonney, Chad, Fryxell, Hoare, and Vanda. These stromatolites represent the highest latitude (>77°S) and only known Recent, cold stromatolites on Earth and, as such, may represent reasonable analogs of the more abundant Precambrian stromatolites. Consequently, they can serve as models for interpreting the development, diagenesis, and paleoecology of ancient stromatolites (Love, Simmons, Parker, and Wharton in press; Parker et al. 1981; Wharton 1982; Wharton et al. 1982). Metabolic activity of the antarctic stromatolite mats results in calcite precipitation, especially under higher alkalinity conditions (Wharton et al. 1982), and probably other minerals biogenically form (Parker et al. 1982). Metabolism and growth of these organisms are influenced by light, temperature, salinity, 02/CO2, nutrient levels, turbulence, or mixing, all of which are under investigation. Organic matter is also well preserved and includes keragen (i.e., organic matter insoluble in organic solvents) and geolipid (i.e., organic matter soluble in organic solvents, e.g., chloroform), the amounts and components of which are currently under investigation. We are grateful for the support of this research by the National Science Foundation under grant DPP 79-20805. References Allnutt, F C. T., Parker, B. C., Seaburg, K. C., and Simmons, G. M., Jr. 1981. In situ nitrogen (C2H2)-fixation in lakes of southern Victoria Land, Antarctica. Hydrobiological Bulletin, 15, 99-109. Awramik, S. M., Margulis, L., and Barghoorn, E. S. 1976. Evolutionary processes in the formation of stromatolites. In M. R. Walter (Ed.), Stromatolites. Amsterdam: Elsevier. Cathey, D. D., Parker, B. C., Simmons, G. M., Jr., VanBrunt, M. R., and Yongue, W. H. In press. Protozoan colonization of artificial substrates in two antarctic lakes. Transactions of the American Microscopical Society.
Physiological adaptations of antarctic terrestrial arthropods RICHARD
E. LEE, JR.* and JOHN G.
BAUST
Department of Biology University of Houston Houston, Texas 77004
*presen t address: Department of Zoology, Miami University-Hamilton, Hamilton, Ohio 45001. 1982 REVIEW
Cathey, D., Yongue, W., Simmons, G. M., Jr., and Parker, B. C. 1981. The microfauna of algal mats and artificial substrates in southern Victoria Land lakes of Antarctica. Hydrobiologia, 85, 3-15. Kaspar, M., Simmons, G. M., Jr., Parker, B. C., Seaburg, K. C., Wharton, R. A., Jr., and Lewis-Smith, R. I. In press. The farthest south deep water moss. The Bryologist. Love, F G., Simmons, C. M., Jr., Parker, B. C., Wharton, R. A., Jr., and Seaburg, K. G. In press. Modern Conophyton-like microbial mats discovered in Lake Vanda, Antarctica. Geomicrobiological Journal. Love, F G., Simmons, G. M., Jr., Wharton, R. A., Jr., and Parker, B. C. In press. Methods for melting dive holes in thick ice and vibraconng beneath ice. Journal of Sedimentary Petrology.
Parker, B. C., and Simmons, C. M., Jr. 1981. Biogeochemical cycles in antarctic oasis lakes. Trends in Biochemistry, 6, 3-4. Parker, B. C., Simmons, G. M., Jr., Seaburg, K. C., Cathey, D. D., and Allnutt, F C. T. In press. Comparative ecology of plankton communities in seven antarctic oasis lakes. Journal of Plankton Research. Parker, B. C., Simmons, G. M., Jr., Seaburg, K. G., and Wharton, R. A., Jr. 1980. Ecosystem comparisons of oasis lakes and soils. Antarctic Journal of the U.S., 15(5), 167-170. Parker, B. C., Simmons, G. M., Jr., Wharton, R. A., Jr., Seaburg, K. G., and Love, F G. 1982. Removal of salts and nutrients from antarctic lakes by aerial escape of bluegreen algal mats. Journal of Phycology, 18, 72-78. Priddle, J. 1980. The production ecology of benthic plants in some antarctic lakes. I. In situ production studies. Journal of Ecology, 68, 141-153. (a) Priddle, J . 1980. The production ecology of benthic plants in some antarctic lakes. II. Laboratory physiological studies. Journal of Ecology, 68, 155-166(b) Seaburg, K. C., Parker, B. C., and Simmons, G. M., Jr. 1981. Temperature-growth responses of algal isolates from antarctic oases. Journal of Phycology, 17, 353-360. Simmons, C. M., Jr., Parker, B. C., Wharton, R. A., Jr., Love, F G., and Seaburg, K. C. 1981. Physiological adaptations of biota in antarctic oasis lakes. Antarctic Journal of the U.S., 16(5), 173-174. Wharton, R. A., Jr. 1982. Ecology of algal mats and their role in the formation of stromatolites in antarctic dry valley lakes. Unpublished doctoral dissertation, Virginia Polytechnic Institute and State University. Wharton, R. A., Jr., Parker, B. C., Simmons, G. M., Jr., Seaburg, K. C., and Love, F G. 1982. Biogenic calcite structures forming in Lake Fryxell, Antarctica. Nature, 295, 403-405. Wharton, R. A., Jr., Vinyard, W. C., Parker, B. C., Simmons, G. M., Jr., and Seaburg, K.G. 1981. Cryoconite holes in antarctic piedmont glaciers. Phycologia, 20, 208-211.
In 1981, investigations of the adaptation of terrestrial arthropods to low temperatures in the maritime Antarctic were expanded to include seasonal monitoring throughout the year at Palmer Station (64°46'S 64°03'W). During the austral summer these species use one of two survival mechanisms, freeze tolerance or freeze avoidance (Lee and Baust 1981). The supercooling point (sCP) refers to the temperature at which spontaneous freezing of body water occurs. For species susceptible to freezing, it represents the lower survival limit. Freeze-tolerant larvae of the chironomid Belgica antarctica maintained their SCP's at relatively high levels throughout the year (table). Winter-acclimatized larvae were freeze-tolerant to - 15°C. This level of tolerance is similar to that of larvae collected 193
