Metamorphosis alters concentrations of bioaccumulated pharmaceuticals and endocrine disruptors in caddisflies: Implications for transfer of aquatic–terrestrial subsidies

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Abstract Aquatic insects serve as vital inter‐habitat linkages between aquatic and terrestrial ecosystems, as their life cycle includes both aquatic and terrestrial stages. They facilitate the flow of energy and nutrients and play an important role in the transport of waterborne contaminants to terrestrial environments. This study focused on the under‐investigated environmental fate of emerging contaminants (ECs), particularly pharmaceuticals (PhACs) and endocrine‐disrupting compounds (EDCs), which originate from wastewater effluents and accumulate in aquatic insects. Using an in situ study of a highly abundant caddisfly species (Trichoptera), Silo nigricornis (Pictet, 1834), inhabiting a wastewater‐impacted drainage ditch, we examined the bioaccumulation and bioamplification of PhACs and EDCs across the aquatic and terrestrial life stages of the caddisfly. We observed variations in the highest concentrations of PhACs and EDCs in different sample types, including water, biofilm and different life stages of S. nigricornis. Adult S. nigricornis exhibited the highest total concentrations of ECs among the different life stages, with 17 different ECs bioaccumulated in caddisfly tissues. Most of these ECs had higher concentrations in terrestrial adults compared to aquatic larvae and pupae. The total concentration of ECs increased significantly with development, revealing a 41% higher concentration in adult terrestrial caddisflies compared to pupae and larvae. Bioamplification factors provided insights into the increased body burden of the majority of compounds during at least one stage of metamorphosis in S. nigricornis. Evidence of bioamplification was observed in both metamorphosis stages, with certain compounds, such as antibiotics (azithromycin and tilmicosin), endocrine disruptors (TCPP – tris[1‐chloro‐2‐propyl]phosphate and parabens; methylparaben, propylparaben), consistently exhibiting increased concentrations from larval to pupal and from pupal to adult stages. The observed pattern of increasing body burden of contaminants during the caddisfly life cycle emphasises the effects of metamorphosis on the concentration of PhACs and EDCs in adult holometabolous aquatic insects. Our results emphasise the importance of adult caddisflies for the transport of waterborne contaminants such as PhACs and EDCs from aquatic to terrestrial environments. Therefore, our results emphasise the need to include adult trichopterans in the assessment of habitat quality, as their influence extends beyond the boundaries of the aquatic ecosystem.