Prevalence and consequences of microplastic ingestion in the world's southernmost insect, Belgica antarctica

Abstract

Plastic pollution has reached the remote terrestrial ecosystems of Antarctica, but the extent to which microplastics are affecting native terrestrial invertebrates has not been assessed. Using Antarctica's only endemic insect, the chironomid midge Belgica antarctica, as a focal species, the objectives of this study were two-fold: 1) Investigate the physiological consequences of polyethylene microplastic exposure in a laboratory setting and 2) Determine the extent to which field-collected larvae contain ingested microplastics. We exposed B. antarctica larvae to ingestible polyethylene microplastic beads (∼27-45 μm diameter) at various concentrations (up to 2000 mg kg^-1 substrate) for 10 days. Ingestion of beads was only observed at the two highest concentrations, and survival and metabolic rates were unchanged across all concentrations. While carbohydrates and proteins stores were unaffected by plastic exposure, lipid stores tended to decrease with increasing plastics concentration. For Objective 2, field-collected larvae from 13 islands were screened for microplastics with two approaches, either imaging digestive samples with μ-FTIR and μ-Raman microscopy or spotting digested guts onto glass filters and scanning with μ-Raman. While the latter approach was inconclusive, two of the 29 larvae (7 %) imaged with μ-FTIR had potential plastics, and one of these particles was confirmed as plastic using μ-Raman. Thus, the presence of plastics in larvae is likely rare at present, although our results do provide further evidence that microplastics can enter Antarctic food webs. Taken together, our results indicate that high concentrations of plastics can have physiological consequences, although it appears unlikely that these levels are currently approached in the field.

Keywords: Antarctica; FTIR; Insects; Metabolism; Microplastics; Raman.