Presence of microplastics in upper infralittoral soft sediment habitat and influence on infaunal assemblages

Abstract

The purpose of this research was to establish the presence of microplastics in upper infralittoral soft sediment habitat and influence on infaunal assemblages. Ten beaches were selected from Malta, Comino and Gozo and samples were collected at 0m, 3m and 7m depth using traditional SCUBA techniques. Samples were then analyzed for percentage organic carbon, mean grain size, levels of microplastic and biotic studies. The present results indicate a relationship between mean sediment grain size and percentage organic carbon in sediment, both of which appear to affect macrofauna found in sediments. Sediment grain size appears to have an overriding effect on other variables. On the other hand, the present results do not indicate a relationship between levels of microplastics in sediment and biological attributes of the macrofaunal assemblages associated with soft sediment habitat. Microplastics sizes ranged from 0.5mm to 5mm whilst the majority of the microplastics identified were filamentous with a variety of colours. Lowest levels were found at 7m depth Mellieha Bay with no microplastics collected whereas highest levels were found at 0m depth Mellieha Bay and St George’s Bay at 7.5 items per 50g. These values are considerably higher than those recorded in the Maltese Islands in previous studies as well as higher than most global studies suggesting a substantial problem in the Maltese Islands. Sizes ranged from 0.5mm to 5mm whilst the majority of the microplastics identified were filamentous with a variety of colours. Findings of this study are useful as they represent a first indication of levels of microplastics in shallow waters infralittoral coastal waters around the Maltese Islands, however future studies should be aimed at a design that considers extensive sampling effort over smaller spatial scales.