Micro algae production raises hope in various ways. For the agricultural and fishing sector as a mean to diversify source of income, for health care and science…Brittany has an enormous production potential, with several projects of seaweed farm in development contraty to Japan or China where seaweed production is booming. Micro Algae production could significantly improve the economy of Brittany, at the same time, it means a concentration of seaweed farm sometimes in protected areas which can threat ocean biodiversity. How can we use this potential without threatening ocean biodiversity ?