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Combined use of optical (satellite imagery), and acoustic (sidescan sonar) remote sensing techniques, as well as in situ methodologies (visual census; SCUBA diving, Towed Underwater Cameras, and Remotely Operated Vehicles) was employed to map the spatial distribution of seagrass habitats in the coastal waters of the Hellenic territory. Seagrass meadows were recorded at approximately 70% of the Hellenic coastline (Eastern Ionian, Aegean and Levantine Seas), and their surface area exceeded 2,673.1 km2. Posidonia oceanica is -by far- the dominant seagrass species of the Hellenic seas, covering the vast majority of seabed at depths between the shoreline and 25 – 30 m (or deeper in insular areas), followed by the species Cymodocea nodosa, Zostera noltei, and Halophila stipulacea, which, however, presenting local presence and limited areal extent. Habitat suitability in terms of the seabed spatial extent that is available for the growth of seagrass meadows (i.e., the spatial extent of coastal areas between the shoreline and the isobath of 20m) and the seawater clarity conditions are highlighted as the critical factors for the formation of well-structured and extensive meadows. The results of this study are of great importance and usefulness for the effective management and conservation of valuable marine ecosystems. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.
This report describes the results from an interdisciplinary field survey aimed at identifying the location, extent and condition of Annex I habitat features in the Large Shallow Inlet and Bay of The Wash and North Norfolk Coast SAC. The habitat features of interest are (i) subtidal boulder and cobble communities, and (ii) Sabellaria spinulosa reefs. Information presented is intended to serve as a baseline for future monitoring of the identified features. Acoustic sidescan data were acquired from selected areas within the broader SAC area, together with grountruthing samples representative of distinct acoustic signatures. Groundtruthing techniques included the acquisition of video and still images of the seabed and of sediment and faunal sample. Of particular interest was an area to the north of the eastern Well survey area between 10 and 47 m deep which exhibited a high density of hard and rugged features, confirmed as boulder and cobble reef on chalk bedrock by the photographic record. This area also harboured a high number of epifaunal taxa not observed in the surrounding sediments. The area has been delimited and covers approximately 470 ha. The acoustic record did not reveal the occurrence of areas of Sabellaria spinulosa reef. Infaunal samples did collect representatives of this species but in densities too small to be considered as reef. At most sites where S. spinulosa was observed, the abundance and diversity of the whole infaunal assemblage was higher than in areas where S. spinulosa was absent. Analysis of both infaunal and epifaunal assemblages revealed several distinct communities throughout the survey area.