Apparent return of free-living Fucus vesiculosus to the Polish Baltic waters

Abstract

The underwater meadows of the Puck Bay, once thriving with eelgrass Zostera marina, bladderwrack Fucus vesiculosus and black carrageen Furcellaria lumbricalis, experienced a decline in water quality during the 1960s and 1970s due to untreated sewage pollution. This, together with commercial exploitation, led to the disappearance of bladderwrack in 1977, with unsuccessful attempts at reintroduction in the early 2000s. In December 2023, a SCUBA survey near Rzucewo revealed a numerous bladderwrack in a benthic free-living form after 46 years of absence. The algae were found between 1.7 and 2.7 m depth, loosely positioned on the seabed, often within Z. marina beds, and with blue mussels Mytilus edulis attached. This reappearance suggests a positive trend in seawater quality and overall state of the Puck Bay, especially when combined with recent recovery of other algae species. The apparent return of bladderwrack could enhance ecosystem functionality, benefiting fish recruitment, grazer and algal biomass. Further investigations on bladderwrack's reappearance are needed in order to verify whether this is the only ecotype currently present in the Puck Bay.