Inhibition of the decomposition ofZostera capricornii litter by macrobenthos and meiobenthos in a brackish coastal lake system

As part of the development of rapid assays to measure ecological processes, rates of decomposition of eelgrass,Zostera capricornii, were measured using litter bags placed at different distances from the sea in a coastal lake system. Average loss of dry mass over 28 d in bags with coarse mesh, which excluded animals >1.5 mm, varied from 364 to 448 mg in late winter to between 644 and 868 mg in autumn, depending on locality. Rates of loss were significantly greater in bags with small mesh (0.063 mm), from which all macrofauna were excluded, varying from 420 to 532 mg and from 868 to 924 mg in winter and autumn, respectively. There were consistent negative correlations between loss of litter and numbers of macrofauna and meiofauna in the bags. Rates of decrease in the organic fraction of the litter were positively correlated with numbers of animals. The results imply that the fauna inhibited decomposition, possibly by reducing microbial populations through grazing.     

Variations in water clarity and chlorophylla in Tampa Bay, Florida, in response to annual rainfall, 1985–2004

In the Tampa Bay region of Florida, extreme levels of annual and seasonal rainfall are often associated with tropical cyclones and strong El Niño episodes. We used stepwise multiple regression models to describe associations between annual and seasonal rainfall levels and annual, bay-segment mean water clarity (as Secchi depth [m]), chlorophylla (μg I^?1), color (pcu), and turbidity (ntu) over a 20-yr period (1985–2004) during which estimated nutrient loadings have been dominated by non-point sources. For most bay segments, variations in annual mean water clarity were associated with variations in chlorophylla concentrations, which were associated in turn with annual or seasonal rainfall. In two bay segments these associations with annual rainfall were superimposed on significant long-term declining trends in chlorophylla. Color was significantly associated with annual rainfall in all bay segments, and in one segment variations in color were the best predictors of variations in water clarity. Turbidity showed a declining trend over time in all bay segments and no association with annual rainfall, and was significantly associated with variations in water clarity in only one bay segment. While chlorophylla, color, and turbidity a affected water clarity to varying degrees, the effects of extreme rainfall events (El Niño events in 1998 and 2003, and multiple tropical cyclone events in 2004) on water clarity were relatively short-lived, persisting for periods of months rather than years. During the 20-yr period addressed in these analyses, declining temporal trends in chlorophylla and turbidity, produced in part by a long-term watershed management program that has focused on curtailing annual loadings of nitrogen and other pollutants, may have helped to prevent the bay as a whole from responding more adversely to the high rainfall periods that occurred in 1998 and 2003–2004.     

Response of a subtropical estuarine marsh to local climatic change in the southwestern Gulf of Mexico

We examined the contrasting, effects of floods and droughts produced by large changes in local climatology on vegetation patterns in Nueces marsh, a semi-arid subtropical salt marsh in south Texas from 1995 to 2005. Climate variations during the study included an initial 4-yr period of moderate conditions, followed by a 2-yr interval of drought, and a recent 4-yr wet period that included large-scale floods. Variation in freshwater inflow, rainfall, and potential evapotranspiration were used in conjunction with field measurements of salinity, inorganic nitrogen, and vegetation structure collected at sites located at varying distances from Nueces Bay. Tidal creek salinities varied with Nueces Bay salinity, with strength of effect inversely related to distance from the bay. Mean (±standard deviation) pore water salinities ranged from 59±54‰ at two high, marsh stations farthest from the bay (10.1 km distant) to 30±21‰ in soil at a low marsh site closest to the bay (0.5 km distant). Mean pore water ammonium was also higher at stations most distant from the bay; nitrate + nitrite did not exhibit a high marsh to low marsh gradient. Nueces Bay salinity decreased substantially when the 10-d cumulative mean daily Nueces River flows exceeded 10 m³ s⁻¹. During periods of low and moderate flood frequency (flows mostly below 10 m³ s⁻¹), vegetation assemblages were dominated by stress-tolerant clonal plants. A catastrophic flood, which immersed vegetation for several weeks between July and September 2002, resulted in extensive plant mortality, but within months, unvegetated areas were rapidly colonized by the obligate annualSalicornia bigelovii. With the end of major flooding by late 2004, plant community structure began a return to pre-drought assemblages at high and middle marsh stations by summer 2005. At the low marsh station, new conditions favored clonal dominants (Spartina alterniflora andBorrichia frutescens), with the latter replacingSalicornia virginica as the dominant species. Our results support the theory that the importance of competition and abiotic stress in determining community composition are inversely related.     

Engineering geological studies and tunnel support design at Sulakyurt dam site, Turkey

This paper presents the results of engineering geological investigations and tunnel support design studies, carried out at the Sulakyurt dam site, northeast of Ankara, Turkey. The Sulakyurt dam will be used for flow control and water storage for irrigation projects. Studies were carried out both in the field and the laboratory. Field studies include engineering geological mapping, intensive discontinuity surveying, core drilling and sampling for laboratory testing. The diversion tunnel will be driven in rock mass, consisting of granite and diorite. Empirical, analytical and numerical methods were combined for safe tunnel design. Rock mass rating (RMR), Rock mass quality (Q) and Geological strength index (GSI) systems were used for empirical rock mass quality determination, site characterization and support design. The convergence–confinement method was used as analytical method and software called Phase², a 2D finite element program, was utilized as numerical method. According to the results acquired from the empirical, analytical and numerical methods, tunnel stability problems were expected in both granite and diorite rock masses. The support system, suggested by empirical methods, was applied and the performance of suggested support system was evaluated by means of numerical modelling. It was concluded that the suggested support systems were adequate, since after applying the suggested support system to granite and diorite, tunnel deformation and the yielded elements around the tunnel decreased significantly. Thus, it is suggested that for more reliable support design empirical, numerical and analytical methods should be combined.     

Seismic potential of Southern Italy

To improve estimates of the long-term average seismic potential of the slowly straining South Central Mediterranean plate boundary zone, we integrate constraints on tectonic style and deformation rates from geodetic and geologic data with the traditional constraints from seismicity catalogs. We express seismic potential (long-term average earthquake recurrence rates as a function of magnitude) in the form of truncated Gutenberg–Richter distributions for seven seismotectonic source zones. Seismic coupling seems to be large or even complete in most zones. An exception is the southern Tyrrhenian thrust zone, where most of the African–European convergence is accommodated. Here aseismic deformation is estimated to range from at least 25% along the western part to almost 100% aseismic slip around the Aeolian Islands. Even so, seismic potential of this zone has previously been significantly underestimated, due to the low levels of recorded past seismicity. By contrast, the series of 19 M6–7 earthquakes that hit Calabria in the 18th and 19th century released tectonic strain rates accumulated over time spans up to several times the catalog duration, and seismic potential is revised downward. The southern Tyrrhenian thrust zone and the extensional Calabrian faults, as well as the northeastern Sicilian transtensional zone between them (which includes the Messina Straits, where a destructive M7 event occurred in 1908), all have a similar seismic potential with minimum recurrence times of M ≥ 6.5 of 150–220 years. This potential is lower than that of the Southern Apennines (M ≥ 6.5 recurring every 60 to 140 years), but higher than that of southeastern Sicily (minimum M ≥ 6.5 recurrence times of 400 years). The high seismicity levels recorded in southeastern Sicily indicate some clustering and are most compatible with a tectonic scenario where the Ionian deforms internally, and motions at the Calabrian Trench are small. The estimated seismic potential for the Calabrian Trench and Central and Western Sicily are the lowest (minimum M ≥ 6.5 recurrence times of 550–800 years). Most zones are probably capable of generating earthquakes up to magnitudes 7–7.5, with the exception of Central and Western Sicily where maximum events sizes most likely do not exceed 7.     

Modeling of the classification behavior of the diaphragms used in multi-chamber cement mills

A new approach has been developed for describing the classification that arises at the diaphragm in multi-chamber ball mills. Fourteen industrial scale cement mills have been sampled in this study and after mass balancing, model fits of the equipment were done. Successive mill product predictions for the sampled conditions were achieved, and requirements to build up an optimization capable model are discussed.     

Peak discharge of a Pleistocene lava-dam outburst flood in Grand Canyon, Arizona, USA

The failure of a lava dam 165,000 yr ago produced the largest known flood on the Colorado River in Grand Canyon. The Hyaloclastite Dam was up to 366 m high, and geochemical evidence linked this structure to outburst-flood deposits that occurred for 32 km downstream. Using the Hyaloclastite outburst-flood deposits as paleostage indicators, we used dam-failure and unsteady flow modeling to estimate a peak discharge and flow hydrograph. Failure of the Hyaloclastite Dam released a maximum 11 × 10⁹ m³ of water in 31 h. Peak discharges, estimated from uncertainty in channel geometry, dam height, and hydraulic characteristics, ranged from 2.3 to 5.3 × 10⁵ m³ s⁻¹ for the Hyaloclastite outburst flood. This discharge is an order of magnitude greater than the largest known discharge on the Colorado River (1.4 × 10⁴ m³ s⁻¹) and the largest peak discharge resulting from failure of a constructed dam in the USA (6.5 × 10⁴ m³ s⁻¹). Moreover, the Hyaloclastite outburst flood is the oldest documented Quaternary flood and one of the largest to have occurred in the continental USA. The peak discharge for this flood ranks in the top 30 floods (>10⁵ m³ s⁻¹) known worldwide and in the top ten largest floods in North America.     

Late Pleistocene glacial and lake history of northwestern Russia

Five regionally significant Weichselian glacial events, each separated by terrestrial and marine interstadial conditions, are described from northwestern Russia. The first glacial event took place in the Early Weichselian. An ice sheet centred in the Kara Sea area dammed up a large lake in the Pechora lowland. Water was discharged across a threshold on the Timan Ridge and via an ice-free corridor between the Scandinavian Ice Sheet and the Kara Sea Ice Sheet to the west and north into the Barents Sea. The next glaciation occurred around 75-70 kyr BP after an interstadial episode that lasted c. 15 kyr. A local ice cap developed over the Timan Ridge at the transition to the Middle Weichselian. Shortly after deglaciation of the Timan ice cap, an ice sheet centred in the Barents Sea reached the area. The configuration of this ice sheet suggests that it was confluent with the Scandinavian Ice Sheet. Consequently, around 70-65 kyr BP a huge ice-dammed lake formed in the White Sea basin (the 'White Sea Lake'), only now the outlet across the Timan Ridge discharged water eastward into the Pechora area. The Barents Sea Ice Sheet likely suffered marine down-draw that led to its rapid collapse. The White Sea Lake drained into the Barents Sea, and marine inundation and interstadial conditions followed between 65 and 55 kyr BP. The glaciation that followed was centred in the Kara Sea area around 55-45 kyr BP. Northward directed fluvial runoff in the Arkhangelsk region indicates that the Kara Sea Ice Sheet was independent of the Scandinavian Ice Sheet and that the Barents Sea remained ice free. This glaciation was succeeded by a c. 20-kyr-long ice-free and periglacial period before the Scandinavian Ice Sheet invaded from the west, and joined with the Barents Sea Ice Sheet in the northernmost areas of northwestern Russia. The study area seems to be the only region that was invaded by all three ice sheets during the Weichselian. A general increase in ice-sheet size and the westwards migrating ice-sheet dominance with time was reversed in Middle Weichselian time to an easterly dominated ice-sheet configuration. This sequence of events resulted in a complex lake history with spillways being re-used and ice-dammed lakes appearing at different places along the ice margins at different times.     

Rock fracturing by explosive energy: review of state-of-the-art

A study of the dynamic rock fracture initiation and propagation due to explosive energy is presented through a detailed state-of-the-art review. Explosive energy dissipation in crushing and fracturing is examined and the various means to enhance the explosive energy utilization for dynamic rock fracturing are reviewed. The study highlights the need for a better understanding of the dynamic fracturing process particularly in the presence of in situ stresses in the rock mass.