Biodeposition and Biogeochemical Processes in Shallow, Mesohaline Sediments of Chesapeake Bay

Stocks of the eastern oyster, Crassostrea virginica, have been declining in Chesapeake Bay since the late 19th century, and current strategies involve restoring culture of Crassostrea virginica on-bottom and in devices suspended within the water column. Sub-tidal suspension culture of Crassostrea virginica in Chesapeake Bay occurs mostly in sheltered inlets and tidal creeks and, thereby, has the potential to influence shallow water biogeochemical processes. To assess the influence of Crassostrea virginica biodeposits and benthic microalgae on sediment nitrogen and phosphorus exchange, field studies with Crassostrea virginica held in aquaculture floats and laboratory experiments were conducted. Enhanced organic nitrogen deposition from Crassostrea virginica biodeposits led to gradual increases in surface sediment nitrogen and pore water ammonium concentrations; however, modifications to pore water concentrations were not always expressed at the sediment-water interface. Benthic microalgae often modulated the influence of biodeposits on sediment nitrogen exchange but, as observed in laboratory experiments, the supply of nitrogen from Crassostrea virginica biodeposits may exceed their biological demand. Organic carbon from biodeposits had varying influences on aerobic respiration but consistently stimulated anaerobic metabolism. Shifts in net phosphorus exchange were driven by this anaerobic remineralization and concentrations of iron and manganese oxy(hydr)oxides, with transitions in fluxes coinciding with changes in benthic photosynthesis and oxidation of surface sediments. Manganese and iron oxy(hydr)oxides from biodeposits supported incorporation of added phosphorus and prevented exchange at the sediment-water interface in the absence of iron-sulfide mineral formation. Differences in the response of shallow water sediments to Crassostrea virginica biodeposits were due to the quality and quantity of biodeposits supplied, as well as the spatial and temporal variability within these sediments. Initial conditions and corresponding reference sediments illustrated the potential for sediment biogeochemistry and nutrient exchange from tidal creek sediments to vary spatially and temporally on relatively small scales. Factors influencing variability within tidal creek sediments were related to shifts in riverine freshwater inputs, macroalgal blooms, nutrient concentrations in overlying waters, and bioirrigation from the clam, Macoma balthica.

A von Bertalanffy Based Model for the Estimation of Oyster (Crassostrea virginica) Growth on Restored Oyster Reefs in Chesapeake Bay

A model to estimate the mean monthly growth of Crassostrea virginica oysters in Chesapeake Bay was developed. This model is based on the classic von Bertalanffy growth function, however the growth constant is changed every monthly timestep in response to short term changes in temperature and salinity. Using a dynamically varying growth constant allows the model to capture seasonal oscillations in growth, and growth responses to changing environmental conditions that previous applications of the von Bertalanffy model do not capture. This model is further expanded to include an estimation of Perkinsus marinus impacts on growth rates as well as estimations of ecosystem services provided by a restored oyster bar over time. The model was validated by comparing growth estimates from the model to oyster shell height observations from a variety of restoration sites in the upper Chesapeake Bay. Without using the P. marinus impact on growth, the model consistently overestimates mean oyster growth. However, when P. marinus effects are included in the model, the model estimates match the observed mean shell height closely for at least the first 3 years of growth. The estimates of ecosystem services suggested by this model imply that even with high levels of mortality on an oyster reef, the ecosystem services provided by that reef can still be maintained by growth for several years. Because larger oyster filter more water than smaller ones, larger oysters contribute more to the filtration and nutrient removal ecosystem services of the reef. Therefore a reef with an abundance of larger oysters will provide better filtration and nutrient removal. This implies that if an oyster restoration project is trying to improve water quality through oyster filtration, it is important to maintain the larger older oysters on the reef.

The Oud Across Arabic Culture

This study is a compilation and compendium of information on the oud, the most important instrument in Arabic classical music. It has grown out of my own long-time involvement in studying and playing the oud, and in particular out of my interest in the lack of sources and knowledge available to the vast majority of oud players and researchers, as well as for the readers. My own path started from an intensive study of the oud, which included exposure to several treaties; some housed in museums around the globe, and some only available in the Arabic language. The study combines archival research (including Arabic poetry and pre-Islamic Era and medieval treaties), symbolism, new archaeological discoveries, field interviews, and analysis of existing scholarship, and draws on my professional performance experience for detailed stylistic analysis of the oud's performance practice and its historical development. The study consists of participant observation, personal performance, and interviews conducted in person, via telephone, and/or via e-mail, according to the choice of the performers. The performers have been selected from networks of musicians who perform regularly at lounges, concert halls, and private events. These performers have been chosen according to their musical knowledge, technical skill, experience, and activity in Arabic music and oud performance. Chapter one deals with the purpose of this study and the methods of investigation, as well as giving a brief overview of the history of the oud. In addition, there will be an introduction to the Arabic musical system (mâqâm), which is primarily based on the mechanics and sound production of the oud. Chapter two deals with the oud in Arabic sources: the first source is Arabic poetry in the pre-Islamic Era. The second source is Arabic poetry in the medieval era, in which I found a significant number of poets who allude to the oud, providing accurate descriptions of the player, singers, and the scenes within the contexts of oud performance. The third source is the Arab scholars' intensive treatises with meticulous accounts of the instrument's apparatii, including descriptions and measurements of the parts, strings, and tuning. While chapter three deals with the classification, the development of the oud, chapter four deals with topics such as: the symbolism of the oud and its relation to cosmology, astronomy, mathematics and anatomy. In most of the pertinent Arabic writings, philosophers mention a significant correlation between the oud and the other sciences. Chapter five deals with recreating the performance practice of the oud. A case study of the oud performers focuses on their style, technique, training, and personal experiences. Topics such as improvisation and ornamentation, the oud in the Arabic musical ensemble, the social uses and functions, and gender in musical performance practices will be included in detailed analysis. Other important topics will be analyzed such as traditional vs. modern technique, and the repertoire of the oud. Specifically, in regard to technique, the study outline the style of the music, the role of the oud in Arabic ensembles, the function of the oud in music composition, and the form of the ensembles in Arabic performance and practice.