Results of a sediment profile and water analyses from Lake Hancza in northeastern Poland

We investigated the sedimentary record of Lake Hancza (northeastern Poland) using a multi-proxy approach, focusing on early to mid-Holocene climatic and environmental changes. AMS 14C dating of terrestrial macrofossils and sedimentation rate estimates from occasional varve thickness measurements were used to establish a chronology. The onset of the Holocene at c. 11600 cal. a BP is marked by the decline of Lateglacial shrub vegetation and a shift from clastic-detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation. Between 10000 and 9000 cal. a BP, a further environmental and climatic improvement is indicated by the spread of deciduous forests, an increase in lake organic matter and a 1.7% rise in the oxygen isotope ratios of both endogenic calcite and ostracod valves. Rising d18O values were probably caused by a combination of hydrological and climatic factors. The persistence of relatively cold and dry climate conditions in northeastern Poland during the first one and a half millennia of the Holocene could be related to a regional eastern European atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the retreating Scandinavian Ice Sheet might have blocked the influence of warm and moist Westerlies and attenuated the early Holocene climatic amelioration in the Lake Hancza region until the final decay of the ice sheet.

Environmental status of the Lake Michigan region /

Vols. 7, 9 and 15, issued in 1974, prepared for the U. S. Atomic Energy Commission; vols. issued 1975- prepared for the U. S. Energy Research and Development Administration.

Phytoplanktonic microfossil groups of sediments from the South and Equatorial Atlantic

Individual planktonic microfossil species, or assemblage groups of different species, are often used to, qualitatively and/or quantitatively, reconstruct past (sub)surface-water conditions of the world's oceans and seas. Until now, little information has been available on the surface sediment distribution patterns and paleoenvironmental reconstruction potential of coccolith, calcareous dinoflagellate cyst and organic-walled dinoflagellate cyst assemblages of the South and equatorial Atlantic, especially at the species level. This paper (i) summarizes the distributions of these three phytoplanktonic microfossil groups in numerous Atlantic surface sediments from 20°N-50°S and 30°E-65°W and determines their relationship with the physicochemical and trophic conditions of the overlying (sub)surface-waters, and (ii) determines the synecology of the three phytoplankton groups by carrying out statistical analyses (i.e. detrended and canonical correspondence analyses) on all groups simultaneously. Ecological relationships are additionally strengthened by statistically comparing the distribution patterns of the phytoplankton groups with those of planktonic foraminifera (Pflaumann et al. 1996; Niebler et al. 1998), as the ecological preferences of the latter are much better known. Many of the analyzed phytoplanktonic microfossil species or groups of species in the surface sediments do show restricted distributions which primarily reflect the environmental conditions of the upper water masses above them (e.g. sea-surface temperature, productivity, stratification). The acquired 'reference' data sets are large and diverse enough to allow future development of transfer functions for the reconstruction of past surface-water conditions, and show that there is still an enormous paleoenvironmental reconstruction potential concealed in many fossil coccolith and dinoflagellate cyst assemblages.

Population dynamics and net primary production of the aquatic macrophite Nymphaea rudgeana C. F. Mey in a lotic environment of the Itanhaém River basin (SP, Brazil)

Neste trabalho, foi estudada a dinâmica populacional e estimada a produção primária líquida da macrófita aquática Nymphaea rudgeana em um braço do rio Itanhaém (Estado de São Paulo, Brasil). Esta espécie apresenta uma ampla variação anual de biomassa, em função da estação do ano, no local estudado. A partir do mês de novembro (13,1 g PS/m²), pode ser observado um aumento gradual da biomassa, atingindo o máximo em fevereiro (163,1 g PS/m²). Posteriormente, a biomassa diminui, mantendo-se em níveis baixos até um novo período de crescimento. A diminuição de biomassa está associada ao desenvolvimento de macrófitas flutuantes (Pistia stratiotes e Salvinia molesta) e, subseqüentemente, às condições ambientais desfavoráveis (valores de salinidade elevados) ao seu desenvolvimento. A produção primária líquida de N. rudgeana foi obtida a partir dos dados de biomassa e seu valor é estimado entre 3,02 e 3,82 t/ha/ano.

Pollen and macrofossils profiles and age determination from the Pittsburg Basin in the lowlands of south-central Illinois

Pollen and macrofossil evidence for the nature of the vegetation during glacial and interglacial periods in the regions south of the Wisconsinan ice margin is still very scarce. Modern opinions concerning these problems are therefore predominantly derived from geological evidence only or are extrapolated from pollen studies of late Wisconsinan deposits. Now for the first time pollen and macrofossil analyses are available from south-central Illinois covering the Holocene, the entire Wisconsinan, and most probably also Sangamonian and late Illinoian time. The cores studied came from three lakes, which originated as kettle holes in glacial drift of Illinoian age near Vandalia, Fayette County. The Wisconsinan ice sheet approached the sites from the the north to within about 60 km distance only. One of the profiles (Pittsburg Basin) probably reaches back to the late Illinoian (zone 1), which was characterized by forests with much Picea. Zone 2, most likely of Sangamonian age, represents a period of species-rich deciduous forests, which must have been similar to the ones that thrive today south and southeast of the prairie peninsula. During the entire Wisconsinan (14C dates ranging from 38,000 to 21,000 BP) thermophilous deciduous trees like Quercus, Carya, and Ulmus occurred in the region, although temporarily accompanied by tree genera with a more northerly modern distribution, such as Picea, which entered and then left south-central Illinois during the Woodfordian. Thus it is evident that arctic climatic conditions did not prevail in the lowlands of south-central Illinois (about 38°30' lat) during the Wisconsinan, even at the time of the maximum glaciation, the Woodfordian. The Wisconsinan was, however, not a period of continuous forest. The pollen assemblages of zone 3 (Altonian) indicate prairie with stands of trees, and in zone 4 the relatively abundant Artemisia pollen indicates the existence of open vegetation and stands of deciduous trees, Picea, and Pinus. True tundra may have existed north of the sites, but if so its pollen rain apparently is marked by pollen from nearby stands of trees. After the disappearance of Pinus and Picea at about 14,000 BP (estimated!), there developed a mosaic of prairies and stands of Quercus, Carya, and other deciduous tree genera (zone 5). This type of vegetation persisted until it was destroyed by cultivation during the 19th and 20th century. Major vegetational changes are not indicated in the pollen diagram for the late Wisconsinan and the Holocene. The dating of zones 1 and 2 is problematical because the sediments are beyond the14C range and because of the lack of stratigraphic evidence. The zones dated as Illinoian and Sangamonian could also represent just a Wisconsinan stadial and interstadial. This possibility, however, seems to be contradicted by the late glacial and interglacial character of the forest vegetation of that time.