Differences in sensitivity to the fungal pathogen Batrachochytrium dendrobatidis among amphibian populations

Contributing to the worldwide biodiversity crisis are emerging infectious diseases, which can lead to extirpations and extinctions of hosts. For example, the infectious fungal pathogen Batrachochytrium dendrobatidis (Bd) is associated with worldwide amphibian population declines and extinctions. Sensitivity to Bd varies with species, season, and life stage. However, there is little information on whether sensitivity to Bd differs among populations, which is essential for understanding Bd‐infection dynamics and for formulating conservation strategies. We experimentally investigated intraspecific differences in host sensitivity to Bd across 10 populations of wood frogs (Lithobates sylvaticus) raised from eggs to metamorphosis. We exposed the post‐metamorphic wood frogs to Bd and monitored survival for 30 days under controlled laboratory conditions. Populations differed in overall survival and mortality rate. Infection load also differed among populations but was not correlated with population differences in risk of mortality. Such population‐level variation in sensitivity to Bd may result in reservoir populations that may be a source for the transmission of Bd to other sensitive populations or species. Alternatively, remnant populations that are less sensitive to Bd could serve as sources for recolonization after epidemic events.     

Policy Utopias for Nutrient Credit Trading Programs with Nonpoint Sources

A promising program to address water contamination from nutrients is water quality trading (WQT), whereby entities with high abatement costs purchase credits from entities with lower abatement costs. The concept has found some success with point source water pollution, but very few trades have occurred in over 50 programs in the United States (U.S.) that have focused on nonpoint sources (NPSs). To understand why success has been slow, we identified three environments needed for programs to succeed: physical, economic, and institutional. We estimate that only 5% of watersheds in the U.S. currently listed as nutrient impaired provide a viable physical environment for trading nitrogen; 13% are suitable for phosphorus. Economic and institutional challenges would shrink that domain even further. Therefore, we find places with the ideal physical, economic, and institutional environments necessary for feasible WQT programs are virtual policy utopias — rare places with ideal environments. Fortunately, a growing literature provides the tools necessary to identify where these policy utopias are and to expand that domain through a better understanding about how to manage WQT programs more effectively.     

Bioenergetic responses of Chesapeake Bay white perch (<Emphasis Type="Italic">Morone americana</Emphasis>) to nursery conditions of temperature,dissolved oxygen,and salinity

Changes in the physical and chemical structure of estuaries control the aerobic scope for activity of coastal fishes and thereby influence the quality and extent of nursery habitats. We evaluated the effects of temperature, dissolved oxygen, and salinity on the ecophysiology of a species that completes its life cycle in estuaries: white perch (Morone americana), which were reared at treatment levels that emulated nursery conditions in the Chesapeake Bay. Salinity influenced only consumption rate and energy density, which were diminished at the highest salinity level (16). In hypoxic environments (≤40% saturation), routine metabolic rates increased as much as fourfold while growth rate decreased threefold and consumption rate decreased twofold. Experimental growth rates were within the range of growth rates observed in the field. Results indicate that hypoxia substantially reduces potential nursery production for a dominant estuarine species, through its influence on diminished aerobic capacity for growth and activity.     

Simulating property exchange in estuarine ecosystem models at ecologically appropriate scales

A computational scheme has been developed and tested to simulate property exchange by advection and dispersion in estuaries at time and space scales that are well suited to ecological and management simulations, but are coarse relative to the demands of physical hydrodynamic models. An implementation of the Regional Ocean Model System (ROMS) for the Providence River and Narragansett Bay (RI, USA) was used to determine property exchanges between the spatial elements of an ecological box model. The basis for the method is the statistical tabulation of numerical dye experiments done with the full ROMS physical model. The ROMS model domain was subdivided into fifteen coarse boxes, each with two vertical layers, defining 30 elements that were used for the box model simulations. Dye concentrations were set to arbitrary initial concentrations for all ROMS grids in the large elements, and the ROMS model was run for 24 h. The final distribution of the dye among the elements was used as a tracer for property exchange over that day and was used to develop an exchange matrix. Box model predictions of salinity over 77 days in each element compared favorably with ROMS simulated salinity averaged over the same spatial elements, although the disparity was greater in areas where large river inflows caused strong gradients in ROMS within elements assumed to be homogeneous in the box model. The 77-day simulation included periods of high and low river flow. Despite the large size of the spatial elements, dispersion artifacts were small, much less than the modeled daily exchanges. While others have taken a similar approach, we found a number of theoretical and practical considerations deserved careful attention for this approach to perform satisfactorily. Whereas the full ROMS model takes 9 days on a powerful computing cluster to compute the physics simulation for 77 days, the box model simulates physics and biology for the same interval in 5 s on a personal computer, and a full year in under 1 min. The exchange matrix mixing model is a fast, cost effective, and convenient way to simulate daily variation of complex estuarine physics in ecological modeling at appropriate scales of space and time.     

Construction of platinum-tipped redox probes for determining soil redox potential

Redox probes are typically constructed by soldering Pt wire to a metal wire or rod, such as copper or brass. The junction between the Pt and wire or rod is often sealed with an epoxy resin and hardener or with heat-shrink tubing. Microcracks (small cracks invisible to the unaided eye) can form in the hardened resin and result in incorrect readings. The hardened resin is not easily removed, making repairs difficult. Heat-shrink tubing is thin, lacks rigidity, and can be damaged in the soil. The method described in this paper used a thick-walled, adhesive-lined terminal insulator to seal the junction. The terminal insulators were easily applied and removed, which made faulty probes easy to repair. Two-hundred forty probes were made with this method and eight were made with a marine epoxy resin. The probes were tested with a redox buffer solution (Light Solution) and were usable if they read +476 +/- 10 mV. The probes were installed 0.76 and 1.5 m deep in the soil. The ability of the probes to provide reliable redox readings was examined by testing selected probes after 10 mo of use and testing all of the probes after completion of the study (19 mo). Ten of the twelve probes tested after 10 mo worked satisfactorily, while the other two clearly malfunctioned before testing. After the study was completed, 236 of the 240 of the probes worked satisfactorily. These results indicate that the construction method presented produces reliable, long-lasting probes.     

Evaluation of the Drug Evaluation and Classification program: a critical review of the evidence

OBJECTIVE: A critical review of the existing evaluation studies on the Drug Evaluation and Classification (DEC) program was conducted to determine the validity and accuracy of the technique for identifying drivers under the influence of drugs. METHODS: Studies were divided into two categories--laboratory studies and field (i.e., enforcement) studies. A classification process was devised using common criteria based on the toxicology findings (i.e., drug positive or drug negative) and the opinion of the police officer who assessed the driver (i.e., drug positive or drug negative). A series of standard measures (Sensitivity, Specificity, False Alarm Rate, Miss Rate, Corroboration, and Accuracy) were calculated for each to assess the effectiveness of the DEC program. RESULTS: Laboratory studies do not provide overwhelming support for the accuracy with which officers trained in the DEC program can detect and identify the particular class(es) of drug involved based on psychophysical assessment alone. The detection and identification of the relatively low levels of drugs administered were typically better than chance but many cases were missed. The fact that some drugs were detected with greater accuracy than others suggests that the effects of these substances were more prominently manifested in the symptomology assessed by the DEC procedure. Although field enforcement studies are not as scientifically rigorous as laboratory studies, DEC assessments in an enforcement context have the benefit of information obtained from the arresting officer and from interviews with the suspect. In addition, the drug doses consumed by users are typically much higher than those permitted in controlled laboratory studies. In general, officers trained in the DEC program are able to identify persons under the influence of drugs and to specify the drug class responsible with a degree of accuracy that not only exceeds chance, but in some cases reaches a very high level. CONCLUSIONS: There remains room for improvement in the DEC program. As further research becomes available, either from laboratory or field investigations or both, it needs to be incorporated into the program to enhance its validity and accuracy.     

Towards networked governance: improving interagency communication and collaboration for disaster risk management and climate change adaptation in Australia

Major disasters, such as bushfires or floods, place significant stress on scarce public resources. Climate change is likely to exacerbate this stress. An integrated approach to disaster risk management (DRM) and climate change adaptation (CCA) could reduce the stress by encouraging the more efficient use of pooled resources and expertise. A comparative analysis of three extreme climate-related events that occurred in Australia between 2009 and 2011 indicated that a strategy to improve interagency communication and collaboration would be a key factor in this type of policy/planning integration. These findings are in accord with the concepts of Joined-up Government and Network Governance. Five key reforms are proposed: developing a shared policy vision; adopting multi-level planning; integrating legislation; networking organisations; and establishing cooperative funding. These reforms are examined with reference to the related research literature in order to identify potential problems associated with their implementation. The findings are relevant for public policy generally but are particularly useful for CCA and DRM.