Acoustic monitoring of O2 production of a seagrass meadow

P. Felisberto1, S.M. Jesus1, F. Zabel2, R. Santos3, J. Silva3 , S. Gobert4, S. Beer5, M. Bjork6, S. Mazzuca7, G. Proaccini8, J. Runcie9, W. Champenois10 and A.V. Borges10

1LARSyS, University of Algarve, Faro, Portugal
2Marsensing, Campus de Gambelas, Faro, Portugal
3Marine Plant Ecology (ALGAE), Center of Marine Sciences, University of Algarve, Faro, Portugal
4Département de Biologie, Ecologie et Evolution, MARE, Université de Liège, Liège, Belgium
5Department of Plant Sciences, Tel Aviv University, Tel Aviv, Israel
6Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
7Department of Chemistry and Technology, University of Calabria, Rende, Italy
8Stazione Zoologica Anton Dohrn, Naples, Italy
9School of Biological Sciences, University of Sydney, Sydney, NSW, Australia
10Chemical Oceanography Unit, Université de Liège, Liège, Belgium

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Ref.: J. of Experimental Marine biology and Ecology, vol.464, pp.75-87, March 2015.

Acoustic data were acquired in October 2011 over a Posidonia oceanica meadow in the Bay of la Revellata, Calvi, Corsica. The purpose was to develop an acoustic system for monitoring the oxygen (O2) production of an entire seagrass meadow. In a shallow water area (<38 m), densely covered by Posidonia oceanica, a sound source transmitted signals in 3 different bands (400-800Hz, 1.5-3.5kHz and 6.5-8.5kHz) towards three self-recording hydrophones at a distance of 100 m, over the period of one week. The data show a high correlation between the diel cycle of the acoustics signals' energy received by the hydrophones and the temporal changes in water column O2 concentration as measured by optodes. The results thus show that a simple acoustic acquisition system can be used to monitor the O2 -based productivity of a seagrass meadow at the ecosystem level with high temporal resolution. The finding of a significant production of O2 as bubbles in seagrass ecosystems suggests that net primary production is underestimated by methods that rely on the mass balance of dissolved O2 measurements.