Stable Isotopes of Octocorals: Developing Proxies for Coral Reef Health

EPA Grant Number: F5E10998
Title: Stable Isotopes of Octocorals: Developing Proxies for Coral Reef Health
Investigators: Baker, David M.
Institution: Cornell University
EPA Project Officer: Klieforth, Barbara I
Project Period: January 1, 2006 through December 31, 2008
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2005) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


Dissolved inorganic nitrogen (DIN) is a pervasive form of pollution in the marine environment. While it is generally accepted that increased concentrations of DIN contribute to coral reef decline, it is often difficult to identify sources and correlate snapshot measures of DIN with ecological processes. As an alternative, N isotope analysis of coral reef biota provides a temporally integrated measure of the dominant sources of DIN to a reef. I propose to utilize ubiquitous soft coral species as a biological record of anthropogenic N inputs of:

  1. historical collections,
  2. mesocosm experiments,
  3. and in situ sampling, with the goals of developing isotope analyses of soft corals for monitoring N perturbations, and revealing how sources of N affect ecological processes.

To develop nitrogen isotope analyses as a tool for monitoring nitrogen perturbations in coral reef ecosystems and elucidate how N affects coral health.


I propose to establish δ15N analysis of soft corals as a useful monitoring tool for coral reef management. My first project will examine the role of coastal development on sea fan coral δ15N. I will quantify δ15N of tissue from a collection of sea fan corals dating back to 1850, to establish baseline levels of  15N in the environment and how that has changed over time from human activity. Also, I will initiate mesocosm experiments to quantify N uptake in sea fan corals, and how uptake is affected by environmental factors such as light, concentration, N species, flow, etc. Additionally, I plan to determine the isotopic fractionation effects associated with these variables and attempt to establish correction factors to compare data from different locations.

Expected Results:

I am confident that once the fractionation processes of nitrogen uptake are quantified (elucidated, understood?), δ15N signal of octocorals will provide an accurate and temporally integrated record of the magnitude and sources anthropogenic nitrogen inputs on reefs. Furthermore, I expect that historical samples will show an increase in δ15N over time, associated with the rise in the proportion of sewage derived N in the environment.

Supplemental Keywords:

δ15N, stable isotopes, nutrients, nitrogen, sewage, wastewater, pollution, coral reef, sea fan, agriculture, fertilizer, historical ecology,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Environmental Chemistry, Aquatic Ecosystem, Environmental Monitoring, Ecology and Ecosystems, anthropogenic stress, octocorals, ecosystem monitoring, nitrogen isotope analysis, marine biogeochemistry, aquatic ecosystems, coral reef communities, ecosystem response

Progress and Final Reports:

  • 2006
  • 2007
  • Final