The resin and the damp in wood, as well as the cellulose fibres, contains
organic nutrients that enable the algae to establish themselves on the
palings.
Palings consists of many parts: joints, fissures and spaces, which
by that hold damp and dirt –which supplies even more nutrition
to the algae. This increases and speeds up the affection.
Spores of algae and old algae enable the affection to permanently recur
–as long as they remain there.