ABSTRACT: The copepod Lepeophtheirus salmonis is an obligate ectoparasite of salmonids. Salmon lice are major pests in salmon aquaculture and due to its economic impact Lepeophtheirus salmonis is one of the most well studied species of marine parasite. However, there is limited understanding of how increased concentration of pCO2 associated with ocean acidification will impact host-parasite relationships. We investigated the effects of increased pCO2 on growth and metabolic rates in the planktonic stages, rearing L. salmonis from eggs to 12 days post hatch copepodids under three treatment levels: Control (416 µatm), Mid (747 µatm), and High (942 µatm). The pCO2 treatment had a significant effect on oxygen consumption rate with the High treatment animals exhibiting the greatest respiration. The treatments did not have a significant effect on the other biological endpoints measured (carbon, nitrogen, lipid volume, and fatty acid content). The results indicate that L. salmonis have mechanisms to compensate for increased concentration of pCO2 and that populations will be tolerant of projected future ocean acidification scenarios. The work reported here also describes catabolism during the lecithotrophic development of Lepeophtheirus salmonis, information that is not currently available to parameterize models of dispersal and viability of the planktonic free-living stages.

Filename: WaterConditions Routine measurements of water conditions including nutrient levels, alkalinity, water temperature and carbon chemistry as calculated from pH spectroscopy measurements and CO2SYS. Filename: Respiration data.xlsx Oxygen Consumption rates of salmon lice according to age, stage, and pCO2 treatment. Filename: Lipid data.xlsx Lipid volume of salmon lice measured with fluorescence microscopy. Filename: JC10 data.xlsx Metabolic activity observed by measuring mitochondrial membrane potential (MMP). Membrane polarization in mitochondria is an indication of active cells. Polarized mitochondria were represented by red JC-10 aggregate (λ exc/λ em = 488/590 nm) while the green JC-10 monomer (λ exc/λ em = 488/525 nm) labeled the presence of mitochondrial membrane. Filename: Fatty Acid.xlsx Fatty acid profiles of salmon lice according to stage and pCO2 treatment. Data is presented as mass (ng) of the identified fatty acid per individual animal. Columns are separated by the identified fatty acid, '?' indicate ambiguity in the location of the double bond. Filename: CHN data.xlsx Carbon and nitrogen content of individual salmon lice eggs, nauplii, and copepodids.