Microplastic ingestion by coral as a function of the interaction between calyx and microplastic size

Coral reefs have been heavily impacted by anthropogenic stressors, such as global warming, ocean acidification, sedimentation, and nutrients. Recently, microplastics (MP) have emerged as another potential stressor that may also cause adverse impacts to coral. MP ingestion by scleractinian coral among four species, Acropora cervicornis, Montastraea cavernosa, Orbicella faveolata, and Pseudodiploria clivosa, was used to identify the relationship between calyx and MP size as it pertains to active coral ingestion. A range of MP sizes (0.231-2.60 mm) were offered to the coral species across a wide range of calyx sizes (1.33-4.84 mm). Laboratory data showed that as the mean calyx size increased, so too did the mean percent of ingestion with increasing MP size. From laboratory data, a logistic model was developed to extrapolate the range of MP sizes that can be actively ingested by coral species based on calyx size. The data and model presented here offer the first predictive approach that can be used to determine the range of MP sizes that have a high likelihood of being actively ingested by coral of various sizes, thus offering insight to possible impacts on scleractinian coral.