Listening to posidonia seagrasses

By studying variations in oxygen production within posidonia seagrasses it is possible to assess how healthy they are. This is extremely important research because these ecosystems along the Mediterranean coast contain a large biodiversity, play a role in preventing erosion of the seabed and beaches, produce oxygen and store large quantities of CO2. These seagrasses are also excellent indicators of the health of the environment. A new method of detecting oxygen production has been tested at the STARESO station at Calvi in Corsica. This involves an acoustic system which makes it possible to analyse the variations in the speed of sound in these seagrasses and to correlate these variations to a high or low level of oxygen gas present in the form of bubbles. This system is allied to an already well-established set of devices which can make a contribution to an understanding of these ancient and fragile ecosystems.  

The study of sound propagation in aquatic environments is important for very different scientific interests. Some of these are quite original to say the least. This is certainly the case with regard to a recent study(1) during which physicists and oceanographers recorded and “listened” to the production of oxygen in posidonia seagrass meadows. The objective of this operation was to apply a multidisciplinary approach to new techniques for analyzing variations in the production of oxygen. These variations in oxygen production depend directly on photosynthetic activity and the health of the ecosystem. While this approach may appear surprising, it is contributing to the development of new technologies which backs up the data gathered by means of the usual techniques.

“The article was written in the context of a European networking project (ESF COST Action 0906), organised in 2011 at the STARESO station in Calvi Bay in Corsica”, explains Sylvie Gobert, a lecturer and head of the Oceanography Laboratory of the University of Liege. “Some twenty researchers from several countries gathered there to study a posidonia seagrass meadow in all its forms, from a cellular level to the entire ecosystem”. These few days of all-out research created a great synergy, resulting in the acquisition of new knowledge. The choice of the Bay of Calvi in Corsica was no accident. The area is barely affected by pollution and does not suffer any damage due to high frequentation by humans. The water there is very clear and stable and light can penetrate deeply into it (2). These conditions are suitable for the development of healthy posidonia seagrasses and for optimal photosynthetic activity.  

An Environmental challenge

Today, posidonia seagrass meadows are the subject of various research programs, rooted in a politico-scientific movement based on the problem of blue carbon. These initiatives are aimed at preserving oceanic systems that produce a high level of photosynthesis. This preservation can even take the form of attempts to recolonize and redevelop ecosystems that have been damaged by human activity.

Herbier posidonie (c) A.Abadie 

(1) Paulo Felisberto, Sérgio M. Jesus, Friedrich Zabel, Rui Santos, João Silva, Sylvie Gobert, Sven Beer, Mats Björk, Silvia Mazzuca, Gabriele Procaccini, John W. Runcie, Willy Champenois, Alberto V. Borges, Acoustic monitoring of O2 production of a seagrass meadow, Journal of Experimental Marine Biology and Ecology, vol.464, Mars 2015

2() Mazzuca, S., Bjork, M., Beer, S., Felisberto, P., Gobert, S., Procaccini, G., Runcie, J., Silva J, Borges, A., Brunet, C., Buapet, P., Champenois, W., Costa, M., D'esposito, D., Gullstrom, M., Lejeune, P., Lepoint, G., Olivé, I., Rasmusson, L., Richir, J., Ruocco, M., Serra, I., Spadafora, A., & Santos, R. (2013). Establishing research strategies, methodologies and technologies to link genomics and proteomics to seagrass productivity, community metabolism, and ecosystem carbon fluxes. Frontiers in Plant Science, 4(38), 1-19.

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