Seasonally fluctuating chemical microfouling control in Fucus vesiculosus and Fucus serratus from the Baltic Sea

Microfouling in temperate seas underlies seasonal variations. Thus, perennial macroalgae are exposed to fluctuating levels of fouling pressure. Only few studies have examined the link between fouling pressure and algal fouling control. We assessed whether microfouling control of F. vesiculosus and F. serratus against prokaryotes and pennate diatoms fluctuates with season and correlates with microfouling pressure in a 1-year field survey. Microfouler recruitment on glass (reference surface) and on Fucus, microfouling control strength of Fucus surface metabolites (tested by an in situ bioassay approach) and Fucus tissue mannitol content (used as proxy for energy availability) were determined monthly. Microfouling pressure (settled cells per unit time and area) and microfouling control of Fucus varied seasonally. Both Fucus species exhibited cuticula shedding in all seasons. We conclude that microfouling control in both Fucus species showed a lagged or synchronized relationship with mannitol or microfouling pressure