Conference proceeding
Drivers of pCO2 dynamics in two contrasting coral reef lagoons; the influence of submarine groundwater discharge
American Geophysical Union Fall Meeting, Vol.2013
American Geophysical Union 2013 fall meeting (San Francisco, California, 09/12/2013 - 13/12/2013)
12/2013
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Abstract
The carbon chemistry of coral reef lagoons can be highly variable over short time scales. While much of the diel variability in seawater carbon chemistry is explained by biological processes, external sources such as river and groundwater seepage may deliver large amounts of organic and inorganic carbon to coral reefs and represent a poorly understood feedback to ocean acidification. Here, we assess the impact of submarine groundwater discharge (SGD) on pCO2 variability in two coral reef lagoons with distinct SGD driving mechanisms. Diel variability of pCO2 in the two ecosystems was explained by a combination of biological drivers and SGD inputs. In Rarotonga, a South Pacific volcanic island, SGD was driven primarily by a steep terrestrial hydraulic gradient, and the lagoon was influenced by the high pCO2 (5,501 mu atm) of the fresh groundwater. In Heron Island, a Great Barrier Reef coral cay, SGD was dominated by seawater recirculation through sediments (i.e. tidal pumping) and pCO2 was mainly impacted through the stimulation of biological processes. The Rarotonga water column had a relatively higher average pCO2 (549 mu atm) than Heron Island (471 mu atm). However, pCO2 exhibited a greater diel range in Heron Island (778 mu atm) than in Rarotonga (507 mu atm). The Rarotonga lagoon received 31.2 mmol CO2 m-2 d-1 from SGD, while the Heron Island lagoon received 12.3 mmol CO2 m-2 d-1. Over the course of this study both systems were sources of CO2 to the atmosphere (3.00 to 9.67 mmol CO2 m-2 d-1), with SGD-derived CO2 contributing a large portion to the air-sea CO2 flux. The relationship between both water column pH and aragonite saturation state (Omega Ar) and radon (222Rn) concentrations indicate that SGD may enhance the local acidification of some coral reef lagoons. Studies measuring the carbon chemistry of coral reefs (e.g. community metabolism, calcification rates) may need to consider SGD-derived CO2.
Details
- Title
- Drivers of pCO2 dynamics in two contrasting coral reef lagoons; the influence of submarine groundwater discharge
- Creators
- T Cyronak - Southern Cross UniversityI. R SantosD ErlerD. T MaherB Eyre
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2013
- Conference
- American Geophysical Union 2013 fall meeting (San Francisco, California, 09/12/2013 - 13/12/2013)
- Publisher
- American Geophysical Union
- Identifiers
- 991012978048902368
- Academic Unit
- Centre for Coastal Biogeochemistry; Faculty of Science and Engineering; Science
- Language
- English
- Resource Type
- Conference proceeding