Single and combined effects of cadmium, microplastics, and their mixture on whole-body serotonin and feeding behaviour following chronic exposure and subsequent recovery in the freshwater leech, Nephelopsis obscura

• Published in: Aquatic toxicology 2023-06, Vol.259, p.106538-106538, Article 106538
• Main Authors: Zink, Lauren, Wiseman, Steve, Pyle, Gregory G.
• Format: Article
• Language: English
• Subjects: Animals; Behavioural toxicology; Cadmium; Cadmium - toxicity; Feeding Behavior; Fresh Water; Humans; Leeches - physiology; Microplastics; Mixtures toxicity; Plastics - toxicity; Serotonin - pharmacology; Water - pharmacology; Water Pollutants, Chemical - toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2023.106538

•Cadmium is more readily accumulated from waterborne sources compared to sediment-borne, even in environments where both sediment and surface water are contaminated.•Following a 21-day exposure, the co-contamination of cadmium and microplastics resulted in greater adverse effects to serotonin and feeding levels than either contaminant alone.•Leeches recovered from microplastic-induced effects within one week, but alterations to serotonin levels and feeding behaviour from cadmium persisted. Microplastics and metals are contaminants detected in many freshwater systems globally. Interactions of microplastics with other contaminants including cadmium poses potential threats to the health of aquatic organisms including Nephelopsis obscura, a predatory leech species that is widespread and serves important ecological and economic roles. The feeding biology of N. obscura has been well-described, including that serotonin regulates feeding behaviour. Further, exposure to cadmium has been found to cause decrease whole-body concentrations of serotonin. The influence that microplastic contamination and co-contamination of cadmium and microplastics has on N. obscura is unknown. The present study had three objectives: (1) to determine if water or sediment contaminated with cadmium, microplastics, or their mixture resulted in greater cadmium uptake by N. obscura, (2) to assess effects of chronic (21-day) exposure of N. obscura to waterborne cadmium, microplastics, and their mixture on bioaccumulation of cadmium, concentrations of serotonin, and feeding behaviour (latency to feeding, time spent feeding, and distance moved), and (3) to reassess the bioaccumulation of cadmium, concentrations of serotonin, and feeding behaviour following transfer to an uncontaminated environment for a one-week recovery period. This study revealed that access to and presence of sediment is protective against cadmium uptake and that cadmium is more readily accumulated from waterborne sources, even in environments where both sediment and surface water are contaminated. After 21-days of exposure to waterborne cadmium, microplastics, and their mixture, accumulation of cadmium, decreased concentrations of serotonin, and impaired feeding behaviours were greatest in leeches from the co-exposures compared to leeches from either single contaminant exposure group. Finally, after one week of depuration and recovery in freshwater following the 21-day exposures, concentrations of serotonin and feeding beha