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Biogeosciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/bg-2017-459
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
13 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).
Natural ocean acidification at Papagayo upwelling system (North Pacific Costa Rica): implications for reef development
Celeste Sánchez-Noguera1,2, Ines Stuhldreier1,3, Jorge Cortés2, Carlos Jiménez4,5, Álvaro Morales2,6, Christian Wild3, and Tim Rixen1,7 1Leibniz Centre for Tropical Marine Research (ZMT), Bremen, D-28359, Germany
2Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), San José, 11501-2060, Costa Rica
3Faculty of Biology and Chemistry (FB2), University of Bremen, Bremen, 28359, Germany
4Energy, Environment and Water Research Center (EEWRC) of the Cyprus Institute (CyI), Nicosia, 1645, Cyprus
5Enalia Physis Environmental Research Centre (ENALIA), Aglanjia, 2101, Nicosia, Cyprus
6Escuela de Biología, University of Costa Rica, San José, Costa Rica
7Institute of Geology, University Hamburg, Hamburg, 20146, Germany
Abstract. Numerous experiments have shown that ocean acidification impedes coral calcification, but knowledge about in situ reef ecosystem response to ocean acidification is still scarce. Bahía Culebra, situated at the northern Pacific coast of Costa Rica, is a location naturally exposed to acidic conditions due to the Papagayo seasonal upwelling. We measured pH and pCO2 in situ during two non-upwelling seasons (June 2012, May–June 2013), with a high temporal resolution of every 15 and 30 min, respectively, using two Submersible Autonomous Moored Instruments (SAMI-pH, SAMI-CO2). These results were compared with published data from the upwelling season 2009. Findings revealed that the carbonate system in Bahía Culebra shows a high temporal variability. Incoming offshore waters drive inter- and intra-seasonal changes. Lowest pH (7.8) and highest pCO2 (658.3 µatm) values measured during a cold-water intrusion event in the non-upwelling season were similar to those minimum values reported from upwelling season (pH = 7.8, pCO2 = 643.5 µatm), unveiling that natural acidification occurs sporadically also in non-upwelling season. This affects the interaction of photosynthesis, respiration, calcification, and carbonate dissolution and the resulting diel cycle of pH and pCO2 in the reefs of Bahía Culebra. During non-upwelling season, the aragonite saturation state (Ωa) rises to values of > 3.3 and enhances calcification. Aragonite saturation state values during upwelling season falls below 2.5, hampering calcification and coral growth. Low reef accretion in Bahía Culebra indicates high erosion rates and that these reefs grow on the verge of their ecological tolerance. The Ωa threshold values for coral growth, derived from the correlation between Ωa and coral linear extension rates, suggest that future ocean acidification will threaten reefs in Bahía Culebra. These data contribute to build a better understanding of the carbonate system dynamics and coral reefs key response (e.g. coral growth) to natural low-pH conditions, in upwelling areas in the Eastern Tropical Pacific and beyond.

Citation: Sánchez-Noguera, C., Stuhldreier, I., Cortés, J., Jiménez, C., Morales, Á., Wild, C., and Rixen, T.: Natural ocean acidification at Papagayo upwelling system (North Pacific Costa Rica): implications for reef development, Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-459, in review, 2017.
Celeste Sánchez-Noguera et al.
Celeste Sánchez-Noguera et al.
Celeste Sánchez-Noguera et al.

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Short summary
Papagayo upwelling system is a natural laboratory for studying ecosystem's response to ocean acidification (OA). We measured pH and pCO2 in situ with a high temporal resolution and compared them with data available from upwelling season. Local coral reefs are exposed to acidic and undersaturated waters during upwelling and non-upwelling events. These restrictive conditions occur alongside local stressors, potentially decreasing reefs resilience and increasing their vulnerability under future OA.
Papagayo upwelling system is a natural laboratory for studying ecosystem's response to ocean...
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