OBSAM – Restoration of the Posidonia oceanica meadow affected by the intake of water from the seawater desalination plant in Ciutadella (Menorca)
TOTAL PROJECT COST – €138.282,64
- Organisation Applying for Funding: IME-OBSAM
- Project Duration: 6 years – IN PROGRESS.
- Area of Interest: Sea – Marine Research Study
Summary of the Project
Accelerating the natural recovery process of the Posidonia oceanica meadow in the area affected by the construction of the Ciutadella desalination plant collector by planting P. oceanica.
Description of the project
The Ciutadella desalination plant was built in 2010 but did not come into operation until January 2019. During the works on the water intake tower, a spill of bentonite occurred that affected a surface of 1,668 m2 of Posidonia oceanica (Álvarez et al. al., 2012). Bentonite is a type of non-polluting clay that has a high density and compactness, making it difficult for it to disappear from the environment (Tornero and Hanke, 2017). In 2020, the Socio-environmental Observatory of Menorca (OBSAM) carried out a 2-year study, in collaboration with Menorca Preservation, of the affected area following a methodology similar to that of the study carried out in 2012 to assess its current status (Bagur et al., 2020).
For this investigation, the intake tower was located 800 m to the southwest of the desalination plant outfall, marked by a yellow buoy that prohibited anchoring. The collector, located at a depth of 20 m, was situated on top of a mound of stones, 6-8 m high and with a diameter of about 10 m. Around the mound you could see a large clearing of sand devoid of vegetation in which in 2010 and 2012 the discharge of bentonite could be seen (Álvarez et al., 2012; Carreras, 2010), resulting in the interest of this project of naturally restoring this affected area.
The P. oceanica to be used in planting will be live fragments of rhizome with horizontal growth habit, that is, having at least one living leaf bundle (or apical group of leaf bundles) at the apex of a rhizome with this habit. of growth and at least two additional live leaf bundles after the apical group (Molenaar et al., 1993). These fragments will not be uprooted from a donor meadow, but those produced naturally by marine dynamics and that are uprooted, drifting along the seabed, will be used.
The fragments will be planted in groups of 16, arranged in 4 rows of 4 fragments each, about 20 cm apart. This provision allows the individualized monitoring of the fragments during the years following planting. Each fragment will be individually anchored to the substrate by means of an iron stirrup to which it will be securely tied.
The groups of 16 fragments will be arranged regularly over the area to be restored following the pattern established by an imaginary mesh of 5 x 5 m square cells superimposed over the area during planting. The groups of fragments will be placed in the nodes of the mesh. Considering that the surface of the affected area is 1638 m2, that the surface of a grid cell is 25 m2 and that each node would correspond to a cell, that is, a surface in the area to be restored of 25 m2, the maximum number of groups of fragments, of nodes to establish will be 65. Nodes will not be established in the area occupied by the collector and the mound of stones on which it is located. Nor will nodes be established on prairie stands or isolated living clones present in the area. This determines that the actual number of nodes to be established will be less than 65.
Each node will be permanently marked with two metal bars (galvanized iron or rebar) with a minimum length of 60 cm placed at two vertices of the node, on the same diagonal. The bars will be inserted into the substrate a minimum of 30 cm. Each node will be labeled following an X-Y coordinate system defined by the imaginary mesh used for planting. At each node, it will be noted whether the substrate is dead P. oceanica mat or sand.