Sediment dwelling macrofauna (infauna) are important vectors for the transfer of sediment-associated contaminants to higher
trophic levels. Sedimenting organic matter constitutes an important food source for all benthic organisms and changes seasonally in terms of quantity and quality. Sediment organic matter (SOM) quality affects organism activity and feeding behaviour, and is therefore also likely to affect contaminant fate in benthic systems. We investigated the impact of SOM quality (enrichment with either labile
Tetraselmis sp. or refractory lignin) on the accumulation and metabolism of sediment-associated pyrene in
Nereis diversicolor (Annelida) and
Amphiura filiformis (Echinodermata), as well as the combined effect of SOM quality and infaunal bioturbation on pyrene distribution and metabolism in the sediment. After 45 d of exposure, SOM quality almost doubled pyrene bioaccumulation in both species, while pyrene metabolism remained unaffected. Metabolites comprised
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80 % of the total tissue pyrene in
N. diversicolor and
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40 % in
A. filiformis.
A. filiformis arms contained one fifth of the disk pyrene concentration. Approximately 20 % of the pyrene found in
A. filiformis arms was found to be covalently bound to, e.g. DNA, RNA or proteins, thus reducing pyrene bioavailability to arm-cropping
predators. The sedimentary pyrene distribution and metabolism was species-
dependent, but correlated poorly with prevailing knowledge on species-specific bioturbation patterns. This was attributed to the comparably high biodegradability of the contaminant thus altering its sorptive characteristics and
function as inert tracer. Subduction of pyrene and metabolites occurred, and the fraction of pyrene covalently bound to SOM increased with depth, thereby removing pyrene from the bioavailable pool. Our results imply that bioaccumulation and
trophic transfer of sediment-associated PAH should increase following fresh organic matter input, e.g. after sedimentation of phytoplankton blooms. We stress the importance of considering behavioural characteristics of infauna and the
trophic situation of the system when assessing fate and effects of sediment-associated contaminants.