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https://doi.org/10.5194/bg-2018-408
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-408
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 12 Oct 2018

Submitted as: research article | 12 Oct 2018

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This preprint has been withdrawn by the authors.

Seasonal Net Ecosystem Metabolism of the Near-Shore Reef System in La Parguera, Puerto Rico

Melissa Meléndez1, Joseph Salisbury1, Dwight Gledhill2, Chris Langdon3, Julio M. Morell4,5, Derek Manzello6, Sylvia Musielewicz7,8, and Adrienne Sutton7 Melissa Meléndez et al.
  • 1Department of Earth Sciences and Ocean Processes Analysis Laboratory, University of New Hampshire, Durham, New Hampshire, 03824, USA
  • 2National Oceanic and Atmospheric Administration (NOAA), Ocean Acidification Program, Silver Spring, Maryland, 20910, USA
  • 3Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA
  • 4Department of Marine Sciences, University of Puerto Rico, Mayagüez, Puerto Rico, 00680, USA
  • 5Caribbean Coastal Ocean Observing System, NOAA, Magueyes Island, Lajas, Puerto Rico, 00667, USA
  • 6Atlantic Oceanographic and Meteorological Laboratory, NOAA, Miami, Florida, USA
  • 7Pacific Marine Environmental Laboratory, NOAA , Seattle, Washington, 98115, USA
  • 8University of Washington Joint Institute for the Study of the Atmosphere and Ocean, Seattle, WA 98195, USA

Abstract. Changes in ocean chemistry as a direct response to rising atmospheric carbon dioxide (CO2) concentrations is causing a reduction of pH in the surface ocean. While the dynamics and trends in carbonate chemistry are reasonably constrained for open ocean waters, the ways in which ocean acidification (OA) manifests within the shallow near-shore waters, where coral reefs reside, is less understood. Constraining near-reef variability in carbonate chemistry and net ecosystem metabolic processes across diel, seasonal, and annual scales is important in evaluating potential biogeochemical thresholds of OA that could result in ecological community changes. The OA Test-Bed at La Parguera Marine Reserve in Puerto Rico provides long-term carbonate chemistry observations at high-temporal resolution within a Caribbean near-shore coral reef ecosystem. A 1-D model was developed using the carbon mass balance approach to yield information about net ecosystem production and calcification processes occurring in the water column adjacent to the reef. We present results of nine years of sustained monitoring at the Enrique mid-shelf forereef, which provides for the characterization of temporal dynamics in carbonate chemistry and net ecosystem metabolic processes encompassing near-shore and upstream locations. Results indicate that net heterotrophy and net dissolution dominate over most of the year, while net autotrophic conditions coupled with calcification dominated from only January to mid-April. The average carbonate dissolution rate observed during summer is estimated at −2.19 g CaCO3 m−2 day−1 and net community dissolution persists 76 % of the seasonal year despite the water column remaining super-saturated with respect to aragonite. This corresponds to −0.62 kg CaCO3 m−2 year−1, classifying the Enrique fore-reef and off-reef areas in a net dissolutional state. The combination of thermodynamically-driven depressed aragonite saturation state and high rates of respiration during the summer cause conditions that jeopardize the most soluble carbonate minerals and the free energy in the system for calcification. These data suggest that the reef area and associated ecosystems upstream of the sampling location are experiencing a net loss of CaCO3, possibly compromising coral ecosystem health and reef accretion processes necessary for maintenance as sea level increases. Resiliency from other climate-scale stressors including rising sea surface temperatures and coral bleaching is likely to be compromised in a system exhibiting net carbonate loss.

This preprint has been withdrawn.
Melissa Meléndez et al.
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Melissa Meléndez et al.
Melissa Meléndez et al.
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Short summary
Using observations from the NOAA CO2 buoy in La Parguera, Puerto Rico along with modeling approaches yield useful indices of biological processes affecting the water column over the reef. This study provided the first long-term monitoring of coral reef biological processes. Results show that processes that produce CO2 dominated over most of the year leading to high dissolution rates. This can have implications on the reef system's ability to recover to other climate-scale stressors (warming).
Using observations from the NOAA CO2 buoy in La Parguera, Puerto Rico along with modeling...
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