Coral skeleton density banding: biotic response to changes in sea surface temperature

Hill, Carly A.

Permalink

https://hdl.handle.net/2142/16157 Copy

Description

Title

Coral skeleton density banding: biotic response to changes in sea surface temperature

Author(s)

Hill, Carly A.

Issue Date

2010-05-19T18:39:17Z

Director of Research (if dissertation) or Advisor (if thesis)

Fouke, Bruce W.

Department of Study

Geology

Discipline

Geology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• coral
• density banding
• biomineralization
• zooxanthellae
• calmodulin
• mucus
• carbonic anhydrase
• sea surface temperature

Abstract

Density bands in the CaCO3 (aragonite) skeleton of scleractinian corals are commonly used as chronometers, where crystalline couplets of high and low density bands represent the span of one year. Isotopic analysis of these density bands provides a sensitive reconstructive tool for paleoclimatology and paleoecology. However, the detailed biotic mechanisms controlling coral skeleton aragonite nucleation and crystallization events and resulting skeletal growth rate remain uncertain. The coral tissue organic matrix, composed of macromolecules secreted by the calicoblastic ectoderm, is closely associated with skeletal precipitation and is itself incorporated into the skeleton. We postulate that density banding is primarily controlled by changes in the rate of aragonite crystal precipitation mediated by the coral holobiont response to changes in sea surface temperature (SST). To test this hypothesis, data were collected from coral skeleton-tissue biopsies (2.5 cm in diameter) extracted from four species of Montastraea growing on the fringing reef tract of Curaçao, Netherlands Antilles. Annual mean variation in SST on Curaçao range from 29o in mid-September to 26o C in late February. Samples were collected at strategic time periods spanning the 3o C annual variations in SST. Our nanometer-scale optical analyses of skeletal morphology have revealed consistent changes between high- and low-skeletal density bands, resulting in an 11% increase in the volume of aragonite precipitated in high-density skeletal bands. The re-localization and/or change in abundance of mucus, carbonic anhydrase (a molecule that catalyzes the hydration of carbon dioxide), calmodulin (a calcium-binding protein) and the change in density of gastrodermal symbiotic dinoflagellates has permitted estimates of seasonally-fluctuating carbon allocation by the coral holobiont in response to changing environmental conditions.

Graduation Semester

2010-5

Permalink

http://hdl.handle.net/2142/16157

Copyright and License Information

Copyright 2010 Carly A. Hill

Owning Collections