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EVALUATING THE UTILITY OF CRUSTOSE CORALLINE ALGAE AS A Δ11B BIOSENSOR FOR OCEAN ACIDIFICATION MONITORING ON CORAL REEFS

The spatial and temporal variability of seawater pH on coral reefs makes broad-scale monitoring and forecasting of the changes and impacts of ocean acidification in this ecosystem challenging. A single discrete water sample may fail to adequately characterize the pH regime at a site, but practical constraints may preclude repeated diel or seasonal seawater pH measurements at remote sites. There is increasing interest in using the boron isotopic composition (δ11B) of biogenic carbonates as a proxy for seawater pH. To assess if crustose coralline algae (CCA) are effective biosensors of pH, a δ11B-pH field calibration was conducted at a shallow hydrothermal CO2 vent in the Maug Islands where reefs exhibit a localized pH gradient from 8.04 to 7.94. δ11B was measured by multi-collector inductively coupled mass spectrometry in CCA growing in situ from 3 sites. Mean pH values calculated from CCA δ11B at each site (n=10) were regressed against the 3 month mean seawater pH measured via SeaFET, and indicated the CCA δ11B values reliably predicted seawater pH (y=0.84x+1.86, R2=0.98). The efficacy of applying this integrative measure of reef pH will be compared to traditional monitoring using a single discrete carbonate water sample. The δ11B in CCA naturally grown on recruitment panels for 3 years will be analyzed at reefs where discrete carbonate water samples were taken and pH regimes were also independently characterized by repeated seawater measurements. The biases inherent to the two techniques will be assessed and the practical utility of the monitoring approaches discussed.

Authors

Day, R. D., NIST, USA, russell.day@noaa.gov

Stewart, J. A., NIST, USA, joseph.stewart@noaa.gov

Brainard, R. E., NOAA/PIFSC, USA, russell.brainard@noaa.gov

Details

Poster presentation

Session #:056
Date: 03/01/2017
Time: 11:00 - 12:00
Location: Poster/Exhibit Hall

Presentation is given by student: No

PosterID: 473