Trophic transfer of silver nanoparticles in a detritus-based food chain within a karst stream: A comparative study of direct exposure versus trophic transfer

The widespread use of silver nanoparticles (AgNPs) has led to their substantial release into aquatic ecosystems, yet their ecological risks within detritus-based food chains remain poorly understood. This study constructed a model detrital food chain-Pterocarya stenoptera leaf litter (with microbes) → Neocaridina denticulata (shrimp) → Rhinogobius duospilus (fish)-representative of karst river ecosystems, to compare the distribution and toxicity of AgNPs under direct exposure versus trophic transfer scenarios. We identified several key ecological indicators affected by AgNPs: fungal diversity, species co-occurrence network structure, and interspecific interactions on decomposing leaves were significantly compromised, indicating disruption at the detritus-based food chain. While trophic transfer reduced the overall biomagnification factor, it enhanced Ag accumulation in specific organs-shrimp cephalothorax and fish intestine. In the tertiary chain (litter-shrimp-fish), Ag levels in these organs were 14-94% higher than in the secondary chain (shrimp-fish). Directly exposed shrimp accumulated Ag predominantly in the cephalothorax and abdomen (23-55% of total Ag), with trophic transfer further elevating cephalothorax accumulation. In fish, the intestine was the major accumulation site, strongly correlating with severe histopathological damage in the liver and gills, including vacuolation and vascular congestion-critical biomarkers of toxicological impact. This study provides the first evidence that detritus-based food chains serve as a critical entry route for AgNPs into aquatic food webs. Our findings demonstrate that organ-specific Ag accumulation (e.g., in the shrimp cephalothorax and fish intestine) and the disruption of microbial co-occurrence networks are sensitive indicators of AgNPs stress, even when overall biomagnification factors suggest trophic dilution. This study provides empirical evidence that detritus-based food chains are a critical entry route for AgNPs into aquatic food chains, with implications for risk assessment and conservation strategies in geochemically vulnerable karst freshwater ecosystems.