Detection of mRNA sequences homologous to the human glutathione peroxidase and rat cytochrome P-450IVA1 genes in Mytilus edulis

In this study we have used cloned gene probes for human glutathione peroxidase (GPX), rat cytochrome P-450IVA1 and rat cytochrome P-450IIE1 to detect homologous sequences in RNA from the hepato-pancreas of Mytilus edulis. The presence of sequences hybridising to the GPX and P-450IVA1 probes, but not to the P-450IIE1 probe, confirms the ancient origin of the former genes and indicates that conserved-sequence DNA probes from higher organisms can be used to examine the structure and function of genes of environmental interest in marine organisms.     

Assessing the feasibility of ecosystem-based fisheries management in tropical contexts

This analysis documents the reasons for emerging interest in ecosystem-based fisheries management (EBFM) and relates this management model to others. It highlights the central challenges to EBFM in the tropical context and examines an ongoing project, Fisheries Improved for Sustainable Harvest (FISH), in the Philippines—likely the first EBFM project in the tropics. The Philippine legal and institutional context provides major governance challenges to EBFM, especially as management is scaled up. A monitoring framework with process and output criteria is applied to FISH to establish progress to date. Major institutional and governance challenges for EBFM will require monitoring, evaluation, and adaptation.     

Bowers Swell: Evidence for a zone of compressive deformation concentric with Bowers Ridge, Bering Sea

Bowers Swell is a newly discovered bathymetric feature which is up to 90 m high, between 12 and 20 km wide, and which extends arcuately about 400 km along the northern and eastern sides of Bowers Ridge. The swell was first revealed on GLORIA sonographs and subsequently mapped on seismic reflection and 3.5 kHz bathymetric profiles. These geophysical data show that the swell caps an arcuate anticlinal ridge, which is composed of deformed strata in an ancient trench on the northern and eastern sides of Bowers Ridge. The trench fill beneath the swell is actively deforming, as shown by faulting of the sea floor and by thinning of the strata across the crest of the swell. Thinning and faulting of the trench strata preclude an origin for the swell by simple sediment draping over an older basement high. We considered several models for the origin of Bowers Swell, including folding and uplift of the underlying trench sediment during the interaction between the Pacific plate beneath the Aleutian Ridge and a remnant oceanic slab beneath Bowers Ridge. However, such plate motions should generate extensive seismicity beneath Bowers Ridge, which is aseismic, and refraction data do not show any remnant slab beneath Bowers Ridge. Another origin considered for Bowers Swell invokes sediment deformation resulting from differential loading and diapirism in the trench fill. However, diapirism is not evident on seismic reflection profiles across the swell. We favour a model in which sediment deformation and swell formation resulted from a few tens of kilometers of low seismicity motion by intraplate crustal blocks beneath the Aleutian Basin. This motion may result from the translation of blocks in western Alaska to the south-west, forcing the movement of the Bering Sea margin west of Alaska into the abyssal Aleutian Basin.     

The global importance and context of methane escape from the seabed

Seabed fluid flow includes volcanic and hydrothermal fluid emissions from ocean spreading centres, island arcs, and intra-plate volcanism, and groundwater flows in some coastal areas. Of direct concern to this paper is the escape of methane from the seabed. Escaping methane may be of microbial, thermogenic or abiogenic origin. Escapes occur in all seas and oceans, in coastal waters, on continental shelves, slopes and rises, the deep oceans, and deep ocean trenches. These represent a variety of geological contexts on passive continental margins, at convergent plate margins (accretionary wedges) and transform plate boundaries. Seepage is clearly widespread, and it contributes methane to the biosphere, the hydrosphere and the atmosphere, thus making up an important part of the global carbon cycle.     

Possible influence of salinity and temperature on modern shelf carbonate sedimentation

In modern, marine, carbonate sands from shelf areas between the equator and latitudes 60°S and 60°N several major grain associations can be distinguished.On open shelves (< 100 m water depth) there are two skeletal grain associations. One (chlorozoan) is virtually restricted to warm, tropical waters; the other (foramol) characterizes temperate waters but also extends into the tropics. The distribution of these two associations cannot be explained in terms of water temperature alone: salinity is suspected as being a further controlling factor. Indeed, a third skeletal association (chloralgal) appears to be characteristic of areas where salinity is higher than on open shelves.Non-skeletal grains, where present, can be grouped into two associations. In one, pellets are the only non-skeletal grains represented; in the other, ooliths and/or aggregate grains are also present. These non-skeletal associations are restricted to relatively warm waters, but temperature does not determine which one of the associations develops. Again, salinity seems important.As both salinity and temperature apparently influence the grain associations, an attempt is made to present the relationships diagrammatically. By using graph pairs of “maximum temperature/minimum salinity” and “minimum temperature/maximum salinity” (named S.T.A.R. diagrams after Salinity Temperature Annual Ranges), the various grain associations can be classed into separate salinity/temperature fields.Salinity and temperature often seem to have a mutual “compensating” effect. For example, even at high temperatures the chlorozoan association does not develop if the salinity falls below a certain value, but it develops at relatively low temperatures when salinity is sufficiently high.This “compensation” effect also appears on the S.T.A.R. diagram for non-skeletal associations. More striking here, however, is a relationship suggesting that development of the oolith/aggregate association is strongly dependent on salinity.Carbonate muds are not shown on the S.T.A.R. diagrams, but an attempt is made to assimilate them into the model.The S.T.A.R. diagrams have a predictive value. In principle, given salinity and temperature values for an area, the grain associations can be predicted. In fact, the prediction is one of “potential”, i.e. that which is to be expected provided any other necessary environmental conditions are satisfied. Predictions are presented for the shelves of an ideal ocean and of present-day oceans and seas. The S.T.A.R. diagrams thus provide the basis for a tentative global model of present-day shelf carbonate sedimentation.The special problems of land-locked seas are discussed with reference to the Mediterranean Sea and the Persian Gulf. Predictions are presented.To illustrate the possibilities of the S.T.A.R. diagram technique, an attempt at detailed prediction is given for an area — the Gulf of Batabano, Cuba — where the sediments are known and predictions can be checked.In conclusion, the problems inherent in applying the model to ancient sedimentary systems are briefly discussed.     

Mildly peraluminous high-silica granites in a continental rift: the Drammen and Finnemarka batholiths,Oslo Rift,Norway

The peraluminous Drammen batholith (650 km²) is the largest granite complex within the mainly alkaline province of the Permo-Carboniferous Oslo Rift, and peraluminous to metaluminous granites are also present in the southern part of the otherwise alkaline Finnemarka complex (125 km²). The emplacement of the Drammen granite, and probably most of the other biotite granite complexes, predate the alkaline syenites and granites. The eight separate petrographic types of the Drammen batholith range in SiO₂ from 70 to 79 wt.% and have experienced variable amounts of fractionation of feldspars, biotite, zircon, apatite, titanite and Fe–Ti-oxides. The initial Sr, Nd and Pb isotopic ratios and a decoupling between the variations in the SiO₂ content and the aluminum saturation index [ASI=Al₂O₃/(CaO+Na₂O +K₂O)] show that the various intrusive phases are not strictly comagmatic. The _Nd values of the southern part of Finnemarka (+3.5 to +4) and the northern part of the Drammen granite (+1 to +1.5) are high and indicate insignificant (for Finnemarka) to minor Precambrian crustal or enriched mantle contributions. The very low _Sr values of all of these samples (–1 to –12, outside the main Oslo Rift magmatic array), point to a time integrated Rb-depleted crustal contaminant or an EM1 mantle component. The earliest extruded alkali basalts along the southwestern margin of the Oslo Rift are the only other samples within this low _Sr area, but their isotopic signature may also be linked to a mantle enrichment event (involving an EM1 component), e.g. associated with the Fen carbonatite magmatism 540 Ma ago. For a given ²⁰⁶Pb/²⁰⁴Pb, the ²⁰⁸Pb/²⁰⁴Pb ratios of the Drammen and Finnemarka batholiths are distinctly lower than those of the Skien alkaline volcanics and all other magmatic Oslo Rift rocks. This may indicate that the lithosphere of the central part of the rift had a time integrated Th-depletion. The samples from the southern part of the Drammen batholith, characterized by the presence of abundant miarolitic cavities, have _Nd near 0 (–0.7 to +0.4) but strongly elevated _Sr of +35 to +67. The combined Pb isotopic ratios of all the samples analyzed indicate that the Precambrian crustal anatectic contribution is in the form of time integrated Th-and U-depleted lower crust, and the high +_Sr of the sourthern part of the Drammen granite results from shallow level wallrock assimilation or magma-fluid interactions. The remarkably low contribution of old crustal components to the Finnemarka and the northernmost Drammen batholiths may result from extensive late Precambrian intracustal differentiation in southwestern Scandinavia, leading to widespread upper crustal granites ( 900 Ma) and a correspondingly dense and refractory lower crust, in particular in a zone intersecting the central part of the rift. Liquidus phase relations and mass-balance constrainst permit derivation of the granites from mildly alkaline to tholeiitic melts by extensive crystal fractionation of clinopyroxene-and amphibole-rich assemblages. It is equally possible to form the granitic magmas by partial melting of Permian gabbros of similar composition. Either scenario is consistent with the isotopic constrainst and with the presence of dense cumulates and/or residues in the lower crust. The lack of igneous rocks of intermediate composition associated with the Drammen and Finnemarka batholiths point to an efficient upper crustal density filtering. Considerable amounts of heat would be accumulated in this region if differentiated, intermediate melts could not escape to shallower levels. Successive magma injections would therefore easily result in partial melting of already solidified mafic to intermediate melts and cumulates, and it is suggested that the peraluminous granites formed mainly by water-undersaturated anatexis of mafic material.     

External perturbations on distant planetary orbits and objects in the Kuiper disk

We investigate the potential importance of molecular cloud and stellar perturbations on the orbits of Pluto and more distant (hypothetical) planets up to 500 AU from the Sun. It is found that stellar and molecular cloud-core perturbations are of roughly equal importance. It also is found that the likelihood of substantial perturbations on Pluto is not insignificant, and that numerous substantial stellar and molecular cloud perturbations are likely to have influenced the orbits of any planets beyond 200 AU. These perturbations may contribute to a prevalence of moderate eccentricities and inclinations for planets beyond the orbit of Neptune, and may be a characteristic of distant planetary orbits in other solar systems. Given the recent discovery of chaotic behavior in Pluto's orbit (Sussman and Wisdom 1988), the effects of external perturbations on the long-term stability of Pluto's orbit warrant continued study.