“Assessment of the combined effects of plastic pollution and salinity shifts on the biology and physiology of the copepod Nitokra spinipes in the context of global change”
Nault, N. (2023). “Assessment of the combined effects of plastic pollution and salinity shifts on the biology and physiology of the copepod Nitokra spinipes in the context of global change”. MSc Thesis. Université Littoral Côte d'Opale: Dunkerque. 42 pp.
Estuarine harpacticoid copepods are frequently used in ecotoxicological studies worldwide. These organisms often experience a wide range of salinity fluctuation, which is expected to intensify in the future due to global changes. Furthermore, aquatic invertebrates also experience the deleterious effects of plastic pollution, which is on the rise in aquatic environments due to human activities and represents a physical and chemical hazard due to the leaching of chemicals in the media. However, the current knowledge about ecotoxicological effects of salinity shifts in combination with exposures to plastic leachates on aquatic invertebrates remains limited as to-date analyses focus on single-stressor exposures. In our study, we demonstrated that exposures to plastic leachates (80 g / L) produced from fossil fuel-based (PolyVinyl Chloride (PVC), Polyethylene, Polypropylene) and bio-based (Flax- and Self-Reinforced Polylactic Acids) in combination with a salinity shift (from 7 to 15 PSU) affected the physiology of both adult and larval stages of the copepod Nitokra spinipes. Among the tested plastics, only the leachates produced from PVC items significantly affected the survival of adult individuals, probably due to an increased amount of additives and / or adsorption of co-contaminants on these items compared to others. No significant difference of mortality was found between salinities for adults exposed to PVC leachates, likely linked to the wide salinity tolerance of N. spinipes. Exposure to sublethal concentrations of PVC leachates in combination with a salinity shift resulted in larval development retardation and alterations of the filtration rate (adult), suggesting that N. spinipes reallocated energy to cope with the stresses, which in turn reflected in all biological processes. As modifications of the population dynamics of copepods could induce unprecedented trophic cascades in marine ecosystems, we recommend that further ecotoxicological analyses should be conducted at larger ecological scales to predict the consequences of such changes.
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