TIDAL POWER AND THE AQUATIC ENVIRONMENT OF LA-RANCE

The Rance basin, on the northern coast of Brittany, is the only site w here a full-scale evaluation of the ecological impact of a tidal power scheme, after 20 years of operation, has been made. The isolation of the estuary, during the construction phase, was particularly damaging to the environment. Gradually, after the scheme was put into service, an increasingly diverse flora and fauna became established. The patter ns of distribution of this flora and fauna, their groupings into ecolo gical units and the nature of their interrelationships, indicate a var iable degree of biological adjustment to the new environmental conditi ons. Migratory organisms are able to pass via sluice gates and turbine s. However, the new ecological equilibrium, established in the space o f 10 years, remains fragile and, being linked to the degree of stabili ty of abiotic conditions, depends to a large extent on the operating c onditions of the power station.