The technical preparation is a sterile aqueous suspension of the plankton. In vitro studies show that this plankton supports the production of collagen by fibroblasts and reinforces the antioxidants systems; it prevents Langerhans cell alterations (reconstructed skin or organotypic skin culture) exposed to UVB. It exhibits non-specific immunomodulatory effects on cellular immunity and in particular on macrophages (Patent US, 6,190,671 B1; US, 6,242,229 B1; WO-94/02158).