Seagrass Posidonia oceanica diel pH fluctuations reduce the mortality of epiphytic forams under experimental ocean acidification

Abstract
It is hypothesized that pH fluctuations produced by seagrasses metabolism may confer marine calcifiers resistance to ocean acidification. Here, we tested this thesis by comparing the net population growth rate (NPGR) of a foraminifer species (Rosalina sp.) epiphytic of Mediterranean seagrass (Posidonia oceanica) to average current and projected pH scenarios under either stable conditions or diel fluctuations in pH of 0.3 units; variations similar to that experienced in their habitat. No significant differences were found in NPGRs between the fluctuating and stable pH treatments at current pH levels. NPGRs in treatments where pH fluctuated did not present significant differences to the treatment with high and stable pH conditions. In contrast, foraminifers exposed to stable low pH regimes experienced a steep decline in NPGR. These results suggest that diel pH fluctuations generated by P. oceanica photosynthetic activity could confer resistance to ocean acidification to Rosalina sp.

Citation
Ramajo, L., Lagos, N. A., & Duarte, C. M. (2019). Seagrass Posidonia oceanica diel pH fluctuations reduce the mortality of epiphytic forams under experimental ocean acidification. Marine Pollution Bulletin, 146, 247–254. doi:10.1016/j.marpolbul.2019.06.011

Acknowledgements
We are sincerely grateful to Guillem Mateu-Vicens for his generous and valuable help to understand the foraminifera world. We also thank Miguel Martínez, Lorena Basso and Iris Hendriks for their kind support during the fieldwork and the setup installation. This research was funded by projects MedSeA (EU FP7 program, [contract number FP7-2010-265103]) and ESTRESX (Spanish Ministry of Economy and Competitiveness [ref. CTM2012-32603]) to CMD. LR acknowledge the support of FONDECYT [grant number 3170156] project and BECAS CHILE fellowship program from Comisión Nacional de Investigación Científica y Tecnologica de Chile (CONICYT). LR and NAL acknowledge the support of Millennium Nucleus Project MUSELS [grant NC 1200286]. Requests for data and further information should be directed to the corresponding author, Laura Ramajo. Laura Ramajo. Conceptualization, Methodology, Investigation, Writing-Original draft preparation. Carlos Duarte. Conceptualization, Writing- Reviewing and Editing. Nelson Lagos. Writing- Reviewing and Editing.

Publisher
Elsevier BV

Journal
Marine Pollution Bulletin

DOI
10.1016/j.marpolbul.2019.06.011

Additional Links
https://linkinghub.elsevier.com/retrieve/pii/S0025326X19304564

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