Magnitude of harvest of Atlantic horseshoe crabs,<Emphasis Type="Italic">Limulus polyphemus</Emphasis>, in Pleasant Bay,Massachusetts

Atlantic horseshoe crabs,Limulus polyphemus, are currently harvested for biomedical, scientific, and bait purposes. In recent years, changes in population abundance and magnitude of harvesting have raised concerns about the status of this resource. We found horseshoe crab harvest in Pleasant Bay, Massachusetts, was selective by sex and size. Biomedical harvest preferred larger individuals and females, the scientific harvest preferred smaller individuals and males, and the bait harvest preferred females. Total 2001 harvest for all purposes accounted for the mortality of ∼1–2% the adult population. Biomedical harvest accounted for the greatest loss of horseshoe crabs from Pleasant Bay, ∼1–1.6% of the total population. Although biomedical harvest had the lowest associated mortality rate (∼10–15%), many more crabs were harvested from Pleasant Bay for biomedical purposes than for other uses. The scientific harvest accounted for the mortality of ∼0.4% of the population, and bait harvest accounted for the smallest mortality at ∼0.06% of the population. Harvest mortality rate was estimated to be lower in Pleasant Bay than in other Cape Cod areas and may be lower than natural mortality in the population. This study is the first qualitative investigation of commercial harvest on horseshoe crab populations and emphasizes that harvest pressures on different populations need to be individually evaluated.     

Stellar dynamics

This review attempts to place stellar dynamics in relation to other dynamical fields and to describe some of its important techniques and present-day problems. Stellar dynamics has some parallels, in increasing order of closeness, with celestial mechanics, statistical mechanics, kinetic theory, and plasma theory; but even in the last case the parallels are not very close. Stellar dynamics describes, usually through distribution functions, the motions of a large number of bodies as they all act on each other gravitationally. To a good approximation each star can be considered to move in the smoothed-out field of all the others, with random encounters between pairs of stars adding a slow statistical change to these smooth motions. Smooth-field dynamics has a well-developed theory, and the state of smooth stellar systems can be described in some detail. The ‘third integral’ presents an outstanding problem, however. Stellar encounters also have a well-developed theory, but close encounters and encounters of a single star with a binary pose serious problems for the statistical treatment. Star-cluster dynamics can be approached through a theory of smooth-field dynamics plus changes due to encounters, or alternatively through numerical simulations. The relation between the two methods is not yet close enough. The dynamical evolution of star clusters is still not fully understood.     

Reanalysis of four NASA stratospheric particles

Four stratospheric contaminants catalogued in the Cosmic Dust Catalogs published by the NASA Johnson Space Center (JSC) in Houston were reanalysed. The results are compatible with those obtained in JSC, however additional features have occurred in our chemical analyses and their interpretation is also discussed.     

Stage-structured matrix modeling and suggestions for management of atlantic horseshoe crab,Limulus polyphemus, populations on cape cod, massachusetts

The Atlantic horsehoe crab,Limulus polyphemus, is harvested by the biomedical industry for Limulus Amoebocyte Lysate (LAL) a blood compound used to detect endotoxins, for scientific research on vision, and as bait for the eel and conch fisheries. They are also subject to sources of natural mortality such as consumption of eggs by shorebirds and stranding. Recently there has been growing concern over possible declines inLimulus populations along the east coast of the United States. We have used stage-structured matrix modeling to improve our understanding ofLimulus population dynamics in three Cape Cod estuaries (Stage Harbor, Pleasant Bay, and Barnstable Harbor) with differing harvest pressures. The results suggest that a low level of harvest is sustainable, particularly if timing and size-specificity of the harvest are taken into consideration. The model also suggests that efforts should be made to avoid harvesting crabs prior to sexual maturity, as the population growth rate is more sensitive to changes in survival rate of older juveniles than of other stages. The information the model provides could assist local and regional fisheries managers in establishing appropriate regulations for the horseshoe crab fishery.     

The liquefaction of clayey soils under cyclic loading

This paper seeks to investigate the liquefaction of clayey soils, a phenomenon that has been the trigger for many natural disasters in the last few decades, including landslides. Research was conducted on artificial clay-sand mixtures and natural clayey soils collected from the sliding surfaces of earthquake-induced landslides. The undrained response of normally consolidated clayey soils to cyclic loading was studied by means of a ring-shear apparatus. For the artificial clay-sand mixtures, it was found that the presence of a small amount of bentonite (≤ 7%) would cause rapid liquefaction, while a further increase in bentonite content (≥ 11%) produced the opposite effect of raising soil resistance to liquefaction by a significant degree. It was demonstrated that the bentonite-sand mixture was considerably more resistant to liquefaction than the kaolin-, and illite-mixtures, given the same clay content. The test results of plastic soils revealed the significant influence of plasticity on the liquefaction resistance of soil. The microfabric of clayey soil was investigated by means of a scanning electron microscope. The analysis showed that the liquefaction potential of soil was strongly related to certain particle arrangements. For example, soil vulnerable to liquefaction had an open microfabric in which clay aggregations generally gathered at the sand particle contact points, forming low-strength “clay bridges” that were destroyed easily during cyclic loading. On the other hand, the microfabric of soil that was resistant to liquefaction appeared to be more compact, with the clay producing a matrix that prevented sand grains from liquefying. In the case of the natural soils, the obtained results indicated that their cyclic behavior was similarly influenced by factors such as clay content, clay mineralogy and plasticity. The relation between the liquefaction potential of natural soil and its microfabric was thus also established. On the basis of the obtained results, the authors posited an explanation on the mechanism of liquefaction for clayey soil.     

Radiochemical Determination of Gold in Rocks

A method developed for radiochemical determination of gold in rock samples has been applied to six Bulgarian, four ZGI (GDR) and one USGS geostandards. The method is based on acid dissolution of the sample, followed by extraction of gold with copper diethyldithiocarbamate solution in CHCl₃. The chemical yield was determined by using ¹⁹⁹Au tracer. The present data are compared with published values for the ZGI and USGS samples.     

Kinematics of refracted and reflected waves in inhomogeneous media with non-planar interfaces

Zusammenfassung Es werden die Grundbeziehungen für die Berechnung von Strahlen seismischer Wellen in inhomogenen Milieus abgeleitet, in denen die Geschwindigkeit allgemein von drei krummlinigen Koordinaten abhängt. Die angeführten Beziehungen stellen ein System von gewöhnlichen Differentialgleichungen erster Ordnung dar. Die numerische Lösung dieses Systems bietet eine Möglichkeit, die Strahlendiagramme, Laufzeitkurven und Isochronen für die gegebenen Geschwindigkeitsmodelle zu konstruieren. Aufmerksamkeit wird ebenfalls dem Einfall der Strahlen auf eine unebene Grenzschicht gewidmet. Die Beziehungen für die Berechnung reflektierter und refraktierter Strahlen werden abgeleitet. Anhand der abgeleiteten Beziehungen werden Strahlendiagramme und Laufzeitkurven für eine Geschwindigkeitsverteilung berechnet, die durch die vorläufige Interpretation der Ergebnisse von seismischen Tiefensondierungen am tschechoslowakischen Teil des Profils VI gewonnen wurden.     

Metamorphic assemblages and the direction of flow of metamorphic fluids in four instances of serpentinization

Fluids related to Serpentinization are of at least three types. The first reported (Barnes and O'Neil, 1969) is a fluid of local meteoric origin, the chemical and thermodynamic properties of which are entirely controlled by olivine, orthopyroxene, brucite, and serpentine reactions. It is a Ca⁺²-OH^–1 type and is shown experimentally to be capable of reacting with albite to yield calcium hydroxy silicates. Rodingites may form where the Ca⁺²-OH^–1 type waters flow across the ultramafic contact and react with siliceous country rock.The second type of fluid has its chemical composition largely controlled before it enters the ultramafic rocks, but reactions within the ultramafic rocks fix the thermodynamic properties by reactions of orthopyroxene, olivine, calcite, brucite, and serpentine. The precipitation of brucite from this fluid clearly shows that fluid flow allows reaction products to be deposited at a distance from the point of solution. Thus, textural evidence for volume relations during Serpentinization may not be valid.The third type of fluid has its chemical properties fixed in part before the reactions with ultramafic rocks, in part by the reactions of orthopyroxene, olivine, and serpentine and in part by reactions with siliceous country rock at the contact. The reactions of the ultramafic rock and country rock with the fluid must be contemporaneous and require flow to be along the contact. This third type of fluid is grossly supersaturated with talc and tremolite, both found along the contact. The occurrence of magadiite, kenyaite, mountainite, and rhodesite along the contact is probably due to a late stage low-temperature reaction of fluids of the same thermodynamic properties as those that formed the talc and tremolite at higher temperatures. Oxygen isotope analyses of some of these minerals supports this conclusion.Rodingites form from Ca⁺²-rich fluids flowing across the contact; talc and tremolite form from silica-rich fluids flowing along the contact.Isotopic analyses of the fluids indicate varied origins including unaltered local meteoric water and connate water. Complexion Spring water may be a sample of only slightly altered Jurassic or Cretaceous sea water.Publication authorized by the Director, U.S. Geological Survey.