Underwater landscape index : scuba diving off Saint Jean-De-Luz


CREOCEAN and the Institut des Milieux Aquatiques (IMA) of Bayonne in scuba diving off Saint Jean-De-Luz in order to define a landscape index adapted to the Basque Country.

Subject to strong natural constraints and to economic exploitation, the close underwater space has a temporal dynamic. It raises issues of management, delimitation, attracts the attention of several social groups, and its image is more or less repulsive depending on whether one is land-based, marine or diver. This territorialisation process of the near submarine space between 0 and 40 meters deep is strongly correlated to a sum of intraspecific and interacting constraints structuring a territorial system (Translation : Marchand, 1986 in Musard et al. 2007).

Increasingly frequented and represented, it extends the coastline of which it is a more or less integrated margin or periphery and has therefore ceased to be a "territory of emptiness" in the sense of Alain Corbin (1988).

In this context, the near marine space is perfectly integrated into the work and environmental quality monitoring (WFD, CMSM) and the notion of landscape can be considered as a component accessible for interpretation by managers with the support of scientific structures.

With the scuba diving development, the landscape quality of the seabed has gradually become an important value for managers of maritime spaces. This value is expressed in terms of brand image (area reputation) but also in direct economic terms, diving can constitute a real commercial activity in some areas. The managers of the marine environment then seek to evaluate their underwater heritage, to make known its assets and finally to preserve them

The landscape quality is one of the essential components of this heritage. It involves both the physical environment (relief in particular) and the biological environment (substrate covering). Moreover, it concerns more cyclical characteristics (water clarity) or more subjective characteristics (presence or absence of a flagship species). Its evolution can be an indicator of natural and/or anthropogenic changes.

The characterization of underwater landscapes must therefore reveal all these components.

The underwater landscape approach makes it possible to direct the eye towards "detail", to better understand underwater natural and biological reality, to understand the diversity and ecological and heritage richness of the observed territory and, possibly, to qualify it according to a value scale (Translation - Musard et al., 2007).

Interpretation and use of the underwater landscape as a key to reading allow us to refine our view of ecological systems and provide information to managers.

Following this observation, a partnership agreement was signed on 18/05/2018 between the Institute des Milieux Aquatiques and CREOCEAN in order to start thinking about the concept of underwater landscape, initially within a Natura 2000 marine site (FR 7200813).

The objective of this partnership will be to define a landscape index, adapted to the Basque Country, which will make it possible to synthesize all these compartments to characterize the landscape interest of a site.

A first mission carried out in June 2018 was the opportunity to characterize 4 sites in the Basque Country: "Cambo-bancu", "Ficoa en Cala", "Aroca tiquia" and "Belhara" with, for each site, the implementation of a fact sheet summarising all the components of the defined landscape and the associated index.

A longer-term vision could then be to validate this index on the scale of the Basque Country, then begin the same reflection on the underwater landscapes of the whole New Aquitaine region.

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