Do tubificid worms influence organic matter processing and fate of pollutants in stormwater sediments deposited at the surface of infiltration systems?

The purpose of this study was to examine the influence of tubificid worms on the biogeochemical functioning of water-sediment interface impacted by a stormwater particle deposit. Two other natural particle deposits (one low and one rich POM-deposits) were studied to compare their effects with those of the stormwater deposit in infiltration columns. We measured the effects of invertebrates on sediment reworking, organic matter processing, nutrient fluxes, microbial characteristics, and pollutant release from stormwater deposit to water. Our results showed that tubificid worms had lower effects on microbial activities in the stormwater deposit columns than in columns impacted by the other two deposits. The high lability of the POM of stormwater deposit led to a high microbial activity in the system that could not be easily stimulated by invertebrates under our infiltration conditions. In contrast, tubificid worms stimulated biogeochemical processes in more refractory deposits. Moreover, tubificid worms did not influence the fate of pollutants (heavy metals and PAHs) of the stormwater deposit because the chemical characteristics of this polluted deposit acted as a sink for most contaminants. Therefore, our study demonstrated that the influence of invertebrates on biogeochemical processes in sediments was strongly linked to the organic matter characteristics of the sediments (quantity and quality of POM).