Ingestion of <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> under different microalgae conditions

The effects of four microalgae,Chlorella vulgaris,Platymonas helgolandicavar,Isochrysis galbana,and Nitzschia closterium on the grazing and filtering rates of the marine rotifer,Brachionus plicatilis,were evaluated under laboratory conditions.The grazing rates in separate cultures of the four microalga were as follows:C.vulgaris > P.helgolandicavar > I.galbana > N.closterium.However,the filtering rates occurred in the following order:P.helgolandicavar > N.closterium > C.vulgaris > I.galbana.A mixed diets ex...     

X-ray imagery and physical core logging as a proxy of the content of sediment cores in cold-water coral mound provinces: a case study from Porcupine Seabight,SW of Ireland

Three provinces, characterized by the presence of carbonate mounds interpreted as cold-water coral banks have been reported in Porcupine Seabight, SW of Ireland and were recently subjected to many detailed studies. This contribution discusses the use of X-ray imagery and physical properties in deciphering palaeoceanographic, sedimentological and biological processes. Physical property core logging and X-ray imagery are used to identify and describe sedimentation regimes and so their respective palaeoceanographic and palaeoclimatological settings in two mound provinces, respectively the Belgica mound province and the Magellan mound province. Both provinces show at present time clear differences in the hydrodynamic environment. This study confirms that also during the past the oceanographic and sedimentological environment of both provinces differ clearly. Impacts of glacial–interglacial variations and locally derived ice rafting events (IRE), comparable with the North Atlantic Heinrich events (HE) have been recognized in both provinces. Moreover, the combination of X-ray imagery, magnetic susceptibility, gamma density and P-wave velocity makes it possible to estimate the coral content and coral distribution in unopened cores localized on top of carbonate mounds. A comparison between on-mound and off-mound cores in both provinces allowed revealing some mechanisms of mound evolution and coral growth versus time.     

Geochemical processes in a Mediterranean Lake: a high-resolution study of the last 4,000 years in Zoñar Lake,southern Spain

High-resolution geochemical analysis of a 6-m-long sediment core from Zoñar Lake, southern Spain, provides a detailed characterization of major changes in lake and watershed processes during the last 4,000 years. Geochemical variables were used as paleolimnological indicators and complement Zoñar Lakes’s paleoenvironmental reconstruction based on sedimentological and biological proxies, which define periods of increasing allochthonous input to the lake and periods of dominant autochthonous sedimentation. Chemical ratios identify periods of endogenic carbonate formation (higher Ca/Al, Sr/Al and Ba/Al ratios), evaporite precipitation (higher S/Al, Sr/Al ratios), and anoxic conditions (higher Mo/Al, U/Th ratios and Eu anomaly). Higher productivity is marked by elevated organic carbon content and carbonate precipitation (Mg/Ca). Hydrological reconstruction for Zoñar Lake was based on sedimentological, mineralogical and biological proxies, and shows that lower lake levels are characterized by Sr-rich sediments (a brackish lake with aragonite) and S-rich sediments (a saline lake with gypsum), while higher lake levels are characterized by sediments enriched in elements associated with alumino-silicates (Al, K, Ti, Fe, trace and rare earth elements), reflecting fresher conditions. Geochemical indicators also mark periods of higher detrital input to the lake related to human activity in the watershed: (1) during the Iberian Roman Humid Period (650 BC–AD 300), around the onset of the Little Ice Age (AD 1400), during the relatively drier Post-Roman and Middle Ages (AD 800–1400), and over the last 50 years, due to mechanized farming practices. Heavy metal enrichment in the sediments (Cu and Ni) suggests intensification of human activities during the Iberian Roman Period, and the use of fertilizers during the last 50 years.     

Impacts of systematic precipitation bias on simulations of water and energy balances in Northwest America

At high latitudes and in mountainous areas, evaluation and validation of water and energy flux simu-lations are greatly affected by systematic precipitation errors. These errors mainly come from topographic effects and undercatch of precipitation gauges. In this study, the Land Dynamics （LAD） land surface model is used to investigate impacts of systematic precipitation bias from topography and wind-blowing on water and energy flux simulation in Northwest America. The results show that topographic and wind adjustment reduced bias of streamflow simulations when compared with observed streamflow at 14 basins. These systematic biases resulted in a -50%-100% bias for runoff simulations, a -20%-20% bias for evapotranspiration, and a -40%-40% bias for sensible heat flux, subject to different locations and adjustments, when compared with the control run. Uncertain gauge adjustment leads to a 25% uncertainty for precipitation, a 20% 100% uncertainty for runoff simulation, a less-than-10% uncertainty for evapotranspiration, and a less-than-20% uncertainty for sensible heat flux.     

Refinement of the late Quaternary geologic history of Erebus volcano,Antarctica using Ar/Ar and Cl age determinations

Six new ⁴⁰Ar/³⁹Ar and three cosmogenic ³⁶Cl age determinations provide new insight into the late Quaternary eruptive history of Erebus volcano. Anorthoclase from 3 lava flows on the caldera rim have ⁴⁰Ar/³⁹Ar ages of 23 ± 12, 81 ± 3 and 172 ± 10 ka (all uncertainties 2σ). The ages confirm the presence of a second, younger, superimposed caldera near the southwestern margin of the summit plateau and show that eruptive activity has occurred in the summit region for 77 ± 13 ka longer than previously thought. Trachyte from “Ice Station” on the eastern flank is 159 ± 2 ka, similar in age to those at Bomb Peak and Aurora Cliffs. The widespread occurrences of trachyte on the eastern flank of Erebus suggest a major previously unrecognized episode of trachytic volcanism. The trachyte lavas are chemically and isotopically distinct from alkaline lavas erupted contemporaneously in the summit region < 5 km away.     

The Pemali Formation of Central Java and equivalents: Indicators of sedimentation on an active plate margin

The Pemali Formation is revised from being the oldest known sedimentary unit in north Central Java to being almost the youngest. This, and a new examination of its composition, has implications for regional geological models and petroleum geology. The Pemali Formation was originally interpreted as “early Miocene” but is now shown to be latest Miocene through Pliocene in age, and characterised by both very high rates of sedimentation and a particularly high degree of reworking. The mid-Late Miocene tectonic event that initiated deposition of this formation created a new series of basins that were filled by erosion of new structural highs. Continuing constriction of the basins resulted in the uplift of older Pemali sediments on the basin margins, being reworked into the youngest Pemali strata.Neither the Pemali Formation nor the associated uplift and erosion are seen in the basins in the Java Sea a short distance to the north. Both the severe effects of the mid-Late Miocene tectonism and the Pemali-type sediments are restricted to a particular geologic zone, which is roughly the same as the modern island of Java. This may be above lithosphere of mixed terranes that forms a rim to the sialic Sunda Plate. The onshore Java area has a history of severe tectonism through the Tertiary and consequently a stratigraphy that greatly contrasts with that of the present-day Java Sea.The localised and thick Pemali deposition affected the burial history and the generation of hydrocarbons around the mid-Late Miocene basins, whilst the uplifted areas may include hydrocarbon traps. If basement composition influenced the location and thickness of the Pemali Formation then it is also likely to have fundamentally controlled deposition of older formations, including the unknown source rock for surface oil seeps. Likewise, these controls appear to contrast strongly with the better known rift-sag basins of the Java Sea.     

NPZ Models of Plankton Dynamics: Their Construction, Coupling to Physics, and Application

Nutrient-phytoplankton-zooplankton (NPZ) models have been in use in oceanography for at least three decades, and are still a common research tool. Given the discoveries of the last two decades, particularly concerning the role of bacteria in the plankton, there are questions as to whether NPZ models can still be supported as a useful tool in planktonic research. Here I review the construction of NPZ models, and some of the physical platforms they have been coupled to. I then discuss the applications of NPZ-physical models, and conclude that they still constitute an important and viable research tool, provided that the questions being explored are clearly stated. This revised version was published online in August 2006 with corrections to the Cover Date.     

High resolution seismic investigations for the determination of water flow directions during sulphur deposits exploitation

This paper shows the results of seismic research on some problems of sulphur in-situ mining. The difficulties during exploitation were mainly connected with the lack of detailed information on the structure and tectonics of deposit and overburden strata. This kind of information could be obtained using the High Resolution Seismic method. The use of seismic method allows to determine the range of subsidence provoked by well mining of sulphur. It is very important to undertake the measurements before exploitation, because the comparison of seismic sections before and during exploitation creates a possibility of determining the process of changes in the structure of the deposit and overburden strata.