Seagrass, in particular Posidonia oceanica, plays an important role in the ecosystem and provides several services. It ensures the maintenance of physical, chemical and biological conditions. It provides a habitat for many different species, is a nursery, hunting and predator area. Furthermore, it mediates flow, is a coastal erosion protection by stabilizing the sea beds and it decreases the water power and current. Seagrass provides regulation and maintenance services like water purification by filtration, sequestration of nutrients and contaminants (Campagne, Salles, Boissery, & Deter, 2014). Because of its ecological importance and vulnerability to a variety of anthropogenic influences, there is an increasing interest in using P. oceanica as an indicator of the health of the Mediterranean coastal systems (Balestri, Cinelli & Lardicci, 2003).
Picture 1.Following a transect to estimate the P.oceanica precentage cover.
When analyzing seagrass health, it is important to look at many different parameters. The method was partly developed following the Seagrass Watch protocol (McKenzie, Campbell, Vidler & Mellors, 2007). Within a 50m by 50m site, three transects will be laid out parallel to each other, 25m apart and perpendicular to shore. Every five meters a quadrant (50cm x 50cm) will be placed along the transect and different parameters will be analyzed, like depth, sediment composition, percentage cover of three different seagrass species (Posidonia oceanica, Halophila stipulacea, Cymodocea nodosa), algal cover, the blade length of three different leaves of P. oceanica and the abundance of epiphytes. Epiphytic a bundance is mainly controlled by the nutrient availability, the physical constraints and biological interactions
Picture 2. A member of the team counting the shoot density teractions.
Discharge of products from human activity including industrial effluence, mining wastes, fish farming, drilling fluids, sewage and agricultural runoff or effluents from desalination plants can alter the composition and abundance of epibiota. In order to analyze the nutrient availability, phosphorus and nitrite values will also be collected from each side. Moreover, the shoot density of the P. oceanica meadows will be counted by using a 20cm by 20cm quadrat to get a picture of the different densities of the meadows.
Seagrass health surveys will be conducted all around Lipsi island to get an understanding of the different health status and which parameters are influencing them.
Clara Gütte,
BSc in Environment and Energy,
Rhine-Waal University of Applied Sciences
References:
Campagne, C. S., Salles, J. M., Boissery, P., & Deter, J. (2014). The seagrass Posidonia oceanica: Ecosystem services identification and economic evaluation of goods and benefits. Marine Pollution Bulletin, 97(1–2), 391–400. https://doi.org/10.1016/j.marpolbul.2015.05.061
Balestri, E., Cinelli, F., & Lardicci, C. (2003). Spatial variation in Posidonia oceanica structural, morphological and dynamic features in a northwestern Mediterranean coastal area: A multi-scale analysis. Marine Ecology Progress Series, 250, 51–60. https://doi.org/10.3354/meps250051
McKenzie, L. J., Campbell, J., Vidler, S. J., & Mellors, K. E. (2007). Seagrass-Watch: Manual for Mapping & Monitoring Seagrass Resources. Seagrass-Watch HQ, Cairns, 114.
