Due to increasing urban development, such as expanding road networks and housing development, the accumulation of microplastics is likely to impact coastal areas. Drainage systems collect plastics from terrestrial sources and channel them into distributaries, polluting freshwater, coastal, and oceanic ecosystems. Although the scientific community is becoming increasingly aware of microplastic accumulation within these systems, there is little experimental data on how this pollution might influence reproductive success in species that occupy impacted habitats. Here, we used laboratory experiments and the Atlantic purple sea urchin (Arbacia punctulata) to test how the presence of microplastics effects reproductive success and sperm availability in organisms that spawn their gametes for external fertilization. Sea urchins were induced to spawn, and fertilization success was measured under three polyethylene microplastic concentrations at three different sperm concentrations. The effect of microplastics on sperm availability was investigated by using a one-way ANOVA after quantifying the sperm concentration in each vial. Fertilization data were analyzed using a two-way ANOVA to investigate the effects of sperm concentration and microplastics on fertilization.
Results/Conclusions
We found a significant reduction in the percentage of eggs fertilized in trials where microplastics were present. Fertilization success, on average, across all treatments containing microplastics was 8.75% compared to 76.25% in controls. While the presence of microplastics diminished fertilization success, we did not detect differences between trials with varying concentrations of plastic. The availability of sperm declined in treatments with greater concentrations of microplastics and we found visual evidence of sperm clumping on microplastic particles, but this trend was not statistically significant. Our results suggest that ecologically relevant concentrations of microplastics severely diminish fertilization success in A. punctulata. Microplastics reduce sperm availability, but also appear to reduce fertilization efficiency by interfering with gamete performance. Overall, this study indicates that microplastic pollution represents a significant threat to aquatic and marine species that reproduce by broadcast spawning.