Archives of Environmental Contamination and Toxicology, 2001
The cellular stress responses of most organisms in part involve the induction of a class of prote... more The cellular stress responses of most organisms in part involve the induction of a class of proteins called heat shock or stress proteins (HSPs) as a result of damage to existing proteins. Cellular proteins can be damaged by chemical exposures known to induce various HSPs. In these experiments, we examine the HSP responses of mussel (Mytilus galloprovincialis) and abalone (Haliotis rufescens) tissues to both thermal and chemical exposures. HSP70 isoforms, HSP60, and HSP90 all show varying induction capabilities. The results demonstrate that the extent of stress exposure as both a time- and dose-dependent phenomena can be ascertained by examining changes in mollusc HSP protein levels. We also examined the relationship between HSP induction and levels of a mussel cytochrome P450 (CYP4Y1) mRNA in dose-response experiments with the products of biologically degraded weathered crude oil. The increases in HSP70 isoforms and HSP90 were correlated with decreases in CYP4Y1 expression levels in a dose-dependent manner. HSP responses may therefore be a valuable part of a suite of biomarkers in biomonitoring for hydrocarbon exposures in nearshore environments.
Guidelines for protecting and managing identified wildlands in the Sierra Nevada are included in ... more Guidelines for protecting and managing identified wildlands in the Sierra Nevada are included in this document to assist conservation practitioners and resource managers in the maintenance of vital wildlands and wildlife. These guidelines recommend limiting habitat fragmentation by controlling road density and habitat loss in wildlands. This will directly benefit wildlife species and maintain the health of ecosystems. Other guidelines recommend the establishment of conservation easements, wildlife friendly zoning ordinances, and wildlife under-and over-passes where roads prohibit movement. These guidelines will become more specific through the site planning process, which will be encouraged at the local scale.
The United States Forest Service is required to analyze road systems on each of the national fore... more The United States Forest Service is required to analyze road systems on each of the national forests for potential environmental impacts. We have developed a novel and inexpensive way to do this using the Ecosystem Management Decision Support program (EMDS). We used EMDS to integrate a user-developed fuzzy logic knowledge base with a grid-based geographic information system to evaluate the degree of truth for assertions about a road’s environmental impact. Using spatial data for natural and human processes in the Tahoc National Forest (TNF, California, USA), we evaluated the assertion “the road has a high potential for impacting the environment.” We found a high level of agreement between the products of this evaluation and ground observations of a TNF transportation engineer, as well as occurrences of road failures. We used the modeled potential environmental impact to negatively weight roads for a least-cost path network analysis to 1573 points of interest in the forest. The network analysis showed that out of 8233 km of road analyzed in the forest, 3483 km (42%) must be kept in a modified road network to ensure access to these points. We found that the modified network had improved patch characteristics, such as significantly fewer “cherry stem” roads intruding into patches, an improved area-weighted mean shape index, and larger mean patch sizes, as compared to the original network. This analysis system could be used by any public agency to analyze infrastructure for environmental or other risk and included in other mandated analyses such as risks to watersheds.
To understand the potential financial cost of acquiring lands within a proposed reserve network f... more To understand the potential financial cost of acquiring lands within a proposed reserve network for the Sierra Nevada, CA, USA, we used an assessors GIS database to estimate the acquisition cost in one county within the network to be US$ 2.5 billion. When only larger parcels were selected for the reserve network, the cost of the network decreased exponentially as the size-threshold for parcel selection increased, while the total area of the network decreased only linearly. Although acquiring only larger parcels may make sense financially, it does not result in adequate habitat representation because the spatial distribution of parcels is such that the lower elevation oak woodland and mid-elevation conifer forests tend to be on smaller parcels, which fall below the larger size thresholds and the resulting potential reserve areas are fragmented. Then, for the area surrounding the two major highways that cross the Sierra Nevada, we identified seventeen road barrier areas and six urban conflict areas that pose major, but possibly mitigable barriers to wildlife movement at different time scales. We propose that (1) wildlife conflicts with highway traffic could be feasibly mitigated by installing wildlife overcrossings at the identified locations and (2) constraints on development rather than land acquisition are necessary to protect biodiversity. Finally, we suggest that a combination of highway crossings and restrictions on land-use may be the cheapest way to protect biodiversity in the Sierra Nevada.
Caribbean yellow band syndrome (YBS) is a poorly understood, progressively fatal disease primaril... more Caribbean yellow band syndrome (YBS) is a poorly understood, progressively fatal disease primarily affecting Montastraea spp. coral. This disease has exhibited rapid spread throughout the entire Caribbean over the last few decades. In this study, geographical information systems (GIS) and spatial statistics were used to analyze the distribution of YBS in Akumal Bay, Mexico, and host and environmental risk factors for YBS were evaluated epidemiologically. In this Bay, there are hundreds of colonies of Montastraea annularis from 1 m depths inside the fringing reefs to reef crests and beyond. Of 63 corals that were evaluated, the overall prevalence of YBS in Akumal Bay was 28.6%, with 35.7% in large colonies, 23.8% in medium-sized colonies, and 23.8% in small colonies, where small colonies were 500 cm. Lesions covered 3.8% (±1.3 s.e.) of the surface of colonies assessed, compared with a mean percentage of dead colony cover of 54.4% (±4.2 s.e.). Analysis for spatial clustering documented that M. annularis colonies (well and sick) were highly spatially clustered, compared to expected complete spatial randomness. However, compared with all M. annularis corals, colonies with YBS tended to be less spatially clustered (i.e. within the overall clustered spatial distribution of M. annularis colonies, YBS-affected colonies’ distribution was more regular). These findings are consistent with several hypotheses for the etiology of YBS, including near-shore pathogens or toxins either directly inducing disease or indirectly leading to disease by increasing host susceptibility. Ongoing investigations into the management and cause of YBS can use this information to develop management strategies and more efficiently target future sampling.
Plague is an enzootic disease in the western United States, even though long-term persistent infe... more Plague is an enzootic disease in the western United States, even though long-term persistent infections do not seem to occur. Enzootic persistence may occur as a function of dynamic interactions between flea vectors and transiently infected hosts, but the specific levels of vector competence, host competence, and transmission and recovery rates that would promote persistence and emergence among wild hosts and vectors are not known. We developed a mathematical model of enzootic plague in the western United States and implemented the model with the following objectives: 1) to use matrix manipulation within a classic susceptibleRinfecti-veRresistantRsusceptible (SIRS) model framework to describe transmission of the plague bacterium Yersinia pestis among rodents and fleas in California, 2) to perform sensitivity analysis with model parameters and variables to indicate which values tended to dominate model output, and 3) to determine whether enzootic maintenance would be predicted with realistic parameter values obtained from the literature for Y. pestis in California rodents and fleas. The model PlagueSIRS was implemented in discrete time as a computer simulation incorporating environmental stochasticity and seasonality, by using matrix functions in the computer language R, allowing any number of rodent and flea species to interact through parasitism and disease transmission. Sensitivity analysis indicated that the model was sensitive to flea attack rate, host recovery rate, and rodent host carrying capacity but relatively insensitive to changes in the duration of latent infection in the flea, host and vector competence, flea recovery from infection, and host mortality attributable to plague. Realistic parameters and variable values did allow for the model to predict enzootic plague in some combinations, specifically when rodent species that were susceptible to infection but resistant to morbidity were parasitized by multiple poorly competent flea species, including some that were present year-round. This model could be extended to similar vectorborne disease systems and could be used iteratively with data collection in sylvatic plague studies to better understand plague persistence and emergence in nature.
Archives of Environmental Contamination and Toxicology, 2001
The cellular stress responses of most organisms in part involve the induction of a class of prote... more The cellular stress responses of most organisms in part involve the induction of a class of proteins called heat shock or stress proteins (HSPs) as a result of damage to existing proteins. Cellular proteins can be damaged by chemical exposures known to induce various HSPs. In these experiments, we examine the HSP responses of mussel (Mytilus galloprovincialis) and abalone (Haliotis rufescens) tissues to both thermal and chemical exposures. HSP70 isoforms, HSP60, and HSP90 all show varying induction capabilities. The results demonstrate that the extent of stress exposure as both a time- and dose-dependent phenomena can be ascertained by examining changes in mollusc HSP protein levels. We also examined the relationship between HSP induction and levels of a mussel cytochrome P450 (CYP4Y1) mRNA in dose-response experiments with the products of biologically degraded weathered crude oil. The increases in HSP70 isoforms and HSP90 were correlated with decreases in CYP4Y1 expression levels in a dose-dependent manner. HSP responses may therefore be a valuable part of a suite of biomarkers in biomonitoring for hydrocarbon exposures in nearshore environments.
Guidelines for protecting and managing identified wildlands in the Sierra Nevada are included in ... more Guidelines for protecting and managing identified wildlands in the Sierra Nevada are included in this document to assist conservation practitioners and resource managers in the maintenance of vital wildlands and wildlife. These guidelines recommend limiting habitat fragmentation by controlling road density and habitat loss in wildlands. This will directly benefit wildlife species and maintain the health of ecosystems. Other guidelines recommend the establishment of conservation easements, wildlife friendly zoning ordinances, and wildlife under-and over-passes where roads prohibit movement. These guidelines will become more specific through the site planning process, which will be encouraged at the local scale.
The United States Forest Service is required to analyze road systems on each of the national fore... more The United States Forest Service is required to analyze road systems on each of the national forests for potential environmental impacts. We have developed a novel and inexpensive way to do this using the Ecosystem Management Decision Support program (EMDS). We used EMDS to integrate a user-developed fuzzy logic knowledge base with a grid-based geographic information system to evaluate the degree of truth for assertions about a road’s environmental impact. Using spatial data for natural and human processes in the Tahoc National Forest (TNF, California, USA), we evaluated the assertion “the road has a high potential for impacting the environment.” We found a high level of agreement between the products of this evaluation and ground observations of a TNF transportation engineer, as well as occurrences of road failures. We used the modeled potential environmental impact to negatively weight roads for a least-cost path network analysis to 1573 points of interest in the forest. The network analysis showed that out of 8233 km of road analyzed in the forest, 3483 km (42%) must be kept in a modified road network to ensure access to these points. We found that the modified network had improved patch characteristics, such as significantly fewer “cherry stem” roads intruding into patches, an improved area-weighted mean shape index, and larger mean patch sizes, as compared to the original network. This analysis system could be used by any public agency to analyze infrastructure for environmental or other risk and included in other mandated analyses such as risks to watersheds.
To understand the potential financial cost of acquiring lands within a proposed reserve network f... more To understand the potential financial cost of acquiring lands within a proposed reserve network for the Sierra Nevada, CA, USA, we used an assessors GIS database to estimate the acquisition cost in one county within the network to be US$ 2.5 billion. When only larger parcels were selected for the reserve network, the cost of the network decreased exponentially as the size-threshold for parcel selection increased, while the total area of the network decreased only linearly. Although acquiring only larger parcels may make sense financially, it does not result in adequate habitat representation because the spatial distribution of parcels is such that the lower elevation oak woodland and mid-elevation conifer forests tend to be on smaller parcels, which fall below the larger size thresholds and the resulting potential reserve areas are fragmented. Then, for the area surrounding the two major highways that cross the Sierra Nevada, we identified seventeen road barrier areas and six urban conflict areas that pose major, but possibly mitigable barriers to wildlife movement at different time scales. We propose that (1) wildlife conflicts with highway traffic could be feasibly mitigated by installing wildlife overcrossings at the identified locations and (2) constraints on development rather than land acquisition are necessary to protect biodiversity. Finally, we suggest that a combination of highway crossings and restrictions on land-use may be the cheapest way to protect biodiversity in the Sierra Nevada.
Caribbean yellow band syndrome (YBS) is a poorly understood, progressively fatal disease primaril... more Caribbean yellow band syndrome (YBS) is a poorly understood, progressively fatal disease primarily affecting Montastraea spp. coral. This disease has exhibited rapid spread throughout the entire Caribbean over the last few decades. In this study, geographical information systems (GIS) and spatial statistics were used to analyze the distribution of YBS in Akumal Bay, Mexico, and host and environmental risk factors for YBS were evaluated epidemiologically. In this Bay, there are hundreds of colonies of Montastraea annularis from 1 m depths inside the fringing reefs to reef crests and beyond. Of 63 corals that were evaluated, the overall prevalence of YBS in Akumal Bay was 28.6%, with 35.7% in large colonies, 23.8% in medium-sized colonies, and 23.8% in small colonies, where small colonies were 500 cm. Lesions covered 3.8% (±1.3 s.e.) of the surface of colonies assessed, compared with a mean percentage of dead colony cover of 54.4% (±4.2 s.e.). Analysis for spatial clustering documented that M. annularis colonies (well and sick) were highly spatially clustered, compared to expected complete spatial randomness. However, compared with all M. annularis corals, colonies with YBS tended to be less spatially clustered (i.e. within the overall clustered spatial distribution of M. annularis colonies, YBS-affected colonies’ distribution was more regular). These findings are consistent with several hypotheses for the etiology of YBS, including near-shore pathogens or toxins either directly inducing disease or indirectly leading to disease by increasing host susceptibility. Ongoing investigations into the management and cause of YBS can use this information to develop management strategies and more efficiently target future sampling.
Plague is an enzootic disease in the western United States, even though long-term persistent infe... more Plague is an enzootic disease in the western United States, even though long-term persistent infections do not seem to occur. Enzootic persistence may occur as a function of dynamic interactions between flea vectors and transiently infected hosts, but the specific levels of vector competence, host competence, and transmission and recovery rates that would promote persistence and emergence among wild hosts and vectors are not known. We developed a mathematical model of enzootic plague in the western United States and implemented the model with the following objectives: 1) to use matrix manipulation within a classic susceptibleRinfecti-veRresistantRsusceptible (SIRS) model framework to describe transmission of the plague bacterium Yersinia pestis among rodents and fleas in California, 2) to perform sensitivity analysis with model parameters and variables to indicate which values tended to dominate model output, and 3) to determine whether enzootic maintenance would be predicted with realistic parameter values obtained from the literature for Y. pestis in California rodents and fleas. The model PlagueSIRS was implemented in discrete time as a computer simulation incorporating environmental stochasticity and seasonality, by using matrix functions in the computer language R, allowing any number of rodent and flea species to interact through parasitism and disease transmission. Sensitivity analysis indicated that the model was sensitive to flea attack rate, host recovery rate, and rodent host carrying capacity but relatively insensitive to changes in the duration of latent infection in the flea, host and vector competence, flea recovery from infection, and host mortality attributable to plague. Realistic parameters and variable values did allow for the model to predict enzootic plague in some combinations, specifically when rodent species that were susceptible to infection but resistant to morbidity were parasitized by multiple poorly competent flea species, including some that were present year-round. This model could be extended to similar vectorborne disease systems and could be used iteratively with data collection in sylvatic plague studies to better understand plague persistence and emergence in nature.
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Papers by Evan Girvetz