Page 260 - Manual for Activities directed at the Underwater Cultural Heritage

© A.Vanzo. Shipwreck in the Golf of Sagone, France.
The site has become a haven for marine life, attracting leisure divers as well as fishermen to its surroundings.
Marine life, archaeological sites, site management and environmental policies
Underwater archaeological sites
as specific biotopes
Underwater cultural heritage sites tend to auto- matically develop into a sensitive ecological niche, within the wider area. Many algae and sessile animals need hard substrate to hold onto. They will colonize ‘foreign bodies’ and foreign materials extensively, including artefacts. In turn, this plant and animal cover will attract sedentary fish and predators that stand higher in the food chain. Isolated spots of foreign materials at the bottom surface therefore automatically tend to create a rich biotope. It is also for this reason that many initiatives around the world seek to intensify bioproduction by creating artificial reefs. Car tyres have been dumped for the purpose and worn out ship’s hulks have been scuttled. Sometimes such efforts have been integrated with the creation of an underwater park for recreational divers; sometimes the purpose is purely ecological, although mostly with the expectation of economic spin-off for fisheries.
The described process does not apply for sites that are deeply buried, but it does for sites that occur at the bottom surface of a body of water. Their specific ecological qualities derive from the fact that their substance is alien to the environment. This brings positive effects in that it allows for colonising by other species and creating biotopes that allow more biodiversity. This may be considered of great significance for conservation of nature in a wider area. As in many ‘life cycles’, these positive effects may be of a temporary nature. Wooden structures, for instance, are attacked by animals and wood- eating micro-organisms. Mechanical resistance decreases and eventually the structures collapse. Although the biotopical advantages may disappear when what finally remains is covered in sand and
259
11
Environment