Cold tolerance in Tardigrada from Dronning Maud Land,Antarctica

Survival at low temperatures was studied in three species of Tardigrada from Müihlig-Hofmannfjella, Dronning Maud Land, Antarctica. Both hydrated and dehydrated specimens of Echiniscus jenningsi, Macrobiotus furciger and Diphascon chilenense had high survival rates following exposure to -22°C for ca. 600 days, and dehydrated specimens following 3040 days at this temperature. In hydrated E. jenningsi, mortality increased with the duration of exposure from 7 to 150 days at -80°C, while mortalities of the two other species did not change. Hydrated specimens of all species were rapidly killed at -180°C, but all species exhibited good survivorship in the dehydrated state after 14 days at -180°C. In conclusion, hydrated tardigrades are able to survive extended periods at low temperatures, and dehydrated specimens are even better adapted to survive overwintering on Antarctic nunataks.     

Nematodes,rotifers and tardigrades from nunataks in Dronning Maud Land,East Antarctica

Four species of nematodes, sixteen species of rotifers and seven species of tardigrades were found in samples from nunataks in Vestfjella and Heimefrontfjella in Dronning Maud Land, East Antarctica. The distribution of the fauna was very aggregated and some samples contained no animals. The degree of similarity in species composition between various nunataks was low. The highest abundances and number of species were found on the largest and highest nunataks in the most southern position.     

Ecology of Cryptopygus sverdrupi (Insecta: Collembola) from Dronning Maud Land,Antarctica

Summary Observations on the ecology of Cryptopygus sverdrupi Lawrence (Collembola, Isotomidae) were made with specimens from the Mühlig-Hofmannfjella, Dronning Maud Land, Antarctica. At an elevation of 1600 m a.s.l. the species was numerous in association with the green alga Prasiola on gravel fields and in crevices of large boulders. The distribution of size-classes in field samples suggested that the population comprised several overlapping generations. Growth and development is probably very slow due to long winters and daily periods of subzero temperatures in their microhabitat during the summer. Specimens collected in mid-January had a mean supercooling point of-24.6°C with small individual variations. The lack of high supercooling points in the summer suggests that the springtails feed on a nuleatorfree diet. The ability to supercool was increased during prolonged starvation and acclimation at 0,-4 and-8°C. Glycerol and other potential low molecular weight cryoprotective substances were demonstrated in specimens acclimated at-4 and-8°C. The species possessed a relatively high tolerance to desiccation.Publication No. 81 of the Norwegian Antarctic Research Expeditions (1984/85)     

Origin of the inland Acari of Continental Antarctica, with particular reference to Dronning Maud Land

The extant Acari occurring on the inland mountain ranges and nunataks of Continental Antarctica comprise only pre-Pleistocene endemic Prostigmata and Cryptostigmata of which the Prostigmata are the probable earlier colonists. The inland acarofauna of Continental Antarctica has a different origin from that of Maritime Antarctica, though both are the relict descendants of a Mesozoic acarofauna, which has been radically depleted by one or more Mesozoic and/or Cenozoic glacial events.     

Chiloplectus masleni sp. nov. and variability in populations of Plectus acuminatus Bastian 1865 (Nematoda: Plectidae) from the nunatak Basen,Vestfjella, Dronning Maud Land,East Antarctica

 A new species, Chiloplectus masleni sp. nov., and 12 populations of Plectus acuminatus are described from the nunatak Basen, Vestfjella, Dronning Maud Land, East Antarctica. C. masleni sp. nov. is distinguished from the closely related C. loricatus by a broader lip region, longer stoma, the more posterior position of amphids, a pear-shaped basal bulb, more narrow annuli, anterior annuli that are evenly rounded and a larger number of tail setae. New information is provided on internal and external morphology of specimens of P. acuminatus from Basen. Received: 20 December 1995/Accepted: 17 March 1996     

First records of primary producers of epiglacial and supraglacial lakes in western Dronning Maud Land, Antarctica

Epiglacial and supraglacial lakes are characteristic lake types in Antarctica, and regardless of their mostly seasonal existence and ultraoligotrophy, some lakes have a relatively diverse microbial community. The results of water chemistry and phytoplankton, based on basic limnological methods, from five epiglacial and two supraglacial seasonal lakes are presented from western Dronning Maud Land, an area where only physical studies have been previously carried out. Electric conductivity varied mostly between 0.1 and 10 mS m^?1 (25 °C), phosphorus concentration was <5 mg m^?3, and nitrogen concentration was <300 mg m^?3 except in some shore areas, and water pH ranged from 6 to 11. Low phytoplankton biomasses (in most cases <10 mg m^?3) supported the ultraoligotrophic status of the lakes. Phytoplankton was found from both types of lakes, but less was found from supraglacial lakes. The charophyte Mesotaenium cf. berggrenii dominated the supraglacial lakes, while cyanoprokaryotes such as Gloeocapsopsis cf. magma, Planktothrix prolifica/rubescens, Nostoc cf. sphaericum, Cyanothece sp. and Phormidium sp. dominated the biomass in some epiglacial lakes. Chrysophytes (e.g. Pseudopedinella-type flagellates) were observed in both types of lakes, and they were occasionally dominant. The green alga Botryococcus braunii, some diatoms (Cyclotella sp., Diatoma tenuis, Luticola muticopsis), and non-planktonic microalgal colonies visible to the eye (incl. the cyanoprokaryote Nostoc commune) were also found. Signs of a living ecosystem with a food web were observed in one epiglacial lake, but not elsewhere, which indicates extreme circumstances in the Antarctic seasonal lakes. Altogether, only some 25 taxa were discovered.     

Diet and prey consumption of Antarctic petrels Thalassoica antarctica at Svarthamaren, Dronning Maud Land, and at sea outside the colony

The diet of the Antarctic petrel Thalassoica antarctica was studied during two seasons at Svarthamaren, an inland colony in Dronning Maud Land, Antarctica, and in the pack ice off the coast of Svarthamaren. The most important food (wet mass) at Svarthamaren was crustaceans (67%), fish (29%) and squid (5%); however, individuals collected in the pack ice took mostly fish (87%). The prey composition and lengths of prey are comparable to what has been documented in other studies on this species. Estimates of food consumption by birds breeding at Svarthamaren (ca. 250,000 pairs) suggest that approximately 6500 tonnes of crustaceans, 2800 tonnes of fish and 435 tonnes of squid are consumed during the breeding season. The annual consumptions of these birds are estimated to be 34,100 tonnes of crustaceans, 14,700 tonnes of fish, and 2300 tonnes of squid. Satellite telemetry data indicate that Antarctic petrels from Svarthamaren may fly more than 3000 km during one foraging trip, and thus may cover a huge ocean area to obtain their prey. Received: 1 September 1997 / Accepted: 3 February 1998     

On the uptake of ornithogenic products by plants on the inland mountains of Dronning Maud Land, Antarctica, using stable isotopes

Breeding snow petrels (Pagodroma nivea) may be a major source of nutrients for the ecosystems on the inland nunataks (mountain outcrops) of continental Antarctica. To test this theory, the δ¹⁵N and δ¹³C values of soil and plants (moss, lichen and algae) from 11 nunataks with and without breeding snow petrels in northwestern Dronning Maud Land were compared. High δ¹⁵N values in all samples from nunataks with breeding birds provide a strong indication of the presence of breeding birds, as well as the use of bird-derived nitrogen by the plants of these ecosystems. The δ¹³C values showed little difference between the nunataks and are not a useful indicator of bird effects on ecosystem development. Received: 3 March 1997 / Accepted: 30 March 1998     

An extreme inland breeding locality of snow petrels (Pagodroma nivea) in the southern Prince Charles Mountains, Antarctica

Bird observations were made as part of a preliminary biological survey of the southern half of the Mawson Escarpment in the southern Prince Charles Mountains, Mac.Robertson Land between 26 January and 4 February 1998. A new breeding colony of snow petrels (Pagodroma nivea) is described, together with details of individual snow petrel sightings. At 440 km from the coast, the snow petrel colony is the furthest inland of any confirmed breeding site for this species. Accepted: 1 May 2000     

Rates of soluble carbohydrate utilization in soils from the Windmill Islands Oasis,Wilkes Land,continental Antarctica

A time course study of the fate of glucose, sucrose, and arabitol added to surface soils collected from vegetated and bare sites near Casey Station, Wilkes Land, Antarctica, was performed using gas-liquid chromatography. For both soils, hydrolysis of added sucrose was observed after 24 hours. Following 168 hours incubation at both 5°C and 15°C, hydrolysis of sucrose to glucose and fructose was greater than 95%. Maximum rates of sugar uptake were observed in soils from the vegetated site incubated at 15°C. After 168 hours 44%, 52% and 94% of the added arabitol, glucose and sucrose respectively had been consumed. There did not appear to be any cell-free extracellular enzymatic activity in the soils as levels of added sucrose, trehalose and maltose within soil water extracts showed no change after 168 hours incubation. The results are discussed in relation to earlier work on the microbial activity of Antarctic soils and the sources of carbohydrate input into this ecosystem.     

Ross seal (<Emphasis Type="Italic">Ommatophoca rossii</Emphasis>) annual distribution,diving behaviour,breeding and moulting,off Queen Maud Land,Antarctica

Six out of ten adult Ross seals that were tagged with Argos satellite-linked dive recorders off Queen Maud Land, just after the moult in February, provided data on location and diving activity throughout a year. Shortly after tagging, the animals headed 2,000 km north and stayed pelagic in the area south of the Antarctic Polar Front, until October when they went south into the pack-ice. Throughout the year they made about 100 dives a day, most to a depth of 100–300 m, the deepest dive on record being 792 m, while some dives were very shallow during their stay in the pack-ice. Most dives, outside the breeding and moulting period, lasted for 5–15 min throughout the year. This diving behaviour is consistent with feeding on mid-water fish, like Pleurogramma antarcticum, squid, and to some extent krill (Euphausia superba), when in the pack-ice, and myctophid fish and several species of squid, when in the open ocean. The nursing period was 13 days in mid-November, and moulting occurs in late January–early February, which is the period when sightings surveys for this species should be done.     

Distribution of organic carbon and nitrogen in surface soils in the McMurdo Dry Valleys, Antarctica

The organic carbon and nitrogen contents of sediments in the upper 2 cm of the soils surrounding several lakes in the McMurdo Dry Valleys were measured in a relatively high-density sampling grid, in order to better understand the present-day distribution of organic matter in the ecosystem that is most readily transportable via aeolean processes. Carbon and nitrogen contents of the bulk sediments and size-differentiated sediments decreased in a series according to lake basins oriented along the Taylor Valley's main axis (Lake Fryxell > Hoare ≥ west lobe Bonney ≥ east lobe Bonney). Samples were also obtained around Lake Vida and showed this basin to contain less organic matter than those in the Taylor Valley. This regional spatial analysis supports the emerging view that each basin provides distinct environments for in situ microbial activity, lithogenic weathering, aeolian deposition and sorting that can be detected through synoptic sampling. Accepted: 2 August 1999     

Mobilization of non-exchangeable K by ryegrass in five Moroccan soils with and without mica

Intensive cropping of Italian ryegrass (Lolium multiforum L.) in pots was used to assess the contribution of non-exchangeable K to plant uptake. The soils used were: two soils high in mica (illite) developed on recent alluvium plus two smectitic (beidellitic) soils and a soil of mixed mineralogy rich in mica. Four K treatments were used (0, 28.6, 143, and 286 mg kg^-1 soil) with 8 successive monthly cuttings. A response of plant K uptake to added K was observed in all soils. Both 1.0 M NH₄0Ac and 0.2 M CaCl₂ extractable K were depleted to a minimum level specific for each soil. The minima were lower in the old upland soils compared to the young alluvial soils. Uptake of K by Italian ryegrass induced K release from the non-exchangeable K to replenish the plant available pool of K ions. The release of mica interlayer K in the alluvial and in the high K smectitic soil supplied sufficient K to plants even under intensive cropping. The rate of mobilization of interlayer K was low in the smectitic soil with lower K. The lowest release rate was in the old high mica soil. Iron coatings may have inhibited mobilization of interlayer K. The rates of mobilization cannot be predicted from mineralogical and K-extraction data only. The rates of K uptake and the rates of K release by ryegrass under intensive cropping are potential values which can be used for modelling K availability to plants in the soils studied.     

Microclimates and water budget of algae,lichens and a moss on some nunataks in Queen Maud Land

During the Norwegian Antarctic Expedition of 1984–1985, land parties worked in the area of Mühlig-Hofmannfjella and Gjelsvikfjella in Queen Maud Land (5° 20E, 1° 37W, 1000–1600 m a.s.l.). The nunataks in this area, which represents one of the climatic limits for terrestrial life on earth, is among those areas absorbing the highest quantity of shortwave radiation during a period of 24 h in summer. In spite of this the air temperature never, or very seldom, exceeds 0° C. The limiting factor for photosynthesis over most of the summer was water availability. Melt-water plays an important role in spring. During rest of the growth season, water from condensation is probably the most important water source for plants. On calm nights the rate of condensation during 6 h may reach 0.5 mm, which constitutes only 10%–30% of daily potential evapotranspiration. Plants situated in narrow clefts or shielded by stone blocks have the highest rate of potential photosynthesis. These locations are shielded from direct solar radiation most of the time, but the radiation from surrounding stone surfaces is higher than from the atmosphere and heat loss by turbulence is smaller than for exposed locations. These locations also probably have the highest rate of actual photosynthesis.     

Interannual meteorological variability and its effects on a lake from maritime Antarctica

The present study shows the occurrence of remarkable interannual variation in the meteorological conditions at Byers Peninsula (Livingston Island, South Shetlands Islands, Antarctica), in which one of the summers was significantly colder than the others. Within this climatic scenario, a limnological study was carried out at Lake Limnopolar during three consecutive summer seasons (2001/2002, 2002/2003 and 2003/2004). The year-to-year meteorological variation observed during this period resulted in marked differences in the timing and duration of the ice-free period. As a result, physical and chemical conditions changed and were followed by variations in the biological characteristics of the lake. More significant dissimilarities took place during summer 2003/2004 relative to the preceding years. This season was characterized by a delay of 55 or 25 days in the ice-out timing compared to 2001/2002 or 2002/2003, respectively, and also a much shorter ice-free period. Higher algal and bacterial abundances in the surface layers occurred at the onset of ice melting due to increases in nutrients and light availability. The trophic interactions could also be affected by ice-out timing, as a consequence of the prolongation of the ice-cover period. From our findings, we describe links between the meteorological variations during those 3 years and the shifts in the water bodies, pointing out their high sensitivity to environmental changes that may occur at different time-scales. Furthermore, our results emphasize how the interannual meteorological variability needs to be investigated as a triggering factor of the limnological variations to understand the effects of global change on limnetic ecosystems in Maritime Antarctica.     

Nectar, nectaries, flower visitors, and breeding system in five terrestrial Orchidaceae from central Argentina

Floral nectar sugar composition, nectary anatomy, and visitors are studied in five Argentine Orchidaceae, from 18 populations. Hand-pollinations were performed to evaluate their breeding system. We found two different types of perigonal nectaries located either in the spur (Habenaria gouriieana, H. hieronymi, Habenariinae), or in the basal lateral parts of the labellum (Beadlea dutraei, Pelexia bonariensis, Stenorrhynchos orchioides, Spiranthinae). The spur ofHabenaria is a nonvascularised and nonstructural nectary. The inner epidermis bears one-celled long papillae. In bud stage, the papillae are filled with starch grains, but when the flower opens and nectar secretion starts, they show no starch grains. This fact may indicate that starch is a source for some of the secreted nectar. In the remainder genera, the lateral basal parts of the labellum are secretory. The two glands are located in the adaxial basal lateral faces of the labellum. These nectaries are structural and nonvascularised.Stenorrhynchos produces abundant, concentrated nectar (40–50%).Habenaria gourlieana accumulates copious nectar in a lower concentration (<20%), whereas the other species produce small quantities of concentrated nectar (ca. 50%). Three of the studied species have sucrose predominant nectar (Beadlea dutrael, Habenaria gourlieana, andPelexia bonariensis) whileH. hieronymi, Stenorrhynchos orchioides have hexose predominant ones. Nectar removal and/or pollination induce flower senescence.H. gouriieana is visited by sphingids,S. orchioides by hummingbirds, andB. dutrael by bees. For the two other species we did not record flower visitors.Pelexia bonariensis, B. dutrael, andS. orchiodes are self-compatible species but a pollinator is needed.     

Climate change and Cognettia sphagnetorum: effects on carbon dynamics in organic soils

1. A microcosm experiment was performed to test the impacts of Cognettia sphagnetorum on carbon leaching in a cambic stagnohumic gley soil.
2. Leaching of dissolved organic carbon (DOC) was significantly enhanced by C.sphagnetorum, with the greatest effect being found in the upper, 0–6 cm, soil layers. The ratio of DOC to dissolved organic nitrogen (DON) in the leachate decreased in faunated systems, indicating that the enchytraeids were mobilizing carbon from organic matter with a low C to N ratio.
3. The vertical distribution of the enchytraeids had an effect on the production of DOC, and this vertical distribution is affected strongly by climate. It is proposed that increases in DOC found in a field soil-warming experiment with the same soil are largely a result of changes in the vertical distribution of these organisms.