Field observations in pebble beach habitats link plastiglomerate to pyroplastic via pebble clasts

Plastiglomerate and pyroplastic are two novel plastic debris forms that were originally discovered on sandy beaches in Hawaii and the UK, respectively. While plastiglomerate consists of plastic melted together with rocks or pebbles, pyroplastic is melted plastic. Although both plastic debris forms were related to campfires, it is unclear whether they are related to each other. Also, plastiglomerate and pyroplastic records from other shore types are missing. Therefore, we surveyed pebble beach habitats in Madeira Island (Atlantic Ocean) for plastiglomerate and pyroplastic. We detected one plastiglomerate (PG₁, including a pebble) and four pyroplastics (PP_1-4). While PP_2-4 consisted of polypropylene, PG₁ and PP₁ consisted of polyethylene and polypropylene. Furthermore, PG₁ and PP₁ included previously undescribed pebble shaped clasts that unequivocally linked plastiglomerate to pyroplastic. Thereby, our findings provide the first record of plastiglomerate and pyroplastic from pebble beach habitats worldwide and establish the link between these two novel plastic debris forms.