Is the invasive Caprella scaura Templeton, 1836 displacing its resident congener Caprella equilibra Say, 1818 in marinas of the South Iberian Peninsula? A long-term spatio-temporal approach.

Although marine invasions are increasingly a matter of concern, the impact of invasive species in the ecosystem and their ability to replace native taxa is still little understood. Data from 2011 to 2021 in marinas of the Southern Iberian Peninsula supported that the invasive amphipod Caprella scaura is replacing the resident Caprella equilibra over time. Six marinas where C. equilibra was abundant in 2011 and C. scaura was absent, are now dominated by C. scaura. Although this displacement is more evident in Mediterranean shores than in Atlantic coasts, it is very variable between marinas. The spreading of the invasive species in marinas of the Alboran Sea mainly occurred from 2011 to 2017, preventing C. equilibra from regaining its former distribution. The ultimate factors responsible for the displacement, such as the aggressive behaviour of C. scaura, environmental influences or physiological performance in a global warming context, should be further investigated experimentally.

Estuarine versus coastal marinas: Influence of the habitat on the settlement of non-indigenous peracarids on the polychaete Sabella spallanzanii (Gmelin, 1791).

Recreational marinas are key points for the introduction and secondary spread of non-indigenous species (NIS). However, little is known about the influence of the habitat surrounding the marina on NIS communities. To explore this issue, we compared peracarid assemblages associated to the widespread ecosystem engineer Sabella spallanzanii in lower estuarine marinas (with oceanic salinity) and coastal marinas of the south of the Iberian Peninsula. Sabella spallanzanii hosted a total of 23 species, 7 of them NIS. While NIS richness was similar between marinas located in estuaries and coastal habitats, NIS abundance was significantly higher in estuarine marinas. The NIS community structure was influenced by both the marina itself and the surrounding habitat. These results suggest that lower estuarine conditions promote NIS abundance in marinas, increasing potential invasion risks. This supports prioritization of estuarine marinas in NIS monitoring programs and the suitability of S. spallanzanii as a bioinvasion monitoring tool.