Seasonal and interannual variability of the planktic foraminiferal flux in the vicinity of the Azores Current

Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002–2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic.     

Alkaline phosphatase activity in the western English Channel: Elevations induced by high summertime rainfall

Alkaline phosphatase activity (APA) was determined in bulk particulate material and in a single-cell (ELF) assay at station L4 in the western English Channel during the summer of 2007. Throughout this period, the UK experienced its heaviest summertime rainfall since records began in 1914; with the result that riverine run-off into coastal waters was also elevated relative to long-term averages. Between May and August 2007, three distinct periods of elevated river run-off were observed which resulted in salinity minima at L4 on days 141, 190 and 232. An extended period of high river run-off between days 170 and 210 was responsible for decreases in near-surface salinity at L4 from 35.2068 to a minimum on day 190 of 34.7422. This contributed to the development of haline stratification which supported the development of an intense bloom of the centric diatom Chaetoceros debelis, with maximum observed chlorophyll a concentration of 8.69 μg l⁻¹. Minima in salinity, and maxima in chlorophyll concentration on day 190 were coincident with a peak in river-derived dissolved inorganic nitrogen (DIN) of 1.9 μmol l⁻¹ which was >5 times greater than the summertime mean and 24 times the concentrations experienced at L4 on weeks immediately before and after. There was no accompanying increase in dissolved inorganic phosphorus (DIP), and the DIN:DIP ratio increased to 49. With the inherent phosphorus stress that this caused, rates of APA increased from <4 to 42.4 nmolP l⁻¹ h⁻¹. ELF analysis on day 197 identified two taxa actively expressing alkaline phosphatase: the dinoflagellate Prorocentrum micans and ciliate Tiarana sp.     

Social and Geographic Contexts of Water Concerns in Utah

Public concerns about water issues are key considerations in responding to changing hydrologic conditions. Literature is mixed on the social profiles associated with resource-related risks. Using data from a household survey, we compare concerns about water shortage, climate change impacts on water supply, poor water quality, and flooding. We assess the combined influence of social and locational factors on each concern and variations across three valleys in northern Utah. Generalized linear mixed modeling is used, given the ordinal nature of most variables. Water shortage was the greatest concern, and female, older, nonwhite, and recreationally active respondents were generally more concerned about water issues than their counterparts. Education, income, and religious identity presented more complicated relationships with water concerns, with significant interaction effects with valley geography. This study has implications for improving public involvement in risk management and engendering support for future water policy and planning strategies to address these risks.     

Dune mobility and vegetation cover in the Southwest Kalahari desert

As part of a wider project investigating the palaeoenvironmental significance of partially vegetated linear dunes in the southwest Kalahari, data collected in the latter part of 1992 concerning dune movement and vegetation cover suggest that sediment transport is occurring on some dune surfaces, and that the majority of surface activity occurs on the crests and upper slopes of the dunes. The data suggest that the limiting variables on surface sediment movement vary on different parts of a dune. On interdunes and lower dune slopes the primary limiting variable is available wind energy, while on dune crests and upper slopes it is vegetation cover. Ground cover by litter has much greater importance in protecting the surface sediment from erosion than rooted vegetation. From individual data points, no evidence is found to support a threshold vegetation cover below which sediment movement occurs. Rather, a gradient of activity is suggested whereby a reduction in vegetation cover increases the potential for sediment movement and surface change. However, dunes with differing amounts of mean vegetation cover display differing degrees of surface activity, and at this scale, a vegetation cover threshold in the region of 14 per cent may be recognized.     

Determination of particulate organic carbon (POC) in seawater: The relative methodological importance of artificial gains and losses in two glass-fiber-filter-based techniques

Particulate matter in aquatic systems is an important vehicle for the transport of particulate organic carbon (POC). Its accurate measurement is of central importance for the understanding of marine carbon cycling. Previous work has shown that GF/F-filter-based bottle-sample-derived concentration estimates of POC are generally close to or higher than large-volume in-situ-pump-derived values (and in some rare cases in subzero waters are up to two orders of magnitude higher). To further investigate this phenomenon, water samples from the surface and mid-water Northeast Atlantic and the Baltic Sea were analyzed. Our data support a bias of POC concentration estimates caused by adsorption of nitrogen-rich dissolved organic material onto GF/F filters. For surface-ocean samples the mass per unit area of exposed filter and composition of adsorbed material depended on the filtered volume. Amounts of adsorbed OC were enhanced in the surface ocean (typically 0.5 μmol cm^− 2 of exposed filter) as compared to the deep ocean (typically 0.2 μmol cm^− 2 of exposed filter). These dependencies should be taken into account for future POC methodologies. Bottle/pump differences of samples that were not corrected for adsorption were higher in the deep ocean than in the surface ocean. This discrepancy increased in summer. It is shown that POC concentration estimates that were not corrected for adsorption depend not only on the filtered volume, true POC concentration and mass of adsorbed OC, but also on the filter area. However, in all cases we studied, correction for adsorption was important, but not sufficient, to explain bottle/pump differences. Artificial formation of filterable particles and/or processes leading to filterable material being lost from and/or missed by sample-processing procedures must be considered. It can be deduced that the maximum amounts of POC and particulate organic nitrogen (PON) that can be artificially formed per liter of filtered ocean water are  3–4 μM OC (5–10% of dissolved OC) and  0.2–0.5 μM ON (2–10% of dissolved ON), respectively. The relative sensitivities of bottle and pump procedures, and of surface- and deep-ocean material, to artificial particle formation and the missing/losing of material are evaluated. As present procedures do not exist to correct for all possible biasing effects due to artificial particle formation and/or miss/loss of filterable material, uncertainties of filtration-based estimates of POC concentrations need further testing. The challenge now is to further constrain the magnitude of the biasing effects that add to the adsorption effect to reduce the uncertainties of estimates of POC concentrations, inventories and fluxes in the ocean.     

Jamaica Bay studies VII: Factors affecting the distribution and abundance of ducks in a New York estuary

The abundance and distribution of ducks (Anatini, Cairinini, Aythyini, Mergini, Oxyurini) were examined at Jamaica Bay Wildlife Refuge, a coastal estuary on Long Island, New York. The refuge contains a variety of tidal habitats as well two freshwater impoundments. The largest concentrations of diving ducks were present in March and April, and from October through December; while the largest concentrations of dabbling ducks were present from June through December. Thus, diving ducks used the refuge on migration whereas dabbling ducks used the refuge during and following the breeding season. Time of year was thus the most significant factor affecting distribution and abundance. Some species were present all year, including Black Duck Anas rubripes, Mallard A. platyrhynchos, Gadwall A. strepera, and Ruddy Duck Oxyura jamaicensis. Although both dabblers and divers used all areas of the bay, dabblers used both ponds while divers used only the East Pond. Dabbling ducks concentrated in the bay at low tide, and on the ponds at high tide. There were more divers on the bay on a falling tide although tide direction did not influence the abundance or distribution of dabblers. Temperature and wind variables influenced the distribution of all ducks: they used the bay at low temperatures, and rafted in large flocks on the bay in intermediate, Northwest winds. Only the numbers and distribution of dabblers were significantly influenced by cloud cover. We conclude that abiotic factors influence the abundance and distribution of ducks on Jamaica Bay Wildlife Refuge, and that tidal factors should be considered when managing migratory or wintering populations of ducks.     

The close approaches and coalescence in triple systems of gravitating masses,I

By computer simulations, the dynamical evolution of plane triple systems of gaseous protogalaxies and galaxies with zero initial velocities has been studied. Inside the regionD of initial configurations some subregions have been revealed corresponding to a coalescence of protogalaxies on the first double approach. The average spin momenta of mergers are approximately equal to those typical of disk galaxies. In triple galaxies, a coalescence on the first double approach does not occur. The presence of significant hidden mass makes the approaches wider and prevents the coalescence of bodies in the systems without a central object. A central pair in a group of galaxies aids to coalescence. Also the change during time of the virial coefficient has been investigated.     

Shallow-generated damage within non-planar strike-slip fault zones: role of sedimentary rocks in slip accommodation,SW Holy Cross Mountains,Poland

International Journal of Earth Sciences - We investigated exhumed damage zones of dextral strike-slip faults dissecting the south-western part of the Mesozoic cover of the Late Palaeozoic Holy...