Medusahead (Taeniatherum caput-medusae (L.) Nevski) is currently one of the biggest threats to rangelands and livestock operations in the Western US. High silica concentrations in medusahead contribute to its invasiveness. I developed a model to explain how silica is involved in the invasion process, and attempted to manipulate silica to increase use of the grass by livestock. Experiments were conducted to determine: 1) whether rotational grazing on established forages of improved nutritional quality would provide supplemental nutrients to increase cattle use of medusahead; 2) evaluate intake of and preference for medusahead treated with a glyphosate herbicide at different rates by sheep; and 3) evaluate intake and selection of medusahead by cattle by separating the effects of a glyphosate herbicide (Roundup®) from other chemicals in the formulation (salt, adjuvant). Additionally, experiments were conducted to 4) determine the nutritional value and digestibility of medusahead treated with Roundup® at different rates and at different plant particle sizes; and 5) determine if cattle grazing with trampling can increase seeding success on medusahead-invaded rangelands. Rotational grazing from supplemental pastures to medusahead-invaded pastures increased medusahead use by cattle during the second year of the study. Furthermore, glyphosate did not increase medusahead consumption in a choice between three glyphosate treatments, but did in a two-way choice test. Cattle grazed glyphosate-treated medusahead more than that of the non-treated grass and completely avoided the salt-treated grass. The active ingredient in a glyphosate herbicide increased consumption of medusahead while other ingredients in the herbicide (i.e., salt and adjuvant) had no influence on this choice. A smaller particle size increased the digestibility of medusahead compared to larger particle sizes. Glyphosate also increases digestibility, but not as much as particle size. Finally, cattle trampling did not help establish seeded plant species, and the seeding attempt was unsuccessful. Thus, grazing rotations between improved pastures and medusahead-infested rangeland, and the combined glyphosate application-grazing are new approaches for medusahead control, as they prepare a seed bed for revegetation and increase the nutritional quality of the grass for improved livestock nutrition.

No description available.

No description available.

Western forests dominated by aspen (Populus tremuloides Michx.) are highly regarded by most resource managers for their ability to provide a variety of benefits (Bartos and Mueggler 1982, Mueggler 1988). They noted aspen to be beneficial for production of livestock forage, wildlife habitat, and scenic beauty, and they are a potentially valuable source of wood products. However, in the West, communities are concerned about the dwindling acreage of aspen. The decline of aspen has been partly attributed to excessive ungulate browsing (Smith et al. 1972, Collins and Urness 1983, Bartos and Campbell 1998). Long-term grazing exclosures have also revealed that browsing by native and domestic ungulates hindered aspen regeneration throughout south-central Utah, including changes in understory species composition ( e.g. Kay and Bartos 2000). However, though ungulate browsing is an established cause of poor success in aspen regeneration, beyond that fact, very little is known about the particulars of the response, especially how it is affected by time and intensity of browsing.

Teleosts are one of the most diverse groups of vertebrates. They utilize a wide array of reproductive strategies and tactics to overcome the challenges of the many ecological niches they inhabit. The most common reproductive method for teleosts is oviparity. Oviparous animals lay eggs with little or no embryonic development from the mother. The embryos are supplied with nutrition via yolk. Vitellogenesis is the process of the ovary sequestering yolk. It is regulated by exogenous environmental cues that act on the hypothalamus-pituitary-gonad axis. Through a series of hormonal controls, the liver produces the yolk precursor, vitellogenin. Vitellogenin is secreted by the liver and absorbed by the growing oocyte by receptor mediated endocytosis. There it is cleaved into the two main yolk proteins which are subsequently used by the growing embryo. The biggest source of nutrition is the yolk protein lipovitellin which also plays a key role in marine teleosts’ ability to osmoregulate their eggs. Lipovitellin is a large glyco-phospho-lipo-protein ca. 200 kDa. Large proteins usually denature easily. However, prior evidence shows that fish lipovitellins are thermally stable. Using differential scanning calorimetry, I quantify lipovitellin’s thermostability amongst four right-eye flounders (Pleuronectidae: winter flounder, American plaice, witch flounder, and yellowtail flounder). Differential scanning calorimetry allows direct interpretation of all thermodynamic properties; however, Lipovitellin was too large and precipitated before other thermodynamic properties could be determined. Pleuronectid lipovitellins all showed high melting points indicative of high thermostability. This shows that despite differing life histories, lipovitellin is conserved. Presence of the pre-cursor, vitellogenin in male or juvenile fish is used as a biomarker for xenoestrogens, a type of endocrine disrupting chemicals that blocks or mimics natural estrogens. They are known to disrupt aquatic life by interfering with natural development and reproduction. A major biological side effect of xenoestrogens is the accumulation of vitellogenin. This effect has made vitellogenin a useful biomarker for monitoring levels of contamination. Unfortunately, vitellogenin can vary greatly in its immunological and structural characteristics, which means that species-specific assays are necessary. This study took the first step in developing an immunoassay for bluefish (Pomatomus saltatrix). Vitellogenin was induced by injecting a group of bluefish with an estrogen, estradiol, and the resulting vitellogenin was isolated from the serum of males. The protein was characterized as vitellogenin by determining its large Stokes radius in gel permeation chromatography combined with its characteristic peptide molecular weight in sodium dodecyl sulfate polyacrylamide gel electrophoresis.

No description available.

No description available.

In the Chesapeake Bay, < 1% of the historic oyster population remains, and efforts have been increasing to restore oysters and the services they provide. Building reefs that successfully provide ecosystem services–especially habitat and foraging grounds–may require different restoration techniques than those previously used, and success may depend on reef morphology (complexity), location, and environmental conditions. Salinity and habitat complexity are two important factors that may interact to effect benthic communities and predator-prey interactions on restored reefs. The goals of this project were: (1) Characterize the benthic communities on restored oyster reefs in lower Chesapeake Bay, and (2) examine the effects of structural complexity and salinity on benthic communities and predator-prey interactions. A two-year field survey of restored reefs was carried out in four rivers in lower Chesapeake Bay to characterize faunal communities on restored reefs and to quantify the effect of reef complexity on faunal communities. A laboratory mesocosm experiment was conducted to examine the effect of reef complexity on predator foraging. In total, 61 macrofaunal species were identified among all samples, and restored reefs supported on average, 6,169 org/m2 and 67.88 g-AFDW/m2. There were significant differences in the community composition and diversity among the rivers, and salinity was the environmental factor that best explained the observed differences in species composition across the rivers. Salinity and rugosity (i.e., structural complexity) both positively affected diversity, while salinity negatively affected macrofaunal abundance and biomass. Oyster density and rugosity positively affected macrofaunal biomass, and oyster density positively affected mud crab, polychaete, and mussel densities. In the mesocosm experiment, predator foraging, measured by proportion and number of prey consumed, was significantly reduced in the presence of oyster shell structure. However, predators were able to consume more prey when prey density was increased, even in the presence of oyster shell structure. These results combine to enhance our understanding of the benefits of increased habitat complexity for both prey and predators on restored oyster reefs. Increasing complexity worked to increase the abundance, biomass, and diversity of organisms inhabiting restored reefs, and even though predator consumption was reduced in the presence of structure compared to non-structured habitat, predators were able to consume more prey individuals when prey density was increased. Therefore, increasing the structure of oyster reef habitat may benefit prey species by providing refuge habitat, and benefit predators by providing an increased abundance of available prey items.

The eastern oyster Crassostrea virginica is an ecologically and commercially important species whose natural populations have been devastated by overharvesting, habitat destruction, and disease, but the rapid growth of oyster aquaculture has shown potential to restore the economic significance of this species. A key threat to the growth and sustainability of oyster aquaculture is the association of human-pathogenic Vibrio bacteria with product marketed for raw consumption. Two Vibrio species, Vibrio vulnificus and Vibrio parahaemolyticus, are the causes of the highest rates of seafood consumption-related mortality and gastrointestinal illness, respectively. Identification of the factors influencing V. vulnificus and V. parahaemolyticus prevalence and intensity in oysters is fundamental to better risk management. Within the oyster, these bacterial species interact with the same tissues as the prevalent oyster parasite, Perkinsus marinus, yet little is known about the effect of P. marinus infection on bacterial levels. Answering the fundamental question of whether P. marinus correlates with V. vulnificus and V. parahaemolyticus levels in oysters was the focus of this research. Oysters were deployed in the York River, Gloucester Point, VA, where both Vibrio species and P. marinus are endemic, and were sampled at five time points when levels of both P. marinus and Vibrio spp. were expected to be high in oysters. Abundance of all three organisms and pathogenic strains of V. parahaemolyticus were determined in individual oysters using molecular methods to investigate potential correlations between parasite and bacterial abundance. Additionally, the levels of V. vulnificus and V. parahaemolyticus in relation to histopathology associated with P. marinus infection and other conditions were determined. The following year, manipulation of P. marinus disease progression, which is slowed by lower salinities and favored by higher salinities, was attempted by deploying oysters at two additional sites of different salinities to gain insight into whether the timing of P. marinus infection emergence directly influences Vibrio levels. No correlation was observed between total abundance of P. marinus and either V. vulnificus or V. parahaemolyticus. Manipulation of P. marinus disease progression produced no effect on P. marinus emergence, so this yielded no insight into P. marinus-Vibrio interactions. Histopathological analyses did not reveal any correlations between P. marinus ranking, distribution, or associated tissue damage and Vibrio spp. levels. Though few in number, oysters infected by Haplosporidium nelsoni were characterized by higher levels of V. vulnificus, and oysters of peak gametogenic development had significantly higher levels of pathogenic strains of V. parahaemolyticus. The results with regard to H. nelsoni and gametogenic state warrant further study. The primary conclusion of this study is that oyster health has little influence on levels of human-pathogenic Vibrio species in oysters, inter-host variability in Vibrio levels is likely explained by other factors.

Muscle and hepatopancreas of blue crabs (Callinectes sapidus), collected from the Elizabeth River, Virginia, contained residues of polycyclic aromatic hydrocarbon (PAHs}, polychlorinated biphenyls (PCBs) and organochlorine pesticides. Analytical procedures involved dichloromethane extraction of lyophilized tissue, followed by molecular size and polarity-based purification of the extract. capillary gas chromatography with flame ionization detection and electrolytic conductivity detection was used for quantitation and tentative identification of the xenobiotic compounds. Mass spectrometry was used for confirmation of these identities. Contaminant concentrations were greater in hepatopancreas than in muscle in crabs from every site examined. Hepatopancreas PAH burdens were as high as 11 mg/kg dry weight, with an accompanying muscle level of 3.1 mg/kg. The PAHs present consisted mainly of alkylated low molecular weight compounds (e.g., acenaphthenes and naphthalenes), except near a creosote-impacted site. At the latter location, unsubstituted, higher molecular weight PAHs (e.g., pyrene and chrysene) dominated. Organochlorines, which included PCBs, 4,4'-DDE, and chlordane were found in lower concentrations. The effect of molting on xenobiotic accumulation in Crustacea was also examined. Molting is essential for crustacean growth and is integral to the reproductive process in some species. Molting and intermolt blue crabs were maintained in cages at the creosoted-impacted Elizabeth River site mentioned above. PAH concentration in muscle and hepatopancreas was measured for both molt groups. Newly molted blue crabs possessed statistically higher tissue burdens than intermolt crabs of three unsubstituted PAHs (cyclopenta(def)phenanthrene, fluoranthene, and pyrene) characteristic of the creosote-contaminated exposure site. Mean concentration of the three PAHs in hepatopancreas was 9560 μg/kg in newly molted crabs and 3360 μg/kg in intermolt crabs. Mean PAH concentration in muscle was 1380 μg/kg in new-molts and 498 μg/kg in intermolts. The elevated tissue burdens may be due to increased water uptake and shell permeability at ecdysis or decreased metabolism of PAH during the molt process. Newly molted blue crabs are regarded as a seafood delicacy and tissue burdens of xenobiotics, such as PAHs, may be of human health concern.