Plastic pollution has become an increasing worldwide concern, especially as high quantities of this material enters into the marine environment. Once in the oceans, the plastics fragment into smaller pieces and become available not only to top predators but down to micro-sized plankton. Filter-feeders, i.e. mussels play an important role as they are ubiquitous and seem to filter unselectively. Among mussels, Xenostrobus securis is known to be widespread and invasive, especially in the northern coast of Spain. Until now, only limited knowledge is available on the effects of invasive species and their possible role as a vector for microplastic into the marine foodweb. This study aims to answer 3 questions: Does the native crab Pachygrapsus marmoratus prefer the invasive mussel X. securis or the native Mytilus galloprovincialis? Does the crab predation behaviour change when exposed to different microplastic concentrations? And can X. securis introduce microplastic into the marine foodweb? Different experimental aggregations involving both native and invasive mussels were simultaneously deployed in experimental tanks: 50/50 of M. galloprovincialis and X. securis, 60/30 of M. galloprovincialis and X. securis et vice versa, and aggregations formed by each species separately. All aggregations were exposed to four treatments, involving different microplastics (MP) concentrations, namely only microalgae (i.e., without MP), and three MP concentrations (1000parts/mL, 10.000parts/mL and 100.000parts/mL). After an exposure period of 1 hour, one P. marmoratus was added to each aggregation and predation behaviour was observed. After first visual inspections of the mussels, both species seem to have incorporated microplastics. Preliminary results show that P. marmoratus seems to feed on both species, but prefers the native M. galloprovincialis. The final results will show the difference of microplastic incorporation between M. galloprovincialis and X. securis and, furthermore, if there was a trophic transfer from the mussels to the crab P. marmoratus.