Pollutants in marine biota from three Mascarene islands

Abstract

The Indian Ocean is the third-largest body of water on the planet. It is a source of food and livelihood for millions of people—most of them from developing countries. The western Indian Ocean (WIO) extends from the shores of Somalia to South Africa, and as far eastward as the Mauritian Outer Islands. Fewer ecotoxicological studies have been conducted in the WIO compared with other regions, and even less in the Mascarene Basin. This study aims to enhance the ecotoxicological knowledge of three tropical islands in the Mascarene Basin. Four aspects of ecotoxicology are covered in four article manuscripts published or submitted to international journals. The first ecotoxicological aspect is the transport of pollutants to remote islands through shipwrecks. Shipwrecks cause ecological harm by physically damaging reef systems when grounding and subsequently causing long-term toxicological harm when pollutants leach from the wreck to the surrounding reef system. This has the potential to kill corals, destabilising the base of the coral reef ecosystem. Secondly, halogenated pollutants were quantified in coral reef biota. This is also the first report of brominated compounds in coral. Brominated and chlorinated compounds were quantified in hard- and soft coral and fish from St. Brandon’s Atoll (SBR), Agalega, and Rodrigues for the first time. Soft coral contained higher concentrations than hard coral for all persistent organic pollutants (POPs). Hard coral contained higher concentrations of novel brominated flame retardants than soft coral. Fish consistently had higher concentrations than hard coral but did not differ significantly. The widespread occurrence of pentabromotoluene (PBT) was confirmed in reef biota for the first time, raising the question if PBT should be considered as a candidate POP. The third article investigated the concentrations of POPs in seabird eggs of fairy terns, sooty terns, and common noddies from SBR. Sooty- and fairy terns forage further offshore and were seemingly exposed to more pollutants. This study also reported POPs in the eggs of a terrestrial species—chicken—from the Mascarene Basin for the first time. This suggests aerial transport of pollutants to the WIO. Concentrations of pollutants in the eggs were lower than other values found in literature. I quantified perfluoroalkyl substances (PFAS) in the eggs of seabirds and chickens from SBR in the final article – the first for the WIO. Fairy tern eggs contained the highest concentrations of PFAS, followed by sooty terns, then common noddies. Long-chained PFAS were prevalent over short chained PFAS. All chicken eggs contained quantifiable concentrations of PFAS, again suggesting aerial transport. The concentrations of pollutants in all biota that were quantified were lower than reported from elsewhere. The remote nature and lack of industry in the Mascarene Basin contributed to low concentrations of pollutants in biota. The Mascarene Basin would be an ideal location to monitor background concentrations of pollutants. The fact that pollutants could be quantified in remote tropical islands in the WIO shows how ubiquitous pollutants are distributed in the environment and may contribute towards identifying candidate POPs.