|Seagrass ecosystem in decline: application of low-cost techniques for monitoring Posidonia oceanica meadow health|
De Borger, E. (2015). Seagrass ecosystem in decline: application of low-cost techniques for monitoring Posidonia oceanica meadow health. MSc Thesis. Vrije Universiteit Brussel: Brussel.  pp.
Posidonia oceanica (Linnaeus) Delile, 1813 [WoRMS]
ecosystem health, Posidonia oceanica, remote sensing, low-cost, health monitoring, Mediterranean Sea
The endemic Mediterranean seagrass species Posidonia oceanica (L.) Delile is an important ecosystem engineer providing a multitude of services both ecologically and economically. Since anthropogenic impacts have steadily increased around the Mediterranean basin the presence of this species has strongly declined. With the goal to provide low-cost, non-destructive monitoring methods to use for the conservation of this seagrass species, a sonar device and a quadcopter were used to evaluate what information these tools can provide researchers with. These techniques were supplemented with wellestablished underwater survey methods to provide ground-truthing data. Low-cost methods are needed as more and more research is done by non-governmental organisations (NGO's) that can have limited funding, and funding for monitoring programs is easily diminished in times of economic hardship. With four different sites investigated in the SE of Samos (Greece) the sonar device classified the bottom in unvegetated or seagrass cover correctly in 82% of the cases, with the best performance over a sandy substrate with unfragmented meadows. The quadcopter was used to generate panoramic photographs, which had an average deviation of 8.6% in calculating the total Posidonia oceanica cover in a certain area as compared to freely available satellite images, and with a spatial resolution of consistently greater, with pixels on average 63.3% finer. Results indicate that these methods can certainly contribute to seagrass monitoring schemes, but more calibration studies are needed first. As well as certain limitations of the devices used that became clear during the research, these must be addressed before expanding and adopting the new technologies.