134 research outputs found

    Brief Note: Growth of Pisidium Casertanum (Poli) in West Central Ohio

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    Author Institution: Department of Biology, University of Dayto

    Growth of Pisidium casertanum (Poli) in West Central Ohio

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    Clarke (1973) states that Pisidium casertanum (Poli) is perhaps the most common species of Pisidium and is truly cosmopolitan, occurring throughout Eurasia, Africa, Australia, and South, Central and North America. Populations of these clams are reported in habitats ranging from ephemeral ponds to benthic zones of deep lakes. Our study describes Manuscript received 29 May 1979 and in revised form 25 July 1980 (#79-34). 2 Present address: Department of Biology, University of Virginia, Charlottesville, VA 22901. 3 Present address: Department of Zoology, Miami University, Oxford, OH 45056. 41 aspects of the life-cycle of P. casertanum in a spring-fed stream with a relatively small annual temperature range. Clams were collected monthly during the winter and bimonthly or weekly during the summer of 1974 and less regularly during 1975 from the west branch of Cedar Run at Cedar Bog, near Urbana, Ohio (USGS) map quadrangle Urbana West, Champaign County, Ohio: 40° 03.42\u27N 83°47.98\u27W). At certain times (see fig. 1) physical and chemical characteristics of the stream were recorded, including temperature and oxygen concentration (YSI Model 54 oxygen meter), conductivity (YSI Model 33 conductivity meter) and hardness (EDTA method, American Public Health Association 1976)

    Interpopulation Variation in Calcareous and Proteinaceous Shell Components in the Stream Limpet, Ferrissia rivularis

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    Natural populations of the North American stream limpet, F. rivularis, were studied in upstate New York [USA], in a set of localities whose waters have a 15-fold range of dissolved Ca (4.6-67.6 mg/liter) and also range from oligotrophy to eutrophy. Shell component analyses (CaCO3, total organic C and total N) are reported as component mass-fractions (mg/g or .mu.g/g dry weight) and as values for a standard limpet shell of 35 mm aperture length (AL). More than 2-fold differences occur between populations in all 3 components, with relatively little variation occurring within each population. Expressed per standard limpet, CaCO3 values for different populations range from 0.8-1.97 mg with no direct relationship to environmental dissolved Ca. Nominal concentration ratios of body Ca to environmental Ca range from 1953:1-29,130:1. Values for total organic C (9.13-21.0 .mu.g) and total N (2.7-6.69 .mu.g) in the shells parallel each other, all C:N ratios being relatively uniform (3.0:1-3.4:1), and indicating that the non-calcareous components are largely proteinaceous. Although alternative hypotheses predict an inverse or a direct relationship between the organic and the calcareous components, neither is shown by these populations. Genetic controls of shell secretion for the 2-major components apparently are independent, and chance dispersal has resulted in some rather inappropriate shells in certain habitats. This irregular variation in Ferrissia is 1st discussed in relation to other patterns of shell component relationships known for other freshwater mollusk, including direct relationship of the mass of shell CaCO3 to the dissolved Ca available as in Lymnaea peregra and Laevapex fuscus and the apparent regulation producing standard shell weights in L. palustris and Physa gyrina. The results are then discussed in relation to assessment of radionuclide pollution using molluscan shells from fresh waters and in their more general relationship to modes and rates of evolutionary change in freshwater faunas

    Seasonal Metabolism of the Sphaeriid Clam, Musculium partumeium (Say), from a Permanent and a Temporary Pond

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    Seasonal metabolic rates were examined for the sphaeriid clam, Musculium partumeium (Say) from a permanent and a temporary pond. For the fall-born generation from the permanent pond and for the single generation from the temporary pond, metabolic rates peak during periods of greatest growth and reproduction. Metabolic rates were consistently higher for the permanent pond population. These rates for Musculium partumeium extend the available information on the family Sphaeriidae to the genus Musculium

    Rapid onset of mafic magmatism facilitated by volcanic edifice collapse: MAFIC MAGMATISM FACILITATED BY VOLCANIC EDIFICE COLLAPSE

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    Volcanic edifice collapses generate some of Earth's largest landslides. How such unloading affects the magma storage systems is important for both hazard assessment and for determining long-term controls on volcano growth and decay. Here we present a detailed stratigraphic and petrological analyses of volcanic landslide and eruption deposits offshore Montserrat, in a subduction zone setting, sampled during Integrated Ocean Drilling Program Expedition 340. A large (6–10 km3) collapse of the Soufrière Hills Volcano at ~130 ka was followed by explosive basaltic volcanism and the formation of a new basaltic volcanic center, the South Soufrière Hills, estimated to have initiated <100 years after collapse. This basaltic volcanism was a sharp departure from the andesitic volcanism that characterized Soufrière Hills' activity before the collapse. Mineral-melt thermobarometry demonstrates that the basaltic magma's transit through the crust was rapid and from midcrustal depths. We suggest that this rapid ascent was promoted by unloading following collapse

    Investigation of the role of gas hydrates in continental slope stability west of Fiordland, New Zealand

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    Sediment weakening due to increased local pore fluid pressure is interpreted to be the cause of a submarine landslide that has been seismically imaged off the southwest coast of New Zealand. Data show a distinct and continuous bottom‐simulating reflection (BSR)—a seismic phenomena indicative of the presence of marine gas hydrate—below the continental shelf from water depths of c. 2400 m to c. 750 m, where it intersects the seafloor. Excess pore fluid pressure (EPP) generated in a free gas zone below the base of gas hydrate stability is interpreted as being a major factor in the slope's destabilisation. Representative sediment strength characteristics have been applied to limit‐equilibrium methods of slope stability analysis with respect to the Mohr‐Coulomb failure criterion to develop an understanding of the feature's sensitivity to EPP. EPP has been modelled with representative material properties (internal angle of friction, bulk soil unit weight and cohesion) to show the considerable effect it has on stability. The best estimate of average EPP being solely responsible for failure is 1700 kPa, assuming a perfectly elastic body above a pre‐defined failure surface in a static environment
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