RIM20(1): Cartography of Zostera noltii on the Basque coast: recent changes in its distribution (2008-2012)

Author /Editor: Joxe Mikel Garmendia, Mireia Valle, Ángel Borja, Guillem Chust and Javier Franco (AZTI-Tecnalia)

Year: 2013

Content: Seagrasses are important for the marine ecosystem because of the ecological functions they perform (habitat and food for some species, primary production, resistance to sediment erosion, nutrient cycling…). In the Basque Country, only 3 of the 12 estuaries have these valuable ecosystems, which correspond to intertidal marine meadows of the species Zostera noltii, included in the Catalogue of Threatened Species of the Basque Country as a species in danger of extinction. Their scarcity and vulnerability raise even more interest in their study and conservation. For this reason, in 2008 and 2012 detailed studies were carried out on the presence and distribution of this plant in Basque estuaries: as a result, in 2012 a total area of 19.79 ha is estimated to be occupied by Zostera noltii, of which 86.9% is in the Oka, 9.9% in the Bidasoa and 3.2% in the Lea. Between 2008 and 2012 there was a decrease of 2.88 ha in the total area of the Basque Country: in the Bidasoa area the area of grassland increased by 0.13 ha; in the Lea area it also increased by 0.48 ha; in the Oka area the area increased by 0.12 ha in the Kanala area, while it decreased by 2.3 ha in the San Kristobal area and 1.33 ha in the Arketas area. Despite the net decrease observed (10%), the populations of the Basque estuaries show a high rate of change (53.1%) compared to the stable fraction of the meadow (46.9%). Given the impacts to which the meadows are exposed, it is recommended that environmental awareness and sensitisation campaigns are carried out to ensure the conservation of the species.


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