EFFECTS OF GLORIA STORM ON THE BIODIVERSITY AND CONSERVATION OF POSIDONIA OCEANICA MEADOWS
Posidonia oceanica is an endemic marine angiosperm of the Mediterranean. It forms long-lived meadows that can extend from shallow water to 40 m depth, depending on the clarity of the water. They constitute one of the most important and productive ecosystems in the Mediterranean coast , providing habitat and refuge to a large number of species. These extraordinarily complex ecosystems also play a very important role in coastal dynamics: attenuating hydrodynamics, trapping particles and promoting the stabilization of sediments thanks to its complex web of leaves, rhizomes and roots. In addition, P. oceanica meadows are highly productive , fixing CO2 through the photosynthesis and increasing oxygen concentration in the water . This “blue carbon” can be stored in seagrass sediments and therefore the meadows are considered an important carbon sink.
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| Shoots of a P. oceanica meadow in Cabrera National Park |
Posidonia oceanica is the slowest growing species among all the marine seagrass in the world, with known values between 1 and 10 cm per year, which makes the colonization of the substrate a process that can take hundreds of years. Furthermore, Posidonia oceanica meadows are systems highly sensitive to variations in sediment deposition and sediment quality. For this reason, extreme meteorological events such as storms can have devastating effects on these meadows, affecting the ecosystem services they provide (e.g., the 2008 Sant Esteve storm on the Costa Brava)
THE STUDY OF POSIDONIA IN THE BIGPARK PROJECT
The storm Gloria (January 2020), had a devastating effect on Posidonia oceanica meadows all along the Spanish Mediterranean coast (including the Balearic Islands) with losses in some locations that exceeded 20% of its surface. In Cabrera Archipelago National Park, some of the meadows were highly exposed to the storm (SE orientation), and were presumably more affected than the meadows oriented NW. The direct impact of the storm on the meadow takes place through different mechanisms. The energy of the waves can move important amounts of sediment, burying shoots in some areas (which can trigger shoots’ mortality in the short term), or unburying shoots, leaving rhizomes, roots and shoots exposed and vulnerable to be detached, and therefore, causing mortality on a longer time frame. The third mechanism of impact takes place by direct shoots’ uprooting, which leaves evident patches of recent dead matte and drifting shoots that usually end accumulated on the beaches. All mechanisms can cause significant losses of meadow coverage. Indirect effects are produced by the loss of ecosystem services provided by these meadows, for example, in terms of biodiversity (by habitat loss) or carbon storage (by remobilizing the carbon stored in their soils).
Within the framework of the BigPark project, we aim to investigate the effects of the Gloria storm on the P. oceanica meadows in the Cabrera Archipelago, and on its main associated services (biodiversity and carbon storage). This information can help to improve management policies and prioritize areas to protect to avoid further loss of these emblematic ecosystems..
