Variation in the Sizes of Chthamalid ­Barnacle Post-Settlement Cyprids on European Shores

Abstract. As part of a wider study on the settlement and recruitment of Chthamalus spp. in Europe, this study investigated whether chthamalid cyprids can be separated by length on a European scale. Variation in cyprid length with latitude and temporal variation at selected localities were also examined. The lengths of cyprids collected between 1996 – 1999 on nine rocky shores in Europe are reported. Elminius modestus cyprids were found only at Roscoff, NW France and could be distinguished due to their carapace shape and length. They showed a unimodal length distribution, measuring between 450 and 625 µm, with no variation in length between the two sampling dates (1997 and 1998). Based on carapace shape and length, the remaining cyprids in the collections were identified as one of three chthamalid species, Chthamalus montagui, Chthamalus stellatus or Euraphia depressa. Bimodal length distributions of chthamalid cyprids were seen on some shores, while others had a single small‐sized modal group (representing C. montagui on Atlantic shores and/or E. depressa in the Mediterranean) separated from a few distinctly larger cyprids (C. stellatus). Metamorphs collected simultaneously with cyprid collections were identified as C. stellatus or C. montagui, except at Roscoff, where E. modestus were also found. In southern Portugal, where all metamorphs collected were C. montagui and adult C. montagui were the dominant barnacles, most cyprids measured between 350 and 550 µm long and this size distribution coincides with the distribution expected for C. montagui. Cyprids collected on these four more southerly Portuguese shores had the same modal length class (475 µm) and this remained constant between successive years at Luz and Albufeira, Algarve. The smallest (350 µm long) wild chthamalid cyprids found were from southern Portugal and Italy. In Spain, France and Ireland the smallest chthamalid cyprid was 425 µm long. The results from the present study support the hypothesis that on Atlantic shores cyprids of C. montagui can be separated from those of C. stellatus based on size, although there is some variation in cyprid length with latitude as well as temporal variation at selected localities.     

Sedimentary diatom and pigment-inferred recent anthropogenic accelerated eutrophication of a Mediterranean lake (Lake Dojran,Republic of North Macedonia / Greece)

Journal of Oceanology and Limnology - Lake eutrophication is recognised as a serious global challenge, and many regional legislative programmes are being made to attempt to relieve nutrient...     

Response to pumping of a weathered-fractured granite aquifer

A pumping test in a granite aquifer provides information about the interaction between the upper weathered zone and lower fractured zone. A radial flow numerical model is used to interpret the test and estimate aquifer parameters. This model successfully reproduces both the fractured zone response and the shallow weathered zone response which is characterised by increasing drawdown even after abstraction ceases. When the deep fractured aquifer was exploited, a serious decline in groundwater heads and yields occurred; this behaviour can be reproduced by the model. The model is then used to investigate the effective long-term exploitation of the aquifer and the results indicate that dug-cum-bore wells can be used for the safe and efficient exploitation of the aquifer resources.     

On the siting of noble gases in E-chondrites

We have investigated the siting of noble gases in 6 E-chondrites, by analyzing fractions separated by density, grain size, and chemical resistance from Qingzhen (E3), Indarch (E4), Abee and Saint Sauveur (E4-5) and Yilmia and North West Forrest (E6).The new “subsolar” (i.e. Ar-rich) component in E6's is concentrated in the main, ensatite-rich fraction of the meteorites, with density 3.06–3.3 g/cm³. It is unaffected by HCl and HNO₃ treatments of such fractions and remains in unchanged concentration when the samples are partially dissolved by HF. These properties suggest that the subsolar component is located in enstatite, or less likely, in a phase closely associated with it. E4-5's have at least half of their subsolar gases in HCl- and HNO₃-resistant sites (enstatite?), but fail to show the increasing gas concentration with decreasing grain size that is characteristic of most other primordial gas carriers. This may mean that the subsolar gases originally were in some other phase, but were then transferred to enstatite by metamorphism.Most of the ¹²⁹Xe_r of E6's is concentrated in the same fractions as the subsolar gases, again suggesting enstatite or an associated phase as the host. Only a few percent of the ¹²⁹Xe_r is contained in fractions enriched in other major and minor minerals. In E4's, on the other hand, ¹²⁹Xe_r is enhanced in finegrained, low density fractions and is also partly associated with chondrules. Perhaps ¹²⁹I was originally contained in fine-grained matrix, but was transferred to enstatite during metamorphism.A carbon-rich fraction of Indarch (E4) is enhanced in Ne-A, CCF-Xe, and L-Xe. Interestingly, both the isotopic composition of Xe and the Ne/CCF-Xe ratios resemble those of C-chondrites, yet these two meteorite classes probably formed rather far apart. Thus, if these components were mixed at a late stage, it must have been in fairly constant ratio over a large scale. Alternatively, they may have been mixed at an earlier stage, into a common carrier that was spread through a significant portion of the solar nebula.The primordial gases of Qingzhen (E3) resemble those of Indarch: they are present in moderate amounts (${}^{20}\text{Ne}{}_{\mathrm{p}}\text{= 1.2 × 10}{}^{\mathrm{?8}}\text{cc/g,}{}^{132}\text{Xe = 10 × 10}{}^{\mathrm{?10}}\text{cc/g)}$, with little or no contribution from the subsolar component. Thus Qingzhen reinforces our earlier finding that E-chondrites show no regular increase in noble gas content with decreasing petrologic type. One notable feature of Qingzhen is its very low ${}^3\text{He}{}^{21}\text{Ne}$ ratio of 1.07, which indicates that ³He has been lost by solar heating. Solar heating may also account for its low, discordant gas retention ages (U,Th-He age = 1.1 AE, KAr age = 3.2AE).     

Remote Sensing and Geophysical Investigations of Glacial Buried Valleys in Northeastern Kansas

Aquifers found in glacial buried valleys are a major source of good-quality ground water in northeastern Kansas. The extent and character of many of these deposits are not precisely known, so a detailed study of the buried valleys was undertaken. Test drilling, Landsat imagery, shallow-earth temperature measurements, seismic refraction, surface electrical resistivity, and gravity data were used to evaluate two sites in Nemaha and Jefferson Counties. Tonal patterns on springtime Landsat imagery and winter/summer anomalies in shallow-earth temperatures were quick and inexpensive methods for locating some glacial buried aquifers and suggested areas for more intensive field studies. Reversed seismic refraction and resistivity surveys were generally reliable indicators of the presence or absence of glacial buried valleys, with most depth determinations being within 25% of test-drilling results. The effectiveness of expensive test-hole drilling was greatly increased by integrating remote sensing, shallow-earth temperature, seismic, and resistivity techniques in the two buried valley test areas. A gravity profile allowed precise definition of the extent of one of the channels after the other techniques had been used for general information.     

Control of the variability of nutrients and suspended sediments in a gulf coast estuary by climatic forcing and spring discharge of the Atchafalaya River

Water column nutrients (nitrate, ammonium, soluble reactive phosphate, total Kjeldahl nitrogen, and total phosphorus) and suspended sediments (SS) were measured during one 44-h and two 28-h periods in March 1982 at two stations in Fourleague Bay, Louisiana, which is located at the mouth of the Atchafalaya River, a distributary of the Mississippi River. River water (a source of nitrate, total Kjeldahl nitrogen, total phosphorus, and suspended sediments to Fourleague Bay) flows into the upper reaches of the bay during high tide and frontal overrunning conditions with northerly and westerly winds. During one sampling period, decreasing wind speed and the rising tide resulted in Atchafalaya River water inundating the bay and nitrate concentrations in the upper bay increasing from 30–70 μM to 90–118 μM. Significant variations in nutrients associated with the movement of water masses from the river, marshes, and Gulf of Mexico occurred over several different time scales. Tidal transport occurred over 25-h periods, while frontal passages occurred at 3-d to 5-d intervals. Variability in nutrient and suspended sediment concentrations over these relatively short time scales can be as great as seasonal variability in the bay.     

Petrogenesis of the magmatic complex at Mount Ascutney,Vermont, USA

The Ascutney Mountain igneous complex in eastern Vermont, USA, is composed of three principal units with compositions ranging from gabbro to granite. Sr and O isotopic and major element relationships for mafic rocks, granites, and nearby gneissic and schistose country rock have been investigated in order to describe the petrogenesis of the mafic suite which ranges from gabbro to diorite. The entire complex appears to have been formed within a short interval 122.2±1.2 m.y. ago. The granites with ¹⁸O near +7.8 had an initial ⁸⁷Sr/⁸⁶Sr of 0.70395(±6) which is indistinguishable from the initial ratio of the most primitive gabbro. Initial ⁸⁷Sr/⁸⁶Sr ratios and ¹⁸O values for the mafic rocks range from 0.7039 to 0.7057 and +6.1 to +8.6, respectively. The isotopic ratios are highly correlated with major element trends and reflect considerable crustal contamination of a mantle-derived basaltic parent magma. The likely contaminant was Precambrian gneiss similar to exposed bedrock into which the basic rocks were emplaced. A new approach to modelling of assimilation during the formation of a cogenetic igneous rock suite is illustrated. Chemical and isotopic modelling indicate that the mafic rocks were produced by simultaneous assimilation and fractional crystallization. The relative amounts of fractionation and assimilation varied considerably. The mafic suite was not produced by a single batch of magma undergoing progressive contamination; rather, the various rocks probably were derived from separate batches of magma each of which followed a separate course of evolution. The late stage granite was apparently derived from basaltic magma by fractionation with little or no crustal assimilation. The early intrusive phases are much more highly contaminated than the final one. The observed relationships have important implications for the formation of comagmatic complexes and for isotopic modelling of crustal contamination.