Microplastic contamination has limited effects on coral fertilisation and larvae

Microplastics are ubiquitous throughout the world's oceans and contaminate coral reef ecosystems. There is evidence of microplastic ingestion by corals and passive contact with coral tissues, causing adverse health effects that include energy expenditure for particle removal from the tissue surface, as well as reduced growth, tissue bleaching, and necrosis. Here, it was examined whether microplastic contamination impairs the success of gamete fertilisation, embryo development and larval settlement of the reef-building coral Acropora tenuis. Coral gametes and larvae were exposed to fifteen microplastic treatments using two types of plastic: (1) weathered polypropylene particles and (2) spherical polyethylene microbeads. The treatments ranged from five to 50 polypropylene pieces L-1 and 25 to 200 microbeads L-1. Fertilisation was only negatively affected by the largest weathered microplastics (2 mm2), but the effects were not dose dependent. Embryo development and larval settlement were not significantly impacted by either microplastic type. The study shows that moderate-high levels of marine microplastic contamination, specifically particles <2 mm2, will not substantially interfere with the success of critical early life coral processes.