Colonization Dynamics of Potential Stowaways Inhabiting Marinas: Lessons from Caprellid Crustaceans

Abstract

Despite the fact that stowaway transport is an increasingly common invasion pathway, its key ecological aspects, such as colonization dynamics of potential invaders on human transport vectors, are poorly understood. Considering that marinas may function as stepping-stone habitats for the spread of marine invaders, they provide a unique opportunity for understanding the first steps in the stowaway pathway. One of the dominant groups inhabiting marinas are caprellid crustaceans. These small invertebrates have demonstrated a high potential for introduction and establishment far beyond their distribution range. Here, we analyzed the colonization dynamics of caprellid species inhabiting marinas of Cádiz Bay (Spain) on plastic collectors and discussed their implications on invasion success. We found that collectors largely mirrored the resident caprellid community assemblages after just one month of deployment, showing that caprellid species inhabiting marina structures have a high capacity to colonize new artificial substrates. Moreover, the two non-indigenous species found, Caprella scaura and Paracaprella pusilla, successfully established dense and well-structured populations in the collectors (including all sex/age groups considered). We suggest a potential interplay between colonization ability and stowaway organisms’ invasion success. Furthermore, collectors used are supported as a useful tool in the early detection of non-indigenous species and their monitoring in relation to resident species.

Monitoring Non-Indigenous Species with Passive Sampling Methods in an Oceanic Island

“…An explanation for the spatial variation could be that NIS tend to settle on artificial substrates, which are more commonly found inside marinas [18,53,61], or they colonize novel empty substrates more efficiently than native species. Their potential adaptation to novel habitat conditions would promote their settlement success in harbor environments during the invasion process's early stages and increase their chances of overcoming the subsequent stages (i.e., the establishment of self-sustaining populations and spread [62]). These findings also go in line with the study of Airoldi et al [56], which further outlined the effect of exposure: in sheltered artificial habitats, the abundance of NIS was double (compared with the respective exposed habitat), whereas native ascidians preferred exposed artificial rocky habitats over sheltered ones.…”

“…The different prototypes tested here also affected the settlement of the NIS, possibly altering the invasion process, with PVC collecting greater NIS cover and richness. Moreover, these plates are usually used to assess the sessile benthic community, although some recently conducted trials focused on sampling mobile biota (e.g., [62]).…”

Quick spreading of the exotic amphipod Laticorophium baconi (Shoemaker, 1934): another small stowaway overlooked?

“…To assess the colonisation and recruitment ability of L. baconi in artificial substrates, three-dimensionally folded plastic extendable meshes (30 x 50 cm, and 50 ml volume) were randomly placed in each marina (three replicates per marina) submerged at a depth of 1 m. These collectors can recruit a high abundance and diversity of species, including NIS, and constitute a standardised methodology for the study of motile macroinvertebrates in marinas (Ros et al, 2019(Ros et al, , 2020Scribano et al, 2021;Revanales et al, 2022).…”