Graduation Year

2011

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Marine Science

Major Professor

Benjamin P. Flower

Co-Major Professor

Ashanti Johnson

Keywords

Climate change, foraminifera, heavy metals, radionuclide, sediment

Abstract

The Manatee River Watershed (Manatee County, FL) has experienced heavy anthropogenic development over the last 100 years and was relatively pristine previous to this development. The population growth within the watershed has surpassed the national trends and has doubled in the last 30 years. The heavy anthropogenic development has led to depletion in natural resources, nutrient loading, coastal erosion, and increased pollution. This study constructs records of sedimentological processes to compare the pre-development records to the past 100 years of anthropogenic development. The first portion of this study identifies specific changes in sedimentation attributed to anthropogenic activity in the Manatee River. Anthropogenic development has increased the input of terrigenous material into the river by as much as an order of magnitude (0.3-3.0 g/cm2/yr) over three periods; 1) the predevelopment period (1900-1941), 2) the agricultural development period (1941-1970's), and 3) the urban development period (1970's-2010). The second portion of this study examines records of heavy metal (As, Cu, Pb) enrichment in the Manatee River. There are areas in the Manatee River that currently have, or recently have had, concentrations of heavy metals above the EPA regional screening levels. Throughout all of the Manatee River sediment cores there has been a continuous increase in the concentration of arsenic (0.32-20.91 ppm), lead (0.35-35.79 ppm) and copper (1.49-49.55 ppm) from 1900-2010. The third portion of this study utilizes calcareous tests from benthic foraminifera (Ammonia beccarii) in the longest sediment core to determine the Mg/Ca, 18O/ 16O, and 13C/ 12C ratios as proxies for river water temperature, salinity and nutrient content. These proxies allow for the assessment of changes in rates and range of river water parameters from the pre-anthropogenic to the anthropogenic periods. A Manatee River temperature record, precipitation/evaporation record and nutrification record have been constructed for the last 450 years (1550-2009 CE). These records are necessary to inform and enhance future coastal resource management practices.

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