Applying dendrochronology visual crossdating techniques to the marine bivalve Arctica islandica and assessing the utility of master growth chronologies as proxies for temperature and secondary productivity in the Gulf of Maine

• Main Author: Griffin, Shelly
• Other Authors: Alan D. Wanamaker Jr., Department of the Earth, Atmosphere, and Climate
• Format: Thesis
• Language: English
• Published: 2012
• Subjects: Climate; Geology; Oceanography; Paleontology; Arctica islandica; climate variability; crossdating; Gulf of Maine; sclerochronology; shell growth
• Online Access: https://dr.lib.iastate.edu/handle/20.500.12876/26875; https://hdl.handle.net/20.500.12876/26875; https://doi.org/10.31274/etd-180810-1103

The work that follows is aimed at providing a more comprehensive understanding of relationships between growth variability within and among populations of A. islandica in the Gulf of Maine. An essential goal of this work is to establish the level of coherence of A. islandica growth (that is the common growth signal) within the Gulf of Maine. Further, the relationships between variable growth rates and environmental conditions will be investigated. This research presents preliminary findings in the context of a larger project, with a goal to establish a master shell chronology and to reconstruct hydrographic conditions, including seawater temperatures, for the last 1000 years in the Gulf of Maine. In order to determine the relationship between shell growth and potential environmental forcings, site-specific calibrations between growth and environmental conditions must be developed. First, the strength of a common growth signal (how synchronous growth is at the population level) must be determined at each site. Then, ecologically relevant comparisons with environmental can be investigated. However, prior to any proxy-based climate or environmental reconstruction, a calibration between the proxy archive and an instrumental series is required. Dendrochronology techniques were applied to the marine bivalve Arctica islandica to demonstrate the benefits of visual crossdating and replication of growth series (growth within one shell and between multiple shells in the same population). Prior to measuring the thickness of annual increments, individual shell increments were visually inspected and temporally aligned using several visual crossdating techniques (marker years, modified list method, and skeleton plots). Applying these techniques of crossdating sclerochronological archives resulted in precisely dated and a highly replicated master shell chronology (average expressed population signal = 0.94; series intercorrelation =0.76) from a site within the central Gulf of Maine (northwestern Atlantic Ocean). Such ...