California State University, Bakersfield, United States
Abstract: The increasing abundance of plastic pollution in the environment has altered resource subsidies available to freshwater and terrestrial habitats. Due to the durable nature of plastics, plastic pollution is estimated to persist in the environment for centuries and can interact with natural ecosystems. To understand the fate of plastic pollution in arid landscapes, we investigated the degradation of low-density polyethylene (LDPE) compared to naturally occurring leaves from Plantanus acerifolia ([Aiton] Wild.; London planetree) in terrestrial and freshwater habitats. Specifically, we explored 1) if leaf and plastic degradation rates differ, and if pattern are consistent across habitats, and 2) how leaf and plastic materials impact terrestrial and aquatic macroinvertebrate communities that colonize leaf packs. To accomplish this, a traditional leaf pack experiment was conducted with three experimental treatments: natural leaves, plastics, and a mix of both materials. Leaf packs were anchored in an ephemeral pond and an arid grassland (n = 55 treatment habitat-1) and subsets were harvested every 1-3 months over the course of a year (n = 3-6 leaf packs treatment-1 habitat-1). Results indicated that plastic leaf packs degraded 115 × faster in the grassland compared to the pond habitat, and natural leaves degraded 1.7 × faster in the pond compared to the grassland. Macroinvertebrates density was similar across leaf packs; however, mixed leaf packs supported greater taxonomic and functional feeding group diversity compared to plastic and natural leaf pack (all P < 0.001), suggesting that plastics could serve as an alternative habitat resource for macroinvertebrates. This study provides insight into how varying environmental conditions can impact the degradation rates of plastics in the environment, advancing knowledge on the fates of plastics in terrestrial and freshwater habitats.
