Geochemical proxies of Crassostrea virginica (Bivalvia) for reconstructing estuarine environments: Assessment of pre-disturbance environmental conditions, southwest Florida.
Surge, Donna Marie
2001
Abstract
Sensitivity of coastal settings to natural and human influences generates interesting problems for scientific study and attracts much public attention. Despite this interest, study of coastal habitats provides many challenges given the dynamic nature of the physical environment and ecosystem. In particular, continental runoff and precipitation create an environment with fluctuating salinity overprinted on seasonal temperature variation. The present study sought to deconvolute some of these complexities and reconstruct temperature, salinity, and landscape evolution in the changing environments of estuaries in southwest Florida. Faka-Union Canal and its watershed is targeted for restoration. To plan and monitor restoration efforts, pre-canal environmental conditions are required. The lack of historical information recording natural, seasonal conditions necessitates alternative means of acquiring predisturbance environmental information. Environmental archives contained in oyster (<italic>Crassostrea virginica </italic>) shells potentially contain useful information to reconstruct environmental conditions before channelization of the watershed. Analysis of delta<super>18</super>O<sub>SHELL</sub> and delta<super> 13</super>C<sub>SHELL</sub> demonstrate that oysters record modern estuarine conditions, though delta<super>13</super>C<super>SHELL</super> is 1--2‰ more positive than predicted delta<super>13</super>C<sub>DIC</sub> during winter months reflecting a vital effect. A radiocarbon-calibrated, amino acid geochronology was established to date pre-canal shells near Naples, Florida. The local reservoir effect (130 +/- 30 years) for the Gulf of Mexico near Naples, Florida was determined to correct AMS ages of marine samples. Pre-canal shells from Blackwater River are older (ranging 780--1810 years before 1998) than those from Faka-Union Bay (ranging 140--730 years before 1998). Subfossil shells from Blackwater River record winter temperatures that are ∼1--5°C colder than shells recording temperatures in Winter 1999. They also record comparable salinities to modern conditions. However, subfossil shells from Faka-Union Bay suggest a complicated hydrology that cannot be easily deconvoluted based on isotopic compositions alone. Therefore, a Mg/Ca thermometer that is less sensitive to salinity variation was developed to estimate temperature (+/-2.5°C). delta<super>13</super>C of subfossil shells suggest change in vegetation from a freshwater prairie-like ecosystem to the saltwater-tolerant mangrove forests of today, possibly due to local influence of relative sea level fluctuation.Subjects
Assessment Bivalvia Conditions Crassostrea Virginica Disturbance Environmental Environments Estuarine Florida Geochemical Magnesium/calcium Ratios Oxygen Isotopes Pre Proxies Reconstructing Southwest
Types
Thesis
Metadata
Show full item recordCollections
Remediation of Harmful Language
The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.
Accessibility
If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.