Pollen-based quantitative reconstructions of Holocene climate variability in NW Romania

A modern analogue technique is applied to two high-resolution pollen sequences from NW Romania to provide the first quantitative evidence for winter, summer and annual temperatures and for precipitation across the Holocene in this region.

The pollen-based climate reconstructions allow the identification of four main intervals: i) an early, less stable period between 11,700 and 11,200 cal. yr BP; (ii) generally stable conditions between 11,200 and 8300 cal. yr BP with winter and annual temperatures and precipitation higher than at present, and summer temperatures about the same; (iii) lower winter and annual temperatures, and higher summer temperatures and precipitation between 8000 and 2400 cal. yr BP; (iv) warmer winter and annual temperatures and lower precipitation for the last 2400 years, whereas summer temperatures became cooler at Steregoiu and remained stable at Preluca Tiganului.

The pollen-based climate reconstructions at the two sites show similar patterns in annual and winter temperatures and precipitation changes during the Holocene, but the trends appear to be less consistent for summer temperatures.

Our pollen-based reconstructions revealed several short-term climatic oscillations during the Holocene, the strongest of which occur between 10,300–10,100, 8300–8000, 6800–6400, 5100–4900, 4000–3600 and 3200–3000 cal. yr BP.     

A late pleistocene and holocene vegetation and environmental record from Lake Wangoom, Western Plains of Victoria, Australia

Pollen, microfaunal and sedimentological evidence from the top 20 m of sediment in a closed volcanic crater lake is used to construct a detailed record of vegetation and environmental conditions through the Holocene and a substantial part of the Late Pleistocene. Radiocarbon dating suggests that the sequence covers tha last 51,000 yr or so. High lake-levels and the presence of forest or woodland vegetation indicate that the Holocene and the basal few thousand years of the record experienced wet and warm conditions. The earliest period was succeeded by a long phase of lower but variable moisture levels before more arid conditions resulted in the replacement of forest and woodland by herbaceous vegetation and frequent lake drying. Periods of slight amelioration occurred between about 27,000 and 19,000 and before 15,000 radiocarbon yr ago. Maximum aridity occurred between about 19,000 and 10,000 yr B.P., a period incorporating the height of the last glacial. During the Pleistocene, the lake became gradually more saline but has been fresh during the Holocene, even under low lake-levels.

An increase in charcoal values is recorded, probably around 20,000 years ago, and this could have resulted from increased burning as a result of the activities of Aboriginal people. This may have also caused a change in understorey vegetation from one composed largely of Asteraceae, to grassland.

The record is compared with others from southeastern Australia and there is good correspondence through the last 20,000 or 30,000 yr but, before this, problems of dating and the condensed nature of most sequences prevent detailed correlation.     

Southern kalahari phytosociology

Summary The vegetation of the Kalahari Gemsbok National Park, which lies in the centre of the semi-arid Southern Kalahari, was studied. This area is considered to be largely representative of the Southern Kalahari in general. The region is covered by a layer of red sand piled into dunes. Two large dry river-beds cross the area and numerous pans occur. Calcrete outcrops are found along rivercourses and around pans. The vegetation is generally an extremely open shrub or tree savanna and phytogeographically the area is regarded as belonging to the Karoo-Namib Region. 132 quadrats, most of which covered 100 m², were studied and the vegetation is classified according to the Zürich-Montpellier method. The physiognomy of all phytocoenoses was determined according to the system ofFosberg (1967). A striking correlation was found between plant communities and the four main habitats: sand, calcrete, pans and river-beds. Twelve syntaxa were recognized, eight of these are described as associations and one as a subassociation. They are as follows:— 1. On sand: Stipagrostietum amabilis (with subass. terminalietosum) found on dune crests, Hirpicio echini-Asthenatheretum on more compact red sand in dune valleys, Monechma incanum-Stipagrostis ciliata (two communities) on pink to whitish sand, Peliostomo-Stipagrostietum obtusae on whitish compact sand; 2. On calcrete: Aizoo-Indigoferetum auricomae; 3. On pans and pan-like formations: Sporobolo lampranthi-Zygophylletum tenuis on pan-like alluvial flats in the Nossob rivercourse, Sporoboletum coromandelianion the central parts of pans, Sporoboletum rangei along the periphery of pans and on sand accretions on the pan surface, Lycium tenue community on small loamy sand accretions on pans or in river-beds; 4. In river-beds: Panicetum colorati. Life form spectra based on total cover-abundance values are given. Differences in the spectra of various communities are briefly discussed with reference to their habitats. Therophytes were shown to be the most important life form in all syntaxa except the Sporoboletum rangei. The vegetation exhibits a very marked zonation and a sequential relationship between communities is demonstrated.

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Zusammenfassung Die Vegetation des Kalahari Gemsbok Nationalparks, welcher im Zentrum der semi-ariden Südlichen Kalahari gelegen ist, wurde untersucht. Der Park wird als weitgehend typisch für die gesamte Südliche Kalahari betrachtet. Das Gebiet wird von einer Sandschicht bedeckt die zu Dünen aufgeworfen ist. Zwei grosse Flussbetten durchqueren das Gebiet und zahlreiche Pfannen werden angetroffen. Oberfl?chenkalk kommt l?ngs den Flussl?ufen und um Pfannen herum vor. Die Vegetation ist im allgemeinen eine extrem offene Strauch- oder Baumsavanne und phytogeographisch wird das Gebiet zur Karoo-Namib Florenregion gerechnet. 132 Relevés, von denen die meisten eine Oberfl?che von 100 m² hatten, wurden aufgenommen, und die Vegetation wurde nach der Zürich-Montpellier-Methode klassifiziert. Die Physiognomie aller Phytoz?nosen wurde nach dem System vonFosberg (1967) bestimmt. Eine auffallende Wechselbeziehung zwischen Pflanzengesellschaften und den folgenden vier wichtigsten Standorten wurde festgestellt: Sand, Kalk, Pfannen und Flussbetten. Zw?lf Syntaxa wurden erkannt, wovon acht als Assoziationen und eine als Subassoziation beschrieben werden. Sie sind die folgenden: (1) Auf Sand: Stipagrostietum amabilis (mit Subass. terminalietosum) auf Dünenk?mmen, Hirpicio echini-Asthenatheretum auf kompakterem roten Sand in Dünent?lern, Monechma incanum-Stipagrostis ciliata (zwei Gesellschaften) auf rosa bis weisslichem Sand, und Peliostomo-Stipagrostietum obtusaeauf weisslichem kompaktem Sand; (2) Auf Oberfl?chenkalk: Aizoo-Indigoferetum auricomae; (3) Auf Pfannen und pfannenartigen Formationen: Sporobolo lampranthi-Zygophylletum tenuis auf pfannenartigen Alluvialfl?chen im Flusslauf des Nossob, Sporoboletum coromandeliani im Zentrum von Pfannen, Sporoboletum rangei auf Pfannenr?ndern und auf Sandanh?ufungen auf Pfannenoberfl?chen, Lycium tenue-Gesellschaft auf kleinen lehmigen Sandanh?ufungen auf Pfannen oder in Flussbetten; (4) In Flussbetten: Panicetum colorati. Lebensformspektren, die auf Artm?chtigkeitswerten basieren, sind in Diagrammen für die verschiedenen Syntaxa zusammengestellt. Unterschiede zwischen den Spektren der verschiedenen Gesellschaften werden besprochen mit Bezug auf ihre Standorte. Therophyten sind in allen Syntaxa, mit Ausnahme des Sporoboletum rangei, die wichtigste Lebensform. Die Vegetation l?sst deutliche Zonierung erkennen. Es wird gezeigt in welcher wechselseitigen Beziehung die Gesellschaften zueinander stehen.

     

Paleoenvironmental implications of fixed dune systems in Southern Africa

Extensive systems of fixed linear dunes occur in the Kalahari region of southern Africa, from 28°S to 16°30′S. They provide evidence for large-scale expansion of arid climates in the subcontinent during the Quaternary. On the basis of differing dune morphologies and alignments, three periods of Upper Pleistocene aridity are recognised.Patterns of dune alignments reflect paleosand flow regimes and permit deduction of past winds and circulation patterns, leading to the conclusion that arid episodes were associated with, and probably caused by, greater strength and persistence of the South African anticyclone.A tentative chronology of the arid periods tends to support the hypothesis that subtropical aridity was contemporaneous with glacial conditions in high latitudes.     

The Quaternary eolian sequence of Madeira: stratigraphy, chronology, and paleoenvironmental interpretation

A thick (ca. 40 m) sequence of coastal eolian sediments occurs on a narrow peninsula on the eastern end of the island of Madeira, located in the Eastern Atlantic at 33°N latitude. The sediments consist of black volcanic sands (with or without bioclasts) as well as clay units up to 2 m thick. A series of inceptisols (Eutrochrepts) and one alfisol (a Hapludalf) are developed in these sediments. Land snail shells and secondary carbonates, in the form of well-developed rhizoliths, calcretes, fissure-fills, and soil nodules, are present in abundance. The chronology of the sequence was determined by ¹⁴C and U---Th analyses of land snail shells and secondary carbonates and amino acid epimerization analysis of land snail shells. All sediments, including the clay units, are originally of eolian origin, derived from the beach to the south of the deposit, but some have been redeposited by colluviation. Temporal variation in the lithology of the sediments relates to variations in sea-level, with black sands being deposited during lower sea level stands and clays at the lowest. It is suggested that fine marine sediments, exposed during low sea-level stands, may also be the dominant source of silty or clayey units in other coastal eolian deposits in the subtropical Atlantic and Mediterranean.

The sequence spans from 200,000–300,000 years ago up to the 20th century. Sedimentation was discontinuous and often rapid; erosional hiatuses are present. During the Holocene, eolian sands started accumulating at 8200 yr B.P. during a transgressive phase and stopped at 4500 yr B.P. as sea level approached its present height. Colluviation increased dramatically following the first human settlement of the island in the 15th century and continued up to the 20th century, as dated by amino acid epimerization analysis of land snails. Earlier periods of colluviation were identified from the age distribution of land snail shells redeposited in younger colluvium.

Paleoenvironmental reconstruction was based mainly on soil and sediment features (including rhizolith morphology) and land snail faunas but also on stable isotope variations (¹³C, ¹⁸O) in land snails and secondary carbonates, pollen (generally not well preserved), and phytoliths. Most of the portion of the Middle Pleistocene represented in the sequence was characterized by moderately dry conditions, in comparison to the late Pleistocene and Holocene. During the last interglacial, relatively wet conditions occurred, wetter than during the Holocene interglacial. Moderately moist conditions were present during the accumulation of the thick unit dating to ca. 80,000 yr B.P. As sea level fell subsequent to this period, conditions appear to have become drier. Starting ca. 50,000–55,000 yr B.P., conditions were especially wet, but prior to the last glacial maximum, markedly arid conditions ensued. Toward the end of the last glacial, wet conditions returned and produced the best-developed soil preserved in the sequence. Moderately moist conditions occurred during the early to middle Holocene but apparently become slightly drier after 4500 yr B.P. The impact of human settlement can be seen in the loss of woody vegetation and enhanced gullying and colluviation during the last ca. 500 years.     

Age-related changes in 11β-hydroxyandrostenedione concentration in normal and osteoporotic women

The secretion of dehydroepiandrosterone (DHEA) and its sulfate is known to decline gradually with advancing age. Furthermore DHEA is known to be significantly lower in osteoporotic subjects than in normals. Recently 11β-hydroxyandrostenedione (11-OHA) has been proposed as an important indicator of the adrenal source of hormone excess in different hyperandrogenic states. In the present study we measured 11-OHA in 224 normal women aged 20–79 yr and 130 osteoporotic women aged 40–79 yr. RIA of 11-OHA was performed with highly specific antiserum raised in rabbits.

The mean 11-OHA serum concentration was 2.20±0.90 ng/ml in normal women and 1.75±0.58 ng/ml in osteoporotic women. In contrast to DHEA there was no age-related decrease in 11-OHA serum concentrations in normal and osteoporotic women. Osteoporotic subjects showed statistically significantly lower 11-OHA serum concentrations than normal women. Therefore low serum 11-OHA might represent a further risk factor for osteoporosis.     

A 36,000-yr vegetation history from the Peloncillo Mountains, southeastern Arizona, USA

A 36,200 cal yr B.P. vegetation history was developed from macrofossils and pollen from 55 packrat middens from 1287 to 1442 m elevation in the Peloncillo Mountains of southeasternmost Arizona, USA. Today, these elevations are dominated by semidesert grassland with a mixture of Chihuahuan and Sonoran Desert shrubs, including an eastern disjunct population of jojoba (Simmondsia chinensis). From 36,200 to 15,410 cal yr B.P., rocky areas just above large, pluvial lakes that occupied what are now dry playas supported Pinus edulis, Juniperus osteosperma, Juniperus cf. coahuilensis, Quercus cf. turbinella and a rich understory of summer-flowering C₄ annuals and grasses, indicating abundant summer rains and mild winters. After  15,410 cal yr B.P., P. edulis declined in abundance and disappeared briefly at 13,925 cal yr B.P., coincident with expansion of more xeric species and paleohydrological evidence for regional aridity during the Bølling–Allerød warm interval. P. edulis rebounded briefly during the Younger Dryas at 12,405 cal yr B.P. before disappearing along with other mesic woodland species sometime after 12,100 cal yr B.P. The few middens dating from the early to middle Holocene (10,000–4000 yr B.P.) indicate wetter conditions than today at 7790 cal yr B.P. followed by a general drying trend. The 35 middens from the late Holocene detail the sequential arrival of desertscrub species as vegetation became more modern in character.     

Wet dune slacks: decline and new opportunities

For a number of infiltrated coastal dune areas it is discussed to what extent artificial infiltration for the public water supply affects the quality of soil, groundwater and vegetation around pools and ponds, and what its effect is on the vegetation. Further, the results of investigations into the quality of vegetation, soil and water of a number of non-infiltrated, less affected dune areas are presented. The emphasis is on changes in groundwater flow pattern and on changes in the chemical composition of groundwater on the vegetation of wet dune slacks. Finally, recommendations for the management of wet dune slacks are presented. It can be concluded that the introduction of nutrients through infiltration causes an abundance of nitrophilous herbaceous vegetation along the banks of all infiltration ponds and most dune pools. Of the three investigated macro-nutrients, nitrate, potassium and phosphate, the latter shows the most significant correlation with the composition, cover and biomass of the vegetation. The moist biotopes of non-infiltrated dunes have largely disappeared because of desiccation, mainly as a consequence of water withdrawal, afforestation and coastal erosion. Relatively unaffected dune slacks can be found in the dunes on the Dutch Wadden Sea islands and a small number of dune areas on the mainland. In most areas, however, a serious decline in many rare species has been observed during the past twenty years because of eutrophic and acid precipitation, often in combination with disturbances of the groundwater regime.     

Prodynorphin processing by rat CNS fractions and purified enzymes: Formation of Dynorphin A 1–8 by sulfhydryl-activated carboxypeptidase and peptidyl dipeptidase

The conversion of selected prodynorphin fragments to form the octapeptide Dynorphin A 1–8 was studied in rat brain or spinal cord fractions, and the results compared to the action of purified carboxypeptidases and angiotension converting enzyme. The particulates were shown to convert Dynorphin A or 1–13 to the octapeptide as measured by radioimmunoassay, and by reverse phase high performance liquid chromatography. Detergent extracts of these particulates contained and enzyme converting 1–13 to 1–12 with release of C-terminal lysine, and active over a wide pH range of 4.8–7.6. Purification of these extracts by affinity chromatography (p-amino-benzoyl-arginine-Sepharose-6B) using Bz-Ala-Arg as the substrate led to isolation of a carboxypeptidase converting 1–13 to 1–12 active over the same pH range. Since Dynorphin 1–13 was converted to 1–8 by the consecutive use of purified carboxypeptidase B and angiotensin converting enzyme, the possibility exists that this mechanism might account for some octapeptide production in situ.

The properties and substrate specificity of the carboxypeptidase B were compared to a carboxypeptidase A active optimally at pH 5.5 and assayed with Z-Glu-Tyr. The carboxypeptidase B acted only on prodynorphins with C-terminal basic residues as contrasted to a nonspecific action by the carboxypeptidase A. The carboxypeptidase B was characterized by a strong activation by -SH agents and Zn²⁺, and thus could be differentiated from other opioid converting enzymes. The enzyme was inhibited by guanidinoethyl succinic acid (GEMSA), and p-chloromercuriphenyl-sulphonic acid (PCMS) but not by benzylsuccinic acid, a potent inhibitor of carboxypeptidase A.     

Latest Quaternary oceanographic changes in the Okhotsk Sea based on diatom records

The Okhotsk Sea is a locus of the North Pacific Intermediate Water formation today. The formation of the Okhotsk Intermediate Water is linked with seasonal sea-ice cover. Diatom records from the Okhotsk Sea show the following. (1) During the last glacial maximum (between 21,000 yr B.P. and 18,000 yr B.P.), sea ice covered the western side of the sea throughout the whole year, but the eastern part was open. This permitted more efficient heat exchange with the atmosphere than waters and hence ventilation of the glacial Okhotsk Sea waters which in turn caused a greater extent of Intermediate Water formation through the Bussol' Strait. (2) The perennial sea-ice cover extended northward, and sea ice was present throughout the whole year over a great part of the sea except for the eastern part between 18,000 yr B.P. and 17,000 yr B.P. (3) The ice-free area extended greatly to the south during the interval between 17,000 yr B.P. and 11,000 yr B.P. (4) There was no perennial ice cover over the whole sea, and the ice-free area that appeared as the seasonal ice area began to extend to the western part between 11,000 yr B.P. and 8,000 yr B.P. (5) After 8000 yr B.P. the ice-free waters contracted to the present extent.     

Dune slack restoration in Dutch mainland coastal dunes

The 45,000 ha Dutch dunes are relatively well protected but they suffer from severe desiccation. During the last decade a lot of knowledge has been obtained about the steering processes of eco-hydrology in dunes resulting in well-founded schemes to restore wet dune slack communities. In two case studies a large-scale restoration of the landscape was necessary. Since 1987 in the North-Holland Dune Reserve the groundwater catchment has been reduced (from 8 million m³ to 2 million m³ per year) and the resulting development monitored. In another case, large-scale intervention on 35 ha of the Amsterdam Water Supply Dunes in 1995 resulted in the restoration of active sand drift with opportunities for the establishment of pioneer vegetation. In small parts of the area, the surface has stabilised as a result of vegetation growth, but elsewhere drifting sand has spread and covered previously stable surfaces. Many wet to moist dune slacks developed and results relating to geomorphology, hydrology and vegetation are presented. Finally, in 1996 yet another project of 50 ha was carried out in the Meijendel dunes, in which infiltration ponds were removed to allow vegetation succession to develop from scratch. Results of these three case studies will be presented. If only hydrological restoration is carried out, sod-cutting was found to be necessary to restore the whole series of vegetation types of dune slacks. In two cases an area was denuded. The seed bank and surrounding slacks seem to play an important role in the success of restoration, this is especially true for the pioneer vegetation types. Future monitoring will prove whether critical (Red List) plant species will return.     

Sources and accumulation rates of organic carbon in an equatorial peat bog (Burundi, East Africa) during the Holocene: carbon isotope constraints

The relationship between organic carbon accumulation rates and ¹³C/¹²C ratios of total organic carbon (TOC) was investigated in an highland peat bog core (Ru-3) from Equatorial Africa. This core yielded a sequence spanning the last 14 kyr and was analysed with a 100–300 yr resolution for TOC-δ¹³C values. The Holocene section shows contrasted TOC accumulation regimes and TOC δ¹³C varying between −28.5 and −19.5‰ with a few very short ‘isotopic excursions' (dated at ca. 9.3, 7.5, 4.2 ka B.P.). The organic carbon accumulation rates range from 2 to 20 mg C cm⁻² yr⁻¹. They increase when TOC becomes more depleted in ¹³C, notably between 12 and 9.8 ka B.P., 8.5 and 7.8 ka B.P. and after 1.6 ka B.P. Periods of restricted carbon storage correspond to heavier TOC accumulation at 9.3, and between 7.5 and 1.6 ka B.P. At the study site, the δ-variations can be related to variable C4-plant inputs, and possibly, to changes in the fractionation between CO₂ and the organic carbon in C3 vascular plants. The Ru-3 record indicates restricted carbon storage during the periods of increased contribution from C4 plants and/or of decreased fractionation between CO₂ and organic carbon in C3 plants. Changes in TOC-δ¹³C values in core Ru-3 seem to match fluctuations of East Equatorial African lakes. High lake stands correspond to low δ¹³C intervals and vice versa. This points to indirect climatic forcing of δ¹³C changes in intertropical peats.     

Plasma selenium levels in healthy blood bank donors in the central-eastern part of Belgium

Graphite furnace atomic absorption spectrometry, with Zeeman background correction and after improved matrix modification, was used to measure the plasma selenium content of healthy blood bank donors in the central part of Belgium.

The mean plasma selenium concentration of 80 men and 80 women was 79.7±4.4 ng/mL with a range of 55.0–117.4 ng/mL.

There was no gender difference observed. Plasma selenium level was significantly highest for the adult group, aged 45–64 years, compared to the others, except the young adults (18–24 years).

The mean plasma selenium concentration measured corresponded well with literature data for Belgium. The obtained values were found to be in the medium range, compared with recent literature values for the European countries.     

The dimerization of protochlorophyll pigments in non-polar solvents

The infrared, visible and nuclear magnetic resonance spectra of protochlorophyll a and vinylprotochlorophyll a in dry non-polar solvents (carbon tetrachloride, chloroform, cyclohexane) are presented and interpreted in terms of dimer interaction.

The infrared spectra in the 1600–1800 cm⁻¹ region clearly show the existence of a coordination interaction between the C-9 ketone oxygen function of one molecule and the central magnesium atom of another molecule. Infrared spectra in the OH stretching region (3200–3800 cm⁻¹) provide a valuable test of the water content in the samples.

The analysis of the absorption and circular dichroism spectra of protochlorophyll a and vinylprotochlorophyll a in carbon tetrachloride demonstrates the existence of a monomer-dimer equilibrium in the concentration range from 10⁻⁶ to 5 · 10⁻⁴ M. The dimerization constants are (6±2) · 10⁵ 1 · M⁻¹ for protochlorophyll a and (4.5±2) · 10⁵ 1 · M⁻¹ for vinylprotochlorophyll a at 20 °C. The deconvolution of visible spectra in the red region has been performed in order to obtain quantitative information on the dimer structure. Two models involving a parallel or a perpendicular arrangement of the associated molecules are considered.

From ¹H NMR spectra, it appears that the region of overlap occurs near ring V, in agreement with the interpretation of the infrared spectra.     

Effects of defined synthetic phospholipids on glycosylation processes. Modifications of membrane-bound N-acetylglucosaminyl-transferase and solubilized sialyl-transferase activities

In cultures of hamster embryo cells, benzo[a]pyrene (B[a]P) is metabolized primarily in the bay region. In contrast, little or no bay region metabolism of the noncarcinogenic isomer benzo[e]pyrene (B[e]P) could be detected during 12–96-h incubations of hamster embryo cells with 4 μM [³H]B[e]P. The upper limit to 9,10-dihydro-9,10-dihydroxy-B[e]P formation is about 0.2% of the ethyl acetate-soluble metabolites ( <0.1% of the total metabolites). The major identified metabolites of B[e]P were 4,5-dihydro-4,5-dihydroxy B[e]P and the glucuronide conjugates of 3-OH-B[e]P and 4,5-dihydro-4,5-dihydroxy B[e]P. Simultaneous treatment of cells with either B[a]P or 7,8-benzoflavone (BF) did not induce bay region metabolism of [³H]B[e]P.     

Fluorescence of bacteriochlorophyll as related to the photochemistry of chromatophores of photosynthetic bacteria

Time courses and the emission spectra of fluorescence and light-induced absorption changes of P890 in chromatophores of the photosynthetic bacteria Chromatium D, Rhodopseudomonas spheroides and Rhodospirillum rubrum were investigated.

The time course of fluorescence in chromatophores was separated into two phases, i.e. an initial rapid rise (ƒ_i) and a subsequent slow increase towards a steady level of emission (ƒ_v). The ƒ_i and the ƒ_v components showed different emission spectra having different peak position. The ƒ_v component was emitted from the longest wavelength-absorbing form of bulk bacteriochlorophyll (B890), the ƒ_i component from both B890 and B850.

The magnitude of the ƒ_v component depended on experimental conditions controlling the states of the cyclic electron transport in chromatophores, including changes in levels of redox potential of the medium, additions of electron donors and inhibitors. The magnitude of the ƒ_i component was not affected by these experimental conditions. It was, therefore, concluded that only the ƒ_v component is related to the cyclic electron transport, and that the magnitude of ƒ_v is controlled by the oxidation-reduction state of the primary electron acceptor for the photochemical reaction center in chromatophores.     

The physicochemistry of some dune ponds on the Outer Banks,North Carolina

A survey of the chemical composition of five coastal dune ponds on the Outer Banks, North Carolina, showed the ponds to be more similar to underlying groundwater than to dilute seawater or average river water. With a mean total ionic content of 3.14 mmol l^–1 the ponds were decidedly fresh. Variations in chemistry between the ponds resulted from physiographic association with leached or unleached dunes, and from different soil types in the pond basins. Near isothermal conditions were found in all but one pond. Oxygen levels were reduced at depth in every pond (10 to 25% saturation). Comparative data show the influences on major ion chemistry in these ponds to be substantially different from those of some other coastal dune waters.     

Tracks and trackways of Myotragus balearicus Bate (Artiodactyla, Caprinae) in Pleistocene aeolianites from Mallorca (Balearic Islands, Western Mediterranean)

Tracks and trackways of the ruminant goat, Myotragus balearicus Bate, 1909 are abundant in the Late Pleistocene aeolianites of the south coast of Mallorca, Spain. The carbonate aeolianites form impressive dunes and related sand ramps that were initiated as echo dunes in front of a 20–40 m high paleocliff of Miocene reefal limestone. Where the dunes built up to the cliff top, they covered it as an aeolian ramp. The dunes and sand ramps were active during the dry summer months but were passive during the wet winter period. The small, goat-like animals were abundant on the island, and for unknown reasons crossed the aeolian accumulations in large numbers. This study deals with the tracks formed in the dune deposits. All preserved trackways indicate impression into moist sand. Special features of the tracks include the structure produced by the withdrawal of the foot, here called the ‘axis’, and a disturbance zone of plastic deformation around this. On dune crests, the disturbance zone surrounds the axis more or less symmetrically. However, in addition, a ‘pressure pad’ of dislocated, slightly rotated sediment bound by curved microfaults is commonly produced posterior to the axis by propulsive pressure of the foot. On steep stoss and lee slopes, the pressure pad becomes oriented in a down-slope position as a result of gravitational slip of the walking animal. Combination of disturbance of the sediment in this way by manus followed by overprinting of similar disturbance by pes produces highly complicated track structure. This structure may be characteristic of artiodactylous mammals in soft sand, particularly aeolian deposits. The structure is designated as Bifidipes aeolis isp. nov.     

Porphyrin-sensitized photodynamic damage of isolated rat liver mitochondria

The respiration rates and the respiratory control ratios of isolated rat liver mitochondria have been measured following exposure to 0–160 kJ/m² of near-ultraviolet radiation (blacklight) in the presence of low concentrations of porphyrins (0.1–0.2 μmol/l).

Depending on the light dose, the concentration and the type of porphyrin, the following sequence of reactions occurred: uncoupling and inhibition of oxidative phosphorylation, energy dissipation, inhibition of respiration and swelling and disruption of the mitochondria.

The detrimental effects could not be elicited in the absence of oxygen, neither could they be elicited by porphyrins or light alone.

At equimolar concentrations, the effectiveness of the porphyrins as photosensitizers were: deuteroporphyrin > protoporphyrin coproporphyrin > murophorphyrin.

The results may be of importance to explain the skin lesions seen when porphyrins of different hydrophobicity accumulate in the skin.     

Variation in plant diversity and dominance across dune fixation stages in the Chinese steppe zone

Aims Our aim was to study how diversity and dominance of plant species and plant functional types (PFTs) change and covary across three dune fixation stages in the Chinese steppe zone.Methods In the Chinese steppe zone, we measured coverage, mean height and density of each plant species in three types of dunes (mobile, semi-fixed and fixed dunes) in four sites (Mu Us, Otindag, Hulunbeir and Horqin). Plant species were grouped into 24 PFTs according to their lifespan, photosynthetic pathway, reproductive mode and life form. Dominance of each plant species and PFT were determined, and species diversity and PFT diversity were quantified using Shannon–Wiener index.Important findings PFT diversity was positively related to plant species diversity in each dune stage, but PFT diversity increased more with increasing plant species diversity in the mobile and semi-fixed dunes than in the fixed dunes. Dune fixation stage explained 87.2% of the variation in plant species diversity and 84.8% of the variation in PFT diversity. Dominant species and PFTs differed among the three dune fixation stages; the more fixed the dunes were, the more perennial, shrubby, clonal and C₃ species co-dominated. Specifically, in mobile dunes annual C₄ non-clonal herbs were the most dominant, and in semi-fixed and fixed dunes perennial C₃ clonal shrubs were most dominant.