Giant Reed (Arundo donax) wrack as sink for plastic beach litter: First evidence and implication

Abstract

In order to maintain the hydraulic outflow in land reclaimed canalizations, the competent agencies provide to mechanically mow the Giant Reed (Arundo donax, L. 1753) along the aquatic ecosystem banks. Nevertheless, the reeds mowed can be transported away from the waters following storm surges and can be deposited in large quantities along the sandy beaches. We carried out a stratified study in a Mediterranean sandy beach to test the hypothesis that Giant Reed wrack may act as a sink and barrier for plastic beach litter. We observed a large amount of plastic litter entrapped in the Arundo donax wrack (density of 0.868 items/m2), with a higher density when compared to both the inner and the shoreline belts. Density of litter is significantly higher considering the categories of meso- and micro-plastics. Organic macrophyte wrack is useful for dunal macrodetritivorous invertebrates and generally for fauna communities, which use this litter as refuge and trophic pabulum. Significant accumulations of organic wrack can mitigate coastal erosion; nevertheless, for its structural characteristics, Arundo wrack can also act as a barrier for litter towards the inner vegetated dunes, so entrapping a large amount of anthropogenic litter. In this regard, Arundo wrack can represent a sink habitat, first attracting (due to large availability of detritus with a relative high rate of decomposition) and then, entrapping many organisms in anthropogenic litter. We suggest that, once mechanically mowed, the land reclaimed agencies should periodically remove from the channel banks the Arundo donax reeds, impeding the accumulation of incoherent vegetated matter along the aquatic ecosystem banks.

TSC Opinion

La canne de Provence est une sorte de roseau qui pousse dans les marais maritime où l’eau est légèrement salée et sur les dunes côtières. Les cannes sont hautes et leur croissance est rapide. De nombreux déchets, en particulier plastiques, sont piégés dans le réseau de cannes et ne peuvent ainsi plus être repris par la mer ou le vent. Les auteurs suggèrent de planter des zones avec ces cannes pour piéger les déchets et ensuite récolter les cannes avec les déchets afin de les traiter. Les moyens mécaniques de récolte existent déjà. Une idée qui a le mérite d’être une solution pour la pollution plastique diffuse dont le nettoyage est fastidieux. Les impacts sur la flore locale sont à vérifier.