Running on empty: Diesel-Contaminated sediments impair feeding and behaviour in the marine gastropod Tritia neritea

Diesel contamination is a pervasive threat to coastal ecosystems, yet the sublethal behavioural effects on benthic invertebrates remain poorly understood. We exposed the marine gastropod Tritia neritea to sediments spiked with two diesel concentrations (DIE-1: 1.4 × 10⁶ ng/g; DIE-2: 3.5 × 10⁶ ng/g) over 28 days to assess survival, foraging, predator-avoidance, burrowing, and biochemical responses. Diesel addition led to initial contamination dominated by heavy hydrocarbons, BTEX compounds, and naphthalene, with DIE-2 exceeding sediment quality guideline thresholds. Hydrocarbon concentrations declined sharply (>96% for C₅-C₄₀, >97% for LMW PAHs) over the experiment, reducing TEQ and MEQ values by > 99%. Despite chemical remediation, snails exposed to DIE-2 exhibited reduced survival (79 ± 7.5%), impaired foraging success (<25%), prolonged searching times, diminished feeding, and increased immobility. Burrowing activity was slightly enhanced in DIE-2, while righting responses were moderately affected. Biochemical markers related to oxidative stress, neurotransmission and energy reserves remained largely unchanged across treatments. Our results indicate that diesel-contaminated sediments can disrupt feeding and behavioural performance in T. neritea, with potential ecological consequences even when contaminant levels decline. These findings highlight the importance of including behavioural endpoints in sediment toxicity assessments.