Food web on ice: a pragmatic approach to investigate the trophic magnification of chemicals of concern

Abstract

Background The trophic magnification factor (TMF) is a metric that describes the average trophic magnification of a chemical through a food web. TMFs may be used for the risk assessment of chemicals, although TMFs for single compounds can vary considerably between studies despite thorough guidance available in the literature to eliminate potential sources of error. The practical realization of a TMF investigation is quite complex and often only a few chemicals can be investigated due to low sample masses. This study evaluated whether a pragmatic approach involving the large-scale cryogenic sample preparation practices of the German Environmental Specimen Bank (ESB) is feasible. This approach could provide sufficient sample masses for a reduced set of samples allowing screenings for a broad spectrum of substances and by that enabling a systematic comparison of derived TMFs. Furthermore, it was assessed whether plausible TMFs can be derived with the ‘Food web on ice’ approach via a comparison with literature TMF values. Results This investigation at Lake Templin near Potsdam is the first TMF study for a German freshwater ecosystem and aimed to derive TMFs that are appropriate for regulatory purposes. A set of 15 composite biota samples was obtained and analyzed for an extended set of benchmark chemicals such as persistent organic pollutants, mercury and perfluoroalkyl substances. TMFs were calculated for all substances that were present in > 80% of the biota samples. For example, in the case of polychlorinated biphenyls, TMFs from 1.7 to 2.5 were determined and comparisons to literature TMFs determined in other freshwater ecosystems showed similarities. We showed that 32 out of 35 compounds analyzed had TMFs significantly above 1. In the remaining three cases, the correlations were not statistically significant. Conclusions The derived food web samples allow for an on-demand analysis and are ready-to-use for additional investigations. Since substances with non-lipophilic accumulation properties were also included in the list of analyzed substances, we conclude that the ‘Food web on ice’ provides samples which could be used to characterize the trophic magnification potential of substances with unknown bioaccumulation properties in the future which in return could be compared directly to the benchmarking patterns provided here.

Exploring the partitioning of hydrophobic organic compounds between water, suspended particulate matter and diverse fish species in a German river ecosystem

“…Similarly, contradictory observations can also be found in the literature. In a comprehensive biomagnification study in a trophic network in a German lake, Kosfeld et al [ 46 ] found a positive log-linear relationship between C Lip of HOCs and the TL of fish. In contrast, Dufour et al [ 47 ] did not find a correlation between C Lip of HOCs and the TL of Arctic char ( Salvelinus alpinus ) in Lake Geneva, Switzerland.…”

Using environmental monitoring data from apex predators for chemicals management: towards better use of monitoring data from apex predators in support of prioritisation and risk assessment of chemicals in Europe

“…This screening could support prioritisation [48] and decision-making processes for follow-up regulatory action for emerging compounds and chemical groups. c. To provide evidence to better understand and assess biomagnification processes of chemicals, for example using samples from selected food webs [49] and/or matched samples of predator and prey. d. To provide evidence on the occurrence of (bio)transformation products and typical chemical mixtures in top predators of different food webs, which can support advancements in risk modelling and assessment methods that are currently being developed with the ultimate goal to identify and manage hazardous chemicals more efficiently.…”

How error‐prone bioaccumulation experiments affect the risk assessment of hydrophobic chemicals and what could be improved

“…Even if the model only represents reality in a simplified way, it can help to identify potentially bioaccumulative substances in a WoE approach. Supporting evidence could also come from existing biomonitoring studies in humans, mammals, and fish or newly generated data in approaches like "Food web on ice," which is a pragmatic approach to identifying the trophic magnification from historical data (Kosfeld et al, 2021). Monitoring studies have the advantage that they reveal directly what is happening in the environment.…”