Molecular differentiation by PCR-RFLP technique shows that Antarctic fishes of the genus Notothenia, claimed to be two species, are phenotypic varieties with the same genetic pattern (Table 1)

The taxonomy of Antarctic fishes has been predominantly based on morphological characteristics rather than on genetic criteria. A typical example is the Notothenia group, which includes N. coriiceps Richardson, 1844, N. neglecta Nybelin, 1951 and N. rossii Richardson, 1844. The Polymerase Chain Reaction and Restriction Fragment Length Polymorphism (PCR-RFLP) technique was used to determine whether N. coriiceps Richardson, 1844 and N. neglecta Nybelin, 1951 are different or whether they are the same species with morphological, physiological and behavioural variability. N. rossii was used as control. Mitochondrial DNA (mtDNA) was isolated from muscle specimens of N. coriiceps Richardson, 1844, N. neglecta Nybelin, 1951 and N. rossii, which were collected in Admiralty Bay, King George Island. The DNA was used to amplify a fragment (690 base pairs) of the mitochondrial gene coding region of NADH dehydrogenase subunit 2. Further, the amplicon was digested with the following restriction enzymes: DdeI, HindIII and RsaI. The results showed a variation of the digestion pattern of the fragment amplified between N. rossii, and N. coriiceps Richardson, 1844 or N. neglecta Nybelin, 1951. However, no differences were found between N. coriiceps Richardson, 1844 and N. neglecta Nybelin, 1951, on the grounds of the same genetic pattern shown by the two fish.

Fatty acids and intact polar lipids of laminated microbial sediments from St. Peter Ording, German Wadden Sea

Hidden for the untrained eye through a thin layer of sand, laminated microbial sediments occur in supratidal beaches along the North Sea coast. The inhabiting microbial communities organize themselves in response to vertical gradients of light, oxygen or sulfur compounds. We performed a fine-scale investigation on the vertical zonation of the microbial communities using a lipid biomarker approach, and assessed the biogeochemical processes using a combination of microsensor measurements and a 13C-labeling experiment. Lipid biomarker fingerprinting showed the overarching importance of cyanobacteria and diatoms in these systems, and heterocyst glycolipids revealed the presence of diazotrophic cyanobacteria even in 9 to 20 mm depth. High abundance of ornithine lipids (OL) throughout the system may derive from sulfate reducing bacteria, while a characteristic OL profile between 5 and 8 mm may indicate presence of purple non-sulfur bacteria. The fate of 13C-labeled bicarbonate was followed by experimentally investigating the uptake into microbial lipids, revealing an overarching importance of cyanobacteria for carbon fixation. However, in deeper layers, uptake into purple sulfur bacteria was evident, and a close microbial coupling could be shown by uptake of label into lipids of sulfate reducing bacteria in the deepest layer. Microsensor measurements in sediment cores collected at a later time point revealed the same general pattern as the biomarker analysis and the labeling experiments. Oxygen and pH-microsensor profiles showed active photosynthesis in the top layer. The sulfide that diffuses from deeper down and decreases just below the layer of active oxygenic photosynthesis indicates the presence of sulfur bacteria, like anoxygenic phototrophs that use sulfide instead of water for photosynthesis.

Feldspar Pb-isotope ratios for earliest Pleistocene sediments of the sub-polar North Atlantic Ocean

Relatively little is known in detail about the locations of the early Pleistocene ice-sheets responsible for ice-rafted debris (IRD) inputs to the sub-polar North Atlantic Ocean during intensification of northern hemisphere glaciation (iNHG). To shed new light on this problem, we present the first combined in-depth analysis of IRD flux and geochemical provenance of individual sand-sized IRD deposited in the sub-polar North Atlantic Ocean during the earliest large amplitude Pleistocene glacial, marine isotope stage (MIS) 100 (~2.52 Ma), arguably the key glacial during iNHG. IRD provenance is assessed using laser ablation lead (Pb) isotope analyses of single feldspar grains. We find that the Pb-isotope composition (206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb) of individual ice-rafted (>150 µm) feldspars deposited at DSDP Site 611A, ODP Site 981 and IODP Site U1308 during MIS 100 records a shift from predominantly Archaean-aged circum-North Atlantic Ocean continental sources during early glacial ice-rafting events to dominantly Palaeozoic and Proterozoic-aged sources during full glacial conditions. The distribution of feldspars in Pb-Pb space for full glacial MIS 100 more closely resembles that documented for feldspars deposited at the centre of the last glacial IRD belt (at IODP/DSDP Site U1308/609) during ambient (non-Heinrich-event) ice-rafting episodes of MIS 2 (~23.8 ka) than that documented for MIS 5d (~106 ka). Comparison of our early Pleistocene and last glacial cycle datasets suggests that MIS 100 was characterised by abundant iceberg calving from large ice-sheets on multiple continents in the high northern latitudes (not just on Greenland).

Meteorological measurements from the Fourcade and Polar Club Glacier, Warszawa Icefield, King George Island, West Antarctica

The South Shetland Islands are located at the northern tip of the AP which is among the fastest warming regions on Earth. The islands are especially vulnerable to climate change due to their exposure to transient low-pressure systems and their maritime climate. Surface air temperature increases (2.5K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, ice surface lowering and rapid break-up and disintegration of ice shelves. We have compiled a unique meteorological data set for the King George Island (KGI)/Isla 25 de Mayo, the largest of the South Shetland Islands. It comprises high-temporal resolution and spatially distributed observations of surface air temperature, wind directions and wind velocities, as well as glacier ice temperatures in profile with a fully equipped automatic weather station on the Warszawa Icefield, from November 2010 and ongoing. In combination with two long-term synoptic datasets (40 and 10 years, respectively) and NCEP/NCAR reanalysis data, we have looked at changes in the climatological drivers of the glacial melt processes, and the sensitivity of the inland ice cap with regard to winter melting periods and pressure anomalies. The analysis has revealed, a positive trend of 5K over four decades in minimum surface air temperatures for winter months, clearly exceeding the published annual mean statistics, associated to a decrease in mean monthly winter sea level pressure. This concurs with a positive trend in the Southern Annular Mode (SAM) index, which gives a measure for the strength and extension of the Antarctic vortex. We connect this trend with a higher frequency of low-pressure systems hitting the South Shetland Islands during austral winter, bringing warm and moist air masses from lower latitudes. Due to its exposure to the impact of transient synoptic weather systems, the ice cap of KGI is especially vulnerable to changes during winter glacial mass accumulation period. A revision of seasonal changes in adiabatic air temperature lapse rates and their dependency on exposure and elevation has shown a clear decoupling of atmospheric surface layers between coastal areas and the higher-elevation ice cap, showing the higher sensitivity to free atmospheric flow and synoptic changes. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0K/100 m), and a distinct spatial variability reflecting the impact of synoptic weather patterns. The observed advective conditions bringing warm, moist air with high temperatures and rain, lead to melt conditions on the ice cap, fixating surface air temperatures to the melting point. This paper assesses the impact of large-scale atmospheric circulation variability and climatic changes on the atmospheric surface layer and glacier mass accumulation of the upper ice cap during winter season for the Warszawa Icefield on KGI.