Impacts of spilled debris from the X-Press Pearl disaster in Sri Lanka on marine plankton

Accidents of ships carrying diverse hazardous chemicals and plastics can lead to complex spills of pollutants in marine ecosystems. One such incident was the catastrophic fire on the container ship X-Press Pearl which sank off the Sri Lankan coast in 2021. Explosions and fire resulted in plastic pellets and burnt clumps of melted plastic and combustion residues washing ashore. In this study, we analyzed the acute toxicity of the leached chemicals from this debris on various planktonic organisms: phytoplankton (Rhodomonas salina), meroplankton (Paracentrotus lividus larvae) and holoplankton (Acartia tonsa nauplii and adults). Acute exposures were conducted with a range of leachate dilutions for 72 h. The growth of R. salina was slightly affected by the leachates. Larvae of P. lividus showed a concentration-dependent reduction in growth and normal development (EC50 0.56 g L^-1), with 94% of larvae showing malformations in the highest concentration. The hatching of A. tonsa decreased from 89% in the control to 29% at 0.75 g L-1. Nauplii mortality reached 46% and there was a trend of decreased growth. Mortality of the adults increased with concentration, reaching 51% in the highest concentration. Our results show that the complex mixture of spilled chemicals and debris from the X-Press Pearl accident can potentially harm the planktonic food web, particularly zooplankton. These findings highlight the urgent need for effective mitigation strategies and response measures to reduce impacts of accidental spills in sensitive and ecologically relevant areas, especially those located in major shipping lanes, such as the Sri Lankan coastal waters.