Coralligenous formations with gorgonian populations in Alonnisos Marine Park / Image by Dimitris Poursanidis - terraSolutions m.e.r.

The Coral gardens of Alonnisos Northern Sporades Marine Park

One of the most heterogeneous and diverse habitats of the Mediterranean Sea is represented by coralligenous bioconstructions. This biogenic habitat is mainly produced by organisms able to deposit calcium carbonate (e.g., calcareous red algae, corals, mollusks, bryozoans, polychaetes), growing one on the other, generation after generation (Ballesteros, 2006; Ingrosso et al., 2018). Although it is more extended in the circalittoral zone, it can also develop in the infralittoral zone, provided that light is dim enough to allow the growth of the sciophilous community of bioconstructors. Alonnisos Northern Sporades Marine Park host among the most important populations in the East Mediterranean Sea, vastly unexplored. The activities foreseen in the project includes:

  • the collection of data regarding the assembly of the coral forests in the bathymetric distribution 0-45m using scientific diving protocols and non destructive methodology

  • the collection of data regarding the recorded pressures and the hypotesized causes.

  • the collection of data regarding the pressures of local origin such as fishing impacts and suggestions for their mitigation

  • the collection of data regarding pressures related to climate change

All that aiming at the support of the management plan related to the coral gardnes of the Marine Park.

Funding: Thalassa Foundation

Degraded seagrass meadow in Alonnisos Marine Park / Image by Dimitris Poursanidis - terraSolutions m.e.r.

Estimation of the conservation status of the habitat 1120* in Alonissos Northern Sporades Marine Park

P. oceanica is an endemic species to the Mediterranean Sea that forms dense and extensive green meadows whose leaves can attain 1 meter in height. These underwater meadows provide important ecological functions and services and harbour a highly diverse community, with some species of economic interest. P. oceanica meadows are identified as a priority habitat type for conservation under the Habitats Directive (Dir 92/43/CEE).

They require transparent, nutrient-poor waters and sediments devoid of labile organic matter. Over the last decades, following increased coastal urbanisation and industrialisation, many Posidonia meadows have disappeared or have been altered. It is estimated that 46% of the underwater meadows in the Mediterranean have experienced some reduction in range, density and/or coverage, and 20% have severely regressed since the 1970s. Current main threats to the habitat are related to: water and sediment enrichment (eutrophication), the disruption of the sedimentation/erosion balance along the coast and direct destruction by human modifications of the coastline, degradation by boat trawling and anchoring, salinity increase in the vicinity of water desalination facilities and the proliferation of invasive algal species.

The project aims at the estimation of the Conservation Status of the habitat in the boundaries of the Marine Park by applying non-destructive methodology following the described methods in UNEP/MAP 2019 working document (Agenda Item 8: Monitoring Protocols for IMAP Common Indicators related to Pollution and Guidance on monitoring concerning IMAP Common Indicators related to Biodiversity and Non-Indigenous Species)

Funding: The National Marine Park of Alonissos Northern Sporades