During the winter 1988-89, diurnal and nocturnal habitat use by juvenile female canvasbacks wintering on the upper Chesapeake Bay was determined. Radio-implanted canvasbacks used shallow water (0-2 m) areas near artificial feeding sites during the day, and deeper water (2-6 m) that had an abundant (> 200/m²) population of small (< 25 mm) Macoma balthica at night. Because of poorer Macoma populations on the east side of the Bay, canvasbacks there may feed more during the day and are in lower Macoma densities at night than west shore canvasbacks. Management of Chesapeake Bay canvasback populations should focus on providing natural foods and rest areas. / Master of Science

Nonpoint source pollution from cropland has been identified as the primary source of nitrogen and sediment, and a significant source of phosphorus in the Chesapeake Bay. These pollutants, whether from point or nonpoint sources, have been found to be the primary cause of declining water quality in the Bay. Numerous studies have indicated that, for many watersheds, a few critical areas are responsible for a disproportionate amount of the nutrient and sediment yield. Consequently, if pollution control activities are concentrated in these critical areas, then a far greater improvement in downstream water quality can be expected with limited funds. In this research a phosphorus transport model is incorporated into ANSWERS, a distributed parameter watershed model. The version of ANSWERS used has an extended sediment transport model which is capable of simulating the transport of individual particle classes in a sediment mixture during the overland flow process. The phosphorus model uses a nonequilibrium desorption equation to account for the desorption of phosphorus from the soil surface into surface runoff. The sediment-bound phosphorus is modeled as a function of the specific surface area of the soil and transported sediment. The equilibrium between the soluble and sediment-bound phosphorus is modeled using a Langmuir isotherm. The extended ANSWERS model was verified using water quality data collected from rainfall simulator plot studies conducted on the Prices Fork Research Farm in Blacksburg, Virginia. The plots consisted of four 5.5 m wide by 18.3 m long strips with average slopes ranging from 6.2 to 11 percent. Two of the plots were tilled conventionally, and the remaining two were no-till. Simulated rainfall at an intensity of 5 cm/h was applied to the plots and runoff samples were analysed for sediment and phosphorus. The model was then verified by comparing the simulated responce with the observed data. The results of the verification runs ranged from satisfactory to excellent. Also developed is a technique for selecting a design storm for ANSWERS. The technique creates an n-year recurrence interval storm with a duration equal to the time of concentration of the watershed. The intensity pattern is simulated on a ten-minute interval using a first-order Markov model with a lognormal distribution. Using a two-year recurrence interval design storm, the use of the model is demonstrated for evaluating the application of conservation practices to critical areas on a Virginia watershed. Application of BMP's to critical areas is shown to be substantially more cost effective in terms of pollutant reduction than nonselective placement of BMP's if cost sharing funds are involved. / M.S.

Blue Catfish were introduced in the tidal tributaries of the Chesapeake Bay in the 1970s and 1980s to establish new fisheries during a time period when many fisheries were in decline due to pollution, habitat alteration, disease, overfishing, and environmental catastrophes. Having expanded their range to most Bay tributaries, the species has drawn concern from many stakeholders and scientists for its effects on at-risk and economically important native and naturalized species. My study focused on understanding the dynamics of this species based on multiple long-term monitoring data and evaluating potential management strategies to meet stakeholder needs. I sought to understand how is growth variability was partitioned over time and space, how Blue Catfish populations changed from 1994 to 2016, and how predation on native species and fishery-based performance measures may respond to management intervention. As Blue Catfish length-at-age is exceptionally variable in Virginia tributaries of the Chesapeake Bay, I evaluated the variability in growth using candidate non-linear mixed effects models that described variability in growth over time and space. Linear trend tests supported declines in growth over time within river systems, but did not support the presence of synchronous growth responses among river systems. To better understand population dynamics of Blue Catfish in the Chesapeake Bay watershed, I developed a statistical catch-at-length model for the James River to estimate population size, instantaneous fishing mortality, and size structure over time. The statistical catch-at-length model estimated that Blue Catfish abundance increased slowly and peaked in the mid-2000s before undergoing a recent decline. The model estimated a large spike in abundance due to an estimated large recruitment event in 2011, but may be an artifact of missing data in 2012 in both relative abundance indices examined. The newly developed statistical catch-at-length model provides most detailed information on population dynamics of Blue Catfish in the James River and can be expanded and updated as new data become available. Based on results of the statistical catch-at-length model, I examined population responses to unregulated, maximum length limit (60 cm), and harvest slot limit regulations (harvest allowed 25 –60 cm) in a management strategy evaluation framework. The management strategy evaluation supported that the James River Blue Catfish population could be reduced with increased harvest, but trophy-size fish would decline. Consequently, fishery managers tasked with invasive species management must consider this tradeoff of fishery economic benefits and predation on native populations, especially those prey in which population sizes are unknown. / Doctor of Philosophy / Blue Catfish are non-native to the Chesapeake Bay watershed, but were stocked in the 1970s and 1980s to provide fishing opportunities to the region. Unknowingly, Blue Catfish expanded downstream and beyond the boundaries of the rivers to which they were originally stocked and now exist in extremely dense populations in places. This expansion in population size and distribution has generated concern for the health of the Chesapeake Bay and calls for population control. I wanted to learn more about Blue Catfish in Virginia, specifically Blue Catfish growth rates, population dynamics, and how they might respond to control efforts. I examined Blue Catfish growth rates and found growth rates differed over time and across river systems. Blue Catfish tended to grow more slowly over time as their populations matured. As growth rates declined, population size increased with maximum population sizes in the late 2000s in the James River with a subsequent decline in abundance. Many invasive species exhibit this sort of phenomenon, where population sizes increase and reach a maximum before declining. Finally, I looked at Blue Catfish responses to different fishing regulations and harvest levels, finding that increased harvest could help control Blue Catfish population sizes. However, Blue Catfish management objectives are in conflict as regulations that limit predation of native species of interest also reduce the proportion of large fish in populations. Blue Catfish management will require stakeholder-driven approaches to ensure buy-in and reduce user conflicts.

I studied bald eagle (Haliaeetus leucocephalus) distribution, abundance, roost use and response to human activity on the northern Chesapeake Bay from 1984-89. The eagle population consisted of Chesapeake breeding eagles, Chesapeake nonbreeding eagles, northern-origin eagles and southern-origin eagles; changes in overall eagle distribution and abundance reflected the net changes in these 4 groups. Breeding territories on the northern Chesapeake increased from 12 to 28 from 1984 to 1988. Breeding eagles were resident all year, always ~7 km from the nest. Chesapeake nonbreeding eagles moved throughout most of the bay, but rarely left it (~5% of the radio-tagged eagles were off the bay during any month). Northern eagles migrated into the bay in late fall (x = 21 December! n = 7! range = 61 days) and departed in early spring (x = 27 March, n = 14, range = 43 days). Southern eagles arrived on the northern bay throughout April-August (x = 6 June, n = 11, range = 94 days) and departed from June - October (x = 3 September, n = 22, range = 119 days). Northern Chesapeake eagle abundance peaked twice annually; in winter (261 eagles, December 1987), driven by the presence of northern eagles, and in summer (604 eagles, August 1988), driven by the presence of southern birds. Of 1,117 radio-tagged eagle locations, only 55 (4.90/0) occurred in human-developed habitat, which composed 27.7% of 1,442 km2 of potential eagle habitat on the northern Chesapeake Bay (P < 0.001). During 36 aerial shoreline surveys, eagles were observed on only 111 of 700 (15.9%) 250-m shoreline segments that had development within 100 m, whereas eagles were observed on 312 of 859 (36.30/0) segments when development was absent (P < 0.001). On average, eagles were observed on 1.0 segment/survey that had coincident pedestrian use within 500 m, compared to 3.6 segments/survey expected if eagles and pedestrians were distributed along the shoreline independently (n = 34 surveys, P < 0.001). / Ph. D.

Availability of dead fish to bald eagles (Haliaeetus leucocephalus), prey preferences of bald eagles, and the effects of food on their distribution and movements on the northern Chesapeake Bay were examined from April 1988-July 1989. Dead fish surveys were conducted, by boat, to monitor dead fish availability in several eagle-use areas of the northern Bay, and 3 methods were used to describe disappearance rates of dead fish: dead fish cages, anchored dead fish and floating dead fish. Live fish availability was monitored using gillnets. Dead fish were most available to eagles from May through September, with a peak in availability in June (0.75 dead fish/km with fish die-offs not included, and 3.5 dead fish/km with fish die-offs included). Channel catfish (Ictalurus punctatus) comprised the largest portion of dead fish in early summer months (30% and 28% of total seen, excluding fish die-offs). In contrast, live catfish comprised only 0.4% and 2.1% of the fish caught near the surface in gillnets during spring and summer indicating that dead catfish may be more available, relative to other species, than live catfish. Atlantic menhaden (Brevoortia tyranus) comprised 83-98% of the fish seen in 2 fish die-offs (175 total fish). Only 2 dead fish were seen along 147.7 km of dead fish surveys in winter (0.014 dead fish/km). Most (95%) dead menhaden that we anchored near the bottom off Aberdeen Proving Ground (APG) in summer were scavenged before becoming rancid (X̅= 0.4 days). In contrast, 70% of dead menhaden that we put out in winter became rancid before being scavenged (X̅= 9 days). Pairs of prey items were offered on shoreline areas to wild bald eagles and on platforms to 2 captive bald eagles. All pair-wise combinations of channel catfish, gizzard shad (Dorosoma cepedianum), menhaden and white perch (Morone americana) were offered. We also paired gizzard shad with mallards (Anas platyrhynchos) and rabbits (eastern cottontails, Sylvilagus floridanus, or domestic rabbits, Oryctolagus cuniculus) in shoreline trials, and gizzard shad with mallards and eastern gray squirrels (Sciurus carolinensis) in captive eagle trials. Wild and captive eagles preferred catfish (P=0.0072 and P<0.0002, respectively), and showed no preference for gizzard shad, menhaden nor white perch. Wild eagles preferred gizzard shad over mallards in summer and in winter (P= 0.062 and P=0.002, respectively), while captive eagles preferred mallards over gizzard shad (P= 0.039). Wild eagles selected gizzard shad 4 of 4 times over rabbits (P= 0.125), while captive eagles selected squirrels 5 of 5 times over gizzard shad (P=0.062, both eagles combined). Handling time and familiarity with prey seem to be major factors influencing prey preference, though prey availability seems to determine the actual diet of eagles on the northern Bay. The prediction that the autumn decline in fish abundance on the northern Chesapeake Bay causes eagle distribution to shift from APG to 2 autumn/early winter concentration areas on the northern Bay (Susquehanna River and the Eastern Shore) and then to Blackwater National Wildlife Refuge (BWNWR) and vicinity (winter concentration area on the lower Bay) was tested. By supplying fish (mostly gizzard shad) ad libidum each morning at 2 sites from 28 September through 11 December 1988 a situation in which fish availability did not decline on APG was simulated. Eagle use of the sites increased from 4 eagles seen on first morning that we supplied fish to a peak of 63 eagles seen on the morning of 8 December. Based on shoreline surveys and relocations of 39 radio-tagged nonbreeding Chesapeake hatched eagles, eagle distribution shifted to the Susquehanna River, where eagles feed on gizzard shad, as in 1986 and 1987. However, they did not shift to the Eastern Shore to feed on waterfowl as they had done in 1986 and 1987. Supplemental feeding on APG failed to keep eagles from moving to the lower Bay. Although local eagle distribution on the northern Bay in autumn seems to be dependent on food availability, the autumn decline in fish abundance may not be the proximate factor causing movement to BWNWR and vicinity. / Master of Science

Research was conducted in soils of the Chesapeake Bay area primarily to determine the combined effects of tillage practice and N fertilizer application rates on N leaching and denitrification losses from corn fields. Three well known models - the NTRM, CERES- Maize, and VT-MAIZE - were also tested to determine their predictive ability of N distribution in soil and crop, the various components of the N cycle, and corn yields. To accomplish the above objectives, two field sites were located (in 1986) for a 3 year study on agronomically important and representative soils that are used for corn production in the Chesapeake Bay drainage basin. The main plot treatment was tillage and consisted of no-till and conventional-till. The subplot treatments were N application rates which consisted of 6 levels with 4 inorganic and 2 organic (sewage sludge) N fertilizers. Denitrification experiments were also conducted on the Groseclose silt loam soil to estimate and compare N loss through denitrification from both till and no-till practices. C₂H₂ was used to inhibit N₂ production and N₂O was collected in closed chambers located on the soil surface. Tensiometers and neutron moisture meter access tubes were also installed to monitor soil moisture and energy levels. Nitrogen leaching losses were determined by applying the principle of N mass balance. Denitrification N loss during the corn growing season was less than 2% of the applied N fertilizer. The N losses from the two tillage systems were not significant at p > 0.10. If Fick’s law is to be applied for predicting N loss from the soil subsequent to C₂H₂ application, sampling must occur after a minimum preset critical time. In the Groseclose soil, there was an increase in both total yield and total N uptake when sewage sludge was applied compared to the split and preplant inorganic fertilizers applied at the same rate. There was no difference in yield or N uptake due to applying N as either preplant or a split application. Where no-till management was used, there was an increase in both yield and N uptake as compared with conventional tillage. In the Suffolk soil, tillage management did not influence yield or N uptake where time and source of N application were studied. The relationship between yield and N application rates for both soil types could be described with quadratic equations. The total N recovery could also be described with quadratic equations. However, these relationships do not hold every year for every season or tillage management practice. The no-till plots retained higher moisture content than conventional tillage plots in the upper 0-100 cm depth. Below 100 cm depth, however, no-till retained less than conventional till. The gain and loss of N in soil was dependent on the tillage type and seasons of the year. During the growing season, generally the conventional tillage gained more N than the no-till. During winter, however, the N losses due to leaching were proportional to the amount of N retained at the end of the growing season. Thus, conventional tillage lost more N by leaching during the winter months. Mineralization of N was higher in conventional till, while denitrification was higher in no-till. Split application has shown less N loss due to leaching than the preplant. Mineralization, denitrification, and leaching took place from both the upper and lower zones of the soil profile. The model performances varied from year to year and from one tillage practice to another. Since they were generally written for average (normal) soil and climatic conditions, they did not make satisfactory predictions under the severe moisture conditions experienced during this study. Thus, they require a great deal of readjustment. Considering all aspects, however, the NTRM is the best model. The unmodified VT-MAIZE is the next best. / Ph. D.

The crab processing industry of the Chesapeake Bay region has, until recently, been able to dispose of their processing wastewaters by discharging them, largely untreated, directly to the receiving waters along which their plants are located. With the upcoming implementation of new NPDES discharge limits, this practice will no longer be possible. This study investigated the potential of two different technologies for treating the processing wastewaters. Bench-scale anaerobic contact type reactors were studied for effectiveness in the removal of organics from the processor’s wastewaters, and a pilot-scale countercurrent air stripping tower was studied for ammonia removal. Two anaerobic reactors which were fed retort process wastewater at F/M ratios of 0.35 and 0.25 lb COD/1b MLVSS/day, were found to achieve organics removals (on a BOD₅ basis) of 88% and 94% respectively. Similarly, a second pair of anaerobic reactors were fed a mixed wastewater, representative of a mechanized processing plant’s total wastewater flow, at F/M ratios of 0.10 and 0.07 lb COD/1b MLVSS/day. These reactors were found to achieve organics removals (on a BOD₅ basis) of 79% and 83% respectively. All four of the reactors were eventually shut down after exhibiting signs of failure. These failures were attributed to possible sodium and ammonia toxicity problems. The effectiveness of the air stripping tower in the removal of ammonia from retort process wastewater was tested in relation to liquid flow rate, influent temperature, and influent pH. A maximum ammonia removal of 71% was observed when treating a waste, with an influent temperature of 580C and pH level of 12.2, at an air-to-water ratio of approximately 825 ft³/gal. Similarly, an ammonia removal rate of 67% was observed while treating a waste, with an influent temperature of 650°C and pH level of 11.0, at an air-to-water ratio of approximately 412 ft³/gal. / Master of Science

This study analyses the spatial and temporal variability of chlorophyll-a in Chesapeake Bay; assesses the performance of Ocean Color 3M (OC3M) algorithm; and develops a novel algorithm to estimate chlorophyll-a for coastal shallow water. The OC3M algorithm yields an accurate estimate of chlorophyll-a concentration for deep ocean water (RMSE=0.016), but it failed to perform well in the coastal water system (RMSE=23.17) of Chesapeake Bay. A novel algorithm was developed which utilizes green and red bands of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. The novel algorithm derived the chlorophyll-a concentration more accurately in Chesapeake Bay (RMSE=4.20) than the OC3M algorithm. The study indicated that the algorithm that uses red bands could improve the satellite estimation of chlorophyll-a in the coastal water system by reducing the noise associated with bottom reflectance and colored dissolved organic matter (CDOM)

Monticello, the plantation home of Thomas Jefferson, was also home to more than 100 African American slaves between 1771 and 1826. As many as 40 members of this community lived and worked on Mulberry Row, once a bustling avenue of residential and industrial activity adjacent to the Palladian mansion. Archaeological excavations in 1957 and 1982–-1983 uncovered the remains of Mulberry Row's nailery, where preteen and teenaged enslaved "“nail boys”" manufactured nails for internal use and sale. These excavations revealed surprisingly high amounts of domestic artifacts, particularly ceramics and glass, indicating the young nailers also may have lived inside the nailery. This study investigates whether the nail boys maintained some semblance of childhood through ongoing participation in their parents'’ households or fully took on the mantle of adulthood by forming a household of their own, independent of their parents, as expressed in the local production and consumption of household goods. This question is explored within the contexts of the archaeology of slavery, household archaeology, and the archaeology of children. The intersection of these three themes provides a richer and more realistic understanding of the boys'’ complex lives. In this study, artifact abundance indices and Pearson residuals are used to compare artifacts from the nailery to artifacts from industrial and dwelling sites across Monticello plantation. I hypothesized that if the nail boys were participating in food production and consumption, the abundance of refined and utilitarian ceramics and glass would be similar to or higher than the abundance of those artifacts in dwelling sites. If the abundance of the nailery artifacts was lower than those for dwelling sites and was therefore more similar to those for industrial sites, the nail boys probably did not participate in domestic activities. The indices and residuals reveal a high abundance of refined ceramics and glass in the nailery and a low abundance of utilitarian ceramics, which would have been needed to cook and store food. The data suggest the nail boys engaged in the consumption of food and associated artifacts but participated in little or no food production. It is likely that their age and gender prevented them from fully engaging in food production within the nailery. This project adds to the fledgling research into slave children, who have traditionally been ignored by childhood, slave, and household archaeologists.

No description available.