Dietary absorption of sediment-bound fluoranthene by a deposit-feeding gastropod using the ¹⁴C:⁵¹CR dual-labeling method

Polycyclic aromatic hydrocarbons (PAH) constitute a broad class of toxic, environmentally persistent, particle-reactive organic compounds that are ubiquitous in aquatic and terrestrial ecosystems. This study was designed to measure ingestion and dietary absorption of the PAH, fluoranthene, by two genotypes of a deposit-feeding gastropod using the ¹⁴C:⁵¹Cr dual-labeling method. Sediment processing rate, fluoranthene ingestion rate, selective ingestion of fluoranthene-containing particles, and fluoranthene absorption rate varied as a function of snail body size and genotype. Absorption efficiency of sediment-bound fluoranthene did not vary as a function of body size but differed between genotypes, averaging 42 to 46% for Clone A and 22 to 36% for Clone B. We could detect no significant metabolism of ingested fluoranthene to dissolved organic carbon or CO₂ during 24 h following its ingestion. The ¹⁴C:⁵¹Cr dual-labeling method provides a powerful approach for investigating the dietary absorption of sediment-bound contaminants by (1) allowing the calculation of ingestion selectivity, sediment processing rate, contaminant ingestion rate, and absorption efficiency in individual small invertebrates; (2) permitting estimation of the fraction of ingested/absorbed contaminant that is metabolized and released via different routes following its ingestion; and (3) facilitating evaluation of the relative importance of porewater versus ingested sediment as routes of contaminant uptake by animals.