Organic-walled dinoflagellate cysts analysis and statistical analysis of 116 surface sediment samples from the eastern Indian Ocean

Assemblages of organic-walled dinoflagellate cysts (dinocysts) from 116 marine surface samples have been analysed to assess the relationship between the spatial distribution of dinocysts and modern local environmental conditions [e.g. sea surface temperature (SST), sea surface salinity (SSS), productivity] in the eastern Indian Ocean. Results from the percentage analysis and statistical methods such as multivariate ordination analysis and end-member modelling, indicate the existence of three distinct environmental and oceanographic regions in the study area. Region 1 is located in western and eastern Indonesia and controlled by high SSTs and a low nutrient content of the surface waters. The Indonesian Throughflow (ITF) region (Region 2) is dominated by heterotrophic dinocyst species reflecting the region's high productivity. Region 3 is encompassing the area offshore north-west and west Australia which is characterised by the water masses of the Leeuwin Current, a saline and nutrient depleted southward current featuring energetic eddies.

Investigation of cell fate decision in Schizosaccharomyces pombe by ncRNA annotation and statistical analyses

Studies in the fission yeast Schizosaccharomyces pombe (S. pombe) have done much to inform the view of heterochromatin and its control by the RNA interference (RNAi) machinery. Using cDNA synthesised from poly(A)-enriched RNA samples, numerous novel ncRNA loci were discovered, and the 50 and 30 ends of many other genes were refined in previous studies. Although some of these transcripts may encode novel proteins the function of the majority is yet to be determined. The authors have used strand-specific deep sequencing of RNA, irrespective of poly(A) status, to reveal a highly structured antisense programme that modulates gene expression to dictate cell fate decisions during sexual differentiation. They show that an extensive and elaborate array of ncRNA production accompanies sexual differentiation in the fission yeast S. pombe. Experimental manipulation suggests that these transcripts specifically regulate the function of the target genes.

Foraminiferal assemblage and statistical analysis of surface sediment samples from the Golfe d'Arguin, Mauritania

With the growing pressure of eutrophication in tropical regions, the Mauritian shelf provides a natural situation to understand the variability in mesotrophic assemblages. Site-specific dynamics occur throughout the 1200 m depth gradient. The shallow assemblages divide into three types of warm-water mesotrophic foraminiferal assemblages, which is not only a consequence of high primary productivity restricting light to the benthos but due to low pore water oxygenation, shelf geomorphology, and sediment partitioning. In the intermediate depth (approx. 500 m), the increase in foraminiferal diversity is due to the cold-water coral habitat providing a greater range of micro niches. Planktonic species characterise the lower bathyal zone, which emphasizes the reduced benthic carbonate production at depth. Although, due to the strong hydrodynamics within the Golf, planktonic species occur in notable abundances through out the whole depth gradient. Overall, this study can easily be compared to other tropical marine settings investigating the long-term effects of tropical eutrophication and the biogeographic distribution of carbonate producing organisms.

Operator and replicability bias in comparative taphonomic studies

The operator effect is a well-known methodological bias already quantified in some taphonomic studies. However, the replicability effect, i.e., the use of taphonomic attributes as a replicable scientific method, has not been taken into account to the present. Here, we quantified for the first time this replicability bias using different multivariate statistical techniques, testing if the operator effect is related to the replicability effect. We analyzed the results reported by 15 operators working on the same dataset. Each operator analyzed 30 biological remains (bivalve shells) from five different sites, considering the attributes fragmentation, edge rounding, corrasion, bioerosion and secondary color. The operator effect followed the same pattern reported in previous studies, characterized by a worse correspondence for those attributes having more than two levels of damage categories. However, the effect did not appear to have relation with the replicability effect, because nearly all operators found differences among sites. Despite the binary attribute bioerosion exhibited 83% of correspondence among operators it was the taphonomic attributes that showed the highest dispersion among operators (28%). Therefore, we conclude that binary attributes (despite showing a reduction of the operator effect) diminish replicability, resulting in different interpretations of concordant data. We found that a variance value of nearly 8% among operators, was enough to generate a different taphonomic interpretation, in a Q-mode cluster analysis. The results reported here showed that the statistical method employed influences the level of replicability and comparability of a study and that the availability of results may be a valid alternative to reduce bias.

Chemical composition of surficial bottom sediments from the Chukchi Sea and adjacent part of the Arctic Ocean

This paper presents data on chemical composition of bottom sediments from the Chukchi Sea and the adjacent Arctic Ocean. Multivariate statistical techniques were used for analysis of the data set and revealed that grain size fractionation of the original terrigenous component during sedimentation was the major factor of clustering of the samples in study. Secondary factors include accumulation of biogenic siliceous and carbonate material and chemogenic or biochemical accumulation of iron, manganese, and some trace elements. The latter factor was significant in areas of tectonic activity within the graben-rift system of the Chukchi Sea.

Standardized rainfall indices for the West and Central Sahel, and the Guinea Coast

For years, various indices of seasonal West African precipitation have served as useful predictors of the overall tropical cyclone activity in the Atlantic Ocean. Since the mid-1990s, the correlation unexpectedly deteriorated. In the present study, statistical techniques are developed to describe the nonstationary nature of the correlations between annual measures of Atlantic tropical cyclone activity and three selected West African precipitation indices (namely, western Sahelian precipitation in June-September, central Sahelian precipitation in June-September, and Guinean coastal precipitation in the preceding year's August-November period). The correlations between these parameters are found to vary over the period from 1921 to 2007 on a range of time scales. Additionally, considerable year-to-year variability in the strength of these correlations is documented by selecting subsamples of years with respect to various meteorological factors. Broadly, in years when the environment in the main development region is generally favorable for enhanced tropical cyclogenesis (e.g., when sea surface temperatures are high, when there is relatively little wind shear through the depth of the troposphere, or when the relative vorticity in the midtroposphere is anomalously high), the correlations between indices of West African monsoon precipitation and Atlantic tropical cyclone activity are considerably weaker than in years when the overall conditions in the region are less conducive. Other more remote climate parameters, such as the phase of the Southern Oscillation, are less effective at modulating the nature of these interactions.

Major components and major and trace elements from ODP Site 175-1085

We have analyzed 33 Pliocene bulk sediment samples from Ocean Drilling Program Site 1085 in the Cape Basin, located offshore of western Africa in the Angola-Benguela Current system, for 17 major and trace elements, and interpreted their associations and temporal variations in the context of an allied data set of CaCO3, opal, and Corg. We base our interpretations on elemental ratios, accumulation rates, inter-element correlations, and several multi-element statistical techniques. On the basis of qualitative assessment of downhole changes in the distributions of P and Ba, utilized as proxies of export production, we conclude that highs in bulk and biogenic accumulation that occur at 3.2 Ma, 3.0 Ma, 2.4 Ma, and 2.25 Ma were caused by increases in export production as well as terrigenous flux, and record a greater sequestering of organic matter during these time periods. Studies of refractory elements and other indicator proxies (SiO2, Al2O3, TiO2, Fe2O3, MgO, V, Cr, Sr, and Zr) strongly suggest that the terrigenous component of the bulk sediment is composed of two compositional end-members, one being 'basaltic' in composition and the other similar to an 'average shale'. The basaltic end-member comprises approximately 10-15% of the total bulk sediment and its presence is consistent with the local geology of source material in the drainage basin of the nearby Orange River. The increase in bulk accumulation at 2.4 Ma appears to reflect a greater relative increase in basaltic input than the relative increase in shale-type input. Although studies such as this cannot precisely identify the transport mechanisms of the different terrigenous components, these results are most consistent with variations in sea level (and associated changes in shelf geometry and fluvial input) being responsible for the changing depositional conditions along the Angolan Margin during this time period.

Distribution of coarse and fine sediment fractions at Site 178-1095

Fine-fraction (<63 µm) grain-size analyses of 530 samples from Holes 1095A, 1095B, and 1095D allow assessment of the downhole grain-size distribution at Drift 7. A variety of data processing methods, statistical treatment, and display techniques were used to describe this data set. The downhole fine-fraction grain-size distribution documents significant variations in the average grain-size composition and its cyclic pattern, revealed in five prominent intervals: (1) between 0 and 40 meters composite depth (mcd) (0 and 1.3 Ma), (2) between 40 and 80 mcd (1.3 and 2.4 Ma), (3) between 80 and 220 mcd (2.4 and 6 Ma), (4) between 220 and 360 mcd, and (5) below 360 mcd (prior to 8.1 Ma). In an approach designed to characterize depositional processes at Drift 7, we used statistical parameters determined by the method of moments for the sortable silt fraction to distinguish groups in the grainsize data set. We found three distinct grain-size populations and used these for a tentative environmental interpretation. Population 1 is related to a process in which glacially eroded shelf material was redeposited by turbidites with an ice-rafted debris influence. Population 2 is composed of interglacial turbidites. Population 3 is connected to depositional sequence tops linked to bioturbated sections that, in turn, are influenced by contourite currents and pelagic background sedimentation.