The increased input of darker terrestrial derived dissolved organic matter to northern coastal systems has been a growing environmental concern in recent years. Terrestrial dissolved organic matter (terrDOM) is typically comprised of larger humic molecules with stronger amphipathic properties compared to phytoplankton-derived marine DOM (marDOM) and thus has a more favourable adsorption profile for lipophilic contaminants. Previous studies show that some contaminants adsorb well to terrDOM, leading to reduced bioconcentration (direct uptake from water) at the base of aquatic food webs. However, the very same properties may lead to an increased contaminant uptake via feeding processes in filter feeding organisms under terrDOM exposure. To test whether the presence of terrDOM leads to higher contaminant uptake then marDOM, we exposed blue mussels (Mytilus edulis) and, in a second experiment, ascidians (Ciona intestinalis) to teflubenzuron - a lipophilic (log K_OW: 5.39) veterinary drug commonly used in aquaculture against sea lice - under four different DOM conditions: terrDOM, marDOM, mixDOM (a mixture of terrDOM and marDOM) and seawater only. Each of the two experiments used a factorial design including the four DOM conditions and teflubenzuron exposure (exposure, control), with triplicate aquaria for each treatment (n= 24 aquaria). Contrary to expectations, our results showed that terrDOM exposure did not lead the highest bioaccumulation for either of the two taxa, but we rather observed higher bioaccumulation for the marDOM or mixDOM exposure. However, terrDOM exposure also did not lead to lower bioaccumulation than the seawater only treatment. Bioaccumulation of teflubenzuron was overall higher in blue mussels than ascidians. We conclude that the overall small difference in accumulation rates observed in both taxa is likely not environmentally relevant and the effect of terrDOM alone as a vector for teflubenzuron under comparable conditions is likely negligible.

Primary Presenter: Sabrina Schultze, University of Oslo (sabrina.schultze@ibv.uio.no)

Authors:

Sabrina Schultze, University of Oslo  (sabrina.schultze@ibv.uio.no)

Hilde Langva, University of Oslo  (Hildelangva@gmail.com)

Nina Knudtzon, University of Oslo  (Nina.cathrine@hotmail.com)

Jan Thomas Rundberget, Norwegian Institute for Water Research (NIVA)  (thomas.rundberget@niva.no)

Marios Chatzigeorgiou, University of Bergen  (Marios.Chatzigeorgiou@uib.no)

Steven Brooks, Norwegian Institute for Water Reserach (NIVA)  (steven.brooks@niva.no)

Amanda Poste, Norwegian Institute for Water Reserach (NIVA); UiT the Arctic University of Norway  (Amanda.Poste@niva.no)

Dag Hessen, University of Oslo  (d.o.hessen@mn.uio.no)

Anders Ruus, University of Oslo; Norwegian Institute for Water Reserach (NIVA)  (Anders.Ruus@niva.no)

Tom Andersen, University of Oslo  (tom.andersen@ibv.uio.no)

Katrine Borgå, University of Oslo  (Katrine.Borga@ibv.uio.no)