Trophic Positioning and Habitat Ecology: A Comparative Review of PFAS Bioaccumulation Dynamics in Pelagic versus Demersal Fish Species

Abstract

Global concern and pose a significant threat to aquatic ecosystems and to the health of human consumers. Due to their extraordinary chemical stability and amphiphilic nature, these persistent chemicals are effectively biomagnified in marine and freshwater food webs. However, the spatial distribution of PFAS in the water column leads to different bioaccumulation pathways between pelagic and bottom species. Understanding these habitat-specific variations is essential for an accurate assessment of the environmental risks and for the development of targeted frameworks for food safety monitoring. Pelagic species that are present in the upper water column (e.g. mackerel, tuna and bluefin tuna) are primarily exposed to waterborne fractions of PFAS and highly mobile, water-soluble short-chain alternatives through the uptake of pelagic food webs and by the fishery. As these species often exhibit high metabolic rates and extensive migration patterns, their PFAS profiles are strongly influenced by horizontal spatial changes in water contamination and by rapid trophic translocation. Conversely, demersal and benthic species (e.g. flatfish, cod and turbot) are found close to the seabed and are therefore very vulnerable to long-chain variants of PFOS, which are highly organic in nature and accumulate in benthic sediments. The demersal food web is intrinsically linked to the detrital routes and to the organisms living in the sediment, which results in a long-term, chronic exposure matrix for pelagic and demersal fish species. Recent toxicokinetic studies show that while pelagic fish often show a rapid response to changing surface water concentrations, demersal species tend to have significantly higher steady state bioconcentration factors and a higher body weight of hydrochlorofluorocarboxylic and sulphonic PCBs. This comparative analysis highlights that the primary drivers of tissue distribution of PFAS are habitat ecology, interaction with sediments and trophic distribution. Therefore, in order to accurately mitigate the risks of chemical exposure in human food, reliable environmental monitoring and safety regulations need to implement stratified sampling strategies, distinguishing between pelagic and demersal habitats.