Bioaccumulation and trophic transfer of cyclic volatile methylsiloxanes (cVMS) in the aquatic marine food webs of the Oslofjord, Norway

Abstract

The trophic transfer of cyclic methylsiloxanes (cVMS) in aquatic ecosystems is an important criterion for assessing bioaccumulation and ecological risk. Bioaccumulation and trophic transfer of cVMS, specifically octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6), were evaluated for the marine food webs of the Inner and Outer Oslofjord, Norway. The sampled food webs included zooplankton, benthic macroinvertebrates, shellfish, and finfish species. Zooplankton, benthic macroinvertebrates, and shellfish occupied the lowest trophic levels (TL ≈2 to 3); northern shrimp (Pandalus borealis) and Atlantic herring (Clupea harengus) occupied the middle trophic levels (TL ≈3 to 4), and Atlantic cod (Gadus morhua) occupied the highest tropic level (TL>4.0). Trophic dynamics in the Oslofjord were best described as a compressed food web defined by demersal and pelagic components that were confounded by a diversity in prey organisms and feeding relationships. Lipid-normalized concentrations of D4, D5, and D6 were greatest in the lowest trophic levels and significantly decreased up the food web, with the lowest concentrations being observed in the highest trophic level species. Trophic magnification factors (TMF) for D4, D5, and D6 were <1.0 (range 0.3 to 0.9) and were consistent between the Inner and Outer Oslofjord, indicating that exposure did not impact TMF across the marine food web. There was no evidence to suggest biomagnification of cVMS in the Oslofjord. Rather, results indicated that trophic dilution of cVMS, not trophic magnification, occurred across the sampled food webs.

Growth‐Correcting the Bioconcentration Factor and Biomagnification Factor in Bioaccumulation Assessments

“…The lipid-normalized BMFs (BMF L ) of D4 and D5 derived from the results of the dietary bioaccumulation tests are 0.34 × (0.148/ 0.0632) or 0.80 kg lipid kg lipid -1 for D4 and 0.33 × (0.148/0.0564) or 0.87 kg lipid kg lipid -1 for D5 in growing and nongrowing fish. These BMFs are in reasonable agreement with observed trophic magnification factors of D4 and D5 in aquatic food webs, which range between 0.31 and 1.3 kg lipid kg lipid -1 for D4 and between 0.18 and 2.3 kg lipid kg lipid -1 for D5 (Powell et al 2009(Powell et al , 2017(Powell et al , 2018Borga et al 2012Borga et al , 2013McGoldrick et al 2014;Jia et al 2015). In contrast, corresponding BMFs calculated with the OECD-305 growth correction are 4.0 and 2.5 kg lipid kg lipid -1 and are greater than observed trophic magnification factors of D4 and D5 in aquatic ecosystems.…”

Practical advice for selecting or determining trophic magnification factors for application under the European Union Water Framework Directive

“…zooplankton, several different benthic invertebrate families). Reasonable balance with respect to sample numbers of lower‐ versus higher‐trophic‐level organisms. Adequate and balanced representation of samples for each TL. Differences in sample size among different levels of the food web can produce an “unbalanced” sampling design that requires the application of appropriate statistical methods to determine the TMF (Borgå et al ; Powell et al , ). An unbalanced design may contribute to uncertainty in the TMF estimate. Measurements are on organisms that are known to be linked by diet through the food web.…”

“…Adequate and balanced representation of samples for each TL. Differences in sample size among different levels of the food web can produce an “unbalanced” sampling design that requires the application of appropriate statistical methods to determine the TMF (Borgå et al ; Powell et al , ). An unbalanced design may contribute to uncertainty in the TMF estimate. …”

Chemicals of emerging concern in marine specimens of the German Environmental Specimen Bank

“…Comparative wet weight concentrations of siloxanes in marine fish are, for instance, available from coastal waters of Norway and from the Baltic Sea. In whole fish samples of eelpout from the inner Oslo Fjord, Powell et al [77] detected concentrations in the range of < 3.7-2.3 µg kg −1 (D4), 14.4-72.8 µg kg −1 (D5) and < 4.7-6.67 µg kg −1 (D6). Filet concentrations are available for herring from the Baltic Sea (D4: < 4.4-0.5 µg kg −1 ; D5: 10-21 µg kg −1 ; D6: 2-5.4 µg kg −1 ) [78].…”