25 years of observations on non-indigenous Caprella species on navigation buoys.

The global expansion of marine infrastructure, or ‘ocean sprawl’—creates extensive new artificial habitat for hard substrate-associated species. Structures such as offshore energy installations, aquaculture systems, and navigation buoys support biofouling communities of native, introduced, and range-expanding species. Caprellid amphipods are typical members of these communities and can reach high densities. Using a unique 25-year dataset (1998–2023) from the Belgian part of the North Sea, we documented occurrence patterns of four Caprella species: the native C. linearis, the introduced C. mutica and the range-expanding C. equilibra and C. penantis. This long-term dataset reveals dynamic shifts in species dominance, co-occurrence, and spatial range, highlighting how introduced and range-expanding species successively establish and interact in biofouling communities in an increasingly warmer, busier, and more cosmopolitan ocean.