Microplastic Contamination Has Limited Effects on Coral Fertilisation and Larvae

Abstract

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.

What are the toxicity thresholds of chemical pollutants for tropical reef-building corals? A systematic review

“…verrucosa (200 particles/L (size 65-410 µm) for 6 months exposure) [81] as well as for A. millepora (4000 particles/L (size 37-163 µm) for 4 weeks) [82]. Also, no statistically significant effect was found on chlorophyll concentration in symbiont (five coral species, 5 or 50 particles/L (size 106-125 µm) for 28 days or 200 particles/L (size 65-410 µm) for 6 month exposure) [81,83] or on A. tenuis embryo development (gametes exposure at 5-200 particles/L (size 1 or 6 µm) for 3 h) [84]. However, exposure to polyethylene particles decreased tissue growth of Pseudodiploria clivosa and A. cervi- Chemical name and CAS number, risk of bias (L low , U unclear, or M medium), outcome (Fert fertilisation, Settl settlement, Bleach symbiont density, Photo symbiont photosynthesis and Mort mortality), temperature and pH conditions of the studies used to determine the TT, lowest TT concentration value in µg/L (nominal and effective when measured) and exposure duration in hour, reference value used to contextualise the TT and source of the reference value.…”

“…pistillata (50 particles/L (size 106-125 µm) for 28 days) [83]. Regarding short-term exposure to polypropylene particles, no statistically significant effect was found on the embryo development of A. tenuis (gametes exposure at 5, 15 or 50 particles/L (size 0.5, 1 or 2 mm 2 ) for 3 h [84]. Overall, these studies on polyethylene suggest that the effects of this plastic compound on corals are species-specific, as well as concentration and duration dependent.…”

Microplastics: impacts on corals and other reef organisms

“…The level of knowledge around the effect of MNPs on corals remains unclear, and further research is required. Many negative impacts have been identified and include host-symbiont relationship, photosynthetic efficiency, tissue necrosis, calcification rates, energy demand, reproductive success and overall fitness [41,79,80,82,83,86,87,89,[92][93][94][95][96][97][98][99]. Perturbation of photophysiology, bleaching and tissue necrosis have been observed in laboratorybased studies in response to exposure to MNPs [79,85,89,96] and may demonstrate coral species-specificity.…”

Microplastics in the Food Chain

“…Microplastics may accumulate cause blockage in the gut or several species of organisms. This may induce gradual inflammations to organs [67,68]. Accumulation of microplastics also causes disruptions and decline to the production of oxygen from algae and microalgae [70] and have a disrupted effect in the consumption of zooplanktons [71].…”