Short‐term microscale topographic changes of coastal bedrock on shore platforms

We report a series of short‐term (diurnal) rock surface monitoring studies on inter‐ and supra‐tidal shore platforms using a traversing micro‐erosion meter at two sites, Kaikoura Peninsula, New Zealand, and Apollo Bay, Victoria, Australia. Statistically signi?cant day‐to‐day changes were measured. Surface rise and lowering occurred at rates above instrument error, with a maximum range of 3·378 mm between 1·697 mm (lowering) and ‐1·681 mm (rise). Individual measurements showed rises greater than 2 mm. These daily variations reveal that surface lowering and rise occur at a much shorter time scale than previously reported from other studies. The patterns observed suggest wetting and drying is the most likely process causing surface changes at these temporal scales. We argue that traversing micro‐erosion meter studies operating at a short‐term time scale of day‐to‐day provide meaningful results that open new opportunities for studying rock weathering and erosion in a coastal environment. Copyright © 2004 John Wiley & Sons, Ltd.     

Obelia (Cnidaria,Hydrozoa, Campanulariidae): a microphagous,filter‐feeding medusa

Obelia is used in many zoology textbooks to exemplify the Hydrozoa life cycle. The body plan of Obelia medusae, however, is unique among the Hydrozoa. Contrary to all other hydromedusae, Obelia medusae do not derive from a medusary nodule, have neither a velum nor a subumbrellar cavity, the umbrella is flat, and swimming is achieved by umbrellar flapping and does not involve jet propulsion. The medusae of most Obelia species do not grow well on a diet of Artemia salina nauplii, the usual food for laboratory‐reared hydrozoans, and their rearing is often difficult. Previous observations reported that Obelia medusae might eat phytoplankton, driven to the mouth by movements of both the bell and the tentacles. To evaluate the efficiency of this feeding mechanism, we gave a suspension of genetically modified Escherichia coli expressing GFP to starved, newly released medusae of both O. dichotoma and Clytia hemisphaerica (the other campanulariid genus with medusae). Obelia medusae are able to concentrate bacteria in their gastric cavity, whereas Clytia medusae are not. Contrary to other Hydromedusae that are macrophagous, Obelia is a microphagous and filter‐feeding medusa, at least at the onset of its medusan life. As Cnidaria evolved before their current metazoan prey, their ancestral diet was probably microphagous. Obelia’s microphagous feeding habits could thus represent an example of the ancestral feeding condition in Cnidaria, but the apomorphic characters of its medusa suggest that its body architecture is not ancestral, and that its microphagy evolved relatively recently.     

The development of a physiologically-based pharmacokinetic model using the distribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the tissues of the eastern oyster (Crassostrea virginica)

A physiologically-based pharmacokinetic model (PBPK) was developed to describe the kinetics of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the eastern oyster (Crassostrea virginica). The estimated t(1/2) of elimination for a bolus dose of TCDD in C. virginica is approximately 14-24 days based on both the experimental data and the PBPK model. The highest dioxin concentration reached during 28-days was in the digestive gland followed by the mantle, gonad, hemolymph, gill, adductor muscle, and the kidney/heart. A binding protein for 2,3,7,8-TCDD had been reported in the literature for both the digestive gland and gonad. Incorporating a binding component in the model resulted in a better fit for the data. The PBPK model predicted the distribution and the elimination concentrations for 2,3,7,8-TCDD within each of the tissue compartments. This model will serve as a useful tool for predicting the kinetics of other persistent organic pollutants as well as, allow for a more refined ecological risk assessment by estimating dioxin concentrations in sensitive tissues such as the gonad.     

Multi-Annual Variations of Macrobenthos along the Emilia-Romagna Coast (Northern Adriatic)

Abstract. A three-year set of data from six stations is analysed in order to monitor the environmental quality by use of macrobenthos in addition to chemical data. The communities differ along the depth gradient and no seasonal cycle is evident. Stronger temporal differences in community composition are evident when examining a four-year cycle at one of the stations in connection with an improvement of environmental parameters.     

An explanation for the light curve of Jupiter's and Saturn's satellites

Several satellites of Jupiter and Saturn show an asymmetric reflectance between the leading hemisphere (which is generally brighter for the inner satellites of both systems) and the trailing one (which is brighter for the outer satellites Callisto and Iapetus). In order to seek a unified explantation of these observational data we assume that, during the final phase of the satellite accumulation process, the surfaces were subjected to a heavy meteoroidal bombardment by the residual bodies in the circumplanetary protosatellite swarms. With suitable hypotheses about the orbital elements of these bodies, the resulting collision rate is anisotropic in an opposite way for inner and outer satellites, with a difference between the two hemispheres of the order of 10–20% for all satellites except Iapetus (for which the anisotropy is larger). We conclude that the model can qualitatively account for the observed effect, even if it is difficult to propose a detailed mechanism for changing the albedo properties of the satellite surfaces by means of meteoroidal collisions.     

Hydrogeological controls of variable microbial water quality in a complex subtropical karst system in Northern Vietnam

Karst aquifers are particularly vulnerable to bacterial contamination. Especially in developing countries, poor microbial water quality poses a threat to human health. In order to develop effective groundwater protection strategies, a profound understanding of the hydrogeological setting is crucial. The goal of this study was to elucidate the relationships between high spatio-temporal variability in microbial contamination and the hydrogeological conditions. Based on extensive field studies, including mapping, tracer tests and hydrochemical analyses, a conceptual hydrogeological model was developed for a remote and geologically complex karst area in Northern Vietnam called Dong Van. Four different physicochemical water types were identified; the most important ones correspond to the karstified Bac Son and the fractured Na Quan aquifer. Alongside comprehensive investigation of the local hydrogeology, water quality was evaluated by analysis for three types of fecal indicator bacteria (FIB): Escherichia coli, enterococci and thermotolerant coliforms. The major findings are: (1) Springs from the Bac Son formation displayed the highest microbial contamination, while (2) springs that are involved in a polje series with connections to sinking streams were distinctly more contaminated than springs with a catchment area characterized by a more diffuse infiltration. (3) FIB concentrations are dependent on the season, with higher values under wet season conditions. Furthermore, (4) the type of spring capture also affects the water quality. Nevertheless, all studied springs were faecally impacted, along with several shallow wells within the confined karst aquifer. Based on these findings, effective protection strategies can be developed to improve groundwater quality.     

Acervulinid macroid and rhodolith facies in the Eocene Nummulitic Limestone of the Dauphinois Domain (Maritime Alps,Liguria, Italy)

The Eocene Nummulitic Limestone of the Dauphinois domain in the Argentina Valley (Maritime Alps, Liguria, Italy) is characterized by the local presence of carbonate ramp facies rich in acervulinid macroids, rhodoliths and larger foraminifera. The development of these particular facies is mainly controlled by palaeomorphology of the substratum, tectonics, type and amount of terrigenous supply and global sea level changes.

The Upper Cretaceous to Eocene succession outcropping in the Argentina Valley shows differences in facies and age if compared to the typical succession of the Maritime Alps:

• the Cretaceous substratum is younger (early Maastrichtian) and is followed by an unconformity that is interpreted as a submarine discontinuity surface;
• the first Eocene carbonate deposits are older (late Lutetian);
• the Nummulitic Limestone is characterized by the development of carbonate facies deposited in a deep infralittoral-circalittoral setting of a carbonate ramp, sheltered from terrigenous input; in these facies encrusting foraminifera (Solenomeris) replace calcareous red algae in nodules similar to rhodoliths (acervulinid macroids);
• the Nummulitic Limestone is thicker than usual, reaching 110–160 m of thickness.

The Eocene tectonostratigraphic evolution can be summarized as follow: (1) synsedimentary tectonic activity that causes the development of a carbonate ramp with an adjacent structural trough where ramp-derived bioclastic material is deposited (late Lutetian); (2) interruption of the tectonic activity and uniform deposition of deep circalittoral sediments, characterized by deepening upward trend (late Lutetian?); (3) regression indicated by an abrupt shallowing of the depositional setting (Bartonian); and (4) deepening of the depositional setting, ending with the drowning of the carbonate ramp (late Bartonian).The evolution of the Eocene Argentina Valley succession is strongly influenced by tectonics related to the Alpine foreland basin development, but locally, and during definite time intervals, the global sea level changes could be recorded by the sediments during periods of stasis in tectonic activity. The regressive events recognized in the studied succession could be related to the sea level fall reported in the global sea level curve during the Bartonian.