Late Holocene changes in cyanobacterial community structure in maritime Antarctic lakes

Despite the dominance of cyanobacteria in polar freshwater aquatic ecosystems, little is known about their past biodiversity and response to climate and environmental changes. We explored the use of light microscopy of microfossils, high performance liquid chromatography of the fossil pigment composition and denaturing gradient gel electrophoresis of fossil 16S rRNA genes to study past and present-day differences in cyanobacterial community structure in response to climate changes in two adjacent maritime Antarctic lakes with contrasting depths (4 and 26 m) and light climates. Light microscopy was of limited use because of degradation of cell structures. Fossil cyanobacterial pigment concentrations were below the detection limits of our method in several sediment samples in the deep lake, but abundant and diverse in the sediment core from the shallow pond, probably as a consequence of increased light availability and/or a more diverse and abundant benthic cyanobacterial flora. Total carotenoid and chlorophyll concentrations were highest in both lakes between ca. 2,950 and 1,800 cal yr BP, which coincides with the late Holocene climate optimum recognised elsewhere in maritime Antarctica. Cyanobacterial molecular diversity was higher in the top few centimeters of the sediments in both lakes. In deeper sediments, the taxonomic turnover of cyanobacteria appeared to be relatively small in response to past climate anomalies in both lakes, underscoring the broad tolerance of cyanobacteria to environmental variability. This, however, may in part be explained by the low taxonomic resolution obtained with the relatively conserved 16S rRNA gene and/or the preferential preservation of particular taxa. Our results highlight the potential of fossil DNA in lake sediments to study colonization and succession dynamics of lacustrine cyanobacteria and warrant further investigation of the factors that affect preservation of cyanobacterial DNA.     

A model of the gravitational field of Amalthea

Utilizing the topographic model of Jovian moon Amalthea (Stooke, 1994) and supposing that its mass density is constant we derived its basic geometrical and dynamical characteristics. For calculations the harmonic model of topography of the degree and order 18 was selected. The model appears to fit the entire surface to a mean accuracy of a few hundred meters, except in the regions localized around longitudes 0° and 180°. On the basis of the harmonic expansion of the topography we estimated the volume (V = 2.43 ± 0.02 km³) and the mean radius of topographyr ₀ = (79.7 ± 0.2) km. Generalized moments of inertia up to the order 2, principal moments of inertia and orientation of the principal axes with respect to the original reference frame were also calculated. The results show that although Amalthea has extremely irregular shape it may be treated dynamically as an almost symmetric body (B C). Finally, the set of the Stokes coefficients up to the degree and order 9 was evaluated. The results are verified by direct numerical integration.     

Pleurozium schreberi as bioindicator of mercury pollution in heavily industrialized region

This research is continuation of the investigation of metal accumulation in native and transplanted moss Pleurozium schreberi in the most industrialized and affected region in Poland (Upper Silesia). We tested the hypotheses that in Upper Silesia transplants of P. schreberi may be used in a 90 days bioindication experiment in case native specimens are absent; a 90 days exposure of transplanted P. schreberi was long enough for evaluation of Hg pollution of the environment. An assay was carried out with native mosses at 27 polluted sites and mosses from an uncontaminated control site transplanted to the same 27 polluted sites. P. schreberi collected from the same sites as classified for more and less polluted basing on Pb and Zn concentrations show quite different pattern of pollution with mercury; The accumulation of Hg by the transplants increased much faster in the first 45 days of the experiment (accumulation factor 1.5–6.7; mean 3.4?±?0.5) in comparison with the second period from day 45 to 90 (accumulation factor 1.0–1.6; mean 1.2?±?0.1). The 90 days exposure of transplanted P. schreberi was long enough for evaluation of Hg pollution of the environment. Transplants of P. schreberi may be used in a 90 days bioindication experiment in case native specimens are absent.     

Do mowing regimes affect plant and soil biological activity in the mountain meadows of Southern Poland?

The soil biological activity of mountain meadows is a significant factor that determines the health and utility of these regions. The climax stage of this area is forest, but to maintain semi-natural grassland, which is characterised by high biodiversity,low-intensity land use(mowing or grazing) is necessarily required. To understand the effect of various mowing regimes on the soil biological activity and plants, the soil microbial activity(microbial biomass carbon, dehydrogenase activity and number of the cultivable fraction of soil microbial community),annelids community(density and species composition earthworms and enchytraeids) and plant species composition were investigated. The study area was located in the Pieniny National Park in the Carpathian Mountains, in a meadow belonging to the association Dactylis glomerata-Poa trivialis. The investigated variants were divided according to mowing regime:traditional scything – hand mowing(HM), mechanical mowing(MM), or the abandonment of mowing – nonmowing(NM). The microbial activities(expressed by,e.g. microbial biomass carbon and the number of phosphorus bacteria) were affected by the mowing regime. The density of earthworms was higher in the HM and MM than in the NM variants. The largest changes in plant species composition were caused by the abandonment of mowing(NM). The mean number of plant species was positively correlated with soil moisture, earthworm density, and microbial activity(expressed indirectly by dehydrogenases activity). The soil microbial community, such as vegetative bacteria forms and ammonifying bacteria,were positively associated with pH value, and the microbial and total organic carbon content. The results presented here indicate that there is no single form of optimal management for all living organisms.Decisions about mowing regimes, or abandonment of use, should be preceded by multi-aspect studies,including plants and soil biota.     

Measurement of aerosol optical thickness over the Atlantic Ocean and in West Antarctica, 2006–2007

In this paper, optical measurements of aerosol properties made during a ship cruise from Poland to Antarctic Station in September and October 2006, and during the cruise back to Gdynia in April and May 2007 are described. A large gradient of pollution between the clear South Atlantic and the dusty North Atlantic was observed. The maximum of aerosol optical thickness at a wavelength of 500 nm reached 0.4 at 20°N in September 2006 and 0.3 at 40°N in May 2007, respectively. Strong Saharan dust transport is suggested as an explanation for the small values of Ångström exponent observed (values of 0.2 and 0.4 on these respective dates). On the Southern Hemisphere the aerosol optical thickness at 500 nm ranged from 0.05 to 0.2. Significant increases of the aerosol optical thickness were associated with strong wind and sea salt production. Good agreement was found when the in situ measurements of aerosol optical thickness were compared to satellite retrievals and modelling results.     

Remnants of altered meteorite in the Cretaceous‐Paleogene clay boundary in Poland

Fossil iron meteorites are extremely rare in the geological sedimentary record. The paleometeorite described here is the first such finding at the Cretaceous‐Paleogene (K‐Pg) boundary. In the boundary clay from the outcrop at the Lechówka quarry (Poland), fragments of the paleometeorite were found in the bottom part of the host layer. The fragments of meteorite (2–6 mm in size) and meteoritic dust are metallic‐gray in color and have a total weight of 1.8181 g. Geochemical and petrographic analyses of the meteorite from Lechówka reveal the presence of Ni‐rich minerals with a total Ni amount of 2–3 wt%. The identified minerals are taenite, kamacite, schreibersite, Ni‐rich magnetite, and Ni‐rich goethite. No relicts of silicates or chromites were found. The investigated paleometeorite apparently represents an independent fall and does not seem to be derived from the K‐Pg impactor. The high degree of weathering did not permit the chemical classification of the meteorite fragments. However, the recognized mineral inventory, lack of silicates, and their pseudomorphs and texture may indicate that the meteorite remains were an iron meteorite.     

New possibilities in controlled-source seismology with a magnetic levitation vibrator

Summary. A new-technology, broad-band seismic land source based on the principle of magnetic levitation is under development. The new source is designed to overcome limitations experienced with controlled-signal seismic sources at the present time, and to create new possibilities. In particular, She new source extends the constant peak force frequency band down to 2 Hz, and is capable of at least several weeks continuous, coherent transmission. It will enable three-dimensional long-range (>200 km) controlled-signal seismology with the potential for active earth tomography down into the mantle and systematic earthquake precursor measurement, and should improve shallow and deep seismic profiling technology. The optimum transmission frequencies depend on Q, transmission range, and noise spectrum.