Marine plastic debris (MPD) impacts on marine ecosystems is among the most important environmental concerns of the past decades. Virgin-plastic manufacture is often cheaper than recycled plastics, which increases the rate of plastic release in the environment. Along with other environmental effects, MPD can serve as vector for marine hitchhikers, facilitating spread of unwanted organisms. In this context, there is a growing demand in eco-friendly replacements to conventional plastic polymers, ideally with fit-for-purpose properties and a well understandable life cycle. In response to this demand, biodegradable polymers made of, or augmented with biological material are being considered and tested as a future alternative to plastics. In this experimental study, formulated biopolymer compounds with different concentrations of oyster shell filler were tested to determine: (i) their degradation rate in the natural marine environment; (ii) preferential recruitment of a non-indigenous tunicate Styela clava; (iii) temporal evolution and peculiarities of bacterial and eukaryotic communities associated with the different shell concentration in polymers. Composites were deployed at Nelson Marina (New Zealand) in January 2019 and dynamics of biofouling formation and biodegradation was observed over an 18-week period. Here we present the results of this investigation and outline further steps of this research.