Southern Ocean Pleistocene calcareous nannofossil events: calibration with isotope and geomagnetic stratigraphies

Several cores recovered from the northern belt of the Southern Ocean were analysed to study the Pleistocene calcareous nannofossil records. Calcareous nannofossil events previously described in medium and low latitudes were identified and calibrated with the oxygen isotope and geomagnetic time scales. Although sedimentation rates, hiatuses and degree of calcareous nannofossil preservation sometimes prevent the identification and/or accurate calibration of some of these events, a useful stratigraphic framework was obtained. The possibility of using these calibrated events from high to low latitudes facilitates correlations and should facilitate isotope event identification in a region with low temperature, where calcareous plankton stratigraphies are in general restricted. In general, Pleistocene southern high latitude calcareous nannofossil events show synchronism with those observed in warm and temperate surficial waters. Small discrepancies in the assigned ages are sometimes related to low sampling resolution due to low sedimentation rates. The first occurrence (FO) of Emiliania huxleyi and the last occurrence (LO) of Pseudoemiliania lacunosa are observed in Marine Isotope Stages (MIS) 8 and 12, respectively. A reversal in abundance between Gephyrocapsa muellerae and E. huxleyi is observed close to the MIS 4/5 boundary. MIS 6 is characterised by an increase in G. muellerae and MIS 7 features a dramatic decrease in the proportion of Gephyrocapsa caribbeanica. This latter species began to increase its proportions from the MIS 13/14 boundary to MIS13, showing diachronism between the different sites. The LO of Reticulofenestra asanoi is observed at MIS 22, confirming this event as a global synchronous reference datum. By contrast, the FO of R. asanoi occurs at MIS 35 and is diachronous with the existing data from other oceanic regions. A re-entry of medium sized Gephyrocapsa (3–5 μm maximum diameters) can be identified in some cores close to MIS 25; although the low abundance of this taxon prevents an accurate calibration, it may be concluded that this event is diachronous as compared with the existing low-latitude data. The LO of large morphotypes of Gephyrocapsa is well correlated with MIS 37, showing synchronism with other oceanic regions, whereas the FO of this species is not well calibrated due to the absence of age-control points.     

New examples of holococcolith–heterococcolith combination coccospheres and their implications for coccolithophorid biology

Recently discovered coccospheres with combinations of coccoliths normally considered to belong to different taxa are presented here. By analogy with other coccolithophorids especially Coccolithus pelagicus we can hypothesize that these associations probably represent moments of phase change in a complex, possibly haplo-diplontic, life-cycle. Seven of these associations are composed of heterococcoliths with holococcoliths; five of them are presented here for the first time: Helicosphaera carteri with Syracolithus catilliferus, Syracosphaera pulchra with Calyptrosphaera oblonga, Syracosphaera anthos with Periphyllophora mirabilis, Acanthoica quattrospina with holococcolithophorid sp. and Syracosphaera sp. with Corisphaera sp. type A (see Kleijne, A., 1991. Holococcolithophorids from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean. Mar. Micropaleontol. 17, 1–76); the other two are Coronosphaera mediterranea with Calyptrolithina wettsteinii, found previously by Kamptner (Kamptner, E., 1941. Die Coccolithineen der Südwestküste von Istrien. Naturhistorischen Museum in Wien. Annalen 51, 54–149), and Syracosphaera nana with undescribed holococcoliths, figured previously by Kleijne (1991) as Syracosphaera sp. type A. In addition the association of Neosphaera coccolithomorpha and Ceratolithus cristatus, recently presented by Alcober and Jordan (Alcober, J., Jordan, R.W., 1997. An interesting association between Neosphaera coccolithomorpha and Ceratolithus cristatus (Haptophyta). Eur. J. Phycol. 32, 91–93) is verified by discovery of a further example. A further five combinations of heterococcoliths and holococcoliths are shown, these probably mostly represent life-cycle combinations but the evidence in each case is insufficient to consider these as definite associations although in these collapsed coccospheres the association of different species is less certain. Two examples of holococcolith–holococcolith associations are presented: S. catilliferus with Syracolithus confusus, and Zygosphaera bannockii with Corisphaera sp. type A. These are probably examples of intra-specific variation.A new species, Syracosphaera delicata sp. nov., is described.     

Integrated stratigraphy and astronomical calibration of the Serravallian/Tortonian boundary section at Monte Gibliscemi (Sicily, Italy)

Results are presented of an integrated stratigraphic (calcareous plankton biostratigraphy, cyclostratigraphy and magnetostratigraphy) study of the Serravallian/Tortonian (S/T) boundary section of Monte Gibliscemi (Sicily, Italy). Astronomical calibration of the sedimentary cycles provides absolute ages for calcareous plankton bio-events in the interval between 9.8 and 12.1 Ma. The first occurrence (FO) of Neogloboquadrina acostaensis, usually taken to delimit the S/T boundary, is dated astronomically at 11.781 Ma, pre-dating the migratory arrival of the species at low latitudes in the Atlantic by almost 2 million years. In contrast to delayed low-latitude arrival of N. acostaensis, Paragloborotalia mayeri shows a delayed low-latitude extinction of slightly more than 0.7 million years with respect to the Mediterranean (last occurrence (LO) at 10.49 Ma at Ceara Rise; LO at 11.205 Ma in the Mediterranean). The Discoaster hamatus FO, dated at 10.150 Ma, is clearly delayed with respect to the open ocean. The ages of D. kugleri first and last common occurrence (FCO and LCO), Catinaster coalitus FO, Coccolithus miopelagicus last (regular) occurrence (L(R)O) and the D. hamatus/neohamatus cross-over, however, are in good to excellent agreement with astronomically tuned ages for the same events at Ceara Rise (tropical Atlantic), suggesting that both independently established timescales are consistent with one another. The lack of a reliable magnetostratigraphy hampers a direct comparison with the geomagnetic polarity timescale of Cande and Kent (1995; CK95), but ages of calcareous nannofossil events suggests that CK95 is significantly younger over the studied time interval. Approximate astronomical ages for the polarity reversals were obtained by exporting astronomical ages of selected nannofossil events from Ceara Rise (and the Mediterranean) to eastern equatorial Pacific ODP Leg 138 Site 845, which has a reliable magnetostratigraphy.Our data from the Rio Mazzapiedi–Castellania section reveal that the base of the Tortonian stratotype corresponds almost exactly with the first regular occurrence (FRO) of N. acostaensis s.s. as defined in the present study, dated at 10.554 Ma. An extrapolated age of 11.8 Ma calculated for the top of the Serravallian stratotype indicates that there is a gap between the top of the Serravallian and the base of the Tortonian stratotype, potentially rendering all bio-events in the interval between 11.8 and 10.554 Ma suitable for delimiting the S/T boundary. Despite the tectonic deformation and the lack of a magnetostratigraphy, Gibliscemi remains a candidate to define the S/T boundary by means of the Tortonian global boundary stratotype section and point (GSSP).     

Drought reduces floral resources for pollinators

Climate change is predicted to result in increased occurrence and intensity of drought in many regions worldwide. By increasing plant physiological stress, drought is likely to affect the floral resources (flowers, nectar and pollen) that are available to pollinators. However, little is known about impacts of drought at the community level, nor whether plant community functional composition influences these impacts. To address these knowledge gaps, we investigated the impacts of drought on floral resources in calcareous grassland. Drought was simulated using rain shelters and the impacts were explored at multiple scales and on four different experimental plant communities varying in functional trait composition. First, we investigated the effects of drought on nectar production of three common wildflower species (Lathyrus pratensis, Onobrychis viciifolia and Prunella vulgaris). In the drought treatment, L. pratensis and P. vulgaris had a lower proportion of flowers containing nectar and O. viciifolia had fewer flowers per raceme. Second, we measured the effects of drought on the diversity and abundance of floral resources across plant communities. Drought reduced the abundance of floral units for all plant communities, irrespective of functional composition, and reduced floral species richness for two of the communities. Functional diversity did not confer greater resistance to drought in terms of maintaining floral resources, probably because the effects of drought were ubiquitous across component plant communities. The findings indicate that drought has a substantial impact on the availability of floral resources in calcareous grassland, which will have consequences for pollinator behaviour and populations.     

Palaeoecological evolution of a spring-fed fen in Pawłów (eastern Poland)

A continuous record of sedimentation in spring-fed fens makes them suitable for detailed palaeoenvironmental studies. A newly investigated cupola spring-fed fen (Paw?ów site), located in the Lublin chalkland, eastern Poland, was the object of our study. This special karst region is characterised by the occurrence of Upper Cretaceous carbonate rocks in the substratum. Sedimentological observations indicated strong variability of biogenic-carbonate series in the deposits (=peat-tufa rhythmite), reflects changes of accumulation conditions (oxidising versus reducing), resulting from alternate occurrence of warmer and cooler periods. Difficulties in pollen analysis due to oxidising conditions necessitate a multidisciplinary approach for palaeoenvironmental reconstruction. We used a multidisciplinary approach (sedimentological, palaeobotanical, geochemical analyses and radiocarbon dating) to determine the main evolutionary stages of this unique fen ecosystem and to discuss the role of local or/and regional factors in its development. Pollen and plant macrofossil analyses, supported by radiocarbon dating, proved that the bottom part of the cores represents the Late Glacial–Early Holocene stages of the fen development. A comparative analysis of palaeoenvironmental data showed close resemblance between the Paw?ów fen and the earlier studied fens in eastern Poland and Central-Eastern Europe, and the connection between their development and supraregional hydrological-climatic factors. The results indicated also the influence of the morphological position of such a type of ecosystem on the development of a continuous deposit succession. The occurrence of a river valley in close proximity of the Paw?ów site resulted in the lack of tufa deposits from the Atlantic period, because of an erosional phase in the river valley.     

Climate and land use change impacts on Mediterranean high-mountain vegetation in the Apennines since the 1950s

Background: High-mountain ecosystems are centres of plant diversity that are particularly sensitive to land-use and climate change.

Aims: We investigated the ecological trends associated with land use and climate change since the 1950s in different vegetation types in high-mountain habitats in the central Apennines.

Methods: We analysed temporal changes in: Pinus mugo scrub, calcareous subalpine grasslands and alpine scree vegetation, comparing historical and recent vegetation records from vegetation plots from two periods (1955–1980 and 1990–2014) for their ecological indicator values (Landolt temperature and nutrient indicators) and structural traits (growth forms) over time using generalised linear models (GLMs).

Results: We observed significant temporal differences in the ecology and structure of the analysed habitats. In the Pinus mugo scrub we detected a reduction of subalpine and herbaceous species and in calcareous alpine screes we observed an increment of the lower montane, montane and subalpine species and of dwarf shrubs. Conversely, subalpine grasslands were stable over time.

Conclusions: Ecological changes that have occurred in the Central Apennines, following changes in type and intensity of land use and recent warming are consistent with those observed in other European mountains, for which climate and land-use changes are claimed as the main driving forces.     

江苏海门王浩钻孔全新世钙质超微化石的环境意义

初步研究了海门王浩地区ＷＺＫ０１０、ＷＺＫ２１４、ＷＺＫ３００３钻孔中的全新世钙质超微化石组合,优势种Ｇ．ｏｃｅａｎｉｃａ在组合中平均占９７％,依据化石的种数,丰度和保存状况,自下而上划分３个亚组合,第Ｉ亚组合,深度７４－４７ｍ,由Ｇ．ｏｃｅａｎｉｃａ,Ｈ．ｃａｒｔｅｒｉｉ,Ｈ．ｗａｌｌｉｃｈ ｉｉ,Ｓ．ｌａｍｉｎａ,Ｕ．ｓｉｂｏｇａｅ组成,丰度较高,保存较好,代表前三角洲－浅海环境,第Ⅱ亚组合,     

Zinc deficiency as a critical problem in wheat production in Central Anatolia

In a soil and plant survey, and in field and greenhouse experiments the nutritional status of wheat plants was evaluated for Zn, Fe, Mn and Cu in Central Anatolia, a semi-arid region and the major wheat growing area of Turkey.All 76 soils sampled in Central Anatolia were highly alkaline with an average pH of 7. 9. More than 90% of soils contained less than 0.5 mg kg^-1 DTPA-extractable Zn, which is widely considered to be the critical deficiency concentration of Zn for plants grown on calcareous soils. About 25% of soils contained less than 2.5 mg kg^-1 DTPA-extractable Fe which is considered to be the critical deficiency concentration of Fe for plants. The concentrations of DTPA-extractable Mn and Cu were in the sufficiency range. Also the Zn concentrations in leaves were very low. More than 80% of the 136 leaf samples contained less than 10 mg Zn kg^–1. By contrast, concentrations of Fe, Mn and Cu in leaves were in the sufficient range.In the field experiments at six locations, application of 23 kg Zn ha^-1 increased grain yield in all locations. Relative increases in grain yield resulting from Zn application ranged between 5% to 554% with a mean of 43%. Significant increases in grain yield (more than 31%) as a result of Zn application were found for the locations where soils contained less than 0.15 mg kg^-1 DTPA-extractable Zn.In pot experirnents with two bread (Triticum aestivum, cvs. Gerek-79 and Kirac-66) and two durum wheats (Triticum durum, cvs. Kiziltan-91 and Kunduru-1149), an application of 10 mg Zn kg^-1 soil enhanced shoot dry matter production by about 3.5-fold in soils containing 0.11 mg kg^-1 and 0.15 mg kg^-1 DTPA-extractable Zn. Results from both field observations and greenhouse experiments showed that durum wheats were more susceptible to Zn deficiency than the bread wheats. On Zn deficient soils, durum wheats as compared to bread wheats developed deficiency symptoms in shoots earlier and to a greater extent, and had lower Zn concentration in shoot tissue and lower Zn content per shoot than the bread wheats.The results presented in this paper demonstrate that (i) Zn deficiency is a critical nutritional problem in Central Anatolia substantially limiting wheat production, (ii) durum wheats possess higher sensitivity to Zn deficient conditions than bread wheats, and (iii) wheat plants grown in calcareous soils containing less than 0.2 mg kg^-1 DTPA-extractable Zn significantly respond to soil Zn applications. The results also indicate that low levels of Zn in soils and plant materials (i.e. grains) could be a major contributing factor for widespread occurrence of Zn deficiency in children in Turkey, whose diets are dominated by cereal-based foods.     

Ca2+-dependent ATPase associated with plasma membrane from a calcareous alga, Serraticardia maxima (Corallinaceae, Rhodophyta)

The plasma membrane was isolated from a calcareous red alga, Serraticardia maxima (Yendo) Silva (Corallinaceae), by aqueous two-phase partitioning. Its purity was examined with marker enzymes, Mg²⁺-dependent ATPase, inosine diphosphatase, cytochrome c oxidase and NADH-cytochrome c reductase, as well as the sensitivity of Mg²⁺-dependent ATPase to vanadate, azide and nitrate. The results showed that the isolated plasma membrane was purified enough to study its functions. Electron microscopic observations on thin tissue sections revealed that most vesicles of the isolated plasma membrane were stained by the plasma membrane specific stain, phosphotungstic acid-chromic acid. Mg²⁺- or Ca²⁺-dependent ATPases were associated with the plasma membrane. Ca²⁺-dependent ATPase was activated at physiological cytoplasmic concentrations of Ca²⁺ (0.1–10 μmol/L). However, calmodulin (0.5 μmol/L) did not affect its activity. The pH optimum was 8.0, in contrast to 7.0 for Mg²⁺-dependent ATPase. The isolated plasma membrane vesicles were mostly right side-out. To test for H⁺-translocation, right side-out vesicles were inverted; 27% of vesicles were inside-out after treatment with Triton X-100. The inside-out plasma membrane vesicles showed reduction of quinacrine fluorescence in the presence of 1 mmol/L ATP and 100 μmol/L Ca²⁺. The reduced fluorescence was recovered with the addition of 10 mmol/L NH₄Cl, or 5 μmol/L nigericin plus 50 mmol/L KCl. UTP and CTP substituted for ATP, but ADP did not. Ca²⁺-dependent ATPase might pump H⁺ out in the physiological state. The acidification by this pump might be coupled with alkalinization at the calcifying sites, which induces calcification.     

Availability of phosphorus in a calcareous soil treated with rock phosphate or superphosphate as affected by phosphate-dissolving fungi

A study was undertaken to isolate some fungi exhibiting phosphate-dissolution ability, and to test whether these fungi are capable of increasing the amount of available P in a calcareous soil treated with rock phosphate (RP) or with triple superphosphate (TSP) and its subsequent uptake by sorghum (Sorghum bicolor L. Moench).Penicillium sp. and twoAspergillus foetidus (Naka) isolates significantly increased the availability of P in soil treated with RP or TSP during the growing season.Penicillium sp. isolate was more effective in increasing available P in the soil treated with RP or TSP than were Aspergillus isolates. However, the dry matter and P uptake responses to inoculation with these fungi were better in the soil treated with RP than in soil treated with TSP. In the TSP treated soil, the fungi achieved their maximum P releasing capacity two weeks earlier than in soil treated with RP. Positive and significant correlation coefficients among available P, P uptake and dry matter production at different periods of the growing season were observed following inoculation. However, none of these variables were found to be significantly correlated with the fungal populations.