High-Pressure Iron-Sulfur Compound, Fe3S2, and Melting Relations in the Fe-FeS System

An iron-sulfur compound (Fe3S2) was synthesized at pressures greater than 14 gigapascals in the system Fe-FeS. The formation of Fe3S2 changed the melting relations from a simple binary eutectic system to a binary system with an intermediate compound that melted incongruently. The eutectic temperature in the system at 14 gigapascals was about 400°C lower than that extrapolated from Usselman's data, implying that previous thermal models of Fe-rich planetary cores could overestimate core temperature. If it is found in a meteorite, the Fe3S2 phase could also be used to infer the minimum size of a parent body.     

Consequences of adult and juvenile movement for marine protected areas

Adult and juvenile mobility has a considerable influence on the functioning of marine protected areas. It is recognized that adult and juvenile movement reduces the core benefits of protected areas, namely protecting the full age–structure of marine populations, while at the same time perhaps improving fisheries yield over the no-reserve situation through export of individuals from protected areas. Nevertheless, the study of the consequences of movement on protected area functioning is unbalanced. Significant attention has been paid to the influence of certain movement patterns, such as diffusive movement and home ranges, while the impacts of others, such as density-dependent movements and ontogenetic migrations, have been relatively ignored. Here we review the diversity of density-independent and density-dependent movement patterns, as well as what is currently known about their consequences for the conservation and fisheries effects of marine protected areas. We highlight a number of ‘partially addressed’ issues in marine protected area research, such as the effects of reserves targeting specific life phases, and a number of essentially unstudied issues, such as density-dependent movements, nomadism, ontogenetic migrations, behavioral polymorphism and ‘dynamic’ reserves that adjust location as a realtime response to habitat changes. Assessing these issues will be essential to creating effective marine protected area networks for mobile species and accurately assessing reserve impacts on these species.     

Historical overfishing and the recent collapse of coastal ecosystems

Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.     

The utility and limitations of size and spacing guidelines for designing marine protected area (MPA) networks

Marine protected areas (MPAs) implemented to conserve biodiversity must protect many species with a broad range of movement characteristics. To meet that goal, size and spacing guidelines have been used in MPA network design as a proxy for explicitly representing connectivity and species movement. However, there has been no assessment of the biological effects of these simple rules. We evaluated these guidelines by estimating population persistence with a spatially explicit population model over: (1) an idealized coastline and (2) an example from California, USA. Persistence of a species within an MPA network depends strongly on its movement characteristics; therefore we used the number of combinations of larval dispersal distances and adult home range diameters as an index representing the number of species that could be protected by a MPA network. The index of species protected usually increased steadily with increasing MPA size. By contrast, decreasing MPA spacing only produced large increases in the index when spacing became close enough to allow species persistence via network connectivity rather than self replenishment. Species persistence also depended on the exploitation rate outside MPAs. Size and spacing guidelines are a simple and useful way to begin the MPA network design process, but meeting these guidelines does not guarantee persistence for all populations one may wish to protect. The use of spatially explicit population dynamics models that evaluate population persistence directly provides a more comprehensive basis for comparing proposed MPA network designs.     

Ecosystem models for fisheries management: finding the sweet spot

The advent of an ecosystem‐based approach dramatically expanded the scope of fisheries management, creating a critical need for new kinds of data and quantitative approaches that could be integrated into the management system. Ecosystem models are needed to codify the relationships among drivers, pressures and resulting states, and to quantify the trade‐offs between conflicting objectives. Incorporating ecosystem considerations requires moving from the single‐species models used in stock assessments, to more complex models that include species interactions, environmental drivers and human consequences. With this increasing model complexity, model fit can improve, but parameter uncertainty increases. At intermediate levels of complexity, there is a ‘sweet spot’ at which the uncertainty in policy indicators is at a minimum. Finding the sweet spot in models requires compromises: for example, to include additional component species, the models of each species have in some cases been simplified from age‐structured to logistic or bioenergetic models. In this paper, we illuminate the characteristics, capabilities and short‐comings of the various modelling approaches being proposed for ecosystem‐based fisheries management. We identify key ecosystem needs in fisheries management and indicate which types of models can meet these needs. Ecosystem models have been playing strategic roles by providing an ecosystem context for single‐species management decisions. However, conventional stock assessments are being increasingly challenged by changing natural mortality rates and environmentally driven changes in productivity that are observed in many fish stocks. Thus, there is a need for more tactical ecosystem models that can respond dynamically to changing ecological and environmental conditions.     

High-Pressure Framework Silicates

Recent syntheses of high-pressure alkali and alkaline earth silicates reveal a class of framework structures with corner-linked 4- and 6-coordinated silicon. These compounds possess the structural formula (A4-2x1+Bx2+)SimVI(SinIVO2(m+n)+2), where x, m, and n specify the amounts of alkaline earth, 6-coordinated silicon, and 4-coordinated silicon, respectively. Appropriate values of m and n yield a range of high-pressure structures, from fully 4-coordinated to fully 6-coordinated silicate frameworks. Recognition of this class of framework silicates leads to predictions of high-pressure structures as well as room-pressure isomorphs of high-pressure silicates.     

Spatial variability in red sea urchin (Strongylocentrotus franciscanus) recruitment in northern California

To better understand the spatial distribution of recruitment in the northern California red sea urchin ( Strongylocentrotus franciscanus ) population, we sampled size distributions at each of 12 locations in 1995 and 1996, two of those locations in 1994, and 5 of those locations in 1997. An index of recent recruitment in these size distributions and an estimate of density of recent recruitment reflect a similar spatial pattern of recruitment. This pattern appears to be determined by the effect of coastal circulation on larval delivery during relaxation of upwelling, and not the result of the positive effect of the adult spine canopy on juvenile survival. Recent recruitment of red sea urchins in northern California is higher in areas more frequently subjected to onshore and poleward flow during relaxation of upwelling. These results are consistent with a mechanism by which alongshore spatial variability in southward, offshore flow during upwelling winds allows larvae to maintain latitudinal position, whereas flows during event-scale relaxations in upwelling winds serve to distribute settling larvae alongshore, favouring areas north of promontories. The consequent spatial pattern of red sea urchin settlement varies from year to year, and there are not yet sufficient data to demonstrate the degree to which this spatial pattern in recruitment determines a spatial pattern in fishable adult abundance.     

Induction of heat stress in beef cattle by feeding the ergots of Claviceps purpurea

Two groups of 4 Hereford steers were housed in a controlled environment room and exposed to simulated high summer temperatures. Both groups were fed a barley grain and hay diet ad libitum. The barley in one diet contained 0.5% w/w ergots of Claviceps purpurea. Within one week of feeding the ergot diet mean rectal temperature was significantly elevated (P less than 0.05) each afternoon (up to 41 degrees C) but returned to normal overnight. Elevated rectal temperature was accompanied by other signs of heat stress, reduced feed intake, body weight loss and depression or serum prolactin concentration. Symptoms disappeared within 1 week of ceasing to feed the ergot diet.