A new approach to overcome shortcomings with multiple testing of reproduction data in ecotoxicology

In ecotoxicology species reproduction tests and multiple testing of reproduction data are wide spread. While normal approximation of the data is a minor problem often the requirement of variance homogeneity is not fulfilled. Variance homogeneity is necessary to assure the proper application of statistical procedures like pairwise t tests, Dunnett t test, and Williams t test. A Poisson model can solve this issue preserving meaningful results and rendering statistical analysis more reliable. Moreover, sequential application of pairwise statistical “control vs. treatment” tests is a drawback concerning \(\alpha \)-inflation. The closure principle (CP) for hypothesis testing is used to generate a step-wise approach for detection of the No/Lowest Observed Effect Concentration using the computational approach test (CAT). The advantages and disadvantages of the combined CPCAT approach compared to the widely used t tests are pointed out and results of real data and fictitious data analysis are compared revealing the superiority of the Poisson model and CPCAT.     

Passive seismic source localization via common-reflection-surface attributes

The common-reflection-surface (CRS) stack can be viewed as a physically justified extension of the classical common-midpoint (CMP) stack, utilizing redundant information not only in a single, but in several neighboring CMP gathers. The zero-offset CRS moveout is parameterized in terms of kinematic attributes, which utilize reciprocity and raypath symmetries to describe the two-way process of the actual wave propagation in active seismic experiments by the propagation of auxiliary one-way wavefronts. For the diffraction case, only the attributes of a single one-way wavefront, originating from the diffractor are sufficient to explain the traveltime differences observed at the surface. While paraxial ray theory gives rise to a second-order approximation of the CRS traveltime, many higher-order approximations were subsequently introduced either by squaring the second-order expression or by employing principles of optics and geometry. It was recently discovered that all of these higher-order operators can be formulated either for the optical projection or in an auxiliary medium of a constant effective velocity. Utilizing this duality and the one-way nature of the CRS parameters, we present a simple data-driven stacking scheme that allows for the estimation of the a priori unknown excitation time of a passive seismic source. In addition, we demonstrate with a simple data example that the output of the suggested workflow can directly be used for subsequent focusing-based normal-incidence-point (NIP) tomography, leading to a reliable localization in depth.     

Modeling multiple elementary waves in layered media using ray field maps

Seismic ray tracing in layered media becomes complicated and demanding when modeling for multiple ray codes (reflection/transmission sequences) and/or dense acquisition geometries. However, we observe some redundancies in current algorithms: (a) the same layers are crossed repeatedly by similar ray segments, and (b) the effort of tracing through a layer is determined by variations in the incoming wavefront rather than the medium. We deal with these redundancies by separating the modeling process in two stages: (Stage 1) compute ray field maps representing all ray segments between each pair of adjacent interfaces, then (Stage 2) for each desired ray code assemble the complete ray field from ray segments by iterative lookup in the ray field maps.     

Improving hydrodynamic modeling of an estuary in a mixed tidal regime by grid refining and aligning

Water levels and flows in the Singapore coastal waters are driven by the complex interactions of the Indian and Pacific Ocean tides, seasonal monsoon-driven contributions and also forced by local winds. The Singapore Regional Model was developed to simulate hydrodynamics in the Strait of Singapore which produces representative sea level variation in this region. However, resolution and alignment of the grid system of the model with respect to depth contours in some of its subregions, i.e., the Johor Estuary area require further improvement. For this, the grid system of the model was modified and compared the simulated results with field measurements. The computed flow velocities agreed better with field observations when the grid resolution was increased. However, improving the alignment of the grid with the channel boundary (with a much lower increase in grid resolution) provided a substantially larger improvement of the model performance. The grid modification greatly influenced the computed salinity in the estuary, while water levels are slightly affected. Further analysis of model results showed a pronounced ebb tidal asymmetry generated by the O1–K1–M2 tidal constituents in the estuary.     

Sidescan sonar imagery of widespread fossil and active cold seeps along the central Chilean continental margin

The central Chilean subduction zone between 35°S and 37°S was investigated in order to identify, document and possibly understand fluid flow and fluid venting within the forearc region. Several areas were mapped using multibeam bathymetry and backscatter, high-resolution sidescan sonar, chirp subbottom profiling and reflection seismic data. On a subsequent cruise ground-truthing observations were made using a video sled. In general, this dataset shows surprisingly little evidence of fluid venting along the mid-slope region, in contrast to other subduction zones such as Central America and New Zealand. There were abundant indications of active and predominantly fossil fluid venting along the upper slope between 36.5°S and 36.8°S at the seaward margin of an intraslope basin. Here, backscatter anomalies suggest widespread authigenic carbonate deposits, likely the result of methane-rich fluid expulsion. There is unpublished evidence that these fluids are of biogenic origin and generated within the slope sediments, similar to other accretionary margins but in contrast to the erosional margin off Central America, where fluids have geochemical signals indicating an origin from the subducting plate.     

The global thermohaline circulation in box and spectral low-order models. Part 1: single basin models

Much of the knowledge about ocean circulation stems from rather simple analytical models. The behavior of the meridional overturning and, more specifically, the thermohaline-induced part of the global ocean circulation, under changing surface conditions, is often judged by the bifurcation structure of box models with very low (low-order) resolution. The present study proposes a new low-order model of the thermohaline-driven circulation, which is constructed by severe truncation of a spectral decomposition of the two-dimensional equations of motion (vorticity and heat/salt balances). The physical ingredients of the new model are superior to box models because it has a continuous lateral and vertical representation of the fields and finite diffusion coefficients for heat and salt. The building of the spectral model involves much mathematical labor because the structure functions must be constructed in accordance with the boundary conditions for conservation of momentum, mass, heat, and salt. Furthermore, a number of complicated coupling coefficients must be evaluated. Like the box models, the spectral model is a dynamical system with mathematical complexity, but in most of the versions that we analyze, it still can be handled by standard analytical procedures. These versions are the spectral counterparts of the classical box models of Stommel, Rooth, and Welander, adjusted to the Atlantic overturning. A detailed comparison of the model types reveals a similar bifurcation pattern of box and spectral low-order configurations under symmetric and asymmetric forcing conditions and slight perturbations thereof (we use mixed boundary conditions for heat and salt and the surface freshwater flux as a continuation parameter). Comparison of the spectral low-order models with models towards a higher resolved range, namely, the two-dimensional overturning models for the meridional plane, reveals a close resemblance as well. A major difference of box and spectral models is the appearance of parameter windows in the latter, where only unstable steady states exist. The spectral models then show limit cycles, as well as chaotic trajectories with time scales of thousands of years.     

Techniques to measure the dry aeolian deposition of dust in arid and semi‐arid landscapes: a comparative study in West Niger

Seven techniques designed to measure the dry aeolian deposition of dust on a desert surface were tested during field experiments in Niger, central‐west Africa. Deposition fluxes were measured during eight periods of 3–4 days each. Experimental techniques tested were the MDCO (marble dust collector) method, the Frisbee method, the glass plate method (optical analysis of dust deposited on glass surfaces using particle imaging software), the soil surface method (deposition on a simulated desert floor) and the CAPYR (capteur pyramidal) method. Theoretical techniques tested were the inferential method and the combination method (gradient method extended with a deposition term for coarse dust particles). The results obtained by the MDCO, Frisbee, inferential and combination methods could be directly compared by converting the data to identical standard conditions (deposition on a water surface producing no resuspension). The results obtained by the other methods (glass plate, soil surface, CAPYR) were compared relatively. The study shows that the crude (unconverted) deposition fluxes of the five experimental techniques were similar, while the crude deposition fluxes calculated by the two theoretical techniques were substantially higher, of the order of four to five times as high as for the experimental techniques. Recalculation of the data to identical environmental conditions (the standard water surface) resulted in nearly identical deposition fluxes for the MDCO, Frisbee, inferential and combination techniques, although the latter two still had slightly higher values (but the differences remained small). The measurements illustrate the need to include a grain shape factor in theoretical dust deposition models. Without such a factor, theoretical models overestimate the deposition. The paper also discusses the advantages and disadvantages of the techniques tested. Copyright © 2007 John Wiley & Sons, Ltd.     

A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England)

A concretion from the lower Tithonian Kimmeridge Clay Formation (Pectinatus Zone) found by Steve Etches yielded a gladius of a coleoid cephalopod. It is peculiar in shape and has an unusual ornamentation of radiating ribs and tubercles. The new form is named Etchesia martilli n. gen. n. sp. and preliminarily placed within the octobrachian family Muensterellidae based on its limpet-like gladius. Through the presence of radiating ribs as well as the absence of a narrow anterior rachis E. martilli n. gen. n. sp. is similar to Pearceiteuthis buyi from the Oxford Clay Formation (Callovian). The new muensterellid is unique in having an enrolled patella apex, which is located close to the posterior gladius rim. E. martilli n. gen. n. sp. represents the first muensterellid coleoid from the Kimmeridge Clay Formation. A phylogenetic relationship of E. martilli n. gen. n. sp. (and Pearceiteuthis) with cirrate and incirrate octopods is discussed, although further information on soft parts such as the muscular mantle is necessary.     

The use of benthic indicators in Europe: from the Water Framework Directive to the Marine Strategy Framework Directive

The Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) are the European umbrella regulations for water systems. It is a challenge for the scientific community to translate the principles of these directives into realistic and accurate approaches. The aim of this paper, conducted by the Benthos Ecology Working Group of ICES, is to describe how the principles have been translated, which were the challenges and best way forward. We have tackled the following principles: the ecosystem-based approach, the development of benthic indicators, the definition of ‘pristine’ or sustainable conditions, the detection of pressures and the development of monitoring programs. We concluded that testing and integrating the different approaches was facilitated during the WFD process, which led to further insights and improvements, which the MSFD can rely upon. Expert involvement in the entire implementation process proved to be of vital importance.