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ABSTRACT
The aim of this study was to investigate impacts of fine particulate fraction of a commonly used barite-containing drilling mud on the pelagic filter feeding copepod Calanus finmarchicus. The results show that the tested drilling mud had a low acute toxicity on C. finmarchicus (LC50 > 320 mg/L) and that the observed toxicity was likely caused by dissolved constituents in the mud and not the particle phase containing the weighting agent barite. Further, animals were exposed to drilling mud at a concentration of 10 mg/L for 168 hr followed by a 100 hr recovery phase. A rapid uptake of drilling mud particles was observed, while the excretion was slow and incomplete even after 100 hr recovery in clean seawater. The uptake of drilling mud particles caused a significant increase in sinking velocity of copepods, indicating that uptake of drilling mud particles affected their buoyancy. Long-term exposure to low concentrations of drilling mud could therefore cause physical effects such as impacts on the animal's buoyancy which may affect the energy budget of the copepods.
Acknowledgments
The authors would like to thank the following people for valuable contribution to the project: Rolf Arne Kleiv, Syverin Lierhagen, Torill Sørlokk and Ingrid Overrein.
Funding
The project was financed by internal funding by the contributing research institutes SINTEF (project number 809T1601), NTNU and BioTrix. The establishment of the Calanus finmarchicus cultures was financed by the Research Council of Norway (157687/S40 and 170429/S40).
Supplemental data
Supplemental data for this article can be accessed on the publisher’s website.
