Ammothea hilgendorfi (Böhm, 1879), an Adventitious Pycnogonid new for the Mediterranean Sea

Abstract. The authors demonstrate the probable immigration and stable settling of the pycnogonid Ammothea hilgendorfi (B öhm , 1879) at one station in the lagoon of Venice. The species is widely distributed naturally on both sides of the Pacific Ocean and has probably immigrated on ship hulls through the Suez Canal to the Mediterranean. Two more cases (the pycnogonid Anoplodactylus portus and the amphipod Elasmopus pectenicrus ) of adventitious species in this sea are compared.     

Bottom-up and top-down controls of walleye pollock (Theragra chalcogramma) on the Eastern Bering Sea shelf

Control of walleye pollock (Theragra chalcogramma) recruitment in the Eastern Bering Sea involves complex interactions between bottom-up and top-down processes, although the mechanisms are poorly understood. We used statistical models to test the leading hypotheses linking recruitment variability to biotic and abiotic factors. Consistent with a “cold-pool hypothesis”, recruitment of pollock was significantly stronger if winters preceding the larval (age-0) and juvenile stages (age-1) were mild. However, our results did not support the proposed top-down mechanism (cannibalism) underlying this hypothesis. Several empirical relationships support an “oscillating control hypothesis”. As predicted by it, the effect of ice conditions on survival during the larval and early juvenile stages was modified by the abundance of adult pollock, implying stronger bottom-up control when adult abundance (hence cannibalism) was low. The proposed bottom-up mechanism predicts that the survival of pelagic-feeding walleye pollock (benthic-feeding yellowfin sole), should be higher during years with an early (late) ice retreat, which was confirmed by our analysis. Our results also provide additional evidence for a “larval transport hypothesis”, which states that cannibalism of larval and juvenile pollock is reduced in years when strong northward advection separates juveniles from cannibalistic adults.In addition to testing existing hypotheses, we identified new relationships between spawner-to-recruit survival rates of walleye pollock and several indicators of mixed layer dynamics during the spring and summer. Survival rates and recruitment were significantly reduced when larval or early juvenile stages experienced a delay in the (non-ice-associated) spring bloom as a result of stormy spring conditions, suggesting that the timing of the spring bloom is critical to both first-feeding larvae and age-1 juveniles. Furthermore, a dome-shaped relationship between pollock survival and summer wind mixing at the early juvenile stage is consistent with modeling and laboratory studies showing an increase in survival at low to moderate levels of wind mixing, but a decrease in feeding success at high levels of wind mixing.Top-down controls also regulate recruitment of walleye pollock. At least one-third of the variability in spawner-to-recruit survival could be accounted for by predation mortality at the early juvenile stage (age-1). Predation of juvenile pollock can be attributed largely to cannibalism, which varies with the abundance of adult pollock and with the availability of juveniles to adult predators. A simple index reflecting the spatial overlap between juvenile and adult pollock explained 30–50% of the overall variability in recruitment, similar to the variability explained by the best environmental predictors. Although environmental effects are difficult to separate from the effects of predation, we conclude that bottom-up and top-down processes are equally important in controlling the survival of pollock from spawning to recruitment at age 2. However, the magnitude of top-down control is itself modified by environmental factors that control the availability of juvenile pollock to adults (through impacts on spatial distribution) and the abundance of adult predators (through effects on productivity and carrying capacity).     

Retrograde formation of NaCl-scapolite in high pressure metaevaporites from the Cordilleras Béticas (Spain)

A Permo-Triassic pelite-carbonate rock series (with interacalated metabasitic rocks) in the Cordilleras Béticas, Spain, was metamorphosed during the Alpine metamorphism at high pressures (P _min near 18 kbar). The rocks show well preserved sedimentary features of evaporites such as pseudomorphs of talc, of kyanite-phengitetalc-biotite, and of quartz after sulfate minerals, and relicts of baryte, anhydrite, NaCl, and KCl, indicating a salt-clay mixture of illite, chlorite, talc, and halite as the original rock. The evaporitic metapelites have a whole rock composition characterized by high Mg/(Mg+Ca) ratios>0.7, variable alkaline and Sr, Ba, contents, but are mostly K₂O rich (<8.8 wt%). The F (<2600 ppm), Cl (<3600 ppm), and P₂O₅ (<0.24 wt%) contents are also high. The pelitic member of this series is a fine grained biotite rock. Kyanite-phengite-talc-biotite aggregates in pseudomorphs developed in the high pressure stage. Albite-rich plagioclase was formed when the rocks crossed the albite stability curve in the early stages of the uplift. Scapolite, rich in NaCl (Ca/(Ca+Na) mol% 24–40) and poor in SO₄, with Cl/(Cl+CO₃) ratios between 0.6 and 0.8, formed as porphyroblasts, sometimes replacing up to 60% of the rock in a late stage of metamorphism (between 10 and 5 kbar, near 600°C). No reaction with albite is observed, and the scapolite formed from biotite by: $$\begin{gathered} Al - biotite + CaCO_3 + NaCl + SiO_2 \hfill \\ = Al - poor biotite + scapolite + MgCO_3 + KCl \hfill \\ + MgCl_2 + H_2 O \hfill \\ \end{gathered}$$ Calculated fluid composition in equilibrium with scapolite indicates varying salt concentrations in the fluid. Distribution of Cl and F in biotite and apatite also indicates varying fluid compositions.     

A modified profile method for determining the vertical fluxes of NO,NO2, ozone,and HNO3 in the atmospheric surface layer

A modified profile method for determining the vertical deposition (or/and exhalation) fluxes of NO, NO₂, ozone, and HNO₃ in the atmospheric surface layer is presented. This method is based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these trace gases. The analysis (aerodynamic profile method) includes a detailed determination of the micrometeorological quantities (such as the friction velocity, the fluxes of sensible and latent heat, the roughness length and the zero plane displacement), and of the height-invariant fluxes of the composed chemically conservative trace gases with group concentrations c ₁=[NO]+[NO₂]+[HNO₃], c ₂=[NO₂]+[O₃]+3/2·[HNO₃], and c ₃=[NO]–[O₃]–1/2·[HNO₃]. The fluxes of the individual species are finally determined by the numerical solution of a system of coupled nonlinear ordinary differential equations for the concentrations of ozone and HNO₃ (decoding method). The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The model requires only the vertical profile data of wind velocity, temperature and humidity and concentrations of NO, NO₂, ozone, and HNO₃.The method has been applied to vertical profile data obtained at Jülich (September 1984) and collected in the BIATEX joint field experiment LOVENOX (Halvergate, U.K., September 1989).     

Intercomparison of Two Hydroxyl Radical Measurement Techniques at the Atmosphere Simulation Chamber SAPHIR

At the atmosphere simulation chamber SAPHIR in Jülich both Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS) are operational for the detection of OH radicals at tropospheric levels. The two different spectroscopic techniques were compared within the controlled environment of SAPHIR based on all simultaneous measurements acquired in 2003 (13 days). Hydroxyl radicals were scavenged by added CO during four of these days in order to experimentally check the calculated precisions at the detection limit. LIF measurements have a higher precision (σ= 0.88×10⁶ cm^–3) and better time resolution (Δt = 60 s), but the DOAS method (σ= 1.24×10⁶ cm^–3, Δt = 135 s) is regarded as primary standard for comparisons because of its good accuracy. A high correlation coefficient of r = 0.95 was found for the whole data set highlighting the advantage of using a simulation chamber. The data set consists of two groups. The first one includes 3 days, where the LIF measurements yield (1 – 2) ×10⁶ cm^–3 higher OH concentrations than observed by the DOAS instrument. The experimental conditions during these days are characterized by increased NO_x concentration and a small dynamic range in OH. Excellent agreement is found within the other group of 6 days. The regression to the combined data of this large group yields unity slope without a significant offset.     

Analysis of Low-Frequency Turbulence Above Tall Vegetation Using a Doppler Sodar

This study applies acoustic sounding to observe coherent structures in the roughness sublayer (RSL) above tall vegetated surfaces. Data were collected on 22 days during two separate field experiments in summer 2003. A quality control scheme was developed to ensure high data quality of the collected time series. The data analysis was done using both discrete and continuous wavelet transform. The flow in the RSL was found to be a superposition of dynamic Kelvin–Helmholtz instabilities and convective mixing. The characteristic time scales for coherent structures resulting from the dynamic instabilities were observed to be approximately 20–30 s while thermal eddies have much larger time scales of 190–210 s. The degree of vertical coherency in the RSL increases with the flow evolving from neutral to near-convective conditions. This increase in the degree of organisation is attributed to the evolution of attached thermal eddies. The coherent structures resulting from instabilities were found to be present throughout the RSL but do not contribute to the increased vertical coherency. An alternative conceptual approach for the definition of the RSL is proposed, which yields its maximum vertical extent to five times the canopy height.     

Latent heat fluxes simulated with a non-hydrostatic weather forecast model using actual surface properties from measurements and remote sensing

In this study the influence of land-surface parameters on latent heat fluxes simulated with the numerical weather prediction model Lokalmodell (LM) of the German Meteorological Service is investigated. The area of interest is the LITFASS area during the LITFASS-2003 campaign. Based on simulations with varying soil and vegetation properties, we confirm that simulated latent heat fluxes strongly depend on soil moisture and leaf area index. Both parameters are difficult to obtain from in situ measurements with sufficient spatial resolution over heterogeneous land surfaces. Therefore, a procedure is proposed to determine area average values of soil moisture from time domain reflectometer measurements performed at a limited number of sites. The area averages cover the 7 × 7 km² grid cells of the LM around Lindenberg (south-east of Berlin). Furthermore, satellite inferred plant parameters from NOAA–AVHRR are used to initialise model runs; the derived vegetation parameters show notable differences with those in the standard input of LM. The latent heat fluxes from the LM are compared with the aggregated eddy-covariance-measurements, and while the operational LM shows a strong overestimation of latent heat fluxes, it is demonstrated that the application of land-surface parameters derived from measurements can significantly reduce the deviation between the simulated and measured latent heat fluxes.     

江南造山带雪峰隆起区元古宙浊积岩沉积构造背景的地球化学制约

江南造山带雪峰隆起区元古宙浊积岩的地球化学组成良好地反映了沉积盆地的板块构造性质,并为解释区域大地构造的性质和演化提供了有用的信息。中元古代冷家溪群和新元古代板溪群(包括下部马底驿组和上部五强溪组)地层在主元素成分上无明显区别,总体上以中等SiO2含量和K2O/Na2O比值以及较高的(Fe2O3+MgO)含量为特征。稀土元素球粒陨石标准化曲线与典型的后太古宙页岩(如PAAS或NASC)和上陆壳相似,以轻稀土富集、显著的铕负异常和重稀土平坦为特征。大离子亲石元素和铁镁族元素的含量中等。主元素和微量元素特征指示了研究区元古宙浊积岩很可能代表了一套活动大陆边缘弧后沉积盆地的产物。陆内裂谷盆地模式对于解释新元古代华南地区的构造性质和演化可能并不合适。华夏陆块与扬子陆块的拼接以及Rodinia超大陆的最终形成可能发生在约0.8Ga左右的晋宁(雪峰)造山运动期,而不是全球Grenville造山期末的四堡(东安)运动期。     

Basement-Cover Sequences within the UHP unit of the Dabie Shan

Field data define two lithologically distinct basement‐cover sequences within the ultrahigh‐pressure metamorphic (UHPM) unit of the Dabie Shan, eastern China. One of the cover units, the Changpu unit, comprises calc‐arenitic metasediments in stratigraphic contact with a basement consisting of gneisses of the Yangtze craton. The second cover unit, the Ganghe unit, consists of felsic‐intermediate metavolcanics and clastic metasediments. Basement exposure of the Ganghe unit is not known. Fold axes in the Ganghe unit are oblique to those of the Changpu unit, which are parallel to those of the Yangtze gneisses. Preservation of primary textures in some volcanic rocks, and tectonic separation from the Yangtze gneisses by a greenschist facies mylonite, support an interpretation of the Ganghe unit as a low‐strain domain. Protolith associations in the Ganghe and Changpu units are compatible with deposition in a rift setting and along a passive continental margin, respectively. A U–Pb single zircon age of 761 ± 33 Ma for volcanoclastic rocks of the Ganghe unit demonstrates a Neoproterozoic deposition age, concordant with inferred rifting at that time. Eclogite facies parageneses in the gneisses and both cover units, along with P–T data demonstrate regional UHPM in the Dabie Shan.     

Mesoscale Heat Transport Over Complex Terrain By Slope Winds – A Conceptual Model And Numerical Simulations

Vertical heat fluxes induced by mesoscale thermally driven circulations maycontribute significantly to the subgrid-scale fluxes in large-scale models (e.g.,general circulation models). However, they are not considered in these modelsyet. To gain insight into the importance and possible parameterisation of themesoscale flux associated with slope winds, an analytical (conceptual) modelis developed to describe the relationship between the mesoscale heat flux andatmospheric and land-surface characteristics. The analytical model allows usto evaluate the mesoscale flux induced by slope winds from only a few profilemeasurements within a domain. To validate the analytical model the resultingheat flux profiles are compared to profiles of highly resolved wind and temperaturefields obtained by simulations with a mesoscale numerical model.With no or moderate synoptic wind the mesoscale heat flux generated by the slopewind circulation may be as large as, or even larger than, the turbulent fluxes at thesame height. At altitudes lower than the crest of the hills the mesoscale flux is alwayspositive (upward). Generally it causes cooling within the boundary layer and heatingabove. Despite the simplifications made to derive the analytical model, it reproducesthe profiles of the mesoscale flux quite well. According to the analytical model, themesoscale heat flux is governed by the temperature deviation at the slope surface, thedepth of the slope-wind layer, the large-scale lapse rate, and the wavelength of thetopographical features.