Microplastics Not Shown to Affect Coral Mortality in the Field Like in Laboratory Studies

Overview

Microplastics, an emerging pollutant shorter than 5mm, pose a significant threat as their concentrations increase. With coral reef health in decline, particularly due to rising temperatures, concerns on the effect of microplastics on reef health have arisen. Previous studies investigating this relationship in laboratories have poorly imitated the complexity of field conditions. Therefore, this study explores the effect of microplastics on coral mortality in the field, globally, to better understand this pollutant’s threat. By utilizing two databases and filtering data points to those within a 0.2 degree overlap (longitude and latitude), coral mortality, and secondarily, bleaching, were analyzed against the amount of microplastics. Data cleaning was performed to remove invalid or non-quantitative values such as “low” and “severe.” Initial analysis revealed that all variables lacked a normal distribution, and various transformations failed to produce a normal curve. Hence, nonparametric statistical tests were used, such as Spearman’s Rank Correlation. Mortality data exhibited a weak positive correlation to microplastics; however, at lower quantities of microplastics, there was a range in coral mortality, while at higher quantities, only high mortality values were present. The same analysis conducted with bleaching data showed no correlation. This suggests microplastics are a factor adversely affecting coral mortality, but not bleaching, in conjunction with other environmental concerns. Hence, these findings do not support that of laboratory studies, which find significant negative effects to coral. This study demonstrates the need for further field research to understand microplastics’ role compared to other threats corals face.

Competition history

• JSHS 2022 Category not listed

Resources

• National JSHS abstract book ↗

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