One size fits all: stability of metabolic scaling under warming and ocean acidification in echinoderms

Responses by marine species to ocean acidification (OA) have recently been shown to be modulated by external factors including temperature, food supply and salinity. However the role of a fundamental biological parameter relevant to all organisms, that of body size, in governing responses to multiple stressors has been almost entirely overlooked. Recent consensus suggests allometric scaling of metabolism with body size differs between species, the commonly cited ‘universal’ mass scaling exponent (b) of ¾ representing an average of exponents that naturally vary. One model, the Metabolic-Level Boundaries hypothesis, provides a testable prediction: that b will decrease within species under increasing temperature. However, no previous studies have examined how metabolic scaling may be directly affected by OA. We acclimated a wide body-mass range of three common NE Atlantic echinoderms (the sea star Asterias rubens, the brittlestars Ophiothrix fragilis and Amphiura filiformis) to two levels of pCO₂ and three temperatures, and metabolic rates were determined using closed-chamber respirometry. The results show that contrary to some models these echinoderm species possess a notable degree of stability in metabolic scaling under different abiotic conditions; the mass scaling exponent (b) varied in value between species, but not within species under different conditions. Additionally, we found no effect of OA on metabolic rates in any species. These data suggest responses to abiotic stressors are not modulated by body size in these species, as reflected in the stability of the metabolic scaling relationship. Such equivalence in response across ontogenetic size ranges has important implications for the stability of ecological food webs.     

Adaptive Management of Flows in the Lower Roanoke River, North Carolina, USA

The lower Roanoke River in North Carolina, USA, has been regulated by a series of dams since the 1950s. This river and its floodplain have been identified by The Nature Conservancy, the US Fish and Wildlife Service, and the State of North Carolina as critical resources for the conservation of bottomland hardwoods and other riparian and in-stream biota and communities. Upstream dams are causing extended floods in the growing season for bottomland hardwood forests, threatening their survival. A coalition of stakeholders including public agencies and private organizations is cooperating with the dam managers to establish an active adaptive management program to reduce the negative impacts of flow regulation, especially extended growing season inundation, on these conservation targets. We introduce the lower Roanoke River, describe the regulatory context for negotiating towards an active adaptive management program, present our conservation objective for bottomland hardwoods, and describe investigations in which we successfully employed a series of models to develop testable management hypotheses. We propose adaptive management strategies that we believe will enable the bottomland hardwoods to regenerate and support their associated biota and that are reasonable, flexible, and economically sustainable.     

A new approach for facility siting using mapping risks on a plant grid area and optimization

The present work is focused on developing a methodology to find the optimal placement of a hazardous process unit and other facilities using optimization theory while considering a risk map in the plant area. Incidents can have possible consequences resulting from flammable gas releases, which can be evaluated by using consequence modeling programs. The probability of each incident can be derived from initial leak hole size estimation through event tree analysis. In this methodology the plant area was divided into square grids and risk scores were estimated for each grid. The overall cost is a function of the probable cost of property damage due to fires or explosions and the interconnection cost including piping, cable, and management. The proposed approach uses a mixed integer linear optimization programming (MILP) that identifies attractive locations by minimizing the overall cost. A case study is presented for a hexane–heptane separation facility that considers the meteorological data for the given area in order to show the applicability of the proposed methodology. Results from this study will be useful in assisting the selection of locations for facilities and for risk management.     

An approach for risk reduction (methodology) based on optimizing the facility layout and siting in toxic gas release scenarios

In this work, a new approach to optimize facility layout for toxic release is presented. By integrating a risk analysis in the optimization formulation, we propose a safer assignment for facility layout and siting. Accompanying with the economical concepts used in a plant layout, the new model considers the cost of willing to avoid a fatality, i.e. the potential injury cost due to accidents associated with toxic release near residential areas. The proposed formulation incorporates a real meteorological data to calculate the injury risk through the probit model and Monte Carlo simulation using dense gas dispersion modeling (DEGADIS). The overall problem was initially modeled as a disjunctive program where the coordinates of each facility and cost-related variables are the main unknowns. Then, the convex hull approach was used to reformulate the problem as a Mixed Integer Non-Linear Program (MINLP) that identifies potential layouts by minimizing overall costs. This approach gives the coordinates of each facility, and estimates for the total length of pipes, the land area, and the selection of safety devices. Finally, the 3D-computational fluid dynamics (CFD) was used to compare between the initial layout and the final layout. Moreover, analyses of separation distances fr2om hazard facilities and hindrance effects will be discussed based on the approach used in this work.     

Desorption characteristics of kaolin clay contaminated with zinc from electrokinetic soil processing

A number of bench scale laboratory column tests were carried out using a newly designed and developed electrokinetic cell to investigate the fundamental behavior of zinc-spiked kaolin clay subjected to an electric field. Laboratory investigations focused on (i) zinc migration by the combined effects of electromigration and electro-osmosis and (ii) the electrically induced desorption characteristics of zinc-contaminated kaolin that occurred during processing. The correlations of the applied voltage gradient, electro-osmotic flow rate, and the development of a pH gradient were examined and evaluated. The results showed that the removal efficiency was high during the early stage of processing due to rapid desorption by electrokinetic effects in the cathode region. However, the majority of zinc migrating from the anode was precipitated due to the high pH environment in the cathode region.     

Soil profile distribution of phosphorus and other nutrients following wetland conversion to beef cattle pasture

Largely influenced by the passage of the Swamp Land Act of 1849, many wetlands were lost in the coastal plain region of the southeastern United States, primarily as a result of drainage for agricultural activities. To better understand the chemical response of soils during wetland conversion, soil core samples were collected from the converted beef cattle pastures and from the natural wetland at Plant City, FL in the summers of 2002 and 2003. Data collected from the natural wetland sites were used as reference data to detect potential changes in soil properties associated with the conversion of wetlands to improved beef cattle (Bos taurus) pastures from 1940 to 2003. The average concentration of total phosphorus (TP) in pasture soils (284 mg kg(-1)) was significantly (p 相似文献