Rising tide of microplastics: contamination in filter-feeding ascidians

Ascidians are marine filter feeders that play a vital role in keeping our oceans healthy. They hold significance in evolutionary biology and serve as valuable models in evolutionary and marine pollution studies. Also, they are successful models for comprehending the impacts of anthropogenic compounds on ontogeny, as their larvae comprise fewer than 3,000 cells. The filtration in ascidians involves inhalant and exhalant siphons, by beating the tentacles lying at the base of the siphon. The aqueous medium passes through the branchial basket, which orchestrates the direction of water for processes such as nutrition, respiration, and clearance management. It actively removes suspended matter from the water, enhancing nutrient cycling. However, the intrusion of microplastics (MPs) (¡ 5 mm), into the ocean has posed a severe threat, as they are widely distributed in water and sediments. When ingested by organisms, it compromises the nutrition of these filter feeders and impairs various organ systems. Specifically, the presence of MP in ascidians has been associated with alterations in metamorphosis and embryonic development. A question that scientists are trying to answer is how ascidians select particles during filter feeding. Understanding this process is crucial for assessing the true impact of MP contamination. To address this issue, this study was conducted on Phallusia nigra from Todos os Santos Bay (TSB), collected in natural and artificial substrates. They were manually sampled and dissected into a tunic, branchial basket, and inner body, and the MPs were extracted through density separation. This study elucidated the extent of MP contamination and accumulation in ascidians. These findings clarified unexplored information regarding the retention of MP particles in ascidian tissues. Also, it revealed MP accumulation within ascidians from different sites around TSB, providing valuable data on the distribution of contamination in coastal ecosystems. Also see: https://micro2024.sciencesconf.org/559486/document