Nanoplastic incorporation into an organismal skeleton

Abstract

Studies on the effects of global marine plastic pollution have largely focused on physiological responses of few organism groups (e.g., corals, fishes). Here, we report the first observation of polymer nanoparticles being incorporated into the calcite skeleton of a large benthic foraminifera (LBF), a significant contributor to global carbonate production. While previous work on LBF has documented selectivity in feeding behaviour and a high degree of specialization regarding skeletal formation, in this study, abundant cases of nanoplastic encrustation into the calcite tests were observed. Nanoplastic incorporation was associated with formation of new chambers, in conjunction with rapid nanoplastic ingestion and subsequent incomplete egestion. Microalgae presence in nanoplastic treatments significantly increased the initial feeding response after 1 day, but regardless of microalgae presence, nanoplastic ingestion was similar after 6 weeks of chronic exposure. While ~ 40% of ingesting LBF expelled all nanoplastics from their cytoplasm, nanoplastics were still attached to the test surface and subsequently encrusted by calcite. These findings highlight the need for further investigation regarding plastic pollution impacts on calcifying organisms, e.g., the function of LBF as potential plastic sinks and alterations in structural integrity of LBF tests that will likely have larger ecosystem-level impacts on sediment production.

Foraminifera and plastic pollution: Knowledge gaps and research opportunities

“…1). Protists were critically underrepresented (i.e., 2%) and amongst the 24 papers that considered them, ten of these studies focused on benthic foraminifera; amongst which four observed benthic 7 foraminifera on floating and benthic plastic debris (Jorissen 2014, Finger 2017, Birarda et al 2021, ub as-Baratau et al 2022, four focused on the inclusion of plastic particles in foraminiferal tests (Tsuchiya and Nomaki 2019, Birarda et al 2021, Joppien et al 2022a, Romano et al 2023) and only four stricto sensu monitored the effect of MPs or NPs (Ciacci et al 2019, Birarda et al 2021, Joppien et al 2022b. A recent review (Delaeter et al 2022) showed that, in plastic leachates-related studies, only 0.64% studies considered benthic foraminifera, while about 98% were on macro-invertebrates.…”

“…Foraminifera have mainly four types of tests: those that assemble calcium carbonate crystals constructed intracellularly and build tests (porcelaneous test), those that crystallized calcium carbonate (mainly) extracellularly (hyaline), those that collect sediment particle in the habitat for a test (agglutinated), and those with an organic membrane. Plastic particles were found to be included in the test of hyaline (Joppien et al 2022a) and agglutinated foraminifera (Tsuchiya and Nomaki 2019, Birarda et al 2021, Romano et al 2023, and, as such, might further be transferred to predators of foraminifera like gastropods, copepods, polychaetes, decapods, polychaetes and fishes (Buzas and Carle 1979, Culver and Lipps 2003, Nomaki et al 2008. Inclusion of plastic particles into the test of benthic foraminifera may likely expose them to the harmful effects of plastic additives; see Delaeter et al (2022) for a specific review on the impacts of plastic leachates on organisms.…”

“…However, sub-sediments may also constitute a reservoir where plastics are trapped and be further re-introduced in the food-web by benthic organisms feeding in this compartment (Sandgaard et al 2023). In addition, the inclusion of plastic particles in the test of hyaline and agglutinated benthic foraminifera (Tsuchiya and Nomaki 2019, Birarda et al 2021, Joppien et al 2022a, Romano et al 2023) possibly contributes to the transfer of plastic particles and additives through the food web, and to the trapping of MPs and NPs in the sediment. In this specific context, benthic foraminifera became their own victims as the burial of MPs and NPs is likely to expose them to ever increasing concentrations of the countless additives and chemicals carried by plastic items.…”