Microplastic Occurrence in Marine Invertebrates Sampled from Kwazulu-Natal, South Africa in Different Seasons

Abstract

The occurrence of microplastics in the environment, together with increasing temperatures as a result of climate change, has become a global concern. However, few reports are available on microplastic ingestion in lower benthic marine animals sampled from their natural environment during different seasons of the year. This study investigated microplastic uptake in Dotilla fenestrata (Hilgendorf 1869), Holothuria cinerascens (Brandt 1835) and Pyura stolonifera (Heller 1878) sampled from their natural environment during winter and summer. Animals sampled were cleaned of sand and attached animals and transported on ice to the laboratory. D. fenestrata, H. cinerascens (guts), and P. stolonifera (soft tissues) were digested in 10% potassium hydroxide (KOH) solution for 24 hours at 60°C and analysed for microplastics. The per cent occurrences of microplastics found in sampled animals were more than 95 % in both seasons, and fibres were the most predominant microplastic types found. Season significantly affect microplastic uptake in Dotilla fenestrata (t-test: t-value = 2.915, df = 58, p = 0.01) while it had no effect in H. cinerascens and P. stolonifera sampled. A significantly higher number of microplastics were found in D. fenestrata than H. cinerascens (ANOVA HSD: df = 2, p = 008) and P. stolonifera (ANOVA HSD: df = 2, p = 000) in winter while H. cinerascens had a higher number of microplastics than P. stolonifera in summer (ANOVA HSD: df = 2, p = 002). These results show that microplastic uptake in some ectotherms may be season-dependent and that feeding method impacts the accessibility of marine invertebrates to microplastics in their environment.

Keywords

• microplastic, feeding method, dotilla fenestrata, holothuria cinerascens, pyura stolonifera