Abundance and dispersal trajectories of floating Fucus vesiculosus in the Northern Baltic Sea

Abstract

Floating macroalgae play a fundamental role for the connectivity of littoral marine habitats. They can be found throughout the world's oceans but information on their abundance and dispersal abilities is scarce. This information, however, is essential to evaluate their ecological role and the potential connectivity between populations of both the algae and associated biota. Here, we survey the abundance and spatiotemporal dispersal patterns of the floating brown alga Fucus vesiculosus in the Northern Baltic Sea. By incorporating a biophysical modeling approach, based on ocean circulation and surface winds, we demonstrate potential dispersal ranges, such as floating distances and directional trajectories of F. vesiculosus at different times of their reproductive season. Abundance of floating algae varied both spatially and temporally, with the highest densities being found during reproductive seasons. Evidenced by the fact that many algae were held back and accumulated in archipelagoes, the model suggests that a combination of local oceanographic features and seascapes strongly influences the dispersal of floating algae. However, a relatively high fraction of rafts spilled to more open sea areas, causing them to travel in multiple directions (e.g., Baltic Proper, Bothnian Bay, and Gulf of Finland) that are hundreds of kilometers away from their original sources, implying long-distance dispersal. We propose that the Northern Baltic Sea rocky littoral habitats are potentially well connected through abundant and long-reaching floating algae, with a chance to contribute to gene flow among F. vesiculosus populations.

Oceanic currents drove population genetic connectivity of the brown alga Sargassum thunbergii in the north‐west Pacific

“…In conclusion, the phylogeographical structure of S. thunbergii in the NWP suggests that long‐distance dispersal of floating seaweeds driven by oceanic currents can potentially homogenize population structure over their distribution ranges (Olsen et al ., ), and local oceanographic features greatly influence the dispersal of floating algae as well (Rothäusler et al ., ). Such environmentally mediated biogeographical shifts may impose considerable conservation risk to ecologically and evolutionarily significant genetic lineages, populations and/or patches of seaweeds in the context of increasing environmental shifts.…”

No sex-related dispersal limitation in a dioecious, oceanic long-distance traveller: the bull kelp Durvillaea antarctica

“…Also, prevailing winds and currents (e.g. Humboldt Current System) can greatly influence the dispersal trajectories of algal rafts (Rothäusler et al 2015), possibly causing certain areas of the coast to receive less input. Future studies should concentrate on studying the impact of density-blocking and currents on the population connectivity of rafting seaweed species.…”

High climate velocity and population fragmentation may constrain climate‐driven range shift of the key habitat former Fucus vesiculosus

“…Fucus vesiculosus may disperse in several ways including short‐distance dispersal of gametes and zygotes to occasional long‐distance dispersal of dislodged and rafting buoyant sexually mature plants (Rothäusler, Corell, & Jormalainen, ; Thiel & Gutow, ). Also, dispersal on intermediate scales may occur through bed load transport of negatively buoyant plants and in some cases vegetative, adventitious branches (Johansson et al., ; Pereyra et al., ).…”