| Sediment cores were used to reconstruct past Chesapeake Bay environments. This work is divided into two parts, due to time scale differences of the cores. Part I, the main body of work, focuses on the late Holocene (1000 to 2000 AD); part II on a previous early interglacial record, the Sangamon (100,000 to 120,000 yBP). The late Holocene record was used to study food web changes and natural versus anthropogenic alterations to Chesapeake Bay. The early interglacial record is presented as the first evidence of environmental conditions in Chesapeake Bay during the early Sangamon interglacial.; There have been clear food web changes in Chesapeake Bay in the last century. Previously, the food web was characterized by autotrophic pathways that passed large amounts of energy to higher trophic levels. The present system, dominated by heterotrophic and detrital pathways, leads to very little production at higher trophic levels. The primary goal of Part I was to investigate if and how the paleoecological record of organisms and chemicals preserved in sediment cores could be used to interpret food web interactions. Trends in the food web were investigated and shifts in major taxonomic groups identified.; Two long sediment cores collected from the mesohaline section of Chesapeake Bay were dated using carbon-14, lead-210, and pollen analyses. Foraminifera, ostracods, gastropods, a bivalve Mulinia lateralis, polychaetes, the geochemical record, and carbon and nitrogen stable isotope signatures were investigated to better understand the driving forces behind the food web changes that have occurred. An attempt was made to link shifts seen at the bottom of the food web with higher trophic level species.; Climatic and anthropogenic activity led to changes in precipitation, upland freshwater inputs, and nutrient inputs, over the past 1000 years. The results of Part I suggest that the losses and changes to benthic diatoms and the deterioration of the benthic faunal community are connected to decreased populations of higher trophic level organisms. It is proposed that alterations in the benthic community have consequences for organisms at higher trophic levels relying on benthic energy pathways. |
